feat(core): new event streaming

.changeset/swift-dodos-attack.md

@@ -0,0 +1,5 @@
+---
+"@langchain/core": patch
+---
+
+chore(core): new stream primitives

.github/workflows/test-exports.yml

@@ -57,6 +57,7 @@ jobs:
           --filter @langchain/openai
           --filter @langchain/ollama
           --filter @langchain/google-gauth
+          --filter @langchain/google-common
           --filter @langchain/textsplitters
         shell: bash
 
@@ -86,6 +87,7 @@ jobs:
           --filter @langchain/openai
           --filter @langchain/ollama
           --filter @langchain/google-gauth
+          --filter @langchain/google-common
 
         shell: bash
 
@@ -115,6 +117,7 @@ jobs:
           --filter @langchain/openai
           --filter @langchain/ollama
           --filter @langchain/google-gauth
+          --filter @langchain/google-common
 
         shell: bash
 
@@ -144,6 +147,7 @@ jobs:
           --filter @langchain/openai
           --filter @langchain/ollama
           --filter @langchain/google-gauth
+          --filter @langchain/google-common
 
         shell: bash
 
@@ -173,6 +177,7 @@ jobs:
           --filter @langchain/openai
           --filter @langchain/ollama
           --filter @langchain/google-gauth
+          --filter @langchain/google-common
 
         shell: bash
 
@@ -202,6 +207,7 @@ jobs:
           --filter @langchain/openai
           --filter @langchain/ollama
           --filter @langchain/google-gauth
+          --filter @langchain/google-common
 
         shell: bash
 
@@ -231,6 +237,7 @@ jobs:
           --filter @langchain/openai
           --filter @langchain/ollama
           --filter @langchain/google-gauth
+          --filter @langchain/google-common
 
         shell: bash
 
@@ -261,6 +268,7 @@ jobs:
           --filter @langchain/openai
           --filter @langchain/ollama
           --filter @langchain/google-gauth
+          --filter @langchain/google-common
 
         shell: bash
 

.vscode/settings.json

@@ -1,11 +1,4 @@
 {
-  "eslint.workingDirectories": [
-    "./langchain",
-    "./langchain-core",
-    "./examples",
-    "./docs",
-    "./test-exports-vercel"
-  ],
   "yaml.schemas": {
     "https://json.schemastore.org/github-workflow.json": "./.github/workflows/deploy.yml"
   },
@@ -30,12 +23,12 @@
     "**/pnpm-lock.yaml": true
   },
   "typescript.preferences.importModuleSpecifier": "relative",
-  "editor.defaultFormatter": "esbenp.prettier-vscode",
+  "editor.defaultFormatter": "oxc.oxc-vscode",
   "[javascript]": {
-    "editor.defaultFormatter": "esbenp.prettier-vscode"
+    "editor.defaultFormatter": "oxc.oxc-vscode"
   },
   "[typescript]": {
-    "editor.defaultFormatter": "esbenp.prettier-vscode"
+    "editor.defaultFormatter": "oxc.oxc-vscode"
   },
   "deno.enable": false
 }

environment_tests/docker-compose.yml

@@ -17,6 +17,7 @@ services:
 
       - ../libs/providers/langchain-ollama:/langchain-ollama
       - ../libs/providers/langchain-google-gauth:/langchain-google-gauth
+      - ../libs/providers/langchain-google-common:/langchain-google-common
       - ../internal/standard-tests:/langchain-standard-tests
       - ../libs/langchain-scripts:/langchain-scripts
       - ../libs/langchain-textsplitters:/langchain-textsplitters
@@ -41,6 +42,7 @@ services:
 
       - ../libs/providers/langchain-ollama:/langchain-ollama
       - ../libs/providers/langchain-google-gauth:/langchain-google-gauth
+      - ../libs/providers/langchain-google-common:/langchain-google-common
       - ../internal/standard-tests:/langchain-standard-tests
       - ../libs/langchain-scripts:/langchain-scripts
       - ../libs/langchain-textsplitters:/langchain-textsplitters
@@ -65,6 +67,7 @@ services:
 
       - ../libs/providers/langchain-ollama:/langchain-ollama
       - ../libs/providers/langchain-google-gauth:/langchain-google-gauth
+      - ../libs/providers/langchain-google-common:/langchain-google-common
       - ../internal/standard-tests:/langchain-standard-tests
       - ../libs/langchain-scripts:/langchain-scripts
       - ../libs/langchain-textsplitters:/langchain-textsplitters
@@ -89,6 +92,7 @@ services:
 
       - ../libs/providers/langchain-ollama:/langchain-ollama
       - ../libs/providers/langchain-google-gauth:/langchain-google-gauth
+      - ../libs/providers/langchain-google-common:/langchain-google-common
       - ../internal/standard-tests:/langchain-standard-tests
       - ../libs/langchain-scripts:/langchain-scripts
       - ../libs/langchain-textsplitters:/langchain-textsplitters
@@ -113,6 +117,7 @@ services:
 
       - ../libs/providers/langchain-ollama:/langchain-ollama
       - ../libs/providers/langchain-google-gauth:/langchain-google-gauth
+      - ../libs/providers/langchain-google-common:/langchain-google-common
       - ../internal/standard-tests:/langchain-standard-tests
       - ../libs/langchain-scripts:/langchain-scripts
       - ../libs/langchain-textsplitters:/langchain-textsplitters
@@ -137,6 +142,7 @@ services:
 
       - ../libs/providers/langchain-ollama:/langchain-ollama
       - ../libs/providers/langchain-google-gauth:/langchain-google-gauth
+      - ../libs/providers/langchain-google-common:/langchain-google-common
       - ../internal/standard-tests:/langchain-standard-tests
       - ../libs/langchain-scripts:/langchain-scripts
       - ../libs/langchain-textsplitters:/langchain-textsplitters
@@ -161,6 +167,7 @@ services:
 
       - ../libs/providers/langchain-ollama:/langchain-ollama
       - ../libs/providers/langchain-google-gauth:/langchain-google-gauth
+      - ../libs/providers/langchain-google-common:/langchain-google-common
       - ../internal/standard-tests:/langchain-standard-tests
       - ../libs/langchain-scripts:/langchain-scripts
       - ../libs/langchain-textsplitters:/langchain-textsplitters
@@ -182,6 +189,7 @@ services:
 
       - ../libs/providers/langchain-ollama:/langchain-ollama
       - ../libs/providers/langchain-google-gauth:/langchain-google-gauth
+      - ../libs/providers/langchain-google-common:/langchain-google-common
       - ../internal/standard-tests:/langchain-standard-tests
       - ../libs/langchain-scripts:/langchain-scripts
       - ../libs/langchain-textsplitters:/langchain-textsplitters
@@ -206,6 +214,7 @@ services:
 
       - ../libs/providers/langchain-ollama:/langchain-ollama
       - ../libs/providers/langchain-google-gauth:/langchain-google-gauth
+      - ../libs/providers/langchain-google-common:/langchain-google-common
       - ../internal/standard-tests:/langchain-standard-tests
       - ../libs/langchain-scripts:/langchain-scripts
       - ../libs/langchain-textsplitters:/langchain-textsplitters

environment_tests/scripts/test-runner.ts

@@ -29,6 +29,10 @@ const dockerPackages: WorkspacePackage[] = [
     pkg: { name: "@langchain/google-gauth" },
     path: "/langchain-google-gauth",
   },
+  {
+    pkg: { name: "@langchain/google-common" },
+    path: "/langchain-google-common",
+  },
   {
     pkg: { name: "@langchain/standard-tests" },
     path: "/langchain-standard-tests",

libs/langchain-core/package.json

@@ -276,6 +276,28 @@
         "default": "./dist/language_models/chat_models.js"
       }
     },
+    "./language_models/compat": {
+      "input": "./src/language_models/compat.ts",
+      "require": {
+        "types": "./dist/language_models/compat.d.cts",
+        "default": "./dist/language_models/compat.cjs"
+      },
+      "import": {
+        "types": "./dist/language_models/compat.d.ts",
+        "default": "./dist/language_models/compat.js"
+      }
+    },
+    "./language_models/event": {
+      "input": "./src/language_models/event.ts",
+      "require": {
+        "types": "./dist/language_models/event.d.cts",
+        "default": "./dist/language_models/event.cjs"
+      },
+      "import": {
+        "types": "./dist/language_models/event.d.ts",
+        "default": "./dist/language_models/event.js"
+      }
+    },
     "./language_models/llms": {
       "input": "./src/language_models/llms.ts",
       "require": {
@@ -298,6 +320,17 @@
         "default": "./dist/language_models/profile.js"
       }
     },
+    "./language_models/stream": {
+      "input": "./src/language_models/stream.ts",
+      "require": {
+        "types": "./dist/language_models/stream.d.cts",
+        "default": "./dist/language_models/stream.cjs"
+      },
+      "import": {
+        "types": "./dist/language_models/stream.d.ts",
+        "default": "./dist/language_models/stream.js"
+      }
+    },
     "./language_models/structured_output": {
       "input": "./src/language_models/structured_output.ts",
       "require": {
@@ -782,6 +815,17 @@
         "default": "./dist/utils/types/index.js"
       }
     },
+    "./utils/uuid": {
+      "input": "./src/utils/uuid/index.ts",
+      "require": {
+        "types": "./dist/utils/uuid/index.d.cts",
+        "default": "./dist/utils/uuid/index.cjs"
+      },
+      "import": {
+        "types": "./dist/utils/uuid/index.d.ts",
+        "default": "./dist/utils/uuid/index.js"
+      }
+    },
     "./vectorstores": {
       "input": "./src/vectorstores.ts",
       "require": {

libs/langchain-core/src/callbacks/base.ts

@@ -1,6 +1,7 @@
 import * as uuid from "../utils/uuid/index.js";
 import type { ChainValues } from "../utils/types/index.js";
 import type { BaseMessage } from "../messages/base.js";
+import type { ChatModelStreamEvent } from "../language_models/event.js";
 import type { AgentAction, AgentFinish } from "../agents.js";
 import type {
   ChatGenerationChunk,
@@ -90,6 +91,17 @@ abstract class BaseCallbackHandlerMethodsClass {
   ): // oxlint-disable-next-line @typescript-eslint/no-explicit-any
     Promise<any> | any;
 
+  /**
+   * Called when a Chat Model emits a content-block-centric stream event.
+   */
+  handleChatModelStreamEvent?(
+    event: ChatModelStreamEvent,
+    runId: string,
+    parentRunId?: string,
+    tags?: string[]
+  ): // oxlint-disable-next-line @typescript-eslint/no-explicit-any
+    Promise<any> | any;
+
   /**
    * Called if an LLM/ChatModel run encounters an error
    */
@@ -314,6 +326,23 @@ export function callbackHandlerPrefersStreaming(x: BaseCallbackHandler) {
   return "lc_prefer_streaming" in x && x.lc_prefer_streaming;
 }
 
+/**
+ * Interface for handlers that prefer chat model stream events instead of
+ * legacy token/chunk callbacks.
+ */
+export interface CallbackHandlerPrefersChatModelStreamEvents {
+  readonly lc_prefer_chat_model_stream_events: boolean;
+}
+
+export function callbackHandlerPrefersChatModelStreamEvents(
+  x: BaseCallbackHandler
+) {
+  return (
+    "lc_prefer_chat_model_stream_events" in x &&
+    x.lc_prefer_chat_model_stream_events
+  );
+}
+
 /**
  * Abstract base class for creating callback handlers in the LangChain
  * framework. It provides a set of optional methods that can be overridden

libs/langchain-core/src/callbacks/manager.ts

@@ -17,6 +17,7 @@ import { LangChainTracer } from "../tracers/tracer_langchain.js";
 import { consumeCallback } from "./promises.js";
 import { Serialized } from "../load/serializable.js";
 import type { DocumentInterface } from "../documents/document.js";
+import type { ChatModelStreamEvent } from "../language_models/event.js";
 import { isTracingEnabled } from "../utils/callbacks.js";
 import { isBaseTracer } from "../tracers/base.js";
 import {
@@ -302,6 +303,35 @@ export class CallbackManagerForLLMRun
     );
   }
 
+  async handleChatModelStreamEvent(event: ChatModelStreamEvent): Promise<void> {
+    await Promise.all(
+      this.handlers.map((handler) =>
+        consumeCallback(async () => {
+          if (!handler.ignoreLLM) {
+            try {
+              await handler.handleChatModelStreamEvent?.(
+                event,
+                this.runId,
+                this._parentRunId,
+                this.tags
+              );
+            } catch (err) {
+              const logFunction = handler.raiseError
+                ? console.error
+                : console.warn;
+              logFunction(
+                `Error in handler ${handler.constructor.name}, handleChatModelStreamEvent: ${err}`
+              );
+              if (handler.raiseError) {
+                throw err;
+              }
+            }
+          }
+        }, handler.awaitHandlers)
+      )
+    );
+  }
+
   async handleLLMError(
     err: Error | unknown,
     _runId?: string,