ersatztv/docs/ci-cd.md

# CI/CD for the ErsatzTV Fork

The fork builds its own Docker image via **Gitea Actions** on the homelab and pushes
to the **Gitea container registry**. Runner + registry were provisioned in
server-management#172; the build pipeline is ersatztv#4; test/prod containers are
server-management#481.

## Hosts (read this before trusting a hostname below)

| Host | IP | Role |
|---|---|---|
| **jazz** | 192.168.1.29 | **Docker host for the media transcoders** — prod `ersatztv` (8409), `ersatztv-test` (8410), Jellyfin. Release scans (`security-scan.sh`) and the prod-copy `migration-smoke.sh` run here. |
| **bumblebee** | 192.168.1.99 | CI runners (`bumblebee-runner`, `small-runner`), plus every other Docker stack. All the memory/lane measurements below were taken here. |
| **ci-runner** | VM 127 (pve4) | The other `ubuntu-latest` CI runner. |

The transcoders moved bumblebee → jazz on **2026-07-20** (server-management#633).

> **Name-reuse trap.** `jazz` was an **earlier name for the .99 host**. Anything written before
> 2026-07-20 that says "jazz" means today's **bumblebee** — resolve hostnames by **IP**, not by name,
> and don't "fix" a historical bumblebee reference into jazz.

## Versioning & releases

The fork inherits upstream ErsatzTV's scheme: **`vYY.<release-seq>.<patch>`** (lightweight, `v`-prefixed git tags).

- **`YY`** — two-digit year.
- **`<release-seq>`** — a sequential release counter **within the year**, reset at each year boundary. It is **not** the calendar month. (Evidence: `v25.2.0` shipped in June 2025, `v25.5.0` in Sep, `v26.3.0` in Feb 2026 — minors don't track months; and `v25.9.0` → `v26.1.0` shows the year-reset.)
- **`<patch>`** — a small follow-up/hotfix on the *same* release line (e.g. `v26.1.0` → `v26.1.1`, days later).

Upstream's final release was **`v26.3.0`** (archived). Our line continues from there:

| Tag | Meaning |
|-----|---------|
| `v26.3.1` | Upstream 26.3.0 **rebuilt on our infra** (Gitea CI/registry, fork ffmpeg base) — **no application changes**. A patch bump, because nothing functional changed. |
| `v26.4.0` | First fork release carrying application changes. Later 2026 releases continue `26.5.0`, `26.6.0`, …; a new year resets to `27.1.0`. |
| `v26.7.0` | Blazor-removal release: ChicoryTV became the only UI. |
| `v26.8.0` | Secured/versioned ChicoryTV SPA + REST API go-live release (#335). |
| `v26.9.0` | Configurable advertised IPTV base URL for M3U/XMLTV (#340) + SPA shell/routing + playouts modularization (#247/#245); on-air/Plex/library-path fixes (#99/#345/#371); coverage + functional-E2E CI (#15/#299). |
| `v26.10.0` | Auto-Tune channel workflow (#69) + weighted content distribution (#70); scheduling refactors, health-check remediation UX (#164), HLS cold-start instrumentation (#350), security hardening (#293/#376/#308). |
| `v26.11.0` | **QSV profiles decode via VA-API** — `QsvPreferNativeDecoder`, default **on**, fixes ~50% channel cold-start failures on Intel (#498); unified logo/on-screen bug via a shared watermark preset (#67). Media-scanner resilience: Jellyfin mixed-content libraries (#489), music-video scan correctness (#488/#494/#497), remote-stream probing before ffmpeg (#473/#480); weighted-distribution SPA (#404). **First release deployed to `jazz`** (server-management#633). |
| `v26.12.0` | **`ErsatzTV.Mcp` MCP server** — read + cautious-write over `/api/v1`, `ERSATZTV_ALLOW_WRITES`-gated (#58). **External channel-logo URLs download + cache at save time** (#525), with the on-screen bug now rendered for external-URL logos (#502). HLS cold-start hardening: burst-read the first segments so start isn't `-readrate`-bound (#350) and floor QSV extra hardware frames so an unthrottled read can't exhaust the pool (#529); remote graphics-engine image fetches bounded — timeout, size cap, decode cap, redirects, pooling (#511). Decision-lifecycle tooling + parallel-orientation startup rewrite (#520/#521); CI `docker build` lane rebalance (#508). |
| `v26.13.0` | **RuleBuilder maturation** — arbitrary-depth group nesting (#436), inline smart-query authoring in Channel Builder (#437), DB-sourced facet typeahead + relative-date operators + validation (#434/#435/#438), and an artist typeahead covering music-video/song credits with `album_artist` no longer 404ing (#578). **Per-channel On Now/Next transient overlay** (#74/#570) and **per-schedule clock-boundary padding** (#392); in-browser channel preview (#60); Auto-Tune per-source weight steppers + exclude/add-untagged (#440). Library-browse pickers now resolve by search instead of a 100-row window, closing several silent at-cap truncations (#644/#650/#651/#634). Correctness: one watermark resolver for all four attachment points, incl. `MiddleCenter` (#503/#510); QSV HDR tonemaps through OpenCL because `vpp_qsv=tonemap` is a silent no-op (#505); `LibraryFolder` unique index + concurrent-insert tolerance (#491); per-library music-video identity with soft trash (#496); Jellyfin Album/Track music-video projection (#177); metadata-collection dedup (#500); accented facet values via a registered Unicode fold on SQLite (#668); `WorkAheadSlots` atomic slot claim, never a negative count (#536/#539); on-demand guide rebuild on thaw (#68). Process/CI: the H10 review-verdict gate became a sha-bound **required** commit status and was hardened through its false-open chain (#622/#629/#632/#648/#649/#672/#698), the decision corpus split to one YAML-frontmatter record per file (#610/#620), and headless Playwright UI-E2E flows landed (#445/#533). Five dual-provider migrations. |
| `v26.14.0` | **Live TV no longer starves on embedded bitmap subtitles** — `-readrate` paces an input off its *furthest-behind* stream, and a PGS/DVD subtitle read through the video's own `-i` is sparse enough to drag the whole process to **0.53x realtime** against the 1.0x a client consumes, draining the buffer until the channel stalls. Fixed with a capability-gated `-readrate_catchup` (ffmpeg 8.0+) on realtime inputs, keeping `-readrate` on the frame-producing path so the `ffmpeg.qsv-extra-hw-frames-floor` bound is untouched; measured 0.533x → 1.067x on QSV and software, with a 240s QSV soak clean of allocation errors (#726). Affects items carrying an embedded bitmap subtitle matching the channel's subtitle mode — 3,182 of 24,646 media versions on prod, and a property of the *item*, not the channel, which is why the stall presented as random. Process/CI: the H10 review-verdict gate's repair sentinel became a fixed point and its write is now fenced on the timeline retarget count, closing a raced-sentinel false-open (#706/#707/#711). **The decisions validator now cross-checks its dependency-free frontmatter parse against PyYAML** and reports both the truncating unquoted `` #`` and the scalar-closing bare apostrophe as errors, so a record whose `rule:` silently halves under PyYAML fails the local gate instead of CI (#674/#688) — the ceiling-calibration claim was also split so the suite pins what the derivation MEANS rather than live-corpus order statistics. Dependencies: CliWrap 3.10.4, JetBrains.ReSharper.GlobalTools 2025.3.5. |

**Before cutting a release — sweep `docs/decisions.md` + `docs/decisions/`** (ersatztv#521, supersedes
the ersatztv#303 H9 append-only ritual). Supersession/retirement is now a same-PR act (add the new
active record, relocate the predecessor to `docs/decisions/archive/` with reciprocal
`supersedes`/`superseded-by` links), not a release-boundary batch job — most of the old "consolidate"
step is now continuous. The release boundary is instead where you:
1. Run `PYTHONPATH=. python3 scripts/decisions_validate.py` — confirms lifecycle metadata is
   well-formed and every `supersedes`/`superseded-by` link resolves both ways. Since **ersatztv#674**
   it also cross-checks its dependency-free frontmatter parse against **PyYAML when PyYAML is
   importable**, failing on any file PyYAML rejects (a bare apostrophe in a single-quoted value) or
   reads differently (an unquoted ` #`, which YAML truncates as a comment). Where PyYAML is absent —
   the `decisions-guard` job, the Husky hooks — the cross-check is **skipped with a `::notice::`**
   and every other check still runs; the read path stays dependency-free.
2. Confirm every record already classified `superseded`/`retired` actually lives under
   `docs/decisions/archive/` (the validator fails this, but eyeball it at the boundary too).
3. Regenerate the active catalog: `PYTHONPATH=. python3 scripts/build_decisions_catalog.py` and
   commit any drift.
4. Read the corpus size signals. Since **ersatztv#620** these are two separate things:
   - a **per-record prose ceiling** (`decisions_validate.py --record-ceiling <n>`, default **60**)
     — a **non-blocking `::warning::`** naming every record over it. This is the actionable signal:
     it points at a file. The 60 is derived from the distribution, not picked as a round number.
     Its **calibration is guarded in two pieces of different robustness** (ersatztv#688), because
     four earlier single-assertion versions all failed — the first two by being vacuous or
     accepting an absurd ceiling, the last two by ratcheting:
     - **blocking** (`script-tests`) — only the coarse property that the ceiling flags a
       **meaningful minority** of records (`0.02 <= fraction_over <= 0.25`). One record moves a
       fraction by at most 1/N, so no SINGLE ordinary addition can cross it. This is measured
       headroom, not immunity: from today's 18/183 it takes 38 consecutive over-ceiling additions to
       breach the cap, 718 short ones to dilute below the floor, or — the tightest arm —
       consolidating 15 of the 18 offenders away. The floor is
       a fraction rather than "at least one record", which would accept any ceiling up to 229 on the
       live corpus; as a fraction the accepted range is 43..180.
     - **reported, never asserted against the LIVE corpus** — the fine claim that the ceiling sits
       between the **90th and 95th percentile**, i.e. at the tail boundary. `main()` prints a
       `::notice::` when it drifts; the tests assert it only on distributions they own.
       It is an order statistic over a sparse distribution, so a single new record could move p90 by
       21 lines and red the blocking job for whoever wrote it; a ceiling going out of date is
       the passage of corpus growth, not a defect in the commit under test, so it is treated like
       `stale-after`. Re-derive the constant when the notice says so.
   - the **aggregate prose total**, printed every run as an unthresholded `::notice::` **trend**.
     It has no pass/fail. A total over a monotonically growing corpus can only ratchet: the old
     4800→5600 budget went quiet at 5228 after #610 changed the metric and was back over at 5658
     **three and a half hours later the same evening**, with nobody consolidating anything — the
     "permanently red = no signal" failure, not in slow motion at all. It reports record prose and
     non-record scaffolding separately, because they are not the same unit. The generated catalog is no longer counted at all — it
     gains one row per record and cannot be consolidated away.

   **Being listed by the ceiling is an invitation to check for redundancy, not an instruction to
   cut.** A long record that is entirely distinct findings is a legitimate decline — say so in the
   record and move on. (`--budget` is still accepted and ignored, so old invocations keep working.)
5. Report the remaining `legacy-unmigrated` count (the validator prints it as a `::notice::`) so the
   backlog is visible, even though it isn't required to hit zero before a release.
A genuine rationale-prose rewrite still needs a `Decisions-Edit: yes` git trailer on a **non-merge**
commit in the range (see the `decisions.md` header) — routine lifecycle metadata writes above do not.

**Cutting a release:** keep build and promotion as two explicit phases (#335):

1. Confirm `main` CI is green; run the full local gate plus `dotnet list package --vulnerable
   --include-transitive`; then push a `vYY.N.P` tag on that exact `main` commit.
2. Wait for tag CI to build `:prod` + the immutable `:<version>` + `:<sha>` images. Run
   `scripts/security-scan.sh` on jazz against **the immutable `:<version>` image**, not a
   moving tag, and triage every ZAP/semgrep finding.
3. Only after the candidate passes, manually `DeployStack jazz-media` and observe its pre-deploy
   output. Prod's compose deliberately follows floating `:prod` (Timothy's 2026-07-11 decision), so
   no CI push or pin bump is needed.

> **The Komodo stack is `jazz-media`, not `media-servers`** (verified live 2026-07-20 during the
> v26.11.0 cut). The *compose project* is still `media-servers` — which is what the container labels
> show — but the **Komodo stack name** changed with the move to jazz. A stack named `media-servers`
> still exists on bumblebee and is `unhealthy` (the stopped migration leftovers), so
> `DeployStack media-servers` silently targets the **dead** stack. Confirm with
> `/read ListStacks` before deploying.
>
> **A third stack, literally named `ersatztv`, is also live and is NOT prod**: it owns
> `ersatztv-test`, tracks the floating `:latest` tag, and runs with `auto_update: true`. (Stack
> name, compose project, config-file path and image tag re-confirmed from the container labels on
> jazz 2026-08-11; the `auto_update` flags and the bumblebee `unhealthy` status are carried from
> the earlier checks noted above, not re-measured that day.)
> `DeployStack ersatztv` succeeds and looks healthy — it just promotes nothing to prod. Three names,
> one target:
>
> | Stack name | project_name | auto_update | owns |
> |---|---|---|---|
> | `jazz-media` | `media-servers` | `false` | `ersatztv` (**prod**, tracks `:prod`) |
> | `ersatztv` | `ersatztv` | `true` | `ersatztv-test` (tracks `:latest`) |
> | `media-servers` | — | — | dead stack on bumblebee, `unhealthy` |
>
> Don't resolve the prod stack by name at all — resolve it by the **container's**
> `com.docker.compose.project.config_files` label (e.g. via `docker inspect`), which points at the
> actual compose file path and can't be confused by a same-named stack.
>
> **There is no Global Auto Update fallback anymore**: `jazz-media` has `auto_update: false`
> (`poll_for_updates: true` only), so nothing promotes `:prod` on a timer — promotion is manual,
> full stop. The old "don't cut a tag near the 03:00 run" caveat no longer applies.

server-management#585 source-confirmed that Global Auto Update invokes the **same** `DeployStack`
execution as a manual promotion, and extended the #553 pre-deploy hook to detect a floating-tag
**digest** change. Either path now takes the fail-closed prod backup; server-management#589 then
wired `migration-smoke.sh` into that hook, against the exact candidate and the backup it just made.
A backup, fetch, or migration-smoke failure aborts before the live container is recreated. See
`homelab-docs/Docker/ErsatzTV.md` for the operational evidence and rollback procedure.

**Gotcha:** never put a `[skip ci]` token in a commit you intend to tag — Gitea reads skip-ci from the *tagged* commit and will **suppress the release build**. (Also, `workflow_dispatch` on a tag ref isn't supported on this Gitea version, so the tag *push* must do the triggering.) Release commits, and anything you'll tag, must not contain skip-ci.

**Also avoid firing several pushes back-to-back** (e.g. a `[skip ci]` commit, then `main`, then a tag, all within ~1s). Observed once on this Gitea instance: the later events were silently dropped — no `ActionRun` records created at all, even though the runner was online and the workflow `active`. Pushing again, spaced out, created the runs normally. If a push/tag doesn't produce a run, re-push (or push an empty commit) rather than assuming the runner is broken.

## The workflow: `.gitea/workflows/docker-build.yml`

Single workflow. Gating jobs `test` + `migrations` run in parallel and gate `build`; a
non-blocking `docs-reminder` job runs on PRs only (see below). Prod deploy is **not** a CI
job — it's Komodo Global Auto Update off the `:prod` tag (see "Cutting a release").

### Triggers & tags

| Trigger | `test` job | `build` job | Image tags pushed |
|---------|:----------:|:-----------:|-------------------|
| `pull_request` | ✅ | — (skipped) | none |
| push to `main` | ✅ | ✅ | `:latest` + `:<short-sha>` |
| push tag `v*` | ✅ | ✅ | `:prod` + `:<version>` + `:<short-sha>` |
| `workflow_dispatch` | ✅ | ✅ | only if ref is `main`/`v*`, else build-only (no push) |

A **docs-only** change (see "Docs-only skip" below) reduces every ✅ above to a seconds-long no-op
that still reports its status.

`:latest` is the **test/dev** channel (every `main` commit). Prod's compose **follows the
floating `:prod`** tag (reverted from the 2026-07-07 version pin on 2026-07-11) — never
`:latest`. Both `:prod` and `:<version>` are produced by pushing a `v*` tag; prod tracks
`:prod` and is redeployed by Komodo Global Auto Update (see "Cutting a release"). The
immutable `:<version>` tags remain for reproducible rollback (`docker run …:26.6.0`).

Concurrency is scoped **per event+ref** (`group: ersatztv-build-${{ github.event_name }}-${{ github.ref }}`,
`cancel-in-progress` for PRs): PR runs parallelize across PRs, a new sync auto-cancels
its superseded run, and image builds still serialize within their own ref. Do NOT push
`main` and a `v*` tag simultaneously — those are separate groups but share the
`:buildcache` tag and the smoke container name; tag only after the main build is green.
(History: originally one global group serializing ALL runs for the single runner —
with three runners that starved the queue; changed 2026-07-11, server-management#574.)

**Four** runners serve the fork (server-management#570/#574/#639):

| Runner | Host | Label | Slots | Per-job cap |
|---|---|---|---|---|
| `ci-runner` | VM 127 (pve4) — no prod workload | `ubuntu-latest` | 4 | `--cpus=4 --memory=10g` |
| `bumblebee-runner` | bumblebee — prod media | `ubuntu-latest` | 2 | `--cpus=4 --memory=10g --cpu-shares=256` |
| `small-runner` | bumblebee — prod media | **`small`** | 2 | `--cpus=1 --memory=1g --cpu-shares=256` |
| `jazz-small-runner` | jazz — prod media (#633) | **`small`** | 2 | `--cpus=1 --memory=1g --cpu-shares=128` |

The `small` lane exists because Gitea dispatches a job as a runner task **even when its
`if` skips it**, and those skip-tasks used to wait behind long builds (observed 31 min),
stalling every PR run. `--cpu-shares` below the default 1024 is what makes a runner on a
prod media host acceptable: under contention CI loses to the transcoders (ersatztv 1536 /
jellyfin), which are the reason those hosts exist.

That same "dispatched even when `if` skips it" behavior is why the git-only PR gates live in
their own **[PR gates workflow](#pr-gates-workflow)** (`pr-checks.yml`, `on: pull_request`)
rather than in `docker-build.yml` — see that section (ersatztv#535).

**`small` is git-only, and that is load-bearing (server-management#639).** Everything in
the lane is a checkout plus a `git diff`: `decisions-guard`, `ci-image-pin`,
`docs-reminder` — plus `prove-fix` (ersatztv#794), the heaviest member: per commit carrying a
`Proves:` trailer it makes two `git worktree add`s and runs an arbitrary pytest selection twice,
so a PR claiming many proofs costs proportionally more than the rest of the lane combined — plus
`script-tests`, which is a checkout plus a `pytest` run needing only
`pytest` and `pyyaml` (ersatztv#631; it is NOT stdlib-only — that assumption is what turned the
job red on its first CI run, see below) — plus **`scan`** (ersatztv#767), the same
lightweight-Python shape. `scan` is the lane member to think hardest about before changing anything
here: it is the only one that lives in `docker-build.yml` rather than `pr-checks.yml`, so the only
one that runs on a **tag push**, and the only one whose failure does not merely redden a status but
**skips `build`** — an OOM or a wedge there yields no release image at all.
Nothing there runs a compiler or a `docker build`, which is why the lane
can be capped at 1 GiB per job. The lightweight-Python jobs are the deliberate edge of the
"git-only" rule, not an exception to it: `setup-python` + `pip install pytest` + a suite whose
heaviest allocation is a handful of temp-dir git repos stays far under the cap. Route a heavy job here and it will OOM — give it
`ubuntu-latest`, or its own label on `ci-runner`, the only host with no prod workload.

**Lane assignment (ersatztv#390).** *Slot counts below are as-of 2026-07-17; the table above is
current.* At the time, the `ubuntu-latest` lane had **4 slots** (2 + 2) and the
`small` lane 4. A 2026-07-17 audit of the Actions API found the `ubuntu-latest` lane
saturated and the `small` lane idle — **queue wait exceeded every job's runtime**:

| Job | Runtime | Queue wait | Lane |
|---|---|---|---|
| `test` | 354s | 1363s | ubuntu-latest |
| `migrations` | 639s | 1428s | ubuntu-latest |
| `functional-e2e` | 520s | 1447s | ubuntu-latest |
| `api-docs` | 5s | **1722s** | ubuntu-latest → `small` → **reverted to ubuntu-latest** (#406) |
| `format` | 37s → **~0.5s** (#469) | **1731s** | ubuntu-latest → `small` → **reverted to ubuntu-latest** (#406) |
| `docs-reminder` / `decisions-guard` | 10s | **5s** | small |

`api-docs` and `format` moved to `small` because the queue wait dwarfed their runtime. Both lanes
run the *identical* `runner-images:ubuntu-latest` base, so `small` was a label with spare capacity,
not a different capability — a move only possible because those jobs now run in the **CI toolchain
image** (below) and no longer need the runner image to supply .NET/Node.

**Reverted 2026-07-17 (ersatztv#406 / server-management#604).** #390's own caveat — *"on an
API-touching PR `api-docs` does a full `dotnet build`, so it is not always small"* — turned out to
be the deciding factor, and "capacity 4 absorbs that" held only because **nothing enforces the sum**
of the lanes' per-job caps. Each job container is correctly capped (`--memory=10g`), but 6 slots ×
10 GiB = **60 GiB on a 25 GiB host** that also runs prod media; on 2026-07-17 bumblebee hit load
340 with 21 GiB swapped. These were not small jobs — a live `docker stats` caught the `format` job
container at **3.95 GiB**, which the re-sized 2 GiB `small` lane would OOM-kill outright. #604 fixes
the queue at the source instead (`ubuntu-latest` grown to 5 slots: a 48 GiB ci-runner at capacity 4
plus a bumblebee overflow slot), so the `small` lane can be reserved for genuinely-tiny shell jobs.
(The `format` half of this is now **moot**: **ersatztv#469** moved it to `dotnet format whitespace .
--folder`, which loads no Roslyn workspace — the job's 3.95 GiB heap and multi-minute runtime are
gone, so it is no longer a reason to keep the lane large. `api-docs` on an API-touching PR still is.)

Queue wait is still a dominant cost and capacity is server-management's boundary — tracked in
**server-management#604**. The redundant triple-build behind those runtimes is **ersatztv#398**.

**The other failure mode: setup-phase starvation (server-management#639, 2026-07-20).** The
table above measures *queue wait* — time before a job is dispatched. A saturated lane also
produces a second, much more confusing symptom: a job that *is* dispatched, sits `in_progress`
for >10 minutes, writes **no log file at all** (`OpenLogs … .log.zst: file does not exist`),
and then fails — wedged in act's job-**setup** phase, before Checkout. Same-config siblings
that started 90s earlier finished in seconds; a concurrent job's log showed a normally-fast
compile taking a 7-minute gap between projects. This is the origin of the "`decisions.md` is a
known flake, just rerun it" folklore: the rerun succeeds only because it lands after load
clears, so the guard's logic gets blamed for a capacity problem.

The fix was **not** more capacity for its own sake. `small` was stuck at one slot because it
still held two heavy jobs — `docker-build.yml`'s image build and `ci-image.yml`'s toolchain
buildx (the latter reads as lightweight because it is "docker-only", but it is the heaviest
thing that ran in the lane) — and their 10 GiB requirement set the lane's per-job cap, which
on a 25 GiB host permits exactly one slot. Moving both to `ubuntu-latest` made the lane
genuinely tiny, so it could widen to **4 slots across two hosts while committing less RAM to
CI than the single slot did**. `docker-build.yml`'s `build` does not re-create #574's
skip-task queueing, because `needs: [test, migrations, scan]` means it cannot be dispatched until
the lane it would queue behind has already drained.

### CI build memory: no persistent compiler servers (ersatztv#406)

Roslyn's `VBCSCompiler` is a **persistent** compiler server — it outlives the `dotnet build` that
started it and keeps its heap warm for the next one. Locally that is a genuine speedup; in CI it
buys nothing, because each job container is torn down at the end of the run and there is never a
"next build" to warm. It was measured at **7.8 GB RSS** on bumblebee — the single largest consumer
on the host, and the reason each job needed a 10 GiB cap in the first place.

So the workflow's top-level `env:` disables the servers for every runner-side dotnet job:

| Variable | Effect |
|---|---|
| `UseSharedCompilation=false` | no persistent `VBCSCompiler`; `csc` runs per project and exits |
| `DOTNET_CLI_USE_MSBUILD_SERVER=0` | no persistent MSBuild server process |
| `MSBUILDDISABLENODEREUSE=1` | MSBuild worker nodes exit with the build instead of lingering |

These are MSBuild properties set as environment variables so they apply to every `dotnet`
invocation without touching each call site (MSBuild surfaces env vars as properties, and
`UseSharedCompilation` is only defaulted to `true` when empty, so the env var wins).

**What this does and does not shrink.** It helps the jobs that *compile* — `test`, `migrations`,
`api-docs` on an API-touching PR, and the in-Docker `build`. It never helped `format`: `dotnet
format` loaded Roslyn in-process via MSBuildWorkspace and never spawned `csc`, so the compiler-server
env vars left its measured 3.95 GiB untouched. (Moot since **ersatztv#469** switched `format` to
`dotnet format whitespace . --folder`, which skips the MSBuild/Roslyn workspace entirely — the job is
now a ~0.5 s, low-memory whitespace/BOM check with no Roslyn heap. See *Static analysis &
formatting → Formatting* below.)

The same three are repeated in `dependency-scan.yml`; workflow `env:` does not cross workflow files.
That one is lower-stakes (restore/list are MSBuild-driven, so it's lingering worker nodes rather
than a 7.8 GB VBCSCompiler) but it runs unattended on a cron against the prod media host.

**The workflow `env:` does not reach the `build` job's compilation**, which happens inside
`docker build` — the same three are set as `ENV` in the SDK stage of `docker/Dockerfile`. That is
the job server-management#570 measured pegging 5.999/6 GiB, so it is the one that most needs this.
Build-stage only; the final image is `FROM runtime-base`, so nothing lands in the shipped image.

The `test` job samples its own memory and reports it every run. Two steps (`continue-on-error`, so
they never fail a build), driven by `scripts/ci-peak-anon.sh` (ersatztv#412):

- **Start peak-anon sampler** (before the dotnet Build/Test/Coverage steps) launches a detached
  background poller that tracks the high-water mark of the cgroup's **anon** memory every 2 s.
- **Report peak container memory** (the job's last step) stops the sampler and prints the sampled
  **peak anon** — the headline number — alongside `memory.peak` and the end-of-job `anon`/`file`
  split, to the log and the job step summary.

Read the **peak anon** off a recent run to size a cap — not `memory.peak`, and here is why:

> ⚠️ **`memory.peak` is not "peak RSS".** It is the high-water mark of `memory.current`, which
> charges **page cache** to the cgroup as well as anonymous memory. Proven on bumblebee: a
> container with `anon=0` that merely reads an 800 MB file reports `memory.peak=826 MiB`, of which
> `file=800 MiB`.
>
> This matters because the naive reading **inverts the decision**: page cache is *reclaimed* under a
> tighter cap, not OOM-killed, so a big peak that is mostly `file` is **not** evidence that the cap
> must stay high. `anon` is the part that actually forces an OOM. **Size caps on peak `anon`, not on
> `peak`.**
>
> Why a *sampler* and not just the end-of-job split: the kernel exposes `memory.peak` (peak of
> anon+cache) but has **no peak-anon counter**, and the end-of-job `anon` is the composition *then*,
> not at the peak instant — a job that peaks mid-`dotnet test` and then frees reports a misleadingly
> low `anon`. The 2 s background sampler catches the true peak-anon instant; `memory.peak` and the
> end-of-job split stay in the report as a cache-inflated ceiling and a reference. (Before #412 the
> instrument printed only `memory.peak` + the end-of-job split — see #411.)

**The compiler-server A/B (ersatztv#412).** Measured on bumblebee in the CI toolchain image,
swap-off (`--memory-swap == --memory`), full-solution `dotnet build --no-incremental`, peak anon
sampled by *this* instrument, servers shut down between arms (n=2 each, interleaved):

| Arm | shared-compilation env | peak anon (2 runs) | resident after build |
|---|---|---|---|
| **OFF** (the CI config) | disabled | **5818 / 5854 MiB** (~5.84 GiB, tight) | none |
| **ON** (dotnet defaults) | enabled | **6305 / 7604 MiB** (~7.0 GiB, noisy) | ~3 GiB `VBCSCompiler` |

Two things are solid: OFF is **consistently ~5.84 GiB** and ON is **always higher** (mean delta
~1.1 GiB, up to ~1.8 GiB), so disabling the servers is worth it; and ON leaves a ~3 GiB
`VBCSCompiler` **resident** after the build — the host-between-jobs cost #406 removed. Don't read a
*precise* delta into the ON peak: it is noisy because a parallel build's peak depends on how many
`csc`/project compilations overlap at the peak instant.

**#406's premise — *"if disabling shared compilation brings peak RSS well under 6 GiB, the whole
budget loosens"* — is NOT supported.** OFF sits at ~5.84 GiB for the *build phase alone* — right at
the 6 GiB line, not well under it — and the `test` job adds `dotnet test` + coverlet +
reportgenerator on top. Disabling the compiler servers stays right (consistent reduction, no 3 GiB
resident server) but **do not bank a looser cap budget on it**: size the cap off the **live
test-job peak anon this instrument now reports** (build + test + coverage), not off this build-only
A/B.

> The earlier PR #411 probe (`peak 9457 / anon 7134 / file 421 MiB`) read *higher* than these
> swap-off sampled numbers. Swap settings and read-method (end-of-job snapshot vs sampled peak) move
> these figures by >1 GiB (#406), so treat the committed instrument's sampled peak-anon as
> authoritative and that probe as superseded.

What *is* established: no persistent compiler server survives a build, `migrations` is green with
mysql capped at 2g swap-off, and the `test` job now self-reports a true peak-anon every run.

### `services:` containers are capped explicitly (ersatztv#406)

A runner's `container.options` (`--cpus=4 --memory=10g`) applies to the **job container only, not
to `services:`**. Verified on a live `migrations` job: the job container reported
`HostConfig.Memory=10737418240`; its `mysql:8.4` service reported `mem=0 nanocpus=0` — unbounded.
So `migrations` runs added an uncapped MySQL to an already-tight host.

The mysql service now sets `--memory=2g --memory-swap=2g --cpus=2`.

**`--memory-swap` is the part that matters, and it is easy to get wrong.** Docker defaults an unset
`--memory-swap` to **twice** `--memory`, so `--memory=2g` *alone* grants 2g RAM **plus 2g of swap**.
Verified on bumblebee:

| Options | `memory.max` | `memory.swap.max` |
|---|---|---|
| `--memory=2g` | 2147483648 | **2147483648** ← 2 GiB of swap |
| `--memory=2g --memory-swap=2g` | 2147483648 | **0** ← swap disabled |

Setting `--memory-swap` equal to `--memory` disables swap for the container. On this host that is
the whole point: swap thrash is what took prod down, and a swapping mysqld mid-DDL is precisely the
pathology behind the known `Command Timeout expired` migrations flake. **Prefer a loud OOM over
silent swapping** — an OOM is a clear signal to raise the cap; swapping just degrades everything.

⚠️ **The same 2× applies to the runners' `container.options: --memory=10g`** — each job slot is
really 10 GiB RAM *plus* 10 GiB swap. The "6 slots × 10 GiB = 60 GiB on a 25 GiB host" framing
understates the promise by 2×, and it is a plausible direct mechanism for the incident's 21 GiB of
swap. Fixing that is server-management#604's call (reported there).

**On the 2g figure, honestly:** a `mysql:8.4` container with this exact env peaked at **543 MiB**
during init and settled at 481 MiB idle (probed on bumblebee, 2026-07-17) — but that is init+idle,
**not** the 787-migration replay, which grows table/definition caches idle never touches. So 2g is a
measured *floor* plus headroom, not a measured ceiling; the `migrations` job going green is what
validates it. `--cpus=2` has no measurement behind it at all — 787 sequential DDL statements on one
connection are ~1-core-bound, so it is judgement; revisit if the apply step's tail latency grows.

**Any new `services:` container needs its own explicit cap** — it will not inherit one, and it needs
`--memory-swap` set alongside `--memory` or it silently gets 2× in swap.

### `test` job

`dotnet restore` → strip the Scanner project ref (`sed -i '/Scanner/d'`, matching the
Docker build) → `dotnet build -c Release` → `dotnet test -c Release --no-build`. Gates
the image build.

- **Code coverage** (ersatztv#15): `dotnet test` runs with `--collect:"XPlat Code Coverage"
  --settings coverlet.runsettings --results-directory ./coverage`, so `coverlet.collector`
  (referenced by every `*.Tests` project) emits a Cobertura report per project. A follow-up
  **Coverage summary** step merges them with ReportGenerator (`TextSummary` to the log,
  `MarkdownSummaryGithub` to the job step summary). No floor is enforced yet ("decide on a
  floor later" — #15); the step is `continue-on-error: true`, so a missing report or a
  transient tool install never blocks a build.
  - **`coverlet.runsettings` excludes generated EF migration code** (`**/Migrations/*.cs`,
    ~2.59M generated lines vs ~200k authored). Instrumenting it OOM-killed the shared `test`
    job (exit 137); excluding it cuts the instrumented surface ~126× (2.5M→20k coverable
    lines in the whole-solution `Architecture.Tests` process) and makes the percentage reflect
    authored code.
- **Shallow checkout**: `fetch-depth: 1` (ersatztv#190) — this job never runs `git
  describe`/`git log`, only `build` needs full history/tags for version computation, so
  `test` and `migrations` both check out shallow. `build`'s checkout stays `fetch-depth: 0`.
- **NuGet package cache**: both `test` and `migrations` cache `~/.nuget/packages` via
  `actions/cache@v4`, keyed on `hashFiles('Directory.Packages.props', 'global.json')` with
  a `restore-keys` OS-level fallback (ersatztv#190). Avoids a from-scratch `dotnet restore`
  on every run; the key only changes when the central package manifest or SDK pin changes.

### `build` job

1. Compute `INFO_VERSION` (`git describe` + short sha on `main`; tag version on `v*`).
2. `docker/setup-buildx-action` with `buildkitd-config-inline` setting `http = true`
   for `192.168.1.95:3000` — **BuildKit does not inherit the host daemon's
   `insecure-registries`**, so without this, cache/base-image/push over the HTTP
   registry fails (`http: server gave HTTP response to HTTPS client`).
3. `docker/login-action` with repo secrets `REGISTRY_USER` / `REGISTRY_PASSWORD`.
   **`REGISTRY_PASSWORD` is a scoped PAT (`write:package` + `read:repository`), not an account
   password** — deliberately, so head-resolved PR code cannot use it to forge a commit status
   (`ci.actions-credential-scoping`, ersatztv#697). If a job ever fails with `token does not have at
   least one of required scope(s)`, the fix is to narrow what the job does, **never** to widen the
   token to `write:repository` or to put the admin password back. Note what the scope still reaches:
   `write:package` covers `ersatztv:prod` (the tag prod's stack follows) and `ersatztv-ci:<sha>` (the
   toolchain image five `container:` jobs execute), so this is the deployment supply chain, not an
   inert endpoint — see `ci.actions-credential-scoping`.
4. `docker/build-push-action@v6`: amd64-only, `docker/Dockerfile`, `INFO_VERSION`
   build-arg, registry layer cache (`type=registry,ref=…:buildcache`,
   `cache-to … ignore-error=true`).
5. **Smoke + IPTV E2E test**: pull the just-pushed `:<sha>`, run it, poll for HTTP
   readiness (`docker exec … python3` → `http://localhost:8409/`), then assert the real
   Jellyfin-facing surfaces on the freshly built image (ersatztv#16): `/iptv/channels.m3u`
   returns 2xx containing `#EXTM3U`, and `/iptv/xmltv.xml` returns 2xx containing a `<tv`
   root. `xmltv.xml` needs `channels.xml` (written by the scheduler a few seconds after
   boot), so each endpoint is polled with a deadline. Unique container name + `trap … EXIT`
   cleanup; dumps container logs on failure. Catches routing / base-URL (#1) / migration
   regressions that leave the app "up" but serving broken output.

### `functional-e2e` job (advisory; PR + main)

Boots the app **from source** and drives the manual live-E2E curl flows sessions have historically
re-run by hand, turning them into a CI regression net (ersatztv#299). It is the automatable half of
`docs/e2e-local.md`; every script it chains runs identically locally and in CI:

1. `npm ci` + `npm run build` (SPA), `dotnet build ErsatzTV.sln -c Release`. (ffmpeg comes from the
   CI toolchain image; the old `apt-get install ffmpeg` step is gone — see below.)
2. `ETV_BUILD_CONFIG=Release scripts/e2e-local.sh <fresh-config>` — copies `wwwroot`, launches
   `dotnet ErsatzTV.dll` in the background (logging to a file so the launch step returns once the app
   is ready), prints `PID`/`CONFIG_DIR`.
3. `scripts/e2e-functional.sh http://localhost:8409 <config>` — asserts. Mostly curl-only: the
   **legacy→SPA redirect sweep** (+ the `/api`, `/artwork` never-redirect exemption), the
   **auth/CSRF/security-stamp** flow (setup-claim → read-gate 401/200 → re-claim 409 → CSRF 403 →
   login 401/200 → logout 403/204 → post-logout stamp-revocation 401), the **library-scan status
   contract** (404 unknown / 202 queued / `scan-status` 200), and the **If-Match/412** round-trip on
   `rerun-collections`. Since ersatztv#363 (extended by #444) it also asserts three **lock-contention
   409s** that aren't curl-only — see below. A `trap` kills the instance on step exit.
4. `ETV_UI_PORT=8410 scripts/e2e-ui.sh` — boots a second, **fresh** instance and runs the headless
   Playwright UI flows (ersatztv#445). See "UI-E2E step" below.

**Lock-contention 409s (ersatztv#363).** The harness now seeds rows the API can't create — a
`LibraryPath` and a Jellyfin media-source — directly into the running instance's SQLite DB (via
python3's stdlib `sqlite3`, whose busy-timeout retry serializes behind the app's writer), and synthesizes media with the
image's ffmpeg, to exercise two `IEntityLocker` contracts **deterministically** (it only fires the
racing request once the lock is *provably* held, never a sleep-and-hope): (a) the **library-scan
"already scanning" 409** — seed ~60 tiny clips into the built-in Shows library so the scanner
subprocess runs a few seconds, poll `GET /libraries/scan-status` until the library shows active (that
window is a strict subset of the scan lock's held window), then a second `POST .../scan` is a 409
(deterministic bar a tiny residual TOCTOU gap the multi-second scan covers); (b) the
**external-collections "already scanning" 409** — the per-family lock is taken
synchronously *before* the 202, so the 202 proves it held, and pointing the seeded source at a
non-routable address keeps the background sync hung so the window stays open; and (c) the
**playout-build "build in progress" 409 + `isLocked` projection** (#215/#444) — a build is enqueued
onto the single-consumer `WorkerService` and the trigger returns *before* the handler locks, so poll
`GET /playouts/{id}` until `isLocked:true` (not the accepted trigger), then fire. Seed a Classic Flood
schedule over a few short episodes and crank `PlayoutDaysToBuild` (`playout.days_to_build`) so one
build is wide enough to observe (~5 days ≈ 43k items ≈ ~1s locally, wider on slower CI); assert `PUT
/playouts/{id}` 409, `POST .../playout/reset` 409, the list `isLocked:true`, then post-build the same
`PUT` 200s. No new CI step or dependency: ffmpeg ships in the toolchain image, and python3 was already
a harness dependency (`json_field`). The scan + build flows self-skip (advisory) if ffmpeg is ever
absent, and the build flow also self-skips if the build is never observed locked (never asserts an
unproven race).

**Advisory, by design** (the issue's "keep it a separate job so a functional-E2E flake can't block the
unit-test gate"): it is **not** a `needs:` of `build` and **not (yet) a required check**, so a flake
blocks nothing. Promote it to a required check / `build` dependency once it's proven reliable — the
same staged rollout the `migrations` job used. SQLite is the default provider, so unlike `migrations`
it needs **no** DB service container. Runs on PRs and on `main` (regression net); skipped for `v*` tag
builds. The playout-build lock 409 + `isLocked` projection (#215) landed in #444.

**UI-E2E step (ersatztv#445).** The last step of this same job (item 4 in the summary above; the
`Run UI-E2E Playwright flows (headless)` entry in the YAML) runs the headless-browser flows the curl
harness structurally cannot express — client-side form validation, `AuthGate`'s rendered states, the
session cookie authenticating the **SPA's own** `/api` XHRs, and sign-out via the `UserMenu`:

```
ETV_BUILD_CONFIG=Release ETV_UI_PORT=8410 scripts/e2e-ui.sh
```

`e2e-ui.sh` owns the lifecycle (fresh config dir → boot → `playwright test` → always kill the server)
and exits with Playwright's status. Three deliberate choices:
- **This job, not a new one.** The dominant cost here is `npm ci` + the Release build, both already
  done; a separate job would duplicate them to add ~5s of browser work. The browser is baked into the
  toolchain image, so the step installs nothing.
- **Its own fresh instance on port 8410.** The first spec asserts the one-shot **Setup** gate, which
  step 3's auth section has already claimed on its config dir; a separate port also keeps this step
  independent of step 3's teardown timing.
- **`retries: 0`, `serial`, single worker.** #445 asked for deterministic flows and a retry would let a
  flaky flow merge looking green (measured: 4 consecutive clean runs, ~2s each). Full rationale and the
  rule for extending the suite: `docs/e2e-local.md` → "UI-E2E harness".

### Docs-only skip (ersatztv#416)

A change that touches **only** `docs/**` or `*.md` (anywhere: `README.md`, `CLAUDE.md`, handoff
files) has nothing for the heavy jobs to validate. Before this, such a change ran the entire matrix
— `test`, `migrations` (with its `mysql:8.4` service), `functional-e2e`, `format`, `api-docs` —
~9 min of warm CI for a Markdown edit.

**The mechanism, and why it is shaped this way.** Each heavy job (`test`, `migrations`,
`functional-e2e`, `build`) runs `scripts/ci-detect-docs-only.sh` as its first post-checkout step
(`id: detect`), which emits `docs_only=true|false` to `$GITHUB_OUTPUT`. Every real step in the job
is gated `if: steps.detect.outputs.docs_only != 'true'`. On a docs-only change the job runs only
checkout + detect and **reports `success` in seconds**.

**Shallow-checkout safe (the change-set diff).** `test`/`migrations` check out `fetch-depth: 1`, and
a shallow clone has **no `origin/<base>` tracking ref and no merge-base** — so a three-dot
`origin/main...HEAD` diff *errors*, the fail-safe returns `docs_only=false`, and the skip silently
never fires (the first cut shipped this bug — every docs-only PR still ran the full matrix; caught by
#416's "verify on a real PR" box). The script therefore fetches the base and diffs against
**`FETCH_HEAD`** (always written by `git fetch`, resolves in a shallow clone) with a **two-dot** tree
diff (`git diff --no-renames FETCH_HEAD HEAD`) — no merge-base required. (`api-docs`/`format` avoided
the bug only because they check out `fetch-depth: 0`.)

The jobs are **not** `if:`-skipped. That is deliberate and it is the whole trap of this issue:

- `main`'s branch protection requires two checks **by name** — `Build ErsatzTV Image / Build & test
  (.NET) (pull_request)` and `Build ErsatzTV Image / EF migration integrity (SQLite + MySql)
  (pull_request)`. If a docs-only PR produced **no run** for those (a workflow-level `paths-ignore`,
  or an `if:`-skipped job), those contexts would never report and the PR could **never merge** — the
  naive fix *bricks* docs PRs rather than speeding them up.
- On Gitea **1.25.4** an `if:`-skipped job reports commit-status state **`skipped`**, a distinct
  state (verified with a throwaway probe, PR #418) — not `success`. We do **not** rely on how branch
  protection treats a `skipped` **required** context. Keeping the job running and gating its *steps*
  makes the required context report `success` unconditionally, which is safe by construction.
- Non-required jobs may skip freely: production already proves a `skipped` **non-required** context
  does not block merge (`build` is `skipped` on every PR). So `build` skips its image steps on a
  **docs-only push to `main`** (docs are not in the image, so there is nothing to rebuild); tag
  builds force `docs_only=false` in the script so a release is never skipped.

The detection **biases toward running more**: `docs_only=true` only when *every* changed path is
docs; any code path, a tag build, a non-merge push, or an undeterminable diff resolves to `false`
(run the full matrix). A false `true` would skip real tests on a code change — a correctness bug —
so every ambiguous case runs everything. The `migrations` job's `mysql` service still starts on a
docs-only run (a `services:` container starts with the job regardless of step `if:`), but the
expensive 787-migration replay is skipped; the service is capped and idle for seconds.

`api-docs` and `format` already short-circuit on docs-only changes via their own path detection (no
API path / no `.cs` changed → they pass in ~5s), so they needed no change. `docs-reminder`,
`decisions-guard`, `ci-image-pin` and `script-tests` keep running on docs-only changes — the first
two are *about* docs and must, and `script-tests` is unconditional by design (ersatztv#631).

Not in scope: the within-run triple `dotnet build` (ersatztv#398; measured and rejected as
build-once — see `docs/decisions.md`). The separate redundancy of running the **whole matrix on a
PR and again on the merge-to-`main`** over identical code (ersatztv#420) is addressed below.

### Cross-run tree-identity skip (ersatztv#420)

A merge to `main` re-runs the entire matrix over code the PR's last run already validated — the
same redundancy as docs-only, but for identical code rather than docs. On a `push` to `main` that
is a real merge commit, `test`/`migrations`/`functional-e2e` each run
`scripts/ci-detect-already-validated.sh` as a **second** detect step (`id: revalidate`, right after
the docs-only detect), and every heavy step gains an added `&& steps.revalidate.outputs.skip !=
'true'` to its existing `if:`.

**Skip condition — all four required, else fail-safe `skip=false`:**

- the event is a push to `refs/heads/main`;
- `HEAD` has a second parent `HEAD^2` (a real merge commit — the PR head CI already validated;
  squash, rebase, fast-forward, or a direct push have no `HEAD^2`, so they run);
- `git rev-parse HEAD^{tree}` equals `HEAD^2^{tree}` — main did not advance since the PR's last run,
  a byte-identical tree;
- `HEAD^2` has a **green Gitea combined commit status**, queried via the API with
  `ETV_STATUS_AUTH`. Trusting the aggregate `.state` is sound: a `skipped` context does **not** drag
  the combined state below `success` (verified live against this instance — a real merge commit with
  four `skipped` PR-only contexts still reported `.state == success`), and the two required jobs
  never report `skipped` (they always run and report a real `success`/`failure`), so
  `.state == success` implies they were green.

Those three jobs check out `fetch-depth: 2` so `HEAD^2` and its tree resolve.

**Why it's safe: `build` is not gated.** The three heavy jobs skip their *steps* (same
required-context reasoning as docs-only — they still run and report `success` in seconds), but
**`build` always runs on `main`, ungated**, building and pushing the image from that identical,
already-validated tree. No image ships from unvalidated source. The required contexts are
unchanged (`Build & test (.NET)`, `EF migration integrity (SQLite + MySql)`) — no branch-protection
change.

**Fail-safe bias.** Any uncertainty — not a main push, no `HEAD^2`, a differing tree, a
missing/failing/non-`success` status, missing auth — resolves to `skip=false` and runs the full
matrix. A false skip could ship an under-validated image, so every ambiguous case runs everything.

**Honest limitation — this fires rarely here, by design.** The tree is identical only on a
*fast-forward-equivalent* merge: main did not advance since the PR's last green run **and** the PR
head was not rebased at merge time. Two routine patterns defeat it in this repo: (1) under parallel
merges main usually advances; and (2) — the bigger one — the standard workflow **rebases a PR
before merging** to resolve the `docs/decisions.md` lifecycle conflict (see MEMORY: the
"decisions.md conflict treadmill"), which mints a new head SHA whose tree was never itself
CI-validated, so the tree-match check correctly declines. So the skip is a genuine but *occasional*
win (clean, up-to-date, un-rebased merges in quiet periods) — correct-but-conservative by
construction, not a general dedup. It never fires unsafely; when in doubt it runs the full matrix.

### Dropped-step guard on the required jobs (ersatztv#756)

`test` and `migrations` write the only two `docker-build.yml` contexts branch protection requires on
`main`. A step the runner declines to interpolate is **dropped, and the job still concludes
`success`** (ersatztv#751), so in these two jobs that failure is **fail-OPEN**: a required check
reports green having done no work. In `review-verdict.yml` the same drop is fail-closed — the status
is simply absent and the merge is blocked — which is why #751 fixed the safe direction first.

Two independent mechanisms hold it, and neither is redundant:

- **A static ban on expression delimiters** in any `run:` body of `test`, `migrations` **and
  `build`**. The drop mechanism *requires* an opener in the scalar, so this makes the class
  unreachable rather than merely detected — and it is the raw `${{` opener that is banned, not a
  well-formed pair, because an unclosed one triggers the same rewrite. When a step genuinely needs a
  value, pass it through the step's `env:` block, which is interpolated **per value**, so a bad
  payload there cannot take the body with it.

  **Why `build` is in the ban although it is not a required context.** Its one delimiter-bearing body
  was `Smoke + IPTV E2E`, which runs *after* `Build and push` — so on a `v*` tag the image is already
  in the registry as the release candidate and that step is what decides whether the candidate was
  ever booted. A drop there publishes an unsmoked candidate, reports green, and `DeployStack
  jazz-media` promotes exactly that image. Its two payloads moved into the step's `env:`, so the ban
  cost nothing.

  **The ban is re-checked on the release path itself (ersatztv#767).** It used to be enforced only by
  the `script-tests` job, which lives in `pr-checks.yml` (`on: pull_request`) and is **not** a
  required context — a *review-time* check on the PR that would introduce a delimiter, not a gate on
  the release. `pr-checks.yml` does not run on a `v*` tag push at all, so a delimiter that ever
  reached `main` would still drop `Smoke` on the tag build and go green; `main` being PR-only (#743)
  meant such a change had to pass through a PR where `script-tests` reddens, but a red on a
  non-required check does not block the merge server-side.

  There is now a **`scan` job** (`Delimiter ban (release path)`) that runs the PyYAML-based ban test,
  and **`build` lists it in `needs:`**. That single edge is the fail-closed property: a red `scan`
  means `build` is skipped outright, so the image is never built, let alone pushed.

  **Why a job and not a step inside `build`.** A step cannot protect the job it lives in. `build` is
  what publishes, so a guard step there fails **open** if the runner drops it — and the defence
  ("the guard's own body has no opener, so it cannot be dropped") is circular when the only thing
  enforcing that property is the same PR-only test being backstopped. This was the first design and
  two independent reviews rejected it for exactly that.

  **Why it runs the real pytest and not a bespoke scanner.** The same first cut hand-parsed the
  workflow YAML in stdlib Python, to avoid provisioning PyYAML on `build`'s bare runner. Review found
  ~10 **false negatives** in that parser in one round — flow mappings (`{run: …}`), a quoted
  `"run":` key, aliases, multiline quoted scalars — making it strictly *weaker* than the check it
  backstopped, in the only direction that matters for a security gate. Running the existing test
  needs no second definition of "what is a `run:` body", so it has no drift surface at all. `scan`
  runs on `small` and provisions Python the same way `script-tests` does.

  The wiring is held by `scripts/tests/test_ci_release_path_scan_job.py` — `build` depends on it, it
  carries **no job-level `if:`** (one that excluded the tag push would restore the hole; one that
  skipped the job would skip `build` too), no step is `continue-on-error`, and every one of its own
  `run:` bodies is delimiter-free. Its steps also carry #756 markers and a trailing assert, so a drop
  *inside this job* is caught as well.

  The gate's guarantee is one **execution probe**, not a set of assertions about the command: it runs
  the scan step's real `run:` body — with the workflow, job and step `env:` tiers layered as the
  runner would — against a copy of the repo whose `Smoke` body carries an injected delimiter, and
  requires a non-zero exit, with a clean-tree negative control. Shape assertions were tried twice and
  lost twice (nine disarms across two rounds, from `echo`ing the command to `PYTEST_ADDOPTS` one env
  tier up), so **do not replace the probe with cheaper checks about the command.** One tier is
  unreachable by any static reconstruction — a step writing to `$GITHUB_ENV` injects into later steps
  at runtime — and is therefore **banned** in this job rather than modelled.

  **And one check deliberately is not a test at all.** The tests above prove the ban *holds*; they
  cannot prove it would *notice*, because pytest's own configuration outranks them — a repo-root
  `pytest.ini` with `addopts = -k "not delimiter_banned"`, or a `conftest.py` with
  `pytest_collection_modifyitems`, deselects the ban test and every test guarding it, leaving the
  whole suite green with a delimiter sitting in `Smoke`. So `scan`'s last working step runs
  **`scripts/ci-prove-ban-detects.sh`**, which poisons the checked-out workflow, re-runs the ban
  test, and requires **the ban test's `build` parametrisation to be the failure**. Not "the same
  command" (the step also runs the wiring tests; the script runs only the ban file) and not merely
  "fails if it passes": any other outcome — exit 5 because everything was deselected, exit 2 on a
  collection error, or a failure in some unrelated test — is a **refusal**, not a pass. That
  exhaustiveness is the load-bearing part, because each weaker reading was a live bug in an earlier
  draft: "non-zero means it noticed" vouched for the gate on a collection error, and the deselection
  disarm this script exists to catch exits **5**, not 1.

  It runs in the **real checkout** — an isolated copy does not inherit the repo-root config a disarm
  would live in, which is exactly how the first version of that script reported healthy while the
  real invocation was deselected. The workflow file is
  restored by an `EXIT` trap, and the step carries a `selfcheck` marker so dropping it reddens the
  job.

  Two further tests exist because review disarmed the gate in ways an obvious test misses. **The
  pytest invocation is checked as a command, not as a substring**: the ban test's path must appear as
  a bare token on the real `python3 -m pytest` line, that line may carry none of
  `-k`/`-m`/`--deselect`/`--ignore`/`--collect-only`, and its exit status may not be swallowed by
  `||`/`&&`/`;`/`|`. Commenting the invocation out and echoing instead, or appending
  `-k 'not delimiter_banned'`, each left the suite green with the release path unguarded. And **the
  ban's SCOPE is pinned** — `DELIMITER_BAN_JOBS` must still contain `build`, because dropping that
  one literal makes `scan` pass while checking nothing about the job that publishes the image.

  Two operational notes. `scan` is a `small`-lane job on the tag path, which ersatztv#535 moved away
  from after such jobs wedged in act's setup phase on the v26.12.0 tag; that is safe again only
  because server-management#639 took `build` off the lane. If it ever returns, move `scan` to
  `ubuntu-latest` — never weaken the `needs:` edge. And `scan` installs from PyPI, so a network blip
  now sits between a `v*` tag and its image; fail-closed and loud, but real.

  What this does **not** claim: that no step can ever fail to run for a reason other than the
  interpolation drop. It moves the terminal assumption — to fail open you must now drop the pytest
  step **and** the assert step, rather than either one alone.

  Measuring a guard on this path does **not** require cutting a release, and an earlier draft here
  claiming it would was simply wrong: `build` runs on every push to `main`
  (`if: github.event_name != 'pull_request'`), and a `workflow_dispatch` on any other ref runs the
  job while `Build and push` publishes nothing (its `push:` is gated on `main`/`v*`). That is how
  #767 was verified — see the decision record for the run ids.

  `functional-e2e` is delimiter-free too but is deliberately **not** banned: it is
  advisory by declaration, and the rule is "ban where a drop is consequential", not "ban wherever it
  is currently free". `api-docs` and `format` keep one `github.base_ref` each in a detect step and
  gate nothing that ships.
- **Runtime per-step markers**, for a step that fails to run for any *other* reason. Every `run:`
  step that is not `continue-on-error: true` calls
  `"$GITHUB_WORKSPACE/scripts/ci-step-ran.sh" mark <key>` as its **first act**, and the job's last
  step calls `ci-step-ran.sh assert --always … --gated …`, which fails the job when an expected key
  was never recorded.

**Per step, not per job.** A marker written by the first step only proves the job *began*, which was
never in doubt. The drop that costs something is `Test`, `Build` or a migration replay — all well
past step one — so a job-level marker would have been a guard that cannot see the case it exists for.

**The guard carries no `if:`, and that is deliberate.** The #751 guard uses `if: always()` because its
job has one real step. These have a dozen, and a genuine failure in an early step legitimately skips
every later one — an `always()` guard would then announce a false *"these steps never executed:
typecheck web-test build dotnet-test"* on top of every ordinary red build, and a guard that cries wolf
gets deleted. (`migrations` is smaller — six marked steps — but the same argument applies, and its
guard comment is worded for its own keys rather than copied from `test`'s.) The default `if:` is `success()`, which is the wanted condition, and the invariant that
makes relying on it safe rather than lucky is: **the guard is skipped only when an earlier step
failed, and that already fails the job**. So *guard skipped ⇒ job red*, and every path to a green job
runs the guard. A dropped step is invisible precisely *because* it concludes `success` — which keeps
the job green and therefore reaches the guard.

That invariant has one path where it could plausibly be false and where being wrong would be silent:
a step marked `continue-on-error: true` that FAILS. If that flipped `success()`, the guard would be
skipped on a job that still concluded green — the guard rendered a no-op by exactly the failure mode
it exists to catch, with no signal. The `test` job has three `continue-on-error` steps and two of them sit immediately before the guard,
so this is a live path, not a theoretical one. **Measured** (scratch PR #766, run 1913 job 8075): the last
advisory step was made to `exit 1`, the log carries `❌ Failure - Main Report peak container memory`,
and the guard **still ran**, reported `All 12 expected step(s) executed`, and the job concluded
`success`. A failing `continue-on-error` step does not flip `success()` on this runner, so the
invariant holds where it mattered most. That run is also the `test` job's full twelve-key positive
control on the build lane.

**Adding a step to either job?** Mark it, and add its key to that job's guard list in the right
bucket (`--always` for the two detect steps, `--gated` for anything carrying the docs-only /
already-validated `if:`). `scripts/tests/test_ci_dropped_step_guard.py` derives the expected set from
the workflow, so an unmarked step or a bucket mismatch is a red — it does not rely on anyone
remembering. One caveat, since this section is careful about it elsewhere: that red is `script-tests`,
the same non-required, PR-only check discussed above. For the delimiter ban on `test`/`migrations`
that hardly matters, because the runtime guard is the fail-closed backstop — but a **newly added,
unmarked** step is caught by the static test *alone*, since the runtime guard cannot expect a key
nobody declared.

**The marker path is keyed on job + run id + attempt** — and be precise about why, because the
obvious justification is a #751 measurement that does *not* transfer. #751 found `RUNNER_TEMP` to be
`/tmp` and called it "not a private per-job directory", but that was taken on `review-verdict.yml`,
which runs *without* a `container:`. These two jobs run **inside** the CI toolchain image, so their
`/tmp` is the job container's own and starts empty. The fresh container is therefore what actually
rules out a stale marker here; the keying is defence in depth against a lane change nobody would
think to re-check this against. `GITHUB_JOB` and `GITHUB_RUN_ID` are *measured* present and the
script refuses without them rather than falling back to a name other runs share.
`GITHUB_RUN_ATTEMPT` is required too — but **how** that was established is the part worth keeping,
because the first two attempts at it were both worthless. Grepping a job log for the variable *name*
proves nothing: logs do not dump the environment. Inferring it from the *absence* of the script's
"not set" warning proves nothing either, because that warning goes to **stderr**, and whether step
stderr reaches a job log here was itself never established — the control offered for that turned out
to be an `::error::` line this script writes to *stdout*. So the script was made to **report its
resolved identity on stdout**, where capture is not in question, and the answer was simply read off
this change's own run: `Marker identity: job=test run=1916 attempt=1 (from the runner)`, and the same
for `migrations`. Both required jobs, on the lane that matters.

That measurement is what promoted it from warn-and-default to required, and it is why the residual
this paragraph used to describe — a rerun inheriting attempt 1's markers — no longer exists. The
identity line stays, as the standing evidence a future reader checks first if the keying is ever
doubted again.

**The premise was re-measured on the build lane.** The whole thing rests on the runner still executing
a later step after dropping an earlier one. #751 established that on the `small` lane; these jobs run
in a `container:` on `ubuntu-latest`, so it was measured there rather than assumed — scratch PR #765
(Gitea 1.27.1, 2026-08-10) reintroduced the exact #751 defect in the `test` job's `revalidate` step.
Recorded outcome (job `test`, run 1910, 20:03:49→20:13:31Z — a full 9m42s heavy run, so `Build` and
`Test` really executed):

- `Unable to interpolate expression 'format('# PROBE ONLY … {0}\n…', pr number)'` at 20:04:06 — the
  step was **dropped**, exactly as #751 describes, and it reported conclusion `success`.
- **Every other marked step still ran** — eleven markers were recorded, ten of them AFTER the drop
  (`restore npm-ci check-api lint typecheck web-test web-build strip-scanner build dotnet-test`),
  `detect` being the eleventh and earlier. The premise holds on this lane.
- The guard ran at 20:13:29, reported `These steps of job 'test' never executed: revalidate`, and was
  the **only** ❌ in the entire job log — every other step succeeded. Without it this run would have
  concluded `success` having never executed that step, which is precisely the fail-open being closed.
- Incidental but kept: the dropped step's output arrived as `ETV_REVALIDATE_SKIP:` **empty**, not
  `false` — the case the guard must read as "widen what is required", never as a skip.

**The positive control is the same run's `migrations` job**, which the probe did not touch: it marked
all six steps, the guard reported `All 6 expected step(s) executed: detect revalidate restore build
sqlite mysql`, and the job concluded **success**. So one run demonstrates both directions on the build
lane — a drop caught and reddened, and a clean job passing. The twelve-step `test` positive control is
this change's own CI run.

Full rationale: `docs/decisions/records/ci/required-job-step-execution-markers.md`.

### `docs-reminder` job (non-blocking, PR-only — in `pr-checks.yml`)

Two lightweight nudges, both `::warning::`-only. Neither can fail the build — they are reminders,
not gates; prose-doc gates get gamed with token edits.

**1. The parity-doc reminder** enforces the CLAUDE.md "docs-update is part of done" rule for the
one case that's easy to forget and easy to detect: a PR that touches a SPA screen
(`web/src/screens/*.tsx`) or `ErsatzTV/LegacyUiRedirects.cs` but **does not** update
`docs/blazor-route-parity.md`. It diffs the PR against its base branch and emits a
`::warning::` annotation.

**2. The session-narrative reminder** (ersatztv#784) runs `scripts/check-doc-narrative.py --diff`
over the lines this PR **adds** to `docs/**/*.md` (minus `docs/decisions/**`, exempt wholesale) and
root-level `*.md`, flagging text that narrates the document's own revision history —
`docs.no-session-narrative`. It is advisory **by design and permanently**: a narrative detector is a
string predicate over prose, the class `docs/defect-shapes-773.md` §4 argues must never be
load-bearing, so the script exits 0 on every path including a bad argument or an unresolvable base
ref. It does NOT rest on prose alone, and it does not rest wholly on tests either: the record's
COVERAGE BOUNDARY names which clauses carry a mutation proof and which are defensive and unproven
(the unhandled-exception arm among them). Every argument shape is asserted per shape in
`scripts/tests/test_check_doc_narrative.py` rather than only in prose. When it cannot resolve the
base it prints `SCANNED NOTHING` instead of a clean-looking line, because a silent zero-file scan is
indistinguishable from a clean one — the same failure `ci.required-job-step-execution-markers`
exists for.

Because this step needs an interpreter, the job DOES carry `actions/setup-python` — the one
exception to the no-setup-actions note below, since `python3` is not guaranteed on the bare `small`
lane. Both it and the script step carry `continue-on-error: true`: a script that exits 0 does not by
itself keep the JOB green, and a setup-action download failure would redden an advisory check just
as effectively as a hit would.

The job deliberately has **no** `setup-dotnet`/`setup-node` (and
thus no `actions/cache`), so it can't hit the cache-save hangs seen on the VM-127 runner
(server-management#570). It does not cover the remaining doc obligations in the CLAUDE.md table
(domain-model, spa-conventions) — those stay on the author. (The API contract is mechanized by the
blocking `api-docs` job, and `docs/decisions.md` by the blocking `decisions-guard` job below.)

### `decisions-guard` job (`decisions lifecycle`, blocking, PR-only — in `pr-checks.yml`)

Enforces decision-record lifecycle invariants (ersatztv#521, supersedes the ersatztv#303 H9
append-only mechanic): well-formed 5-field metadata, exactly one `active` record per `key`,
reciprocal `supersedes`/`superseded-by` links, no record vanishing from the active set without an
archive copy, no rationale-prose rewrite without a `Decisions-Edit: yes` trailer on a non-merge commit
in the range (ersatztv#609), a structural per-path check that every `*.md` under
`docs/decisions/records/**` and `docs/decisions/archive/**` parses to **exactly one keyed
record** (ersatztv#621 — without it, a file the dependency-free frontmatter reader cannot parse,
such as one using a YAML block scalar, yields `[]` and vanishes from the corpus with every check
still reporting green; a file directly in `archive/` is exempt only when it really is a stripped index — one keyless
record with a known generated heading — never merely by its location; the single further exemption,
`archive/README.md`, is by exact relative path, never by basename, which would otherwise exempt the
same filename in the active wing),
and the generated active catalog (`docs/decisions/README.md`) in sync with source. Two steps:
`scripts/decisions_validate.py --base origin/<base> --head HEAD` (the merge-base diff checks, which
need a base/head range — CI-only) and `scripts/build_decisions_catalog.py --check` (catalog drift).
The **same validator** backs the Husky `pre-commit` hook (`.claude/hooks/decisions-guard.sh`, no
base/head there — structural checks only, over the working tree), so local and CI enforcement can't
drift on the rules that don't need a range. `python3` isn't guaranteed on the bare `small` lane, so
the job adds `actions/setup-python@v5` before invoking it; that install is lightweight (no
compiler/docker build), so it doesn't violate the "small is git-only" lane rule. Like
`docs-reminder`, otherwise a seconds-long `git diff` + parse with no dotnet/node setup
(`runs-on: small`).

### `prove-fix` job (`Fix proofs (Proves trailers)`, PR-only — in `pr-checks.yml`)

Runs `scripts/prove-fix.sh` for **every commit in the PR that carries a `Proves: <pytest selector>`
trailer**, and fails the PR if a claimed proof does not hold. The rule and its rationale are
`testing.fix-ships-a-witnessed-red-test`; this section is the CI-side contract.

**Opt-in by trailer, enforced when present.** Requiring `Proves:` on every commit would block docs,
CI and refactor commits that have no code side to revert, and a gate that blocks ordinary work gets
switched off — which is how a check ends up running nowhere (ersatztv#631). So the trailer is the
author's *claim* and this job checks claims. **When a PR carries none, the job emits a `::notice::`
saying it asserted nothing** — its green must not be read as fix coverage.

**It needs full history** (`fetch-depth: 0`): the script reverts each commit against its PARENT, and
a shallow clone cannot resolve `<sha>^`.

Three refusals worth knowing before you write a trailer:
- a **merge** commit is rejected — several parents means "the code before this change" is ambiguous;
  put the trailer on the commit carrying the fix;
- **more than one** `Proves:` trailer is rejected — only the first would be checked, so the rest
  would read as proven without ever running (the job checks this itself, because passing the
  selector explicitly bypasses the script's own guard);
- a **test-only** commit is rejected — there is no code side to revert.

**Only pytest exit 1 counts as red.** 2 is an interrupted collection, 3 internal, 4 usage, 5 nothing
collected, 143 a signal; `--continue-on-collection-errors` converts a genuine collection failure to
1 so add-a-file fixes stay provable. The job inherits that. Note the direction: a wobble DOES redden
this job (`prove-fix.sh` exits 5 on a harness/git failure or a signal, and the job turns that into an
error), so what the exit-code discipline buys is the other way round — a **green** here means a claim
was witnessed, never that a run was cancelled or broke.

### `script-tests` job (`Script lint and tests (ruff + pytest)`, PR-only — in `pr-checks.yml`)

> Reddens the run on failure, but like the other `pr-checks.yml` gates it is **not** one of the
> three required status checks on `main` (`Build & test (.NET)`, `EF migration integrity`,
> `review-verdict/h10`). Promoting it to required is a branch-protection change, tracked separately.

Runs the repository's Python test suite: `PYTHONPATH=. python3 -m pytest scripts/tests -q`
(773 tests at `706674272`, ~4.5 min; the suite grows fast — it was ~190 tests / ~10s when this job landed in #631 — so treat the figure as a dated snapshot, not a budget). It covers the decision-corpus parser/validator/catalog builder, the ersatztv#610
migration-equivalence harness, the merge-consent exemption logic and the ersatztv#622 review-verdict
poster.

**Until ersatztv#631, nothing ran these tests.** No workflow and no Husky hook invoked `pytest`.
`decisions-guard` executes `decisions_validate.py` and `build_decisions_catalog.py` directly — it
exercises that *code* but never its *tests* — and the `test` job is `dotnet test` only. The suite
guarding our merge-gating machinery was therefore local-only, and a test added "for CI enforcement"
was decorative.

**Why it is its own job, not a step inside `decisions-guard`.** `decisions-guard` is covered by the
standing `ci.decisions-lifecycle-flake` rule: a lone `decisions lifecycle` red is a known infra
flake and sessions are instructed *not to investigate it*. Adding the suite there would make a
genuine pytest regression surface as precisely the red everyone is told to wave through — the same
"reports success while doing nothing" failure mode ersatztv#631 exists to close. A distinct job
name keeps a real failure unambiguous.

**Why it runs unconditionally** rather than behind a `scripts/**` path filter: the suite's true
input set spans more than one directory — `test_post_review_verdict.py` and
`test_merge_consent_exemption.py` execute the real `scripts/post-review-verdict.sh` and
`.claude/hooks/pretooluse-merge-consent.sh` — so a `scripts/**` filter would silently miss a
`.claude/hooks/**` edit. The reason is the input set, not the cost: the suite was ~10s when that was
decided and is now ~4.5 min, and it would still be wrong to filter on `scripts/**`.

**It also lints (ersatztv#780).** Early in the job it installs a **pinned** `ruff==0.12.11` and runs
`ruff check` and `ruff format --check` against the repo-root `ruff.toml`. Five things are deliberate:

- The config is **committed**. Without it ruff falls back to whatever `~/.config/ruff/ruff.toml` the
  operator's machine has, so a second machine lints this repo differently or not at all.
- The version is **pinned** — an unpinned install makes the verdict a function of when the job ran,
  the same divergence one layer up, and the same argument as the `jq` pin below. `pytest`/`pyyaml`
  stay unpinned on purpose: a pytest release does not add assertions to your suite, a ruff release
  adds rules to your lint.
- Lint runs **before the jq preflight**, and after the `git` one. `Preflight jq version` is a hard
  `--expect` tripwire; a lint sitting behind it goes dark for as long as the jq contract is broken,
  under a red that says "jq". `Preflight external tools` stays ahead, because the lint steps consume
  `git` — without it a missing git reaches them as an empty population and they blame the glob.
- Neither step is `ruff check .`. Both pass an **explicit population** from
  `git ls-files -z '*.py' '*.pyi' '*.ipynb'` with `--no-force-exclude`, and fail if that list is
  empty. Discovery-based invocation is silently emptied by an `exclude` in the right config scope —
  top level empties both commands, `[lint]` empties `check`, `[format]` empties `format --check`
  (and `[format]` is where an appended line lands) — and
  `ruff check .` over zero files exits **0** with only a stderr warning, so the failure mode is a
  green gate. The measured matrix is in `ci.python-lint-ruff-config-committed`.
- `RUF100` is selected, so a `# noqa` that no longer matches anything is itself a finding.

`pyright` is not gated; the reasoning and the exemption list are in
`ci.python-lint-ruff-config-committed`.

**Dependencies: `pytest` and `pyyaml`** — the complete third-party set across `scripts/`, established
by an AST import scan rather than by reading the files that looked relevant. PyYAML does **not**
contradict the dependency-free decisions *read* path: `decisions_lib._read_frontmatter` is
hand-written exactly so validation runs where nothing is installed, but the one-shot *write* path
`migrate_decisions_split.py` uses PyYAML by design, and `test_migration_equivalence.py` imports that
module. (The first cut of this job claimed "pure stdlib + pytest", passed locally on a machine that
happened to have PyYAML installed, and went red in CI on a `ModuleNotFoundError` at collection —
which is itself a small demonstration of why the suite needed to run in CI at all.) Like the other
`small`-lane Python jobs it adds `actions/setup-python@v5` first. Checkout is at default depth: every `git` call in the suite runs
against a temp repo it creates itself, never this repository's history.

Two **preflight steps** run before the suite. The first asserts `git` is on PATH; the second runs
`scripts/jq-preflight.sh --expect 1.6`, which checks jq's **version**, not merely its presence (see
"The jq contract" below). Those two tests exec the real shell scripts, which shell out to `jq` ~26
times; the tests shim `curl` on PATH but not `jq`, so a runner image without it would surface as ~20
opaque assertion failures instead of one diagnosis. Both deliberately **check** rather than install —
ersatztv#390 removed run-time `apt-get` from CI; the fix for a genuine miss is to bake the tool into
the runner image.

### The jq contract (ersatztv#648)

> Full rationale: `docs/decisions/records/ci/jq-version-contract.md`.

Every shell gate in this repo — `decisions-guard`, `script-tests`'s own harness,
`pretooluse-merge-consent.sh`, `review-verdict.yml`, `scripts/pr-changed-files.sh` — is authored and
tested on a developer Mac shipping **jq 1.8.x**. The CI runner ships **jq 1.6**. Author to the
1.6-compatible subset; three concrete constructs diverge between the two and each one produced a real
bug when it hit CI for the first time:

- **`jq -e` over EMPTY input.** Exits 4 on jq >= 1.7, but **0** on jq 1.6. A guard that infers
  "transport failure" from that exit status silently passes an empty/failed page on 1.6.
- **`` contains("\u0000") `` (or any NUL literal).** The NUL escape truncates to `""` on jq 1.6, so
  the containment test is vacuously true for **every** string, not just ones containing a NUL. Use
  `explode | index(0)` instead — it is version-stable.
- **Parse-error exit code.** `jq empty` exits 5 on jq >= 1.7 but **4** on jq 1.6 — the same code 1.6
  uses for "no output produced". Reading that exit code as a specific failure mode conflates garbage
  input with an empty-but-valid response.

`scripts/jq-preflight.sh` makes the running version **observable** in every gate job's log (it prints
the parsed version and asserts a floor of 1.6) so a future divergence can be diagnosed from the log
alone instead of guessing at the runner image.

**Pin vs floor is deliberately asymmetric.** `scripts/jq-preflight.sh --expect 1.6` additionally pins
the version and fails loudly if it drifts, but that mode is used **only** by `script-tests`
(`.gitea/workflows/pr-checks.yml`) — advisory, not a required check. `review-verdict.yml` runs the
no-args floor-only mode and never pins, because that workflow writes `review-verdict/h10`, the
branch-protection-**required** status check on `main`: a hard pin there would mean the day the
runner's jq version changes (a base-image bump, a host reimage — nothing this repo controls), every
PR on `main` stops merging until someone notices and re-pins. A required merge gate cannot fail
because an upstream package manager did its job. The narrower pin on `script-tests` exists precisely
because that job is the suite's only 1.6 coverage — if the runner's jq silently changed, that coverage
would evaporate with no signal, so failing loudly there forces a human decision instead.

Baking a pinned jq into `docker/ci/Dockerfile` was considered and rejected: `review-verdict.yml` is
`runs-on: small` with no toolchain-image pin, and per `ci.small-lane-git-only` the small lane is
git-only, so it gets the **host's** jq regardless of what the toolchain image contains — a pin in the
image provably cannot reach the gate that broke. This was checked against the running binary, not
assumed.

## PR gates workflow

**File:** `.gitea/workflows/pr-checks.yml` — `on: pull_request` only.

The five PR gates — `ci-image-pin`, `docs-reminder`, `decisions-guard`, `script-tests`, and `prove-fix` (the one member that is NOT merely checkout + `git diff`: it installs pytest and creates worktrees)
(all described above) — live here, **not** in `docker-build.yml`, and that separation is the fix
for **ersatztv#535**.

**Why they are split out.** All three are pure `checkout + git diff` gates on the `small` lane
(no `container:`) and are PR-only (`if: github.event_name == 'pull_request'`). While they lived in
`docker-build.yml` — which also triggers on push to `main` and on `v*` tags — Gitea still
**dispatched them as runner tasks on every such push to evaluate the skip** (the `small`-lane
behavior documented above: *a job is dispatched even when its `if` skips it*). On the **v26.12.0**
release tag those dispatched skip-tasks wedged in act's setup phase and were killed by a runner
restart mid-setup, so they reported `failure` (no logs) and reddened the tag's overall commit
status even though the release built, scanned, and deployed fine. The two PR-only jobs on
`ubuntu-latest` (`api-docs`, `format`) carry the **identical** `if:` and skipped cleanly on the
same tag — the job logic was never the problem; the kill lands in the dispatch window, before any
step or `if:`-skip runs, so tweaking the `if:`/step logic could not fix it.

**Why a separate workflow fixes it.** Gitea evaluates a workflow's **trigger** before creating any
job, so a `pull_request`-only workflow produces **zero** jobs on a tag/main push: no dispatch, no
kill, no spurious red — for the whole class, permanently. The per-job `if:` guards are kept as
belt-and-suspenders (they also encode "these steps need a PR `base_ref`").

**What stays put and why.** These three carry **no** CI toolchain image pin, so `ci-image-pin`'s
grep of `docker-build.yml` still validates the five pin-bearing jobs
(`test`/`migrations`/`functional-e2e`/`api-docs`/`format`) that remain there. `api-docs` and
`format` stay in `docker-build.yml` because they carry the shared-image `container:` + pin and run
on the healthy `ubuntu-latest` lane (where they skipped correctly). None of the three moved jobs is
a **required** check — branch protection requires `Build & test (.NET)`, `EF migration integrity`
and `review-verdict/h10` (next section) — so relocating them (their status-context prefix changes
from `Build ErsatzTV Image / …` to `PR Gates / …`) does not affect merges. The file declares
`defaults: run: shell: bash` because `ci-image-pin` uses `mapfile`/`set -o pipefail`.

## Review-verdict gate (`review-verdict/h10`, required — `.gitea/workflows/review-verdict.yml`)

**A required status check named `review-verdict/h10`, written per-sha, is what actually stops an
unreviewed commit from merging** (ersatztv#622). It is not produced by a job's success/failure; it
is a commit status that `scripts/post-review-verdict.sh` POSTs onto one specific sha.

**`main` is PR-only AND admin-override-proof, and it takes both to make the check load-bearing**
(ersatztv#743, `release.main-direct-push-disabled`). Gitea evaluates `status_check_contexts` when it
**merges a PR** — a direct `git push origin HEAD:main` never consults them. So until 2026-08-05 the
entire gate was skippable with no forgery at all, which was cheaper than every route enumerated in
#697. `main` now carries **two** fields, and citing either alone is a mistake:

- `enable_push: false` — a direct push is refused server-side at pre-receive (`Not allowed to push to
  protected branch main`), for every account including a site admin. The contents API is refused too
  — measured, HTTP 403 `user cannot commit to repo`. The web editor, upload, apply-patch, revert and
  cherry-pick paths share that same `CanUserPush` predicate and are therefore expected to refuse as
  well, but were not probed (source-attested only).
- `block_admin_merge_override: true` — without it (the default is `false`), a repo admin could
  `POST /pulls/{n}/merge` with `force_merge: true` and merge straight past a missing or red
  `review-verdict/h10`. Disabling push alone just moves the bypass from the push path to the merge
  path, since `timothy` is admin and is the identity every session already uses. **Source-attested,
  not probed** (Gitea 1.27 `CanBypassBranchProtection`): verifying it by experiment means merging an
  unreviewed PR, so the field was set rather than measured. Setting it is safe under either
  semantics; re-confirming the bypass itself rides with ersatztv#747.

**Operator recovery when a required context gets stuck.** `block_admin_merge_override: true` removes
the "Merge (admin)" / `force_merge: true` escape that used to unstick a PR whose required context was
absent or wrongly red — a recurring situation here (a killed run overwriting a newer green, an
advisory red counted into the combined status, a gate workflow that cannot post). That escape is gone
*by design*: it was also the bypass. The supported recovery is to fix the status
(re-run the job, or re-post the verdict with `scripts/post-review-verdict.sh`); the last resort is to
`PATCH .../branch_protections/main` setting `block_admin_merge_override: false`, merge, and set it
straight back. Do the last one deliberately and say so in the PR — it is the one action that
re-opens the hole this section exists to close.

Practical consequences: **every** change to `main` goes through a PR, including a one-line docs fix;
and the client-side Husky guards (H6/H11/H13) remain useful friction but were never the control —
they are fail-open and `--no-verify` bypasses them. Tag pushes are unaffected (separate mechanism;
`tag_protections` is empty), so the release cut in "Cutting a release" still works unchanged.

**The hole it closes.** `pretooluse-merge-consent.sh` proves its three consent conditions at the
moment the merge tool is called. Pass `merge_when_checks_succeed=true` and Gitea performs the merge
*later*, against whatever head is green then — while the Done-when and review-verdict checks were
proven against the head at **scheduling** time. Every commit pushed in between merges unreviewed.

This was demonstrated as a controlled A/B rather than inferred (`ci/fake` stands in for a slow CI
check so Gitea waits, as it really does): review head A → post its verdict → schedule auto-merge →
push an unreviewed commit B → CI greens on B. **Without** the required verdict context, B merged.
**With** it, the same sequence was refused, and merged only once B itself was reviewed.

Note the motivating anecdote in ersatztv#622 — "PR #619 merged 263 insertions with no verdict" —
is **wrong**: #619 does carry `Review-verdict: MERGEABLE @ 02c82b35`, posted six seconds before the
merge, explicitly re-reviewing the follow-up commits. It was filed from an API read that lagged.
The gap is real anyway, and structural: nothing *forced* that re-review inside the 45-minute window
where Gitea would have merged whatever went green. This turns diligence into construction.

**Why a commit status fixes it and a smarter hook cannot.** A status belongs to exactly one sha, so
a new commit *cannot inherit it*: the required context is simply absent on the new head, Gitea's
merge-requirement check reads that as not-passing, and the scheduled auto-merge refuses to fire.
The invariant self-invalidates — nothing has to notice the push. It also covers merge paths the
hook never sees (Gitea UI, raw API, another agent's session).

**Posting a verdict.** After reviewing a PR's *current* head:

```bash
ETV_GITEA_BASICAUTH=user:pass scripts/post-review-verdict.sh <pr> MERGEABLE [note...]
```

That posts both the `Review-verdict: … @ <sha>` comment (the human-readable artifact, and the
hook's condition (c)) and the `review-verdict/h10` status on the same sha. `BLOCKED` /
`NOT-MERGEABLE` post a `failure` status instead. The script re-reads the head after commenting: if
a commit landed mid-flight it writes **no** status and exits non-zero rather than retargeting your
verdict at a commit you never read.

The status description also records the base branch — `Review-verdict: MERGEABLE @ abc1234 (base:
main)` — and the merge-consent hook denies when that no longer matches the PR's live `base.ref`
(ersatztv#632). Retargeting a PR changes the effective diff without moving the head sha, so the
per-sha binding alone cannot see it. This is **detection on the hook path only**: a commit status
carries no base of its own, so a merge driven through the Gitea UI or API is unaffected. The
comparator is the base *branch*, never its tip sha — a base that merely advances is ordinary churn,
and comparing tips would invalidate every open verdict on every unrelated merge to `main`.

**Exemptions** are handled by `review-verdict.yml` on every `pull_request_target` event, which posts the
status as `success` for **Renovate-authored** PRs (it uses `platformAutomerge: true`, so a required
verdict with no exemption would stall every dependency bump) and for **docs-only** PRs, and as
`pending` for everything else so the block has a visible reason. Both exemptions are **void when the
PR touches `.claude/`, `.codex/`, `.gitea/`, `.husky/`, `scripts/` or `docker/ci/`** — a PR that can weaken the
gate must not be able to exempt itself from the gate. That includes Renovate's `docker/ci` base
bumps, which already need the manual publish-then-pin two-step anyway.

The Renovate exemption additionally requires **every** changed path to be a dependency manifest —
`Directory.Packages.props` or `.config/dotnet-tools.json`, and only those (ersatztv#698). The npm
manifests are deliberately excluded: `renovate.json` enables only `nuget`/`github-actions`/`dockerfile`,
so npm is unmanaged here, while `package.json` `scripts` are executed by CI (`npm ci`, `npm run build`)
— exempting it would put a code-execution path inside the allow-list for no benefit. An author match alone is not enough, because `pull_request.user.login` is the PR's
*immutable creator* while its head is not: pushing application code onto an open Renovate branch
leaves the PR still "authored by renovate" and, previously, still exempt. A Renovate PR touching
anything else — a `.csproj`, a source file — is not blocked, it just needs a real verdict. **If a
dependency PR is unexpectedly asking for a verdict, this is why**; the status description says so.

The two exemptions are evaluated as **independent predicates**, never as an `elif` chain: a Renovate
PR touching only `docs/` still gets the docs-only exemption on its own merits.

An existing `review-verdict/h10` on the head is **only** left alone when it is positively identifiable
as a human verdict — a non-null `.creator.login` **and** a `Review-verdict:` description, which is what
`post-review-verdict.sh` writes. Anything else, including any shape the workflow does not recognise, is
**re-derived** rather than inherited. (Measured: a status POSTed with a user credential carries a
creator; one POSTed by an Actions job carries `"creator": null`.) Without this, an exemption obtained
once was accepted unchanged on every later run. This is a *provenance* check, not an authentication
one — someone who can POST statuses directly can still impersonate a verdict (ersatztv#697). That
provenance asymmetry is *why* the credential scoping in `ci.actions-credential-scoping` mattered: a
forgery through a **user** credential inherits as a human verdict, while one through a job's
`GITEA_TOKEN` carries `creator: null` and is re-derived, so it must win a race. CI's registry secret
was a user credential — the admin account — and no longer carries status-write. **`RENOVATE_TOKEN`
still is one** (`write:repository`, a real bot account), and secrets are a per-repo store any
PR-added workflow can reference, so that route is narrowed rather than closed; tightening this check
from "non-null creator" to an allow-list of approved reviewers is what would close it
(ersatztv#742). A collaborator's own personal token still can, and no repo-side change closes that.
Note also that re-derivation is **not** a race the attacker can lose: it fires only on the trigger's
`types`, and posting a status is not one of them, so a POST timed after the last PR event stands
until the next one.

Deciding either exemption requires the PR's **complete** changed-file list, which the workflow does
not compute itself: it calls `scripts/pr-changed-files.sh`, the single shared implementation also
used by the advisory hook `.claude/hooks/pretooluse-merge-consent.sh` (ersatztv#649). The workflow
reads that script's **exit status** — a non-zero exit means "could not tell" and withholds the
exemption; its stdout is meaningless on any failure path and is never consumed.

**Never write a classification guard as `producer | grep -q…` here.** Under `set -o pipefail`, `grep -q`
exits at its first match, the producer takes SIGPIPE (141), and a MATCH is reported as a failed
pipeline — inverting the guard for any PR whose path list exceeds the pipe buffer. That let a large PR
be classified docs-only, and let one editing `.gitea/` skip the protected-path check entirely. A
here-string is **also** wrong (bash spills a large one to temp storage, which fails the same way when
temp is full). **Count** instead — `grep -c` drains stdin over an ordinary pipe — evaluate the counts
once at top level rather than inline in an `if`, and fail closed on a non-numeric result. Full detail:
`ci.grep-q-pipefail-inversion`.

That script takes the expected base branch as a **required 5th argument** and refuses to enumerate when
the PR's live base does not match it, checked both before and after paging (ersatztv#698).
`/pulls/{n}/files` diffs against the PR's *live* base, so retargeting changes the answer without moving
the head sha — a PR opened into `main` and retargeted mid-run was granted a docs-only exemption while
its diff against `main` carried a C# file. The workflow passes the base from the `pull_request_target`
payload, which a retarget cannot rewrite, and `edited` is in `types:` so a retarget reclassifies.
`edited` gives **detection, not atomicity**: runs are not serialized, so a stale run could still post
`success` after the reclassifying run posted `pending`.

**That residual is now fenced (ersatztv#706).** Runs are still not serialized — instead a run that was
overtaken *declines to write*. The job counts `change_target_branch` events on the PR's issue timeline
at start and again immediately before its POST, and posts **nothing** if the count moved. The count is
the key precisely because the branch *name* is ABA-vulnerable: `main → scratch → main` reads `main` at
both ends, which is how the forged exemption was obtained in the first place. Abstaining never strands
a PR, because every retarget fires `edited` — the event that makes one run abstain has already queued
its successor.

If the count can't be established (unreadable timeline, paging that never reached a validated empty
page), only the exemption `success` is withheld; `pending` still posts, since `pending` cannot turn an
unreviewed head green and withholding it would strand ordinary PRs for nothing. **If an exempt PR is
unexpectedly missing its status after a retarget, this is why** — the job log names the counts.

Worth knowing before reaching for the obvious alternative: **a concurrency group does not work here**,
measured rather than assumed. Gitea 1.25.4 auto-cancels superseded `push` runs on a branch, but *not*
`pull_request_target` runs — two runs for one PR genuinely overlap, and adding
`concurrency: {…, cancel-in-progress: false}` changed nothing (probe runs still overlapped by 36s).
`cancel-in-progress: true` is deliberately untried, because a cancelled run leaves an exempt PR
statusless with nothing left to re-trigger it. Full measurements and the two surviving residuals:
`ci.verdict-write-retarget-fence`.

Separately, after posting an exemption `success` the job re-reads the per-POST status history and, if
a human `Review-verdict:` row appeared during the write window, overwrites its own status with
`pending` and logs an error — so a human `BLOCKED` can never be silently turned green. The repair is
`pending`, never a copy of the human's verdict, which would attribute a human decision to the job.

Three properties of this workflow are security-relevant and are **structurally** asserted by tests in
`scripts/tests/test_pr_changed_files.py` — those tests pin the workflow's shape, which is not the same
as establishing that the gate cannot be forged (see the residual below, and ersatztv#697/#698):

- **The trigger is `pull_request_target`, scoped to `branches: [main]`** — never plain
  `pull_request` (ersatztv#672). Gitea resolves a `pull_request` workflow *definition* from the PR's
  own head, so under that trigger a PR editing `review-verdict.yml` ran its own rewritten copy and
  could post `review-verdict/h10=success` for itself. The base-ref checkout below binds the scripts
  this job runs; only the trigger binds the definition. The `branches` filter is half the fix, not a
  refinement of it: base resolution means the *base branch* supplies the gate, so an unfiltered
  trigger merely moves the rewrite to an attacker-pushed base — and a status forged there is
  inherited by any later PR carrying the same head sha (ersatztv#663). `pull_request_target` is safe
  here **only** because this job never checks out or executes head-supplied code. Verified on this
  instance with four scratch PRs rather than inferred from GitHub; full rationale in
  `docs/decisions/records/ci/gate-trigger-base-resolved.md`. **This closes the rewrite route through
  this workflow, not the class:** `docker-build.yml` is also head-resolved and must stay on
  `pull_request` because it builds the PR's code, so it got the read-only status identity instead —
  its `ETV_STATUS_AUTH` is now a PAT scoped `write:package` + `read:repository`, which the status
  endpoint refuses (`ci.actions-credential-scoping`, ersatztv#697). The inventory was never that one
  workflow, though: Gitea injects a write-capable `GITEA_TOKEN` into every job and branch protection
  binds the *context*, not its issuer. Gitea >=1.26 with the Actions default set to **Restricted**
  (server-management#714) binds the injected token, but does not close the class either — not against
  a personal token, and not against `RENOVATE_TOKEN` (ersatztv#742). **And none of it was necessary:
  direct pushes to `main` were server-side permitted, so the gate could be skipped without any forgery
  (ersatztv#743). That is now CLOSED — `main` carries `enable_push: false` **and**
  `block_admin_merge_override: true`, so it is reachable only through the PR merge path, the one path
  on which Gitea evaluates `status_check_contexts`, and an admin cannot `force_merge` past them
  (`release.main-direct-push-disabled` — neither field is citable alone).** Note the fix is *disabling* push, not whitelisting it: a
  push whitelist naming `timothy` was measured to still admit the push, and `timothy` is the identity
  every session, PAT and injected `GITEA_TOKEN` already acts as, so the whitelist form would have
  closed nothing. The block binds a site admin at pre-receive but not a credential that can first
  PATCH branch protection off — an accepted residual, recorded in that decision. The
  exemption path has separate defects of its own (ersatztv#698). One operational
  consequence of the trigger change: a PR whose base is not `main` now gets **no**
  `review-verdict/h10` at all. That is fail-closed. `edited` **is** now among the trigger's `types`
  (ersatztv#698), so a PR retargeted onto `main` reclassifies instead of staying statusless until its
  next push — but note that only gives *detection*: runs are not serialized, so a stale run can still
  post `success` after the reclassifying run posts `pending` (ersatztv#706).
- **The checkout takes the PR's BASE ref**, `ref: ${{ github.event.pull_request.base.sha }}` with
  `persist-credentials: false` — never the head. This job judges the PR, so the PR must not supply
  the code that judges it; a head checkout would let a PR edit the enumeration to return an empty
  list and exempt itself.
- **`scripts/jq-preflight.sh` runs in floor-only mode**, never `--expect`. This job writes a
  branch-protection-**required** status, so an exact version pin would turn any jq upgrade on the
  runner into a repo-wide merge deadlock.

A PR whose base predates ersatztv#658 has no such script on its base ref; that case posts `pending`
with the reason rather than dying with no status at all.

⚠️ **Changing `review-verdict.yml` itself: it is not exercised by its own PR.** Base resolution cuts
both ways — the PR editing this workflow runs the version already on `main`, so an edit goes live
**only on merge**, repo-wide, having never run. A broken edit merges green and then breaks the gate
for every subsequent PR, and the PR that would repair it is gated by the same broken workflow. Do not
trust the editing PR's own checks. Verify the way ersatztv#672 did:

1. Push a scratch **base** branch carrying the candidate workflow.
2. Open a throwaway PR from a scratch head *into that base*, so the candidate is the definition that
   runs. Have it post a **probe-named** context (e.g. `review-verdict/h10-PROBE`), never the real
   `review-verdict/h10` — a probe must not be able to forge the gate it is testing.
3. Read the resulting commit statuses to see which definition actually ran, then delete both
   branches.

The same shape is what makes a `branches:`/`types:` change verifiable at all, since neither can be
observed from the editing PR. Note step 2 requires the scratch **base**'s own `branches:` filter to
name that base — the definition comes from the base, so a base the filter does not admit produces no
run at all.

⚠️ **Never write an expression delimiter inside a `run:` body here — a comment is NOT inert**
(ersatztv#751, `ci.workflow-run-body-no-expressions`). A `run:` body is not shell when the runner
reads it. The runner scans the whole scalar for the expression opener and, on finding one, rewrites
the **entire** body into a single `format(...)` call so the result can be spliced back in. That
rewrite is all-or-nothing: a payload that does not evaluate fails the interpolation of the whole
scalar, and **the runner then drops the step and concludes the job `success`**.

That is not hypothetical. From 8f6d4f443 (2026-08-03) to 2026-08-06 the classify step **never ran**.
The #706 note above, explaining why a concurrency group does not work here, quoted a `concurrency:`
snippet containing a PR-number expression *as an illustration*, in a shell comment. `pr number` is not
a valid expression. So `review-verdict/h10` was posted by nothing but a human hand for three days,
both exemption classes silently stopped working, and every run reported success. The prose documenting
a fix disabled the fix.

**The silent green is the real defect.** An absent required status reads as "not reviewed yet", which
is indistinguishable from the correct pending state — so an ordinary PR looked ordinary while the gate
was dead, and the cost landed only where no human was in the loop. PR #739 (docs-only) merged
2026-08-05 with **zero** commit statuses on its head, and got in only because admin force-merge was
still enabled; ersatztv#743 removed that escape the next day, so a docs-only or Renovate-manifest PR
arriving after that would simply have been stuck with no bypass. The two Renovate PRs in the window
escaped by timing, merging minutes before the bad commit.

Three things now hold the line, and they are deliberately different in kind:

- **The prose names expressions instead of quoting them** — write "a
  `github.event.pull_request.number` expression", not the delimiters. Pass values in through the
  step's `env:` block, which is interpolated per value, so a bad payload there cannot take the body
  with it.
- **A start-marker guard turns a dropped step RED.** The classifier writes a marker as its first act
  and an `if: always()` step fails the job when it is missing. It asserts execution *started*, never
  that it completed — the classifier has several legitimate `exit 0` abstention paths. The guard's own
  body must stay expression-free, or the mechanism it guards against can delete the guard too, and
  that absence would be silent as well.
- **Two static guards**, in `scripts/tests/test_pr_changed_files.py`: no delimiter in *any* `run:`
  body of this file (absolute — a dropped step here is a dead merge gate, and its bodies are ~700
  lines of prose), and repo-wide, every expression payload's **head token** must name a context or
  function the runner can resolve (permissive, because the other workflows interpolate into `run:`
  legitimately — 5 occurrences today, in `ci-image.yml`, `docker-build.yml`'s `api-docs`/`format`
  and `pr-checks.yml`'s two git-diff gates; #756 removed `build`'s two and banned that job as
  well, so the ban now covers `test`, `migrations` and `build`). Be precise about the second
  one's reach: it catches the
  historical defect (`pr number`) and a nonexistent context, but **not** a syntactically invalid
  payload whose tokens are all known (`${{ github.ref == }}` passes), nor a renamed output
  (`steps.metadata.outputs.shortsha` passes — every token after the first is preceded by `.` and is
  skipped), nor an unclosed opener. Catching those needs an expression parser. An earlier draft of
  this section claimed it caught "a payload that cannot evaluate, wherever it sits"; that was false,
  and the corrected claim is the one to rely on.

Worth knowing why nothing caught this for three days: every *other* workflow-shape test in that file
reads `_code_lines()`, which strips comments. That is correct for what it was for, but it encodes the
assumption this bug falsifies. The strict test reads the raw scalar, and must never adopt
`_code_lines`.

⚠️ **A page past the end of `/issues/{n}/timeline` is JSON `null`, not `[]`** — and this instance is
not consistent between endpoints (`/issues/{n}/comments` returns `[]` when empty). The retarget
fence's `count_retargets` gated on `type == "array"`, so it read the real terminator as *unreadable*:
the walk never reached a validated empty page, `rt_ok` was never `yes` for **any** PR, and the fence
therefore withheld **every** exemption `success`. Renovate and docs-only PRs got no status at all —
the same user-visible outcome as the dropped step above, by a completely unrelated route. So fixing
the interpolation alone would not have restored the exemptions.

Two things kept it invisible, and both are worth generalising:

- It shipped in the **same commit** (8f6d4f443) that stopped the step executing, so the fence had
  never once run in production. A guard's first real execution is not the same event as its merge.
- The **test double asserted the wrong shape while claiming measured fidelity.** Its comment read
  "Real shapes, measured on this instance and deliberately mirrored" and it printed `[]` for a page
  past the end. Every fence test was green against a response the server never produces, so the
  `array`-only gate was never exercised by the suite either. With the double corrected and the old
  gate restored, **most of the fence suite fails** — 18 tests when first measured at `c710db4a1`, 21
  once three more fence-dependent tests existed. The invariant is the point, not the count: they had
  all been passing for the wrong reason. (Given as a range on purpose — an earlier draft cited a bare
  "18", which was stale two commits later, inside a section about stale claims.) When a double claims
  fidelity, that claim is a test assertion and needs re-measuring like any other.

The type is now read as a value (`case` over `jq -r 'type'`) rather than through `jq -e`, whose
exit-status semantics already bit this workflow once at jq 1.6, and both `null` and `[]` terminate the
walk. The regression test is parameterised over both shapes because both are live on this server.
`null` is accepted as exhaustion only from **page 2 on** — every real PR's first page carries events
(spot-checked non-empty across #752/#753/#749/#739/#717; the counts are deliberately not recorded here
because timelines grow and an earlier draft's five figures were stale within days), so a `null` first
page is anomalous rather
than empty, and the walk should not certify "no retarget happened" from a response it cannot explain.

**The same nil-slice shape bites `/commits/{sha}/status`** — a third instance, found by cold review of
the fix for the second. A head with no statuses yet returns
`{"state":"pending","total_count":0,"statuses":null}` (measured on PR #739's head). `read_existing_verdict`
gated on `.statuses | type == "array"`, so it hit its `exit 1` and posted nothing at all — fail-closed,
same user-visible outcome. `null` is now accepted there only when `total_count` is 0, so a body that
merely lost its array is still refused and an existing verdict is still protected from a transient
error. `scripts/pr-changed-files.sh` was swept and is unaffected (`pulls/{n}/files` returns `[]`).
**The generalisable rule: a nil Go slice serialises to `null`, so every list-shaped field on this API
is suspect and only a per-endpoint measurement settles it.**

**Establishing that "no verdict exists" needs a second page, and both arithmetic guards for it are
no-ops here.** `read_existing_verdict` concluding absence is what licenses posting an exemption over a
verdict the job cannot see, so that conclusion has to be earned. Two obvious checks were tried and both
proved empty:

- **`.statuses | length` vs `.total_count`** — `total_count` is the count for the **page returned**, not
  for the commit. Measured at 1.27.1 on `3aed43c6` (6 contexts): `?limit=1` returns
  `len=1, total_count=1`, `?limit=3` returns `len=3, total_count=3`. Equal by construction, so the check
  reads as a completeness proof while proving nothing.
- **"refuse when the page comes back full at the requested `limit=100`"** — this instance caps `limit`
  at the server-wide `MAX_RESPONSE_ITEMS`, **measured at 50** (`/issues?limit=100` returns 50). A
  response can therefore never carry 100 rows, and the comparison was **dead code**. The repo already
  documented that cap in `scripts/pr-changed-files.sh`, two test files and `ci.script-tests-job`; the
  guard was written against 100 anyway, and a cold review caught it. Hardcoding 50 instead would
  re-break the day the setting changes.

So the job **asks the server, and only when it matters**: if the `review-verdict/h10` row is on page 1
there is nothing further to learn (this endpoint returns the latest status per *context*, and a context
cannot recur on a later page). When the row is absent it reads **page 2** — any rows there mean the list
runs longer than one page and a verdict could be beyond it, so it refuses instead of concluding absence.
Cap-independent by construction. Paging is real here: measured `?limit=3&page=2` returning three further
rows, and `page=9` returning the same `statuses: null` terminator.

The `total_count` zero-check also requires the JSON **type** to be a number: `jq -r` renders `0` and
`"0"` identically, so a text compare would accept a schema-corrupted `"total_count": "0"` as "no
statuses".

**The repo-wide expression guard scans PARSED scalars, not raw file text.** A delimiter in an ordinary
top-level YAML comment is inert — the runner never evaluates it — so redding on it is a false positive,
and this file has now produced that false red twice. PyYAML drops those comments. A `run:` body is
itself a scalar and keeps its *shell* comments, which is the point: inside a `run:` scalar a comment is
not inert. Verified both directions by mutation — an inert top-level comment passes; the same payload
in a run-body comment still reds.

**`CLAUDE.md` and `AGENTS.md` are now PROTECTED paths.** `DOCS_ONLY` matched them, so the documents
that *define* the completion protocol, the merge-consent convention and the H10 rule were themselves
docs-only-exemptible while `.claude/` was protected — the same self-exemption the gate rules out, one
directory over. Driving the real classify body with a lone `CLAUDE.md` change produced
`review-verdict/h10=success`. It is fixed here rather than deferred because restoring the exemptions is
what makes it reachable: no exemption `success` was writable at all while the classify step was
dropped. `README.md` is deliberately not listed — ordinary prose, no enforcement. For the same reason,
#706's known residual returns with the working fence: while `rt_ok` was never `yes`, route 1 was closed
by accident.

**That gap is now closed** — `docker-build.yml`'s `test` and `migrations` jobs are also required
contexts, and there a dropped step is **fail-OPEN**: the required check goes green having done no work,
which is strictly worse than an absent status (compare #684). ersatztv#756 gave those two jobs
per-**step** execution markers and extended the delimiter ban to them; see
"Dropped-step guard on the required jobs" above.

It lives in its **own workflow file** on purpose: `pr-checks.yml` sets `cancel-in-progress: true`,
and a cancelled run there would leave an exempt PR with no status and no further push to
re-trigger it. Its own job context (`Review verdict / Set review-verdict status`) is **not** the
required check — a workflow must not satisfy the gate merely by running successfully.

Full rationale: `docs/decisions/records/release/verdict-status-check.md` and
`docs/decisions/records/ci/shared-pr-file-enumeration.md`.

## CI toolchain image (`docker/ci/Dockerfile`, `.gitea/workflows/ci-image.yml`)

The jobs that need a toolchain — `test`, `migrations`, `functional-e2e`, `api-docs`, `format` —
run **inside** a shared image via `container:` instead of installing their toolchain per run
(ersatztv#390). They therefore carry **no** `setup-dotnet`, **no** `setup-node`, **no** `apt-get`,
and **no** `dotnet tool install`.

**What it ships:** .NET 10 SDK, Node 22, prod-identical ffmpeg/ffprobe, `git`/`python3`/`jq`/`zstd`,
the `dotnet-ef` + `dotnet-reportgenerator-globaltool` global tools (which the `migrations` and
`test` jobs used to install on every run — **bump those versions in the Dockerfile, not the
workflow**), and **headless Chromium** for the UI-E2E flows (below). Project dependencies (NuGet/npm)
are deliberately **not** baked in — they change per commit and stay on `actions/cache`
(`~/.nuget/packages`, `~/.npm`).

**Headless Chromium for UI-E2E (ersatztv#445).** `PLAYWRIGHT_BROWSERS_PATH=/ms-playwright` holds
`chromium-headless-shell`, installed with `--with-deps` at image build time so the `functional-e2e`
job installs no browser per run. Measured on this exact base: the headless shell is **267M** where
full `chromium` is **656M**, and `chromium.launch()` resolves to the shell anyway because
`web/playwright.config.ts` never asks for headed — the accepted tradeoff being that a *headed* run
inside this image would fail. Also verified on the real base rather than assumed: Chromium launches
as **root inside a container with no `--no-sandbox`/`chromiumSandbox:false` opt-out**, so the config
carries no sandbox workaround. The Dockerfile's build-time smoke test actually *launches* the browser,
so a missing system library fails the image build rather than a CI run.

⚠️ **`ARG PLAYWRIGHT_VERSION` must equal `web/package.json`'s `@playwright/test` pin**, which is
deliberately **EXACT** (no caret): Playwright ties a browser *revision* to the package version, so a
mismatch leaves no usable browser. Renovate bumps the npm pin but cannot know about this ARG — when it
does, bump the ARG, let `ci-image.yml` publish the new `:<sha>`, then update all five container pins.
`scripts/e2e-ui.sh` guards the drift by *launching* a browser up front and failing with exactly that
instruction (it probes by launch, not by path, because `chromium.executablePath()` reports the
full-chromium path that a headless-shell-only image deliberately lacks).

**How it's layered:** `FROM ersatztv-ffmpeg:8.1.2` + `COPY --from=mcr.microsoft.com/dotnet/sdk:10.0-noble-amd64
/usr/share/dotnet` — the same pattern `docker/Dockerfile` uses for the prod image. Our ffmpeg base is
`ghcr.io/linuxserver/baseimage-ubuntu:noble`, the same Ubuntu release as the SDK image, so the copied
SDK matches the base's glibc/ICU. Keep the ffmpeg tag on that `FROM` equal to the one
`docker/Dockerfile` pins, so CI's ffmpeg stays prod-identical — that fidelity is what the
ersatztv#299 seeded-media/scanner E2E follow-ups will need.

**Bumping the toolchain is a deliberate two-step.** The jobs pin an immutable `:<sha>`, never
`:latest`, so a bad toolchain push cannot break every job at once:

1. Merge a `docker/ci/Dockerfile` change. `ci-image.yml` publishes `ersatztv-ci:<sha>` (+ `:latest`
   from `main` only — a human pointer; **jobs must never consume it**).
2. In a follow-up PR, update the pin in `docker-build.yml` — **all five jobs together**. That PR's own
   CI is what proves the new image works. The pin is repeated per job because
   `jobs.<id>.container.image` cannot read the workflow `env` context.

**The tag is exactly 7 hex chars — get the length right, not just the commit** (ersatztv#594).
`ci-image.yml` tags with `git rev-parse --short HEAD` under `fetch-depth: 1`, and that shallow clone
holds few enough objects that git always abbreviates to **7**. A full local clone abbreviates to **8**,
so the natural command prints one character too many:

```bash
git rev-parse --short HEAD     # 8 chars in a full clone — WRONG, no such registry tag
git rev-parse --short=7 HEAD   # 7 chars — what ci-image.yml publishes. Use this.
```

An 8-char pin names the *right commit* but *no existing image*: it satisfies a resolve-and-compare
check, then every `container:` job dies at image-pull with `manifest unknown`, which reads like a
registry outage rather than a one-character pin error. `ci-image-pin` therefore checks the pin's
**length** as an invariant separate from its correctness, and prints the exact tag to use.

> **Caveat worth knowing before you trust the 7:** `ci-image.yml` still tags with a plain `--short`,
> whose length git *auto-scales* to the object count. 7 is therefore an empirical property of today's
> shallow clone, not an enforced invariant — if that count ever crosses git's threshold, the publisher
> emits 8, the correct pin becomes 8, and the gate's hardcoded 7 goes permanently red demanding a tag
> with no image behind it. Making the publisher emit `--short=7` is tracked as ersatztv#597.

`ci-image.yml` triggers on pushes touching `docker/ci/**`, `workflow_dispatch`, and a weekly Monday
05:00 UTC cron (base-image security updates; Gitea registers `schedule` only from `main`). It runs on
`ubuntu-latest` — it was on `small` until server-management#639, where "docker-only" was found to be
a poor proxy for "small": this is a full buildx of the .NET toolchain image, the heaviest job in that
lane. Like `docker-build.yml`, it needs BuildKit's inline `http = true` for the HTTP
registry. Renovate tracks the Dockerfile's image pins (`dockerfile` manager, see `renovate.json`).

**Three container-specific gotchas** — worth knowing if you add a job or a step:
- **`sh`, not bash, is the default shell inside a `container:`.** act_runner runs steps as
  `sh -e {0}` (dash) because it can't assume bash exists in an arbitrary image — even though ours
  has it. Every bashism (`set -o pipefail`, arrays, `shopt`, `mapfile`) then dies instantly with
  `set: Illegal option -o pipefail`. `docker-build.yml` therefore declares a workflow-level
  `defaults: run: shell: bash`. **If you add a workflow with containerized jobs, do the same** —
  outside a container the shell defaults to bash, so this failure only appears once you containerize
  and it looks nothing like a shell problem (it surfaced as the `migrations` job dying in 0.13s).
- `actions/checkout` clones as root into a mounted workspace, which trips git's *"detected dubious
  ownership"* guard and breaks every `git` call in a step. Fixed in the Dockerfile with
  `git config --global --add safe.directory '*'`.
- *(defensive, not load-bearing)* The ffmpeg base sets `ENTRYPOINT ["ffmpeg"]` because it ships as an
  ffmpeg CLI, so the Dockerfile resets `ENTRYPOINT`/`CMD`. act overrides the entrypoint anyway
  (`entrypoint=["/bin/sleep" "10800"]`), so this is belt-and-braces for anyone running the image by
  hand — unlike the two above, which are real.

⚠️ **A REBASE invalidates the pin.** The pin must equal the short sha of the commit that touched
`docker/ci/**`, and a rebase **rewrites that commit's sha** — so `ci-image-pin` goes red on a branch
that was green before, with a pin that still resolves to a real (now-orphaned) commit and an image
that still exists in the registry. Worse, the force-push usually does **not** rebuild: `ci-image.yml`
filters on `paths: docker/ci/**`, and a rebase that doesn't change the Dockerfile's *content*
produces no diff for that path, so nothing republishes. And you cannot simply re-dispatch it —
`ci-image.yml` tags `git rev-parse --short HEAD`, i.e. whatever the branch HEAD is when it runs, not
the commit that touched `docker/ci`. Those two coincide only when the `docker/ci` commit *is* HEAD.

Recovery (ersatztv#445 hit this): make the `docker/ci` commit be HEAD again — push a commit that
really does change `docker/ci/**`, let `ci-image.yml` publish `:<its short sha>`, then bump the pin in
a follow-up commit. That is the same two-step below, just re-run after the rebase. The cheapest way to
avoid it entirely is to **land a toolchain-image change on its own, before** the work that consumes
it, so the consuming branch never carries the `docker/ci` commit through a rebase.

**Bumping the pin is enforced, not remembered.** The `ci-image-pin` job (blocking, PR-only; defined
in `pr-checks.yml`, but it greps `docker-build.yml` where the pins live) fails if
`docker-build.yml`'s pin isn't the short sha of the last commit to touch `docker/ci/**` or
`ci-image.yml`, if that pin isn't exactly 7 chars long (see above), or if the five jobs ever pin
different tags. This exists because **Renovate manages
`docker/ci/Dockerfile`'s base pins but cannot bump an opaque `:<sha>`** in `container.image` — so a
Renovate base bump would otherwise publish a new image, test the *old* one, and merge with the
Dockerfile disagreeing with the pin. A red `ci-image-pin` means: let `ci-image.yml` publish the new
`:<sha>`, then update all five pins to it.

**What it is and isn't worth.** Measured honestly (ersatztv#390): the image saves ~15–40s per job
(`setup-dotnet` is 8–19s, `setup-node` 2–5s cached, the two tool installs ~9s) plus the 110s
apt-ffmpeg step — roughly 3–8% of runtime. It is **not** where CI time goes; see the lane table above
(queue wait, server-management#604) and ersatztv#398 (742s of redundant compilation). Its durable
value is prod-identical ffmpeg, a pinned/consistent toolchain, and making jobs runner-agnostic — the
last is what allowed the lane rebalance.

## Dockerfile notes (`docker/Dockerfile`)

- Base image: **`192.168.1.95:3000/timothy/ersatztv-ffmpeg:8.1.2`** (our Gitea fork of
  the archived `ghcr.io/ersatztv/ersatztv-ffmpeg`). FFmpeg 8 base image work landed in
  ersatztv-ffmpeg#4; app-side compatibility work landed in ersatztv#9.
- Copies `Directory.Build.props`, `Directory.Build.targets`, `Directory.Packages.props`,
  `global.json`, `.editorconfig` before `dotnet restore` so the image build uses the same
  MSBuild config, central package versions, SDK pin, and analyzer severities as local/CI
  builds (it previously copied only `*.sln`). `Directory.Packages.props` is **required**
  here: under Central Package Management the csproj carry no inline versions, so the
  image's restore fails (`NU1015`) without the central manifest.
- amd64-only (the runner/build host is x86_64). No arm32/arm64, no DMG/exe artifacts, no GHCR/DockerHub.
- **openapi-generator jar layer ordering** (ersatztv#190): the `wget` for the
  openapi-generator-cli jar runs *before* the `COPY` of `ErsatzTV/wwwroot/openapi/`, so the
  ~30MB download layer is cached independently of the openapi spec. Previously the jar was
  downloaded after that `COPY`, so any PR touching the spec (e.g. `v1.json`) busted the
  download layer too and re-fetched the jar on every such change. Codegen itself still runs
  after the spec `COPY`, since it needs both the jar and the spec files.

## Dependency management (Central Package Management + scans)

**Central Package Management (CPM)** — package versions live in a single repo-root
`Directory.Packages.props` (`ManagePackageVersionsCentrally=true`); the per-project
csproj reference packages by name only (no `Version=`). One source of truth, atomic
one-line bumps, and cross-project version drift is structurally impossible. To add or
change a dependency, edit the `<PackageVersion>` entry centrally — never put a `Version=`
back on a `<PackageReference>` (that trips `NU1008`). The Docker build must copy this file
before restore (see Dockerfile notes). The `.mcp/` vendored tool (gitignored, not in the
solution) keeps inline versions via a **local-only** `.mcp/Directory.Packages.props`
opt-out (`ManagePackageVersionsCentrally=false`). (ersatztv#14)

**NuGet audit** — .NET 10 runs NuGet audit on restore. Several projects set
`TreatWarningsAsErrors=true`, so vulnerable transitive packages failed the build.
`Directory.Build.props` demotes low/moderate/high advisories (NU1901-1903) to warnings
and promotes NU1904 (critical) to an error in **every** project via `WarningsAsErrors`.
The advisories that prompted this were resolved in ersatztv#8 (NCalcSync→6.x; SQLitePCLRaw
bundle 3.x) and ersatztv#314 (**Microsoft.OpenApi 2.0.0→2.7.5**, GHSA-v5pm-xwqc-g5wc High —
direct-pinned in `ErsatzTV.csproj` over the 2.0.0 that `Microsoft.AspNetCore.OpenApi` +
`Scalar.AspNetCore` pull transitively; the SQLitePCLRaw override pattern; regenerates the
OpenAPI doc byte-identically). The NU1901-1903 demotion is **kept by design**: criticals (NU1904)
still hard-block, while low/moderate/high advisories surface as warnings + via the weekly scan and
Renovate security PRs, rather than breaking unrelated PRs the moment a new transitive
advisory drops.

**Scheduled vulnerability scan** — `.gitea/workflows/dependency-scan.yml` runs weekly
(cron `0 6 * * 1`) + on `workflow_dispatch`: `dotnet list package --vulnerable
--include-transitive` over the **full** solution (incl. Scanner, which the image build
strips). `dotnet list` exits 0 even with findings, so the step (`bash -euo pipefail`)
greps for the "has the following vulnerable packages" marker and fails the run if present.
Detection only — it surfaces advisories on a schedule, a Gitea-native stand-in for
Dependabot; it does **not** open update PRs (that's Renovate — server-management#484).
Gitea registers `schedule` triggers only from the default branch, so the cron starts
after merge to `main`; use `workflow_dispatch` to run on demand. It went **green** once
ersatztv#8 cleared the NCalcSync/SQLitePCLRaw advisories — a red run now means a **new**
advisory has appeared. (ersatztv#14, ersatztv#8)

**Renovate (automated update PRs)** — `.gitea/workflows/renovate.yml` runs self-hosted
[Renovate](https://docs.renovatebot.com) weekly (cron `0 3 * * 1`) + on `workflow_dispatch`,
as a `renovate/renovate:43` container job on the shared act_runner. This is the *proposing*
layer the scan above deliberately omits: it opens grouped dependency-update PRs and
OSV-driven vulnerability-fix PRs against `main`, and maintains a **Dependency Dashboard**
issue listing the full backlog. Config is the repo-root `renovate.json` — managers `nuget`
(via CPM), `github-actions`, and `dockerfile` (scoped to the built `docker/Dockerfile`; it reads the
HTTP-only Gitea registry for the `ersatztv-ffmpeg` base via a `RENOVATE_HOST_RULES` host rule —
`insecureRegistry` + registry read creds, set in the workflow env, not the committed config). The
docker-compose manager is unused (repo compose files are `build:`-only). Auth: a dedicated
**`renovate` Gitea bot** (Write
collaborator) via repo Actions secrets `RENOVATE_TOKEN` (bot PAT) + `GH_COM_TOKEN` (no-scope
github.com PAT for changelogs — named `GH_`, **not** `GITHUB_`, a prefix Gitea reserves).
**Patch** bumps to test/dev-only packages (NUnit\*, NSubstitute, Shouldly, coverlet,
`Microsoft.NET.Test.Sdk`, `Testably.Abstractions*`, threading analyzer) **auto-merge** once
the `Build & test (.NET)` check passes — branch protection on `main` requires that context;
everything else is manual review (ersatztv is prod-bearing). Range-pinned packages (e.g. EF
Core `[9.0.x,10)`) are respected — no v10 jump. PR volume is throttled (`prConcurrentLimit`
5 + `config:recommended`'s `prHourlyLimit` 2); tick a dashboard checkbox or raise the limits
to drain faster. `workflow_dispatch` defaults to a safe **dry run**. Cross-repo rollout
tracked in server-management#484. (server-management#484)

## Security scanning — black-box DAST + SAST (`scripts/security-scan.sh`, ersatztv#314)

Every other security check we run is **in-ecosystem / white-box** — SonarAnalyzer, NetArchTest, the
adversarial fork + Codex review passes, the api-docs/format/decisions CI gates, `dotnet list package
--vulnerable` — so they share our blind spots. `scripts/security-scan.sh` is the **out-of-ecosystem,
black-box** complement and a **#197 exit criterion** (HARD GATE before remote exposure): it drives the
running product from outside our C#/review stack.

- **What it does.** Boots a **throwaway** container from the image under test (fresh empty config volume;
  never the deployed prod/test container — the authenticated *active* scan sends attack payloads to write
  endpoints), reads the generated machine key, and runs an **authenticated OWASP ZAP** API scan
  (`zap-api-scan.py`) that imports the static `/openapi/v1.json` so it exercises **every** declared
  `/api/v1` operation, injecting `X-Api-Key` on every request via a ZAP replacer rule so it reaches the
  `[RequiresAuthentication]` + `RequireKeyForReads` surface (not just the `/app` shell an unauthenticated
  spider sees). Then a **semgrep** SAST cross-check (`p/security-audit` + `p/secrets` + `p/csharp`). The
  container is torn down on exit.
- **Where/when.** Runs on the **docker host** (jazz — the Mac has no docker), like
  `migration-smoke.sh`: `scripts/security-scan.sh [IMAGE] [PORT]` (defaults `…:latest` / `8411`). It is a
  **manual release-gate**, deliberately **not** a per-PR CI job — it needs docker + a booted image, takes
  several minutes, and is noisy (expect to tune, not take raw). The continuous layer is the per-PR
  white-box gates + the weekly `dependency-scan`; this is the per-release black-box pass. Re-run it each
  release and before any change to the exposure posture.
- **Exit-code contract (ersatztv#338).** `zap-api-scan.py`'s raw exit code is NOT a simple pass/fail — it
  conflates a clean run with a warnings-only run unless you know its wrapper contract: **0** clean (no
  FAIL or WARN alerts), **2** WARN-only (triage required, but **not** release-blocking), **1** FAIL (at
  least one FAIL-level alert — release-blocking), **124** the script's own `timeout` wrapper killed a
  hung post-scan cleanup (the report written before the hang is still usable — triage it), any other
  code means the scanner/tool itself errored (not a scan result at all). `scripts/security-scan.sh`
  encodes this in `classify_zap_exit()` and prints an unambiguous `==> ZAP result: <PASS|WARN|FAIL|
  TIMEOUT|TOOL ERROR> ...` line; the script's own exit status reflects that classification (0 for
  clean/WARN, 1 for FAIL/timeout/tool-error) rather than ZAP's raw code, so a warnings-only run no longer
  reads as a failed scan. Found when the v26.8.0 release scan (#335) returned raw exit 2 for a report with
  `FAIL-NEW: 0` and two known/expected warning classes — the shell result looked like a failure though the
  release gate had actually passed. Run `scripts/security-scan.sh --selftest` for a docker-free regression
  check of the classification logic.
- **Triage.** Triage each WARN/FAIL finding false-positive vs real. Real, in-scope, go-live-blocking
  findings get fixed (e.g. the security headers from the #319 baseline; the Microsoft.OpenApi pin above);
  LAN-expected noise (Private-IP disclosure) is revisited only for genuine remote exposure. nuclei
  (template-based CVE fingerprinting) is an optional third pass — deferred while its template fetch is
  blocked in the runner env (pre-seed a template volume to add it); ZAP covers the DAST baseline and
  semgrep the SAST, so it is not on the critical path.

## Static analysis & formatting

**Analyzers** — `Directory.Build.props` enables the SDK analyzers at `latest-All` and turns on
`Microsoft.VisualStudio.Threading.Analyzers` for every centrally managed project.
`Directory.Build.targets` also references
**Roslynator**, **SonarAnalyzer.CSharp**, **Meziantou.Analyzer**, and **AsyncFixer** repo-wide (versions
central via CPM). All analyzer package references are guarded on `ManagePackageVersionsCentrally`, so the
gitignored `.mcp` tool—which deliberately uses inline package versions—does not inherit versionless
references.
They are introduced **incrementally** (ersatztv#15). `eng/analyzers/sdk-all-suggestion.globalconfig`
enumerates the .NET 10 SDK `All` inventory at `suggestion`; this exact-ID baseline is necessary because
the SDK's generated `latest-All` severities outrank `.editorconfig` bulk settings. `.editorconfig` keeps
the threading and curated-pack baselines at `suggestion`. Diagnostics remain visible to IDEs and
`dotnet format analyzers`, but do not create a wall of failures (a direct `latest-All` trial activated
455 existing errors in the TWAE projects).

**Promotion is the enforcement** — set a reviewed rule to `warning` in `.editorconfig` and append its ID
to the central `WarningsAsErrors` list in `Directory.Build.props`. The explicit list makes the rule block
in every project, including test projects that do not otherwise use TWAE. On a major SDK upgrade,
regenerate the checked-in SDK baseline from `analysislevel_<major>_all.globalconfig`, preserve SDK `none`
entries, and review newly introduced rules before accepting the snapshot.

Promoted rules are recorded here so the blocking subset stays intentional and reviewable:
- **Sonar `S3981` — `warning` + `WarningsAsErrors`** (ersatztv#15): rejects collection-count comparisons that are constant
  regardless of collection size. Its first finding exposed `Workers.Count >= 0`, which permanently
  classified scheduled memory releases as busy and skipped the intended aggressive idle collection.

- **StyleCop.Analyzers is intentionally excluded**: its latest stable (1.1.118) crashes (`AD0001`) on
  C# `record` declarations, and its rules overlap the existing `.editorconfig`/Roslynator. Revisit via
  the record-compatible `1.2.0-beta` only if specifically wanted.
- **The former Blazor `.razor` caveat is retired**: Blazor removal deleted the Razor sources and their
  temporary Sonar `NoWarn` list. The `.razor`/`.cshtml` suggestion scopes remain in `.editorconfig` only
  as a defensive default if server-rendered view code is ever reintroduced.

**Formatting** — the inherited tree still contains legacy UTF-8 BOM/whitespace debt, so the standing
policy is **format as you touch**, not a mass rewrite (ersatztv#311). The Husky pre-commit hook and
the blocking `format` CI job both run `dotnet format whitespace . --folder --verify-no-changes
--include <changed .cs>` — scoped to the files the commit/PR touches. Untouched legacy files remain
outside the gate; `.gitattributes` pins line endings. A one-time full-tree normalization remains a
separate, unmade decision.

*Why `whitespace . --folder`, not the full `dotnet format <sln>` (ersatztv#469)* — the gate only
needs to enforce `.editorconfig` **whitespace** (indent/EOL/trailing/final-newline) and **charset**
(no UTF-8 BOM). The old recipe (`dotnet format ErsatzTV.sln --no-restore --verify-no-changes
--include`) loaded the entire ~10-project MSBuild workspace and built a Roslyn compilation per
project *before* checking a single file — `--include` narrows *which* files are checked, never what
gets loaded. Measured whole-solution `dotnet format` ran **~480s locally**; folder mode runs in
**~0.5s** and needs no `dotnet restore` (the NuGet-cache + Restore steps were removed from the job).
`--folder` treats the tree as a plain folder of files, skipping MSBuild/Roslyn entirely, and still
reads `.editorconfig`. Verified **non-vacuous**: it exits non-zero on an injected trailing-whitespace
line (`error WHITESPACE`) and on a prepended UTF-8 BOM (`error CHARSET`), and exits 0 on a clean file.
**No coverage was lost**: the full `dotnet format` gate did **not** enforce the style/analyzer pass
either — a probe injecting a `warning`-severity naming violation (`local_constants` not `ALL_UPPER`)
passed the *full* solution format (exit 0): the only `.editorconfig` rule above `:suggestion`/`:none`
severity is that one naming rule, and naming violations have no `dotnet format` batch code-fixer, so
`--verify-no-changes` reports no change regardless of severity. The analyzers that **must** block
(`NU1904`, `S3981`) are enforced at *compile time* via
`WarningsAsErrors` in `Directory.Build.props`, not by this job. Devs fix a violation with `dotnet
format whitespace . --folder --include <files>` (the full `dotnet format ErsatzTV.sln --include
<files>` is a superset and also works).

## Migration integrity (EF Core, both providers)

`TvContext` (`ErsatzTV.Infrastructure/Data/TvContext.cs`) has **two** migration sets — one per
provider project: `ErsatzTV.Infrastructure.Sqlite/Migrations` and
`ErsatzTV.Infrastructure.MySql/Migrations`, each with its own `TvContextModelSnapshot`. **A model
change needs a migration in BOTH.** Add them with `scripts/add-migration.sh <Name>` (runs the EF CLI
for each provider). The EF CLI pattern (provider selected by the post-`--` arg, which `Startup`
reads as the `provider` config key):

```
dotnet ef <cmd> --context TvContext --startup-project ErsatzTV \
  --project ErsatzTV.Infrastructure.{Sqlite|MySql} -- --provider {Sqlite|MySql}
```

The **`migrations` job** in `docker-build.yml` runs on every push/PR and, for **each** provider:

1. `dotnet ef migrations has-pending-model-changes` — fails if an entity changed without a matching
   migration (**model drift**), so a forgotten migration can't merge.
2. `dotnet ef database update` against a **fresh empty DB** — applies *all* migrations in order and
   fails on any broken/un-orderable one.

- **SQLite** (the prod provider) uses a throwaway file (`ETV_CONFIG_FOLDER=$(mktemp -d)`); no service
  needed. Validated: 787 migrations → 139 tables.
- **MySql** uses `ServerVersion.AutoDetect`, which **connects at config time**, so the job needs a
  reachable server — provided by a `services: mysql:8.4` container (the act_runner uses Docker
  execution with an auto-created per-job network — service reachable as `mysql:3306` (the old
  bumblebee runner pinned network `downloadswarm`; relocated in server-management#570)). Connection
  string via `MySql__ConnectionString` (→ config key `MySql:ConnectionString`). Validated: 305
  migrations → 137 tables. It's an **independent gate** (not yet a `needs:` of the image build) so
  the new MySql-service dependency can't block image builds until it's proven; promote it to a
  required check once stable.

**Caveat — non-transactional operations**: some migrations (e.g. SQLite `PRAGMA foreign_keys`) run
outside a transaction and warn at startup; they can't be rolled back mid-migration, so review such
migrations carefully (this is part of what motivated the apply-to-fresh check before the prod
cutover, server-management#481).

**Resilience — the MySql apply is retried (concurrent-runner contention, not a model bug)**: both
runners (`ci-runner` VM 127 + `bumblebee-runner`) serve `ubuntu-latest`, and when two migration jobs
land on the **same host at once** (common when several PRs push together), each spins its own
`mysql:8.4` service container and they starve each other — producing intermittent `Command Timeout
expired` **or** mid-replay `MySqlEndOfStreamException` (dropped connection) on the MySql
apply-to-fresh-DB step. This is pure infra flakiness — `has-pending-model-changes` (the actual model
check) still passes, and the *same commit* passes on a quieter host. The job hardens against it two
ways: the connection string sets `DefaultCommandTimeout=300` (up from MySqlConnector's 30s default),
and the apply is wrapped in a **3× retry** that resumes from `__EFMigrationsHistory` (EF commits each
migration in its own transaction, so an interrupted one rolls back and the retry continues). A *real*
migration failure fails deterministically on every attempt, so the retry never masks it. If a run
still flakes past the retry, re-trigger (Gitea has no rerun API on this version — push, or the run
drains); don't treat a lone MySql-apply red as a code problem without checking the failure mode.

### Migration-on-prod-copy smoke — release path (`scripts/migration-smoke.sh`, ersatztv#315)

The `migrations` job above only proves a migration is **well-formed against a fresh, empty DB**. It
can't prove it applies cleanly to the **accumulated prod SQLite** — real row volume, historical values,
and the post-migration data steps ErsatzTV runs on startup: `DatabaseMigratorService` (a
`BackgroundService`) applies pending migrations, then `DbInitializer.Initialize` + `PopulatePathHashes`
(an `UPDATE` over the real `MediaFile` table). A migration green on a fresh DB can still fail or corrupt
on prod, and today you'd only find out mid-deploy after the container recreates.

`scripts/migration-smoke.sh` rehearses it on a **throwaway copy** of the latest prod backup — it never
touches the live DB:

```
scripts/migration-smoke.sh --image <ref-about-to-be-promoted> [--db <backup.sqlite3>] [--timeout 180]
```

It copies the backup into a temp config dir, boots the new image against it (`ETV_CONFIG_FOLDER`), and
**gates PASS on the `Done applying database migrations` log line** — not merely on HTTP readiness, since
the migrator runs concurrently with Kestrel, so the web server can serve before/while migrations run.
FAIL = the container exits before finishing, a migration exception appears in the logs, migrations
don't finish within `--timeout`, or the app won't serve `/iptv/channels.m3u` afterwards. The smoke
container, the DB copy, and the temp dir are always torn down on exit (the ErsatzTV image runs as root,
so cleanup deletes its root-owned config files from inside a throwaway root container — otherwise each
run would leak the multi-hundred-MB copy). Exit 0 = clean, 1 = migration/boot failure, 2 = usage error.

- **`--db` default**: the newest `ersatztv.sqlite3` under `$ETV_BACKUP_DIR`
  (default `~/downloadswarm/ersatztv-backups` — where the host-side pre-deploy backup hook writes
  timestamped snapshots). Pass `--image` = the version tag about to be promoted.
- **Where it runs**: it's meant to run **on the docker host** as a **Komodo pre-deploy step** (which
  already produces the backup — see "Cutting a release" and the #553 pre-deploy backup caveat), so a
  bad migration aborts the promote before the live container recreates. Wiring it into that hook is a
  server-management concern (cross-repo — this repo owns the script + docs, server-management owns the
  Komodo hook). Until wired, run it by hand before cutting a migration-bearing release.
- Validated live 2026-07-12: `:latest` against a copy of the 283 MB prod backup → migrations applied
  cleanly, app booted and served, temp dir removed.

## Pre-commit hooks (web/)

The repo uses **husky** git hooks (installed via `web/`'s **lint-staged** + npm) to catch
lint/format/type/API-drift errors locally, before they reach CI. Because the git root and
the npm project dir differ (monorepo: no root `package.json`, the JS/TS project lives
entirely in `web/`), the wiring is:

- `husky` + `lint-staged` are devDependencies of `web/package.json` (not a root package —
  there isn't one).
- The committed hook scripts live at the repo root: `.husky/pre-commit`, `.husky/pre-push`,
  `.husky/commit-msg`.
- `web/package.json`'s `prepare` script (`cd .. && husky`) runs on `npm install` inside
  `web/` and points git at the repo-root `.husky` dir (`git config core.hooksPath
  .husky/_` — the `_` subdir is husky's generated internal dir, gitignored via its own
  `.husky/_/.gitignore`; only the hook scripts themselves are committed). This works
  because npm keeps `web/node_modules/.bin` on `PATH` for the `prepare` script even after
  it `cd ..`s to the repo root (which husky's init requires — it hard-checks for `.git`
  in the *current* directory).

**The four hooks:**

1. **`pre-commit`** — (a) `cd web && npx lint-staged`: runs `eslint --fix` on staged
   `web/src/**/*.{ts,tsx}` files, then a project-wide `npm run typecheck` (`tsc -b` isn't
   file-scoped, so it runs the full check, but only when a `.ts`/`.tsx` file is staged);
   (b) back at the repo root, if any **`*.cs`** files are staged, `dotnet format
   ErsatzTV.sln --verify-no-changes --include <staged .cs>` — a formatting violation
   blocks the commit. The .cs step is **skipped entirely when no .cs is staged**, so
   web-only commits don't pay the sln-load cost; when it does run it's scoped to the staged
   files (~6-7s wall in practice, dominated by the workspace load); (c) **H3** (ersatztv#303) —
   refuses a staged **root-level `*.png`** (`git diff --cached --name-only | grep -E '^[^/]+\.png$'`),
   belt-and-suspenders with the `.gitignore` screenshot rule so a forced `git add -f` still can't land
   a review/debug screenshot at the repo root. Nested `*.png` (real assets) pass; (d) **decision
   lifecycle validator** (ersatztv#521, supersedes the ersatztv#303 H9 append-only mechanic) — runs
   `.claude/hooks/decisions-guard.sh` (no args; a fail-open shim around
   `scripts/decisions_validate.py`), the structural checks over the working tree (metadata
   well-formedness, one active record per key, reciprocal links). It has no base/head here, so the
   body-diff/no-vanish checks it also knows about are skipped locally and only run in the CI
   `decisions lifecycle` job, which has a PR base to diff against.
2. **`pre-push`** — CI-parity gate: `cd web && npm run check:api && npm run lint && npm run
   typecheck && npm run build`. `check:api` guards generated-OpenAPI drift
   (`ErsatzTV/wwwroot/openapi/v1.json` → `web/src/api/generated/v1.d.ts`); the full
   lint/typecheck/build catch a staged change that breaks an *unstaged* file (lint-staged
   only sees staged files). Any failure blocks the push.
3. **`commit-msg`** — enforces the CLAUDE.md protocol: the message must carry a
   `Co-Authored-By:` trailer, else the commit is rejected (merge commits are exempt, detected
   via `git rev-parse --verify MERGE_HEAD`). The decision-lifecycle check lives in `pre-commit`
   (above), not here — the `Decisions-Edit:` trailer is read from the commit message, but only by the CI
   `decisions lifecycle` job's body-diff step (`range` mode over the PR's merge-base diff), which is
   the only place a base/head range exists to diff against.

- **Worktree/subdir gotcha**: git exports `GIT_DIR` (and friends) while running hooks. In a
  worktree or any subdir, an explicit `GIT_DIR` makes nested `git` commands mislocate the
  working tree — `pre-push`'s `check:api` (`git diff --exit-code`, run from `web/`) then
  silently reports "no diff" and lets drift through. `pre-push` therefore `unset`s
  `GIT_DIR GIT_WORK_TREE GIT_INDEX_FILE` first. (`pre-commit`'s `.cs` collection uses
  `git diff --cached`, index-vs-HEAD, which needs only `GIT_DIR` and is unaffected.)
- **Practical effect**: a fresh `web/` `npm install` (after cloning or pulling this change)
  installs all four hooks automatically — no separate setup step. Commits that touch only
  non-`web/`, non-`.cs` files skip linting/formatting (lint-staged no-ops with nothing to
  run, the `.cs` step is skipped).

## Registry

Gitea Packages, HTTP-only at `192.168.1.95:3000`. the `ci-runner` VM's Docker daemon (192.168.1.127) has it as an
insecure-registry (server-management#172; runner relocated off bumblebee in #570). Images: `192.168.1.95:3000/timothy/ersatztv:<tag>`.

## Test / prod environments

Container/compose wiring lives in **server-management** (project boundary): test
`ersatztv-test` on 8410 (`:latest`), prod `ersatztv` on 8409 (`:prod`). See
server-management#481 for the full spec (registry pull on the docker host, volumes, Jellyfin
isolation for test, Watchtower/manual promotion).

## Retired upstream workflows

The upstream `.github/workflows/` (`ci.yml`, `docker.yml`, `artifacts.yml`,
`release.yml`, `pr.yml`, `issue-stale.yml`) were removed — they targeted
GHCR/DockerHub + Azure/Apple signing and called reusable workflows at dead
`ersatztv/ersatztv@main` paths, and ran as noise (incl. a daily stale-issue cron) on
the Gitea runner. Upstream is archived, so there are no future merges to preserve them
for. The dead `.github/dependabot.yml` and `FUNDING.yml` (upstream-pointed) were also
removed.

## Known follow-ups

- Pin third-party actions to commit SHAs (currently floating major tags cloned from
  github.com at runtime) — low priority for a homelab; tracked informally.