Mirror of headroomlabs-ai/headroom (AI context compression proxy)
Find a file
Andrei Boldyrev 6744833afe
fix(proxy): key drift detector on conversations, not credentials; canonicalize drift hashes (#2301)
## Description

The Rust proxy's cache-bust drift detector
(`crates/headroom-proxy/src/cache_stabilization/drift_detector.rs`,
PR-E6) cannot currently tell drift from normal operation on interactive
agentic traffic, so it warns on nearly every turn and a real bust drowns
in the noise. Three compounding defects, all verified against live
Claude Code traffic:

1. `derive_session_key` stops at the credential hash — Claude Code sends
one OAuth bearer for every conversation, so all concurrent conversations
share one LRU slot and every conversation switch logs a false
`cache_drift_observed` (with `drift_dims` computed against the wrong
conversation's baseline).
2. The `early_messages` axis hashes the raw first-3-messages window, so
a lone conversation's normal growth (1 → 3 messages) and the client
relocating its `cache_control` breakpoint to the newest block both fire
a false `early_messages` drift at turn 2–3 of essentially every session.
3. `x-headroom-session-id` — the explicit session identity the Python
proxy honors everywhere session-sticky state exists — is ignored on the
Rust path.

This PR makes the detector's session identity conversation-scoped and
its comparison canonical, the same shape as the merged Python-side fix
for #2085 (`SessionTrackerStore.resolve_tracker` lineage resolution +
`_canonicalize_for_prefix_compare`):

- **`derive_session_key`**: honors `x-headroom-session-id` first
(hashed, like every other key input), then folds a conversation
discriminator into the credential/network arms: a 16-hex-char SHA-256
fingerprint of `(model, canonicalized first message)`. Provider prompt
caches are per-model, so a small-model sidecar call (title generation)
that reuses a conversation's opener stays a separate session instead of
false-drifting on `system`.
- **`canonicalize_for_hash`** on all axes and the discriminator: objects
rebuilt with sorted keys (this workspace enables serde_json
`preserve_order`, so a plain re-serialize would keep client wire order
and leave the hashes key-order sensitive) and `cache_control` stripped
outside opaque tool payloads (`input`/`arguments`/`json`/`input_schema`
— mirroring the Python canonicalizer's `_OPAQUE_PAYLOAD_KEYS`, so a user
field that happens to be *named* `cache_control` still counts as drift).
- **`early_messages`** becomes per-message hashes (`[Option<[u8; 32]>;
3]`) with a prefix-aware comparison: growing into the window is benign;
a settled message changing or disappearing under a stable session key is
still drift. `observe_drift` now gates the warning on drifted dimensions
rather than raw hash inequality.

True positives are preserved (`system`/`tools` changes, in-place history
rewrites under a pinned identity), and the detector remains a pure
observer — no forwarded byte changes, `does_not_mutate_input` still pins
that.

**Documented trade-off** (module doc + `conversation_discriminator`
doc): without the explicit header, a client that rewrites its first
message (history compaction, rolling-window truncation, Responses
chained mode) re-keys to a fresh session — the rewrite surfaces as
`cache_drift_first_request` rather than `cache_drift_observed` against
the old baseline. That is deliberate: the credential-keyed alternative
false-warned on every conversation switch, which buried those same
events anyway. `x-headroom-session-id` pins the identity and reports
rewrites as drift. Byte-identical openers on the same model under one
credential still conflate (rare; documented).

Closes #2300

## 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

- `derive_session_key`: `x-headroom-session-id` (hashed) wins;
credential/IP arms fold in `conversation_discriminator` — `(model,
canonicalized first message)`, 16 hex chars
- New `canonicalize_for_hash`: sorted-key object rebuild +
`cache_control` stripped outside `OPAQUE_PAYLOAD_KEYS`; applied to the
`system`/`tools`/`early_messages` axes and the discriminator
- `StructuralHash.early_messages`: `[u8; 32]` → `[Option<[u8; 32]>;
EARLY_MESSAGES_WINDOW]` per-message hashes;
`drift_dims`/`early_window_drifted` implement the prefix-aware rule;
`observe_drift` warns on non-empty dims instead of `!=`
- `conversation_messages` shape guard: bare-string message containers
only count for the Responses `input` sugar
- Docs: module header (canonicalization, trade-off, honest cost),
`conversation_discriminator` rationale + blind spots,
`DRIFT_DETECTOR_CAPACITY` cardinality note (per-conversation keys,
163-byte entry), `structural_hash_log_prefix` hex-length fix
- Tests: 13 new unit tests (conversation separation, turn-growth key
stability, explicit header priority, marker relocation + growth not
drift, rewrite/shrink still drift, per-model separation, key-order
neutrality, opaque-payload fields still count, Responses/Chat
discriminator shapes, string-container gating)
- `CHANGELOG.md`: Unreleased → Fixed entry

## Testing

- [x] Unit tests pass (`cargo test -p headroom-proxy` — full crate: lib
+ integration suites)
- [x] Linting passes (`cargo clippy -p headroom-proxy --all-targets` —
zero warnings; `cargo fmt --check` clean)
- [ ] Type checking passes (`mypy headroom`) — n/a, no Python files
touched
- [x] New tests added for new functionality
- [x] Manual testing performed

### Test Output

```text
$ cargo test -p headroom-proxy --lib drift_detector
test result: ok. 27 passed; 0 failed; 0 ignored; 0 measured; 221 filtered out

$ cargo test -p headroom-proxy
(all suites) test result: ok. 248 passed (lib) + integration suites, 0 failed

$ cargo clippy -p headroom-proxy --all-targets
(no warnings)
```

## Real Behavior Proof

- Environment: macOS 15 (arm64), rustc 1.95.0, repo @ 718c8dc + this
branch
- Exact command / steps: captured two real Claude Code conversations ×
two turns through a local proxy
(`ANTHROPIC_BASE_URL=http://localhost:8791 claude -p …` / `--resume …`),
rebuilt the wire bodies, and replayed them through the real
`derive_session_key` / `compute_structural_hash` / `drift_dims` in a
local `cargo test` harness — before and after this change.
- Observed result: **before** — all four requests share one `auth:` key,
and the raw early-window hash flips between turn 1 and turn 2 of the
*same* conversation (false `early_messages` drift; interleaving also
flips `system`). **After** — turn 1/turn 2 map to one stable key with
`drift_dims == ""`, the two conversations map to distinct keys, and a
rewritten/shrunk settled window still reports `early_messages`.
- Not tested: live OpenAI Chat/Responses traffic (shape-level unit tests
only); log pipeline consumers (event names/fields unchanged).

## 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
- [x] 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
- [x] I have updated the CHANGELOG.md if applicable

## Screenshots (if applicable)

n/a — log-only telemetry change.

## Additional Notes

- `StructuralHash` is `pub`, but the workspace has no external consumers
(checked `sdk/`, `plugins/`, Python, docs) — the field-type change is
contained to `proxy.rs` and the module tests. `[Option<[u8; 32]>; 3]`
keeps `Copy` for the LRU and adds no dependency.
- LRU cardinality: keys moved per-credential → per-conversation;
`DRIFT_DETECTOR_CAPACITY`'s comment now documents the working set, the
~250-byte entry, and the graceful eviction failure mode (repeated
`cache_drift_first_request`, telemetry-only).
- Not in scope, noted for follow-up: keying Responses chained mode
(`previous_response_id`) as a lineage; surfacing mid-history
`role:"system"` insertions on the OpenAI Chat shape (pre-existing blind
spot on all axes).

---------

Co-authored-by: Tejas Chopra <chopratejas@gmail.com>
2026-07-16 14:34:26 -07:00
.claude-plugin fix(release): sync all package versions to v0.31.0 (#1882) 2026-07-09 16:53:55 -05:00
.codegraph perf(compression): take large cold-start contexts off the synchronous kompress path (#1171) (#1298) 2026-06-23 10:48:06 -05:00
.devcontainer fix(transforms): use thread-local tree-sitter parsers to prevent pyo3 Unsendable panic (#604) 2026-06-10 18:30:00 -05:00
.github ci(changelog): stop the CHANGELOG cascade — release-please owns it (#2329) 2026-07-16 14:28:57 -07:00
.serena feat: headroom wrap opencode / unwrap opencode CLI (#1105) 2026-06-22 11:07:12 -05:00
benchmarks feat(text-crusher): CJK-aware segmentation + relevance via ICU (#1504) 2026-07-15 19:58:48 +00:00
crates fix(proxy): key drift detector on conversations, not credentials; canonicalize drift hashes (#2301) 2026-07-16 14:34:26 -07:00
docker fix(install): default docker image to headroomlabs-ai GHCR registry (#1867) (#2039) 2026-07-13 14:01:28 -04:00
docs Clarify uv tool install path on macOS (#1196) 2026-07-15 21:06:30 +00:00
e2e fix(codex): preserve wrapped sessions and recover state (#2160) 2026-07-15 19:58:21 +00:00
examples docs(metrics): ship an importable Grafana dashboard (#2168) 2026-07-14 16:07:25 -04:00
headroom fix(proxy): quarantine compression while timed-out workers run (#2292) 2026-07-16 14:30:06 -07:00
plugins docs(ccr): correct stale 5-minute TTL hints to 30 minutes (#2224) 2026-07-15 18:15:53 +00:00
REALIGNMENT docs: add Realignment plan (40 PRs, 9 phases) 2026-05-01 23:34:46 -07:00
sbom fix(deps): remediate dependency CVEs and publish SBOM (#1509) 2026-06-27 15:28:12 -07:00
scripts chore(release): harden local artifact smokes (#1824) 2026-07-14 16:07:34 -04:00
sdk/typescript fix(deps): clear Dependabot lockfile alerts (#2175) 2026-07-14 20:40:28 -07:00
sql feat(telemetry): add headroom_stack and install_mode identity fields 2026-04-17 17:12:38 +02:00
tests fix(proxy): quarantine compression while timed-out workers run (#2292) 2026-07-16 14:30:06 -07:00
wiki Clarify uv tool install path on macOS (#1196) 2026-07-15 21:06:30 +00:00
.actrc feat: add act testing config, fix gitignore, make workflow production-ready 2026-04-15 20:28:29 -05:00
.actrc.local.example feat: add act testing config, fix gitignore, make workflow production-ready 2026-04-15 20:28:29 -05:00
.changelog.md fix: use /tmp for changelog artifact to avoid . file matching issues 2026-04-15 22:54:34 -05:00
.commitlintrc.json ci: fix smart_crusher branch CI failures + add make ci-precheck pre-push gate 2026-04-27 11:13:47 -07:00
.dockerignore fix(docker): report source build version (#1862) 2026-07-08 13:32:04 -05:00
.env.act.example feat: add act testing config, fix gitignore, make workflow production-ready 2026-04-15 20:28:29 -05:00
.env.example fix(security): patch loopback guard, retry None raise, blocking subprocess, and cache stats race 2026-06-04 16:09:53 -04:00
.git-blame-ignore-revs chore: add .git-blame-ignore-revs 2026-04-24 15:35:29 +02:00
.gitattributes chore: union-merge CHANGELOG.md to stop cross-PR merge conflicts (#2118) 2026-07-13 10:18:04 -04:00
.gitguardian.yaml fix: harden Copilot API auth token handling (#557) 2026-06-11 12:57:48 -05:00
.gitignore feat(grok-build): add Grok Build wrap command and MCP integration (#1629) 2026-07-15 20:51:52 +00:00
.gitleaks.toml fix(ci): extend gitleaks allowlist to cover test fixtures + verified examples (#1539) 2026-06-28 13:10:58 -07:00
.pre-commit-config.yaml ci: guard against committed merge-conflict markers (#1505) 2026-06-30 14:20:25 -05:00
.release-please-config.json ci(release-please): set versioned PR title pattern to fix tagging jam 2026-06-04 09:56:35 -07:00
.release-please-manifest.json fix(deps): clear Dependabot lockfile alerts (#2175) 2026-07-14 20:40:28 -07:00
Cargo.lock feat(text-crusher): CJK-aware segmentation + relevance via ICU (#1504) 2026-07-15 19:58:48 +00:00
Cargo.toml feat(simulators): add provider simulator service (#2014) 2026-07-11 09:41:49 -07:00
CHANGELOG.md fix(memory): preserve semantically similar memories (#2303) 2026-07-16 11:32:38 -07:00
claude_analysis_ttl.py chore: add cache TTL cost analysis script 2026-05-13 10:49:17 -07:00
CODE_OF_CONDUCT.md chore(telemetry): remove Supabase anonymous beacon; fix contact domain to headroomlabs.ai (#1526) 2026-06-27 22:48:26 -07:00
codecov.yml fix(codex): poll /wham/usage for subscription limits (handshake no longer sends x-codex-* headers) (#924) 2026-06-12 17:03:14 -05:00
CONTRIBUTING.md ci(changelog): stop the CHANGELOG cascade — release-please owns it (#2329) 2026-07-16 14:28:57 -07:00
deny.toml feat(rust): scaffold workspace + parity harness (phase-0) 2026-04-24 13:39:48 -07:00
docker-bake.hcl refactor(docker): migrate to bake with multi-variant distroless images 2026-04-04 21:51:37 +05:30
docker-compose.yml docs(compose): document the memory-stack docker-compose services (#1242) 2026-07-15 20:38:55 +00:00
Dockerfile fix(docker): report source build version (#1862) 2026-07-08 13:32:04 -05:00
Headroom-2.gif Add demo GIF to README 2026-01-20 18:57:17 -08:00
headroom-savings.png docs: rewrite README for clarity and highlight Kompress-base, leaderboard, RTK 2026-04-18 09:36:49 -07:00
headroom_learn.gif docs: add headroom learn demo GIF to README 2026-03-07 17:56:17 -08:00
HeadroomDemo-Fast.gif Replace demo GIF with HeadroomDemo-Fast.gif 2026-04-10 15:05:25 -07:00
LICENSE Prepare for OSS release v0.2.0 2026-01-07 11:36:44 -08:00
llms.txt feat(wrap): add omp target (Oh My Pi) with models.yml override and unwrap (#1811) 2026-07-15 19:30:19 +00:00
Makefile feat: headroom wrap opencode / unwrap opencode CLI (#1105) 2026-06-22 11:07:12 -05:00
mkdocs.yml feat: add Vertex AI proxy routing (#793) 2026-06-09 23:05:30 -07:00
NOTICE Prepare for OSS release v0.2.0 2026-01-07 11:36:44 -08:00
pyproject.toml fix(code): pin tree-sitter-language-pack <1.0.0 in [code] extra (#1219) 2026-07-15 20:54:25 +00:00
README.md feat(wrap): add headroom wrap kimi for Kimi CLI (#1426) 2026-07-15 21:40:58 +00:00
rust-toolchain.toml fix(rust): clippy 1.95 unnecessary_sort_by + pin toolchain 2026-04-27 12:11:49 -07:00
RUST_DEV.md chore: remove committed node_modules + stray/internal markdown (repo hygiene) (#1528) 2026-06-27 23:32:54 -07:00
SECURITY.md chore(telemetry): remove Supabase anonymous beacon; fix contact domain to headroomlabs.ai (#1526) 2026-06-27 22:48:26 -07:00
server.json fix(mcp): regenerate stale server.json (0.27.0 -> 0.32.0) (#2218) 2026-07-14 22:49:39 -07:00
TESTING-copilot-subscription.md fix(copilot): restore generic endpoint for non-subscription OAuth (#610) (#612) 2026-06-04 16:27:54 -07:00
uv.lock fix(codex): preserve wrapped sessions and recover state (#2160) 2026-07-15 19:58:21 +00:00

  ██╗  ██╗███████╗ █████╗ ██████╗ ██████╗  ██████╗  ██████╗ ███╗   ███╗
  ██║  ██║██╔════╝██╔══██╗██╔══██╗██╔══██╗██╔═══██╗██╔═══██╗████╗ ████║
  ███████║█████╗  ███████║██║  ██║██████╔╝██║   ██║██║   ██║██╔████╔██║
  ██╔══██║██╔══╝  ██╔══██║██║  ██║██╔══██╗██║   ██║██║   ██║██║╚██╔╝██║
  ██║  ██║███████╗██║  ██║██████╔╝██║  ██║╚██████╔╝╚██████╔╝██║ ╚═╝ ██║
  ╚═╝  ╚═╝╚══════╝╚═╝  ╚═╝╚═════╝ ╚═╝  ╚═╝ ╚═════╝  ╚═════╝ ╚═╝     ╚═╝
              The context compression layer for AI agents

6095% fewer tokens (for JSON data), 15-20% fewer tokens (for coding agents) · library · proxy · MCP · content-aware compressors · local-first · reversible

CI codecov PyPI npm Model: Kompress-v2-base License: Apache 2.0 Docs

Docs · Install · Proof · Agents · Discord · llms.txt

AI agents / LLMs: read /llms.txt here, or fetch the live index / full docs blob.


chopratejas%2Fheadroom | Trendshift

Headroom compresses everything your AI agent reads — tool outputs, logs, RAG chunks, files, and conversation history — before it reaches the LLM. Same answers, fraction of the tokens.

Headroom in action
Live: 10,144 → 1,260 tokens — same FATAL found.

What it does

  • Librarycompress(messages) in Python or TypeScript, inline in any app
  • Proxyheadroom proxy --port 8787, zero code changes, any language
  • Agent wrapheadroom wrap claude|codex|grok|copilot|cursor|aider|opencode|cline|continue|goose|openhands|openclaw|vibe|omp|zcode in one command; undo with headroom unwrap <tool>
  • MCP serverheadroom_compress, headroom_retrieve, headroom_stats for any MCP client
  • Cross-agent memory — shared store across Claude, Codex, Gemini, Grok, auto-dedup
  • headroom learn — mines failed sessions, writes corrections to CLAUDE.local.md (default, gitignored) or CLAUDE.md / AGENTS.md / GEMINI.md / GROK.md
  • Output token reduction — trims what the model writes back (not just what you send): drops ceremony/restated code and skips deep "thinking" on routine steps. See Output token reduction.
  • Reversible (CCR) — originals are cached for retrieval on demand

How it works (30 seconds)

 Your agent / app
   (Claude Code, Cursor, Codex, LangChain, Agno, Strands, your own code…)
        │   prompts · tool outputs · logs · RAG results · files
        ▼
    ┌────────────────────────────────────────────────────┐
    │  Headroom   (runs locally — your data stays here)  │
    │  ────────────────────────────────────────────────  │
    │  CacheAligner  →  ContentRouter  →  CCR            │
    │                    ├─ SmartCrusher   (JSON)        │
    │                    ├─ CodeCompressor (AST)         │
    │                    └─ Kompress-v2-base (text, HF)  │
    │                                                    │
    │  Cross-agent memory  ·  headroom learn  ·  MCP     │
    └────────────────────────────────────────────────────┘
        │   compressed prompt  +  retrieval tool
        ▼
 LLM provider  (Anthropic · OpenAI · Bedrock · …)
  • ContentRouter — detects content type, selects the right compressor
  • SmartCrusher / CodeCompressor / Kompress-v2-base — compress JSON, AST, or prose
  • CacheAligner — stabilizes prefixes so provider KV caches actually hit
  • CCR — stores originals locally; LLM calls headroom_retrieve if it needs them

Architecture · CCR reversible compression · Kompress-v2-base model card

Get started (60 seconds)

# 1 — Install
uv tool install --python 3.13 "headroom-ai[all]"  # CLI as a global tool in a self-contained virtual env
pip install "headroom-ai[all]"                    # Python — ships the `headroom` CLI
npm install headroom-ai                           # TypeScript SDK only — no `headroom` CLI

# 2 — Pick your mode  (the `headroom` commands below come from the uv or pip install)
headroom deploy                         # turnkey local deployment + agent config
headroom wrap claude                    # wrap a coding agent
headroom proxy --port 8787              # drop-in proxy, zero code changes
# or: from headroom import compress      # inline library

# 3 — Verify setup and see the savings
headroom doctor                         # health check — confirms routing is working
headroom perf
headroom dashboard                      # live savings dashboard (proxy must be running)

To use headroom, it is recommended you launch a wrapped agent session each time so that all necessary setup is completed. When wrapping a coding agent, headroom starts a local proxy, sets up an MCP server that provides tools such as rtk and tokensave, and launches a coding agent session configured to proxy requests to headroom.

The headroom CLI ships only via the PyPI package. The npm headroom-ai is the TypeScript SDK — a library you import (import { compress } from 'headroom-ai'), not a CLI, so it provides no headroom command.

Granular extras: [proxy], [mcp], [ml], [code], [memory], [vector] (optional HNSW backend — needs a C++ toolchain, not in [all]), [relevance], [image], [agno], [langchain], [evals], [pytorch-mps] (Apple-GPU memory-embedder offload — set HEADROOM_EMBEDDER_RUNTIME=pytorch_mps). Requires Python 3.10+.

Codex / global install

If Codex or another MCP client cannot inherit a shell PATH reliably, install Headroom as a persistent uv tool and point the client at the absolute binary path:

uv tool install "headroom-ai[all]"
command -v headroom

Then use the returned path in MCP config:

[mcp_servers.headroom]
command = "/absolute/path/from/command-v/headroom"
args = ["mcp", "serve"]

command = "headroom" only works when the client starts with a PATH that already includes the uv tool directory.

Proof

Savings on real agent workloads:

Workload Before After Savings
Code search (100 results) 17,765 1,408 92%
SRE incident debugging 65,694 5,118 92%
GitHub issue triage 54,174 14,761 73%
Codebase exploration 78,502 41,254 47%

Accuracy preserved on standard benchmarks:

Benchmark Category N Baseline Headroom Delta
GSM8K Math 100 0.870 0.870 ±0.000
TruthfulQA Factual 100 0.530 0.560 +0.030
SQuAD v2 QA 100 97% 19% compression
BFCL Tools 100 97% 32% compression

Reproduce: python -m headroom.evals suite --tier 1 · Full benchmarks & methodology

Output token reduction (cut what the model writes back)

Everything above shrinks the prompt you send. But you also pay for every token the model writes back — and on Opus-class models output costs 5× input. A lot of that output is waste: "Great, let me…" preambles, re-printing code you just showed it, and deep "thinking" on routine steps like reading a file.

Headroom can trim that too, from the proxy, without you changing any code:

  • Verbosity steering — appends a short "be terse, don't restate context" note to the end of the system prompt (so your prompt cache still hits).
  • Effort routing — when a turn is just the model resuming after a tool result (a file read, a passing test), it dials the model's thinking effort down. New questions and errors keep full effort.

Applies to Anthropic /v1/messages and OpenAI-compatible endpoints (/v1/chat/completions, /v1/responses). Effort routing uses reasoning_effort on OpenAI, thinking.budget_tokens / output_config.effort on Anthropic — same clamp-only invariant on both paths, same output_shaper:* label vocabulary.

Turn it on:

export HEADROOM_OUTPUT_SHAPER=1     # off by default
headroom proxy --port 8787

Already running a proxy? These switches are read live on every request, so a proxy that headroom wrap reused (rather than started) would not see a value you export afterwards — its environment was snapshotted at launch. headroom wrap now hot-syncs your current settings to the running proxy via a loopback POST /admin/runtime-env, so they take effect immediately with no restart (no cold start, no dropped requests, no lost caches). Set them before you wrap. On a shared proxy these overrides are global — the last explicit setting wins.

Learn the right terseness for you. People don't say how terse they want answers — they show it (they interrupt long replies, or move on before they could have read them). headroom learn --verbosity reads your past sessions and picks the level automatically:

headroom learn --verbosity            # preview what it found (dry run)
headroom learn --verbosity --apply    # save it; the proxy uses it from now on

See how many output tokens you saved. Output savings are counterfactual — we never see what the model would have written — so Headroom reports an honest estimate with a confidence range, never a made-up number:

headroom output-savings
# Reduction: 31.7%  (95% CI 27.7% … 35.7%)   [estimated]

Want a measured number instead of an estimate? Leave 10% of conversations unshaped as a control group: export HEADROOM_OUTPUT_HOLDOUT=0.1. The dashboard shows an Output Tokens Saved card next to input compression, labelled measured or estimated with the confidence band.

→ Full write-up incl. the measurement methodology: Output token reduction

Star History Chart

Agent compatibility matrix

Agent headroom wrap Notes
Claude Code --memory · --code-graph · --1m · --tool-search
Codex shares memory with Claude
Grok CLI routes via GROK_CLI_CHAT_PROXY_BASE_URL
Cursor Manual setup starts proxy and prints base URLs for Cursor settings
Aider starts proxy + launches
Copilot CLI starts proxy + launches
OpenClaw installs as ContextEngine plugin
OpenCode injects config · starts proxy + launches
Cline starts proxy + injects config
Continue starts proxy + injects config
Goose starts proxy + launches
OpenHands starts proxy + launches
Mistral Vibe starts proxy + launches
Oh My Pi injects config · starts proxy + launches
Cortex Code Library only 6065% savings (library mode; no wrap)
Kimi CLI OAuth bearer forwarded — log in once
ZCode starts proxy and prints base URLs for ZCode settings

Any OpenAI-compatible client works via headroom proxy. MCP-native: headroom mcp install. Undo durable wrapping with headroom unwrap <tool> (supports: claude, copilot, codex, grok, kimi, omp, opencode, openclaw, zcode). Registry authors can use the canonical server.json in the repo root instead of reconstructing the headroom mcp serve contract from prose.

GitHub Copilot CLI subscription mode

Headroom can route GitHub Copilot CLI subscription traffic through the local proxy:

headroom copilot-auth login
headroom wrap copilot --subscription -- --model gpt-4o

This lets Headroom intercept OpenAI-compatible Copilot CLI requests and apply the same proxy compression pipeline before forwarding to GitHub Copilot's hosted API. The wrapper exchanges Headroom's reusable GitHub OAuth token for Copilot's short-lived API token and prints the upstream endpoint as COPILOT_PROVIDER_API_URL=... during launch.

headroom copilot-auth login stores a Headroom-specific Copilot OAuth token. This avoids relying on generic GitHub or Copilot CLI tokens that can read Copilot account metadata but may still be rejected by Copilot's token-exchange endpoint.

For GitHub Enterprise Server or custom-domain Copilot deployments, set one of these before launching:

export GITHUB_COPILOT_ENTERPRISE_DOMAIN=ghe.example.com
# or
export GITHUB_COPILOT_ENTERPRISE_URL=https://ghe.example.com

Both variables are supported. If both are set, GITHUB_COPILOT_ENTERPRISE_URL takes precedence.

For GitHub.com Enterprise Cloud URLs such as github.com/enterprises/your-enterprise, do not set an enterprise-domain override. Headroom uses GitHub's normal token-exchange endpoint and the Copilot API endpoint advertised for the signed-in account.

Platform support note: macOS auth reuse via Copilot CLI Keychain storage has been smoke-tested. Windows Credential Manager, Linux Secret Service / secret-tool, and Docker/CI token-injection paths are implemented or planned as auth-discovery paths, but still need real OS validation before they should be considered fully vetted. For Docker and CI, prefer passing an explicit GITHUB_COPILOT_TOKEN or GITHUB_COPILOT_GITHUB_TOKEN rather than relying on host keychain access.

When to use · When to skip

Great fit if you…

  • run AI coding agents daily and want savings without changing your code
  • work across multiple agents and want shared memory
  • need reversible compression — originals are retrievable via CCR within the configured TTL

Skip it if you…

  • only use a single provider's native compaction and don't need cross-agent memory
  • work in a sandboxed environment where local processes can't run
Integrations — drop Headroom into any stack
Your setup Hook in with
Any Python app compress(messages, model=…)
Any TypeScript app await compress(messages, { model })
Anthropic / OpenAI SDK withHeadroom(new Anthropic()) · withHeadroom(new OpenAI())
Vercel AI SDK wrapLanguageModel({ model, middleware: headroomMiddleware() })
LiteLLM litellm.callbacks = [HeadroomCallback()]
LangChain HeadroomChatModel(your_llm)
Agno HeadroomAgnoModel(your_model)
Strands Strands guide
ASGI apps app.add_middleware(CompressionMiddleware)
Multi-agent SharedContext().put / .get
MCP clients headroom mcp install
What's inside
  • SmartCrusher — universal JSON: arrays of dicts, nested objects, mixed types.
  • CodeCompressor — AST-aware for Python, JS/TS, Go, Rust, Java, C/C++, Perl.
  • Kompress-v2-base — our HuggingFace model, trained on agentic traces.
  • Image compression — 4090% reduction via trained ML router.
  • CacheAligner — stabilizes prefixes so Anthropic/OpenAI KV caches actually hit.
  • Live-zone compression — compresses only new bytes (fresh tool output, latest turn); frozen prefix stays byte-identical so provider cache is not busted. History is never dropped.
  • CCR — reversible compression; LLM retrieves originals on demand.
  • Cross-agent memory — shared store, agent provenance, auto-dedup.
  • SharedContext — compressed context passing across multi-agent workflows.
  • headroom learn — plugin-based failure mining for Claude, Codex, Gemini.
Pipeline internals

Headroom exposes one stable request lifecycle across compress(), the SDK, and the proxy:

SetupPre-StartPost-StartInput ReceivedInput CachedInput RoutedInput CompressedInput RememberedPre-SendPost-SendResponse Received

  • Transforms do the work: CacheAligner → ContentRouter → SmartCrusher / CodeCompressor / Kompress-base (live-zone only; IntelligentContext and RollingWindow were retired in PR-B1).
  • Pipeline extensions observe or customize lifecycle stages via on_pipeline_event(...).
  • Compression hooks sit alongside the canonical lifecycle as an additional extension seam.
  • Proxy extensions remain the server/app integration seam for ASGI middleware, routes, and startup policy.

Provider and tool-specific behavior lives under headroom/providers/ so core orchestration stays focused on lifecycle, sequencing, and policy.

  • CLI/tool slices: headroom/providers/claude, copilot, codex, grok, openclaw
  • Provider runtime slices: headroom/providers/claude, gemini, plus shared backend/runtime dispatch in headroom/providers/registry.py
  • Core files stay orchestration-first: wrap.py, client.py, cli/proxy.py, and proxy/server.py delegate provider-specific env shaping, API target normalization, backend selection, and transport dispatch.

Headroom for teams

Headroom OSS is built for individual developers: run headroom proxy or headroom wrap on your laptop and start cutting tokens in minutes — free, local-first, your data never leaves your machine.

Running it across a whole engineering org is a different job: a shared, always-on deployment; centralized config and version rollout; org-wide savings dashboards; SSO and access controls; air-gapped / VPC installs; and someone to call when it matters. That's what we help companies with — self-hosted with support, or fully managed.

If your team is spending real money on LLM tokens — Claude Code, Codex, Cursor, or agents running in CI — and you want those savings across everyone, not just one laptop:

→ Email hello@headroomlabs.ai with your stack and rough monthly LLM spend, and we'll help you roll Headroom out across your organization.

Everything in this repo stays open source (Apache 2.0). The managed offering is simply for teams that would rather have it deployed, supported, and scaled for them.

Install

uv tool install --python 3.13 "headroom-ai[all]"  # CLI, isolated app env
pip install "headroom-ai[all]"                    # Python, everything — includes the `headroom` CLI
npm install headroom-ai                           # TypeScript SDK (library only — no `headroom` CLI)
docker pull ghcr.io/chopratejas/headroom:latest

Granular extras: [proxy], [mcp], [ml] (Kompress-v2-base), [code], [memory], [vector] (optional HNSW backend — needs a C++ toolchain, not in [all]), [relevance], [image], [agno], [langchain], [evals], [pytorch-mps] (Apple-GPU memory-embedder offload — set HEADROOM_EMBEDDER_RUNTIME=pytorch_mps). Requires Python 3.10+.

Note

: [all] covers the core stack but excludes framework adapters. Install them separately: pip install "headroom-ai[langchain]" (also [agno], [strands], [anyllm], [bedrock]).

Using uv for the headroom CLI? Prefer uv tool install so the command lives in an isolated app environment. On macOS, pass --python 3.13 if your default python3 is newer than the current wheel set:

brew install python@3.13  # if Python 3.13 is not already available
uv tool install --python 3.13 "headroom-ai[all]"
uv tool update-shell      # if ~/.local/bin is not already on PATH
headroom --version

For MCP clients such as Codex that do not inherit your interactive shell PATH, configure the absolute executable path returned by command -v headroom:

[mcp_servers.headroom]
command = "/Users/you/.local/bin/headroom"
args = ["mcp", "serve"]

Current native wheels cover macOS Apple Silicon and Linux. On Intel macOS, use Docker-native install until native wheel support lands.

Using pipx? Choose a supported interpreter explicitly:

pipx install --python python3.13 "headroom-ai[all]"

Pick 3.13 if you want dollar savings. The dashboard's Proxy $ Saved tile prices compression with LiteLLM, and LiteLLM can't be installed on Python 3.14+. On 3.14 token savings still track, but the dollar figure stays $0.00. If you already installed on 3.14, switch with pipx reinstall headroom-ai --python python3.13 and restart the proxy.

Installation guide — Docker tags, persistent service, PowerShell, devcontainers.

CPU requirement (x86/x86_64): the ONNX-backed features — Magika content detection and embedding relevance — use a precompiled ONNX Runtime that needs AVX2. On x86 hosts without AVX2 (some Docker/QEMU setups and older cloud VMs) Headroom automatically falls back to its non-ONNX paths (BM25 relevance, heuristic detection) rather than crashing. arm64/Apple Silicon needs no AVX2.

Updating

headroom update          # detects pip / pipx / uv tool and upgrades in place
headroom update --check  # report the latest release without upgrading
headroom update --pre    # include pre-releases

headroom update figures out how Headroom was installed (pip/venv, pip --user, pipx, uv tool) and runs the matching upgrade across macOS, Linux, and Windows. For git checkouts, editable installs, Docker images, and externally-managed system Pythons (PEP 668) it prints the correct manual step instead of guessing.

The proxy also shows a one-line "update available" notice on startup. It checks PyPI at most once a day, in the background, and never blocks. Opt out with HEADROOM_UPDATE_CHECK=off (also skipped in --stateless mode and CI).

Corporate / SSL-inspection environments

If pip install "headroom-ai[all]" fails with CERTIFICATE_VERIFY_FAILED (unable to get local issuer certificate), your network uses SSL inspection — a MITM proxy presenting a company-issued CA. The build backend (maturin) downloads rustup over a connection your TLS stack doesn't trust. Install Rust first so the build doesn't fetch it:

# macOS / Linux
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh && rustup default stable
# Windows
winget install Rustlang.Rustup && rustup default stable

Restart your shell, then pip install "headroom-ai[all]". A prebuilt wheel avoids the Rust build entirely where available: pip install --only-binary headroom-ai headroom-ai. Prebuilt wheels are published for Windows (win_amd64), Linux (x86_64 / aarch64), and macOS (Apple Silicon and Intel), so installs on those platforms never need a local Rust toolchain — the Rust-first dance above is only for the platform-independent sdist fallback when no wheel matches.

Two runtime assets are fetched over TLS; if they are blocked, trust your corporate CA via REQUESTS_CA_BUNDLE / SSL_CERT_FILE / CURL_CA_BUNDLE:

  • cdn.pyke.io — the ONNX Runtime for the Rust core. Alternatively pre-provide it with ORT_STRATEGY=system and ORT_LIB_LOCATION=/path/to/onnxruntime.
  • huggingface.co — the kompress-base compression model. Pre-download it and run with HF_HUB_OFFLINE=1, or set HF_ENDPOINT to a trusted mirror.

Running with compression disabled (pure gateway) requires neither asset.

Intel macOS (x86_64-apple-darwin): no prebuilt ONNX Runtime binary (#941)

ort-sys ships no prebuilt ONNX Runtime binary for Intel macOS, so a source build fails by default even outside a corporate-proxy environment. The same ORT_STRATEGY=system mechanism above fixes it — point it at a system ONNX Runtime instead:

brew install onnxruntime
ORT_STRATEGY=system \
ORT_LIB_LOCATION="$(brew --prefix onnxruntime)/lib" \
ORT_PREFER_DYNAMIC_LINK=1 \
  pip install "headroom-ai[all]"

# ORT is dlopen'd at runtime too:
export ORT_DYLIB_PATH="$(brew --prefix onnxruntime)/lib/libonnxruntime.dylib"

ORT_LIB_LOCATION must point at lib/ (not the bare prefix) and ORT_PREFER_DYNAMIC_LINK=1 is required, or ORT_STRATEGY=system still attempts static linking, which the Homebrew keg doesn't provide.

"Basic Constraints of CA cert not marked critical" (Python 3.13+ strict mode)

A different failure from the one above. If TLS fails with:

[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed:
Basic Constraints of CA cert not marked critical

then the corporate CA is found and trusted — adding it to a CA bundle changes nothing. Python 3.13 + OpenSSL 3.x enable VERIFY_X509_STRICT by default, which enforces RFC 5280 §4.2.1.9: a CA cert's basicConstraints must be marked critical. Inspection roots like Zscaler set CA:TRUE without the critical bit, so the chain is rejected.

Set HEADROOM_TLS_STRICT=0 to clear only the strict flag from every TLS context Headroom controls — the proxy's httpx upstream client and the urllib3/huggingface_hub path used for model downloads. Chain validation, signature, expiry, and hostname checks all stay on; this is strictly narrower than disabling verification.

HEADROOM_TLS_STRICT=0 headroom proxy --port 8787

The Rust core's ONNX download (cdn.pyke.io) uses a separate TLS stack (rustls / OS trust store), unaffected by HEADROOM_TLS_STRICT. On Windows the corporate root must be in the machine certificate store (browsers already trust it there); or pre-provision ONNX Runtime with ORT_STRATEGY=system + ORT_LIB_LOCATION=/path/to/onnxruntime to skip the download entirely.

headroom learn

headroom learn in action

headroom learn — mines failed sessions, writes corrections to CLAUDE.local.md (default, gitignored; use --target CLAUDE.md for the shared team file) / AGENTS.md / GEMINI.md.

Documentation

Start here Go deeper
Quickstart Architecture
Proxy How compression works
MCP tools CCR — reversible compression
Memory Cache optimization
Failure learning Benchmarks
Configuration Limitations
Persistent installs (headroom init / headroom install apply) Savings analytics (headroom savings / headroom perf / headroom doctor)

Compared to

Headroom runs locally, covers every content type, works with every major framework, and is reversible.

Scope Deploy Local Reversible
Headroom All context — tools, RAG, logs, files, history Proxy · library · middleware · MCP Yes Yes
RTK CLI command outputs CLI wrapper Yes No
lean-ctx Tool output, files, shell, history Proxy · library · middleware · MCP · CLI Yes Yes
Compresr, Token Co. Text sent to their API Hosted API call No No
OpenAI Compaction Conversation history Provider-native No No

Attribution. Headroom ships with the excellent RTK binary for shell-output rewriting — git show --short, scoped ls, summarized installers. Huge thanks to the RTK team; their tool is a first-class part of our stack, and Headroom compresses everything downstream of it. Headroom can also use lean-ctx as the selected CLI context tool; set HEADROOM_CONTEXT_TOOL=lean-ctx before running headroom wrap ....

Contributing

git clone https://github.com/chopratejas/headroom.git && cd headroom
uv sync --extra dev && uv run pytest

Devcontainers in .devcontainer/ (default + memory-stack with Qdrant & Neo4j). See CONTRIBUTING.md.

Community

Community projects

  • Claude Code status-line indicator — a Claude Code plugin that shows live Headroom usage in your status line: idle until headroom_compress fires, then the running total of tokens saved.

License

Apache 2.0 — see LICENSE.