fix(core): change response metadata type mismatch (#9010)

Author: hntrl

libs/langchain-core/src/messages/ai.ts

@@ -146,13 +146,15 @@ export class AIMessage<TStructure extends MessageStructure = MessageStructure>
 
   get contentBlocks(): Array<ContentBlock.Standard> {
     if (
+      this.response_metadata &&
       "output_version" in this.response_metadata &&
       this.response_metadata.output_version === "v1"
     ) {
       return this.content as Array<ContentBlock.Standard>;
     }
 
     if (
+      this.response_metadata &&
       "model_provider" in this.response_metadata &&
       typeof this.response_metadata.model_provider === "string"
     ) {
@@ -369,13 +371,15 @@ export class AIMessageChunk<
 
   get contentBlocks(): Array<ContentBlock.Standard> {
     if (
+      this.response_metadata &&
       "output_version" in this.response_metadata &&
       this.response_metadata.output_version === "v1"
     ) {
       return this.content as Array<ContentBlock.Standard>;
     }
 
     if (
+      this.response_metadata &&
       "model_provider" in this.response_metadata &&
       typeof this.response_metadata.model_provider === "string"
     ) {

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

@@ -413,9 +413,9 @@ export function isOpenAIToolCallArray(
 
 export function _mergeDicts(
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
-  left: Record<string, any>,
+  left: Record<string, any> = {},
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
-  right: Record<string, any>
+  right: Record<string, any> = {}
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
 ): Record<string, any> {
   const merged = { ...left };

libs/langchain-core/src/messages/message.ts

@@ -390,21 +390,21 @@ export interface StandardMessageStructure extends MessageStructure {
     /** Properties specific to AI messages */
     ai: {
       /** Metadata about the AI model response */
-      response_metadata?: ResponseMetadata;
+      response_metadata: ResponseMetadata;
       /** Usage statistics for the AI response */
-      usage_metadata?: UsageMetadata;
+      usage_metadata: UsageMetadata;
     };
     human: {
       /** Metadata about the human message */
-      response_metadata?: Record<string, unknown>;
+      response_metadata: Record<string, unknown>;
     };
     system: {
       /** Metadata about the system message */
-      response_metadata?: Record<string, unknown>;
+      response_metadata: Record<string, unknown>;
     };
     tool: {
       /** Metadata about the tool message */
-      response_metadata?: Record<string, unknown>;
+      response_metadata: Record<string, unknown>;
     };
   };
 }
@@ -650,7 +650,7 @@ export type $InferResponseMetadata<
   TRole,
   "response_metadata"
 > extends infer P
-  ? [P] extends [unknown]
+  ? [P] extends [never]
     ? Record<string, unknown>
     : P
   : never;

libs/langchain-core/src/messages/tests/messages.test-d.ts

@@ -14,6 +14,7 @@ import {
   $InferMessageContentBlocks,
   $InferMessageProperty,
   $InferMessageProperties,
+  $InferResponseMetadata,
 } from "../message.js";
 import { ContentBlock } from "../content/index.js";
 import { ResponseMetadata, UsageMetadata } from "../metadata.js";
@@ -617,17 +618,17 @@ describe("$NormalizedMessageStructure<T>", () => {
     // Properties backfilled for all standard roles
     type AIP = NonNullable<N["properties"]>["ai"];
     expectTypeOf<AIP>().toEqualTypeOf<{
-      response_metadata?: ResponseMetadata | undefined;
-      usage_metadata?: UsageMetadata | undefined;
+      response_metadata: ResponseMetadata;
+      usage_metadata: UsageMetadata;
     }>();
     expectTypeOf<NonNullable<N["properties"]>["human"]>().toEqualTypeOf<{
-      response_metadata?: Record<string, unknown> | undefined;
+      response_metadata: Record<string, unknown>;
     }>();
     expectTypeOf<NonNullable<N["properties"]>["system"]>().toEqualTypeOf<{
-      response_metadata?: Record<string, unknown> | undefined;
+      response_metadata: Record<string, unknown>;
     }>();
     expectTypeOf<NonNullable<N["properties"]>["tool"]>().toEqualTypeOf<{
-      response_metadata?: Record<string, unknown> | undefined;
+      response_metadata: Record<string, unknown>;
     }>();
   });
 });
@@ -840,23 +841,23 @@ describe("$InferMessageProperties<TStructure, TRole>", () => {
 
     type AIProps = $InferMessageProperties<S, "ai">;
     expectTypeOf<AIProps>().toEqualTypeOf<{
-      response_metadata?: ResponseMetadata | undefined;
-      usage_metadata?: UsageMetadata | undefined;
+      response_metadata: ResponseMetadata;
+      usage_metadata: UsageMetadata;
     }>();
 
     type HumanProps = $InferMessageProperties<S, "human">;
     expectTypeOf<HumanProps>().toEqualTypeOf<{
-      response_metadata?: Record<string, unknown> | undefined;
+      response_metadata: Record<string, unknown>;
     }>();
 
     type SystemProps = $InferMessageProperties<S, "system">;
     expectTypeOf<SystemProps>().toEqualTypeOf<{
-      response_metadata?: Record<string, unknown> | undefined;
+      response_metadata: Record<string, unknown>;
     }>();
 
     type ToolProps = $InferMessageProperties<S, "tool">;
     expectTypeOf<ToolProps>().toEqualTypeOf<{
-      response_metadata?: Record<string, unknown> | undefined;
+      response_metadata: Record<string, unknown>;
     }>();
   });
 
@@ -871,12 +872,12 @@ describe("$InferMessageProperties<TStructure, TRole>", () => {
     type HumanProps = $InferMessageProperties<S, "human">;
 
     expectTypeOf<AIProps>().toEqualTypeOf<{
-      response_metadata: ResponseMetadata | undefined;
-      usage_metadata: UsageMetadata | undefined;
+      response_metadata: ResponseMetadata;
+      usage_metadata: UsageMetadata;
       foo: { bar: number };
     }>();
     expectTypeOf<HumanProps>().toEqualTypeOf<{
-      response_metadata: Record<string, unknown> | undefined;
+      response_metadata: Record<string, unknown>;
       metadata: { qux: string };
     }>();
   });
@@ -895,8 +896,8 @@ describe("$InferMessageProperties<TStructure, TRole>", () => {
     type AIProps = $InferMessageProperties<S, "ai">;
 
     expectTypeOf<AIProps>().toEqualTypeOf<{
-      response_metadata: ResponseMetadata | undefined;
-      usage_metadata: UsageMetadata | undefined;
+      response_metadata: ResponseMetadata;
+      usage_metadata: UsageMetadata;
       keep: boolean;
       nested: { a: number };
     }>();
@@ -929,8 +930,8 @@ describe("$InferMessageProperties<TStructure, TRole>", () => {
     type AIProps = $InferMessageProperties<M, "ai">;
 
     expectTypeOf<AIProps>().toEqualTypeOf<{
-      response_metadata: ResponseMetadata | undefined;
-      usage_metadata: UsageMetadata | undefined;
+      response_metadata: ResponseMetadata;
+      usage_metadata: UsageMetadata;
       foo: { bar: string; baz: number };
       baz: { qux: string };
     }>();
@@ -969,6 +970,10 @@ describe("$InferMessageProperty<TStructure, TRole, K>", () => {
 
 describe("$InferResponseMetadata<TStructure, TRole>", () => {
   // TODO(hntrl): implement
+  test("should return `ResponseMetadata | undefined` when using `<MessageStructure, 'ai'>`", async () => {
+    type AIResponseMetadata = $InferResponseMetadata<MessageStructure, "ai">;
+    expectTypeOf<AIResponseMetadata>().toEqualTypeOf<ResponseMetadata>();
+  });
 });
 
 describe("Message", () => {

libs/langchain-core/src/messages/tool.ts

@@ -190,7 +190,8 @@ export class ToolMessageChunk<
 
 export interface ToolCall<
   TName extends string = string,
-  TArgs extends Record<string, unknown> = Record<string, unknown>
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  TArgs extends Record<string, any> = Record<string, any>
 > {
   readonly type?: "tool_call";
   /**