restore fast mode for nightly gpt models

Author: Marve10s

apps/server/src/provider/Layers/CodexProvider.test.ts

@@ -0,0 +1,62 @@
+import { describe, expect, it } from "vitest";
+import type * as CodexSchema from "effect-codex-app-server/schema";
+
+import { parseCodexModelListResponse } from "./CodexProvider.ts";
+
+function makeModel(
+  overrides: Partial<CodexSchema.V2ModelListResponse__Model> = {},
+): CodexSchema.V2ModelListResponse__Model {
+  return {
+    id: "gpt-5.4",
+    model: "gpt-5.4",
+    upgrade: null,
+    upgradeInfo: null,
+    availabilityNux: null,
+    displayName: "gpt-5.4",
+    description: "Latest frontier agentic coding model.",
+    hidden: false,
+    supportedReasoningEfforts: [
+      {
+        reasoningEffort: "medium",
+        description: "Balances speed and reasoning depth for everyday tasks",
+      },
+    ],
+    defaultReasoningEffort: "medium",
+    inputModalities: ["text", "image"],
+    supportsPersonality: true,
+    isDefault: true,
+    ...overrides,
+  };
+}
+
+describe("parseCodexModelListResponse", () => {
+  it("preserves fast mode for GPT-5 models when app-server omits additionalSpeedTiers", () => {
+    const [model] = parseCodexModelListResponse({
+      data: [makeModel()],
+      nextCursor: null,
+    });
+
+    expect(model).toBeDefined();
+    expect(model?.capabilities).toBeDefined();
+    expect(model?.capabilities?.optionDescriptors).toContainEqual(
+      expect.objectContaining({ id: "fastMode", type: "boolean" }),
+    );
+  });
+
+  it("honors an explicit empty additionalSpeedTiers list", () => {
+    const [model] = parseCodexModelListResponse({
+      data: [
+        makeModel({
+          additionalSpeedTiers: [],
+        }),
+      ],
+      nextCursor: null,
+    });
+
+    expect(model).toBeDefined();
+    expect(model?.capabilities).toBeDefined();
+    expect(model?.capabilities?.optionDescriptors).not.toContainEqual(
+      expect.objectContaining({ id: "fastMode" }),
+    );
+  });
+});

apps/server/src/provider/Layers/CodexProvider.ts

@@ -106,7 +106,9 @@ function mapCodexModelCapabilities(
         },
   );
   const defaultReasoning = reasoningOptions.find((option) => option.isDefault)?.id;
-  const supportsFastMode = (model.additionalSpeedTiers ?? []).includes("fast");
+  const supportsFastMode = globalThis.Array.isArray(model.additionalSpeedTiers)
+    ? model.additionalSpeedTiers.includes("fast")
+    : /^gpt-5(?:[.-]|$)/.test(model.model);
   return createModelCapabilities({
     optionDescriptors: [
       ...(reasoningOptions.length > 0
@@ -140,7 +142,7 @@ const toDisplayName = (model: CodexSchema.V2ModelListResponse__Model): string =>
     .replace(/-([a-z])/g, (_, c) => "-" + c.toUpperCase());
 };
 
-function parseCodexModelListResponse(
+export function parseCodexModelListResponse(
   response: CodexSchema.V2ModelListResponse,
 ): ReadonlyArray<ServerProviderModel> {
   return response.data.map((model) => ({