1.1 changelog

pipeline/preprocessors/link_map.py

@@ -333,6 +333,7 @@ class LinkMap(TypedDict):
             "BaseMessage": "classes/_langchain_core.messages.BaseMessage.html",
             "HumanMessage": "classes/_langchain_core.messages.HumanMessage.html",
             "SystemMessage": "classes/_langchain_core.messages.SystemMessage.html",
+            "SystemMessage.concat": "classes/_langchain_core.messages.SystemMessage.html#concat",
             "ToolMessage": "classes/_langchain_core.messages.ToolMessage.html",
             "ToolCallChunk": "classes/_langchain_core.messages.ToolCallChunk.html",
             "BaseChatModel": "classes/_langchain_core.language_models_chat_models.BaseChatModel.html",
@@ -350,8 +351,8 @@ class LinkMap(TypedDict):
             "Document": "classes/_langchain_core.documents.Document.html",
             "Embeddings": "classes/_langchain_core.embeddings.Embeddings.html",
             "initChatModel": "functions/langchain.chat_models_universal.initChatModel.html",
-            "RunnableConfig": "interfaces/_langchain_core.runnables.RunnableConfig.html",
             "Runnable": "classes/_langchain_core.runnables.Runnable.html",
+            "RunnableConfig": "interfaces/_langchain_core.runnables.RunnableConfig.html",
             "Retrievers": "interfaces/_langchain_core.retrievers.BaseRetriever.html",
             "VectorStore": "classes/_langchain_core.vectorstores.VectorStore.html",
             "VectorStore.maxMarginalRelevanceSearch": "classes/_langchain_core.vectorstores.VectorStore.html#maxMarginalRelevanceSearch",
@@ -376,7 +377,9 @@ class LinkMap(TypedDict):
             "BaseCheckpointSaver": "classes/_langchain_langgraph-checkpoint.BaseCheckpointSaver.html",
             "BaseStore": "classes/_langchain_langgraph-checkpoint.BaseStore.html",
             "BaseStore.put": "classes/_langchain_langgraph-checkpoint.BaseStore.html#put",
+            "InMemorySaver": "classes/_langchain_langgraph-checkpoint.MemorySaver.html",
             "MemorySaver": "classes/_langchain_langgraph-checkpoint.MemorySaver.html",
+            "AsyncPostgresSaver": "classes/_langchain_langgraph-checkpoint-postgres.AsyncPostgresSaver.html",
             "PostgresSaver": "classes/_langchain_langgraph-checkpoint-postgres.index.PostgresSaver.html",
             "protocol": "interfaces/_langchain_langgraph-checkpoint.SerializerProtocol.html",
             "SerializerProtocol": "interfaces/_langchain_langgraph-checkpoint.SerializerProtocol.html",
@@ -390,24 +393,22 @@ class LinkMap(TypedDict):
             "addEdge": "classes/_langchain_langgraph.index.StateGraph.html#addEdge",
             "add_node": "classes/_langchain_langgraph.index.StateGraph.html#addNode",
             "add_messages": "functions/_langchain_langgraph.index.messagesStateReducer.html",
+            "LastValue": "classes/_langchain_langgraph.channels.LastValue.html",
+            "Topic": "classes/_langchain_langgraph.channels.Topic.html",
             "BinaryOperatorAggregate": "classes/_langchain_langgraph.index.BinaryOperatorAggregate.html",
             "Command": "classes/_langchain_langgraph.index.Command.html",
             "CompiledStateGraph": "classes/_langchain_langgraph.index.CompiledStateGraph.html",
-            "create_agent": "functions/langchain.index.createAgent.html",
-            "create_react_agent": "functions/_langchain_langgraph.prebuilt.createReactAgent.html",
-            "create_supervisor": "functions/_langchain_langgraph-supervisor.createSupervisor.html",
+            "createAgent": "functions/langchain.index.createAgent.html",
+            "createReactAgent": "functions/_langchain_langgraph.prebuilt.createReactAgent.html",
+            "createSupervisor": "functions/_langchain_langgraph-supervisor.createSupervisor.html",
             "entrypoint": "functions/_langchain_langgraph.index.entrypoint.html",
             "entrypoint.final": "functions/_langchain_langgraph.index.entrypoint.html#final",
             "get_state_history": "classes/_langchain_langgraph.pregel.Pregel.html#getStateHistory",
             "getStateHistory": "classes/_langchain_langgraph.pregel.Pregel.html#getStateHistory",
             "HumanInterrupt": "interfaces/_langchain_langgraph.prebuilt.HumanInterrupt.html",
             "interrupt": "functions/_langchain_langgraph.index.interrupt.html",
-            "InMemorySaver": "classes/_langchain_langgraph-checkpoint.MemorySaver.html",
-            "AsyncPostgresSaver": "classes/_langchain_langgraph-checkpoint-postgres.index.PostgresSaver.html",
             "CompiledStateGraph.invoke": "classes/_langchain_langgraph.index.CompiledStateGraph.html#invoke",
             "langgraph.json": "cloud/reference/cli/#configuration-file",
-            "LastValue": "classes/_langchain_langgraph.channels.LastValue.html",
-            "Topic": "classes/_langchain_langgraph.channels.Topic.html",
             "messagesStateReducer": "functions/_langchain_langgraph.index.messagesStateReducer.html",
             "Pregel": "classes/_langchain_langgraph.pregel.Pregel.html",
             "Pregel.stream": "classes/_langchain_langgraph.pregel.Pregel.html#stream",
@@ -435,6 +436,7 @@ class LinkMap(TypedDict):
             "ContextEdit": "interfaces/langchain.index.ContextEdit.html",
             "toolRetryMiddleware": "functions/langchain.index.toolRetryMiddleware.html",
             "modelRetryMiddleware": "functions/langchain.index.modelRetryMiddleware.html",
+            "systemPrompt": "types/langchain.index.CreateAgentParams.html#systemprompt",
         },
     },
 ]

src/docs.json

@@ -146,9 +146,10 @@
                   "pages": [
                     "oss/python/langchain/overview",
                     {
-                      "group": "LangChain v1.0",
+                      "group": "Releases",
                       "pages": [
                         "oss/python/releases/langchain-v1",
+                        "oss/python/releases/changelog",
                         "oss/python/migrate/langchain-v1"
                       ]
                     },
@@ -417,6 +418,7 @@
                         {
                           "group": "Releases",
                           "pages": [
+                            "oss/python/releases/changelog",
                             "oss/python/releases/langchain-v1"
                           ]
                         },
@@ -487,9 +489,10 @@
                   "pages": [
                     "oss/javascript/langchain/overview",
                     {
-                      "group": "LangChain v1.0",
+                      "group": "Releases",
                       "pages": [
                         "oss/javascript/releases/langchain-v1",
+                        "oss/javascript/releases/changelog",
                         "oss/javascript/migrate/langchain-v1"
                       ]
                     },
@@ -792,6 +795,7 @@
                         {
                           "group": "Releases",
                           "pages": [
+                            "oss/javascript/releases/changelog",
                             "oss/javascript/releases/langchain-v1"
                           ]
                         },

src/langsmith/rate-limiting.mdx

@@ -30,7 +30,7 @@ def evaluator(inputs: dict, outputs: dict, reference_outputs: dict) -> dict:
     ...
 ```
 
-See the [`langchain`](oss/langchain/models#rate-limiting) documentation for more on how to configure rate limiters.
+See the [`langchain`](/oss/langchain/models#rate-limiting) documentation for more on how to configure rate limiters.
 
 ## Retrying with exponential backoff
 

src/oss/javascript/releases/changelog.mdx

@@ -0,0 +1,29 @@
+---
+title: Changelog
+sidebarTitle: Changelog
+rss: true
+---
+
+A chronological log of updates and improvements to LangChain JavaScript.
+
+<Update label="v1.1" description="November 25, 2025">
+
+* [Model profiles](/oss/langchain/models#model-profiles): Chat models now expose supported features and capabilities through a `.profile` getter. These data are derived from [models.dev](https://github.com/sst/models.dev), an open source project providing model capability data.
+* [Model retry middleware](/oss/langchain/middleware/built-in#model-retry): New middleware for automatically retrying failed model calls with configurable exponential backoff, improving agent reliability.
+* [Content moderation middleware](/oss/langchain/middleware/built-in#content-moderation): OpenAI content moderation middleware for detecting and handling unsafe content in agent interactions. Supports checking user input, model output, and tool results.
+* [Summarization middleware](/oss/langchain/middleware/built-in#summarization): Updated to support flexible trigger points using model profiles for context-aware summarization.
+* [Structured output](/oss/langchain/structured-output): `ProviderStrategy` support (native structured output) can now be inferred from model profiles.
+* [`SystemMessage` for `createAgent`](/oss/langchain/middleware/custom#working-with-system-messages): Support for passing `SystemMessage` instances directly to `createAgent`'s `systemPrompt` parameter and a new `concat` method for extending system messages. Enables advanced features like cache control and structured content blocks.
+* [Dynamic system prompt middleware](/oss/langchain/agents#dynamic-system-prompt): Return values from `dynamicSystemPromptMiddleware` are now purely additive. When returning a @[`SystemMessage`] or `string`, they are merged with existing system messages rather than replacing them, making it easier to compose multiple middleware that modify the prompt.
+* **Compatibility improvements:** Fixed error handling for Zod v4 validation errors in structured output and tool schemas, ensuring detailed error messages are properly displayed.
+
+</Update>
+
+## Resources
+
+- [V1 Migration guide](/oss/migrate/langchain-v1) - How to migrate to LangChain v1
+- [V1 Release notes](/oss/releases/langchain-v1) - Detailed release notes
+- [Release policy](/oss/release-policy) - Detailed release policies
+- [Versioning](/oss/versioning) - Understanding version numbers
+- [Report issues on GitHub](https://github.com/langchain-ai/langchainjs/issues)
+

src/oss/javascript/releases/langchain-v1.mdx

@@ -1,6 +1,6 @@
 ---
 title: What's new in v1
-sidebarTitle: Release notes
+sidebarTitle: V1 Release Notes
 ---
 
 **LangChain v1 is a focused, production-ready foundation for building agents.** We've streamlined the framework around three core improvements:
@@ -310,7 +310,7 @@ Please report any issues discovered with 1.0 on [GitHub](https://github.com/lang
     <Card title="LangChain 1.0" icon="rocket" href="https://blog.langchain.com/langchain-langchain-1-0-alpha-releases/">
         Read the announcement
     </Card>
-    <Card title="Middleware Guide" icon="puzzle-piece" href="https://blog.langchain.com/agent-middleware/">
+    <Card title="Middleware guide" icon="puzzle-piece" href="https://blog.langchain.com/agent-middleware/">
         Deep dive into middleware
     </Card>
     <Card title="Agents Documentation" icon="book" href="/oss/langchain/agents" arrow>

src/oss/langchain/middleware/custom.mdx

@@ -919,6 +919,201 @@ const agent = createAgent({
 
 :::
 
+### Working with system messages
+
+:::python
+
+Modify system messages in middleware using the `system_message` field on `ModelRequest`. The `system_message` field contains a @[`SystemMessage`] object (even if the agent was created with a string `system_prompt`).
+
+**Example: Adding context to system message**
+
+<Tabs>
+<Tab title="Decorator">
+
+```python
+from langchain.agents.middleware import wrap_model_call, ModelRequest, ModelResponse
+from langchain.messages import SystemMessage
+from typing import Callable
+
+
+@wrap_model_call
+def add_context(
+    request: ModelRequest,
+    handler: Callable[[ModelRequest], ModelResponse],
+) -> ModelResponse:
+    # Always work with content blocks
+    new_content = list(request.system_message.content_blocks) + [
+        {"type": "text", "text": "Additional context."}
+    ]
+    new_system_message = SystemMessage(content=new_content)
+    return handler(request.override(system_message=new_system_message))
+```
+
+</Tab>
+
+<Tab title="Class">
+
+```python
+from langchain.agents.middleware import AgentMiddleware, ModelRequest, ModelResponse
+from langchain.messages import SystemMessage
+from typing import Callable
+
+
+class ContextMiddleware(AgentMiddleware):
+    def wrap_model_call(
+        self,
+        request: ModelRequest,
+        handler: Callable[[ModelRequest], ModelResponse],
+    ) -> ModelResponse:
+        # Always work with content blocks
+        new_content = list(request.system_message.content_blocks) + [
+            {"type": "text", "text": "Additional context."}
+        ]
+        new_system_message = SystemMessage(content=new_content)
+        return handler(request.override(system_message=new_system_message))
+```
+
+</Tab>
+</Tabs>
+
+**Example: Working with cache control (Anthropic)**
+
+When working with Anthropic models, you can use structured content blocks with cache control directives to cache large system prompts:
+
+<Tabs>
+<Tab title="Decorator">
+
+```python
+from langchain.agents.middleware import wrap_model_call, ModelRequest, ModelResponse
+from langchain.messages import SystemMessage
+from typing import Callable
+
+
+@wrap_model_call
+def add_cached_context(
+    request: ModelRequest,
+    handler: Callable[[ModelRequest], ModelResponse],
+) -> ModelResponse:
+    # Always work with content blocks
+    new_content = list(request.system_message.content_blocks) + [
+        {
+            "type": "text",
+            "text": "Here is a large document to analyze:\n\n<document>...</document>",
+            # content up until this point is cached
+            "cache_control": {"type": "ephemeral"}
+        }
+    ]
+
+    new_system_message = SystemMessage(content=new_content)
+    return handler(request.override(system_message=new_system_message))
+```
+
+</Tab>
+
+<Tab title="Class">
+
+```python
+from langchain.agents.middleware import AgentMiddleware, ModelRequest, ModelResponse
+from langchain.messages import SystemMessage
+from typing import Callable
+
+
+class CachedContextMiddleware(AgentMiddleware):
+    def wrap_model_call(
+        self,
+        request: ModelRequest,
+        handler: Callable[[ModelRequest], ModelResponse],
+    ) -> ModelResponse:
+        # Always work with content blocks
+        new_content = list(request.system_message.content_blocks) + [
+            {
+                "type": "text",
+                "text": "Here is a large document to analyze:\n\n<document>...</document>",
+                "cache_control": {"type": "ephemeral"}  # This content will be cached
+            }
+        ]
+
+        new_system_message = SystemMessage(content=new_content)
+        return handler(request.override(system_message=new_system_message))
+```
+
+</Tab>
+</Tabs>
+
+**Notes:**
+- `ModelRequest.system_message` is always a @[`SystemMessage`] object, even if the agent was created with `system_prompt="string"`
+- Use `SystemMessage.content_blocks` to access content as a list of blocks, regardless of whether the original content was a string or list
+- When modifying system messages, use `content_blocks` and append new blocks to preserve existing structure
+- You can pass @[`SystemMessage`] objects directly to `create_agent`'s `system_prompt` parameter for advanced use cases like cache control
+
+:::
+
+:::js
+Modify system messages in middleware using the `systemMessage` field in `ModelRequest`. It contains a @[`SystemMessage`] object (even if the agent was created with a string @[`systemPrompt`]).
+
+**Example: Chaining middleware** - Different middleware can use different approaches:
+
+```typescript
+import { createMiddleware, SystemMessage, createAgent } from "langchain";
+
+// Middleware 1: Uses systemMessage with simple concatenation
+const myMiddleware = createMiddleware({
+  name: "MyMiddleware",
+  wrapModelCall: async (request, handler) => {
+    return handler({
+      ...request,
+      systemMessage: request.systemMessage.concat(`Additional context.`),
+    });
+  },
+});
+
+// Middleware 2: Uses systemMessage with structured content (preserves structure)
+const myOtherMiddleware = createMiddleware({
+  name: "MyOtherMiddleware",
+  wrapModelCall: async (request, handler) => {
+    return handler({
+      ...request,
+      systemMessage: request.systemMessage.concat(
+        new SystemMessage({
+          content: [
+            {
+              type: "text",
+              text: " More additional context. This will be cached.",
+              cache_control: { type: "ephemeral", ttl: "5m" },
+            },
+          ],
+        })
+      ),
+    });
+  },
+});
+
+const agent = createAgent({
+  model: "anthropic:claude-3-5-sonnet",
+  systemPrompt: "You are a helpful assistant.",
+  middleware: [myMiddleware, myOtherMiddleware],
+});
+```
+
+The resulting system message will be:
+```typescript
+new SystemMessage({
+  content: [
+    { type: "text", text: "You are a helpful assistant." },
+    { type: "text", text: "Additional context." },
+    {
+        type: "text",
+        text: " More additional context. This will be cached.",
+        cache_control: { type: "ephemeral", ttl: "5m" },
+    },
+  ],
+});
+```
+
+Use @[`SystemMessage.concat`] to preserve cache control metadata or structured content blocks created by other middleware.
+
+:::
+
 ## Additional resources
 
 - [Middleware API reference](https://reference.langchain.com/python/langchain/middleware/)