diff --git a/tools/dev-deploy/KNOWN-ISSUES.md b/tools/dev-deploy/KNOWN-ISSUES.md
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+# `tools/dev-deploy/` — known issues
+
+Issues that surface in the long-lived dev environment but are not yet
+fixed. Each entry lists the observed symptom, the diagnostic evidence,
+the working hypothesis, and the open questions that have to be
+answered before a fix lands.
+
+## Dev Sandbox game flips to `cancelled` after a `dev-deploy` redispatch
+
+### Symptom
+
+A previously `running` "Dev Sandbox" game (created by
+`backend/internal/devsandbox`) transitions to `cancelled` ~15 minutes
+after a `dev-deploy.yaml` workflow_dispatch run finishes. The user's
+browser session survives (the same `device_session_id` keeps working),
+but the lobby shows no game because the only game it had is now
+terminal. `purgeTerminalSandboxGames` does pick it up on the **next**
+boot and creates a fresh sandbox — but the first redispatch leaves
+the user with an empty lobby until backend restarts again.
+
+### Diagnostic evidence
+
+Backend logs from the broken cycle (timestamps abbreviated):
+
+```text
+20:24:40 dev_sandbox: purged terminal sandbox game game_id=<prev> status=cancelled
+20:24:40 dev_sandbox: memberships ensured count=20 game_id=<new>
+20:24:40 dev_sandbox: bootstrap complete user_id=<owner> game_id=<new> status=starting
+...
+20:25:09 user mail sent failed (diplomail tables missing — unrelated)
+...
+20:39:40 lobby: game cancelled by runtime reconciler game_id=<new>
+         op=reconcile status=removed message="container disappeared"
+```
+
+Between 20:24:40 (`status=starting`) and 20:39:40 (reconciler cancel)
+the backend logs are silent on the runtime / engine paths — no
+`engine spawned`, no `engine container started`, no `runtime
+transition` lines. The reconciler then fires and reports the engine
+container as missing.
+
+`docker ps -a --filter 'label=org.opencontainers.image.title=galaxy-game-engine'`
+returns no rows during this window — the engine container is neither
+running nor stopped on the host, so it either was never spawned or
+was removed before the host snapshot.
+
+### What has been ruled out
+
+A live `docker inspect` on a healthy engine container shows:
+
+```text
+Labels: galaxy.backend=1, galaxy.engine_version=0.1.0,
+        galaxy.game_id=<uuid>,
+        org.opencontainers.image.title=galaxy-game-engine,
+        com.galaxy.{cpu_quota,memory,pids_limit}
+AutoRemove:    false
+RestartPolicy: on-failure
+NetworkMode:   galaxy-dev-internal
+```
+
+There are no `com.docker.compose.*` labels and `AutoRemove=false`,
+so `--remove-orphans` cannot reap the engine and a `--rm`-style
+self-destruct is not in play. Two redispatches captured under
+`docker events --filter event=create,start,die,destroy,kill,stop`
+also confirmed it: across both runs the only `die` / `destroy`
+events were for `galaxy-dev-{backend,api,caddy}`. The live engine
+container survived both redispatches, and the reconciler that
+fires 60 seconds after the new backend boots correctly matched
+it through `byGameID` / `byContainerID`.
+
+`backend/internal/runtime/service.go` only removes engine
+containers from the explicit `runStop` / `runRestart` / `runPatch`
+paths. There is no `runtime.Service.Shutdown` that proactively
+kills containers on backend exit, so a graceful SIGTERM to
+`galaxy-dev-backend` will not touch its child engine containers.
+
+### Host-side hypotheses considered and rejected by the owner
+
+The natural follow-up suspects after compose was cleared — host-side
+`docker prune` cron jobs, a manual `docker rm`, an out-of-band
+`dockerd` restart, and an idle-state engine crash — were all
+rejected by the project owner: the dev host runs none of those
+periodic cleanups, no one manually removed the container, dockerd
+was not restarted in the window, and the engine binary does not
+crash while idling on API calls.
+
+### Best remaining suspicion
+
+Something the `dev-deploy.yaml` CI run does between successful
+image builds and the final `docker compose up -d --wait
+--remove-orphans` clobbers the previously-spawned engine container.
+The chain at runtime contains:
+
+1. `docker build -t galaxy-engine:dev -f game/Dockerfile .`
+2. `docker compose build galaxy-backend galaxy-api`
+3. `docker run --rm` alpine for the UI volume seed
+4. `docker compose up -d --wait --remove-orphans`
+
+None of these *should* touch an unmanaged engine container, but
+the reproduction window points squarely inside this sequence. A
+deliberate next reproduction with `docker events --since 0` armed
+*before* the deploy starts and live for the entire job — captured
+end-to-end on the dev host, not just the chunk after backend
+recreate — would pin which step emits the `destroy` on the engine.
+
+### Status
+
+Parked. The bug is mildly disruptive (one redispatch + a manual
+`make seed-ui`-style follow-up brings the sandbox back) and the
+remaining hypotheses are speculative. If the symptom recurs, attach
+the next bad-window `docker events` capture to this entry and
+reopen. A `tools/dev-deploy/` rewrite may obviate the issue
+entirely; that is on the project owner's medium-term list.
+
+### Workaround in use today
+
+When the sandbox game flips to `cancelled`, redispatch `dev-deploy`:
+
+```sh
+curl -X POST -n -H 'Content-Type: application/json' \
+  -d '{"ref":"<branch>"}' \
+  https://gitea.iliadenisov.ru/api/v1/repos/developer/galaxy-game/actions/workflows/dev-deploy.yaml/dispatches
+```
+
+The next boot's `purgeTerminalSandboxGames` removes the cancelled
+row, `findOrCreateSandboxGame` creates a fresh one, and
+`ensureMembershipsAndDrive` puts the new game back to `running`.
+
+### Owner
+
+Unassigned. File an issue once we have the runtime / reconciler
+analysis above; reference this section in the issue body so future
+redeploys can short-circuit the diagnostic loop.
diff --git a/tools/dev-deploy/README.md b/tools/dev-deploy/README.md
index 1a04485..5d3f68c 100644
--- a/tools/dev-deploy/README.md
+++ b/tools/dev-deploy/README.md
@@ -177,6 +177,12 @@ make clean-data     Stop everything and wipe volumes + game-state dir
 - `.env.example` — non-secret defaults for the compose `${VAR:-}`
   expansions. Copy to `.env` if you want host-local overrides.
 
+## Known issues
+
+See [`KNOWN-ISSUES.md`](KNOWN-ISSUES.md) for symptoms that surface
+in the long-lived dev environment but are not yet fixed (currently:
+the sandbox game flipping to `cancelled` after a redispatch).
+
 ## Relationship to other infrastructure
 
 - `tools/local-dev/` — single-developer playground, host-port mapped,