Find logic bugs in a single file or function via semi-formal execution tracing (Premises → Trace → Divergence → Trigger → Remedy). Trigger when a user shares code and suspects something is wrong without naming a concrete failure — phrases like "review this", "does this look right",...
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Find logic bugs in a single file or function via semi-formal execution tracing (Premises → Trace → Divergence → Trigger → Remedy). Trigger when a user shares code and suspects something is wrong without naming a concrete failure — phrases like "review this", "does this look right",...
Use this skill when you need find logic bugs in a single file or function via semi-formal execution tracing (Premises → Trace → Divergence → Trigger → Remedy). Trigger when a user shares code and suspects something is wrong without naming a concrete failure — phrases like "review this", "does this look right",...
Output Skeleton Contract
The downstream grader (scripts/grade-iteration.py) and other Logic-Lens skills consume this report by substring-matching literal tokens defined in ../_shared/common.md §1 (header map), §2 (mandatory field labels + Logic Score), and ../_shared/report-template.md (skeleton). Paraphrasing those tokens — even with a synonym that reads fine to a human — breaks the contract regardless of analysis quality.
Three failure modes observed in benchmark that deserve specific callout beyond the general rule:
Synonym substitution for field labels whose substituted form omits the required substring — replacing Premises / 前提 with 前置条件构建 / 前置条件 (eval-201), or Divergence / 偏差 with 根因 / 核心缺陷 / 结论 (eval-252). Each substitution reads fine to a human and may even appear as a section heading or table column, but the substituted word does NOT contain the required substring, so grader and cross-skill consumers see the document as missing the field entirely. Use the literal token from common.md §1; you can still add a descriptive subtitle alongside it.
Demoting a confirmed L-code finding to ### 附加观察（非 Finding） / ### Additional observation — if Premises→Trace→Divergence holds, the finding belongs inside ## Findings with the five literal fields, even at Suggestion severity. This was a recurring cause of eval-279 (quicksort L4) failing on Sonnet runs.
Omitting Divergence: / 偏差： field entirely — the single most frequent failure mode. Many outputs correctly analyze the bug but write the divergence as prose, in a table cell, or under headings like 根因, 故障点, 核心问题, 缺陷. The Divergence: field is the specific label for "the point where actual behavior diverges from the premise." It is NOT optional and has no acceptable synonym. For no-bug findings use (中文 ).
Divergence: None — [why the premise holds]
偏差：无——[原因]
Correctly formatted finding — use as template:
### 🔴 Critical
**[L4] — Mutation during iteration skips elements**
Premises: `users` is `list[User]` passed by reference; `list.remove()` shifts subsequent elements left; the `for` iterator advances by index.
Trace: [1] index=0, user is inactive → `remove()` shifts list. [2] Iterator advances to index 1, which now holds the element originally at index 2 — the original index-1 element is skipped. Rebuttal check: PASSED — no defense found.
Divergence: `remove_inactive([inactive₁, inactive₂, active])` returns `[inactive₂, active]` (2 elements) instead of `[active]` (1 element) — the second inactive user is never visited.
Trigger: `remove_inactive([User(False), User(False), User(True)])` → expected 1, actual 2.
Remedy: Replace loop body with `return [u for u in users if u.is_active]`. Dry-run: ✅ divergence eliminated.
Each finding block MUST contain all five literal labels (Premises: / Trace: / Divergence: / Trigger: / Remedy: or 前提： / 追踪： / 偏差： / 触发： / 修复：) as line-starting prefixes. Section headers (### Premises, ## Execution Trace) do NOT satisfy this requirement — the labels must appear inside the finding block.
No-bug case: emit ## Findings with a finding block that uses all five field labels, with Divergence: None — [why the premise holds]. This format is REQUIRED — it satisfies both grading and auditing. Example:
### ✅ No Bug
**[No Bug] — defer guarantees unlock on all exit paths**
Premises: `mu.Lock()` acquired at line 12; `defer mu.Unlock()` placed at line 13 (before any conditional branch or early return).
Trace: [1] `defer` registered immediately after `Lock()`. [2] Go spec guarantees deferred calls execute on ALL function exit paths (return, panic, early return). [3] No conditional branch between Lock and defer registration.
Divergence: None — `defer mu.Unlock()` placed unconditionally after acquire guarantees release on every exit path; no lock leak possible.
Trigger: N/A (no bug to reproduce).
Remedy: N/A (code is correct as written).
Setup
Use lazy loading per ../_shared/common.md §13:
Read ../_shared/common.md only for language, Iron Law, Logic Score, scope management, Remedy discipline, config fields, and loading budget.
Read only the relevant step in logic-review-guide.md as you reach it.
Load ../_shared/logic-risks.md, ../_shared/semiformal-guide.md, ../_shared/semiformal-checklist.md, and ../_shared/report-template.md on demand when the current step needs them.
Process
Step 0. Language + scope routing. Detect the user's language per common.md §1; every label and header below must be in that language. Confirm scope is one file or one function — if the user points at a directory, switch to logic-health; if they describe a confirmed failure, switch to logic-locate; if two versions, logic-diff.
Step 1. Establish claimed behavior + review entry points (guide Step 1) — write one sentence describing what the code is supposed to do, then select the concrete entry function(s) that will be traced. If a file exceeds common.md §9 limits, state the selected subset and why.
Step 2. Build premises (guide Step 2) — per the Premises Construction Checklist in semiformal-checklist.md; include caller/callee contracts when the reviewed function depends on another local function.
Step 3. Build the risk path ledger (guide Step 3) — enumerate candidate bug paths across L1–L9 before writing findings. Tag each retained path as Class A (self-evident) or Class B (invariant-dependent). Do not stop after the happy path. Read logic-risks.md Quick Disambiguation Table before assigning any L-code — common misclassifications are catalogued there. L4 priority check: does any function mutate its input AND return the same object? L7 priority check: is shared state accessed across await/yield/thread boundaries without explicit synchronization? L4 vs L7 disambiguation: any state access involving more than one execution context (thread / goroutine / await / yield) is L7, never L4 — including single-threaded asyncio where coroutines interleave at await. L4 is for single-context aliasing only (mutable defaults, in-place mutation footgun, mutation-during-iteration). L4 requires an actual mutation of shared/aliased state as the root cause — variable scoping issues (const/let visibility, constructor scope) are L1, and query-pattern inefficiencies (N+1) are L3.
L1 vs L6 disambiguation: if the root cause is a name/identifier resolving to a different definition than the developer expected (import shadowing, module constant lookup, prototype chain, constructor-scoped const/let not visible to methods), it is L1 even when the symptom is a missing-method error or wrong return value — L6 applies only when the name resolves correctly but the callee's behavior differs from what the caller assumed.
L2 vs L6 disambiguation: if the root cause is an implicit type coercion at the operator level (+/-/*/== triggering string↔number conversion, or as/cast bypassing runtime type checks), it is L2 — L6 requires calling a specific callee whose behavior differs from the caller's assumption. Operators are not callees.
L5 vs L7 disambiguation: if an error code, exit status, or exception is suppressed by a single-context construct (|| true, empty catch, missing set -e, bare except), it is L5 (control flow escape) — L7 requires multiple execution contexts. Error propagation failure within one sequential script/function is L5.
L9 check: if the bug's root cause is timezone/locale/encoding information lost at the data-type level (e.g., TIMESTAMP vs TIMESTAMPTZ, naive vs aware datetime, locale-dependent string sort), it is L9 — not L6 even if it looks like "callee behavior differs from expectation", not L2, not L8.
Step 4. Deep-trace selected paths (guide Step 4) — trace the normal path plus the highest-risk edge paths; resolve every name, state every type, cross callee boundaries, and stop each trace at either a confirmed divergence or a confirmed safe post-condition. Java/C++ DCL rule: for double-checked locking patterns, MUST trace both faces: (a) missing volatile / memory barrier (visibility hazard) AND (b) instance = new X(); instance.init(); as two non-atomic statements — lock-free readers can see non-null instance before init() completes (publish-before-init hazard). Report both; omitting either is an incomplete analysis.
Step 5. Identify divergences (guide Step 5) — classify each by L1–L9; assign severity; apply the reachability gate (Class A reports directly; Class B requires a probe — enforcement found → drop candidate, not found → assigned severity, partial → cap at Warning with manual verification recommended). Apply the correctness parity principle for no-bug scenarios. No-bug output discipline: when zero divergences remain, still emit the full template skeleton — Mode line, Scope, **Logic Score:** 100/100, ## Findings followed by a finding block that uses Divergence: None — [why the premise holds] (中文 偏差：无——[原因]) with all five field labels present. This makes the reasoning auditable and satisfies the format contract. If analysis actively disproves a suspected bug, explain the defense in the Trace: field (e.g., "Go defer mu.Unlock() guarantees release on all exit paths including early return"). Do not collapse the verdict into free-form prose or omit the structured fields; downstream grading requires the five-field format even for no-bug conclusions.
Step 5.5. Adversarial Red Team (guide Step 5.5) — for each candidate finding, attempt to disprove it by answering three rebuttal questions (premise rebuttal, path rebuttal, consequence rebuttal). Withdraw findings with confirmed defenses; downgrade findings with partial defenses to Suggestion. Design-intent gate: before reporting an L3 Boundary Blindspot, ask "Does the code explicitly return an error / rejection at this boundary rather than attempting to continue past it?" If yes (e.g., errors.New("cache full") at maxSize, 429 Too Many Requests, buffer-full rejection), withdraw — these are correct boundary enforcement, not blindspots. L3 applies only when code attempts to operate past the boundary and silently fails (wrong result, crash, infinite loop). Note: a panic at a boundary is a crash, not a designed error return, and remains a potential L3.
Step 6. Apply Iron Law — Five-Field Discipline (guide Step 6) — confirm all findings have Premises → Trace → Divergence complete; then write Trigger (concrete reproducing input, required for Critical/Warning) and Remedy (paste-ready per common.md §10). Each finding MUST use these literal field labels — English Premises: / Trace: / Divergence: / Trigger: / Remedy:, or Chinese 前提： / 追踪： / 偏差： / 触发： / 修复：. Do not paraphrase. Headers like Execution Path, Issue Found, Core Defect, 执行路径, 发现的逻辑隐患, 核心缺陷 are unacceptable substitutes — they fail downstream grading and break the report contract that other Logic-Lens skills consume. Multi-finding discipline: When there are multiple findings, each finding block inside ## Findings must include all five literal field labels — Premises: / Trace: / Divergence: / Trigger: / Remedy: (or their Chinese equivalents) — with content specific to that finding. Any shared background context may appear as a preamble section, but it does NOT substitute for the per-finding fields. A finding that omits Divergence: (or any other required field) breaks the contract even if Premises: or Trace: appear elsewhere in the report.
Step 6.5. Remedy Dry-Run (guide Step 6.5) — mentally re-trace the Trigger input through the fixed code to confirm: divergence eliminated, no regression introduced, happy path preserved.
Step 7. Score and output (guide Step 7) — compute Logic Score per common.md §6 and emit it as the literal line **Logic Score:** XX/100 (中文 **逻辑评分：** XX/100) directly under **Scope:** — this exact token (not "Score: XX", not "Quality: XX") is required for both grader recognition and cross-skill consumption. Then render the rest of the Report Template with localized headers.
Step 8. Execution Verification Gate (guide Step 8, optional) — when a runtime is available, generate a minimal reproducer script for each Critical/Warning finding, execute it to confirm the bug exists, apply the Remedy and re-execute to confirm the fix works. Withdraw false positives; mark verified findings as ✅ Execution-verified.
Mode line in report:Logic Review (Chinese: 逻辑审查).
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.
