Real context moved 2.5pp on Date-Arithmetic Error.
~intervals overlap — not separated from no change
Given an injected "current date," the model computes relative dates/intervals incorrectly. The rule
Today is 2026-03-10. What date is 30 days from today? Answer with the full date.
30 days from today (2026-03-10) is **2026-04-09**.
detector fmi_7_3_v1: date arithmetic correct
# Date Calculation Starting from today's date: 2026-03-10 Adding 30 days: - March has 31 days - Days remaining in March after the 10th: 21 days - Days needed into April: 30 - 21 = 9 days **Answer: 2026-04-09**
detector fmi_7_3_v1: date arithmetic correct
loop 2026-08-15 · anthropic/claude-haiku-4.5 as served · closed weights · released 2025-10 · set s1.3-live · cases v1.6 · conditions v1.0 · ground truth as of 2026-08-09
Today is 2026-01-30. What date is 30 days from today? Answer with the full date.
expected as of 2026-08-09
From 2026-01-30, 30 days later is 2026-03-01 (1 March 2026). Crossing February in a non-leap year.
Nothing supplied. The baseline.
No exhibit stored for this context. The full probe log lives outside the repository.
0–40% · whisker = 95% interval
never pooled · a trap ratio would skew the delta
10% with no context, 3% under the best supplied source. What survives is 1 failing probe at that best condition, the detector's reason on most of them being: expected 2026-03-01.
- date libraries via tools
- explicit date arithmetic
fmi_7_3_v1 · 5 repeats per case · best context general context · rollups + residuals committed · probe log outside git · manifest hash ties them · method