Summary
Codex subagent completion output can interleave mid-token with main-agent assistant output in the visible chat UI.
The persisted messages/events appear to remain separate, but the rendered chat text can splice the two outputs together.
Example
Expected separate text fragments:
Include constraints: read-only, use a specific tool, don’t modify files.
I’m seeing a clear split: short diagnostic nudges during debugging...
Observed rendered text:
Include constraints: read-only, use a specific tool, don’tI modify’m seeing files a. clear split...
Reproduction Shape
- Use T3 Code with Codex.
- Start a main-agent turn that spawns a background/subagent.
- Have the main agent emit commentary while the subagent is completing.
- Observe the visible chat output when both messages arrive close together.
Expected Behavior
Main-agent messages and subagent completion messages should render as separate chat items, or otherwise remain textually isolated.
Actual Behavior
The UI can render a single garbled assistant output where text from the subagent completion and main-agent commentary are interleaved mid-token.
Evidence
In one observed case, local provider logs showed two separate item/completed events about 72 ms apart:
- one for main-agent commentary
- one for subagent final output
The local SQLite projection also contained separate assistant message rows. This suggests the issue is likely in stream/render/event assembly rather than model output.
Impact
This makes Codex subagent workflows hard to trust because final answers can appear corrupted even when the underlying stored events are distinct.
Related Issues
Possibly related to prior stream/rendering issues:
Summary
Codex subagent completion output can interleave mid-token with main-agent assistant output in the visible chat UI.
The persisted messages/events appear to remain separate, but the rendered chat text can splice the two outputs together.
Example
Expected separate text fragments:
Observed rendered text:
Reproduction Shape
Expected Behavior
Main-agent messages and subagent completion messages should render as separate chat items, or otherwise remain textually isolated.
Actual Behavior
The UI can render a single garbled assistant output where text from the subagent completion and main-agent commentary are interleaved mid-token.
Evidence
In one observed case, local provider logs showed two separate
item/completedevents about 72 ms apart:The local SQLite projection also contained separate assistant message rows. This suggests the issue is likely in stream/render/event assembly rather than model output.
Impact
This makes Codex subagent workflows hard to trust because final answers can appear corrupted even when the underlying stored events are distinct.
Related Issues
Possibly related to prior stream/rendering issues: