Conversation permanently stuck after 'vision is not enabled' error from GitHub Copilot provider #29571

Bug: Conversation becomes permanently stuck after "vision is not enabled" error from GitHub Copilot

Environment

• opencode version: 1.15.11
• Client: opencode Desktop
• Provider: GitHub Copilot (organization-managed)

Description

When the organization has vision (image support) disabled for GitHub Copilot, opencode hits a 400 error and the entire conversation becomes permanently stuck. No further messages can be sent or received — the session is completely bricked.

Error message

Request Failed: 400 {"error":{"message":"vision is not enabled for this organization","code":""}}

Steps to reproduce

1. Use opencode Desktop with a GitHub Copilot provider where the organization has disabled vision/image capabilities.
2. Trigger a request that includes image content (this may happen automatically, e.g., when the model tries to read an image file, or when the conversation context includes image attachments).
3. The request fails with the 400 error above.
4. All subsequent messages in the conversation also fail — the conversation is permanently stuck.

Expected behavior

1. Graceful error recovery: The failed message should be retried without the image content, or the user should be informed that vision is disabled and given the option to continue the conversation without image content.
2. Conversation should not be bricked: After a transient or capability-related error, the user should still be able to send new messages in the same conversation.
3. Fork/retry option: The UI should offer a way to fork the conversation or retry the last message (without the problematic image content) to recover from this state. Currently there is no fork option available in the Desktop UI.

Actual behavior

• The conversation is permanently stuck after the error.
• No further messages can be produced.
• There is no fork or retry option in the Desktop UI to recover.
• The only workaround is to start an entirely new conversation and lose all context.

Suggested fixes

• Detect the "vision is not enabled" error and automatically strip image content from the request, then retry.
• Don't let a single failed request brick the conversation — subsequent new messages should still be sendable.
• Add a fork/branch option in the Desktop UI so users can recover from stuck conversations without losing context.