## Description LiteLLM/Bedrock streaming never surfaces prompt tokens mid-stream — it emits `message_start` with `usage.input_tokens=0` and only reports `output_tokens` (at the end, in `message_delta`). Anthropic clients such as Claude Code read `usage.input_tokens` from the **first** SSE event (`message_start`) to emit OTel/cost metrics, so every Headroom + Bedrock streaming request reported ~0 input tokens — underreporting token usage by ~99% in Athena/CloudWatch dashboards. Only `output_tokens` was tracked correctly. `StreamingMixin._stream_response_bedrock` now backfills `input_tokens` on `message_start` with the count Headroom actually sent upstream (`optimized_tokens`, already a parameter of that method) when the backend left it unset/zero. A non-zero value the backend genuinely reports is preserved untouched. Closes #1132 ## 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 - `headroom/proxy/handlers/streaming.py`: in `_stream_response_bedrock`, rewrite the `message_start` event's `usage.input_tokens` to `optimized_tokens` before it is serialized to the client, when the backend reported `0`/unset (and `optimized_tokens > 0`). Non-zero upstream values pass through unchanged. - `tests/test_bedrock_streaming_input_tokens.py`: new test that drives the Bedrock streaming route end-to-end with a LiteLLM-shaped backend (data-only `StreamEvent`s, `raw_sse=None`) and asserts the client-received `message_start` carries a real input-token count; plus a guard that a genuine non-zero upstream value is preserved. - `CHANGELOG.md`: Bug Fixes entry under Unreleased. ## 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_bedrock_streaming_input_tokens.py \ tests/test_backend_streaming_cache_metrics.py \ tests/test_proxy_streaming_resilience.py tests/test_streaming_usage_parser.py -q 39 passed, 1 warning in 46.59s $ uv run ruff check headroom/proxy/handlers/streaming.py tests/test_bedrock_streaming_input_tokens.py All checks passed! $ uv run ruff format --check ... # 2 files already formatted $ uv run mypy headroom/proxy/handlers/streaming.py Success: no issues found in 1 source file ``` ## TDD verification (RED → GREEN) The new test exercises the exact bug path (LiteLLM-shaped `message_start` with `input_tokens=0`, `raw_sse=None` → handler re-serializes `event.data`). **RED** — prod fix reverted (`git stash push -- headroom/proxy/handlers/streaming.py`): ```text FAILED tests/test_bedrock_streaming_input_tokens.py::test_bedrock_streaming_backfills_input_tokens_on_message_start E AssertionError: message_start.usage.input_tokens reached the client as 0; expected the upstream-sent token count (#1132). E assert 0 > 0 1 failed, 1 passed ``` (The 1 passing test on RED is the backwards-compat guard — it asserts a genuine non-zero upstream value is *preserved*, which holds with or without the fix.) **GREEN** — fix applied: ```text tests/test_bedrock_streaming_input_tokens.py .. [100%] 2 passed, 1 warning in 27.88s ``` ## Real Behavior Proof - Environment: Linux, Python 3.13.12, headroom-ai @ this branch, `uv run`. - Exact command / steps: drive the real `/v1/messages` streaming route through `create_app(ProxyConfig(backend="anyllm", anyllm_provider="anthropic", optimize=False))` with a LiteLLM-shaped backend whose `message_start` reports `usage.input_tokens=0` (exactly what `LiteLLMBackend.stream_message` emits), then parse the SSE the client receives. - Observed result: **before fix** the client's `message_start` event carries `usage.input_tokens=0`; **after fix** it carries the real upstream-sent token count (`> 0`), matching the issue's expected behavior. Captured verbatim in the RED→GREEN block above. - Not tested: a live AWS Bedrock account end-to-end (no Bedrock credentials available). The test reproduces the exact SSE shape `LiteLLMBackend.stream_message` produces — `message_start` with `input_tokens=0` and no `raw_sse` — which is the code path the issue identifies. Cache-token fields (`cache_read_input_tokens`/`cache_creation_input_tokens`) are out of scope: LiteLLM streaming does not surface them mid-stream and they cannot be reliably known at `message_start` time. ## 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 — N/A (no doc surface enumerates this behavior) - [x] My changes generate no new warnings - [x] I have added tests that prove my fix is effective - [x] New and existing unit tests pass locally with my changes - [x] I have updated the CHANGELOG.md ## Additional Notes - The fix lives in the proxy handler (`_stream_response_bedrock`), not the LiteLLM backend, because that is the layer that knows `optimized_tokens` — the authoritative count of input tokens Headroom sent upstream. Wiring it into the generic backend interface would be invasive and would duplicate tokenization. - Scope is intentionally limited to `input_tokens` (the headline metric from the issue). Cache-token fields are not inferable upfront and are left as-is. Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com> |
||
|---|---|---|
| .claude-plugin | ||
| .codegraph | ||
| .devcontainer | ||
| .github | ||
| .serena | ||
| agent-evals | ||
| 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 | ||
| AGENTS.md | ||
| 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 | ||
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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- 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-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
headroom dashboard # live savings dashboard (proxy must be running)
Granular extras: [proxy], [mcp], [ml], [code], [memory], [relevance], [image], [agno], [langchain], [evals], [pytorch-mps] (Apple-GPU memory-embedder offload — set HEADROOM_EMBEDDER_RUNTIME=pytorch_mps). 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
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.
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 wrapreused (rather than started) would not see a value you export afterwards — its environment was snapshotted at launch.headroom wrapnow hot-syncs your current settings to the running proxy via a loopbackPOST /admin/runtime-env, so they take effect immediately with no restart (no cold start, no dropped requests, no lost caches). Set them before youwrap. 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: docs/proposals/output-token-reduction.md
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 |
| Cortex Code | ✅ | 60–65% savings · library mode |
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 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 the deployment domain before launching:
export GITHUB_COPILOT_ENTERPRISE_DOMAIN=ghe.example.com
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, 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], [pytorch-mps] (Apple-GPU memory-embedder offload — set HEADROOM_EMBEDDER_RUNTIME=pytorch_mps). 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.
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.
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
uv sync --extra dev && uv run 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.