fix: prevent extension command shadowing (#1994)

* fix: prevent extension command shadowing

* Validate extension command namespaces

* Reuse extension command name pattern

extensions/EXTENSION-API-REFERENCE.md

@@ -44,7 +44,7 @@ provides:
     - name: string       # Required, pattern: ^speckit\.[a-z0-9-]+\.[a-z0-9-]+$
       file: string       # Required, relative path to command file
       description: string # Required
-      aliases: [string]  # Optional, array of alternate names
+      aliases: [string]  # Optional, same pattern as name; namespace must match extension.id and must not shadow core or installed extension commands
 
   config:                # Optional, array of config files
     - name: string       # Config file name

extensions/EXTENSION-DEVELOPMENT-GUIDE.md

@@ -41,7 +41,7 @@ provides:
     - name: "speckit.my-ext.hello"      # Must follow pattern: speckit.{ext-id}.{cmd}
       file: "commands/hello.md"
       description: "Say hello"
-      aliases: ["speckit.hello"]        # Optional aliases
+      aliases: ["speckit.my-ext.hi"]    # Optional aliases, same pattern
 
   config:                               # Optional: Config files
     - name: "my-ext-config.yml"
@@ -186,7 +186,7 @@ What the extension provides.
 - `name`: Command name (must match `speckit.{ext-id}.{command}`)
 - `file`: Path to command file (relative to extension root)
 - `description`: Command description (optional)
-- `aliases`: Alternative command names (optional, array)
+- `aliases`: Alternative command names (optional, array; each must match `speckit.{ext-id}.{command}`)
 
 ### Optional Fields
 

extensions/EXTENSION-USER-GUIDE.md

@@ -214,8 +214,8 @@ Extensions add commands that appear in your AI agent (Claude Code):
 # In Claude Code
 > /speckit.jira.specstoissues
 
-# Or use short alias (if provided)
-> /speckit.specstoissues
+# Or use a namespaced alias (if provided)
+> /speckit.jira.sync
 ```
 
 ### Extension Configuration

extensions/RFC-EXTENSION-SYSTEM.md

@@ -223,7 +223,7 @@ provides:
     - name: "speckit.jira.specstoissues"
       file: "commands/specstoissues.md"
       description: "Create Jira hierarchy from spec and tasks"
-      aliases: ["speckit.specstoissues"]  # Alternate names
+      aliases: ["speckit.jira.sync"]  # Alternate names
 
     - name: "speckit.jira.discover-fields"
       file: "commands/discover-fields.md"
@@ -1517,7 +1517,7 @@ specify extension add github-projects
 /speckit.github.taskstoissues
 ```
 
-**Compatibility shim** (if needed):
+**Migration alias** (if needed):
 
 ```yaml
 # extension.yml
@@ -1525,10 +1525,10 @@ provides:
   commands:
     - name: "speckit.github.taskstoissues"
       file: "commands/taskstoissues.md"
-      aliases: ["speckit.taskstoissues"]  # Backward compatibility
+      aliases: ["speckit.github.sync-taskstoissues"]  # Alternate namespaced entry point
 ```
 
-AI agent registers both names, so old scripts work.
+AI agents register both names, so callers can migrate to the alternate alias without relying on deprecated global shortcuts like `/speckit.taskstoissues`.
 
 ---
 

extensions/template/extension.yml

@@ -47,8 +47,8 @@ provides:
     - name: "speckit.my-extension.example"
       file: "commands/example.md"
       description: "Example command that demonstrates functionality"
-      # Optional: Add aliases for shorter command names
-      aliases: ["speckit.example"]
+      # Optional: Add aliases in the same namespaced format
+      aliases: ["speckit.my-extension.example-short"]
 
     # ADD MORE COMMANDS: Copy this block for each command
     # - name: "speckit.my-extension.another-command"

src/specify_cli/extensions.py

@@ -25,6 +25,49 @@ import yaml
 from packaging import version as pkg_version
 from packaging.specifiers import SpecifierSet, InvalidSpecifier
 
+_FALLBACK_CORE_COMMAND_NAMES = frozenset({
+    "analyze",
+    "checklist",
+    "clarify",
+    "constitution",
+    "implement",
+    "plan",
+    "specify",
+    "tasks",
+    "taskstoissues",
+})
+EXTENSION_COMMAND_NAME_PATTERN = re.compile(r"^speckit\.([a-z0-9-]+)\.([a-z0-9-]+)$")
+
+
+def _load_core_command_names() -> frozenset[str]:
+    """Discover bundled core command names from the packaged templates.
+
+    Prefer the wheel-time ``core_pack`` bundle when present, and fall back to
+    the source checkout when running from the repository. If neither is
+    available, use the baked-in fallback set so validation still works.
+    """
+    candidate_dirs = [
+        Path(__file__).parent / "core_pack" / "commands",
+        Path(__file__).resolve().parent.parent.parent / "templates" / "commands",
+    ]
+
+    for commands_dir in candidate_dirs:
+        if not commands_dir.is_dir():
+            continue
+
+        command_names = {
+            command_file.stem
+            for command_file in commands_dir.iterdir()
+            if command_file.is_file() and command_file.suffix == ".md"
+        }
+        if command_names:
+            return frozenset(command_names)
+
+    return _FALLBACK_CORE_COMMAND_NAMES
+
+
+CORE_COMMAND_NAMES = _load_core_command_names()
+
 
 class ExtensionError(Exception):
     """Base exception for extension-related errors."""
@@ -149,7 +192,7 @@ class ExtensionManifest:
                 raise ValidationError("Command missing 'name' or 'file'")
 
             # Validate command name format
-            if not re.match(r'^speckit\.[a-z0-9-]+\.[a-z0-9-]+$', cmd["name"]):
+            if EXTENSION_COMMAND_NAME_PATTERN.match(cmd["name"]) is None:
                 raise ValidationError(
                     f"Invalid command name '{cmd['name']}': "
                     "must follow pattern 'speckit.{extension}.{command}'"
@@ -446,6 +489,126 @@ class ExtensionManager:
         self.extensions_dir = project_root / ".specify" / "extensions"
         self.registry = ExtensionRegistry(self.extensions_dir)
 
+    @staticmethod
+    def _collect_manifest_command_names(manifest: ExtensionManifest) -> Dict[str, str]:
+        """Collect command and alias names declared by a manifest.
+
+        Performs install-time validation for extension-specific constraints:
+        - commands and aliases must use the canonical `speckit.{extension}.{command}` shape
+        - commands and aliases must use this extension's namespace
+        - command namespaces must not shadow core commands
+        - duplicate command/alias names inside one manifest are rejected
+
+        Args:
+            manifest: Parsed extension manifest
+
+        Returns:
+            Mapping of declared command/alias name -> kind ("command"/"alias")
+
+        Raises:
+            ValidationError: If any declared name is invalid
+        """
+        if manifest.id in CORE_COMMAND_NAMES:
+            raise ValidationError(
+                f"Extension ID '{manifest.id}' conflicts with core command namespace '{manifest.id}'"
+            )
+
+        declared_names: Dict[str, str] = {}
+
+        for cmd in manifest.commands:
+            primary_name = cmd["name"]
+            aliases = cmd.get("aliases", [])
+
+            if aliases is None:
+                aliases = []
+            if not isinstance(aliases, list):
+                raise ValidationError(
+                    f"Aliases for command '{primary_name}' must be a list"
+                )
+
+            for kind, name in [("command", primary_name)] + [
+                ("alias", alias) for alias in aliases
+            ]:
+                if not isinstance(name, str):
+                    raise ValidationError(
+                        f"{kind.capitalize()} for command '{primary_name}' must be a string"
+                    )
+
+                match = EXTENSION_COMMAND_NAME_PATTERN.match(name)
+                if match is None:
+                    raise ValidationError(
+                        f"Invalid {kind} '{name}': "
+                        "must follow pattern 'speckit.{extension}.{command}'"
+                    )
+
+                namespace = match.group(1)
+                if namespace != manifest.id:
+                    raise ValidationError(
+                        f"{kind.capitalize()} '{name}' must use extension namespace '{manifest.id}'"
+                    )
+
+                if namespace in CORE_COMMAND_NAMES:
+                    raise ValidationError(
+                        f"{kind.capitalize()} '{name}' conflicts with core command namespace '{namespace}'"
+                    )
+
+                if name in declared_names:
+                    raise ValidationError(
+                        f"Duplicate command or alias '{name}' in extension manifest"
+                    )
+
+                declared_names[name] = kind
+
+        return declared_names
+
+    def _get_installed_command_name_map(
+        self,
+        exclude_extension_id: Optional[str] = None,
+    ) -> Dict[str, str]:
+        """Return registered command and alias names for installed extensions."""
+        installed_names: Dict[str, str] = {}
+
+        for ext_id in self.registry.keys():
+            if ext_id == exclude_extension_id:
+                continue
+
+            manifest = self.get_extension(ext_id)
+            if manifest is None:
+                continue
+
+            for cmd in manifest.commands:
+                cmd_name = cmd.get("name")
+                if isinstance(cmd_name, str):
+                    installed_names.setdefault(cmd_name, ext_id)
+
+                aliases = cmd.get("aliases", [])
+                if not isinstance(aliases, list):
+                    continue
+
+                for alias in aliases:
+                    if isinstance(alias, str):
+                        installed_names.setdefault(alias, ext_id)
+
+        return installed_names
+
+    def _validate_install_conflicts(self, manifest: ExtensionManifest) -> None:
+        """Reject installs that would shadow core or installed extension commands."""
+        declared_names = self._collect_manifest_command_names(manifest)
+        installed_names = self._get_installed_command_name_map(
+            exclude_extension_id=manifest.id
+        )
+
+        collisions = [
+            f"{name} (already provided by extension '{installed_names[name]}')"
+            for name in sorted(declared_names)
+            if name in installed_names
+        ]
+        if collisions:
+            raise ValidationError(
+                "Extension commands conflict with installed extensions:\n- "
+                + "\n- ".join(collisions)
+            )
+
     @staticmethod
     def _load_extensionignore(source_dir: Path) -> Optional[Callable[[str, List[str]], Set[str]]]:
         """Load .extensionignore and return an ignore function for shutil.copytree.
@@ -861,6 +1024,9 @@ class ExtensionManager:
                 f"Use 'specify extension remove {manifest.id}' first."
             )
 
+        # Reject manifests that would shadow core commands or installed extensions.
+        self._validate_install_conflicts(manifest)
+
         # Install extension
         dest_dir = self.extensions_dir / manifest.id
         if dest_dir.exists():

tests/test_extensions.py

@@ -18,6 +18,7 @@ from datetime import datetime, timezone
 
 from specify_cli.extensions import (
     CatalogEntry,
+    CORE_COMMAND_NAMES,
     ExtensionManifest,
     ExtensionRegistry,
     ExtensionManager,
@@ -63,7 +64,7 @@ def valid_manifest_data():
         "provides": {
             "commands": [
                 {
-                    "name": "speckit.test.hello",
+                    "name": "speckit.test-ext.hello",
                     "file": "commands/hello.md",
                     "description": "Test command",
                 }
@@ -71,7 +72,7 @@ def valid_manifest_data():
         },
         "hooks": {
             "after_tasks": {
-                "command": "speckit.test.hello",
+                "command": "speckit.test-ext.hello",
                 "optional": True,
                 "prompt": "Run test?",
             }
@@ -189,7 +190,18 @@ class TestExtensionManifest:
         assert manifest.version == "1.0.0"
         assert manifest.description == "A test extension"
         assert len(manifest.commands) == 1
-        assert manifest.commands[0]["name"] == "speckit.test.hello"
+        assert manifest.commands[0]["name"] == "speckit.test-ext.hello"
+
+    def test_core_command_names_match_bundled_templates(self):
+        """Core command reservations should stay aligned with bundled templates."""
+        commands_dir = Path(__file__).resolve().parent.parent / "templates" / "commands"
+        expected = {
+            command_file.stem
+            for command_file in commands_dir.iterdir()
+            if command_file.is_file() and command_file.suffix == ".md"
+        }
+
+        assert CORE_COMMAND_NAMES == expected
 
     def test_missing_required_field(self, temp_dir):
         """Test manifest missing required field."""
@@ -589,6 +601,172 @@ class TestExtensionManager:
         with pytest.raises(ExtensionError, match="already installed"):
             manager.install_from_directory(extension_dir, "0.1.0", register_commands=False)
 
+    def test_install_rejects_extension_id_in_core_namespace(self, temp_dir, project_dir):
+        """Install should reject extension IDs that shadow core commands."""
+        import yaml
+
+        ext_dir = temp_dir / "analyze-ext"
+        ext_dir.mkdir()
+        (ext_dir / "commands").mkdir()
+
+        manifest_data = {
+            "schema_version": "1.0",
+            "extension": {
+                "id": "analyze",
+                "name": "Analyze Extension",
+                "version": "1.0.0",
+                "description": "Test",
+            },
+            "requires": {"speckit_version": ">=0.1.0"},
+            "provides": {
+                "commands": [
+                    {
+                        "name": "speckit.analyze.extra",
+                        "file": "commands/cmd.md",
+                    }
+                ]
+            },
+        }
+
+        (ext_dir / "extension.yml").write_text(yaml.dump(manifest_data))
+        (ext_dir / "commands" / "cmd.md").write_text("---\ndescription: Test\n---\n\nBody")
+
+        manager = ExtensionManager(project_dir)
+        with pytest.raises(ValidationError, match="conflicts with core command namespace"):
+            manager.install_from_directory(ext_dir, "0.1.0", register_commands=False)
+
+    def test_install_rejects_alias_without_extension_namespace(self, temp_dir, project_dir):
+        """Install should reject legacy short aliases that can shadow core commands."""
+        import yaml
+
+        ext_dir = temp_dir / "alias-shortcut"
+        ext_dir.mkdir()
+        (ext_dir / "commands").mkdir()
+
+        manifest_data = {
+            "schema_version": "1.0",
+            "extension": {
+                "id": "alias-shortcut",
+                "name": "Alias Shortcut",
+                "version": "1.0.0",
+                "description": "Test",
+            },
+            "requires": {"speckit_version": ">=0.1.0"},
+            "provides": {
+                "commands": [
+                    {
+                        "name": "speckit.alias-shortcut.cmd",
+                        "file": "commands/cmd.md",
+                        "aliases": ["speckit.shortcut"],
+                    }
+                ]
+            },
+        }
+
+        (ext_dir / "extension.yml").write_text(yaml.dump(manifest_data))
+        (ext_dir / "commands" / "cmd.md").write_text("---\ndescription: Test\n---\n\nBody")
+
+        manager = ExtensionManager(project_dir)
+        with pytest.raises(ValidationError, match="Invalid alias 'speckit.shortcut'"):
+            manager.install_from_directory(ext_dir, "0.1.0", register_commands=False)
+
+    def test_install_rejects_namespace_squatting(self, temp_dir, project_dir):
+        """Install should reject commands and aliases outside the extension namespace."""
+        import yaml
+
+        ext_dir = temp_dir / "squat-ext"
+        ext_dir.mkdir()
+        (ext_dir / "commands").mkdir()
+
+        manifest_data = {
+            "schema_version": "1.0",
+            "extension": {
+                "id": "squat-ext",
+                "name": "Squat Extension",
+                "version": "1.0.0",
+                "description": "Test",
+            },
+            "requires": {"speckit_version": ">=0.1.0"},
+            "provides": {
+                "commands": [
+                    {
+                        "name": "speckit.other-ext.cmd",
+                        "file": "commands/cmd.md",
+                        "aliases": ["speckit.squat-ext.ok"],
+                    }
+                ]
+            },
+        }
+
+        (ext_dir / "extension.yml").write_text(yaml.dump(manifest_data))
+        (ext_dir / "commands" / "cmd.md").write_text("---\ndescription: Test\n---\n\nBody")
+
+        manager = ExtensionManager(project_dir)
+        with pytest.raises(ValidationError, match="must use extension namespace 'squat-ext'"):
+            manager.install_from_directory(ext_dir, "0.1.0", register_commands=False)
+
+    def test_install_rejects_command_collision_with_installed_extension(self, temp_dir, project_dir):
+        """Install should reject names already claimed by an installed legacy extension."""
+        import yaml
+
+        first_dir = temp_dir / "ext-one"
+        first_dir.mkdir()
+        (first_dir / "commands").mkdir()
+        first_manifest = {
+            "schema_version": "1.0",
+            "extension": {
+                "id": "ext-one",
+                "name": "Extension One",
+                "version": "1.0.0",
+                "description": "Test",
+            },
+            "requires": {"speckit_version": ">=0.1.0"},
+            "provides": {
+                "commands": [
+                    {
+                        "name": "speckit.ext-one.sync",
+                        "file": "commands/cmd.md",
+                        "aliases": ["speckit.shared.sync"],
+                    }
+                ]
+            },
+        }
+        (first_dir / "extension.yml").write_text(yaml.dump(first_manifest))
+        (first_dir / "commands" / "cmd.md").write_text("---\ndescription: Test\n---\n\nBody")
+        installed_ext_dir = project_dir / ".specify" / "extensions" / "ext-one"
+        installed_ext_dir.parent.mkdir(parents=True, exist_ok=True)
+        shutil.copytree(first_dir, installed_ext_dir)
+
+        second_dir = temp_dir / "ext-two"
+        second_dir.mkdir()
+        (second_dir / "commands").mkdir()
+        second_manifest = {
+            "schema_version": "1.0",
+            "extension": {
+                "id": "shared",
+                "name": "Shared Extension",
+                "version": "1.0.0",
+                "description": "Test",
+            },
+            "requires": {"speckit_version": ">=0.1.0"},
+            "provides": {
+                "commands": [
+                    {
+                        "name": "speckit.shared.sync",
+                        "file": "commands/cmd.md",
+                    }
+                ]
+            },
+        }
+        (second_dir / "extension.yml").write_text(yaml.dump(second_manifest))
+        (second_dir / "commands" / "cmd.md").write_text("---\ndescription: Test\n---\n\nBody")
+
+        manager = ExtensionManager(project_dir)
+        manager.registry.add("ext-one", {"version": "1.0.0", "source": "local"})
+
+        with pytest.raises(ValidationError, match="already provided by extension 'ext-one'"):
+            manager.install_from_directory(second_dir, "0.1.0", register_commands=False)
+
     def test_remove_extension(self, extension_dir, project_dir):
         """Test removing an installed extension."""
         manager = ExtensionManager(project_dir)
@@ -852,10 +1030,10 @@ $ARGUMENTS
         )
 
         assert len(registered) == 1
-        assert "speckit.test.hello" in registered
+        assert "speckit.test-ext.hello" in registered
 
         # Check command file was created
-        cmd_file = claude_dir / "speckit.test.hello.md"
+        cmd_file = claude_dir / "speckit.test-ext.hello.md"
         assert cmd_file.exists()
 
         content = cmd_file.read_text()
@@ -885,9 +1063,9 @@ $ARGUMENTS
             "provides": {
                 "commands": [
                     {
-                        "name": "speckit.alias.cmd",
+                        "name": "speckit.ext-alias.cmd",
                         "file": "commands/cmd.md",
-                        "aliases": ["speckit.shortcut"],
+                        "aliases": ["speckit.ext-alias.shortcut"],
                     }
                 ]
             },
@@ -907,10 +1085,10 @@ $ARGUMENTS
         registered = registrar.register_commands_for_claude(manifest, ext_dir, project_dir)
 
         assert len(registered) == 2
-        assert "speckit.alias.cmd" in registered
-        assert "speckit.shortcut" in registered
-        assert (claude_dir / "speckit.alias.cmd.md").exists()
-        assert (claude_dir / "speckit.shortcut.md").exists()
+        assert "speckit.ext-alias.cmd" in registered
+        assert "speckit.ext-alias.shortcut" in registered
+        assert (claude_dir / "speckit.ext-alias.cmd.md").exists()
+        assert (claude_dir / "speckit.ext-alias.shortcut.md").exists()
 
     def test_unregister_commands_for_codex_skills_uses_mapped_names(self, project_dir):
         """Codex skill cleanup should use the same mapped names as registration."""
@@ -951,11 +1129,11 @@ $ARGUMENTS
         registrar = CommandRegistrar()
         registrar.register_commands_for_agent("codex", manifest, extension_dir, project_dir)
 
-        skill_file = skills_dir / "speckit-test-hello" / "SKILL.md"
+        skill_file = skills_dir / "speckit-test-ext-hello" / "SKILL.md"
         assert skill_file.exists()
 
         content = skill_file.read_text()
-        assert "name: speckit-test-hello" in content
+        assert "name: speckit-test-ext-hello" in content
         assert "description: Test hello command" in content
         assert "compatibility:" in content
         assert "metadata:" in content
@@ -982,7 +1160,7 @@ $ARGUMENTS
             "provides": {
                 "commands": [
                     {
-                        "name": "speckit.test.plan",
+                        "name": "speckit.ext-scripted.plan",
                         "file": "commands/plan.md",
                         "description": "Scripted command",
                     }
@@ -1020,7 +1198,7 @@ Agent __AGENT__
         registrar = CommandRegistrar()
         registrar.register_commands_for_agent("codex", manifest, ext_dir, project_dir)
 
-        skill_file = skills_dir / "speckit-test-plan" / "SKILL.md"
+        skill_file = skills_dir / "speckit-ext-scripted-plan" / "SKILL.md"
         assert skill_file.exists()
 
         content = skill_file.read_text()
@@ -1051,9 +1229,9 @@ Agent __AGENT__
             "provides": {
                 "commands": [
                     {
-                        "name": "speckit.alias.cmd",
+                        "name": "speckit.ext-alias-skill.cmd",
                         "file": "commands/cmd.md",
-                        "aliases": ["speckit.shortcut"],
+                        "aliases": ["speckit.ext-alias-skill.shortcut"],
                     }
                 ]
             },
@@ -1070,13 +1248,13 @@ Agent __AGENT__
         registrar = CommandRegistrar()
         registrar.register_commands_for_agent("codex", manifest, ext_dir, project_dir)
 
-        primary = skills_dir / "speckit-alias-cmd" / "SKILL.md"
-        alias = skills_dir / "speckit-shortcut" / "SKILL.md"
+        primary = skills_dir / "speckit-ext-alias-skill-cmd" / "SKILL.md"
+        alias = skills_dir / "speckit-ext-alias-skill-shortcut" / "SKILL.md"
 
         assert primary.exists()
         assert alias.exists()
-        assert "name: speckit-alias-cmd" in primary.read_text()
-        assert "name: speckit-shortcut" in alias.read_text()
+        assert "name: speckit-ext-alias-skill-cmd" in primary.read_text()
+        assert "name: speckit-ext-alias-skill-shortcut" in alias.read_text()
 
     def test_codex_skill_registration_uses_fallback_script_variant_without_init_options(
         self, project_dir, temp_dir
@@ -1100,7 +1278,7 @@ Agent __AGENT__
             "provides": {
                 "commands": [
                     {
-                        "name": "speckit.fallback.plan",
+                        "name": "speckit.ext-script-fallback.plan",
                         "file": "commands/plan.md",
                     }
                 ]
@@ -1132,7 +1310,7 @@ Then {AGENT_SCRIPT}
         registrar = CommandRegistrar()
         registrar.register_commands_for_agent("codex", manifest, ext_dir, project_dir)
 
-        skill_file = skills_dir / "speckit-fallback-plan" / "SKILL.md"
+        skill_file = skills_dir / "speckit-ext-script-fallback-plan" / "SKILL.md"
         assert skill_file.exists()
 
         content = skill_file.read_text()
@@ -1163,7 +1341,7 @@ Then {AGENT_SCRIPT}
             "provides": {
                 "commands": [
                     {
-                        "name": "speckit.list.plan",
+                        "name": "speckit.ext-script-list-init.plan",
                         "file": "commands/plan.md",
                     }
                 ]
@@ -1194,7 +1372,7 @@ Run {SCRIPT}
         registrar = CommandRegistrar()
         registrar.register_commands_for_agent("codex", manifest, ext_dir, project_dir)
 
-        content = (skills_dir / "speckit-list-plan" / "SKILL.md").read_text()
+        content = (skills_dir / "speckit-ext-script-list-init-plan" / "SKILL.md").read_text()
         assert '.specify/scripts/bash/setup-plan.sh --json "$ARGUMENTS"' in content
 
     def test_codex_skill_registration_fallback_prefers_powershell_on_windows(
@@ -1221,7 +1399,7 @@ Run {SCRIPT}
             "provides": {
                 "commands": [
                     {
-                        "name": "speckit.windows.plan",
+                        "name": "speckit.ext-script-windows-fallback.plan",
                         "file": "commands/plan.md",
                     }
                 ]
@@ -1253,7 +1431,7 @@ Then {AGENT_SCRIPT}
         registrar = CommandRegistrar()
         registrar.register_commands_for_agent("codex", manifest, ext_dir, project_dir)
 
-        skill_file = skills_dir / "speckit-windows-plan" / "SKILL.md"
+        skill_file = skills_dir / "speckit-ext-script-windows-fallback-plan" / "SKILL.md"
         assert skill_file.exists()
 
         content = skill_file.read_text()
@@ -1275,14 +1453,14 @@ Then {AGENT_SCRIPT}
         )
 
         assert len(registered) == 1
-        assert "speckit.test.hello" in registered
+        assert "speckit.test-ext.hello" in registered
 
         # Verify command file uses .agent.md extension
-        cmd_file = agents_dir / "speckit.test.hello.agent.md"
+        cmd_file = agents_dir / "speckit.test-ext.hello.agent.md"
         assert cmd_file.exists()
 
         # Verify NO plain .md file was created
-        plain_md_file = agents_dir / "speckit.test.hello.md"
+        plain_md_file = agents_dir / "speckit.test-ext.hello.md"
         assert not plain_md_file.exists()
 
         content = cmd_file.read_text()
@@ -1302,12 +1480,12 @@ Then {AGENT_SCRIPT}
         )
 
         # Verify companion .prompt.md file exists
-        prompt_file = project_dir / ".github" / "prompts" / "speckit.test.hello.prompt.md"
+        prompt_file = project_dir / ".github" / "prompts" / "speckit.test-ext.hello.prompt.md"
         assert prompt_file.exists()
 
         # Verify content has correct agent frontmatter
         content = prompt_file.read_text()
-        assert content == "---\nagent: speckit.test.hello\n---\n"
+        assert content == "---\nagent: speckit.test-ext.hello\n---\n"
 
     def test_copilot_aliases_get_companion_prompts(self, project_dir, temp_dir):
         """Test that aliases also get companion .prompt.md files for Copilot."""
@@ -1328,9 +1506,9 @@ Then {AGENT_SCRIPT}
             "provides": {
                 "commands": [
                     {
-                        "name": "speckit.alias-copilot.cmd",
+                        "name": "speckit.ext-alias-copilot.cmd",
                         "file": "commands/cmd.md",
-                        "aliases": ["speckit.shortcut-copilot"],
+                        "aliases": ["speckit.ext-alias-copilot.shortcut"],
                     }
                 ]
             },
@@ -1357,8 +1535,8 @@ Then {AGENT_SCRIPT}
 
         # Both primary and alias get companion .prompt.md
         prompts_dir = project_dir / ".github" / "prompts"
-        assert (prompts_dir / "speckit.alias-copilot.cmd.prompt.md").exists()
-        assert (prompts_dir / "speckit.shortcut-copilot.prompt.md").exists()
+        assert (prompts_dir / "speckit.ext-alias-copilot.cmd.prompt.md").exists()
+        assert (prompts_dir / "speckit.ext-alias-copilot.shortcut.prompt.md").exists()
 
     def test_non_copilot_agent_no_companion_file(self, extension_dir, project_dir):
         """Test that non-copilot agents do NOT create .prompt.md files."""
@@ -1431,7 +1609,7 @@ class TestIntegration:
         assert installed[0]["id"] == "test-ext"
 
         # Verify command registered
-        cmd_file = project_dir / ".claude" / "commands" / "speckit.test.hello.md"
+        cmd_file = project_dir / ".claude" / "commands" / "speckit.test-ext.hello.md"
         assert cmd_file.exists()
 
         # Verify registry has registered commands (now a dict keyed by agent)
@@ -1439,7 +1617,7 @@ class TestIntegration:
         registered_commands = metadata["registered_commands"]
         # Check that the command is registered for at least one agent
         assert any(
-            "speckit.test.hello" in cmds
+            "speckit.test-ext.hello" in cmds
             for cmds in registered_commands.values()
         )
 
@@ -1465,8 +1643,8 @@ class TestIntegration:
         assert "copilot" in metadata["registered_commands"]
 
         # Verify files exist before cleanup
-        agent_file = agents_dir / "speckit.test.hello.agent.md"
-        prompt_file = project_dir / ".github" / "prompts" / "speckit.test.hello.prompt.md"
+        agent_file = agents_dir / "speckit.test-ext.hello.agent.md"
+        prompt_file = project_dir / ".github" / "prompts" / "speckit.test-ext.hello.prompt.md"
         assert agent_file.exists()
         assert prompt_file.exists()
 
@@ -2776,7 +2954,7 @@ class TestExtensionUpdateCLI:
             "provides": {
                 "commands": [
                     {
-                        "name": "speckit.test.hello",
+                        "name": "speckit.test-ext.hello",
                         "file": "commands/hello.md",
                         "description": "Test command",
                     }
@@ -2784,7 +2962,7 @@ class TestExtensionUpdateCLI:
             },
             "hooks": {
                 "after_tasks": {
-                    "command": "speckit.test.hello",
+                    "command": "speckit.test-ext.hello",
                     "optional": True,
                 }
             },
@@ -2813,7 +2991,7 @@ class TestExtensionUpdateCLI:
                 "description": "A test extension",
             },
             "requires": {"speckit_version": ">=0.1.0"},
-            "provides": {"commands": [{"name": "speckit.test.hello", "file": "commands/hello.md"}]},
+            "provides": {"commands": [{"name": "speckit.test-ext.hello", "file": "commands/hello.md"}]},
         }
 
         with zipfile.ZipFile(zip_path, "w") as zf:
@@ -3442,15 +3620,15 @@ class TestHookInvocationRendering:
             [
                 {
                     "extension": "test-ext",
-                    "command": "speckit.test.hello",
+                    "command": "speckit.test-ext.hello",
                     "optional": False,
                 }
             ],
         )
 
-        assert "Executing: `/skill:speckit-test-hello`" in message
-        assert "EXECUTE_COMMAND: speckit.test.hello" in message
-        assert "EXECUTE_COMMAND_INVOCATION: /skill:speckit-test-hello" in message
+        assert "Executing: `/skill:speckit-test-ext-hello`" in message
+        assert "EXECUTE_COMMAND: speckit.test-ext.hello" in message
+        assert "EXECUTE_COMMAND_INVOCATION: /skill:speckit-test-ext-hello" in message
 
     def test_hook_executor_caches_init_options_lookup(self, project_dir, monkeypatch):
         """Init options should be loaded once per executor instance."""