Preserve provider instance fallback ids

Author: lintowe

apps/web/src/components/ChatView.tsx

@@ -1294,6 +1294,10 @@ export default function ChatView(props: ChatViewProps) {
       selectedProvider,
       lockedProvider,
       lockedContinuationGroupKey,
+      fallbackInstanceIds: [
+        activeThread?.modelSelection.instanceId,
+        activeProject?.defaultModelSelection?.instanceId,
+      ],
     });
     const selectedEntry = providerInstanceEntries.find(
       (entry) => entry.instanceId === selectedInstanceId,

apps/web/src/components/chat/ChatComposer.tsx

@@ -635,6 +635,10 @@ export const ChatComposer = memo(
         selectedProvider,
         lockedProvider,
         lockedContinuationGroupKey,
+        fallbackInstanceIds: [
+          activeThreadModelSelection?.instanceId,
+          activeProjectDefaultModelSelection?.instanceId,
+        ],
       });
     }, [
       activeProjectDefaultModelSelection?.instanceId,

apps/web/src/providerInstances.test.ts

@@ -149,4 +149,17 @@ describe("resolveSelectedProviderInstanceId", () => {
       }),
     ).toBe("codex");
   });
+
+  it("keeps persisted model selections as the last fallback before codex", () => {
+    const persistedInstanceId = ProviderInstanceId.make("codex_saved");
+
+    expect(
+      resolveSelectedProviderInstanceId({
+        entries: [],
+        candidates: [null],
+        selectedProvider: ProviderDriverKind.make("codex"),
+        fallbackInstanceIds: [persistedInstanceId],
+      }),
+    ).toBe(persistedInstanceId);
+  });
 });

apps/web/src/providerInstances.ts

@@ -190,6 +190,7 @@ export function resolveSelectedProviderInstanceId(input: {
   selectedProvider: ProviderDriverKind;
   lockedProvider?: ProviderDriverKind | null | undefined;
   lockedContinuationGroupKey?: string | null | undefined;
+  fallbackInstanceIds?: ReadonlyArray<ProviderInstanceId | null | undefined>;
 }): ProviderInstanceId {
   const lockedProvider = input.lockedProvider ?? null;
   const lockedContinuationGroupKey = input.lockedContinuationGroupKey ?? null;
@@ -220,7 +221,14 @@ export function resolveSelectedProviderInstanceId(input: {
   if (byKind) return byKind.instanceId;
 
   const anyEnabled = input.entries.find((entry) => entry.enabled);
-  return anyEnabled?.instanceId ?? input.entries[0]?.instanceId ?? ProviderInstanceId.make("codex");
+  const fallbackSelection = input.fallbackInstanceIds?.find((instanceId) => instanceId != null);
+  return (
+    anyEnabled?.instanceId ??
+    input.entries[0]?.instanceId ??
+    (fallbackSelection
+      ? ProviderInstanceId.make(fallbackSelection)
+      : ProviderInstanceId.make("codex"))
+  );
 }
 
 /**