# 落盘存储

[English](spill.md) | 中文

落盘存储 seam 是一项[能力 seam](../../.agents/notes/implemented/architecture/2026-07-08-tool-output-spill-files.md)，它持久保存工具的超大文本，并返回面向模型的定位符与检索指引；该能力拆分到三个包（package）：接口（[dsh-spill](../../packages/spill/spill)，`ctx.spillStore`）、实现（[dsh-spill-local](../../packages/spill/spill-local)，宿主文件系统中会话作用域的私有文件）和消费方（[dsh-spill-policy](../../packages/spill/spill-policy)，`tools/post-execute` 策略）。落盘是**一项可选能力**，不属于 agent loop（智能体循环）主干，因此其词汇记录在此处，而不在 [core.md](core.md) 中。预览机制仍归 [dsh-retention](../../packages/util/retention) 所有；该 seam 只保存策略交给它的最终文本。

源码：[`packages/spill/spill/src/types.ts`](../../packages/spill/spill/src/types.ts)

## 保存请求

`saveText` 是整个 seam：原样持久保存 `content`，并返回不透明的定位符、后端提供的检索提示和准确字节数。请求携带保存时的存储命名空间（`owner`）、内容来源（`source`，用于命名和检查的描述性来源信息，而非访问控制）以及后端可用作命名提示的 `suggestedName`（它不是路径）。

```ts type-equiv
/** One request to persist text to a spill artifact. */
interface SaveTextSpill {
  owner: SpillOwner
  source: SpillSource
  /**
   * A caller-suggested base name (e.g. `web_fetch.txt`). The backend sanitizes
   * it to a single safe path segment before use — it is a hint, never a path.
   */
  suggestedName: string
  /** The full text to persist (UTF-8). */
  content: string
}
```

```ts type-equiv
/**
 * Save-time storage namespace for a spilled artifact. The session id lets a
 * backend group storage under the producing session, but the returned
 * {@link SpillLocator} is the model-facing handle. Forked sessions inherit
 * locators already present in the seeded log; those artifacts are not copied or
 * re-owned, and spills produced after the fork use the child session id.
 */
interface SpillOwner {
  sessionId: SessionId
}
```

`SpillOwner.sessionId` 是保存时的存储命名空间。fork 后的会话会从种子日志继承已有的落盘定位符；这些产物不会被复制或重新取得所有权，fork 后产生的落盘则使用子会话 id。保留期清理可以连同其他旧会话产物一起使旧定位符失效；落盘 seam 不定义逐会话的清理策略。

```ts type-equiv
/**
 * Provenance of one spilled artifact — recorded by the backend for a readable
 * filename and inspection. Not interpreted for access control; purely
 * descriptive.
 */
interface SpillSource {
  /** The tool whose result was spilled (e.g. `web_fetch`). */
  toolName: string
  /** The model-issued call id the result belongs to. */
  callId: CallId
  /** A short human label for the artifact (e.g. `result`). */
  label: string
}
```

## 结果

```ts type-equiv
/** A saved spill artifact: its locator, byte length, and backend-specific retrieval guidance. */
interface SpillRef {
  locator: SpillLocator
  bytes: number
  retrievalHint: string
}
```

`SpillLocator` 是后端返回的[品牌化](core.md#branded-ids)面向模型句柄。本地后端将它渲染为文件系统路径；远程或数据库后端可以渲染 URI、键或命令 token。消费方将它视为不透明值，并使用 `retrievalHint` 渲染，而不是假定 `read` 始终是正确的检索机制。

```ts type-equiv
/**
 * Opaque model-facing handle for one spilled artifact. A local backend may use a
 * filesystem path; a remote or database backend may use a URI or key. Consumers
 * render it with {@link SpillRef.retrievalHint}, but do not parse it.
 */
type SpillLocator = Branded<'SpillLocator'>
```

## 服务

`SpillStore`（`ctx.spillStore`，定义于 [`packages/spill/spill/src/index.ts`](../../packages/spill/spill/src/index.ts)）是只有一个方法的抽象服务：`saveText(input) → Promise<SpillRef>`。它持久保存完整的 `content`，并在实际存储失败（权限、ENOSPC、后端不可用）时拒绝。该 seam 只负责存储：不负责保留策略、工具结果替换或检索／搜索 API。

本地后端（[dsh-spill-local](../../packages/spill/spill-local)）写入 `<root>/session-<hash>/<random>-<safeName>`：根目录是已配置或延迟创建的私有（0700）目录，会话子目录采用 `sha256(sessionId)`，并通过排他的仅所有者可访问写入（`open(path, 'wx', 0o600)`）防止预先植入的符号链接重定向写入。其 `locator` 是本地路径，`retrievalHint` 则告知模型在该路径上使用 `read` 或 `grep`。策略消费方（[dsh-spill-policy](../../packages/spill/spill-policy)）会把超过 `maxInlineBytes` 的纯文本最终结果替换为保留库生成的首尾预览和落盘引用；该过程尽力而为：保存失败时保留原始内联结果，而不会把成功的调用变成 `isError`。
