diff --git a/.changeset/assistant-storage-cleanup.md b/.changeset/assistant-storage-cleanup.md
new file mode 100644
index 000000000..891460a6b
--- /dev/null
+++ b/.changeset/assistant-storage-cleanup.md
@@ -0,0 +1,5 @@
+---
+"@sapiom/harness": patch
+---
+
+Preserve Assistant storage commit uncertainty when temporary-file cleanup also fails.
diff --git a/packages/harness/docs/assistant-history.md b/packages/harness/docs/assistant-history.md
index 7e32e068f..9343c95bb 100644
--- a/packages/harness/docs/assistant-history.md
+++ b/packages/harness/docs/assistant-history.md
@@ -163,3 +163,7 @@ Continue allows up to 45 seconds total for cold startup and frozen preparation.
 Selected inspection retains its separate 15-second limit. The caller's remaining
 deadline and End can cancel either operation sooner; provisional cleanup remains
 bound to the exact runtime that the operation started.
+
+Temporary-file cleanup cannot replace the primary storage failure. An unconfirmed
+publication remains distinguishable for Resume reconciliation even when rollback
+and cleanup also fail; cleanup failures after successful publication are surfaced.
diff --git a/packages/harness/src/core/assistant-session-files.test.ts b/packages/harness/src/core/assistant-session-files.test.ts
index 27cc0be86..c9a203fa6 100644
--- a/packages/harness/src/core/assistant-session-files.test.ts
+++ b/packages/harness/src/core/assistant-session-files.test.ts
@@ -3,15 +3,84 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { afterEach, expect, it, vi } from "vitest";
 import { AssistantSessionStore } from "./assistant-session-store.js";
+import {
+  AssistantStorageCommitUnconfirmedError,
+  writeAssistantJson,
+} from "./assistant-session-files.js";
 
 vi.mock("node:fs/promises", async (original) => {
   const fs = await original<typeof import("node:fs/promises")>();
-  return { ...fs, open: vi.fn(fs.open), rename: vi.fn(fs.rename) };
+  return {
+    ...fs,
+    open: vi.fn(fs.open),
+    rename: vi.fn(fs.rename),
+    rm: vi.fn(fs.rm),
+  };
 });
 let root: string;
 afterEach(async () => {
   vi.restoreAllMocks();
-  if (root) await fs.rm(root, { recursive: true, force: true });
+  const actual = await vi.importActual<typeof fs>("node:fs/promises");
+  if (root) await actual.rm(root, { recursive: true, force: true });
+});
+
+it("preserves uncertain publication proof when rollback and temporary cleanup also fail", async () => {
+  root = await fs.mkdtemp(join(tmpdir(), "assistant-files-"));
+  const actual = await vi.importActual<typeof fs>("node:fs/promises");
+  const destination = join(root, "lifecycle.json");
+  const prior = { lifecycleRevision: 1 };
+  const next = {
+    lifecycleRevision: 2,
+    resumeOperation: { operationId: "retained-proof" },
+  };
+  await actual.writeFile(destination, JSON.stringify(prior));
+  let published = false;
+  vi.mocked(fs.rename).mockImplementation(async (from, to) => {
+    if (String(from).endsWith(".rollback")) throw new Error("rollback failed");
+    await actual.rename(from, to);
+    if (to === destination) published = true;
+  });
+  vi.mocked(fs.open).mockImplementation(async (path, flags, mode) => {
+    if (flags === "r" && published)
+      throw Object.assign(new Error("durability failed"), { code: "EIO" });
+    return actual.open(path, flags, mode);
+  });
+  const removed: unknown[] = [];
+  vi.mocked(fs.rm).mockImplementation(async (path) => {
+    removed.push(path);
+    throw new Error("cleanup failed");
+  });
+
+  await expect(
+    writeAssistantJson(root, "lifecycle.json", next),
+  ).rejects.toBeInstanceOf(AssistantStorageCommitUnconfirmedError);
+  expect(removed).toHaveLength(3);
+  expect(JSON.parse(await actual.readFile(destination, "utf8"))).toEqual(next);
+  expect(
+    JSON.parse(await actual.readFile(`${destination}.previous`, "utf8")),
+  ).toEqual(prior);
+});
+
+it("preserves a pre-publication failure when temporary cleanup fails", async () => {
+  root = await fs.mkdtemp(join(tmpdir(), "assistant-files-"));
+  const primary = Object.assign(new Error("write failed"), { code: "ENOSPC" });
+  vi.mocked(fs.open).mockRejectedValue(primary);
+  vi.mocked(fs.rm).mockRejectedValue(new Error("cleanup failed"));
+  await expect(writeAssistantJson(root, "lifecycle.json", {})).rejects.toBe(
+    primary,
+  );
+});
+
+it("reports temporary cleanup failure after an otherwise successful publication", async () => {
+  root = await fs.mkdtemp(join(tmpdir(), "assistant-files-"));
+  const cleanup = new Error("cleanup failed");
+  vi.mocked(fs.rm).mockRejectedValue(cleanup);
+  await expect(
+    writeAssistantJson(root, "lifecycle.json", { revision: 1 }),
+  ).rejects.toBe(cleanup);
+  expect(
+    JSON.parse(await fs.readFile(join(root, "lifecycle.json"), "utf8")),
+  ).toEqual({ revision: 1 });
 });
 
 it.each(["EPERM", "EINVAL", "ENOTSUP"])(
diff --git a/packages/harness/src/core/assistant-session-files.ts b/packages/harness/src/core/assistant-session-files.ts
index 3dd7961fb..d805ae66e 100644
--- a/packages/harness/src/core/assistant-session-files.ts
+++ b/packages/harness/src/core/assistant-session-files.ts
@@ -95,6 +95,7 @@ export async function writeAssistantJson(
     rollback = `${temporary}.rollback`;
   let retained = false,
     published = false;
+  let cleanupFailure: PromiseRejectedResult | undefined;
   try {
     const file = await fs.open(temporary, "wx", 0o600);
     try {
@@ -135,10 +136,13 @@ export async function writeAssistantJson(
       throw new AssistantStorageCommitUnconfirmedError();
     throw error;
   } finally {
-    await Promise.all(
+    const cleanup = await Promise.allSettled(
       [temporary, backup, rollback].map((file) => fs.rm(file, { force: true })),
     );
+    // Cleanup must not disguise whether the durable publication is uncertain.
+    cleanupFailure = cleanup.find((result) => result.status === "rejected");
   }
+  if (cleanupFailure) throw cleanupFailure.reason;
 }
 
 /** Match DurableFileLock on platforms without directory-handle fsync support. */