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blue/.blue/docs/spikes/2026-01-26T1700Z-mcp-project-detection.wip.md
Eric Garcia 0fea499957 feat: lifecycle suffixes for all document states + resolve all clippy warnings 
Every document filename now mirrors its lifecycle state with a status
suffix (e.g., .draft.md, .wip.md, .accepted.md). No more bare .md for
tracked document types. Also renamed all from_str methods to parse to
avoid FromStr trait confusion, introduced StagingDeploymentParams struct,
and fixed all 19 clippy warnings across the codebase.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
2026-01-26 12:19:46 -05:00

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Spike: MCP Project Detection
Status In Progress
Date 2026-01-26
Time Box 30 minutes

Question

Why does the Blue MCP server fail to detect the project directory, and what's the correct solution?

Investigation

Current Behavior

  1. Claude Code starts Blue MCP server via blue mcp
  2. Server starts with unknown working directory
  3. First tool call without cwd param fails: "Blue not detected in this directory"
  4. Tool call with explicit cwd works

Root Cause Analysis

Hypothesis 1: Process working directory

  • MCP servers are child processes of Claude Code
  • Working directory may be Claude Code's install location, not project

Hypothesis 2: MCP protocol provides workspace info

  • MCP spec has roots capability for filesystem boundaries
  • Claude Code may send roots during initialize or via roots/list

Hypothesis 3: Environment variables

  • Claude Code sets CLAUDECODE=1, CLAUDE_CODE_SSE_PORT, CLAUDE_CODE_ENTRYPOINT
  • No project path variable observed

MCP Protocol Research

Per MCP Specification:

  1. Roots - Servers can request roots from clients
  2. Initialize params - May contain client capabilities but not workspace path
  3. No standard workspace field - Unlike LSP's rootUri/workspaceFolders

Attempted Fixes

Attempt Result
Fall back to current_dir() Failed - wrong directory
Parse roots from initialize Unknown - needs testing
Walk up directory tree Implemented but untested

Key Finding

The MCP protocol does not provide a standard way for servers to know the user's project directory. This is a gap compared to LSP.

Options Discovered

  1. Require cwd in every tool call - Current workaround, verbose
  2. Walk up directory tree - Find .blue/ from process cwd
  3. Use MCP roots - Request roots from client, use first root
  4. Wrapper script - Shell wrapper that sets cwd before starting server
  5. Config file - Store project path in ~/.blue/projects.json

Alignment Dialogue Result

6 experts, 98% convergence on Option 1: C → B → fail

Round Result
R1 B (3), C (2), Combined (1)
R2 Option 1 (3), Option 2 (2), Option 3 (1)
R3 Option 1 unanimous

Consensus: MCP roots first → Walk tree fallback → Fail with guidance

The current code already implements this. The remaining issue is that:

  1. Claude Code may not send roots during initialize
  2. Process cwd starts outside project tree (e.g., $HOME)

Conclusion

Root cause: Claude Code starts MCP servers from a non-project directory and doesn't send MCP roots.

Solution: The C → B fallback chain is correct. Need to verify Claude Code sends roots, or ensure walk-tree can find project from wherever the process starts.

Recommended next step: Draft RFC to formalize the detection algorithm and add better error messaging.