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href="/docs/how_to/callbacks_constructor/">How to propagate callbacks constructor</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/callbacks_custom_events/">How to dispatch custom callback events</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/callbacks_runtime/">How to pass callbacks in at runtime</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/character_text_splitter/">How to split by character</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/chat_model_caching/">How to cache chat model responses</a></li><li class="theme-doc-sidebar-item-link 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theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/custom_embeddings/">Custom Embeddings</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/custom_llm/">How to create a custom LLM class</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/custom_retriever/">Custom Retriever</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/custom_tools/">How to create tools</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/debugging/">How to debug your LLM apps</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/document_loader_csv/">How to load CSVs</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/document_loader_directory/">How to load documents from a directory</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/document_loader_html/">How to load HTML</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/document_loader_json/">How to load JSON</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/document_loader_markdown/">How to load 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tabindex="0" href="/docs/how_to/embed_text/">Text embedding models</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/ensemble_retriever/">How to combine results from multiple retrievers</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/example_selectors_langsmith/">How to select examples from a LangSmith dataset</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/example_selectors_length_based/">How to select examples by length</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/example_selectors_mmr/">How to select examples by maximal marginal relevance 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API</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/inspect/">How to inspect runnables</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/lcel_cheatsheet/">LangChain Expression Language Cheatsheet</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/llm_caching/">How to cache LLM responses</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/llm_token_usage_tracking/">How to track token usage for LLMs</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" 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class="menu__link" tabindex="0" href="/docs/how_to/multimodal_prompts/">How to use multimodal prompts</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/output_parser_custom/">How to create a custom Output Parser</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/output_parser_fixing/">How to use the output-fixing parser</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/output_parser_json/">How to parse JSON output</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/output_parser_retry/">How to retry when a parsing error occurs</a></li><li 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href="/docs/how_to/runnable_runtime_secrets/">How to pass runtime secrets to runnables</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/self_query/">How to do "self-querying" retrieval</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/semantic-chunker/">How to split text based on semantic similarity</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/sequence/">How to chain runnables</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/serialization/">How to save and load LangChain objects</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/split_by_token/">How to split text by tokens</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/split_html/">How to split HTML</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/sql_csv/">How to do question answering over CSVs</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/sql_large_db/">How to deal with large databases when doing SQL question-answering</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item hidden"><a class="menu__link" tabindex="0" href="/docs/how_to/sql_prompting/">How to better 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href="/docs/concepts/"><span itemprop="name">Conceptual guide</span></a><meta itemprop="position" content="1"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">Messages</span><meta itemprop="position" content="2"></li></ul></nav><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div style="display:flex;flex-direction:column;align-items:flex-end;float:right;margin-left:12px"><a href="https://github.com/langchain-ai/langchain/blob/master/docs/docs/concepts/messages.mdx" target="_blank"><img src="https://img.shields.io/badge/Open%20on%20GitHub-grey?logo=github&logoColor=white" alt="Open on GitHub"></a></div><div class="theme-doc-markdown markdown"><header><h1>Messages</h1></header> <div class="theme-admonition theme-admonition-info admonition_xJq3 alert alert--info"><div class="admonitionHeading_Gvgb"><span class="admonitionIcon_Rf37"><svg viewBox="0 0 14 16"><path fill-rule="evenodd" d="M7 2.3c3.14 0 5.7 2.56 5.7 5.7s-2.56 5.7-5.7 5.7A5.71 5.71 0 0 1 1.3 8c0-3.14 2.56-5.7 5.7-5.7zM7 1C3.14 1 0 4.14 0 8s3.14 7 7 7 7-3.14 7-7-3.14-7-7-7zm1 3H6v5h2V4zm0 6H6v2h2v-2z"></path></svg></span>Prerequisites</div><div class="admonitionContent_BuS1"><ul> <li><a href="/docs/concepts/chat_models/">Chat Models</a></li> </ul></div></div> <h2 class="anchor anchorWithStickyNavbar_LWe7" id="overview">Overview<a href="#overview" class="hash-link" aria-label="Direct link to Overview" title="Direct link to Overview"></a></h2> <p>Messages are the unit of communication in <a href="/docs/concepts/chat_models/">chat models</a>. They are used to represent the input and output of a chat model, as well as any additional context or metadata that may be associated with a conversation.</p> <p>Each message has a <strong>role</strong> (e.g., "user", "assistant") and <strong>content</strong> (e.g., text, multimodal data) with additional metadata that varies depending on the chat model provider.</p> <p>LangChain provides a unified message format that can be used across chat models, allowing users to work with different chat models without worrying about the specific details of the message format used by each model provider.</p> <h2 class="anchor anchorWithStickyNavbar_LWe7" id="what-is-inside-a-message">What is inside a message?<a href="#what-is-inside-a-message" class="hash-link" aria-label="Direct link to What is inside a message?" title="Direct link to What is inside a message?"></a></h2> <p>A message typically consists of the following pieces of information:</p> <ul> <li><strong>Role</strong>: The role of the message (e.g., "user", "assistant").</li> <li><strong>Content</strong>: The content of the message (e.g., text, multimodal data).</li> <li>Additional metadata: id, name, <a href="/docs/concepts/tokens/">token usage</a> and other model-specific metadata.</li> </ul> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="role">Role<a href="#role" class="hash-link" aria-label="Direct link to Role" title="Direct link to Role"></a></h3> <p>Roles are used to distinguish between different types of messages in a conversation and help the chat model understand how to respond to a given sequence of messages.</p> <table><thead><tr><th><strong>Role</strong></th><th><strong>Description</strong></th></tr></thead><tbody><tr><td><strong>system</strong></td><td>Used to tell the chat model how to behave and provide additional context. Not supported by all chat model providers.</td></tr><tr><td><strong>user</strong></td><td>Represents input from a user interacting with the model, usually in the form of text or other interactive input.</td></tr><tr><td><strong>assistant</strong></td><td>Represents a response from the model, which can include text or a request to invoke tools.</td></tr><tr><td><strong>tool</strong></td><td>A message used to pass the results of a tool invocation back to the model after external data or processing has been retrieved. Used with chat models that support <a href="/docs/concepts/tool_calling/">tool calling</a>.</td></tr><tr><td><strong>function</strong> (legacy)</td><td>This is a legacy role, corresponding to OpenAI's legacy function-calling API. <strong>tool</strong> role should be used instead.</td></tr></tbody></table> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="content">Content<a href="#content" class="hash-link" aria-label="Direct link to Content" title="Direct link to Content"></a></h3> <p>The content of a message text or a list of dictionaries representing <a href="/docs/concepts/multimodality/">multimodal data</a> (e.g., images, audio, video). The exact format of the content can vary between different chat model providers.</p> <p>Currently, most chat models support text as the primary content type, with some models also supporting multimodal data. However, support for multimodal data is still limited across most chat model providers.</p> <p>For more information see:</p> <ul> <li><a href="#systemmessage">SystemMessage</a> -- for content which should be passed to direct the conversation</li> <li><a href="#humanmessage">HumanMessage</a> -- for content in the input from the user.</li> <li><a href="#aimessage">AIMessage</a> -- for content in the response from the model.</li> <li><a href="/docs/concepts/multimodality/">Multimodality</a> -- for more information on multimodal content.</li> </ul> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="other-message-data">Other Message Data<a href="#other-message-data" class="hash-link" aria-label="Direct link to Other Message Data" title="Direct link to Other Message Data"></a></h3> <p>Depending on the chat model provider, messages can include other data such as:</p> <ul> <li><strong>ID</strong>: An optional unique identifier for the message.</li> <li><strong>Name</strong>: An optional <code>name</code> property which allows differentiate between different entities/speakers with the same role. Not all models support this!</li> <li><strong>Metadata</strong>: Additional information about the message, such as timestamps, token usage, etc.</li> <li><strong>Tool Calls</strong>: A request made by the model to call one or more tools> See <a href="/docs/concepts/tool_calling/">tool calling</a> for more information.</li> </ul> <h2 class="anchor anchorWithStickyNavbar_LWe7" id="conversation-structure">Conversation Structure<a href="#conversation-structure" class="hash-link" aria-label="Direct link to Conversation Structure" title="Direct link to Conversation Structure"></a></h2> <p>The sequence of messages into a chat model should follow a specific structure to ensure that the chat model can generate a valid response.</p> <p>For example, a typical conversation structure might look like this:</p> <ol> <li><strong>User Message</strong>: "Hello, how are you?"</li> <li><strong>Assistant Message</strong>: "I'm doing well, thank you for asking."</li> <li><strong>User Message</strong>: "Can you tell me a joke?"</li> <li><strong>Assistant Message</strong>: "Sure! Why did the scarecrow win an award? Because he was outstanding in his field!"</li> </ol> <p>Please read the <a href="/docs/concepts/chat_history/">chat history</a> guide for more information on managing chat history and ensuring that the conversation structure is correct.</p> <h2 class="anchor anchorWithStickyNavbar_LWe7" id="langchain-messages">LangChain Messages<a href="#langchain-messages" class="hash-link" aria-label="Direct link to LangChain Messages" title="Direct link to LangChain Messages"></a></h2> <p>LangChain provides a unified message format that can be used across all chat models, allowing users to work with different chat models without worrying about the specific details of the message format used by each model provider.</p> <p>LangChain messages are Python objects that subclass from a <a href="https://python.langchain.com/api_reference/core/messages/langchain_core.messages.base.BaseMessage.html" target="_blank" rel="noopener noreferrer">BaseMessage</a>.</p> <p>The five main message types are:</p> <ul> <li><a href="#systemmessage">SystemMessage</a>: corresponds to <strong>system</strong> role</li> <li><a href="#humanmessage">HumanMessage</a>: corresponds to <strong>user</strong> role</li> <li><a href="#aimessage">AIMessage</a>: corresponds to <strong>assistant</strong> role</li> <li><a href="#aimessagechunk">AIMessageChunk</a>: corresponds to <strong>assistant</strong> role, used for <a href="/docs/concepts/streaming/">streaming</a> responses</li> <li><a href="#toolmessage">ToolMessage</a>: corresponds to <strong>tool</strong> role</li> </ul> <p>Other important messages include:</p> <ul> <li><a href="#removemessage">RemoveMessage</a> -- does not correspond to any role. This is an abstraction, mostly used in <a href="/docs/concepts/architecture/#langgraph">LangGraph</a> to manage chat history.</li> <li><strong>Legacy</strong> <a href="#legacy-functionmessage">FunctionMessage</a>: corresponds to the <strong>function</strong> role in OpenAI's <strong>legacy</strong> function-calling API.</li> </ul> <p>You can find more information about <strong>messages</strong> in the <a href="https://python.langchain.com/api_reference/core/messages.html" target="_blank" rel="noopener noreferrer">API Reference</a>.</p> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="systemmessage">SystemMessage<a href="#systemmessage" class="hash-link" aria-label="Direct link to SystemMessage" title="Direct link to SystemMessage"></a></h3> <p>A <code>SystemMessage</code> is used to prime the behavior of the AI model and provide additional context, such as instructing the model to adopt a specific persona or setting the tone of the conversation (e.g., "This is a conversation about cooking").</p> <p>Different chat providers may support system message in one of the following ways:</p> <ul> <li><strong>Through a "system" message role</strong>: In this case, a system message is included as part of the message sequence with the role explicitly set as "system."</li> <li><strong>Through a separate API parameter for system instructions</strong>: Instead of being included as a message, system instructions are passed via a dedicated API parameter.</li> <li><strong>No support for system messages</strong>: Some models do not support system messages at all.</li> </ul> <p>Most major chat model providers support system instructions via either a chat message or a separate API parameter. LangChain will automatically adapt based on the provider’s capabilities. If the provider supports a separate API parameter for system instructions, LangChain will extract the content of a system message and pass it through that parameter.</p> <p>If no system message is supported by the provider, in most cases LangChain will attempt to incorporate the system message's content into a HumanMessage or raise an exception if that is not possible. However, this behavior is not yet consistently enforced across all implementations, and if using a less popular implementation of a chat model (e.g., an implementation from the <code>langchain-community</code> package) it is recommended to check the specific documentation for that model.</p> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="humanmessage">HumanMessage<a href="#humanmessage" class="hash-link" aria-label="Direct link to HumanMessage" title="Direct link to HumanMessage"></a></h3> <p>The <code>HumanMessage</code> corresponds to the <strong>"user"</strong> role. A human message represents input from a user interacting with the model.</p> <h4 class="anchor anchorWithStickyNavbar_LWe7" id="text-content">Text Content<a href="#text-content" class="hash-link" aria-label="Direct link to Text Content" title="Direct link to Text Content"></a></h4> <p>Most chat models expect the user input to be in the form of text.</p> <div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#000000;--prism-background-color:#F5F5F5"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar" style="color:#000000;background-color:#F5F5F5"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#000000"><span class="token keyword" style="color:rgb(0, 0, 255)">from</span><span class="token plain"> langchain_core</span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><span class="token plain">messages </span><span class="token keyword" style="color:rgb(0, 0, 255)">import</span><span class="token plain"> HumanMessage</span><br></span><span class="token-line" style="color:#000000"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain">model</span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><span class="token plain">invoke</span><span class="token punctuation" style="color:rgb(4, 81, 165)">(</span><span class="token punctuation" style="color:rgb(4, 81, 165)">[</span><span class="token plain">HumanMessage</span><span class="token punctuation" style="color:rgb(4, 81, 165)">(</span><span class="token plain">content</span><span class="token operator" style="color:rgb(0, 0, 0)">=</span><span class="token string" style="color:rgb(163, 21, 21)">"Hello, how are you?"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">)</span><span class="token punctuation" style="color:rgb(4, 81, 165)">]</span><span class="token punctuation" style="color:rgb(4, 81, 165)">)</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><div style="padding-top:1.3rem;background:var(--prism-background-color);color:var(--prism-color);margin-top:calc(-1 * var(--ifm-leading) - 5px);margin-bottom:var(--ifm-leading);box-shadow:var(--ifm-global-shadow-lw);border-bottom-left-radius:var(--ifm-code-border-radius);border-bottom-right-radius:var(--ifm-code-border-radius)"><b style="padding-left:0.65rem;margin-bottom:0.45rem;margin-right:0.5rem">API Reference:</b><span><a href="https://python.langchain.com/api_reference/core/messages/langchain_core.messages.human.HumanMessage.html">HumanMessage</a></span></div> <div class="theme-admonition theme-admonition-tip admonition_xJq3 alert alert--success"><div class="admonitionHeading_Gvgb"><span class="admonitionIcon_Rf37"><svg viewBox="0 0 12 16"><path fill-rule="evenodd" d="M6.5 0C3.48 0 1 2.19 1 5c0 .92.55 2.25 1 3 1.34 2.25 1.78 2.78 2 4v1h5v-1c.22-1.22.66-1.75 2-4 .45-.75 1-2.08 1-3 0-2.81-2.48-5-5.5-5zm3.64 7.48c-.25.44-.47.8-.67 1.11-.86 1.41-1.25 2.06-1.45 3.23-.02.05-.02.11-.02.17H5c0-.06 0-.13-.02-.17-.2-1.17-.59-1.83-1.45-3.23-.2-.31-.42-.67-.67-1.11C2.44 6.78 2 5.65 2 5c0-2.2 2.02-4 4.5-4 1.22 0 2.36.42 3.22 1.19C10.55 2.94 11 3.94 11 5c0 .66-.44 1.78-.86 2.48zM4 14h5c-.23 1.14-1.3 2-2.5 2s-2.27-.86-2.5-2z"></path></svg></span>tip</div><div class="admonitionContent_BuS1"><p>When invoking a chat model with a string as input, LangChain will automatically convert the string into a <code>HumanMessage</code> object. This is mostly useful for quick testing.</p><div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#000000;--prism-background-color:#F5F5F5"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar" style="color:#000000;background-color:#F5F5F5"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#000000"><span class="token plain">model</span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><span class="token plain">invoke</span><span class="token punctuation" style="color:rgb(4, 81, 165)">(</span><span class="token string" style="color:rgb(163, 21, 21)">"Hello, how are you?"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">)</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div></div> <h4 class="anchor anchorWithStickyNavbar_LWe7" id="multi-modal-content">Multi-modal Content<a href="#multi-modal-content" class="hash-link" aria-label="Direct link to Multi-modal Content" title="Direct link to Multi-modal Content"></a></h4> <p>Some chat models accept multimodal inputs, such as images, audio, video, or files like PDFs.</p> <p>Please see the <a href="/docs/concepts/multimodality/">multimodality</a> guide for more information.</p> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="aimessage">AIMessage<a href="#aimessage" class="hash-link" aria-label="Direct link to AIMessage" title="Direct link to AIMessage"></a></h3> <p><code>AIMessage</code> is used to represent a message with the role <strong>"assistant"</strong>. This is the response from the model, which can include text or a request to invoke tools. It could also include other media types like images, audio, or video -- though this is still uncommon at the moment.</p> <div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#000000;--prism-background-color:#F5F5F5"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar" style="color:#000000;background-color:#F5F5F5"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#000000"><span class="token keyword" style="color:rgb(0, 0, 255)">from</span><span class="token plain"> langchain_core</span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><span class="token plain">messages </span><span class="token keyword" style="color:rgb(0, 0, 255)">import</span><span class="token plain"> HumanMessage</span><br></span><span class="token-line" style="color:#000000"><span class="token plain">ai_message </span><span class="token operator" style="color:rgb(0, 0, 0)">=</span><span class="token plain"> model</span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><span class="token plain">invoke</span><span class="token punctuation" style="color:rgb(4, 81, 165)">(</span><span class="token punctuation" style="color:rgb(4, 81, 165)">[</span><span class="token plain">HumanMessage</span><span class="token punctuation" style="color:rgb(4, 81, 165)">(</span><span class="token string" style="color:rgb(163, 21, 21)">"Tell me a joke"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">)</span><span class="token punctuation" style="color:rgb(4, 81, 165)">]</span><span class="token punctuation" style="color:rgb(4, 81, 165)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain">ai_message </span><span class="token comment" style="color:rgb(0, 128, 0)"># <-- AIMessage</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><div style="padding-top:1.3rem;background:var(--prism-background-color);color:var(--prism-color);margin-top:calc(-1 * var(--ifm-leading) - 5px);margin-bottom:var(--ifm-leading);box-shadow:var(--ifm-global-shadow-lw);border-bottom-left-radius:var(--ifm-code-border-radius);border-bottom-right-radius:var(--ifm-code-border-radius)"><b style="padding-left:0.65rem;margin-bottom:0.45rem;margin-right:0.5rem">API Reference:</b><span><a href="https://python.langchain.com/api_reference/core/messages/langchain_core.messages.human.HumanMessage.html">HumanMessage</a></span></div> <p>An <code>AIMessage</code> has the following attributes. The attributes which are <strong>standardized</strong> are the ones that LangChain attempts to standardize across different chat model providers. <strong>raw</strong> fields are specific to the model provider and may vary.</p> <table><thead><tr><th>Attribute</th><th style="text-align:left">Standardized/Raw</th><th>Description</th></tr></thead><tbody><tr><td><code>content</code></td><td style="text-align:left">Raw</td><td>Usually a string, but can be a list of content blocks. See <a href="#content">content</a> for details.</td></tr><tr><td><code>tool_calls</code></td><td style="text-align:left">Standardized</td><td>Tool calls associated with the message. See <a href="/docs/concepts/tool_calling/">tool calling</a> for details.</td></tr><tr><td><code>invalid_tool_calls</code></td><td style="text-align:left">Standardized</td><td>Tool calls with parsing errors associated with the message. See <a href="/docs/concepts/tool_calling/">tool calling</a> for details.</td></tr><tr><td><code>usage_metadata</code></td><td style="text-align:left">Standardized</td><td>Usage metadata for a message, such as <a href="/docs/concepts/tokens/">token counts</a>. See <a href="https://python.langchain.com/api_reference/core/messages/langchain_core.messages.ai.UsageMetadata.html" target="_blank" rel="noopener noreferrer">Usage Metadata API Reference</a>.</td></tr><tr><td><code>id</code></td><td style="text-align:left">Standardized</td><td>An optional unique identifier for the message, ideally provided by the provider/model that created the message.</td></tr><tr><td><code>response_metadata</code></td><td style="text-align:left">Raw</td><td>Response metadata, e.g., response headers, logprobs, token counts.</td></tr></tbody></table> <h4 class="anchor anchorWithStickyNavbar_LWe7" id="content-1">content<a href="#content-1" class="hash-link" aria-label="Direct link to content" title="Direct link to content"></a></h4> <p>The <strong>content</strong> property of an <code>AIMessage</code> represents the response generated by the chat model.</p> <p>The content is either:</p> <ul> <li><strong>text</strong> -- the norm for virtually all chat models.</li> <li>A <strong>list of dictionaries</strong> -- Each dictionary represents a content block and is associated with a <code>type</code>.<!-- --> <ul> <li>Used by Anthropic for surfacing agent thought process when doing <a href="/docs/concepts/tool_calling/">tool calling</a>.</li> <li>Used by OpenAI for audio outputs. Please see <a href="/docs/concepts/multimodality/">multi-modal content</a> for more information.</li> </ul> </li> </ul> <div class="theme-admonition theme-admonition-important admonition_xJq3 alert alert--info"><div class="admonitionHeading_Gvgb"><span class="admonitionIcon_Rf37"><svg viewBox="0 0 14 16"><path fill-rule="evenodd" d="M7 2.3c3.14 0 5.7 2.56 5.7 5.7s-2.56 5.7-5.7 5.7A5.71 5.71 0 0 1 1.3 8c0-3.14 2.56-5.7 5.7-5.7zM7 1C3.14 1 0 4.14 0 8s3.14 7 7 7 7-3.14 7-7-3.14-7-7-7zm1 3H6v5h2V4zm0 6H6v2h2v-2z"></path></svg></span>important</div><div class="admonitionContent_BuS1"><p>The <strong>content</strong> property is <strong>not</strong> standardized across different chat model providers, mostly because there are still few examples to generalize from.</p></div></div> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="aimessagechunk">AIMessageChunk<a href="#aimessagechunk" class="hash-link" aria-label="Direct link to AIMessageChunk" title="Direct link to AIMessageChunk"></a></h3> <p>It is common to <a href="/docs/concepts/streaming/">stream</a> responses for the chat model as they are being generated, so the user can see the response in real-time instead of waiting for the entire response to be generated before displaying it.</p> <p>It is returned from the <code>stream</code>, <code>astream</code> and <code>astream_events</code> methods of the chat model.</p> <p>For example,</p> <div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#000000;--prism-background-color:#F5F5F5"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar" style="color:#000000;background-color:#F5F5F5"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#000000"><span class="token keyword" style="color:rgb(0, 0, 255)">for</span><span class="token plain"> chunk </span><span class="token keyword" style="color:rgb(0, 0, 255)">in</span><span class="token plain"> model</span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><span class="token plain">stream</span><span class="token punctuation" style="color:rgb(4, 81, 165)">(</span><span class="token punctuation" style="color:rgb(4, 81, 165)">[</span><span class="token plain">HumanMessage</span><span class="token punctuation" style="color:rgb(4, 81, 165)">(</span><span class="token string" style="color:rgb(163, 21, 21)">"what color is the sky?"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">)</span><span class="token punctuation" style="color:rgb(4, 81, 165)">]</span><span class="token punctuation" style="color:rgb(4, 81, 165)">)</span><span class="token punctuation" style="color:rgb(4, 81, 165)">:</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token keyword" style="color:rgb(0, 0, 255)">print</span><span class="token punctuation" style="color:rgb(4, 81, 165)">(</span><span class="token plain">chunk</span><span class="token punctuation" style="color:rgb(4, 81, 165)">)</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div> <p><code>AIMessageChunk</code> follows nearly the same structure as <code>AIMessage</code>, but uses a different <a href="https://python.langchain.com/api_reference/core/messages/langchain_core.messages.tool.ToolCallChunk.html#langchain_core.messages.tool.ToolCallChunk" target="_blank" rel="noopener noreferrer">ToolCallChunk</a> to be able to stream tool calling in a standardized manner.</p> <h4 class="anchor anchorWithStickyNavbar_LWe7" id="aggregating">Aggregating<a href="#aggregating" class="hash-link" aria-label="Direct link to Aggregating" title="Direct link to Aggregating"></a></h4> <p><code>AIMessageChunks</code> support the <code>+</code> operator to merge them into a single <code>AIMessage</code>. This is useful when you want to display the final response to the user.</p> <div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#000000;--prism-background-color:#F5F5F5"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar" style="color:#000000;background-color:#F5F5F5"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#000000"><span class="token plain">ai_message </span><span class="token operator" style="color:rgb(0, 0, 0)">=</span><span class="token plain"> chunk1 </span><span class="token operator" style="color:rgb(0, 0, 0)">+</span><span class="token plain"> chunk2 </span><span class="token operator" style="color:rgb(0, 0, 0)">+</span><span class="token plain"> chunk3 </span><span class="token operator" style="color:rgb(0, 0, 0)">+</span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="toolmessage">ToolMessage<a href="#toolmessage" class="hash-link" aria-label="Direct link to ToolMessage" title="Direct link to ToolMessage"></a></h3> <p>This represents a message with role "tool", which contains the result of <a href="/docs/concepts/tool_calling/">calling a tool</a>. In addition to <code>role</code> and <code>content</code>, this message has:</p> <ul> <li>a <code>tool_call_id</code> field which conveys the id of the call to the tool that was called to produce this result.</li> <li>an <code>artifact</code> field which can be used to pass along arbitrary artifacts of the tool execution which are useful to track but which should not be sent to the model.</li> </ul> <p>Please see <a href="/docs/concepts/tool_calling/">tool calling</a> for more information.</p> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="removemessage">RemoveMessage<a href="#removemessage" class="hash-link" aria-label="Direct link to RemoveMessage" title="Direct link to RemoveMessage"></a></h3> <p>This is a special message type that does not correspond to any roles. It is used for managing chat history in <a href="/docs/concepts/architecture/#langgraph">LangGraph</a>.</p> <p>Please see the following for more information on how to use the <code>RemoveMessage</code>:</p> <ul> <li><a href="https://langchain-ai.github.io/langgraph/concepts/memory/" target="_blank" rel="noopener noreferrer">Memory conceptual guide</a></li> <li><a href="https://langchain-ai.github.io/langgraph/how-tos/memory/delete-messages/" target="_blank" rel="noopener noreferrer">How to delete messages</a></li> </ul> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="legacy-functionmessage">(Legacy) FunctionMessage<a href="#legacy-functionmessage" class="hash-link" aria-label="Direct link to (Legacy) FunctionMessage" title="Direct link to (Legacy) FunctionMessage"></a></h3> <p>This is a legacy message type, corresponding to OpenAI's legacy function-calling API. <code>ToolMessage</code> should be used instead to correspond to the updated tool-calling API.</p> <h2 class="anchor anchorWithStickyNavbar_LWe7" id="openai-format">OpenAI Format<a href="#openai-format" class="hash-link" aria-label="Direct link to OpenAI Format" title="Direct link to OpenAI Format"></a></h2> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="inputs">Inputs<a href="#inputs" class="hash-link" aria-label="Direct link to Inputs" title="Direct link to Inputs"></a></h3> <p>Chat models also accept OpenAI's format as <strong>inputs</strong> to chat models:</p> <div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#000000;--prism-background-color:#F5F5F5"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar" style="color:#000000;background-color:#F5F5F5"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#000000"><span class="token plain">chat_model</span><span class="token punctuation" style="color:rgb(4, 81, 165)">.</span><span class="token plain">invoke</span><span class="token punctuation" style="color:rgb(4, 81, 165)">(</span><span class="token punctuation" style="color:rgb(4, 81, 165)">[</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(4, 81, 165)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"role"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">:</span><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"user"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"content"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">:</span><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"Hello, how are you?"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(4, 81, 165)">}</span><span class="token punctuation" style="color:rgb(4, 81, 165)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(4, 81, 165)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"role"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">:</span><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"assistant"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"content"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">:</span><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"I'm doing well, thank you for asking."</span><span class="token punctuation" style="color:rgb(4, 81, 165)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(4, 81, 165)">}</span><span class="token punctuation" style="color:rgb(4, 81, 165)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(4, 81, 165)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"role"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">:</span><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"user"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"content"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">:</span><span class="token plain"> </span><span class="token string" style="color:rgb(163, 21, 21)">"Can you tell me a joke?"</span><span class="token punctuation" style="color:rgb(4, 81, 165)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(4, 81, 165)">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#000000"><span class="token plain"></span><span class="token punctuation" style="color:rgb(4, 81, 165)">]</span><span class="token punctuation" style="color:rgb(4, 81, 165)">)</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div> <h3 class="anchor anchorWithStickyNavbar_LWe7" id="outputs">Outputs<a href="#outputs" class="hash-link" aria-label="Direct link to Outputs" title="Direct link to Outputs"></a></h3> <p>At the moment, the output of the model will be in terms of LangChain messages, so you will need to convert the output to the OpenAI format if you need OpenAI format for the output as well.</p> <p>The <a href="https://python.langchain.com/api_reference/core/messages/langchain_core.messages.utils.convert_to_openai_messages.html" target="_blank" rel="noopener noreferrer">convert_to_openai_messages</a> utility function can be used to convert from LangChain messages to OpenAI format.</p></div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="row margin-top--sm theme-doc-footer-edit-meta-row"><div class="col"><a 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