code-context-gate

An MCP server that acts as a context-aware code retrieval broker for AI coding agents. It sits between the agent and your codebase, enforcing backpressure so the agent never receives more context than it can use.

Why use it?

Without a gate, AI agents call raw grep/find/cat on source files. On a large codebase that means:

• A single broad search returns 800 lines from 60 files — flooding the context window
• Irrelevant comments, tests, and vendored code push the signal out of the model's attention
• There is no token budget, no relevance ranking, and no guidance on how to narrow a bad query

code-context-gate solves this with four disciplined tools that rank, gate, and budget every result before it reaches the agent. Over-broad queries get a structured refine refusal with a per-directory hit distribution and actionable suggestions — so the next call is deterministic.

Relationship to codebase-memory-mcp

code-context-gate can connect to a graph backend (codebase-memory-mcp or codegraph) for semantic symbol lookup and architecture overviews. But the gate's core value — ranking, backpressure, token budgeting, block expansion — is its own, independent of any graph backend. Even with --graph-backend none, it outperforms raw file access on any codebase where result volume is a concern.

codebase-memory-mcp     ← semantic understanding (what code MEANS)
        ↑ consumed by
code-context-gate       ← budget discipline (HOW MUCH reaches the agent)
        ↑ consumed by
AI agent

How it works

Every tool call flows through the same pipeline:

Tool call (locate / read / explore / search)
  └─ Dispatcher         — routes by query shape (symbol → graph, phrase → merge, pattern → fileio)
       ├─ Graph adapter  — codebase-memory-mcp or codegraph (optional)
       └─ FileIO adapter — async line-by-line file scan with gitignore support
            └─ Shaper   — BM25 lexical scoring + kind weighting → ranked ResultItem[]
                 └─ Gatekeeper — enforces maxFiles / maxHits / maxTokens / minRelevance
                      └─ OkEnvelope  (results fit budget)
                      └─ RefineEnvelope  (too broad — includes distribution + suggestions)

Query shape routing in the dispatcher:

Installation

npx code-context-gate --project-root /path/to/your/project

Or install globally:

npm install -g code-context-gate
code-context-gate --project-root .

MCP Configuration

Add to your MCP client config (e.g. Claude Desktop claude_desktop_config.json or Claude Code .mcp.json):

{
  "mcpServers": {
    "code-context-gate": {
      "command": "npx",
      "args": ["code-context-gate", "--project-root", "/path/to/project"]
    }
  }
}

With a graph backend

{
  "mcpServers": {
    "code-context-gate": {
      "command": "npx",
      "args": [
        "code-context-gate",
        "--project-root", "/path/to/project",
        "--graph-backend", "codebase-memory-mcp"
      ]
    }
  }
}

CLI flags

Project root resolution order

1. --project-root CLI flag
2. CODE_CONTEXT_GATE_ROOT environment variable
3. process.cwd() — the working directory of the process that launched the server

For stdio-mode MCP clients (Claude Code CLI, Cursor, etc.) option 3 already points at the correct project root. For GUI clients (Claude Desktop) set the env var in your MCP config:

{
  "mcpServers": {
    "code-context-gate": {
      "command": "npx",
      "args": ["code-context-gate"],
      "env": { "CODE_CONTEXT_GATE_ROOT": "/path/to/your/project" }
    }
  }
}

Tools

locate — find where something lives

Returns file paths and line ranges only — no source bodies. Use first, before read.

{ "query": "OrderHandler", "kind": "definition", "scope": "src/" }

read — get the actual source

Reads a symbol by name or an explicit file:start-end range. Block-expands to enclosing function/class boundaries. Size-bounded so a single call never dumps an entire file.

{ "target": "OrderHandler.handle" }
{ "target": "src/payments/OrderHandler.ts:142-179", "expand": false }
{ "target": "src/config.ts" }

search — keyword or regex search

The sanctioned replacement for grep. Always ranked, gated, and token-budgeted.

{ "pattern": "PathDeniedError", "scope": "src/" }
{ "pattern": "export.*function", "regex": true, "max_hits": 20 }

explore — understand structure and relationships

Answers structural questions: callers, callees, dependencies, blast radius, architecture overview. Requires a graph backend for full results; falls back to a file scan summary when no graph is available.

{ "question": "what calls resolveSafe", "anchor": "resolveSafe", "relation": "callers" }
{ "question": "overview of the payments module", "relation": "overview" }
{ "question": "what would break if I change UserSession", "relation": "impact" }

Backpressure

When a query is too broad, tools return a refine envelope instead of overwhelming the agent:

{
  "status": "refine",
  "reason": "breadth",
  "summary": { "totalFound": 340, "files": 48, "estTokens": 28000, "topScore": 0.21 },
  "distribution": [
    { "dir": "src/auth", "hits": 120 },
    { "dir": "src/core", "hits": 80 }
  ],
  "suggestions": [
    { "action": "narrow_scope", "arg": "src/auth", "wouldYield": 120 },
    { "action": "use_force", "hint": "Set force:true to bypass gating" }
  ],
  "refusalCount": 1
}

Refusal reasons:

Deadlock cap: after maxRefusals (default 3) consecutive refusals, the gate opens automatically. Compound margin: single-axis near-misses within 15% of a threshold pass through without refusal.

Config file

Place a JSON file anywhere and pass it with --config:

{
  "gates": {
    "maxFiles": 25,
    "maxHits": 120,
    "maxTokens": 6000,
    "minRelevance": 0.35
  },
  "scan": {
    "excludeDirs": ["node_modules", "dist", ".git"],
    "respectGitignore": true
  }
}

Full config schema (all fields optional — shown with defaults):

{
  "gates": {
    "maxFiles": 25,
    "maxHits": 120,
    "maxTokens": 6000,
    "minRelevance": 0.35,
    "compoundMargin": 0.15
  },
  "limits": {
    "maxRefusals": 3,
    "absoluteMaxTokens": 24000
  },
  "estimation": {
    "charsPerToken": 3.5
  },
  "scoring": {
    "weights": {
      "kind": 0.30,
      "lexical": 0.25,
      "proximity": 0.20,
      "shape": 0.15,
      "recency": 0.10
    }
  },
  "backend": {
    "graph": "codebase-memory-mcp"
  },
  "scan": {
    "excludeDirs": ["node_modules", "dist", "build", "target", ".venv", "vendor", ".git"],
    "respectGitignore": true
  }
}

Logging

All tool activity is written as newline-delimited JSON to code-context-gate.log in the project root. Pass --debug to also stream logs to stderr.

Log events

Reading the log

A typical symbol lookup with graph hit:

{"ts":"...","event":"tool_call","tool":"locate","args":{"query":"resolveSafe","kind":"definition"}}
{"ts":"...","event":"dispatch","query":"resolveSafe","shape":"symbol","graphAvailable":true}
{"ts":"...","event":"graph_search","backend":"codebase-memory-mcp","count":2}
{"ts":"...","event":"dispatch_result","query":"resolveSafe","strategy":"graph_symbol","count":2}
{"ts":"...","event":"gate","tool":"locate","pass":true,"reason":null}
{"ts":"...","event":"tool_result","tool":"locate","returned":2}

A broad search that triggers a refusal:

{"ts":"...","event":"tool_call","tool":"search","args":{"pattern":"export"}}
{"ts":"...","event":"dispatch","query":"export","shape":"symbol","graphAvailable":true}
{"ts":"...","event":"graph_search","backend":"codebase-memory-mcp","count":148}
{"ts":"...","event":"dispatch_result","query":"export","strategy":"graph_symbol","count":148}
{"ts":"...","event":"gate","tool":"search","pass":false,"reason":"breadth"}
{"ts":"...","event":"tool_result","tool":"search","returned":0}

Source structure (src/)

Result scoring

Each result gets a composite score before ranking:

score = kindScore × 0.30 + BM25lexical × 0.25 + graphScore × 0.45

Kind weights:

Graph backends

Both graph backends are optional. Without one, all four tools work using FileIO only.

Agent Instructions (CLAUDE.md)

This repo ships a CLAUDE.md that Claude Code and compatible agents load automatically. It routes all code discovery through code-context-gate and prohibits direct calls to lower-level tools like codebase-memory-mcp.

When an agent session starts it first probes code-context-gate with a lightweight locate call:

• Server responds → the four tools are used for all code access
• Server unavailable → the agent stops and prompts the user to enable code-context-gate or re-enable the cbm-session-reminder fallback hook

Re-enabling the fallback hook

If you want agents to fall back to raw codebase-memory-mcp calls when code-context-gate is not running, add to ~/.claude/settings.json:

{
  "hooks": {
    "SessionStart": [
      { "matcher": "startup", "hooks": [{ "type": "command", "command": "~/.claude/hooks/cbm-session-reminder" }] },
      { "matcher": "resume",  "hooks": [{ "type": "command", "command": "~/.claude/hooks/cbm-session-reminder" }] },
      { "matcher": "clear",   "hooks": [{ "type": "command", "command": "~/.claude/hooks/cbm-session-reminder" }] },
      { "matcher": "compact", "hooks": [{ "type": "command", "command": "~/.claude/hooks/cbm-session-reminder" }] }
    ]
  }
}

Requirements

• Node.js 20+
• No native build tools required

License

MIT © 2026 wisdom rock — see LICENSE for full text.