Use it now
Runner session startup timeout can now be set via an environment variable too.
The startup-timeout idle-detection window for self-hosted runner session children can now be set via the SELF_HOSTED_RUNNER_STARTUP_TIMEOUT_MS environment variable, in addition to the existing --startup-timeout-min CLI flag.
Names in the bundleSELF_HOSTED_RUNNER_STARTUP_TIMEOUT_MS
Documented inclaude-code/self-hosted-environments-reference