diff --git a/apps/server/src/provider/ProviderInstanceRegistry.test.ts b/apps/server/src/provider/ProviderInstanceRegistry.test.ts
index 1872eeb64ec2a..571240c1174df 100644
--- a/apps/server/src/provider/ProviderInstanceRegistry.test.ts
+++ b/apps/server/src/provider/ProviderInstanceRegistry.test.ts
@@ -23,6 +23,8 @@ import * as HostProcess from "@t3tools/shared/HostProcess";
 import * as DateTime from "effect/DateTime";
 import * as Deferred from "effect/Deferred";
 import * as Effect from "effect/Effect";
+import * as Exit from "effect/Exit";
+import * as Scope from "effect/Scope";
 import * as Fiber from "effect/Fiber";
 import * as FileSystem from "effect/FileSystem";
 import * as Layer from "effect/Layer";
@@ -41,6 +43,7 @@ import * as ModelManifest from "./ModelManifest.ts";
 import * as ResetCreditCoordinator from "./resetCreditCoordinator.ts";
 import * as ProviderEventLoggers from "@t3tools/provider-core/server/ProviderEventLoggers";
 import { makeProviderInstanceRegistry } from "./ProviderInstanceRegistry.ts";
+import { ProviderDriverError } from "./Errors.ts";
 import * as ProviderOrchestrationAdapterInfrastructure from "./ProviderOrchestrationAdapterInfrastructure.ts";
 import * as PortScanner from "../preview/PortScanner.ts";
 import * as ProviderHostLive from "./ProviderHostLive.ts";
@@ -202,6 +205,81 @@ describe("ProviderInstanceRegistry — multi-instance codex slice", () => {
     Layer.provideMerge(layerBase),
   );
 
+  it.effect.each(["replacement", "removal", "creation failure"] as const)(
+    "detaches retired provider scopes after repeated %s",
+    (scenario) =>
+      Effect.gen(function* () {
+        const parent = yield* Scope.make();
+        const fileSystem = yield* FileSystem.FileSystem;
+        const homePath = yield* fileSystem.makeTempDirectoryScoped();
+        let creates = 0;
+        let closes = 0;
+        const driver: typeof CodexDriver = {
+          ...CodexDriver,
+          create: Effect.fn("ProviderInstanceRegistry.test.create")(function* (
+            input: Parameters<typeof CodexDriver.create>[0],
+          ) {
+            creates++;
+            yield* Effect.addFinalizer(() =>
+              Effect.sync(() => {
+                closes++;
+              }),
+            );
+            if (input.config.binaryPath === "creation-failure") {
+              return yield* new ProviderDriverError({
+                driver: CodexDriver.driverKind,
+                instanceId: input.instanceId,
+                detail: "fixture creation failed",
+              });
+            }
+            return yield* CodexDriver.create(input);
+          }),
+        };
+        const siblingId = ProviderInstanceId.make("sibling");
+        const retiredId = ProviderInstanceId.make("retired");
+        const entry = {
+          driver: CodexDriver.driverKind,
+          enabled: false,
+          config: makeCodexConfig({ homePath }),
+        };
+        yield* Effect.gen(function* () {
+          const { registry, mutator } = yield* makeProviderInstanceRegistry({
+            drivers: [driver],
+            configMap: { [siblingId]: entry },
+          });
+          const sibling = yield* registry.getInstance(siblingId);
+          const finalizerCount = () => {
+            const state = parent.state;
+            return state._tag === "Open" ? (state.finalizers?.size ?? 1) : 0;
+          };
+          const baseline = finalizerCount();
+          for (let index = 0; index < 20; index++) {
+            yield* mutator.reconcile({
+              [siblingId]: entry,
+              [retiredId]: {
+                ...entry,
+                config: makeCodexConfig({
+                  homePath,
+                  binaryPath: scenario === "creation failure" ? "creation-failure" : "unused-codex",
+                  customModels: [`revision-${index}`],
+                }),
+              },
+            });
+            if (scenario === "removal") yield* mutator.reconcile({ [siblingId]: entry });
+          }
+          yield* mutator.reconcile({ [siblingId]: entry });
+          expect(yield* registry.getInstance(siblingId)).toBe(sibling);
+          expect(closes).toBe(creates - 1);
+          expect(parent.state._tag).toBe("Open");
+          expect(finalizerCount()).toBe(baseline);
+        }).pipe(
+          Effect.provideService(Scope.Scope, parent),
+          Effect.ensuring(Scope.close(parent, Exit.void)),
+        );
+        expect(closes).toBe(creates);
+      }).pipe(Effect.provide(layerTest)),
+  );
+
   it.effect.each(["replacement", "removal"] as const)(
     "hides retired instances during reconcile (%s)",
     (scenario) =>
diff --git a/apps/server/src/provider/ProviderInstanceRegistry.ts b/apps/server/src/provider/ProviderInstanceRegistry.ts
index 37f0aa55e09c5..466ace232eb33 100644
--- a/apps/server/src/provider/ProviderInstanceRegistry.ts
+++ b/apps/server/src/provider/ProviderInstanceRegistry.ts
@@ -194,8 +194,7 @@ const buildEntry = Effect.fn("ProviderInstanceRegistry.buildEntry")(function* <R
     };
   }
 
-  const childScope = yield* Scope.make();
-  yield* Scope.addFinalizer(parentScope, Scope.close(childScope, Exit.void).pipe(Effect.ignore));
+  const childScope = yield* Scope.fork(parentScope);
 
   const createResult = yield* driver
     .create({