feat: add tool permissions

Author: damassi

Makefile

@@ -1,13 +1,13 @@
-.PHONY: chat dev console
+.PHONY: dev console install start
 
 install:
 	uv sync && uv run pre-commit install && cp .env.example .env && echo "Please edit the .env file with your API keys."
 
-chat:
-	uv run chat
-
 console:
 	uv run textual console -x SYSTEM -x EVENT -x DEBUG -x INFO
 
 dev:
 	uv run textual run --dev -c chat
+
+start:
+	uv run chat

README.md

@@ -24,7 +24,7 @@ make install
 Update the `.env` with your `ANTHROPIC_API_KEY` and then run:
 
 ```bash
-make chat
+make start
 
 # Alternatively, if in dev (see below)
 make dev

agent-chat-cli.config.yaml

@@ -10,7 +10,7 @@ model: haiku
 include_partial_messages: true
 
 # Enable dynamic MCP server inference
-mcp_server_inference: true
+mcp_server_inference: false
 
 # Named agents with custom configurations
 # agents:
@@ -57,4 +57,4 @@ mcp_servers:
 disallowed_tools: []
 
 # Permission mode for tool execution
-permission_mode: "bypassPermissions"
+permission_mode: "default"

src/agent_chat_cli/app.py

@@ -7,6 +7,7 @@
 from agent_chat_cli.components.header import Header
 from agent_chat_cli.components.chat_history import ChatHistory, MessagePosted
 from agent_chat_cli.components.thinking_indicator import ThinkingIndicator
+from agent_chat_cli.components.tool_permission_prompt import ToolPermissionPrompt
 from agent_chat_cli.components.user_input import UserInput
 from agent_chat_cli.system.agent_loop import AgentLoop
 from agent_chat_cli.system.message_bus import MessageBus
@@ -38,12 +39,14 @@ def __init__(self) -> None:
         )
 
         self.actions = Actions(self)
+        self.pending_tool_permission: dict | None = None
 
     def compose(self) -> ComposeResult:
         with VerticalScroll():
             yield Header()
             yield ChatHistory()
             yield ThinkingIndicator()
+            yield ToolPermissionPrompt(actions=self.actions)
             yield UserInput(actions=self.actions)
 
     async def on_mount(self) -> None:

src/agent_chat_cli/components/tool_permission_prompt.py

@@ -0,0 +1,92 @@
+from typing import Any, TYPE_CHECKING
+
+from textual.widget import Widget
+from textual.app import ComposeResult
+from textual.widgets import Label, Input
+from textual.reactive import reactive
+
+from agent_chat_cli.components.caret import Caret
+from agent_chat_cli.components.flex import Flex
+from agent_chat_cli.components.spacer import Spacer
+from agent_chat_cli.utils import get_tool_info
+from agent_chat_cli.utils.logger import log_json
+
+if TYPE_CHECKING:
+    from agent_chat_cli.system.actions import Actions
+
+
+class ToolPermissionPrompt(Widget):
+    is_visible = reactive(False)
+    tool_name = reactive("")
+    tool_input: dict[str, Any] = reactive({}, init=False)  # type: ignore[assignment]
+
+    def __init__(self, actions: "Actions") -> None:
+        super().__init__()
+        self.actions = actions
+
+    def compose(self) -> ComposeResult:
+        yield Label("", id="tool-display")
+        yield Label("  [dim]Allow? (Enter=yes, ESC=no, or ask another question):[/dim]")
+
+        yield Spacer()
+
+        with Flex():
+            yield Caret()
+            yield Input(placeholder="Yes", id="permission-input")
+
+    def watch_is_visible(self, is_visible: bool) -> None:
+        self.display = is_visible
+
+        if is_visible:
+            input_widget = self.query_one("#permission-input", Input)
+            input_widget.value = ""
+            input_widget.focus()
+
+    def watch_tool_name(self, tool_name: str) -> None:
+        if not tool_name:
+            return
+
+        tool_info = get_tool_info(tool_name)
+        tool_display_label = self.query_one("#tool-display", Label)
+
+        if tool_info["server_name"]:
+            tool_display = (
+                rf"[bold]Confirm Tool:[/] [cyan]\[{tool_info['server_name']}][/] "
+                f"{tool_info['tool_name']}"
+            )
+        else:
+            tool_display = f"[bold]Confirm Tool:[/] {tool_name}"
+
+        tool_display_label.update(tool_display)
+
+    async def on_input_submitted(self, event: Input.Submitted) -> None:
+        raw_value = event.value
+        response = event.value.strip() or "yes"
+
+        log_json(
+            {
+                "event": "permission_input_submitted",
+                "raw_value": raw_value,
+                "stripped_value": event.value.strip(),
+                "final_response": response,
+            }
+        )
+
+        await self.actions.respond_to_tool_permission(response)
+
+    async def on_input_blurred(self, event: Input.Blurred) -> None:
+        if self.is_visible:
+            input_widget = self.query_one("#permission-input", Input)
+            input_widget.focus()
+
+    async def on_key(self, event) -> None:
+        if event.key == "escape":
+            log_json({"event": "permission_escape_pressed"})
+
+            event.stop()
+            event.prevent_default()
+
+            input_widget = self.query_one("#permission-input", Input)
+            input_widget.value = "no"
+
+            await input_widget.action_submit()

src/agent_chat_cli/docs/architecture.md

@@ -15,6 +15,7 @@ Textual widgets responsible for UI rendering:
 - **Message widgets**: SystemMessage, UserMessage, AgentMessage, ToolMessage
 - **UserInput**: Handles user text input and submission
 - **ThinkingIndicator**: Shows when agent is processing
+- **ToolPermissionPrompt**: Interactive widget for approving/denying tool execution requests
 
 ### System Layer
 
@@ -26,6 +27,9 @@ Manages the conversation loop with Claude SDK:
 - Emits AgentMessageType events (STREAM_EVENT, ASSISTANT, RESULT)
 - Manages session persistence via session_id
 - Supports dynamic MCP server inference and loading
+- Implements `_can_use_tool` callback for interactive tool permission requests
+- Uses `permission_lock` (asyncio.Lock) to serialize parallel permission requests
+- Manages `permission_response_queue` for user responses to tool permission prompts
 
 #### MCP Server Inference (`system/mcp_inference.py`)
 Intelligently determines which MCP servers are needed for each query:
@@ -42,19 +46,23 @@ Routes agent messages to appropriate UI components:
 - Controls thinking indicator state
 - Manages scroll-to-bottom behavior
 - Displays system messages (e.g., MCP server connection notifications)
+- Detects tool permission requests and shows ToolPermissionPrompt
+- Manages UI transitions between UserInput and ToolPermissionPrompt
 
 #### Actions (`system/actions.py`)
 Centralizes all user-initiated actions and controls:
 - **quit()**: Exits the application
 - **query(user_input)**: Sends user query to agent loop queue
-- **interrupt()**: Stops streaming mid-execution by setting interrupt flag and calling SDK interrupt
+- **interrupt()**: Stops streaming mid-execution by setting interrupt flag and calling SDK interrupt (ignores ESC when tool permission prompt is visible)
 - **new()**: Starts new conversation by sending NEW_CONVERSATION control command
+- **respond_to_tool_permission(response)**: Handles tool permission responses, manages UI state transitions between permission prompt and user input
 - Manages UI state (thinking indicator, chat history clearing)
-- Directly accesses agent_loop internals (query_queue, client, interrupting flag)
+- Directly accesses agent_loop internals (query_queue, client, interrupting flag, permission_response_queue)
 
 Actions are triggered via:
 - Keybindings in app.py (ESC → action_interrupt, Ctrl+N → action_new)
 - Text commands in user_input.py ("exit", "clear")
+- Component events (ToolPermissionPrompt.on_input_submitted → respond_to_tool_permission)
 
 ### Utils Layer
 
@@ -211,6 +219,103 @@ mcp_servers:
     # ... rest of config
 ```
 
+## Tool Permission System
+
+The application implements interactive tool permission requests that allow users to approve or deny tool execution in real-time.
+
+### Components
+
+#### ToolPermissionPrompt (`components/tool_permission_prompt.py`)
+Textual widget that displays permission requests to the user:
+- Shows tool name with MCP server info
+- Provides input field for user response
+- Supports Enter (approve), ESC (deny), or custom text responses
+
+### Permission Flow
+
+```
+Tool Execution Request (from Claude SDK)
+    ↓
+AgentLoop._can_use_tool (callback with permission_lock acquired)
+    ↓
+Emit SYSTEM AgentMessage with tool_permission_request data
+    ↓
+MessageBus._handle_system detects permission request
+    ↓
+Show ToolPermissionPrompt, hide UserInput
+    ↓
+User Response:
+    - Enter (or "yes") → Approve
+    - ESC (or "no") → Deny
+    - Custom text → Send to Claude as alternative instruction
+    ↓
+Actions.respond_to_tool_permission(response)
+    ↓
+Put response on permission_response_queue
+    ↓
+Hide ToolPermissionPrompt, show UserInput
+    ↓
+AgentLoop._can_use_tool receives response
+    ↓
+Return PermissionResultAllow or PermissionResultDeny
+    ↓
+Next tool permission request (if multiple tools called)
+```
+
+### Serialization with Permission Lock
+
+When multiple tools request permission in parallel, a `permission_lock` (asyncio.Lock) ensures they are handled sequentially:
+
+1. First tool acquires lock → Shows prompt → Waits for response → Releases lock
+2. Second tool acquires lock → Shows prompt → Waits for response → Releases lock
+3. Third tool acquires lock → Shows prompt → Waits for response → Releases lock
+
+This prevents race conditions where multiple prompts would overwrite each other and ensures each tool gets a dedicated user response.
+
+### Permission Responses
+
+The `_can_use_tool` callback returns typed permission results:
+
+**Approve (CONFIRM)**:
+```python
+return PermissionResultAllow(
+    behavior="allow",
+    updated_input=tool_input,
+)
+```
+
+**Deny (DENY)**:
+```python
+return PermissionResultDeny(
+    behavior="deny",
+    message="User denied permission",
+    interrupt=True,
+)
+```
+
+**Custom Response**:
+```python
+return PermissionResultDeny(
+    behavior="deny",
+    message=user_response,  # Alternative instruction sent to Claude
+    interrupt=True,
+)
+```
+
+### ESC Key Handling
+
+When ToolPermissionPrompt is visible, the ESC key is intercepted:
+- `Actions.interrupt()` checks `permission_prompt.is_visible`
+- If visible, returns early without interrupting the agent
+- ToolPermissionPrompt's `on_key` handler processes ESC to deny the tool
+- If not visible, ESC performs normal interrupt behavior
+
+### System Messages
+
+Permission denials generate system messages in the chat:
+- **Denied**: `"Permission denied for {tool_name}"`
+- **Custom response**: `"Custom response for {tool_name}: {user_response}"`
+
 ## User Commands
 
 ### Text Commands
@@ -219,7 +324,7 @@ mcp_servers:
 
 ### Keybindings
 - **Ctrl+C**: Quit application
-- **ESC**: Interrupt streaming response
+- **ESC**: Interrupt streaming response (or deny tool permission if prompt visible)
 - **Ctrl+N**: Start new conversation
 
 ## Session Management
@@ -274,3 +379,5 @@ SDK reconnects to previous session with full history
 - Control commands are queued alongside user queries to ensure proper task ordering
 - Agent loop processes both strings (user queries) and ControlCommands from the same queue
 - Interrupt flag is checked on each streaming message to enable immediate stop
+- Tool permission requests are serialized via asyncio.Lock to handle parallel tool calls sequentially
+- Permission responses use typed SDK objects (PermissionResultAllow, PermissionResultDeny) rather than plain dictionaries

src/agent_chat_cli/system/actions.py

@@ -1,7 +1,11 @@
+from textual.widgets import Input
+
 from agent_chat_cli.system.agent_loop import AgentLoop
 from agent_chat_cli.utils.enums import ControlCommand
 from agent_chat_cli.components.chat_history import ChatHistory
 from agent_chat_cli.components.thinking_indicator import ThinkingIndicator
+from agent_chat_cli.components.tool_permission_prompt import ToolPermissionPrompt
+from agent_chat_cli.utils.logger import log_json
 
 
 class Actions:
@@ -16,6 +20,10 @@ async def query(self, user_input: str) -> None:
         await self.agent_loop.query_queue.put(user_input)
 
     async def interrupt(self) -> None:
+        permission_prompt = self.app.query_one(ToolPermissionPrompt)
+        if permission_prompt.is_visible:
+            return
+
         self.agent_loop.interrupting = True
         await self.agent_loop.client.interrupt()
 
@@ -30,3 +38,26 @@ async def new(self) -> None:
 
         thinking_indicator = self.app.query_one(ThinkingIndicator)
         thinking_indicator.is_thinking = False
+
+    async def respond_to_tool_permission(self, response: str) -> None:
+        from agent_chat_cli.components.user_input import UserInput
+
+        log_json(
+            {
+                "event": "permission_response_action",
+                "response": response,
+            }
+        )
+
+        await self.agent_loop.permission_response_queue.put(response)
+
+        thinking_indicator = self.app.query_one(ThinkingIndicator)
+        thinking_indicator.is_thinking = True
+
+        permission_prompt = self.app.query_one(ToolPermissionPrompt)
+        permission_prompt.is_visible = False
+
+        user_input = self.app.query_one(UserInput)
+        user_input.display = True
+        input_widget = user_input.query_one(Input)
+        input_widget.focus()