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ci(viewer): run each shard serially, so a timing test does not race three others #3061

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Merged
louistrue merged 1 commit into from
Aug 21, 2026
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ci(viewer): run each shard serially, so a timing test does not race three others #3061

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10 changes: 10 additions & 0 deletions .github/workflows/test.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -373,6 +373,16 @@ jobs:
# knows what good looks like rather than only what broken looked like:
# 2:29, 2:01, 1:50 against a 25 minute cap.
#
# Parallelism comes from the SHARDS, not from concurrency inside a shard.
# `--test-concurrency=1` is deliberate: at 4 a timing-sensitive test races
# three neighbours, and `useSandbox.runSupersession.test.tsx` failed on three
# unrelated PRs in one hour that way (issue #3060) while passing locally 3/3.
# The bump to 4 came from an earlier attempt at this lane that was MEASURED
# not to help on CI, and it was carried forward as harmless once sharding
# worked. It is not harmless, and its speedup is redundant with sharding.
# Cost of going back to 1, measured: ~70s versus ~19s per shard locally,
# roughly 8 minutes versus 2 on CI, against a 25 minute cap.
#
# Two earlier explanations in this file were WRONG and are corrected here,
# because a confident wrong comment is worse than none:
#
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2 changes: 1 addition & 1 deletion apps/viewer/package.json
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Expand Up @@ -14,7 +14,7 @@
"build": "vite build && node ../../scripts/check-tla-chunk-await.mjs",
"typecheck": "tsc --noEmit",
"preview": "vite preview",
"test": "tsx --import ./src/test/vite-module-hooks.mjs --test --test-timeout=120000 --test-concurrency=4 $(find src -type f \\( -name '*.test.ts' -o -name '*.test.tsx' \\) | sort | awk -v s=\"${TEST_SHARD:-0}\" -v n=\"${TEST_SHARDS:-1}\" 'NR % n == s')",
"test": "tsx --import ./src/test/vite-module-hooks.mjs --test --test-timeout=120000 --test-concurrency=1 $(find src -type f \\( -name '*.test.ts' -o -name '*.test.tsx' \\) | sort | awk -v s=\"${TEST_SHARD:-0}\" -v n=\"${TEST_SHARDS:-1}\" 'NR % n == s')",

@chatgpt-codex-connector chatgpt-codex-connector Bot Aug 21, 2026

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P2 Badge Limit serial execution to CI shards

When the canonical root pnpm test runs with TEST_SHARDS unset, this hardcoded value serializes all 521 viewer test files, not merely each CI shard. The four-way parallelism described in test.yml exists only in CI, while the preceding change measured the unsharded suite at 142s with concurrency 4 versus 295s with concurrency 1, so every developer/full Turbo run now incurs this regression. Keep the package default parallel and pass concurrency 1 specifically from the viewer-tests workflow.

AGENTS.md reference: AGENTS.md:L12-L13

Useful? React with 👍 / 👎.

"check:templates": "tsc -p src/lib/scripts/templates/tsconfig.json --noEmit"
},
"dependencies": {
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