[Jammy2211]

Short, well-mixed Emcee/Zeus chains could request thin=0 and crash; Emcee also tried to estimate previous autocorrelations from an empty chain. Clamp thinning to at least one and return an unavailable previous estimate for an empty history, so convergence remains false until there is evidence. Remove the check_size=5 workarounds from the real-sampler alignment tests.

Closes #1725.

API Changes

No signature or output-identifier changes. Chains with autocorrelation time below two use thin=1 (no thinning). This repairs previously failing runs; normal thinning and paired sample/log-probability ordering are unchanged.

Validation

Full library suite: 3922 passed, 1 skipped, 1 xfailed (Python 3.12.14). Focused MCMC tests: 14 passed, including real Emcee/Zeus reduced fits with default check_size=100. Additional real Emcee smoke: 10 walkers, 50 steps, test mode disabled, samples built and previous_times=None. Six new regression cases fail on unchanged main (zero thin and empty previous chain), while ordinary thinning remains unchanged. Author diff review passed.

No downstream API migration. The actual search.fit integration tests and real 50-step smoke exercise the changed paths; the six-workspace smoke matrix was not run. Required CI remains pending at PR creation.

Heart and authorization

User authorized "Find 4 grouped tasks and do them", then "Yes I authorise" after the RED gate was disclosed. Development PR only; no merge or release. Fresh published vitals: organism RED, PyAutoFit scope GREEN; local readiness STALE (fresh checkout has no release evidence). This does not repair or clear the organism's RED.

Disclosed RED reasons

• install verification FAILED (testpypi; checks F)
• release validation FAILED (stage integrate)
• PyAutoHeart/workflows/Release Integrate: failure
• manifest_drift/checks/workspace checkouts (manifest ↔ disk): red
• Release readiness: release validation FAILED (stage integrate)
• Release readiness: install verification FAILED (testpypi; checks F)
• PyAutoArray/test_autoarray/inversion/inversion/interferometer/test_interferometer.py::test__interferometer_sparse_operator__mapped_reconstructed_data_dict_matc…
• Unit-test timing: 1 test regressions (>3× baseline), 11 slow (>1.5×)
• Release validation: NOT release_ready — v2026.10.25.1.dev83701 profile=release (2026-10-25T07:21:05+00:00)
• validation_report/stages/integrate: fail
• verify_install FAILED: verify_install FAILED
• F: colab gate: finufft (declared by autoarray, absent on Colab, imported)
• Install verification: FAILED (testpypi; F) (2026-10-25T07:42:48.134987+00:00)
• verify_install: red
• PyAutoBrain: red
• PyAutoLens: red
• autolens_profiling: red
• Worktree drift: 1 orphan / 0 missing / 3 dirty