Remote-control: Sending image from mobile crashes session with API 400 - missing media_type field

Bug Description

When sending an image via /remote-control from a mobile device (Claude.ai mobile app), the image is transmitted without the required media_type field in the base64 source payload. This causes a 400 API error that poisons the conversation context, making every subsequent message in the session also fail with the same error — effectively crashing the remote-control session entirely.

Steps to Reproduce

1. Start a claude session on desktop with /remote-control active
2. From mobile (Claude.ai), send an image (e.g., a photo from phone camera roll)
3. Observe 400 API error

Error Message

API Error: 400
{"type":"error","error":{"type":"invalid_request_error","message":"messages.78.content.1.image.source.base64.media_type: Field required"},"request_id":"req_011CYzLqiH3hVWkpSqoePJT4"}

Cascade Behavior

Once the malformed image message lands in context, all subsequent messages fail with the same 400 error — the session becomes completely unusable and must be abandoned.

Expected Behavior

• Image from mobile should include media_type field (e.g., "image/jpeg" or "image/png")
• OR: graceful error handling that removes/ignores the malformed message rather than poisoning the entire context

Environment

• Platform: Linux (Fedora 42)
• Claude Code version: 2.1.63
• Node: v22
• Remote-control session: via claude CLI → /remote-control (workaround for #28854)
• Mobile client: Claude.ai web/app on Android/iOS

Related Issues

• #28854 (Node v22 claude remote-control terminal command bug — separate issue, this is a new bug specific to image sending)

Impact

Session completely lost — user must reconnect and loses conversation context.