diff --git a/solstone/convey/utils.py b/solstone/convey/utils.py
index c2fb13260..fe20de74f 100644
--- a/solstone/convey/utils.py
+++ b/solstone/convey/utils.py
@@ -6,7 +6,6 @@ import logging
 import math
 import re
 import secrets
-import sys
 import time
 from datetime import datetime
 from pathlib import Path
@@ -18,7 +17,6 @@ from solstone.convey.reasons import Reason
 
 DATE_RE = re.compile(r"\d{8}")
 _REQUEST_ID_ALPHABET = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
-_LEGACY_ERROR_RESPONSE_SEEN: set[str] = set()
 _LOGGER = logging.getLogger("solstone.convey.utils")
 
 
@@ -249,20 +247,8 @@ def save_json(
         return False
 
 
-def _log_legacy_error_response_string_form() -> None:
-    frame = sys._getframe(2)
-    key = f"{frame.f_code.co_filename}:{frame.f_lineno}"
-    if key in _LEGACY_ERROR_RESPONSE_SEEN:
-        return
-    _LEGACY_ERROR_RESPONSE_SEEN.add(key)
-    _LOGGER.warning(
-        "legacy error_response string form at %s — migrate to Reason",
-        key,
-    )
-
-
 def error_response(
-    reason: Reason | str,
+    reason: Reason,
     status: int | None = None,
     *,
     detail: str | None = None,
@@ -272,29 +258,24 @@ def error_response(
     Provides consistent error response format across all API endpoints.
 
     Args:
-        reason: Reason constant, or legacy string message during migration
+        reason: Reason constant
         status: Optional HTTP status override
         detail: Optional implementation-specific context
 
     Returns:
         Tuple of (jsonify response, status_code) ready for Flask return
     """
-    if isinstance(reason, Reason):
-        response_status = status if status is not None else reason.status
-        return (
-            jsonify(
-                {
-                    "error": reason.message,
-                    "reason_code": reason.code,
-                    "detail": detail or "",
-                }
-            ),
-            response_status,
-        )
-
-    _log_legacy_error_response_string_form()
-    response_status = status if status is not None else 400
-    return jsonify({"error": reason}), response_status
+    response_status = status if status is not None else reason.status
+    return (
+        jsonify(
+            {
+                "error": reason.message,
+                "reason_code": reason.code,
+                "detail": detail or "",
+            }
+        ),
+        response_status,
+    )
 
 
 def error_response_with_reason(
diff --git a/tests/test_convey_reasons.py b/tests/test_convey_reasons.py
index 59d70963d..31995b67f 100644
--- a/tests/test_convey_reasons.py
+++ b/tests/test_convey_reasons.py
@@ -1,13 +1,10 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 # Copyright (c) 2026 sol pbc
 
-import logging
-
 from flask import Flask
 
 from solstone.convey.reasons import AUTH_REQUIRED, Reason
 from solstone.convey.utils import (
-    _LEGACY_ERROR_RESPONSE_SEEN,
     error_response,
     error_response_with_reason,
 )
@@ -18,11 +15,6 @@ def _app_context():
     return app.app_context()
 
 
-def _legacy_error_response_from_same_site():
-    with _app_context():
-        return [error_response("legacy", 400) for _ in range(2)]
-
-
 def test_reason_status_defaults_to_400():
     reason = Reason("test_reason", "Test message.")
 
@@ -61,24 +53,6 @@ def test_error_response_reason_includes_detail():
     assert response.get_json()["detail"] == "some detail"
 
 
-def test_error_response_legacy_shape_and_logs_once(caplog):
-    _LEGACY_ERROR_RESPONSE_SEEN.clear()
-    caplog.set_level(logging.WARNING, logger="solstone.convey.utils")
-
-    (first_response, first_status), (second_response, second_status) = (
-        _legacy_error_response_from_same_site()
-    )
-
-    assert first_status == 400
-    assert second_status == 400
-    assert first_response.get_json() == {"error": "legacy"}
-    assert second_response.get_json() == {"error": "legacy"}
-    assert "reason_code" not in first_response.get_json()
-    assert "detail" not in first_response.get_json()
-    assert len(caplog.records) == 1
-    assert "legacy error_response string form at" in caplog.records[0].message
-
-
 def test_error_response_with_reason_emits_legacy_reason_key():
     with _app_context():
         response, status = error_response_with_reason(AUTH_REQUIRED, detail="x")