Signalint

Signalint is a local MCP server for JavaScript and TypeScript diagnostics. It runs Oxlint, TypeScript, and optionally Biome; caches unchanged checks; clusters repeated issues; and warns when the same diagnostic disappears and repeatedly returns. Loop history is restored from valid.signalint/session.jsonlentries when the MCP server restarts; malformed or crash-truncated lines are skipped.

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- mcpservers.org
- Official MCP Registry (API listing)

[ { "issueId": "ts-01", "file": "src/file01.ts", "line": 10, "col": 5, "engine": "tsc", "rule": "TS2322", "severity": "error", "message": "Type 'string' is not assignable to type 'number' in fixture assignment 01.", "fixable": false }, // ... 39 more raw normalized issues ]

Clustered response returned to agent (4 clusters · 1,233 bytes · 86.5% reduction)

{ "schemaVersion": "1.1", "status": "issues_found", "engines": { "oxlint": { "status": "ok" }, "tsc": { "status": "ok" }, "biome": { "status": "disabled" } }, "totalIssues": 40, "clusters": [ { "clusterId": "c1", "rootCauseSummary": "10 TS2322 issues across 10 files", "ruleIds": ["TS2322"], "issueCount": 10, "fileCount": 10, "priority": 1, "suggestedAction": "Review the shared cause of TS2322 across 10 files", "sampleIssueIds": ["ts-01", "ts-02"] }, { "clusterId": "c2", "rootCauseSummary": "10 no-unused-vars issues across 10 files", "ruleIds": ["no-unused-vars"], "issueCount": 10, "fileCount": 10, "priority": 2, "suggestedAction": "Review the shared cause of no-unused-vars across 10 files", "sampleIssueIds": ["unused-01", "unused-02"] }, { "clusterId": "c3", "rootCauseSummary": "10 eqeqeq issues across 10 files", "ruleIds": ["eqeqeq"], "issueCount": 10, "fileCount": 10, "priority": 5, "suggestedAction": "Apply structured fixes for eqeqeq across 10 files", "sampleIssueIds": ["eqeqeq-01", "eqeqeq-02"] }, { "clusterId": "c4", "rootCauseSummary": "10 prefer-const issues across 10 files", "ruleIds": ["prefer-const"], "issueCount": 10, "fileCount": 10, "priority": 5, "suggestedAction": "Apply structured fixes for prefer-const across 10 files", "sampleIssueIds": ["const-01", "const-02"] } ], "truncated": false, "loopWarning": null }

The agent receives a concise summary with priority-ordered clusters and sample issue IDs. When deeper detail is needed for a specific cluster or issue, the agent callsget_issue_detailwithout re-running the whole-project scan.

- Node.js 20.19 or later in the Node 20 line, or Node.js 22.12 or later
- A JavaScript or TypeScript project; TypeScript checks require atsconfig.json
- pnpm 11.9.0 for source development

Install Signalint in the project it should check:

Run the setup command from that project root. It detects TypeScript, Oxlint, and Biome configuration, writessignalint.config.json, and offers to update a nearby Claude Code, Cursor, Codex CLI, or Antigravity MCP configuration:

If no MCP client can be selected safely, the command prints exact configuration snippets to copy. TypeScript is enabled only when a roottsconfig.jsonexists; Biome is enabled when its config exists; Oxlint is the fallback when no configured linter is detected. To configure Signalint manually, createsignalint.config.json:

{ "engines": { "oxlint": true, "tsc": true, "biome": false }, "ignore": ["node_modules/", "dist/", ".signalint/"], "timeoutsMs": { "oxlint": 30000, "tsc": 120000, "biome": 30000 } }

claude mcp add --scope project signalint -- npx --no-install signalint-mcp claude mcp get signalint

claude mcp add --scope project signalint -- cmd /c npx --no-install signalint-mcp claude mcp get signalint

{ "mcpServers": { "signalint": { "command": "npx", "args": ["--no-install", "signalint-mcp"] } } }

codex mcp add signalint -- npx --no-install signalint-mcp

[mcp_servers.signalint] command = "npx" args = ["--no-install", "signalint-mcp"]

[mcp_servers.signalint] command = "cmd" args = ["/c", "npx", "--no-install", "signalint-mcp"]

{ "mcpServers": { "signalint": { "command": "cmd", "args": ["/c", "npx", "--no-install", "signalint-mcp"], "cwd": "<absolute-path-to-your-project>" } } }

Note on Antigravity product variants:Antigravity has split into separate products (IDE, CLI, SDK). Each variant may use a different config path — the IDE path above is the one confirmed working; other variants may use~/.gemini/config/mcp_config.jsonor a project-scoped.agents/mcp_config.json. Seeantigravity.google/docs/mcpfor the authoritative list per product.

node C:\absolute\path\to\Signalint\dist\src\index.js node C:\absolute\path\to\Signalint\dist\src\cli.js stats

- pingchecks that the local server is connected and returnspong.
- check_projectaccepts optional{ "paths": ["."] }and returns clustered diagnostics.
- check_filesaccepts{ "files": ["src/file.ts"] }and uses incremental caching.
- get_issue_detailaccepts exactly oneclusterIdorissueIdfrom the latest successful check and returns its full issues, or astatus: "stale"response.
- get_loop_statusreturns issue signatures currently flagged as oscillating.

Cache and session artifacts are written under.signalint/and should not be committed.

Run the same project check without an MCP client:

After MCP checks have accumulated in.signalint/session.jsonl, print the Phase 6 measurement summary:

The report includes average normalized-raw-to-clustered JSON payload reduction, engine-file cache hit rate, average and maximum check latency, and the number of distinct issue signatures that triggered loop warnings. An engine-file lookup counts each enabled engine separately, so one changed TypeScript file can miss once for Oxlint and once for tsc. Latency covers handler work from MCP tool entry through engine/cache work, clustering, and loop evaluation; it excludes the telemetry append and stdio transport. Statistics include the active session log and its rotated.1backup, with their retained overlap counted once. Clean checks with zero raw payload are excluded from the reduction average, and older checks with missing metrics remain counted without contributing to the unavailable aggregate.

The CLI exits with code 1 when issues are found. Two flags support CI use:--format githubprints one GitHub Actions annotation (::error file=...,line=...,col=...::messageor::warning ...) per issue instead of JSON, and--fail-on-priority <N>exits non-zero only if a cluster's priority is at or belowNinstead of on any issue found.

To exercise an actual MCPcheck_projectcall against the installed package, run:

node node_modules/signalint-mcp/examples/check-project.mjs .

action.ymlat the repository root wrapssignalint checkas a composite action for CI. It installs Node, installssignalint-mcpfrom npm, and runs the check with--format githubso issues appear as inline annotations on the pull request diff:

- uses: TranQui004/signalint@main with: fail-on-priority: "3"

fail-on-prioritydefaults to5, which fails the job on any issue found, matchingsignalint check's default behavior without the flag. Lower values only fail the job when a cluster is at least that urgent: priority 1 is an error with no structured fix, and priority increases toward 5 as issues become more fixable or more systemic (seescorePriorityinsrc/cluster/clusterEngine.ts).

pnpm 11.9.0 is the canonical package manager for source development. The repository commitspnpm-lock.yaml, declares pnpm inpackage.json, and uses pnpm in CI.

pnpm install --frozen-lockfile pnpm lint pnpm typecheck pnpm test pnpm build

If a global npm shim cannot findnpm-cli.js, build directly withnode node_modules/typescript/bin/tsc -p tsconfig.json.

Before preparing a release, usenpm pack --dry-runand verify the packed tarball in a clean project. Publishing requires explicit release approval.

SeeSECURITY.mdfor the current npm audit advisory, its evaluated runtime reachability, and the conditions that require reassessment.

- Website— overview, docs, and live examples.
- ARCHITECTURE.md— how the layers fit together and what each module does.
- CONTRIBUTING.md— development setup, verification, and pull requests.
- AGENTS.md— coding standards for this repository.
- SECURITY.md— threat model, trust boundaries, and audit status.
- CHANGELOG.md— notable changes by release.
- docs/history/— original build plan and pre-launch audit trail.

Signalint is available under theMIT License.

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