CodeTruth

A verification layer that lets AI agents safely delete code in large codebases.

Agents hallucinate absence of usage. CodeTruth inverts the question — instead of "is this code used?" it asks "can we prove this code is used?" — and only surfaces a symbol for deletion when it fails to find any usage path: no call, no import, no inheritance, no string reference, no reflection target, no framework registration. Detection is deterministic; the agent only reads the evidence and decides. It is a risk assessor for code deletion, not a dead code detector.

Statuses

Related MCP server: PrecisionContextEngine

Install

Requires Python 3.10+. The core is lightweight (networkx + PyYAML); the MCP server and the JS plugin are opt-in extras.

pip install codetruth                 # CLI + Python API (dead-code gate, CI, scripts)
pip install "codetruth[mcp]"          # + the agent-facing MCP server
pip install "codetruth[javascript]"   # + the JS/TS plugin
pip install "codetruth[mcp,javascript]"   # everything (or: codetruth[all])

• Not using an agent? Plain pip install codetruth is all you need — the CLI (codetruth scan), Python API (from codetruth import scan), HTML report, and --ci gate work with no extra dependencies. The mcp extra pulls a web-server stack (pydantic/starlette/uvicorn) and is only for the MCP server, so the core deliberately doesn't require it.

• Using it with Claude Code / an MCP agent? Install "codetruth[mcp]", then claude mcp add codetruth -- codetruth mcp.

• If the codetruth command isn't found, your Python scripts dir isn't on PATH — use python -m codetruth.cli (and python -m codetruth.mcp_server).

MCP (the primary interface — for agents)

pip install "codetruth[mcp]"
claude mcp add codetruth -- codetruth mcp

Tools exposed: check_deletion_safety(repo, symbol) (the one to call before deleting), scan(repo, ...) (the whole review queue), plan_deletion(repo, symbol) (advisory removal plan), and scan_workspace(repos, ...) (cross-service usage across repos). The agent workflow: identify symbol → call check_deletion_safety → only delete on safe_to_delete; everything else routes to human review.

CLI

codetruth scan ./repo                     # review queue, strongest candidates first
codetruth scan ./repo -v --json out.json  # full evidence
codetruth scan ./repo --app-mode          # application (not library) repos:
                                          # public symbols may be safe_to_delete
codetruth scan ./repo --strict            # flag orphaned "useless clumps"
codetruth scan ./repo --min-rank 0.5 --group   # trim the tail, group by file
codetruth scan ./repo --html report.html  # self-contained HTML report
codetruth scan ./repo --ci                # exit 1 if dead code exists (report gate)
codetruth scan ./repo --progress          # live progress line (auto on a TTY)
codetruth baseline ./repo                 # accept current findings (see below)
codetruth check ./repo pkg.module:func    # one symbol's evidence record
codetruth plan  ./repo pkg.module:func    # advisory deletion plan (never applied)

Long scans show a live progress line (files scanned, then graph/rules/verify phases) on a terminal; it's auto-silenced when output is piped (--progress / --no-progress to override). Ctrl+C cancels cleanly.

The --ci gate is advisory like everything else: it fails the build so a human looks at provably-dead code — it never deletes. Mark false alarms with # codetruth: keep or a .codetruth.toml entrypoint.

Adopting on an existing codebase (baseline)

A gate that fails on all pre-existing dead code never gets switched on. Accept the current state once, commit the baseline, and the gate only fails on newly introduced dead code:

codetruth baseline ./repo        # writes .codetruth.baseline.json — commit it
codetruth scan ./repo --ci       # now fails ONLY on new safe_to_delete code

The baseline keys on symbol ids, so line churn doesn't invalidate it. A previously-hedged symbol whose deadness becomes provable (its last caller was removed) counts as new. When accepted findings get cleaned up, the gate tells you to refresh with codetruth baseline.

What gets scanned (scope)

CodeTruth scans the directory you point it at. It never descends into dependency, VCS, build, or environment folders — they're pruned from the walk (so they don't slow it down or pollute results): node_modules, .git/.hg/ .svn, .venv/venv/env/virtualenv, site-packages, __pycache__, build/dist/.eggs/wheels, the various caches, and vendored-code dirs (vendor, third_party, _vendor, vendored). So a virtualenv or installed package left inside your repo won't be treated as your code.

To exclude your own folders (generated code, migrations, fixtures), add a .codetruth.toml at the repo root:

[codetruth]
ignore_paths = ["generated/", "migrations/", "**/fixtures/**"]

Ignored folders are pruned from the walk too, so excluding a large directory also makes the scan faster. To scan just one package of a monorepo, point codetruth scan at that package's directory.

Python API

from codetruth import scan, check_deletion_safety

result = scan("./repo")
for rec in result.candidates():
    print(rec.status.value, rec.symbol, rec.evidence_against_deletion)

Cross-repo / cross-service (workspace scan)

Single-repo analysis can't see that an endpoint is called over the wire or a shared package is imported by a sibling service — the exact usage that makes distributed deletion dangerous. Scan several repos as one system:

codetruth workspace ./service-api ./service-worker ./shared-lib

from codetruth import scan_repos
ws = scan_repos(["./service-api", "./service-worker"])
for xref in ws.crossrefs:
    print(xref.symbol, "<-", xref.reason)

It matches HTTP routes to client calls (a FastAPI/Flask route linked to a requests/httpx call in another repo, path templates and params normalized) and shared imports across repos. A symbol that looks dead in its own repo but is reached cross-repo is raised from likely_dead/safe_to_delete to uncertain_dynamic_risk with an explicit reason — the overlay only ever moves a verdict toward keep. Also exposed as the scan_workspace MCP tool.

Runtime evidence (v1.5)

Static analysis can't see cross-service usage (HTTP calls, queues, cron in other repos). @codetruth.track logs real invocations in production:

import codetruth

@codetruth.track
def maybe_dead(): ...

Or instrument a whole package with zero source edits:

import codetruth.runtime
codetruth.runtime.instrument_package("myapp")   # or CODETRUTH_AUTOTRACK=myapp

Then feed the trace back: codetruth scan ./repo --runtime-log runtime.jsonl. Observed calls promote a symbol to definitely_used; "0 calls over N days" becomes the strongest evidence tier for deletion.

Tracing is production-safe: each process writes its own runtime-<pid>.jsonl (merged at read — no lock contention between workers), and a daemon thread flushes counts every $CODETRUTH_FLUSH_INTERVAL seconds (default 60), so long-running servers land evidence without a clean exit.

Finding useless clumps (strict reachability)

codetruth scan ./repo --strict asks a harder question: is this code reachable from any real entry point (HTTP route, CLI command, __main__, test, declared entrypoint)? Code that is internally well-connected — functions calling each other — but never reached from an entry point surfaces as an orphaned clump, with every member carrying a cluster field listing its fellow members so the whole island can be reviewed (and deleted) as a group. Dead-cluster grouping also applies in default mode whenever unreachable symbols reference each other.

Configuration (.codetruth.toml)

Teach the scanner about usage it can't see:

[codetruth]
app_mode = true                    # public symbols are internal (application)
entrypoints = [                    # externally-reached symbols (cron, RPC, ...)
    "jobs.nightly:run",
    "services.handlers.*",
]
ignore_paths = ["migrations/", "vendor/**"]

Inline: a # codetruth: keep comment on (or above) a definition marks it as an entry point.

Deletion plans (advisory)

codetruth plan ./repo pkg.mod:symbol (also the plan_deletion MCP tool, and attached automatically to every safe_to_delete record) describes exactly what a removal would involve: the decorator-to-end source span, imports that become orphaned, and any __all__ entry. CodeTruth never applies a plan — it is information for whoever decides.

Review-queue ranking

Every record carries a rank_score in [0, 1] — a deterministic ordering heuristic (not a calibrated probability; see PLAN.md §4). Higher means weaker evidence of use, so scan() and the CLI surface the strongest deletion targets first. Within uncertain_dynamic_risk it separates a lone string-literal reference from forty fuzzy attribute-name matches, so a big review queue is triageable instead of flat.

Performance

Scans are cached at <repo>/.codetruth/index.json, keyed by a fingerprint of every source and config file's (mtime, size). An unchanged repo returns the cached result (≈15× faster on an 8k-symbol repo); any file change triggers a full rescan. The cache never patches the graph incrementally — a stale cross-file edge could mask a real usage path, so correctness always wins. Bypass with --no-cache (CLI) or force_rescan (MCP). Add .codetruth/ to .gitignore.

Architecture

Layer 1  Symbol Extraction    codetruth/languages/python/extractor.py
Layer 2  Relationship Graph   codetruth/languages/python/edges.py   (strong/weak edges)
Layer 3  Semantic Rules       codetruth/languages/python/rules.py + codetruth/rules/python/*.yaml
Layer 4  Evidence + Decision  codetruth/core/evidence.py            (4-way status)

The core engine is language-agnostic (codetruth/core/, LanguagePlugin interface).

Python is the full plugin. Framework awareness covers FastAPI/Flask/ Starlette routes, Django (signals, URLs, admin, management commands, migrations), Celery, click/Typer, pytest, SQLAlchemy events, and — as of 0.5.0 — declarative schema models: fields of pydantic BaseModel/ BaseSettings/SQLModel, Django models/forms, DRF serializers, TypedDict/NamedTuple, and marshmallow/msgspec are treated as framework-used (populated, validated and serialized, not referenced like ordinary attributes), transitively through subclasses, with the Config/Meta convention honoured. Function-signature annotations (def f(u: User) -> Order) create usage edges, so a model referenced only in type hints stays alive. New framework rules go in codetruth/rules/python/*.yaml — no code changes.

JavaScript/TypeScript (pip install "codetruth[javascript]", then scan --language javascript): tree-sitter extraction, ESM/CommonJS import resolution, tsconfig/jsconfig paths + baseUrl aliases and monorepo workspace packages, barrel re-export chains, Vue SFC (.vue) scripts, package.json entry points (incl. scripts), Express/Fastify/emitter callback handlers, React/JSX component and event-handler usage, string/config wiring, eval poisoning, and external-base cautions — the shared evidence, ranking, cluster, backstop, and cache layers work unchanged. Validated on real apps (RealWorld React, preact, jupyterlab) with zero false positives; a hand-labelled JS recall study is the remaining polish. Go is a stub.

Validation

The metric that matters is false positives — a symbol called safe_to_delete that's actually used. Across 10 real Python packages (requests, flask, click, jinja2, werkzeug, rich, pydantic, urllib3, sqlalchemy, networkx — 36,457 symbols), the false-positive audit is 0 — and it still finds genuine dead code (e.g. urllib3._url_from_pool, rich._svg_hash, requests.dict_to_sequence). Empirical calibration on labelled data: safe_to_delete is 100% dead, monotone across tiers. JS is validated on the RealWorld React app and preact (0 unsafe verdicts). Reproduce with scripts/validation_report.py; details in validation/VALIDATION.md.

Known limitations

• Cross-service usage is invisible to static analysis alone — runtime tracing is the partial fix.

• 100% certainty is impossible; safe_to_delete means "no usage path found under the defined rules," not a mathematical proof.

• Framework rule coverage (Layer 3) is a maintained knowledge base, never finished. New rules go in codetruth/rules/python/*.yaml — no code changes.