refactor: consolidate _parse_retry_after_headers into base class

Merge the three retry-after header parsers (base, OpenAI, Anthropic)
into a single _extract_retry_after_from_headers on LLMProvider that
handles retry-after-ms, case-insensitive lookup, and HTTP date.

Remove the per-provider _parse_retry_after_headers duplicates and
their now-unused email.utils / time imports. Add test for retry-after-ms.

Made-with: Cursor

nanobot/providers/anthropic_provider.py

@@ -3,12 +3,10 @@
 from __future__ import annotations
 
 import asyncio
-import email.utils
 import os
 import re
 import secrets
 import string
-import time
 from collections.abc import Awaitable, Callable
 from typing import Any
 
@@ -54,49 +52,6 @@ class AnthropicProvider(LLMProvider):
         client_kw["max_retries"] = 0
         self._client = AsyncAnthropic(**client_kw)
 
-    @staticmethod
-    def _parse_retry_after_headers(headers: Any) -> float | None:
-        if headers is None:
-            return None
-
-        def _header_value(name: str) -> Any:
-            if hasattr(headers, "get"):
-                value = headers.get(name) or headers.get(name.title())
-                if value is not None:
-                    return value
-            if isinstance(headers, dict):
-                for key, value in headers.items():
-                    if isinstance(key, str) and key.lower() == name.lower():
-                        return value
-            return None
-
-        try:
-            retry_ms = _header_value("retry-after-ms")
-            if retry_ms is not None:
-                value = float(retry_ms) / 1000.0
-                if value > 0:
-                    return value
-        except (TypeError, ValueError):
-            pass
-
-        retry_after = _header_value("retry-after")
-        try:
-            if retry_after is not None:
-                value = float(retry_after)
-                if value > 0:
-                    return value
-        except (TypeError, ValueError):
-            pass
-
-        if retry_after is None:
-            return None
-        retry_date_tuple = email.utils.parsedate_tz(retry_after)
-        if retry_date_tuple is None:
-            return None
-        retry_date = email.utils.mktime_tz(retry_date_tuple)
-        value = float(retry_date - time.time())
-        return value if value > 0 else None
-
     @classmethod
     def _handle_error(cls, e: Exception) -> LLMResponse:
         response = getattr(e, "response", None)
@@ -115,7 +70,7 @@ class AnthropicProvider(LLMProvider):
                     payload = None
         payload_text = payload if isinstance(payload, str) else str(payload) if payload is not None else ""
         msg = f"Error: {payload_text.strip()[:500]}" if payload_text.strip() else f"Error calling LLM: {e}"
-        retry_after = cls._parse_retry_after_headers(headers)
+        retry_after = cls._extract_retry_after_from_headers(headers)
         if retry_after is None:
             retry_after = LLMProvider._extract_retry_after(msg)
 

nanobot/providers/base.py

@@ -524,14 +524,28 @@ class LLMProvider(ABC):
     def _extract_retry_after_from_headers(cls, headers: Any) -> float | None:
         if not headers:
             return None
-        retry_after: Any = None
+
-        if hasattr(headers, "get"):
+        def _header_value(name: str) -> Any:
-            retry_after = headers.get("retry-after") or headers.get("Retry-After")
+            if hasattr(headers, "get"):
-        if retry_after is None and isinstance(headers, dict):
+                value = headers.get(name) or headers.get(name.title())
-            for key, value in headers.items():
+                if value is not None:
-                if isinstance(key, str) and key.lower() == "retry-after":
+                    return value
-                    retry_after = value
+            if isinstance(headers, dict):
-                    break
+                for key, value in headers.items():
+                    if isinstance(key, str) and key.lower() == name.lower():
+                        return value
+            return None
+
+        try:
+            retry_ms = _header_value("retry-after-ms")
+            if retry_ms is not None:
+                value = float(retry_ms) / 1000.0
+                if value > 0:
+                    return value
+        except (TypeError, ValueError):
+            pass
+
+        retry_after = _header_value("retry-after")
         if retry_after is None:
             return None
         retry_after_text = str(retry_after).strip()

nanobot/providers/openai_compat_provider.py

@@ -3,13 +3,11 @@
 from __future__ import annotations
 
 import asyncio
-import email.utils
 import hashlib
 import importlib.util
 import os
 import secrets
 import string
-import time
 import uuid
 from collections.abc import Awaitable, Callable
 from typing import TYPE_CHECKING, Any
@@ -636,38 +634,6 @@ class OpenAICompatProvider(LLMProvider):
             reasoning_content="".join(reasoning_parts) or None,
         )
 
-    @staticmethod
-    def _parse_retry_after_headers(headers: Any) -> float | None:
-        if headers is None:
-            return None
-
-        try:
-            retry_ms = headers.get("retry-after-ms")
-            if retry_ms is not None:
-                value = float(retry_ms) / 1000.0
-                if value > 0:
-                    return value
-        except (TypeError, ValueError):
-            pass
-
-        retry_after = headers.get("retry-after")
-        try:
-            if retry_after is not None:
-                value = float(retry_after)
-                if value > 0:
-                    return value
-        except (TypeError, ValueError):
-            pass
-
-        if retry_after is None:
-            return None
-        retry_date_tuple = email.utils.parsedate_tz(retry_after)
-        if retry_date_tuple is None:
-            return None
-        retry_date = email.utils.mktime_tz(retry_date_tuple)
-        value = float(retry_date - time.time())
-        return value if value > 0 else None
-
     @classmethod
     def _extract_error_metadata(cls, e: Exception) -> dict[str, Any]:
         response = getattr(e, "response", None)
@@ -712,7 +678,7 @@ class OpenAICompatProvider(LLMProvider):
             "error_kind": error_kind,
             "error_type": error_type,
             "error_code": error_code,
-            "error_retry_after_s": cls._parse_retry_after_headers(headers),
+            "error_retry_after_s": cls._extract_retry_after_from_headers(headers),
             "error_should_retry": should_retry,
         }
 

tests/providers/test_provider_retry.py

@@ -254,6 +254,14 @@ def test_extract_retry_after_from_headers_supports_numeric_and_http_date() -> No
     ) == 0.1
 
 
+def test_extract_retry_after_from_headers_supports_retry_after_ms() -> None:
+    assert LLMProvider._extract_retry_after_from_headers({"retry-after-ms": "250"}) == 0.25
+    assert LLMProvider._extract_retry_after_from_headers({"Retry-After-Ms": "1000"}) == 1.0
+    assert LLMProvider._extract_retry_after_from_headers(
+        {"retry-after-ms": "500", "retry-after": "10"},
+    ) == 0.5
+
+
 @pytest.mark.asyncio
 async def test_chat_with_retry_prefers_structured_retry_after_when_present(monkeypatch) -> None:
     provider = ScriptedProvider([