deepseek-harness/docs/core-data-structures/session-title.md

Session Titles

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Durable latest-wins title state and the optional asynchronous provider vocabulary owned by @deepseek-ai/dsh-session-title. The shared LLM helper owns the exact auxiliary request record. Package READMEs own timing, fallback, failure, and fork behavior; the generated persistence catalog owns the complete event declarations.

Sources: packages/session-title/session-title/src/index.ts, packages/session-title/session-title-llm/src/index.ts

Durable title state

SessionTitleProviderId is recorded for provider-produced revisions. SessionTitleEventData carries exact human-message provenance, while SessionTitleSnapshot adds the durable event envelope facts selected by foldSessionTitle().

/** Identifies one session-title provider registration. */
type SessionTitleProviderId = Branded<'SessionTitleProviderId'>

/** Exact auxiliary model route that produced a title. */
interface SessionTitleModelProvenance {
  /** Registered LLM provider route. */
  readonly provider: string
  /** Provider model id. */
  readonly model: string
}

/** Durable ownership record for an accepted session title. */
type SessionTitleSource =
  | { readonly kind: 'fallback' }
  | {
    readonly kind: 'provider'
    readonly provider: SessionTitleProviderId
    readonly model?: SessionTitleModelProvenance
  }

/** Payload of the log-only `session/title` event. */
interface SessionTitleEventData {
  /** Normalized non-empty title text. */
  readonly title: string
  /** Exact human `user/message` seqs used to derive this title. */
  readonly messageSeqs: number[]
  /** Built-in fallback or registered-provider provenance. */
  readonly source: SessionTitleSource
}

/** Latest folded title plus the title event's durable envelope facts. */
interface SessionTitleSnapshot extends SessionTitleEventData {
  /** Seq of the latest `session/title` event. */
  readonly eventSeq: number
  /** Timestamp of the latest `session/title` event. */
  readonly updatedAt: number
}

Auxiliary request record

The shared LLM helper records each validated, dispatchable title request before calling the model. The payload reproduces the model-visible system and message input, routing, output limit, provider ownership, and source-message attribution even when generation later fails.

/** Exact model-visible request recorded before one auxiliary title dispatch. */
interface SessionTitleLlmRequestEventData {
  /** Registered title-provider identity responsible for the request. */
  readonly titleProvider: SessionTitleProviderId
  /** Exact human `user/message` seqs represented in `messages`. */
  readonly messageSeqs: number[]
  /** Exact auxiliary LLM route. */
  readonly route: SessionTitleModelProvenance
  /** Exact auxiliary system prompt. */
  readonly system: string
  /** Exact auxiliary message list. */
  readonly messages: Message[]
  /** Exact auxiliary output-token cap. */
  readonly maxTokens: number
}

Provider input and output

The service snapshots eligible messages through one revision. A provider returns only seqs from that request; service-owned acceptance verifies ordering, normalizes the title, enforces the byte limit, and appends provenance.

/** One eligible human text message exposed to title providers. */
interface SessionTitleUserMessage {
  /** Source `user/message` event seq. */
  readonly seq: number
  /** Exact concatenated text-block content. */
  readonly text: string
}

/** Automatic generation cadence owned by a registered provider. */
type SessionTitleAutomaticMode = 'first-message' | 'all-user-messages'

/** Immutable input supplied to one title-provider call. */
interface SessionTitleProviderRequest {
  /** Live session being titled. */
  readonly session: Session
  /** All eligible human messages through this generation revision. */
  readonly messages: readonly SessionTitleUserMessage[]
  /** Exact current logged main-request route, when one has been recorded. */
  readonly route?: SessionTitleModelProvenance
  /** Cancellation for supersession, disposal, timeout composition, or the explicit caller. */
  readonly signal: AbortSignal
}

/** Provider output before service-owned normalization and log acceptance. */
interface SessionTitleProviderResult {
  /** Proposed title text. */
  readonly title: string
  /** Exact seqs from `request.messages` used by this result. */
  readonly messageSeqs: readonly number[]
  /** Auxiliary LLM route, when generation used a model. */
  readonly model?: SessionTitleModelProvenance
}

/** One optional asynchronous title implementation registered with the service. */
interface SessionTitleProvider {
  /** Stable provider identity recorded in title provenance. */
  readonly id: SessionTitleProviderId
  /** When new human prompts start automatic generation. */
  readonly automatic: SessionTitleAutomaticMode
  /**
   * Produce one title revision.
   * @param request - message snapshot, current route, session, and cancellation.
   * @returns proposed title plus exact input seqs and optional model provenance.
   */
  generate(request: SessionTitleProviderRequest): Promise<SessionTitleProviderResult>
}