Session breaks after regressing a user message that contains an inline image

Summary

Attempting to regress/retract a user message that contains an attached image appears to leave the Claude Code session in a broken state. Subsequent messages don't process correctly and the session has to be abandoned or forked to continue meaningful work.

Environment

• OS: Windows
• Model: claude-opus-4-7[1m] (1M context)
• Context: Long-running session

Reproduction (as best observed)

1. In an active Claude Code session, send a user message that includes an inline image (pasted/attached screenshot).
2. Use the regress/retract affordance to roll back past that message.
3. Session enters a bad state — user inputs don't get processed normally, or the next response is inconsistent with the regressed state (observed error framing: "Claude couldn't process that message. Try sending it again.")
4. Resending does not recover; the session remains broken until abandoned or forked.

Expected

Regressing a message with an image should remove both the text and the image cleanly, reverting to the prior turn, with the session fully usable afterward.

Actual

Session becomes unresponsive / inconsistent. Symptoms consistent with corrupted message history or orphaned image references in the transcript.

Notes

• Not every image-bearing message regression breaks the session, but the failure is reproducible enough to be avoided in practice.
• Long-running 1M-context session may exacerbate; possible interaction between transcript size and image attachment handling.
• No obvious recovery path short of forking or starting a new session.