## Description
Extracts output verbosity steering text and sentinel replacement into a
pure `output_verbosity_policy` module. `output_shaper` continues to
mutate Anthropic/OpenAI request bodies, while the byte-stable steering
block and replacement rules now live behind deterministic, directly
tested policy functions.
Closes #
## Type of Change
- [ ] 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
- [x] Code refactoring (no functional changes)
## Changes Made
- Added `headroom.proxy.output_verbosity_policy` for steering sentinels,
level text, `steering_text`, and `replace_or_append_steering_block`.
- Updated `output_shaper` to delegate pure steering text/replacement
rules while preserving existing public imports and request mutation
behavior.
- Added direct policy tests for byte-stable steering text, append,
replacement, malformed sentinel handling, and idempotency.
- Included the current LiteLLM callback signature compatibility shim
required for repo-wide mypy on main-based slices.
## Testing
- [x] Unit tests pass (`pytest`)
- [x] Linting passes (`ruff check .`)
- [x] Type checking passes (`mypy headroom`)
- [x] New tests added for new functionality
- [ ] Manual testing performed
### Test Output
```text
python -m pytest tests/test_output_verbosity_policy.py tests/test_output_shaper.py tests/test_litellm_callback.py -q
58 passed in 6.23s
python -m ruff check .
All checks passed!
python -m ruff format --check .
1095 files already formatted
python -m mypy headroom --ignore-missing-imports
Success: no issues found in 409 source files
gitleaks protect --staged --no-banner --redact
no leaks found
```
## Real Behavior Proof
- Environment: Windows, Python 3.13.13, clean worktree based on
`headroomlabs/main`.
- Exact command / steps: targeted pytest, ruff, format check, repo-wide
mypy, staged gitleaks scan.
- Observed result: output verbosity policy/shaper/callback tests pass;
static checks pass; no staged secrets detected.
- Not tested: live provider calls; this slice preserves existing request
mutation behavior and only moves pure steering rules.
## 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
- [x] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [x] 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
- [ ] I have updated the CHANGELOG.md if applicable
## Screenshots (if applicable)
N/A
## Additional Notes
Documentation and changelog updates are not applicable for this internal
architecture slice. PR-specific GHAS checks will be monitored after
opening.
