how ยท diff
git:20261006.df58112 to git:20261010.00b14f1
11 added, 33 removed. Audit A to A.
---
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
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-models.mdc` rule and a default. Set `model` to that line's value, or to the default if the rule or the line is missing. Leave `model` unset when the value is `auto` or `inherit-parent`. If the Task 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.
+ Every spawn is a Task subagent with `subagent_type: generalPurpose` and `readonly: true`. Explorers use the `how explorer` line in the `pstack-models.mdc` rule (default `grok-4.7-xhigh-fast`), and every explainer uses the `how explainer` line (default `claude-opus-5-5-xhigh`). Set `model` to that line's value, or to the default if the rule or the line is missing. Leave `model` unset when the value is `auto` or `inherit-parent`. If the Task 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.
- ## Step 1. Assess Complexity
+ ## 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.
+ - **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.
- ## 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`: `generalPurpose`
- - `model`: the `how explorer` line, default `grok-4.7-xhigh-fast`
- - `readonly`: `true`
-
- 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 Task subagent that explores and explains in one pass:
-
- - `subagent_type`: `generalPurpose`
- - `model`: the `how explainer` line, default `claude-opus-5-5-xhigh`
- - `readonly`: `true`
-
- Build its prompt from `references/explainer-prompt.md` without the explorer-findings section. Go to Step 4.
-
- ## Step 3. Synthesize (complex questions only)
+ ## 2. Explore (complex only)
- Once all explorers have returned, spawn one Task subagent to synthesize their findings into one explanation:
+ 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.
- - `subagent_type`: `generalPurpose`
- - `model`: the `how explainer` line, default `claude-opus-5-5-xhigh`
- - `readonly`: `true`
+ ## 3. Synthesize (complex only)
- Build its prompt from `references/explainer-prompt.md` with every explorer's findings filled in.
+ Once all explorers have returned, spawn one explainer with `references/explainer-prompt.md` and every explorer's findings filled in.
- ## Step 4. Present
+ ## 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.
+ Present the explainer's output. Light edits for clarity or context from the conversation are fine. Do not substantially rewrite it.
- ## Output Format
+ ## 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.