README.md 9.4 KB
description: "Session-telemetry capture seam for deployments and backend authors choosing a reporting backend, mounting redaction rules, or implementing the backend contract."
kind: "package-library"
@deepseek-ai/dsh-session-telemetry
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Summary
dsh-session-telemetry captures session activity for outbound reporting: it projects session events into telemetry records, lets a deployment redact them, and hands them to a reporting backend that implements its contract. Deployments do not load this package directly — they load exactly one backend (the shipped OpenTelemetry backend is dsh-session-telemetry-otel), which registers ctx.sessionTelemetry and composes the capture coordinator. The seam owns capture, redaction, and the sharing disclosure; batching, retry, queueing, and loss policy belong to the backend's SDK and stop at emit(). Every mounted backend discloses its deployment-selected sharing policy so acknowledgement surfaces can report whether and how a session is shared. The contract and capture behavior come first; the implementation internals live in a collapsible developer section below.
Table of Contents
- Use this package
- Understand the implementation
- Further Exploration
- Model Experience
- Known Limitations and Deferred Work
- Dev Note
Use this package
As a deployment, choose a backend, mount it, and add redaction rules when records must not leave the process as captured. As a backend author, implement the three-member contract and compose the coordinator with a capture mode.
Choosing and mounting a backend
Load exactly one backend plugin; it registers ctx.sessionTelemetry with the capture coordinator and its own delivery pipeline, and a duplicate load throws. The mounted backend discloses its sharing policy through the required sharing member, which the /feedback acknowledgement renders; a consumer renders "not configured" only when no telemetry service is mounted.
The backend contract
A backend implements three members: emit(record) must be a non-blocking enqueue because it runs synchronously on the session-event path; optional flush() is a fire-and-forget hint after a turn ends, which most backends omit in favor of their SDK's own batching schedule; shutdown() drains queued records and resolves when the SDK stops, and disposal awaits it. A backend that implements flush() must order concurrent flushes with the final shutdown() drain.
What gets captured
Capture runs in one of two modes. live capture follows session events as they are appended, replays already-live sessions at mount time, and records lifecycle markers; on-demand capture reads the canonical session log only when the backend requests a prefix through captureSession(session, throughSeq?). Ledger records mirror session events one to one except for one projection: only the first assistant/chunk of each (turn, step) ships, so seq gaps on the wire are routine and never a loss signal. Each record carries the event's complete data, minimal identity attributes, and a pre-mapped severity (error for tool/result.isError, turn/end error reasons, and agent-error; info otherwise).
The sharing disclosure
Every backend discloses its deployment-selected sharing policy through the seam's sharing vocabulary: full (every event is handed over as it happens), feedback-only (nothing is handed over until a feedback/record event releases the unreleased prefix), or disabled (nothing is handed over at all). The acknowledgement of a recorded feedback entry reports this status; the disclosure never claims delivery — handoff is the non-blocking enqueue, and batching, retry, and loss policy stay the backend SDK's.
Redacting records
Every outbound record passes the sessionTelemetry/record waterfall immediately after projection. This package ships no rules: with no listener mounted, records reach the backend exactly as captured, so exported data is as clean as the rules a deployment mounts. Listeners stack by transforming next()'s return value; a throwing listener withholds that one record fail-closed. Redaction applies to the outbound copy only — the canonical session log is never rewritten.
Understand the implementation
Implementation internals — click to expand
This section explains the capture design; the observable behavior is fully covered in [Use this package](#use-this-package). ### Design concept The seam is built on one boundary: the harness's aspect ends at `emit()`. Capture, projection, redaction, and the handoff cursor live here; batching, retry, queueing, and loss policy are the reporting SDK's, deliberately not modelled or wrapped. The design and rejected alternatives are pinned in the [revival Agent Note](../../../.agents/notes/implemented/feature/2026-07-23-session-telemetry-otel-revival.md). ### Source map | File | Role | |---|---| | [`src/index.ts`](src/index.ts) | Service Definition: `SessionTelemetryBackend`/`SessionTelemetrySink` contract, record vocabulary, `session-telemetry/record` waterfall declaration | | [`src/coordinator.ts`](src/coordinator.ts) | Capture: live listeners, on-demand replay, chunk projection, redaction, handoff cursor, containment | ### Capture flow Live capture registers, through the composing fiber's effects: `session/created` adopts the session and replays its log from the handoff cursor; `session/event` projects, deep-copies, redacts, and hands off with zero I/O; `session/flush` forwards the optional hint and returns void so the loop's awaited parallel never waits on telemetry; `session/disposed` captures the session's `shutdown` marker and retires it; `agent/error` is the one live-bus relay, because the session-event vocabulary intentionally has no operational-error record. Disposal captures shutdown markers for still-live sessions, then awaits the backend's `shutdown()`. On-demand capture registers only the disposal effect and reads the canonical log on request. Every synchronous handler runs inside containment so a failing backend or rule can never starve other listeners or reach the agent loop. ### The handoff cursor A module-scope `WeakMap` records, per session, the highest seq handed off (not delivered). Live capture advances it at append time; on-demand capture advances it only while handing a requested prefix. An uncaptured prefix remains solely in the canonical log, so a coordinator reload adds no telemetry-owned recovery state; a missing cursor safely degrades to re-handing from the session's construction boundary, absorbed by receiver-side dedupe on `(session.id, event.seq)`. This is a narrow, documented exception to the registrations-are-effects discipline: entries die with their sessions, the value is a monotonic watermark, and losing it is never an error. The accepted cost matches at-most-once delivery: a resumed session does not backfill records a previous process failed to deliver.Further Exploration
Read these pages when the seam contract is not enough. They move from the shipped backend to the subsystem reference and the decision evidence.
- OpenTelemetry telemetry backend — the shipped backend deployments load, with mode and exporter configuration.
- Session telemetry subsystem — the capability split and type declarations.
- Session telemetry revival decision — rationale, trade-offs, and rejected alternatives.
- Session package map — adjacent persistence, projection, title, and telemetry packages.
Model Experience
None, as the seam observes the session stream and hands redacted copies outward; it registers nothing model-facing.
KV Cache effect
None; the package neither assembles nor sends a provider request.
Known Limitations and Deferred Work
These limits define the delivery and data-protection guarantees a deployment gets. They are current package constraints.
- Best-effort delivery — the cursor marks handed-off, not delivered; a session torn down inside a reload window cannot be re-adopted, and whatever sits in a backend queue at crash time is lost. A durable outbox (spool, per-sink cursors, at-least-once) is deferred until a deployment states a crash-loss requirement.
- No built-in redaction rules — with no
sessionTelemetry/recordlistener mounted, records leave the process exactly as captured, including any credentials embedded in file contents or command output; a deployment exporting to a shared collector owns its rule set. - On-demand redaction uses current state — uncaptured events exist only in the canonical session log; a later
captureSession()deep-copies and redacts their current values with the policy mounted at that time, and there is no capture-time telemetry snapshot or durable pre-capture spool.