Stage 3c.2 PR3a. Walks any JSON value and applies lossless compaction
in place at every compactable spot (arrays of objects, stringified-
JSON cells, long opaque strings — anywhere in the tree). The wrapping
JSON structure is preserved; only bulky leaves get replaced.
# The whole algorithm
match value {
Object(m) => recurse into each field's value
Array(xs) => recurse into each item, then try TabularCompactor on the array
String(s) => parse-as-JSON-and-recurse / CCR-substitute / leave
scalar => unchanged
}
That's it. ~30 lines of core code. Recursive descent — the simplest
shape for "find compactable spots anywhere in a document."
# Why recurse-then-compact (not compact-then-recurse)
Walking children first means inner sub-tables / opaque markers are
already in their compacted form when the outer compact runs. Cascading
nesting becomes mechanical: a stringified-JSON cell turns into a
rendered string before the outer table sees it as a value. No
double-processing, no "compact in two passes" complexity.
# What gets compacted
- Array of objects with uniform-ish schema → CSV+schema string
- Stringified-JSON inside a string field → parse, recurse, replace
- Long opaque blobs (base64, HTML, long-string) → <<ccr:HASH,KIND,SIZE>>
marker, anywhere in the tree (not just inside table cells like PR2)
- Everything else → unchanged
# Public API (deliberately small)
DocumentCompactor::new() // OSS default
DocumentCompactor::with_formatter(f) // override formatter
DocumentCompactor::with_config(c) // override CompactConfig
.compact(doc) -> Value // walk + replace
compact_document(doc) -> Value // free-function shorthand
That's the whole surface. No new traits. No new IR. Reuses every PR2
primitive (compact, classify_cell, Formatter, opaque_kind handling).
# Tests
13 unit tests covering: top-level array, nested-in-object, deeply-
nested, stringified-JSON, top-level opaque, in-field opaque, pure-
scalar pass-through, mixed doc, cascading recursion (inner table
visible to outer compact), array-of-scalars pass-through, empty
container edges, malformed-JSON pass-through.
All 462 headroom-core lib tests pass (was 449 before PR3a).
17/17 SmartCrusher parity fixtures byte-equal (untouched).
185/185 Python tests pass.
make ci-precheck green.
# What this PR is NOT
- NOT a default-flip. SmartCrusher::new() still produces a
no-compaction crusher. DocumentCompactor is a separate entry point
for callers who explicitly want document-level walking.
- NOT a budget enforcer. PR3b adds document-level token budget +
selective lossy escalation when the lossless walk doesn't fit.
- NOT a SmartCrusher integration. crush_array operates on a single
array; this is a sibling primitive for whole-payload compaction.
Wiring SmartCrusher's compaction stage to use the walker (so
crush_array becomes a special case of "walk a document with a
single-array root") is a follow-up.
Module: crates/headroom-core/src/transforms/smart_crusher/compaction/walker.rs
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| .claude-plugin | ||
| .devcontainer | ||
| .github | ||
| benchmarks | ||
| crates | ||
| docker | ||
| docs | ||
| e2e | ||
| examples | ||
| headroom | ||
| plugins | ||
| scripts | ||
| sdk/typescript | ||
| sql | ||
| tests | ||
| wiki | ||
| .actrc | ||
| .actrc.local.example | ||
| .changelog.md | ||
| .commitlintrc.json | ||
| .dockerignore | ||
| .env.act.example | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitignore | ||
| .pre-commit-config.yaml | ||
| Cargo.lock | ||
| Cargo.toml | ||
| CHANGELOG.md | ||
| CODE_OF_CONDUCT.md | ||
| codecov.yml | ||
| CONTRIBUTING.md | ||
| deny.toml | ||
| docker-bake.hcl | ||
| docker-compose.yml | ||
| Dockerfile | ||
| Headroom-2.gif | ||
| headroom-savings.png | ||
| headroom_learn.gif | ||
| HeadroomDemo-Fast.gif | ||
| LICENSE | ||
| Makefile | ||
| mkdocs.yml | ||
| NOTICE | ||
| PR.md | ||
| pyproject.toml | ||
| README.md | ||
| rust-toolchain.toml | ||
| RUST_DEV.md | ||
| SECURITY.md | ||
| uv.lock | ||
Every tool call, log line, DB read, RAG chunk, and file your agent injects into a prompt is mostly boilerplate. Headroom strips the noise and keeps the signal — losslessly, locally, and without touching accuracy.
100 logs. One FATAL error buried at position 67. Both runs found it. Baseline 10,144 tokens → Headroom 1,260 tokens — 87% fewer, identical answer.
python examples/needle_in_haystack_test.py
Quick start
Works with Anthropic, OpenAI, Google, Bedrock, Vertex, Azure, OpenRouter, and 100+ models via LiteLLM.
Wrap your coding agent — one command:
pip install "headroom-ai[all]"
headroom wrap claude # Claude Code
headroom wrap codex # Codex
headroom wrap cursor # Cursor
headroom wrap aider # Aider
headroom wrap copilot # GitHub Copilot CLI
Drop it into your own code — Python or TypeScript:
from headroom import compress
result = compress(messages, model="claude-sonnet-4-5")
response = client.messages.create(model="claude-sonnet-4-5", messages=result.messages)
print(f"Saved {result.tokens_saved} tokens ({result.compression_ratio:.0%})")
import { compress } from 'headroom-ai';
const result = await compress(messages, { model: 'gpt-4o' });
Or run it as a proxy — zero code changes, any language:
headroom proxy --port 8787
ANTHROPIC_BASE_URL=http://localhost:8787 your-app
OPENAI_BASE_URL=http://localhost:8787/v1 your-app
Why Headroom
- Accuracy-preserving. GSM8K 0.870 → 0.870 (±0.000). TruthfulQA +0.030. SQuAD v2 and BFCL both 97% accuracy after compression. Validated on public OSS benchmarks you can rerun yourself.
- Runs on your machine. No cloud API, no data egress. Compression latency is milliseconds — faster end-to-end for Sonnet / Opus / GPT-4 class models than a hosted service round-trip.
- Kompress-base on HuggingFace. Our open-source text compressor, fine-tuned on real agentic traces — tool outputs, logs, RAG chunks, code. Install with
pip install "headroom-ai[ml]". - Cross-agent memory and learning. Claude Code saves a fact, Codex reads it back.
headroom learnmines failed sessions and writes corrections straight toCLAUDE.md/AGENTS.md/GEMINI.md— reliability compounds over time. - Reversible (CCR). Compression is not deletion. The model can always call
headroom_retrieveto pull the original bytes. Nothing is thrown away.
Bundles the RTK binary for shell-output rewriting — full attribution below.
How it fits
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 · …)
→ Architecture · CCR reversible compression · Kompress-base model card
Canonical pipeline lifecycle
Headroom now 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 still do the work: CacheAligner, ContentRouter, SmartCrusher, CodeCompressor, Kompress-base, IntelligentContext / RollingWindow.
- Pipeline extensions observe or customize those lifecycle stages via
on_pipeline_event(...). - Compression hooks still work and now sit alongside the canonical lifecycle instead of being the only extension seam.
- Proxy extensions remain the server/app integration seam for ASGI middleware, routes, and startup policy.
Provider slices
Provider and tool-specific behavior is being moved behind dedicated modules 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.pynow delegate provider-specific env shaping, API target normalization, backend selection, and transport dispatch instead of inlining those rules.
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
Community, live:
→ Full benchmarks & methodology
Built for coding agents
| Agent | One-command wrap | Notes |
|---|---|---|
| Claude Code | headroom wrap claude |
--memory for cross-agent memory, --code-graph for codebase intel |
| Codex | headroom wrap codex --memory |
Shares the same memory store as Claude |
| Cursor | headroom wrap cursor |
Prints Cursor config — paste once, done |
| Aider | headroom wrap aider |
Starts proxy, launches Aider |
| Copilot CLI | headroom wrap copilot |
Starts proxy, launches Copilot |
| OpenClaw | headroom wrap openclaw |
Installs Headroom as ContextEngine plugin |
MCP-native too — headroom mcp install exposes headroom_compress, headroom_retrieve, and headroom_stats to any MCP client.
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.
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), [agno], [langchain], [evals]. Requires Python 3.10+.
→ Installation guide — Docker tags, persistent service, PowerShell, devcontainers.
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 (not just CLI or text), 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 |
| 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→git show --short, noisyls→ scoped, chatty installers → summarized. Huge thanks to the RTK team; their tool is a first-class part of our stack, and Headroom compresses everything downstream of it.
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
- Live leaderboard — 60B+ tokens saved and counting.
- Discord — questions, feedback, war stories.
- Kompress-base on HuggingFace — the model behind our text compression.
License
Apache 2.0 — see LICENSE.