context-guru

Provider-agnostic context engineering for LLM agents: a Go library that shrinks the tokens a request carries — losslessly, or lossy-but-reversible — without touching the agent. Same core runs as an HTTP proxy/gateway or an in-process plugin.

• Fail open, always — any component error/panic reverts that component only; the original request is always a valid fallback.
• Never worse — a component that grows the request is reverted.
• Reversible — every lossy drop leaves a <<cg:HASH>> marker and stashes the original, recoverable via a model-callable context_guru_expand tool or GET /expand.

Architecture

flowchart LR
  A[Agent] -->|chat request| H{Host adapter}
  H -->|proxy: proxy.Handler| P[apply.Body]
  H -->|in-process: AuthBridge plugin| P
  P -->|messages array| PIPE[Pipeline<br/>ordered components]
  PIPE --> P
  P -->|byte-lossless splice| UP[Upstream provider]
  UP -->|response| EX[expand loop]
  EX -->|resolve markers from Store| UP
  EX --> A
  PIPE -.per-component Report.-> M[Emitter / Aggregator]
  PIPE -.stash originals.-> S[(Store<br/>TTL+LRU)]
  EX -.resolve.-> S

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Components implement one of two lossiness-typed interfaces and are stacked in config order:

flowchart TD
  C["Component — Name() · Enabled(ctx)"]
  C --> R["Reformat: lossless repack<br/>format · cacheinject"]
  C --> O["Offload: drop + stash, returns cache_keys<br/>skeleton · dedup · collapse · failed_run<br/>cmdfilter · extract · smartcrush · mask · phi_evict"]

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Install

Requires Go 1.26 and a C toolchain (CGO_ENABLED=1; the skeleton component uses tree-sitter via cgo). The module pins bifrost with a local replace to ../bifrost/core, so build from the parent directory that holds both repos:

cd .../context-engineering            # dir containing lab-context-engineering/ and bifrost/
CGO_ENABLED=1 go build -o bin/context-guru-proxy \
  ./lab-context-engineering/cmd/context-guru-proxy

Or build the gateway image (see docs/setup.md):

docker build -f lab-context-engineering/Dockerfile -t context-guru:local .

Run the proxy

context-guru-proxy --preset balanced          # or --config cg.yaml

Point any agent at it (one port serves both dialects):

ANTHROPIC_BASE_URL=http://localhost:4000/anthropic
OPENAI_BASE_URL=http://localhost:4000/openai/v1

Flag / env	Default	Purpose
--preset / PRESET	balanced	pipeline preset when no --config
--config / CONFIG	—	YAML config (overrides preset)
LISTEN_ADDR	:4000	listen address
--openai-upstream / OPENAI_UPSTREAM	https://api.openai.com	OpenAI upstream base
--anthropic-upstream / ANTHROPIC_UPSTREAM	https://api.anthropic.com	Anthropic upstream base
OPENAI_API_KEY / ANTHROPIC_API_KEY	—	real key injected on forward (gateway mode); empty = pass client auth through
FORCE_MODEL	—	overwrite the request model (eval-containers EVAL_MODEL)

Routes: POST /openai/v1/chat/completions, POST /anthropic/v1/messages, GET /healthz, GET /stats (savings rollups), GET /expand?id= (recover an offloaded original). Per-request: header x-context-guru-session sets the session key; x-context-guru-bypass: true skips the pipeline.

Integrate

Option	What	Where
Proxy / gateway	context-guru-proxy in front of the provider; the eval-containers gateway image	proxy/, cmd/context-guru-proxy/
In-process plugin	AuthBridge (Kagenti sidecar) plugin importing this module, running the same pipeline on pctx.Body	plugin lives in kagenti-extensions; reuses apply.Body + expand/
(also) bifrost LLMPlugin	run the pipeline as a PreRequestHook inside any bifrost deployment	adapters/bifrost/

Details in docs/integrations.md.

Docs

• docs/design.md — architecture: component model, fail-open pipeline, store, session, expand loop, metrics.
• docs/components.md — every registered component: how it works, before→after, lossiness, config, best use.
• docs/integrations.md — proxy gateway vs AuthBridge plugin, with request paths.
• docs/setup.md — setup + a concrete SWE-bench run through the eval-containers gateway.
• docs/RESULTS.md — per-component SWE-bench benchmark (Claude Code, claude-sonnet-4-6): mask ≈27% token savings, no reward loss.

License

Apache-2.0. See LICENSE.