Document cache_control_injection_points on OpenAI GPT-5.6 targets

docs/completion/prompt_caching.md

@@ -268,6 +268,83 @@ print(response.usage)
 </TabItem>
 </Tabs>
 
+### OpenAI explicit breakpoints (GPT-5.6 and newer)
+
+GPT-5.6 and newer also accept [explicit cache breakpoints](https://developers.openai.com/api/docs/guides/prompt-caching#prompt-cache-breakpoints): a `prompt_cache_breakpoint` marker on a content block plus a request-level `prompt_cache_options` that picks the mode (`implicit` keeps OpenAI's automatic breakpoint on the latest message alongside yours, `explicit` uses only yours) and the cache `ttl` (`30m`). LiteLLM passes both through on `/chat/completions`, `/responses` and, for Anthropic-shaped clients, `/v1/messages`. Models that accept the marker carry `supports_prompt_cache_breakpoint: true` in the cost map, and a GPT-5.6 or newer OpenAI model name the map has not flagged yet is treated the same way. To have LiteLLM place the marker for you from the deployment config, see the [auto-inject tutorial](../tutorials/prompt_caching.md#openai-gpt-56-and-newer)
+
+<Tabs>
+<TabItem value="sdk" label="SDK">
+
+```python
+from litellm import completion
+import os
+
+os.environ["OPENAI_API_KEY"] = ""
+
+response = completion(
+    model="openai/gpt-5.6",
+    messages=[
+        {
+            "role": "system",
+            "content": [
+                {
+                    "type": "text",
+                    "text": "You are an AI assistant tasked with analyzing legal documents. "
+                    + "Here is the full text of a complex legal agreement " * 400,
+                    "prompt_cache_breakpoint": {"mode": "explicit"},
+                }
+            ],
+        },
+        {
+            "role": "user",
+            "content": "What are the key terms and conditions?",
+        },
+    ],
+    prompt_cache_options={"mode": "explicit", "ttl": "30m"},
+)
+print(response.usage.prompt_tokens_details)
+```
+
+</TabItem>
+<TabItem value="proxy" label="PROXY">
+
+```python
+from openai import OpenAI
+
+client = OpenAI(
+    api_key="LITELLM_PROXY_KEY",
+    base_url="LITELLM_PROXY_BASE",
+)
+
+response = client.responses.create(
+    model="gpt-5.6",
+    input=[
+        {
+            "type": "message",
+            "role": "developer",
+            "content": [
+                {
+                    "type": "input_text",
+                    "text": "You are an AI assistant tasked with analyzing legal documents. "
+                    + "Here is the full text of a complex legal agreement " * 400,
+                    "prompt_cache_breakpoint": {"mode": "explicit"},
+                }
+            ],
+        },
+        {
+            "type": "message",
+            "role": "user",
+            "content": [{"type": "input_text", "text": "What are the key terms and conditions?"}],
+        },
+    ],
+    extra_body={"prompt_cache_options": {"mode": "explicit", "ttl": "30m"}},
+)
+print(response.usage.input_tokens_details)
+```
+
+</TabItem>
+</Tabs>
+
 ### Anthropic Example 
 
 Anthropic charges for cache writes. 

docs/tutorials/prompt_caching.md

@@ -20,8 +20,11 @@ Supported Providers (`cache_control` marker):
 - MiniMax (`minimax/`)
 - Z.ai / GLM (`zai/`)
 
+Supported Providers (`prompt_cache_breakpoint` marker):
+- OpenAI GPT-5.6 and newer (`openai/`), see [OpenAI GPT-5.6 and newer](#openai-gpt-56-and-newer)
+
 Provider Managed (automatic, no marker needed):
-- OpenAI (`openai/`)
+- OpenAI, models before GPT-5.6 (`openai/`)
 - DeepSeek (`deepseek/`)
 - xAI (`xai/`)
 
@@ -108,6 +111,44 @@ LiteLLM will then automatically add a `cache_control` directive to the specified
 }
 ```
 
+### OpenAI GPT-5.6 and newer
+
+The same `cache_control_injection_points` work when the deployment resolves to an OpenAI model that supports [explicit prompt cache breakpoints](https://developers.openai.com/api/docs/guides/prompt-caching#prompt-cache-breakpoints), which the cost map marks with `supports_prompt_cache_breakpoint` (GPT-5.6 and newer on `openai/`). LiteLLM looks at the resolved deployment, not at the shape of the incoming request, so one config pattern covers a mixed Anthropic and OpenAI fleet and Anthropic-shaped clients on `/v1/messages` get the OpenAI markers too
+
+| Anthropic target | OpenAI GPT-5.6+ target |
+|---|---|
+| `"cache_control": {"type": "ephemeral"}` on the targeted block | `"prompt_cache_breakpoint": {"mode": "explicit"}` on the targeted block |
+| nothing at the request level | `"prompt_cache_options": {"mode": "explicit"}` at the request root |
+| `control.ttl` picks the 5m or 1h cache | `control` is ignored; set `prompt_cache_options` yourself for `ttl` |
+
+The request-level `prompt_cache_options` LiteLLM adds switches OpenAI to explicit mode, so the configured checkpoints are the whole caching strategy, exactly as they are on Anthropic. A `prompt_cache_options` already on the request wins and is never overwritten, which is how you change the mode or ask for the 30 minute cache per deployment:
+
+```yaml showLineNumbers title="config.yaml"
+model_list:
+  - model_name: gpt-5.6
+    litellm_params:
+      model: openai/gpt-5.6
+      api_key: os.environ/OPENAI_API_KEY
+      cache_control_injection_points:
+        - location: message
+          role: system
+      prompt_cache_options:
+        mode: implicit
+        ttl: 30m
+```
+
+With `mode: implicit` OpenAI keeps its automatic checkpoint on the latest user or tool message alongside the explicit one LiteLLM placed, which suits long multi-turn sessions; with the default `explicit` only the configured checkpoints write to the cache, which suits many single-turn requests that share one long system prompt. Either way OpenAI serves reads from the longest cached prefix it can match
+
+What to know about the OpenAI mapping:
+
+- **Block-level only.** OpenAI accepts the marker on text, image and file blocks. A string system prompt or message is wrapped into a one-block list before the marker is placed. Assistant blocks and tool results cannot carry a breakpoint, so an injection point that lands there is skipped
+- **`/v1/messages` system prompt.** OpenAI does not accept a breakpoint on the top-level `instructions` field, so when the Anthropic `system` carries a checkpoint LiteLLM sends it as a leading `developer` message instead. OpenAI treats both shapes as the same cache prefix, so switching does not cold-start the cache
+- **Stands down like Anthropic.** A request that already carries its own `cache_control` or `prompt_cache_breakpoint` markers keeps them; configured points are not added. Claude Code sets its own `cache_control`, so a Claude Code session on a GPT-5.6 deployment stays on OpenAI's implicit caching
+- **Respects the 4 breakpoint limit**, counting client-supplied markers toward it
+- **Only for requests that go to OpenAI itself.** The mapping fires for a GPT-5.6 or newer OpenAI model (the cost map's `supports_prompt_cache_breakpoint` flag when the entry carries one, otherwise the GPT version in the model name) when the deployment talks to `api.openai.com` (or a regional `*.api.openai.com` host), meaning no `api_base` (or `base_url`) or one on those hosts. A deployment with a custom `api_base`, such as another LiteLLM proxy or gateway in front of OpenAI, keeps today's behavior unless its `litellm_params` also set `prompt_cache_options`, which opts it in. `litellm_proxy/` deployments and Azure OpenAI deployments are not covered yet
+- **`/v1/responses`.** The marker lands on `input_text` blocks of the targeted message, and a string message is wrapped into a one-block list first. OpenAI does not accept a marker on the top-level `instructions` field, so a system prompt sent there stays on implicit caching; send it as a `developer` or `system` message to get the checkpoint. A `prompt_cache_options` the client sends is forwarded as is
+- **Cost reporting is unchanged.** OpenAI's `cached_tokens` and `cache_write_tokens` already come back as `cache_read_input_tokens` and `cache_creation_input_tokens` on `/v1/messages` and as `prompt_tokens_details` on `/chat/completions`
+
 ## LiteLLM Python SDK Usage
 
 Use the `cache_control_injection_points` parameter in your completion calls to automatically inject caching directives.
@@ -283,7 +324,16 @@ model_list:
       cache_control_injection_points:
         - location: message
           role: system
+  - model_name: gpt-5.6
+    litellm_params:
+      model: openai/gpt-5.6
+      api_key: os.environ/OPENAI_API_KEY
+      cache_control_injection_points:
+        - location: message
+          role: system
 ```
+
+The second entry resolves to an OpenAI GPT-5.6 model, so the same injection point becomes a `prompt_cache_breakpoint` marker plus `prompt_cache_options` on the outbound request, as described in [OpenAI GPT-5.6 and newer](#openai-gpt-56-and-newer)
 </TabItem>
 
 <TabItem value="UI" label="LiteLLM UI">
@@ -358,6 +408,37 @@ LiteLLM auto-injects the caching directive into the system message based on our
 
 When the model provider processes this request, it will recognize the caching directive and only process the system message once, caching it for subsequent requests.
 
+### 3. The same request on an OpenAI GPT-5.6 deployment
+
+With the deployment pointing at `openai/gpt-5.6` instead, the same configuration produces OpenAI's explicit breakpoint on the block and explicit mode at the request root:
+
+```json showLineNumbers title="modified_request_openai.json"
+{
+    "prompt_cache_options": {"mode": "explicit"},
+    "messages": [
+        {
+            "role": "system",
+            "content": [
+                {
+                    "type": "text",
+                    "text": "You are a helpful assistant. This is a set of very long instructions that you will follow. Here is a legal document that you will use to answer the user's question.",
+                    "prompt_cache_breakpoint": {"mode": "explicit"}
+                }
+            ]
+        },
+        {
+            "role": "user",
+            "content": [
+                {
+                    "type": "text",
+                    "text": "What is the main topic of this legal document?"
+                }
+            ]
+        }
+    ]
+}
+```
+
 ## Related Documentation
 
 - [Manual Prompt Caching](../completion/prompt_caching.md) - Learn how to manually add `cache_control` directives to your messages