---
name: how
description: "Use for \"how does X work\", code walkthroughs before changing something, and placement / ownership / layering questions (\"where should this live\", \"which package owns this\", \"is this the right layer\"). Explains subsystem architecture, runtime flow, onboarding mental models. Use why for motivation."
disable-model-invocation: true
---

# How

Use `delegate_task` for every spawn. Arena runners, architect runners, and interrogate reviewers are panels: one child per seat, including fallbacks. Every other role is a pool: pick the seat whose model best fits the job; spread same-role children in a wave across seats. Arena cross-judges prefer a different model family. Copy the chosen target from `<t3_pstack>` exactly, including all options; `inherit` means the parent model and omits `target`. If a pool spawn is rejected, report it and try the next seat; never invent targets or change options. Repeat fallback notes and report provider, model, or option mismatches. If a required role is missing, stop that spawn. Call `orchestrator_capabilities` once before the first delegation. Start each brief with the absolute `<pstack>` and `<models>` paths; include the relevant resolved role lines when children will delegate. Retain every `taskId`. With `mode: "async"`, spawn the wave and end the turn; completion wakes the parent. Do not poll children. Use `mode: "wait"` only when this turn needs the result; a wait timeout does not cancel the child. Cancel replaced or unneeded work with `task_cancel`.

Explore the codebase to answer "how does X work?" questions. Produce architectural explanations at the level of a senior engineer onboarding onto a subsystem, enough to build a working mental model, not so much that it reads like annotated source code.

Explorers use the `how explorer` role and explainers use `how explainer`. Set `role: "research"` and include "Do not edit files, commit, or push" in each brief. Check `git status` afterward. Child MCP access remains available.

## 1. Assess complexity

If the scope is ambiguous, state your interpretation and explore. The user can redirect.

- **Simple** (a single module, a small utility, a narrow question such as "how does function X work"): no explorers. Spawn one explainer that explores and explains in one pass, built from `references/explainer-prompt.md` without the explorer-findings section. Go to step 4.
- **Complex** (a subsystem spanning multiple files or services, a cross-cutting feature, a full architectural overview): go to step 2.

When in doubt, take the simple path.

## 2. Explore (complex only)

Decompose the question into 2 to 4 angles, each a distinct slice of the subsystem. Spawn all explorers in a single message, each with `references/explorer-prompt.md` and its angle filled in.

## 3. Synthesize (complex only)

Once all explorers have returned, spawn one explainer with `references/explainer-prompt.md` and every explorer's findings filled in.

## 4. Present

Present the explainer's output. Light edits for clarity or context from the conversation are fine. Do not substantially rewrite it.

## Output format

The explanation uses the sections defined in `references/explainer-prompt.md`, dropping any that do not apply: Overview, Key Concepts, How It Works, Where Things Live, Gotchas.