# Logic Explain

> Explain what a specific piece of code actually does for a given input by producing a step-by-step execution trace (interprocedural, with name resolution and type transitions). Trigger when the user is confused about behavior or asks why code produces X instead of Y — "walk me through this", "trace through X with input Y", "why does this return X", "what does yield-from do here", "explain the execution path". SCOPE HARD RULE: a specific function + a specific input scenario. If the user wants to find bugs without a scenario in mind, use logic-review; two-version comparison uses logic-diff; concrete failures use logic-locate; codebase-wide audit uses logic-health. Do NOT trigger for: finding bugs without a behavioral question, style or design discussion, or concept explanations not tied to specific code.

- Skill: `hyhmrright/logic-explain-2` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add hyhmrright/logic-explain-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/hyhmrright/logic-explain-2/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Security
- Author: hyhmrright (https://skillmd.com/u/hyhmrright)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/hyhmrright/logic-explain-2

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# Logic-Lens — Execution Explain

## Setup

Use lazy loading per `../_shared/common.md` §13:
1. Read `../_shared/common.md` only for language, report header variants, scope routing, and loading budget.
2. Read only the relevant step in `logic-explain-guide.md` as you reach it.
3. Load `../_shared/semiformal-guide.md`, `../_shared/semiformal-checklist.md`, and `../_shared/report-template.md` on demand when the current step needs them.

Note: `logic-risks.md` is intentionally skipped — logic-explain does not produce L-code findings, and Remedy is intentionally out of scope for this mode. If the trace reveals a bug, stop and recommend logic-review or logic-locate. When handing off, do not discard work already done — present the premises established and trace steps completed under a **"Partial trace context (carry into next skill):"** heading so the user can pass them directly to the follow-on skill.

## Process

**Step 0. Language + scope routing.** Detect language per `common.md` §1. Confirm a single function + a single input scenario. If the user wants bug-finding without a scenario, hand off to logic-review.

**Step 1. Entry point and scenario** (guide Step 1) — name the function, the input scenario, and what the user is trying to understand.

**Step 2. Build premises** (guide Step 2) — resolve every non-obvious name, state the types of key variables at entry, note global/module state accessed.

**Step 3. Produce step-by-step trace** (guide Step 3) — numbered, interprocedural, active voice; cross function boundaries whenever relevant to the user's scenario. Keep the trace scenario-bound; do not branch into alternative paths unless they explain the user's confusion.

**Step 4. Highlight non-obvious behavior** (guide Step 4) — name resolutions, implicit coercions, hidden side effects; the "gotchas" the casual reader would miss.

**Step 5. Summarize actual vs. assumed** (guide Step 5) — one sentence each; this is the core value for the user.

**Mode line in report:** `Execution Explain` (Chinese: `执行解释`).

**Note:** Execution Explain is descriptive, not evaluative. Omit the Logic Score / Fault Confidence / Verdict line from the report header.