agentclientprotocol · benbrandt · Feb 11, 2026 · Feb 6, 2026 · Feb 10, 2026
diff --git a/.github/workflows/build_registry.py b/.github/workflows/build_registry.py
@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-"""Build aggregated registry.json from individual agent and extension directories."""
+"""Build aggregated registry.json from individual agent directories."""
 
 import json
 import os
@@ -268,11 +268,9 @@ def validate_icon_monochrome(content: str) -> list[str]:
                 reported_colors.add(style_stroke.group(1).strip())
 
     # Check that currentColor is actually used (icons without fill default to black)
-    has_current_color = bool(re.search(r'currentColor', content, re.IGNORECASE))
+    has_current_color = bool(re.search(r"currentColor", content, re.IGNORECASE))
     if not has_current_color:
-        errors.append(
-            'Icon must use currentColor for fills/strokes to support theming'
-        )
+        errors.append("Icon must use currentColor for fills/strokes to support theming")
 
     # Deduplicate errors
     return list(dict.fromkeys(errors))
@@ -475,7 +473,7 @@ def process_entry(
     base_url: str,
     seen_ids: dict,
 ) -> tuple[dict | None, list[str]]:
-    """Process a single agent or extension entry. Returns (entry, errors)."""
+    """Process a single registry entry. Returns (entry, errors)."""
     entry_path = entry_dir / entry_file
 
     # Parse JSON with error handling
@@ -485,7 +483,7 @@ def process_entry(
     except json.JSONDecodeError as e:
         return None, [f"{entry_dir.name}/{entry_file} is invalid JSON: {e}"]
 
-    # Validate entry (uses same schema for both agents and extensions)
+    # Validate entry
     validation_errors = validate_agent(entry, entry_dir.name, schema)
     if validation_errors:
         return None, [f"{entry_dir.name}/{entry_file} validation failed:"] + [
@@ -502,7 +500,7 @@ def process_entry(
                 f"  - {e}" for e in version_errors
             ]
 
-    # Check for duplicate IDs (across both agents and extensions)
+    # Check for duplicate IDs
     entry_id = entry["id"]
     if entry_id in seen_ids:
         return None, [
@@ -532,15 +530,14 @@ def process_entry(
 
 
 def build_registry():
-    """Build registry.json from agent and extension directories."""
+    """Build registry.json from agent directories."""
     registry_dir = Path(__file__).parent.parent.parent
     base_url = get_base_url()
     agents = []
-    extensions = []
     seen_ids = {}
     has_errors = False
 
-    # Load schema for validation (used for both agents and extensions)
+    # Load schema for validation
     schema = load_schema(registry_dir)
     if schema and not HAS_JSONSCHEMA:
         print("Warning: jsonschema not installed, skipping schema validation")
@@ -551,56 +548,32 @@ def build_registry():
             continue
 
         agent_json_path = entry_dir / "agent.json"
-        extension_json_path = entry_dir / "extension.json"
-
-        has_agent = agent_json_path.exists()
-        has_extension = extension_json_path.exists()
 
-        if has_agent and has_extension:
-            print(f"Error: {entry_dir.name}/ has both agent.json and extension.json")
-            has_errors = True
+        if not agent_json_path.exists():
+            print(f"Warning: {entry_dir.name}/ has no agent.json, skipping")
             continue
 
-        if not has_agent and not has_extension:
-            print(
-                f"Warning: {entry_dir.name}/ has no agent.json or extension.json, skipping"
-            )
+        entry, errors = process_entry(
+            entry_dir, "agent.json", "agent", schema, base_url, seen_ids
+        )
+        if errors:
+            for error in errors:
+                print(f"Error: {error}")
+            has_errors = True
             continue
-
-        if has_agent:
-            entry, errors = process_entry(
-                entry_dir, "agent.json", "agent", schema, base_url, seen_ids
-            )
-            if errors:
-                for error in errors:
-                    print(f"Error: {error}")
-                has_errors = True
-                continue
-            agents.append(entry)
-            print(f"Added agent: {entry['id']} v{entry['version']}")
-        else:
-            entry, errors = process_entry(
-                entry_dir, "extension.json", "extension", schema, base_url, seen_ids
-            )
-            if errors:
-                for error in errors:
-                    print(f"Error: {error}")
-                has_errors = True
-                continue
-            extensions.append(entry)
-            print(f"Added extension: {entry['id']} v{entry['version']}")
+        agents.append(entry)
+        print(f"Added agent: {entry['id']} v{entry['version']}")
 
     if has_errors:
         print("\nBuild failed due to validation errors")
         sys.exit(1)
 
-    if not agents and not extensions:
-        print("\nWarning: No agents or extensions found")
+    if not agents:
+        print("\nWarning: No agents found")
 
     registry = {
         "version": REGISTRY_VERSION,
         "agents": agents,
-        "extensions": extensions,
     }
 
     # Create dist directory
@@ -618,15 +591,14 @@ def build_registry():
     jetbrains_registry = {
         "version": REGISTRY_VERSION,
         "agents": [a for a in agents if a["id"] not in JETBRAINS_EXCLUDE_IDS],
-        "extensions": extensions,
     }
     jetbrains_output_path = dist_dir / "registry-for-jetbrains.json"
     with open(jetbrains_output_path, "w") as f:
         json.dump(jetbrains_registry, f, indent=2)
         f.write("\n")
 
-    # Copy icons to dist (for both agents and extensions)
-    for entry in agents + extensions:
+    # Copy icons to dist
+    for entry in agents:
         entry_id = entry["id"]
         icon_src = registry_dir / entry_id / "icon.svg"
         if icon_src.exists():
@@ -641,9 +613,11 @@ def build_registry():
             schema_dst.write_bytes(schema_src.read_bytes())
 
     jetbrains_agent_count = len(jetbrains_registry["agents"])
-    print(f"\nBuilt dist/ with {len(agents)} agents and {len(extensions)} extensions")
+    print(f"\nBuilt dist/ with {len(agents)} agents")
     print(f"  registry.json: {len(agents)} agents")
-    print(f"  registry-for-jetbrains.json: {jetbrains_agent_count} agents (excluded: {', '.join(JETBRAINS_EXCLUDE_IDS)})")
+    print(
+        f"  registry-for-jetbrains.json: {jetbrains_agent_count} agents (excluded: {', '.join(JETBRAINS_EXCLUDE_IDS)})"
+    )
 
 
 if __name__ == "__main__":

diff --git a/AGENTS.md b/AGENTS.md
@@ -14,25 +14,24 @@ python .github/workflows/build_registry.py
 
 ## Architecture
 
-This is a registry of ACP (Agent Client Protocol) agents and extensions. The structure is:
+This is a registry of ACP (Agent Client Protocol) agents. The structure is:
 
 ```
 <id>/
 ├── agent.json      # Agent metadata and distribution info
-├── extension.json  # OR extension metadata (same schema as agent.json)
 └── icon.svg        # Icon: 16x16 SVG, monochrome with currentColor (optional)
 ```
 
-Each directory contains either `agent.json` (for agents) or `extension.json` (for extensions), but not both. Extensions use the same schema as agents (`agent.schema.json`).
-
 **Build process** (`.github/workflows/build_registry.py`):
-1. Scans directories for `agent.json` or `extension.json` files
+
+1. Scans directories for `agent.json` files
 2. Validates against `agent.schema.json` (JSON Schema)
 3. Validates icons (16x16 SVG, monochrome with `currentColor`)
-4. Aggregates into `dist/registry.json` with separate `agents` and `extensions` arrays
+4. Aggregates into `dist/registry.json`
 5. Copies icons to `dist/<id>.svg`
 
 **CI/CD** (`.github/workflows/build-registry.yml`):
+
 - PRs: Runs validation only
 - Push to main: Validates, then publishes versioned + `latest` GitHub releases
 
@@ -53,6 +52,7 @@ Set `SKIP_URL_VALIDATION=1` to bypass URL checks during local development.
 ### Automated Updates
 
 Agent versions are automatically updated via `.github/workflows/update-versions.yml`:
+
 - **Schedule:** Runs hourly (cron: `0 * * * *`)
 - **Scope:** Checks all agents in root and `_not_yet_unsupported/`
 - **Supported distributions:** `npx` (npm), `uvx` (PyPI), `binary` (GitHub releases)
@@ -78,6 +78,7 @@ To update agents manually:
 2. **For GitHub binaries** (`binary` distribution): Check latest release at `https://api.github.com/repos/<owner>/<repo>/releases/latest`
 
 Update `agent.json`:
+
 - Update the `version` field
 - Update version in all distribution URLs (use replace-all for consistency)
 - For npm: update `package` field (e.g., `@google/gemini-cli@0.22.5`)
@@ -96,20 +97,23 @@ Run build to validate: `uv run --with jsonschema .github/workflows/build_registr
 ## Icon Requirements
 
 Icons must be:
+
 - **SVG format** (only `.svg` files accepted)
 - **16x16 dimensions** (via width/height attributes or viewBox)
 - **Monochrome using `currentColor`** - all fills and strokes must use `currentColor` or `none`
 
 Using `currentColor` enables icons to adapt to different themes (light/dark mode) automatically.
 
 **Valid example:**
+
 ```svg
 <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16">
   <path fill="currentColor" d="M..."/>
 </svg>
 ```
 
 **Invalid patterns:**
+
 - Hardcoded colors: `fill="#FF5500"`, `fill="red"`, `stroke="rgb(0,0,0)"`
 - Missing currentColor: `fill` or `stroke` without `currentColor`
 
@@ -118,6 +122,7 @@ Using `currentColor` enables icons to adapt to different themes (light/dark mode
 Agents must support ACP authentication. The CI verifies auth via `.github/workflows/verify_agents.py --auth-check`.
 
 **Requirements:**
+
 - Return `authMethods` array in `initialize` response
 - At least one method must have type `"agent"` or `"terminal"`
 

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -1,6 +1,6 @@
 # Contributing to the ACP Registry
 
-## Adding a New Agent or Extension
+## Adding a New Agent
 
 1. **Fork this repository**
 
@@ -12,9 +12,7 @@
 
    The directory name must match your entry's `id` field.
 
-3. **Create `agent.json` or `extension.json`**
-
-   Use `agent.json` for agents, `extension.json` for extensions. Both use the same schema.
+3. **Create `agent.json`**
 
    ```json
    {
@@ -40,6 +38,7 @@
    - **Monochrome using `currentColor`** - enables theme support (light/dark mode)
 
    Example:
+
    ```svg
    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16">
      <path fill="currentColor" d="M..."/>
@@ -126,21 +125,21 @@ Supported platforms: `darwin-aarch64`, `darwin-x86_64`, `linux-aarch64`, `linux-
 
 ## Required Fields
 
-| Field | Type | Description |
-|-------|------|-------------|
-| `id` | string | Unique identifier (lowercase, hyphens allowed) |
-| `name` | string | Display name |
-| `version` | string | Semantic version |
-| `description` | string | Brief description |
-| `distribution` | object | At least one distribution method |
+| Field          | Type   | Description                                    |
+| -------------- | ------ | ---------------------------------------------- |
+| `id`           | string | Unique identifier (lowercase, hyphens allowed) |
+| `name`         | string | Display name                                   |
+| `version`      | string | Semantic version                               |
+| `description`  | string | Brief description                              |
+| `distribution` | object | At least one distribution method               |
 
 ## Optional Fields
 
-| Field | Type | Description |
-|-------|------|-------------|
-| `repository` | string | Source code URL |
-| `authors` | array | List of author names/emails |
-| `license` | string | SPDX license identifier |
+| Field        | Type   | Description                 |
+| ------------ | ------ | --------------------------- |
+| `repository` | string | Source code URL             |
+| `authors`    | array  | List of author names/emails |
+| `license`    | string | SPDX license identifier     |
 
 ## Automatic Version Updates
 
@@ -154,9 +153,9 @@ You don't need to submit a PR for version bumps.
 
 ## Manual Updates
 
-To manually update your agent or extension (e.g., changing description, adding platforms):
+To manually update your agent (e.g., changing description, adding platforms):
 
-1. Fork and update the `agent.json` or `extension.json` file
+1. Fork and update the `agent.json` file
 2. Submit a Pull Request
 3. CI will validate and merge will trigger a new registry release
 
@@ -173,7 +172,7 @@ Entries are validated against the [JSON Schema](agent.schema.json).
 - Must be lowercase letters, digits, and hyphens only
 - Must start with a letter
 - Must match the directory name
-- Must be unique across all agents and extensions
+- Must be unique across all agents
 
 ### Version Validation
 
@@ -183,11 +182,13 @@ Entries are validated against the [JSON Schema](agent.schema.json).
 ### Distribution Validation
 
 **Structure:**
+
 - At least one distribution method required (`binary`, `npx`, or `uvx`)
 - Binary distributions require `archive` and `cmd` fields per platform
 - Package distributions (`npx`, `uvx`) require `package` field
 
 **Platforms** (for binary):
+
 - `darwin-aarch64`, `darwin-x86_64`
 - `linux-aarch64`, `linux-x86_64`
 - `windows-aarch64`, `windows-x86_64`
@@ -201,12 +202,14 @@ Entries are validated against the [JSON Schema](agent.schema.json).
 - Missing OS families will produce a warning but will not fail validation
 
 **Version matching:**
+
 - Distribution versions must match the entry's `version` field
 - Binary URLs containing version (e.g., `/download/v1.0.0/`) are checked
 - npm package versions (`@scope/pkg@1.0.0`) are checked
 - PyPI package versions (`pkg==1.0.0` or `pkg@1.0.0`) are checked
 
 **No `latest` allowed:**
+
 - Binary URLs must not contain `/latest/`
 - npm packages must not use `@latest`
 - PyPI packages must not use `@latest`
@@ -239,6 +242,7 @@ python3 .github/workflows/verify_agents.py --auth-check
 ```
 
 **What gets checked:**
+
 - Agent must return `authMethods` in the `initialize` response
 - At least one method must have `type: "agent"` or `type: "terminal"`
 - See [AUTHENTICATION.md](AUTHENTICATION.md) for implementation details

diff --git a/FORMAT.md b/FORMAT.md
@@ -1,16 +1,15 @@
 # Registry Format
 
-The registry contains both agents and extensions:
+The registry contains agents:
 
 ```json
 {
   "version": "1.0.0",
-  "agents": [...],
-  "extensions": [...]
+  "agents": [...]
 }
 ```
 
-Each entry (agent or extension) has the same structure:
+Each agent has the following structure:
 
 ```json
 {
@@ -46,7 +45,7 @@ Each entry (agent or extension) has the same structure:
 ## Distribution Types
 
 | Type     | Description                   | Command                |
-|----------|-------------------------------|------------------------|
+| -------- | ----------------------------- | ---------------------- |
 | `binary` | Platform-specific executables | Download, extract, run |
 | `npx`    | npm packages                  | `npx <package> [args]` |
 | `uvx`    | PyPI packages via uv          | `uvx <package> [args]` |