fix: MCP server bd executable path resolution

Fixes issue where MCP tools failed with "bd executable not found"
when BEADS_PATH was set to command name instead of absolute path.

Changes:
- Remove BEADS_PATH=bd from plugin.json (use auto-detection)
- Enhance config validator to resolve command names via PATH
- Add comprehensive config validation tests (11 new tests)

The validator now accepts both:
  - Absolute paths: /usr/local/bin/bd
  - Command names: bd (resolved via shutil.which)

This makes the MCP server more robust and user-friendly while
maintaining backward compatibility.

All 90 tests pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.claude-plugin/plugin.json

@@ -26,7 +26,6 @@
         "beads-mcp"
       ],
       "env": {
-        "BEADS_PATH": "bd",
         "BEADS_ACTOR": "${USER}"
       }
     }

integrations/beads-mcp/src/beads_mcp/config.py

@@ -43,21 +43,27 @@ class Config(BaseSettings):
         """Validate BEADS_PATH points to an executable bd binary.
 
         Args:
-            v: Path to bd executable
+            v: Path to bd executable (can be command name or absolute path)
 
         Returns:
-            Validated path
+            Validated absolute path
 
         Raises:
             ValueError: If path is invalid or not executable
         """
         path = Path(v)
 
+        # If not an absolute/existing path, try to find it in PATH
         if not path.exists():
-            raise ValueError(
-                f"bd executable not found at: {v}\n"
-                + "Please verify BEADS_PATH points to a valid bd executable."
-            )
+            found = shutil.which(v)
+            if found:
+                v = found
+                path = Path(v)
+            else:
+                raise ValueError(
+                    f"bd executable not found at: {v}\n"
+                    + "Please verify BEADS_PATH points to a valid bd executable."
+                )
 
         if not os.access(v, os.X_OK):
             raise ValueError(

integrations/beads-mcp/tests/test_config.py

@@ -0,0 +1,129 @@
+"""Tests for beads_mcp.config module."""
+
+import os
+import shutil
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+from beads_mcp.config import Config, ConfigError, load_config
+
+
+class TestConfig:
+    """Tests for Config class."""
+
+    def test_default_beads_path_auto_detection(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that bd is auto-detected from PATH when BEADS_PATH not set."""
+        # Clear BEADS_PATH if set
+        monkeypatch.delenv("BEADS_PATH", raising=False)
+
+        # Mock shutil.which to return a test path
+        with patch("shutil.which", return_value="/usr/local/bin/bd"):
+            config = Config()
+            assert config.beads_path == "/usr/local/bin/bd"
+
+    def test_beads_path_from_env(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that BEADS_PATH environment variable is respected."""
+        # Create a fake bd executable
+        bd_path = tmp_path / "bd"
+        bd_path.touch(mode=0o755)
+
+        monkeypatch.setenv("BEADS_PATH", str(bd_path))
+        config = Config()
+        assert config.beads_path == str(bd_path)
+
+    def test_beads_path_command_name_resolution(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that command names like 'bd' are resolved via PATH."""
+        # Set BEADS_PATH to just "bd" (command name, not path)
+        monkeypatch.setenv("BEADS_PATH", "bd")
+
+        # Mock shutil.which to simulate finding bd in PATH
+        with patch("shutil.which", return_value="/usr/local/bin/bd"):
+            # Mock os.access to say the file is executable
+            with patch("os.access", return_value=True):
+                config = Config()
+                assert config.beads_path == "/usr/local/bin/bd"
+
+    def test_beads_path_not_found(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that invalid BEADS_PATH raises ValueError."""
+        monkeypatch.setenv("BEADS_PATH", "/nonexistent/bd")
+
+        with pytest.raises(ValueError, match="bd executable not found"):
+            Config()
+
+    def test_beads_path_not_executable(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that non-executable bd raises ValueError."""
+        # Create a non-executable file
+        bd_path = tmp_path / "bd"
+        bd_path.touch(mode=0o644)  # rw-r--r--
+
+        monkeypatch.setenv("BEADS_PATH", str(bd_path))
+
+        with pytest.raises(ValueError, match="not executable"):
+            Config()
+
+    def test_beads_db_validation(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that BEADS_DB must point to existing file."""
+        # Create valid bd executable
+        bd_path = tmp_path / "bd"
+        bd_path.touch(mode=0o755)
+        monkeypatch.setenv("BEADS_PATH", str(bd_path))
+
+        # Set BEADS_DB to non-existent file
+        monkeypatch.setenv("BEADS_DB", "/nonexistent/db.sqlite")
+
+        with pytest.raises(ValueError, match="non-existent file"):
+            Config()
+
+    def test_beads_db_none_allowed(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that BEADS_DB can be unset (None)."""
+        # Create valid bd executable
+        bd_path = tmp_path / "bd"
+        bd_path.touch(mode=0o755)
+        monkeypatch.setenv("BEADS_PATH", str(bd_path))
+        monkeypatch.delenv("BEADS_DB", raising=False)
+
+        config = Config()
+        assert config.beads_db is None
+
+    def test_beads_actor_from_env(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that BEADS_ACTOR is read from environment."""
+        bd_path = tmp_path / "bd"
+        bd_path.touch(mode=0o755)
+        monkeypatch.setenv("BEADS_PATH", str(bd_path))
+        monkeypatch.setenv("BEADS_ACTOR", "test-user")
+
+        config = Config()
+        assert config.beads_actor == "test-user"
+
+    def test_auto_flags_default_false(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that auto-flush and auto-import default to False."""
+        bd_path = tmp_path / "bd"
+        bd_path.touch(mode=0o755)
+        monkeypatch.setenv("BEADS_PATH", str(bd_path))
+
+        config = Config()
+        assert config.beads_no_auto_flush is False
+        assert config.beads_no_auto_import is False
+
+
+class TestLoadConfig:
+    """Tests for load_config function."""
+
+    def test_load_config_success(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that load_config returns valid Config."""
+        bd_path = tmp_path / "bd"
+        bd_path.touch(mode=0o755)
+        monkeypatch.setenv("BEADS_PATH", str(bd_path))
+
+        config = load_config()
+        assert isinstance(config, Config)
+        assert config.beads_path == str(bd_path)
+
+    def test_load_config_error_handling(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Test that load_config raises ConfigError with helpful message."""
+        monkeypatch.setenv("BEADS_PATH", "/nonexistent/bd")
+
+        with pytest.raises(ConfigError, match="Configuration Error"):
+            load_config()