add copilot gpt-5.4 xhigh support

packages/opencode/src/provider/transform.ts

@@ -440,7 +440,9 @@ export namespace ProviderTransform {
         const copilotEfforts = iife(() => {
           if (id.includes("5.1-codex-max") || id.includes("5.2") || id.includes("5.3"))
             return [...WIDELY_SUPPORTED_EFFORTS, "xhigh"]
-          return WIDELY_SUPPORTED_EFFORTS
+          const arr = [...WIDELY_SUPPORTED_EFFORTS]
+          if (id.includes("gpt-5") && model.release_date >= "2025-12-04") arr.push("xhigh")
+          return arr
         })
         return Object.fromEntries(
           copilotEfforts.map((effort) => [

packages/opencode/test/provider/transform.test.ts

@@ -2002,6 +2002,35 @@ describe("ProviderTransform.variants", () => {
       const result = ProviderTransform.variants(model)
       expect(Object.keys(result)).toEqual(["low", "medium", "high", "xhigh"])
     })
+
+    test("gpt-5.3-codex includes xhigh", () => {
+      const model = createMockModel({
+        id: "gpt-5.3-codex",
+        providerID: "github-copilot",
+        api: {
+          id: "gpt-5.3-codex",
+          url: "https://api.githubcopilot.com",
+          npm: "@ai-sdk/github-copilot",
+        },
+      })
+      const result = ProviderTransform.variants(model)
+      expect(Object.keys(result)).toEqual(["low", "medium", "high", "xhigh"])
+    })
+
+    test("gpt-5.4 includes xhigh", () => {
+      const model = createMockModel({
+        id: "gpt-5.4",
+        release_date: "2026-03-05",
+        providerID: "github-copilot",
+        api: {
+          id: "gpt-5.4",
+          url: "https://api.githubcopilot.com",
+          npm: "@ai-sdk/github-copilot",
+        },
+      })
+      const result = ProviderTransform.variants(model)
+      expect(Object.keys(result)).toEqual(["low", "medium", "high", "xhigh"])
+    })
   })
 
   describe("@ai-sdk/cerebras", () => {