Escape-to-interrupt spawns duplicate agent instances; scrollback replays prompts and drains tokens

Summary

After pressing Escape to interrupt a running turn, subsequent activity in the same CLI window suggests multiple instances of the assistant are running in parallel. Additionally, scrolling up in the terminal appears to re-submit prior prompts, which:

• Wastes tokens (duplicate turns appear to be charged)
• Causes the assistant to redo work unnecessarily
• Produces confusing, interleaved output across what seem to be concurrent sessions

Expected behavior

• Pressing Escape cleanly cancels the in-flight turn with no lingering background instance.
• Scrolling back through the terminal is read-only — it should never re-submit prior prompts.

Actual behavior

• Duplicate assistant instances appear to persist after Escape.
• Scrolling replays input, triggering duplicate turns.

When it started

Noticed since Opus 4.7, possibly earlier.

Environment

• Model: claude-opus-4-7 (1M context)
• Platform: darwin (macOS 25.3.0)
• Shell: zsh

Repro notes

Hard to capture in a minimal repro without a recording. Next occurrence I'll try to attach an asciinema / script session so the scroll-replay behavior is visible.