how

Files (3)

• SKILL.md
• explainer-prompt.md · references/
• explorer-prompt.md · references/

SKILL.md (first lines)

# How

*pstack sibling skills named in this file (**how**, `/how`, **principle-…**, and so on) live at `../<name>/SKILL.md` relative to this skill's base directory. They are not model-invocable, so "run `/x`" means Read `../x/SKILL.md` and follow it.*

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.

Each spawn below names a role line in the pstack model rule (`~/.claude/rules/pstack-models.md`, written by `/setup-pstack`; read it if it exists and is not already in context) and a default. Set `model` to that line's value, or to the default if the rule or the line is missing. Leave the Agent tool's `model` unset when the value is `auto` or `inherit-parent`. If the Agent tool rejects an alias (the provider may not serve it), use the default and say so. If it rejects the default, fall back down the tiers `opus` → `sonnet` → `haiku` and say so.

## Step 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. One explainer explores and explains in a single pass. Go to Step 2b.
- **Complex** (a subsystem spanning multiple files or services, a cross-cutting feature, a full architectural overview): spawn parallel explorers first, then hand off to the explainer. Go to Step 2a.

When in doubt, take the simple path.

## Step 2a. Explore (complex questions only)

Decompose the question into 2 to 4 exploration angles, each a distinct slice of the subsystem. Spawn all explorers in a single message:

- `subagent_type`: `general-purpose`
- `model`: the `how explorer` line, default `sonnet`
- read-only: tell it in the prompt not to edit files (Claude Code has no readonly flag)

Each explorer gets the prompt in `references/explorer-prompt.md` with its angle filled in. Then go to Step 3.

## Step 2b. Direct Explain (simple questions)

Spawn one Agent subagent that explores and explains in one pass:

- `subagent_type`: `general-purpose`
- `model`: the `how explainer` line, default `opus`
- read-only: tell it in the prompt not to edit files (Claude Code has no readonly flag)

Build its prompt from `references/explainer-prompt.md` without the explorer-findings section. Go to Step 4.

## Step 3. Synthesize (complex questions only)

Once all explorers have returned, spawn one Agent subagent to synthesize their findings into one explanation:

- `subagent_type`: `general-purpose`
- `model`: the `how explainer` line, default `opus`
- read-only: tell it in the prompt not to edit files (Claude Code has no readonly flag)

Build its prompt from `references/explainer-prompt.md` with every explorer's findings filled in.

## Step 4. Present

Present the explainer's output to the user. 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.

From milantracy/pstack, MIT.

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