Intent-Diff MCP

Catch context drift — the scope an AI coding agent quietly adds beyond what you actually asked for.

An MCP server with two tools. You lock in your original request; the agent, before it declares "done", diffs the actual code changes against that request and reports anything it added on its own — an unrequested library, a metrics layer, a new abstraction — so you can Keep it or Roll it back.

The diff is deterministic ground truth (git doesn't lie). The judgment is a fresh Claude call that didn't write the code, so it has no stake in rationalizing the additions.

🤖 Intent Diff Report

Requested: Add a Postgres connection pool in db.ts — ✅ done

[+] Added on my own (drift candidates):
- New metrics.ts with Prometheus instrumentation — you never asked for
  observability or a new dependency (prom-client).

[?] Worth confirming:
- Should metrics.ts stay, or be removed?

→ Keep or Rollback?

Tools

Related MCP server: Waymark

Install

Requires Node ≥ 18 and either a logged-in Claude Code session or an ANTHROPIC_API_KEY (see Auth).

Add to your MCP client config (Claude Code .mcp.json, mcporter.json, etc.):

{
  "mcpServers": {
    "intent-diff": {
      "command": "npx",
      "args": ["-y", "@ssh00n/intent-diff-mcp"]
    }
  }
}

That's the whole setup — npx fetches and runs it.

Recommended workflow (hybrid)

Intent-Diff is not meant to gate every edit — that just taxes trivial work. The sweet spot: always snapshot (cheap), judge on demand (costly). Drop this into your project's CLAUDE.md (a ready copy is in examples/CLAUDE.md):

# Intent-Diff workflow (hybrid)
- When starting a non-trivial feature or refactor, call `start_task` with the
  user's request verbatim. (It's cheap — just a git snapshot.)
- Before declaring a substantial change "done" — new feature, or edits spanning
  multiple files — run `get_intent_diff` and show the report.
- Treat the report as advisory: surface drift to the user and ask Keep/Rollback.
  Skip it for one-line fixes and pure exploration.

Prefer softer or stricter? See Tuning the rules.

Auth

The judge needs to call Claude. Two ways, checked in this order:

1. ANTHROPIC_API_KEY (recommended for CI and contributors) — normal API billing.

2. Local Claude Code subscription — if no API key is set, the server reuses the OAuth token your Claude Code login already stores (macOS Keychain or ~/.claude/.credentials.json), refreshing it when near expiry. No extra setup if you're already logged into Claude Code.

Pick the judge model with INTENT_DIFF_MODEL (default claude-sonnet-4-6).

Tuning the rules

The workflow above is the hybrid default. Adjust to taste:

• Softer — drop the get_intent_diff line; call it only when you ask "check drift". The agent self-checks the rest of the time.

• Stricter — make both calls mandatory ("always start_task first; never say done without get_intent_diff") and require an explicit Keep/Rollback answer. Good for team enforcement; higher overhead.

Note: a heavy-handed rule can bias an agent toward under-implementing (skipping necessary error handling for fear of "drift"). The judge is told to ignore refactors and necessary error handling, but keep the rule proportional to the stakes.

How it works

start_task writes <repo>/.mcp/intent_state.json, keyed by git branch, with your request and the HEAD SHA. get_intent_diff collects git diff <baseSha> plus any untracked files (skipping binaries, lockfiles, and .mcp/), caps it, and sends { original intent, actual diff } to the judge, which returns structured JSON that's rendered into the report.

Development

npm install
npm run typecheck    # tsc --noEmit
npm test             # Tier-1 unit tests (no network)
npm run test:smoke   # end-to-end via MCP client, stub judge (no network)
npm run eval         # judge accuracy over labeled fixtures (needs auth — real calls)

Contributing

Contributions welcome — see CONTRIBUTING.md. Good first areas: more judge fixtures, additional credential sources, non-git VCS support.

License

MIT © ssh00n