headroom/crates/headroom-core
AxelRay ef7e07e0f5
fix(policy): price net-cost mutations with the 1h cache-write tier (#2780)
## Description

This fixes the net-cost mutation gate for requests using Anthropic's
1-hour prompt-cache TTL.

The gate previously hardcoded the 5-minute cache-write multiplier of
1.25x. A 1-hour cache write costs 2.0x, so the old calculation
understated the true write penalty and could incorrectly recommend
mutation for 1-hour clients.

Closes #2773

## Type of Change

- [x] Bug fix (non-breaking change that fixes an issue)
- [ ] New feature (non-breaking change that adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
- [ ] Performance improvement
- [ ] Code refactoring (no functional changes)

## Changes Made

- Added TTL-aware cache-write multiplier selection for 5-minute and
1-hour tiers.
- Threaded the resolved TTL through the content router and compression
policy helpers.
- Preserved the existing 5-minute behavior as the default.
- Added Python and Rust regression coverage for the 1-hour tier.
- Retuned the netcost gate fixtures so the 1-hour write tier flips the
decision in the full ContentRouter path.
- Did not edit CHANGELOG.md.

## Testing

- [x] Unit tests pass (pytest)
- [x] Linting passes (ruff check .)
- [ ] Type checking passes (mypy headroom)
- [x] New tests added for new functionality
- [ ] Manual testing performed

### Test Output

```text
pytest tests/test_compression_policy.py -q
20 passed

cargo test -p headroom-core --lib compression_policy -- --nocapture
14 passed

pytest tests/test_netcost_gate.py -q
27 passed

Ruff checks and formatting passed.
git diff --check passed.
```

## Real Behavior Proof

- Environment: Linux x86_64 contributor checkout with Python and Rust
test environments.
- Exact command / steps:
  - Ran the Python compression policy test suite.
  - Ran the Rust compression policy unit tests.
- Ran the netcost gate suite, including the 1-hour env and
request-marker cases.
- Exercised the new 1-hour TTL golden case alongside the existing
5-minute cases.
- Observed result: The 1-hour case uses the 2.0x write multiplier and
skips the same candidate that still mutates under 5-minute pricing.
Existing 5-minute behavior remains covered and passing.
- Not tested: A live Anthropic request through the proxy and production
traffic.

## Review Readiness

- [x] I have performed a self-review
- [x] This PR is ready for human review

## Checklist

- [x] My code follows the project's style guidelines
- [x] I have performed a self-review of my code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] I did **not** edit CHANGELOG.md - it is generated by
release-please from my Conventional Commit PR title (a CI guard enforces
this)

## Screenshots (if applicable)

Not applicable for this backend policy fix.

## Additional Notes

Ready for review. CI is green on the current tip.
2026-08-16 15:09:50 -07:00
..
benches fix: PR-F1 classify_auth_mode helper (Phase F kickoff) 2026-05-03 17:20:14 -07:00
config feat(rust): add structured prose offload plumbing (#334) (#2378) 2026-07-18 09:53:44 -07:00
proptest-regressions/transforms fix: A9 — tag protector discards wrap on placeholder loss 2026-05-02 18:01:24 -07:00
src fix(policy): price net-cost mutations with the 1h cache-write tier (#2780) 2026-08-16 15:09:50 -07:00
tests test(ccr): cross SQLite max lifetime boundary (#2794) 2026-08-05 08:33:21 -07:00
Cargo.toml deps: bump sha2 from 0.10.9 to 0.11.0 (#2288) 2026-08-14 16:40:45 -05:00