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0005, Defer subagent fan-out pending a design pass

  • Status: Deferred (2026-06-02)
  • Deciders: Ariadne maintainers

Context

The best-practice research names an orchestrator-worker design, a lead agent dispatching parallel, context-isolated subagents, one per source, as the headline architecture. The obvious next step would be to fan out the graph and SQL retrieval into separate subagents.

Decision drivers

  • Cross-store reconciliation (corroborate facts, flag conflicts about the same entity) is a shared-context task.
  • Provenance is the spine: a parent-side PostToolUse hook assigns each evidence call a gN id that citations resolve to.
  • Add cost and complexity only when they buy something the current slice needs.

Considered options

  • Fan out now: one subagent per store, run in parallel.
  • Defer: keep the single lead agent with both connectors until a design resolves the conflicts below.

Decision

Defer. Naive fan-out collides with two load-bearing properties of the current slice:

  1. Shared context. Reconciliation needs both stores' evidence in one context; the research explicitly flags multi-agent fan-out as not generalising to shared-context tasks.
  2. Provenance. Subagents run in isolated contexts and return only a summary, their raw tool calls never reach the parent's gN hook, so citations would attach to a worker's prose instead of to evidence entries.

A correct design (workers retrieve in parallel and return pre-cited evidence; the lead reconciles) is a real redesign of the provenance layer. It is not blocked on research, it needs a focused design pass.

Consequences

  • The 2-store slice keeps the single-agent design and already scores grounded=True on the eval harness.
  • Revisit when store count or context pressure justifies the cost (multi-agent fan-out runs ~15× the tokens of a single agent).
  • When revisited, the provenance redesign is the gating work, not the parallelism itself.