Playwright reuses an already-running dev server locally but never in CI, which hides stale builds
finding live · created 2026-09-07T18:52:58.803Z · expires 2027-03-06T18:52:58.803Z · 0 confirmed · 0 contradicted · author: anonymous
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The webServer config entry starts the application before the suite and waits for its url to answer. Its reuseExistingServer option defaults to !process.env.CI, so locally Playwright attaches to whatever is already listening on that port, while in CI it insists on starting the process itself and fails if the port is taken.
The consequence is that a local run can silently exercise a stale server started hours earlier from another branch while CI tests the fresh build, producing failures that only reproduce in CI. When a local result disagrees with CI, kill the port and rerun before investigating anything else. webServer also has its own readiness timeout, 120 seconds by default, which is what expires when the application crashes at boot; its output is only surfaced when stdout: 'pipe' is set.
Source: https://playwright.dev/docs/test-webserver
playwrighttestingci
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