screen #3587: merge b1dd0dc396 onto main edf4c2e581

docs/TESTING_INTERNALS.md

@@ -1125,6 +1125,15 @@ list each unmapped file that caused a fallback with one of these labels:
   list classifies (for example `ETHOS.md`); map it, exempt it, or derive its
   directory.
 
+Narrow screens (`gstack-ship-queue ready --screen` without `--broad`) and
+`eval:bg:pr` (`test:pr` defaults `EVALS_SCREEN_POLICY=narrow`) leave out a
+derived file whose closure reaches every gate case; the plan lists it as left to
+the train gate's full census, and that census runs those cases.
+`pull_request` runs, broad screens, `EVALS_SCREEN_POLICY=broad` and
+`--profile full` keep every derived dependent. Full-gate inputs and unknown files
+still restore the full gate on a narrow screen. The policy is in
+[ship-policy.md](ship-policy.md#run-a-merge-train).
+
 The fallback rate is a label, not the bill: a dependents run whose derived
 closure reaches every gate case costs about what a full-fallback run does.
 `bun run test:health` leads with the cost per merged PR and reports

docs/ship-policy.md

@@ -422,7 +422,13 @@ case counts and the recommendation only. A lane that already ran focused
 local cases says so in the READY block and may pass `--no-screen`. `--screen`
 dispatches `gate_workflow` with `screen_pr`, `screen_merge_sha` (the
 `refs/pull/<n>/merge` SHA) and `screen_policy` (`narrow`, or `broad` with
-`--broad`, today's full PR selection). The nonce key carries the purpose and
+`--broad`, the full PR selection). A narrow screen, and `eval:bg:pr`, skip a
+changed file whose derived references reach every gate case and nothing
+narrower selects, along with its derived judges: the plan's reason names it,
+and the train gate's full census runs those cases. A `pull_request` run, the
+merge gate when the base has no `train` block, keeps the broad selection. Full-gate files, shared runtime and paid-runner
+inputs, and files the derivation cannot place still run the full gate on a
+narrow screen. The nonce key carries the purpose and
 the policy, so a repeat follows the same run and a broad screen never adopts
 a narrow one. The READY block gains `screen: …`, and the receipt is written
 locally and to the notes ref. `--dry-run` prints the dispatch without sending
@@ -760,7 +766,7 @@ reorder with `--order`. The default command is `bun --no-env-file
 
 **Escape hatches.** Remove the `train` block on the base branch to return
 every lane to the per-PR queue at once. `--urgent` ships one PR alone,
-`--no-screen` skips the paid screen, `--broad` widens it to today's selection,
+`--no-screen` skips the paid screen, `--broad` widens it to the full PR selection,
 and `train build --prs <list without it>` drops a PR at any step.
 
 <a id="ship"></a>