diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 0d3df21..94a25b0 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -6,6 +6,7 @@
 # the test matrix across all supported Python versions.
 #
 # Jobs: quality → test (matrix: 3.10–3.14)
+# quality: lint, format-check, typecheck, security, license
 # Secrets required: none
 # ---
 name: CI
@@ -28,7 +29,7 @@ permissions:
 jobs:
 
   # -- quality
-  # Runs all non-test checks from `make ci`: lint, format, security, license.
+  # Runs all non-test checks from `make ci`: lint, format, typecheck, security, license.
   # Executes once on Python 3.13 — these checks are Python-version-independent.
   # The test matrix will not start until this job passes.
   quality:
@@ -53,6 +54,9 @@ jobs:
       - name: Check formatting
         run: make format-check
 
+      - name: Type check
+        run: make typecheck
+
       - name: Security scan
         run: make security
 
diff --git a/AGENTS.md b/AGENTS.md
index 0eda9b3..62e1aff 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -51,6 +51,7 @@ make test              # pytest
 make coverage          # pytest --cov (100% required)
 make lint              # ruff check
 make format            # ruff format
+make typecheck         # mypy static type checking
 make security          # bandit security scan
 make license           # Check GPL headers
 make license-fix       # Add missing headers
@@ -72,7 +73,7 @@ tox -e ci              # All checks
 
 **Note**: `make ci` includes the license header check; `tox -e ci` does not. Run `make ci` locally before pushing.
 
-CI (`ci.yaml`): runs `make ci` then a separate coverage check with `--cov-fail-under=95`.
+CI (`ci.yaml`): runs lint, format-check, typecheck, security, license, then a matrix test run with `--cov-fail-under=95`.
 
 ## Code Standards
 
@@ -99,14 +100,6 @@ CI (`ci.yaml`): runs `make ci` then a separate coverage check with `--cov-fail-u
 
 ## Known Issues
 
-**mypy is broken (~22 errors)**:
-- `logging.py`: Custom `TRACE`/`NONE`/`FATAL` constants assigned to `logging` module (stdlib doesn't declare these attributes)
-- `heuristics.py`: Lambda type inference and `Callable` annotation mismatches
-- `http.py`: `HTTPMethod` import/redefinition conflict (stdlib vs. fallback enum)
-- `platform.py`: Return type annotation uses dynamic `type()` result
-
-**Impact**: Mypy is not run in CI, so this doesn't block development. Runtime behavior is correct. Fix approach: add `# type: ignore[misc]` to custom level assignments in `logging.py`.
-
 **Missing `.pre-commit-config.yaml`**: `pre-commit` is listed as a dev dependency but the config file doesn't exist in the repo.
 
 ## Gotchas
diff --git a/Makefile b/Makefile
index 7b9cec0..d801289 100644
--- a/Makefile
+++ b/Makefile
@@ -53,7 +53,10 @@ build: ## Build distribution packages (wheel + sdist)
 # Quality checks
 # ------------------------------------------------------------------------------
 
-.PHONY: lint format format-check ruff-fix security license license-fix notice-check
+.PHONY: lint format format-check ruff-fix security typecheck license license-fix notice-check
+
+typecheck: ## Run mypy static type checking
+	$(UV) run mypy $(SRC)
 
 lint: ## Lint with ruff
 	$(UV) run ruff check $(SRC) $(TESTS)
@@ -94,7 +97,7 @@ notice-check: ## Verify NOTICE file lists all packages in uv.lock
 
 .PHONY: ci
 
-ci: clean lint format-check security license tox ## Run all checks (required before committing)
+ci: clean lint format-check typecheck security license tox ## Run all checks (required before committing)
 
 # ------------------------------------------------------------------------------
 # Tox (multi-version)
diff --git a/src/ipsdk/gateway.py b/src/ipsdk/gateway.py
index f1eba76..4716585 100644
--- a/src/ipsdk/gateway.py
+++ b/src/ipsdk/gateway.py
@@ -279,10 +279,10 @@ async def authenticate(self) -> None:
 # Define dynamically created classes for runtime and type checking
 if TYPE_CHECKING:
     # For type checkers: provide explicit class definitions
-    class Gateway(AuthMixin, connection.Connection):
+    class Gateway(AuthMixin, connection.Connection):  # type: ignore[misc]
         """Synchronous Gateway client with authentication."""
 
-    class AsyncGateway(AsyncAuthMixin, connection.AsyncConnection):
+    class AsyncGateway(AsyncAuthMixin, connection.AsyncConnection):  # type: ignore[misc]
         """Asynchronous Gateway client with authentication."""
 
 else:
diff --git a/src/ipsdk/heuristics.py b/src/ipsdk/heuristics.py
index 32d59b2..43d403e 100644
--- a/src/ipsdk/heuristics.py
+++ b/src/ipsdk/heuristics.py
@@ -21,6 +21,10 @@
     from re import Pattern
 
 
+def _make_redaction_func(name: str) -> Callable[[str], str]:
+    return lambda _: f"[REDACTED_{name.upper()}]"
+
+
 class Scanner:
     """Scanner for detecting and redacting sensitive data patterns in text.
 
@@ -84,7 +88,8 @@ def __init__(self, custom_patterns: dict[str, str | None] | None = None) -> None
             # Add custom patterns if provided
             if custom_patterns is not None:
                 for name, pattern in custom_patterns.items():
-                    self.add_pattern(name, pattern)
+                    if pattern is not None:
+                        self.add_pattern(name, pattern)
 
             # Mark as initialized
             Scanner._initialized = True
@@ -148,13 +153,10 @@ def _init_default_patterns(self) -> None:
             for name, pattern_str in patterns_to_compile.items():
                 compiled_pattern = re.compile(pattern_str)
                 Scanner._default_patterns[name] = compiled_pattern
-                # Use default argument to capture current value of name
-                # (avoid late-binding closure issue)
-                Scanner._default_redactions[name] = lambda _, n=name: (
-                    f"[REDACTED_{n.upper()}]"
-                )
+                Scanner._default_redactions[name] = _make_redaction_func(name)
 
         # Copy pre-compiled patterns to instance
+        assert Scanner._default_redactions is not None
         self._patterns = Scanner._default_patterns.copy()
         self._redaction_functions = Scanner._default_redactions.copy()
 
@@ -162,14 +164,14 @@ def add_pattern(
         self,
         name: str,
         pattern: str,
-        redaction_func: Callable[[str | None, str]] | None = None,
+        redaction_func: Callable[[str], str] | None = None,
     ) -> None:
         """Add a new sensitive data pattern to scan for.
 
         Args:
             name (str): Name of the pattern for identification.
             pattern (str): Regular expression pattern to match sensitive data.
-            redaction_func (Callable[[str | None, str]]): Custom function
+            redaction_func (Callable[[str], str]): Custom function
                 to redact matches. If None, uses default redaction with
                 pattern name.
 
@@ -239,10 +241,7 @@ def scan_and_redact(self, text: str) -> str:
 
         for pattern_name, pattern in self._patterns.items():
             redaction_func = self._redaction_functions[pattern_name]
-            # Use lambda with default arg to capture current redaction_func
-            result = pattern.sub(
-                lambda match, func=redaction_func: func(match.group(0)), result
-            )
+            result = pattern.sub(lambda match: redaction_func(match.group(0)), result)  # noqa: B023
 
         return result
 
diff --git a/src/ipsdk/http.py b/src/ipsdk/http.py
index d8040a7..3ca4297 100644
--- a/src/ipsdk/http.py
+++ b/src/ipsdk/http.py
@@ -23,12 +23,12 @@
 
 # Import HTTPMethod from standard library (Python 3.11+) or define fallback
 try:
-    from http import HTTPMethod
+    from http import HTTPMethod  # type: ignore[attr-defined]
 except ImportError:
     # Python < 3.11: Define HTTPMethod enum for backward compatibility
     from enum import Enum
 
-    class HTTPMethod(Enum):
+    class HTTPMethod(Enum):  # type: ignore[no-redef]
         """Enumeration of HTTP methods.
 
         Includes all standard HTTP methods defined in RFC specifications.
diff --git a/src/ipsdk/logging.py b/src/ipsdk/logging.py
index 8c0d17f..0bee902 100644
--- a/src/ipsdk/logging.py
+++ b/src/ipsdk/logging.py
@@ -124,26 +124,28 @@ def process_data(data):
 
 logging_message_format = "%(asctime)s: [%(name)s] %(levelname)s: %(message)s"
 
-# Add the FATAL logging level
-logging.FATAL = 90  # type: ignore[misc]
-logging.addLevelName(logging.FATAL, "FATAL")
+# Custom logging level constants
+TRACE = 5
+FATAL = 90
+NONE = 100
 
-logging.NONE = logging.FATAL + 10
-logging.addLevelName(logging.NONE, "NONE")
+# Register custom levels on the stdlib logging module
+logging.FATAL = FATAL  # type: ignore[misc]
+logging.addLevelName(FATAL, "FATAL")
 
-logging.TRACE = 5
-logging.addLevelName(logging.TRACE, "TRACE")
+logging.NONE = NONE  # type: ignore[attr-defined]
+logging.addLevelName(NONE, "NONE")
+
+logging.TRACE = TRACE  # type: ignore[attr-defined]
+logging.addLevelName(TRACE, "TRACE")
 
 # Logging level constants that wrap stdlib logging module constants
 NOTSET = logging.NOTSET
-TRACE = logging.TRACE
 DEBUG = logging.DEBUG
 INFO = logging.INFO
 WARNING = logging.WARNING
 ERROR = logging.ERROR
 CRITICAL = logging.CRITICAL
-FATAL = logging.FATAL
-NONE = logging.NONE
 
 # Set initial log level to NONE (disabled)
 logging.getLogger(metadata.name).setLevel(NONE)
@@ -237,16 +239,16 @@ def process_data(data):
         @wraps(f)
         async def async_wrapper(*args: Any, **kwargs: Any) -> Any:
             start_time = time.perf_counter()
-            log(logging.TRACE, f"→ {func_name}")
+            log(TRACE, f"→ {func_name}")
             try:
                 result = await f(*args, **kwargs)
             except Exception:
                 elapsed_ms = (time.perf_counter() - start_time) * 1000
-                log(logging.TRACE, f"← {func_name} (exception, {elapsed_ms:.2f}ms)")
+                log(TRACE, f"← {func_name} (exception, {elapsed_ms:.2f}ms)")
                 raise
             else:
                 elapsed_ms = (time.perf_counter() - start_time) * 1000
-                log(logging.TRACE, f"← {func_name} ({elapsed_ms:.2f}ms)")
+                log(TRACE, f"← {func_name} ({elapsed_ms:.2f}ms)")
                 return result
 
         return async_wrapper  # type: ignore[return-value]
@@ -254,16 +256,16 @@ async def async_wrapper(*args: Any, **kwargs: Any) -> Any:
     @wraps(f)
     def sync_wrapper(*args: Any, **kwargs: Any) -> Any:
         start_time = time.perf_counter()
-        log(logging.TRACE, f"→ {func_name}")
+        log(TRACE, f"→ {func_name}")
         try:
             result = f(*args, **kwargs)
         except Exception:
             elapsed_ms = (time.perf_counter() - start_time) * 1000
-            log(logging.TRACE, f"← {func_name} (exception, {elapsed_ms:.2f}ms)")
+            log(TRACE, f"← {func_name} (exception, {elapsed_ms:.2f}ms)")
             raise
         else:
             elapsed_ms = (time.perf_counter() - start_time) * 1000
-            log(logging.TRACE, f"← {func_name} ({elapsed_ms:.2f}ms)")
+            log(TRACE, f"← {func_name} ({elapsed_ms:.2f}ms)")
             return result
 
     return sync_wrapper  # type: ignore[return-value]
@@ -307,7 +309,7 @@ def fatal(msg: str) -> None:
     Raises:
         SystemExit: Always raised with exit code 1 after logging the fatal error.
     """
-    log(logging.FATAL, msg)
+    log(FATAL, msg)
     print(f"ERROR: {msg}", file=sys.stderr)
     sys.exit(1)
 
diff --git a/src/ipsdk/platform.py b/src/ipsdk/platform.py
index ff05b14..da0714e 100644
--- a/src/ipsdk/platform.py
+++ b/src/ipsdk/platform.py
@@ -596,10 +596,10 @@ async def authenticate_oauth(self) -> None:
 # Define dynamically created classes for runtime and type checking
 if TYPE_CHECKING:
     # For type checkers: provide explicit class definitions
-    class Platform(AuthMixin, connection.Connection):
+    class Platform(AuthMixin, connection.Connection):  # type: ignore[misc]
         """Synchronous Platform client with authentication."""
 
-    class AsyncPlatform(AsyncAuthMixin, connection.AsyncConnection):
+    class AsyncPlatform(AsyncAuthMixin, connection.AsyncConnection):  # type: ignore[misc]
         """Asynchronous Platform client with authentication."""
 
 else: