hypothesis-dies

A hypothesis that dies

The purest case for the whole tool: a plan that is confidently wrong, and the record of learning it was wrong.

The situation

CI builds average 34 minutes and block every merge. The cache hit rate reads 12%, so the cache is the obvious suspect. The plan says: measure first, then fix the cache.

The measurement comes back and kills the hypothesis. 26 of the 34 minutes are artifact download from a single-homed mirror; cache misses cost about 90 seconds in total. The cache was never the problem.

What the lineage says

001  cos   The cache is the obvious suspect. Measure first, then fix it.
              + measure       Measure where the 34 minutes actually go
              + fixCache      Fix cache key instability

002  cos   The measurement kills the hypothesis. 26 minutes are artifact
           download from a single-homed mirror. Retiring the cache work.
              ~ fixCache      retired
              + mirror        Put build artifacts behind a regional mirror

003  cos   A mirror still leaves the cold-start case. Adding a warm path.
              + prewarm       Pre-warm the mirror on branch create

Read the why column on its own and it is an argument: we thought it was the cache → the measurement said it was the network → a mirror alone leaves cold starts. The plan at the tip — mirror plus pre-warm — is disposable. The reasoning that arrived there is the artifact, and it survives the first version being wrong.

What to look at in the files

• 002 retires fixCache, it does not delete it. The abandoned hypothesis stays in the record with its acceptance criterion, marked retired. You can read what was tried and why it was dropped — which is exactly the thing a mutable todo list throws away.
• 002 is a function of 001. It imports it and calls .revise. The measure step is never mentioned, and is carried forward untouched. There is no way the retarget could have dropped it.
• The rationale is required. A version that changed intent without saying why would be invalid — the reason is the point, not a courtesy.

Files

This plan has no name. Its identity — its PlanId — is the content hash of its origin, the first version (decision 0017), so the plan directory is 634e2a7c458b, the same hash the 001 file carries. To a person it is its goal, "CI builds finish under 10 minutes"; the hash is only for exactness.

• 001-634e2a7c458b.ts — the hypothesis
• 002-68fdda593f4d.ts — it dies
• 003-55ca61867911.ts — the cold-start follow-on