Cannot resume session after a restart

[gsabran]

Continuing the Claude Code specific aspects of https://github.com/orgs/agentclientprotocol/discussions/202#discussioncomment-14813341 here

There's two issues preventing resuming an existing conversation with Claude Code after restarting the client:

• newSession returns an internal session id, not the one used by Claude Code. I don't think this is too hard to fix.
• Even with a matching session id, there is not a straighfoward way to resume the session:
  • newSession doesn't have resume parameter. We could pass it through the _meta property of NewSessionRequest, but this is somewhat using private apis.
  • loadSession requires that The Agent MUST replay the entire conversation to the Client in the form of session/update notifications (like session/prompt). In my knowledge this is not possible with Claude Code (ie you can resume, not replay). So no loadSession
  • Alternatively, prompt could call into newSession with a resume parameter when given a session id it doesn't have in memory, instead of throwing. However PromptRequest is missing some property required in NewSessionRequest (cwd, mcpServers)

[ileixe]

I believe this is important feature that every serious user wonder first.

Did you find any alternatives?

[gsabran]

I didn't find an alternative strictly within ACP. I have my own version for cmd, where I:

• attach Claude Code's session id once received (after prompting, after initializing ACP's session)
• persist this session id in my client
• support the full Options parameters when starting an ACP session with Claude Code, so I put the persisted session id in this params that gets forwarded to Claude Code.