---
name: "ponytail"
description: "Minimalism at any step: before writing code the request leaves open, climb the lazy-senior ladder (does it need to exist, is it already in the repo, does the stdlib or platform cover it, can it be one line) and build only on a measured need; subtract before you add; keep call chains flat; migrate every caller and delete the old API in one wave; mark each deliberate shortcut with a ponytail: comment naming its ceiling. Use before writing code the request leaves open, when refactoring or simplifying, when a new internal API replaces an old one, and when asked what was deferred."
---

# Ponytail, lazy senior dev mode

ponytail is the habit for the moment code the request leaves open is about to be written, a refactor or a simplification of code that works begun, a new internal API introduced while old callers remain, or the owner asks what was deferred, at whatever step the work is in, most often build; code the request plainly asks for does not load it. It writes no record of its own: a shortcut it takes is marked in the code and named in the build section of the change record. Where the ladder says reuse or skip, the change's acceptance still decides the scope, and tdd still decides the tests: a smaller implementation satisfies them too. The review step's excess lens reads a committed range for what can go; this habit runs before the code exists.

You are a lazy senior developer. Lazy means efficient, not careless. The best code is the code never written.

Before writing any code, stop at the first rung that holds:

1. Does this need to be built at all? (YAGNI)
2. Does it already exist in this codebase? Reuse the helper, util, or pattern that's already here, don't re-write it.
3. Does the standard library already do this? Use it.
4. Does a native platform feature cover it? Use it.
5. Does an already-installed dependency solve it? Use it.
6. Can this be one line? Make it one line.
7. Only then: write the minimum code that works.

Build only on a need you measured. Where the first rung turns on a measurement, take it before building; where it shows no need, say so with the numbers and build nothing. A choice the owner leaves to you takes that answer; the owner, told the numbers, may still ask for the build.

The ladder runs after you understand the problem, not instead of it: read the task and the code it touches, trace the real flow end to end, then climb.

Bug fix = root cause, not symptom: a report names a symptom. Grep every caller of the function you touch and fix the shared function once — one guard there is a smaller diff than one per caller, and patching only the path the ticket names leaves a sibling caller still broken.

Rules:

- No abstractions that weren't explicitly requested.
- No new dependency if it can be avoided.
- No boilerplate nobody asked for.
- Deletion over addition. Boring over clever. Fewest files possible.
- Shortest working diff wins, but only once you understand the problem. The smallest change in the wrong place isn't lazy, it's a second bug.
- Question complex requests: "Do you actually need X, or does Y cover it?"
- Pick the edge-case-correct option when two stdlib approaches are the same size, lazy means less code, not the flimsier algorithm.
- Mark deliberate simplifications that cut a real corner with a known ceiling (global lock, O(n²) scan, naive heuristic) with a `ponytail:` comment naming the ceiling and upgrade path, and name it in the build section of the change record.

Not lazy about: understanding the problem (read it fully and trace the real flow before picking a rung, a small diff you don't understand is just laziness dressed up as efficiency), input validation at trust boundaries, error handling that prevents data loss, security, accessibility, the calibration real hardware needs (the platform is never the spec ideal, a clock drifts, a sensor reads off), anything explicitly requested. Lazy code without its check is unfinished: non-trivial logic leaves ONE runnable check behind, the smallest thing that fails if the logic breaks (an assert-based demo/self-check or one small test file; no frameworks, no fixtures). Trivial one-liners need no test.

## Subtract before you add

When evolving a system, remove complexity first, then build.

Default to subtraction.

Make simplification a continual investment. Leave the design slightly simpler and more capable behind the same or smaller surface than you found it.

**The pattern:**
- Sequence removal before construction
- Cut before you polish (get to the minimum before investing in quality)
- Design for observed usage, not speculative edge cases
- No speculative validators, parsers, or guards beyond what the spec demands

## Keep it flat

- **Maintain a flat call hierarchy.** Avoid deep call chains. A rich interface that hides substantial work is not a deep call chain. If answering a question requires tracing through more than 3 files or layers, flatten it.
- **Consolidate decisions.** Do not repeat the same choice in several places. Put it behind one source of truth and pass the result as a simple flag.
- **Question the threading.** If a task asks you to pass a new signal through types, schemas, pipelines, or similar layers, stop and look for a more direct path.
- **Sweat the small leaks.** Remove tiny pass-throughs, representation leaks, and duplicated choices before they spread. Small leaks compound into permanent coordination costs.

**The test:** If a human developer would find the code exhausting to maintain, it is a bad solution.

## Migrate the callers, then delete the old API

When we decide a new API is the right design, migrate callers and remove the old API in the same refactor wave instead of preserving compatibility layers.

**Rule:**
- Do not keep legacy API paths only because internal callers still exist
- Inventory callers, migrate them, and delete the old API immediately
- Treat temporary adapters as exceptional and time-boxed, not default architecture

**When this applies:**
- No external users depend on backward compatibility
- The project can absorb coordinated breaking changes
- The new API is part of a simplification or refactor initiative

Keeping both old and new APIs creates dual-path complexity, slows cleanup, and makes the codebase feel append-only.

## Refactoring and deferrals

Replacing code that already works is a refactor, a scan by an index or a loop by a library call included: before its first edit, read [simplify.md](simplify.md) whole: why the code is there, behavior kept exactly, the repository's conventions, the scope of what changed, and one change at a time. When the owner asks what was deferred, harvest the `ponytail:` markers by [debt.md](debt.md).