Codex App: full-history subagent forks can lose workspace tools after compaction #40890

What version of the Codex App are you using (From “About Codex” dialog)?

26.818.61809 (build 7019)

What subscription do you have?

ChatGPT Pro

What platform is your computer?

Darwin 25.6.0 arm64 arm

What issue are you seeing?

In Multi-Agent V2, a subagent spawned with fork_turns="all" from a compacted parent thread can receive no workspace tools. The child cannot invoke exec, read files, or edit the workspace; only the codex_app dynamic namespace is present.

From the same parent thread, spawning the same agent type with fork_turns="none" immediately provides exec and normal workspace access.

What steps can reproduce the bug?

1. Use a long-running Codex App thread that has undergone compaction.
2. Spawn a subagent with fork_turns="all" and ask it to run a command or read a workspace file.
3. Observe that the child has no callable workspace tools. A follow-up turn does not restore them.
4. From the same parent, spawn the same agent type with fork_turns="none".
5. Observe that the new child can invoke exec immediately.

Observed in the same parent thread:

• Parent session: 01a03db5-5284-7352-8680-f149957387be
• fork_turns="all" failures: 01a03e5f-18f5-7150-8538-344970d8ca80, 01a03e5f-e357-7d73-b22a-a8e422c5da72, 01a03e6c-9c2b-7811-b382-e0d1f745a257
• fork_turns="none" success: 01a03e6d-0737-7131-8efa-374e5838d032

The result was 3/3 failures for full-history forks and 1/1 success for the context-free fork. Context-window usage was not displayed, but the parent had just undergone compaction.

What is the expected behavior?

History inheritance and compaction should not change the workspace tool set available to a subagent. A child spawned with fork_turns="all" should retain the same applicable workspace tools as one spawned with fork_turns="none".

Additional information

• Embedded CLI recorded in session metadata: 0.149.0-alpha.4.3
• Multi-agent version: v2
• Workaround: use fork_turns="none"
• Full rollout files contain private repository context and are not attached publicly. Sanitized excerpts can be provided if needed.