Expose session.continueWithReplay on daemon HTTP API for cross-device transfer

[lucharo]

Summary

The daemon has a session.continueWithReplay RPC handler that enables proper cross-device session transfer — it fetches the encrypted transcript from the relay, decrypts it, builds a replay prompt, and spawns a new session linked to previousSessionId. This is exactly the right primitive for "start a session on machine A, continue it on machine B."

However, this RPC is only accessible via socket.io from the relay cloud. The local HTTP daemon API (/spawn-session, /list, /stop-session) doesn't expose it. There's no way for a local tool (like a TUI or script) to call it.

Use Case

I'm building a TUI session manager that lists all relay sessions across machines and lets you:

• Enter → chat view via relay stream API (works)
• R → resume the session locally on a different machine (blocked)

The "resume locally" flow needs continueWithReplay to properly transfer the session. Without it, the only options are:

1. Bypass happier entirely (claude --resume) — loses relay sync, phone access, session management
2. Reconstruct the JSONL manually — creates a clone/fork, not a transfer. Happier daemon then auto-registers it as a new session, creating duplicates

Proposed Solution

Any of these would work:

Option A: HTTP endpoint (simplest)

Add /continue-with-replay to the daemon HTTP server with the same schema as the existing RPC handler:

POST /continue-with-replay
{
  "directory": "/home/user/Projects/myapp",
  "agent": "claude",
  "replay": {
    "previousSessionId": "cmmroxg6kk2ods93cm406fy53",
    "strategy": "recent_messages",
    "recentMessagesCount": 16
  }
}

Option B: CLI command

happier session continue <session-id> [--directory <path>] [--agent claude]

Option C: Extend /spawn-session

Add optional replay field to the existing /spawn-session endpoint.

Context

Related: #131 (happier --resume doesn't accept happier session IDs)

The RPC handler already exists and works (line ~24444 in the bundled api-BauLSAv8.mjs). It calls hydrateReplayDialogFromTranscript → buildHappierReplayPromptFromDialog → spawnSession. The plumbing is all there — it just needs an HTTP route or CLI command to expose it.

🤖 Generated with Claude Code