## Description `ContentRouter.eager_load_compressors()` runs a network `hf_hub_download` of the Kompress ONNX model on the **blocking startup/lifespan path**, before the proxy binds its port. On a cold cache this is unsafe: - the download can hang long enough to blow the supervisor's bind timeout, or - a native crash in the download/ML stack (an **uncatchable `Fatal Python error: Aborted` / SIGABRT**) kills the interpreter before it ever `listen()`s. Either way the supervisor sees "proxy never opened its port" and gives up. We observed this in the field from the desktop app (process aborted during `eager_load_compressors -> _load_kompress_onnx -> hf_hub_download` of `onnx/kompress-int8.onnx`, while the only Python thread was parked in the HuggingFace download file-lock; the abort came from a native thread, so `try/except` at the call site cannot catch it). The eager preload is a latency optimization and must never be able to block — or kill — startup. This change makes startup preload **cache-only**: if the model isn't already cached, we defer the download to first use (off the startup path) and bind the port normally. Warm starts are unchanged. ## 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 - `onnx_runtime.hf_hub_download_local_first(...)`: added `allow_network` (default `True`). When `False`, a cache miss re-raises the local-lookup error instead of falling back to a network download. - `kompress_compressor`: added `allow_download` (default `True`) threaded through `preload()` -> `_load_kompress()` -> `_load_kompress_onnx()` / `_load_kompress_pytorch()` and the ModernBERT tokenizer load. Added `KompressModelNotCached`, raised when a cache-only load misses. Auto-mode no longer falls back to a PyTorch network download on a cache-only miss — it propagates so the caller can defer. - `content_router.eager_load_compressors()`: calls `preload(allow_download=False)`. On `KompressModelNotCached` it logs and reports the component as `"deferred"` (a status `warmup.merge_transform_status` already handles gracefully) instead of letting a cold download run on the startup path. Default (first-request) loading behavior and warm-start preload are unchanged. ## 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 New tests in `tests/test_kompress_preload_deferral.py` cover: cache-only `hf_hub_download_local_first` never hits the network; default still falls back; cache-only ONNX load raises `KompressModelNotCached`; auto-mode does **not** trigger a PyTorch download on a cache-only miss; and `eager_load_compressors` reports `deferred` (cold) / `enabled` (warm). Existing `_load_kompress` dispatch tests updated for the new keyword-only param. > Note on environment: I do not have a clean reproduction of the native SIGABRT itself (it depends on a specific machine's HF download/ML native stack), so the "Manual testing performed" box is left unchecked. The tests target the structural fix — that startup preload can no longer perform a network download — which is the precondition for the crash. ## Test Output ``` $ uv run pytest -v tests/test_kompress_preload_deferral.py tests/test_kompress_preload_deferral.py::test_local_first_no_network_when_disallowed PASSED tests/test_kompress_preload_deferral.py::test_local_first_falls_back_to_network_by_default PASSED tests/test_kompress_preload_deferral.py::test_load_kompress_onnx_cache_miss_raises_not_cached PASSED tests/test_kompress_preload_deferral.py::test_load_kompress_auto_does_not_pytorch_download_on_cache_miss PASSED tests/test_kompress_preload_deferral.py::test_eager_load_defers_when_model_not_cached PASSED tests/test_kompress_preload_deferral.py::test_eager_load_enabled_when_model_cached PASSED 6 passed in 4.82s $ uv run pytest tests/test_transforms/test_kompress_compressor.py tests/test_transforms_content_router.py tests/test_onnx_runtime.py tests/test_proxy_warmup.py 63 passed $ uv run ruff check <changed files> # All checks passed! $ uv run mypy headroom/onnx_runtime.py headroom/transforms/kompress_compressor.py headroom/transforms/content_router.py Success: no issues found ``` ## 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 (auto-generated from conventional commits) ## Additional Notes This contains the cold-start case. A native crash in onnxruntime *session init* (as opposed to the download) on first request would still be a separate issue; it is not what was observed here (the abort was during the HF download), and isolating it would be a larger, separate change. --------- Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com> |
||
|---|---|---|
| .claude-plugin | ||
| .devcontainer | ||
| .github | ||
| benchmarks | ||
| crates | ||
| docker | ||
| docs | ||
| e2e | ||
| examples | ||
| headroom | ||
| plugins | ||
| REALIGNMENT | ||
| scripts | ||
| sdk/typescript | ||
| sql | ||
| tests | ||
| wiki | ||
| .actrc | ||
| .actrc.local.example | ||
| .changelog.md | ||
| .commitlintrc.json | ||
| .dockerignore | ||
| .env.act.example | ||
| .env.example | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitguardian.yaml | ||
| .gitignore | ||
| .pre-commit-config.yaml | ||
| .release-please-config.json | ||
| .release-please-manifest.json | ||
| Cargo.lock | ||
| Cargo.toml | ||
| CHANGELOG.md | ||
| claude_analysis_ttl.py | ||
| CODE_OF_CONDUCT.md | ||
| codecov.yml | ||
| CONTRIBUTING.md | ||
| deny.toml | ||
| docker-bake.hcl | ||
| docker-compose.yml | ||
| Dockerfile | ||
| ENTERPRISE.md | ||
| Headroom-2.gif | ||
| headroom-savings.png | ||
| headroom_learn.gif | ||
| HeadroomDemo-Fast.gif | ||
| LICENSE | ||
| llms.txt | ||
| Makefile | ||
| mkdocs.yml | ||
| NOTICE | ||
| PR.md | ||
| pyproject.toml | ||
| README.md | ||
| rust-toolchain.toml | ||
| RUST_DEV.md | ||
| SECURITY.md | ||
| TESTING-copilot-subscription.md | ||
| uv.lock | ||
██╗ ██╗███████╗ █████╗ ██████╗ ██████╗ ██████╗ ██████╗ ███╗ ███╗
██║ ██║██╔════╝██╔══██╗██╔══██╗██╔══██╗██╔═══██╗██╔═══██╗████╗ ████║
███████║█████╗ ███████║██║ ██║██████╔╝██║ ██║██║ ██║██╔████╔██║
██╔══██║██╔══╝ ██╔══██║██║ ██║██╔══██╗██║ ██║██║ ██║██║╚██╔╝██║
██║ ██║███████╗██║ ██║██████╔╝██║ ██║╚██████╔╝╚██████╔╝██║ ╚═╝ ██║
╚═╝ ╚═╝╚══════╝╚═╝ ╚═╝╚═════╝ ╚═╝ ╚═╝ ╚═════╝ ╚═════╝ ╚═╝ ╚═╝
The context compression layer for AI agents
60–95% fewer tokens · library · proxy · MCP · 6 algorithms · local-first · reversible
Docs · Install · Proof · Agents · Discord · llms.txt · Enterprise
AI agents / LLMs: read /llms.txt here, or fetch the live index / full docs blob.
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.
Live: 10,144 → 1,260 tokens — same FATAL found.
What it does
- Library —
compress(messages)in Python or TypeScript, inline in any app - Proxy —
headroom proxy --port 8787, zero code changes, any language - Agent wrap —
headroom wrap claude|codex|cursor|aider|copilotin one command - MCP server —
headroom_compress,headroom_retrieve,headroom_statsfor any MCP client - Cross-agent memory — shared store across Claude, Codex, Gemini, auto-dedup
headroom learn— mines failed sessions, writes corrections toCLAUDE.md/AGENTS.md- 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-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-base — compress JSON, AST, or prose
- CacheAligner — stabilizes prefixes so provider KV caches actually hit
- CCR — stores originals locally; LLM calls
headroom_retrieveif it needs them
→ Architecture · CCR reversible compression · Kompress-v2-base model card
Get started (60 seconds)
# 1 — Install
pip install "headroom-ai[all]" # Python
npm install headroom-ai # Node / TypeScript
# 2 — Pick your mode
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 — See the savings
headroom perf
Granular extras: [proxy], [mcp], [ml], [code], [memory], [relevance], [image], [agno], [langchain], [evals]. Requires Python 3.10+.
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
Agent compatibility matrix
| Agent | headroom wrap |
Notes |
|---|---|---|
| Claude Code | ✅ | --memory · --code-graph |
| Codex | ✅ | shares memory with Claude |
| Cursor | ✅ | prints config — paste once |
| Aider | ✅ | starts proxy + launches |
| Copilot CLI | ✅ | starts proxy + launches |
| OpenClaw | ✅ | installs as ContextEngine plugin |
Any OpenAI-compatible client works via headroom proxy. MCP-native: headroom mcp install.
GitHub Copilot CLI subscription mode
Headroom can route GitHub Copilot CLI subscription traffic through the local proxy:
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 resolves the account-specific Copilot API endpoint and prints it as COPILOT_PROVIDER_API_URL=... during launch.
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, Go, Rust, Java, C++.
- Kompress-base — our HuggingFace model, trained on agentic traces.
- Image compression — 40–90% reduction via trained ML router.
- CacheAligner — stabilizes prefixes so Anthropic/OpenAI KV caches actually hit.
- IntelligentContext — score-based context fitting with learned importance.
- 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:
Setup → Pre-Start → Post-Start → Input Received → Input Cached → Input Routed → Input Compressed → Input Remembered → Pre-Send → Post-Send → Response Received
- Transforms do the work: CacheAligner, ContentRouter, SmartCrusher, CodeCompressor, Kompress-base, IntelligentContext / RollingWindow.
- 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,openclaw - Provider runtime slices:
headroom/providers/claude,gemini, plus shared backend/runtime dispatch inheadroom/providers/registry.py - Core files stay orchestration-first:
wrap.py,client.py,cli/proxy.py, andproxy/server.pydelegate provider-specific env shaping, API target normalization, backend selection, and transport dispatch.
Install
pip install "headroom-ai[all]" # Python, everything
npm install headroom-ai # TypeScript / Node
docker pull ghcr.io/chopratejas/headroom:latest
Granular extras: [proxy], [mcp], [ml] (Kompress-base), [code], [memory], [relevance], [image], [agno], [langchain], [evals]. Requires Python 3.10+.
Using pipx? Choose a supported interpreter explicitly:
pipx install --python python3.13 "headroom-ai[all]"
→ Installation guide — Docker tags, persistent service, PowerShell, devcontainers.
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.
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 withORT_STRATEGY=systemandORT_LIB_LOCATION=/path/to/onnxruntime.huggingface.co— thekompress-basecompression model. Pre-download it and run withHF_HUB_OFFLINE=1, or setHF_ENDPOINTto a trusted mirror.
Running with compression disabled (pure gateway) requires neither asset.
headroom learn
headroom learn — mines failed sessions, writes corrections to CLAUDE.md / 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 |
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 | CLI commands, MCP tools, editor rules | CLI wrapper · MCP | Yes | No |
| 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, scopedls, 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; setHEADROOM_CONTEXT_TOOL=lean-ctxbefore runningheadroom wrap ....
Contributing
git clone https://github.com/chopratejas/headroom.git && cd headroom
pip install -e ".[dev]" && pytest
Devcontainers in .devcontainer/ (default + memory-stack with Qdrant & Neo4j). See CONTRIBUTING.md.
Community
- Discord — questions, feedback, war stories.
- Kompress-v2-base on HuggingFace — the model behind our text compression.
License
Apache 2.0 — see LICENSE.