Graceful handling when API returns 'Could not process image' - session becomes unrecoverable

Problem

When too many images accumulate in the conversation context (e.g., >20 images from user uploads or MCP tool results), the Anthropic API returns:

API Error: 400
{"type":"error","error":{"type":"invalid_request_error","message":"Could not process image"}}

This error makes the entire session unrecoverable:

1. Every subsequent API call resends the full context (including the problematic images)
2. Every call fails with the same error
3. /compact also fails — because compaction itself requires an API call that includes the same context
4. /exit says "Bye!" but the session continues and keeps failing
5. The user is trapped in a dead session with no way to recover except force-killing the terminal

Expected Behavior

1. Pre-flight image count check: Before sending a request, count the number of image blocks in the conversation context. If approaching the API limit (~20), warn the user and suggest compacting or splitting the work.

1. Graceful error recovery: When receiving "Could not process image" error, Claude Code should:

• Detect this specific error pattern
• Automatically strip/drop the problematic image(s) from the context
• Retry the request without the images
• Inform the user that some images were dropped to recover the session

1. Emergency compaction: /compact should have a fallback mode that strips all image blocks from context before attempting the compaction API call, so it can always succeed as a last resort.

Reproduction Steps

1. Start a Claude Code session
2. Upload or generate 20+ images in the conversation (e.g., via chrome-devtools MCP extracting charts from a paper)
3. Every subsequent interaction fails with "Could not process image"
4. /compact fails, /exit fails, session is dead

Impact

• Lost a 23-hour session ($66+ in API costs)
• All conversation context lost (file changes on disk were preserved)
• No warning before hitting the limit
• No recovery mechanism once the limit is hit

Environment

• Claude Code (latest)
• macOS