[BUG] Conversations do not sync between mobile and desktop on the same account (persistent, not a one-off incident)

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?

Summary

Conversations started on one surface do not reliably appear on another surface signed in to the same account. This is not a transient outage — it has persisted across multiple sessions and multiple days, with status.claude.com reporting all systems operational at the time.

This is closely related to #81658 ("Cross-platform sync failure (Desktop/Web/Android) causing Cowork conversations and chats to disappear"), which is still open and unassigned, and to the reports referenced there: #59850, #54113, #22931, #60669. The volume of separate reports over several months suggests a systemic issue rather than a set of isolated incidents.

Environment
<!-- Fill in / correct before posting -->
Desktop: macOS, 24" iMac + MacBook (both signed in), Claude desktop app vX.Y.Z
Mobile: iOS / Android, Claude app vX.Y.Z
Account: single personal account, same email on all surfaces
Surfaces affected: claude.ai chats and/or Cowork sessions
Anthropic status at time of failure: All Systems Operational

What Should Happen?

Expected

The conversation appears in the mobile recents list within seconds, with full message history, and vice versa.

Actual

The conversation is absent from the other device's list — sometimes indefinitely, sometimes appearing hours later. Existing conversations have also been observed to lag or go missing in the other direction.

Why this matters

Cross-device continuity is a headline promise of the product — the docs state plainly that "your sessions and files live with your Claude account and go where you go, on any device" (support article). When that promise is unreliable, the failure is silent and indistinguishable from data loss: an empty list on the phone gives the user no way to tell whether the conversation is syncing slowly, sitting under a different account, filed inside a Project, or actually gone.

Requested changes
Fix the underlying sync reliability. Conversations created or updated on any surface should converge across all surfaces of the same account within seconds, with retry on failure.
Make sync state observable. A "last synced" timestamp and a manual refresh control, so a lagging sync is distinguishable from a missing conversation.
Surface account mismatch explicitly. If a device is signed in to a different account or org than the user expects, say so — an empty recents list is the worst possible signal for the most common cause.
Fail loudly, not silently. If a sync request errors, tell the user rather than rendering an empty state.

Error Messages/Logs

Steps to Reproduce

Steps to reproduce
Sign in to the Claude desktop app and the Claude mobile app with the same account.
Start a conversation on desktop and exchange a few messages.
Open the mobile app and pull to refresh / force-quit and reopen.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.247 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_