Windows Desktop + VS Code: legacy thread history stops at an inner turn completion despite valid later records

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

26.730.7989.0

What subscription do you have?

Pro 20x

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 x64

What issue are you seeing?

On Windows, a conversation used from both Codex Desktop and the VS Code
extension is consistently truncated at the completion of an inner turn.

The UI always stops at the same task_complete boundary. It does not display
any subsequent messages, although valid records after that boundary are still
present in the rollout JSONL file.

No error message is shown in the UI.

What steps can reproduce the bug?

1. Open or resume the same existing thread in Codex Desktop and the VS Code

extension on Windows.

1. Start a turn in one client.
2. Before it completes, submit another prompt from the other client.
3. Allow the newer inner turn to complete before the older outer turn.
4. Reload or resume the thread in Codex Desktop.
5. Observe that history stops at the inner turn's completion.

Affected session ID:

019fc57f-8aea-7241-bad5-bf69a124b66a

Rollout metadata:

• history_mode: legacy
• cli_version at the cutoff: 0.147.0-alpha.1.2
• VS Code extension: 26.727.40816-win32-x64
• Desktop client recorded during the incident: 26.730.61309
• Model context window: 258,400 tokens
• Inner turn at completion: 183,745 / 258,400 tokens (71.1%)
• Outer turn near the cutoff: 218,803 / 258,400 tokens (84.7%)
• No context-limit error occurred

Exact persisted lifecycle order:

• Line 3047: outer Turn A starts
• Line 3186: inner Turn B starts before Turn A completes
• Line 3237: Turn B completes
• Line 3238: Turn A continues
• Line 3270: Turn A completes

The UI always stops at line 3237 and does not render line 3238 onward.

Local logs also show two app-server processes handling the same thread:
PID 8888 identified as Codex Desktop, and PID 15548 identified as VS Code.

What is the expected behavior?

Completing an inner turn must not end the entire displayed conversation while
an outer turn continues in later rollout records.

The UI should render all persisted records. If overlapping clients are not
supported, Codex should reject or serialize the second writer and display an
explicit error instead of silently truncating history.

Additional information

This may be related to #33241, but the environment and primary symptom differ.

#33241 reports divergent histories being merged after two app-server processes
write to one rollout. This report concerns Windows Desktop + VS Code and a
deterministic rendering cutoff at an inner turn's task_complete event.

The rollout's large size may amplify loading costs, but it does not explain
the fixed event-boundary cutoff. The JSONL remains valid, and the hidden tail
was successfully recovered into a new thread.

Related: #33241, #34034, #34767