prompt: complete covariance-interpolator-rng-seed (PyAutoFit#1451 merged)

[Jammy2211]

Closes out the task now that PyAutoLabs/PyAutoFit#1451 is merged (282d8e1e,
auto-closing PyAutoLabs/PyAutoFit#1450). The Class B release blocker that killed
the 2026.8.2.1 live release is cleared, green on Python 3.12 and 3.13.

Branch restarted from main — the previous PR (#127) is merged, so this is fresh
work rather than commits stacked on merged history. The force-with-lease that
repointed the branch discarded only e3419110, the commit squash-merged as
acc4a7dd; verified the tree diff against main for every touched path is empty
before pushing.

What changed

All four edits produced by scripts/lifecycle.py record ... --apply — the ship
skills' own primitive, not hand-editing:

• complete/2026/08/covariance-interpolator-rng-seed.md — new rich completion
  record, with the original prompt folded in under ## Original prompt.
• active/covariance_interpolator_test_unseeded_rng.md — removed (folded into
  the record).
• active.md — covariance-interpolator-rng-seed section removed.
• complete/index.md — regenerated (890 records).

lifecycle.py check → OK · lifecycle.py index --check → OK.

Why the record leads with the finding, not the fix

The prompt's premise was wrong, and that is the part worth surviving:

• It blamed the unseeded np.random.random() in the test body and called seeding
  "a one-liner". Seeding only that leaves std at 1.95 of 2.05 — the test still
  fails. The dominant source is dynesty's rstate
  (Generator(PCG64(None)), OS entropy, reachable from neither np.random nor a
  local Generator), with the stdlib random module used by initializer.py
  third. All three must be seeded.
• Measured pre-fix failure rate 1.65% (33/2000, 95% CI 1.18–2.31%) — taken
  before any change, as the prompt's step 2 required.
• The tolerance is not mis-calibrated. A full untruncated search recovers
  25.0496 ± 0.0039 — 500× tighter — so abs=5.0 is correct and must not be
  loosened. limit_maxcall is what turns the assertion into a coin flip.
• The sibling was worse. test_single_variable has no random call of its own
  yet was flaking at 3.6%, more than double the test that got blamed.
• The LinAlgError guards are a separate defect — rank-deficient fixture
  matrix (rank 6 of 9, cond 1.3e17), deterministic input — not the same
  nondeterminism in disguise.

The record also carries the known limitation, so nobody later reads "seeded" as
"the assertion is now meaningful": under maxcall=1 both are frozen-RNG
regression checks, with the measured cost of restoring real convergence.

It also notes this closes the "gate said GREEN, then the live release
contradicted it" question in draft/triage/nightly_release_blocked_eight_nights.md
— the gate's evidence was not stale; the release run drew a different random
sample. That removes the motive for a gate-vs-release redesign this evidence was
about to justify.

Still open

draft/feature/autofit/search_seed_reproducibility.md stays in draft/ — the
real fix. PyAutoFit has no supported way to seed a search, which is why the
merged change must monkeypatch a third-party module from a test, and why users
cannot reproduce a fit.

🤖 Generated with Claude Code

https://claude.ai/code/session_016vdGab4C5rWumTCXkWHPyh

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Generated by Claude Code