---
name: control-flow
description: >
  Analyze and design control flows and data structures. Produces compact
  ASCII tree diagrams showing triggers, call chains, payload shapes, state
  mutations, and re-render effects. Use when user asks to diagram, trace,
  visualize, or design a flow or data structure.
---

# /control-flow — Analyze and design control flows and data structures

Read the relevant source code and produce ASCII tree diagrams inside ```txt blocks.

## Format

- Each user action or IO event is a separate tree root
- Real function names and types — never invent
- Payload shapes as TypeScript types, not prose
- State mutations: which fields change, what triggers
- Re-render chain: which components and why
- Cross-package when the flow spans app → CLI → server
- Compact — skip trivial pass-throughs, show decisions

Example:

```txt
User taps "Archive"
│
├─ handleActionPress(action: SessionActionItem)
│  └─ onClose() → setActionsAnchor(null)
│
├─ sessionKill(sessionId: string)
│  ├─ POST /api/sessions/:id/kill
│  └─ → { success: boolean, message?: string }
│
└─ deleteSession(sessionId)
   ├─ mutates: sessions, sessionMessages, gitStatus, fileCache
   ├─ rebuilds: sessionListViewData
   └─ re-renders: SessionsListWrapper (data ref changed)
```

For data structures, show the shape and what depends on it:

```txt
SessionRowData (flat primitives, cheap deep-equal)
├─ id, name, subtitle, avatarId     ← identity + display
├─ state: SessionState              ← collapsed from presence + agentState + thinking
├─ hasDraft: boolean                ← collapsed from draft string
├─ activeAt?: number                ← only inactive sessions (avoids heartbeat diffs)
├─ machineId, path, homeDir         ← grouping in ActiveSessionsGroup
└─ completedTodosCount, totalTodosCount
   │
   consumed by:
   ├─ SessionItem         → renders purely from props, no store hooks
   ├─ ActiveSessionsGroup → groups by machineId + path
   └─ useDeepEqual        → 12 primitive comparisons vs full Session tree
```

## Principles

- Expressive yet compact — every line earns its place
- Show payload SHAPE not description
- Show state mutations → which store fields, what rebuilds
- Show re-render chain → component + reason
- Pseudo code only for branching logic between nodes
- Always output inside ```txt for alignment
- File:line refs when helpful, not mandatory — the flow matters more than the location

## Process

1. Parse topic into entry points
2. Grep/Explore to find the call chain
3. Read each step at the relevant lines
4. Build tree from trigger → final effect
5. Output as ```txt blocks