witan-code 0.2.1

witan-code — tree-sitter code graph + cross-repo bridge (mounts under `witan code`)

witan-code

"witan" is pronounced WIT-ən (/ˈwɪtən/) — rhymes with "written" minus the r.

A tree-sitter-based code graph MCP server (Layer 2) for coding agents, backed by Omnigraph. It indexes a repository's symbols (functions, methods, classes, modules) and their relationships, then exposes definition / reference / caller / impact queries to the agent.

It is a self-contained sibling of witan (Layer 1) and shares its subprocess/CLI conventions, but stores a separate, per-repo, local-only graph.

Wiring it into your agents locally (MCP server, the PostToolUse reindex hook, and the indexer CLI, run straight from your checkout): see Local Development Setup.

When to use this vs. grep / the Explore agent

Reach for code_* tools when the question is structural, not textual: exact symbol definitions, who calls/references a symbol (and transitively — change-impact / blast radius before an edit), what a file defines, or which other repo provides/consumes a shared contract (env var, endpoint, package, service). Grep still wins for literal string/comment searches and one-off text matches — it finds text; this finds symbols and their relationships, including things grep structurally cannot answer (a function's transitive callers, or which service consumes an endpoint another service serves). See the /witan-code skill for a full tool-selection guide and reference table.

Calls/References/Imports/Inherits edges are heuristic (syntactic name resolution, not a true call graph) — see Heuristic edges below.

Two-layer composition

Layer	Server	Stores	Scope	Synced
1	witan	patterns, project facts, lessons, workflow traces	team-wide	yes (S3)
2	witan-code	code symbols + edges	per-repo	no — local only

The two layers compose through soft symbol-ID references. A Layer-1 node (e.g. a lesson or agent_context) can record symbol ids of the form:

repo#relative/path.py::QualifiedName
e.g. https://github.com/mitodl/ol-django#app/svc.py::Service.run

in a symbolRefs-style field. There is no hard cross-store edge: the id is just a string that resolves in the code graph via code_find_definition / get_symbol. This keeps the team-synced memory graph independent of any machine's local code index.

Documentation

• User guide — task-oriented walkthrough: install, first index, definition/caller/impact queries, cross-repo bridge basics, troubleshooting.
• CLI reference — every witan-code command with its full flag table and an example invocation.

Cross-repo context bridge (Layer 2.5)

The per-repo graph stops at a repo boundary, but service-oriented architectures couple repos through shared contracts: an env var that infra sets and an app reads, an HTTP endpoint one service serves and another calls, a package one repo publishes and others import. The bridge records these as interface bindings in a single shared, local-only store (_bridge.omni, a sibling of the per-repo stores) so linkages can be queried across every indexed repo.

It is zero-config: every index/reindex of a repo also extracts that repo's bindings into the bridge store. Linkages are then computed by grouping bindings on (kind, key_norm) — no registry of repos to maintain, no link edges.

Four binding kinds (all extraction is heuristic/syntactic, like the symbol edges):

Kind	Provider	Consumer	Join key
env_var	Pulumi <app>:env_vars keys in Pulumi.*.yaml	get_string("NAME",…) / os.environ / process.env.X / env("NAME")	the UPPER_SNAKE name
endpoint	drf-spectacular OpenAPI spec (paths.<path>.<method>)	/api/… path literals in TS (generated client / fetch)	normalized path (params → {})
package	a repo whose package.json name is @mitodl/*	from mitol.* / include("mitol.*") / @mitodl/* imports	the package name
service	applications/<svc>/__main__.py (repo / image / service name)	the deployed repo itself (key_norm = its canonical URI)	repo:<uri> / image:… / name:…

Generic env names (DEBUG, PORT, SECRET_KEY, …) are flagged generic and excluded from cross-repo impact fan-out so a trivial edit doesn't appear to touch every repo.

The bridge is written in a separate phase after the per-repo store write, so the two stores' advisory write locks never nest (no deadlock) and a bridge failure never corrupts a per-repo store. A full-repo index runs the repo-level provider extractors (OpenAPI / Pulumi / service / package.json) and clears bindings for files deleted from disk; all purging is per-file, so unchanged (skipped) files — and, for a narrow target like the reindex hook, sibling files — keep their bindings.

Every binding also carries a canonical symbol string ({scheme}:{manager}:{package}:{version}:{descriptor}, SCIP-inspired) — the join key for the precise cross-repo linking tier. Provider symbols are qualified by the repo's declared package identity from an optional witan-code.toml at the repo root; repos without one get a fallback identity derived from the repo URI. See docs/SYMBOL_FORMAT.md and docs/PACKAGE_MAP.md.

Each bridge write also rebuilds the repo's symbol table — one RepoSymbol row per (repo, role, symbol): exported rows are the repo's public contract surface, external rows are unresolved references to other repos' contracts. This deduplicated table is the Stage-2 read-time join artifact; inspect it with witan code symbols. See docs/SYMBOL_TABLE.md.

Stage 2 itself — joining external symbol references against other repos' exported symbols by canonical string, entirely at read time, never stored — is witan_code.stitch.resolve(). Inspect it with witan code stitch (--unresolved for indexing-coverage gaps) or the code_precise_edges / code_unresolved_symbols MCP tools. See docs/STAGE2_STITCHING.md.

Precise (Stage 2) and heuristic (Stage 3) edges are merged into one typed, precision-tiered result by witan_code.edges.cross_repo_edges(). Every tool that produces cross-repo links — witan code deps, code_interface_providers/_consumers/_search, code_cross_repo_impact — accepts min_precision ("precise" | "heuristic" | "fuzzy", default "heuristic" = current behavior unchanged). See docs/EDGE_PRECISION_TIERS.md.

Heuristic edges (important)

Defines and Contains are exact (derived from the syntax tree). But:

• Calls, References, Imports, and Inherits are HEURISTIC. They are produced by syntactic name resolution: a call/base/ import identifier is matched to a known Symbol name, preferring same-file definitions. Dynamic dispatch, re-exports, shadowing, and cross-file resolution beyond name matching are not modeled precisely.

Treat caller/impact results as a high-recall starting point for investigation, not a verified call graph.

Symbol id scheme

• CodeFile.id = repo#relative/path.py
• Symbol.id = repo#relative/path.py::QualifiedName (e.g. Class.method)

The repo key is the canonical HTTPS remote URI (https://github.com/org/repo, matching witan's repo.py), falling back to the git-root directory name when there is no remote.

Supported languages

Language	Extensions	Symbols extracted
Python	.py .pyi	functions, classes, methods, module
TypeScript / JS / JSX / TSX	.ts .tsx .mts .cts .js .jsx .mjs .cjs	functions, arrow consts, classes, methods (incl. arrow fields), interfaces, types, enums
Bash / Zsh	.sh .bash .zsh	functions
YAML	.yaml .yml	mapping keys as dotted paths (e.g. jobs.build.steps)

Each symbol also carries richer attributes for agent context: the full signature (name + multi-line params + return/param types), a docstring (Python docstrings and TS/JS /** … */ JSDoc), and decorators (@app.route(...), @task, @Input(), … — framework semantics that also feed the cross-repo bridge). These are returned by code_find_definition / code_search_symbol / code_symbols_in_file.

All JS/TS variants are parsed with the tsx grammar (a superset of TS, JS, and JSX) — the plain javascript grammar rejects the TS node types in the shared query. YAML indexes every mapping key as a navigable key symbol, so large config trees (CI, k8s, Pulumi) can be searched by path; expect many such symbols.

Grammars come from individual tree-sitter-<lang> wheels (e.g. tree-sitter-python), loaded as standalone tree_sitter.Languages — not tree-sitter-language-pack (whose 1.9 line returns an incompatible binding and downloads grammars on demand). Adding a language means: add its tree-sitter-<lang> wheel to pyproject.toml (tight-pinned), add an entry to indexer._GRAMMAR_MODULES (grammar name → module + capsule factory), add one LanguageSpec (extensions + grammar name + a queries_ts/<lang>.scm capture file + a capture→kind map), and any new node types to _DEF_NODE_TYPES.

Not indexed yet (from a file-type survey of ol-infrastructure + mit-learn)

• HCL / Terraform / Packer (.hcl, .tf) — the strongest candidate to add next (~50 files in ol-infrastructure); grammar is available and blocks map to symbols (variable.x, source.amazon-ebs.caddy, resource.<type>.<name>).
• VCL (Varnish/Fastly, .vcl) — no published tree-sitter-vcl wheel, so it can't be added without vendoring/building one.
• Markdown (.md/.mdx) — could index headings as a doc outline, but adds low-signal symbols; left out for now.
• Config/markup (.json, .toml, .ini, .scss, .html, .j2) is not symbol-bearing enough to index. Go/Rust grammars exist but neither repo uses them.

Install

witan-code is usually installed as part of the witan umbrella — witan setup wires both servers together via uvx --from … --with …. See the witan README for the one-step setup.

To use witan-code standalone (code graph only, no memory/task tools):

From PyPI:

# One-shot (uvx):
uvx --from witan-code witan-code index

# Persistent CLI install:
uv tool install witan-code
witan-code index

From the published git repo (to track pre-release/unreleased code):

# One-shot (uvx):
uvx --from git+https://github.com/mitodl/agent-kit#subdirectory=mcp/servers/witan-code \
    witan-code index

# Persistent CLI install:
uv tool install git+https://github.com/mitodl/agent-kit#subdirectory=mcp/servers/witan-code
witan-code index

From a local checkout (inside mcp/servers/witan-code/):

uvx --from . witan-code index          # incremental
uvx --from . witan-code reindex        # force rebuild
uvx --from . witan-code index path/to/file.py   # single file/subpath

# Or via uv run:
uv run witan-code index

Full standalone install: witan-code setup installs everything a witan-code-only deployment needs — the omnigraph binary, the /witan-code skill, all four hooks (or the Pi extension), and the MCP server entry — for one agent or all detected ones:

witan-code setup                    # Claude Code (default)
witan-code setup --agent pi         # Pi
witan-code setup --agent all        # every detected agent
witan-code setup --dry-run          # preview without writing
witan-code setup --author "Jane Doe"  # attribution (default: git config user.name)

If witan is also installed and witan-code is importable in that same environment (e.g. via the --with in the uv tool install/MCP server's uvx invocation), witan setup folds this same bundle in automatically — skill and hooks (registered as witan code …, so only witan needs to be on PATH), but not a second MCP server entry, since witan serve already mounts witan-code's tools in-process. One witan setup then covers both packages, and a separate witan-code setup isn't required (though re-running it afterwards is harmless — apply() is an idempotent read-merge-write, and it will add its own standalone MCP entry/witan-code … hooks alongside witan's). Run witan-code setup on its own for a witan-code-only install, or when witan-code isn't importable from witan's environment. See Hooks and Skill.

This downloads the omnigraph release pinned by _OMNIGRAPH_VERSION in witan_code/setup.py — the same pin witan's own setup.py uses, kept in lockstep by Renovate (see the repo-root renovate.json's omnigraph-version customManager, which bumps both files in one PR). There is no build-time bundling of the binary into the wheel — witan-code setup (or witan setup) is the only source of the binary, and re-running it is how you pick up a version bump.

Per-repo stores are created lazily on the first index — the indexer runs omnigraph init --schema code-schema.pg <store> when the store is missing. The ./install.sh script only verifies the omnigraph binary (installing the latest upstream release directly if missing, independent of the witan-code setup/_OMNIGRAPH_VERSION pin) and prints a hint; it is not required when installing via uvx/uv.

Manual / unsupported-agent install: for an agent witan-code setup doesn't cover, copy the appropriate MCP snippet from config/ into your agent's config, and see Hooks/Skill for the manual symlink alternative:

• pi: config/pi.json → ~/.pi/agent/mcp.json
• Claude: config/claude.json → claude_desktop_config.json
• Copilot: config/copilot.json → .vscode/mcp.json

Environment variables

Variable	Default	Purpose
WITAN_CODE_DIR	~/.local/share/witan/code	directory of per-repo <slug>.omni stores
WITAN_AUTHOR / USER	unknown	attribution string
WITAN_REPO	—	override the detected repo slug
WITAN_CODE_OPTIMIZE_INTERVAL	86400 (daily)	throttle window (seconds) for checkpoint's opportunistic store compaction; 0 disables it

The store URI for a repo is <dir>/<sanitized-slug>.omni, where the slug's / and : are replaced with _. The shared cross-repo bridge lives alongside them at <dir>/_bridge.omni and is created lazily on the first index that yields any bindings.

MCP tools

Each tool resolves the per-repo store from the current working directory and returns [] / null gracefully when the store does not exist yet (run the indexer first).

Tool	Returns
code_find_definition(name)	symbols whose name / qualified name matches
code_find_references(symbol_id)	incoming References + Calls
code_callers(symbol_id)	incoming Calls
code_impact(symbol_id, max_depth=5, max_nodes=200)	transitive callers via BFS
code_symbols_in_file(path)	symbols defined in a file
code_search_symbol(query)	BM25 search over symbol qualified names
code_reindex(path=None)	index/re-index the repo or a subpath

Cross-repo bridge tools (resolve the shared _bridge.omni store; return [] / an empty shape when it does not exist yet). When the current checkout is on a non-default git branch with in-flight bindings, these auto-detect and read that repo's bridge branch overlay instead of main — see docs/BRANCH_INDEXING.md § Bridge store:

Tool	Returns
code_interface_providers(kind, key)	repos that provide a contract (env_var/endpoint/package/service)
code_interface_consumers(kind, key)	repos that consume it (endpoint keys are normalized from raw paths)
code_cross_repo_impact(symbol_id)	the symbol's own bindings + every binding for those same contracts in other repos
code_interface_search(query, kind=None)	BM25 search over interface bindings by normalized key

CLI

witan-code (cyclopts); also available as witan code … when witan-code is installed alongside witan:

• setup [--dry-run] — fetch the pinned omnigraph binary to ~/.local/bin/ for standalone use (see Install).
• index [PATH] — incremental; skips files whose content hash is unchanged.
• reindex [PATH] — force rebuild a path.
• repos — list all indexed repos with file count, symbol count, and store size.
• branches [--prune] — list omnigraph branches per store; --prune deletes the current repo's store branches whose git branch is gone (plus _detached). Non-default git branches index onto same-named omnigraph branches so in-flight work never overwrites the shared main view — see docs/BRANCH_INDEXING.md.
• deps [--kind K] [--repo SUBSTR] [--html PATH] [--open-browser] — visualize cross-repo dependencies from the bridge store. Prints a Rich summary of "repo A depends on repo B" links (A consumes a contract B provides; for service, the deploying repo depends on what it deploys) and, with --html, writes a self-contained interactive force-directed graph (click an edge to list the individual linkages — env vars, endpoints, packages, deployed repos — behind it). Defaults to a repos-only view; --kind filters to one contract kind and --repo keeps only links touching a matching repo.
• session-init — seed/refresh the whole repo's code graph in the background (see Hooks); registered as the SessionStart hook, not usually run by hand.
• reindex-hook — incrementally reindex the file named in stdin's hook JSON (see Hooks); registered as the PostToolUse hook, not usually run by hand.
• inject-context — print the UserPromptSubmit status block (see Hooks); registered as the UserPromptSubmit hook, not usually run by hand.
• optimize [--store PATH] [--bridge] — compact a store's Lance fragments (non-destructive; see Store compaction). Defaults to the current repo's store; --bridge targets the shared bridge store instead.
• cleanup [--store PATH] [--bridge] [--keep N] [--older-than DUR] --yes — reclaim disk by GC'ing old Lance versions (destructive; requires --yes).
• checkpoint — opportunistically compact the current repo's store and the bridge store if due (see Hooks); registered as the Stop hook, not usually run by hand.

Both print a summary: files scanned/indexed/skipped, symbols, edges, errors. A parse failure on one file logs to stderr and continues.

Store compaction

Every load()/mutate() call (indexing) appends a new tiny Lance fragment + manifest version to a store; left uncompacted, it bloats until opening the store dominates query latency, regardless of row count — the same failure mode witan's own store hit (PR #98; see witan/witan/maintenance.py). Two mechanisms keep this in check, mirroring that module (deliberately duplicated — no cross-package import):

• Opportunistic: the witan-code checkpoint Stop hook spawns a throttled, detached witan-code optimize for the current repo's store and the shared bridge store, at most once per WITAN_CODE_OPTIMIZE_INTERVAL (default daily; 0 disables) each — see Hooks.
• Scheduled: witan-code optimize [--store PATH | --bridge] / witan-code cleanup --yes for cron/systemd-timer driven maintenance on a busy store. optimize is non-destructive and safe to run repeatedly; cleanup GCs old Lance versions to reclaim disk and is destructive, so it requires --yes.

Skill

witan_code/skills/witan-code/SKILL.md is a /witan-code entry point covering tool selection (vs. grep/Explore), a quick tool reference, and linking symbol ids into witan tasks/memories. Installed automatically by witan-code setup (to ~/.claude/skills/, or ~/.pi/agent/skills/ under --agent pi); to install it manually instead, symlink or copy the directory into the equivalent path for your agent.

Hooks

Four hooks — all bare CLI commands, no wrapper scripts, so they're portable to any platform witan-code installs on (Windows included — no bash/setsid dependency). Named witan-code <command> below (standalone install via witan-code setup); when witan setup folds this bundle in instead (see Install), they register as witan code <command> so only witan needs to be on PATH. Register manually per configs/hooks/README.md for either form. A Pi equivalent of all four lives in one extension, witan_code/extensions/pi/codegraph.ts (see configs/pi/README.md):

• witan-code session-init (SessionStart) — seeds/refreshes the whole repo in the background on session start (first run builds the full index; later runs re-hash and skip unchanged files). Detaches a background child and returns immediately; never delays session start. A per-repo lock (${TMPDIR:-/tmp}/codegraph-init-<sha256(project_dir)[:16]>.lock, released by the detached child when it finishes) prevents overlapping sessions from indexing at once — hashed rather than a sanitized path so two distinct paths can't collide on the same lock and a long checkout path can't exceed a filesystem's filename length limit.
• witan-code reindex-hook (PostToolUse, matcher Edit|Write) — reads the tool payload from stdin and incrementally re-indexes the changed file in the foreground (fast — one file). Best-effort — a missing/malformed payload or parse failure is a silent no-op, never interrupting the agent.
• witan-code inject-context (UserPromptSubmit) — prints a short status block: whether the current repo is indexed (file count, last-updated time), or that a background index from session-init is still running (checking the same lock path above), plus a nudge to prefer code_* tools over grep. Independent of witan's own inject-context hook (no cross-package coupling) — register it alone for a witan-code-only install. Prints nothing when the repo has neither a store nor an index in flight.
• witan-code checkpoint (Stop) — spawns a throttled, detached witan-code optimize for the current repo's store and the shared bridge store if either is due (see Store compaction). Independent of witan's own session-checkpoint hook (no cross-package coupling). Best-effort and non-blocking.

Manual install: register the bare commands directly under the matching event in settings.json (see the linked README for the exact JSON) — there are no scripts to symlink.

Incremental indexing

Each CodeFile stores a sha256 contentHash. On reindex, if the hash is unchanged the file is skipped. Otherwise its Symbols and CodeFile are deleted (as separate delete.gq calls — Omnigraph cannot mix deletes with inserts in one query) and then re-parsed and re-inserted.