refactor: generalize managed hook transactions

src/plugins/codex-installation.ts

@@ -33,8 +33,7 @@ export async function preflightCodexInstallation(
 ): Promise<CodexRuntimePaths> {
   return preflightManagedInstallation({
     agentKey: AGENT_KEY,
-    hooksDirectoryLabel: HOOKS_DIRECTORY_LABEL,
+    hookLocations: [{ directoryLabel: HOOKS_DIRECTORY_LABEL, filePath: hooksPath }],
-    hooksPath,
     config,
   }, GUARD_SCRIPT, AUDIT_SCRIPT);
 }
@@ -51,11 +50,13 @@ export async function prepareCodexInstallation(
   return prepareManagedInstallation({
     agentKey: AGENT_KEY,
     displayName: DISPLAY_NAME,
-    hooksDirectoryLabel: HOOKS_DIRECTORY_LABEL,
+    hookSources: [{
-    hooksLabel: HOOKS_LABEL,
+      directoryLabel: HOOKS_DIRECTORY_LABEL,
-    hooksPath: rendered.document.filePath,
+      label: HOOKS_LABEL,
-    expectedHooksSource: rendered.document.raw,
+      filePath: rendered.document.filePath,
-    hooksSource,
+      expectedSource: rendered.document.raw,
+      source: hooksSource,
+    }],
     config,
     auditOptions: { nativePayload: true },
   }, GUARD_SCRIPT, AUDIT_SCRIPT);

src/plugins/cursor-installation.ts

@@ -33,8 +33,10 @@ export async function preflightCursorInstallation(
 ): Promise<CursorRuntimePaths> {
   return preflightManagedInstallation({
     agentKey: AGENT_KEY,
-    hooksDirectoryLabel: HOOKS_DIRECTORY_LABEL,
+    hookLocations: [{
-    hooksPath: cursorConfigPath(),
+      directoryLabel: HOOKS_DIRECTORY_LABEL,
+      filePath: cursorConfigPath(),
+    }],
     config,
   }, GUARD_SCRIPT, AUDIT_SCRIPT);
 }
@@ -51,11 +53,13 @@ export async function prepareCursorInstallation(
   return prepareManagedInstallation({
     agentKey: AGENT_KEY,
     displayName: DISPLAY_NAME,
-    hooksDirectoryLabel: HOOKS_DIRECTORY_LABEL,
+    hookSources: [{
-    hooksLabel: HOOKS_LABEL,
+      directoryLabel: HOOKS_DIRECTORY_LABEL,
-    hooksPath: rendered.document.filePath,
+      label: HOOKS_LABEL,
-    expectedHooksSource: rendered.document.raw,
+      filePath: rendered.document.filePath,
-    hooksSource,
+      expectedSource: rendered.document.raw,
+      source: hooksSource,
+    }],
     config,
     guardOptions: {
       failClosed: true,

src/plugins/managed-installation.ts

@@ -1,38 +1,23 @@
-import { randomUUID } from 'node:crypto';
-import fsp from 'node:fs/promises';
-import type { FileHandle } from 'node:fs/promises';
 import os from 'node:os';
 import path from 'node:path';
 import { ensurePrivateDirectory, resolvePrivateChildDirectory } from '../runtime-paths.js';
 import type { InstallConfig } from './base.js';
 import { generateGuardScript, type GuardScriptOptions } from './guard-template.js';
 import { generateHookScript, type HookScriptOptions } from './hook-template.js';
+import { inspectPhysicalDirectory, readPhysicalFile } from './managed-files.js';
 import {
-  inspectPhysicalDirectory,
+  commitManagedTransaction,
-  readPhysicalFile,
+  prepareManagedFileChange,
-  type FileSnapshot,
+  type ManagedDirectory,
-} from './managed-files.js';
+  type ManagedFileChange,
+  type PreparedManagedTransaction,
+  type RenameFile,
+} from './managed-transaction.js';
 import { parseStrictJsonObject } from './strict-json.js';
 
 const MAX_SECRET_BYTES = 64 * 1024;
 const MAX_CONFIG_BYTES = 512 * 1024;
-const MAX_SOURCE_BYTES = 2 * 1024 * 1024;
 
-interface FileChange {
-  readonly filePath: string;
-  readonly label: string;
-  readonly next: string;
-  readonly mode: number;
-  readonly maximumBytes: number;
-  readonly original?: FileSnapshot;
-}
-interface StagedChange {
-  readonly change: FileChange;
-  readonly temporaryPath: string;
-  rollbackPath?: string;
-  committedSnapshot?: FileSnapshot;
-  committed: boolean;
-}
 export interface ManagedRuntimePaths {
   readonly runtimeRoot: string;
   readonly agentDirectory: string;
@@ -41,41 +26,39 @@ export interface ManagedRuntimePaths {
   readonly guardPath: string;
   readonly auditPath: string;
 }
+
+export interface ManagedHookLocation {
+  readonly directoryLabel: string;
+  readonly filePath: string;
+}
+
+export interface ManagedHookSource extends ManagedHookLocation {
+  readonly label: string;
+  readonly expectedSource?: string;
+  readonly source: string;
+}
+
 export interface ManagedInstallationSpec {
   readonly agentKey: string;
   readonly displayName: string;
-  readonly hooksDirectoryLabel: string;
+  readonly hookSources: readonly ManagedHookSource[];
-  readonly hooksLabel: string;
-  readonly hooksPath: string;
-  readonly expectedHooksSource?: string;
-  readonly hooksSource: string;
   readonly config: InstallConfig;
   readonly guardOptions?: GuardScriptOptions;
   readonly auditOptions?: HookScriptOptions;
 }
+
 export interface ManagedPreflightSpec {
   readonly agentKey: string;
-  readonly hooksDirectoryLabel: string;
+  readonly hookLocations: readonly ManagedHookLocation[];
-  readonly hooksPath: string;
   readonly config: InstallConfig;
 }
+
 export interface PreparedManagedInstallation {
-  readonly displayName: string;
-  readonly hooksDirectoryLabel: string;
   readonly paths: ManagedRuntimePaths;
-  readonly changes: readonly FileChange[];
+  readonly transaction: PreparedManagedTransaction;
-}
-export type RenameFile = (source: string, destination: string) => Promise<void>;
-function asError(error: unknown): Error {
-  return error instanceof Error ? error : new Error(String(error));
 }
 
-function errorMessage(error: unknown): string {
+export type { RenameFile };
-  return error instanceof Error ? error.message : String(error);
-}
-function hasCode(error: unknown, code: string): boolean {
-  return typeof error === 'object' && error !== null && 'code' in error && error.code === code;
-}
 
 export function samePath(left: string, right: string): boolean {
   const normalizedLeft = path.resolve(left);
@@ -84,6 +67,7 @@ export function samePath(left: string, right: string): boolean {
     ? normalizedLeft.toLowerCase() === normalizedRight.toLowerCase()
     : normalizedLeft === normalizedRight;
 }
+
 function validateInstallConfig(config: InstallConfig, agentKey: string): void {
   for (const [field, value] of [
     ['agentName', config.agentName],
@@ -108,7 +92,7 @@ function validateInstallConfig(config: InstallConfig, agentKey: string): void {
     throw new Error('privateKey must be a canonical 32-byte base64url value');
   }
   const baseUrl = new URL(config.baseUrl);
-  if (!['http:', 'https:'].includes(baseUrl.protocol)) {
+  if (!['http:', 'https:'].includes(baseUrl.protocol) || !baseUrl.hostname) {
     throw new Error('baseUrl must use HTTP or HTTPS');
   }
   if (baseUrl.username || baseUrl.password || baseUrl.search || baseUrl.hash) {
@@ -188,7 +172,9 @@ export async function preflightManagedInstallation(
   auditScript: string,
 ): Promise<ManagedRuntimePaths> {
   const paths = managedRuntimePaths(spec.config, spec.agentKey, guardScript, auditScript);
-  await inspectPhysicalDirectory(path.dirname(spec.hooksPath), spec.hooksDirectoryLabel);
+  for (const location of spec.hookLocations) {
+    await inspectPhysicalDirectory(path.dirname(location.filePath), location.directoryLabel);
+  }
   await validateRuntimeIdentity(paths, spec.agentKey);
   return paths;
 }
@@ -209,21 +195,11 @@ function runtimeConfig(config: InstallConfig, agentKey: string): string {
   return encoded;
 }
 
-async function prepareChange(
+function hookDirectories(sources: readonly ManagedHookSource[]): ManagedDirectory[] {
-  filePath: string,
+  return sources.map((source) => ({
-  label: string,
+    path: path.dirname(source.filePath),
-  next: string,
+    label: source.directoryLabel,
-  mode: number,
+  }));
-  maximumBytes = MAX_SOURCE_BYTES,
-): Promise<FileChange> {
-  return {
-    filePath,
-    label,
-    next,
-    mode,
-    maximumBytes,
-    original: await readPhysicalFile(filePath, label, maximumBytes),
-  };
 }
 
 export async function prepareManagedInstallation(
@@ -231,250 +207,64 @@ export async function prepareManagedInstallation(
   guardScript: string,
   auditScript: string,
 ): Promise<PreparedManagedInstallation> {
-  const paths = await preflightManagedInstallation(spec, guardScript, auditScript);
+  if (spec.hookSources.length === 0) throw new Error('At least one hook source is required');
+  const paths = await preflightManagedInstallation({
+    agentKey: spec.agentKey,
+    hookLocations: spec.hookSources,
+    config: spec.config,
+  }, guardScript, auditScript);
   const changes = await Promise.all([
-    prepareChange(
+    prepareManagedFileChange({
-      paths.guardPath,
+      filePath: paths.guardPath,
-      'Elydora guard runtime',
+      label: 'Elydora guard runtime',
-      generateGuardScript(spec.agentKey, spec.config.agentId, spec.guardOptions),
+      next: generateGuardScript(spec.agentKey, spec.config.agentId, spec.guardOptions),
-      0o700,
+      mode: 0o700,
-    ),
+    }),
-    prepareChange(
+    prepareManagedFileChange({
-      paths.configPath,
+      filePath: paths.configPath,
-      'Elydora runtime config',
+      label: 'Elydora runtime config',
-      runtimeConfig(spec.config, spec.agentKey),
+      next: runtimeConfig(spec.config, spec.agentKey),
-      0o600,
+      mode: 0o600,
-      MAX_CONFIG_BYTES,
+      maximumBytes: MAX_CONFIG_BYTES,
-    ),
+    }),
-    prepareChange(
+    prepareManagedFileChange({
-      paths.keyPath,
+      filePath: paths.keyPath,
-      'Elydora private key',
+      label: 'Elydora private key',
-      spec.config.privateKey,
+      next: spec.config.privateKey,
-      0o600,
+      mode: 0o600,
-      MAX_SECRET_BYTES,
+      maximumBytes: MAX_SECRET_BYTES,
-    ),
+    }),
-    prepareChange(
+    prepareManagedFileChange({
-      paths.auditPath,
+      filePath: paths.auditPath,
-      'Elydora audit runtime',
+      label: 'Elydora audit runtime',
-      generateHookScript(spec.agentKey, spec.config.agentId, spec.auditOptions),
+      next: generateHookScript(spec.agentKey, spec.config.agentId, spec.auditOptions),
-      0o700,
+      mode: 0o700,
-    ),
+    }),
-    prepareChange(spec.hooksPath, spec.hooksLabel, spec.hooksSource, 0o600),
+    ...spec.hookSources.map((source) => prepareManagedFileChange({
+      filePath: source.filePath,
+      label: source.label,
+      next: source.source,
+      mode: 0o600,
+      expectedSource: source.expectedSource,
+      verifyExpectedSource: true,
+    })),
   ]);
-  const hooksSource = changes.at(-1)!.original?.contents;
-  if (hooksSource !== spec.expectedHooksSource) {
-    throw new Error(`${spec.hooksLabel} changed before installation: ${spec.hooksPath}`);
-  }
   await validateRuntimeIdentity(paths, spec.agentKey);
   return {
-    displayName: spec.displayName,
-    hooksDirectoryLabel: spec.hooksDirectoryLabel,
     paths,
-    changes,
+    transaction: {
+      displayName: spec.displayName,
+      directories: hookDirectories(spec.hookSources),
+      changes: changes.filter((change): change is ManagedFileChange => change !== undefined),
+    },
   };
 }
 
-async function unlinkOptional(filePath: string): Promise<void> {
-  try {
-    await fsp.unlink(filePath);
-  } catch (error) {
-    if (!hasCode(error, 'ENOENT')) throw error;
-  }
-}
-
-async function assertUnchanged(change: FileChange, displayName: string): Promise<void> {
-  const current = await readPhysicalFile(change.filePath, change.label, change.maximumBytes);
-  if ((!current && change.original)
-    || (current && !change.original)
-    || (current && change.original && (
-      current.contents !== change.original.contents
-      || current.device !== change.original.device
-      || current.inode !== change.original.inode
-    ))) {
-    throw new Error(`${change.label} changed during ${displayName} installation: ${change.filePath}`);
-  }
-}
-
-async function writeExclusive(
-  filePath: string,
-  contents: string,
-  mode: number,
-  label: string,
-): Promise<void> {
-  let handle: FileHandle | undefined;
-  try {
-    handle = await fsp.open(filePath, 'wx', mode);
-    await handle.writeFile(contents, 'utf-8');
-    await handle.sync();
-    await handle.close();
-    handle = undefined;
-    if (process.platform !== 'win32') await fsp.chmod(filePath, mode);
-  } catch (error) {
-    const failures = [asError(error)];
-    if (handle) {
-      try { await handle.close(); } catch (closeError) { failures.push(asError(closeError)); }
-    }
-    try { await unlinkOptional(filePath); } catch (cleanupError) {
-      failures.push(asError(cleanupError));
-    }
-    if (failures.length > 1) throw new AggregateError(failures, `Stage ${label}`);
-    throw new Error(`Stage ${label}: ${errorMessage(error)}`, { cause: failures[0] });
-  }
-}
-
-async function stage(change: FileChange, displayName: string): Promise<StagedChange> {
-  await assertUnchanged(change, displayName);
-  const token = randomUUID();
-  const directory = path.dirname(change.filePath);
-  const temporaryPath = path.join(directory, `.${path.basename(change.filePath)}.${token}.tmp`);
-  const rollbackPath = change.original
-    ? path.join(directory, `.${path.basename(change.filePath)}.${token}.rollback`)
-    : undefined;
-  try {
-    await writeExclusive(temporaryPath, change.next, change.mode, change.label);
-    if (rollbackPath && change.original) {
-      await writeExclusive(
-        rollbackPath,
-        change.original.contents,
-        change.original.mode,
-        `${change.label} rollback`,
-      );
-    }
-    return { change, temporaryPath, rollbackPath, committed: false };
-  } catch (error) {
-    const failures = [asError(error)];
-    for (const item of [temporaryPath, rollbackPath]) {
-      if (!item) continue;
-      try { await unlinkOptional(item); } catch (cleanupError) {
-        failures.push(asError(cleanupError));
-      }
-    }
-    if (failures.length > 1) throw new AggregateError(failures, `Stage ${change.label}`);
-    throw error;
-  }
-}
-
-async function commit(
-  staged: StagedChange,
-  displayName: string,
-  renameFile: RenameFile,
-): Promise<void> {
-  await assertUnchanged(staged.change, displayName);
-  await renameFile(staged.temporaryPath, staged.change.filePath);
-  staged.committed = true;
-  const current = await readPhysicalFile(
-    staged.change.filePath,
-    staged.change.label,
-    staged.change.maximumBytes,
-  );
-  if (!current || current.contents !== staged.change.next) {
-    throw new Error(
-      `${staged.change.label} changed immediately after commit: ${staged.change.filePath}`,
-    );
-  }
-  staged.committedSnapshot = current;
-}
-
-async function assertCommittedUnchanged(staged: StagedChange): Promise<void> {
-  const current = await readPhysicalFile(
-    staged.change.filePath,
-    staged.change.label,
-    staged.change.maximumBytes,
-  );
-  const committed = staged.committedSnapshot;
-  if (!current || !committed
-    || current.contents !== committed.contents
-    || current.device !== committed.device
-    || current.inode !== committed.inode) {
-    throw new Error(
-      `${staged.change.label} changed during transaction recovery: ${staged.change.filePath}`,
-    );
-  }
-}
-
-function preserveRollback(staged: StagedChange, cause: unknown): Error {
-  if (!staged.rollbackPath) return asError(cause);
-  const rollbackPath = staged.rollbackPath;
-  staged.rollbackPath = undefined;
-  return new Error(
-    `${errorMessage(cause)}; original content preserved at ${rollbackPath}`,
-    { cause: asError(cause) },
-  );
-}
-
-async function rollback(staged: StagedChange, renameFile: RenameFile): Promise<void> {
-  if (!staged.committed) return;
-  try {
-    await assertCommittedUnchanged(staged);
-  } catch (error) {
-    throw preserveRollback(staged, error);
-  }
-  if (!staged.change.original) {
-    await unlinkOptional(staged.change.filePath);
-    return;
-  }
-  if (!staged.rollbackPath) throw new Error(`Missing rollback data for ${staged.change.label}`);
-  try {
-    await renameFile(staged.rollbackPath, staged.change.filePath);
-  } catch (error) {
-    throw preserveRollback(staged, error);
-  }
-}
-
-async function cleanup(staged: StagedChange): Promise<void> {
-  await Promise.all(
-    [staged.temporaryPath, staged.rollbackPath].filter(Boolean).map((item) => unlinkOptional(item!)),
-  );
-}
-
-async function ensureManagedDirectory(directory: string, label: string): Promise<void> {
-  await fsp.mkdir(directory, { recursive: true, mode: 0o700 });
-  if (!await inspectPhysicalDirectory(directory, label)) {
-    throw new Error(`${label} is missing: ${directory}`);
-  }
-}
-
 export async function commitManagedInstallation(
   prepared: PreparedManagedInstallation,
-  renameFile: RenameFile = fsp.rename,
+  renameFile?: RenameFile,
 ): Promise<void> {
   await ensurePrivateDirectory(prepared.paths.runtimeRoot);
   await ensurePrivateDirectory(prepared.paths.agentDirectory);
-  await ensureManagedDirectory(
+  await commitManagedTransaction(prepared.transaction, renameFile);
-    path.dirname(prepared.changes.at(-1)!.filePath),
-    prepared.hooksDirectoryLabel,
-  );
-  const staged: StagedChange[] = [];
-  try {
-    for (const change of prepared.changes) {
-      staged.push(await stage(change, prepared.displayName));
-    }
-    for (const item of staged) await commit(item, prepared.displayName, renameFile);
-  } catch (error) {
-    const failures = [asError(error)];
-    for (const item of [...staged].reverse()) {
-      try { await rollback(item, renameFile); } catch (rollbackError) {
-        failures.push(asError(rollbackError));
-      }
-    }
-    for (const item of staged) {
-      try { await cleanup(item); } catch (cleanupError) {
-        failures.push(asError(cleanupError));
-      }
-    }
-    throw new AggregateError(
-      failures,
-      `Install ${prepared.displayName} hooks: ${errorMessage(error)}`,
-    );
-  }
-  const failures: Error[] = [];
-  for (const item of staged) {
-    try { await cleanup(item); } catch (error) { failures.push(asError(error)); }
-  }
-  if (failures.length > 0) {
-    throw new AggregateError(
-      failures,
-      `Clean ${prepared.displayName} installation transaction files`,
-    );
-  }
 }

src/plugins/managed-transaction.ts

@@ -0,0 +1,366 @@
+import { randomUUID } from 'node:crypto';
+import fsp from 'node:fs/promises';
+import type { FileHandle } from 'node:fs/promises';
+import path from 'node:path';
+import {
+  inspectPhysicalDirectory,
+  readPhysicalFile,
+  type FileSnapshot,
+} from './managed-files.js';
+
+const MAX_SOURCE_BYTES = 2 * 1024 * 1024;
+
+export interface ManagedChangeSpec {
+  readonly filePath: string;
+  readonly label: string;
+  readonly next?: string;
+  readonly mode: number;
+  readonly maximumBytes?: number;
+  readonly expectedSource?: string;
+  readonly verifyExpectedSource?: boolean;
+}
+
+export interface ManagedFileChange {
+  readonly filePath: string;
+  readonly label: string;
+  readonly next?: string;
+  readonly mode: number;
+  readonly maximumBytes: number;
+  readonly original?: FileSnapshot;
+}
+
+export interface ManagedDirectory {
+  readonly path: string;
+  readonly label: string;
+}
+
+export interface PreparedManagedTransaction {
+  readonly displayName: string;
+  readonly directories: readonly ManagedDirectory[];
+  readonly changes: readonly ManagedFileChange[];
+}
+
+interface StagedChange {
+  readonly change: ManagedFileChange;
+  temporaryPath?: string;
+  rollbackPath?: string;
+  committedSnapshot?: FileSnapshot;
+  committed: boolean;
+}
+
+export type RenameFile = (source: string, destination: string) => Promise<void>;
+
+function asError(error: unknown): Error {
+  return error instanceof Error ? error : new Error(String(error));
+}
+
+function errorMessage(error: unknown): string {
+  return error instanceof Error ? error.message : String(error);
+}
+
+function hasCode(error: unknown, code: string): boolean {
+  return typeof error === 'object' && error !== null && 'code' in error && error.code === code;
+}
+
+function targetKey(filePath: string): string {
+  const resolved = path.resolve(filePath);
+  return process.platform === 'win32' ? resolved.toLowerCase() : resolved;
+}
+
+async function unlinkOptional(filePath?: string): Promise<void> {
+  if (!filePath) return;
+  try {
+    await fsp.unlink(filePath);
+  } catch (error) {
+    if (!hasCode(error, 'ENOENT')) throw error;
+  }
+}
+
+export async function prepareManagedFileChange(
+  spec: ManagedChangeSpec,
+): Promise<ManagedFileChange | undefined> {
+  const maximumBytes = spec.maximumBytes ?? MAX_SOURCE_BYTES;
+  if (spec.next !== undefined && Buffer.byteLength(spec.next) > maximumBytes) {
+    throw new Error(`${spec.label} exceeds ${maximumBytes} bytes: ${spec.filePath}`);
+  }
+  const original = await readPhysicalFile(spec.filePath, spec.label, maximumBytes);
+  if (spec.verifyExpectedSource && original?.contents !== spec.expectedSource) {
+    throw new Error(`${spec.label} changed before installation: ${spec.filePath}`);
+  }
+  if (!original && spec.next === undefined) return undefined;
+  return {
+    filePath: spec.filePath,
+    label: spec.label,
+    next: spec.next,
+    mode: spec.mode,
+    maximumBytes,
+    original,
+  };
+}
+
+async function assertUnchanged(change: ManagedFileChange, displayName: string): Promise<void> {
+  const current = await readPhysicalFile(change.filePath, change.label, change.maximumBytes);
+  if ((!current && change.original)
+    || (current && !change.original)
+    || (current && change.original && (
+      current.contents !== change.original.contents
+      || current.device !== change.original.device
+      || current.inode !== change.original.inode
+    ))) {
+    throw new Error(`${change.label} changed during ${displayName} installation: ${change.filePath}`);
+  }
+}
+
+async function writeExclusive(
+  filePath: string,
+  contents: string,
+  mode: number,
+  label: string,
+): Promise<void> {
+  let handle: FileHandle | undefined;
+  try {
+    handle = await fsp.open(filePath, 'wx', mode);
+    await handle.writeFile(contents, 'utf-8');
+    await handle.sync();
+    await handle.close();
+    handle = undefined;
+    if (process.platform !== 'win32') await fsp.chmod(filePath, mode);
+  } catch (error) {
+    const failures = [asError(error)];
+    if (handle) {
+      try { await handle.close(); } catch (closeError) { failures.push(asError(closeError)); }
+    }
+    try { await unlinkOptional(filePath); } catch (cleanupError) {
+      failures.push(asError(cleanupError));
+    }
+    if (failures.length > 1) throw new AggregateError(failures, `Stage ${label}`);
+    throw new Error(`Stage ${label}: ${errorMessage(error)}`, { cause: failures[0] });
+  }
+}
+
+async function reservePath(filePath: string, label: string): Promise<void> {
+  let handle: FileHandle | undefined;
+  try {
+    handle = await fsp.open(filePath, 'wx', 0o600);
+    await handle.close();
+    handle = undefined;
+    await fsp.unlink(filePath);
+  } catch (error) {
+    const failures = [asError(error)];
+    if (handle) {
+      try { await handle.close(); } catch (closeError) { failures.push(asError(closeError)); }
+    }
+    try { await unlinkOptional(filePath); } catch (cleanupError) {
+      failures.push(asError(cleanupError));
+    }
+    if (failures.length > 1) throw new AggregateError(failures, `Reserve ${label}`);
+    throw new Error(`Reserve ${label}: ${errorMessage(error)}`, { cause: failures[0] });
+  }
+}
+
+async function stage(change: ManagedFileChange, displayName: string): Promise<StagedChange> {
+  await assertUnchanged(change, displayName);
+  const token = randomUUID();
+  const directory = path.dirname(change.filePath);
+  const temporaryPath = change.next === undefined
+    ? undefined
+    : path.join(directory, `.${path.basename(change.filePath)}.${token}.tmp`);
+  const rollbackPath = change.original
+    ? path.join(directory, `.${path.basename(change.filePath)}.${token}.rollback`)
+    : undefined;
+  const staged: StagedChange = {
+    change,
+    temporaryPath,
+    rollbackPath,
+    committed: false,
+  };
+  try {
+    if (temporaryPath && change.next !== undefined) {
+      await writeExclusive(temporaryPath, change.next, change.mode, change.label);
+    }
+    if (rollbackPath && change.original) {
+      if (change.next === undefined) {
+        await reservePath(rollbackPath, `${change.label} rollback`);
+      } else {
+        await writeExclusive(
+          rollbackPath,
+          change.original.contents,
+          change.original.mode,
+          `${change.label} rollback`,
+        );
+      }
+    }
+    return staged;
+  } catch (error) {
+    const failures = [asError(error)];
+    for (const item of [temporaryPath, rollbackPath]) {
+      try { await unlinkOptional(item); } catch (cleanupError) {
+        failures.push(asError(cleanupError));
+      }
+    }
+    if (failures.length > 1) throw new AggregateError(failures, `Stage ${change.label}`);
+    throw error;
+  }
+}
+
+async function commit(
+  staged: StagedChange,
+  displayName: string,
+  renameFile: RenameFile,
+): Promise<void> {
+  await assertUnchanged(staged.change, displayName);
+  if (staged.change.next === undefined) {
+    if (!staged.rollbackPath) throw new Error(`Missing rollback data for ${staged.change.label}`);
+    await renameFile(staged.change.filePath, staged.rollbackPath);
+  } else {
+    if (!staged.temporaryPath) throw new Error(`Missing staged file for ${staged.change.label}`);
+    await renameFile(staged.temporaryPath, staged.change.filePath);
+  }
+  staged.committed = true;
+  const current = await readPhysicalFile(
+    staged.change.filePath,
+    staged.change.label,
+    staged.change.maximumBytes,
+  );
+  if (staged.change.next === undefined) {
+    if (current) throw new Error(`${staged.change.label} remained after removal`);
+    return;
+  }
+  if (!current || current.contents !== staged.change.next) {
+    throw new Error(
+      `${staged.change.label} changed immediately after commit: ${staged.change.filePath}`,
+    );
+  }
+  staged.committedSnapshot = current;
+}
+
+async function assertCommittedUnchanged(staged: StagedChange): Promise<void> {
+  const current = await readPhysicalFile(
+    staged.change.filePath,
+    staged.change.label,
+    staged.change.maximumBytes,
+  );
+  if (staged.change.next === undefined) {
+    if (current) {
+      throw new Error(
+        `${staged.change.label} changed during transaction recovery: ${staged.change.filePath}`,
+      );
+    }
+    return;
+  }
+  const committed = staged.committedSnapshot;
+  if (!current || !committed
+    || current.contents !== committed.contents
+    || current.device !== committed.device
+    || current.inode !== committed.inode) {
+    throw new Error(
+      `${staged.change.label} changed during transaction recovery: ${staged.change.filePath}`,
+    );
+  }
+}
+
+function preserveRollback(staged: StagedChange, cause: unknown): Error {
+  if (!staged.rollbackPath) return asError(cause);
+  const rollbackPath = staged.rollbackPath;
+  staged.rollbackPath = undefined;
+  return new Error(
+    `${errorMessage(cause)}; original content preserved at ${rollbackPath}`,
+    { cause: asError(cause) },
+  );
+}
+
+async function rollback(staged: StagedChange, renameFile: RenameFile): Promise<void> {
+  if (!staged.committed) return;
+  try {
+    await assertCommittedUnchanged(staged);
+  } catch (error) {
+    throw preserveRollback(staged, error);
+  }
+  try {
+    if (staged.change.next === undefined || staged.change.original) {
+      if (!staged.rollbackPath) throw new Error(`Missing rollback data for ${staged.change.label}`);
+      await renameFile(staged.rollbackPath, staged.change.filePath);
+    } else {
+      await unlinkOptional(staged.change.filePath);
+    }
+  } catch (error) {
+    throw preserveRollback(staged, error);
+  }
+}
+
+async function cleanup(staged: StagedChange): Promise<void> {
+  await Promise.all([
+    unlinkOptional(staged.temporaryPath),
+    unlinkOptional(staged.rollbackPath),
+  ]);
+}
+
+async function ensureManagedDirectory(directory: string, label: string): Promise<void> {
+  await fsp.mkdir(directory, { recursive: true, mode: 0o700 });
+  if (!await inspectPhysicalDirectory(directory, label)) {
+    throw new Error(`${label} is missing: ${directory}`);
+  }
+}
+
+function transactionDirectories(transaction: PreparedManagedTransaction): ManagedDirectory[] {
+  const directories = new Map<string, ManagedDirectory>();
+  for (const item of transaction.directories) directories.set(targetKey(item.path), item);
+  for (const change of transaction.changes) {
+    const directory = path.dirname(change.filePath);
+    const key = targetKey(directory);
+    if (!directories.has(key)) {
+      directories.set(key, { path: directory, label: `Directory for ${change.label}` });
+    }
+  }
+  return [...directories.values()];
+}
+
+export async function commitManagedTransaction(
+  transaction: PreparedManagedTransaction,
+  renameFile: RenameFile = fsp.rename,
+): Promise<void> {
+  const targets = new Set<string>();
+  for (const change of transaction.changes) {
+    const key = targetKey(change.filePath);
+    if (targets.has(key)) {
+      throw new Error(
+        `${transaction.displayName} installation contains duplicate file target ${change.filePath}`,
+      );
+    }
+    targets.add(key);
+  }
+  for (const directory of transactionDirectories(transaction)) {
+    await ensureManagedDirectory(directory.path, directory.label);
+  }
+  const staged: StagedChange[] = [];
+  try {
+    for (const change of transaction.changes) staged.push(await stage(change, transaction.displayName));
+    for (const item of staged) await commit(item, transaction.displayName, renameFile);
+  } catch (error) {
+    const failures = [asError(error)];
+    for (const item of [...staged].reverse()) {
+      try { await rollback(item, renameFile); } catch (rollbackError) {
+        failures.push(asError(rollbackError));
+      }
+    }
+    for (const item of staged) {
+      try { await cleanup(item); } catch (cleanupError) {
+        failures.push(asError(cleanupError));
+      }
+    }
+    throw new AggregateError(
+      failures,
+      `Install ${transaction.displayName} hooks: ${errorMessage(error)}`,
+    );
+  }
+  const failures: Error[] = [];
+  for (const item of staged) {
+    try { await cleanup(item); } catch (error) { failures.push(asError(error)); }
+  }
+  if (failures.length > 0) {
+    throw new AggregateError(
+      failures,
+      `Clean ${transaction.displayName} installation transaction files`,
+    );
+  }
+}

test/managed-transaction.test.mjs

@@ -0,0 +1,106 @@
+import assert from 'node:assert/strict';
+import {
+  mkdir,
+  mkdtemp,
+  readFile,
+  readdir,
+  rename,
+  rm,
+  writeFile,
+} from 'node:fs/promises';
+import os from 'node:os';
+import path from 'node:path';
+import test from 'node:test';
+import { pathToFileURL } from 'node:url';
+
+const transactionModuleUrl = pathToFileURL(
+  path.resolve('dist/plugins/managed-transaction.js'),
+).href;
+
+async function fixture() {
+  const root = await mkdtemp(path.join(os.tmpdir(), 'elydora-managed-transaction-'));
+  const directory = path.join(root, 'managed');
+  await mkdir(directory);
+  const updatePath = path.join(directory, 'update.txt');
+  const removePath = path.join(directory, 'remove.txt');
+  const createPath = path.join(directory, 'create.txt');
+  await writeFile(updatePath, 'old update\n');
+  await writeFile(removePath, 'old remove\n');
+  return {
+    root,
+    directory,
+    updatePath,
+    removePath,
+    createPath,
+    close: () => rm(root, { recursive: true, force: true }),
+  };
+}
+
+async function prepareTransaction(state) {
+  const { prepareManagedFileChange } = await import(transactionModuleUrl);
+  const changes = await Promise.all([
+    prepareManagedFileChange({
+      filePath: state.updatePath,
+      label: 'updated source',
+      next: 'new update\n',
+      mode: 0o600,
+    }),
+    prepareManagedFileChange({
+      filePath: state.removePath,
+      label: 'removed source',
+      mode: 0o600,
+    }),
+    prepareManagedFileChange({
+      filePath: state.createPath,
+      label: 'created source',
+      next: 'new create\n',
+      mode: 0o600,
+    }),
+  ]);
+  return {
+    displayName: 'test adapter',
+    directories: [{ path: state.directory, label: 'test directory' }],
+    changes: changes.filter(Boolean),
+  };
+}
+
+async function assertNoTransactionFiles(directory) {
+  const names = await readdir(directory);
+  assert.equal(names.some((name) => /\.(tmp|rollback)$/.test(name)), false, names.join(', '));
+}
+
+test('managed transaction commits update, removal, and creation atomically', async () => {
+  const state = await fixture();
+  try {
+    const { commitManagedTransaction } = await import(transactionModuleUrl);
+    await commitManagedTransaction(await prepareTransaction(state));
+    assert.equal(await readFile(state.updatePath, 'utf-8'), 'new update\n');
+    await assert.rejects(readFile(state.removePath), { code: 'ENOENT' });
+    assert.equal(await readFile(state.createPath, 'utf-8'), 'new create\n');
+    await assertNoTransactionFiles(state.directory);
+  } finally {
+    await state.close();
+  }
+});
+
+test('managed transaction restores update and removal after a later commit fails', async () => {
+  const state = await fixture();
+  try {
+    const { commitManagedTransaction } = await import(transactionModuleUrl);
+    let calls = 0;
+    await assert.rejects(
+      commitManagedTransaction(await prepareTransaction(state), async (source, destination) => {
+        calls += 1;
+        if (calls === 3) throw new Error('injected create failure');
+        await rename(source, destination);
+      }),
+      /injected create failure/,
+    );
+    assert.equal(await readFile(state.updatePath, 'utf-8'), 'old update\n');
+    assert.equal(await readFile(state.removePath, 'utf-8'), 'old remove\n');
+    await assert.rejects(readFile(state.createPath), { code: 'ENOENT' });
+    await assertNoTransactionFiles(state.directory);
+  } finally {
+    await state.close();
+  }
+});