diff --git a/apps/web/src/modelSelection.test.ts b/apps/web/src/modelSelection.test.ts
index a35fb752b446..cf24a2a89651 100644
--- a/apps/web/src/modelSelection.test.ts
+++ b/apps/web/src/modelSelection.test.ts
@@ -195,6 +195,86 @@ describe("instance-scoped model selection", () => {
     ).not.toContain("openai/gpt-5.5");
   });
 
+  it("removes a custom model immediately when the provider snapshot is stale", () => {
+    const baseProvider = provider({
+      instanceId: "claudeAgent",
+      models: ["claude-sonnet-4-6"],
+    });
+    const staleProviders: ServerProvider[] = [
+      {
+        ...baseProvider,
+        models: [
+          ...baseProvider.models,
+          {
+            slug: "removed-preview-model",
+            name: "Removed Preview Model",
+            isCustom: true,
+            capabilities: {},
+          },
+        ],
+      },
+    ];
+    const settings: UnifiedSettings = {
+      ...settingsWithProviderInstances(),
+      providerInstances: {
+        ...settingsWithProviderInstances().providerInstances,
+        [ProviderInstanceId.make("claudeAgent")]: {
+          driver: ProviderDriverKind.make("claudeAgent"),
+          config: { customModels: [] },
+        },
+      },
+    };
+    const stock = deriveProviderInstanceEntries(staleProviders)[0]!;
+
+    expect(getAppModelOptionsForInstance(settings, stock).map((option) => option.slug)).toEqual([
+      "claude-sonnet-4-6",
+    ]);
+    expect(
+      resolveAppModelSelectionForInstance(
+        ProviderInstanceId.make("claudeAgent"),
+        settings,
+        staleProviders,
+        "removed-preview-model",
+      ),
+    ).toBe("claude-sonnet-4-6");
+  });
+
+  it("does not fall back to a stale custom model when no configured models remain", () => {
+    const baseProvider = provider({ instanceId: "claudeAgent" });
+    const staleProviders: ServerProvider[] = [
+      {
+        ...baseProvider,
+        models: [
+          {
+            slug: "removed-preview-model",
+            name: "Removed Preview Model",
+            isCustom: true,
+            capabilities: {},
+          },
+        ],
+      },
+    ];
+    const settings: UnifiedSettings = {
+      ...settingsWithProviderInstances(),
+      providerInstances: {
+        ...settingsWithProviderInstances().providerInstances,
+        [ProviderInstanceId.make("claudeAgent")]: {
+          driver: ProviderDriverKind.make("claudeAgent"),
+          config: { customModels: [] },
+        },
+      },
+    };
+
+    expect(
+      resolveAppModelSelectionForInstance(
+        ProviderInstanceId.make("claudeAgent"),
+        settings,
+        staleProviders,
+        "removed-preview-model",
+      ),
+    ).toBeNull();
+  });
+
   it("hides server models from the instance option list", () => {
     const providers = [
       provider({
diff --git a/apps/web/src/modelSelection.ts b/apps/web/src/modelSelection.ts
index 2763245299db..b50204e54e26 100644
--- a/apps/web/src/modelSelection.ts
+++ b/apps/web/src/modelSelection.ts
@@ -152,10 +152,16 @@ export function getAppModelOptions(
   provider: ProviderDriverKind,
   _selectedModel?: string | null,
 ): AppModelOption[] {
-  const options: AppModelOption[] = getProviderModels(providers, provider).map(toAppModelOption);
+  const liveModels = getProviderModels(providers, provider);
+  const options: AppModelOption[] = liveModels
+    .filter((model) => !model.isCustom)
+    .map(toAppModelOption);
+  const liveCustomModelsBySlug = new Map(
+    liveModels.filter((model) => model.isCustom).map((model) => [model.slug, model] as const),
+  );
   const seen = new Set(options.map((option) => option.slug));
   const builtInModelSlugs = new Set(
-    Arr.filterMap(getProviderModels(providers, provider), (model) =>
+    Arr.filterMap(liveModels, (model) =>
       model.isCustom ? Result.failVoid : Result.succeed(model.slug),
     ),
   );
@@ -172,11 +178,16 @@ export function getAppModelOptions(
     }
 
     seen.add(slug);
-    options.push({
-      slug,
-      name: slug,
-      isCustom: true,
-    });
+    const liveCustomModel = liveCustomModelsBySlug.get(slug);
+    options.push(
+      liveCustomModel
+        ? toAppModelOption(liveCustomModel)
+        : {
+            slug,
+            name: slug,
+            isCustom: true,
+          },
+    );
   }
 
   return applyInstanceModelPreferences(
@@ -200,7 +211,12 @@ export function getAppModelOptionsForInstance(
   settings: UnifiedSettings,
   entry: ProviderInstanceEntry,
 ): AppModelOption[] {
-  const options: AppModelOption[] = entry.models.map(toAppModelOption);
+  const options: AppModelOption[] = entry.models
+    .filter((model) => !model.isCustom)
+    .map(toAppModelOption);
+  const liveCustomModelsBySlug = new Map(
+    entry.models.filter((model) => model.isCustom).map((model) => [model.slug, model] as const),
+  );
   const seen = new Set(options.map((option) => option.slug));
   const builtInModelSlugs = new Set(
     Arr.filterMap(entry.models, (model) =>
@@ -215,7 +231,10 @@ export function getAppModelOptionsForInstance(
     }
 
     seen.add(slug);
-    options.push({ slug, name: slug, isCustom: true });
+    const liveCustomModel = liveCustomModelsBySlug.get(slug);
+    options.push(
+      liveCustomModel ? toAppModelOption(liveCustomModel) : { slug, name: slug, isCustom: true },
+    );
   }
 
   return applyInstanceModelPreferences(
@@ -253,8 +272,8 @@ export function resolveAppModelSelectionForInstance(
     resolveSelectableModel(entry.driverKind, selectedModel, options) ??
     options.find((option) => option.isDefault)?.slug ??
     options[0]?.slug ??
-    entry.models.find((model) => model.isDefault)?.slug ??
-    entry.models[0]?.slug ??
+    entry.models.find((model) => model.isDefault && !model.isCustom)?.slug ??
+    entry.models.find((model) => !model.isCustom)?.slug ??
     null
   );
 }