diff --git a/invokeai/app/services/object_serializer/object_serializer_disk.py b/invokeai/app/services/object_serializer/object_serializer_disk.py
index bbd3f785507..611f6c41026 100644
--- a/invokeai/app/services/object_serializer/object_serializer_disk.py
+++ b/invokeai/app/services/object_serializer/object_serializer_disk.py
@@ -65,7 +65,7 @@ def save(self, obj: T) -> str:
 
     def delete(self, name: str) -> None:
         file_path = self._get_path(name)
-        file_path.unlink()
+        file_path.unlink(missing_ok=True)
 
     @property
     def _obj_class_name(self) -> str:
diff --git a/invokeai/app/services/object_serializer/object_serializer_forward_cache.py b/invokeai/app/services/object_serializer/object_serializer_forward_cache.py
index ae00173e422..2bd044c5b2d 100644
--- a/invokeai/app/services/object_serializer/object_serializer_forward_cache.py
+++ b/invokeai/app/services/object_serializer/object_serializer_forward_cache.py
@@ -1,5 +1,5 @@
-from queue import Queue
-from threading import Lock
+from queue import Empty, Queue
+from threading import RLock
 from typing import TYPE_CHECKING, Optional, TypeVar
 
 from invokeai.app.services.object_serializer.object_serializer_base import ObjectSerializerBase
@@ -22,9 +22,9 @@ def __init__(self, underlying_storage: ObjectSerializerBase[T], max_cache_size:
         self._cache: dict[str, T] = {}
         self._cache_ids = Queue[str]()
         self._max_cache_size = max_cache_size
-        # Guards the in-memory cache so concurrent session-processor workers (multi-GPU) can't race
-        # the check-then-evict in `_set_cache` (which could otherwise raise KeyError on eviction).
-        self._cache_lock = Lock()
+        # Guards the in-memory cache and eviction queue so concurrent session-processor workers (multi-GPU)
+        # cannot interleave cache transitions. Reentrancy allows transition helpers to share this lock.
+        self._cache_lock = RLock()
 
     def start(self, invoker: "Invoker") -> None:
         self._invoker = invoker
@@ -39,13 +39,14 @@ def stop(self, invoker: "Invoker") -> None:
             stop_op(invoker)
 
     def load(self, name: str) -> T:
-        cache_item = self._get_cache(name)
-        if cache_item is not None:
-            return cache_item
+        with self._cache_lock:
+            cache_item = self._get_cache(name)
+            if cache_item is not None:
+                return cache_item
 
-        obj = self._underlying_storage.load(name)
-        self._set_cache(name, obj)
-        return obj
+            obj = self._underlying_storage.load(name)
+            self._set_cache(name, obj)
+            return obj
 
     def save(self, obj: T) -> str:
         name = self._underlying_storage.save(obj)
@@ -53,11 +54,30 @@ def save(self, obj: T) -> str:
         return name
 
     def delete(self, name: str) -> None:
-        self._underlying_storage.delete(name)
+        try:
+            with self._cache_lock:
+                try:
+                    self._underlying_storage.delete(name)
+                finally:
+                    if name in self._cache:
+                        del self._cache[name]
+                        self._remove_cache_id(name)
+        finally:
+            self._on_deleted(name)
+
+    def _remove_cache_id(self, name: str) -> None:
         with self._cache_lock:
-            if name in self._cache:
-                del self._cache[name]
-        self._on_deleted(name)
+            remaining_ids: list[str] = []
+            while True:
+                try:
+                    cache_id = self._cache_ids.get_nowait()
+                except Empty:
+                    break
+                if cache_id != name:
+                    remaining_ids.append(cache_id)
+
+            for cache_id in remaining_ids:
+                self._cache_ids.put(cache_id)
 
     def _get_cache(self, name: str) -> Optional[T]:
         with self._cache_lock:
diff --git a/tests/test_object_serializer_disk.py b/tests/test_object_serializer_disk.py
index 70b18d0547b..6d7084fb017 100644
--- a/tests/test_object_serializer_disk.py
+++ b/tests/test_object_serializer_disk.py
@@ -1,6 +1,9 @@
 import tempfile
+from concurrent.futures import ThreadPoolExecutor
 from dataclasses import dataclass
 from pathlib import Path
+from queue import Empty
+from threading import Event, get_ident
 
 import pytest
 import torch
@@ -71,6 +74,12 @@ def test_obj_serializer_disk_deletes(obj_serializer: ObjectSerializerDisk[MockDa
     assert Path(obj_serializer._output_dir, obj_2_name).exists()
 
 
+def test_obj_serializer_disk_delete_is_noop_when_object_is_missing(
+    obj_serializer: ObjectSerializerDisk[MockDataclass],
+):
+    obj_serializer.delete("missing_object_name")
+
+
 def test_obj_serializer_ephemeral_creates_tempdir(tmp_path: Path):
     obj_serializer = ObjectSerializerDisk[MockDataclass](tmp_path, safe_globals=[MockDataclass], ephemeral=True)
     assert isinstance(obj_serializer._tempdir, tempfile.TemporaryDirectory)
@@ -186,3 +195,126 @@ def on_deleted(name: str):
     obj_1_name = fwd_cache.save(obj_1)
     fwd_cache.delete(obj_1_name)
     assert called_name == obj_1_name
+
+
+def test_obj_serializer_fwd_cache_removes_deleted_ids_from_eviction_queue(
+    fwd_cache: ObjectSerializerForwardCache[MockDataclass],
+):
+    obj_1_name = fwd_cache.save(MockDataclass(foo="bar"))
+    obj_2_name = fwd_cache.save(MockDataclass(foo="baz"))
+    fwd_cache.delete(obj_1_name)
+
+    obj_3_name = fwd_cache.save(MockDataclass(foo="qux"))
+
+    assert obj_1_name not in fwd_cache._cache
+    assert obj_2_name in fwd_cache._cache
+    assert obj_3_name in fwd_cache._cache
+    assert fwd_cache._cache_ids.qsize() == 2
+
+
+def test_obj_serializer_fwd_cache_cleans_up_when_storage_object_is_missing(
+    fwd_cache: ObjectSerializerForwardCache[MockDataclass],
+):
+    called_names: list[str] = []
+    fwd_cache.on_deleted(called_names.append)
+    obj_name = fwd_cache.save(MockDataclass(foo="bar"))
+    underlying_storage = fwd_cache._underlying_storage
+    assert isinstance(underlying_storage, ObjectSerializerDisk)
+    underlying_storage._get_path(obj_name).unlink()
+
+    fwd_cache.delete(obj_name)
+
+    assert obj_name not in fwd_cache._cache
+    assert fwd_cache._cache_ids.qsize() == 0
+    assert called_names == [obj_name]
+
+
+def test_obj_serializer_fwd_cache_preserves_fifo_order_after_deletion(tmp_path: Path):
+    fwd_cache = ObjectSerializerForwardCache(
+        ObjectSerializerDisk[MockDataclass](tmp_path, safe_globals=[MockDataclass]), max_cache_size=3
+    )
+    obj_1_name = fwd_cache.save(MockDataclass(foo="one"))
+    obj_2_name = fwd_cache.save(MockDataclass(foo="two"))
+    obj_3_name = fwd_cache.save(MockDataclass(foo="three"))
+    fwd_cache.delete(obj_2_name)
+    obj_4_name = fwd_cache.save(MockDataclass(foo="four"))
+    obj_5_name = fwd_cache.save(MockDataclass(foo="five"))
+
+    assert obj_1_name not in fwd_cache._cache
+    assert obj_2_name not in fwd_cache._cache
+    assert obj_3_name in fwd_cache._cache
+    assert obj_4_name in fwd_cache._cache
+    assert obj_5_name in fwd_cache._cache
+    assert fwd_cache._cache_ids.qsize() == 3
+
+
+def test_obj_serializer_fwd_cache_delete_of_evicted_object_is_noop(
+    fwd_cache: ObjectSerializerForwardCache[MockDataclass],
+):
+    obj_1_name = fwd_cache.save(MockDataclass(foo="one"))
+    obj_2_name = fwd_cache.save(MockDataclass(foo="two"))
+    obj_3_name = fwd_cache.save(MockDataclass(foo="three"))
+    cache_before_delete = fwd_cache._cache.copy()
+    queue_size_before_delete = fwd_cache._cache_ids.qsize()
+
+    fwd_cache.delete(obj_1_name)
+
+    assert fwd_cache._cache == cache_before_delete
+    assert fwd_cache._cache_ids.qsize() == queue_size_before_delete
+    assert obj_2_name in fwd_cache._cache
+    assert obj_3_name in fwd_cache._cache
+
+
+def test_obj_serializer_fwd_cache_concurrent_deletes_do_not_leave_stale_eviction_ids(
+    fwd_cache: ObjectSerializerForwardCache[MockDataclass], monkeypatch: pytest.MonkeyPatch
+):
+    obj_1_name = fwd_cache.save(MockDataclass(foo="one"))
+    obj_2_name = fwd_cache.save(MockDataclass(foo="two"))
+    first_delete_thread_id: int | None = None
+    first_drained_queue = Event()
+    release_first_delete = Event()
+    second_delete_started = Event()
+    second_delete_finished = Event()
+    original_get_nowait = fwd_cache._cache_ids.get_nowait
+
+    def controlled_get_nowait():
+        try:
+            return original_get_nowait()
+        except Empty:
+            if get_ident() == first_delete_thread_id:
+                first_drained_queue.set()
+                assert release_first_delete.wait(timeout=5)
+            raise
+
+    monkeypatch.setattr(fwd_cache._cache_ids, "get_nowait", controlled_get_nowait)
+
+    def delete_first():
+        nonlocal first_delete_thread_id
+        first_delete_thread_id = get_ident()
+        fwd_cache.delete(obj_1_name)
+
+    def delete_second():
+        second_delete_started.set()
+        fwd_cache.delete(obj_2_name)
+        second_delete_finished.set()
+
+    with ThreadPoolExecutor(max_workers=2) as executor:
+        first_delete = executor.submit(delete_first)
+        assert first_drained_queue.wait(timeout=5)
+        second_delete = executor.submit(delete_second)
+        assert second_delete_started.wait(timeout=5)
+        try:
+            assert not second_delete_finished.wait(timeout=0.1)
+        finally:
+            release_first_delete.set()
+        first_delete.result(timeout=5)
+        second_delete.result(timeout=5)
+
+    assert fwd_cache._cache == {}
+    assert fwd_cache._cache_ids.qsize() == 0
+
+    obj_3_name = fwd_cache.save(MockDataclass(foo="three"))
+    obj_4_name = fwd_cache.save(MockDataclass(foo="four"))
+
+    assert set(fwd_cache._cache) == {obj_3_name, obj_4_name}
+    assert fwd_cache._cache_ids.qsize() == 2