feat(speculate): bypass unsettled deps on full passed coverage - #656
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behinddwalls
marked this pull request as ready for review
August 31, 2026 20:41
## Summary ### Why? A batch's merge used to wait for every dependency to resolve even when its passed builds already covered every way those dependencies could turn out. That made a small change sit behind a slow one for no reason: both the with- and without-dependency trees were validated, so whichever future arrives is already green. ### What? Adds bypassablePath to the speculate controller: decide() merges a head once passed, unbroken, well-formed paths cover every 2^n combination of its unsettled dependencies. Settled dependencies still pin each path to reality through assumptionBroken. Finalize prefers a strict mergeable path and falls back to bypass coverage, superseding siblings either way. Tightened isWellFormed to require dependencies in the head's canonical order, and read the coverage signature positionally off the slice (dropping the per-path map). Order is load-bearing: Base() projects the path positionally, so a permuted path is a different stack, and a reordered path can no longer masquerade as coverage for the canonical combination. The NoBypassWhenCoverageIsIncomplete e2e test asserts ordering (follower lands only after the lead) rather than the racy intermediate speculating state: waiting is a recorded history event, and once the ungated lead lands the seeded path is strictly mergeable — the old assertion raced the queue and flaked on fast runners. ## Test Plan - ./tool/bazel test //submitqueue/orchestrator/controller/speculate:go_default_test - ./tool/bazel test //submitqueue/extension/speculation/... //submitqueue/entity:go_default_test //submitqueue/orchestrator/controller/build:go_default_test - New TestBypassablePath "does not count a reordered path" and TestIsWellFormed "dependencies out of queue order" fail before, pass after. - Four bypass E2E tests pass (BypassedHeadLandsFirst, BypassesMergingDependency, NoBypassWhenCoverageIsIncomplete, BypassesAnUnresolvedDependency); full e2e suite green twice locally.
mnoah1
approved these changes
Sep 1, 2026
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Summary
Why?
A batch's merge used to wait for every dependency to resolve even when its passed builds already covered every way those dependencies could turn out. That made a small change sit behind a slow one for no reason: both the with- and without-dependency trees were validated, so whichever future arrives is already green.
What?
Adds bypassablePath to the speculate controller: decide() merges a head once passed, unbroken, well-formed paths cover every 2^n combination of its unsettled dependencies. Settled dependencies still pin each path to reality through assumptionBroken. Finalize prefers a strict mergeable path and falls back to bypass coverage, superseding siblings either way.
Tightened isWellFormed to require dependencies in the head's canonical order, and read the coverage signature positionally off the slice (dropping the per-path map). Order is load-bearing: Base() projects the path positionally, so a permuted path is a different stack, and a reordered path can no longer masquerade as coverage for the canonical combination.
The NoBypassWhenCoverageIsIncomplete e2e test asserts ordering (follower lands only after the lead) rather than the racy intermediate speculating state: waiting is a recorded history event, and once the ungated lead lands the seeded path is strictly mergeable — the old assertion raced the queue and flaked on fast runners.
Test Plan