diff --git a/pyproject.toml b/pyproject.toml
index f267c7d..6f8a0a1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,3 +35,9 @@ where = ["src"]
 [tool.pytest.ini_options]
 testpaths = ["tests"]
 pythonpath = ["src"]
+
+[tool.pyright]
+include = ["src"]
+extraPaths = ["src"]
+pythonVersion = "3.11"
+reportMissingImports = true
diff --git a/src/atm/main.py b/src/atm/main.py
index 297128f..03995d7 100644
--- a/src/atm/main.py
+++ b/src/atm/main.py
@@ -6,9 +6,13 @@ import os
 import sys
 import time
 from pathlib import Path
+from typing import TYPE_CHECKING, cast
 
 from atm.config import Config  # stdlib-only (tomllib); safe at module level
 
+if TYPE_CHECKING:
+    from atm.state_machine import DotColor
+
 # Module-level reference — set lazily by _cmd_dryrun; tests may monkeypatch it.
 dryrun = None
 
@@ -208,7 +212,7 @@ def run_live(cfg, duration_s=None, capture_stub: bool = False) -> None:
             # detection
             res = detector.step(now)
             if res.accepted and res.color:
-                tr = fsm.feed(res.color, now)
+                tr = fsm.feed(cast("DotColor", res.color), now)
                 audit.log({
                     "ts": now, "event": "tick",
                     "color": res.color, "state": tr.next.value, "reason": tr.reason,