Playwright E2E MCP

An MCP server that diagnoses and fixes failing Playwright tests. It is the layer that sits next to a browser-driving MCP: Playwright MCP gives an agent hands in the browser; this server gives it a test runner, a failure analyst and a verified fixer.

run-test ──▶ get-failure ──▶ suggest-fix (apply + re-run) ──▶ green
   │              │                 └─ refuses when the element is really gone (app bug)
   │              └─ DOM at failure, failed requests, console errors
   └─ background runs, progress ──▶ analyze-history (flaky / broken / regressed)

What it does that a browser-driving MCP or a raw npx playwright test does not:

• Structured runs. Stats plus each failure's file:line, kind (assertion, timeout, dead dev server, syntax error, crash, full disk…) and a concrete fix hint. Long suites run in the background with live progress.
• Diagnosis from the trace. The DOM at the moment of failure, the failed action, the 4xx/5xx requests and console errors, read from Playwright's own trace.
• Fixes that are proven, not guessed. suggest-fix matches a broken locator against the DOM at failure, swaps in a Playwright locator proven unique on the page (getByRole('button', { name: 'Proceed to checkout' })), re-runs the test and reverts the edit if it is still red. When nothing on the page plausibly matches, it says the element is missing and does not patch the test to hide a real bug.
• Flakiness across runs. Every run is recorded locally; analyze-history separates tests that flip (flaky) from ones that started failing (regressed) or always fail (broken), and groups failures that share one cause.
• Pages behind a login. Every page tool accepts a Playwright storageState, extra headers, and click/fill steps to reach a modal or a later step.
• Small on the wire. In the benchmark, diagnosing and fixing one drifted locator cost about 5,300 tokens here against about 7,400 with Playwright MCP plus a shell, and the fix was applied and verified without the agent editing anything.

What it does not do

It does not drive an exploratory browsing session step by step, and it does not replace Playwright's own Test Agents (planner, generator, healer) inside VS Code. Use Playwright MCP for interactive browsing and this server for running, diagnosing and fixing the suite; they work side by side in the same client.

Demo

Hosted endpoint — what an initialize + tools/list round-trip against https://playwright-e2e-mcp.vercel.app/api/mcp returns for a client that sends the bearer token (without one, only list-tests and get-failure are listed):

A real test run — run-test served over stdio by npx -y playwright-e2e-mcp against the bundled examples/sample-test.spec.ts (actual output, unedited):

Images are rendered with node scripts/gen-demo-images.mjs: the run-test card is real captured output; the endpoint card is an illustration of the authenticated listing.

Install

Works with Claude Desktop, Claude Code, Cursor, Windsurf, Codex, Gemini CLI, Freebuff and every other MCP client — pick whichever route fits:

One line for the common clients:

claude mcp add playwright-e2e -- npx -y playwright-e2e-mcp
code --add-mcp '{"name":"playwright-e2e","command":"npx","args":["-y","playwright-e2e-mcp"]}'

Details and per-client config: Installation · MCP client configuration.

Tools

Two prompts package the main workflows for clients that show them as slash commands: fix-failing-test (optional test) and triage-flaky-tests.

Page state: signed-in pages, headers and steps

inspect-page, validate-selector and compare-visual-state accept the same page-state arguments (suggest-fix accepts storageState and headers for a live url):

A failing step reports which one failed and how many ran. When the page lands on a login screen, the response says so and suggests storageState.

run-test

Progress: clients that send a progress token get a notification as each test finishes (3/12 tests done, 1 failed). Every run is appended to the local history used by analyze-history.

Flakiness handling: by default the server injects --retries=1 (unless the config already sets retries), so a test that passes on the retry is reported as flaky, not failed. Traces are captured automatically (--trace=retain-on-failure) so get-failure can show the DOM at the moment of failure.

Example result:

## Playwright run — ❌ FAILED

**Command:** `playwright test --config playwright.config.ts tests/checkout.spec.ts --reporter=json`
**duration 4.2s · exit 1 · config `playwright.config.ts`**

| passed | failed | flaky | skipped | duration |
| ---: | ---: | ---: | ---: | ---: |
| 0 | 1 | 0 | 0 | 1.1s |

### ❌ 1 failing test(s)

### 1 of 1. checkout.spec.ts › pays with card
**File:** `checkout.spec.ts:5`  |  **failed · server-unreachable**

### ⚠️ SERVER_NOT_RUNNING
Your app (dev server) does not appear to be reachable. Start it in another terminal
(e.g. npm run dev / npm start), keep it running, then retry — or configure `webServer`
in playwright.config.* so Playwright starts it automatically.

get-failure

Returns the message/code frame, expected vs actual, stack, failure kind with a diagnosis, the test's console output, the DOM snapshot from the Playwright trace (plus the failed action, its selector, and the action log leading up to it), the network requests that failed (4xx/5xx, dead endpoints, no-response — with method, URL, status and resource type), the console errors/warnings the page logged before the failure, and numbered next steps (re-run this single test by file:line, headed/debug mode, validate-selector when the message mentions a locator, …).

inspect-page

Each element comes with Playwright locators that were checked on the page to resolve to exactly that element, best first (role + accessible name, test id, label, placeholder, text, then CSS), plus its unique CSS selector, visibility, box and text. Console messages are captured, errors first. A locator map looks like:

1. `getByRole('button', { name: 'Proceed to checkout' })` — button "Proceed to checkout" · also `getByTestId('checkout-btn')`
2. `getByLabel('Search')` — searchbox "Search"

list-tests

Uses playwright test --list when Playwright works, and falls back to a source scan (keeping the reason) when the install or a spec file is broken.

validate-selector

Locator expressions are parsed into a whitelisted call chain (getByRole, getByText, getByLabel, getByPlaceholder, getByAltText, getByTitle, getByTestId, locator, first, last, nth, filter) and are never evaluated as code.

Verdicts: ✅ VALID — N matches with a sample of matches and a unique locator for each, a strict-mode warning when more than one element matches, a hint when a CSS selector is brittle (:nth-child, long descendant chains, XPath), ✅ VALID — 0 matches with debugging advice, or ❌ INVALID with the parse error.

generate-e2e-test

Reads the agent's recent changes (git status, falling back to git diff HEAD~1, then recent mtimes), extracts the locators those files actually declare (data-testid, getByRole, aria-label, placeholder, id, name, element text), ranks verified-live selectors first, writes a spec built from them, and reports each selector with its source file:line. When the source has no usable selectors, it uses the verified locators from the live page that best match the description.

compare-visual-state

The first call saves a baseline under .pw-mcp/visual/ (add that to .gitignore, or commit it for CI comparisons). Later calls report changed-pixel counts, merged regions ((x, y) 120×40 — 1,200 px), the average color shift ("blue → red"), and write a red-highlighted diff image for review.

diagnose-flaky

Every run executes with --retries=0 and auto-retry disabled, so each result is honest evidence. The response contains a per-run table (status, duration, first failure), the count of distinct normalized error signatures, and one of:

• ❌ CONSISTENTLY FAILING — failed every run (same error → reproducible bug, different errors → still broken, just noisy). Fix it; it is not flaky.
• ⚠️ FLAKY — some runs passed. Includes N of M counts and whether the failures share one signature (real intermittent bug) or vary (timing/environment instability).
• ✅ NOT REPRODUCING — passed every re-run; the original failure was one-off.

The last run is stored, so get-failure can analyze it immediately afterwards.

suggest-fix

Two kinds of fix:

• Locator drift. The broken locator is read from the error, its words are matched (with synonyms such as btn → button, checkout → proceed to checkout) against every element in the DOM at failure, and the best match's verified-unique locator replaces it. Confidence is high when the match is clear, medium otherwise.
• Changed copy. For toHaveText, toContainText, toHaveValue, toHaveTitle, toHaveURL and toHaveAttribute, it proposes the value the page actually showed. It is only applied with allowExpectationUpdate: true.

The response is a unified diff. With apply: true the file is written only if it has not changed since the failure, the single test is re-run (same project, no retries), and the edit is reverted when it is still red. If nothing on the page shares the locator's distinctive words, it refuses and reports that the element is most likely missing.

get-run-status

While running it reports tests done / total and failures so far; once finished it returns the full run-test result, which also becomes the last run for get-failure and suggest-fix. The 20 most recent runs are kept in memory.

analyze-history

Every run-test, diagnose-flaky and suggest-fix run appends a line to <project>/.playwright-e2e-mcp/history.jsonl (the folder carries its own .gitignore; nothing leaves the machine; PW_MCP_HISTORY=0 turns it off). The flaky view separates tests that flip between pass and fail, tests that started failing and stayed red (regressed), and tests that failed every run (broken), each with a PFFP~ timeline.

Installation

Requirements:

• Node.js ≥ 20 (the server is built on MCP SDK v2 — the 2026-07-28 spec line)
• A project with @playwright/test installed and browsers available (npx playwright install chromium)

No npm account needed — install straight from GitHub (the prepare script builds dist/ automatically on install). Pin a release tag: an unpinned github:trajectiq-ai/E2E runs whatever is on the default branch at that moment.

npx -y github:trajectiq-ai/E2E#v0.2.2
npm install -D github:trajectiq-ai/E2E#v0.2.2 @playwright/test   # or as a project dependency
npx playwright install chromium

Or grab the packaged tarball from the repo's GitHub Releases page and install it locally:

npm install -D https://github.com/trajectiq-ai/E2E/releases/download/v0.2.2/playwright-e2e-mcp-0.2.2.tgz

Listed in the official MCP Registry as io.github.trajectiq-ai/E2E — registry-aware clients discover it there, and every v* release tag republishes the entry from CI via server.json.

MCP client configuration

Claude Code / generic (project-scoped):

{
  "mcpServers": {
    "playwright-e2e": {
      "command": "npx",
      "args": ["-y", "github:trajectiq-ai/E2E#v0.2.2"],
      "env": { "PW_MCP_PROJECT_ROOT": "/absolute/path/to/your/project" }
    }
  }
}

Claude Desktop / Cursor / Windsurf: add the same block to their MCP config file. The server uses its working directory as the project root; set PW_MCP_PROJECT_ROOT when the client launches it somewhere else (e.g. your home directory).

Codex / VS Code / Copilot CLIs:

codex mcp add playwright-e2e -- npx -y github:trajectiq-ai/E2E#v0.2.2
code --add-mcp '{"name":"playwright-e2e","command":"npx","args":["-y","github:trajectiq-ai/E2E#v0.2.2"]}'

Codex's defaults fight this server: the first launch clones the repo and runs tsc (measured 30 s on a cold npx cache, against a 10 s startup_timeout_sec default), and a Playwright run with retries beats the 60 s tool_timeout_sec default. Raise both in ~/.codex/config.toml:

[mcp_servers.playwright-e2e]
command = "npx"
args = ["-y", "github:trajectiq-ai/E2E#v0.2.2"]
startup_timeout_sec = 60
tool_timeout_sec = 600

Claude Desktop (one-click): download and double-click the .mcpb Desktop Extension attached to the latest release — the bundle ships its own dependencies, so no Node setup is required. On install it asks you to pick your project root (required, no default: choose the project folder, not your home directory) and wires it into PW_MCP_PROJECT_ROOT, so the tools point at a real project from the first call.

Claude Code:

claude mcp add playwright-e2e -- npx -y github:trajectiq-ai/E2E#v0.2.2

Gemini CLI / Qwen Code: paste the mcpServers block above into .gemini/settings.json (Qwen Code: .qwen/settings.json) — both speak the same MCP settings format.

Freebuff / Codebuff (project-scoped): this repo ships a committed .agents/mcp.json, so opening the checkout in Freebuff attaches the server workspace-wide — no global config needed. Your own projects can do the same: drop an mcp.json with the block above into their .agents/ directory. Freebuff asks you to trust a repository's .agents/ on first run.

All tools ship MCP tool annotations (readOnlyHint, destructiveHint, idempotentHint, openWorldHint), so clients can show accurate safety prompts before running anything.

From a local checkout:

{
  "mcpServers": {
    "playwright-e2e": {
      "command": "node",
      "args": ["/path/to/playwright-e2e-mcp/dist/index.js"],
      "env": { "PW_MCP_PROJECT_ROOT": "/path/to/your/project" }
    }
  }
}

Hosted endpoint (ChatGPT & remote clients)

Some clients — ChatGPT custom connectors especially — only accept remote HTTPS MCP servers and refuse to spawn a local npx process. This repo ships a Streamable HTTP bridge for exactly that case:

The bridge runs the same createServer() as the stdio transport; the SDK serves every request with a fresh server instance, which is what a serverless function wants. test/http-bridge.test.mjs drives the real Node adapter over node:http so a broken bridge fails in CI, not in ChatGPT.

This deployment is token-protected. https://playwright-e2e-mcp.vercel.app has PW_MCP_HTTP_TOKEN set, so a request without Authorization: Bearer <token> — including a ChatGPT connector created with authentication None — gets 401 {"error":"unauthorized"}. Ask the operator for the token, or run your own bridge (below).

Open vs. token-protected. With PW_MCP_HTTP_TOKEN set (at least 16 characters; use a random value) every tool is served to clients that send Authorization: Bearer <token>, and every other request gets 401. Without that variable anyone who reaches the URL can call the bridge, so it degrades to list-tests and get-failure in restricted mode: list-tests scans sources instead of running playwright test --list (which would execute the project's config), callers cannot pick another projectRoot, and nothing spawns a process, drives a browser or writes a file. Child processes started over HTTP get only an allowlisted environment. PW_MCP_ALLOWED_HOSTS (comma separated, * for any) limits the accepted Host header; without a token and without that variable, only localhost names and the deployment's own Vercel hostnames are accepted (DNS-rebinding protection).

Add it to ChatGPT: Settings → Connectors → turn on Advanced → Developer mode → Create custom connector → paste the endpoint above. Authentication None only works against a bridge with no token (read-only tools), so for this deployment choose the connector's API key authentication and send Authorization: Bearer <token> — or point the connector at your own deployment with PW_MCP_HTTP_TOKEN unset.

To self-host the open, read-only variant, deploy this repo with PW_MCP_HTTP_TOKEN unset; nothing else changes.

Codex can also take the remote transport instead of spawning npx, if you'd rather not ship Playwright to every machine. Point it at the token through an environment variable so the secret stays out of the config file:

export PW_MCP_HTTP_TOKEN=…   # ask the operator for the value
codex mcp add playwright-e2e-remote --url https://playwright-e2e-mcp.vercel.app/api/mcp \
  --bearer-token-env-var PW_MCP_HTTP_TOKEN

What to expect: list-tests works and reports the specs bundled with the deployment. Even with a token, tools that spawn a browser (run-test, inspect-page, validate-selector, diagnose-flaky, …) cannot download Chromium in a serverless function, so they return their normal NO_PLAYWRIGHT hint. Use the stdio install for real runs; the hosted endpoint is for discovery and for clients that cannot run local processes.

# verify the handshake without any client (the live deployment needs the token;
# drop the authorization header and it answers 401 instead)
curl -X POST https://playwright-e2e-mcp.vercel.app/api/mcp \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -H "authorization: Bearer $PW_MCP_HTTP_TOKEN" \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"curl","version":"1.0"}}}'

Redeploy after a change: merge to main. Vercel's Git integration deploys every push, so there is no token to manage and no CLI step — watch the Vercel commit status for the deployment result.

Configuration

Logs always go to stderr — stdout is reserved for the MCP protocol. Unrecognized values fall back to the default, so a typo in LOG_LEVEL logs at info and one in LOG_FORMAT logs as text rather than silencing the server. With LOG_FORMAT=json each line is a single object (time, level, message plus context):

{"time":"2026-10-07T08:00:00.000Z","level":"info","message":"server ready","name":"playwright-e2e-mcp"}

Typical workflow

1. run-test { "testFiles": ["tests/checkout.spec.ts"] }, or { "background": true } for a long suite and get-run-status { "waitSeconds": 30 } until it finishes.
2. get-failure { "index": 1 } to read the code frame, expected/actual, the DOM snapshot at failure, the failed network requests and the page's console errors.
3. suggest-fix { "index": 1 } for a locator or copy change: review the diff, then { "index": 1, "apply": true } to write it and verify with a re-run. If it reports the element is missing, fix the app, not the test.
4. For anything it cannot patch: inspect-page { "url": "…", "view": "locators" } (add storageState or actions to reach the right screen), then validate-selector to prove the new locator before editing.
5. If a failure looks intermittent: diagnose-flaky { "runs": 3 } for fresh evidence, and analyze-history to see how the test behaved across earlier runs.
6. After changing CSS or components: compare-visual-state { "url": "…", "name": "checkout" }.
7. Re-run only what failed with run-test { "lastFailed": true } until green.

To write a new test, start with generate-e2e-test { "description": "checkout with a saved card" }.

Benchmark

bench/token-benchmark.mjs breaks a checkout button's test id on a storefront page and fixes it two ways: with this server (run-test → suggest-fix → apply) and with Playwright MCP plus a shell (playwright test, browser_navigate + browser_snapshot, edit, re-run). Latest result (full output):

Tokens are characters ÷ 4. The Playwright MCP route is a lower bound: it assumes the agent picks the right locator from the snapshot on the first try, which the server does for it here.

Edge cases handled

Security notes

• No shell: Playwright is spawned as node <playwright/cli.js> … with an argument array — no command interpolation. Extra args are limited to an allowlist of Playwright flags, each with a checked value (--flag=value), so a caller cannot swap in another --config or --output or hand git an option through --only-changed. Paths with a segment starting with - are rejected, so a test file name cannot be read as a flag.
• Path sandbox: user paths must stay inside the project root, checked lexically and again with symlinks resolved. A caller-supplied projectRoot must sit inside PW_MCP_PROJECT_ROOT (or a PW_MCP_ALLOWED_ROOTS entry).
• Generated code: generate-e2e-test only writes *.spec.* / *.test.* files, only overwrites specs whose header it wrote itself, never writes through a symlink, and escapes every value it puts into strings or comments.
• HTTP bridge: read-only tools unless PW_MCP_HTTP_TOKEN is set; child processes started over HTTP get only an allowlisted environment (PATH, HOME, temp dirs, locale, CI, PLAYWRIGHT_*, npm_config_* without embedded credentials, plus anything in PW_MCP_PASSTHROUGH_ENV), at most PW_MCP_MAX_CHILDREN run at once (a disconnected client frees its slot immediately), and internal error messages are not returned to clients. The allowlist only covers the child's own environment: test code runs as the same OS user, so on Linux it could still read the server's startup environment from /proc. That is why only token holders can run project code; keep other secrets out of the bridge's environment, or run it under a separate user.
• SSRF guard: on the HTTP bridge (or with PW_MCP_BLOCK_PRIVATE_URLS=1) the URL tools refuse hosts that resolve to loopback, private, link-local/metadata or reserved addresses, and route the browser through a local proxy that applies the same check to every redirect hop and subresource; IPv6 forms that embed an IPv4 address (mapped, NAT64, 6to4, Teredo) are blocked too, and WebRTC UDP is disabled so a page cannot reach the network around the proxy. It is off for stdio by default because opening http://localhost dev servers is what these tools are for.
• Cleanup: temp report/script files are written to the OS temp dir and removed; child processes are tracked and killed on shutdown. Trace decompression has one size budget per archive, and PNGs are capped at 16,384 px per side and 50 M pixels.

Development

src/
├── index.ts            # bin entry point (--version/--help, main-module guard)
├── server.ts           # McpServer setup, tool registration, shutdown handling
├── tools/              # the eleven tools, the probe script + shared plumbing
├── prompts.ts          # fix-failing-test, triage-flaky-tests
├── utils/              # playwright-runner, report-parser, project-detector, path-utils,
│                       # logger, trace-reader (trace.zip → DOM/network/console),
│                       # image-diff (PNG codec + pixel diff), change-analyzer,
│                       # locator-expr, run-history, run-registry
└── types/              # shared interfaces and the ErrorKind taxonomy

Built on @modelcontextprotocol/server v2 (the 2026-07-28 MCP spec line) with Zod v4 standard schemas; every tool declares spec tool annotations.

npm install
npm run build   # tsc → dist/ (zero errors)
npm test        # build + test/run-tests.mjs (unit tests, any Node ≥20)
npm run e2e     # build + e2e/run.mjs: live MCP ↔ Playwright integration suite
npm run mcpb    # build + bundle dist/ into playwright-e2e-mcp-<version>.mcpb (+ .sha256)
npm run mcpb:smoke   # ...then install that bundle in a temp dir, launch it and assert the handshake
npm run mcpb:sign    # ...then sign it with MCPB_CERT/MCPB_KEY → <version>.signed.mcpb

Tests cover the report parser (sample Playwright JSON, trace attachments), path utils (Windows and macOS paths, sandboxing), the project detector (temp-dir fixtures: config discovery, multiple configs, missing install, test-file scanning), the shared tool helpers, the trace reader (synthetic trace.zip: error, failed action, DOM snapshot, *.network failed-request parsing, console error/warning events), the image diff (PNG round-trip, regions, color shift, dimension changes), the change analyzer (selector extraction, git + mtime paths), the flaky verdict logic (failure signatures, CONSISTENTLY FAILING / FLAKY / NOT REPRODUCING / NO TESTS RAN), the HTTP bridge (token, restricted mode, Host allowlist), the security regressions (sandbox escapes, argument smuggling, symlink writes, code injection, SSRF ranges, env scrubbing, decode limits), the .mcpb manifest, the .mcpb zip extractor, and the MCP config files.

Integration suite (npm run e2e)

Unit tests prove the logic; the integration suite proves the loop. It boots the real server over stdio against a live fixture app and a Playwright project under e2e/fixture/, then drives it exactly like an MCP client and asserts ~40 behaviours that only appear end-to-end:

• initialize handshake, 11 tools, 2 prompts, spec tool annotations and object input schemas,
• verified locators, locator validation, signed-in pages (storageState) and page steps,
• background runs with progress, run history views, and suggest-fix healing a drifted locator and verifying it with a re-run (and refusing when the element is missing),
• live DOM inspection, CSS selector validation (matches, zero matches, engine syntax, parse errors), dead-server detection,
• visual regression: baseline → unchanged compare → blue → red diff detection,
• run-test pass/fail/lastFailed stats and meta lines,
• get-failure trace diagnostics: DOM at failure, the 404 network request, the console.error message, diagnosis and next steps,
• auto-retry turning a first-run failure into PASSED (1 flaky),
• diagnose-flaky verdict FLAKY (2 of 3 runs) with retries disabled,
• generate-e2e-test writing its scaffold, plus error paths (missing test path, unknown tool, unreachable server).

First run needs the browser once: npx playwright install chromium. CI runs the suite on Ubuntu and Windows (see .github/workflows/ci.yml).

Signing the bundle

MCPB_CERT=~/signing/cert.pem MCPB_KEY=~/signing/key.pem npm run mcpb:sign

Signing appends a PKCS#7 signature block to the bundle, so the signed file is the reproducible bundle plus that block. That ordering is the point: the bytes CI proved identical across platforms stay inside the signed file, and mcpb unsign returns them exactly. scripts/sign-mcpb.mjs asserts that round trip on every run and deletes its output if it fails, which is what keeps <version>.signed.mcpb tied to <version>.mcpb.

The private key is read from a path you pass in (--cert/--key or MCPB_CERT/MCPB_KEY) and never from the repository — keep it outside version control, and back it up: the same key across releases is what makes the signer recognisable.

What signing does and does not buy you is decided by the certificate, not by this script. mcpb verify and mcpb info accept a signature only when the certificate chains to something in the OS trust store, so with a self-signed certificate a host still reports Not signed — the signature is real integrity and key continuity, verifiable by the fingerprint the script prints, but not third-party identity. A certificate issued by a public CA, or an internal one installed on your machines, is what makes hosts report it as signed.

Verifying a published release

git checkout v0.2.2 && npm ci && npm run mcpb
npm run release:verify -- v0.2.2

The release notes promise that the tag rebuilds the published bundle byte for byte. scripts/verify-release.mjs checks that promise from a checkout of the tag: the published bundle against your fresh build, every checksum the release publishes (and that nothing shippable is missing from SHA256SUMS.txt), a signed bundle against the bytes its signature wraps, and that the published archive still extracts with that version's manifest. .github/workflows/verify-release.yml runs it on every published release and on demand for any past tag. The .tgz is checked for download integrity only: npm records the packer's line endings, so a tarball packed locally on another OS is legitimately different.

Try the example

With Playwright installed in your project:

npx playwright test examples/sample-test.spec.ts

or ask your agent to call run-test with "testFiles": ["examples/sample-test.spec.ts"] — it hits the public example.com page, so it verifies browsers, network and the MCP pipeline in one shot.

License

MIT