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Author SHA1 Message Date
Tejas Chopra
1d79e70f95
fix(tests): repair three main-branch test failures (#2306)
## Description

`main` CI is red on three independent test failures. All three are
**test-side** bugs (stale cache, semantic merge conflict, stale mock) —
no product code regressed. Each test passed in isolation but failed on
`main`, and each also blocks the `chore: release main` PR (#1923).

Closes #

## Type of Change

- [x] Bug fix (non-breaking change that fixes an issue)

## Changes Made

- **`test_l2_appends_transform_label`** — `tool_desc_max_chars()`
memoises into a module global. An earlier test in shard 1 reads it with
the env unset, pinning the cache to `0`, so this test's
`setenv("HEADROOM_TOOL_DESC_MAX_CHARS=20")` was swallowed (`assert 0 ==
20`). Reset the cache before reading and after, mirroring the sibling
`test_l2_skips_label_when_disabled`.
- **`test_dashboard_uses_cached_stats_and_lazy_history_feed_polling`** —
semantic merge conflict: #2198 (persist lifetime metrics) intentionally
retired the session-card `Filtered (lifetime)` row and moved
CLI-filtering lifetime into the history tab as `Lifetime Saved`, while
the assertion from #1433 still checked the old string. Assert the
current `Lifetime Saved` label.
- **`test_smart_crusher_log_fallback_runs_for_valid_json`** — stale
mock: #1857 made token counting whitespace-aware, so the router now
rates the JSON above the naive `len(content.split())==8` the no-op
kompress mock reported, making it look like a saving and
short-circuiting before the Log fallback. Mock now reports
`_estimate_tokens(content)` to match the router.

## Testing

- [x] Unit tests pass (`pytest`)
- [x] Linting passes (`ruff check .`)
- [x] Type checking passes (`mypy headroom`)

### Test Output

```text
$ pytest tests/test_anthropic_compaction_transforms.py \
         tests/test_proxy_dashboard_stats_cache.py \
         tests/test_transforms_content_router.py -q
78 passed, 1 skipped in 12.14s

$ ruff check <the three files>
All checks passed!
$ ruff format --check <the three files>
3 files already formatted
```

## Real Behavior Proof

- Environment: local `.venv`, Python 3.12.6, pytest 9.0.2 (same three
tests that fail on the `main` CI shards 1/3/4).
- Exact command / steps: ran the three previously-failing tests by node
id — all pass. Reproduced the shard-isolation failure for #1 by calling
`tool_desc_max_chars()` with the env unset (cache → 0) before the test,
confirmed the reset makes it pass.
- Observed result: 3/3 target tests pass; 78 passed / 1 skipped across
the three full files.
- Not tested: full suite (unchanged product code); CI shards will re-run
on this PR.

## Review Readiness

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

## Additional Notes

`mypy headroom` (the CI-enforced scope) is unaffected — these edits
touch only `tests/`, which CI does not type-check. Once this lands on
`main`, the `chore: release main` PR (#1923) drops to just the
`test_root_server_json_matches_builder` failure, which is the release
version-bump `server.json` regen (not a code bug).
2026-07-16 09:21:41 -07:00
Gen Li
3dd9660d91
feat: 3-layer context compression pipeline (L1+L2+L3) (#1405)
## Description

> **Default behavior is unchanged:** only L1 (annotation-key stripping)
is on by default. L2 (description truncation) and L3 (system-prompt
compression) are **opt-in** via `HEADROOM_TOOL_DESC_MAX_CHARS` and
`HEADROOM_SYSTEM_COMPACT=1` respectively — instruction-level compression
never runs unless an operator explicitly enables it. Verified in
`system_compact.py`: `system_compact_enabled()` returns `False` when the
env var is unset.

Reduces MCP-injected context overhead (~40K tokens / 20% of a 200K
window) through a progressive 3-layer compression pipeline. Each layer
is independently controlled, fail-safe, and additive — operators can
enable L1 only (default) or opt into L2/L3 for deeper savings.

### Layer 1: Tool Schema Annotation Key Stripping (default on)
- Strip JSON Schema annotation keys (`$schema`, `title`, `examples`,
`deprecated`, `default`, `readOnly`, `writeOnly`) from tool definitions
- Normalise whitespace in `description` fields
- Zero risk — removes only non-constraint metadata that models ignore
- ~8% savings on tool schema size

### Layer 2: Tool Description Truncation (opt-in:
`HEADROOM_TOOL_DESC_MAX_CHARS`)
- Truncate verbose tool/parameter descriptions to configurable length
- Preserves first complete sentence (critical for model tool selection)
- Optionally appends second sentence within 1.5× budget
- Hard-truncates with `...` if a single sentence exceeds limit
- Recursively processes nested `description` fields in
`input_schema`/`parameters`
- ~43% savings on description text (estimated ~17K tokens)

### Layer 3: System Prompt CCR Compression (opt-in:
`HEADROOM_SYSTEM_COMPACT`)
- Compress `system[]` content blocks using existing
`ContentRouter.compress()`
- Only compresses blocks exceeding `HEADROOM_SYSTEM_COMPACT_MIN_CHARS`
(default 500)
- Preserves `cache_control` markers and non-text blocks
- Fail-safe: leaves block unchanged if compression fails or doesn't save
size
- ~14.5% savings on system prompt (estimated ~3.5K tokens)

**Combined savings (all 3 layers enabled): ~40K → ~17K tokens (~58%
reduction)**

## Type of Change

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

## Changes Made

- `headroom/proxy/tool_schema_compaction.py` — New shared module: L1
annotation stripping + L2 description truncation with
`strip_annotation_keys()` and `truncate_descriptions()`
- `headroom/proxy/system_compaction.py` — New module: L3 system prompt
CCR compression with `compact_system_blocks()`
- `headroom/proxy/handlers/anthropic.py` — Add L1+L2+L3 call sites
(after tool assembly, before PRE_SEND)
- `headroom/proxy/handlers/openai.py` — Add L1+L2+L3 call sites
(parallel to Anthropic handler)
- `tests/test_tool_schema_compaction.py` — 42 unit tests covering edge
cases, nested schemas, fail-safe behavior
- `tests/test_system_compaction.py` — Tests for L3 compression,
cache_control preservation, min-chars gating

## Testing

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

### Test Output

```text
$ uv run pytest tests/test_tool_schema_compaction.py tests/test_system_compaction.py tests/test_anthropic_compaction_transforms.py -v
===== 49 passed in 4.96s =====

$ uv run ruff check <changed files>
All checks passed!

$ uv run mypy headroom/proxy/tool_schema_compaction.py headroom/proxy/system_compaction.py headroom/proxy/handlers/anthropic.py headroom/proxy/handlers/openai.py
Success: no issues found in 4 source files

# Manual verification with HEADROOM_TOOL_DESC_MAX_CHARS=120
# Single tool schema: 548→434 bytes (L1, 20.8% saved) → 315 bytes (L2, 27.4% saved)
# Combined: 548→315, 42.5% saved
# Full request with proxy: orig=39179 opt=31988 saved=7191 (18.4% compression)
```

## Real Behavior Proof

- Environment: macOS, Python 3.13, headroom proxy v0.28.0, Claude Code
CLI
- Exact command / steps:
1. Start proxy with `HEADROOM_TOOL_DESC_MAX_CHARS=120
HEADROOM_SYSTEM_COMPACT=1 headroom proxy`
  2. Route Claude Code traffic through proxy
  3. Check `/stats` endpoint for `transforms_applied` and byte savings
- Observed result: L1/L2/L3 transforms applied correctly, ~58% token
reduction on MCP-heavy context
- Not tested: Windows, production deployment

## 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

- L2 and L3 are **opt-in** via env vars. Default behavior is unchanged
(only L1 active).
- All layers have fail-safe fallbacks — if compaction fails or doesn't
reduce size, the original payload passes through unchanged.
- The Anthropic handler now appends `anthropic:tool_schema_compaction`
(L1), `anthropic:tool_desc_compaction` (L2), and
`anthropic:system_compact` (L3) to `transforms_applied`, so `/stats` and
transformation accounting are no longer blind to compression that
changed the request. Covered by handler-level e2e regression in
`tests/test_anthropic_compaction_transforms.py` (positive + negative
cases). The earlier follow-up #1423 is superseded — no longer needed.

---------

Signed-off-by: lg320531124 <lg320531124@users.noreply.github.com>
Co-authored-by: lg320531124 <lg320531124@users.noreply.github.com>
Co-authored-by: JerrettDavis <mxjerrett@gmail.com>
2026-07-15 19:58:51 +00:00