feat: Add ty for type-checking, remove mypy

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
         run: uv sync --all-groups
 
       - name: Run type checker
-        run: uv run mypy src
+        run: uv run ty check src
 
   test:
     runs-on: ubuntu-latest

.gitignore

@@ -154,11 +154,6 @@ venv.bak/
 # mkdocs documentation
 /site
 
-# mypy
-.mypy_cache/
-.dmypy.json
-dmypy.json
-
 # Pyre type checker
 .pyre/
 

.pre-commit-config.yaml

@@ -6,9 +6,12 @@ repos:
         args: [--fix]
       - id: ruff-format
 
-  - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v1.13.0
+  - repo: local
     hooks:
-      - id: mypy
+      - id: ty
+        name: ty
+        entry: uv run ty check src
+        language: system
+        types: [python]
+        pass_filenames: false
         stages: [pre-push]
-        additional_dependencies: [textual, claude-agent-sdk, pydantic, types-PyYAML]

.vscode/settings.json

@@ -3,20 +3,14 @@
   "editor.tabSize": 4,
   "editor.insertSpaces": true,
   "files.exclude": {
-    "**/.mypy_cache": true,
     "**/.ruff_cache": true,
     "**/.venv": true,
     "**/__pycache__": true,
     "**/agent_chat_cli.egg-info": true,
   },
-  "mypy.dmypyExecutable": "${workspaceFolder}/.venv/bin/dmypy",
-  "mypy.runUsingActiveInterpreter": true,
   "ruff.enable": true,
   "ruff.lint.enable": true,
-  "python.analysis.autoImportCompletions": true,
-  "python.analysis.typeCheckingMode": "basic",
-  "python.analysis.inlayHints.functionReturnTypes": false,
-  "python.analysis.inlayHints.variableTypes": false,
+  "python.languageServer": "None",
 
   "[python]": {
     "editor.defaultFormatter": "charliermarsh.ruff",

CLAUDE.md

@@ -3,7 +3,7 @@
 ## Rules
 
 - Read `docs/architecture.md` for an architectural overview of the project. Refactors should always start here first.
-- The project uses `uv`, `ruff` and `mypy`
+- The project uses `uv`, `ruff` and `ty`
 - Run commands should be prefixed with `uv`: `uv run ...`
 - Use `asyncio` features, if such is needed
 - Prefer early returns

Makefile

@@ -19,4 +19,4 @@ test:
 	uv run pytest
 
 type-check:
-	uv run mypy src
+	uv run ty check src

README.md

@@ -38,7 +38,7 @@ Additional MCP servers are configured in `agent-chat-cli.config.yaml` and prompt
 
 - Install pre-commit hooks via [pre-commit](https://pre-commit.com/)
   - `uv run pre-commit install`
-- Type-checking is via [MyPy](https://github.com/python/mypy):
+- Type-checking is via [ty](https://github.com/astral-sh/ty):
   - `make type-check`
 - Linting and formatting is via [Ruff](https://docs.astral.sh/ruff/)
   - `make lint`

pyproject.toml

@@ -7,7 +7,6 @@ requires-python = ">=3.14"
 dependencies = [
     "asyncio>=4.0.0",
     "claude-agent-sdk>=0.1.10",
-    "mypy>=1.19.0",
     "pydantic>=2.12.5",
     "python-dotenv>=1.2.1",
     "pyyaml>=6.0.3",
@@ -17,14 +16,13 @@ dependencies = [
 
 [dependency-groups]
 dev = [
-    "mypy>=1.19.0",
     "pre-commit>=4.3.0",
     "pytest>=8.0.0",
     "pytest-asyncio>=0.24.0",
     "pytest-textual-snapshot>=1.0.0",
     "ruff>=0.14.7",
     "textual-dev>=1.8.0",
-    "types-pyyaml>=6.0.12.20250915",
+    "ty>=0.0.2",
 ]
 
 [project.scripts]

src/agent_chat_cli/core/agent_loop.py

@@ -9,6 +9,7 @@
 from claude_agent_sdk.types import (
     AssistantMessage,
     Message,
+    StreamEvent,
     SystemMessage,
     TextBlock,
     ToolUseBlock,
@@ -124,8 +125,8 @@ async def _handle_message(self, message: Message) -> None:
                 MCPServerStatus.update(message.data["mcp_servers"])
 
         # Handle streaming messages
-        if hasattr(message, "event"):
-            event = message.event  # type: ignore[attr-defined]
+        if isinstance(message, StreamEvent):
+            event = message.event
 
             if event.get("type") == ContentType.CONTENT_BLOCK_DELTA.value:
                 delta = event.get("delta", {})

tests/core/test_agent_loop.py

@@ -5,6 +5,7 @@
 
 from claude_agent_sdk.types import (
     AssistantMessage,
+    StreamEvent,
     SystemMessage,
     TextBlock,
     ToolUseBlock,
@@ -141,14 +142,17 @@ class TestHandleMessageStreamEvent:
     async def test_handles_text_delta_stream_event(self, mock_app, mock_config):
         agent_loop = AgentLoop(app=mock_app)
 
-        message = MagicMock()
-        message.event = {
-            "type": ContentType.CONTENT_BLOCK_DELTA.value,
-            "delta": {
-                "type": ContentType.TEXT_DELTA.value,
-                "text": "Hello world",
+        message = StreamEvent(
+            uuid="test-uuid",
+            session_id="test-session",
+            event={
+                "type": ContentType.CONTENT_BLOCK_DELTA.value,
+                "delta": {
+                    "type": ContentType.TEXT_DELTA.value,
+                    "text": "Hello world",
+                },
             },
-        }
+        )
 
         await agent_loop._handle_message(message)
 
@@ -160,14 +164,17 @@ async def test_handles_text_delta_stream_event(self, mock_app, mock_config):
     async def test_ignores_empty_text_delta(self, mock_app, mock_config):
         agent_loop = AgentLoop(app=mock_app)
 
-        message = MagicMock()
-        message.event = {
-            "type": ContentType.CONTENT_BLOCK_DELTA.value,
-            "delta": {
-                "type": ContentType.TEXT_DELTA.value,
-                "text": "",
+        message = StreamEvent(
+            uuid="test-uuid",
+            session_id="test-session",
+            event={
+                "type": ContentType.CONTENT_BLOCK_DELTA.value,
+                "delta": {
+                    "type": ContentType.TEXT_DELTA.value,
+                    "text": "",
+                },
             },
-        }
+        )
 
         await agent_loop._handle_message(message)