diff --git a/run_agent.py b/run_agent.py
index d6af4a1b579e8..e7ae9b77f89fa 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -66,6 +66,14 @@
     logger.info("No .env file found. Using system environment variables.")
 
 
+def _is_local_validation_error(error: BaseException) -> bool:
+    """Return True for local request-shaping bugs, not transport failures."""
+    return (
+        isinstance(error, (ValueError, TypeError))
+        and not isinstance(error, (UnicodeEncodeError, json.JSONDecodeError, ssl.SSLError))
+    )
+
+
 # Import our tool system
 from model_tools import (
     get_tool_definitions,
@@ -11344,27 +11352,7 @@ def _stop_spinner():
                     # already accounts for 413, 429, 529 (transient), context
                     # overflow, and generic-400 heuristics.  Local validation
                     # errors (ValueError, TypeError) are programming bugs.
-                    # Exclude UnicodeEncodeError — it's a ValueError subclass
-                    # but is handled separately by the surrogate sanitization
-                    # path above.  Exclude json.JSONDecodeError — also a
-                    # ValueError subclass, but it indicates a transient
-                    # provider/network failure (malformed response body,
-                    # truncated stream, routing layer corruption), not a
-                    # local programming bug, and should be retried (#14782).
-                    is_local_validation_error = (
-                        isinstance(api_error, (ValueError, TypeError))
-                        and not isinstance(
-                            api_error, (UnicodeEncodeError, json.JSONDecodeError)
-                        )
-                        # ssl.SSLError (and its subclass SSLCertVerificationError)
-                        # inherits from OSError *and* ValueError via Python MRO,
-                        # so the isinstance(ValueError) check above would
-                        # misclassify a TLS transport failure as a local
-                        # programming bug and abort without retrying.  Exclude
-                        # ssl.SSLError explicitly so the error classifier's
-                        # retryable=True mapping takes effect instead.
-                        and not isinstance(api_error, ssl.SSLError)
-                    )
+                    is_local_validation_error = _is_local_validation_error(api_error)
                     is_client_error = (
                         is_local_validation_error
                         or (
diff --git a/tests/run_agent/test_run_agent.py b/tests/run_agent/test_run_agent.py
index f58ebbf14c714..166e3a2563904 100644
--- a/tests/run_agent/test_run_agent.py
+++ b/tests/run_agent/test_run_agent.py
@@ -9,6 +9,7 @@
 import json
 import logging
 import re
+import ssl
 import uuid
 from logging.handlers import RotatingFileHandler
 from pathlib import Path
@@ -52,6 +53,31 @@ def test_is_destructive_command_treats_install_as_mutating():
     assert run_agent._is_destructive_command("install template.env .env") is True
 
 
+def test_ssl_cert_verification_error_is_not_local_validation():
+    """TLS certificate failures inherit ValueError but should remain retryable transport errors."""
+    error = ssl.SSLCertVerificationError("certificate verify failed")
+
+    assert isinstance(error, (ValueError, OSError))
+    assert run_agent._is_local_validation_error(error) is False
+
+
+@pytest.mark.parametrize("error", [ValueError("bad request"), TypeError("bad type")])
+def test_request_shaping_errors_are_local_validation(error):
+    assert run_agent._is_local_validation_error(error) is True
+
+
+def test_unicode_encode_error_is_not_local_validation():
+    error = UnicodeEncodeError("ascii", "é", 0, 1, "ordinal not in range")
+
+    assert run_agent._is_local_validation_error(error) is False
+
+
+def test_json_decode_error_is_not_local_validation():
+    error = json.JSONDecodeError("bad response", "", 0)
+
+    assert run_agent._is_local_validation_error(error) is False
+
+
 @pytest.fixture()
 def agent():
     """Minimal AIAgent with mocked OpenAI client and tool loading."""