[VSCode Extension] Attaching an image to the prompt causes complete chat stall and irreversible history loss

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Bug Description

When attempting to attach an image to the chat prompt in the Claude Code VSCode extension, the entire chat session freezes/stalls completely. The UI becomes unresponsive, and no further interaction is possible.

The critical part: if the user attempts to restart the extension or the chat to recover from the stall, all conversation history is permanently lost. There is no way to recover the previous session context.

This is a data-destructive bug — it silently destroys potentially hours of accumulated conversation context with no warning and no recovery path.

Steps to Reproduce

1. Open Claude Code in VSCode
2. Have an active conversation with significant history (multiple tool calls, file reads, etc.)
3. Attempt to attach an image file (PNG/JPG) to the chat prompt
4. Observe: the chat stalls — no response, UI becomes unresponsive
5. Attempt to restart the extension or chat session
6. Observe: all previous conversation history is gone

Expected Behavior

• Image attachment should work without stalling the chat
• If attachment fails, it should fail gracefully with an error message
• Conversation history should never be silently destroyed under any circumstance
• At minimum, history should persist across restarts

Actual Behavior

• Chat enters a permanent stall state upon image attachment
• Restart is the only recovery option
• Restart destroys all conversation history irreversibly
• No error message, no warning, no recovery option

Environment

• Extension: Claude Code for VSCode
• OS: Windows 10 Home 10.0.19045
• Hardware: ASUS GL553VE, GTX 1050 Ti 4GB
• Model: Claude Opus 4.6

Impact

This bug has severe practical consequences:

• Loss of work context: In long-running sessions involving multi-step pipelines, file analysis, and iterative development, the accumulated context is extremely valuable. Losing it forces complete reconstruction from scratch.
• Workflow disruption: Users cannot safely use image attachment, which is a core advertised feature.
• Trust erosion: Silent, irreversible data loss is the most damaging class of bug for user trust.

Suggested Fix Priority

This should be treated as P0/Critical because:

1. It involves silent data loss with no recovery
2. It's triggered by a standard UI action (attaching an image), not an edge case
3. The failure mode is catastrophic (total history loss), not graceful

Workaround

Avoid attaching images via the UI. Instead, save the image to disk and ask Claude to read it via file path (using the Read tool), which works correctly.

What Should Happen?

Expected Behavior

• Image attachment should work without stalling the chat
• If attachment fails, it should fail gracefully with an error message
• Conversation history should never be silently destroyed under any circumstance
• At minimum, history should persist across restarts

Error Messages/Logs

"prompt too long"

Steps to Reproduce

Steps to Reproduce

1. Open Claude Code in VSCode
2. Have an active conversation with significant history (multiple tool calls, file reads, etc.)
3. Attempt to attach an image file (PNG/JPG) to the chat prompt
4. Observe: the chat stalls — no response, UI becomes unresponsive
5. Attempt to restart the extension or chat session
6. Observe: all previous conversation history is gone

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

OPUS 4.6

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_