Codex Desktop becomes unresponsive when opening previous conversations; thread history loading appears too eager

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

26.616.71553

What subscription do you have?

business

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 x64

What issue are you seeing?

Problem

When opening previous conversations in Codex Desktop, the app often becomes very slow or temporarily unresponsive while loading conversation history.

logs showed slow thread operations:

• thread/list: up to about 29.9s
• thread/resume: up to about 18.3s
• thread/start: up to about 23.7s

This happens even with a relatively small number of saved sessions.

Local Findings

Raw file I/O does not appear to be the main bottleneck:

• Reading the largest 11.14 MB transcript from disk: about 38ms
• Parsing that transcript as JSONL: about 176ms
• Parsing all 25 session files, about 48 MB: about 962ms

Isolated app-server tests using a temporary CODEX_HOME with only one copied session showed:

• thread/list default scan: 77ms
• thread/list with useStateDbOnly=true: 10ms
• thread/read includeTurns=false: 40-87ms
• thread/read includeTurns=true: 479ms
• thread/turns/list summary 20: 357ms
• thread/resume default: about 2.1s

So the long Desktop stalls are likely not caused by JSONL file size alone. They seem to come from higher-level Desktop/app-server behavior around session listing, resume semantics, plugin/network initialization, UI state, or foreground metadata repair.

During isolated app-server tests, thread/resume also attempted plugin/network-related work, including featured/curated plugin fetches and websocket connection attempts. That suggests thread/resume may be too heavy for simply opening/viewing an old conversation.

Expected Behavior

Opening the conversation list or clicking an old thread should remain responsive. The app should show lightweight metadata quickly and load detailed history progressively.

What steps can reproduce the bug?

The bug happens when opening/resuming previous conversations in Codex Desktop on Windows. The app can become very slow or temporarily unresponsive while loading local conversation history.

Observed affected session:

• Session ID: 019ed607-cdbe-7f52-b24e-ff56a519e8fd
• Token/context window usage: not applicable / not captured. The slowdown occurs before sending a new prompt or starting a model turn. No new token generation is required to reproduce the loading issue.

Steps to reproduce:

1. On Windows, use Codex Desktop with several saved local conversations under ~/.codex/sessions.
2. Ensure at least one previous conversation has a relatively large transcript. In my case:

019ed607-cdbe-7f52-b24e-ff56a519e8fd, about 11.14 MB.

1. Open Codex Desktop.
2. Open the previous conversation list / history.
3. Click the old conversation above.
4. Observe that Codex Desktop may become very slow or temporarily unresponsive while loading/resuming the conversation.

What is the expected behavior?

Opening a previous conversation should be responsive and fast.

Additional information

_No response_