refactoring

Quick Summary

Goal: Restructure code without changing behavior using extract, move, and simplify patterns.

Workflow:

1. Analysis — Identify target, map dependencies with Grep, assess impact, verify test coverage
2. Plan — Document refactoring type, changes, and risks
3. Execute — Apply refactoring (extract method/​class, move to entity/​extension, simplify conditionals)
4. Verify — Run tests, confirm no behavior change, check compilation

Key Rules:

• Establish test coverage first, then refactor — never refactor code that has no existing tests — why: tests are the only proof the refactor preserved behavior
• Make small incremental changes; never mix refactoring with feature work
• Place logic in the lowest appropriate layer (Entity > Service > Component)

First Principle — Easy to Change

The success metric of every coding decision is future change cost. DRY, SRP, abstraction, design patterns, naming, layering, tests — every technique exists to serve one goal: making the next change cheaper.

When evaluating code, a refactor, a test, or an abstraction, ask: does this make the next change cheaper or more expensive?

• Reject "best practices" that raise change cost (premature abstraction, speculative generality, leaky indirection, ceremony without payoff).
• Name the real enemies in findings: coupling, hidden state, duplicated knowledge, unclear intent, irreversible decisions exposed too early.
• A simpler design that is easy to change beats a sophisticated design that isn't.

Apply this lens before invoking any specific rule, pattern, or checklist below — if a downstream rule would raise change cost, this principle wins.

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Investigation Mindset (NON-NEGOTIABLE)

Be skeptical. Apply critical thinking, sequential thinking. Every claim needs traced proof, confidence percentages (Idea should be more than 80%).

• Verify any "unused" code with grep across ALL services before touching it — do NOT assume it is dead — why: dynamic/​reflection/​cross-service callers don't surface in a casual read
• Every refactoring recommendation must include file:line evidence
• If you cannot prove a code path is safe to change, state "unverified, needs investigation"
• Question assumptions: "Is this really dead code?" → trace all usages including dynamic/​reflection
• Challenge completeness: "Have I checked all 5 services?" → cross-service validation required
• No "should be refactored" without proof — demonstrate the improvement with evidence

⚠️ MANDATORY: Confidence & Evidence Gate

MANDATORY IMPORTANT MUST ATTENTION declare Confidence: X% with evidence list + file:line proof for EVERY claim. 95%+ recommend freely | 80-94% with caveats | 60-79% list unknowns | <60% STOP — gather more evidence. Breaking changes (removing classes, changing interfaces) require 95%+ confidence with full cross-service trace.

Code Refactoring

Expert code restructuring agent. Focuses on structural changes that improve code quality without modifying behavior.

Refactoring Catalog

Extract Patterns

Move Patterns

Simplify Patterns

Workflow

Phase 1: Analysis

1. Identify Target: Locate code to refactor
2. Map Dependencies: Find all usages with Grep
3. Assess Impact: List affected files and tests
4. Verify Tests: Ensure test coverage exists
5. External Memory: Write analysis to .ai/​workspace/​analysis/​{refactoring-name}.analysis.md. Re-read before planning.

Phase 2: Plan

Document refactoring plan:

## Refactoring Plan

**Target**: [file:line_number]
**Type**: [Extract Method | Move to Extension | etc.]
**Reason**: [Why this refactoring improves code]

### Changes

1. [ ] Create/​modify [file]
2. [ ] Update usages in [files]
3. [ ] Run tests

### Risks

- [Potential issues]

Phase 3: Execute

The principle below is stack-neutral: push logic down to the lowest layer that owns the data (here, an entity-owned predicate replaces an inline condition in the handler/​use-case). The code is one stack's instantiation — translate the shape to your language.

Example (illustrative — adapt to your language):

// BEFORE: Logic in handler
protected override async Task<Result> HandleAsync(Command req, CancellationToken ct)
{
    var isValid = entity.Status == Status.Active &&
                  entity.User?.IsActive == true &&
                  !entity.IsDeleted;
    if (!isValid) throw new Exception();
}

// AFTER: Extracted to entity static expression
// In Entity.cs
public static Expression<Func<Entity, bool>> IsActiveExpr()
    => e => e.Status == Status.Active &&
            e.User != null && e.User.IsActive &&
            !e.IsDeleted;

// In Handler
var entity = await repository.FirstOrDefaultAsync(Entity.IsActiveExpr(), ct)
    .EnsureFound("Entity not active");

Phase 4: Verify

1. Run affected tests
2. Verify no behavior change
3. Check code compiles
4. Review for consistency

Layer-Down Refactorings (worked examples)

These three refactorings share one principle: move logic out of the orchestration layer (handler/​use-case) into the layer that owns the concern — reused logic into a shared helper, query logic into a data-access extension, mapping into the DTO. The shapes translate to any stack (a "helper" is any cohesive collaborator; an "extension" is any way your language attaches reusable query methods; "DTO owns mapping" is the rule that the data-transfer type, not the orchestrator, defines its own conversion). See the project's backend-patterns reference for the concrete primitives on your stack.

Example (illustrative — adapt to your language):

Handler to Helper — reused logic moves to a shared collaborator

// BEFORE: Reused logic in multiple handlers
var order = await repo.FirstOrDefaultAsync(Order.UniqueExpr(userId, customerId), ct)
    ?? await CreateOrderAsync(userId, customerId, ct);

// AFTER: Extracted to Helper
// In OrderHelper.cs
public async Task<Order> GetOrCreateOrderAsync(string userId, string customerId, CancellationToken ct)
{
    return await repo.FirstOrDefaultAsync(Order.UniqueExpr(userId, customerId), ct)
        ?? await CreateOrderAsync(userId, customerId, ct);
}

Handler to Repository Extension — query logic moves to the data-access layer

// BEFORE: Query logic in handler
var orders = await repo.GetAllAsync(
    e => e.CustomerId == customerId && e.Status == Status.Active && e.WarehouseIds.Contains(warehouseId), ct);

// AFTER: Extracted to extension
// In OrderRepositoryExtensions.cs
public static async Task<List<Order>> GetActiveByWarehouseAsync(
    this I{Service}RootRepository<Order> repo, string customerId, string warehouseId, CancellationToken ct)
{
    return await repo.GetAllAsync(
        Order.OfCustomerExpr(customerId)
            .AndAlso(Order.IsActiveExpr())
            .AndAlso(e => e.WarehouseIds.Contains(warehouseId)), ct);
}

Mapping to DTO — the data-transfer type owns its own conversion

// BEFORE: Mapping in handler
var config = new AuthConfig
{
    ClientId = req.Dto.ClientId,
    Secret = encryptService.Encrypt(req.Dto.Secret)
};

// AFTER: DTO owns mapping
// In AuthConfigDto.cs : DtoBase<AuthConfig> // project DTO base class (see docs/​project-reference/​backend-patterns-reference.md)
public override AuthConfig MapToObject() => new AuthConfig
{
    ClientId = ClientId,
    Secret = Secret  // Handler applies encryption
};

// In Handler
var config = req.Dto.MapToObject()
    .With(c => c.Secret = encryptService.Encrypt(c.Secret));

Index Impact Check

[IMPORTANT] Database Performance Protocol (MANDATORY):

1. Paging Required — ALL list/​collection queries MUST ATTENTION use pagination. NEVER load all records into memory. Verify: no unbounded GetAll(), ToList(), or Find() without Skip/​Take or cursor-based paging.
2. Index Required — ALL query filter fields, foreign keys, and sort columns MUST ATTENTION have database indexes configured. Verify: entity expressions match index field order, database collections have index management methods, migrations include indexes for WHERE/​JOIN/​ORDER BY columns.

When extracting expressions or moving queries, verify index coverage:

• New expression fields have indexes in DbContext?
• Moved queries still use indexed fields?
• Refactored filters maintain index selectivity order?
• List queries use pagination (no unbounded GetAll/​ToList)?

Safety Checklist

Before any refactoring:

• Searched all usages across ALL services (static + dynamic + reflection)?
• Test coverage exists?
• Documented in todo list?
• Changes are incremental?
• No behavior change verified?
• Confidence declared — Confidence: X% with evidence list?

If ANY checklist item incomplete → STOP. State "Insufficient evidence to proceed."

Code Responsibility Refactoring (Priority Check)

⚠️ MUST ATTENTION READ: CLAUDE.md "Code Responsibility Hierarchy" for the Entity/​Model > Service > Component layering rule. When refactoring, verify logic is in the LOWEST appropriate layer.

Component HTML & SCSS Standards

⚠️ MUST ATTENTION READ: CLAUDE.md "Component HTML Template Standard (BEM Classes)" and docs/​project-reference/​scss-styling-guide.md for BEM class requirements and host/​wrapper styling patterns. When refactoring components, ensure all HTML elements have proper BEM classes.

Anti-Patterns

• Big Bang Refactoring: Make small, incremental changes
• Refactoring Without Tests: Ensure coverage first
• Mixing Refactoring with Features: Do one or the other
• Breaking Public APIs: Maintain backward compatibility
• Logic in Wrong Layer: Leads to duplicated code - move to lowest appropriate layer

Run python .claude/​scripts/​code_graph connections <file> --json on refactored files to find all consumers needing updates.

Graph Intelligence (RECOMMENDED if graph.db exists)

If .code-graph/​graph.db exists, enhance analysis with structural queries:

• Impact of restructuring -- trace callers: python .claude/​scripts/​code_graph query callers_of <function> --json
• Impact of restructuring -- check importers: python .claude/​scripts/​code_graph query importers_of <module> --json
• Batch analysis: python .claude/​scripts/​code_graph batch-query file1 file2 --json

See <!-- SYNC:graph-assisted-investigation --> block above for graph query patterns.

Graph-Trace for Refactoring Impact

When graph DB is available, BEFORE refactoring, trace to verify all consumers:

• python .claude/​scripts/​code_graph trace <file-to-refactor> --direction downstream --json — all downstream consumers that depend on this code
• python .claude/​scripts/​code_graph trace <file-to-refactor> --direction both --json — full picture: callers + consumers
• Flag any consumer NOT covered in your refactoring plan — it may break silently

Related

• code-simplifier
• code-review

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Workflow Recommendation

MANDATORY IMPORTANT MUST ATTENTION — NO EXCEPTIONS: If you are NOT already in a workflow, you MUST ATTENTION use AskUserQuestion to ask the user. Do NOT judge task complexity or decide this is "simple enough to skip" — the user decides whether to use a workflow, not you:

1. Activate workflow-refactor workflow (Recommended) — scout → investigate → plan → code → review → sre-review → test → docs
2. Execute /​refactoring directly — run this skill standalone

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AI Agent Integrity Gate (NON-NEGOTIABLE)

Completion ≠ Correctness. Before reporting ANY work done, prove it:

1. Grep every removed name. Extraction/​rename/​delete touched N files? Grep confirms 0 dangling refs across ALL file types.
2. Ask WHY before changing. Existing values are intentional until proven otherwise. No "fix" without traced rationale.
3. Verify ALL outputs. One build passing ≠ all builds passing. Check every affected stack.
4. Evaluate pattern fit. Copying nearby code? Verify preconditions match — same scope, lifetime, base class, constraints.
5. New artifact = wired artifact. Created something? Prove it's registered, imported, and reachable by all consumers.

[IMPORTANT] Use TaskCreate to break ALL work into small tasks BEFORE starting — including tasks for each file read. This prevents context loss from long files. For simple tasks, AI MUST ATTENTION ask user whether to skip.

• docs/​project-reference/​domain-entities-reference.md — Domain entity catalog, relationships, cross-service sync (read when task involves business entities/​models) (read directly when relevant; do not rely on hook-injected conversation text)

<!-- SYNC:graph-assisted-investigation -->

Graph-Assisted Investigation — MANDATORY when .code-graph/​graph.db exists.

HARD-GATE: MUST ATTENTION run at least ONE graph command on key files before concluding any investigation.

Pattern: Grep finds files → trace --direction both reveals full system flow → Grep verifies details

Task	Minimum Graph Action
Investigation/​Scout	trace --direction both on 2-3 entry files
Fix/​Debug	callers_of on buggy function + tests_for
Feature/​Enhancement	connections on files to be modified
Code Review	tests_for on changed functions
Blast Radius	trace --direction downstream

CLI: python .claude/​scripts/​code_graph {command} --json. Use --node-mode file first (10-30x less noise), then --node-mode function for detail.

<!-- /​SYNC:graph-assisted-investigation --> <!-- SYNC:nested-task-creation -->

Nested Task Expansion Contract — For workflow-step invocation, the [Workflow] ... row is only a parent container; the child skill still creates visible phase tasks.

1. Call TaskList first. If a matching active parent workflow row exists, set nested=true and record parentTaskId; otherwise run standalone.
2. Create one task per declared phase before phase work. When nested, prefix subjects [N.M] $skill-name — phase.
3. When nested, link the parent with TaskUpdate(parentTaskId, addBlockedBy: [childIds]).
4. Orchestrators must pre-expand a child skill's phase list and link the workflow row before invoking that child skill or sub-agent.
5. Mark exactly one child in_progress before work and completed immediately after evidence is written.
6. Complete the parent only after all child tasks are completed or explicitly cancelled with reason.

Blocked until: TaskList done, child phases created, parent linked when nested, first child marked in_progress.

<!-- /​SYNC:nested-task-creation --> <!-- SYNC:project-reference-docs-guide -->

Project Reference Docs Gate — Run after task-tracking bootstrap and before target/​source file reads, grep, edits, or analysis. Project docs override generic framework assumptions.

1. Identify scope: file types, domain area, and operation.
2. Required docs by trigger: always docs/​project-reference/​lessons.md; doc lookup docs-index-reference.md; review code-review-rules.md; backend/​CQRS/​API backend-patterns-reference.md; domain/​entity domain-entities-reference.md; frontend/​UI frontend-patterns-reference.md; styles/​design scss-styling-guide.md + design-system/​design-system-canonical.md; integration tests integration-test-reference.md; E2E e2e-test-reference.md; feature docs/​specs feature-spec-reference.md + spec-system-reference.md + spec-principles.md; behavior/​public-contract/​spec-test-code sync workflow-spec-test-code-cycle-reference.md; derived spec index/​ERD/​reimplementation guides spec-system-reference.md + source Feature Specs under docs/​specs/; architecture/​new area project-structure-reference.md.
3. Read every required doc. If docs/​project-config.json, the docs index, lessons.md, CLAUDE.md, AGENTS.md, or any task-required reference doc is missing or stale, auto-run /​project-init or the narrow lower-level route (/​project-config, /​docs-init, /​scan-all, /​scan --target=<key>, /​claude-md-init) before ordinary project-specific work. If Codex mirrors or AGENTS.md are missing/​stale, ask the user to run /​sync-codex; do not auto-run it.
4. Before target work, state: Reference docs read: ... | Not applicable: ....

Ready when: scope evaluated, required docs checked/​read or setup route completed, lessons.md confirmed, citation emitted.

<!-- /​SYNC:project-reference-docs-guide --> <!-- SYNC:critical-thinking-mindset -->

Critical Thinking Mindset — Apply critical thinking, sequential thinking. Every claim needs traced proof, confidence >80% to act. Anti-hallucination: Never present guess as fact — cite sources for every claim, admit uncertainty freely, self-check output for errors, cross-reference independently, stay skeptical of own confidence — certainty without evidence root of all hallucination.

<!-- /​SYNC:critical-thinking-mindset --> <!-- SYNC:understand-code-first -->

Understand Code First — HARD-GATE: Do NOT write, plan, or fix until you READ existing code.

1. Search 3+ similar patterns (grep/glob) — cite file:line evidence
2. Read existing files in target area — understand structure, base classes, conventions
3. Run python .claude/​scripts/​code_graph trace <file> --direction both --json when .code-graph/​graph.db exists
4. Map dependencies via connections or callers_of — know what depends on your target
5. Write investigation to .ai/​workspace/​analysis/ for non-trivial tasks (3+ files)
6. Re-read analysis file before implementing — never work from memory alone. — why: long context drifts from the file; the file is ground truth
7. NEVER invent new patterns when existing ones work — match exactly or document deviation. — why: divergent patterns fragment the codebase and slow every future reader

BLOCKED until: - [ ] Read target files - [ ] Grep 3+ patterns - [ ] Graph trace (if graph.db exists) - [ ] Assumptions verified with evidence

<!-- /​SYNC:understand-code-first --> <!-- SYNC:evidence-based-reasoning -->

Evidence-Based Reasoning — Speculation is FORBIDDEN. Every claim needs proof.

1. Cite file:line, grep results, or framework docs for EVERY claim
2. Declare confidence: >80% act freely, 60-80% verify first, <60% DO NOT recommend
3. Cross-service validation required for architectural changes
4. "I don't have enough evidence" is valid and expected output

BLOCKED until: - [ ] Evidence file path (file:line) - [ ] Grep search performed - [ ] 3+ similar patterns found - [ ] Confidence level stated

Forbidden without proof: "obviously", "I think", "should be", "probably", "this is because" If incomplete → output: "Insufficient evidence. Verified: [...]. Not verified: [...]."

<!-- /​SYNC:evidence-based-reasoning --> <!-- SYNC:design-patterns-quality -->

Design Patterns Quality — Priority checks for every code change:

1. DRY via OOP: Identify classes/​modules with the same purpose, naming pattern, or lifecycle. Apply your knowledge of the project's language/​framework to determine the idiomatic abstraction (base class, mixin, trait, protocol, decorator). 3+ similar patterns → extract to shared abstraction.
2. Right Responsibility: Logic in LOWEST layer (Entity > Domain Service > Application Service > Controller). Never business logic in controllers.
3. SOLID: Single responsibility (one reason to change). Open-closed (extend, don't modify). Liskov (subtypes substitutable). Interface segregation (small interfaces). Dependency inversion (depend on abstractions).
4. After extraction/​move/​rename: Grep ENTIRE scope for dangling references. Zero tolerance.
5. YAGNI gate: NEVER recommend patterns unless 3+ occurrences exist. Don't extract for hypothetical future use.

Anti-patterns to flag: God Object, Copy-Paste inheritance, Circular Dependency, Leaky Abstraction.

Serial Attention for Design Quality — Scan one quality dimension at a time (serial passes), not all concerns at once. — why: split attention misses violations that single-focus passes catch.

1. Identify applicable dimensions — Based on the code's language, domain, and patterns, determine which quality dimensions apply: DRY, SOLID principles (SRP/​OCP/​LSP/​ISP/​DIP), OOP idioms, cohesion/​coupling, GRASP, Law of Demeter, CQRS invariants, etc. Your list is NOT fixed — derive from what the code actually does.
2. One focused pass per dimension — Dedicate single-focus attention to EACH dimension in sequence. Do NOT mix concerns across passes.
3. Threshold: 3+ similar patterns = MANDATORY extraction — Not optional suggestion. Flag as mandatory structural fix requiring action.
4. 2+ violations of same kind = structural finding — Report as "pattern problem" needing architectural resolution, not a list of individual instances.

<!-- /​SYNC:design-patterns-quality --> <!-- SYNC:source-test-drift-check -->

Source/​test drift check. For coding, fix, debug, investigation, test, or review work: when source behavior changes, inspect affected unit/​integration/​E2E tests and decide from evidence whether tests should change to match intended behavior or the source change is an unintended bug to fix. Do not write tests for migration code; schema/​data migrations are one-time execution paths, not core application logic.

<!-- /​SYNC:source-test-drift-check --> <!-- SYNC:ai-mistake-prevention -->

AI Mistake Prevention — Failure modes to avoid on every task:

Check downstream references before deleting. Deleting components causes documentation and code staleness cascades. Map all referencing files before removal. Verify AI-generated content against actual code. AI hallucinates APIs, class names, and method signatures. Always grep to confirm existence before documenting or referencing. Trace full dependency chain after edits. Changing a definition misses downstream variables and consumers derived from it. Always trace the full chain. Trace ALL code paths when verifying correctness. Confirming code exists is not confirming it executes. Always trace early exits, error branches, and conditional skips — not just happy path. When debugging, ask "whose responsibility?" before fixing. Trace whether bug is in caller (wrong data) or callee (wrong handling). Fix at responsible layer — never patch symptom site. Assume existing values are intentional — ask WHY before changing. Before changing any constant, limit, flag, or pattern: read comments, check git blame, examine surrounding code. Verify ALL affected outputs, not just the first. Changes touching multiple stacks require verifying EVERY output. One green check is not all green checks. Holistic-first debugging — resist nearest-attention trap. When investigating any failure, list EVERY precondition first (config, env vars, DB names, endpoints, DI registrations, data preconditions), then verify each against evidence before forming any code-layer hypothesis. Surgical changes — apply the diff test. Bug fix: every changed line must trace directly to the bug. Don't restyle or improve adjacent code. Enhancement task: implement improvements AND announce them explicitly. Surface ambiguity before coding — don't pick silently. If request has multiple interpretations, present each with effort estimate and ask. Never assume all-records, file-based, or more complex path. Keep domain concepts out of generic/​shared/​infrastructure layers. A reusable layer (shared library, framework, infra module) must reference NO consumer-specific domain concept — tenant/​customer/​product IDs, business entities, feature rules. The leak compiles and runs, so it passes review silently while coupling the "reusable" layer to one consumer. Push domain fields/​logic down into the consumer via subclass or composition.

<!-- /​SYNC:ai-mistake-prevention --> <!-- SYNC:understand-code-first:reminder -->

IMPORTANT MUST ATTENTION search 3+ existing patterns and read code BEFORE any modification. Run graph trace when graph.db exists.

<!-- /​SYNC:understand-code-first:reminder --> <!-- SYNC:evidence-based-reasoning:reminder -->

IMPORTANT MUST ATTENTION cite file:line evidence for every claim. Confidence >80% to act, <60% = do NOT recommend.

<!-- /​SYNC:evidence-based-reasoning:reminder --> <!-- SYNC:design-patterns-quality:reminder -->

IMPORTANT MUST ATTENTION check DRY via OOP, right responsibility layer, SOLID. Grep for dangling refs after moves.

<!-- /​SYNC:design-patterns-quality:reminder --> <!-- SYNC:graph-assisted-investigation:reminder -->

IMPORTANT MUST ATTENTION run at least ONE graph command on key files when graph.db exists. Pattern: grep → trace → verify.

<!-- /​SYNC:graph-assisted-investigation:reminder --> <!-- SYNC:critical-thinking-mindset:reminder -->

MUST ATTENTION apply critical thinking — every claim needs traced proof, confidence >80% to act. Anti-hallucination: never present guess as fact.

<!-- /​SYNC:critical-thinking-mindset:reminder --> <!-- SYNC:ai-mistake-prevention:reminder -->

MUST ATTENTION apply AI mistake prevention — holistic-first debugging, fix at responsible layer, surface ambiguity before coding, re-read files after compaction.

<!-- /​SYNC:ai-mistake-prevention:reminder --> <!-- SYNC:project-reference-docs-guide:reminder -->

• MANDATORY After task-tracking bootstrap and before target/​source work, read required project-reference docs and cite Reference docs read: ....
• MANDATORY Always include lessons.md; project conventions override generic defaults.
• MANDATORY If project config, root instruction files, or any required reference doc is missing, stop and run or ask the user to run /​project-init.

<!-- /​SYNC:project-reference-docs-guide:reminder --> <!-- SYNC:nested-task-creation:reminder -->

• MANDATORY Parent workflow rows do not replace child phase tracking; expand phases and link the parent when nested.
• MANDATORY Orchestrators pre-expand child skill phases before invocation; use [N.M] $skill-name — phase prefixes and one-in_progress discipline.

<!-- /​SYNC:nested-task-creation:reminder -->

Closing Reminders

IMPORTANT MUST ATTENTION break work into small todo tasks using TaskCreate BEFORE starting IMPORTANT MUST ATTENTION search codebase for 3+ similar patterns before creating new code IMPORTANT MUST ATTENTION cite file:line evidence for every claim (confidence >80% to act) IMPORTANT MUST ATTENTION add a final review todo task to verify work quality MANDATORY IMPORTANT MUST ATTENTION READ the following files before starting:

[TASK-PLANNING] Before acting, analyze task scope and systematically break it into small todo tasks and sub-tasks using TaskCreate.

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Closing reminder — Easy to Change is the success metric. Every finding, test, refactor, and abstraction must answer one question: does this make the next change cheaper or more expensive? If it doesn't reduce future change cost, reject it. Coupling, hidden state, duplicated knowledge, and unclear intent are the real enemies — call them out by name.