revert(sandbox): withdraw the credential-document read denial

The `readDenyPaths` policy field shipped in the previous commit broke Linux
confinement outright. bwrap has to create the `/dev/null` bind's mount point
inside a tree its own profile has already made read-only, so it refused the
entire confinement whenever the parent directory was absent — every host that
has not stored a credential yet, including a fresh install:

  bwrap: Can't mkdir parents for /home/runner/.dsh/.env: Read-only file system

which the executor correctly classifies as SANDBOX_UNAVAILABLE, so every
confined bash call failed closed. Landlock cannot subtract from its own `/`
read grant, so it reported `partial` enforcement on every confined call for a
file it never hid, with no way to switch the denial off (schemastery fills an
omitted array with `[]`, so empty and omitted were indistinguishable).

A protection that breaks confinement where it works and misreports it where it
does not is worse than a documented absence. Revert the field, both expressible
backends, the enforcement downgrade, and the policy default; state the residue
plainly in the credentials-local READMEs — file mode stops other OS users, not
the model — and keep the OS-keychain provider recorded as the real answer.

The narrower discipline stands: no surface hoists the credential document into
`process.env`, and the model is never handed a resolved path to it.

.agents/notes/implemented/architecture/2026-07-30-credential-boundaries-and-atomic-registration.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/architecture/2026-07-30-credential-boundaries-and-atomic-registration.md
-2026-07-30-credential-boundaries-and-atomic-registration.md: 837aa3e7b8ed30c66aad880ab2d76eee376e1854
-2026-07-30-credential-boundaries-and-atomic-registration.zh.md: a00c3d93d2dc0451ed29613c4a804b0e518264ed
+2026-07-30-credential-boundaries-and-atomic-registration.md: 6fe5f554acbfd804db9625fcaa794d513c8799c4
+2026-07-30-credential-boundaries-and-atomic-registration.zh.md: 3eb3b022064124aad2a389abba3063af4e2110fa

.agents/notes/implemented/architecture/2026-07-30-credential-boundaries-and-atomic-registration.md

@@ -16,7 +16,7 @@ Two request-path defects sat beside them. DeepSeek's per-request resolution kept
 
 **`$DSH_HOME/.env` belongs to the credential provider alone.** No surface loads it into `process.env`. The genuine launch environment and the invoking directory's `.env` (loaded by the bin) stay the read-only ambient layer, so a composition without the provider resolves keys exactly as before, while a stored key stays file-sourced and writable across restarts — proven by a real restart in the loader composition rather than by a unit assertion about `describe()`.
 
-**The confining sandbox is the only real read boundary, and it names the file.** `SandboxExecutionPolicy` grows `readDenyPaths`, defaulted by `sandbox-policy` to `$DSH_HOME/.env`. Seatbelt appends a trailing `deny file-read* file-write*` (SBPL's last matching rule wins) and bwrap maps `/dev/null` over each path after any workspace bind; Landlock grants are a pure allow-list that cannot subtract from its own `/` read grant, so `confine()` reports `partial` enforcement instead of claiming a boundary the process lacks. Denials name exact paths, not roots: denying the whole harness home would also take away the model's documented access to its own session log. Both READMEs state the residue plainly — under the shipped `danger-full-access` default nothing is confined and the file is protected only by the OS user — and record an OS-keychain provider as the real answer.
+**The stored credential has no boundary against the model, and the READMEs say so.** `0600` under a `0700` directory stops other OS users; the model's bash and filesystem tools run as that same user, and the shipped default confines nothing. What the harness does hold to is narrower and stated as exactly that: no surface hoists the document into `process.env`, and the model is never handed a resolved path to it, so reaching the value takes a deliberate read of a path it was not given. An OS-keychain provider — a store the model's processes cannot read at all — is recorded as the real answer rather than implied by a partial one.
 
 **One request, one generation.** DeepSeek's resolved snapshot carries the credential facts (literal key and reference) beside the endpoint, and `resolveApiKey` receives that snapshot instead of re-reading configuration. A rejected generation now contributes nothing at all. pi-ai defers to provider-native discovery only for a profile naming no credential; a configured reference that misses fails with `MISSING_CREDENTIAL` naming the route and the reference. The boot-time credential probe is deleted: it could run before the credentials service mounted and reported every failure as a missing key, while the first request already gives the accurate error.
 
@@ -26,12 +26,11 @@ Two request-path defects sat beside them. DeepSeek's per-request resolution kept
 
 ## Alternatives considered
 
-- **Denying the whole harness home** — one root would have covered the credential document and any future secret file, but it also covers `sessions/`, and `DSH_SESSION_JSONL` is a documented model-visible capability. Exact paths keep the denial to what is actually secret.
-- **Removing `DSH_HOME` from the model's bash environment** — considered as defense in depth and rejected as theater with a real cost: the default home is a documented convention the agent can reconstruct, while the variable is how legitimate tooling finds harness state. The sandbox denial is the boundary; hiding the pointer is not.
+- **A sandbox read-denial naming `$DSH_HOME/.env`** — implemented as a `readDenyPaths` policy field (a trailing SBPL `deny file-read* file-write*`, a `/dev/null` bwrap bind) and withdrawn on its own evidence. bwrap must create that bind's mount point inside a tree its profile has already made read-only, so it refuses the entire confinement whenever the parent directory is absent — every host that has not stored a credential yet, including a fresh install; Landlock cannot subtract from its own `/` read grant, so every confined call would report `partial` for a file it never hid. A protection that breaks confinement where it works and misreports it where it does not is worse than a documented absence. Denying the whole harness home was rejected earlier for a separate reason: it also covers `sessions/`, and `DSH_SESSION_JSONL` is a documented model-visible capability.
+- **Removing `DSH_HOME` from the model's bash environment** — considered as defense in depth and rejected as theater with a real cost: the default home is a documented convention the agent can reconstruct, while the variable is how legitimate tooling finds harness state. There is no boundary here for it to complement; hiding the pointer would only make the absence harder to see.
 - **Shipping the OS-keychain provider in this round** — it is the only design where the model's processes genuinely cannot read the secret, and it is a sibling package with three platform backends. Sizing it against the rest of this review round would have delayed every other fix; it is recorded as the deferred answer, not as a maybe.
-- **Treating `readDenyPaths: []` as an opt-out** — schemastery fills an omitted array with `[]`, so empty and omitted are indistinguishable at the constructor. Empty therefore means "protect the default document"; a deployment that stores credentials elsewhere names its own paths, and a denial on a path nothing reads costs nothing.
 - **A `replaceRegistration(previous, next)` service method** — the review's shape, but it makes the caller carry the previous handle and lets it pass a mismatched one. Hanging `replace` on the registration handle makes ownership structural: only the registration that holds routes can replace them.
 
 ## Consequences
 
-`update()`-adjacent behavior gained documented failure modes: a credential write can now fail on the lock deadline or on an unparsable on-disk document, and `describe()` reports `writable: false` for multi-line entries it will not rewrite. A confined execution loses read access to `$DSH_HOME/.env` — deployments that deliberately let an agent read its own credential file must configure `readDenyPaths` themselves. `LlmAdapter` registrants keep working unchanged (the handle is still callable as the disposer), and `DeepSeekConnectionOptions` gained credential fields, so a programmatic constructor of the adapter must supply `apiKeyEnv`. Deferred: the OS-keychain credential provider, and per-value revision checks for two writers editing one reference (last-write-wins remains the documented resolution).
+`update()`-adjacent behavior gained documented failure modes: a credential write can now fail on the lock deadline or on an unparsable on-disk document, and `describe()` reports `writable: false` for multi-line entries it will not rewrite. `LlmAdapter` registrants keep working unchanged (the handle is still callable as the disposer), and `DeepSeekConnectionOptions` gained credential fields, so a programmatic constructor of the adapter must supply `apiKeyEnv`. Deferred: the OS-keychain credential provider, and per-value revision checks for two writers editing one reference (last-write-wins remains the documented resolution).

.agents/notes/implemented/architecture/2026-07-30-credential-boundaries-and-atomic-registration.zh.md

@@ -20,7 +20,7 @@ Status: implemented
 
 **`$DSH_HOME/.env` 只归凭据提供方所有。**没有任何一个面会把它加载进 `process.env`。真正的启动环境，以及调用目录中由 bin 加载的 `.env`，仍然是那一层只读的环境来源，因此不挂载该提供方的组合，解析密钥的方式与从前完全一致，而存下的密钥跨重启仍然来源于文件、仍然可写——这一点由 Loader 组合中的一次真实重启来证明，而不是靠对 `describe()` 的单元断言。
 
-**受限沙箱才是唯一真正的读取边界，而且它点名到具体文件。**`SandboxExecutionPolicy` 新增 `readDenyPaths`，由 `sandbox-policy` 默认设为 `$DSH_HOME/.env`。Seatbelt 在末尾追加一条 `deny file-read* file-write*`（SBPL 中最后一条匹配规则胜出），bwrap 则在所有工作区 bind 之后把 `/dev/null` 映射到每条路径上；Landlock 的授权是纯粹的允许列表，无法从它自己对 `/` 的读取授权中减去任何东西，因此 `confine()` 报告 `partial` 强制执行，而不是声称一条该进程其实并不具备的边界。拒绝点名的是确切路径，而不是根目录：把整个 harness home 都拒掉，会连带夺走模型对自身会话日志的成文访问权。两个 README 都直白写明残留风险——在已交付的 `danger-full-access` 默认值下没有任何东西受限，这个文件只靠 OS 用户身份保护——并记下 OS 钥匙串（keychain）提供方才是真正的答案。
+**存下的凭据对模型没有边界，而 README 就是这么写的。**`0700` 目录下的 `0600` 挡得住其他 OS 用户；模型的 bash 与文件系统工具正是以同一用户身份运行，而已交付的默认值不约束任何东西。harness 真正守住的更窄，也就照这个宽度写下来：没有任何一个面会把该文档提升进 `process.env`，模型也从不会拿到它的解析后路径，因此要拿到这个值，需要刻意去读一条并未交给它的路径。OS 钥匙串（keychain）提供方——一个模型的进程根本读不到的存储——被记录为真正的答案，而不是靠一个残缺的方案去暗示它。
 
 **一次请求，一代设置。**DeepSeek 解析出的快照在端点旁一并携带凭据事实（字面密钥与引用），`resolveApiKey` 接收这份快照，而不再重新读取配置。被拒绝的那一代如今完全不再贡献任何东西。只有当一个 profile 完全没有点名凭据时，pi-ai 才交给提供方原生的发现流程；配置了引用却解析不到，就以 `MISSING_CREDENTIAL` 失败，并点名该路由与该引用。启动时的凭据探测被删除：它可能在凭据服务挂载之前就运行，并把每一种失败都报成密钥缺失，而第一次请求本就会给出准确的错误。
 
@@ -30,12 +30,11 @@ Status: implemented
 
 ## 曾考虑的替代方案
 
-- **拒掉整个 harness home**——一个根目录本可覆盖凭据文档以及将来任何机密文件，但它同时也覆盖 `sessions/`，而 `DSH_SESSION_JSONL` 是一项成文的、模型可见的能力。用确切路径可以把拒绝范围限定在真正属于机密的东西上。
-- **把 `DSH_HOME` 从模型的 bash 环境中移除**——作为纵深防御考虑过，最终按「有真实代价的表演」不予采纳：默认 home 是 agent（智能体）能自行重建的成文约定，而这个变量正是正当工具链定位 harness 状态的途径。沙箱拒绝才是边界，藏起指针不是。
+- **用沙箱点名拒读 `$DSH_HOME/.env`**——已按 `readDenyPaths` 策略字段实现过（末尾一条 SBPL `deny file-read* file-write*`、一条 `/dev/null` 的 bwrap bind），又被它自己的证据推翻。bwrap 必须在自己 profile 已经置为只读的目录树内部创建该 bind 的挂载点，因此只要父目录不存在，它就会拒绝整次约束——那是每一台还没有存过凭据的主机，包括全新安装；Landlock 无法从它自己对 `/` 的读取授权中减去任何东西，于是每一次受限调用都会为一个它其实从未藏起的文件报 `partial`。一项在生效之处破坏约束、在不生效之处误报的保护，比一条写明的「没有保护」更糟。至于拒掉整个 harness home，早先另有理由被否：它同时覆盖 `sessions/`，而 `DSH_SESSION_JSONL` 是一项成文的、模型可见的能力。
+- **把 `DSH_HOME` 从模型的 bash 环境中移除**——作为纵深防御考虑过，最终按「有真实代价的表演」不予采纳：默认 home 是 agent（智能体）能自行重建的成文约定，而这个变量正是正当工具链定位 harness 状态的途径。这里并不存在一条需要它来补强的边界，藏起指针只会让这份缺席更难被看见。
 - **本轮就交付 OS 钥匙串提供方**——只有这个设计能让模型的进程真正读不到机密，而它是一个带三种平台后端的兄弟包（package）。把它与本轮评审的其余工作放在一起评估体量，会拖慢其他每一项修复；它被记录为那个延后的答案，而不是一个「也许」。
-- **把 `readDenyPaths: []` 当作 opt-out**——schemastery 会把省略的数组填成 `[]`，因此在构造函数处空数组与省略无从分辨。于是空数组的含义就是「保护默认文档」；把凭据存在别处的部署自行点名它自己的路径，而在没人读取的路径上设一条拒绝并不产生任何代价。
 - **做成 `replaceRegistration(previous, next)` 服务方法**——这是评审给出的形状，但它要求调用方自行携带上一个句柄，也允许它传入一个不匹配的句柄。把 `replace` 挂在注册句柄上，让归属关系变成结构性的：只有持有路由的那一项注册才能替换它们。
 
 ## 后果
 
-`update()` 邻近的行为多了成文的失败模式：凭据写入现在可能因锁截止时间到期、或磁盘文档无法解析而失败，`describe()` 对它不会改写的多行条目报告 `writable: false`。受限执行会失去对 `$DSH_HOME/.env` 的读取权限——刻意让 agent 读取自身凭据文件的部署，必须自行配置 `readDenyPaths`。`LlmAdapter` 的注册方无需改动即可继续工作（句柄本身仍可当作释放器调用），`DeepSeekConnectionOptions` 则新增了凭据字段，因此以编程方式构造该适配器必须提供 `apiKeyEnv`。延后事项：OS 钥匙串凭据提供方，以及针对两个写方编辑同一引用的逐值修订号检查（后写胜出仍是成文的解决方式）。
+`update()` 邻近的行为多了成文的失败模式：凭据写入现在可能因锁截止时间到期、或磁盘文档无法解析而失败，`describe()` 对它不会改写的多行条目报告 `writable: false`。`LlmAdapter` 的注册方无需改动即可继续工作（句柄本身仍可当作释放器调用），`DeepSeekConnectionOptions` 则新增了凭据字段，因此以编程方式构造该适配器必须提供 `apiKeyEnv`。延后事项：OS 钥匙串凭据提供方，以及针对两个写方编辑同一引用的逐值修订号检查（后写胜出仍是成文的解决方式）。