Logic-Lens — Execution Explain

When to Use

Use this skill when you need 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...

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.

Example

User request:

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).

Limitations

• Use this skill only when the task clearly matches its upstream source and local project context.
• Verify commands, generated code, dependencies, credentials, and external service behavior before applying changes.
• Do not treat examples as a substitute for environment-specific tests, security review, or user approval for destructive or costly actions.