fix(app): use agent configured variant (#12993)

packages/app/src/context/model-variant.test.ts

@@ -0,0 +1,66 @@
+import { describe, expect, test } from "bun:test"
+import { cycleModelVariant, getConfiguredAgentVariant, resolveModelVariant } from "./model-variant"
+
+describe("model variant", () => {
+  test("resolves configured agent variant when model matches", () => {
+    const value = getConfiguredAgentVariant({
+      agent: {
+        model: { providerID: "openai", modelID: "gpt-5.2" },
+        variant: "xhigh",
+      },
+      model: {
+        providerID: "openai",
+        modelID: "gpt-5.2",
+        variants: { low: {}, high: {}, xhigh: {} },
+      },
+    })
+
+    expect(value).toBe("xhigh")
+  })
+
+  test("ignores configured variant when model does not match", () => {
+    const value = getConfiguredAgentVariant({
+      agent: {
+        model: { providerID: "openai", modelID: "gpt-5.2" },
+        variant: "xhigh",
+      },
+      model: {
+        providerID: "anthropic",
+        modelID: "claude-sonnet-4",
+        variants: { low: {}, high: {}, xhigh: {} },
+      },
+    })
+
+    expect(value).toBeUndefined()
+  })
+
+  test("prefers selected variant over configured variant", () => {
+    const value = resolveModelVariant({
+      variants: ["low", "high", "xhigh"],
+      selected: "high",
+      configured: "xhigh",
+    })
+
+    expect(value).toBe("high")
+  })
+
+  test("cycles from configured variant to next", () => {
+    const value = cycleModelVariant({
+      variants: ["low", "high", "xhigh"],
+      selected: undefined,
+      configured: "high",
+    })
+
+    expect(value).toBe("xhigh")
+  })
+
+  test("wraps from configured last variant to first", () => {
+    const value = cycleModelVariant({
+      variants: ["low", "high", "xhigh"],
+      selected: undefined,
+      configured: "xhigh",
+    })
+
+    expect(value).toBe("low")
+  })
+})