[FEATURE] Cross-machine session resume — sync session state for CLI-to-CLI handoff

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Summary

• Allow a Claude Code CLI session started on one machine to be resumed from another machine's CLI, enabling true cross-device session handoff without requiring SSH or shared filesystems.

Current Workarounds

• SSH + tmux: SSH into the original machine and reattach to a tmux session. Works, but requires the original machine to stay on and accessible.
• Remote Control via claude.ai/code: Lets you view/interact with a running CLI session remotely, but the CLI must remain running on the host and you can't detach it to run locally on the second machine.
• --from-pr: Resumes from a PR's context, but doesn't carry over the full conversation history.

None of these provide a true "hand off and continue locally" experience.

Proposed Solution

Sync session state (conversation history, tool outputs, working directory context) to the cloud so that claude --resume <session-id> works from any authenticated machine. This could involve:

1. Cloud-backed session storage — Opt-in sync of session data to Anthropic's servers (tied to the user's account)
2. Session export/import — A simpler alternative: claude session export <id> produces a portable file, claude session import <file> loads it on another machine
3. Hybrid approach — Cloud sync for conversation history, with a prompt to re-establish local context (working directory, file state) on the new machine

Considerations

• Privacy: Session data may contain sensitive code/context — cloud sync should be opt-in with clear data handling policies
• File state divergence: The working directory on machine B may differ from machine A — the resumed session should handle this gracefully (e.g., warn about missing files, re-read changed files)
• Authentication: Should be scoped to the same Anthropic account

Environment

• macOS (both machines)
• Claude Code CLI

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

Use Case

• I work across multiple machines (e.g., Mac Studio at my desk, MacBook Pro on the go). When I start a Claude Code session on one machine, I'd like to pick it up seamlessly on another — continuing the same conversation, context, and working state.

Additional Context

_No response_