claude-code-acp: Method 'session/set_mode' not found

[dcguim]

Environment

• ralph: v0.1.14
• claude-code-acp (cc-acp): v0.1.1
• Claude Code CLI: latest (installed via npm)
• OS: macOS Darwin 25.4.0

Error

Running ralph run immediately fails on the first iteration with:

ERROR service=default e=message is not an Object. (evaluating '"method" in message') rejection
ERROR service=adapter-source error=Method 'session/set_mode' not found on_error
ERROR service=session-machine iteration=1 error=Method 'session/set_mode' not found iteration_error

Steps to reproduce

1. npm install -g ralph@0.1.14 claude-code-acp
2. ralph init (select claude adapter)
3. Add a valid prd.json with at least one feature
4. ralph run

Analysis

Ralph calls session/set_mode via ACP, but claude-code-acp v0.1.1 does not implement this method. The binary is also installed as cc-acp rather than claude-code-acp — required a manual symlink to resolve the initial "not found" error.

Expected

Ralph should either:

• Use a method supported by the current cc-acp version
• Document the minimum compatible version of claude-code-acp