feat: Add support for chat resume via session_id

Makefile

@@ -0,0 +1,13 @@
+.PHONY: chat dev console
+
+install:
+	uv sync && uv run pre-commit install
+
+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

README.md

@@ -15,8 +15,8 @@ This tool is for those who wish for slightly more control over their MCP servers
 This app uses [uv](https://github.com/astral-sh/uv) for package management so first install that. Then:
 
 - `git clone https://github.com/damassi/agent-chat-cli-python.git`
-- `uv sync`
-- `uv run chat`
+- `make install`
+- `make chat`
 
 Additional MCP servers are configured in `agent-chat-cli.config.yaml` and prompts added within the `prompts` folder.
 
@@ -27,3 +27,19 @@ Additional MCP servers are configured in `agent-chat-cli.config.yaml` and prompt
 - Typechecking is via [MyPy](https://github.com/python/mypy):
   - `uv run mypy src`
 - Linting and formatting is via [Ruff](https://docs.astral.sh/ruff/)
+
+Textual has an integrated logging console which one can boot separately from the app to receive logs.
+
+In one terminal pane boot the console:
+
+```bash
+make console
+```
+
+> Note: this command intentionally filters out more verbose notifications. See the Makefile to configure.
+
+And then in a second, start the textual dev server:
+
+```bash
+make dev
+```

agent-chat-cli.config.yaml

@@ -4,7 +4,7 @@
 system_prompt: system.md
 
 # Model to use (e.g., sonnet, opus, haiku)
-model: sonnet
+model: haiku
 
 # Enable streaming responses
 include_partial_messages: true

src/agent_chat_cli/app.py

@@ -1,4 +1,5 @@
 import asyncio
+
 from textual.app import App, ComposeResult
 from textual.containers import VerticalScroll
 from textual.binding import Binding
@@ -9,10 +10,12 @@
 from agent_chat_cli.components.user_input import UserInput
 from agent_chat_cli.utils import AgentLoop
 from agent_chat_cli.utils.message_bus import MessageBus
+from agent_chat_cli.utils.logger import setup_logging
 
 from dotenv import load_dotenv
 
 load_dotenv()
+setup_logging()
 
 
 class AgentChatCLIApp(App):

src/agent_chat_cli/docs/architecture.md

@@ -0,0 +1,137 @@
+# Architecture
+
+## Overview
+
+Agent Chat CLI is a Python TUI application built with Textual that provides an interactive chat interface for Claude AI with MCP (Model Context Protocol) server support.
+
+## Core Components
+
+### App Layer (`app.py`)
+Main Textual application that initializes and coordinates all components.
+
+### Components Layer
+Textual widgets responsible for UI rendering:
+- **ChatHistory**: Container that displays message widgets
+- **Message widgets**: SystemMessage, UserMessage, AgentMessage, ToolMessage
+- **UserInput**: Handles user text input and submission
+- **ThinkingIndicator**: Shows when agent is processing
+
+### Utils Layer
+
+#### Agent Loop (`agent_loop.py`)
+Manages the conversation loop with Claude SDK:
+- Maintains async queue for user queries
+- Handles streaming responses
+- Parses SDK messages into structured AgentMessage objects
+- Emits AgentMessageType events (STREAM_EVENT, ASSISTANT, RESULT)
+
+#### Message Bus (`message_bus.py`)
+Routes agent messages to appropriate UI components:
+- Handles streaming text updates
+- Mounts tool use messages
+- Controls thinking indicator state
+- Manages scroll-to-bottom behavior
+
+#### Config (`config.py`)
+Loads and validates YAML configuration:
+- Filters disabled MCP servers
+- Loads prompts from files
+- Expands environment variables
+- Combines system prompt with MCP server prompts
+
+## Data Flow
+
+```
+User Input
+    ↓
+UserInput.on_input_submitted
+    ↓
+MessagePosted event → ChatHistory (immediate UI update)
+    ↓
+AgentLoop.query (added to queue)
+    ↓
+Claude SDK (streaming response)
+    ↓
+AgentLoop._handle_message
+    ↓
+AgentMessage (typed message) → MessageBus.handle_agent_message
+    ↓
+Match on AgentMessageType:
+    - STREAM_EVENT → Update streaming message widget
+    - ASSISTANT → Mount tool use widgets
+    - RESULT → Reset thinking indicator
+```
+
+## Key Types
+
+### Enums (`utils/enums.py`)
+
+**AgentMessageType**: Agent communication events
+- ASSISTANT: Assistant message with content blocks
+- STREAM_EVENT: Streaming text chunk
+- RESULT: Response complete
+- INIT, SYSTEM: Initialization and system events
+
+**ContentType**: Content block types
+- TEXT: Text content
+- TOOL_USE: Tool call
+- CONTENT_BLOCK_DELTA: SDK streaming event type
+- TEXT_DELTA: SDK text delta type
+
+**MessageType** (`components/messages.py`): UI message types
+- SYSTEM, USER, AGENT, TOOL
+
+### Data Classes
+
+**AgentMessage** (`utils/agent_loop.py`): Structured message from agent loop
+```python
+@dataclass
+class AgentMessage:
+    type: AgentMessageType
+    data: Any
+```
+
+**Message** (`components/messages.py`): UI message data
+```python
+@dataclass
+class Message:
+    type: MessageType
+    content: str
+    metadata: dict[str, Any] | None = None
+```
+
+## Configuration System
+
+Configuration is loaded from `agent-chat-cli.config.yaml`:
+- **system_prompt**: Base system prompt (supports file paths)
+- **model**: Claude model to use
+- **include_partial_messages**: Enable streaming
+- **mcp_servers**: MCP server configurations (filtered by enabled flag)
+- **agents**: Named agent configurations
+- **disallowed_tools**: Tool filtering
+- **permission_mode**: Permission handling mode
+
+MCP server prompts are automatically appended to the system prompt.
+
+## Event Flow
+
+### User Message Flow
+1. User submits text → UserInput
+2. MessagePosted event → App
+3. App → MessageBus.on_message_posted
+4. MessageBus → ChatHistory.add_message
+5. MessageBus → Scroll to bottom
+
+### Agent Response Flow
+1. AgentLoop receives SDK message
+2. Parse into AgentMessage with AgentMessageType
+3. MessageBus.handle_agent_message (match/case on type)
+4. Update UI components based on type
+5. Scroll to bottom
+
+## Notes
+
+- Two distinct MessageType enums exist for different purposes (UI vs Agent events)
+- Message bus manages stateful streaming (tracks current_agent_message)
+- Config loading combines multiple prompts into final system_prompt
+- Tool names follow format: `mcp__servername__toolname`

src/agent_chat_cli/utils/agent_loop.py

@@ -6,7 +6,12 @@
     ClaudeAgentOptions,
     ClaudeSDKClient,
 )
-from claude_agent_sdk.types import AssistantMessage, TextBlock, ToolUseBlock
+from claude_agent_sdk.types import (
+    AssistantMessage,
+    SystemMessage,
+    TextBlock,
+    ToolUseBlock,
+)
 
 from agent_chat_cli.utils.config import load_config
 from agent_chat_cli.utils.enums import AgentMessageType, ContentType
@@ -22,12 +27,16 @@ class AgentLoop:
     def __init__(
         self,
         on_message: Callable[[AgentMessage], Awaitable[None]],
+        session_id: str | None = None,
     ) -> None:
         self.config = load_config()
+        self.session_id = session_id
+
+        config_dict = self.config.model_dump()
+        if session_id:
+            config_dict["resume"] = session_id
 
-        self.client = ClaudeSDKClient(
-            options=ClaudeAgentOptions(**self.config.model_dump())
-        )
+        self.client = ClaudeSDKClient(options=ClaudeAgentOptions(**config_dict))
 
         self.on_message = on_message
         self.query_queue: asyncio.Queue[str] = asyncio.Queue()
@@ -49,6 +58,12 @@ async def start(self) -> None:
             await self.on_message(AgentMessage(type=AgentMessageType.RESULT, data=None))
 
     async def _handle_message(self, message: Any) -> None:
+        if isinstance(message, SystemMessage):
+            if message.subtype == AgentMessageType.INIT.value and message.data.get(
+                "session_id"
+            ):
+                self.session_id = message.data["session_id"]
+
         if hasattr(message, "event"):
             event = message.event  # type: ignore[attr-defined]
 

src/agent_chat_cli/utils/logger.py

@@ -0,0 +1,20 @@
+import json
+import logging
+from typing import Any
+
+from textual.logging import TextualHandler
+
+
+def setup_logging():
+    logging.basicConfig(
+        level="NOTSET",
+        handlers=[TextualHandler()],
+    )
+
+
+def log(message: str):
+    logging.info(message)
+
+
+def log_json(message: Any):
+    logging.info(json.dumps(message, indent=2))

src/agent_chat_cli/utils/message_bus.py

@@ -23,12 +23,6 @@ def __init__(self, app: "App") -> None:
         self.current_agent_message: AgentMessageWidget | None = None
         self.current_response_text = ""
 
-    async def _scroll_to_bottom(self) -> None:
-        """Scroll the container to the bottom after a slight pause."""
-        await asyncio.sleep(0.1)
-        container = self.app.query_one("#container")
-        container.scroll_end(animate=False, immediate=True)
-
     async def handle_agent_message(self, message: AgentMessage) -> None:
         match message.type:
             case AgentMessageType.STREAM_EVENT:
@@ -38,6 +32,12 @@ async def handle_agent_message(self, message: AgentMessage) -> None:
             case AgentMessageType.RESULT:
                 await self._handle_result()
 
+    async def _scroll_to_bottom(self) -> None:
+        """Scroll the container to the bottom after a slight pause."""
+        await asyncio.sleep(0.1)
+        container = self.app.query_one("#container")
+        container.scroll_end(animate=False, immediate=True)
+
     async def _handle_stream_event(self, message: AgentMessage) -> None:
         text_chunk = message.data.get("text", "")