diff --git a/packages/core/src/integrations/openai/OpenAIEmbeddingGenerator.ts b/packages/core/src/integrations/openai/OpenAIEmbeddingGenerator.ts
index 6989ec521..db0330f2f 100644
--- a/packages/core/src/integrations/openai/OpenAIEmbeddingGenerator.ts
+++ b/packages/core/src/integrations/openai/OpenAIEmbeddingGenerator.ts
@@ -15,6 +15,7 @@ export class OpenAIEmbeddingGenerator implements EmbeddingGenerator {
     const api = new OpenAI({
       apiKey: this.#settings.openAiKey,
       organization: this.#settings.openAiOrganization,
+      baseURL: this.#settings.openAiEndpoint,
       dangerouslyAllowBrowser: true, // It's fine in Rivet
     });
 
diff --git a/packages/core/src/model/nodes/ChatNodeBase.ts b/packages/core/src/model/nodes/ChatNodeBase.ts
index 06df5157c..80647e77d 100644
--- a/packages/core/src/model/nodes/ChatNodeBase.ts
+++ b/packages/core/src/model/nodes/ChatNodeBase.ts
@@ -22,7 +22,6 @@ import type { Inputs, Outputs } from '../GraphProcessor.js';
 import { cleanHeaders, getInputOrData } from '../../utils/inputs.js';
 import type { InternalProcessContext } from '../ProcessContext.js';
 import { chatMessageToOpenAIChatCompletionMessage } from '../../utils/chatMessageToOpenAIChatCompletionMessage.js';
-import { DEFAULT_CHAT_ENDPOINT } from '../../utils/defaults.js';
 import type { TokenizerCallInfo } from '../../integrations/Tokenizer.js';
 import { addWarning } from '../../utils/outputs.js';
 import retry from 'p-retry';
@@ -1008,7 +1007,8 @@ export const ChatNodeBase = {
     const isMultiResponse = data.useNumberOfChoicesInput || (data.numberOfChoices ?? 1) > 1;
 
     // Resolve to final endpoint if configured in ProcessContext
-    const configuredEndpoint = endpoint || context.settings.openAiEndpoint || DEFAULT_CHAT_ENDPOINT;
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const configuredEndpoint = endpoint || `${baseUrl}/chat/completions`;
     const resolvedEndpointAndHeaders = context.getChatNodeEndpoint
       ? await context.getChatNodeEndpoint(configuredEndpoint, finalModel)
       : {
diff --git a/packages/core/src/plugins/openai/nodes/AttachAssistantFileNode.ts b/packages/core/src/plugins/openai/nodes/AttachAssistantFileNode.ts
index 7cac1e67d..0ba319fa7 100644
--- a/packages/core/src/plugins/openai/nodes/AttachAssistantFileNode.ts
+++ b/packages/core/src/plugins/openai/nodes/AttachAssistantFileNode.ts
@@ -120,7 +120,8 @@ export const AttachAssistantFileNodeImpl: PluginNodeImpl<AttachAssistantFileNode
       throw new Error('OpenAI key is not set.');
     }
 
-    const url = `https://api.openai.com/v1/assistants/${assistantId}/files`;
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const url = `${baseUrl}/assistants/${assistantId}/files`;
 
     const response = await fetch(url, {
       method: 'POST',
diff --git a/packages/core/src/plugins/openai/nodes/CreateAssistantNode.ts b/packages/core/src/plugins/openai/nodes/CreateAssistantNode.ts
index 159886f2b..b1f053032 100644
--- a/packages/core/src/plugins/openai/nodes/CreateAssistantNode.ts
+++ b/packages/core/src/plugins/openai/nodes/CreateAssistantNode.ts
@@ -323,9 +323,10 @@ export const CreateAssistantNodeImpl: PluginNodeImpl<CreateAssistantNode> = {
       throw new Error('OpenAI key is not set.');
     }
 
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
     const url = assistantId.trim()
-      ? `https://api.openai.com/v1/assistants/${assistantId}`
-      : 'https://api.openai.com/v1/assistants';
+      ? `${baseUrl}/assistants/${assistantId}`
+      : `${baseUrl}/assistants`;
 
     const response = await fetch(url, {
       method: 'POST',
diff --git a/packages/core/src/plugins/openai/nodes/CreateThreadMessageNode.ts b/packages/core/src/plugins/openai/nodes/CreateThreadMessageNode.ts
index 6985be9d8..2eb495062 100644
--- a/packages/core/src/plugins/openai/nodes/CreateThreadMessageNode.ts
+++ b/packages/core/src/plugins/openai/nodes/CreateThreadMessageNode.ts
@@ -194,7 +194,8 @@ export const CreateThreadMessageNodeImpl: PluginNodeImpl<CreateThreadMessageNode
       throw new Error('OpenAI key is not set.');
     }
 
-    const url = `https://api.openai.com/v1/threads/${threadId}/messages`;
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const url = `${baseUrl}/threads/${threadId}/messages`;
 
     const response = await fetch(url, {
       method: 'POST',
diff --git a/packages/core/src/plugins/openai/nodes/CreateThreadNode.ts b/packages/core/src/plugins/openai/nodes/CreateThreadNode.ts
index 85ada3deb..02302c4df 100644
--- a/packages/core/src/plugins/openai/nodes/CreateThreadNode.ts
+++ b/packages/core/src/plugins/openai/nodes/CreateThreadNode.ts
@@ -161,7 +161,8 @@ export const CreateThreadNodeImpl: PluginNodeImpl<CreateThreadNode> = {
       return message as CreateMessageBody;
     });
 
-    const url = threadId.trim() ? `https://api.openai.com/v1/threads/${threadId}` : 'https://api.openai.com/v1/threads';
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const url = threadId.trim() ? `${baseUrl}/threads/${threadId}` : `${baseUrl}/threads`;
 
     if (threadId && messages.length > 0) {
       throw new Error('Cannot provide messages when modifying an existing thread.');
diff --git a/packages/core/src/plugins/openai/nodes/DeleteAssistantNode.ts b/packages/core/src/plugins/openai/nodes/DeleteAssistantNode.ts
index 24074d23f..ca9c45967 100644
--- a/packages/core/src/plugins/openai/nodes/DeleteAssistantNode.ts
+++ b/packages/core/src/plugins/openai/nodes/DeleteAssistantNode.ts
@@ -99,7 +99,8 @@ export const DeleteAssistantNodeImpl: PluginNodeImpl<DeleteAssistantNode> = {
       throw new Error('OpenAI key is not set.');
     }
 
-    const response = await fetch(`https://api.openai.com/v1/assistants/${assistantId}`, {
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const response = await fetch(`${baseUrl}/assistants/${assistantId}`, {
       method: 'DELETE',
       headers: {
         'OpenAI-Beta': 'assistants=v1',
diff --git a/packages/core/src/plugins/openai/nodes/DeleteThreadNode.ts b/packages/core/src/plugins/openai/nodes/DeleteThreadNode.ts
index 8640854ad..a118dc383 100644
--- a/packages/core/src/plugins/openai/nodes/DeleteThreadNode.ts
+++ b/packages/core/src/plugins/openai/nodes/DeleteThreadNode.ts
@@ -90,7 +90,8 @@ export const DeleteThreadNodeImpl: PluginNodeImpl<DeleteThreadNode> = {
       throw new Error('OpenAI key is not set.');
     }
 
-    const response = await fetch(`https://api.openai.com/v1/threads/${threadId}`, {
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const response = await fetch(`${baseUrl}/threads/${threadId}`, {
       method: 'DELETE',
       headers: {
         'OpenAI-Beta': 'assistants=v1',
diff --git a/packages/core/src/plugins/openai/nodes/GetAssistantNode.ts b/packages/core/src/plugins/openai/nodes/GetAssistantNode.ts
index d9b96cbff..9c728f94d 100644
--- a/packages/core/src/plugins/openai/nodes/GetAssistantNode.ts
+++ b/packages/core/src/plugins/openai/nodes/GetAssistantNode.ts
@@ -106,7 +106,8 @@ export const GetAssistantNodeImpl: PluginNodeImpl<GetAssistantNode> = {
       throw new Error('OpenAI key is not set.');
     }
 
-    const response = await fetch(`https://api.openai.com/v1/assistants/${assistantId}`, {
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const response = await fetch(`${baseUrl}/assistants/${assistantId}`, {
       method: 'GET',
       headers: {
         'OpenAI-Beta': 'assistants=v1',
diff --git a/packages/core/src/plugins/openai/nodes/GetOpenAIFileNode.ts b/packages/core/src/plugins/openai/nodes/GetOpenAIFileNode.ts
index df3dda2cc..990f061fe 100644
--- a/packages/core/src/plugins/openai/nodes/GetOpenAIFileNode.ts
+++ b/packages/core/src/plugins/openai/nodes/GetOpenAIFileNode.ts
@@ -96,7 +96,8 @@ export const GetOpenAIFileNodeImpl: PluginNodeImpl<GetOpenAIFileNode> = {
       throw new Error('OpenAI key is not set.');
     }
 
-    const url = `https://api.openai.com/v1/files/${fileId}`;
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const url = `${baseUrl}/files/${fileId}`;
 
     const response = await fetch(url, {
       method: 'GET',
diff --git a/packages/core/src/plugins/openai/nodes/GetThreadNode.ts b/packages/core/src/plugins/openai/nodes/GetThreadNode.ts
index a4edc3246..ffe3b877a 100644
--- a/packages/core/src/plugins/openai/nodes/GetThreadNode.ts
+++ b/packages/core/src/plugins/openai/nodes/GetThreadNode.ts
@@ -104,7 +104,8 @@ export const GetThreadNodeImpl: PluginNodeImpl<GetThreadNode> = {
       throw new Error('OpenAI key is not set.');
     }
 
-    const response = await fetch(`https://api.openai.com/v1/threads/${threadId}`, {
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const response = await fetch(`${baseUrl}/threads/${threadId}`, {
       method: 'GET',
       headers: {
         'OpenAI-Beta': 'assistants=v1',
diff --git a/packages/core/src/plugins/openai/nodes/ListAssistantsNode.ts b/packages/core/src/plugins/openai/nodes/ListAssistantsNode.ts
index f14a868b5..18ba7c39e 100644
--- a/packages/core/src/plugins/openai/nodes/ListAssistantsNode.ts
+++ b/packages/core/src/plugins/openai/nodes/ListAssistantsNode.ts
@@ -212,7 +212,8 @@ ${
     }
 
     const query = new URLSearchParams(queryParams);
-    const url = `https://api.openai.com/v1/assistants?${query.toString()}`;
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const url = `${baseUrl}/assistants?${query.toString()}`;
 
     const response = await fetch(url, {
       method: 'GET',
diff --git a/packages/core/src/plugins/openai/nodes/ListOpenAIFilesNode.ts b/packages/core/src/plugins/openai/nodes/ListOpenAIFilesNode.ts
index 308ff17a2..a0ddb6d5a 100644
--- a/packages/core/src/plugins/openai/nodes/ListOpenAIFilesNode.ts
+++ b/packages/core/src/plugins/openai/nodes/ListOpenAIFilesNode.ts
@@ -98,7 +98,8 @@ export const ListOpenAIFilesNodeImpl: PluginNodeImpl<ListOpenAIFilesNode> = {
       throw new Error('OpenAI key is not set.');
     }
 
-    const url = `https://api.openai.com/v1/files?purpose=${purpose}`;
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const url = `${baseUrl}/files?purpose=${purpose}`;
 
     const response = await fetch(url, {
       method: 'GET',
diff --git a/packages/core/src/plugins/openai/nodes/ListThreadMessagesNode.ts b/packages/core/src/plugins/openai/nodes/ListThreadMessagesNode.ts
index 5dd3b0aad..281ff3737 100644
--- a/packages/core/src/plugins/openai/nodes/ListThreadMessagesNode.ts
+++ b/packages/core/src/plugins/openai/nodes/ListThreadMessagesNode.ts
@@ -238,7 +238,8 @@ ${
     }
 
     const query = new URLSearchParams(queryParams);
-    const url = `https://api.openai.com/v1/threads/${threadId}/messages?${query.toString()}`;
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const url = `${baseUrl}/threads/${threadId}/messages?${query.toString()}`;
 
     const response = await fetch(url, {
       method: 'GET',
diff --git a/packages/core/src/plugins/openai/nodes/RunThreadNode.ts b/packages/core/src/plugins/openai/nodes/RunThreadNode.ts
index b3e06cc61..d747f23c3 100644
--- a/packages/core/src/plugins/openai/nodes/RunThreadNode.ts
+++ b/packages/core/src/plugins/openai/nodes/RunThreadNode.ts
@@ -380,6 +380,7 @@ export const RunThreadNodeImpl: PluginNodeImpl<RunThreadNode> = {
   async process(data, inputData, context) {
     const threadId = getInputOrData(data, inputData, 'threadId');
     const assistantId = getInputOrData(data, inputData, 'assistantId');
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
 
     let metadata = data.metadata.reduce(
       (acc, { key, value }) => {
@@ -448,7 +449,7 @@ export const RunThreadNodeImpl: PluginNodeImpl<RunThreadNode> = {
         ? arrayizeDataValue(unwrapDataValue(messagesInput)).map((message) => coerceToThreadMessage(message))
         : [];
 
-      response = await fetch('https://api.openai.com/v1/threads/runs', {
+      response = await fetch(`${baseUrl}/threads/runs`, {
         method: 'POST',
         headers: {
           'OpenAI-Beta': 'assistants=v1',
@@ -465,7 +466,7 @@ export const RunThreadNodeImpl: PluginNodeImpl<RunThreadNode> = {
         }),
       });
     } else {
-      response = await fetch(`https://api.openai.com/v1/threads/${threadId}/runs`, {
+      response = await fetch(`${baseUrl}/threads/${threadId}/runs`, {
         method: 'POST',
         headers: {
           'OpenAI-Beta': 'assistants=v1',
@@ -509,7 +510,7 @@ export const RunThreadNodeImpl: PluginNodeImpl<RunThreadNode> = {
           order: 'desc',
         } satisfies OpenAIPaginationQuery);
 
-        const url = `https://api.openai.com/v1/threads/${body.thread_id}/runs/${body.id}/steps?${query.toString()}`;
+        const url = `${baseUrl}/threads/${body.thread_id}/runs/${body.id}/steps?${query.toString()}`;
         const response = await fetch(url, {
           method: 'GET',
           headers: {
@@ -547,7 +548,7 @@ export const RunThreadNodeImpl: PluginNodeImpl<RunThreadNode> = {
           const messageId = step.step_details.message_creation.message_id;
 
           const messageResponse = await fetch(
-            `https://api.openai.com/v1/threads/${body.thread_id}/messages/${messageId}`,
+            `${baseUrl}/threads/${body.thread_id}/messages/${messageId}`,
             {
               method: 'GET',
               headers: {
@@ -598,7 +599,7 @@ export const RunThreadNodeImpl: PluginNodeImpl<RunThreadNode> = {
         latestBody.status === 'queued' ||
         latestBody.status === 'requires_action'
       ) {
-        const runResponse = await fetch(`https://api.openai.com/v1/threads/${body.thread_id}/runs/${body.id}`, {
+        const runResponse = await fetch(`${baseUrl}/threads/${body.thread_id}/runs/${body.id}`, {
           method: 'GET',
           headers: {
             'OpenAI-Beta': 'assistants=v1',
@@ -681,7 +682,7 @@ export const RunThreadNodeImpl: PluginNodeImpl<RunThreadNode> = {
           }));
 
           const submitResponse = await fetch(
-            `https://api.openai.com/v1/threads/${body.thread_id}/runs/${body.id}/submit_tool_outputs`,
+            `${baseUrl}/threads/${body.thread_id}/runs/${body.id}/submit_tool_outputs`,
             {
               method: 'POST',
               headers: {
@@ -720,7 +721,7 @@ export const RunThreadNodeImpl: PluginNodeImpl<RunThreadNode> = {
       });
 
       const listStepsResponsePromise = await fetch(
-        `https://api.openai.com/v1/threads/${body.thread_id}/runs/${body.id}/steps?${listStepsQuery.toString()}`,
+        `${baseUrl}/threads/${body.thread_id}/runs/${body.id}/steps?${listStepsQuery.toString()}`,
         {
           method: 'GET',
           headers: {
@@ -738,7 +739,7 @@ export const RunThreadNodeImpl: PluginNodeImpl<RunThreadNode> = {
       } satisfies OpenAIPaginationQuery);
 
       const messagesResponsePromise = await fetch(
-        `https://api.openai.com/v1/threads/${body.thread_id}/messages?${getMessagesQuery.toString()}`,
+        `${baseUrl}/threads/${body.thread_id}/messages?${getMessagesQuery.toString()}`,
         {
           method: 'GET',
           headers: {
diff --git a/packages/core/src/plugins/openai/nodes/UploadFileNode.ts b/packages/core/src/plugins/openai/nodes/UploadFileNode.ts
index 22abdbb2e..6c579e6e5 100644
--- a/packages/core/src/plugins/openai/nodes/UploadFileNode.ts
+++ b/packages/core/src/plugins/openai/nodes/UploadFileNode.ts
@@ -124,7 +124,8 @@ export const UploadFileNodeImpl: PluginNodeImpl<UploadFileNode> = {
     formData.append('purpose', purpose);
     formData.append('file', file);
 
-    const response = await fetch('https://api.openai.com/v1/files', {
+    const baseUrl = context.settings.openAiEndpoint ?? 'https://api.openai.com/v1';
+    const response = await fetch(`${baseUrl}/files`, {
       method: 'POST',
       headers: {
         Authorization: `Bearer ${context.settings.openAiKey}`,
diff --git a/packages/core/src/utils/defaults.ts b/packages/core/src/utils/defaults.ts
index 7ffc76f88..d73a3bce1 100644
--- a/packages/core/src/utils/defaults.ts
+++ b/packages/core/src/utils/defaults.ts
@@ -1,3 +1 @@
-export const DEFAULT_CHAT_ENDPOINT = 'https://api.openai.com/v1/chat/completions';
-
 export const DEFAULT_CHAT_NODE_TIMEOUT = 30_000;