[Bug] Concurrent mobile Claude Code session corrupts text/document content in desktop claude.ai session

Bug Description
TITLE: Concurrent mobile Claude Code session causes pasted text/documents in an existing desktop claude.ai session to arrive empty

SEVERITY: High — silently corrupts an active working session; no error shown to the user; the desktop session's model receives empty content and the user doesn't know until the assistant reports it can't see anything.

ENVIRONMENT:

Desktop: claude.ai in Chrome on Windows, long-running conversation, signed in as [account]
Mobile: Claude Code on the Claude mobile app (iOS), same account — session either running concurrently or resumed from the chat-history window
Date/time observed: 2026-08-10, roughly [your local window, e.g. late morning CT]

STEPS TO REPRODUCE:

Start a long-running conversation in claude.ai on desktop; confirm pasting text/documents into it works.
On the mobile app, open (or resume from chat history) a Claude Code session on the same account.
Interact with the mobile Claude Code session — issue a work order, have it create a document.
Return to the desktop claude.ai session and paste text or attach a text document into the message box; send.

EXPECTED: Desktop session receives the pasted/attached content normally.

ACTUAL: The message sends and the attachment/paste appears present in the UI, but the assistant receives it with empty content — it reports the document arrived with no readable text. Reproduced on four consecutive attempts during the mobile session's active window. No error, no warning, no retry prompt anywhere.

KEY DIAGNOSTIC DETAILS:

Failure is selective by content path: during the same window, image uploads (.png screenshots) worked normally and a .docx file attachment uploaded and was fully readable by the assistant. Only pasted text / text-document ingestion failed.
Failure is silent on the sender side: the desktop UI gives no indication anything is wrong; the assistant's inability to see the content is the only signal.
Recovery occurred without desktop restart, correlating with the mobile Claude Code session becoming inactive.
Assistant-side confirmation available: the desktop session's model explicitly reported receiving document blocks with no extractable content on each failed attempt, then confirmed normal reception after recovery — timestamps in the conversation history.

HYPOTHESIS (user-level, unverified): Some per-account session/upload state is shared or locked between the mobile Claude Code session and the desktop claude.ai session, such that active mobile Claude Code file/document operations block or null the text-ingestion path for the concurrent desktop session.

IMPACT: Broke a production content-workflow session mid-stream (completion reports from Claude Code could not be reviewed); cost ~4 failed exchanges before workaround found.

WORKAROUND FOUND: Attach content as .docx (survives), or screenshot it (survives) — or close/idle the mobile Claude Code session, after which plain paste recovers.

Environment Info

• Platform: linux
• Terminal: wsl-Ubuntu-22.04
• Version: 2.1.226
• Feedback ID: 4147e239-9f35-4bd6-b6a3-3117db114930

Errors

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