diff --git a/.changeset/ollama-parallel-tool-call-ids.md b/.changeset/ollama-parallel-tool-call-ids.md
new file mode 100644
index 0000000000..a326d44012
--- /dev/null
+++ b/.changeset/ollama-parallel-tool-call-ids.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/ai-ollama': patch
+---
+
+Keep parallel calls to the same tool apart when Ollama sends no tool-call id. The fallback id was `<name>_<Date.now()>`, so two calls to one tool in the same millisecond shared an id and the second call was dropped. The fallback id now also carries the call's index.
diff --git a/packages/ai-ollama/src/adapters/text.ts b/packages/ai-ollama/src/adapters/text.ts
index 67a456aba6..2b16553bb8 100644
--- a/packages/ai-ollama/src/adapters/text.ts
+++ b/packages/ai-ollama/src/adapters/text.ts
@@ -332,8 +332,10 @@ export class OllamaTextAdapter<TModel extends string> extends BaseTextAdapter<
           id: string
           function: { index: number }
         }
+        // Ollama sends no id: tell parallel calls to the same tool apart by index
         const toolCallId =
-          actualToolCall.id || `${actualToolCall.function.name}_${Date.now()}`
+          actualToolCall.id ||
+          `${actualToolCall.function.name}_${Date.now()}_${actualToolCall.function.index ?? toolCallsEmitted.size}`
         const events: Array<AdapterYieldChunk> = []
 
         // Emit TOOL_CALL_START if not already emitted for this tool call
diff --git a/packages/ai-ollama/tests/text-adapter.test.ts b/packages/ai-ollama/tests/text-adapter.test.ts
index 6ed3ff47c1..ade4888e63 100644
--- a/packages/ai-ollama/tests/text-adapter.test.ts
+++ b/packages/ai-ollama/tests/text-adapter.test.ts
@@ -280,6 +280,51 @@ describe('OllamaTextAdapter.chatStream (tool calls)', () => {
     expect(startChunk!.toolCallId).toMatch(/^search_\d+/)
   })
 
+  it('keeps two parallel calls to the same tool apart when Ollama omits ids', async () => {
+    vi.spyOn(Date, 'now').mockReturnValue(1_700_000_000_000)
+    try {
+      chatMock.mockResolvedValueOnce(
+        asyncIterable([
+          {
+            message: {
+              role: 'assistant',
+              content: '',
+              tool_calls: [
+                { function: { name: 'search', arguments: { q: 'cats' } } },
+                { function: { name: 'search', arguments: { q: 'dogs' } } },
+              ],
+            },
+            done: true,
+            done_reason: 'stop',
+          },
+        ]),
+      )
+
+      const chunks = await collectStream(
+        createOllamaChat('llama3.2').chatStream({
+          threadId: 'thread-1',
+          logger: testLogger,
+          model: 'llama3.2',
+          messages: [{ role: 'user', content: 'find cats and dogs' }],
+          tools: [searchTool],
+        }),
+      )
+
+      const starts = chunks.filter((c) => c.type === 'TOOL_CALL_START') as Array<{
+        toolCallId: string
+      }>
+      const ends = chunks.filter((c) => c.type === 'TOOL_CALL_END') as Array<{
+        toolCallId: string
+        args: string
+      }>
+      expect(starts).toHaveLength(2)
+      expect(new Set(starts.map((s) => s.toolCallId)).size).toBe(2)
+      expect(ends.map((e) => e.args)).toEqual(['{"q":"cats"}', '{"q":"dogs"}'])
+    } finally {
+      vi.restoreAllMocks()
+    }
+  })
+
   async function toolCallEnd(args: unknown) {
     chatMock.mockResolvedValueOnce(
       asyncIterable([