diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index 027efc0974b0..e86b70bdc067 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -22,6 +22,17 @@ export const OUTPUT_TOKEN_MAX = 32_000
 // branch that requests it stays in lockstep.
 const INCLUDE_ENCRYPTED_REASONING = ["reasoning.encrypted_content"] as const
 
+function responsesItemIDOptionKeys(model: Provider.Model, sdkOptionKey: string | undefined) {
+  if (model.api.npm === "@ai-sdk/github-copilot") return ["openai", "copilot"]
+  if (
+    sdkOptionKey &&
+    ["@ai-sdk/openai", "@ai-sdk/azure", "@ai-sdk/amazon-bedrock/mantle"].includes(model.api.npm)
+  ) {
+    return [sdkOptionKey]
+  }
+  return []
+}
+
 export function sanitizeSurrogates(content: string) {
   return content.replace(/[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]/g, "\uFFFD")
 }
@@ -460,16 +471,18 @@ export function message(msgs: ModelMessage[], model: Provider.Model, options: Re
   }
 
   // Strip Responses item IDs before serialization, following Codex and keeping signed request bodies immutable.
-  if (
-    options.store !== true &&
-    key &&
-    ["@ai-sdk/openai", "@ai-sdk/azure", "@ai-sdk/amazon-bedrock/mantle"].includes(model.api.npm)
-  ) {
+  const itemIDKeys = options.store !== true ? responsesItemIDOptionKeys(model, key) : []
+  if (itemIDKeys.length > 0) {
     msgs = mapProviderOptions(msgs, (options) => {
-      if (!options?.[key] || !("itemId" in options[key])) return options
-      const metadata = { ...options[key] }
-      delete metadata.itemId
-      return { ...options, [key]: metadata }
+      if (!options) return options
+      let result = options
+      for (const itemIDKey of itemIDKeys) {
+        if (!result[itemIDKey] || !("itemId" in result[itemIDKey])) continue
+        const metadata = { ...result[itemIDKey] }
+        delete metadata.itemId
+        result = { ...result, [itemIDKey]: metadata }
+      }
+      return result
     })
   }
 
diff --git a/packages/opencode/test/provider/transform.test.ts b/packages/opencode/test/provider/transform.test.ts
index c23a2aa9995c..128cbe67ff79 100644
--- a/packages/opencode/test/provider/transform.test.ts
+++ b/packages/opencode/test/provider/transform.test.ts
@@ -1928,6 +1928,58 @@ describe("ProviderTransform.message - strip openai metadata when store=false", (
     expect(result[0].content[1].providerOptions?.openai?.itemId).toBeUndefined()
   })
 
+  test("strips Copilot Responses itemId while preserving encrypted reasoning", () => {
+    const copilotModel = {
+      ...openaiModel,
+      id: "github-copilot/gpt-5.5",
+      providerID: "github-copilot",
+      api: {
+        id: "gpt-5.5",
+        url: "https://api.githubcopilot.com",
+        npm: "@ai-sdk/github-copilot",
+      },
+    }
+    const msgs = [
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "reasoning",
+            text: "thinking...",
+            providerOptions: {
+              openai: {
+                itemId: "rs_123",
+                reasoningEncryptedContent: "encrypted",
+              },
+              copilot: {
+                itemId: "rs_123",
+                reasoningEncryptedContent: "encrypted",
+              },
+            },
+          },
+          {
+            type: "text",
+            text: "Hello",
+            providerOptions: {
+              openai: {
+                itemId: "msg_456",
+              },
+            },
+          },
+        ],
+      },
+    ] as any[]
+
+    const result = ProviderTransform.message(msgs, copilotModel, { store: false }) as any[]
+
+    expect(result).toHaveLength(1)
+    expect(result[0].content[0].providerOptions?.openai?.itemId).toBeUndefined()
+    expect(result[0].content[0].providerOptions?.openai?.reasoningEncryptedContent).toBe("encrypted")
+    expect(result[0].content[0].providerOptions?.copilot?.itemId).toBeUndefined()
+    expect(result[0].content[0].providerOptions?.copilot?.reasoningEncryptedContent).toBe("encrypted")
+    expect(result[0].content[1].providerOptions?.openai?.itemId).toBeUndefined()
+  })
+
   test("uses the SDK package namespace rather than provider ID", () => {
     const zenModel = {
       ...openaiModel,