From 29a898ecb1efdcd14905ccc7e6e61bd9bba92649 Mon Sep 17 00:00:00 2001
From: mihneanob <mihneanob@gmail.com>
Date: Sat, 25 Jul 2026 00:04:31 +0300
Subject: [PATCH 1/2] Preserve Opus fallback on older Claude Code

---
 packages/shared/src/model.test.ts | 21 +++++++++++++++++++++
 packages/shared/src/model.ts      | 25 ++++++++++++++++++++++++-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/packages/shared/src/model.test.ts b/packages/shared/src/model.test.ts
index b67c4574473..642019ea89d 100644
--- a/packages/shared/src/model.test.ts
+++ b/packages/shared/src/model.test.ts
@@ -12,6 +12,7 @@ import {
   getProviderOptionStringSelectionValue,
   normalizeCustomModelSlug,
   normalizeModelSlug,
+  resolveSelectableModel,
 } from "./model.ts";
 
 const codexCaps: ModelCapabilities = createModelCapabilities({
@@ -154,4 +155,24 @@ describe("model slug normalization", () => {
     expect(normalizeModelSlug("opus", claude)).toBe("claude-opus-5");
     expect(normalizeCustomModelSlug(" opus ")).toBe("opus");
   });
+
+  it("resolves the bare Opus alias to the newest available Claude model", () => {
+    const claude = ProviderDriverKind.make("claudeAgent");
+    const currentModels = [
+      { slug: "claude-opus-5", name: "Claude Opus 5" },
+      { slug: "claude-opus-4-8", name: "Claude Opus 4.8" },
+    ];
+    const olderModels = [
+      { slug: "claude-opus-custom", name: "Custom Opus" },
+      { slug: "claude-opus-4-6", name: "Claude Opus 4.6" },
+      { slug: "claude-sonnet-5", name: "Claude Sonnet 5" },
+      { slug: "claude-opus-4-8", name: "Claude Opus 4.8" },
+    ];
+    const customModels = [{ slug: "claude-opus-custom", name: "Custom Opus" }];
+
+    expect(resolveSelectableModel(claude, "opus", currentModels)).toBe("claude-opus-5");
+    expect(resolveSelectableModel(claude, "opus", olderModels)).toBe("claude-opus-4-8");
+    expect(resolveSelectableModel(claude, "opus-5", olderModels)).toBeNull();
+    expect(resolveSelectableModel(claude, "opus", customModels)).toBeNull();
+  });
 });
diff --git a/packages/shared/src/model.ts b/packages/shared/src/model.ts
index bdc0c0cc8ef..6ac7b39a240 100644
--- a/packages/shared/src/model.ts
+++ b/packages/shared/src/model.ts
@@ -12,6 +12,14 @@ import {
 
 const DEFAULT_PROVIDER_DRIVER_KIND = ProviderDriverKind.make("codex");
 
+const CLAUDE_OPUS_FALLBACK_MODELS = [
+  "claude-opus-5",
+  "claude-opus-4-8",
+  "claude-opus-4-7",
+  "claude-opus-4-6",
+  "claude-opus-4-5",
+] as const;
+
 export interface SelectableModelOption {
   slug: string;
   name: string;
@@ -287,7 +295,22 @@ export function resolveSelectableModel(
   }
 
   const resolved = options.find((option) => option.slug === normalized);
-  return resolved ? resolved.slug : null;
+  if (resolved) {
+    return resolved.slug;
+  }
+
+  // The bare Claude `opus` alias tracks the newest Opus model, but newer
+  // models can be omitted from the live catalog when the installed Claude
+  // Code version is too old. In that case, preserve the model family instead
+  // of falling through to the provider's unrelated default model. Use a fixed
+  // built-in priority so user-defined picker ordering and custom model slugs
+  // cannot change which fallback is selected.
+  if (provider === ProviderDriverKind.make("claudeAgent") && trimmed === "opus") {
+    const availableSlugs = new Set(options.map((option) => option.slug));
+    return CLAUDE_OPUS_FALLBACK_MODELS.find((slug) => availableSlugs.has(slug)) ?? null;
+  }
+
+  return null;
 }
 
 function resolveModelSlug(model: string | null | undefined, provider: ProviderDriverKind): string {

From de4da06b92b3165cbcc6a748fb8de07fd9715541 Mon Sep 17 00:00:00 2001
From: mihneanob <mihneanob@gmail.com>
Date: Sat, 25 Jul 2026 11:18:09 +0300
Subject: [PATCH 2/2] Add regression coverage for the bare Opus fallback

---
 apps/web/src/modelSelection.test.ts | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/apps/web/src/modelSelection.test.ts b/apps/web/src/modelSelection.test.ts
index e8fc8a244d0..f47e7944691 100644
--- a/apps/web/src/modelSelection.test.ts
+++ b/apps/web/src/modelSelection.test.ts
@@ -4,6 +4,7 @@ import { describe, expect, it } from "vite-plus/test";
 import { deriveProviderInstanceEntries } from "./providerInstances";
 import {
   getAppModelOptionsForInstance,
+  resolveAppModelSelection,
   resolveAppModelSelectionForInstance,
   resolveAppModelSelectionState,
 } from "./modelSelection";
@@ -303,3 +304,28 @@ describe("instance-scoped model selection", () => {
     });
   });
 });
+
+describe("provider-scoped model selection", () => {
+  it("keeps the bare Opus alias in the Opus family when Opus 5 is gated out", () => {
+    // Mirrors Claude Code 2.1.169-2.1.218, where Opus 5 is filtered out of the
+    // served catalog. The provider default is the first built-in that survives
+    // filtering (Fable 5), so without the family fallback `opus` resolves to a
+    // different model family while Opus 4.8 is still available.
+    const providers = [
+      provider({
+        provider: ProviderDriverKind.make("claudeAgent"),
+        instanceId: "claudeAgent",
+        models: ["claude-fable-5", "claude-opus-4-8", "claude-sonnet-5"],
+      }),
+    ];
+
+    expect(
+      resolveAppModelSelection(
+        ProviderDriverKind.make("claudeAgent"),
+        settingsWithProviderInstances(),
+        providers,
+        "opus",
+      ),
+    ).toBe("claude-opus-4-8");
+  });
+});