fix(vertex): add fallback for providerOptions key (#12403)

aayush-kapoor · web-flow · commit 051361b4f463 · 2026-02-12T12:30:22.000-05:00
## Background multi step tool calls fail because the `thoughtSignature` gets lost due to a key mismatch in providerOptions. if the `thoughtSignature` is passed under the google key, the vertex provider silently drops it. the api then rejects the request and we see the errors as observed in #12351 ## Summary fallback check to see if `vertex` key doesn't have a `thoughtSignature`, we check if it's passed within the google key ## Manual Verification verified via the repro code given in the original issue, which is resolved after the fix ## Checklist - [x] Tests have been added / updated (for bug fixes / features) - [ ] Documentation has been added / updated (for bug fixes / features) - [x] A _patch_ changeset for relevant packages has been added (for bug fixes / features - run `pnpm changeset` in the project root) - [x] I have reviewed this pull request (self-review) ## Related Issues fixes #12351
diff --git a/.changeset/clean-books-peel.md b/.changeset/clean-books-peel.md
@@ -0,0 +1,5 @@
+---
+'@ai-sdk/google': patch
+---
+
+fix(vertex): add fallback for providerOptions keyname
diff --git a/packages/google/src/convert-to-google-generative-ai-messages.test.ts b/packages/google/src/convert-to-google-generative-ai-messages.test.ts
@@ -85,6 +85,130 @@ describe('thought signatures', () => {
   });
 });
 
+describe('thought signatures with vertex providerOptionsName', () => {
+  it('should resolve thoughtSignature from google namespace when using vertex providerOptionsName', async () => {
+    const result = convertToGoogleGenerativeAIMessages(
+      [
+        {
+          role: 'assistant',
+          content: [
+            {
+              type: 'text',
+              text: 'Regular text',
+              providerOptions: { google: { thoughtSignature: 'sig1' } },
+            },
+            {
+              type: 'reasoning',
+              text: 'Reasoning text',
+              providerOptions: { google: { thoughtSignature: 'sig2' } },
+            },
+            {
+              type: 'tool-call',
+              toolCallId: 'call1',
+              toolName: 'getWeather',
+              input: { location: 'London' },
+              providerOptions: { google: { thoughtSignature: 'sig3' } },
+            },
+          ],
+        },
+      ],
+      { providerOptionsName: 'vertex' },
+    );
+
+    expect(result).toMatchInlineSnapshot(`
+      {
+        "contents": [
+          {
+            "parts": [
+              {
+                "text": "Regular text",
+                "thoughtSignature": "sig1",
+              },
+              {
+                "text": "Reasoning text",
+                "thought": true,
+                "thoughtSignature": "sig2",
+              },
+              {
+                "functionCall": {
+                  "args": {
+                    "location": "London",
+                  },
+                  "name": "getWeather",
+                },
+                "thoughtSignature": "sig3",
+              },
+            ],
+            "role": "model",
+          },
+        ],
+        "systemInstruction": undefined,
+      }
+    `);
+  });
+
+  it('should prefer vertex namespace over google namespace when both are present', async () => {
+    const result = convertToGoogleGenerativeAIMessages(
+      [
+        {
+          role: 'assistant',
+          content: [
+            {
+              type: 'tool-call',
+              toolCallId: 'call1',
+              toolName: 'getWeather',
+              input: { location: 'London' },
+              providerOptions: {
+                vertex: { thoughtSignature: 'vertex_sig' },
+                google: { thoughtSignature: 'google_sig' },
+              },
+            },
+          ],
+        },
+      ],
+      { providerOptionsName: 'vertex' },
+    );
+
+    expect(result.contents[0].parts[0]).toEqual({
+      functionCall: {
+        name: 'getWeather',
+        args: { location: 'London' },
+      },
+      thoughtSignature: 'vertex_sig',
+    });
+  });
+
+  it('should resolve thoughtSignature from vertex namespace directly', async () => {
+    const result = convertToGoogleGenerativeAIMessages(
+      [
+        {
+          role: 'assistant',
+          content: [
+            {
+              type: 'tool-call',
+              toolCallId: 'call1',
+              toolName: 'getWeather',
+              input: { location: 'London' },
+              providerOptions: {
+                vertex: { thoughtSignature: 'vertex_sig' },
+              },
+            },
+          ],
+        },
+      ],
+      { providerOptionsName: 'vertex' },
+    );
+
+    expect(result.contents[0].parts[0]).toEqual({
+      functionCall: {
+        name: 'getWeather',
+        args: { location: 'London' },
+      },
+      thoughtSignature: 'vertex_sig',
+    });
+  });
+});
+
 describe('Gemma model system instructions', () => {
   it('should prepend system instruction to first user message for Gemma models', async () => {
     const result = convertToGoogleGenerativeAIMessages(
diff --git a/packages/google/src/convert-to-google-generative-ai-messages.ts b/packages/google/src/convert-to-google-generative-ai-messages.ts
@@ -82,7 +82,11 @@ export function convertToGoogleGenerativeAIMessages(
           role: 'model',
           parts: content
             .map(part => {
-              const providerOpts = part.providerOptions?.[providerOptionsName];
+              const providerOpts =
+                part.providerOptions?.[providerOptionsName] ??
+                (providerOptionsName !== 'google'
+                  ? part.providerOptions?.google
+                  : undefined);
               const thoughtSignature =
                 providerOpts?.thoughtSignature != null
                   ? String(providerOpts.thoughtSignature)

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +---
 +'@ai-sdk/google': patch
 +---
++
 +fix(vertex): add fallback for providerOptions keyname