fix(core): harden model selection edges (#30987)

packages/core/test/catalog.test.ts

@@ -281,6 +281,34 @@ describe("CatalogV2", () => {
     }),
   )
 
+  it.effect("ignores a configured default on a disabled provider", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const disabledProvider = ProviderV2.ID.make("disabled")
+      const enabledProvider = ProviderV2.ID.make("enabled")
+      const disabledModel = ModelV2.ID.make("configured")
+      const fallbackModel = ModelV2.ID.make("fallback")
+      const transform = yield* catalog.transform()
+
+      yield* transform((catalog) => {
+        catalog.provider.update(disabledProvider, (provider) => {
+          provider.enabled = false
+        })
+        catalog.model.update(disabledProvider, disabledModel, () => {})
+        catalog.provider.update(enabledProvider, (provider) => {
+          provider.enabled = { via: "custom", data: {} }
+        })
+        catalog.model.update(enabledProvider, fallbackModel, () => {})
+        catalog.model.default.set(disabledProvider, disabledModel)
+      })
+
+      expect(Option.getOrUndefined(yield* catalog.model.default())).toMatchObject({
+        providerID: enabledProvider,
+        id: fallbackModel,
+      })
+    }),
+  )
+
   it.effect("small model prefers small keyword candidates before cost scoring", () =>
     Effect.gen(function* () {
       const catalog = yield* Catalog.Service

packages/core/test/session-create.test.ts

@@ -356,12 +356,23 @@ describe("SessionV2.create", () => {
       expect(
         Array.from(yield* session.events({ sessionID: created.id }).pipe(Stream.take(1), Stream.runCollect)),
       ).toMatchObject([{ event: { type: "session.next.model.switched", data: { model } } }])
+    }),
+  )
+
+  it.effect("persists repeated switches as distinct durable Session events", () =>
+    Effect.gen(function* () {
+      const session = yield* SessionV2.Service
+      const created = yield* session.create({ location })
+      const model = ModelV2.Ref.make({ id: ModelV2.ID.make("sonnet"), providerID: ProviderV2.ID.anthropic })
 
       yield* session.switchModel({ sessionID: created.id, model })
+      yield* session.switchModel({ sessionID: created.id, model })
+
       const { db } = yield* Database.Service
       expect(
         yield* db.select().from(EventTable).where(eq(EventTable.aggregate_id, created.id)).all().pipe(Effect.orDie),
-      ).toHaveLength(2)
+      ).toHaveLength(3)
+      expect(yield* session.get(created.id)).toMatchObject({ model })
     }),
   )