fix(core): Support streamed reasoning from custom AI endpoints (no-changelog) (#37875)

packages/@n8n/agents/src/runtime/__tests__/model-factory-stream.test.ts

@@ -0,0 +1,70 @@
+import { streamText } from 'ai';
+
+import { createModel } from '../model/model-factory';
+
+describe('createModel streaming', () => {
+	it('streams array-based reasoning and text from a custom endpoint', async () => {
+		const deltas = [
+			...['Let me ', 'think.'].map((text) => ({
+				content: [{ type: 'thinking', thinking: [{ type: 'text', text }], closed: true }],
+				tool_calls: [],
+			})),
+			{ content: [{ type: 'text', text: 'The answer ' }] },
+			{ content: 'is 391.' },
+		];
+		const responseChunks = [
+			...deltas.map((delta) => ({ choices: [{ index: 0, delta, finish_reason: null }] })),
+			{ choices: [{ index: 0, delta: {}, finish_reason: 'stop' }] },
+			{
+				choices: [],
+				usage: { prompt_tokens: 120, completion_tokens: 30, total_tokens: 150 },
+			},
+		];
+		const body = responseChunks
+			.map((chunk) => {
+				const payload = {
+					id: 'completion-1',
+					object: 'chat.completion.chunk',
+					created: 1,
+					model: 'zai-glm-5-2',
+					...chunk,
+				};
+				return `data: ${JSON.stringify(payload)}\n\n`;
+			})
+			.join('');
+		const fetch = vi.fn<typeof globalThis.fetch>().mockResolvedValue(
+			new Response(`${body}data: [DONE]\n\n`, {
+				headers: { 'content-type': 'text/event-stream' },
+			}),
+		);
+		const model = createModel(
+			{
+				id: 'custom/zai-glm-5-2',
+				url: 'https://model.example.com/v1',
+				apiKey: 'test-key',
+			},
+			fetch,
+		);
+		const result = streamText({ model, prompt: 'Hello', maxRetries: 0 });
+		const chunks = [];
+		for await (const chunk of result.fullStream) chunks.push(chunk);
+
+		expect(fetch).toHaveBeenCalledOnce();
+		expect(fetch.mock.calls[0][0]).toBe('https://model.example.com/v1/chat/completions');
+		const requestBody = fetch.mock.calls[0][1]?.body;
+		expect(requestBody).not.toContain('"stream_options"');
+		expect(chunks.filter((chunk) => chunk.type === 'error')).toEqual([]);
+		expect(chunks.filter((chunk) => chunk.type.startsWith('reasoning-'))).toEqual([
+			{ type: 'reasoning-start', id: 'reasoning-0' },
+			{ type: 'reasoning-delta', id: 'reasoning-0', text: 'Let me ' },
+			{ type: 'reasoning-delta', id: 'reasoning-0', text: 'think.' },
+			{ type: 'reasoning-end', id: 'reasoning-0' },
+		]);
+		await expect(result.text).resolves.toBe('The answer is 391.');
+		await expect(result.totalUsage).resolves.toMatchObject({
+			inputTokens: 120,
+			outputTokens: 30,
+			totalTokens: 150,
+		});
+	});
+});

pnpm-lock.yaml

@@ -207,8 +207,8 @@ catalogs:
       specifier: ^4.0.20
       version: 4.0.20
     '@ai-sdk/openai-compatible':
-      specifier: ^3.0.14
-      version: 3.0.28
+      specifier: ^3.0.44
+      version: 3.0.44
     '@ai-sdk/otel':
       specifier: ^1.0.66
       version: 1.0.74
@@ -1209,7 +1209,7 @@ importers:
         version: 4.0.20([email protected])
       '@ai-sdk/openai-compatible':
         specifier: 'catalog:'
-        version: 3.0.28([email protected])
+        version: 3.0.44([email protected])
       '@ai-sdk/otel':
         specifier: 'catalog:'
         version: 1.0.74([email protected])
@@ -4723,7 +4723,7 @@ importers:
         version: 4.0.39([email protected])
       '@ai-sdk/openai-compatible':
         specifier: 'catalog:'
-        version: 3.0.28([email protected])
+        version: 3.0.44([email protected])
       '@apidevtools/json-schema-ref-parser':
         specifier: 12.0.2
         version: 12.0.2
@@ -8772,6 +8772,12 @@ packages:
     peerDependencies:
       zod: 3.25.76
 
+  '@ai-sdk/[email protected]':
+    resolution: {integrity: sha512-pK7mERd/aIJVtyQCe/nV3G3iEJCY1no8GHDOGbgpNC+petjSfsxj+ni0Q8WVVehTUiY9B04F3Xvir+icBgORCg==}
+    engines: {node: '>=22'}
+    peerDependencies:
+      zod: 3.25.76
+
   '@ai-sdk/[email protected]':
     resolution: {integrity: sha512-/Hu+btLIO2zuYqCp//vBBAGdM/BeN4gds+NWrlv7Y9WrcTXwnEEwh6P3QZIWh2Tt1I1lswuDIpAJ4t/c/rws3Q==}
     engines: {node: '>=22'}
@@ -8806,6 +8812,16 @@ packages:
     peerDependencies:
       zod: 3.25.76
 
+  '@ai-sdk/[email protected]':
+    resolution: {integrity: sha512-MFXBn6XDyf37PNQAge/HTatPJE8Vmg/g/w4WPtjSV53jq8FKAzoaN5+43hsdQa9bqgN+/13jxug9ChvsG+godQ==}
+    engines: {node: '>=22'}
+    peerDependencies:
+      zod: 3.25.76
+
+  '@ai-sdk/[email protected]':
+    resolution: {integrity: sha512-fX2ENAc7iDpZ+Wp4+Rk06Usn/Ys7dI9uAkGv0jlF6XVrW13NkRWx5Ou+U6lIM2E1fTLkCs16GGrUAaVvroag7A==}
+    engines: {node: '>=22'}
+
   '@ai-sdk/[email protected]':
     resolution: {integrity: sha512-e0CpNWJUY7OxAFAnCZkw+ri9QOHWwTs1tXP42782KFGCU07qt8NiXCrCVowyCB5dP2r5/Uls+g2oPd8kOJn9dw==}
     engines: {node: '>=22'}
@@ -25311,6 +25327,12 @@ snapshots:
       '@ai-sdk/provider-utils': 5.0.25([email protected])
       zod: 3.25.76
 
+  '@ai-sdk/[email protected]([email protected])':
+    dependencies:
+      '@ai-sdk/provider': 4.0.10
+      '@ai-sdk/provider-utils': 5.0.36([email protected])
+      zod: 3.25.76
+
   '@ai-sdk/[email protected]([email protected])':
     dependencies:
       '@ai-sdk/provider': 4.0.3
@@ -25360,6 +25382,19 @@ snapshots:
       undici: 7.29.1
       zod: 3.25.76
 
+  '@ai-sdk/[email protected]([email protected])':
+    dependencies:
+      '@ai-sdk/provider': 4.0.10
+      '@standard-schema/spec': 1.1.0
+      '@workflow/serde': 4.1.0
+      eventsource-parser: 3.0.8
+      undici: 7.29.1
+      zod: 3.25.76
+
+  '@ai-sdk/[email protected]':
+    dependencies:
+      json-schema: 0.4.0
+
   '@ai-sdk/[email protected]':
     dependencies:
       json-schema: 0.4.0

pnpm-workspace.yaml

@@ -65,7 +65,7 @@ catalog:
   '@ai-sdk/mistral': ^4.0.14
   '@ai-sdk/moonshotai': ^3.0.35
   '@ai-sdk/openai': ^4.0.20
-  '@ai-sdk/openai-compatible': ^3.0.14
+  '@ai-sdk/openai-compatible': ^3.0.44
   '@ai-sdk/otel': ^1.0.66
   '@ai-sdk/provider-utils': ^5.0.27
   '@ai-sdk/xai': ^4.0.18