Side chat panel hangs indefinitely ("Waiting for Claude...") on slash-command invocations

Environment

• Claude Code desktop app, macOS (Mac mini)
• Model: Fable 5.1, effort: Medium
• Feature: the "Side chat" panel opened from within an active main session

Steps to reproduce

1. In an active, long-running main session, open the "Side chat" panel (opened from within the session itself, not a separate session).
2. In the side chat, invoke a slash command — reproduced with both /goal-evaluator (a custom project skill) and /reload-skills (a built-in command).
3. Observe the side chat's status indicator.

Expected behavior
The side chat command completes and returns output within a reasonable time (seconds to low minutes for a Medium-effort request).

Actual behavior
The side chat shows "Waiting for Claude..." indefinitely — observed hangs of 3+ minutes and 6+ minutes with no completion, no error, and no partial output. The main chat pane continues to function normally and shows its own separate "thinking" indicator during this time, suggesting the side chat's request is stuck rather than the whole app being blocked.

Notes

• Reproduced with two unrelated slash commands (a custom project skill and the built-in /reload-skills), suggesting the issue is with side-chat command execution generally, not specific to one skill's content.
• No error surfaces in the UI — the panel just spins with no way to tell if it's still working or truly stuck.

🤖 Generated with Claude Code