Fixes #160.

Problem

Every app compose invocation was unpinned — docker compose <cmd> with only cwd, no -f, no -p. Compose v2 derives both the compose file and the project name from the working directory and walks up the tree when cwd has no compose file. App dirs live under the core dir:

/core/docker-compose.yml                        <- CORE stack (postgres, traefik, shard_core, web-terminal)
/core/installed_apps/<app>/docker-compose.yml   <- per-app stack

So an app command run from installed_apps/<app> with a missing compose file resolved to /core/docker-compose.yml, project name core — and stop/down then stopped shard_core itself through the mounted docker socket. That is the root cause of the recent full-shard outage: core stopped itself while uninstalling a malformed custom app.

Fix

• New app_compose_command(app_dir) in shard_core/util/subprocess.py builds a command pinned with -f <app_dir>/docker-compose.yml -p <project> --project-directory <app_dir>.
• It refuses to run when the app's compose file is missing (ComposeFileNotFound) — compose never gets the chance to walk up.
• Defense in depth: ComposeProjectNotAllowed when the resolved project would be core (or is empty).
• Every app compose call now goes through it: up --no-start, up -d, down, stop, pause, unpause in app_tools.py, plus the pause-time ps -q lookup in memory_pressure.reclaim_compose_stack.

Project name compatibility

The pinned -p must keep matching the project name compose previously derived from the app dir name, or already-installed app stacks would be orphaned. normalize_project_name mirrors compose's own normalization (lowercase, drop everything outside [a-z0-9_-], strip leading _/-), verified empirically against docker compose config (v5.0.2): My_App.v2-x → my_appv2-x, _-Foo → foo. This matters because custom-app names come from the uploaded zip filename and can contain uppercase or dots.

Blast radius of the new error

Failing loudly is the point, and the existing callers already contain it: _uninstall_app and _reinstall_app wrap stop/shutdown in try/except Exception (logged), and the installation worker loop catches every exception per task. So uninstalling a malformed app now logs the error, removes the app dir and DB row, and leaves core running — instead of taking the shard offline. docker_stop_all_apps / docker_shutdown_all_apps gather with return_exceptions=True.

Tests

New tests/test_app_compose_pinning.py (16 tests, unit tier — no Docker):

• Acceptance from the issue: with installed_apps/<app>/docker-compose.yml deleted, each of docker_create_app_containers, docker_start_app, docker_pause_app, docker_unpause_app, docker_stop_app, docker_shutdown_app raises ComposeFileNotFound and runs no compose command at all (subprocess never called), so the core project cannot be touched.
• With the compose file present, the command carries -f and -p for the app.
• Helper-level: missing file raises, core project rejected, project-name normalization cases.

Verified to have teeth: checked out the pre-fix app_tools.py / memory_pressure.py and re-ran the file — 7 failed, 9 passed. With the fix: 16 passed.

One existing test needed fixing, and the reason is the guard doing its job: test_reclaim_compose_stack_reclaims_each_container called reclaim_compose_stack for an app dir that never existed, which now raises ComposeFileNotFound. That state is unreachable in production — reclaim only runs right after a successful compose pause — so the test now creates the compose file it implicitly assumed.

Note: docker_start_app's @throttle(5) is global across apps and tests — a start triggered by an earlier test would silently drop the call under test and fail it spuriously, so the throttle clock is reset in an autouse fixture.

Local run: 2 failed, 188 passed — the memory_pressure one above (now fixed) and test_app_lifecycle.py::test_app_starts_and_stops, which fails only on this dev box because another container already binds host port 80 (Bind for 0.0.0.0:80 failed: port is already allocated); it passed on CI's clean runner. CI's first run: 1 failed, 189 passed — only the memory_pressure test, fixed in the last commit.

Recommended reading order

1. shard_core/util/subprocess.py — the pinned-command helper and its guards
2. shard_core/service/app_tools.py — all app compose calls routed through it
3. shard_core/service/memory_pressure.py — the one remaining cwd-based call
4. agents.md
5. tests/test_app_compose_pinning.py
6. tests/test_memory_pressure.py