How

---
name: how
description: "Use for runtime, ownership, layering, code-walkthrough, and placement questions."
license: MIT
metadata:
  author: jstack-maintainers
  source: michael-denyer/pstack-claude
  source-version: "0.9.130"
  source-commit: d88063f3355a5ecff0e6dbb890a11bab4b08bc2e
  owner: software-factory
  risk: low
  capabilities: jstack,engineering-research
---

# How

On Codex, Cursor, or another non-Claude runtime, read the [runtime mapping](../poteto-mode/references/harness-tools.md), including its per-skill notes, before following this skill.

On GitHub Copilot, read the [platform mapping](../poteto-mode/references/copilot-tools.md), including its per-skill notes, before following this skill.

On Muse, read the [platform mapping](../poteto-mode/references/muse-tools.md), including its per-skill notes, before following this skill.

On Antigravity, read the [platform mapping](../poteto-mode/references/agy-tools.md), including its per-skill notes, before following this skill.

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.

Every spawn is a `Agent` subagent with `subagent_type: "general-purpose"` and `readonly: true`. Explorers use the `how explorer` line in `jstack-models.md` (default in [Models](#models)), and every explainer uses the `how explainer` line (default in [Models](#models)). Set `model` to that line's value, or to the default if the sheet or the line is missing. Leave `model` unset when the value is `auto` or `inherit-parent`. If the `Agent` tool rejects a slug, use the default and say so. If it rejects the default, use the closest valid slug of the same family from its error message. Pick each subagent's reasoning level for the job, per the Subagents section of the **poteto-mode** skill.

## 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.

## Models

Role defaults originate from the upstream `plugins/pstack/models.json`. Refresh them through `scripts/vendor_jstack.py` after reviewing the upstream change. A matching role line in the `jstack-models.md` override sheet overrides each at runtime; `/setup-jstack` writes it and lists its path per runtime.

- how explorer: `opus`
- how explainer: `opus`

## Reasoning effort

A role value in the override sheet may name a reasoning effort after its model, as in `opus @xhigh`. Levels on Claude Code: `low`, `medium`, `high`, `xhigh`, `max`. Which ones apply depends on the model. A value without `@` takes the sheet's `default effort` line, a level or `session`, and `session` when the sheet has no such line. On Claude Code, `session` sets no effort. On other runtimes, follow the platform mapping for `session`. Strip the suffix before reading the model: `inherit-parent` or `auto` still omits `model` at every level, and a model name is passed as `model`. Pass the level as the dispatch's effort field and keep the `subagent_type` you would otherwise use. That is `effort` on the Claude Code `Agent` call and `reasoning_effort` on Codex's `spawn_agent`. On Muse it is `effort` on a Workflow child; a `subagent_spawn` dispatch keeps the session's effort.