DSH plugin Conversation node: match, register, replay

To add a business row to the Web Client's Chat view, a DeepSeek Harness (DSH) plugin registers a Conversation node: match a group of persistent Session events into one Context with a stable (kind, id), fold a Definition into State, and inject a conversation.chat.node renderer by key. Conversation is the target-neutral assembly layer between the client event window and the browser view, and a business row is its established extension path.

How a DSH plugin Conversation node matches: linking an event family by stable (kind, id)

Before writing a Definition, choose a stable business id — every event that forms the same Node must carry that id, or derive it independently from its own payload (source). The official docs use a review job to define the event contract:

The core discipline: match(event) is an identity extractor, not a fold — it receives only the current SessionEventLike and returns the Definition's internal id and lifecycle role; after a hit the Assembler locates the Context by (kind, id). A client must never guess that an update belongs to "the most recent unfinished Context", and each (kind, id) may have at most one start event.

How a DSH plugin registers a Conversation node: Definition and the chat node slot

A Definition needs match, start, and update, plus target and buildViewNode; registration has two steps — register the Definition, then inject the renderer (source).

export const inject = ['uiConversation', 'slots']

export function apply(ctx: ClientContext): void {
  ctx.uiConversation.events.register(reviewDefinition)
  ctx.slots.inject('conversation.chat.node', () => ctx.slots.register({
    name: 'conversation.chat.node',
    key: 'review-job',
  }, ReviewNodeView))
}

Read it as three steps:

1. Register the Definition — ctx.uiConversation.events.register(definition), declaring kind and target. Expect: the same key on the same target registers only once and is identifiable at render time.
2. Inject the renderer by key — register the component into the conversation.chat.node slot. Expect: the renderer reads only node.data and restricted Location hooks.
3. Handle visibility — when temporarily leaving the visible stream return visibility: 'hidden', and do not return null to retract an already-published node. Expect: the key stays stable so replay does not misalign.

Node identity must be stable: once a target Node is published it must keep returning the same key and preserve context.key as the React-side identity; anchorSeq is chosen from persistent ordering evidence.

How a DSH plugin Conversation node replays: replace, prepend, and publication

History may be requested from the tail backward, page by page; the Assembler sorts accepted inputs by their first seq and then enters State replay (source). There are three window paths:

1. replace (open / resync / gap repair) — rebuild the loaded window, match each event once per Definition, then replay Contexts that already have a start. Expect: start first, then update in ascending seq.
2. prepend (an earlier page) — match only the newly added earlier inputs, merge them into Contexts by (kind, id), and replay only the affected ones. Expect: a newly discovered start activates the updates already collected.
3. append (live events) — call match once per Definition and update only the hit Context. Expect: the hot path does not scan the whole window.

publication controls when State is materialized: use immediate for structural or terminal changes, animation-frame for high-frequency visible deltas, and none to only accumulate State for a later publication. Hard performance constraint: the normal append hot path must not walk the full event window, all Contexts, or already-rendered Nodes — put accumulated facts in State, put per-Turn/Step shared information in Location data, and use reader.previous() for indexed prior dependencies.

Three self-checks before you finish: is the business id carried stably on every event; does the renderer consume only node.data; and can you add an earlier page without replacing existing keyed nodes? To put UI into a different slot, see plugin UI; for ready-made DSH plugins to compare against, search the DSH Plugin Hub.