[erkancamli]

Description

base_fee_change_calculator (EIP-1559 fork helper) can return more gas than the parent gas limit when the parent base fee is below 8.

For an increase, the estimate assumes the proportional change parent_base_fee * (gas_used - target) / target / 8. Below a base fee of 8 that term rounds down to zero, and the spec's max(..., 1) in calculate_base_fee_per_gas raises the base fee by exactly 1 for any block above target. The estimate ignores that floor, so for the framework's default base fee of 7 and a 30M gas limit it returns 32,142,857 gas, and from a base fee of 1 it returns 135M. The final check only compares the resulting base fee, so the impossible value is returned silently.

This clamps the estimate to parent_gas_limit, where a full block reaches the increase. Results that already fit within the limit are unchanged, so no existing fixtures change. #3721 recently fixed rounding in the same helper; its tests use base fees of 20 and above, which is why this case was not covered.

test_base_fee_change_calculator_minimum_increase covers London and Amsterdam at parent base fees 1, 7 and 8: 4 cases fail on forks/bogota and all pass with the fix. The whole forks/tests suite passes (248 tests). ruff, ruff format, mypy and codespell are clean on the changed files.

Related Issues or PRs

Related to #3721.

Checklist

• Ran fast static checks to avoid CI fails (ruff, ruff format, mypy, codespell on the changed files; just is not available in my environment)
• PR title has the form <type>(<area>): <title>

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.98%. Comparing base (dfd1c72) to head (aa3884f).

Additional details and impacted files

@@              Coverage Diff              @@
##           forks/bogota    #3760   +/-   ##
=============================================
  Coverage         94.98%   94.98%           
=============================================
  Files               673      673           
  Lines             40831    40831           
  Branches           3747     3747           
=============================================
  Hits              38785    38785           
  Misses             1429     1429           
  Partials            617      617           

Flag	Coverage Δ
unittests	94.98% <ø> (ø)

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[spencer-tb]

Thanks @erkancamli! Pushed a small follow-up so unreachable base fees fail instead of returning out-of-block gas.