---
name: code-simplification
description:
  Simplifies code for clarity. Use when refactoring code for clarity without
  changing behavior. Use when code works but is harder to read, maintain, or
  extend than it should be. Use when reviewing code that has accumulated
  unnecessary complexity.
---

# Code Simplification

## Policy Capsule

- Preserve behaviour **exactly**: inputs, outputs, side effects, error semantics, and ordering must be identical. If you're not sure a change preserves behaviour, don't make it.
- Every simplification MUST leave existing tests passing without modification; if tests need to change, the refactor changed behaviour and is no longer a simplification.
- Follow project conventions (CLAUDE.md, neighbour-code patterns, import style, naming, error handling). Simplification that breaks consistency is churn, not improvement.
- Prefer clarity over cleverness: explicit code beats compact code whenever the compact form requires a mental pause to parse.
- Comprehend before you simplify — never refactor code you don't yet fully understand.
- Do not simplify for its own sake: skip when code is already clean, when performance would measurably regress, or when the module is about to be rewritten.
- Lines-of-code is **not** the goal. The metric is "would a new team member understand this faster than the original?".
- Make each simplification an isolated commit, not a drive-by inside a feature change (see `git-workflow-and-versioning`).
- Verify behaviourally: run the full test suite, exercise affected paths, and diff the runtime output against the original before claiming the simplification is safe.

> Inspired by the
> [Claude Code Simplifier plugin](https://github.com/anthropics/claude-plugins-official/blob/main/plugins/code-simplifier/agents/code-simplifier.md).
> Adapted here as a model-agnostic, process-driven skill for any AI coding
> agent.

## Overview

Simplify code by reducing complexity while preserving exact behavior. The goal
is not fewer lines — it's code that is easier to read, understand, modify, and
debug. Every simplification must pass a simple test: "Would a new team member
understand this faster than the original?"

## When to Use

- After a feature is working and tests pass, but the implementation feels
  heavier than it needs to be
- During code review when readability or complexity issues are flagged
- When you encounter deeply nested logic, long functions, or unclear names
- When refactoring code written under time pressure
- When consolidating related logic scattered across files
- After merging changes that introduced duplication or inconsistency

**When NOT to use:**

- Code is already clean and readable — don't simplify for the sake of it
- You don't understand what the code does yet — comprehend before you simplify
- The code is performance-critical and the "simpler" version would be measurably
  slower
- You're about to rewrite the module entirely — simplifying throwaway code
  wastes effort

## The Five Principles

### 1. Preserve Behavior Exactly

Don't change what the code does — only how it expresses it. All inputs, outputs,
side effects, error behavior, and edge cases must remain identical. If you're
not sure a simplification preserves behavior, don't make it.

```text
ASK BEFORE EVERY CHANGE:
→ Does this produce the same output for every input?
→ Does this maintain the same error behavior?
→ Does this preserve the same side effects and ordering?
→ Do all existing tests still pass without modification?
```

### 2. Follow Project Conventions

Simplification means making code more consistent with the codebase, not imposing
external preferences. Before simplifying:

```text
1. Read CLAUDE.md / project conventions
2. Study how neighboring code handles similar patterns
3. Match the project's style for:
   - Import ordering and module system
   - Function declaration style
   - Naming conventions
   - Error handling patterns
   - Type annotation depth
```

Simplification that breaks project consistency is not simplification — it's
churn.

### 3. Prefer Clarity Over Cleverness

Explicit code is better than compact code when the compact version requires a
mental pause to parse.

```typescript
// UNCLEAR: Dense ternary chain
const label = isNew
  ? 'New'
  : isUpdated
    ? 'Updated'
    : isArchived
      ? 'Archived'
      : 'Active';

// CLEAR: Readable mapping
function getStatusLabel(item: Item): string {
  if (item.isNew) return 'New';
  if (item.isUpdated) return 'Updated';
  if (item.isArchived) return 'Archived';
  return 'Active';
}
```

```typescript
// UNCLEAR: Chained reduces with inline logic
const result = items.reduce(
  (acc, item) => ({
    ...acc,
    [item.id]: { ...acc[item.id], count: (acc[item.id]?.count ?? 0) + 1 },
  }),
  {},
);

// CLEAR: Named intermediate step
const countById = new Map<string, number>();
for (const item of items) {
  countById.set(item.id, (countById.get(item.id) ?? 0) + 1);
}
```

### 4. Maintain Balance

Simplification has a failure mode: over-simplification. Watch for these traps:

- **Inlining too aggressively** — removing a helper that gave a concept a name
  makes the call site harder to read
- **Combining unrelated logic** — two simple functions merged into one complex
  function is not simpler
- **Removing "unnecessary" abstraction** — some abstractions exist for
  extensibility or testability, not complexity
- **Optimizing for line count** — fewer lines is not the goal; easier
  comprehension is

### 5. Scope to What Changed

Default to simplifying recently modified code. Avoid drive-by refactors of
unrelated code unless explicitly asked to broaden scope. Unscoped simplification
creates noise in diffs and risks unintended regressions.

## The Simplification Process

### Step 1: Understand Before Touching (Chesterton's Fence)

Before changing or removing anything, understand why it exists. This is
Chesterton's Fence: if you see a fence across a road and don't understand why
it's there, don't tear it down. First understand the reason, then decide if the
reason still applies.

```text
BEFORE SIMPLIFYING, ANSWER:
- What is this code's responsibility?
- What calls it? What does it call?
- What are the edge cases and error paths?
- Are there tests that define the expected behavior?
- Why might it have been written this way? (Performance? Platform constraint? Historical reason?)
- Check git blame: what was the original context for this code?
```

If you can't answer these, you're not ready to simplify. Read more context
first.

### Step 2: Identify Simplification Opportunities

Scan for these patterns — each one is a concrete signal, not a vague smell:

**Structural complexity:**

| Pattern                    | Signal                             | Simplification                                            |
| -------------------------- | ---------------------------------- | --------------------------------------------------------- |
| Deep nesting (3+ levels)   | Hard to follow control flow        | Extract conditions into guard clauses or helper functions |
| Long functions (50+ lines) | Multiple responsibilities          | Split into focused functions with descriptive names       |
| Nested ternaries           | Requires mental stack to parse     | Replace with if/else chains, switch, or lookup objects    |
| Boolean parameter flags    | `doThing(true, false, true)`       | Replace with options objects or separate functions        |
| Repeated conditionals      | Same `if` check in multiple places | Extract to a well-named predicate function                |

**Naming and readability:**

| Pattern                    | Signal                                         | Simplification                                                           |
| -------------------------- | ---------------------------------------------- | ------------------------------------------------------------------------ |
| Generic names              | `data`, `result`, `temp`, `val`, `item`        | Rename to describe the content: `userProfile`, `validationErrors`        |
| Abbreviated names          | `usr`, `cfg`, `btn`, `evt`                     | Use full words unless the abbreviation is universal (`id`, `url`, `api`) |
| Misleading names           | Function named `get` that also mutates state   | Rename to reflect actual behavior                                        |
| Comments explaining "what" | `// increment counter` above `count++`         | Delete the comment — the code is clear enough                            |
| Comments explaining "why"  | `// Retry because the API is flaky under load` | Keep these — they carry intent the code can't express                    |

**Redundancy:**

| Pattern                   | Signal                                                       | Simplification                                            |
| ------------------------- | ------------------------------------------------------------ | --------------------------------------------------------- |
| Duplicated logic          | Same 5+ lines in multiple places                             | Extract to a shared function                              |
| Dead code                 | Unreachable branches, unused variables, commented-out blocks | Remove (after confirming it's truly dead)                 |
| Unnecessary abstractions  | Wrapper that adds no value                                   | Inline the wrapper, call the underlying function directly |
| Over-engineered patterns  | Factory-for-a-factory, strategy-with-one-strategy            | Replace with the simple direct approach                   |
| Redundant type assertions | Casting to a type that's already inferred                    | Remove the assertion                                      |

### Step 3: Apply Changes Incrementally

Make one simplification at a time. Run tests after each change. **Submit
refactoring changes separately from feature or bug fix changes.** A PR that
refactors and adds a feature is two PRs — split them.

```text
FOR EACH SIMPLIFICATION:
1. Make the change
2. Run the test suite
3. If tests pass → commit (or continue to next simplification)
4. If tests fail → revert and reconsider
```

Avoid batching multiple simplifications into a single untested change. If
something breaks, you need to know which simplification caused it.

**The Rule of 500:** If a refactoring would touch more than 500 lines, invest in
automation (codemods, sed scripts, AST transforms) rather than making the
changes by hand. Manual edits at that scale are error-prone and exhausting to
review.

### Step 4: Verify the Result

After all simplifications, step back and evaluate the whole:

```text
COMPARE BEFORE AND AFTER:
- Is the simplified version genuinely easier to understand?
- Did you introduce any new patterns inconsistent with the codebase?
- Is the diff clean and reviewable?
- Would a teammate approve this change?
```

If the "simplified" version is harder to understand or review, revert. Not every
simplification attempt succeeds.

## Language-Specific Guidance

### TypeScript / JavaScript

```typescript
// SIMPLIFY: Unnecessary async wrapper
// Before
async function getUser(id: string): Promise<User> {
  return await userService.findById(id);
}
// After
function getUser(id: string): Promise<User> {
  return userService.findById(id);
}

// SIMPLIFY: Verbose conditional assignment
// Before
let displayName: string;
if (user.nickname) {
  displayName = user.nickname;
} else {
  displayName = user.fullName;
}
// After
const displayName = user.nickname || user.fullName;

// SIMPLIFY: Manual array building
// Before
const activeUsers: User[] = [];
for (const user of users) {
  if (user.isActive) {
    activeUsers.push(user);
  }
}
// After
const activeUsers = users.filter((user) => user.isActive);

// SIMPLIFY: Redundant boolean return
// Before
function isValid(input: string): boolean {
  if (input.length > 0 && input.length < 100) {
    return true;
  }
  return false;
}
// After
function isValid(input: string): boolean {
  return input.length > 0 && input.length < 100;
}
```

### Python

```python
# SIMPLIFY: Verbose dictionary building
# Before
result = {}
for item in items:
    result[item.id] = item.name
# After
result = {item.id: item.name for item in items}

# SIMPLIFY: Nested conditionals with early return
# Before
def process(data):
    if data is not None:
        if data.is_valid():
            if data.has_permission():
                return do_work(data)
            else:
                raise PermissionError("No permission")
        else:
            raise ValueError("Invalid data")
    else:
        raise TypeError("Data is None")
# After
def process(data):
    if data is None:
        raise TypeError("Data is None")
    if not data.is_valid():
        raise ValueError("Invalid data")
    if not data.has_permission():
        raise PermissionError("No permission")
    return do_work(data)
```

### React / JSX

```tsx
// SIMPLIFY: Verbose conditional rendering
// Before
function UserBadge({ user }: Props) {
  if (user.isAdmin) {
    return <Badge variant="admin">Admin</Badge>;
  } else {
    return <Badge variant="default">User</Badge>;
  }
}
// After
function UserBadge({ user }: Props) {
  const variant = user.isAdmin ? 'admin' : 'default';
  const label = user.isAdmin ? 'Admin' : 'User';
  return <Badge variant={variant}>{label}</Badge>;
}

// SIMPLIFY: Prop drilling through intermediate components
// Before — consider whether context or composition solves this better.
// This is a judgment call — flag it, don't auto-refactor.
```

## Common Rationalizations

| Rationalization                                      | Reality                                                                                                                                               |
| ---------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- |
| "It's working, no need to touch it"                  | Working code that's hard to read will be hard to fix when it breaks. Simplifying now saves time on every future change.                               |
| "Fewer lines is always simpler"                      | A 1-line nested ternary is not simpler than a 5-line if/else. Simplicity is about comprehension speed, not line count.                                |
| "I'll just quickly simplify this unrelated code too" | Unscoped simplification creates noisy diffs and risks regressions in code you didn't intend to change. Stay focused.                                  |
| "The types make it self-documenting"                 | Types document structure, not intent. A well-named function explains _why_ better than a type signature explains _what_.                              |
| "This abstraction might be useful later"             | Don't preserve speculative abstractions. If it's not used now, it's complexity without value. Remove it and re-add when needed.                       |
| "The original author must have had a reason"         | Maybe. Check git blame — apply Chesterton's Fence. But accumulated complexity often has no reason; it's just the residue of iteration under pressure. |
| "I'll refactor while adding this feature"            | Separate refactoring from feature work. Mixed changes are harder to review, revert, and understand in history.                                        |

## Red Flags

- Simplification that requires modifying tests to pass (you likely changed
  behavior)
- "Simplified" code that is longer and harder to follow than the original
- Renaming things to match your preferences rather than project conventions
- Removing error handling because "it makes the code cleaner"
- Simplifying code you don't fully understand
- Batching many simplifications into one large, hard-to-review commit
- Refactoring code outside the scope of the current task without being asked

## Verification

After completing a simplification pass:

- [ ] All existing tests pass without modification
- [ ] Build succeeds with no new warnings
- [ ] Linter/formatter passes (no style regressions)
- [ ] Each simplification is a reviewable, incremental change
- [ ] The diff is clean — no unrelated changes mixed in
- [ ] Simplified code follows project conventions (checked against CLAUDE.md or
      equivalent)
- [ ] No error handling was removed or weakened
- [ ] No dead code was left behind (unused imports, unreachable branches)
- [ ] A teammate or review agent would approve the change as a net improvement
