Add support for multiple auto-detected platforms in install

When no --platform is specified and multiple platforms are detected,
install now adds all of them to config.yml instead of erroring.
This simplifies setup for projects using multiple AI platforms.

Changes:
- Modified install to detect and add all available platforms when
  no specific platform is specified
- Updated success message to list all installed platforms
- Added test fixtures for gemini and multi-platform projects
- Added test for multi-platform auto-detection behavior

Author: claude

src/deepwork/cli/install.py

@@ -174,8 +174,10 @@ def _install_deepwork(platform_name: str | None, project_path: Path) -> None:
         )
     console.print("  [green]✓[/green] Git repository found")
 
-    # Step 2: Detect or validate platform
+    # Step 2: Detect or validate platform(s)
     detector = PlatformDetector(project_path)
+    platforms_to_add: list[str] = []
+    detected_adapters: list[AgentAdapter] = []
 
     if platform_name:
         # User specified platform - check if it's available
@@ -192,10 +194,11 @@ def _install_deepwork(platform_name: str | None, project_path: Path) -> None:
             )
 
         console.print(f"  [green]✓[/green] {adapter.display_name} detected")
-        platform_to_add = adapter.name
+        platforms_to_add = [adapter.name]
+        detected_adapters = [adapter]
     else:
-        # Auto-detect platform
-        console.print("[yellow]→[/yellow] Auto-detecting AI platform...")
+        # Auto-detect all available platforms
+        console.print("[yellow]→[/yellow] Auto-detecting AI platforms...")
         available_adapters = detector.detect_all_platforms()
 
         if not available_adapters:
@@ -209,17 +212,11 @@ def _install_deepwork(platform_name: str | None, project_path: Path) -> None:
                 "Please set up one of these platforms first, or use --platform to specify."
             )
 
-        if len(available_adapters) > 1:
-            # Multiple platforms - ask user to specify
-            platform_names = ", ".join(a.display_name for a in available_adapters)
-            raise InstallError(
-                f"Multiple AI platforms detected: {platform_names}\n"
-                "Please specify which platform to use with --platform option."
-            )
-
-        adapter = available_adapters[0]
-        console.print(f"  [green]✓[/green] {adapter.display_name} detected")
-        platform_to_add = adapter.name
+        # Add all detected platforms
+        for adapter in available_adapters:
+            console.print(f"  [green]✓[/green] {adapter.display_name} detected")
+            platforms_to_add.append(adapter.name)
+        detected_adapters = available_adapters
 
     # Step 3: Create .deepwork/ directory structure
     console.print("[yellow]→[/yellow] Creating DeepWork directory structure...")
@@ -256,12 +253,16 @@ def _install_deepwork(platform_name: str | None, project_path: Path) -> None:
     if "platforms" not in config_data:
         config_data["platforms"] = []
 
-    # Add platform if not already present
-    if platform_to_add not in config_data["platforms"]:
-        config_data["platforms"].append(platform_to_add)
-        console.print(f"  [green]✓[/green] Added {adapter.display_name} to platforms")
-    else:
-        console.print(f"  [dim]•[/dim] {adapter.display_name} already configured")
+    # Add each platform if not already present
+    added_platforms: list[str] = []
+    for i, platform in enumerate(platforms_to_add):
+        adapter = detected_adapters[i]
+        if platform not in config_data["platforms"]:
+            config_data["platforms"].append(platform)
+            added_platforms.append(adapter.display_name)
+            console.print(f"  [green]✓[/green] Added {adapter.display_name} to platforms")
+        else:
+            console.print(f"  [dim]•[/dim] {adapter.display_name} already configured")
 
     save_yaml(config_file, config_data)
     console.print(f"  [green]✓[/green] Updated {config_file.relative_to(project_path)}")
@@ -280,8 +281,9 @@ def _install_deepwork(platform_name: str | None, project_path: Path) -> None:
 
     # Success message
     console.print()
+    platform_names = ", ".join(a.display_name for a in detected_adapters)
     console.print(
-        f"[bold green]✓ DeepWork installed successfully for {adapter.display_name}![/bold green]"
+        f"[bold green]✓ DeepWork installed successfully for {platform_names}![/bold green]"
     )
     console.print()
     console.print("[bold]Next steps:[/bold]")

tests/conftest.py

@@ -35,6 +35,26 @@ def mock_claude_project(mock_git_repo: Path) -> Path:
     return mock_git_repo
 
 
+@pytest.fixture
+def mock_gemini_project(mock_git_repo: Path) -> Path:
+    """Create a mock project with Gemini CLI setup."""
+    gemini_dir = mock_git_repo / ".gemini"
+    gemini_dir.mkdir(exist_ok=True)
+    return mock_git_repo
+
+
+@pytest.fixture
+def mock_multi_platform_project(mock_git_repo: Path) -> Path:
+    """Create a mock project with multiple AI platforms setup."""
+    claude_dir = mock_git_repo / ".claude"
+    claude_dir.mkdir(exist_ok=True)
+    (claude_dir / "settings.json").write_text('{"version": "1.0"}')
+
+    gemini_dir = mock_git_repo / ".gemini"
+    gemini_dir.mkdir(exist_ok=True)
+    return mock_git_repo
+
+
 @pytest.fixture
 def fixtures_dir() -> Path:
     """Return the path to the fixtures directory."""

tests/integration/test_install_flow.py

@@ -79,8 +79,38 @@ def test_install_fails_without_platform(self, mock_git_repo: Path) -> None:
         assert result.exit_code != 0
         assert "No AI platform detected" in result.output
 
-    # NOTE: Multiple platform detection test removed since we currently only support Claude.
-    # When more adapters are added, this test should be reinstated.
+    def test_install_with_multiple_platforms_auto_detect(
+        self, mock_multi_platform_project: Path
+    ) -> None:
+        """Test installing with auto-detection when multiple platforms are present."""
+        runner = CliRunner()
+
+        result = runner.invoke(
+            cli,
+            ["install", "--path", str(mock_multi_platform_project)],
+            catch_exceptions=False,
+        )
+
+        assert result.exit_code == 0
+        assert "Auto-detecting AI platforms" in result.output
+        assert "Claude Code detected" in result.output
+        assert "Gemini CLI detected" in result.output
+        assert "DeepWork installed successfully for Claude Code, Gemini CLI" in result.output
+
+        # Verify config.yml has both platforms
+        config_file = mock_multi_platform_project / ".deepwork" / "config.yml"
+        config = load_yaml(config_file)
+        assert config is not None
+        assert "claude" in config["platforms"]
+        assert "gemini" in config["platforms"]
+
+        # Verify commands were created for both platforms
+        claude_dir = mock_multi_platform_project / ".claude" / "commands"
+        assert (claude_dir / "deepwork_jobs.define.md").exists()
+
+        # Gemini uses job_name/step_id.toml structure
+        gemini_dir = mock_multi_platform_project / ".gemini" / "commands"
+        assert (gemini_dir / "deepwork_jobs" / "define.toml").exists()
 
     def test_install_with_specified_platform_when_missing(self, mock_git_repo: Path) -> None:
         """Test that install fails when specified platform is not present."""