diff --git a/libs/providers/langchain-openai/src/azure/chat_models/common.ts b/libs/providers/langchain-openai/src/azure/chat_models/common.ts
index 4cf133c343dd..ee6dcde7502d 100644
--- a/libs/providers/langchain-openai/src/azure/chat_models/common.ts
+++ b/libs/providers/langchain-openai/src/azure/chat_models/common.ts
@@ -1,4 +1,4 @@
-import { AzureOpenAI as AzureOpenAIClient } from "openai";
+import { AzureOpenAI as AzureOpenAIClient, type ClientOptions } from "openai";
 import { getEnv, getEnvironmentVariable } from "@langchain/core/utils/env";
 import type { Serialized } from "@langchain/core/load/serializable";
 import { ChatOpenAICallOptions } from "../../chat_models/index.js";
@@ -56,8 +56,10 @@ export function _constructAzureFields(
 ) {
   this.azureOpenAIApiKey =
     fields?.azureOpenAIApiKey ??
-    fields?.openAIApiKey ??
-    fields?.apiKey ??
+    (typeof fields?.openAIApiKey === "string"
+      ? fields?.openAIApiKey
+      : undefined) ??
+    (typeof fields?.apiKey === "string" ? fields?.apiKey : undefined) ??
     getEnvironmentVariable("AZURE_OPENAI_API_KEY");
 
   this.azureOpenAIApiInstanceName =
@@ -106,8 +108,9 @@ export function _getAzureClientOptions(
 
     const endpoint = getEndpoint(openAIEndpointConfig);
 
-    const params = {
-      ...this.clientConfig,
+    const { apiKey: existingApiKey, ...clientConfigRest } = this.clientConfig;
+    const params: Omit<ClientOptions, "apiKey"> & { apiKey?: string } = {
+      ...clientConfigRest,
       baseURL: endpoint,
       timeout: this.timeout,
       maxRetries: 0,
diff --git a/libs/providers/langchain-openai/src/azure/embeddings.ts b/libs/providers/langchain-openai/src/azure/embeddings.ts
index 70a6ffbc104c..1b807f01883e 100644
--- a/libs/providers/langchain-openai/src/azure/embeddings.ts
+++ b/libs/providers/langchain-openai/src/azure/embeddings.ts
@@ -41,7 +41,7 @@ export class AzureOpenAIEmbeddings extends OpenAIEmbeddings {
     this.batchSize = fields?.batchSize ?? 1;
     this.azureOpenAIApiKey =
       fields?.azureOpenAIApiKey ??
-      fields?.apiKey ??
+      (typeof fields?.apiKey === "string" ? fields?.apiKey : undefined) ??
       getEnvironmentVariable("AZURE_OPENAI_API_KEY");
 
     this.azureOpenAIApiVersion =
@@ -81,8 +81,9 @@ export class AzureOpenAIEmbeddings extends OpenAIEmbeddings {
 
       const endpoint = getEndpoint(openAIEndpointConfig);
 
-      const params = {
-        ...this.clientConfig,
+      const { apiKey: existingApiKey, ...clientConfigRest } = this.clientConfig;
+      const params: Omit<ClientOptions, "apiKey"> & { apiKey?: string } = {
+        ...clientConfigRest,
         baseURL: endpoint,
         timeout: this.timeout,
         maxRetries: 0,
diff --git a/libs/providers/langchain-openai/src/azure/llms.ts b/libs/providers/langchain-openai/src/azure/llms.ts
index c22f1fbc9ce2..a7167d23569e 100644
--- a/libs/providers/langchain-openai/src/azure/llms.ts
+++ b/libs/providers/langchain-openai/src/azure/llms.ts
@@ -70,8 +70,10 @@ export class AzureOpenAI extends OpenAI {
 
     this.azureOpenAIApiKey =
       fields?.azureOpenAIApiKey ??
-      fields?.openAIApiKey ??
-      fields?.apiKey ??
+      (typeof fields?.openAIApiKey === "string"
+        ? fields?.openAIApiKey
+        : undefined) ??
+      (typeof fields?.apiKey === "string" ? fields?.apiKey : undefined) ??
       getEnvironmentVariable("AZURE_OPENAI_API_KEY");
 
     this.azureOpenAIApiInstanceName =
@@ -113,8 +115,9 @@ export class AzureOpenAI extends OpenAI {
 
       const endpoint = getEndpoint(openAIEndpointConfig);
 
-      const params = {
-        ...this.clientConfig,
+      const { apiKey: existingApiKey, ...clientConfigRest } = this.clientConfig;
+      const params: Omit<ClientOptions, "apiKey"> & { apiKey?: string } = {
+        ...clientConfigRest,
         baseURL: endpoint,
         timeout: this.timeout,
         maxRetries: 0,
diff --git a/libs/providers/langchain-openai/src/chat_models/base.ts b/libs/providers/langchain-openai/src/chat_models/base.ts
index 594a0b53f735..c2a1e5ef455b 100644
--- a/libs/providers/langchain-openai/src/chat_models/base.ts
+++ b/libs/providers/langchain-openai/src/chat_models/base.ts
@@ -39,6 +39,7 @@ import {
   type ChatOpenAIResponseFormat,
   ResponseFormatConfiguration,
   OpenAIVerbosityParam,
+  type OpenAIApiKey,
 } from "../types.js";
 import { type OpenAIEndpointConfig, getEndpoint } from "../utils/azure.js";
 import {
@@ -245,7 +246,7 @@ export abstract class BaseChatOpenAI<
 
   topLogprobs?: number;
 
-  apiKey?: string;
+  apiKey?: OpenAIApiKey;
 
   organization?: string;
 
@@ -420,7 +421,8 @@ export abstract class BaseChatOpenAI<
     super(fields ?? {});
 
     const configApiKey =
-      typeof fields?.configuration?.apiKey === "string"
+      typeof fields?.configuration?.apiKey === "string" ||
+      typeof fields?.configuration?.apiKey === "function"
         ? fields?.configuration?.apiKey
         : undefined;
     this.apiKey =
@@ -615,7 +617,7 @@ export abstract class BaseChatOpenAI<
           : this._convertChatOpenAIToolToCompletionsTool(tool, { strict })
       ),
       ...kwargs,
-    });
+    } as Partial<CallOptions>);
   }
 
   override async stream(input: BaseLanguageModelInput, options?: CallOptions) {
@@ -894,7 +896,7 @@ export abstract class BaseChatOpenAI<
           kwargs: { method: "json_mode" },
           schema: { title: name ?? "extract", ...asJsonSchema },
         },
-      });
+      } as Partial<CallOptions>);
     } else if (method === "jsonSchema") {
       const openaiJsonSchemaParams = {
         name: name ?? "extract",
@@ -917,7 +919,7 @@ export abstract class BaseChatOpenAI<
             ...asJsonSchema,
           },
         },
-      });
+      } as Partial<CallOptions>);
       if (isInteropZodSchema(schema)) {
         const altParser = StructuredOutputParser.fromZodSchema(schema);
         outputParser = RunnableLambda.from<AIMessageChunk, RunOutput>(
@@ -960,7 +962,7 @@ export abstract class BaseChatOpenAI<
           },
           // Do not pass `strict` argument to OpenAI if `config.strict` is undefined
           ...(config?.strict !== undefined ? { strict: config.strict } : {}),
-        });
+        } as Partial<CallOptions>);
         outputParser = new JsonOutputKeyToolsParser({
           returnSingle: true,
           keyName: functionName,
@@ -1004,7 +1006,7 @@ export abstract class BaseChatOpenAI<
           },
           // Do not pass `strict` argument to OpenAI if `config.strict` is undefined
           ...(config?.strict !== undefined ? { strict: config.strict } : {}),
-        });
+        } as Partial<CallOptions>);
         outputParser = new JsonOutputKeyToolsParser<RunOutput>({
           returnSingle: true,
           keyName: functionName,
diff --git a/libs/providers/langchain-openai/src/embeddings.ts b/libs/providers/langchain-openai/src/embeddings.ts
index 6394f4076aaf..550b8eef8f37 100644
--- a/libs/providers/langchain-openai/src/embeddings.ts
+++ b/libs/providers/langchain-openai/src/embeddings.ts
@@ -2,6 +2,7 @@ import { type ClientOptions, OpenAI as OpenAIClient } from "openai";
 import { getEnvironmentVariable } from "@langchain/core/utils/env";
 import { Embeddings, type EmbeddingsParams } from "@langchain/core/embeddings";
 import { chunkArray } from "@langchain/core/utils/chunk_array";
+import type { OpenAIApiKey } from "./types.js";
 import { getEndpoint, OpenAIEndpointConfig } from "./utils/azure.js";
 import { wrapOpenAIClientError } from "./utils/client.js";
 
@@ -102,6 +103,8 @@ export class OpenAIEmbeddings<TOutput = number[]>
 
   protected clientConfig: ClientOptions;
 
+  protected apiKey?: OpenAIApiKey;
+
   constructor(
     fields?: Partial<OpenAIEmbeddingsParams> & {
       verbose?: boolean;
@@ -109,9 +112,9 @@ export class OpenAIEmbeddings<TOutput = number[]>
        * The OpenAI API key to use.
        * Alias for `apiKey`.
        */
-      openAIApiKey?: string;
+      openAIApiKey?: OpenAIApiKey;
       /** The OpenAI API key to use. */
-      apiKey?: string;
+      apiKey?: OpenAIApiKey;
       configuration?: ClientOptions;
     }
   ) {
diff --git a/libs/providers/langchain-openai/src/llms.ts b/libs/providers/langchain-openai/src/llms.ts
index b918a2908b38..34f31bd34c48 100644
--- a/libs/providers/langchain-openai/src/llms.ts
+++ b/libs/providers/langchain-openai/src/llms.ts
@@ -10,6 +10,7 @@ import {
 } from "@langchain/core/language_models/llms";
 import { chunkArray } from "@langchain/core/utils/chunk_array";
 import type {
+  OpenAIApiKey,
   OpenAICallOptions,
   OpenAICoreRequestOptions,
   OpenAIInput,
@@ -121,9 +122,9 @@ export class OpenAI<CallOptions extends OpenAICallOptions = OpenAICallOptions>
 
   streaming = false;
 
-  openAIApiKey?: string;
+  openAIApiKey?: OpenAIApiKey;
 
-  apiKey?: string;
+  apiKey?: OpenAIApiKey;
 
   organization?: string;
 
diff --git a/libs/providers/langchain-openai/src/types.ts b/libs/providers/langchain-openai/src/types.ts
index 47b9ad576ce6..22e041cb30a4 100644
--- a/libs/providers/langchain-openai/src/types.ts
+++ b/libs/providers/langchain-openai/src/types.ts
@@ -1,4 +1,4 @@
-import type { OpenAI as OpenAIClient } from "openai";
+import type { OpenAI as OpenAIClient, ClientOptions } from "openai";
 import type {
   ResponseFormatText,
   ResponseFormatJSONObject,
@@ -24,6 +24,8 @@ export type OpenAIChatModelId =
 
 export type OpenAIVerbosityParam = "low" | "medium" | "high" | null;
 
+export type OpenAIApiKey = ClientOptions["apiKey"];
+
 export declare interface OpenAIBaseInput {
   /** Sampling temperature to use */
   temperature: number;
@@ -103,12 +105,12 @@ export declare interface OpenAIBaseInput {
    * `OPENAI_API_KEY` environment variable.
    * Alias for `apiKey`
    */
-  openAIApiKey?: string;
+  openAIApiKey?: OpenAIApiKey;
   /**
    * API key to use when making requests to OpenAI. Defaults to the value of
    * `OPENAI_API_KEY` environment variable.
    */
-  apiKey?: string;
+  apiKey?: OpenAIApiKey;
 
   /**
    * The verbosity of the model's response.
@@ -285,7 +287,6 @@ export interface AzureOpenAIInput {
 export interface AzureOpenAIChatInput
   extends OpenAIChatInput,
     AzureOpenAIInput {
-  openAIApiKey?: string;
   openAIApiVersion?: string;
   openAIBasePath?: string;
   deploymentName?: string;