91 lines
4.2 KiB
TypeScript
91 lines
4.2 KiB
TypeScript
/**
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* The in-process FORK subagent backend: registers a {@link SubagentProvider} on
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* `ctx.subagents` that runs each child as a child {@link Agent} SEEDED with a
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* prefix of the parent's session log — so the child inherits the parent's
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* conversation context instead of starting fresh. The run mechanics live in
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* `@deepseek-ai/dsh-subagent-inprocess` ({@link startInProcessRun}); this
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* backend just computes the seed. The spawn backend is an independent peer over
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* the same driver.
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*
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* The seed boundary is the crux: at the moment a subagent tool's `execute`
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* runs, the parent's CURRENT turn is open and unbalanced (it holds the
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* `assistant/message` with this spawn's tool-call, plus the dangling `tool/call`
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* with no `tool/result`). Seeding that raw prefix gives the child an open turn
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* the session constructor and the dev-mode invariants replay REJECT. So the
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* fork seeds only the **balanced completed-turn prefix**: the parent's log up
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* to and including its last `turn/end`, excluding the in-flight turn entirely.
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*
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* Plugin export shape: named `name`/`inject`/`Config`/`apply`, NO default.
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*
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* @module @deepseek-ai/dsh-subagent-fork
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*/
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import type { Context } from 'cordis'
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import z from 'schemastery'
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import type { SessionEvent } from '@deepseek-ai/dsh-session'
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import type { Agent } from '@deepseek-ai/dsh-agent'
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import type { SubagentCapabilities, SubagentProvider, SubagentStartRequest } from '@deepseek-ai/dsh-subagent'
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import { startInProcessRun } from '@deepseek-ai/dsh-subagent-inprocess'
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export const name = 'subagent-fork'
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// `tools` is deliberately NOT injected — same rationale as subagent-spawn: the
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// per-run structured runtime gates its capture-tool registration on `tools`
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// itself, so this backend's apply timing (and the delegation tool's position
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// in the model-visible tool list) is unchanged by structured output.
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export const inject = ['subagents', 'agents']
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/** Config: the registry name to register the provider under. */
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export interface Config {
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/** Provider name on `ctx.subagents` (default `fork`). */
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providerName: string
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}
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export const Config: z<Config> = z.object({
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providerName: z.string().default('fork'),
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})
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/**
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* The balanced completed-turn prefix of `parent`'s log: every event up to and
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* including the last `turn/end`. Empty if the parent has never completed a turn
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* (the in-flight turn is excluded, so a parent on its very first turn forks an
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* empty — i.e. fresh — child). The result is contiguous from seq 0 (the live
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* log keeps `seq === index`), so it is a valid session seed; the in-flight,
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* unbalanced turn is dropped so the invariants replay accepts it.
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* @param parent - the agent whose session log to slice.
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* @returns the seed events, contiguous from seq 0; empty when no turn has completed.
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*/
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export function completedTurnPrefix(parent: Agent): SessionEvent[] {
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const events = parent.session.events
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const lastEnd = events.findLast(e => e.type === 'turn/end')
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if (lastEnd === undefined) return []
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// seq === array index (the append contract), so slice up to and including it.
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return events.slice(0, lastEnd.seq + 1)
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}
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/**
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* The fork provider. Supports `depthLimit` and `outputSchema` (via the shared
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* in-process structured runtime); NOT `toolFilter` this cut (the service
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* rejects a request needing it before `start` runs).
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*/
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class ForkProvider implements SubagentProvider {
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readonly capabilities: SubagentCapabilities = { outputSchema: true, depthLimit: true, toolFilter: false }
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// Context contract: a forked child IS seeded with the parent's completed-turn prefix.
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readonly inheritsParentContext = true
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constructor(readonly name: string, private readonly ctx: Context) {}
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start(request: SubagentStartRequest) {
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const seed = completedTurnPrefix(request.parent)
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return startInProcessRun(this.ctx, request, {
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providerName: this.name,
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// Only pass a seed when there's a completed turn to inherit; an empty seed
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// is equivalent to a fresh child, so omit it to keep the session unseeded.
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...seed.length > 0 ? { seed } : {},
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})
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}
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}
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export function apply(ctx: Context, config: Config): void {
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ctx.subagents.registerProvider(new ForkProvider(config.providerName, ctx))
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}
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