diff --git a/agents-api/agents_api/routers/sessions/session.py b/agents-api/agents_api/routers/sessions/session.py
index 93e8ab9b8..51fd41500 100644
--- a/agents-api/agents_api/routers/sessions/session.py
+++ b/agents-api/agents_api/routers/sessions/session.py
@@ -86,7 +86,7 @@ def rm_thoughts(m):
         def rm_user_assistant(m):
             return m.role in ("user", "assistant")
 
-        token_count = reduce(lambda c, e: e.token_count + c, messages, 0)
+        token_count = reduce(lambda c, e: (e.token_count or 0) + c, messages, 0)
 
         if token_count <= summarization_tokens_threshold:
             return messages
diff --git a/agents-api/pyproject.toml b/agents-api/pyproject.toml
index 6c854942a..9acfb217f 100644
--- a/agents-api/pyproject.toml
+++ b/agents-api/pyproject.toml
@@ -46,7 +46,7 @@ build-backend = "poetry.core.masonry.api"
 [tool.poe.tasks]
 format = "black ."
 lint = "ruff agents_api/**/*.py migrations/**/*.py tests/**/*.py --fix --unsafe-fixes"
-typecheck = "pytype -j auto -k agents_api"
+typecheck = "pytype --config pytype.toml"
 check = [
     "format",
     "lint",
diff --git a/agents-api/pytype.toml b/agents-api/pytype.toml
new file mode 100644
index 000000000..1b95217a6
--- /dev/null
+++ b/agents-api/pytype.toml
@@ -0,0 +1,91 @@
+# NOTE: All relative paths are relative to the location of this file.
+
+[tool.pytype]
+
+# Space-separated list of files or directories to exclude.
+exclude = [
+    '**/*_test.py',
+    '**/test_*.py',
+]
+
+# Space-separated list of files or directories to process.
+inputs = [
+    'agents_api',
+]
+
+# Keep going past errors to analyze as many files as possible.
+keep_going = true
+
+# Run N jobs in parallel. When 'auto' is used, this will be equivalent to the
+# number of CPUs on the host system.
+jobs = 'auto'
+
+# All pytype output goes here.
+output = '.pytype'
+
+# Platform (e.g., "linux", "win32") that the target code runs on.
+platform = 'linux'
+
+# Paths to source code directories, separated by ':'.
+pythonpath = '.'
+
+# Python version (major.minor) of the target code.
+python_version = '3.10'
+
+# Bind 'self' in methods with non-transparent decorators. This flag is temporary
+# and will be removed once this behavior is enabled by default.
+bind_decorated_methods = true
+
+# Don't allow None to match bool. This flag is temporary and will be removed
+# once this behavior is enabled by default.
+none_is_not_bool = false
+
+# Enable parameter count checks for overriding methods with renamed arguments.
+# This flag is temporary and will be removed once this behavior is enabled by
+# default.
+overriding_renamed_parameter_count_checks = true
+
+# Variables initialized as None retain their None binding. This flag is
+# temporary and will be removed once this behavior is enabled by default.
+strict_none_binding = true
+
+# Support the third-party fiddle library. This flag is temporary and will be
+# removed once this behavior is enabled by default.
+use_fiddle_overlay = true
+
+# Opt-in: Do not allow Any as a return type.
+no_return_any = false
+
+# Opt-in: Require decoration with @typing.override when overriding a method or
+# nested class attribute of a parent class.
+require_override_decorator = false
+
+# Experimental: Infer precise return types even for invalid function calls.
+precise_return = true
+
+# Experimental: Solve unknown types to label with structural types.
+protocols = false
+
+# Experimental: Only load submodules that are explicitly imported.
+strict_import = true
+
+# Experimental: Enable exhaustive checking of function parameter types.
+strict_parameter_checks = false
+
+# Experimental: Emit errors for comparisons between incompatible primitive
+# types.
+strict_primitive_comparisons = false
+
+# Experimental: Check that variables are defined in all possible code paths.
+strict_undefined_checks = false
+
+# Experimental: FOR TESTING ONLY. Use pytype/rewrite/.
+use_rewrite = false
+
+# Space-separated list of error names to ignore.
+disable = [
+    'pyi-error',
+]
+
+# Don't report errors.
+report_errors = true