[kixelated]

Problem

The lang fixture's harness picks a case by the input's first byte, modulo the case count, and op(name) truncates a case's index to u8. Byte 0xff is reserved for Fault's printing. So the harness can address only 255 cases, and main has exactly 255. A PR that adds a case past index 254 compiles and passes, but the new case is never run differentially: op("new::case") wraps to an existing case, and both sides run that one and agree. #400 (259 cases, 260 after main) and its follow-up would have landed with none of their new cases run.

On main, no case was skipped: indices 0 through 254 are all reachable. Queued PRs that add lang cases (#387, #391, #394 may) get theirs exercised once this lands.

Approach

• harness::run picks a case by the first two bytes, big-endian, modulo the count. The kind is the third byte and the case's input the rest. op(name) returns that u16, and panics, loudly on both sides, for a case two bytes can't pick (a first byte of 0xff stays Fault's).
• caller.ts wraps op to give both bytes and spreads them into each named input. It exports ops, every case's bytes, built through op from the harness's own cases() list, so a case that can't be picked fails at load. within reads the two-byte selector and the kind from the third byte, and skips a Fault input.
• differential.ts sweeps each op the harness exports as ops (default: each first byte alone, as before, for the other fixtures) with every short tail, and runs its full-width values through the first eight. It fails if two ops share bytes, which a repeated case name would cause. So every named case runs, each with its sweep.

Impact

• Test harness only: no output, runtime, or public API change.
• Other fixtures' harnesses keep the one-byte selector; a harness opts into another by exporting ops.

Tests: just ci passes, including the lang differential over the new selector (UPDATE_EXPECT changed only expected/harness.ts, for run and op).

Alternatives

• An escape byte, such as 0xfe, picking a second table. Rejected: two selection rules, and the next overflow would need another.
• A unit test in the lang fixture asserting each case's index fits. Rejected: just ts test tests only rust2-ts, so the fixture's own tests would not run; the guard is in op and the differential, which do run.

Follow-ups

None.

Review

• Codex gpt-6.1-sol at medium effort (quest review), round 2 on 6741cad9: no findings.
• Round 1 on fb013bd4: an input starting with 0xff, which prints a Fault, could decode as a float case in within and throw on its output. Fixed in be197682: within skips it.
• just ci passes locally on 6741cad9, with main merged in.

(written by Claude Opus 5.5)

🤖 Generated with Claude Code

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Commits

Reviewing files that changed from the base of the PR and between 6ff36bb and 6741cad.

Files selected for processing: 4

• ts/fixtures/lang/caller.ts
• ts/fixtures/lang/expected/harness.ts
• ts/fixtures/lang/src/harness.rs
• ts/tests/differential.ts

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[kixelated]

Superseded: #417 was stacked on this branch, and its squash (b1656c9) landed this PR's two-byte selector and its Fault fix on main. Nothing is left to merge.

(written by Claude Opus 5.5)

[moq-bot]

codex / Codex land fixer: PR cl·osed or head moved while fixing; inspect and pick it again. Recommendation: run /quest-iterate before picking it again.

(HEAD detached at 6ec33a9) 6ec33a9058c2e8417e9a5aeb175b59d1824d7a36
base 6ec33a9058c2e8417e9a5aeb175b59d1824d7a36
batch ffaa75f9cee1e73b8fb32773c092bf60e88150fb
pr-407 cea21c2be0424d72bc92338cf785f763ead65ee9
pr-414 6741cad939352cec24c8038167f8852210f0e584
pr-416 67a1ac4c3567755320c4d4cf1bff3c784faa31ed

codex
All TypeScript tests passed, including `lang` and `stock`. I’ll record unchanged requeues for all three PRs and name the flaky `stock` failure. No mechanical source fix was needed, and the PR branches remain at their pinned heads.
apply patch
patch: completed
/work/quest-land-result.json
diff --git a/quest-land-result.json b/quest-land-result.json
new file mode 100644
index 0000000000000000000000000000000000000000..b5ae8af80eacadbc2b1fa713c9339aceb89eef04
--- /dev/null
+++ b/quest-land-result.json
@@ -0,0 +1,17 @@
+[
+  {
+    "number": 407,
+    "action": "requeue",
+    "reason": "Healthy against base; flaky ts fixtures::stock failed writing CACHEDIR.TAG in the shared build directory. Validation passed: quest check; just ffi test plus just ffi test --test fixtures -- api_kotlin api_swift with the installed coroutine jar and Swift library paths configured; just ts test on the shared TS code. PR head unchanged."
+  },
+  {
+    "number": 414,
+    "action": "requeue",
+    "reason": "Healthy against base; flaky ts fixtures::stock failed writing CACHEDIR.TAG in the shared build directory, whose setup this PR does not change. Validation passed: quest check; just ts test (7 unit, 12 fixture and 8 runtime tests, including stock). PR head unchanged."
+  },
+  {
+    "number": 416,
+    "action": "requeue",
+    "reason": "Healthy documentation-only PR against base; flaky ts fixtures::stock failed writing CACHEDIR.TAG in unchanged code. Validation passed: quest check; just ts test --test fixtures stock -- --exact. PR head unchanged."
+  }
+]

exec
/bin/bash -lc "python3 -c 'import json, pathlib, subprocess; p=pathlib.Path(\"quest-land-result.json\"); r=json.loads(p.read_text()); expected={407:\"cea21c2be0424d72bc92338cf785f763ead65ee9\",414:\"6741cad939352cec24c8038167f8852210f0e584\",416:\"67a1ac4c3567755320c4d4cf1bff3c784faa31ed\"}; assert len(r)==3 and {x[\"number\"] for x in r}==set(expected); assert all(set(x)=={\"number\",\"action\",\"reason\"} and x[\"action\"]==\"requeue\" for x in r); assert all(subprocess.check_output([\"git\",\"rev-parse\",f\"pr-{n}\"],text=True).strip()==sha for n,sha in expected.items()); print(\"Result schema and unchanged PR heads verified\")'; git status --short" in /work
 succeeded in 0ms:
Result schema and unchanged PR heads verified
?? quest-land-result.json

diff --git a/quest-land-result.json b/quest-land-result.json
new file mode 100644
index 0000000000000000000000000000000000000000..b5ae8af80eacadbc2b1fa713c9339aceb89eef04
--- /dev/null
+++ b/quest-land-result.json
@@ -0,0 +1,17 @@
+[
+  {
+    "number": 407,
+    "action": "requeue",
+    "reason": "Healthy against base; flaky ts fixtures::stock failed writing CACHEDIR.TAG in the shared build directory. Validation passed: quest check; just ffi test plus just ffi test --test fixtures -- api_kotlin api_swift with the installed coroutine jar and Swift library paths configured; just ts test on the shared TS code. PR head unchanged."
+  },
+  {
+    "number": 414,
+    "action": "requeue",
+    "reason": "Healthy against base; flaky ts fixtures::stock failed writing CACHEDIR.TAG in the shared build directory, whose setup this PR does not change. Validation passed: quest check; just ts test (7 unit, 12 fixture and 8 runtime tests, including stock). PR head unchanged."
+  },
+  {
+    "number": 416,
+    "action": "requeue",
+    "reason": "Healthy documentation-only PR against base; flaky ts fixtures::stock failed writing CACHEDIR.TAG in unchanged code. Validation passed: quest check; just ts test --test fixtures stock -- --exact. PR head unchanged."
+  }
+]

codex
Wrote [quest-land-result.json](/work/quest-land-result.json), uncommitted.

All three PRs are marked for requeue unchanged. The flaky `stock` test passed on rerun; validation completed successfully. No PR was blamed.
diff --git a/quest-land-result.json b/quest-land-result.json
new file mode 100644
index 0000000000000000000000000000000000000000..b5ae8af80eacadbc2b1fa713c9339aceb89eef04
--- /dev/null
+++ b/quest-land-result.json
@@ -0,0 +1,17 @@
+[
+  {
+    "number": 407,
+    "action": "requeue",
+    "reason": "Healthy against base; flaky ts fixtures::stock failed writing CACHEDIR.TAG in the shared build directory. Validation passed: quest check; just ffi test plus just ffi test --test fixtures -- api_kotlin api_swift with the installed coroutine jar and Swift library paths configured; just ts test on the shared TS code. PR head unchanged."
+  },
+  {
+    "number": 414,
+    "action": "requeue",
+    "reason": "Healthy against base; flaky ts fixtures::stock failed writing CACHEDIR.TAG in the shared build directory, whose setup this PR does not change. Validation passed: quest check; just ts test (7 unit, 12 fixture and 8 runtime tests, including stock). PR head unchanged."
+  },
+  {
+    "number": 416,
+    "action": "requeue",
+    "reason": "Healthy documentation-only PR against base; flaky ts fixtures::stock failed writing CACHEDIR.TAG in unchanged code. Validation passed: quest check; just ts test --test fixtures stock -- --exact. PR head unchanged."
+  }
+]

tokens used
141,481
Wrote [quest-land-result.json](/work/quest-land-result.json), uncommitted.

All three PRs are marked for requeue unchanged. The flaky `stock` test passed on rerun; validation completed successfully. No PR was blamed.
fixer result written

(written by codex / Codex)