feat: publish Tend v0.2 Preview 2 source

Export the reviewed allowlisted snapshot from private source commit 8aab3db43f35e6a49aa497f45d73701b13fc9f32 and tree 992132ea4703437dc13ffdbb04a077816c02caf9. This includes routed singleton continuity, deployment evidence, strict schema-2 configuration, restricted transport, and the independently compilable public-tree guard.

AI-Assisted: OpenAI Codex
Signed-off-by: Cole Speelman <crspeelman@gmail.com>

.gitignore

@@ -1,3 +1,5 @@
 /bin/
 /dist/
 *.tmp
+.env.local
+*.env.local

PUBLIC-SNAPSHOT.json

@@ -1 +1 @@
-{"schema_version":1,"source_commit":"a72903c63e1753f9e6ffbf40453c0830bdfc05c5","source_tree":"295641e67eef5979da76746d8ae271249568263e","source_date_epoch":1786730082,"file_count":44}
+{"schema_version":1,"source_commit":"8aab3db43f35e6a49aa497f45d73701b13fc9f32","source_tree":"992132ea4703437dc13ffdbb04a077816c02caf9","source_date_epoch":1787049308,"file_count":76}

PUBLIC-SNAPSHOT.sha256

@@ -1 +1 @@
-b29d919cefddb06e0c47b453ffd55438944fc92da5732dbb6f98cb509a2c371e  PUBLIC-SNAPSHOT.json
+9c6153ab5b861ec5818591269b2a38a14239f68e89911655aaebec444f54a26d  PUBLIC-SNAPSHOT.json

README.md

@@ -5,7 +5,7 @@ Linux, systemd, and Caddy. It packages a clean pushed commit, records exact
 build provenance, activates a health-checked candidate, and keeps rollback
 state explicit.
 
-The first preview deliberately supports two quiet deployment shapes:
+The v0.2 development line supports two quiet deployment shapes:
 
 - Caddy-switched blue/green services.
 - A singleton service with an isolated transient candidate check.
@@ -17,21 +17,62 @@ shell hooks. Application-specific data activation remains application-specific.
 
 ```text
 tend check    --config tend.json
-tend package  --config tend.json --version v0.1.0-preview.1 --out dist
-tend deploy   --config /etc/example/tend.json --artifact FILE --sha256 HEX --approve-sha256 HEX
-tend status   --config /etc/example/tend.json
-tend rollback --config /etc/example/tend.json
-tend prune    --config /etc/example/tend.json --keep 3 [--apply]
+tend package  --config tend.json --version v0.2.0-preview.2 --out dist
+tend push     --target tend-deploy@host --known-hosts FILE --service NAME --artifact FILE --sha256 HEX --approve-sha256 HEX
+tend receive  --policy /etc/tend/receive-policy.json
+tend check-server --policy /etc/tend/receive-policy.json
+tend deploy   --config /etc/tend/services/example-site.json --artifact FILE --sha256 HEX --approve-sha256 HEX
+tend status   --config /etc/tend/services/example-site.json
+tend rollback --config /etc/tend/services/example-site.json
+tend prune    --config /etc/tend/services/example-site.json --keep 3 [--apply]
 ```
 
-`deploy`, `rollback`, and applied pruning are target-host operations. Transfer
-credentials and production configuration stay outside source repositories.
-Dry-run and digest approval are intentional friction.
+`push` transfers one approved artifact through a pinned OpenSSH connection. A
+forced, no-shell receiver maps the service name to one root-owned configuration;
+it accepts no remote path, environment value, URL, or shell fragment. Production
+hosts receive binaries and evidence, never source or Go dependencies.
 
-The first public preview has completed maintenance releases and explicit
-rollback/reactivation for both Gamertan and the Sandwich Hime website using one
-reviewed Tend candidate. See the dated
+Schema 2 keeps all services under `/etc/tend/services/`, references a distinct
+root-owned `0600` environment file for each service, and serializes activation
+through `/run/lock/tend-deploy.lock`. Builds and transfers remain parallel;
+only the short Caddy/service activation phase is host-wide. Tend is still a
+single command, not a daemon.
+
+Each service also keeps a bounded JSONL deployment-event stream and explicit
+desired, candidate, active, previous, and last-attempt release identities. The
+stream contains only fixed provenance and lifecycle fields; Observatory may
+ingest it later, but an event-write failure never blocks deployment or rollback.
+After Caddy reload, Tend repeatedly probes the configured canonical HTTPS
+origins for the activation window. Blue/green deployments simultaneously keep
+checking the previous slot, restoring the prior handler and inactive-slot state
+if routed traffic or continuity fails.
+
+Dry-run and digest approval are intentional friction. See the
+[schema-2 migration guide](docs/SCHEMA_V2_MIGRATION.md) and the
+[two-service walkthrough](docs/WALKTHROUGH.md).
+
+Run `./scripts/verify.sh` on Linux. That required release lane exercises tests,
+the race detector, vet, deterministic builds, schema-2 examples, and the
+dependency-free module graph. Tend supports Linux hosts with systemd and Caddy;
+WSL may be used as a Linux development environment, but native Windows is not a
+supported execution, deployment, or release-gate platform.
+
+The v0.1 public preview and immutable `v0.2.0-preview.1` each completed
+maintenance releases and explicit rollback/reactivation for both Gamertan and
+the Sandwich Hime website using one reviewed candidate. See the dated
 [dogfood evidence](docs/DOGFOOD_EVIDENCE.md) for exact scope and limitations.
+
+The additive `v0.2.0-preview.2` candidate keeps that transport and activation
+contract while adding bounded deployment-event JSONL, routed-origin continuity,
+rollback annotations, and the operational findings recorded through real
+dogfooding. Preview 1 remains unchanged. Preview 2 will not be tagged until one
+identical binary has deployed, rolled back, and reactivated Gamertan, the
+Sandwich Hime website, and Gamertan Observatory.
+Operational friction discovered while applying the same contract to new
+services is tracked separately in the
+[dogfood friction ledger](docs/DOGFOOD_FRICTION.md). The ledger preserves the
+fail-closed behavior and records candidate product improvements instead of
+normalizing application-specific deployment workarounds.
 The canonical public repository begins with a sanitized root snapshot rather
 than the private development history.
 

RELEASE.md

@@ -1,6 +1,6 @@
 # Preview release policy
 
-`v0.1.0-preview.1` may be published only after one identical candidate Tend
+`v0.1.0-preview.2` may be published only after one identical candidate Tend
 binary has successfully completed maintenance releases for Gamertan and the
 Sandwich Hime website, including injected-failure restoration and explicit
 rollback proof. The August 14, 2026 campaign met that gate; the scoped,
@@ -19,6 +19,25 @@ The release tag and attached candidate must be built from the final reviewed
 source commit. Documentation-only changes after the recorded campaign require
 one final identical-candidate maintenance pass before tagging.
 
+`v0.2.0-preview.1` is an immutable, additive release line. It requires schema 2,
+the restricted `push`/`receive` transport, root-owned environment-file
+references, host-wide activation serialization, and HTTPS public-origin smoke.
+Its exact released source remains unchanged.
+
+`v0.2.0-preview.2` adds bounded deployment-event JSONL, routed-origin
+activation continuity, rollback annotations, and the reviewed operational
+friction record. It must preserve every Preview 1 security and release gate.
+The exact same Preview 2 binary must deploy, roll back, and reactivate
+Gamertan, the Sandwich Hime website, and Gamertan Observatory before the tag is
+created. EQL is not part of this generic gate; its SQLite/catalog publication
+needs a dedicated adapter rather than arbitrary hooks.
+
+`v0.1.0-preview.1` is immutable but withdrawn: its source and module checksums
+are valid, while a fresh `go install` reports the development identity because
+the CLI did not yet adopt the tagged module version from Go build information.
+Preview 2 adds that identity path and its regression tests; preview 1 is never
+retagged or rewritten.
+
 The canonical public origin is `ssh://git@gitea.speelman.ca:2222/gamertan/tend.git`.
 GitHub is a read-only discovery snapshot. Private development history is not
 published or merged into either public history.

SECURITY.md

@@ -4,11 +4,14 @@ Report suspected vulnerabilities privately to `security@sandwichhime.com`.
 Please include the affected Tend version, configuration shape, reproduction,
 and expected impact. Do not include production credentials or private logs.
 
-Tend treats source repositories, release artifacts, configuration, handwritten
-Caddy templates, and operators as trusted. It treats artifact paths, archives,
+Tend treats reviewed source, pinned toolchains, root-owned server policy and
+configuration, handwritten Caddy templates, and operators as trusted. It treats
+requested service names, protocol frames, artifact paths and bytes, archives,
 filesystem state, process output, HTTP responses, and deployment targets as
 adversarial inputs. It never evaluates configuration as shell code.
 
 The preview is not a sandbox and does not make an untrusted repository safe to
-build. Run `tend package` only for reviewed source. Production configuration
-must be root-owned and kept outside repositories.
+build. Run `tend package` only for reviewed source. Production configuration,
+receive policy, host keys, identities, and `0600` environment files stay outside
+repositories. A secret value appearing in a Tend report, artifact, state file,
+or process argument is a security defect and should be reported.

cmd/tend/main.go

@@ -19,6 +19,8 @@ import (
 	"gamertan.com/tend/internal/deploy"
 	"gamertan.com/tend/internal/packager"
 	"gamertan.com/tend/internal/process"
+	"gamertan.com/tend/internal/serverpolicy"
+	"gamertan.com/tend/internal/transport"
 	"gamertan.com/tend/internal/version"
 )
 
@@ -41,6 +43,12 @@ func run() error {
 		return packageCommand(ctx, os.Args[2:])
 	case "deploy":
 		return deployCommand(ctx, os.Args[2:])
+	case "push":
+		return pushCommand(ctx, os.Args[2:])
+	case "receive":
+		return receiveCommand(ctx, os.Args[2:])
+	case "check-server":
+		return checkServerCommand(os.Args[2:])
 	case "status":
 		return statusCommand(ctx, os.Args[2:])
 	case "rollback":
@@ -54,7 +62,7 @@ func run() error {
 	}
 }
 func usage() error {
-	return errors.New("usage: tend <check|package|deploy|status|rollback|prune|version> [options]")
+	return errors.New("usage: tend <check|package|push|receive|check-server|deploy|status|rollback|prune|version> [options]")
 }
 
 func checkCommand(args []string) error {
@@ -123,7 +131,7 @@ func deployCommand(ctx context.Context, args []string) error {
 		return err
 	}
 	if *activate {
-		if err := requireMutationAuthority(absolute); err != nil {
+		if err := requireMutationAuthority(absolute, cfg); err != nil {
 			return err
 		}
 	}
@@ -137,6 +145,90 @@ func deployCommand(ctx context.Context, args []string) error {
 	}
 	return writeJSON(report)
 }
+
+func pushCommand(ctx context.Context, args []string) error {
+	set := flag.NewFlagSet("push", flag.ContinueOnError)
+	set.SetOutput(os.Stderr)
+	target := set.String("target", "", "dedicated tend-deploy user and host")
+	port := set.Int("port", 22, "pinned SSH port")
+	knownHosts := set.String("known-hosts", "", "absolute pinned known-hosts file")
+	identity := set.String("identity", "", "optional absolute private key")
+	service := set.String("service", "", "allowed service name")
+	artifact := set.String("artifact", "", "immutable release archive")
+	sha := set.String("sha256", "", "expected artifact SHA-256")
+	approved := set.String("approve-sha256", "", "separately reviewed artifact SHA-256")
+	activate := set.Bool("activate", false, "activate after server validation")
+	if err := set.Parse(args); err != nil {
+		return err
+	}
+	if set.NArg() != 0 {
+		return errors.New("push accepts no positional arguments")
+	}
+	artifactAbs, err := filepath.Abs(*artifact)
+	if err != nil {
+		return err
+	}
+	result, err := transport.Push(ctx, transport.ExecSSHRunner{}, transport.PushOptions{Target: *target, Port: *port, KnownHosts: *knownHosts, Identity: *identity, Service: *service, Artifact: artifactAbs, SHA256: *sha, ApprovedSHA256: *approved, Activate: *activate})
+	if err != nil {
+		return err
+	}
+	return writeJSON(result)
+}
+
+func receiveCommand(ctx context.Context, args []string) error {
+	set := flag.NewFlagSet("receive", flag.ContinueOnError)
+	set.SetOutput(os.Stderr)
+	policyPath := set.String("policy", "/etc/tend/receive-policy.json", "root-owned receive policy")
+	if err := set.Parse(args); err != nil {
+		return err
+	}
+	if set.NArg() != 0 {
+		return errors.New("receive accepts no positional arguments")
+	}
+	if runtime.GOOS != "linux" || os.Geteuid() != 0 {
+		return errors.New("receive requires Linux root execution")
+	}
+	if os.Getenv("SSH_ORIGINAL_COMMAND") != transport.Protocol {
+		return errors.New("receive refused unexpected SSH command")
+	}
+	policy, err := serverpolicy.Load(*policyPath)
+	if err != nil {
+		return err
+	}
+	report, err := transport.Receive(ctx, os.Stdin, policy, newManager())
+	if err != nil {
+		return err
+	}
+	return writeJSON(report)
+}
+
+func checkServerCommand(args []string) error {
+	set := flag.NewFlagSet("check-server", flag.ContinueOnError)
+	set.SetOutput(os.Stderr)
+	policyPath := set.String("policy", "/etc/tend/receive-policy.json", "root-owned receive policy")
+	if err := set.Parse(args); err != nil {
+		return err
+	}
+	if set.NArg() != 0 {
+		return errors.New("check-server accepts no positional arguments")
+	}
+	if runtime.GOOS != "linux" || os.Geteuid() != 0 {
+		return errors.New("check-server requires Linux root execution")
+	}
+	policy, err := serverpolicy.Load(*policyPath)
+	if err != nil {
+		return err
+	}
+	services, err := policy.CheckFiles()
+	if err != nil {
+		return err
+	}
+	names := make([]string, 0, len(services))
+	for _, service := range services {
+		names = append(names, service.Name)
+	}
+	return writeJSON(map[string]any{"valid": true, "schema_version": policy.SchemaVersion, "services": names})
+}
 func statusCommand(ctx context.Context, args []string) error {
 	set := flag.NewFlagSet("status", flag.ContinueOnError)
 	set.SetOutput(os.Stderr)
@@ -175,7 +267,7 @@ func rollbackCommand(ctx context.Context, args []string) error {
 	if !*activate {
 		return writeJSON(map[string]any{"validated": true, "mutation": "none", "message": "repeat with --activate to switch to the recorded previous release"})
 	}
-	if err := requireMutationAuthority(absolute); err != nil {
+	if err := requireMutationAuthority(absolute, cfg); err != nil {
 		return err
 	}
 	record, err := newManager().Rollback(ctx, cfg)
@@ -201,7 +293,7 @@ func pruneCommand(args []string) error {
 		return err
 	}
 	if *apply {
-		if err := requireMutationAuthority(absolute); err != nil {
+		if err := requireMutationAuthority(absolute, cfg); err != nil {
 			return err
 		}
 	}
@@ -225,21 +317,14 @@ func loadConfig(path string) (config.Config, string, error) {
 func newManager() deploy.Manager {
 	return deploy.NewManager(deploy.SystemOperator{Runner: process.ExecRunner{}, Timeout: 5 * time.Second})
 }
-func requireMutationAuthority(configPath string) error {
+func requireMutationAuthority(configPath string, cfg config.Config) error {
 	if runtime.GOOS != "linux" {
 		return errors.New("deployment mutations require Linux")
 	}
 	if os.Geteuid() != 0 {
 		return errors.New("deployment mutations require root")
 	}
-	info, err := os.Stat(configPath)
-	if err != nil {
-		return err
-	}
-	if info.Mode().Perm()&0o022 != 0 {
-		return errors.New("production configuration must not be group- or world-writable")
-	}
-	return nil
+	return serverpolicy.CheckConfig(configPath, cfg)
 }
 func writeJSON(value any) error {
 	encoder := json.NewEncoder(os.Stdout)

docs/ARCHITECTURE.md

@@ -17,12 +17,26 @@ requires byte-identical output. The resulting archive contains only:
 
 The external archive digest is the release identity used by deployment.
 
+## Transport boundary
+
+`tend push` sends one bounded protocol frame to a dedicated account through a
+pinned OpenSSH host key. It uses an argument vector, disables config files,
+forwarding, PTYs, local commands, and proxy commands, and requests exactly
+`tend-receive-v1`. The account's forced command invokes only the root-owned
+receiver. The receiver's root-owned policy maps an allowlisted service name to
+one exact configuration path and size ceiling.
+
+The target receives no source, repository credential, Go cache, dependency, or
+arbitrary command. The artifact digest must equal both the produced digest and
+the separately supplied approved digest before it is staged.
+
 ## Target-host boundary
 
-`tend deploy` runs on the Linux target. Transfer and SSH authentication stay
-outside Tend v0.1; application-local transfer commands move the artifact and
-the identical Tend binary to a root-controlled staging directory. Tend then
-requires the expected digest to be repeated as a separately approved digest.
+Schema-2 configurations live below `/etc/tend/services/`. Secrets live only in
+separate `/etc/tend/environment/*.env` files that are root-owned, non-symlink,
+and mode `0600`. Configurations contain the path, never the values. Candidate
+and installed units read the same file; Tend overrides only the candidate's
+loopback listen address.
 
 Dry-run validation extracts into a temporary directory and does not touch the
 release tree. Activation acquires the shared lock, installs a content-addressed
@@ -36,11 +50,31 @@ probes it, atomically replaces one imported Caddy handler, validates the full
 Caddy configuration, reloads Caddy, and records the prior active slot.
 
 Singleton mode starts the new release in a hardened transient systemd unit on a
-separate loopback address, probes it, stops the candidate, changes the current
-release pointer, and restarts the installed singleton unit.
+separate loopback address and probes it. Tend then validates and atomically
+routes the imported Caddy handler to that candidate. While the candidate serves
+the canonical origin, Tend changes the current release pointer, restarts and
+probes the installed fixed-address unit, validates Caddy again, and routes back
+to it. The candidate remains healthy through the activation window and stops
+only after the handoff succeeds.
 
-Any failure before state persistence restores the previously observed Caddy
-bytes and/or release pointers. Rollback is a separate explicit command over the
-recorded state. It rechecks health and readiness, but deliberately does not
-apply the current release's content markers to an older release whose routes
-may differ. Pruning preserves both active and previous releases.
+After the local post-activation probes, Tend also checks configured HTTPS public
+origins throughout a bounded activation window. Blue/green mode also probes the
+previous slot, and singleton mode probes the handoff candidate, for health and
+readiness throughout that window. Any failure before success is recorded
+restores the previously observed Caddy bytes and/or release pointers. State
+records desired, candidate, active, previous, and last-attempt
+release identities, including failed attempts without claiming they became
+active. Rollback is a separate explicit command
+over the recorded state. It rechecks local health/readiness and public reachability,
+but deliberately does not apply a future release's content marker to an older
+release whose routes may differ. Pruning preserves both active and previous releases.
+
+## Evidence boundary
+
+Every attempted activation and explicit rollback emits bounded, versioned JSONL
+events with an operation ID, service, approved artifact digest, source commit,
+release version, phase, slot, elapsed duration, and outcome. Values are
+validated rather than copied from command output. The log contains no
+environment values, arbitrary process output, HTTP bodies, or secret paths.
+Identity, entropy, file, and downstream observability failures are deliberately
+best effort and cannot control Tend's deployment or rollback result.

docs/DOGFOOD_EVIDENCE.md

@@ -1,8 +1,164 @@
 # Preview dogfood evidence
 
 This is maintainer-run operational evidence, not an independent audit or a
-general reliability claim. It records the acceptance campaign completed on
-August 14, 2026 before Tend's first public preview.
+general reliability claim. It preserves each dated campaign and its limitations
+instead of rewriting earlier observations as though later fixes had already
+existed.
+
+## Final Preview 2 code-candidate campaign — August 18, 2026
+
+The final v0.2 Preview 2 implementation candidate completed two explicit
+rollback-and-reactivation cycles for Gamertan, the Sandwich Hime website, and
+Gamertan Observatory on the production Linux/systemd/Caddy host. The candidate
+routed singleton traffic to the already-proven transient process while the
+fixed-address installed unit restarted, then restored the canonical upstream
+only after loopback and public-origin validation.
+
+### Assessed Tend candidate
+
+- Private implementation source commit:
+  `1fd3b9904c46e817c244196dd5d5a90921ca81a2`.
+- Version: `v0.2.0-preview.2`.
+- Linux/amd64 binary SHA-256:
+  `adb4753d4e865775d50d618c999f10dfac9a0de945ccfd9d0b8f2e80d65f4597`.
+- Gitea release-candidate archive SHA-256:
+  `2bdfee2168cb16883d524cf9703adfa6ed5bc2bf44fbbb896993acc5fe6969ec`.
+- Toolchain: Go 1.26.6, `CGO_ENABLED=0`, `-trimpath`.
+- Trusted verification run 286 and release-candidate run 287 passed. The
+  archive's checksums, SPDX SBOM, embedded version, commit, clean VCS state,
+  target, and Go build information were independently rechecked before host
+  installation.
+
+### Application maintenance artifacts
+
+- Gamertan archive SHA-256:
+  `4700b075640b8b2fb5c17e0e02cf8d96ee67ceee10fe76d108c8b411983a88aa`.
+- Sandwich Hime website archive SHA-256:
+  `46b4da41cf6703fb8818e7d25e3a9c13e57cf700f5608b1888c4adb3352e4d38`.
+- Observatory preview 12 archive SHA-256:
+  `9ef0ddd8ec25d8fb75d6a6887e3ba874df7ebba16d3254f6250fcc646f4fd7f4`.
+
+Every service ended with the intended current release active and the older
+release retained as the explicit rollback target. Gamertan returned to its
+green slot; both singleton services returned to their fixed addresses.
+Candidate ports and the shared lock were free afterward. Caddy and all five
+installed application units were active with zero restarts and no failed
+units.
+
+### Continuity and deployment evidence
+
+A seven-minute workstation probe sampled the Gamertan origin, both Sandwich
+Hime origins, Observatory, and EQL health 1,606 times each throughout the
+campaign. It observed no HTTP failure status. One simultaneous client-side
+disconnect affected all five destinations during a reload. A controlled
+90-second replay therefore observed the same validated no-content-change Caddy
+reload from both the workstation and an independent Linux host. The Linux host
+recorded 450 successful responses and zero failures for every origin; the
+workstation alone repeated one common-mode URL transport error across every
+destination. Caddy retained the same PID with zero restarts and continued
+serving unrelated requests. The common-mode workstation event is recorded as
+an observer-path limitation, not server downtime.
+
+The authoritative deployment-event files finished at 18 Gamertan events, 14
+Sandwich Hime events, and 16 Observatory events. Observatory's agent cursor for
+each stream exactly equalled the corresponding file size, proving complete
+consumption. The agent and applications reported no warning-or-higher journal
+entries during the campaign. Representative public routes returned HTTP 200,
+and the EQL origin remained healthy.
+
+### Findings closed before this campaign
+
+Two earlier pre-activation artifacts exposed a mode-restoration defect under a
+hardened root umask. They failed before route or pointer mutation. Tend now
+reapplies validated archive modes explicitly and tests extraction under umask
+`0077`.
+
+The older singleton strategy briefly exposed an unavailable fixed upstream and
+produced transient Observatory-agent `502`s. The final candidate's routed
+handoff removed that failure in repeated production activation and rollback.
+
+This evidence update changes VCS build metadata but not deployment logic. The
+release policy therefore still requires one last maintenance pass with the
+exact evidence-bearing candidate before the signed public tag is created.
+
+## Restricted multi-service campaign — August 16, 2026
+
+Tend's v0.2 implementation candidate completed the same maintenance contract
+through the restricted transport for two independently configured services on
+one Linux/systemd/Caddy host.
+
+### Assessed Tend implementation
+
+- Implementation source commit:
+  `840b77da708bbcd87a3203fb6a1f99b2984b8667`.
+- Linux/amd64 candidate binary SHA-256:
+  `b3961315288871fa6085bf3b75c784a825a88f2bc3dd0694ad5d6c590eddf895`.
+- Candidate archive SHA-256:
+  `948bad5271dca08b9445c387c5aea7f58f22add6b47b9071e1801a756aa71259`.
+- Toolchain: Go 1.26.6, `CGO_ENABLED=0`, `-trimpath`.
+- Trusted Gitea verification run 119 and release-candidate run 120 passed for
+  the exact implementation commit. CI and an independent, network-disabled
+  build each produced the same archive digest twice.
+- The installed receiver accepted only a pinned Ed25519 host key, a dedicated
+  forced-command deployment key, the exact `tend-receive-v1` protocol, two
+  allowlisted service names, and separately repeated artifact digests. An
+  attempted arbitrary SSH command was refused.
+- Production source, Go caches, repository credentials, secret values, remote
+  paths, and shell commands did not cross the transport boundary.
+
+Adding this evidence changes VCS build metadata but not executable logic. The
+signed preview tag and attached release evidence therefore identify the final
+evidence-bearing candidate and its required last maintenance pass.
+
+### Gamertan blue-green campaign
+
+- Application source commit:
+  `a7e54047d3dc11671824b6ecc8ed698a9dd04421`.
+- Preview 27 artifact SHA-256:
+  `edadef3a97c089771e2b6bb7dadd58928762284878f76f23b112c61ae282f17f`.
+- The artifact was built twice, byte-identically, in the pinned Go 1.26.6
+  image with networking disabled and the audited cached module graph.
+- The inactive slot passed health, readiness, page-marker, Caddy validation,
+  public-origin, Sandwich Hime mount, and EQL continuity checks before traffic
+  moved.
+- Explicit rollback restored preview 26; its readiness and public boundary
+  passed; preview 27 was then reactivated through the recorded state.
+- Sandwich Hime's release pointer and service remained unchanged throughout.
+
+### Sandwich Hime singleton campaign
+
+- Application source commit:
+  `435880c6751b773b6c5ee3ae6833d26e8eb7c0df`.
+- Preview 30 artifact SHA-256:
+  `bee8d5bcde2c3c2e8bb96d5909a19889fc7f0be9390046c243fe20c9ff2ca44b`.
+- The artifact was built twice, byte-identically, in the same pinned,
+  network-disabled Go 1.26.6 environment.
+- A transient DynamicUser candidate passed health, readiness, tutorial marker,
+  canonical-origin, and Gamertan-mounted checks before the singleton pointer
+  and installed service changed. The candidate port was released afterward.
+- Explicit rollback restored preview 28; its readiness and public boundary
+  passed; preview 30 was then reactivated through the recorded state.
+- Both Gamertan slots, its selected Caddy upstream, and EQL remained healthy.
+
+### Findings resolved by dogfood
+
+The first restricted transfer stopped before artifact validation because
+`sudo` removed `SSH_ORIGINAL_COMMAND`. The forced account still refused the
+request; no service state changed. The 0BSD sudoers template now preserves only
+that one server-supplied variable, while the receiver requires its exact
+protocol value and rejects every other command.
+
+The first singleton candidate stopped before pointer mutation because the
+shared environment file's live listen value overrode the candidate address.
+The site remained on its former release and retained the same process. Tend now
+rejects singleton shared environment files containing the configured listen
+key; installed units own the non-secret live address and Tend supplies only the
+transient candidate address.
+
+Final verification found both service states valid, every installed unit and
+Caddy active with zero restart failures, the candidate port closed, no warning
+or error entries after the successful campaign, and representative Gamertan,
+Sandwich Hime, mounted, and EQL routes returning HTTP 200.
 
 ## Assessed candidate
 
@@ -22,6 +178,13 @@ The release tag and attached assets must still identify their own exact source
 commit and digests. Any code change after this campaign requires the dogfood
 sequence to be repeated.
 
+A fresh-install check after the first immutable source tag found that the CLI
+reported its development identity instead of the tagged module version. No
+deployment logic or artifact content was ambiguous, but the distribution
+identity was not acceptable. Preview 1 remains immutable and withdrawn;
+Preview 2 adds Go build-information version selection and repeats the release
+gates rather than retagging old content.
+
 ## Sandwich Hime website
 
 The singleton-candidate strategy packaged and activated website preview 25:

docs/DOGFOOD_FRICTION.md

@@ -0,0 +1,328 @@
+# Dogfood friction ledger
+
+This document records friction observed through August 18, 2026 while using
+Tend for real maintenance releases. Friction is evidence about the product: it
+should become either a clearer contract, safer automation, or an explicit
+non-goal. It must not become application-specific shell lore.
+
+The findings below are maintainer observations, not implemented promises. Tend
+continues to fail closed while an option is being designed. In particular,
+there is no `--skip-remote` packaging escape hatch, no arbitrary deployment
+hook, and no relaxation of the host-wide activation lock.
+
+## Design standard
+
+A Tend workflow should make the secure path the short, documented path:
+
+- source, artifact, approval, configuration, and active-release identities are
+  explicit and inspectable;
+- credentials are narrowly scoped, briefly available, and absent from
+  artifacts and logs;
+- application validation is declarative, bounded, and cannot become a shell;
+- first installation, maintenance, activation, rollback, and pruning are
+  distinct operations;
+- every mutation has a recorded prior state and a tested restoration path;
+- unrelated services may build and prepare candidates concurrently, while the
+  shared Caddy activation boundary remains serialized.
+
+## Observed findings
+
+| ID | Status | Finding | Current safe behavior | Candidate direction |
+| --- | --- | --- | --- | --- |
+| F-01 | Workflow mitigation | CI packaging needs proof that the exact commit was pushed. | Packaging verifies the configured remote and fails if Git cannot authenticate. The trusted workflow retains only its job-scoped read-only checkout credential. | Make the proof credential or an authenticated source attestation an explicit Tend input and evidence boundary. |
+| F-02 | Open | Application-owned unit and configuration changes are outside the binary activation transaction. | Operators stage, validate, back up, and restore those files separately. | Add an allowlisted configuration transaction or record and validate exact configuration digests. |
+| F-03 | Open | A singleton candidate may not reproduce the installed unit's arguments and application configuration. | It receives the production environment file and an isolated listen override; activation still fails closed. | Add a bounded application preflight and explicit, validated candidate invocation. |
+| F-04 | Partially resolved | Artifact production, review, approval, transfer, and activation require several identity checks. | v0.2 standardizes the evidence bundle and restricted transfer; the operator still repeats the approved digest intentionally. | Add offline inspection and approval ergonomics without combining build authority and production authority. |
+| F-05 | Partially resolved | Tend maintenance assumes an existing adopted service and current release. | `check-server` validates a prepared host, while first installation remains a separately reviewed operator procedure. | Define an explicit `install` or `adopt` transaction rather than silently treating bootstrap as maintenance. |
+| F-06 | Partially resolved | Binary rollback can be unsafe when service configuration has changed incompatibly. | v0.2 records desired, candidate, active, previous, and last-attempt releases, but external configuration compatibility is operator-owned. | Bind non-secret configuration identities and preflight results to release state. |
+| F-07 | Open | `GOPROXY=off` does not prove that every module metadata lookup is available locally. | Packaging stops before artifact creation when Go cannot resolve the complete pinned module graph. | Separate checksum-verified dependency resolution from a network-disabled, cache-completeness-checked build stage. |
+| F-08 | Open | Packaging an otherwise clean pushed commit from a linked Git worktree fails Go's required VCS-status stamp. | Tend stops before artifact creation; package the same exact commit from a clean standalone clone. | Detect linked worktrees during `check`/`package`, explain the supported source shape, and assess a provenance-preserving worktree build that does not weaken `-buildvcs=true`. |
+| F-09 | Resolved in Preview 2 | Restarting a fixed-address singleton briefly exposed Caddy to an unavailable upstream. | Tend now routes the imported handler to the candidate, restarts and proves the installed unit behind that handoff, then routes back while the candidate remains healthy through the activation window. | Preserve the production regression campaign and failure-injection matrix. |
+| F-10 | Resolved in Preview 2 | A hardened root umask could make an extracted application binary executable only by root. | Tend reapplies every validated archive mode explicitly; extraction is tested under umask `0077`. | Preserve the mode and non-root candidate tests. |
+| F-11 | Evidence practice | A single external observer can report common-mode client or network errors as apparent multi-service downtime. | Production campaigns retain server state and use an independent observer before classifying a continuity failure. | Standardize multi-vantage continuity evidence without making an observability dependency part of deployment authority. |
+
+## F-01: pushed-commit proof in CI
+
+### Observation
+
+During an Observatory release-candidate run, verification intentionally checked
+out source without persisted credentials. Tend later attempted to prove that
+`HEAD` existed on the configured private Gitea branch and Git could not
+authenticate. Packaging stopped before producing an artifact. This was the
+correct fail-closed outcome, but the credential lifecycle was not obvious from
+the workflow contract.
+
+The trusted workflow uses a job-scoped read-only checkout credential so Tend
+can perform the independent remote proof. It is not a long-lived repository or
+deployment credential, and it is removed by checkout cleanup at the end of the
+job. Production credentials remain unavailable to the build job.
+
+### Options to assess
+
+1. Support an explicit read-only Git credential file or credential helper for
+   package-time proof. Never accept a token in arguments, configuration,
+   manifests, artifacts, or logs.
+2. Accept an authenticated CI source-attestation document binding repository,
+   branch, commit, tree, workflow identity, and event identity. Define which
+   CI issuers are trusted and preserve the attestation with release evidence.
+3. Accept a signed, pre-verified source bundle whose identity and policy can be
+   checked without network access.
+
+Do not add a generic skip flag. An unavailable proof must remain a packaging
+failure unless an equally strong proof mode was selected explicitly.
+
+## F-02: application configuration is not binary activation
+
+### Observation
+
+Tend can transact an immutable binary, release pointers, a systemd restart, a
+validated Caddy handler, health checks, and rollback state. It does not
+currently transact application configuration, systemd unit changes, credential
+bindings, or server-local secret files. A first deployment that changes these
+files therefore needs a separate backup, validation, installation, and
+restoration procedure.
+
+This boundary is safe but easy to overlook: restoring the previous binary does
+not restore an incompatible unit or application configuration.
+
+### Options to assess
+
+1. Add strict managed-file entries with exact source and destination paths,
+   content digest, owner, group, mode, and validation type. Permit only regular
+   files beneath configured roots; reject symlinks and unknown destinations.
+2. Add a separate `tend configure` transaction that backs up, atomically
+   replaces, validates, and restores supported systemd/Caddy/application files.
+3. Keep configuration externally managed, but require Tend to record desired
+   and active configuration digests and prove candidate/rollback compatibility.
+
+None of these options should permit arbitrary shell commands. Secret values
+remain referenced server-side and must never enter release artifacts or state.
+
+## F-03: candidate fidelity
+
+### Observation
+
+A hardened singleton candidate receives the configured production environment
+file and Tend's isolated listen-address override. It does not currently model
+the installed systemd unit's complete argument vector. An application whose
+configuration path is supplied by unit arguments may therefore start a
+candidate with defaults instead of the intended production configuration.
+That preserves live-state isolation, but it may prove only executable startup.
+A missing credential, incompatible configuration field, filesystem permission,
+or data migration requirement can then surface at activation time.
+
+### Options to assess
+
+- Define a fixed application preflight command or protocol that validates the
+  production configuration, credentials, permissions, and data compatibility
+  without binding the live port or mutating live state.
+- Add a strict candidate argument vector to schema 2. Validate each argument,
+  reject secret values and paths outside the application contract, and pass it
+  directly to systemd without a shell.
+- Permit an allowlisted `check` argument vector, never a shell string, with
+  bounded time/output and an explicitly non-mutating application contract.
+- Record which checks ran against the binary alone and which ran against the
+  actual production configuration so the evidence cannot overstate coverage.
+
+## F-04: artifact review and approval ergonomics
+
+### Observation
+
+The secure flow deliberately separates build, review, digest approval,
+transfer, candidate validation, and activation. v0.2 now produces a consistent
+archive, manifest, SBOM, and checksum set, then transfers one exact artifact
+through its restricted receiver. In practice, operators still need a
+predictable way to discover that CI artifact, inspect it, approve exactly one
+digest, and retain the review evidence. Without a first-class review path,
+correct manual steps are easy to reconstruct differently for each application.
+
+### Options to assess
+
+- Add `tend inspect` for offline, non-mutating verification and a concise human
+  and JSON summary of source, build, dependency, and archive identities.
+- Add an approval record that binds the artifact digest, service, target,
+  approver, and expiry without containing a credential.
+- Standardize one Gitea artifact layout and documented download-to-activation
+  workflow. Keep production credentials unavailable to verification jobs.
+
+Approval must remain explicit; better ergonomics must not turn a successful
+build into an automatic production mutation.
+
+## F-05: first installation and adoption
+
+### Observation
+
+The maintenance workflow expects an installed service, valid configuration,
+and a current release pointer. `check-server` validates the restricted receiver
+policy and prepared service boundary, but it does not create them. Observatory
+bootstrap therefore required operator-managed service account, directories,
+credentials, unit, configuration, and an initial current release before Tend
+could own later maintenance safely.
+
+### Options to assess
+
+- `tend install`: a deliberately broader, separately approved transaction with
+  a strict schema and complete rollback of every supported created object.
+- `tend adopt`: validate an existing service and release, copy or identify its
+  immutable artifact, establish state, and refuse ambiguous ownership.
+- Keep bootstrap out of Tend, but ship a versioned acceptance checklist and a
+  machine-readable `check-server` result that maintenance can require.
+
+Installation and adoption must not be inferred from a missing state file.
+
+## F-06: release and configuration identity
+
+### Observation
+
+Content-addressed releases and v0.2 state make desired, candidate, active,
+previous, and last-attempt binary identities clear. A live service is still a
+combination of its binary, application configuration, credential bindings,
+unit, routing fragment, and sometimes data schema. Tend cannot yet fully
+explain that combined identity or determine whether a retained binary is
+compatible with the current external configuration.
+
+### Options to assess
+
+- Extend the existing desired, candidate, active, previous, and last-attempt
+  release state with non-secret configuration and unit digests.
+- Require rollback compatibility declarations or read-only application
+  preflight before changing traffic.
+- Expose the identities and last validation results through
+  `tend status --json` for deployment evidence and future Observatory
+  ingestion.
+
+Configuration records contain digests and approved metadata only—not secret
+contents.
+
+## F-07: offline module-cache completeness
+
+### Observation
+
+An exact Observatory package attempt used `GOPROXY=off` and a previously used
+module cache. Source archives for the application dependencies were present,
+but Go still needed several module metadata records while Tend enumerated the
+complete build graph. Go refused the lookup and Tend stopped before building
+or writing an artifact. Re-enabling the checksum-verified public proxy supplied
+the missing metadata; the resulting package was byte-identical to the trusted
+CI candidate.
+
+This is safe failure, but `GOPROXY=off` alone is not evidence of a hermetic
+build. A cache can be partially populated even when ordinary builds happen to
+succeed.
+
+### Options to assess
+
+- Add a resolver stage that runs with the pinned toolchain, proxy, and checksum
+  database, emits the complete module inventory, and materializes a bounded,
+  read-only cache for the builder.
+- Run Tend's package stage with networking disabled and require every module,
+  checksum, source archive, and metadata record to come from that reviewed
+  cache.
+- Add a non-mutating cache-completeness check that reports missing module
+  identities before the expensive double build.
+- Consider a strictly verified vendored-source mode where repository size and
+  update review are acceptable; do not silently change dependency modes.
+
+Do not treat `GONOSUMDB`, `GOPRIVATE`, or a proxy bypass as an offline-build
+solution. They alter verification or routing policy rather than proving cache
+completeness.
+
+## F-08: linked-worktree VCS stamping
+
+### Observation
+
+An exact clean, pushed Observatory main commit passed verification and public
+snapshot isolation from a detached linked Git worktree. Tend accepted its
+source and remote provenance, then Go 1.26.6 stopped both `tend package` and an
+equivalent direct build at the required `-buildvcs=true` step with `error
+obtaining VCS status: exit status 128`. Ordinary Git status and commit queries
+from the same worktree succeeded.
+
+A fresh standalone SSH clone of the identical commit packaged successfully
+twice. Both archives were byte-identical and carried the expected commit, Go
+version, VCS settings, checksums, manifest, and SBOM. This isolates the failure
+to the linked-worktree build shape rather than the application source or module
+graph.
+
+The failure is safe: Tend did not create a partial artifact and must not switch
+to `-buildvcs=false`, because the package gate independently verifies the
+embedded VCS revision and clean state. Until the interaction is resolved, use
+a clean standalone clone for release packaging.
+
+### Options to assess
+
+- Detect a `.git` indirection file during `tend check` and fail before the
+  expensive double build with a precise standalone-clone instruction.
+- Reproduce the interaction in a package integration test against the minimum
+  supported Go release and determine whether it is a Go toolchain limitation
+  or an invocation/environment defect.
+- If linked worktrees can be supported, require the resulting build record to
+  carry the exact expected `vcs.revision` and `vcs.modified=false`; do not
+  synthesize those settings or disable VCS stamping.
+- Consider an explicit, signed source-bundle input as part of the broader
+  source-attestation design. It must remain at least as strong as current
+  pushed-commit proof.
+
+## F-09: singleton traffic continuity
+
+### Observation
+
+During the August 18 Observatory maintenance exercise, the transient candidate
+passed health, readiness, and content checks. Tend then stopped that candidate,
+changed the singleton pointer, and restarted the installed fixed-address unit.
+Caddy still targeted the fixed address during that restart, so the Observatory
+agent observed a small number of transient HTTP `502` responses. Its durable
+spool retried successfully and no accepted telemetry was lost, but the routed
+origin was not continuously available.
+
+The corrected activation contract treats the candidate as a traffic handoff,
+not merely a preflight process. Tend validates and routes the imported Caddy
+handler to the candidate before changing the release pointer. It restarts and
+probes the fixed-address unit without public traffic, routes back only after
+that unit passes, and keeps the candidate healthy throughout the bounded
+activation window. Any failure restores the former pointer and exact handler
+bytes. If restoration itself cannot be completed, Tend leaves the proven
+candidate routed and running for explicit operator recovery instead of causing
+a known outage.
+
+Regression tests cover successful handoff, restart failure, public-origin
+failure during the activation window, pointer and handler restoration, Caddy
+validation/reload boundaries, and candidate cleanup. Final production evidence
+must still repeat deploy, rollback, and reactivation with the exact release
+binary before this finding is treated as released.
+
+## F-10: archive modes under a hardened umask
+
+### Observation
+
+The first two August 18 maintenance candidates stopped before activation. The
+release archives correctly recorded executable mode `0755`, but extraction by
+root under umask `0077` left the installed application binary mode `0700`.
+The unprivileged transient candidate could not execute it. Tend emitted failed
+candidate evidence, retained the prior release and route, and did not expose
+the failed binary to traffic.
+
+Extraction now reapplies the already validated archive mode after file content
+is closed. A Linux regression test sets umask `0077`, extracts the release, and
+requires the installed binary to remain executable by the service identity.
+The successful maintenance campaign used that corrected Tend binary.
+
+## Prioritization
+
+The recommended implementation order is:
+
+1. final production proof of the singleton traffic handoff;
+2. a checksum-verified resolver and network-disabled package contract;
+3. an early linked-worktree diagnostic and a provenance-preserving support
+   decision;
+4. `tend inspect` and a standardized CI artifact/approval contract;
+5. exact release plus configuration identity in status and state;
+6. a bounded application preflight contract;
+7. restricted transfer and receive with host policy;
+8. explicit adoption for existing services;
+9. managed configuration only after its restoration and failure-injection
+   model is as strong as binary activation.
+
+Friction entries should be updated with the implementing version, tests, and
+dogfood evidence when resolved. Resolved entries remain in this ledger so the
+reason for the security boundary is not lost.

docs/PUBLIC_SNAPSHOT.md

@@ -12,3 +12,8 @@ material markers. The resulting directory receives a new public root commit.
 Public Gitea is canonical for issues, contributions, and releases. GitHub is a
 read-only discovery copy of the same public tree. Tags belong only to canonical
 Gitea.
+
+The snapshot includes the program, security and architecture documentation,
+copyable examples, release configuration, and local verification scripts.
+Private workflows, runner configuration, repository credentials, and raw
+operational evidence remain outside the public root.

docs/SCHEMA_V2_MIGRATION.md

@@ -0,0 +1,35 @@
+# Schema 1 to schema 2
+
+Schema 2 is intentionally not loaded as schema 1. Keep the installed v0.1 Tend
+binary available until the first schema-2 activation and rollback have both
+been exercised.
+
+1. Move each configuration to `/etc/tend/services/<service>.json`.
+2. Set `schema_version` to `2`.
+3. Add `service.environment_file` below `/etc/tend/environment/`.
+4. Create that file as a regular root-owned file with mode `0600`. Move secret
+   values out of JSON. Do not put the environment file in Git. For a singleton,
+   keep its `listen_env` key out of this shared file: set the live address in
+   the installed unit and let Tend supply only the candidate address.
+5. Set every service's `deployment.lock_file` to
+   `/run/lock/tend-deploy.lock`.
+6. Add one or more query-free HTTPS `deployment.public_smoke` checks.
+7. Add a per-service `deployment.event_log` below its release root and a
+   bounded `deployment.activation_window_seconds` value. Keep the log
+   root-owned and grant collectors read access explicitly.
+8. For singleton services, add the full Caddy configuration, imported handler,
+   and one-upstream handler-template paths. The template must be reviewed and
+   contain exactly one `{{UPSTREAM}}` marker so Tend can keep traffic on the
+   candidate while the fixed-address unit restarts.
+9. Update installed systemd units to read the same environment file as the
+   transient candidate.
+10. Install a root-owned `0600` receive policy mapping each service name to its
+   exact configuration and artifact-size ceiling.
+11. Run `tend check-server` as root before accepting a transfer.
+12. Validate, activate, rollback, and reactivate one service at a time. Confirm
+    unrelated services never restart.
+
+Tend does not discover `.env`, infer old values, rewrite a production file, or
+silently migrate state. For local development, copy a committed `.env.example`
+to an ignored `.env.local`, restrict its mode, and load it with the application's
+own tooling. Tend never loads local dotenv files implicitly.

docs/THREAT_MODEL.md

@@ -7,33 +7,49 @@
 - Release roots, state, pointers, and Caddy files reject symlink substitution
   at their checked boundaries.
 - Configuration is strict JSON and is never interpolated into a shell command.
-- Candidate health is established before traffic or the singleton current
+- Candidate health is established before traffic or any current release
   pointer changes. New deployments also satisfy configured content smoke
   checks; rollback uses health and readiness because future-release content
   markers are not valid requirements for an older retained release.
 - Caddy configuration validates before reload.
+- Canonical routed origins and the previous blue/green slot or singleton
+  handoff candidate remain under probe for the configured activation window; a
+  failure restores the old handler and release pointer.
+- Desired, candidate, active, previous, and failed-attempt identities remain
+  distinct in state. Bounded deployment events contain no arbitrary command
+  output or environment values and cannot block deployment.
 - An activation failure restores the previously observed state.
 - Active and previous releases survive pruning.
+- The restricted receiver accepts one versioned bounded stream, one allowlisted
+  service name, and one explicitly approved digest. It accepts no remote path,
+  URL, environment value, or shell expression.
+- OpenSSH host keys are pinned; forwarding, PTYs, proxy commands, local commands,
+  and user SSH configuration are disabled by the client invocation.
+- Production secret values are absent from configuration, process arguments,
+  artifacts, manifests, reports, deployment state, and Tend logs.
+- One host-wide lock serializes shared Caddy activation without stopping or
+  reconfiguring unrelated services.
 
 ## Trusted inputs
 
-Reviewed source, the Go toolchain, root-owned `tend.json`, systemd unit files,
-the Caddy handler template, the operator, and the target host's root account are
-trusted. Packaging a hostile repository can execute hostile Go compiler hooks
-or consume resources; Tend is not a source-code sandbox.
+Reviewed source, the pinned Go toolchain, root-owned server policy and service
+configuration, systemd unit files, the Caddy handler template, the operator,
+and the target host's root account are trusted. Packaging a hostile repository
+can execute hostile Go compiler hooks or consume resources; Tend is not a
+source-code sandbox.
 
 ## Adversarial inputs
 
-Artifact paths and bytes, archive metadata, stale or malformed state, HTTP
-responses, subprocess failures, and filesystem objects at managed paths are
-validated and fail closed. Process output is bounded.
+Artifact paths and bytes, protocol frames, requested service names, archive
+metadata, stale or malformed state, HTTP responses, subprocess failures, and
+filesystem objects at managed paths are validated and fail closed. Process
+output and receive fields are bounded.
 
 ## Non-goals and preview limits
 
 Tend does not defend against a concurrently malicious root user, a compromised
-kernel/toolchain/systemd/Caddy installation, denial of service by the trusted
-application, or secrets already exposed through service configuration. v0.1
-does not manage data migrations, databases, containers, Kubernetes, or
-application-specific activation. Transfer remains an application-local,
-reviewed step until a transport can be added without weakening host-key and
-credential boundaries.
+kernel/toolchain/systemd/Caddy/OpenSSH installation, denial of service by the
+trusted application, or secrets an application itself exposes. It does not
+manage data migrations, databases, containers, Kubernetes, or application-specific
+activation. EQL therefore remains outside the generic deployment adapter until
+its SQLite/catalog publication checkpoints can be modeled explicitly.

docs/WALKTHROUGH.md

@@ -0,0 +1,70 @@
+# Two-service build, approval, and deployment
+
+This walkthrough assumes one small Linux host running systemd and Caddy, two Go
+services, and a trusted Gitea build runner. The host has the same root-owned Tend
+binary at `/usr/local/bin/tend`; it does not need Git or Go.
+
+## Prepare the host once
+
+1. Create `/etc/tend/services`, `/etc/tend/environment`, and
+   `/var/lib/tend/incoming`. The incoming and environment directories are
+   root-owned mode `0700`.
+2. Install one schema-2 file per service, one per-service deployment-event log,
+   and one root-owned mode-`0600`
+   environment file per service. A singleton's shared environment file must
+   not define its configured listen key; its installed unit owns the live
+   address and Tend overrides only the transient candidate. Give each
+   singleton an imported Caddy handler and a root-owned handler template with
+   exactly one `{{UPSTREAM}}` marker; this is the bounded traffic handoff while
+   its fixed-address unit restarts.
+3. Install the receive policy, forced `authorized_keys` entry, and exact sudoers
+   rule from `examples/server/` after replacing every placeholder. The sudoers
+   fragment preserves only `SSH_ORIGINAL_COMMAND`; the root receiver requires
+   its exact protocol value and refuses every other requested command.
+4. Pin the server host key in a dedicated client file. Do not accept a new key
+   interactively during deployment.
+5. Run `sudo tend check-server` and inspect the allowlisted service names.
+
+## Build and approve
+
+Trusted CI checks a clean pushed commit, uses a pinned Go toolchain, packages
+twice, and requires byte-identical archives. It publishes the archive,
+`RELEASE.json`, `BUILDINFO.json`, SPDX SBOM, and SHA-256 evidence.
+
+The maintainer reads the candidate report and copies the exact approved digest
+into the deployment command. Tend refuses a digest that is merely inferred from
+the local file or differs from the produced value.
+
+```text
+tend push --target tend-deploy@server.example \
+  --known-hosts /secure/tend_known_hosts \
+  --identity /secure/tend_deploy_ed25519 \
+  --service example-site \
+  --artifact /approved/example-site.tar.gz \
+  --sha256 <produced> --approve-sha256 <reviewed> --activate
+```
+
+Repeat independently with `--service docs-site`. Both builds and transfers can
+run concurrently. The host-wide lock serializes only activation because both
+services share Caddy. Tend does not stop the other application.
+
+## Failure and recovery exercises
+
+- Change a candidate marker: activation must fail, preserve the active release,
+  and record the failed attempt without calling the candidate active.
+- Make a Caddy template invalid: validation must fail and restore prior bytes.
+- Make the public marker fail after an initially successful request: the
+  activation window must catch the transient routed failure and restore the
+  former slot/pointer.
+- For a singleton, verify repeated canonical-origin requests remain successful
+  while Tend routes to the candidate, restarts the fixed-address unit, and
+  returns traffic to it. Inject failure at both Caddy reloads and require the
+  prior handler and pointer to be restored.
+- Stop the previous blue/green slot during the activation window: Tend must
+  restore the old Caddy handler instead of accepting reduced continuity.
+- Run `tend rollback --activate` for one service and verify the other service's
+  units, pointers, and public origin did not change.
+- Interrupt a transfer: no release becomes active and the incomplete incoming
+  file is removed when the receiver exits.
+
+After the soak, prune per service. Active and previous releases remain protected.

examples/README.md

@@ -3,17 +3,39 @@
 This subtree is licensed 0BSD so an operator can copy and adapt it without
 bringing the Tend program's AGPL license into an application configuration.
 
-The blue/green example expects separately reviewed environment files:
+The blue/green example expects one separately reviewed environment file that
+the two installed slots and transient validation use consistently:
 
 ```text
-# /etc/example-site/blue.env
-EXAMPLE_LISTEN=127.0.0.1:8090
-
-# /etc/example-site/green.env
-EXAMPLE_LISTEN=127.0.0.1:8091
+# /etc/tend/environment/example-site.env
+APP_SECRET=replace-on-server
 ```
 
+The blue/green systemd slot units then read the nonsecret listen address from
+`/etc/tend/slots/example-site-blue.env` or `-green.env`; Tend overrides only
+the isolated candidate address. Secret values never enter `tend.json`.
+
+The singleton example follows the same split: its shared root-only environment
+file omits the configured listen key, the installed unit owns the live address,
+and Tend supplies only the transient candidate address. This prevents a shared
+environment file from overriding the isolated candidate port. Its imported
+Caddy handler is also managed from one reviewed template. Tend temporarily
+routes the canonical origin to the proven candidate while the fixed-address
+unit restarts, then returns traffic to that unit only after it passes its local
+checks.
+
 Production configuration belongs outside the source checkout, owned by root,
 and not group- or world-writable. The Caddy handler template is an entire
 imported handler fragment; the enclosing site, matchers, and routing precedence
 remain operator-owned.
+
+`event_log` is a per-service, root-owned JSONL evidence stream below that
+service's release root. Grant an Observatory agent read access explicitly; do
+not make the release root broadly readable. `activation_window_seconds` keeps
+canonical routed probes active after Caddy reload and keeps the previous
+blue/green slot—or the singleton handoff candidate—under health/readiness
+observation until the activation is recorded.
+
+`server/` demonstrates the schema-2 receive policy, forced OpenSSH command,
+restricted sudo entry, two independent service configurations, and secret-file
+placement. The values are placeholders, not an installation script.

examples/blue-green/example-site@.service

@@ -6,7 +6,8 @@ After=network.target
 Type=simple
 DynamicUser=yes
 ExecStart=/opt/example-site/slots/%i/example-site
-EnvironmentFile=/etc/example-site/%i.env
+EnvironmentFile=/etc/tend/environment/example-site.env
+EnvironmentFile=/etc/tend/slots/example-site-%i.env
 NoNewPrivileges=yes
 PrivateTmp=yes
 ProtectSystem=strict

examples/blue-green/tend.json

@@ -1,16 +1,19 @@
 {
-  "schema_version": 1,
-  "service": { "name": "example-site", "allowed_host": "example.test" },
+  "schema_version": 2,
+  "service": { "name": "example-site", "allowed_host": "example.test", "environment_file": "/etc/tend/environment/example-site.env" },
   "build": { "package": "./cmd/site", "binary": "example-site", "branch": "main" },
   "deployment": {
     "strategy": "blue_green",
     "root": "/opt/example-site",
-    "lock_file": "/run/lock/gamertan-deploy.lock",
+    "lock_file": "/run/lock/tend-deploy.lock",
     "state_file": "/opt/example-site/tend-state.json",
+    "event_log": "/opt/example-site/deployment-events.jsonl",
     "health_path": "/healthz",
     "readiness_path": "/readyz",
     "candidate_timeout_seconds": 30,
+    "activation_window_seconds": 10,
     "smoke": [{ "path": "/", "contains": "Example site" }],
+    "public_smoke": [{ "url": "https://example.test/", "contains": "Example site" }],
     "blue_green": {
       "caddy_config": "/etc/caddy/Caddyfile",
       "caddy_handler": "/etc/caddy/example-site-handler.caddy",

examples/local/.env.example

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: 0BSD
+APP_MODE=development
+APP_SECRET=replace-with-a-local-random-value

examples/server/authorized_keys.example

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: 0BSD
+restrict,command="sudo -n /usr/local/bin/tend receive --policy /etc/tend/receive-policy.json" ssh-ed25519 REPLACE_WITH_DEPLOY_KEY tend-deploy

examples/server/caddy/docs-site.template

@@ -0,0 +1,2 @@
+# Managed by Tend. The enclosing site and route matchers remain operator-owned.
+reverse_proxy {{UPSTREAM}}

examples/server/caddy/example-site.template

@@ -0,0 +1,2 @@
+# Managed by Tend. The enclosing site and route matchers remain operator-owned.
+reverse_proxy {{UPSTREAM}}

examples/server/environment/docs-site.env.example

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: 0BSD
+DOCS_LISTEN=127.0.0.1:8102
+APP_SECRET=replace-on-server

examples/server/environment/example-site.env.example

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: 0BSD
+APP_SECRET=replace-on-server

examples/server/example-singleton.service

@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: 0BSD
+[Unit]
+Description=Example singleton site
+After=network.target
+
+[Service]
+Type=simple
+DynamicUser=yes
+ExecStart=/opt/example-site/current/example-site
+EnvironmentFile=/etc/tend/environment/example-site.env
+Environment=EXAMPLE_LISTEN=127.0.0.1:8092
+NoNewPrivileges=yes
+PrivateTmp=yes
+ProtectSystem=strict
+ProtectHome=yes
+Restart=on-failure
+
+[Install]
+WantedBy=multi-user.target

examples/server/receive-policy.json

@@ -0,0 +1,16 @@
+{
+  "schema_version": 1,
+  "config_root": "/etc/tend/services",
+  "incoming_root": "/var/lib/tend/incoming",
+  "shared_lock_file": "/run/lock/tend-deploy.lock",
+  "services": {
+    "docs-site": {
+      "config": "/etc/tend/services/docs-site.json",
+      "max_artifact_bytes": 134217728
+    },
+    "example-site": {
+      "config": "/etc/tend/services/example-site.json",
+      "max_artifact_bytes": 134217728
+    }
+  }
+}

examples/server/services/docs-site.json

@@ -0,0 +1,29 @@
+{
+  "schema_version": 2,
+  "service": { "name": "docs-site", "allowed_host": "docs.example.test", "environment_file": "/etc/tend/environment/docs-site.env" },
+  "build": { "package": "./cmd/docs", "binary": "docs-site", "branch": "main" },
+  "deployment": {
+    "strategy": "singleton_candidate",
+    "root": "/opt/docs-site",
+    "lock_file": "/run/lock/tend-deploy.lock",
+    "state_file": "/opt/docs-site/tend-state.json",
+    "event_log": "/opt/docs-site/deployment-events.jsonl",
+    "health_path": "/healthz",
+    "readiness_path": "/readyz",
+    "candidate_timeout_seconds": 30,
+    "activation_window_seconds": 10,
+    "smoke": [{ "path": "/", "contains": "Documentation" }],
+    "public_smoke": [{ "url": "https://docs.example.test/", "contains": "Documentation" }],
+    "singleton": {
+      "unit": "docs-site.service",
+      "address": "127.0.0.1:8102",
+      "candidate_address": "127.0.0.1:18102",
+      "listen_env": "DOCS_LISTEN",
+      "current_link": "/opt/docs-site/current",
+      "previous_link": "/opt/docs-site/previous",
+      "caddy_config": "/etc/caddy/Caddyfile",
+      "caddy_handler": "/etc/caddy/docs-site-handler.caddy",
+      "caddy_handler_template": "/etc/tend/caddy/docs-site.template"
+    }
+  }
+}

examples/server/services/example-site.json

@@ -0,0 +1,29 @@
+{
+  "schema_version": 2,
+  "service": { "name": "example-site", "allowed_host": "example.test", "environment_file": "/etc/tend/environment/example-site.env" },
+  "build": { "package": "./cmd/site", "binary": "example-site", "branch": "main" },
+  "deployment": {
+    "strategy": "singleton_candidate",
+    "root": "/opt/example-site",
+    "lock_file": "/run/lock/tend-deploy.lock",
+    "state_file": "/opt/example-site/tend-state.json",
+    "event_log": "/opt/example-site/deployment-events.jsonl",
+    "health_path": "/healthz",
+    "readiness_path": "/readyz",
+    "candidate_timeout_seconds": 30,
+    "activation_window_seconds": 10,
+    "smoke": [{ "path": "/", "contains": "Example site" }],
+    "public_smoke": [{ "url": "https://example.test/", "contains": "Example site" }],
+    "singleton": {
+      "unit": "example-site.service",
+      "address": "127.0.0.1:8092",
+      "candidate_address": "127.0.0.1:18092",
+      "listen_env": "EXAMPLE_LISTEN",
+      "current_link": "/opt/example-site/current",
+      "previous_link": "/opt/example-site/previous",
+      "caddy_config": "/etc/caddy/Caddyfile",
+      "caddy_handler": "/etc/caddy/example-site-handler.caddy",
+      "caddy_handler_template": "/etc/tend/caddy/example-site.template"
+    }
+  }
+}

examples/server/slots/example-site-blue.env

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: 0BSD
+EXAMPLE_LISTEN=127.0.0.1:8090

examples/server/slots/example-site-green.env

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: 0BSD
+EXAMPLE_LISTEN=127.0.0.1:8091

examples/server/tend-receive.sudoers

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: 0BSD
+Defaults:tend-deploy env_keep += "SSH_ORIGINAL_COMMAND"
+tend-deploy ALL=(root) NOPASSWD: /usr/local/bin/tend receive --policy /etc/tend/receive-policy.json

examples/singleton/caddy-handler.template

@@ -0,0 +1,2 @@
+# Managed by Tend. The enclosing site and route matchers remain operator-owned.
+reverse_proxy {{UPSTREAM}}

examples/singleton/tend.json

@@ -1,24 +1,29 @@
 {
-  "schema_version": 1,
-  "service": { "name": "example-site", "allowed_host": "example.test" },
+  "schema_version": 2,
+  "service": { "name": "example-site", "allowed_host": "example.test", "environment_file": "/etc/tend/environment/example-site.env" },
   "build": { "package": "./cmd/site", "binary": "example-site", "branch": "main" },
   "deployment": {
     "strategy": "singleton_candidate",
     "root": "/opt/example-site",
-    "lock_file": "/run/lock/gamertan-deploy.lock",
+    "lock_file": "/run/lock/tend-deploy.lock",
     "state_file": "/opt/example-site/tend-state.json",
+    "event_log": "/opt/example-site/deployment-events.jsonl",
     "health_path": "/healthz",
     "readiness_path": "/readyz",
     "candidate_timeout_seconds": 30,
+    "activation_window_seconds": 10,
     "smoke": [{ "path": "/", "contains": "Example site" }],
+    "public_smoke": [{ "url": "https://example.test/", "contains": "Example site" }],
     "singleton": {
       "unit": "example-site.service",
       "address": "127.0.0.1:8092",
       "candidate_address": "127.0.0.1:18092",
       "listen_env": "EXAMPLE_LISTEN",
-      "environment": {},
       "current_link": "/opt/example-site/current",
-      "previous_link": "/opt/example-site/previous"
+      "previous_link": "/opt/example-site/previous",
+      "caddy_config": "/etc/caddy/Caddyfile",
+      "caddy_handler": "/etc/caddy/example-site-handler.caddy",
+      "caddy_handler_template": "/etc/tend/caddy/example-site.template"
     }
   }
 }

internal/config/config.go

@@ -9,13 +9,17 @@ import (
 	"fmt"
 	"io"
 	"net/netip"
+	"net/url"
 	"os"
 	"path/filepath"
 	"regexp"
 	"strings"
 )
 
-const SchemaVersion = 1
+const (
+	SchemaVersion  = 2
+	SharedLockFile = "/run/lock/tend-deploy.lock"
+)
 
 var (
 	namePattern    = regexp.MustCompile(`^[a-z][a-z0-9-]{1,62}$`)
@@ -33,8 +37,9 @@ type Config struct {
 }
 
 type Service struct {
-	Name        string `json:"name"`
-	AllowedHost string `json:"allowed_host"`
+	Name            string `json:"name"`
+	AllowedHost     string `json:"allowed_host"`
+	EnvironmentFile string `json:"environment_file"`
 }
 
 type Build struct {
@@ -47,16 +52,19 @@ type Build struct {
 }
 
 type Deployment struct {
-	Strategy             string     `json:"strategy"`
-	Root                 string     `json:"root"`
-	LockFile             string     `json:"lock_file"`
-	StateFile            string     `json:"state_file"`
-	HealthPath           string     `json:"health_path"`
-	ReadinessPath        string     `json:"readiness_path"`
-	CandidateTimeoutSecs int        `json:"candidate_timeout_seconds"`
-	Smoke                []Smoke    `json:"smoke"`
-	BlueGreen            *BlueGreen `json:"blue_green,omitempty"`
-	Singleton            *Singleton `json:"singleton,omitempty"`
+	Strategy             string        `json:"strategy"`
+	Root                 string        `json:"root"`
+	LockFile             string        `json:"lock_file"`
+	StateFile            string        `json:"state_file"`
+	EventLog             string        `json:"event_log"`
+	HealthPath           string        `json:"health_path"`
+	ReadinessPath        string        `json:"readiness_path"`
+	CandidateTimeoutSecs int           `json:"candidate_timeout_seconds"`
+	ActivationWindowSecs int           `json:"activation_window_seconds"`
+	Smoke                []Smoke       `json:"smoke"`
+	PublicSmoke          []PublicSmoke `json:"public_smoke"`
+	BlueGreen            *BlueGreen    `json:"blue_green,omitempty"`
+	Singleton            *Singleton    `json:"singleton,omitempty"`
 }
 
 type Smoke struct {
@@ -64,6 +72,11 @@ type Smoke struct {
 	Contains string `json:"contains"`
 }
 
+type PublicSmoke struct {
+	URL      string `json:"url"`
+	Contains string `json:"contains"`
+}
+
 type BlueGreen struct {
 	CaddyConfig          string `json:"caddy_config"`
 	CaddyHandler         string `json:"caddy_handler"`
@@ -80,13 +93,15 @@ type Slot struct {
 }
 
 type Singleton struct {
-	Unit             string            `json:"unit"`
-	Address          string            `json:"address"`
-	CandidateAddress string            `json:"candidate_address"`
-	ListenEnv        string            `json:"listen_env"`
-	Environment      map[string]string `json:"environment,omitempty"`
-	CurrentLink      string            `json:"current_link"`
-	PreviousLink     string            `json:"previous_link"`
+	Unit                 string `json:"unit"`
+	Address              string `json:"address"`
+	CandidateAddress     string `json:"candidate_address"`
+	ListenEnv            string `json:"listen_env"`
+	CurrentLink          string `json:"current_link"`
+	PreviousLink         string `json:"previous_link"`
+	CaddyConfig          string `json:"caddy_config"`
+	CaddyHandler         string `json:"caddy_handler"`
+	CaddyHandlerTemplate string `json:"caddy_handler_template"`
 }
 
 func Load(path string) (Config, error) {
@@ -140,6 +155,12 @@ func (c Config) Validate() error {
 	if c.Service.AllowedHost == "" || strings.ContainsAny(c.Service.AllowedHost, "/\\\x00\r\n\t ") {
 		return errors.New("service.allowed_host is invalid")
 	}
+	if err := safeAbsolute("service.environment_file", c.Service.EnvironmentFile); err != nil {
+		return err
+	}
+	if !within("/etc/tend/environment", c.Service.EnvironmentFile) {
+		return errors.New("service.environment_file must be below /etc/tend/environment")
+	}
 	if !packagePattern.MatchString(c.Build.Package) || strings.Contains(c.Build.Package, "..") {
 		return errors.New("build.package must be a local package without traversal")
 	}
@@ -171,12 +192,21 @@ func (c Config) Validate() error {
 	if filepath.Clean(d.StateFile) == filepath.Clean(d.Root) || !within(d.Root, d.StateFile) {
 		return errors.New("deployment.state_file must be below deployment.root")
 	}
+	if err := safeAbsolute("deployment.event_log", d.EventLog); err != nil {
+		return err
+	}
+	if filepath.Clean(d.EventLog) == filepath.Clean(d.Root) || !within(d.Root, d.EventLog) || filepath.Clean(d.EventLog) == filepath.Clean(d.StateFile) {
+		return errors.New("deployment.event_log must be a distinct file below deployment.root")
+	}
 	if !safeHTTPPath(d.HealthPath) || !safeHTTPPath(d.ReadinessPath) {
 		return errors.New("health and readiness paths must be absolute HTTP paths")
 	}
 	if d.CandidateTimeoutSecs < 2 || d.CandidateTimeoutSecs > 300 {
 		return errors.New("candidate_timeout_seconds must be between 2 and 300")
 	}
+	if d.ActivationWindowSecs < 1 || d.ActivationWindowSecs > 120 {
+		return errors.New("activation_window_seconds must be between 1 and 120")
+	}
 	if len(d.Smoke) == 0 || len(d.Smoke) > 32 {
 		return errors.New("deployment.smoke must contain 1 to 32 checks")
 	}
@@ -185,6 +215,15 @@ func (c Config) Validate() error {
 			return fmt.Errorf("deployment.smoke[%d] is invalid", i)
 		}
 	}
+	if len(d.PublicSmoke) == 0 || len(d.PublicSmoke) > 16 {
+		return errors.New("deployment.public_smoke must contain 1 to 16 checks")
+	}
+	for i, smoke := range d.PublicSmoke {
+		parsed, err := url.Parse(smoke.URL)
+		if err != nil || parsed.Scheme != "https" || parsed.Host == "" || parsed.User != nil || parsed.Fragment != "" || parsed.RawQuery != "" || parsed.Opaque != "" || smoke.Contains == "" || len(smoke.Contains) > 4096 || strings.ContainsRune(smoke.Contains, '\x00') {
+			return fmt.Errorf("deployment.public_smoke[%d] is invalid", i)
+		}
+	}
 	switch d.Strategy {
 	case "blue_green":
 		if d.BlueGreen == nil || d.Singleton != nil {
@@ -273,11 +312,14 @@ func validateSingleton(root string, s Singleton) error {
 	if s.CurrentLink == s.PreviousLink {
 		return errors.New("current and previous links must differ")
 	}
-	for key, value := range s.Environment {
-		if !regexp.MustCompile(`^[A-Z][A-Z0-9_]{0,63}$`).MatchString(key) || strings.ContainsAny(value, "\x00\r\n") {
-			return fmt.Errorf("singleton environment entry %q is invalid", key)
+	for label, path := range map[string]string{"caddy_config": s.CaddyConfig, "caddy_handler": s.CaddyHandler, "caddy_handler_template": s.CaddyHandlerTemplate} {
+		if err := safeAbsolute("deployment.singleton."+label, path); err != nil {
+			return err
 		}
 	}
+	if filepath.Clean(s.CaddyHandler) == filepath.Clean(s.CaddyHandlerTemplate) {
+		return errors.New("singleton Caddy handler and template must be different files")
+	}
 	return nil
 }
 

internal/config/config_test.go

@@ -9,13 +9,14 @@ import (
 
 func validConfig() Config {
 	return Config{
-		SchemaVersion: 1,
-		Service:       Service{Name: "example-site", AllowedHost: "example.test"},
+		SchemaVersion: 2,
+		Service:       Service{Name: "example-site", AllowedHost: "example.test", EnvironmentFile: "/etc/tend/environment/example-site.env"},
 		Build:         Build{Package: "./cmd/site", Binary: "example-site", Branch: "main"},
 		Deployment: Deployment{
-			Strategy: "blue_green", Root: "/opt/example-site", LockFile: "/run/lock/example-site.lock",
-			StateFile: "/opt/example-site/state.json", HealthPath: "/healthz", ReadinessPath: "/readyz",
-			CandidateTimeoutSecs: 30, Smoke: []Smoke{{Path: "/", Contains: "Example"}},
+			Strategy: "blue_green", Root: "/opt/example-site", LockFile: SharedLockFile,
+			StateFile: "/opt/example-site/state.json", EventLog: "/opt/example-site/deployment-events.jsonl", HealthPath: "/healthz", ReadinessPath: "/readyz",
+			CandidateTimeoutSecs: 30, ActivationWindowSecs: 10, Smoke: []Smoke{{Path: "/", Contains: "Example"}},
+			PublicSmoke: []PublicSmoke{{URL: "https://example.test/", Contains: "Example"}},
 			BlueGreen: &BlueGreen{
 				CaddyConfig: "/etc/caddy/Caddyfile", CaddyHandler: "/etc/caddy/example.caddy",
 				CaddyHandlerTemplate: "/etc/example/caddy.template",
@@ -33,14 +34,35 @@ func TestValidateAcceptsBlueGreen(t *testing.T) {
 	}
 }
 
+func TestValidateSingletonRequiresDistinctCaddyHandoffFiles(t *testing.T) {
+	cfg := validConfig()
+	cfg.Deployment.Strategy = "singleton_candidate"
+	cfg.Deployment.BlueGreen = nil
+	cfg.Deployment.Singleton = &Singleton{
+		Unit: "example-site.service", Address: "127.0.0.1:8092", CandidateAddress: "127.0.0.1:18092", ListenEnv: "EXAMPLE_LISTEN",
+		CurrentLink: "/opt/example-site/current", PreviousLink: "/opt/example-site/previous", CaddyConfig: "/etc/caddy/Caddyfile",
+		CaddyHandler: "/etc/caddy/example-site.caddy", CaddyHandlerTemplate: "/etc/tend/caddy/example-site.template",
+	}
+	if err := cfg.Validate(); err != nil {
+		t.Fatal(err)
+	}
+	cfg.Deployment.Singleton.CaddyHandlerTemplate = cfg.Deployment.Singleton.CaddyHandler
+	if err := cfg.Validate(); err == nil {
+		t.Fatal("expected shared handler/template path to be rejected")
+	}
+}
+
 func TestValidateRejectsHostileValues(t *testing.T) {
 	tests := map[string]func(*Config){
-		"unknown strategy": func(c *Config) { c.Deployment.Strategy = "shell" },
-		"nonloopback":      func(c *Config) { c.Deployment.BlueGreen.Blue.Address = "203.0.113.7:80" },
-		"root path":        func(c *Config) { c.Deployment.Root = "/" },
-		"traversal":        func(c *Config) { c.Build.Package = "./cmd/../secret" },
-		"shared slot":      func(c *Config) { c.Deployment.BlueGreen.Green.Link = c.Deployment.BlueGreen.Blue.Link },
-		"bad smoke":        func(c *Config) { c.Deployment.Smoke[0].Path = "https://attacker.test/" },
+		"unknown strategy":    func(c *Config) { c.Deployment.Strategy = "shell" },
+		"nonloopback":         func(c *Config) { c.Deployment.BlueGreen.Blue.Address = "203.0.113.7:80" },
+		"root path":           func(c *Config) { c.Deployment.Root = "/" },
+		"traversal":           func(c *Config) { c.Build.Package = "./cmd/../secret" },
+		"shared slot":         func(c *Config) { c.Deployment.BlueGreen.Green.Link = c.Deployment.BlueGreen.Blue.Link },
+		"bad smoke":           func(c *Config) { c.Deployment.Smoke[0].Path = "https://attacker.test/" },
+		"bad public smoke":    func(c *Config) { c.Deployment.PublicSmoke[0].URL = "http://example.test/" },
+		"public secret query": func(c *Config) { c.Deployment.PublicSmoke[0].URL = "https://example.test/?token=secret" },
+		"environment sibling": func(c *Config) { c.Service.EnvironmentFile = "/etc/tend/environment-old/example.env" },
 	}
 	for name, mutate := range tests {
 		t.Run(name, func(t *testing.T) {

internal/deploy/deploy.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"gamertan.com/tend/internal/config"
+	"gamertan.com/tend/internal/eventlog"
 	"gamertan.com/tend/internal/state"
 )
 
@@ -29,6 +30,7 @@ type Report struct {
 	Release         string `json:"release,omitempty"`
 	ActiveRelease   string `json:"active_release,omitempty"`
 	PreviousRelease string `json:"previous_release,omitempty"`
+	EventWarnings   int    `json:"event_warnings,omitempty"`
 }
 type Status struct {
 	State            *state.Record   `json:"state,omitempty"`
@@ -37,14 +39,18 @@ type Status struct {
 }
 
 type Manager struct {
-	Operator Operator
-	Now      func() time.Time
-	Prepare  func(config.Config, string, string, string) (string, error)
-	Inspect  func(config.Config, string, string, string) error
+	Operator     Operator
+	Now          func() time.Time
+	Prepare      func(config.Config, string, string, string) (string, error)
+	Inspect      func(config.Config, string, string, string) error
+	ReadIdentity func(string) (releaseIdentity, error)
+	OperationID  func() (string, error)
+	AppendEvent  func(string, eventlog.Event) error
+	Sleep        func(context.Context, time.Duration) error
 }
 
 func NewManager(operator Operator) Manager {
-	return Manager{Operator: operator, Now: time.Now, Prepare: prepareRelease, Inspect: inspectArtifact}
+	return Manager{Operator: operator, Now: time.Now, Prepare: prepareRelease, Inspect: inspectArtifact, ReadIdentity: readReleaseIdentity, OperationID: eventlog.OperationID, AppendEvent: eventlog.Append, Sleep: sleepContext}
 }
 
 func (m Manager) Deploy(ctx context.Context, cfg config.Config, request Request) (Report, error) {
@@ -66,10 +72,44 @@ func (m Manager) Deploy(ctx context.Context, cfg config.Config, request Request)
 	if err != nil {
 		return Report{}, err
 	}
+	started := m.Now()
+	eventWarnings := 0
+	identity, identityErr := m.ReadIdentity(release)
+	if identityErr != nil {
+		eventWarnings++
+	}
+	operationID := ""
+	if m.OperationID != nil {
+		operationID, err = m.OperationID()
+		if err != nil {
+			eventWarnings++
+			operationID = ""
+		}
+	}
+	emit := func(phase, slot, outcome string) {
+		if m.AppendEvent == nil || identityErr != nil || operationID == "" {
+			return
+		}
+		event := eventlog.Event{Version: eventlog.Version, OperationID: operationID, Service: cfg.Service.Name, ArtifactDigest: request.ApprovedSHA256, Commit: identity.Commit, ReleaseVersion: identity.Version, Phase: phase, Slot: slot, DurationMillis: max(0, m.Now().Sub(started).Milliseconds()), Outcome: outcome, ObservedAt: m.Now().UTC().Format(time.RFC3339Nano)}
+		if eventErr := m.AppendEvent(cfg.Deployment.EventLog, event); eventErr != nil {
+			eventWarnings++
+		}
+	}
 	record, err := loadOrBootstrap(cfg, m.Now())
 	if err != nil {
 		return Report{}, err
 	}
+	attemptAt := m.Now().UTC().Format(time.RFC3339)
+	record.DesiredRelease = release
+	record.CandidateRelease = release
+	record.LastAttemptRelease = release
+	record.LastAttemptOutcome = "running"
+	record.LastAttemptAt = attemptAt
+	record.UpdatedAt = attemptAt
+	if err := state.Store(cfg.Deployment.StateFile, cfg.Deployment.Root, record); err != nil {
+		return Report{}, err
+	}
+	emit("candidate", inactiveSlot(cfg, record), "running")
 	switch cfg.Deployment.Strategy {
 	case "blue_green":
 		err = m.deployBlueGreen(ctx, cfg, record, release)
@@ -79,13 +119,64 @@ func (m Manager) Deploy(ctx context.Context, cfg config.Config, request Request)
 		err = errors.New("unsupported strategy")
 	}
 	if err != nil {
-		return Report{}, err
+		failed := record
+		failed.CandidateRelease = ""
+		failed.LastAttemptOutcome = "failed"
+		failed.UpdatedAt = m.Now().UTC().Format(time.RFC3339)
+		_ = state.Store(cfg.Deployment.StateFile, cfg.Deployment.Root, failed)
+		emit("activation", inactiveSlot(cfg, record), "failed")
+		return Report{EventWarnings: eventWarnings}, err
 	}
+	emit("activation", inactiveSlot(cfg, record), "succeeded")
 	updated, err := state.Load(cfg.Deployment.StateFile, cfg.Deployment.Root, cfg.Deployment.Strategy)
 	if err != nil {
 		return Report{}, err
 	}
-	return Report{Validated: true, Mutation: "activated", Release: release, ActiveRelease: updated.ActiveRelease, PreviousRelease: updated.PreviousRelease}, nil
+	return Report{Validated: true, Mutation: "activated", Release: release, ActiveRelease: updated.ActiveRelease, PreviousRelease: updated.PreviousRelease, EventWarnings: eventWarnings}, nil
+}
+
+type releaseIdentity struct {
+	Version string `json:"version"`
+	Commit  string `json:"commit"`
+}
+
+func readReleaseIdentity(release string) (releaseIdentity, error) {
+	b, err := os.ReadFile(filepath.Join(release, "RELEASE.json"))
+	if err != nil {
+		return releaseIdentity{}, fmt.Errorf("read installed release identity: %w", err)
+	}
+	if len(b) > 1<<20 {
+		return releaseIdentity{}, errors.New("installed release identity is too large")
+	}
+	var identity releaseIdentity
+	if err := json.Unmarshal(b, &identity); err != nil {
+		return releaseIdentity{}, errors.New("decode installed release identity")
+	}
+	if identity.Version == "" || identity.Commit == "" {
+		return releaseIdentity{}, errors.New("installed release identity is incomplete")
+	}
+	return identity, nil
+}
+
+func inactiveSlot(cfg config.Config, record state.Record) string {
+	if cfg.Deployment.Strategy == "singleton_candidate" {
+		return "singleton"
+	}
+	if record.ActiveSlot == "blue" {
+		return "green"
+	}
+	return "blue"
+}
+
+func sleepContext(ctx context.Context, duration time.Duration) error {
+	timer := time.NewTimer(duration)
+	defer timer.Stop()
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-timer.C:
+		return nil
+	}
 }
 
 func loadOrBootstrap(cfg config.Config, now time.Time) (state.Record, error) {
@@ -103,13 +194,13 @@ func loadOrBootstrap(cfg config.Config, now time.Time) (state.Record, error) {
 		if err != nil {
 			return state.Record{}, fmt.Errorf("bootstrap active slot: %w", err)
 		}
-		return state.Record{SchemaVersion: 1, Strategy: cfg.Deployment.Strategy, ActiveSlot: slot, ActiveRelease: release, UpdatedAt: now.UTC().Format(time.RFC3339)}, nil
+		return state.Record{SchemaVersion: 1, Strategy: cfg.Deployment.Strategy, DesiredRelease: release, ActiveSlot: slot, ActiveRelease: release, UpdatedAt: now.UTC().Format(time.RFC3339)}, nil
 	case "singleton_candidate":
 		release, err := resolveReleaseLink(cfg.Deployment.Root, cfg.Deployment.Singleton.CurrentLink)
 		if err != nil {
 			return state.Record{}, fmt.Errorf("bootstrap singleton: %w", err)
 		}
-		return state.Record{SchemaVersion: 1, Strategy: cfg.Deployment.Strategy, ActiveSlot: "singleton", ActiveRelease: release, UpdatedAt: now.UTC().Format(time.RFC3339)}, nil
+		return state.Record{SchemaVersion: 1, Strategy: cfg.Deployment.Strategy, DesiredRelease: release, ActiveSlot: "singleton", ActiveRelease: release, UpdatedAt: now.UTC().Format(time.RFC3339)}, nil
 	}
 	return state.Record{}, errors.New("unsupported strategy")
 }
@@ -177,7 +268,14 @@ func (m Manager) deployBlueGreen(ctx context.Context, cfg config.Config, record
 	if err = m.probeAll(ctx, cfg, slot.Address); err != nil {
 		return fmt.Errorf("post-activation smoke failed: %w", err)
 	}
-	next := state.Record{SchemaVersion: 1, Strategy: cfg.Deployment.Strategy, ActiveSlot: inactive, ActiveRelease: release, PreviousSlot: record.ActiveSlot, PreviousRelease: record.ActiveRelease, UpdatedAt: m.Now().UTC().Format(time.RFC3339)}
+	if err = m.probePublic(ctx, cfg, true); err != nil {
+		return fmt.Errorf("public-origin smoke failed: %w", err)
+	}
+	previous := slotConfig(bg, record.ActiveSlot)
+	if err = m.continuityWindow(ctx, cfg, previous.Address, true); err != nil {
+		return fmt.Errorf("activation continuity failed: %w", err)
+	}
+	next := state.Record{SchemaVersion: 1, Strategy: cfg.Deployment.Strategy, DesiredRelease: release, ActiveSlot: inactive, ActiveRelease: release, PreviousSlot: record.ActiveSlot, PreviousRelease: record.ActiveRelease, LastAttemptRelease: release, LastAttemptOutcome: "succeeded", LastAttemptAt: record.LastAttemptAt, UpdatedAt: m.Now().UTC().Format(time.RFC3339)}
 	if err = state.Store(cfg.Deployment.StateFile, cfg.Deployment.Root, next); err != nil {
 		return err
 	}
@@ -185,60 +283,10 @@ func (m Manager) deployBlueGreen(ctx context.Context, cfg config.Config, record
 }
 
 func (m Manager) deploySingleton(ctx context.Context, cfg config.Config, record state.Record, release string) (err error) {
-	single := *cfg.Deployment.Singleton
-	candidateUnit := cfg.Service.Name + "-tend-candidate.service"
-	env := copyMap(single.Environment)
-	env[single.ListenEnv] = single.CandidateAddress
-	binary := filepath.Join(release, cfg.Build.Binary)
-	if err = m.Operator.StartCandidate(ctx, candidateUnit, binary, env); err != nil {
+	if err = m.activateSingletonRelease(ctx, cfg, release, true); err != nil {
 		return err
 	}
-	defer func() {
-		stopCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-		defer cancel()
-		_ = m.Operator.Stop(stopCtx, candidateUnit)
-	}()
-	if err = m.probeAll(ctx, cfg, single.CandidateAddress); err != nil {
-		return fmt.Errorf("candidate failed: %w", err)
-	}
-	oldCurrent, err := resolveReleaseLink(cfg.Deployment.Root, single.CurrentLink)
-	if err != nil {
-		return err
-	}
-	oldPrevious, previousErr := resolveReleaseLink(cfg.Deployment.Root, single.PreviousLink)
-	currentChanged := false
-	previousChanged := false
-	defer func() {
-		if err == nil {
-			return
-		}
-		if currentChanged {
-			_ = replaceSymlink(single.CurrentLink, oldCurrent)
-			_ = m.Operator.Restart(ctx, single.Unit)
-		}
-		if previousChanged {
-			if previousErr == nil {
-				_ = replaceSymlink(single.PreviousLink, oldPrevious)
-			} else {
-				_ = removeSymlink(single.PreviousLink)
-			}
-		}
-	}()
-	if err = replaceSymlink(single.PreviousLink, oldCurrent); err != nil {
-		return err
-	}
-	previousChanged = true
-	if err = replaceSymlink(single.CurrentLink, release); err != nil {
-		return err
-	}
-	currentChanged = true
-	if err = m.Operator.Restart(ctx, single.Unit); err != nil {
-		return err
-	}
-	if err = m.probeAll(ctx, cfg, single.Address); err != nil {
-		return fmt.Errorf("post-activation smoke failed: %w", err)
-	}
-	next := state.Record{SchemaVersion: 1, Strategy: cfg.Deployment.Strategy, ActiveSlot: "singleton", ActiveRelease: release, PreviousSlot: "singleton", PreviousRelease: record.ActiveRelease, UpdatedAt: m.Now().UTC().Format(time.RFC3339)}
+	next := state.Record{SchemaVersion: 1, Strategy: cfg.Deployment.Strategy, DesiredRelease: release, ActiveSlot: "singleton", ActiveRelease: release, PreviousSlot: "singleton", PreviousRelease: record.ActiveRelease, LastAttemptRelease: release, LastAttemptOutcome: "succeeded", LastAttemptAt: record.LastAttemptAt, UpdatedAt: m.Now().UTC().Format(time.RFC3339)}
 	if err = state.Store(cfg.Deployment.StateFile, cfg.Deployment.Root, next); err != nil {
 		return err
 	}
@@ -258,6 +306,21 @@ func (m Manager) Rollback(ctx context.Context, cfg config.Config) (state.Record,
 	if record.PreviousRelease == "" {
 		return state.Record{}, errors.New("no previous release is recorded")
 	}
+	started := m.Now()
+	identity, identityErr := m.ReadIdentity(record.PreviousRelease)
+	digest, digestErr := releaseDigest(record.PreviousRelease)
+	operationID := ""
+	if m.OperationID != nil {
+		operationID, _ = m.OperationID()
+	}
+	emit := func(outcome string) {
+		if m.AppendEvent == nil || identityErr != nil || digestErr != nil || operationID == "" {
+			return
+		}
+		event := eventlog.Event{Version: eventlog.Version, OperationID: operationID, Service: cfg.Service.Name, ArtifactDigest: digest, Commit: identity.Commit, ReleaseVersion: identity.Version, Phase: "rollback", Slot: record.PreviousSlot, DurationMillis: max(0, m.Now().Sub(started).Milliseconds()), Outcome: outcome, ObservedAt: m.Now().UTC().Format(time.RFC3339Nano)}
+		_ = m.AppendEvent(cfg.Deployment.EventLog, event)
+	}
+	emit("running")
 	switch cfg.Deployment.Strategy {
 	case "blue_green":
 		err = m.rollbackBlueGreen(ctx, cfg, record)
@@ -267,10 +330,29 @@ func (m Manager) Rollback(ctx context.Context, cfg config.Config) (state.Record,
 		err = errors.New("unsupported strategy")
 	}
 	if err != nil {
+		emit("failed")
 		return state.Record{}, err
 	}
+	emit("succeeded")
 	return state.Load(cfg.Deployment.StateFile, cfg.Deployment.Root, cfg.Deployment.Strategy)
 }
+
+func releaseDigest(release string) (string, error) {
+	name := filepath.Base(release)
+	if !strings.HasPrefix(name, "sha256-") {
+		return "", errors.New("release is not content addressed")
+	}
+	digest := strings.TrimPrefix(name, "sha256-")
+	if len(digest) != 64 {
+		return "", errors.New("release digest is invalid")
+	}
+	for _, character := range digest {
+		if !strings.ContainsRune("0123456789abcdef", character) {
+			return "", errors.New("release digest is invalid")
+		}
+	}
+	return digest, nil
+}
 func (m Manager) rollbackBlueGreen(ctx context.Context, cfg config.Config, record state.Record) (err error) {
 	bg := *cfg.Deployment.BlueGreen
 	slot := slotConfig(bg, record.PreviousSlot)
@@ -313,33 +395,151 @@ func (m Manager) rollbackBlueGreen(ctx context.Context, cfg config.Config, recor
 	if err = m.probeHealthReadiness(ctx, cfg, slot.Address); err != nil {
 		return err
 	}
-	next := state.Record{SchemaVersion: 1, Strategy: record.Strategy, ActiveSlot: record.PreviousSlot, ActiveRelease: record.PreviousRelease, PreviousSlot: record.ActiveSlot, PreviousRelease: record.ActiveRelease, UpdatedAt: m.Now().UTC().Format(time.RFC3339)}
+	if err = m.probePublic(ctx, cfg, false); err != nil {
+		return err
+	}
+	next := state.Record{SchemaVersion: 1, Strategy: record.Strategy, DesiredRelease: record.PreviousRelease, ActiveSlot: record.PreviousSlot, ActiveRelease: record.PreviousRelease, PreviousSlot: record.ActiveSlot, PreviousRelease: record.ActiveRelease, LastAttemptRelease: record.PreviousRelease, LastAttemptOutcome: "rolled_back", LastAttemptAt: m.Now().UTC().Format(time.RFC3339), UpdatedAt: m.Now().UTC().Format(time.RFC3339)}
 	return state.Store(cfg.Deployment.StateFile, cfg.Deployment.Root, next)
 }
 func (m Manager) rollbackSingleton(ctx context.Context, cfg config.Config, record state.Record) (err error) {
+	if err = m.activateSingletonRelease(ctx, cfg, record.PreviousRelease, false); err != nil {
+		return err
+	}
+	next := state.Record{SchemaVersion: 1, Strategy: record.Strategy, DesiredRelease: record.PreviousRelease, ActiveSlot: "singleton", ActiveRelease: record.PreviousRelease, PreviousSlot: "singleton", PreviousRelease: record.ActiveRelease, LastAttemptRelease: record.PreviousRelease, LastAttemptOutcome: "rolled_back", LastAttemptAt: m.Now().UTC().Format(time.RFC3339), UpdatedAt: m.Now().UTC().Format(time.RFC3339)}
+	return state.Store(cfg.Deployment.StateFile, cfg.Deployment.Root, next)
+}
+
+// activateSingletonRelease keeps public traffic on a proven process while the
+// installed fixed-address unit changes release. The transient candidate first
+// receives traffic, remains healthy through the handoff, and is stopped only
+// after Caddy points back to the verified installed unit.
+func (m Manager) activateSingletonRelease(ctx context.Context, cfg config.Config, release string, checkMarkers bool) (err error) {
 	single := *cfg.Deployment.Singleton
+	candidateUnit := cfg.Service.Name + "-tend-candidate.service"
+	env := map[string]string{single.ListenEnv: single.CandidateAddress}
+	binary := filepath.Join(release, cfg.Build.Binary)
+	if err = m.Operator.StartCandidate(ctx, candidateUnit, binary, cfg.Service.EnvironmentFile, env); err != nil {
+		return err
+	}
+	stopCandidate := true
+	defer func() {
+		if !stopCandidate {
+			return
+		}
+		stopCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		_ = m.Operator.Stop(stopCtx, candidateUnit)
+	}()
+	probeLocal := m.probeHealthReadiness
+	if checkMarkers {
+		probeLocal = m.probeAll
+	}
+	if err = probeLocal(ctx, cfg, single.CandidateAddress); err != nil {
+		return fmt.Errorf("candidate failed: %w", err)
+	}
+
+	oldHandler, err := os.ReadFile(single.CaddyHandler)
+	if err != nil {
+		return fmt.Errorf("read current Caddy handler: %w", err)
+	}
 	oldCurrent, err := resolveReleaseLink(cfg.Deployment.Root, single.CurrentLink)
 	if err != nil {
 		return err
 	}
-	if err = replaceSymlink(single.CurrentLink, record.PreviousRelease); err != nil {
-		return err
-	}
+	oldPrevious, previousErr := resolveReleaseLink(cfg.Deployment.Root, single.PreviousLink)
+	handlerChanged := false
+	currentChanged := false
+	previousChanged := false
 	defer func() {
-		if err != nil {
-			_ = replaceSymlink(single.CurrentLink, oldCurrent)
-			_ = m.Operator.Restart(ctx, single.Unit)
+		if err == nil {
+			return
+		}
+		recoveryErr := error(nil)
+		if currentChanged {
+			if restoreErr := replaceSymlink(single.CurrentLink, oldCurrent); restoreErr != nil {
+				recoveryErr = errors.Join(recoveryErr, restoreErr)
+			} else if restoreErr = m.Operator.Restart(ctx, single.Unit); restoreErr != nil {
+				recoveryErr = errors.Join(recoveryErr, restoreErr)
+			} else if restoreErr = m.probeHealthReadiness(ctx, cfg, single.Address); restoreErr != nil {
+				recoveryErr = errors.Join(recoveryErr, restoreErr)
+			}
+		}
+		if previousChanged {
+			var restoreErr error
+			if previousErr == nil {
+				restoreErr = replaceSymlink(single.PreviousLink, oldPrevious)
+			} else {
+				restoreErr = removeSymlink(single.PreviousLink)
+			}
+			recoveryErr = errors.Join(recoveryErr, restoreErr)
+		}
+		if handlerChanged && recoveryErr == nil {
+			if restoreErr := atomicWrite(single.CaddyHandler, oldHandler, 0o644); restoreErr != nil {
+				recoveryErr = errors.Join(recoveryErr, restoreErr)
+			} else if restoreErr = m.Operator.ValidateCaddy(ctx, single.CaddyConfig); restoreErr != nil {
+				recoveryErr = errors.Join(recoveryErr, restoreErr)
+			} else if restoreErr = m.Operator.ReloadCaddy(ctx); restoreErr != nil {
+				recoveryErr = errors.Join(recoveryErr, restoreErr)
+			}
+		}
+		if recoveryErr != nil && handlerChanged {
+			stopCandidate = false
+			err = errors.Join(err, fmt.Errorf("singleton recovery incomplete; candidate remains routed for operator recovery: %w", recoveryErr))
 		}
 	}()
+
+	candidateHandler, err := renderHandler(single.CaddyHandlerTemplate, single.CandidateAddress)
+	if err != nil {
+		return err
+	}
+	if err = atomicWrite(single.CaddyHandler, candidateHandler, 0o644); err != nil {
+		return err
+	}
+	handlerChanged = true
+	if err = m.Operator.ValidateCaddy(ctx, single.CaddyConfig); err != nil {
+		return fmt.Errorf("candidate Caddy validation failed: %w", err)
+	}
+	if err = m.Operator.ReloadCaddy(ctx); err != nil {
+		return fmt.Errorf("candidate Caddy reload failed: %w", err)
+	}
+	if err = m.probePublic(ctx, cfg, checkMarkers); err != nil {
+		return fmt.Errorf("candidate public-origin smoke failed: %w", err)
+	}
+
+	if err = replaceSymlink(single.PreviousLink, oldCurrent); err != nil {
+		return err
+	}
+	previousChanged = true
+	if err = replaceSymlink(single.CurrentLink, release); err != nil {
+		return err
+	}
+	currentChanged = true
 	if err = m.Operator.Restart(ctx, single.Unit); err != nil {
 		return err
 	}
-	if err = m.probeHealthReadiness(ctx, cfg, single.Address); err != nil {
+	if err = probeLocal(ctx, cfg, single.Address); err != nil {
+		return fmt.Errorf("post-activation smoke failed: %w", err)
+	}
+	installedHandler, err := renderHandler(single.CaddyHandlerTemplate, single.Address)
+	if err != nil {
 		return err
 	}
-	_ = replaceSymlink(single.PreviousLink, record.ActiveRelease)
-	next := state.Record{SchemaVersion: 1, Strategy: record.Strategy, ActiveSlot: "singleton", ActiveRelease: record.PreviousRelease, PreviousSlot: "singleton", PreviousRelease: record.ActiveRelease, UpdatedAt: m.Now().UTC().Format(time.RFC3339)}
-	return state.Store(cfg.Deployment.StateFile, cfg.Deployment.Root, next)
+	if err = atomicWrite(single.CaddyHandler, installedHandler, 0o644); err != nil {
+		return err
+	}
+	if err = m.Operator.ValidateCaddy(ctx, single.CaddyConfig); err != nil {
+		return fmt.Errorf("installed Caddy validation failed: %w", err)
+	}
+	if err = m.Operator.ReloadCaddy(ctx); err != nil {
+		return fmt.Errorf("installed Caddy reload failed: %w", err)
+	}
+	if err = m.probePublic(ctx, cfg, checkMarkers); err != nil {
+		return fmt.Errorf("public-origin smoke failed: %w", err)
+	}
+	if err = m.continuityWindow(ctx, cfg, single.CandidateAddress, checkMarkers); err != nil {
+		return fmt.Errorf("activation continuity failed: %w", err)
+	}
+	return nil
 }
 
 func (m Manager) Status(ctx context.Context, cfg config.Config) (Status, error) {
@@ -435,6 +635,50 @@ func (m Manager) probeHealthReadiness(ctx context.Context, cfg config.Config, ad
 	return m.probe(ctx, cfg, address, checks)
 }
 
+func (m Manager) probePublic(ctx context.Context, cfg config.Config, checkMarkers bool) error {
+	timeout := time.Duration(cfg.Deployment.CandidateTimeoutSecs) * time.Second
+	for _, check := range cfg.Deployment.PublicSmoke {
+		attempt, cancel := context.WithTimeout(ctx, timeout)
+		contains := check.Contains
+		if !checkMarkers {
+			contains = ""
+		}
+		err := m.Operator.ProbeURL(attempt, check.URL, contains)
+		cancel()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (m Manager) continuityWindow(ctx context.Context, cfg config.Config, previousAddress string, checkMarkers bool) error {
+	steps := cfg.Deployment.ActivationWindowSecs * 4
+	if steps < 1 {
+		steps = 1
+	}
+	for step := 0; step < steps; step++ {
+		if err := m.probePublic(ctx, cfg, checkMarkers); err != nil {
+			return err
+		}
+		if previousAddress != "" {
+			if err := m.probeHealthReadiness(ctx, cfg, previousAddress); err != nil {
+				return fmt.Errorf("previous slot lost continuity: %w", err)
+			}
+		}
+		if step+1 < steps {
+			sleep := m.Sleep
+			if sleep == nil {
+				sleep = sleepContext
+			}
+			if err := sleep(ctx, 250*time.Millisecond); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
 func (m Manager) probe(ctx context.Context, cfg config.Config, address string, checks []config.Smoke) error {
 	timeout := time.Duration(cfg.Deployment.CandidateTimeoutSecs) * time.Second
 	for _, check := range checks {
@@ -465,13 +709,6 @@ func slotConfig(bg config.BlueGreen, name string) config.Slot {
 	}
 	return bg.Green
 }
-func copyMap(source map[string]string) map[string]string {
-	target := make(map[string]string, len(source)+1)
-	for k, v := range source {
-		target[k] = v
-	}
-	return target
-}
 func resolveReleaseLink(root, link string) (string, error) {
 	info, err := os.Lstat(link)
 	if err != nil {

internal/deploy/deploy_test.go

@@ -5,6 +5,7 @@ package deploy
 import (
 	"context"
 	"errors"
+	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
@@ -12,21 +13,33 @@ import (
 	"time"
 
 	"gamertan.com/tend/internal/config"
+	"gamertan.com/tend/internal/eventlog"
 	"gamertan.com/tend/internal/state"
 )
 
 type fakeOperator struct {
 	failReload              bool
+	failReloadAt            int
+	reloads                 int
 	failRestartUnit         string
+	failRestartOnce         bool
 	rejectMarkers           bool
 	active                  map[string]bool
 	starts, stops, restarts []string
 	probes                  []string
+	publicProbes            []string
+	failPublic              bool
+	failPublicAfter         int
+	candidateEnvironment    map[string]string
+	candidateFile           string
 }
 
 func (f *fakeOperator) Restart(_ context.Context, unit string) error {
 	f.restarts = append(f.restarts, unit)
 	if unit == f.failRestartUnit {
+		if f.failRestartOnce {
+			f.failRestartUnit = ""
+		}
 		return errors.New("injected restart failure")
 	}
 	f.active[unit] = true
@@ -40,17 +53,92 @@ func (f *fakeOperator) Stop(_ context.Context, unit string) error {
 func (f *fakeOperator) IsActive(_ context.Context, unit string) (bool, error) {
 	return f.active[unit], nil
 }
-func (f *fakeOperator) StartCandidate(_ context.Context, unit, binary string, env map[string]string) error {
-	if !filepath.IsAbs(binary) || len(env) == 0 {
+func (f *fakeOperator) StartCandidate(_ context.Context, unit, binary, environmentFile string, env map[string]string) error {
+	if !filepath.IsAbs(binary) || !filepath.IsAbs(environmentFile) || len(env) == 0 {
 		return errors.New("bad candidate")
 	}
 	f.starts = append(f.starts, unit)
+	f.candidateFile = environmentFile
+	f.candidateEnvironment = make(map[string]string, len(env))
+	for key, value := range env {
+		f.candidateEnvironment[key] = value
+	}
 	f.active[unit] = true
 	return nil
 }
+func (f *fakeOperator) ProbeURL(_ context.Context, value, contains string) error {
+	f.publicProbes = append(f.publicProbes, value)
+	if f.failPublic || (f.failPublicAfter > 0 && len(f.publicProbes) >= f.failPublicAfter) {
+		return errors.New("injected public smoke failure")
+	}
+	if f.rejectMarkers && contains != "" {
+		return errors.New("unexpected future-release smoke marker")
+	}
+	return nil
+}
+
+func TestPublicSmokeFailureRestoresBlueGreenHandlerAndSlot(t *testing.T) {
+	cfg, old, fresh := baseConfig(t, "blue_green")
+	handler := filepath.Join(cfg.Deployment.Root, "handler.caddy")
+	template := filepath.Join(cfg.Deployment.Root, "handler.template")
+	original := []byte("reverse_proxy 127.0.0.1:8090\n")
+	_ = os.WriteFile(handler, original, 0o644)
+	_ = os.WriteFile(template, []byte("reverse_proxy {{UPSTREAM}}\n"), 0o644)
+	blue := filepath.Join(cfg.Deployment.Root, "slots", "blue")
+	green := filepath.Join(cfg.Deployment.Root, "slots", "green")
+	_ = replaceSymlink(blue, old)
+	_ = replaceSymlink(green, old)
+	cfg.Deployment.BlueGreen = &config.BlueGreen{CaddyConfig: filepath.Join(cfg.Deployment.Root, "Caddyfile"), CaddyHandler: handler, CaddyHandlerTemplate: template, BootstrapActive: "blue", Blue: config.Slot{Unit: "example-blue.service", Address: "127.0.0.1:8090", Link: blue}, Green: config.Slot{Unit: "example-green.service", Address: "127.0.0.1:8091", Link: green}}
+	operator := &fakeOperator{active: map[string]bool{}, failPublic: true}
+	if _, err := manager(operator, fresh).Deploy(context.Background(), cfg, Request{Activate: true}); err == nil {
+		t.Fatal("expected public smoke failure")
+	}
+	body, _ := os.ReadFile(handler)
+	if string(body) != string(original) {
+		t.Fatalf("handler not restored: %q", body)
+	}
+	target, err := resolveReleaseLink(cfg.Deployment.Root, green)
+	if err != nil || target != old {
+		t.Fatalf("green=%q err=%v", target, err)
+	}
+	record, err := state.Load(cfg.Deployment.StateFile, cfg.Deployment.Root, cfg.Deployment.Strategy)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if record.ActiveRelease != old || record.LastAttemptOutcome != "failed" || record.CandidateRelease != "" || record.LastAttemptRelease != fresh {
+		t.Fatalf("failed attempt state=%+v", record)
+	}
+}
+
+func TestContinuityFailureRestoresBlueGreenRoute(t *testing.T) {
+	cfg, old, fresh := baseConfig(t, "blue_green")
+	handler := filepath.Join(cfg.Deployment.Root, "handler.caddy")
+	template := filepath.Join(cfg.Deployment.Root, "handler.template")
+	original := []byte("reverse_proxy 127.0.0.1:8090\n")
+	_ = os.WriteFile(handler, original, 0o644)
+	_ = os.WriteFile(template, []byte("reverse_proxy {{UPSTREAM}}\n"), 0o644)
+	blue := filepath.Join(cfg.Deployment.Root, "slots", "blue")
+	green := filepath.Join(cfg.Deployment.Root, "slots", "green")
+	_ = replaceSymlink(blue, old)
+	_ = replaceSymlink(green, old)
+	cfg.Deployment.BlueGreen = &config.BlueGreen{CaddyConfig: filepath.Join(cfg.Deployment.Root, "Caddyfile"), CaddyHandler: handler, CaddyHandlerTemplate: template, BootstrapActive: "blue", Blue: config.Slot{Unit: "example-blue.service", Address: "127.0.0.1:8090", Link: blue}, Green: config.Slot{Unit: "example-green.service", Address: "127.0.0.1:8091", Link: green}}
+	operator := &fakeOperator{active: map[string]bool{}, failPublicAfter: 3}
+	if _, err := manager(operator, fresh).Deploy(context.Background(), cfg, Request{Activate: true, ApprovedSHA256: strings.Repeat("a", 64)}); err == nil || !strings.Contains(err.Error(), "continuity") {
+		t.Fatalf("expected continuity failure, got %v", err)
+	}
+	body, _ := os.ReadFile(handler)
+	if string(body) != string(original) {
+		t.Fatalf("handler not restored: %q", body)
+	}
+	target, err := resolveReleaseLink(cfg.Deployment.Root, green)
+	if err != nil || target != old {
+		t.Fatalf("green=%q err=%v", target, err)
+	}
+}
 func (f *fakeOperator) ValidateCaddy(context.Context, string) error { return nil }
 func (f *fakeOperator) ReloadCaddy(context.Context) error {
-	if f.failReload {
+	f.reloads++
+	if f.failReload || (f.failReloadAt > 0 && f.reloads == f.failReloadAt) {
 		return errors.New("injected reload failure")
 	}
 	return nil
@@ -69,7 +157,7 @@ func baseConfig(t *testing.T, strategy string) (config.Config, string, string) {
 	if err := os.MkdirAll(filepath.Join(root, "releases"), 0o755); err != nil {
 		t.Fatal(err)
 	}
-	old := filepath.Join(root, "releases", "legacy-old")
+	old := filepath.Join(root, "releases", "sha256-"+strings.Repeat("c", 64))
 	fresh := filepath.Join(root, "releases", "sha256-"+strings.Repeat("a", 64))
 	for _, dir := range []string{old, fresh} {
 		if err := os.Mkdir(dir, 0o755); err != nil {
@@ -79,11 +167,34 @@ func baseConfig(t *testing.T, strategy string) (config.Config, string, string) {
 			t.Fatal(err)
 		}
 	}
-	cfg := config.Config{SchemaVersion: 1, Service: config.Service{Name: "example-site", AllowedHost: "example.test"}, Build: config.Build{Package: "./cmd/site", Binary: "app", Branch: "main"}, Deployment: config.Deployment{Strategy: strategy, Root: root, LockFile: filepath.Join(root, "deploy.lock"), StateFile: filepath.Join(root, "state.json"), HealthPath: "/healthz", ReadinessPath: "/readyz", CandidateTimeoutSecs: 2, Smoke: []config.Smoke{{Path: "/", Contains: "Example"}}}}
+	cfg := config.Config{SchemaVersion: 2, Service: config.Service{Name: "example-site", AllowedHost: "example.test", EnvironmentFile: "/etc/tend/environment/example-site.env"}, Build: config.Build{Package: "./cmd/site", Binary: "app", Branch: "main"}, Deployment: config.Deployment{Strategy: strategy, Root: root, LockFile: filepath.Join(root, "deploy.lock"), StateFile: filepath.Join(root, "state.json"), EventLog: filepath.Join(root, "deployment-events.jsonl"), HealthPath: "/healthz", ReadinessPath: "/readyz", CandidateTimeoutSecs: 2, ActivationWindowSecs: 1, Smoke: []config.Smoke{{Path: "/", Contains: "Example"}}, PublicSmoke: []config.PublicSmoke{{URL: "https://example.test/", Contains: "Example"}}}}
 	return cfg, old, fresh
 }
 func manager(operator Operator, fresh string) Manager {
-	return Manager{Operator: operator, Now: func() time.Time { return time.Unix(100, 0).UTC() }, Prepare: func(config.Config, string, string, string) (string, error) { return fresh, nil }, Inspect: func(config.Config, string, string, string) error { return nil }}
+	return Manager{Operator: operator, Now: func() time.Time { return time.Unix(100, 0).UTC() }, Prepare: func(config.Config, string, string, string) (string, error) { return fresh, nil }, Inspect: func(config.Config, string, string, string) error { return nil }, ReadIdentity: func(string) (releaseIdentity, error) {
+		return releaseIdentity{Version: "v0.2.0-preview.1", Commit: strings.Repeat("b", 40)}, nil
+	}, OperationID: func() (string, error) { return strings.Repeat("d", 32), nil }, Sleep: func(context.Context, time.Duration) error { return nil }}
+}
+
+func singletonSettings(t *testing.T, cfg config.Config, currentRelease string) (*config.Singleton, string) {
+	t.Helper()
+	handler := filepath.Join(cfg.Deployment.Root, "handler.caddy")
+	template := filepath.Join(cfg.Deployment.Root, "handler.template")
+	if err := os.WriteFile(handler, []byte("reverse_proxy 127.0.0.1:8092\n"), 0o640); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(template, []byte("reverse_proxy {{UPSTREAM}}\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	current := filepath.Join(cfg.Deployment.Root, "current")
+	if err := replaceSymlink(current, currentRelease); err != nil {
+		t.Fatal(err)
+	}
+	return &config.Singleton{
+		Unit: "example-site.service", Address: "127.0.0.1:8092", CandidateAddress: "127.0.0.1:18092", ListenEnv: "EXAMPLE_LISTEN",
+		CurrentLink: current, PreviousLink: filepath.Join(cfg.Deployment.Root, "previous"), CaddyConfig: filepath.Join(cfg.Deployment.Root, "Caddyfile"),
+		CaddyHandler: handler, CaddyHandlerTemplate: template,
+	}, handler
 }
 
 func TestBlueGreenActivationAndRollback(t *testing.T) {
@@ -110,13 +221,28 @@ func TestBlueGreenActivationAndRollback(t *testing.T) {
 	}
 	operator := &fakeOperator{active: map[string]bool{"example-blue.service": true, "example-green.service": true}}
 	m := manager(operator, fresh)
-	report, err := m.Deploy(context.Background(), cfg, Request{Activate: true})
+	var events []eventlog.Event
+	m.AppendEvent = func(_ string, event eventlog.Event) error {
+		events = append(events, event)
+		return nil
+	}
+	report, err := m.Deploy(context.Background(), cfg, Request{Activate: true, ApprovedSHA256: strings.Repeat("a", 64)})
 	if err != nil {
 		t.Fatal(err)
 	}
 	if report.ActiveRelease != fresh || report.PreviousRelease != old {
 		t.Fatalf("report=%+v", report)
 	}
+	deployed, err := state.Load(cfg.Deployment.StateFile, cfg.Deployment.Root, cfg.Deployment.Strategy)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if deployed.DesiredRelease != fresh || deployed.CandidateRelease != "" || deployed.LastAttemptRelease != fresh || deployed.LastAttemptOutcome != "succeeded" {
+		t.Fatalf("deployment identity state=%+v", deployed)
+	}
+	if len(events) != 2 || events[0].Phase != "candidate" || events[0].Outcome != "running" || events[1].Phase != "activation" || events[1].Outcome != "succeeded" || events[0].OperationID != events[1].OperationID {
+		t.Fatalf("events=%+v", events)
+	}
 	if info, err := os.Stat(handler); err != nil || info.Mode().Perm() != 0o640 {
 		t.Fatalf("handler mode=%v err=%v", info.Mode().Perm(), err)
 	}
@@ -132,6 +258,9 @@ func TestBlueGreenActivationAndRollback(t *testing.T) {
 	if record.ActiveRelease != old || record.PreviousRelease != fresh {
 		t.Fatalf("rollback=%+v", record)
 	}
+	if len(events) != 4 || events[2].Phase != "rollback" || events[2].Outcome != "running" || events[3].Phase != "rollback" || events[3].Outcome != "succeeded" || events[2].OperationID != events[3].OperationID || events[2].ArtifactDigest != strings.Repeat("c", 64) {
+		t.Fatalf("rollback events=%+v", events)
+	}
 	if len(operator.probes) != 4 {
 		t.Fatalf("rollback probes=%#v", operator.probes)
 	}
@@ -142,6 +271,58 @@ func TestBlueGreenActivationAndRollback(t *testing.T) {
 	}
 }
 
+func TestDeploymentEvidenceCanNeverBlockActivationOrRollback(t *testing.T) {
+	cfg, old, fresh := baseConfig(t, "singleton_candidate")
+	cfg.Deployment.Singleton, _ = singletonSettings(t, cfg, old)
+	m := manager(&fakeOperator{active: map[string]bool{}}, fresh)
+	appendCalls := 0
+	m.AppendEvent = func(string, eventlog.Event) error {
+		appendCalls++
+		return errors.New("injected event failure")
+	}
+	report, err := m.Deploy(context.Background(), cfg, Request{Activate: true, ApprovedSHA256: strings.Repeat("a", 64)})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if report.EventWarnings != 2 || report.ActiveRelease != fresh {
+		t.Fatalf("report=%+v", report)
+	}
+	if _, err := m.Rollback(context.Background(), cfg); err != nil {
+		t.Fatal(err)
+	}
+	record, err := state.Load(cfg.Deployment.StateFile, cfg.Deployment.Root, cfg.Deployment.Strategy)
+	if err != nil || record.ActiveRelease != old || appendCalls != 4 {
+		t.Fatalf("record=%+v appends=%d err=%v", record, appendCalls, err)
+	}
+}
+
+func TestDeploymentEvidenceIdentityAndEntropyAreBestEffort(t *testing.T) {
+	for _, test := range []struct {
+		name   string
+		damage func(*Manager)
+	}{
+		{"identity", func(manager *Manager) {
+			manager.ReadIdentity = func(string) (releaseIdentity, error) {
+				return releaseIdentity{}, errors.New("injected identity failure")
+			}
+		}},
+		{"entropy", func(manager *Manager) {
+			manager.OperationID = func() (string, error) { return "", errors.New("injected entropy failure") }
+		}},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			cfg, old, fresh := baseConfig(t, "singleton_candidate")
+			cfg.Deployment.Singleton, _ = singletonSettings(t, cfg, old)
+			manager := manager(&fakeOperator{active: map[string]bool{}}, fresh)
+			test.damage(&manager)
+			report, err := manager.Deploy(context.Background(), cfg, Request{Activate: true, ApprovedSHA256: strings.Repeat("a", 64)})
+			if err != nil || report.EventWarnings != 1 || report.ActiveRelease != fresh {
+				t.Fatalf("report=%+v err=%v", report, err)
+			}
+		})
+	}
+}
+
 func TestBlueGreenCaddyFailureRestoresHandlerAndSlot(t *testing.T) {
 	cfg, old, fresh := baseConfig(t, "blue_green")
 	handler := filepath.Join(cfg.Deployment.Root, "handler.caddy")
@@ -167,37 +348,47 @@ func TestBlueGreenCaddyFailureRestoresHandlerAndSlot(t *testing.T) {
 	if err != nil || target != old {
 		t.Fatalf("green=%q err=%v", target, err)
 	}
-	if _, err := os.Stat(cfg.Deployment.StateFile); !os.IsNotExist(err) {
-		t.Fatal("failed activation wrote state")
+	failed, err := state.Load(cfg.Deployment.StateFile, cfg.Deployment.Root, cfg.Deployment.Strategy)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if failed.ActiveRelease != old || failed.LastAttemptOutcome != "failed" || failed.CandidateRelease != "" {
+		t.Fatalf("failed state=%+v", failed)
 	}
 }
 
 func TestSingletonRestartFailureRestoresPointers(t *testing.T) {
 	cfg, old, fresh := baseConfig(t, "singleton_candidate")
-	previous := filepath.Join(cfg.Deployment.Root, "previous")
-	current := filepath.Join(cfg.Deployment.Root, "current")
-	_ = replaceSymlink(current, old)
-	cfg.Deployment.Singleton = &config.Singleton{Unit: "example-site.service", Address: "127.0.0.1:8092", CandidateAddress: "127.0.0.1:18092", ListenEnv: "EXAMPLE_LISTEN", CurrentLink: current, PreviousLink: previous}
-	operator := &fakeOperator{active: map[string]bool{}, failRestartUnit: "example-site.service"}
+	settings, handler := singletonSettings(t, cfg, old)
+	cfg.Deployment.Singleton = settings
+	operator := &fakeOperator{active: map[string]bool{}, failRestartUnit: "example-site.service", failRestartOnce: true}
 	m := manager(operator, fresh)
 	if _, err := m.Deploy(context.Background(), cfg, Request{Activate: true}); err == nil {
 		t.Fatal("expected failure")
 	}
-	target, err := resolveReleaseLink(cfg.Deployment.Root, current)
+	target, err := resolveReleaseLink(cfg.Deployment.Root, cfg.Deployment.Singleton.CurrentLink)
 	if err != nil || target != old {
 		t.Fatalf("current=%q err=%v", target, err)
 	}
-	if _, err := os.Lstat(previous); !os.IsNotExist(err) {
+	if _, err := os.Lstat(cfg.Deployment.Singleton.PreviousLink); !os.IsNotExist(err) {
 		t.Fatal("previous pointer was not restored")
 	}
+	body, err := os.ReadFile(handler)
+	if err != nil || string(body) != "reverse_proxy 127.0.0.1:8092\n" {
+		t.Fatalf("handler=%q err=%v", body, err)
+	}
+	if info, err := os.Stat(handler); err != nil || info.Mode().Perm() != 0o640 {
+		t.Fatalf("handler mode=%v err=%v", info.Mode().Perm(), err)
+	}
+	if operator.active["example-site-tend-candidate.service"] {
+		t.Fatal("candidate was not stopped after successful restoration")
+	}
 }
 
-func TestStatePersistsOnlyAfterSuccessfulActivation(t *testing.T) {
+func TestStateRecordsSuccessfulActivation(t *testing.T) {
 	cfg, old, fresh := baseConfig(t, "singleton_candidate")
-	current := filepath.Join(cfg.Deployment.Root, "current")
-	previous := filepath.Join(cfg.Deployment.Root, "previous")
-	_ = replaceSymlink(current, old)
-	cfg.Deployment.Singleton = &config.Singleton{Unit: "example-site.service", Address: "127.0.0.1:8092", CandidateAddress: "127.0.0.1:18092", ListenEnv: "EXAMPLE_LISTEN", CurrentLink: current, PreviousLink: previous}
+	settings, handler := singletonSettings(t, cfg, old)
+	cfg.Deployment.Singleton = settings
 	operator := &fakeOperator{active: map[string]bool{}}
 	m := manager(operator, fresh)
 	if _, err := m.Deploy(context.Background(), cfg, Request{Activate: true}); err != nil {
@@ -210,4 +401,75 @@ func TestStatePersistsOnlyAfterSuccessfulActivation(t *testing.T) {
 	if record.ActiveRelease != fresh || record.PreviousRelease != old {
 		t.Fatalf("state=%+v", record)
 	}
+	if operator.candidateFile != cfg.Service.EnvironmentFile || len(operator.candidateEnvironment) != 1 || operator.candidateEnvironment["EXAMPLE_LISTEN"] != "127.0.0.1:18092" {
+		t.Fatalf("candidate file=%q environment=%#v", operator.candidateFile, operator.candidateEnvironment)
+	}
+	body, err := os.ReadFile(handler)
+	if err != nil || string(body) != "reverse_proxy 127.0.0.1:8092\n" {
+		t.Fatalf("handler=%q err=%v", body, err)
+	}
+	if operator.reloads != 2 || operator.active["example-site-tend-candidate.service"] {
+		t.Fatalf("reloads=%d active=%#v", operator.reloads, operator.active)
+	}
+}
+
+func TestSingletonContinuityFailureRestoresHandlerPointersAndService(t *testing.T) {
+	cfg, old, fresh := baseConfig(t, "singleton_candidate")
+	settings, handler := singletonSettings(t, cfg, old)
+	cfg.Deployment.Singleton = settings
+	operator := &fakeOperator{active: map[string]bool{"example-site.service": true}, failPublicAfter: 4}
+	m := manager(operator, fresh)
+	if _, err := m.Deploy(context.Background(), cfg, Request{Activate: true}); err == nil || !strings.Contains(err.Error(), "continuity") {
+		t.Fatalf("expected continuity failure, got %v", err)
+	}
+	current, err := resolveReleaseLink(cfg.Deployment.Root, cfg.Deployment.Singleton.CurrentLink)
+	if err != nil || current != old {
+		t.Fatalf("current=%q err=%v", current, err)
+	}
+	body, err := os.ReadFile(handler)
+	if err != nil || string(body) != "reverse_proxy 127.0.0.1:8092\n" {
+		t.Fatalf("handler=%q err=%v", body, err)
+	}
+	if operator.active["example-site-tend-candidate.service"] {
+		t.Fatal("candidate was not stopped after continuity restoration")
+	}
+}
+
+func TestSingletonCaddyReloadFailuresRestorePriorRoute(t *testing.T) {
+	for _, reload := range []int{1, 2} {
+		t.Run(fmt.Sprintf("reload-%d", reload), func(t *testing.T) {
+			cfg, old, fresh := baseConfig(t, "singleton_candidate")
+			settings, handler := singletonSettings(t, cfg, old)
+			cfg.Deployment.Singleton = settings
+			operator := &fakeOperator{active: map[string]bool{"example-site.service": true}, failReloadAt: reload}
+			if _, err := manager(operator, fresh).Deploy(context.Background(), cfg, Request{Activate: true}); err == nil || !strings.Contains(err.Error(), "Caddy reload failed") {
+				t.Fatalf("expected Caddy reload failure, got %v", err)
+			}
+			current, err := resolveReleaseLink(cfg.Deployment.Root, settings.CurrentLink)
+			if err != nil || current != old {
+				t.Fatalf("current=%q err=%v", current, err)
+			}
+			body, err := os.ReadFile(handler)
+			if err != nil || string(body) != "reverse_proxy 127.0.0.1:8092\n" {
+				t.Fatalf("handler=%q err=%v", body, err)
+			}
+			if operator.active["example-site-tend-candidate.service"] {
+				t.Fatal("candidate was not stopped after route restoration")
+			}
+		})
+	}
+}
+
+func TestSingletonIncompleteRecoveryKeepsProvenCandidateRunning(t *testing.T) {
+	cfg, old, fresh := baseConfig(t, "singleton_candidate")
+	settings, _ := singletonSettings(t, cfg, old)
+	cfg.Deployment.Singleton = settings
+	operator := &fakeOperator{active: map[string]bool{"example-site.service": true}, failReload: true}
+	_, err := manager(operator, fresh).Deploy(context.Background(), cfg, Request{Activate: true})
+	if err == nil || !strings.Contains(err.Error(), "candidate remains routed for operator recovery") {
+		t.Fatalf("expected explicit incomplete recovery, got %v", err)
+	}
+	if !operator.active["example-site-tend-candidate.service"] {
+		t.Fatal("proven candidate was stopped despite incomplete route restoration")
+	}
 }

internal/deploy/lock_linux_test.go

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+//go:build linux
+
+package deploy
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestHostWideLockSerializesIndependentServices(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "tend-deploy.lock")
+	first, err := acquireLock(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer first.Close()
+	if second, err := acquireLock(path); err == nil {
+		_ = second.Close()
+		t.Fatal("second service acquired the shared activation lock")
+	}
+	if err = first.Close(); err != nil {
+		t.Fatal(err)
+	}
+	third, err := acquireLock(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_ = third.Close()
+}

internal/deploy/operator.go

@@ -20,10 +20,11 @@ type Operator interface {
 	Restart(context.Context, string) error
 	Stop(context.Context, string) error
 	IsActive(context.Context, string) (bool, error)
-	StartCandidate(context.Context, string, string, map[string]string) error
+	StartCandidate(context.Context, string, string, string, map[string]string) error
 	ValidateCaddy(context.Context, string) error
 	ReloadCaddy(context.Context) error
 	Probe(context.Context, string, string, string, string) error
+	ProbeURL(context.Context, string, string) error
 }
 
 type SystemOperator struct {
@@ -49,7 +50,7 @@ func (o SystemOperator) IsActive(ctx context.Context, unit string) (bool, error)
 	}
 	return strings.TrimSpace(string(out)) == "active", nil
 }
-func (o SystemOperator) StartCandidate(ctx context.Context, unit, binary string, env map[string]string) error {
+func (o SystemOperator) StartCandidate(ctx context.Context, unit, binary, environmentFile string, env map[string]string) error {
 	args := []string{
 		"--unit", unit, "--collect",
 		"--property=DynamicUser=yes", "--property=NoNewPrivileges=yes",
@@ -63,6 +64,7 @@ func (o SystemOperator) StartCandidate(ctx context.Context, unit, binary string,
 		"--property=RestrictSUIDSGID=yes", "--property=LockPersonality=yes",
 		"--property=MemoryDenyWriteExecute=yes", "--property=CapabilityBoundingSet=",
 		"--property=AmbientCapabilities=",
+		"--property=EnvironmentFile=" + environmentFile,
 	}
 	keys := make([]string, 0, len(env))
 	for key := range env {
@@ -86,11 +88,23 @@ func (o SystemOperator) ReloadCaddy(ctx context.Context) error {
 }
 func (o SystemOperator) Probe(ctx context.Context, address, host, path, contains string) error {
 	u := url.URL{Scheme: "http", Host: address, Path: path}
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
+	return o.probeRequest(ctx, u.String(), host, contains)
+}
+func (o SystemOperator) ProbeURL(ctx context.Context, value, contains string) error {
+	u, err := url.Parse(value)
+	if err != nil || u.Scheme != "https" || u.Host == "" || u.User != nil || u.Fragment != "" {
+		return errors.New("public probe URL is invalid")
+	}
+	return o.probeRequest(ctx, u.String(), "", contains)
+}
+func (o SystemOperator) probeRequest(ctx context.Context, value, host, contains string) error {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, value, nil)
 	if err != nil {
 		return err
 	}
-	req.Host = host
+	if host != "" {
+		req.Host = host
+	}
 	client := &http.Client{Timeout: o.Timeout, CheckRedirect: func(*http.Request, []*http.Request) error { return errors.New("redirect refused") }}
 	response, err := client.Do(req)
 	if err != nil {

internal/deploy/operator_test.go

@@ -5,6 +5,7 @@ package deploy
 import (
 	"context"
 	"reflect"
+	"strings"
 	"testing"
 )
 
@@ -23,13 +24,13 @@ func TestStartCandidateUsesArgumentVectorAndHardenedUnit(t *testing.T) {
 	runner := &recordingRunner{}
 	operator := SystemOperator{Runner: runner}
 	env := map[string]string{"Z_ENV": "safe value", "A_ENV": "first"}
-	if err := operator.StartCandidate(context.Background(), "example-tend-candidate.service", "/opt/example/releases/sha256-a/app", env); err != nil {
+	if err := operator.StartCandidate(context.Background(), "example-tend-candidate.service", "/opt/example/releases/sha256-a/app", "/etc/tend/environment/example.env", env); err != nil {
 		t.Fatal(err)
 	}
 	if runner.name != "systemd-run" {
 		t.Fatalf("command=%q", runner.name)
 	}
-	required := []string{"--property=DynamicUser=yes", "--property=NoNewPrivileges=yes", "--property=ProtectSystem=strict", "--property=MemoryDenyWriteExecute=yes", "--property=CapabilityBoundingSet=", "--setenv", "A_ENV=first", "--setenv", "Z_ENV=safe value", "--", "/opt/example/releases/sha256-a/app"}
+	required := []string{"--property=DynamicUser=yes", "--property=NoNewPrivileges=yes", "--property=ProtectSystem=strict", "--property=MemoryDenyWriteExecute=yes", "--property=CapabilityBoundingSet=", "--property=EnvironmentFile=/etc/tend/environment/example.env", "--setenv", "A_ENV=first", "--setenv", "Z_ENV=safe value", "--", "/opt/example/releases/sha256-a/app"}
 	cursor := 0
 	for _, arg := range runner.args {
 		if cursor < len(required) && arg == required[cursor] {
@@ -42,4 +43,7 @@ func TestStartCandidateUsesArgumentVectorAndHardenedUnit(t *testing.T) {
 	if reflect.DeepEqual(runner.args, []string{"sh", "-c"}) {
 		t.Fatal("candidate command used a shell")
 	}
+	if strings.Contains(strings.Join(runner.args, "\n"), "SUPER_SECRET") {
+		t.Fatal("candidate arguments exposed a secret value")
+	}
 }

internal/deploy/release.go

@@ -196,6 +196,15 @@ func extractArtifact(artifact, stage string) error {
 			_ = out.Close()
 			return err
 		}
+		// OpenFile modes are filtered through the caller's umask. Tend is
+		// commonly invoked by a root account with umask 0077, while release
+		// binaries must remain executable by their dedicated service users.
+		// Reapply the validated, name-derived mode explicitly before the file
+		// becomes part of an immutable release.
+		if err := out.Chmod(mode); err != nil {
+			_ = out.Close()
+			return err
+		}
 		if err := out.Sync(); err != nil {
 			_ = out.Close()
 			return err

internal/deploy/release_mode_linux_test.go

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+//go:build linux
+
+package deploy
+
+import (
+	"archive/tar"
+	"compress/gzip"
+	"os"
+	"path/filepath"
+	"syscall"
+	"testing"
+)
+
+func TestExtractArtifactAppliesReleaseModesUnderRestrictiveUmask(t *testing.T) {
+	dir := t.TempDir()
+	artifact := filepath.Join(dir, "release.tar.gz")
+	file, err := os.OpenFile(artifact, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
+	if err != nil {
+		t.Fatal(err)
+	}
+	gz := gzip.NewWriter(file)
+	tw := tar.NewWriter(gz)
+	entries := map[string][]byte{
+		"bundle/app":            []byte("executable"),
+		"bundle/BUILDINFO.json": []byte("{}"),
+		"bundle/RELEASE.json":   []byte("{}"),
+		"bundle/SBOM.spdx.json": []byte("{}"),
+		"bundle/SHA256SUMS":     []byte("checksums"),
+	}
+	for name, body := range entries {
+		if err := tw.WriteHeader(&tar.Header{Name: name, Typeflag: tar.TypeReg, Mode: 0o600, Size: int64(len(body))}); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := tw.Write(body); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := tw.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := gz.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := file.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	oldUmask := syscall.Umask(0o077)
+	t.Cleanup(func() { syscall.Umask(oldUmask) })
+	stage := filepath.Join(dir, "stage")
+	if err := os.Mkdir(stage, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	if err := extractArtifact(artifact, stage); err != nil {
+		t.Fatal(err)
+	}
+
+	for name, want := range map[string]os.FileMode{
+		"app":            0o755,
+		"BUILDINFO.json": 0o644,
+		"RELEASE.json":   0o644,
+		"SBOM.spdx.json": 0o644,
+		"SHA256SUMS":     0o644,
+	} {
+		info, err := os.Stat(filepath.Join(stage, name))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got := info.Mode().Perm(); got != want {
+			t.Fatalf("%s mode=%#o want=%#o", name, got, want)
+		}
+	}
+}

internal/eventlog/eventlog.go

@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package eventlog
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+	"syscall"
+	"time"
+)
+
+const Version = 1
+
+var safeValue = regexp.MustCompile(`^[A-Za-z0-9._:/@+-]{1,256}$`)
+var hexDigest = regexp.MustCompile(`^[0-9a-f]{64}$`)
+var gitCommit = regexp.MustCompile(`^[0-9a-f]{40}$`)
+var operationID = regexp.MustCompile(`^[0-9a-f]{32}$`)
+
+type Event struct {
+	Version        int    `json:"version"`
+	OperationID    string `json:"operation_id"`
+	Service        string `json:"service"`
+	ArtifactDigest string `json:"artifact_digest"`
+	Commit         string `json:"commit"`
+	ReleaseVersion string `json:"release_version"`
+	Phase          string `json:"phase"`
+	Slot           string `json:"slot,omitempty"`
+	DurationMillis int64  `json:"duration_ms"`
+	Outcome        string `json:"outcome"`
+	ObservedAt     string `json:"observed_at"`
+}
+
+func OperationID() (string, error) {
+	b := make([]byte, 16)
+	if _, err := rand.Read(b); err != nil {
+		return "", errors.New("cryptographic randomness unavailable")
+	}
+	return hex.EncodeToString(b), nil
+}
+
+func Append(path string, event Event) error {
+	if err := event.validate(); err != nil {
+		return err
+	}
+	if !filepath.IsAbs(path) || filepath.Clean(path) != path {
+		return errors.New("event log path must be absolute and clean")
+	}
+	if err := os.MkdirAll(filepath.Dir(path), 0o750); err != nil {
+		return fmt.Errorf("create event directory: %w", err)
+	}
+	if info, err := os.Lstat(path); err == nil {
+		if !info.Mode().IsRegular() || info.Mode()&os.ModeSymlink != 0 || info.Mode().Perm()&0o022 != 0 {
+			return errors.New("event log must be a non-writable regular non-symlink file")
+		}
+	} else if !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("inspect event log: %w", err)
+	}
+	b, err := json.Marshal(event)
+	if err != nil {
+		return fmt.Errorf("encode deployment event: %w", err)
+	}
+	if len(b) > 4096 {
+		return errors.New("deployment event exceeds bound")
+	}
+	b = append(b, '\n')
+	fd, err := syscall.Open(path, syscall.O_WRONLY|syscall.O_APPEND|syscall.O_CREAT|syscall.O_CLOEXEC|syscall.O_NOFOLLOW, 0o640)
+	if err != nil {
+		return fmt.Errorf("open event log: %w", err)
+	}
+	file := os.NewFile(uintptr(fd), path)
+	if file == nil {
+		_ = syscall.Close(fd)
+		return errors.New("open event log file")
+	}
+	defer file.Close()
+	n, err := file.Write(b)
+	if err != nil || n != len(b) {
+		return errors.New("write complete deployment event")
+	}
+	if err := file.Sync(); err != nil {
+		return fmt.Errorf("sync deployment event: %w", err)
+	}
+	return nil
+}
+
+func (e Event) validate() error {
+	if e.Version != Version || !operationID.MatchString(e.OperationID) {
+		return errors.New("deployment event identity is invalid")
+	}
+	if !hexDigest.MatchString(e.ArtifactDigest) || !gitCommit.MatchString(e.Commit) {
+		return errors.New("deployment event provenance is invalid")
+	}
+	for label, value := range map[string]string{"service": e.Service, "artifact_digest": e.ArtifactDigest, "commit": e.Commit, "release_version": e.ReleaseVersion, "phase": e.Phase, "outcome": e.Outcome} {
+		if !safeValue.MatchString(value) || strings.ContainsRune(value, '\x00') {
+			return fmt.Errorf("deployment event %s is invalid", label)
+		}
+	}
+	if e.Slot != "" && !safeValue.MatchString(e.Slot) {
+		return errors.New("deployment event slot is invalid")
+	}
+	if e.DurationMillis < 0 {
+		return errors.New("deployment event duration is invalid")
+	}
+	if _, err := time.Parse(time.RFC3339Nano, e.ObservedAt); err != nil {
+		return errors.New("deployment event timestamp is invalid")
+	}
+	return nil
+}

internal/eventlog/eventlog_test.go

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package eventlog
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestAppendBoundedEvent(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "events.jsonl")
+	id, err := OperationID()
+	if err != nil {
+		t.Fatal(err)
+	}
+	event := Event{Version: 1, OperationID: id, Service: "site", ArtifactDigest: strings.Repeat("a", 64), Commit: strings.Repeat("b", 40), ReleaseVersion: "v0.2.0-preview.1", Phase: "activation", Slot: "green", Outcome: "succeeded", ObservedAt: time.Now().UTC().Format(time.RFC3339Nano)}
+	if err := Append(path, event); err != nil {
+		t.Fatal(err)
+	}
+	b, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var decoded Event
+	if err := json.Unmarshal(b, &decoded); err != nil {
+		t.Fatal(err)
+	}
+	if decoded.OperationID != id || strings.Contains(string(b), "secret") {
+		t.Fatalf("unexpected event: %s", b)
+	}
+	if info, _ := os.Stat(path); info.Mode().Perm() != 0o640 {
+		t.Fatalf("mode=%04o", info.Mode().Perm())
+	}
+}
+
+func TestAppendRejectsUnboundedValuesAndSymlink(t *testing.T) {
+	id, _ := OperationID()
+	event := Event{Version: 1, OperationID: id, Service: "site\nsecret", ArtifactDigest: "digest", Commit: "commit", ReleaseVersion: "version", Phase: "activation", Outcome: "failed", ObservedAt: time.Now().UTC().Format(time.RFC3339Nano)}
+	if err := Append(filepath.Join(t.TempDir(), "events.jsonl"), event); err == nil {
+		t.Fatal("expected unsafe value rejection")
+	}
+	dir := t.TempDir()
+	target := filepath.Join(dir, "target")
+	if err := os.WriteFile(target, nil, 0o640); err != nil {
+		t.Fatal(err)
+	}
+	link := filepath.Join(dir, "events.jsonl")
+	if err := os.Symlink(target, link); err != nil {
+		t.Skip(err)
+	}
+	event.Service = "site"
+	if err := Append(link, event); err == nil {
+		t.Fatal("expected symlink rejection")
+	}
+}

internal/serverpolicy/ownership_linux.go

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+//go:build linux
+
+package serverpolicy
+
+import (
+	"os"
+	"syscall"
+)
+
+func rootOwned(info os.FileInfo) bool {
+	stat, ok := info.Sys().(*syscall.Stat_t)
+	return ok && stat.Uid == 0
+}

internal/serverpolicy/ownership_other.go

@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+//go:build !linux
+
+package serverpolicy
+
+import "os"
+
+func rootOwned(os.FileInfo) bool { return false }

internal/serverpolicy/policy.go

@@ -0,0 +1,300 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+// Package serverpolicy validates the root-owned allowlist used by Tend's
+// restricted SSH receiver. It contains service names and paths, never secrets.
+package serverpolicy
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+
+	"gamertan.com/tend/internal/config"
+)
+
+const SchemaVersion = 1
+
+var servicePattern = regexp.MustCompile(`^[a-z][a-z0-9-]{1,62}$`)
+
+type Policy struct {
+	SchemaVersion  int                      `json:"schema_version"`
+	ConfigRoot     string                   `json:"config_root"`
+	IncomingRoot   string                   `json:"incoming_root"`
+	SharedLockFile string                   `json:"shared_lock_file"`
+	Services       map[string]ServicePolicy `json:"services"`
+}
+
+type ServicePolicy struct {
+	Config           string `json:"config"`
+	MaxArtifactBytes int64  `json:"max_artifact_bytes"`
+}
+
+type CheckedService struct {
+	Name   string
+	Config config.Config
+	Policy ServicePolicy
+}
+
+func Parse(reader io.Reader) (Policy, error) {
+	limited := io.LimitReader(reader, 1<<20+1)
+	body, err := io.ReadAll(limited)
+	if err != nil {
+		return Policy{}, err
+	}
+	if len(body) > 1<<20 {
+		return Policy{}, errors.New("server policy exceeds 1 MiB")
+	}
+	decoder := json.NewDecoder(bytes.NewReader(body))
+	decoder.DisallowUnknownFields()
+	var policy Policy
+	if err = decoder.Decode(&policy); err != nil {
+		return Policy{}, fmt.Errorf("decode server policy: %w", err)
+	}
+	var trailing any
+	if err = decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
+		return Policy{}, errors.New("server policy contains trailing data")
+	}
+	if err = policy.Validate(); err != nil {
+		return Policy{}, err
+	}
+	return policy, nil
+}
+
+func Load(path string) (Policy, error) {
+	if err := secureDirectory(filepath.Dir(path), 0); err != nil {
+		return Policy{}, fmt.Errorf("server policy directory: %w", err)
+	}
+	if err := secureFile(path, 0o600); err != nil {
+		return Policy{}, fmt.Errorf("server policy: %w", err)
+	}
+	file, err := os.Open(path)
+	if err != nil {
+		return Policy{}, err
+	}
+	defer file.Close()
+	return Parse(file)
+}
+
+func (policy Policy) Validate() error {
+	if policy.SchemaVersion != SchemaVersion {
+		return fmt.Errorf("server policy schema_version must be %d", SchemaVersion)
+	}
+	if policy.ConfigRoot != "/etc/tend/services" {
+		return errors.New("server policy config_root must be /etc/tend/services")
+	}
+	if policy.IncomingRoot != "/var/lib/tend/incoming" {
+		return errors.New("server policy incoming_root must be /var/lib/tend/incoming")
+	}
+	if policy.SharedLockFile != config.SharedLockFile {
+		return fmt.Errorf("server policy shared_lock_file must be %s", config.SharedLockFile)
+	}
+	if len(policy.Services) == 0 || len(policy.Services) > 128 {
+		return errors.New("server policy must allow 1 to 128 services")
+	}
+	for name, service := range policy.Services {
+		if !servicePattern.MatchString(name) {
+			return fmt.Errorf("invalid service name %q", name)
+		}
+		expected := filepath.Join(policy.ConfigRoot, name+".json")
+		if service.Config != expected {
+			return fmt.Errorf("service %s config must be %s", name, expected)
+		}
+		if service.MaxArtifactBytes < 1<<20 || service.MaxArtifactBytes > 512<<20 {
+			return fmt.Errorf("service %s artifact limit is invalid", name)
+		}
+	}
+	return nil
+}
+
+func (policy Policy) CheckFiles() ([]CheckedService, error) {
+	if err := policy.CheckDirectories(); err != nil {
+		return nil, err
+	}
+	names := make([]string, 0, len(policy.Services))
+	for name := range policy.Services {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	checked := make([]CheckedService, 0, len(names))
+	for _, name := range names {
+		service, err := policy.CheckService(name)
+		if err != nil {
+			return nil, err
+		}
+		checked = append(checked, service)
+	}
+	return checked, nil
+}
+
+func (policy Policy) CheckDirectories() error {
+	if err := secureDirectory(policy.ConfigRoot, 0); err != nil {
+		return fmt.Errorf("config root: %w", err)
+	}
+	if err := secureDirectory(policy.IncomingRoot, 0o700); err != nil {
+		return fmt.Errorf("incoming root: %w", err)
+	}
+	if err := secureDirectory("/etc/tend/environment", 0o700); err != nil {
+		return fmt.Errorf("environment root: %w", err)
+	}
+	return nil
+}
+
+func (policy Policy) CheckService(name string) (CheckedService, error) {
+	entry, ok := policy.Services[name]
+	if !ok {
+		return CheckedService{}, errors.New("service is not allowed by server policy")
+	}
+	if err := secureFile(entry.Config, 0); err != nil {
+		return CheckedService{}, fmt.Errorf("service %s config: %w", name, err)
+	}
+	cfg, err := config.Load(entry.Config)
+	if err != nil {
+		return CheckedService{}, fmt.Errorf("service %s config: %w", name, err)
+	}
+	if cfg.Service.Name != name {
+		return CheckedService{}, fmt.Errorf("service %s config identity does not match", name)
+	}
+	if cfg.Deployment.LockFile != policy.SharedLockFile {
+		return CheckedService{}, fmt.Errorf("service %s does not use the host-wide lock", name)
+	}
+	if err = secureFile(cfg.Service.EnvironmentFile, 0o600); err != nil {
+		return CheckedService{}, fmt.Errorf("service %s environment file: %w", name, err)
+	}
+	if cfg.Deployment.Singleton != nil {
+		if err = rejectEnvironmentKey(cfg.Service.EnvironmentFile, cfg.Deployment.Singleton.ListenEnv); err != nil {
+			return CheckedService{}, fmt.Errorf("service %s environment file: %w", name, err)
+		}
+	}
+	return CheckedService{Name: name, Config: cfg, Policy: entry}, nil
+}
+
+func CheckConfig(path string, cfg config.Config) error {
+	expected := filepath.Join("/etc/tend/services", cfg.Service.Name+".json")
+	if path != expected {
+		return fmt.Errorf("production config must be %s", expected)
+	}
+	if err := secureDirectory("/etc/tend/services", 0); err != nil {
+		return fmt.Errorf("config root: %w", err)
+	}
+	if err := secureDirectory("/etc/tend/environment", 0o700); err != nil {
+		return fmt.Errorf("environment root: %w", err)
+	}
+	if err := secureFile(path, 0); err != nil {
+		return fmt.Errorf("production config: %w", err)
+	}
+	if cfg.Deployment.LockFile != config.SharedLockFile {
+		return fmt.Errorf("deployment lock must be %s", config.SharedLockFile)
+	}
+	if err := secureFile(cfg.Service.EnvironmentFile, 0o600); err != nil {
+		return fmt.Errorf("environment file: %w", err)
+	}
+	if cfg.Deployment.Singleton != nil {
+		if err := rejectEnvironmentKey(cfg.Service.EnvironmentFile, cfg.Deployment.Singleton.ListenEnv); err != nil {
+			return fmt.Errorf("environment file: %w", err)
+		}
+	}
+	return nil
+}
+
+func rejectEnvironmentKey(path, key string) error {
+	file, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	body, err := io.ReadAll(io.LimitReader(file, 1<<20+1))
+	if err != nil {
+		return err
+	}
+	if len(body) > 1<<20 {
+		return errors.New("environment file exceeds 1 MiB")
+	}
+	for _, raw := range bytes.Split(body, []byte{'\n'}) {
+		line := strings.TrimSpace(string(raw))
+		if !strings.HasPrefix(line, key) {
+			continue
+		}
+		remainder := strings.TrimSpace(strings.TrimPrefix(line, key))
+		if strings.HasPrefix(remainder, "=") {
+			return errors.New("singleton candidate listen key must not be set in the shared environment file")
+		}
+	}
+	return nil
+}
+
+func secureFile(path string, exactMode os.FileMode) error {
+	if !filepath.IsAbs(path) || filepath.Clean(path) != path || strings.ContainsRune(path, '\x00') {
+		return errors.New("path must be clean and absolute")
+	}
+	if err := rejectSymlinkAncestors(filepath.Dir(path)); err != nil {
+		return err
+	}
+	info, err := os.Lstat(path)
+	if err != nil {
+		return err
+	}
+	if !info.Mode().IsRegular() || info.Mode()&os.ModeSymlink != 0 {
+		return errors.New("must be a regular non-symlink file")
+	}
+	if !rootOwned(info) {
+		return errors.New("must be owned by root")
+	}
+	if exactMode != 0 && info.Mode().Perm() != exactMode {
+		return fmt.Errorf("mode must be %04o", exactMode)
+	}
+	if exactMode == 0 && info.Mode().Perm()&0o022 != 0 {
+		return errors.New("must not be group- or world-writable")
+	}
+	return nil
+}
+
+func secureDirectory(path string, exactMode os.FileMode) error {
+	if !filepath.IsAbs(path) || filepath.Clean(path) != path || strings.ContainsRune(path, '\x00') {
+		return errors.New("path must be clean and absolute")
+	}
+	if err := rejectSymlinkAncestors(filepath.Dir(path)); err != nil {
+		return err
+	}
+	info, err := os.Lstat(path)
+	if err != nil {
+		return err
+	}
+	if !info.IsDir() || info.Mode()&os.ModeSymlink != 0 {
+		return errors.New("must be a real directory")
+	}
+	if !rootOwned(info) {
+		return errors.New("must be owned by root")
+	}
+	if exactMode != 0 && info.Mode().Perm() != exactMode {
+		return fmt.Errorf("mode must be %04o", exactMode)
+	}
+	if exactMode == 0 && info.Mode().Perm()&0o022 != 0 {
+		return errors.New("must not be group- or world-writable")
+	}
+	return nil
+}
+
+func rejectSymlinkAncestors(path string) error {
+	current := string(filepath.Separator)
+	for _, part := range strings.Split(strings.TrimPrefix(filepath.Clean(path), string(filepath.Separator)), string(filepath.Separator)) {
+		if part == "" {
+			continue
+		}
+		current = filepath.Join(current, part)
+		info, err := os.Lstat(current)
+		if err != nil {
+			return err
+		}
+		if !info.IsDir() || info.Mode()&os.ModeSymlink != 0 {
+			return fmt.Errorf("symlink or non-directory ancestor refused: %s", current)
+		}
+	}
+	return nil
+}

internal/serverpolicy/policy_test.go

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package serverpolicy
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestParseAcceptsStrictServiceMap(t *testing.T) {
+	body := `{"schema_version":1,"config_root":"/etc/tend/services","incoming_root":"/var/lib/tend/incoming","shared_lock_file":"/run/lock/tend-deploy.lock","services":{"example-site":{"config":"/etc/tend/services/example-site.json","max_artifact_bytes":1048576}}}`
+	policy, err := Parse(strings.NewReader(body))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if policy.Services["example-site"].MaxArtifactBytes != 1<<20 {
+		t.Fatalf("policy=%+v", policy)
+	}
+}
+
+func TestRejectEnvironmentKeyProtectsSingletonCandidateOverride(t *testing.T) {
+	directory := t.TempDir()
+	path := filepath.Join(directory, "service.env")
+	for _, test := range []struct {
+		name    string
+		body    string
+		wantErr bool
+	}{
+		{name: "shared values only", body: "APP_SECRET=private\n"},
+		{name: "exact listen key", body: "EXAMPLE_LISTEN=127.0.0.1:8092\n", wantErr: true},
+		{name: "spaced listen key", body: "  EXAMPLE_LISTEN = 127.0.0.1:8092\n", wantErr: true},
+		{name: "commented listen key", body: "# EXAMPLE_LISTEN=127.0.0.1:8092\n"},
+		{name: "longer key", body: "EXAMPLE_LISTENER=safe\n"},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			if err := os.WriteFile(path, []byte(test.body), 0o600); err != nil {
+				t.Fatal(err)
+			}
+			err := rejectEnvironmentKey(path, "EXAMPLE_LISTEN")
+			if (err != nil) != test.wantErr {
+				t.Fatalf("error=%v wantErr=%v", err, test.wantErr)
+			}
+		})
+	}
+}
+
+func TestParseRejectsUnknownAndForgedPaths(t *testing.T) {
+	tests := []string{
+		`{"schema_version":1,"config_root":"/etc/tend/services","incoming_root":"/var/lib/tend/incoming","shared_lock_file":"/run/lock/tend-deploy.lock","services":{"example-site":{"config":"/tmp/example.json","max_artifact_bytes":1048576}}}`,
+		`{"schema_version":1,"config_root":"/etc/tend/services","incoming_root":"/var/lib/tend/incoming","shared_lock_file":"/run/lock/tend-deploy.lock","services":{},"surprise":true}`,
+	}
+	for _, body := range tests {
+		if _, err := Parse(strings.NewReader(body)); err == nil {
+			t.Fatalf("accepted %s", body)
+		}
+	}
+}

internal/state/state.go

@@ -17,13 +17,18 @@ import (
 const SchemaVersion = 1
 
 type Record struct {
-	SchemaVersion   int    `json:"schema_version"`
-	Strategy        string `json:"strategy"`
-	ActiveSlot      string `json:"active_slot"`
-	ActiveRelease   string `json:"active_release"`
-	PreviousSlot    string `json:"previous_slot,omitempty"`
-	PreviousRelease string `json:"previous_release,omitempty"`
-	UpdatedAt       string `json:"updated_at"`
+	SchemaVersion      int    `json:"schema_version"`
+	Strategy           string `json:"strategy"`
+	DesiredRelease     string `json:"desired_release,omitempty"`
+	CandidateRelease   string `json:"candidate_release,omitempty"`
+	ActiveSlot         string `json:"active_slot"`
+	ActiveRelease      string `json:"active_release"`
+	PreviousSlot       string `json:"previous_slot,omitempty"`
+	PreviousRelease    string `json:"previous_release,omitempty"`
+	LastAttemptRelease string `json:"last_attempt_release,omitempty"`
+	LastAttemptOutcome string `json:"last_attempt_outcome,omitempty"`
+	LastAttemptAt      string `json:"last_attempt_at,omitempty"`
+	UpdatedAt          string `json:"updated_at"`
 }
 
 func Load(path, root, strategy string) (Record, error) {
@@ -68,6 +73,26 @@ func (r Record) Validate(root, strategy string) error {
 			return fmt.Errorf("previous release: %w", err)
 		}
 	}
+	for label, release := range map[string]string{"desired release": r.DesiredRelease, "candidate release": r.CandidateRelease, "last attempt release": r.LastAttemptRelease} {
+		if release != "" {
+			if err := releaseBelow(root, release); err != nil {
+				return fmt.Errorf("%s: %w", label, err)
+			}
+		}
+	}
+	if r.LastAttemptOutcome != "" {
+		switch r.LastAttemptOutcome {
+		case "running", "succeeded", "failed", "rolled_back":
+		default:
+			return errors.New("last attempt outcome is invalid")
+		}
+		if _, err := time.Parse(time.RFC3339, r.LastAttemptAt); err != nil {
+			return errors.New("last attempt timestamp is invalid")
+		}
+	}
+	if r.LastAttemptOutcome == "running" && r.CandidateRelease == "" {
+		return errors.New("running attempt requires a candidate release")
+	}
 	if strategy == "blue_green" && r.PreviousRelease != "" && r.PreviousSlot == r.ActiveSlot {
 		return errors.New("previous slot must differ from active slot")
 	}

internal/state/state_test.go

@@ -16,7 +16,8 @@ func TestStoreLoadRoundTripAndRejectSymlink(t *testing.T) {
 		t.Fatal(err)
 	}
 	path := filepath.Join(root, "state.json")
-	record := Record{SchemaVersion: 1, Strategy: "singleton_candidate", ActiveSlot: "singleton", ActiveRelease: release, UpdatedAt: time.Unix(1, 0).UTC().Format(time.RFC3339)}
+	at := time.Unix(1, 0).UTC().Format(time.RFC3339)
+	record := Record{SchemaVersion: 1, Strategy: "singleton_candidate", DesiredRelease: release, ActiveSlot: "singleton", ActiveRelease: release, LastAttemptRelease: release, LastAttemptOutcome: "succeeded", LastAttemptAt: at, UpdatedAt: at}
 	if err := Store(path, root, record); err != nil {
 		t.Fatal(err)
 	}
@@ -24,8 +25,8 @@ func TestStoreLoadRoundTripAndRejectSymlink(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if loaded.ActiveRelease != release {
-		t.Fatalf("release=%q", loaded.ActiveRelease)
+	if loaded.ActiveRelease != release || loaded.DesiredRelease != release || loaded.LastAttemptOutcome != "succeeded" {
+		t.Fatalf("state=%+v", loaded)
 	}
 	if err := os.Remove(path); err != nil {
 		t.Fatal(err)
@@ -37,6 +38,15 @@ func TestStoreLoadRoundTripAndRejectSymlink(t *testing.T) {
 		t.Fatal("expected symlink refusal")
 	}
 }
+
+func TestRecordRequiresCandidateForRunningAttempt(t *testing.T) {
+	root := filepath.Join(t.TempDir(), "service")
+	release := filepath.Join(root, "releases", "sha256-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")
+	record := Record{SchemaVersion: 1, Strategy: "singleton_candidate", DesiredRelease: release, ActiveSlot: "singleton", ActiveRelease: release, LastAttemptRelease: release, LastAttemptOutcome: "running", LastAttemptAt: time.Unix(1, 0).UTC().Format(time.RFC3339), UpdatedAt: time.Unix(1, 0).UTC().Format(time.RFC3339)}
+	if err := record.Validate(root, "singleton_candidate"); err == nil {
+		t.Fatal("expected missing candidate rejection")
+	}
+}
 func TestRecordRejectsReleaseOutsideRoot(t *testing.T) {
 	record := Record{SchemaVersion: 1, Strategy: "singleton_candidate", ActiveSlot: "singleton", ActiveRelease: "/tmp/other/release", UpdatedAt: time.Unix(1, 0).UTC().Format(time.RFC3339)}
 	if err := record.Validate("/opt/example", "singleton_candidate"); err == nil {

internal/transport/protocol.go

@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+// Package transport implements Tend's bounded, versioned deployment stream.
+package transport
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/sha256"
+	"encoding/binary"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"regexp"
+	"strings"
+)
+
+const (
+	Protocol         = "tend-receive-v1"
+	MaxArtifactBytes = 512 << 20
+	maxHeaderBytes   = 64 << 10
+	maxArtifactName  = 128
+)
+
+var (
+	servicePattern  = regexp.MustCompile(`^[a-z][a-z0-9-]{1,62}$`)
+	artifactPattern = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._-]{0,127}$`)
+)
+
+type Header struct {
+	Protocol       string `json:"protocol"`
+	Service        string `json:"service"`
+	ArtifactName   string `json:"artifact_name"`
+	Size           int64  `json:"size"`
+	SHA256         string `json:"sha256"`
+	ApprovedSHA256 string `json:"approved_sha256"`
+	Activate       bool   `json:"activate"`
+}
+
+func (h Header) Validate(maxBytes int64) error {
+	if h.Protocol != Protocol {
+		return errors.New("unsupported receive protocol")
+	}
+	if !servicePattern.MatchString(h.Service) {
+		return errors.New("invalid service name")
+	}
+	if len(h.ArtifactName) > maxArtifactName || !artifactPattern.MatchString(h.ArtifactName) {
+		return errors.New("invalid artifact name")
+	}
+	if h.Size <= 0 || h.Size > maxBytes {
+		return errors.New("artifact size exceeds policy")
+	}
+	if h.SHA256 != h.ApprovedSHA256 || len(h.SHA256) != 64 || strings.ToLower(h.SHA256) != h.SHA256 {
+		return errors.New("artifact digest was not explicitly approved")
+	}
+	if _, err := hex.DecodeString(h.SHA256); err != nil {
+		return errors.New("artifact digest is not hexadecimal")
+	}
+	return nil
+}
+
+func Prefix(header Header) ([]byte, error) {
+	if err := header.Validate(MaxArtifactBytes); err != nil {
+		return nil, err
+	}
+	body, err := json.Marshal(header)
+	if err != nil {
+		return nil, err
+	}
+	if len(body) > maxHeaderBytes {
+		return nil, errors.New("receive header exceeds limit")
+	}
+	prefix := make([]byte, 4+len(body))
+	binary.BigEndian.PutUint32(prefix[:4], uint32(len(body)))
+	copy(prefix[4:], body)
+	return prefix, nil
+}
+
+func ReadHeader(reader *bufio.Reader) (Header, error) {
+	var size [4]byte
+	if _, err := io.ReadFull(reader, size[:]); err != nil {
+		return Header{}, fmt.Errorf("read receive header length: %w", err)
+	}
+	length := binary.BigEndian.Uint32(size[:])
+	if length == 0 || length > maxHeaderBytes {
+		return Header{}, errors.New("receive header length is invalid")
+	}
+	body := make([]byte, length)
+	if _, err := io.ReadFull(reader, body); err != nil {
+		return Header{}, fmt.Errorf("read receive header: %w", err)
+	}
+	decoder := json.NewDecoder(bytes.NewReader(body))
+	decoder.DisallowUnknownFields()
+	var header Header
+	if err := decoder.Decode(&header); err != nil {
+		return Header{}, fmt.Errorf("decode receive header: %w", err)
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
+		return Header{}, errors.New("receive header contains trailing data")
+	}
+	return header, nil
+}
+
+func CopyArtifact(destination io.Writer, reader *bufio.Reader, header Header, maxBytes int64) error {
+	if err := header.Validate(maxBytes); err != nil {
+		return err
+	}
+	hash := sha256.New()
+	written, err := io.CopyN(io.MultiWriter(destination, hash), reader, header.Size)
+	if err != nil || written != header.Size {
+		return errors.New("artifact stream ended before declared size")
+	}
+	if _, err = reader.ReadByte(); !errors.Is(err, io.EOF) {
+		return errors.New("artifact stream contains trailing bytes")
+	}
+	if hex.EncodeToString(hash.Sum(nil)) != header.SHA256 {
+		return errors.New("artifact stream digest does not match")
+	}
+	return nil
+}

internal/transport/protocol_test.go

@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package transport
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"strings"
+	"testing"
+)
+
+func validFrame(t *testing.T, artifact string) ([]byte, Header) {
+	t.Helper()
+	hash := sha256.Sum256([]byte(artifact))
+	digest := hex.EncodeToString(hash[:])
+	header := Header{Protocol: Protocol, Service: "example-site", ArtifactName: "example.tar.gz", Size: int64(len(artifact)), SHA256: digest, ApprovedSHA256: digest, Activate: true}
+	prefix, err := Prefix(header)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return append(prefix, artifact...), header
+}
+
+func TestProtocolRoundTrip(t *testing.T) {
+	frame, expected := validFrame(t, "artifact")
+	reader := bufio.NewReader(bytes.NewReader(frame))
+	header, err := ReadHeader(reader)
+	if err != nil || header != expected {
+		t.Fatalf("header=%+v err=%v", header, err)
+	}
+	var artifact bytes.Buffer
+	if err = CopyArtifact(&artifact, reader, header, 1<<20); err != nil {
+		t.Fatal(err)
+	}
+	if artifact.String() != "artifact" {
+		t.Fatalf("artifact=%q", artifact.String())
+	}
+}
+
+func TestProtocolRejectsTrailingAndForgedInputs(t *testing.T) {
+	frame, header := validFrame(t, "artifact")
+	reader := bufio.NewReader(bytes.NewReader(append(frame, 'x')))
+	read, _ := ReadHeader(reader)
+	if err := CopyArtifact(&bytes.Buffer{}, reader, read, 1<<20); err == nil {
+		t.Fatal("accepted trailing bytes")
+	}
+	header.Service = "../../root"
+	if _, err := Prefix(header); err == nil {
+		t.Fatal("accepted forged service")
+	}
+	header.Service = "example-site"
+	header.ApprovedSHA256 = strings.Repeat("0", 64)
+	if _, err := Prefix(header); err == nil {
+		t.Fatal("accepted unapproved digest")
+	}
+}
+
+func FuzzProtocolFraming(f *testing.F) {
+	hash := sha256.Sum256([]byte("artifact"))
+	digest := hex.EncodeToString(hash[:])
+	prefix, err := Prefix(Header{Protocol: Protocol, Service: "example-site", ArtifactName: "example.tar.gz", Size: 8, SHA256: digest, ApprovedSHA256: digest})
+	if err != nil {
+		f.Fatal(err)
+	}
+	frame := append(prefix, []byte("artifact")...)
+	f.Add(frame)
+	f.Add([]byte{0, 0, 0, 0})
+	f.Fuzz(func(t *testing.T, input []byte) {
+		if len(input) > 2<<20 {
+			t.Skip()
+		}
+		reader := bufio.NewReader(bytes.NewReader(input))
+		header, err := ReadHeader(reader)
+		if err != nil {
+			return
+		}
+		_ = CopyArtifact(&bytes.Buffer{}, reader, header, 1<<20)
+	})
+}

internal/transport/push.go

@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package transport
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var targetPattern = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9_.-]*@[A-Za-z0-9][A-Za-z0-9.-]*$`)
+
+type PushOptions struct {
+	Target         string
+	Port           int
+	KnownHosts     string
+	Identity       string
+	Service        string
+	Artifact       string
+	SHA256         string
+	ApprovedSHA256 string
+	Activate       bool
+}
+
+type SSHRunner interface {
+	Run(context.Context, string, []string, io.Reader) ([]byte, error)
+}
+
+type ExecSSHRunner struct{}
+
+func (ExecSSHRunner) Run(ctx context.Context, name string, args []string, stdin io.Reader) ([]byte, error) {
+	command := exec.CommandContext(ctx, name, args...)
+	command.Stdin = stdin
+	var output, diagnostic boundedBuffer
+	command.Stdout = &output
+	command.Stderr = &diagnostic
+	err := command.Run()
+	if err != nil {
+		return output.Bytes(), fmt.Errorf("ssh failed: %w: %s", err, strings.TrimSpace(diagnostic.String()))
+	}
+	return output.Bytes(), nil
+}
+
+type boundedBuffer struct{ bytes.Buffer }
+
+func (b *boundedBuffer) Write(value []byte) (int, error) {
+	written := len(value)
+	remaining := (1 << 20) - b.Len()
+	if remaining > 0 {
+		if len(value) > remaining {
+			value = value[:remaining]
+		}
+		_, _ = b.Buffer.Write(value)
+	}
+	return written, nil
+}
+
+func Push(ctx context.Context, runner SSHRunner, options PushOptions) (json.RawMessage, error) {
+	if !targetPattern.MatchString(options.Target) || strings.HasPrefix(options.Target, "-") {
+		return nil, errors.New("target must be user@host without shell syntax")
+	}
+	if options.Port < 1 || options.Port > 65535 {
+		return nil, errors.New("SSH port is invalid")
+	}
+	if err := safeClientFile(options.KnownHosts, false); err != nil {
+		return nil, fmt.Errorf("known-hosts file: %w", err)
+	}
+	if options.Identity != "" {
+		if err := safeClientFile(options.Identity, true); err != nil {
+			return nil, fmt.Errorf("identity file: %w", err)
+		}
+	}
+	if !filepath.IsAbs(options.Artifact) || filepath.Clean(options.Artifact) != options.Artifact || strings.ContainsAny(options.Artifact, "\x00\r\n\t") {
+		return nil, errors.New("artifact path must be clean and absolute")
+	}
+	artifactInfo, err := os.Lstat(options.Artifact)
+	if err != nil || !artifactInfo.Mode().IsRegular() || artifactInfo.Mode()&os.ModeSymlink != 0 || artifactInfo.Size() <= 0 || artifactInfo.Size() > MaxArtifactBytes {
+		return nil, errors.New("artifact must be a bounded regular non-symlink file")
+	}
+	artifact, err := os.Open(options.Artifact)
+	if err != nil {
+		return nil, err
+	}
+	defer artifact.Close()
+	info, err := artifact.Stat()
+	if err != nil || !info.Mode().IsRegular() || !os.SameFile(artifactInfo, info) {
+		return nil, errors.New("artifact must be a bounded regular file")
+	}
+	hash := sha256.New()
+	if _, err = io.Copy(hash, artifact); err != nil {
+		return nil, err
+	}
+	actual := hex.EncodeToString(hash.Sum(nil))
+	if actual != options.SHA256 || options.SHA256 != options.ApprovedSHA256 {
+		return nil, errors.New("artifact digest was not explicitly approved")
+	}
+	if _, err = artifact.Seek(0, io.SeekStart); err != nil {
+		return nil, err
+	}
+	header := Header{Protocol: Protocol, Service: options.Service, ArtifactName: filepath.Base(options.Artifact), Size: info.Size(), SHA256: options.SHA256, ApprovedSHA256: options.ApprovedSHA256, Activate: options.Activate}
+	prefix, err := Prefix(header)
+	if err != nil {
+		return nil, err
+	}
+	args := []string{"-F", os.DevNull, "-T", "-p", strconv.Itoa(options.Port), "-o", "BatchMode=yes", "-o", "ClearAllForwardings=yes", "-o", "ExitOnForwardFailure=yes", "-o", "ForwardAgent=no", "-o", "IdentitiesOnly=yes", "-o", "LogLevel=ERROR", "-o", "PermitLocalCommand=no", "-o", "ProxyCommand=none", "-o", "RequestTTY=no", "-o", "StrictHostKeyChecking=yes", "-o", "UserKnownHostsFile=" + options.KnownHosts}
+	if options.Identity != "" {
+		args = append(args, "-i", options.Identity)
+	}
+	args = append(args, options.Target, Protocol)
+	output, err := runner.Run(ctx, "ssh", args, io.MultiReader(bytes.NewReader(prefix), artifact))
+	if err != nil {
+		return nil, err
+	}
+	if !json.Valid(output) {
+		return nil, errors.New("receiver returned invalid JSON")
+	}
+	return json.RawMessage(output), nil
+}
+
+func safeClientFile(path string, private bool) error {
+	if !filepath.IsAbs(path) || filepath.Clean(path) != path || strings.ContainsAny(path, "\x00\r\n\t") {
+		return errors.New("path must be clean and absolute")
+	}
+	parent, err := os.Lstat(filepath.Dir(path))
+	if err != nil || !parent.IsDir() || parent.Mode()&os.ModeSymlink != 0 || parent.Mode().Perm()&0o022 != 0 {
+		return errors.New("parent must be a real directory not writable by group or others")
+	}
+	info, err := os.Lstat(path)
+	if err != nil {
+		return err
+	}
+	if !info.Mode().IsRegular() || info.Mode()&os.ModeSymlink != 0 {
+		return errors.New("must be a regular non-symlink file")
+	}
+	if info.Mode().Perm()&0o022 != 0 {
+		return errors.New("must not be group- or world-writable")
+	}
+	if private && info.Mode().Perm()&0o077 != 0 {
+		return errors.New("must not be accessible by group or others")
+	}
+	return nil
+}

internal/transport/push_test.go

@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package transport
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"io"
+	"os"
+	"path/filepath"
+	"slices"
+	"testing"
+)
+
+type captureRunner struct {
+	name  string
+	args  []string
+	input []byte
+	calls int
+}
+
+func (runner *captureRunner) Run(_ context.Context, name string, args []string, input io.Reader) ([]byte, error) {
+	runner.calls++
+	runner.name = name
+	runner.args = append([]string(nil), args...)
+	runner.input, _ = io.ReadAll(input)
+	return []byte(`{"validated":true,"mutation":"activated"}`), nil
+}
+
+func TestPushUsesPinnedSSHAndExactFrame(t *testing.T) {
+	dir := t.TempDir()
+	knownHosts := filepath.Join(dir, "known_hosts")
+	identity := filepath.Join(dir, "identity")
+	artifact := filepath.Join(dir, "release.tar.gz")
+	if err := os.WriteFile(knownHosts, []byte("host key\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(identity, []byte("private\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	content := []byte("artifact")
+	if err := os.WriteFile(artifact, content, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	hash := sha256.Sum256(content)
+	digest := hex.EncodeToString(hash[:])
+	runner := &captureRunner{}
+	result, err := Push(context.Background(), runner, PushOptions{Target: "tend-deploy@example.test", Port: 2222, KnownHosts: knownHosts, Identity: identity, Service: "example-site", Artifact: artifact, SHA256: digest, ApprovedSHA256: digest, Activate: true})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Contains(result, []byte(`"activated"`)) || runner.calls != 1 || runner.name != "ssh" {
+		t.Fatalf("result=%s calls=%d name=%q", result, runner.calls, runner.name)
+	}
+	if !slices.Contains(runner.args, "ProxyCommand=none") || !slices.Contains(runner.args, "StrictHostKeyChecking=yes") || runner.args[len(runner.args)-1] != Protocol {
+		t.Fatalf("args=%#v", runner.args)
+	}
+	reader := bufio.NewReader(bytes.NewReader(runner.input))
+	header, err := ReadHeader(reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var copied bytes.Buffer
+	if err = CopyArtifact(&copied, reader, header, 1<<20); err != nil {
+		t.Fatal(err)
+	}
+	if copied.String() != string(content) || header.Service != "example-site" || !header.Activate {
+		t.Fatalf("header=%+v body=%q", header, copied.String())
+	}
+}
+
+func TestPushRejectsShellTargetBeforeExecution(t *testing.T) {
+	runner := &captureRunner{}
+	_, err := Push(context.Background(), runner, PushOptions{Target: "root@example.test;touch", Port: 22})
+	if err == nil || runner.calls != 0 {
+		t.Fatalf("err=%v calls=%d", err, runner.calls)
+	}
+}

internal/transport/receive.go

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package transport
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"os"
+
+	"gamertan.com/tend/internal/deploy"
+	"gamertan.com/tend/internal/serverpolicy"
+)
+
+func Receive(ctx context.Context, input io.Reader, policy serverpolicy.Policy, manager deploy.Manager) (deploy.Report, error) {
+	if err := policy.CheckDirectories(); err != nil {
+		return deploy.Report{}, err
+	}
+	reader := bufio.NewReaderSize(input, maxHeaderBytes+4)
+	header, err := ReadHeader(reader)
+	if err != nil {
+		return deploy.Report{}, err
+	}
+	service, err := policy.CheckService(header.Service)
+	if err != nil {
+		return deploy.Report{}, err
+	}
+	if err = header.Validate(service.Policy.MaxArtifactBytes); err != nil {
+		return deploy.Report{}, err
+	}
+	file, err := os.CreateTemp(policy.IncomingRoot, ".tend-receive-"+header.Service+"-")
+	if err != nil {
+		return deploy.Report{}, err
+	}
+	path := file.Name()
+	defer os.Remove(path)
+	if err = file.Chmod(0o600); err == nil {
+		err = CopyArtifact(file, reader, header, service.Policy.MaxArtifactBytes)
+	}
+	if closeErr := file.Close(); err == nil {
+		err = closeErr
+	}
+	if err != nil {
+		return deploy.Report{}, fmt.Errorf("receive artifact: %w", err)
+	}
+	return manager.Deploy(ctx, service.Config, deploy.Request{Artifact: path, SHA256: header.SHA256, ApprovedSHA256: header.ApprovedSHA256, Activate: header.Activate})
+}

internal/version/version.go

@@ -2,8 +2,81 @@
 
 package version
 
+import (
+	"regexp"
+	"runtime/debug"
+	"strings"
+)
+
+const developmentVersion = "v0.1.0-dev"
+
 var (
-	Version = "v0.1.0-dev"
+	Version = developmentVersion
 	Commit  = "unknown"
 	Date    = "unknown"
 )
+
+var (
+	taggedVersionPattern       = regexp.MustCompile(`^v(?:0|[1-9][0-9]*)\.(?:0|[1-9][0-9]*)\.(?:0|[1-9][0-9]*)(?:-([0-9A-Za-z-]+(?:\.[0-9A-Za-z-]+)*))?$`)
+	pseudoVersionSuffixPattern = regexp.MustCompile(`(?:^|[.-])(?:0\.)?[0-9]{14}-[0-9a-f]{12,}$`)
+)
+
+func init() {
+	information, ok := debug.ReadBuildInfo()
+	if !ok {
+		return
+	}
+	Version = selectVersion(Version, information.Main.Version)
+	for _, setting := range information.Settings {
+		switch setting.Key {
+		case "vcs.revision":
+			if Commit == "unknown" && setting.Value != "" {
+				Commit = setting.Value
+			}
+		case "vcs.time":
+			if Date == "unknown" && setting.Value != "" {
+				Date = setting.Value
+			}
+		}
+	}
+}
+
+func selectVersion(linkerValue, moduleVersion string) string {
+	if linkerValue != developmentVersion {
+		return linkerValue
+	}
+	moduleVersion = strings.TrimSpace(moduleVersion)
+	if !isTaggedVersion(moduleVersion) {
+		return linkerValue
+	}
+	return moduleVersion
+}
+
+func isTaggedVersion(value string) bool {
+	matches := taggedVersionPattern.FindStringSubmatch(value)
+	if matches == nil {
+		return false
+	}
+	prerelease := matches[1]
+	if pseudoVersionSuffixPattern.MatchString(prerelease) {
+		return false
+	}
+	for _, identifier := range strings.Split(prerelease, ".") {
+		if len(identifier) > 1 && identifier[0] == '0' && allDecimal(identifier) {
+			return false
+		}
+	}
+	return true
+}
+
+func allDecimal(value string) bool {
+	if value == "" {
+		return false
+	}
+	for _, character := range value {
+		if character < '0' || character > '9' {
+			return false
+		}
+	}
+	return true
+}

internal/version/version_test.go

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package version
+
+import "testing"
+
+func TestSelectVersion(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		name, linker, module, want string
+	}{
+		{"local build", developmentVersion, "(devel)", developmentVersion},
+		{"missing build info", developmentVersion, "", developmentVersion},
+		{"preview one install", developmentVersion, "v0.1.0-preview.1", "v0.1.0-preview.1"},
+		{"preview two install", developmentVersion, "v0.1.0-preview.2", "v0.1.0-preview.2"},
+		{"release install", developmentVersion, "v1.0.0", "v1.0.0"},
+		{"linker override", "v0.1.0-preview.2", "(devel)", "v0.1.0-preview.2"},
+		{"pseudo version", developmentVersion, "v0.0.0-20260814120000-0123456789ab", developmentVersion},
+		{"pseudo after release", developmentVersion, "v0.1.1-0.20260814120000-0123456789ab", developmentVersion},
+		{"build metadata", developmentVersion, "v0.1.0+dirty", developmentVersion},
+		{"leading zero release", developmentVersion, "v00.1.0", developmentVersion},
+		{"leading zero prerelease", developmentVersion, "v0.1.0-preview.02", developmentVersion},
+	}
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+			if got := selectVersion(test.linker, test.module); got != test.want {
+				t.Fatalf("selectVersion(%q, %q)=%q want %q", test.linker, test.module, got, test.want)
+			}
+		})
+	}
+}

release/tend.json

@@ -1,6 +1,6 @@
 {
-  "schema_version": 1,
-  "service": { "name": "tend", "allowed_host": "localhost" },
+  "schema_version": 2,
+  "service": { "name": "tend", "allowed_host": "localhost", "environment_file": "/etc/tend/environment/tend-release-test.env" },
   "build": {
     "package": "./cmd/tend",
     "binary": "tend",
@@ -12,20 +12,25 @@
   "deployment": {
     "strategy": "singleton_candidate",
     "root": "/opt/tend-release-test",
-    "lock_file": "/run/lock/tend-release-test.lock",
+    "lock_file": "/run/lock/tend-deploy.lock",
     "state_file": "/opt/tend-release-test/tend-state.json",
+    "event_log": "/opt/tend-release-test/deployment-events.jsonl",
     "health_path": "/healthz",
     "readiness_path": "/readyz",
     "candidate_timeout_seconds": 5,
+    "activation_window_seconds": 5,
     "smoke": [{ "path": "/", "contains": "Tend" }],
+    "public_smoke": [{ "url": "https://example.test/", "contains": "Tend" }],
     "singleton": {
       "unit": "tend-release-test.service",
       "address": "127.0.0.1:19090",
       "candidate_address": "127.0.0.1:19091",
       "listen_env": "TEND_RELEASE_TEST_LISTEN",
-      "environment": {},
       "current_link": "/opt/tend-release-test/current",
-      "previous_link": "/opt/tend-release-test/previous"
+      "previous_link": "/opt/tend-release-test/previous",
+      "caddy_config": "/etc/caddy/Caddyfile",
+      "caddy_handler": "/etc/caddy/tend-release-test-handler.caddy",
+      "caddy_handler_template": "/etc/tend/caddy/tend-release-test.template"
     }
   }
 }

scripts/check-public-tree.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: AGPL-3.0-only
+set -euo pipefail
+root=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+allow=$root/scripts/public-snapshot.allow
+LC_ALL=C sort -c "$allow"
+[[ $(LC_ALL=C sort "$allow" | uniq -d | wc -l) -eq 0 ]]
+mapfile -t files <"$allow"
+[[ ${#files[@]} -gt 0 ]]
+for file in "${files[@]}"; do
+	[[ -n $file && $file != /* && $file != *..* && $file != .gitea/* && $file != .github/* ]]
+	git -C "$root" cat-file -e "HEAD:$file"
+done
+work=$(mktemp -d)
+trap 'rm -rf -- "$work"' EXIT
+mkdir -m 0700 "$work/tree"
+git -C "$root" archive HEAD -- "${files[@]}" | tar -xf - -C "$work/tree"
+test ! -e "$work/tree/.git"
+test ! -e "$work/tree/.gitea"
+test ! -e "$work/tree/.github"
+private_pattern='/home/[[:alnum:]_.-]+/|BEGIN (RSA|OPENSSH|EC) PRIVATE KEY|gitea[-_]api[[:alnum:]_.-]*token'
+if (cd "$work/tree" && rg -n --hidden --glob '!scripts/export-public.sh' --glob '!scripts/check-public-tree.sh' "$private_pattern" .); then
+	echo "private material found in public tree" >&2
+	exit 1
+fi
+(cd "$work/tree" && ./scripts/check-licenses.sh)
+(cd "$work/tree" && GOWORK=off go test -count=1 ./...)
+(cd "$work/tree" && GOWORK=off go vet ./...)
+(cd "$work/tree" && GOWORK=off CGO_ENABLED=0 go build -buildvcs=false -mod=readonly -trimpath -o "$work/tend" ./cmd/tend)
+echo "public tree compiles independently"

scripts/export-public.sh

@@ -44,7 +44,8 @@ done < <(find "$stage" -type f -print | LC_ALL=C sort)
 epoch=$(git -C "$root" show -s --format=%ct "$commit")
 printf '{"schema_version":1,"source_commit":"%s","source_tree":"%s","source_date_epoch":%s,"file_count":%d}\n' "$commit" "$tree" "$epoch" "${#files[@]}" >"$stage/PUBLIC-SNAPSHOT.json"
 (cd "$stage" && sha256sum PUBLIC-SNAPSHOT.json >PUBLIC-SNAPSHOT.sha256)
-if (cd "$stage" && rg -n --hidden --glob '!.git/**' --glob '!PUBLIC-SNAPSHOT.json' --glob '!scripts/export-public.sh' '/home/cole|BEGIN (RSA|OPENSSH|EC) PRIVATE KEY|gitea-api\.token' .); then
+private_pattern='/home/[[:alnum:]_.-]+/|BEGIN (RSA|OPENSSH|EC) PRIVATE KEY|gitea[-_]api[[:alnum:]_.-]*token'
+if (cd "$stage" && rg -n --hidden --glob '!.git/**' --glob '!PUBLIC-SNAPSHOT.json' --glob '!scripts/export-public.sh' "$private_pattern" .); then
 	echo "private material found" >&2
 	exit 1
 fi

scripts/public-snapshot.allow

@@ -8,13 +8,30 @@ SECURITY.md
 cmd/tend/main.go
 docs/ARCHITECTURE.md
 docs/DOGFOOD_EVIDENCE.md
+docs/DOGFOOD_FRICTION.md
 docs/PUBLIC_SNAPSHOT.md
+docs/SCHEMA_V2_MIGRATION.md
 docs/THREAT_MODEL.md
+docs/WALKTHROUGH.md
 examples/LICENSE
 examples/README.md
 examples/blue-green/caddy-handler.template
 examples/blue-green/example-site@.service
 examples/blue-green/tend.json
+examples/local/.env.example
+examples/server/authorized_keys.example
+examples/server/caddy/docs-site.template
+examples/server/caddy/example-site.template
+examples/server/environment/docs-site.env.example
+examples/server/environment/example-site.env.example
+examples/server/example-singleton.service
+examples/server/receive-policy.json
+examples/server/services/docs-site.json
+examples/server/services/example-site.json
+examples/server/slots/example-site-blue.env
+examples/server/slots/example-site-green.env
+examples/server/tend-receive.sudoers
+examples/singleton/caddy-handler.template
 examples/singleton/tend.json
 go.mod
 internal/config/config.go
@@ -22,22 +39,37 @@ internal/config/config_test.go
 internal/deploy/deploy.go
 internal/deploy/deploy_test.go
 internal/deploy/lock_linux.go
+internal/deploy/lock_linux_test.go
 internal/deploy/lock_other.go
 internal/deploy/operator.go
 internal/deploy/operator_test.go
 internal/deploy/ownership_linux.go
 internal/deploy/ownership_other.go
 internal/deploy/release.go
+internal/deploy/release_mode_linux_test.go
 internal/deploy/release_test.go
+internal/eventlog/eventlog.go
+internal/eventlog/eventlog_test.go
 internal/packager/packager.go
 internal/packager/packager_test.go
 internal/process/run.go
 internal/provenance/git.go
+internal/serverpolicy/ownership_linux.go
+internal/serverpolicy/ownership_other.go
+internal/serverpolicy/policy.go
+internal/serverpolicy/policy_test.go
 internal/state/state.go
 internal/state/state_test.go
+internal/transport/protocol.go
+internal/transport/protocol_test.go
+internal/transport/push.go
+internal/transport/push_test.go
+internal/transport/receive.go
 internal/version/version.go
+internal/version/version_test.go
 release/tend.json
 scripts/check-licenses.sh
+scripts/check-public-tree.sh
 scripts/export-public.sh
 scripts/public-snapshot.allow
 scripts/test-public-snapshot.sh

scripts/verify.sh

@@ -4,6 +4,7 @@ set -euo pipefail
 root=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
 cd "$root"
 ./scripts/check-licenses.sh
+./scripts/check-public-tree.sh
 go test -count=1 ./...
 go test -race -count=1 ./...
 go vet ./...
@@ -14,6 +15,11 @@ GOWORK=off CGO_ENABLED=0 go build -mod=readonly -trimpath -o "$work/tend-2" ./cm
 cmp "$work/tend-1" "$work/tend-2"
 "$work/tend-1" check --config "$root/examples/blue-green/tend.json" >/dev/null
 "$work/tend-1" check --config "$root/examples/singleton/tend.json" >/dev/null
+"$work/tend-1" check --config "$root/examples/server/services/example-site.json" >/dev/null
+"$work/tend-1" check --config "$root/examples/server/services/docs-site.json" >/dev/null
+"$work/tend-1" check --config "$root/release/tend.json" >/dev/null
+grep -Fqx 'Defaults:tend-deploy env_keep += "SSH_ORIGINAL_COMMAND"' "$root/examples/server/tend-receive.sudoers"
+grep -Fqx 'tend-deploy ALL=(root) NOPASSWD: /usr/local/bin/tend receive --policy /etc/tend/receive-policy.json' "$root/examples/server/tend-receive.sudoers"
 [[ $(GOWORK=off go list -m all | wc -l) -eq 1 ]]
 git diff --check
 echo "Tend verification passed"