pstack-how

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.

Every spawn is a subagent call with read-only exploration scope. Explorers use the how explorer line in the pstack settings file (~/.omk/agent/pstack-models.md, written by /skill:pstack-setup-pstack), and every explainer uses the how explainer line. OMK subagents inherit the session model, so a missing file or line, or an auto or inherit-parent entry, means the session model. If a configured model is not in the OMK catalog, run that seat on the session model and say so; never claim a cross-model seat you did not run. OMK subagents inherit the session model and effort; pass no model, effort, or speed fields.

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.

Subagent tool. Spawns in this skill use OMK's subagent extension. Call it with agent, task, and agentScope, and use tasks: [{agent, task}, ...] for a parallel fan-out. Keep the prompt and inherit the session model. Pass no model, effort, or speed fields. If the subagent extension is not loaded or the project is not trusted, run each role yourself, one after another.

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.