TestChainBoundBitesAtSameLength inserted its fixture a statement at a time: one blob row per chain node and one delta row per edge, across two arms sized maxDeltaChainDepth and maxDeltaChainDepth+1. At the current constant that is ~65k statements, each in its own implicit transaction and each paying a commit.

The chain is incidental setup; the subject of the test is the bound. But the setup cost dominated the runtime and was sensitive to how loaded the machine was, so on a contended runner it consumed the package's 120s budget and failed a PR that touched only CI YAML.

Wrap both loops in a single db.WithTx so the chain commits once. This follows buildBackwardChain in chain_depth_bench_test.go, which already builds its chain this way in the same package.

The assertions are untouched, byte for byte: the two walks must still agree at maxDeltaChainDepth and disagree one past it. Verified by mutation -- widening one walk's loop bound by a single node still fails the test with the same diagnostic it was written to produce.

Measured on this machine, three runs each, whole-package wall clock:

modernc before 19.7s / 25.0s / 7.1s after 1.19s / 1.36s / 0.80s ncruces before 3.5s / 10.0s / 7.5s after 1.27s / 1.59s / 1.13s

The spread collapsing matters more than the median: the old fixture's cost tracked machine load, which is what made it a timeout risk rather than merely slow.

Refs #179 check-in: 39f9ea4d8a user: [email protected] tags: trunk