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

Status	Meaning	Recommended action
safe_to_delete	zero usage paths found under every analysis rule, and the name verified absent from all repo text outside its own definition	delete
likely_dead	no usage found, but external exposure can't be ruled out (public API, module, test-only)	review_required
uncertain_dynamic_risk	weak evidence exists (string refs, reflection, dynamic module)	review_required
definitely_used	strong reference or framework entry point proven	keep

Install

pip install -e .          # from this repo
pip install -e .[mcp]     # with the MCP server

MCP (the primary interface — for agents)

claude mcp add codetruth -- codetruth mcp

Tools exposed: scan(repo_path, ...) and check_deletion_safety(repo_path, symbol). 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 check ./repo pkg.module:func    # one symbol's evidence record
codetruth plan  ./repo pkg.module:func    # advisory deletion plan (never applied)

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.

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)

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 v1 plugin (FastAPI, Django, Celery, click, pytest, SQLAlchemy, Typer rule coverage). JavaScript/TypeScript is a beta plugin (pip install codetruth[javascript], then scan --language javascript): tree-sitter extraction, ESM/CommonJS import resolution, package.json entry points, string/config wiring, eval poisoning, and external-base cautions — with the shared evidence, ranking, cluster, backstop, and cache layers working unchanged. Go remains a stub.

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.