fix(dev-infra): harden worktree hook ownership

.agents/notes/implemented/process/2026-07-27-worktree-local-lefthook.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/process/2026-07-27-worktree-local-lefthook.md
-2026-07-27-worktree-local-lefthook.md: f35fe4a91063bca6f29d61932e414d7d4843d2f0
-2026-07-27-worktree-local-lefthook.zh.md: c82e81f5a96f122c961234174fd123259f92ab9e
+2026-07-27-worktree-local-lefthook.md: 9d5e5583d6d8e3f15433f8b1a6f26f7b2c8cd854
+2026-07-27-worktree-local-lefthook.zh.md: dfca287ae3bbfc1414322d89da9cd93f78230d3c

.agents/notes/implemented/process/2026-07-27-worktree-local-lefthook.md

@@ -12,13 +12,13 @@ Lefthook-generated hooks prefer an absolute binary path captured from the instal
 
 ## Decision
 
-Hook installation is worktree-scoped. With `CI=true` or `GITHUB_ACTIONS=true`, the installer returns before Git discovery or mutation because automated jobs do not consume contributor hooks. Otherwise, it requires Git 2.26 or newer for configuration-scope provenance, upgrades a format-0 repository to format 1, enables `extensions.worktreeConfig`, and assigns the current worktree an absolute `core.hooksPath` at `$GIT_DIR/dsh-hooks`. Before first enabling the repository-wide extension, it inspects the dormant `config.worktree` file for the main worktree and every registered linked worktree, then refuses any settings whose activation would change the current or a sibling worktree. The main worktree receives `$GIT_COMMON_DIR/dsh-hooks`; each linked worktree receives the corresponding directory under `$GIT_COMMON_DIR/worktrees/<id>`. A repository-scoped lock serializes configuration migration and hook writes, including repeated concurrent installs. Each lock records a process ID and random ownership token; release verifies the same file identity and exact record. A dead or invalid lock is never broken automatically, so the diagnostic requires the contributor to confirm no installer is running and remove the lock manually.
+Hook installation is worktree-scoped. With `CI=true` or `GITHUB_ACTIONS=true`, the installer returns before Git discovery or mutation because automated jobs do not consume contributor hooks. Otherwise, it requires Git 2.26 or newer for configuration-scope provenance, upgrades a format-0 repository to format 1, enables `extensions.worktreeConfig`, and assigns the current worktree an absolute `core.hooksPath` at `$GIT_DIR/dsh-hooks`. Before the format bump, it refuses every existing `extensions.*` key in the common config or a conditional target because format 1 would activate that dormant repository extension. Before first enabling the worktree-config extension, it inspects the `config.worktree` file for the main worktree and every registered linked worktree and refuses dormant settings whose activation would change the current or a sibling worktree. The common repository config and every active or dormant worktree config must be regular files. The main worktree receives `$GIT_COMMON_DIR/dsh-hooks`; each linked worktree receives the corresponding directory under `$GIT_COMMON_DIR/worktrees/<id>`. A repository-scoped lock serializes configuration migration and hook writes, including repeated concurrent installs. Each lock records a process ID and random ownership token; release verifies the same file identity and exact record. A dead or invalid lock is never broken automatically, so the diagnostic requires the contributor to confirm no installer is running and remove the lock manually.
 
-The installer recognizes its hook directory with a private ownership marker and updates it idempotently. It inspects the effective scope, origin, and value of `core.hooksPath`, then refuses an unowned directory, every command-scoped path, and every non-owned worktree-scoped path, including values loaded through `config.worktree` includes. It follows conditional includes with Git's parser and refuses a command- or worktree-scoped include whose target provides, or cannot safely be shown not to provide, a hook path; an inactive condition therefore cannot later hide a user-owned path behind the installer's direct value. The same risk in an inherited system, global, or common-repository include requires `DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE=1`, which explicitly opts only the current worktree into Lefthook while other worktrees retain the inherited path. Unrelated conditional includes remain valid. Command-scoped Git configuration is removed from the Lefthook subprocess environment after validation. This opt-in does not attempt to chain arbitrary hook managers.
+The installer recognizes its hook directory with a private ownership marker and updates it idempotently. The marker records the absolute path last published to worktree config, so moving a checkout permits the installer to replace that exact stale owned value with the moved `$GIT_DIR/dsh-hooks` path and regenerate hooks; any other worktree-scoped value remains user-owned and is refused. Before invoking Lefthook, the marker and every existing generated hook must be an unaliased regular file, preventing a symlink or additional hard link from redirecting an overwrite outside the owned directory. It inspects the effective scope, origin, and value of `core.hooksPath`, then refuses an unowned directory, every command-scoped path, and every non-owned worktree-scoped path, including values loaded through `config.worktree` includes. It follows conditional includes with Git's parser and refuses a command- or worktree-scoped include whose target provides, or cannot safely be shown not to provide, a hook path; an inactive condition therefore cannot later hide a user-owned path behind the installer's direct value. The same risk in an inherited system, global, or common-repository include requires `DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE=1`, which explicitly opts only the current worktree into Lefthook while other worktrees retain the inherited path. Unrelated conditional includes remain valid. Command-scoped Git configuration is removed from the Lefthook subprocess environment after validation. This opt-in does not attempt to chain arbitrary hook managers.
 
-Enabling worktree config removes the standard redundant `core.bare=false` value from the common config because false remains Git's default; an explicit `core.worktree` or `core.bare=true`, whether direct or loaded through an active common-config include, is refused for manual migration. Before enabling the extension, the installer follows common-config conditional includes and refuses a target that provides, or cannot safely be shown not to provide, either migration-sensitive key; unrelated conditional includes remain valid. If Lefthook fails during a first install, the installer removes the new worktree override so the prior inherited or common hooks remain active. Legacy files in `$GIT_COMMON_DIR/hooks` are never removed or rewritten by the worktree-local installer.
+Enabling worktree config removes the standard redundant `core.bare=false` value from the common config because false remains Git's default; an explicit `core.worktree` or `core.bare=true`, whether direct or loaded through an active common-config include, is refused for manual migration. Before enabling the extension, the installer follows common-config conditional includes and refuses a target that provides, or cannot safely be shown not to provide, either migration-sensitive key; unrelated conditional includes remain valid. If Lefthook fails during a first install, the installer removes the new worktree override so the prior inherited or common hooks remain active. If that rollback also fails, one diagnostic preserves both failures for manual recovery. Legacy files in `$GIT_COMMON_DIR/hooks` are never removed or rewritten by the worktree-local installer.
 
-[`install-lefthook.spec.ts`](../../../../scripts/install-lefthook.spec.ts) exercises the CI no-op, main and linked worktrees, removal independence, repeated and concurrent installs, stale and replaced lock ownership, the Git version boundary, dormant sibling-config refusal, migration keys loaded through active and conditional common-config includes, scoped custom-path refusal and opt-in, active and inactive worktree includes, inherited conditional paths, command-environment isolation, legacy common-hook preservation, and failed-install rollback.
+[`install-lefthook.spec.ts`](../../../../scripts/install-lefthook.spec.ts) exercises the CI no-op, main and linked worktrees, removal independence, repeated and concurrent installs, checkout relocation, marker and hook alias refusal, stale and replaced lock ownership, the Git version boundary, dormant repository-extension and sibling-config refusal, common and worktree config file ownership, migration keys loaded through active and conditional common-config includes, scoped custom-path refusal and opt-in, active and inactive worktree includes, inherited conditional paths, command-environment isolation, legacy common-hook preservation, and successful and failed rollback after installation failure.
 
 ## Alternatives considered
 

.agents/notes/implemented/process/2026-07-27-worktree-local-lefthook.zh.md

@@ -12,13 +12,13 @@ Lefthook 生成的钩子会优先使用安装时从对应 worktree 记录的绝
 
 ## 决策
 
-钩子安装以 worktree 为作用域。当 `CI=true` 或 `GITHUB_ACTIONS=true` 时，安装程序会在探测 Git 或做出任何变更之前返回，因为自动化任务不会使用贡献者钩子。否则，为了获取配置作用域的来源信息，安装程序要求 Git 2.26 或更高版本；它会将格式版本为 0 的仓库升级到格式版本 1，启用 `extensions.worktreeConfig`，并将当前 worktree 的 `core.hooksPath` 设为指向 `$GIT_DIR/dsh-hooks` 的绝对路径。首次启用这一仓库级扩展前，安装程序会检查主 worktree 与每个已注册关联 worktree 中尚未生效的 `config.worktree` 文件，并拒绝任何一经激活就会改变当前或其他 worktree 的设置。主 worktree 使用 `$GIT_COMMON_DIR/dsh-hooks`；每个关联 worktree 则使用 `$GIT_COMMON_DIR/worktrees/<id>` 下的对应目录。仓库级锁会串行化配置迁移与钩子写入，包括并发触发的重复安装。每个锁都会记录进程 ID 和随机所有权令牌；释放锁时会验证同一个文件身份与完全一致的记录。安装程序绝不会自动破坏所属进程已结束或内容无效的锁，因此诊断会要求贡献者先确认没有安装程序正在运行，再手动移除该锁。
+钩子安装以 worktree 为作用域。当 `CI=true` 或 `GITHUB_ACTIONS=true` 时，安装程序会在探测 Git 或做出任何变更之前返回，因为自动化任务不会使用贡献者钩子。否则，为了获取配置作用域的来源信息，安装程序要求 Git 2.26 或更高版本；它会将格式版本为 0 的仓库升级到格式版本 1，启用 `extensions.worktreeConfig`，并将当前 worktree 的 `core.hooksPath` 设为指向 `$GIT_DIR/dsh-hooks` 的绝对路径。提升格式版本之前，若共用配置或条件目标中存在任何 `extensions.*` 键，安装程序都会拒绝继续，因为格式 1 会激活这类尚未生效的仓库扩展。首次启用 worktree 配置扩展前，安装程序会检查主 worktree 与每个已注册关联 worktree 中的 `config.worktree` 文件，并拒绝一经激活就会改变当前或其他 worktree 的尚未生效设置。共用仓库配置以及每个生效或尚未生效的 worktree 配置都必须是常规文件。主 worktree 使用 `$GIT_COMMON_DIR/dsh-hooks`；每个关联 worktree 则使用 `$GIT_COMMON_DIR/worktrees/<id>` 下的对应目录。仓库级锁会串行化配置迁移与钩子写入，包括并发触发的重复安装。每个锁都会记录进程 ID 和随机所有权令牌；释放锁时会验证同一个文件身份与完全一致的记录。安装程序绝不会自动破坏所属进程已结束或内容无效的锁，因此诊断会要求贡献者先确认没有安装程序正在运行，再手动移除该锁。
 
-安装程序通过私有所有权标记识别其钩子目录，并以幂等方式更新该目录。它会检查 `core.hooksPath` 的生效作用域、来源和值，并拒绝没有所有权标记的目录、所有命令作用域路径，以及所有非本安装程序所有的 worktree 作用域路径，包括通过 `config.worktree` 中的 include 加载的值。安装程序会用 Git 的解析器跟踪 `includeIf`；若命令作用域或 worktree 作用域的目标配置提供钩子路径，或者无法安全证明它不会提供钩子路径，安装程序就会拒绝继续。因此，安装时未生效的条件日后也无法在安装程序的直接配置值之前隐藏用户自有路径。系统配置、全局配置或共用仓库配置中存在相同风险时，必须设置 `DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE=1`，从而只让当前 worktree 显式启用 Lefthook，其他 worktree 则继续使用继承路径。与钩子无关的 `includeIf` 仍然有效。完成验证后，Lefthook 子进程的环境会移除命令作用域的 Git 配置。这项显式选择不会尝试串联任意钩子管理器。
+安装程序通过私有所有权标记识别其钩子目录，并以幂等方式更新该目录。该标记会记录上次写入 worktree 配置的绝对路径，因此检出目录移动后，安装程序可以将这一确切的陈旧自有值替换为移动后的 `$GIT_DIR/dsh-hooks` 路径并重新生成钩子；其他 worktree 作用域值仍视为用户自有并会被拒绝。调用 Lefthook 前，所有权标记和每个已有的生成钩子都必须是不带别名的常规文件，以防符号链接或额外硬链接把覆盖操作重定向到自有目录外。安装程序会检查 `core.hooksPath` 的生效作用域、来源和值，并拒绝没有所有权标记的目录、所有命令作用域路径，以及所有非本安装程序所有的 worktree 作用域路径，包括通过 `config.worktree` 中的 include 加载的值。安装程序会用 Git 的解析器跟踪 `includeIf`；若命令作用域或 worktree 作用域的目标配置提供钩子路径，或者无法安全证明它不会提供钩子路径，安装程序就会拒绝继续。因此，安装时未生效的条件日后也无法在安装程序的直接配置值之前隐藏用户自有路径。系统配置、全局配置或共用仓库配置中存在相同风险时，必须设置 `DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE=1`，从而只让当前 worktree 显式启用 Lefthook，其他 worktree 则继续使用继承路径。与钩子无关的 `includeIf` 仍然有效。完成验证后，Lefthook 子进程的环境会移除命令作用域的 Git 配置。这项显式选择不会尝试串联任意钩子管理器。
 
-启用 worktree 配置时，安装程序会从共用配置中移除标准但冗余的 `core.bare=false`，因为 false 仍是 Git 的默认值；无论共用配置直接设置了 `core.worktree` 或 `core.bare=true`，还是通过当前生效的 include 加载了这些值，安装程序都会拒绝继续并要求手动迁移。启用扩展之前，安装程序会跟踪共用配置中的 `includeIf`；若目标配置提供任一迁移敏感键，或者无法安全证明它不会提供这些键，安装程序就会拒绝继续。与迁移无关的 `includeIf` 仍然有效。若首次安装期间 Lefthook 失败，安装程序会移除新建的 worktree 覆盖，使原有的继承钩子或共用钩子继续生效。worktree 本地安装程序绝不会移除或改写 `$GIT_COMMON_DIR/hooks` 中的旧文件。
+启用 worktree 配置时，安装程序会从共用配置中移除标准但冗余的 `core.bare=false`，因为 false 仍是 Git 的默认值；无论共用配置直接设置了 `core.worktree` 或 `core.bare=true`，还是通过当前生效的 include 加载了这些值，安装程序都会拒绝继续并要求手动迁移。启用扩展之前，安装程序会跟踪共用配置中的 `includeIf`；若目标配置提供任一迁移敏感键，或者无法安全证明它不会提供这些键，安装程序就会拒绝继续。与迁移无关的 `includeIf` 仍然有效。若首次安装期间 Lefthook 失败，安装程序会移除新建的 worktree 覆盖，使原有的继承钩子或共用钩子继续生效。若回滚也失败，同一条诊断会保留两次失败，供手动恢复。worktree 本地安装程序绝不会移除或改写 `$GIT_COMMON_DIR/hooks` 中的旧文件。
 
-[`install-lefthook.spec.ts`](../../../../scripts/install-lefthook.spec.ts) 覆盖 CI 下不执行操作的行为、主 worktree 和关联 worktree、移除后的相互独立性、重复与并发安装、陈旧锁与锁所有权被替换、Git 版本边界、拒绝激活其他 worktree 中尚未生效的配置、通过生效及条件式共用配置 include 加载的迁移键、按作用域拒绝自定义路径与显式覆盖、生效及未生效的 worktree include、继承的条件式路径、命令环境隔离、保留旧公共钩子，以及安装失败时的回滚。
+[`install-lefthook.spec.ts`](../../../../scripts/install-lefthook.spec.ts) 覆盖 CI 下不执行操作的行为、主 worktree 和关联 worktree、移除后的相互独立性、重复与并发安装、检出目录移动、拒绝标记和钩子别名、陈旧锁与锁所有权被替换、Git 版本边界、拒绝尚未生效的仓库扩展和其他 worktree 配置、共用及 worktree 配置文件的所有权、通过生效及条件式共用配置 include 加载的迁移键、按作用域拒绝自定义路径与显式覆盖、生效及未生效的 worktree include、继承的条件式路径、命令环境隔离、保留旧公共钩子，以及安装失败后成功或失败的回滚。
 
 ## 考虑过的替代方案
 

docs/development.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/development.md
-development.md: dfe99362aa9b881645c69b2bab74180280b4f1b3
-development.zh.md: 10d9129b288d1540b27a9ddc94f1f4acdd3f5f9e
+development.md: f1a853acfd1e89104b8013a5b5e9c4032979234f
+development.zh.md: 493284e38ad68768b1159778d5dd50aecfe9ccd1

docs/development.md

@@ -27,7 +27,7 @@ If hooks are missing because dependencies were restored from cache or `postinsta
 node scripts/install-lefthook.mjs
 ```
 
-The wrapper refuses to replace an existing user-owned `core.hooksPath`. If an inherited system, global, or common-repository path should remain active in other worktrees while this worktree opts into lefthook, inspect that path first and rerun with `DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE=1`; command-scoped and worktree-scoped custom paths are never overridden and must be integrated or removed explicitly. The same rules apply when a currently inactive conditional include can provide a hook path; unrelated conditional includes remain valid. Before enabling the worktree-config extension, conditional common-config targets that may contain `core.worktree` or `core.bare=true` require manual migration. A dormant `config.worktree` in any registered worktree also requires inspection and explicit migration or removal before the extension can be enabled without changing that worktree. If the installer reports a stale or invalid lock, confirm no installer is running, remove the reported lock manually, and rerun the command.
+The wrapper refuses to replace an existing user-owned `core.hooksPath`. If an inherited system, global, or common-repository path should remain active in other worktrees while this worktree opts into lefthook, inspect that path first and rerun with `DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE=1`; command-scoped and worktree-scoped custom paths are never overridden and must be integrated or removed explicitly. The same rules apply when a currently inactive conditional include can provide a hook path; unrelated conditional includes remain valid. Before upgrading a format-0 repository, existing `extensions.*` keys in the common config or a conditional target require manual audit and migration because format 1 activates them. Before enabling the worktree-config extension, conditional common-config targets that may contain `core.worktree` or `core.bare=true` require manual migration. A dormant `config.worktree` in any registered worktree also requires inspection and explicit migration or removal before the extension can be enabled without changing that worktree. The common repository config and every active or dormant worktree config must be regular files. The owned hook directory may contain only unaliased regular files; replace a reported symlink, hard link, or non-file entry before retrying. After moving the checkout, rerun the wrapper so its ownership marker can replace the exact stale path it installed and regenerate hooks at the new Git directory. If the installer reports a stale or invalid lock, confirm no installer is running, remove the reported lock manually, and rerun the command. If Lefthook installation and automatic hook-path rollback both fail, the diagnostic preserves both failures; inspect the worktree config and remove the new path manually before retrying.
 
 Run typecheck once after a fresh clone:
 

docs/development.zh.md

@@ -27,7 +27,7 @@ pnpm install
 node scripts/install-lefthook.mjs
 ```
 
-包装脚本拒绝替换现有且由用户自行管理的 `core.hooksPath`。若要让继承自系统、全局或共用仓库配置的路径在其他 worktree 中继续生效，同时让当前 worktree 显式启用 lefthook，请先检查该路径，再设置 `DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE=1` 重新运行；命令作用域和 worktree 作用域的自定义路径绝不会被覆盖，必须显式集成或移除。当前未生效的 `includeIf` 可能提供钩子路径时，同样适用这些规则；与钩子无关的 `includeIf` 仍然有效。worktree 配置扩展启用之前，可能包含 `core.worktree` 或 `core.bare=true` 的共用配置 `includeIf` 目标需要手动迁移。任一已注册 worktree 中尚未生效的 `config.worktree` 也必须先经过检查并显式迁移或移除，才能在不改变该 worktree 的前提下启用扩展。若安装程序报告陈旧锁或无效锁，请先确认没有安装程序正在运行，手动移除诊断中报告的锁，再重新运行命令。
+包装脚本拒绝替换现有且由用户自行管理的 `core.hooksPath`。若要让继承自系统、全局或共用仓库配置的路径在其他 worktree 中继续生效，同时让当前 worktree 显式启用 lefthook，请先检查该路径，再设置 `DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE=1` 重新运行；命令作用域和 worktree 作用域的自定义路径绝不会被覆盖，必须显式集成或移除。当前未生效的 `includeIf` 可能提供钩子路径时，同样适用这些规则；与钩子无关的 `includeIf` 仍然有效。升级格式版本为 0 的仓库之前，若共用配置或条件目标中已有 `extensions.*` 键，就需要手动审计和迁移，因为格式 1 会激活这些键。worktree 配置扩展启用之前，可能包含 `core.worktree` 或 `core.bare=true` 的共用配置 `includeIf` 目标需要手动迁移。任一已注册 worktree 中尚未生效的 `config.worktree` 也必须先经过检查并显式迁移或移除，才能在不改变该 worktree 的前提下启用扩展。共用仓库配置以及每个生效或尚未生效的 worktree 配置都必须是常规文件。自有钩子目录只能包含不带别名的常规文件；请先替换诊断中报告的符号链接、硬链接或非文件条目，再重试。检出目录移动后，请重新运行包装脚本，使其所有权标记可以替换之前写入的确切陈旧路径，并在新的 Git 目录中重新生成钩子。若安装程序报告陈旧锁或无效锁，请先确认没有安装程序正在运行，手动移除诊断中报告的锁，再重新运行命令。若 Lefthook 安装和钩子路径自动回滚都失败，诊断会保留两次失败；请检查 worktree 配置并手动移除新路径，再重试。
 
 新克隆后请先运行一次类型检查：
 

scripts/install-lefthook.mjs

@@ -7,12 +7,15 @@ import { dirname, isAbsolute, join, resolve } from 'node:path'
 const MINIMUM_GIT = [2, 26, 0]
 const HOOKS_DIRECTORY = 'dsh-hooks'
 const OWNERSHIP_MARKER = '.dsh-lefthook-owned'
-const OWNERSHIP_MARKER_CONTENT = 'deepseek-harness worktree-local lefthook hooks\n'
+const LEGACY_OWNERSHIP_MARKER_CONTENT = 'deepseek-harness worktree-local lefthook hooks\n'
+const OWNERSHIP_MARKER_VERSION = 1
+const OWNERSHIP_MARKER_OWNER = 'deepseek-harness worktree-local lefthook hooks'
 const INSTALL_LOCK = 'dsh-lefthook-install.lock'
 const INSTALL_LOCK_TIMEOUT_MS = 30_000
 const INSTALL_LOCK_POLL_MS = 50
 const ALLOW_HOOKS_PATH_OVERRIDE = 'DSH_LEFTHOOK_ALLOW_HOOKS_PATH_OVERRIDE'
 const CONDITIONAL_INCLUDE_PATTERN = '^includeif\\..*\\.path$'
+const REPOSITORY_EXTENSION_PATTERN = '^extensions\\.'
 
 function errorCode(error) {
   return typeof error === 'object' && error !== null && 'code' in error
@@ -177,17 +180,37 @@ function registeredWorktreeConfigPaths(commonDirectory) {
   return paths
 }
 
-function assertDormantWorktreeConfigs(root, commonDirectory, commonConfigPath, currentConfigPath) {
-  if (worktreeConfigExtensionEnabled(root, commonConfigPath)) return
+function lstatIfPresent(path) {
+  try {
+    return lstatSync(path)
+  } catch (error) {
+    if (errorCode(error) === 'ENOENT') return undefined
+    throw error
+  }
+}
+
+function assertCommonConfigFile(commonConfigPath) {
+  const configStat = lstatIfPresent(commonConfigPath)
+  if (configStat === undefined || !configStat.isFile() || configStat.isSymbolicLink()) {
+    throw new Error(
+      `refusing common repository config ${JSON.stringify(commonConfigPath)} because it is not a regular file`,
+    )
+  }
+}
+
+function assertWorktreeConfigFiles(root, commonDirectory, commonConfigPath, currentConfigPath) {
+  const extensionEnabled = worktreeConfigExtensionEnabled(root, commonConfigPath)
   for (const configPath of registeredWorktreeConfigPaths(commonDirectory)) {
-    if (!existsSync(configPath)) continue
-    const configStat = lstatSync(configPath)
+    const configStat = lstatIfPresent(configPath)
+    if (configStat === undefined) continue
     if (!configStat.isFile() || configStat.isSymbolicLink()) {
+      const state = extensionEnabled ? 'active' : 'dormant'
       throw new Error(
-        `cannot enable extensions.worktreeConfig while dormant worktree config ${JSON.stringify(configPath)} `
-        + 'is not a regular file; inspect it and enable the extension explicitly, or remove it, before retrying',
+        `refusing ${state} worktree config ${JSON.stringify(configPath)} because it is not a regular file; `
+        + 'replace it with a regular worktree config or remove it before retrying',
       )
     }
+    if (extensionEnabled) continue
     if (!hasDirectConfigEntries(root, configPath)) continue
     const isCurrent = normalizedPath(configPath) === normalizedPath(currentConfigPath)
     const owner = isCurrent ? 'current' : 'sibling'
@@ -259,7 +282,13 @@ function conditionalIncludeRisk(root, entry, inspect) {
   return inspectConditionalConfig(root, target, inspect)
 }
 
-function migrationConfigSubject(root, configPath) {
+function migrationConfigSubject(root, configPath, rejectRepositoryExtensions) {
+  if (rejectRepositoryExtensions) {
+    const extensionEntry = fileConfigMatchingEntries(root, configPath, REPOSITORY_EXTENSION_PATTERN)[0]
+    if (extensionEntry !== undefined) {
+      return `${extensionEntry.name} (${configSource(extensionEntry)})`
+    }
+  }
   const worktreeEntry = fileConfigEntries(root, configPath, 'core.worktree')[0]
   if (worktreeEntry !== undefined) return `core.worktree (${configSource(worktreeEntry)})`
   const trueBareEntry = fileConfigEntries(root, configPath, 'core.bare')
@@ -272,7 +301,7 @@ function hooksPathConfigSubject(root, configPath) {
   return entry === undefined ? undefined : `core.hooksPath (${configSource(entry)})`
 }
 
-function ensureWorktreeConfig(root, commonConfigPath) {
+function planWorktreeConfigMigration(root, commonConfigPath) {
   const versions = fileConfigValues(root, commonConfigPath, 'core.repositoryFormatVersion')
   const versionText = assertSingle(versions, 'core.repositoryFormatVersion')
   const version = Number(versionText)
@@ -280,6 +309,21 @@ function ensureWorktreeConfig(root, commonConfigPath) {
     throw new Error(`unsupported core.repositoryFormatVersion: ${JSON.stringify(versionText)}`)
   }
 
+  if (version === 0) {
+    const extensionEntry = fileConfigMatchingEntries(
+      root,
+      commonConfigPath,
+      REPOSITORY_EXTENSION_PATTERN,
+    )[0]
+    if (extensionEntry !== undefined) {
+      throw new Error(
+        `cannot upgrade core.repositoryFormatVersion from 0 while dormant repository extension `
+        + `${extensionEntry.name} is configured (${configSource(extensionEntry)}); `
+        + 'audit and migrate it, then set repository format 1 explicitly before retrying',
+      )
+    }
+  }
+
   const extensionEnabled = worktreeConfigExtensionEnabled(root, commonConfigPath)
 
   if (!extensionEnabled) {
@@ -287,7 +331,7 @@ function ensureWorktreeConfig(root, commonConfigPath) {
       const risk = conditionalIncludeRisk(
         root,
         entry,
-        configPath => migrationConfigSubject(root, configPath),
+        configPath => migrationConfigSubject(root, configPath, version === 0),
       )
       if (risk !== undefined) {
         const reason = risk.subject ?? risk.detail
@@ -318,6 +362,11 @@ function ensureWorktreeConfig(root, commonConfigPath) {
   const directBareText = assertSingle(fileConfigValues(root, commonConfigPath, 'core.bare'), 'core.bare')
   const directBare = directBareText === undefined ? undefined : parseGitBoolean(directBareText, 'core.bare')
 
+  return { directBare, extensionEnabled, version }
+}
+
+function applyWorktreeConfigMigration(root, commonConfigPath, migration) {
+  const { directBare, extensionEnabled, version } = migration
   if (version === 0) {
     git(['config', '--file', commonConfigPath, 'core.repositoryFormatVersion', '1'], root)
   }
@@ -430,13 +479,38 @@ async function acquireInstallLock(commonDirectory) {
   }
 }
 
-function ensureOwnedHooksDirectory(hooksPath) {
-  const markerPath = join(hooksPath, OWNERSHIP_MARKER)
-  if (!existsSync(hooksPath)) {
-    mkdirSync(hooksPath, { mode: 0o700 })
-    writeFileSync(markerPath, OWNERSHIP_MARKER_CONTENT, { flag: 'wx', mode: 0o600 })
-    return
+function ownershipMarkerContent(hooksPath) {
+  return `${JSON.stringify({
+    version: OWNERSHIP_MARKER_VERSION,
+    owner: OWNERSHIP_MARKER_OWNER,
+    hooksPath,
+  })}\n`
+}
+
+function parseOwnershipMarker(content, hooksPath) {
+  if (content === LEGACY_OWNERSHIP_MARKER_CONTENT) return { hooksPath, legacy: true }
+  let parsed
+  try {
+    parsed = JSON.parse(content)
+  } catch {
+    return undefined
   }
+  if (
+    typeof parsed !== 'object'
+    || parsed === null
+    || parsed.version !== OWNERSHIP_MARKER_VERSION
+    || parsed.owner !== OWNERSHIP_MARKER_OWNER
+    || typeof parsed.hooksPath !== 'string'
+    || !isAbsolute(parsed.hooksPath)
+  ) {
+    return undefined
+  }
+  return { hooksPath: parsed.hooksPath, legacy: false }
+}
+
+function inspectOwnedHooksDirectory(hooksPath) {
+  const markerPath = join(hooksPath, OWNERSHIP_MARKER)
+  if (!existsSync(hooksPath)) return undefined
   const hooksStat = lstatSync(hooksPath)
   if (!hooksStat.isDirectory() || hooksStat.isSymbolicLink()) {
     throw new Error(`refusing to use non-directory or symlinked hooks path ${hooksPath}`)
@@ -445,9 +519,36 @@ function ensureOwnedHooksDirectory(hooksPath) {
     throw new Error(`refusing to overwrite unowned hooks directory ${hooksPath}`)
   }
   const markerStat = lstatSync(markerPath)
-  if (!markerStat.isFile() || markerStat.isSymbolicLink() || readFileSync(markerPath, 'utf8') !== OWNERSHIP_MARKER_CONTENT) {
+  const marker = markerStat.isFile() && !markerStat.isSymbolicLink() && markerStat.nlink === 1
+    ? parseOwnershipMarker(readFileSync(markerPath, 'utf8'), hooksPath)
+    : undefined
+  if (marker === undefined) {
     throw new Error(`refusing to overwrite hooks directory with an invalid ownership marker: ${hooksPath}`)
   }
+  for (const name of readdirSync(hooksPath)) {
+    if (name === OWNERSHIP_MARKER) continue
+    const entryPath = join(hooksPath, name)
+    const entryStat = lstatSync(entryPath)
+    if (!entryStat.isFile() || entryStat.isSymbolicLink() || entryStat.nlink !== 1) {
+      throw new Error(
+        `refusing to overwrite non-regular or multiply linked hook entry ${JSON.stringify(entryPath)}`,
+      )
+    }
+  }
+  return { markerPath, ...marker }
+}
+
+function ensureOwnedHooksDirectory(hooksPath) {
+  const inspected = inspectOwnedHooksDirectory(hooksPath)
+  if (inspected !== undefined) return inspected
+  mkdirSync(hooksPath, { mode: 0o700 })
+  const markerPath = join(hooksPath, OWNERSHIP_MARKER)
+  writeFileSync(markerPath, ownershipMarkerContent(hooksPath), { flag: 'wx', mode: 0o600 })
+  return { markerPath, hooksPath, legacy: false }
+}
+
+function updateOwnershipMarker(markerPath, hooksPath) {
+  writeFileSync(markerPath, ownershipMarkerContent(hooksPath), { mode: 0o600 })
 }
 
 function environmentWithoutCommandGitConfig() {
@@ -588,6 +689,13 @@ async function main() {
   let installationError
 
   try {
+    assertCommonConfigFile(commonConfigPath)
+    assertWorktreeConfigFiles(
+      root,
+      commonDirectory,
+      commonConfigPath,
+      worktreeConfigPath,
+    )
     const worktreeEntries = fileConfigEntries(root, worktreeConfigPath, 'core.hooksPath')
     const includedWorktreeEntry = worktreeEntries.find(
       entry => !originIsFile(entry.origin, root, worktreeConfigPath),
@@ -599,14 +707,20 @@ async function main() {
       worktreeEntries.map(entry => entry.value),
       'worktree core.hooksPath',
     )
+    let ownedHooksDirectory
     if (worktreePath !== undefined && worktreePath !== hooksPath) {
-      refuseScopedHooksPath({ origin: `file:${worktreeConfigPath}`, scope: 'worktree', value: worktreePath })
+      ownedHooksDirectory = inspectOwnedHooksDirectory(hooksPath)
+      if (ownedHooksDirectory === undefined || ownedHooksDirectory.hooksPath !== worktreePath) {
+        refuseScopedHooksPath({ origin: `file:${worktreeConfigPath}`, scope: 'worktree', value: worktreePath })
+      }
     }
+    const directWorktreePathIsOwned = worktreePath !== undefined
+      && (worktreePath === hooksPath || ownedHooksDirectory?.hooksPath === worktreePath)
     const effectiveEntry = effectiveConfigEntry(root, 'core.hooksPath')
     if (effectiveEntry !== undefined) {
       const effectivePathIsOwned = effectiveEntry.scope === 'worktree'
-        && effectiveEntry.value === hooksPath
-        && worktreePath === hooksPath
+        && effectiveEntry.value === worktreePath
+        && directWorktreePathIsOwned
         && originIsFile(effectiveEntry.origin, root, worktreeConfigPath)
       if (!effectivePathIsOwned) {
         if (effectiveEntry.scope === 'command' || effectiveEntry.scope === 'worktree') {
@@ -622,19 +736,21 @@ async function main() {
     }
     assertConditionalHooksPaths(root, worktreeConfigPath)
 
-    assertDormantWorktreeConfigs(
-      root,
-      commonDirectory,
-      commonConfigPath,
-      worktreeConfigPath,
-    )
-    ensureOwnedHooksDirectory(hooksPath)
-    ensureWorktreeConfig(root, commonConfigPath)
+    const migration = planWorktreeConfigMigration(root, commonConfigPath)
+    ownedHooksDirectory = ensureOwnedHooksDirectory(hooksPath)
+    if (
+      worktreePath !== undefined
+      && worktreePath !== hooksPath
+      && ownedHooksDirectory.hooksPath !== worktreePath
+    ) {
+      throw new Error(`hooks directory ownership changed while relocating ${JSON.stringify(worktreePath)}`)
+    }
+    applyWorktreeConfigMigration(root, commonConfigPath, migration)
 
     let pathChanged = false
     try {
       git(['config', '--worktree', 'core.hooksPath', hooksPath], root)
-      pathChanged = worktreePath === undefined
+      pathChanged = worktreePath !== hooksPath
       const installedEntry = effectiveConfigEntry(root, 'core.hooksPath')
       if (
         installedEntry === undefined
@@ -645,9 +761,22 @@ async function main() {
         throw new Error('new worktree-local core.hooksPath did not become the effective direct worktree value')
       }
       runLefthook(root, lefthook)
+      updateOwnershipMarker(ownedHooksDirectory.markerPath, hooksPath)
     } catch (error) {
       if (pathChanged) {
-        git(['config', '--worktree', '--unset-all', 'core.hooksPath'], root)
+        try {
+          if (worktreePath === undefined) {
+            git(['config', '--worktree', '--unset-all', 'core.hooksPath'], root)
+          } else {
+            git(['config', '--worktree', 'core.hooksPath', worktreePath], root)
+          }
+        } catch (rollbackError) {
+          throw new AggregateError(
+            [error, rollbackError],
+            `Lefthook installation failed: ${String(error)}; `
+            + `worktree hook rollback also failed: ${String(rollbackError)}`,
+          )
+        }
       }
       throw error
     }

scripts/install-lefthook.spec.ts

@@ -2,10 +2,14 @@ import { spawn, spawnSync } from 'node:child_process'
 import {
   chmodSync,
   existsSync,
+  linkSync,
   mkdirSync,
   mkdtempSync,
+  lstatSync,
   readFileSync,
+  renameSync,
   rmSync,
+  symlinkSync,
   writeFileSync,
 } from 'node:fs'
 import { tmpdir } from 'node:os'
@@ -91,6 +95,10 @@ if (!shouldFail) {
   for (const name of ['pre-commit', 'pre-push']) writeFileSync(join(hooksPath, name), hook, { mode: 0o755 })
 }
 if (existsSync(running)) unlinkSync(running)
+if (process.env.DSH_TEST_LEFTHOOK_BREAK_WORKTREE_CONFIG === '1') {
+  const configPath = execFileSync('git', ['rev-parse', '--git-path', 'config.worktree'], { encoding: 'utf8' }).trim()
+  writeFileSync(configPath, '[invalid\\n')
+}
 if (shouldFail) process.exit(77)
 `
 }
@@ -275,6 +283,125 @@ describe('worktree-local Lefthook installer', () => {
     expect(existsSync(join(hooksPath(fixture, fixture.main), '.fake-lefthook-running'))).toBe(false)
   })
 
+  it('repairs its owned absolute hook path after the checkout moves', async () => {
+    const fixture = createFixture()
+    const oldRoot = fixture.main
+    const first = await runInstaller(fixture, oldRoot)
+    expect(first.status, first.stderr).toBe(0)
+    const oldHooks = hooksPath(fixture, oldRoot)
+    const movedRoot = join(fixture.container, 'moved-main')
+    renameSync(oldRoot, movedRoot)
+
+    const moved = await runInstaller(fixture, movedRoot)
+
+    expect(moved.status, moved.stderr).toBe(0)
+    const movedHooks = hooksPath(fixture, movedRoot)
+    expect(movedHooks).not.toBe(oldHooks)
+    expect(git(fixture, movedRoot, ['config', '--worktree', '--get', 'core.hooksPath'])).toBe(movedHooks)
+    const canonicalMoved = git(fixture, movedRoot, ['rev-parse', '--show-toplevel'])
+    expect(readFileSync(join(movedHooks, 'pre-commit'), 'utf8')).toContain(`# root=${canonicalMoved}`)
+    expect(readFileSync(join(movedHooks, '.dsh-lefthook-owned'), 'utf8')).toContain(
+      JSON.stringify(movedHooks),
+    )
+  })
+
+  it.skipIf(process.platform === 'win32')('refuses a multiply linked ownership marker before relocation rewrites it', async () => {
+    const fixture = createFixture()
+    const oldRoot = fixture.main
+    const first = await runInstaller(fixture, oldRoot)
+    expect(first.status, first.stderr).toBe(0)
+    const oldHooks = hooksPath(fixture, oldRoot)
+    const markerName = '.dsh-lefthook-owned'
+    const externalMarker = join(fixture.container, 'external-marker')
+    linkSync(join(oldHooks, markerName), externalMarker)
+    const externalContent = readFileSync(externalMarker, 'utf8')
+    const movedRoot = join(fixture.container, 'moved-main')
+    renameSync(oldRoot, movedRoot)
+
+    const result = await runInstaller(fixture, movedRoot)
+
+    expect(result.status).toBe(1)
+    expect(result.stderr).toContain('invalid ownership marker')
+    expect(readFileSync(externalMarker, 'utf8')).toBe(externalContent)
+  })
+
+  it.skipIf(process.platform === 'win32')('refuses aliased generated hooks before Lefthook can overwrite their targets', async () => {
+    for (const kind of ['symlink', 'hardlink'] as const) {
+      const fixture = createFixture()
+      const first = await runInstaller(fixture, fixture.main)
+      expect(first.status, first.stderr).toBe(0)
+      const hook = join(hooksPath(fixture, fixture.main), 'pre-commit')
+      const externalHook = join(fixture.container, `${kind}-external-hook`)
+      rmSync(hook)
+      write(externalHook, `external ${kind} target\n`)
+      if (kind === 'symlink') symlinkSync(externalHook, hook)
+      else linkSync(externalHook, hook)
+      const externalContent = readFileSync(externalHook, 'utf8')
+
+      const result = await runInstaller(fixture, fixture.main)
+
+      expect(result.status).toBe(1)
+      expect(result.stderr).toContain('non-regular or multiply linked hook entry')
+      expect(readFileSync(externalHook, 'utf8')).toBe(externalContent)
+    }
+  })
+
+  it('restores the marker-backed stale hook path when relocation reinstall fails', async () => {
+    const fixture = createFixture()
+    const oldRoot = fixture.main
+    const first = await runInstaller(fixture, oldRoot)
+    expect(first.status, first.stderr).toBe(0)
+    const oldHooks = hooksPath(fixture, oldRoot)
+    const markerName = '.dsh-lefthook-owned'
+    const previousMarker = readFileSync(join(oldHooks, markerName), 'utf8')
+    const movedRoot = join(fixture.container, 'moved-main')
+    renameSync(oldRoot, movedRoot)
+
+    const failed = await runInstaller(fixture, movedRoot, { DSH_TEST_LEFTHOOK_FAIL: '1' })
+
+    expect(failed.status).toBe(1)
+    expect(failed.stderr).toContain('exit status 77')
+    const movedHooks = hooksPath(fixture, movedRoot)
+    expect(git(fixture, movedRoot, ['config', '--worktree', '--get', 'core.hooksPath'])).toBe(oldHooks)
+    expect(readFileSync(join(movedHooks, markerName), 'utf8')).toBe(previousMarker)
+  })
+
+  it('refuses dormant repository extensions before upgrading the repository format', async () => {
+    const fixture = createFixture()
+    const commonConfig = join(commonDirectory(fixture), 'config')
+    git(fixture, fixture.main, ['config', 'extensions.dshUnknown', 'true'])
+    expect(gitResult(fixture, fixture.main, ['status', '--porcelain']).status).toBe(0)
+
+    const result = await runInstaller(fixture, fixture.main)
+
+    expect(result.status).toBe(1)
+    expect(result.stderr).toContain('dormant repository extension extensions.dshunknown')
+    expect(git(fixture, fixture.main, [
+      'config', '--file', commonConfig, '--get', 'core.repositoryFormatVersion',
+    ])).toBe('0')
+    expect(gitResult(fixture, fixture.main, ['config', '--get', 'extensions.worktreeConfig']).status).toBe(1)
+    expect(gitResult(fixture, fixture.main, ['status', '--porcelain']).status).toBe(0)
+    expect(existsSync(hooksPath(fixture, fixture.main))).toBe(false)
+  })
+
+  it.skipIf(process.platform === 'win32')('refuses a symlinked common repository config before writing through it', async () => {
+    const fixture = createFixture()
+    const commonConfig = join(commonDirectory(fixture), 'config')
+    const externalConfig = join(fixture.container, 'external-common.gitconfig')
+    renameSync(commonConfig, externalConfig)
+    symlinkSync(externalConfig, commonConfig)
+    const externalContent = readFileSync(externalConfig, 'utf8')
+
+    const result = await runInstaller(fixture, fixture.main)
+
+    expect(result.status).toBe(1)
+    expect(result.stderr).toContain('common repository config')
+    expect(result.stderr).toContain('not a regular file')
+    expect(lstatSync(commonConfig).isSymbolicLink()).toBe(true)
+    expect(readFileSync(externalConfig, 'utf8')).toBe(externalContent)
+    expect(existsSync(hooksPath(fixture, fixture.main))).toBe(false)
+  })
+
   it('leaves stale installer locks for explicit recovery', async () => {
     const fixture = createFixture()
     const lockPath = installLockPath(fixture)
@@ -387,9 +514,33 @@ describe('worktree-local Lefthook installer', () => {
     expect(existsSync(hooksPath(fixture, fixture.main))).toBe(false)
   })
 
+  it.skipIf(process.platform === 'win32')('refuses an active symlinked worktree config before writing through it', async () => {
+    const fixture = createFixture()
+    const commonConfig = join(commonDirectory(fixture), 'config')
+    const worktreeConfig = join(gitDirectory(fixture, fixture.main), 'config.worktree')
+    const externalConfig = join(fixture.container, 'external.gitconfig')
+    const externalContent = '[user]\n\tname = External owner\n'
+    write(externalConfig, externalContent)
+    git(fixture, fixture.main, ['config', '--file', commonConfig, 'core.repositoryFormatVersion', '1'])
+    git(fixture, fixture.main, ['config', '--file', commonConfig, 'extensions.worktreeConfig', 'true'])
+    symlinkSync(externalConfig, worktreeConfig)
+
+    const result = await runInstaller(fixture, fixture.main)
+
+    expect(result.status).toBe(1)
+    expect(result.stderr).toContain('active worktree config')
+    expect(result.stderr).toContain('not a regular file')
+    expect(lstatSync(worktreeConfig).isSymbolicLink()).toBe(true)
+    expect(readFileSync(externalConfig, 'utf8')).toBe(externalContent)
+    expect(gitResult(fixture, fixture.main, [
+      'config', '--file', externalConfig, '--get', 'core.hooksPath',
+    ]).status).toBe(1)
+    expect(existsSync(hooksPath(fixture, fixture.main))).toBe(false)
+  })
+
   it('refuses migration keys loaded through active or conditional common-config includes', async () => {
     for (const includeKey of ['include.path', 'includeIf.onbranch:conditional.path']) {
-      for (const key of ['core.worktree', 'core.bare']) {
+      for (const key of ['core.worktree', 'core.bare', 'extensions.dshunknown']) {
         const fixture = createFixture()
         const commonConfig = join(commonDirectory(fixture), 'config')
         const includedConfig = join(fixture.container, `${includeKey.split('.')[0]}-${key.replace('.', '-')}.gitconfig`)
@@ -597,6 +748,21 @@ describe('worktree-local Lefthook installer', () => {
     expect(readFileSync(legacyHook, 'utf8')).toBe('#!/bin/sh\n# legacy pre-push\n')
   })
 
+  it('reports installation and hook-path rollback failures together', async () => {
+    const fixture = createFixture()
+
+    const result = await runInstaller(fixture, fixture.main, {
+      DSH_TEST_LEFTHOOK_BREAK_WORKTREE_CONFIG: '1',
+      DSH_TEST_LEFTHOOK_FAIL: '1',
+    })
+
+    expect(result.status).toBe(1)
+    expect(result.stderr).toContain('Lefthook installation failed')
+    expect(result.stderr).toContain('exit status 77')
+    expect(result.stderr).toContain('worktree hook rollback also failed')
+    expect(result.stderr).toContain('git config --worktree --unset-all core.hooksPath failed')
+  })
+
   it('refuses an unowned directory at the reserved worktree hook path', async () => {
     const fixture = createFixture()
     const reservedHook = join(hooksPath(fixture, fixture.main), 'pre-commit')