`_probe_remote_backend` spins up an environment with
`task_id="prompt-backend-probe"` purely to run one `uname` for the system
prompt, then drops the reference without cleaning up. Container backends
default to `container_persistent` / `docker_persist_across_processes`, so
that throwaway sandbox stays up for the entire process lifetime, sitting
idle next to the agent's own `default` sandbox.
Observed on a three-profile Docker-backend host: six running containers
where three were doing any work. Every profile permanently paid for one
extra container whose only job had been a single `uname` at startup.
Fix: wrap the probe in `try/finally` and call
`env.cleanup(force_remove=True)` — the explicit-teardown path that
`DockerEnvironment.cleanup` already documents ("No current caller passes
`force_remove=True`; the parameter is here so the explicit-teardown
semantics can be wired up later"). Backends that inherit the kwarg-less
base `cleanup()` fall back to the bare call.
Verified on a live aarch64 Docker backend: the probe container is now
created, used and reclaimed within the same call. Three regression tests
cover the success path, the exception path, and the kwarg-less fallback;
all three fail without the source change.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PLbMzWqHVTPNBFisM8UiNB
Fatmylin
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