Backend
Ruby on Rails rules file
A Rails app that should stay on Hotwire if that is the UI. Strong parameters on every write, eager loading on lists, and the test suite you already run.
Change this stack in the generator
The files
Same rules, wrapped for each tool. Use the file your editor lists. Legacy files are there for older builds.
CursorUse this.cursor/rules/project.mdc
---description: "Project rules for Ruby, Ruby on Rails, PostgreSQL, RSpec, Bundler. Generated by RulePaste."alwaysApply: true--- # Project rules Stack: Ruby, Ruby on Rails, PostgreSQL, RSpec, Bundler. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - Install gems with `bundle install`. Commit `Gemfile.lock` for this application.- Start the app with `bin/dev` if that script exists, otherwise `bin/rails server`.- Tests: `bundle exec rspec` on the file you changed.- Run RuboCop on changed files if the project has it. ## Ruby - Match the Ruby version in `.ruby-version` or the Gemfile.- Run RuboCop if the repo has it. `snake_case` methods, `CamelCase` classes, two-space indent.- Add gems to the Gemfile with a bounded version, then install with Bundler. Commit `Gemfile.lock` for applications. ## Ruby on Rails - If the UI is Hotwire, do not add React or a second API for a server-rendered screen.- Every write uses strong parameters. Never pass raw `params` into `create` or `update`.- Keep validations and associations on the model. Add a service object only if the repo already has that pattern and the action is more than one model write.- Migrations are reversible and append-only. Eager-load associations a list will touch with `includes`.- Use the test suite the repo has, `bin/rails test` or RSpec. Do not introduce the other one. Keep secrets in credentials or the environment. ## PostgreSQL - Every query is parameterized. Never concatenate request data into SQL.- Use the pool the repo already has. Do not open a new client per call on a hot path.- Migrations are append-only SQL. Timestamps are `timestamptz`. New ids match the id type already in the schema.- Name the columns you select. Add an index only for a filter, join, or ordering this change actually runs. ## RSpec - Specs live under `spec/` and mirror the app structure. Use `describe`, `context`, and `it`.- An example name reads as a sentence. Use the factories the repo already has. Do not stub the object under test.- Run `bundle exec rspec` on the file you changed. ## Bundler - Install with `bundle install`. Add gems in the Gemfile, then update the lockfile.- Run project executables with `bin/` or `bundle exec`, not a global gem. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Create `.cursor/rules/` in the project root if it does not exist.
- Save this file as `.cursor/rules/project.mdc`. The `.mdc` extension and the frontmatter are required. A plain `.md` file in that folder is ignored.
- Commit it. Open a new Cursor chat. Check Settings, Rules, and confirm the rule is listed as Always Apply.
- Keep a single rule under a few hundred lines. Split later files by topic and set `alwaysApply: false` plus `globs` when a rule is only for some files.
Cursor (legacy)Legacy.cursorrules
# Project rules Stack: Ruby, Ruby on Rails, PostgreSQL, RSpec, Bundler. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - Install gems with `bundle install`. Commit `Gemfile.lock` for this application.- Start the app with `bin/dev` if that script exists, otherwise `bin/rails server`.- Tests: `bundle exec rspec` on the file you changed.- Run RuboCop on changed files if the project has it. ## Ruby - Match the Ruby version in `.ruby-version` or the Gemfile.- Run RuboCop if the repo has it. `snake_case` methods, `CamelCase` classes, two-space indent.- Add gems to the Gemfile with a bounded version, then install with Bundler. Commit `Gemfile.lock` for applications. ## Ruby on Rails - If the UI is Hotwire, do not add React or a second API for a server-rendered screen.- Every write uses strong parameters. Never pass raw `params` into `create` or `update`.- Keep validations and associations on the model. Add a service object only if the repo already has that pattern and the action is more than one model write.- Migrations are reversible and append-only. Eager-load associations a list will touch with `includes`.- Use the test suite the repo has, `bin/rails test` or RSpec. Do not introduce the other one. Keep secrets in credentials or the environment. ## PostgreSQL - Every query is parameterized. Never concatenate request data into SQL.- Use the pool the repo already has. Do not open a new client per call on a hot path.- Migrations are append-only SQL. Timestamps are `timestamptz`. New ids match the id type already in the schema.- Name the columns you select. Add an index only for a filter, join, or ordering this change actually runs. ## RSpec - Specs live under `spec/` and mirror the app structure. Use `describe`, `context`, and `it`.- An example name reads as a sentence. Use the factories the repo already has. Do not stub the object under test.- Run `bundle exec rspec` on the file you changed. ## Bundler - Install with `bundle install`. Add gems in the Gemfile, then update the lockfile.- Run project executables with `bin/` or `bundle exec`, not a global gem. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Save as `.cursorrules` in the project root only if you are on an older Cursor build that still lists this file.
- Current Cursor uses `.cursor/rules/*.mdc`. If you keep both, they will drift unless you regenerate them together.
Claude CodeUse thisCLAUDE.md
# Project rules Stack: Ruby, Ruby on Rails, PostgreSQL, RSpec, Bundler. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - Install gems with `bundle install`. Commit `Gemfile.lock` for this application.- Start the app with `bin/dev` if that script exists, otherwise `bin/rails server`.- Tests: `bundle exec rspec` on the file you changed.- Run RuboCop on changed files if the project has it. ## Ruby - Match the Ruby version in `.ruby-version` or the Gemfile.- Run RuboCop if the repo has it. `snake_case` methods, `CamelCase` classes, two-space indent.- Add gems to the Gemfile with a bounded version, then install with Bundler. Commit `Gemfile.lock` for applications. ## Ruby on Rails - If the UI is Hotwire, do not add React or a second API for a server-rendered screen.- Every write uses strong parameters. Never pass raw `params` into `create` or `update`.- Keep validations and associations on the model. Add a service object only if the repo already has that pattern and the action is more than one model write.- Migrations are reversible and append-only. Eager-load associations a list will touch with `includes`.- Use the test suite the repo has, `bin/rails test` or RSpec. Do not introduce the other one. Keep secrets in credentials or the environment. ## PostgreSQL - Every query is parameterized. Never concatenate request data into SQL.- Use the pool the repo already has. Do not open a new client per call on a hot path.- Migrations are append-only SQL. Timestamps are `timestamptz`. New ids match the id type already in the schema.- Name the columns you select. Add an index only for a filter, join, or ordering this change actually runs. ## RSpec - Specs live under `spec/` and mirror the app structure. Use `describe`, `context`, and `it`.- An example name reads as a sentence. Use the factories the repo already has. Do not stub the object under test.- Run `bundle exec rspec` on the file you changed. ## Bundler - Install with `bundle install`. Add gems in the Gemfile, then update the lockfile.- Run project executables with `bin/` or `bundle exec`, not a global gem. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Save as `CLAUDE.md` in the project root. `.claude/CLAUDE.md` also works if you want the root left clear.
- Commit it. Start a new Claude Code session. The file loads at session start, not in the middle of an old one.
- When the file gets long, move a topic into `.claude/rules/<topic>.md`. Add a `paths` list only if that topic should load for certain files.
Windsurf / DevinUse this.devin/rules/project.md
---trigger: always_ondescription: "Project rules for Ruby, Ruby on Rails, PostgreSQL, RSpec, Bundler. Generated by RulePaste."--- # Project rules Stack: Ruby, Ruby on Rails, PostgreSQL, RSpec, Bundler. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - Install gems with `bundle install`. Commit `Gemfile.lock` for this application.- Start the app with `bin/dev` if that script exists, otherwise `bin/rails server`.- Tests: `bundle exec rspec` on the file you changed.- Run RuboCop on changed files if the project has it. ## Ruby - Match the Ruby version in `.ruby-version` or the Gemfile.- Run RuboCop if the repo has it. `snake_case` methods, `CamelCase` classes, two-space indent.- Add gems to the Gemfile with a bounded version, then install with Bundler. Commit `Gemfile.lock` for applications. ## Ruby on Rails - If the UI is Hotwire, do not add React or a second API for a server-rendered screen.- Every write uses strong parameters. Never pass raw `params` into `create` or `update`.- Keep validations and associations on the model. Add a service object only if the repo already has that pattern and the action is more than one model write.- Migrations are reversible and append-only. Eager-load associations a list will touch with `includes`.- Use the test suite the repo has, `bin/rails test` or RSpec. Do not introduce the other one. Keep secrets in credentials or the environment. ## PostgreSQL - Every query is parameterized. Never concatenate request data into SQL.- Use the pool the repo already has. Do not open a new client per call on a hot path.- Migrations are append-only SQL. Timestamps are `timestamptz`. New ids match the id type already in the schema.- Name the columns you select. Add an index only for a filter, join, or ordering this change actually runs. ## RSpec - Specs live under `spec/` and mirror the app structure. Use `describe`, `context`, and `it`.- An example name reads as a sentence. Use the factories the repo already has. Do not stub the object under test.- Run `bundle exec rspec` on the file you changed. ## Bundler - Install with `bundle install`. Add gems in the Gemfile, then update the lockfile.- Run project executables with `bin/` or `bundle exec`, not a global gem. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Create `.devin/rules/` and save this file as `.devin/rules/project.md`. Devin Desktop (formerly Windsurf) prefers this path. `.windsurf/rules/` still works as a fallback.
- `trigger: always_on` loads it in every chat. Keep the file under 12,000 characters or it can be truncated with no error.
- Commit it and start a new chat. If you also keep `.windsurfrules`, make sure the two files do not disagree.
Windsurf (legacy)Legacy.windsurfrules
# Project rules Stack: Ruby, Ruby on Rails, PostgreSQL, RSpec, Bundler. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - Install gems with `bundle install`. Commit `Gemfile.lock` for this application.- Start the app with `bin/dev` if that script exists, otherwise `bin/rails server`.- Tests: `bundle exec rspec` on the file you changed.- Run RuboCop on changed files if the project has it. ## Ruby - Match the Ruby version in `.ruby-version` or the Gemfile.- Run RuboCop if the repo has it. `snake_case` methods, `CamelCase` classes, two-space indent.- Add gems to the Gemfile with a bounded version, then install with Bundler. Commit `Gemfile.lock` for applications. ## Ruby on Rails - If the UI is Hotwire, do not add React or a second API for a server-rendered screen.- Every write uses strong parameters. Never pass raw `params` into `create` or `update`.- Keep validations and associations on the model. Add a service object only if the repo already has that pattern and the action is more than one model write.- Migrations are reversible and append-only. Eager-load associations a list will touch with `includes`.- Use the test suite the repo has, `bin/rails test` or RSpec. Do not introduce the other one. Keep secrets in credentials or the environment. ## PostgreSQL - Every query is parameterized. Never concatenate request data into SQL.- Use the pool the repo already has. Do not open a new client per call on a hot path.- Migrations are append-only SQL. Timestamps are `timestamptz`. New ids match the id type already in the schema.- Name the columns you select. Add an index only for a filter, join, or ordering this change actually runs. ## RSpec - Specs live under `spec/` and mirror the app structure. Use `describe`, `context`, and `it`.- An example name reads as a sentence. Use the factories the repo already has. Do not stub the object under test.- Run `bundle exec rspec` on the file you changed. ## Bundler - Install with `bundle install`. Add gems in the Gemfile, then update the lockfile.- Run project executables with `bin/` or `bundle exec`, not a global gem. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Save as `.windsurfrules` in the project root if your build still asks for that filename.
- This file is always on and cannot be scoped. Prefer `.devin/rules/project.md` on current builds.
GitHub CopilotUse this.github/copilot-instructions.md
# Project rules Stack: Ruby, Ruby on Rails, PostgreSQL, RSpec, Bundler. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - Install gems with `bundle install`. Commit `Gemfile.lock` for this application.- Start the app with `bin/dev` if that script exists, otherwise `bin/rails server`.- Tests: `bundle exec rspec` on the file you changed.- Run RuboCop on changed files if the project has it. ## Ruby - Match the Ruby version in `.ruby-version` or the Gemfile.- Run RuboCop if the repo has it. `snake_case` methods, `CamelCase` classes, two-space indent.- Add gems to the Gemfile with a bounded version, then install with Bundler. Commit `Gemfile.lock` for applications. ## Ruby on Rails - If the UI is Hotwire, do not add React or a second API for a server-rendered screen.- Every write uses strong parameters. Never pass raw `params` into `create` or `update`.- Keep validations and associations on the model. Add a service object only if the repo already has that pattern and the action is more than one model write.- Migrations are reversible and append-only. Eager-load associations a list will touch with `includes`.- Use the test suite the repo has, `bin/rails test` or RSpec. Do not introduce the other one. Keep secrets in credentials or the environment. ## PostgreSQL - Every query is parameterized. Never concatenate request data into SQL.- Use the pool the repo already has. Do not open a new client per call on a hot path.- Migrations are append-only SQL. Timestamps are `timestamptz`. New ids match the id type already in the schema.- Name the columns you select. Add an index only for a filter, join, or ordering this change actually runs. ## RSpec - Specs live under `spec/` and mirror the app structure. Use `describe`, `context`, and `it`.- An example name reads as a sentence. Use the factories the repo already has. Do not stub the object under test.- Run `bundle exec rspec` on the file you changed. ## Bundler - Install with `bundle install`. Add gems in the Gemfile, then update the lockfile.- Run project executables with `bin/` or `bundle exec`, not a global gem. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Create `.github/` if needed and save this file as `.github/copilot-instructions.md`.
- Commit it. Copilot picks up repository instructions for Chat and, on supported plans, code review and the cloud agent.
- For rules that should only affect some files, add `.github/instructions/<name>.instructions.md` with `applyTo` frontmatter instead of growing this file.
Codex + AGENTS.mdAGENTS.md
# Project rules Stack: Ruby, Ruby on Rails, PostgreSQL, RSpec, Bundler. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - Install gems with `bundle install`. Commit `Gemfile.lock` for this application.- Start the app with `bin/dev` if that script exists, otherwise `bin/rails server`.- Tests: `bundle exec rspec` on the file you changed.- Run RuboCop on changed files if the project has it. ## Ruby - Match the Ruby version in `.ruby-version` or the Gemfile.- Run RuboCop if the repo has it. `snake_case` methods, `CamelCase` classes, two-space indent.- Add gems to the Gemfile with a bounded version, then install with Bundler. Commit `Gemfile.lock` for applications. ## Ruby on Rails - If the UI is Hotwire, do not add React or a second API for a server-rendered screen.- Every write uses strong parameters. Never pass raw `params` into `create` or `update`.- Keep validations and associations on the model. Add a service object only if the repo already has that pattern and the action is more than one model write.- Migrations are reversible and append-only. Eager-load associations a list will touch with `includes`.- Use the test suite the repo has, `bin/rails test` or RSpec. Do not introduce the other one. Keep secrets in credentials or the environment. ## PostgreSQL - Every query is parameterized. Never concatenate request data into SQL.- Use the pool the repo already has. Do not open a new client per call on a hot path.- Migrations are append-only SQL. Timestamps are `timestamptz`. New ids match the id type already in the schema.- Name the columns you select. Add an index only for a filter, join, or ordering this change actually runs. ## RSpec - Specs live under `spec/` and mirror the app structure. Use `describe`, `context`, and `it`.- An example name reads as a sentence. Use the factories the repo already has. Do not stub the object under test.- Run `bundle exec rspec` on the file you changed. ## Bundler - Install with `bundle install`. Add gems in the Gemfile, then update the lockfile.- Run project executables with `bin/` or `bundle exec`, not a global gem. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Save as `AGENTS.md` in the project root. Codex, Cursor, Copilot CLI, Devin, and many other agents look for this name.
- The file is plain Markdown. Do not add frontmatter.
- In a monorepo, add a nested AGENTS.md next to a service that needs different commands. Do not leave an empty `AGENTS.override.md` beside it. Codex treats that empty file as the instructions for the folder.
- Commit it and start a new agent session.
What each section does
Working agreement
The habits that keep an agent from rewriting the repo while it solves a small task.
Commands
The install, dev, test, and lint commands for this stack, so the agent runs the project's tools instead of guessing.
Ruby
Matches the Ruby version and keeps gems in the Gemfile.
Ruby on Rails
Keeps Hotwire apps on the server and requires strong parameters on every write.
PostgreSQL
Parameterized queries, timestamptz, and append-only migrations.
RSpec
One behavior per example, in the spec folder that mirrors the app.
Bundler
Gems come from the Gemfile, and app commands go through bin/ or bundle exec.
Testing expectations
How much test coverage this project wants from the agent, separate from which test runner is installed.
Code style
How strict the types, lint, and comments should be. This is the knob most people actually want to change.
Safety
Hard stops: secrets, destructive git commands, and generated folders.
Done when
The checklist the agent should satisfy before it calls the task finished.
Questions
What if my app uses minitest, not RSpec?
Switch the test runner in the generator to none, then add one line with your bin/rails test command. This preset assumes spec/ is present.
Will the agent add React?
The rule says not to add React or a second API for a screen that Hotwire already renders.
Related stacks
Newsletter
Stack notes, occasionally
A short email when a tool changes its rules filename or a new stack page ships. No product drip. If this form is not connected yet, your address is not stored.