diff --git a/src/codex/account-lifecycle.ts b/src/codex/account-lifecycle.ts
index 75f748a805..703e08f247 100644
--- a/src/codex/account-lifecycle.ts
+++ b/src/codex/account-lifecycle.ts
@@ -1,6 +1,5 @@
 import { existsSync, readFileSync } from "node:fs";
 import {
-  atomicWriteFile,
   deleteConfigTopLevelKey,
   getConfigPath,
   saveConfigPreservingClaudeCode,
@@ -107,13 +106,10 @@ function restoreRuntimeConfig(target: OcxConfig, snapshot: OcxConfig): void {
   Object.assign(target, snapshot);
 }
 
-function restorePersistedConfig(configPath: string, previousBytes: string): void {
-  try {
-    if (readFileSync(configPath, "utf8") === previousBytes) return;
-  } catch (error) {
-    if ((error as NodeJS.ErrnoException).code !== "ENOENT") throw error;
+function assertPersistedConfigUnchanged(configPath: string, previousBytes: Buffer): void {
+  if (!readFileSync(configPath).equals(previousBytes)) {
+    throw new CodexAccountDeleteRollbackError();
   }
-  atomicWriteFile(configPath, previousBytes);
 }
 
 /**
@@ -133,7 +129,7 @@ export function deleteCodexAccount(runtimeConfig: OcxConfig, accountId: string):
     const previousConfig = structuredClone(runtimeConfig);
     const configPath = getConfigPath();
     const hasPersistedConfig = existsSync(configPath);
-    const previousPersistedConfig = hasPersistedConfig ? readFileSync(configPath, "utf8") : undefined;
+    const previousPersistedConfig = hasPersistedConfig ? readFileSync(configPath) : undefined;
     const hadStoredAccount = (runtimeConfig.codexAccounts ?? [])
       .some(account => !account.isMain && account.id === accountId);
     const hadVisiblePickerBinding = hadStoredAccount
@@ -162,7 +158,7 @@ export function deleteCodexAccount(runtimeConfig: OcxConfig, accountId: string):
       } catch (error) {
         restoreRuntimeConfig(runtimeConfig, previousConfig);
         try {
-          restorePersistedConfig(configPath, previousPersistedConfig);
+          assertPersistedConfigUnchanged(configPath, previousPersistedConfig);
         } catch {
           throw new CodexAccountDeleteRollbackError();
         }
diff --git a/tests/codex-integration/codex-account-delete-atomicity.test.ts b/tests/codex-integration/codex-account-delete-atomicity.test.ts
index fccaa8abe5..3e49033acc 100644
--- a/tests/codex-integration/codex-account-delete-atomicity.test.ts
+++ b/tests/codex-integration/codex-account-delete-atomicity.test.ts
@@ -1,13 +1,23 @@
 import { afterEach, beforeEach, describe, expect, spyOn, test } from "bun:test";
-import { existsSync, mkdirSync, readFileSync} from "node:fs";
+import {
+  existsSync,
+  mkdirSync,
+  readFileSync,
+  unlinkSync,
+  writeFileSync,
+} from "node:fs";
 import { join } from "node:path";
+import * as fsModule from "node:fs";
 import * as accountStoreModule from "../../src/codex/account-store";
+import * as websocketRegistryModule from "../../src/codex/websocket-registry";
+import * as quotaAutoRefreshStateModule from "../../src/codex/quota-auto-refresh-state";
 import {
   getCodexAccountCredential,
   saveCodexAccountCredential,
 } from "../../src/codex/account-store";
 import {
   CodexAccountDeleteCleanupError,
+  CodexAccountDeleteRollbackError,
   deleteCodexAccount,
 } from "../../src/codex/account-lifecycle";
 import {
@@ -85,7 +95,26 @@ describe("Codex account delete persistence ordering", () => {
     }
   });
 
-  test("a failure after durable config replacement restores the prior config", () => {
+  test("a failure before durable config replacement rethrows while disk remains unchanged", () => {
+    const config = seededConfig();
+    const before = structuredClone(config);
+    const beforeBytes = readFileSync(getConfigPath(), "utf8");
+    const saveSpy = spyOn(configModule, "saveConfigPreservingClaudeCode")
+      .mockImplementation(() => { throw new Error("forced pre-write failure"); });
+
+    try {
+      expect(() => deleteCodexAccount(config, ACCOUNT_ID)).toThrow("forced pre-write failure");
+      expect(config).toEqual(before);
+      expect(readFileSync(getConfigPath(), "utf8")).toBe(beforeBytes);
+      expect(getCodexAccountCredential(ACCOUNT_ID)).not.toBeNull();
+      expect(isAccountNeedsReauth(ACCOUNT_ID)).toBe(true);
+      expect(getAccountQuota(ACCOUNT_ID)).not.toBeNull();
+    } finally {
+      saveSpy.mockRestore();
+    }
+  });
+
+  test("a failure after durable config replacement leaves changed disk untouched", () => {
     const config = seededConfig();
     const before = structuredClone(config);
     const beforeBytes = readFileSync(getConfigPath(), "utf8");
@@ -97,11 +126,72 @@ describe("Codex account delete persistence ordering", () => {
       });
 
     try {
-      expect(() => deleteCodexAccount(config, ACCOUNT_ID)).toThrow("forced post-write failure");
+      expect(() => deleteCodexAccount(config, ACCOUNT_ID)).toThrow(CodexAccountDeleteRollbackError);
 
       expect(config).toEqual(before);
-      expect(readFileSync(getConfigPath(), "utf8")).toBe(beforeBytes);
-      expect(loadConfig().codexAccounts?.some(account => account.id === ACCOUNT_ID)).toBe(true);
+      expect(readFileSync(getConfigPath(), "utf8")).not.toBe(beforeBytes);
+      expect(loadConfig().codexAccounts?.some(account => account.id === ACCOUNT_ID)).toBe(false);
+      expect(getCodexAccountCredential(ACCOUNT_ID)).not.toBeNull();
+      expect(isAccountNeedsReauth(ACCOUNT_ID)).toBe(true);
+      expect(getAccountQuota(ACCOUNT_ID)).not.toBeNull();
+    } finally {
+      saveSpy.mockRestore();
+    }
+  });
+
+  test("a concurrent external edit remains byte-identical after uncertain failure", () => {
+    const config = seededConfig();
+    const before = structuredClone(config);
+    let replacementBytes: Buffer | undefined;
+    const realSave = configModule.saveConfigPreservingClaudeCode;
+    const saveSpy = spyOn(configModule, "saveConfigPreservingClaudeCode")
+      .mockImplementation(candidate => {
+        realSave(candidate);
+        const external = loadConfig();
+        external.port = 12345;
+        replacementBytes = Buffer.from(JSON.stringify(external, null, 2) + "\n", "utf8");
+        writeFileSync(getConfigPath(), replacementBytes);
+        throw new Error("forced concurrent failure");
+      });
+
+    try {
+      expect(() => deleteCodexAccount(config, ACCOUNT_ID)).toThrow(CodexAccountDeleteRollbackError);
+      expect(replacementBytes).toBeDefined();
+      expect(readFileSync(getConfigPath())).toEqual(replacementBytes);
+      const persisted = loadConfig();
+      expect(persisted.port).toBe(12345);
+      expect(persisted.codexAccounts?.some(account => account.id === ACCOUNT_ID)).toBe(false);
+      expect(config).toEqual(before);
+      expect(getCodexAccountCredential(ACCOUNT_ID)).not.toBeNull();
+      expect(isAccountNeedsReauth(ACCOUNT_ID)).toBe(true);
+      expect(getAccountQuota(ACCOUNT_ID)).not.toBeNull();
+    } finally {
+      saveSpy.mockRestore();
+    }
+  });
+
+  test("distinct bytes with the same decoded text are treated as changed", () => {
+    const config = seededConfig();
+    const before = structuredClone(config);
+    const validBytes = Buffer.from('{"value":"\uFFFD"}\n', "utf8");
+    const malformedBytes = Buffer.concat([
+      Buffer.from('{"value":"', "utf8"),
+      Buffer.from([0x80]),
+      Buffer.from('"}\n', "utf8"),
+    ]);
+    expect(validBytes.equals(malformedBytes)).toBe(false);
+    expect(validBytes.toString("utf8")).toBe(malformedBytes.toString("utf8"));
+    writeFileSync(getConfigPath(), validBytes);
+    const saveSpy = spyOn(configModule, "saveConfigPreservingClaudeCode")
+      .mockImplementation(() => {
+        writeFileSync(getConfigPath(), malformedBytes);
+        throw new Error("forced byte-alias failure");
+      });
+
+    try {
+      expect(() => deleteCodexAccount(config, ACCOUNT_ID)).toThrow(CodexAccountDeleteRollbackError);
+      expect(readFileSync(getConfigPath()).equals(malformedBytes)).toBe(true);
+      expect(config).toEqual(before);
       expect(getCodexAccountCredential(ACCOUNT_ID)).not.toBeNull();
       expect(isAccountNeedsReauth(ACCOUNT_ID)).toBe(true);
       expect(getAccountQuota(ACCOUNT_ID)).not.toBeNull();
@@ -110,6 +200,111 @@ describe("Codex account delete persistence ordering", () => {
     }
   });
 
+  test("a missing config after uncertain failure is not recreated", () => {
+    const config = seededConfig();
+    const before = structuredClone(config);
+    const realSave = configModule.saveConfigPreservingClaudeCode;
+    const saveSpy = spyOn(configModule, "saveConfigPreservingClaudeCode")
+      .mockImplementation(candidate => {
+        realSave(candidate);
+        unlinkSync(getConfigPath());
+        throw new Error("forced missing-file failure");
+      });
+
+    try {
+      expect(() => deleteCodexAccount(config, ACCOUNT_ID)).toThrow(CodexAccountDeleteRollbackError);
+      expect(existsSync(getConfigPath())).toBe(false);
+      expect(config).toEqual(before);
+      expect(getCodexAccountCredential(ACCOUNT_ID)).not.toBeNull();
+      expect(isAccountNeedsReauth(ACCOUNT_ID)).toBe(true);
+      expect(getAccountQuota(ACCOUNT_ID)).not.toBeNull();
+    } finally {
+      saveSpy.mockRestore();
+    }
+  });
+
+  test("an unreadable config after uncertain failure preserves state and sanitizes errors", () => {
+    const config = seededConfig();
+    const before = structuredClone(config);
+    const configPath = getConfigPath();
+    const beforeBytes = readFileSync(configPath);
+    const readSpy = spyOn(fsModule, "readFileSync");
+    const removeSpy = spyOn(accountStoreModule, "removeCodexAccountCredential");
+    const invalidateSpy = spyOn(websocketRegistryModule, "invalidateCodexWebSocketsForAccount");
+    const forgetSpy = spyOn(quotaAutoRefreshStateModule, "forgetCodexQuotaAutoRefreshAccount");
+    const saveSpy = spyOn(configModule, "saveConfigPreservingClaudeCode")
+      .mockImplementation(() => {
+        readSpy.mockImplementationOnce(() => {
+          throw new Error("EACCES /private/config.json Bearer read-secret-token");
+        });
+        throw new Error("write failed /private/config.json Bearer write-secret-token");
+      });
+
+    try {
+      let thrown: unknown;
+      try {
+        deleteCodexAccount(config, ACCOUNT_ID);
+      } catch (error) {
+        thrown = error;
+      }
+      expect(readSpy).toHaveBeenLastCalledWith(configPath);
+      expect(thrown).toBeInstanceOf(CodexAccountDeleteRollbackError);
+      expect((thrown as Error).message).toBe(
+        "Account deletion failed and the previous config could not be restored. Restart before retrying.",
+      );
+      expect(String(thrown)).not.toContain("/private/config.json");
+      expect(String(thrown)).not.toContain("secret-token");
+      expect((thrown as Error).cause).toBeUndefined();
+      expect(config).toEqual(before);
+      expect(readFileSync(configPath)).toEqual(beforeBytes);
+      expect(getCodexAccountCredential(ACCOUNT_ID)).not.toBeNull();
+      expect(isAccountNeedsReauth(ACCOUNT_ID)).toBe(true);
+      expect(getAccountQuota(ACCOUNT_ID)).not.toBeNull();
+      expect(removeSpy).not.toHaveBeenCalled();
+      expect(invalidateSpy).not.toHaveBeenCalled();
+      expect(forgetSpy).not.toHaveBeenCalled();
+    } finally {
+      readSpy.mockRestore();
+      saveSpy.mockRestore();
+      removeSpy.mockRestore();
+      invalidateSpy.mockRestore();
+      forgetSpy.mockRestore();
+    }
+  });
+
+  test("a transient config skips persistence but still removes credentials and runtime state", () => {
+    const config = seededConfig();
+    const configPath = getConfigPath();
+    unlinkSync(configPath);
+    const saveSpy = spyOn(configModule, "saveConfigPreservingClaudeCode");
+    const removeSpy = spyOn(accountStoreModule, "removeCodexAccountCredential");
+    const invalidateSpy = spyOn(websocketRegistryModule, "invalidateCodexWebSocketsForAccount");
+    const forgetSpy = spyOn(quotaAutoRefreshStateModule, "forgetCodexQuotaAutoRefreshAccount");
+
+    try {
+      expect(deleteCodexAccount(config, ACCOUNT_ID)).toBe(true);
+      expect(saveSpy).not.toHaveBeenCalled();
+      expect(existsSync(configPath)).toBe(false);
+      expect(config.codexAccounts).toEqual([]);
+      expect(config.codexAccountNamespaces).toEqual({ stable: ACCOUNT_ID });
+      expect(config.pausedCodexAccountIds).toBeUndefined();
+      expect(config.codexAccountPriorities).toBeUndefined();
+      expect(config.activeCodexAccountPinned).toBeUndefined();
+      expect(config.activeCodexAccountId).toBeUndefined();
+      expect(getCodexAccountCredential(ACCOUNT_ID)).toBeNull();
+      expect(isAccountNeedsReauth(ACCOUNT_ID)).toBe(false);
+      expect(getAccountQuota(ACCOUNT_ID)).toBeNull();
+      expect(removeSpy).toHaveBeenCalledWith(ACCOUNT_ID);
+      expect(invalidateSpy).toHaveBeenCalledWith(ACCOUNT_ID);
+      expect(forgetSpy).toHaveBeenCalledWith(ACCOUNT_ID);
+    } finally {
+      saveSpy.mockRestore();
+      removeSpy.mockRestore();
+      invalidateSpy.mockRestore();
+      forgetSpy.mockRestore();
+    }
+  });
+
   test("the durable config deletion happens before credential and runtime cleanup", () => {
     const config = seededConfig();
     const realSave = configModule.saveConfigPreservingClaudeCode;