# 遥测（telemetry）

[English](telemetry.md) | 中文

对外的会话上报，拆分为一项[能力 seam](../capability-seams.md)：seam 一侧（[dsh-session-telemetry](../../packages/telemetry/session-telemetry)，`ctx.telemetry`）拥有捕获点、固定分片投影、`telemetry/record` 脱敏 waterfall（瀑布式事件）、handoff 游标与最小后端契约；部署方加载的后端（[dsh-session-telemetry-otel](../../packages/telemetry/session-telemetry-otel)）则是原样配置的 OpenTelemetry JS SDK 日志流水线。它是一项可选能力，不属于 agent loop（智能体循环）主干，这里也没有任何内容会进入模型请求。边界公理（harness 的职责止于 `emit()`；批处理、重试、排队与丢失策略都属于上报 SDK）连同被否决的替代方案，均已在[复活 Agent Note（agent 决策记录）](../../.agents/notes/implemented/feature/2026-07-23-session-telemetry-otel-revival.md)中定案；捕获点、游标与投影的契约见 [seam README](../../packages/telemetry/session-telemetry/README.md)。

源码：[`packages/telemetry/session-telemetry/src/index.ts`](../../packages/telemetry/session-telemetry/src/index.ts)

## 逻辑记录

```ts type-equiv
/**
 * Severity of a telemetry record, pre-mapped at capture so a receiver can
 * alert with zero configuration: `error` for events whose own outcome flag
 * says so (`tool/result.isError`, `turn/end` error reasons) and for
 * `agent-error` operational records. Captured events otherwise default to
 * `info`; `warn` remains available to `telemetry/record` policies and
 * backends.
 */
type TelemetrySeverity = 'info' | 'warn' | 'error'
```

```ts type-equiv
/**
 * One logical record handed to a backend — the seam's whole outbound
 * vocabulary. Ledger records mirror session-log events one-to-one;
 * operational records (`channel: 'ops'`) carry the two signals with no log
 * home (`agent-error`, `shutdown`) and deliberately omit `event.seq`-style
 * identity so they can never be mistaken for ledger rows.
 */
interface TelemetryRecord {
  /** Ledger (session-log mirror) or ops (operational signal) channel; backends keep the two under separate instrumentation scopes. */
  channel: 'ledger' | 'ops'
  /** Unix epoch milliseconds — the source event's append time for ledger records, the emission time for ops records. */
  time: number
  /** Pre-mapped alerting severity; see {@link TelemetrySeverity}. */
  severity: TelemetrySeverity
  /**
   * Identity attributes, deliberately minimal: ledger records carry
   * `session.id`, `event.type`, `event.seq`, plus `session.cwd` /
   * `session.parent_id` when the header has them; ops records carry
   * `telemetry.op`, `session.id`, and (for `agent-error`) `agent.id`,
   * `turn`, `step`, `error.name`. Anything recoverable from the body is
   * intentionally NOT duplicated here.
   */
  attributes: Record<string, string | number>
  /**
   * The complete payload: a deep copy of the session event's `data` for
   * ledger records (JSON-serializable by `Session.append`'s own
   * validation), or the op payload for ops records. Never mutated after
   * handoff.
   */
  body: unknown
}
```

每个 `(turn, step)` 只发出第一条 `assistant/chunk`，即「流已开始」的信号；其余分片在捕获时丢弃，因此导出流中的 `seq` 缺口是常态，绝不是丢失信号。其他所有[会话事件](session.md)类型都会完整透传，包括该 seam 从未听说过、由插件合并进来的事件类型。交接下游的投递为至多一次（at-most-once）；接收端基于 `(session.id, event.seq)` 去重。

## 后端契约

```ts type-equiv
/**
 * The backend contract the coordinator hands records to — the minimum any
 * reporting SDK satisfies with zero bending. {@link Telemetry} is its
 * service-registered form; tests compose the coordinator with a bare
 * implementation of this interface.
 */
interface TelemetryBackend {
  /**
   * Hand one record to the backend's pipeline. MUST be a non-blocking
   * enqueue — the coordinator calls this synchronously from the
   * `session/event` hot path, so anything slower than a queue push would tax
   * the agent loop. Errors thrown here are contained by the coordinator and
   * logged; they never reach the loop.
   * @param record - the logical record to report; owned by the backend after the call.
   */
  emit(record: TelemetryRecord): void
  /**
   * Optional hint that a natural boundary (turn end) passed — a backend may
   * forward it to its SDK's flush so records land at turn boundaries. Called
   * fire-and-forget; implementations must not block and must not throw
   * meaningfully (the coordinator contains exceptions). Most backends should
   * leave this unimplemented and let their SDK's own batching cadence govern
   * export timing: a backend that does implement it owns the interaction
   * between its concurrent flushes and {@link shutdown}'s drain (the OTel
   * backend removed its implementation for exactly that hazard — see the
   * revival Agent Note).
   */
  flush?(): void
  /**
   * Forward the fiber's disposal to the SDK: flush whatever is queued and
   * reach quiescence, per the SDK's own shutdown contract. Everything
   * emitted before this call must still be delivered — including records
   * enqueued while a {@link flush} hint is in flight, so a backend whose SDK
   * guards against concurrent flushes orders behind the outstanding one (the
   * coordinator emits its dispose-time `shutdown` markers immediately before
   * calling this). Awaited by the coordinator's dispose; a rejection is
   * logged as a warning and never fails application teardown.
   * @returns resolves when the backend's pipeline has quiesced.
   */
  shutdown(): Promise<void>
}
```

`Telemetry`（`ctx.telemetry`，[签名](../cordis-catalog/services.md#ctxtelemetry--telemetry-abstract-seam)）是该契约的可加载形态：每个上下文只允许一个实现，重复加载会抛出异常；后端在其构造函数中组合 seam 的 `TelemetryCoordinator`，以此装配捕获侧。

## 脱敏 waterfall：`telemetry/record`

每条记录在投影与 `emit()` 之间都要经过 `telemetry/record` [waterfall](../cordis-primer.md#cordis-waterfall-semantics)（[事件条目](../cordis-catalog/events.md#telemetryrecord--waterfall)）。seam 自身不带任何规则：未挂载监听器时，记录以捕获时的原样到达后端；导出数据能干净到什么程度，恰恰取决于部署方挂载了什么规则。监听器通过变换 `next()` 的返回值来堆叠；不调用 `next()` 就返回，即替换其下方的全部逻辑；抛出异常的监听器会在协调器的隔离范围内以 fail-closed 方式扣下这一条记录。脱敏只作用于导出副本；权威会话日志永不改写。