TUI rendering race condition

[krissetto]

There seems to be a race condition in the TUI when rendering very fast and short responses (e.g. a small model like gpt-5-mini responds to a "hello" very quickly).

When this occurs, resizing the terminal can force the re-render of the response which will then appear correctly

Version affected

c077938 on main branch

How To Reproduce
run cagent run agent.yaml with a small model and send it something short like "Hello"

agent.yaml

version: "2"
agents:
  root:
    model: openai/gpt-5-mini
    instruction: you are a helpful assistant

Expectation

Response always renders correctly

OS and Terminal type

Reproduced on MacOS 26 and Ubuntu 25.10 with vscode and ghostty

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Screenshots