diff --git a/packages/openai/src/hosted-tools.test.ts b/packages/openai/src/hosted-tools.test.ts
index f9124e3..0b61688 100644
--- a/packages/openai/src/hosted-tools.test.ts
+++ b/packages/openai/src/hosted-tools.test.ts
@@ -281,7 +281,15 @@ describe('hosted tool input mapping', () => {
             type: 'function_approval_response',
             id: 'mcpr_1',
             approved: true,
-            functionCall: { type: 'function_call', callId: 'mcpr_1', name: 'delete', arguments: '{}' },
+            // `approvalResponse()` copies the request's call verbatim, so a hosted decision
+            // carries the `server_label` that marks it as the provider's to settle.
+            functionCall: {
+              type: 'function_call',
+              callId: 'mcpr_1',
+              name: 'delete',
+              arguments: '{}',
+              additionalProperties: { server_label: 'docs' },
+            },
           },
         ],
       },
diff --git a/packages/openai/src/to-openai.ts b/packages/openai/src/to-openai.ts
index 1287973..98e9566 100644
--- a/packages/openai/src/to-openai.ts
+++ b/packages/openai/src/to-openai.ts
@@ -12,6 +12,7 @@ import type {
 import {
   ChatClientError,
   isFunctionTool,
+  isHostedApproval,
   MESSAGE_SOURCE_KEY,
   resolveResponseFormat,
   topLevelMediaType,
@@ -566,6 +567,11 @@ export function toResponsesInput(
           break;
         }
         case 'function_approval_request': {
+          // A local tool's approval is resolved in-process: the provider never issued a matching
+          // approval item, so serializing one would orphan it on the wire.
+          if (!isHostedApproval(content)) {
+            break;
+          }
           // The framework models a hosted MCP approval as an approval request; the Responses API
           // models it as an output item that has to be replayed to keep the pairing.
           items.push({
@@ -578,6 +584,11 @@ export function toResponsesInput(
           break;
         }
         case 'function_approval_response': {
+          // Only a hosted decision has a matching approval request on the provider; a local
+          // decision replayed as `mcp_approval_response` would reference an id the API never saw.
+          if (!isHostedApproval(content)) {
+            break;
+          }
           items.push({
             type: 'mcp_approval_response',
             approval_request_id: content.id,
diff --git a/packages/openai/src/to-openai.wire-fallbacks.test.ts b/packages/openai/src/to-openai.wire-fallbacks.test.ts
index 26637c2..1fc4784 100644
--- a/packages/openai/src/to-openai.wire-fallbacks.test.ts
+++ b/packages/openai/src/to-openai.wire-fallbacks.test.ts
@@ -282,6 +282,64 @@ describe('stateless replay validation', () => {
   });
 });
 
+describe('approval serialization boundaries', () => {
+  const localCall = {
+    type: 'function_call',
+    callId: 'local_1',
+    name: 'ask_user',
+    arguments: '{}',
+  } as const;
+  const localApprovalMessages: Message[] = [
+    {
+      role: 'assistant',
+      contents: [{ type: 'function_approval_request', id: 'local_approval_1', functionCall: localCall }],
+    },
+    {
+      role: 'user',
+      contents: [
+        {
+          type: 'function_approval_response',
+          id: 'local_approval_1',
+          approved: true,
+          functionCall: localCall,
+        },
+      ],
+    },
+  ];
+
+  it.each([
+    ['stateless', false],
+    ['storage', true],
+  ])('drops local approval controls from the input (%s)', (_mode, serviceStorage) => {
+    // A local tool's approval is resolved in-process; the provider never issued a matching
+    // MCP approval request, so serializing either half would create an orphaned item.
+    expect(toResponsesInput(localApprovalMessages, { serviceStorage })).toEqual([]);
+  });
+
+  it('keeps a hosted approval pair on the wire', () => {
+    const hostedCall = {
+      type: 'function_call',
+      callId: 'mcpr_1',
+      name: 'sensitive_action',
+      arguments: '{}',
+      additionalProperties: { server_label: 'hosted_server' },
+    } as const;
+    const items = toResponsesInput([
+      {
+        role: 'assistant',
+        contents: [{ type: 'function_approval_request', id: 'mcpr_1', functionCall: hostedCall }],
+      },
+      {
+        role: 'user',
+        contents: [
+          { type: 'function_approval_response', id: 'mcpr_1', approved: true, functionCall: hostedCall },
+        ],
+      },
+    ]);
+    expect(items.map((item) => item.type)).toEqual(['mcp_approval_request', 'mcp_approval_response']);
+  });
+});
+
 describe('tool declarations and choices', () => {
   it('passes a non-function tool without a spec through as itself', () => {
     const opaque = { type: 'web_search' } as unknown as Tool;