Anthropic Claude Haiku 4.5 incident

Fixed public statement

Behavioral change evidence

Estimated effect size (frozen null floor minus observed panel mean): 0.500, with a 95% anytime-valid uncertainty interval [-0.300, 0.700]. statistically significant behavioral change detected. Methodology.

Observed via aggregator: through an aggregator serving layer, not a direct adapter.

Anytime-valid evidence

E-value trajectory

E-value at open: 24.823
log₁₀ E at open: 1.395
Onset estimate: 6

The onset is a diagnostic estimate of the first affected post-calibration observation. Statistical validity attaches to the e-process alarm, not to this estimate.

The trajectory plots log₁₀ E through the incident epoch. The red line is the configured 1/α alarm threshold.

Audit trail

Epoch lineage

Incident epoch: 5cb87853-5444-49c7-8cea-4945a6036d16
Pool version: math-v4
Checker version: math-v1
Previous epoch: 2ac265b1-2400-411f-834e-7102275e3a8e
Epoch transition: operator_rebaseline_after_reference_repair

View model status →

Citing this incident: link this page and name the UTC day. The register is append-only — corrections are published beside the entry, never over it — so a dated citation stays true. The evidence bundle above replays offline.