Agent output withheld until next user turn when long shell commands are backgrounded (Fusion/Auto mode) #5370

Describe the bug

With Copilot Fusion / Auto mode active, the agent's output stops appearing in the session for long stretches. From the user's view, the agent looks stuck. Nothing more appears until the user sends another message; the delayed output then arrives all at once with the reply to that message.

The agent is not stuck: it is waiting on CI or tests, and those keep making progress. The output just isn't shown to the user until they type again.

Observed pattern

1. The agent runs a long bash command synchronously (e.g. sleep 120; gh run view ... with initial_wait: 150).
2. The command is "moved to background by the user" (or otherwise times out). The tool result tells the model not to respond and not to call more tools; it should wait for the user's next instruction.
3. The model obeys and ends its turn without a visible message, and/or the completion notification for the backgrounded command is not processed until the next user turn.
4. To the user, the session appears frozen. Only after they send a message does the agent resume and report status.

This happened several times in one long session. Each time, the user had to ask "Done?", "I think you're stuck?" or "Is it really just taking a long time?" to get output.

Expected behavior

• When a backgrounded or async command finishes, the runtime should wake the agent, or at least show a visible status, without waiting for user input.
• If the agent is told to end its turn silently, the UI should make it clear that the agent is waiting on a background task rather than looking hung.

Related

• Coordinator stuck "Working" while only a background subagent runs — queued input not answered or shown as pending #4225 (coordinator stuck "Working" while a background subagent runs)
• ctrl+x → b  fails to background/interrupt a blocking  read_bash  call (no escape hatch when polling an async command) #4110 (no escape hatch when blocking on read_bash)

Environment

• Copilot CLI 1.0.105
• macOS
• Auto mode / Copilot Fusion (model switched dynamically during the session)