evidrift

Evidrift — evidence lockfile for AI coding agents

Code compiles. APIs drift. Evidrift is the lockfile for AI assumptions.

Coding agents can write against a dependency or JSON contract that changes tomorrow. Evidrift records the exact TypeScript call signature or repository JSON value as a content-addressed Receipt, then makes CI recompute it before merge.

Local-first CLI. STDIO MCP server. No account, no cloud backend, no LLM judge, and no package code execution.

Installation

Requires Node.js 22 or newer. Run Evidrift directly from npm:

npx --yes evidrift init

That command initializes the current repository. No global install, Evidrift account, API key, or cloud backend is required.

To pin Evidrift for a team or CI workflow:

npm install --save-dev evidrift
npx evidrift init

Quick Start

Run the self-contained drift demo:

npx --yes evidrift demo

The demo creates an ignored .evidrift-demo/signature-drift workspace, records the optional options parameter on parseConfig, checks it successfully, changes the fixture so options is required, then shows the deterministic failure. It executes no downloaded package code.

FAIL contract_mismatch sha256:...
Claim: parseConfig accepts an optional options parameter used by the demo.
Expected signature: parseConfig(input:string,options?:ParseOptions):ParseResult
Current signature: parseConfig(input:string,options:ParseOptions):ParseResult
Affected code location: app/src/index.ts:3
Receipt ID: sha256:...
Action: Review the dependency change and affected code, then intentionally record a new receipt.

That is the product: make an AI assumption reviewable now, then make CI check the same contract later.

Use It in a Repository

The dependency must already be installed inside the target repository, and the affected code path must name a real file.

cd /path/to/your/repository
evidrift init

evidrift record \
  --project . \
  --package your-package \
  --symbol exportedFunction \
  --parameter options \
  --claim "exportedFunction accepts the options used here." \
  --code src/caller.ts:12

evidrift check

When --code includes a line containing an overloaded call, Evidrift asks TypeScript which overload that call actually resolves to. --overload <number> remains an explicit fallback for incomplete or non-compiling call sites.

Lock one value from a repository-local OpenAPI or JSON Schema document:

evidrift record \
  --json openapi.json \
  --pointer /paths/~1users/get/operationId \
  --claim "The generated client calls listUsers." \
  --code src/client.ts:24

JSON Pointer follows RFC 6901, including ~1 for / and ~0 for ~. Evidrift reads .json files only; it never fetches URLs or resolves remote references.

Coding agents call the same core through evidrift_record and evidrift_record_json_pointer. Minimal Codex, Claude Code, and Cursor setup is included.

The Files

Evidrift writes one lock and one immutable JSON file per Receipt:

.evidrift/
  evidence.lock
  receipts/
    <64-character-sha256>.json

There is no .evidrift/receipts.json. evidence.lock contains only content-addressed Receipt IDs:

{
  "receipts": ["sha256:9bfbb065cff372abe52e8e269123959e9f2ae84cd02230dc751f768ac5e4c274"],
  "schemaVersion": 1
}

Each Receipt stores the claim and affected code plus one deterministic contract: an installed TypeScript symbol signature, or a repository JSON path, pointer, canonical value, and hashes. See the Receipt schema.

CI Behavior

evidrift check does not trust saved matched or verified flags. It validates the Receipt, reloads the source, and recomputes the selected signature or JSON value.

Result	Meaning	Exit
PASS	The deterministic signature or JSON value still matches	0
WARNING source_changed	Source identity/content changed, but the selected contract matches	0
WARNING unverifiable	Source is missing, invalid, or cannot be inspected	0
FAIL contract_mismatch	Selected TypeScript signature or JSON value changed/disappeared	1
FAIL evidence_integrity	Lock or Receipt is malformed, missing, forged, or hash-invalid	2

A one-line manual edit to a Receipt produces an actionable integrity report:

FAIL evidence_integrity sha256:...
Message: Receipt content hash mismatch.
Receipt ID: sha256:...
Action: Do not trust or hand-edit this Receipt. Restore it from version control, or intentionally create a new Receipt with `evidrift record`.

The included GitHub Actions workflow runs the full gate on Node.js 22 and 24. Third-party Actions are pinned to full commit SHAs.

In a human TTY, check, diff, explain, and demo use a spinner plus green ✅, yellow ⚠, and red ❌ status output. Redirected output, CI, TERM=dumb, and NO_COLOR stay ANSI-free and keep the stable plain-text format used by agents and tests.

Why This Is Not RAG, Sonar, or AI Review

Tool	Its job	Evidrift's job
RAG	Fetch context while an answer is being written	Commit one assumption and check it again later
Sonar/static analysis	Find code patterns and quality problems	Revalidate an explicit external dependency contract
AI code review	Make a probabilistic judgment	Produce a deterministic result without an LLM CI judge

Use all of them if they help. Evidrift covers one gap: the reason code was written can go stale even when the code itself did not change.

CLI

evidrift init
evidrift record --project <path> --package <name> --symbol <name> \
  [--parameter <name>] [--overload <number>] --claim <text> --code <path[:line]>
evidrift record --json <path> --pointer <RFC6901> --claim <text> --code <path[:line]>
evidrift check
evidrift diff
evidrift explain <receipt-id>
evidrift demo
evidrift mcp

All commands accept --root <repo>. record requires an initialized .evidrift/evidence.lock.

evidrift mcp starts the same local STDIO server exposed by the evidrift-mcp bin. It exists so package registries and MCP clients can launch Evidrift deterministically from the main npm package.

Trust Boundary

.evidrift/receipts/*.json is untrusted input. Every check:

• Strictly validates lock and Receipt schemas.
• Derives file paths only from full SHA-256 IDs.
• Recomputes the expected contract hash and Receipt content hash.
• Resolves declarations or repository-local JSON without importing package JavaScript, running shell commands, making network requests, or calling an LLM.
• Reports evidence integrity, source drift, semantic support, and runtime correctness separately.

The parser refuses more than 1,024 Receipt IDs or 64 call signatures per symbol. TypeScript evidence is confined to repository files and capped at 256 source files, 2 MiB per file, and 16 MiB total. JSON sources are capped at 4 MiB and selected canonical values at 1 MiB. Dynamic text is rejected or escaped so a Receipt cannot inject terminal controls or fake CI lines.

Content hashes detect inconsistent edits; they do not prove authorship. Someone who rewrites a Receipt, recalculates its ID, and changes evidence.lock can create new internally valid evidence. Git review and branch protection must catch that replacement. See Architecture.

What Evidrift Does Not Prove

Evidrift does not prove code is correct. It does not prove a free-text claim is true, inspect runtime behavior, eliminate hallucinations, scan dependency vulnerabilities, or validate arbitrary URLs.

The v0.3 source tree resolves overloaded TypeScript calls from the affected path:line when the consumer code compiles and TypeScript can identify one declared overload. Invalid, ambiguous, or missing calls are refused rather than guessed; --overload is the explicit fallback. The Receipt stores the selected normalized signature and hash, so declaration reordering does not cause false drift.

The json.pointer adapter locks canonical values in repository-local .json files. It does not support YAML, URLs, remote $ref, schema validation, or semantic equivalence. It follows repository-local TypeScript declaration imports, but does not expand every named type into a deep structural contract. Missing or unreadable source is a visible but non-blocking warning. These are deliberate limits, not hidden guarantees.

The runnable boss-fight test resolves one of three overloads from a real call using a complex cross-file type alias, survives declaration reordering, and deterministically fails when only the selected overload changes.

Development and UAT

npm run format:check
npm run lint
npm run typecheck
npm test
npm run uat
npm run check

npm run verify runs the release gate. Tests use temporary local fixtures and require no secrets, paid APIs, Evidrift backend, or network access. The detailed UAT report maps each acceptance case to an automated test and states the remaining risks.

License

Mozilla Public License 2.0.