explain

EXPLAIN Task

Persona: Execute this task as the @developer subagent. Load the persona characteristics from .rulesync/subagents/developer.md before proceeding.

Objective

Explain how file/folder/feature works. Break down logic, explain decisions, trace flows, optionally suggest improvements.

Instructions

1. Discovery: - Ask: "What to explain? (file/folder/feature)" - Examine code and context

2. Scope: - Ask: detail level (high-level/detailed/deep-dive), suggest improvements?, specific aspects? (data flow, error handling, performance, security)

3. Analyze: - Read target files - Understand purpose, functionality - Trace execution flow, data transformations - Identify dependencies, integrations - Note error handling, edge cases - Recognize architectural patterns - Check related files (README, tests, types)

4. Structured explanation: - Files: Purpose/context, imports/dependencies, main logic step-by-step, edge cases/error handling/security, non-obvious code/debt - Folders/Modules: Purpose/responsibility, structure/organization, entry points/public API, usage patterns - Features: User perspective, implementation across files (frontend→backend→database), data flow, integration points/business logic

5. Language: - High-level → details - Analogies/examples when helpful - Define technical terms - Break complex logic into chunks - Mermaid diagrams for complex flows - Highlight "why" behind decisions

6. Improvements (if requested): - Analyze using project standards: code quality, performance, security, architecture - Format: Priority (High/Medium/Low), Category, Current vs Suggested, Benefits/trade-offs, Effort estimate

7. Summary: - Recap main points - Highlight takeaways - Top priority suggestions if provided - Offer deeper dive - Ask: "Explain specific part in detail or help implement improvements?"

Example Prompts

• /explain app/api/trpc/routers/channels.ts - Produces a breakdown of the router: purpose, each procedure's logic, input validation, error handling, and database interactions.
• /explain app/lib/auth --detail deep-dive --aspects security,data-flow - Produces a deep-dive covering the auth module's data flow from request to session, security boundaries, token handling, and dependency graph.
• /explain "How does message sending work end-to-end?" - Traces the full flow from UI input through tRPC mutation to database write and real-time update, with a Mermaid sequence diagram.

Quality Criteria

• Explanation covers purpose, data flow, error handling, dependencies, and architectural decisions
• "Why" behind non-obvious design choices is surfaced, not just "what" the code does
• Complex flows include a Mermaid diagram for visual clarity
• All referenced files and functions use actual paths and names from the codebase
• Technical terms are defined on first use
• Detail level matches the requested scope (high-level stays concise, deep-dive is exhaustive)

Scope Boundaries

• Do NOT refactor or modify any code during an explain task
• Do NOT implement suggested improvements -- only describe them
• Do NOT create or update tests
• Do NOT produce spec documents or PRDs

Cross-References

• /diagram - Generate visual flow diagrams discovered during explanation
• /document - Persist explanations as inline comments, JSDoc, or README content
• /audit - Run a deeper structural or quality analysis on the explained code