An MCP (Model Context Protocol) server for running Playwright tests and reading structured results, failed test details, and attachment content — designed for AI agents doing test failure analysis.
Table of contents
MCP server for running Playwright tests and reading structured results — designed for AI agents doing test failure analysis
Playwright Report MCP gives an AI agent structured, token-efficient access to Playwright test outcomes. It runs your test suite, reads the JSON reporter output, and surfaces exactly what the agent needs: which tests failed, what the errors were, and the content of relevant attachments.
What it is NOT
There are many Playwright MCP servers that control a browser — they navigate pages, click elements, fill forms, and take screenshots. Playwright Report MCP is not one of those.
Default reporters (list / dot) — Playwright's default reporters print human-readable output to stdout. Compact, but lossy: no attachment paths, no retry breakdown, no structured data.
HTML reporter (report.html) — A self-contained SPA bundle (typically 2–50 MB). Not machine-readable as text and exceeds any LLM context window.
Reading results.json directly — Works, but a full JSON report for even a small test suite is 10,000–20,000 tokens. For a failing test, most of that is passing test metadata you don't need.
What Playwright Report MCP does instead
Filters results.json to only failed tests
Returns structured, typed JSON the agent can act on immediately
Exposes individual attachments by name so the agent fetches only what it needs
Works on results produced by anyone — CI pipeline, a human, or the agent itself
Token cost comparison (one failed test in a 20-test suite)
Approximate input token counts based on Claude tokenization (~3–4 characters per token for mixed JSON/text content).
What you need
Without MCP — approach
Tokens (no MCP)
With MCP — tool calls
Tokens (MCP)
Savings
Error message only — live run
npx playwright test, read stdout (list/dot)
~500–1,200
run_tests + get_failed_tests
~300–500
~2×
Error message only — existing results
Read full results.json
~12,500–23,000
get_failed_tests
~300–500
~25–45×
+ page state at failure
+ read error-context file
~15,000–26,000
+ get_test_attachment('error-context')
~2,800–3,500
~4–7×
+ custom text attachments¹
+ read attachment files
~16,200–28,500
+ get_test_attachment ×2
~3,300–5,500
~4–5×
+ full page HTML snapshot²
+ read snapshot file
~41,000–103,000
+ get_test_attachment
~33,300–85,500
~1.2×
¹ Custom text attachments — e.g. AI diagnosis (~500–2,000 tokens) and console logs (~200–500 tokens) added via testInfo.attach() in your own fixtures.
² Full page HTML snapshot — a custom fixture that attaches the full rendered page HTML on failure. Large pages alone can reach 30,000–80,000 tokens and dominate cost regardless of whether MCP is used.
Key observations:
For a live run, stdout (list/dot) is compact but gives the agent no path to attachment content — dead end for deeper analysis
Reading results.json directly costs ~12,500–23,000 tokens even when only one test failed — most of it is passing test metadata the agent doesn't need
The biggest MCP gains are in the middle rows: getting error messages + page state from existing results at ~4–45× lower token cost
Full page HTML snapshot dominates cost either way; skipping it in favour of error-context is the single largest optimisation available
CI failure analysis
The primary use case: your CI pipeline runs the tests, the agent picks up the results after the fact and diagnoses failures. get_failed_tests reads results.json regardless of who triggered the run. No re-run needed.
Quick start
1. Install via npx (recommended)
No clone or build step needed — npx downloads and runs the server automatically:
Tested with Claude Code (CLI). Should work with any MCP-compatible client that supports stdio transport, including Claude Desktop, Cursor, Cline, Windsurf, and Continue.dev — but these have not been verified.
The stdio server supports both MCP protocol eras from one entrypoint:
Modern: protocol revision 2026-07-28, selected by clients using version negotiation (for example, versionNegotiation: { mode: "auto" }).
Legacy: supported 2025-era revisions, selected by clients that use the traditional initialize handshake. This remains the default behavior in the MCP client SDK.
The opening exchange pins one era for the connection lifetime. A client that pins an unsupported revision receives an explicit negotiation error; the server does not silently switch it to another era.
Tools
The project-scoped tools accept an optional workingDirectory parameter — see Multi-worktree support. get_run_status can use either a runId from run_tests with wait: false, or a workingDirectory lookup for the latest tracked run.
run_tests
Runs the Playwright test suite and returns structured pass/fail results.
Input
Type
Description
workingDirectory
string (optional)
Playwright project directory. Absolute or relative to the MCP server launch directory. Defaults to ".". Must be under PW_ALLOWED_DIRS — see Multi-worktree support.
spec
string (optional)
Spec file path relative to the project directory, e.g. tests/login.spec.ts. Must stay within the project directory.
browser
enum (optional)
Chromium, Firefox, Webkit, Mobile Chrome, Mobile Safari
tag
string (optional)
Tag filter, e.g. @smoke
timeout
integer (optional)
Timeout in milliseconds for the whole test run. Defaults to 300000 (5 min). Use a larger value for long suites or a smaller one to fail fast. When the run is killed by this timeout, the tool returns an explicit error rather than a generic non-zero exit.
wait
boolean (optional)
Wait for completion before returning. Defaults to true. Set to false to start a background run and poll it with get_run_status.
updateSnapshots
enum (optional)
Update snapshot baselines. One of all, changed, missing, none. Playwright's default is missing; changed updates differing + missing. Omit to leave existing baselines alone.
headed
boolean (optional)
Run with a visible browser window. Omitting or setting false leaves playwright.config.ts intact — Playwright has no --no-headed flag, so false does not force headless when the config sets headed.
workers
integer (optional)
Number of parallel workers. Positive integer only; the "50%" string form is not yet supported.
retries
integer (optional)
Maximum retry count for flaky tests. 0 explicitly disables retries; omit to use the project's config.
maxFailures
integer (optional)
Stop the run after this many failures. Positive integer.
env
object (optional)
String-to-string map merged onto the Playwright child environment. Each key must be listed in PW_ALLOWED_ENV. Dangerous and secret names are always rejected. See Environment overrides.
trace
enum (optional)
Force Playwright tracing mode, overriding playwright.config.ts. One of on, off, on-first-retry, on-all-retries, retain-on-failure, retain-on-first-failure, retain-on-failure-and-retries.
Returns: exit code, run stats, and a summary of all tests with status, duration, and error per project.
When wait is false, returns immediately with runId, process metadata, compact numeric progress, and current results.json status. Poll get_run_status with that runId until state is completed, failed, or timedOut. The server parses Playwright progress markers such as [528/662] from stdout and discards raw stdout/stderr text so repeated polling stays token-efficient. The server allows one active tracked run per working directory, caps active tracked runs globally, and keeps a bounded history of recent terminal runs, so very old runId values can expire.
get_run_status
Returns the current status for a non-blocking run started by run_tests with wait: false.
Input
Type
Description
runId
string (optional)
Run identifier returned by run_tests wait=false. When present, this selects a specific tracked run.
workingDirectory
string (optional)
When runId is omitted, returns the latest tracked run for that directory, or idle if no match. When supplied with runId, it must match that run's directory.
If both fields are omitted, workingDirectory defaults to ".". If no run is tracked for the resolved directory, the tool returns state: "idle" plus results.json metadata and last parsed stats when readable. It does not process-scan for external npx playwright test commands that were not started through this MCP server.
Returns: run state, tracking flag, pid, timestamps, elapsed duration, timeout, command metadata (executable, args, cwd), optional envKeys (override names only — never values), progress: { current, total }, exit code, signal, spawn/timeout error when present, results.json path/existence/mtime/size/freshness, and parsed report stats when the report was updated after the run started. When progress has not appeared yet, current and total are null; when a terminal run has readable final stats, progress is set to the derived completed total.
get_failed_tests
Returns failed tests from the last run with error messages and attachment paths. Does not re-run tests — reads the existing results.json.
Attachment name, e.g. error-context, ai-diagnosis, page-html
Returns: the attachment content as text. Binary attachments and files over 1 MB are rejected with an error. Attachment paths recorded in results.json that escape workingDirectory (via .. or absolute paths pointing elsewhere) are refused.
list_tests
Lists all tests with their spec file and tags without running them.
Playwright attaches files to failed tests automatically. get_test_attachment can read any text attachment by name.
Attachment name
Source
Present in every project
error-context
Playwright built-in — YAML accessibility tree snapshot at the point of failure
Yes
screenshot
Playwright built-in — PNG screenshot (binary, not readable)
Yes
video
Playwright built-in — WebM video (binary, not readable)
Yes
Custom attachments
Added via testInfo.attach() in your fixtures
Depends on project
The error-context attachment is the most useful for projects without custom fixtures — it gives a semantic, structured view of the page at the moment of failure with no setup required.
Installation
Via npx (recommended) — use the npx config shown in Quick start. No local installation needed.
From source:
git clone https://github.com/hubertgajewski/playwright-report-mcp.git
cd playwright-report-mcp
npm install
npm run build
Configuration
Add to your .mcp.json at the root of your project:
path.delimiter-separated list of directories the workingDirectory parameter may point at. Entries may be absolute or relative (resolved once against launch cwd at startup).
PW_ALLOWED_ENV
unset (the env tool argument is disabled)
Comma-separated list of environment variable names run_tests and list_tests may override. Unset or empty rejects any env argument and does not spawn. See Environment overrides.
PW_RESULTS_FILE
<workingDirectory>/test-results/results.json
Absolute path to the JSON reporter output file. If set, overrides the per-call default for every call.
Set PW_RESULTS_FILE if your playwright.config.ts writes the report to a non-default location. Leave it unset in multi-worktree setups so each workingDirectory gets its own test-results/results.json.
Multi-worktree support
run_tests, list_tests, get_failed_tests, and get_test_attachment all accept an optional workingDirectory parameter — absolute, or relative to the MCP server's launch directory. get_run_status also accepts workingDirectory when runId is omitted; when runId is supplied, any supplied workingDirectory must resolve to that run's recorded directory. This lets a single long-lived MCP session drive tests across multiple git worktrees without restarting.
Because a Playwright config is a Node module that executes on playwright test startup, the server guards the parameter with an allowlist. Callers that point workingDirectory at a directory outside PW_ALLOWED_DIRS get a structured error and no child process is spawned.
Default (no worktrees). Leave PW_ALLOWED_DIRS unset. The allowlist becomes "." — only the launch directory — and the default workingDirectory (also ".") resolves to the launch directory. Zero configuration.
Sibling worktrees. Set PW_ALLOWED_DIRS=".." in your .mcp.json to authorize every sibling of the launch directory. Relative entries resolve against the launch cwd at startup, so the same .mcp.json works for every contributor without baking in absolute paths:
Multiple projects. Either launch the MCP client from each project and use the default allowlist, or set PW_ALLOWED_DIRS to the shared parent and pass workingDirectory per call. The allowlist check runs at a path-segment boundary, so an entry authorizing /src/my-app will not authorize /src/my-app-evil.
Breaking change (2.x → next): the PW_DIR env var has been removed. Either launch the MCP client from inside the Playwright project directory (zero-config, default workingDirectory: "." works), or pass workingDirectory per call and set PW_ALLOWED_DIRS accordingly.
Environment overrides
run_tests and list_tests accept an optional env map that is merged onto the MCP process environment before spawning Playwright. The child therefore sees operator-allowlisted overrides on top of launch env and the parent process. Playwright configs that load dotenv without overriding existing variables keep the tool-supplied value.
The env argument is off until the operator sets PW_ALLOWED_ENV in .mcp.json. That is the same containment model as PW_ALLOWED_DIRS: the human expands what the model may do; the model cannot widen it.
A hard denylist always wins over the allowlist (comparison is case-insensitive):
prefixes NODE_, LD_, DYLD_, NPM_CONFIG_ (the child is launched with npx, which reads npm config from the environment)
any name matching PASSWORD, SECRET, TOKEN, API_KEY, ACCESS_KEY, CREDENTIAL, PRIVATE_KEY, AUTH_SOCK, or AUTH_CONFIG
Keys must be POSIX names (^[A-Z_][A-Z0-9_]*$). Values cannot contain a NUL and are capped at 256 characters, with at most 16 entries per call. The value of ENV is further restricted to ^[A-Za-z0-9._-]+$ so it cannot be used as a POSIX shell startup-file path (ENV=/tmp/evil.sh is rejected).
Secrets (basic auth, passwords, API keys) stay in the project .env or in MCP launch env. They are never tool arguments. get_run_status may list override names as envKeys and never echoes override values. There is no envFile tool argument.
JSON reporter configured in your Playwright project
Playwright's default reporters (list locally, dot on CI) write to stdout only — they produce no file that can be read after the run. Add the JSON reporter alongside whatever reporters you already use:
The JSON reporter is not configured or is writing to a different path. Verify your playwright.config.ts has ['json', { outputFile: 'test-results/results.json' }].
list_tests parsed 0 tests from non-empty output
The --list output format may have changed in your version of Playwright. Open an issue with your Playwright version and the raw stdout output.
Attachment "..." is binary and cannot be returned as text
screenshot and video attachments are binary files. Use get_failed_tests to get attachment paths and open them directly if needed.
Attachment "..." is too large to return inline
The attachment exceeds 1 MB. Read the file directly from the path returned by get_failed_tests.
Development
npm test # run tests once
npm run test:watch # watch mode
Runtime code lives under src/ and compiles to dist/. Tests use Vitest with focused unit coverage for helpers plus MCP tool integration coverage via InMemoryTransport. No build step or Playwright installation required to run the regular test suite.
Cutting a release
Releases are produced by pushing a v* tag. .github/workflows/release.yml picks up the tag, verifies the tag matches all three version fields, runs npm ci + npm run build + npm test, creates a GitHub Release with auto-generated notes categorized per .github/release.yml (Features / Bug fixes / Documentation / Dependencies / Other changes), and publishes to npm. .github/workflows/publish-mcp.yml then chains off Release via workflow_run and publishes server.json to the MCP registry. Merging to main does not trigger a publish.
Version lives in three places and all three must match the tag before pushing it:
package.json → version
server.json → top-level version
server.json → packages[0].version
Bump all three in one PR and merge to main before cutting the release. release.yml fails the run if the tag disagrees with any of these values.
Ritual:
# After the version-bump PR has merged to main:
git checkout main && git pull
git tag v1.0.5
git push origin v1.0.5
# → release.yml fires: verifies tag, builds, tests, creates GitHub Release, publishes to npm
# → publish-mcp.yml chains off Release and publishes server.json to the MCP registry
Flow:
Open a bump PR that updates all three version fields. Merge it to main.
Tag the bump commit v<version> and push the tag.
release.yml verifies tag/version alignment, runs npm ci, confirms the version is not already published on npm, runs npm run build + npm test, creates the GitHub Release, then publishes to npm with npm publish --access public --provenance.
publish-mcp.yml (triggered by workflow_run on Release) re-verifies the version fields, confirms the version is not already on the MCP registry, and publishes server.json to registry.modelcontextprotocol.io.
No repository secrets required. Both npm and the MCP registry authenticate via GitHub OIDC (npm trusted publishers). The trusted publisher for npm is configured on npmjs.com under the package's Settings → Publishing access → Trusted Publisher section — no NPM_TOKEN secret exists or is needed.
Recovery from a failed publish: npm refuses to republish an existing version and restricts unpublishing after 72 hours. If a publish fails for any reason, bump to the next patch version in a new PR and cut a new release — do not try to re-run the failed release.
Contributing
See CONTRIBUTING.md for bug reports, pull requests, development setup, and commit conventions.
คัดลอกคอนฟิก stdio สำหรับ Cursor, Claude Desktop, Claude Code หรือ VS Code ได้ในหน้านี้ คอนฟิกนี้ใช้การติดตั้งของผู้เผยแพร่ ไม่ใช่พร็อกซีของ PlugMCP
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ตรวจสอบล่าสุดเมื่อ 2026-11-14 MCP server for running Playwright tests and reading structured results — designed for AI agents doing test failure analysis
