feature-development

A set of step-by-step rules for creating or extending feature modules in a Flutter package. It defines where files go, how they are named, how providers and state notifiers are wired, and how public exports are organized.

In plain words
What is it for?
Use it when creating files under lib/src/features/, implementing fetch or settings patterns, adding SDK setup or configuration, wiring providers, or updating barrel exports.
Why use it?
It reduces uncertainty when adding a feature and helps keep its files and dependencies consistent with the rest of the package.

Cursor rule for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/sampaio-tech/flutter-core-modules/feature-development
Clone the repo
git clone --depth 1 https://github.com/sampaio-tech/flutter-core-modules

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 2,343 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.02343
Opus 5 $0.00000 $0.01171
Sonnet 5 $0.00000 $0.00469
Haiku 4.5 $0.00000 $0.00234

Measured yesterday against content hash 773aadba486f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

feature-development scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/feature-development.mdc · 313 lines

How it starts

The opening of the file, as written. The whole thing — 313 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Feature Development Rules — flutter_core_modules

File Placement

Every feature lives under lib/src/features/<feature-name>/ with this structure:

<feature>/
├── domain/
│   ├── repositories/<feature>_repository.dart      # abstract class
│   ├── data_sources/<feature>_data_source.dart      # abstract class (if remote)
│   ├── entities/<entity>.dart                       # domain models
│   ├── usecases/<verb>_<noun>_usecase.dart          # one file per operation
│   └── failures/<feature>_failure.dart              # sealed class (if custom)
├── data/
│   ├── repositories/<feature>_repository.dart       # impl + provider
│   └── data_sources/<concrete>_data_source.dart     # impl + provider (if remote)
└── presentation/
    ├── notifiers/<noun>_state_notifier.dart          # SafeStateNotifier subclass
    ├── setup/<sdk>/<sdk>.dart                        # SDK init (if needed)
    ├── config/<config>.dart                          # config helpers (if needed)
    ├── providers/<thing>.dart                        # derived providers (if needed)
    └── widgets/<widget>.dart                         # feature widgets (if needed)

Naming Conventions

Thing Pattern Example
Repository interface abstract class FooRepository LocaleRepository
Repository implementation class FooRepositoryImpl LocaleRepositoryImpl
Data source interface abstract class FooDataSource StorageRemoteDataSource
Data source implementation class ConcreteNameDataSource FirebaseStorageRemoteDataSource
Use case class class VerbNounUsecase GetLocaleUsecase, SetThemeDataUsecase
Notifier class class NounStateNotifier ThemeStateNotifier, CustomerInfoStateNotifier
Repository provider fooRepositoryProvider localeRepositoryProvider
Use case provider getEntityUsecaseProvider getLocaleUsecaseProvider
Notifier provider nounStateNotifierProvider themeStateNotifierProvider
Family args class FooFamilyArgs GetDownloadUrlFamilyArgs

Read the full file on GitHub · 313 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 313 lines · 0 tokens per session scan A 773aadba486f

Subscribe to this mod's changes

feature-development is a cursor rule published in the GitHub repository sampaio-tech/flutter-core-modules (2 stars, last pushed 10d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 2,343 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.