fix(ai): wrap invalid tool call input in JSON object to prevent API rejection

.changeset/fix-invalid-tool-call-input-object.md

@@ -0,0 +1,5 @@
+---
+'ai': patch
+---
+
+fix(ai): wrap unparseable tool call input in a JSON object instead of storing the raw string, preventing API rejections (e.g. Amazon Bedrock) on the next step

packages/ai/src/generate-text/parse-tool-call.test.ts

@@ -345,6 +345,35 @@ describe('parseToolCall', () => {
     `);
   });
 
+  it('should wrap unparseable input in a JSON object so API stays valid', async () => {
+    // Regression: previously the raw string was stored as `input`, which causes
+    // providers like Amazon Bedrock to reject the next API call with
+    // "toolUse.input must be a JSON object".
+    const result = await parseToolCall({
+      toolCall: {
+        type: 'tool-call',
+        toolName: 'testTool',
+        toolCallId: '123',
+        input: 'this is not json',
+      },
+      tools: {
+        testTool: tool({
+          inputSchema: z.object({ param1: z.string() }),
+        }),
+      } as const,
+      repairToolCall: undefined,
+      messages: [],
+      instructions: undefined,
+    });
+
+    expect(result.invalid).toBe(true);
+    // input must be a plain object, not a raw string
+    expect(typeof result.input).toBe('object');
+    expect(result.input).toEqual({ rawInvalidInput: 'this is not json' });
+    // error is still surfaced so the model can react
+    expect(result.error).toBeDefined();
+  });
+
   describe('tool call repair', () => {
     it('should invoke repairTool when provided and use its result', async () => {
       const repairToolCall = vi.fn().mockResolvedValue({
@@ -471,7 +500,9 @@ describe('parseToolCall', () => {
           "dynamic": true,
           "error": [AI_InvalidToolInputError: Invalid input for tool testTool: AI_JSONParseError: JSON parsing failed: Text: invalid json.
         Error message: SyntaxError: Unexpected token 'i', "invalid json" is not valid JSON],
-          "input": "invalid json",
+          "input": {
+            "rawInvalidInput": "invalid json",
+          },
           "invalid": true,
           "providerExecuted": undefined,
           "providerMetadata": undefined,
@@ -510,7 +541,9 @@ describe('parseToolCall', () => {
         {
           "dynamic": true,
           "error": [AI_ToolCallRepairError: Error repairing tool call: Error: test error],
-          "input": "invalid json",
+          "input": {
+            "rawInvalidInput": "invalid json",
+          },
           "invalid": true,
           "providerExecuted": undefined,
           "providerMetadata": undefined,

packages/ai/src/generate-text/parse-tool-call.ts

@@ -92,9 +92,12 @@ export async function parseToolCall<TOOLS extends ToolSet>({
       });
     }
   } catch (error) {
-    // use parsed input when possible
+    // use parsed input when possible; fall back to a JSON object so the
+    // conversation history remains API-valid (e.g. Bedrock rejects raw strings)
     const parsedInput = await safeParseJSON({ text: toolCall.input });
-    const input = parsedInput.success ? parsedInput.value : toolCall.input;
+    const input = parsedInput.success
+      ? parsedInput.value
+      : { rawInvalidInput: toolCall.input };
     const tool = tools?.[toolCall.toolName];
 
     // TODO AI SDK 6: special invalid tool call parts