fix(selfhost): keep runner temp files off docker overlay

[JSONbored]

Summary

• Problem: the self-hosted GitHub Actions runner service in docker-compose.yml left TMPDIR/TMP/TEMP unset, so CI job temp writes (language toolchain caches, build artifacts, ad hoc mktemp calls) landed in the container's plain /tmp, which lives in Docker's overlay/containerd snapshot storage — not the mounted runner-work volume. This grows the host's Docker root storage directly and is invisible to volume-scoped cleanup, causing unbounded overlay growth, disk pressure, and docker system df races against disappearing temp files under sustained CI load.
• Fix: the runner service now sets TMPDIR, TMP, and TEMP to /tmp/runner/tmp — a subdirectory of the existing mounted runner-work:/tmp/runner volume — via a reusable x-runner-tmp-env YAML anchor. RUNNER_WORKDIR stays on the same mounted volume as before.
• Guaranteed to exist: a new one-shot runner-tmp-init service (alpine:3.20, mkdir -p + world-writable chmod) bootstraps that directory on the volume before the runner container starts, gated via depends_on: condition: service_completed_successfully. This is idempotent (safe on every docker compose up) and never touches the runner image's own entrypoint/registration flow — it's a pure Compose-level dependency, not an image wrapper.
• Multi-runner scalability: the temp-env pattern is centralized in the x-runner-tmp-env anchor. docker-compose.override.yml.example and the self-hosting operations docs both document that additional runner services (for higher CI throughput) must repeat this same pattern — including the YAML-anchors-don't-cross-files caveat, since an override file can't reference the base file's anchor directly.
• No behavior changes to: RUNNER_WORKDIR placement, Docker socket exposure (still never mounted), or volume-pruning behavior (none introduced; the init step only creates a directory, never deletes anything).

Why

Confirmed in production: runner containers wrote high-volume CI temp files into the container default /tmp, causing Docker root storage growth and disk pressure. The live mitigation was setting TMPDIR=/tmp/runner/tmp by hand per-container; this PR makes that the shipped default so a fresh self-host deploy is correct without any manual step.

Validation

• npm run typecheck
• docker compose --profile runners -f docker-compose.yml config --quiet (also verified with every profile active simultaneously)
• npm run ui:lint / npm run ui:typecheck (docs page change)
• New tests: test/unit/selfhost-compose-runner-tmpdir.test.ts (13 cases — volume mount, RUNNER_WORKDIR, TMPDIR/TMP/TEMP all set and pointed at mounted storage not raw /tmp, no Docker-socket mount, no volume-deleting behavior in the init step, runners-profile gating, and that the runner service actually merges the x-runner-tmp-env anchor rather than a hand-duplicated copy that could drift) and test/unit/docs-selfhost-operations-runner-tmpdir.test.ts (6 cases — drift guard so the docs' multi-runner snippet can't silently diverge from the real compose pattern, mirroring the existing docs-selfhost-troubleshooting-metric-names.test.ts source-of-truth-diff approach).
• npm run test:ci (full local gate) — 7077 tests passed, fully green.
• npm audit --audit-level=moderate — 0 vulnerabilities.
• No src/** files touched by this PR, so Codecov's patch-coverage gate has nothing to measure here; the new regression tests are pure structural/parity checks against docker-compose.yml and the docs page.

Notes

While investigating this, found that an earlier PR (#2717) had already added a different, overlapping Docker-prune script (scripts/docker-prune.sh) without noticing scripts/selfhost-docker-prune.sh (systemd-timer-integrated, docs-referenced, tested) already existed from PR #2576. That's an unrelated cleanup item, tracked separately — not addressed in this PR to keep it focused on the runner-tmpdir fix.

[cloudflare-workers-and-pages]

Deploying with    Cloudflare Workers

The latest updates on your project. Learn more about integrating Git with Workers.

Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	gittensory-ui	3018a99	Commit Preview URL Branch Preview URL	Jul 03 2026, 07:57 AM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.03%. Comparing base (a6f4a36) to head (3018a99).
⚠️ Report is 16 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2720      +/-   ##
==========================================
- Coverage   96.13%   96.03%   -0.11%     
==========================================
  Files         241      244       +3     
  Lines       27033    27271     +238     
  Branches     9822     9909      +87     
==========================================
+ Hits        25988    26189     +201     
- Misses        433      457      +24     
- Partials      612      625      +13     

see 3 files with indirect coverage changes

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.