Problem

The ACP handle_prompt() method in crates/zeph-acp/src/agent/mod.rs intercepts all unknown slash commands and returns an "unknown command" error to the ACP client, instead of passing them to the agent loop.

Root Cause

The current logic routes any /-prefixed input through handle_slash_command() unless it appears in a small hard-coded pass-through list. This means the agent loop never receives these commands in ACP sessions.

Affected Commands

All agent-loop commands are broken in ACP sessions, including:

• /plan, /graph, /status, /skills, /mcp
• /image, /log, /agent, /feedback, /skill
• /debug-dump, /compact (and any future agent-loop commands)

Currently only /compact, /model refresh, /scheduler, and /scheduler <subcommand> are correctly passed through.

Recommended Fix

Invert the logic to an allowlist approach: only intercept the 5 ACP-native commands that handle_slash_command() actually handles — /help, /model, /mode, /clear, /review — and pass everything else through to the agent loop unchanged.

let trimmed_text = text.trim_start();
if trimmed_text.starts_with('/') {
    let is_acp_native = trimmed_text == "/help"
        || trimmed_text == "/mode"
        || trimmed_text.starts_with("/mode ")
        || trimmed_text == "/clear"
        || trimmed_text.starts_with("/review")
        || trimmed_text == "/model"
        || trimmed_text.starts_with("/model ");
    if is_acp_native {
        return self
            .handle_slash_command(&args.session_id, trimmed_text)
            .await;
    }
}

This is more robust: new agent-loop commands work automatically in ACP without requiring changes to the pass-through list.

Related

Fixes partial regression introduced alongside #1658 fix (adding /scheduler to the denylist). The denylist pattern is the root problem.