DiffCI

DiffCI Core

Open-source test-impact analysis for faster CI. For developers and maintainers evaluating which tests a change affects, with conservative full-run fallbacks. Licensed under AGPL-3.0-only.

Coding-agent plugins

The public integrations/agent-plugin package makes the published DiffCI CLI available as a checkout-aware local MCP plugin. It contains only public marketplace metadata, skills, and a pinned npm launcher; it does not include product services or private source. The cross-agent installation guide covers Codex, Claude Code, Cursor, Grok, Meta Muse Code, and generic MCP hosts.

# Codex
codex plugin marketplace add DiffCI/core
codex plugin add diffci@diffci-local

# Claude Code
claude plugin marketplace add DiffCI/core
claude plugin install diffci@diffci-marketplace

Cursor Marketplace reads .cursor-plugin/marketplace.json from this repository. Meta Muse Code reads the native root marketplace.json. Before a public listing is approved, use the local MCP configuration in the agent-plugin package or visit https://diffci.com/mcp-server.

GitHub Action

The public action.yml is an observation-only GitHub Action wrapper. It runs the pinned published DiffCI CLI outside the observed checkout, retains existing CI jobs, and uploads an advisory report. See the observer Action guide and workflow example.

The v0.3.10 corresponding source remains publicly available at tagged Core commit 4c76be14 (cli-v0.3.10-source) while distribution migrates to the Core-native CLI package.

Try the published CLI in an existing Git checkout with Git and Node.js 22.5+:

npx "@diffci.com/diffci@latest" check

It compares full and selected runtime when safe to measure, writes reports outside the checkout, and sends nothing by default. Test commands can generate files; keep required CI authoritative.

Measured example: one controlled Cal.com sandbox replay measured 44.2% net reduction in install + pretest + test runtime including analysis overhead. This is a job-equivalent comparison, not production savings or a forecast for your repository. Method and limitations.

Star Core · Volunteer a pilot repository · Find a first contribution. Watch → Custom → Releases and Discussions for benchmark results and support updates. Public roadmap.

This is the standalone Core engine. It analyzes local JavaScript/TypeScript repositories, supported Vue components, root Go modules and conventional Maven reactors, traces dependency impact, infers GitHub Actions structure and proposes test selections with evidence and full-run fallbacks. It works without a DiffCI account, hosted service or API key. See the release boundary for support limits.

Want to try DiffCI in an existing repository? Use the published CLI: npx @diffci.com/diffci@latest check. See the CLI quickstart for a no-execution analysis option, prerequisites, and result interpretation. The commands below build the standalone engine from source.

Run locally

Requires Git and Node.js 22.5 or later.

git clone https://github.com/DiffCI/core.git
cd core
npm ci
npm run build
npm test
node dist/cli.js plan --repo /path/to/clean-checkout --base HEAD~1 --head HEAD

The target must be a clean Git repository root checked out at --head. Fetch the base commit beforehand if using a shallow clone. JSON goes to stdout; analysis errors exit nonzero and recommend full CI. Core does not execute repository scripts, contact a DiffCI backend or send telemetry. Installation requires the npm registry.

To evaluate the same command on pull requests without changing required jobs, copy the advisory GitHub Actions example.

Plans are advisory. This release does not execute, skip or cancel CI jobs. SKIP_CANDIDATE is a candidate, not permission to bypass a check. Keep full CI authoritative while evaluating Core. Missing command synthesis, unsupported configuration and incomplete evidence must not be treated as an empty test suite. Static analysis is not proof that a test can safely be omitted.

For Maven jobs whose CI runs a lifecycle goal or profiles other than test, declare them in diffci.json (or the diffci key in package.json):

{ "maven": { "goal": "verify", "profiles": ["run-its"] } }

This changes the proposed command, such as mvn -pl tools -am verify -P run-its; Core still does not run it. Confirm the command against the repository's CI workflow before using it for execution.

What is included

Declared pnpm workspaces with a single Vitest test phase can receive package-local command plans. Each selected path must belong to a discovered test in a declared package. Runtime selections are batched to keep commands below Windows limits; packages declaring --typecheck retain a separate full type-test phase. Packages with compound scripts, lifecycle hooks, overlapping ownership or discovery blind spots refuse selective execution. Commands remain advisory and must be executed separately; CLI automatic timing of multiple commands requires additional integration.

Area	Implementation
Changes and dependencies	Git deltas, repository inventory, JS/TS dependency graph, impact traversal
Safety and planning	Risk signals, conservative fallback, always-run policy, test selection and command synthesis
CI analysis	GitHub Actions evidence, job/reference graphs, conditions and matrix inference
Reproducible evaluation	Synthetic benchmark and portable regression tests
Measurement	Current-process wall time, CPU time and ending RSS; explicit-input cost/energy/carbon estimates

The library entry point exports analyzeCheckout, buildDependencyGraph, ImpactAnalyzer, DefaultCIPlanner, collectEvidence, inferPipeline, measure and estimateImpact. Lower-level modules are available as package subpaths. This repository is the engine source, and the published @diffci.com/diffci CLI is released from it. The corresponding source for the previously published v0.3.10 package is retained in the source archive at tagged commit 4c76be14.

npm run typecheck
npm run audit:boundary
npm run benchmark

The benchmark constructs one temporary synthetic repository containing 100 chained modules and 100 importing test files. In one Node.js process it builds that same dependency graph three times, sequentially, and removes the fixture afterward. Install dependencies first with npm ci, then run npm run benchmark under Node.js 22.5 or later. Record the emitted node and platform alongside the machine CPU, memory, operating system, and competing workload when comparing runs. The three builds share process, operating-system, and compiler warmup effects; they are not independent repetitions with controlled cold caches.

Each entry in runs has these fields:

Field	Interpretation
basis: "measured"	The process counters were observed rather than estimated.
scope: "current-process"	Only the benchmark's Node.js process is covered, not the whole host, container, or CI job.
wallSeconds	Elapsed wall-clock time around one buildDependencyGraph call.
cpuSeconds	User plus system CPU time consumed by the current process during that call; it can differ from wall time.
rssBytesAtEnd	Resident-set size sampled after the call. It is neither peak memory nor the memory allocated by that call alone.
nodes, edges	Graph size. The current fixture should produce 200 nodes and 199 dependency edges.
confidence	Dependency-graph confidence for this synthetic fixture. COMPLETE does not prove that a real repository can safely skip tests.

For example, wallSeconds: 0.79, cpuSeconds: 0.84, and rssBytesAtEnd: 327868416 mean that one graph build elapsed for about 0.79 seconds, consumed about 0.84 current-process CPU seconds, and ended with roughly 328 MB RSS. They do not mean that CI became 0.79 seconds faster or saved 328 MB. The script does not execute tests, installation, builds, or a full-versus-selected comparison, so its timings must not be reported as CI savings.

The separate estimateImpact API can calculate estimatedUsd, estimatedKwh, and estimatedKgCo2e only from caller-supplied computeSeconds, price, power, and grid-intensity assumptions. Those values have basis: "estimated"; they are modeled scenarios, not benchmark output, physical measurements, billing records, or verified avoided emissions.

Sponsors

DiffCI Core is supported by its GitHub Sponsors. Sponsorship funds maintenance, broader language and CI support, and reproducible benchmarks.

Partners

No Partner sponsors yet. Become the first.

Team Sponsors

No Team Sponsors yet. Team Sponsor logos also appear on diffci.com/sponsors.

Backers

No Backers yet. Backers at $25/month or above are listed here.

Sponsors' bug reports are labelled sponsor and triaged first.

Core and Cloud

Component	Availability	License
This Core repository	Public source	AGPL-3.0-only
DiffCI Cloud: hosting, billing, organization management, dashboard, managed services	Private source	Proprietary; not included here
Optional enterprise modules	Not released here	A separate source-available license would apply if offered

Only the explicitly extracted Core files and standalone tooling are in this repository. There is no private monorepo history, customer data, deployment configuration or Cloud implementation here. Core is usable independently; it is not a promise that the private product has already migrated to consume this package.

License and contributions

See LICENSE, NOTICE and CONTRIBUTING.md. AGPL permits commercial use; it is not a non-commercial license. Its obligations, including those applicable to modified versions used over a network, are defined by the license. Grant eligibility depends on the particular grant agreement. No eligibility or legal separation is guaranteed by this repository layout.

See the release boundary for scope and current limitations.

Useful? Star the engine and share a reproducible pilot result.