feat: default prime runtime idle timeout to 1h

[mikasenghaas]

Summary

• Add idle_timeout to PrimeConfig (seconds, default 3600 = 1h) and thread it through PrimeRuntime.start into CreateSandboxRequest.
• Prime sandboxes now self-terminate after 1h of inactivity by default, so a leaked sandbox is reclaimed well before its 24h max lifetime (timeout_minutes) instead of costing a full day.
• The config surface is in seconds to match how time is expressed everywhere else in v1 (TimeoutConfig, task timeouts); it's converted to prime's whole-minute API in start (ceil'd, floored to the SDK's 1-minute minimum).
• Reject an idle_timeout above the 24h max sandbox lifetime at config time (via a shared MAX_LIFETIME_MINUTES constant), instead of letting it fail at sandbox creation when the derived minutes exceed timeout_minutes.
• Set tools.runtime.idle_timeout = null to disable, or to any positive number of seconds up to 24h to tune it.

🤖 Generated with Claude Code

---

Note

Medium Risk
Changes default Prime sandbox lifecycle (idle self-delete after 1h), which can terminate long-idle evals unless tuned or disabled via idle_timeout = null.

Overview
Prime sandboxes now get a configurable idle timeout so leaked sandboxes are reclaimed after inactivity instead of running until the 24h max lifetime.

PrimeConfig gains idle_timeout in seconds (default 3600, None disables). A validator rejects values above the shared MAX_LIFETIME (24h) cap. PrimeRuntime.start maps seconds to Prime’s whole-minute API (idle_timeout_minutes, ceil with a 1-minute floor) and uses MAX_LIFETIME for timeout_minutes instead of an inline constant.

^{Reviewed by Cursor Bugbot for commit 7f7c169. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Default prime runtime idle timeout to 1 hour

• Adds an idle_timeout field to PrimeConfig (default 3600s) that is passed to sandbox creation as idle_timeout_minutes, causing sandboxes to self-delete after 60 minutes of inactivity by default.
• A model-level validator enforces that idle_timeout does not exceed the 24h MAX_LIFETIME constant; set idle_timeout=None to disable idle timeout entirely.
• Risk: existing sandboxes that relied on no idle timeout will now be terminated after 1 hour of inactivity unless idle_timeout is explicitly set to None.

^{Macroscope summarized 7f7c169.}

[macroscopeapp]

Approvability

Verdict: Needs human review

This PR changes the default runtime behavior by enabling a 1-hour idle timeout for sandboxes where none existed before. While well-implemented and properly validated, the default behavior change affects all existing users and warrants human review to confirm the intended impact on sandbox lifecycle.

^{You can customize Macroscope's approvability policy. Learn more.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 71a69c0. Configure here.}