feat(anthropic): allow enabling prompt caching via environment variables

Both enable_anthropic_prompt_caching and anthropic_prompt_caching_ttl are
now read from LITELLM_ENABLE_ANTHROPIC_PROMPT_CACHING and
LITELLM_ANTHROPIC_PROMPT_CACHING_TTL at import, so the flag can be turned on
without a config file. An unsupported ttl falls back to the provider default
rather than reaching the provider verbatim

litellm/__init__.py

@@ -315,8 +315,11 @@ disable_token_counter: bool = False
 disable_add_transform_inline_image_block: bool = False
 disable_add_user_agent_to_request_tags: bool = False
 disable_anthropic_gemini_context_caching_transform: bool = False
-enable_anthropic_prompt_caching: bool = False
-anthropic_prompt_caching_ttl: Optional[Literal["5m", "1h"]] = None
+enable_anthropic_prompt_caching: bool = os.getenv("LITELLM_ENABLE_ANTHROPIC_PROMPT_CACHING", "false").lower() == "true"
+_anthropic_prompt_caching_ttl_env: Optional[str] = os.getenv("LITELLM_ANTHROPIC_PROMPT_CACHING_TTL")
+anthropic_prompt_caching_ttl: Optional[Literal["5m", "1h"]] = (
+    "1h" if _anthropic_prompt_caching_ttl_env == "1h" else "5m" if _anthropic_prompt_caching_ttl_env == "5m" else None
+)
 disable_vertex_batch_output_transformation: bool = False
 extra_spend_tag_headers: Optional[List[str]] = None
 in_memory_llm_clients_cache: "LLMClientCache"

tests/test_litellm/integrations/test_anthropic_cache_control_hook.py

@@ -2,7 +2,9 @@ import copy
 import datetime
 import json
 import os
+import subprocess
 import sys
+import textwrap
 import unittest
 from typing import List, Optional, Tuple
 from unittest.mock import ANY, MagicMock, Mock, patch
@@ -1669,3 +1671,53 @@ class TestEnableAnthropicPromptCaching:
 
         assert result_sys == "sys"
         assert result_msgs == messages
+
+
+class TestAnthropicPromptCachingEnvVars:
+    """Both settings are read from the environment at import, so an admin can enable
+    auto-caching without a config file. Each case re-imports litellm in a subprocess
+    so the env is read fresh without contaminating this process's module graph.
+    """
+
+    @staticmethod
+    def _import_litellm_with_env(env_override: dict) -> Tuple[bool, Optional[str]]:
+        env = os.environ.copy()
+        env.pop("LITELLM_ENABLE_ANTHROPIC_PROMPT_CACHING", None)
+        env.pop("LITELLM_ANTHROPIC_PROMPT_CACHING_TTL", None)
+        env.update(env_override)
+        script = textwrap.dedent(
+            """
+            import json, litellm
+            print(json.dumps([litellm.enable_anthropic_prompt_caching, litellm.anthropic_prompt_caching_ttl]))
+            """
+        )
+        result = subprocess.run(
+            [sys.executable, "-c", script], capture_output=True, text=True, env=env, timeout=300
+        )
+        assert result.returncode == 0, result.stderr
+        enabled, ttl = json.loads(result.stdout.strip().splitlines()[-1])
+        return enabled, ttl
+
+    def test_unset_env_leaves_auto_caching_off(self):
+        assert self._import_litellm_with_env({}) == (False, None)
+
+    @pytest.mark.parametrize("value", ["true", "True", "TRUE"])
+    def test_env_enables_auto_caching_case_insensitively(self, value):
+        enabled, _ = self._import_litellm_with_env({"LITELLM_ENABLE_ANTHROPIC_PROMPT_CACHING": value})
+        assert enabled is True
+
+    @pytest.mark.parametrize("value", ["false", "0", "yes", ""])
+    def test_env_only_enables_on_true(self, value):
+        enabled, _ = self._import_litellm_with_env({"LITELLM_ENABLE_ANTHROPIC_PROMPT_CACHING": value})
+        assert enabled is False
+
+    @pytest.mark.parametrize("value", ["5m", "1h"])
+    def test_ttl_env_is_applied(self, value):
+        _, ttl = self._import_litellm_with_env({"LITELLM_ANTHROPIC_PROMPT_CACHING_TTL": value})
+        assert ttl == value
+
+    @pytest.mark.parametrize("value", ["10m", "1H", "3600", "ephemeral"])
+    def test_unsupported_ttl_env_falls_back_to_provider_default(self, value):
+        """An unparseable TTL must fall back to Anthropic's 5m default, never reach the provider verbatim."""
+        _, ttl = self._import_litellm_with_env({"LITELLM_ANTHROPIC_PROMPT_CACHING_TTL": value})
+        assert ttl is None