blue/.blue/docs/spikes/2026-01-26-blue-not-detected-fix.md

Spike: Blue Not Detected Fix

Status	In Progress
Date	2026-01-26
Time Box	1 hour

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Question

Why does blue_rfc_get (and other Blue MCP tools) fail with "Blue not detected in this directory" when called without explicit cwd parameter?

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Investigation

Root Cause

1. MCP servers are started by Claude Code as child processes
2. The server's working directory is NOT the project directory
3. When cwd isn't passed in tool args, ensure_state() can't find .blue/

What We Tried

1. Fall back to std::env::current_dir() - Doesn't work because the MCP server process starts from a different directory (likely Claude Code's install location or $HOME)

2. Extract roots from initialize params - Added code to check for roots and workspaceFolders in initialize params. Need to verify if Claude Code sends these.

MCP Protocol Options

Per MCP Spec:

1. Roots capability - Server can advertise roots capability, then client provides roots via roots/list
2. Client info - Initialize params may include workspace info

Potential Solutions

Option A: Wrapper Script

Create a wrapper that finds the project root:

#!/bin/bash
# blue-mcp-wrapper
cd "$(git rev-parse --show-toplevel 2>/dev/null || pwd)"
exec blue mcp

MCP config:

{
  "mcpServers": {
    "blue": {
      "command": "/path/to/blue-mcp-wrapper"
    }
  }
}

Pros: Simple, works immediately Cons: Requires wrapper script, git dependency

Option B: Environment Variable

Check CLAUDE_PROJECT_DIR or similar env var set by Claude Code.

Status: Need to verify if Claude Code sets such a variable.

Option C: Walk Up Directory Tree

In ensure_state(), if cwd check fails, walk up from process cwd looking for .blue/:

fn find_blue_root() -> Option<PathBuf> {
    let mut dir = std::env::current_dir().ok()?;
    loop {
        if dir.join(".blue").exists() {
            return Some(dir);
        }
        if !dir.pop() {
            return None;
        }
    }
}

Pros: No external dependencies Cons: May find wrong project if nested

Option D: Use MCP Roots Protocol

Properly implement MCP roots:

1. Advertise roots capability in initialize response
2. Handle roots/list request from client
3. Store roots and use first root as project dir

Pros: Standard MCP approach Cons: Requires Claude Code to send roots (need to verify)

Recommendation

Try Option D first (MCP roots), then fall back to Option C (walk up tree) if Claude Code doesn't send roots.

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Next Steps

1. Add logging to see what Claude Code sends in initialize
2. Implement roots handling
3. Add directory tree walk as fallback
4. Test and verify

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Conclusion

Pending investigation completion