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+# Worker telemetry recovery, 2026-09-25
+
+## Failure and evidence
+
+Worker 006 is a remote compute host, not a device required to share the
+operator's LAN. The owner explicitly requires Tailscale access across networks.
+At the initial inspection the Worker was disconnected from its network; after
+Wi-Fi returned the existing strict-pinned Tailscale SSH profile connected.
+
+Read-only audit then established:
+
+- Tailscale and OpenSSH were Running/Automatic; Tailscale ForceDaemon was true.
+- Compute Docker containers were running. A failed historical StartCompute task
+  did not mean the entire Worker or every container was offline.
+- Native Telegraf 1.38.4 was Stopped/Automatic, exit code zero. SCM restart actions
+  and non-crash recovery were already configured.
+- Windows Application events on September 19, 21 and 23 showed Telegraf starting,
+  then terminating about 15 seconds later because its old LAN MQTT destination
+  was unreachable. Source inspection of the pinned upstream release confirms
+  that output retry handles only errors marked retryable; merely configuring
+  `startup_error_behavior=retry` did not cover the observed MQTT failure.
+- Operator Docker was stopped, with login autostart disabled. No broker/query
+  listeners existed. Its saved broker bind belonged to an older DHCP lease.
+- Private telemetry configuration remained in the original installation while
+  Core's network-apply handler assumed its current source checkout owned it.
+
+No credentials, database volumes, Worker computation profiles or inference jobs
+were replaced. Docker Desktop restored its existing unrelated restart-policy
+containers when its engine started; those were not renamed or reconfigured.
+
+## Implemented installation profile
+
+Windows native Telegraf publishes to Worker `127.0.0.1:1883`. A dedicated
+Mac-owned SSH reverse forward exposes that loopback listener and carries data
+through the existing strictly pinned Tailscale SSH profile to operator
+`127.0.0.1:1883`. Broker publication is loopback-only. Query remains
+`127.0.0.1:18030`; Core remains `127.0.0.1:8000`. No `.local` name or LAN lease is
+required by this transport. MQTT credentials and per-agent ACLs are preserved.
+SSH supplies authenticated encryption; this does not claim public MQTT/mTLS
+or multi-tenant enrollment acceptance.
+
+`scripts/manage_telemetry_startup.py` owns a hash-bound plan/apply/rollback:
+
+- preserved prepared stack directory, credentials and named volumes;
+- explicit `MISSIONCORE_TELEMETRY_PLANE_ROOT` for the existing Core handler;
+- `com.nodedc.telemetry-startup.local`: login startup and bounded reconciliation
+  every 30 seconds, including delayed Docker Desktop availability;
+- `com.nodedc.telemetry-tunnel.local`: keepalive/reconnect and loopback-only
+  reverse forwarding, strict known-host verification;
+- only broker, Timescale and normalizer are selected by Compose, no build or
+  image pull; existing database-bootstrap is an idempotent dependency;
+- configuration backups outside Git; apply preserves canonical Core health;
+- rollback restores declarations and credentials; it does not reset volumes or
+  stop Docker/unrelated containers. The restored broker declaration is applied
+  on subsequent reconciliation. Rollback rehearsal is not yet accepted.
+
+`Install-NdcMissionCoreTelemetryRecovery.ps1` is included in the Windows agent
+bundle. Loopback agent install/update invokes it. It installs one SYSTEM task
+at boot and every minute, with no interactive-login requirement. Its script is
+writable only by SYSTEM/Administrators. It starts only a stopped managed
+Telegraf service, and only after the configured loopback endpoint is reachable.
+A missing connection leaves the task retryable. It never restarts a healthy
+agent or starts inference. Maintenance can disable this named task before an
+intentional extended Telegraf stop; rollback restores its predecessor.
+
+## Product status and refresh
+
+Receiver failure now has `telemetry-receiver-unavailable`, distinct from stale
+agent observations. Fleet contour, compute and network views show receiver
+failure as an unconfirmed Worker state, not proof that its host is off. Visible
+connectivity labels are consistently «В сети» / «Не в сети»; failure details
+explain which part of the observation path failed. The
+network view no longer paints the receiver green merely because the configured
+source is agent-mqtt.
+
+A responding Core with `recording_cache=capacity-pressure` is reachable with a
+recording limitation. It is displayed as «В сети» with the limitation separately. This matters on the
+operator host, where free space fell below the existing 2 GiB recording reserve
+(about 1.8 GiB observed); no owner data was deleted.
+
+The contour Refresh action now uses the canonical circular IconButton in the
+outer window header, alongside expand/close. The body copy button is removed.
+
+## Measured acceptance
+
+- Fresh agent-mqtt data reached the canonical Core, with expected node identity.
+- Native Windows service clean-stop test: automatic recovery in 51.7 s, new PID;
+  no manual Start-Service was needed (failure restoration path was not used).
+- Dedicated tunnel SIGKILL: new tunnel process and new source observations in
+  10.43 s. The API's 30 s freshness window did not expire during this short cut.
+- Normalizer stop: receiver-unavailable was observed, then automatic Compose
+  recovery and new source observations in 19.58 s.
+- Tests are reproducible with `Test-NdcMissionCoreTelemetryRecovery.ps1` and
+  `scripts/check_telemetry_recovery.py`; they target telemetry only.
+- 36 focused backend tests, Ruff, 984 frontend tests, TypeScript and production
+  build passed. Four installer/test PowerShell artifacts were parsed by the
+  native Windows parser; install/update hooks were not a clean-host rehearsal.
+- Browser acceptance on canonical port 8000 confirms fresh Worker observations,
+  standardized connectivity labels and the circular Refresh control in the
+  window header (including its checking state).
+
+## Qualification boundary
+
+The accepted live profile is macOS operator session + Windows native telemetry
+agent + the existing Tailscale trust relationship. Automatic recovery of the
+three injected failures is proved. A full physical host power cycle, distinct
+physical networks, extended network-loss soak and clean-host reinstall have
+not been run in this increment. Tailscale may choose a direct encrypted path
+when the peers happen to share a LAN; that does not reintroduce LAN addressing.
+
+Mac LaunchAgents and Docker Desktop start after operator login, not before
+macOS login. Windows Tailscale/SSH/telemetry recovery use system services/tasks.
+Worker Docker computation still has its separate interactive-session lifecycle;
+this work does not claim all GPU jobs should auto-resume after power loss.
+Linux agent lifecycle and an unattended headless compute installation need a
+separate qualified OS profile. Do not label the whole system universally
+portable or cold-boot accepted from these component-level tests.
+
+## Upstream references
+
+- [Telegraf 1.38.4 output lifecycle](https://github.com/influxdata/telegraf/blob/v1.38.4/models/running_output.go)
+- [Telegraf 1.38.4 MQTT connect](https://github.com/influxdata/telegraf/blob/v1.38.4/plugins/outputs/mqtt/mqtt.go)
+- [Windows Tailscale unattended](https://tailscale.com/docs/how-to/run-unattended)
+- [Docker Desktop login startup](https://docs.docker.com/desktop/settings-and-maintenance/settings/)