Karma captureTimeout and browserNoActivityTimeout limits in singleRun mode

Direct answers

1. Yes. In Karma 6.x with singleRun: true, browserNoActivityTimeout applies after successful capture. It measures silence between browser-to-server messages, not total elapsed run time.
2. No. captureTimeout and browserNoActivityTimeout are global karma.conf.js settings. You cannot set different values per browser instance; every launcher plugin reads the same global timers.
3. When browserNoActivityTimeout elapses before completion, Karma forcibly disconnects the browser, fails the run, and exits non-zero. Results received before the timeout are reported, but the suite is marked incomplete. Karma does not restart the browser or persist partial results to disk.

Likely explanation versus confirmed facts

Confirmed behavior (Karma 6.x): captureTimeout covers only initial browser launch and WebSocket handshake. After capture succeeds, browserNoActivityTimeout governs inactivity. If multiple browsers run in parallel, the first browser to exceed the window fails the entire run immediately.

Assumption: You use a pinned Karma 6.x launcher such as karma-chrome-launcher or karma-firefox-launcher with a fixed browser binary.

Uncertainty: Whether a reporter flushes partial results on process termination depends on the reporter. Treat CI logs as the only reliable record unless you verify your reporter's shutdown behavior.

Steps for this case

1. Set both timeouts globally in karma.conf.js:

module.exports = function (config) {
  config.set({
    singleRun: true,
    captureTimeout: 120000,
    browserNoActivityTimeout: 60000,
    browsers: ['ChromeHeadless']
  });
};

1. Add headless stability flags if your launcher supports them, for example Chrome --no-sandbox and --disable-dev-shm-usage in CI.
2. Run npx karma start --single-run and confirm the process exits with a non-zero code when a browser hangs.

Verification

Add a temporary stalling test:

it('stalls the browser', function () {
  return new Promise(function () {});
});

Run npx karma start --single-run with browserNoActivityTimeout: 5000. Expect exit after roughly five seconds with a Disconnected (browserNoActivityTimeout) message and non-zero exit code. Increase to 30000 and confirm failure occurs near thirty seconds.

Missing diagnostic detail: Are you using a cloud launcher such as Sauce Labs or BrowserStack? If yes, its own timeout logic may supplement or override Karma's timers, and the recommendation changes to configure the launcher-specific timeout instead of—or in addition to—Karma's global values.