Files
codegraph/.cursor/rules/codegraph.mdc
T
b48170e69f feat(mcp): per-file staleness banner + tunable watcher debounce (#403) (#428)
Two coupled changes addressing the issue's underlying ask — "how does the
agent know when the index lags" — without resorting to a static wait.

Per-file staleness banner
-------------------------
FileWatcher now tracks per-path `pendingFiles` (path, firstSeenMs,
lastSeenMs, indexing) — events since the last successful sync, cleared
only after a sync whose `syncStartedMs >= lastSeenMs` commits. Chokidar
initial-scan events are gated behind a `ready` flag (with `waitUntilReady()`
exposed so tests can deterministically wait through it) so a fresh startup
doesn't falsely flag every existing file as pending.

ToolHandler now wraps every code-returning response (search, context,
callers, callees, impact, trace, explore, node, files) with
`withStalenessNotice`: intersects "files referenced in the response" with
`getPendingFiles()` and emits a hybrid signal —

  * banner at the top for files referenced AND pending (with edit age +
    indexing/pending-sync state, telling the agent to Read those specific
    files directly; the rest of the response stays fresh and codegraph
    stays authoritative for it),
  * compact footer for pending files elsewhere in the project not
    referenced above (capped at 5).

Cost is one boolean check + N substring matches when pending; zero
allocation when idle. `codegraph_status` surfaces the same data as a
first-class `### Pending sync:` section so the agent can ask "is the index
caught up?" in one call.

Cross-project quirk: when an agent passes `projectPath` matching the
default session's project, the staleness wrapper switches from the cached
cross-project CodeGraph (no watcher) to the default one (with watcher) so
the signal still fires. Same fix applied to `handleStatus`.

CODEGRAPH_WATCH_DEBOUNCE_MS
---------------------------
MCP `serve --mcp` now reads `CODEGRAPH_WATCH_DEBOUNCE_MS` and forwards it
to `cg.watch({ debounceMs })`. Clamped to [100ms, 60s]; out-of-range or
non-numeric values fall back to the FileWatcher default (2000ms). Active
value is logged to stderr on watcher startup so it's discoverable. The
docs in `server-instructions.ts`, `installer/instructions-template.ts`,
and `.cursor/rules/codegraph.mdc` no longer claim "~500ms"; they now
describe the banner mechanism instead — since per-file staleness replaces
the "wait N ms" guidance entirely, the docs become accurate at any
debounce value.

Validation
----------
* 847 unit/integration tests pass (added 15 new ones — pending-file
  tracking, banner/footer routing, status section, env-var parsing).
* Direct MCP probe through a real `codegraph serve --mcp` process: edit a
  file, query within the debounce window, banner fires naming the
  edited file with edit-age.
* Real Claude TUI session via `scripts/agent-eval/itrun.sh` with
  `CODEGRAPH_WATCH_DEBOUNCE_MS=10000`: agent edits `math.ts`, calls
  `codegraph_explore`, reads the banner, **and discloses it unprompted in
  its final reply**: "note: symbol index is mid-sync for the new `divide`,
  but the source it returned is verbatim from disk."

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-25 23:48:10 -05:00

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---
description: CodeGraph MCP usage guide — when to use which tool
alwaysApply: true
---
<!-- CODEGRAPH_START -->
## CodeGraph
This project has a CodeGraph MCP server (`codegraph_*` tools) configured. CodeGraph is a tree-sitter-parsed knowledge graph of every symbol, edge, and file. Reads are sub-millisecond and return structural information grep cannot.
### When to prefer codegraph over native search
Use codegraph for **structural** questions — what calls what, what would break, where is X defined, what is X's signature. Use native grep/read only for **literal text** queries (string contents, comments, log messages) or after you already have a specific file open.
| Question | Tool |
|---|---|
| "Where is X defined?" / "Find symbol named X" | `codegraph_search` |
| "What calls function Y?" | `codegraph_callers` |
| "What does Y call?" | `codegraph_callees` |
| "How does X reach/become Y? / trace the flow from X to Y" | `codegraph_trace` (one call = the whole path, incl. callback/React/JSX dynamic hops) |
| "What would break if I changed Z?" | `codegraph_impact` |
| "Show me Y's signature / source / docstring" | `codegraph_node` |
| "Give me focused context for a task/area" | `codegraph_context` |
| "See several related symbols' source at once" | `codegraph_explore` |
| "What files exist under path/" | `codegraph_files` |
| "Is the index healthy?" | `codegraph_status` |
### Rules of thumb
- **Answer directly — don't delegate exploration.** For "how does X work" / architecture questions, answer with 2-3 codegraph calls: `codegraph_context` first, then ONE `codegraph_explore` for the source of the symbols it surfaces. For a specific **flow** ("how does X reach Y") start with `codegraph_trace` from→to — one call returns the whole path with dynamic hops bridged — then ONE `codegraph_explore` for the bodies; don't rebuild the path with `codegraph_search` + `codegraph_callers`. Codegraph IS the pre-built index, so spawning a separate file-reading sub-task/agent — or running a grep + read loop — repeats work codegraph already did and costs more for the same answer.
- **Trust codegraph results.** They come from a full AST parse. Do NOT re-verify them with grep — that's slower, less accurate, and wastes context.
- **Don't grep first** when looking up a symbol by name. `codegraph_search` is faster and returns kind + location + signature in one call.
- **Don't chain `codegraph_search` + `codegraph_node`** when you just want context — `codegraph_context` is one call.
- **Don't loop `codegraph_node` over many symbols** — one `codegraph_explore` call returns several symbols' source grouped in a single capped call, while each separate node/Read call re-reads the whole context and costs far more.
- **Index lag — check the staleness banner, don't guess a wait.** When a codegraph response starts with "⚠️ Some files referenced below were edited since the last index sync…", the listed files are pending re-index — Read those specific files for accurate content. Files NOT in that banner are fresh and codegraph is authoritative for them. `codegraph_status` also lists pending files under "Pending sync".
### If `.codegraph/` doesn't exist
The MCP server returns "not initialized." Ask the user: *"I notice this project doesn't have CodeGraph initialized. Want me to run `codegraph init -i` to build the index?"*
<!-- CODEGRAPH_END -->