btrc-hub/AGENTS.md

AGENTS.md

Project overview

BTRC Hub / タグ広場 is a split Rails API and React frontend repository.

• Backend: Rails API under backend/.
• Frontend: React + TypeScript + Vite under frontend/.
• Docs: lightweight command notes under docs/.
• There is no README or Makefile at the repository root as of this inspection.

Stack

• Backend: Ruby 3.2.2 from backend/.ruby-version, Rails ~> 8.0.2.
• Backend dependencies include mysql2, sqlite3, rspec-rails, factory_bot_rails, rack-cors, jwt, discard, gollum, whenever, aws-sdk-s3, brakeman, and rubocop-rails-omakase.
• Frontend: React ^19.1.0, TypeScript ~5.8.3, Vite ^6.3.5.
• Frontend data/UI dependencies include Axios, TanStack Query, Tailwind CSS, Framer Motion, Radix UI components, lucide-react, MDX/Markdown tooling, and Zustand.

Main directories

• backend/app/controllers: Rails API controllers.
• backend/app/models: Active Record models.
• backend/app/representations: API response representation classes.
• backend/app/services: domain services such as version recording, wiki commit, YouTube sync, and similarity calculation.
• backend/config/routes.rb: API routes.
• backend/db/migrate: migrations.
• backend/db/schema.rb: current schema snapshot.
• backend/lib/tasks: custom Rake tasks.
• backend/spec: RSpec tests.
• backend/test: Rails minitest files that still exist in the tree.
• frontend/src/App.tsx: frontend route definitions and initial user setup.
• frontend/src/pages: page-level React components.
• frontend/src/components: shared and feature components.
• frontend/src/lib: API client helpers, query keys, prefetchers, and domain helpers.
• frontend/src/stores: Zustand stores.
• docs/commands.md: command notes.

Commands

Only list commands that are backed by files inspected in this repository.

Backend

The following binstubs exist under backend/bin:

cd backend
bin/setup
bin/dev
bin/rails
bin/rake
bin/rubocop
bin/brakeman
bin/kamal
bin/thrust

Common Rails/Rake usage through existing binstubs:

cd backend
bin/rails db:prepare
bin/rails db:migrate
bin/rails routes
bin/rails server
bin/rake
bin/rubocop
bin/brakeman

RSpec is present in Gemfile and .rspec exists:

cd backend
bundle exec rspec

Frontend

The following npm scripts exist in frontend/package.json:

cd frontend
npm run dev
npm run build
npm run lint
npm run test
npm run test:run
npm run preview

npm run build runs tsc -b && vite build, then postbuild runs node scripts/generate-sitemap.js.

npm run test runs Vitest in watch mode. Use npm run test:run for a non-watch frontend test run.

Coding style

• Prefer precise, minimal changes.
• Do not flatter or over-explain.
• Explain risks directly.
• Prefer single quotes for strings unless interpolation or escaping makes double quotes better.
• For Japanese text, follow the 1986 Cabinet Notice 《現代仮名遣い》 as the default orthography.
• For Japanese kanji spelling, do not apply 《当用漢字による書きかえ》; prefer the original spelling as the formal one.
• Ruby: never put a space before method-call parentheses.
• Ruby: render 系メソッド呼び出しでは、keyword 引数付きでも括弧を書かない。
• Ruby: never put a line break immediately before ).
• Ruby: do not use %w or %i.
• Ruby: TypeScript / TSX の associative syntax に近い感覚で読むこと。 Hash の } は block の } ではない。call の ) も function 定義の parameter-list ) ではない。delimiter の役割を見誤らないこと。
• In Ruby, when an if condition is split across multiple lines and combines clauses with && or ||, wrap the whole condition in parentheses.
• Ruby hash / block / call delimiter の詳細は、下の Ruby delimiter and wrapping rules を正本として扱ふこと。
• For arrays, never put whitespace or a line break immediately before ].
• Keep the first element on the same line as [ by default.
• If an array would exceed the line limit, break after [ and indent elements 4 spaces deeper than the statement's base indentation.

Ruby delimiter and wrapping rules

• Ruby でも、closing delimiter は glyph ではなく syntax role で判定する。 } が block close なのか hash close なのか、) が method call なのか grouping なのかを区別してから配置すること。
• Ruby の multi-line method call では、receiver / method と opening ( を 同じ行に保ち、closing ) を単独行へ落とさない。
• Ruby の multi-line hash literal / keyword-like argument hash では、opening { を最初の pair と同じ行に置き、closing } を最後の pair と同じ行に 置く。Prettier 的な縦開き・縦閉じをしない。
• Ruby の guard 条件は、1 行で収まるなら modifier 形式を優先する。 99 文字を超えるなら block 形式へ切り替へるか、message 定数化などで縮める。
• Ruby の method chain や call argument を折り返す際、call-site の ) を block close のやうに独立させない。
• Ruby では、行末の \ を用途を問はず一切使用しない。
• Ruby では、文字列連結、logger message、method call、条件式、SQL 断片、 正規表現その他すべての式で、行末バックスラッシュによる継続を禁止する。
• Ruby の block body は、その基準位置から 2 空白深くする。
• Ruby の wrapped expression、method argument、array element、hash pair などの continuation indentation は、その statement の基準位置から 4 空白深くする。
• Ruby の continuation indentation を、行頭からの絶対空白数として扱はない。
• Ruby では、暗黙的に継続可能な構文を優先し、method call、array、Hash 及び 括弧内ではバックスラッシュなしで改行する。
• Ruby では、行長制限を守るために行末バックスラッシュを導入してはならない。
• Ruby で行末バックスラッシュが必要に見える場合は、括弧内で自然に改行する、 一つの文字列補間へまとめる、中間変数へ分ける、format を使ふ、heredoc を 使ふ、array 又は Hash を組み立ててから処理する、条件式全体を括弧で囲む、 method へ抽出する、のいづれかへ書き換へる。
• formatter 又は自動修正にも、Ruby の行末バックスラッシュを生成させない。
• 新規 code だけでなく、今回触れる Ruby code にも行末バックスラッシュを残さない。
• 例へば class body 内の array は、class body の 2 空白を基準に、更に 4 空白 深くするため、結果として行頭から 6 空白になる。

Bad:

response = Example.fetch(
  value,
  option: option,
)

Good:

response = Example.fetch(
    value,
    option: option)

Bad:

payload = {
  title: title,
  url: url,
}

Good:

payload = {
    title: title,
    url: url }

Bad:

raise ArgumentError, 'URL が長すぎます．' if url.bytesize > MAX_URL_BYTES && flag.present?

Good:

if url.bytesize > MAX_URL_BYTES && flag.present?
  raise ArgumentError, 'URL が長すぎます．'
end

Bad:

Rails.logger.info(
    "post_import_metadata_fetch_failure "\
    "#{ payload.to_json }")

Good:

payload = {
    error: e.class.name,
    message: e.message }

Rails.logger.info(
    "post_import_metadata_fetch_failure #{ payload.to_json }")

Bad:

message = "first "\
          "second"

Good:

message = format(
    '%<first>s %<second>s',
    first: 'first',
    second: 'second')

Bad:

result = first_value + \
         second_value

Bad:

records.each {
  do_work(_1) }

Good:

records.each {
  do_work(_1)
}

• TypeScript and Python: use GNU-style spacing before parentheses where syntactically valid.
• Never write Ruby, TypeScript, or TSX lines longer than 99 characters.
• Aim to keep Ruby, TypeScript, and TSX lines within 79 characters where practical.
• In TypeScript and TSX, use 2-space block indentation.
• In TypeScript and TSX, block bodies for components, functions, callbacks, if, try, catch, finally, loops, and JSX nesting use 2 spaces per level.
• In TypeScript and TSX, put the opening brace of try, catch, and finally blocks on the next line at the same indentation as the keyword.
• Do not indent the opening { one level deeper than try, catch, or finally.
• Indent the block body 2 spaces deeper than the keyword and opening brace.
• Put the closing } on its own line at the same indentation as the keyword.
• Do not write try {, catch {, or finally {.
• In TypeScript and TSX, use 4-space continuation indentation for wrapped expressions, arguments, conditions, arrays, object literals, JSX attributes, and similar continuations.
• Treat the user's PostImportSourcePage.tsx and PostImportReviewPage.tsx formatting as the local reference shape: component and callback bodies use 2-space block indentation, single-line bodies do not gain unnecessary braces, wrapped expressions use 4-space continuation indentation, multi- stage ternaries use explicit parentheses, and TypeScript / TSX indentation and alignment whitespace compress every complete run of 8 spaces to tabs.
• A tab does not represent one indentation level.
• In TypeScript and TSX, first determine visible indentation using 2-space block indentation and 4-space continuation indentation, then compress every complete run of 8 spaces used for indentation or column alignment to tabs.
• In TypeScript and TSX, 8-space compression is mandatory, not optional.
• In TypeScript and TSX, this applies both to leading indentation and to alignment whitespace after non-space text, such as aligned inline type columns.
• In TypeScript and TSX, keep residual 2, 4, or 6 spaces after each tab compression.
• In TypeScript and TSX, do not treat a tab as one logical indentation level.
• In TypeScript and TSX, do not alter string literals, template-literal contents, regular expressions, or user-facing text merely to apply tab compression.
• Examples: 2 columns = 2 spaces, 4 columns = 4 spaces, 6 columns = 6 spaces, 8 columns = 1 tab, 10 columns = 1 tab + 2 spaces, 12 columns = 1 tab + 4 spaces, 14 columns = 1 tab + 6 spaces, 16 columns = 2 tabs.
• When TypeScript or TSX code already uses column alignment, apply the same 8-space compression rule to that alignment whitespace.
• Example:

type Props = {
    row:	      PostImportRow
    displayNumber?:   number
    onEdit?:	  () => void
    onRetry?:	  () => void
    onToggleSkip?:    (checked: boolean) => void }

• TypeScript and TSX imports may stay on one line if they remain within the line limit; do not expand short type-only imports mechanically.
• Keep runtime value imports and type imports in separate declarations.
• Do not write import { value, type TypeName } from ....
• Type-only declarations must use import type.
• Do not merge type imports into value imports merely to save lines.
• In TypeScript and TSX, order imports as four groups with a blank line between groups: external value imports, @/... value imports, external type imports, @/... type imports.
• Do not mechanically split a short value import from one module across multiple lines when it still fits within 99 characters.
• In TypeScript and TSX, when breaking a line at an operator, break before the operator and put the operator at the beginning of the next line. A trailing operator at end of line is unacceptable. This rule does not apply to Ruby, where it can change the syntactic structure.
• In TypeScript and TSX, when a function takes one destructured object argument plus an inline type, prefer this shape when it fits locally:

const helper = (
    { value, flag }: { value: string
		       flag:  boolean },
): Result => {
  // ...
}

• In TypeScript and TSX, put switch case block braces on their own lines when a case needs a lexical block:

case 'yes':
case 'no':
  {
    const expected = valueFor (item)
    return expected == null || expected === answer
  }

• In TypeScript and TSX, use value == null and value != null as the default nullish checks. Do not use === null, === undefined, !== null, or !== undefined.
• In JavaScript, JSX, TypeScript, and TSX, never use _1, _2, or similar Ruby-style numbered parameter names. Reserve numbered parameters for Ruby. Use a meaningful callback parameter name such as row, item, value, entry, or result.
• In JavaScript, JSX, TypeScript, and TSX, use cn from @/lib/utils whenever className combines multiple values, conditional classes, or a caller-provided className prop.
• Do not construct className with template literals, ${ ... }, string concatenation, arrays joined with spaces, or feature-local class-merging helpers.
• A static className="..." containing only fixed classes does not need cn.
• If code appears to need a distinction between null and undefined, treat that as a design smell and revise the logic to avoid the distinction. External library APIs that explicitly require distinguishing the two are the only exception.
• In TypeScript and TSX, keep short arrays on one line when they fit under the line limit; break arrays only when readability or line length requires it.
• In TypeScript and TSX, when a ternary expression is split across multiple lines, align ? and : with the condition expression. Do not indent ? and : one extra level under the condition.

const value =
    condition
    ? consequent
    : alternate

• In TypeScript and TSX, keep short ternary expressions on one line when they fit cleanly under the line limit.
• In TypeScript and TSX, prefer ternary expressions for simple conditional value selection. Do not replace a clear ternary with if statements, and do not introduce immediately invoked functions just to avoid or reformat a ternary expression.
• In TypeScript and TSX, multi-stage ternary expressions must make branch boundaries explicit. Wrap each condition group in parentheses instead of relying on indentation alone to show which ? matches which :.
• In TypeScript and TSX, wrap nested ternary expressions in parentheses. Do not write flat vertical chains of ? and : without explicit grouping.
• In TypeScript and TSX, when a ternary condition contains && or ||, wrap the whole condition in parentheses before ?.
• In TypeScript and TSX, if a ternary reaches three or more stages and still reads poorly after explicit grouping, extract a helper function or use if statements instead of keeping a flat multi-stage ternary.

Bad:

row.skipReason === 'existing' || row.importStatus === 'skipped'
? 'skipped'
: Object.keys (row.validationErrors ?? { }).length > 0
  || row.importStatus === 'failed'
  || row.importStatus === 'created'
? null
: hasWarnings (row) || row.status === 'warning'
? 'warning'
: 'ready'

Good:

(row.skipReason === 'existing' || row.importStatus === 'skipped')
? 'skipped'
: ((Object.keys (row.validationErrors ?? { }).length > 0
    || row.importStatus === 'failed'
    || row.importStatus === 'created')
   ? null
   : ((hasWarnings (row) || row.status === 'warning')
      ? 'warning'
      : 'ready'))

Shared-system discovery and reuse

Before creating a new component, hook, service, helper, utility, concern, representation, normaliser, validator, parser, fetcher, store, context, event bus, API client, query key, permission helper, dialogue, toast, form field, or version recorder, search the existing repository first.

Do not search by name alone. Search by responsibility, behaviour, and usage intent as well. Typical search themes include:

• dialogue, modal, confirm, alert, choice
• validation error, field error, unprocessable entity
• permission, role, member, admin, editable
• URL normalise, sanitise, canonicalise
• API call, query key, prefetch, cache invalidation
• version, snapshot, history, restore
• thumbnail, metadata, HTTP fetch, URL safety
• form, field, input, textarea, warning, status badge
• file storage, Active Storage, ZIP, export
• transaction, locking, race, idempotency

Before deciding that something new is needed, confirm at least:

1. the existing definition
2. its public API
3. representative call sites
4. other implementations with similar responsibility
5. the nearest directory-level AGENTS.md

Do not reject an existing implementation by name alone. Read the code and its usage first.

When new behaviour is needed, make the decision in this order:

1. use the existing common API as-is
2. use the existing extension points of that API
3. extend the existing common API minimally
4. keep the implementation local when the meaning is feature-specific
5. add a new common system only when multiple real users and a stable contract are already clear

Do not create a parallel foundation merely because the existing one feels slightly awkward, because a new one seems faster, or because the current task looks special.

Do not create a second common platform with names such as CommonFoo, SharedFoo, BaseFoo, FooManager, FooService, FooProvider, FooWrapper, FooUtils, or useFoo when an existing system already owns the same responsibility. Judge by responsibility, not by spelling.

Wrapper aliases, barrel exports, and re-export shims do not count as reuse. Using a different import path that merely forwards to the existing system does not satisfy a reuse requirement.

Keep this boundary explicit:

• business meaning stays in feature code
• visual and mechanical shell stays in common code

Common code may hold generic primitives, interaction shells, API transport, auth and permission helpers, query-key and prefetch conventions, validation error conversion, shared normalisation, version-recording mechanisms, storage helpers, HTTP safety, and other contracts that carry the same meaning across multiple features.

Feature code should keep feature-specific states, labels, input fields, workflow steps, payload shapes, validation rules, and business decisions.

Do not commonise business logic merely because the visuals look similar or two code fragments resemble each other.

Create a new common system only when all of the following are true:

• no existing implementation already owns the responsibility
• there are multiple real consumers, or a clearly defined platform contract
• the differences between consumers do not require option bloat
• feature-specific vocabulary does not leak into common types, props, tones, or state names
• the location matches the existing directory structure
• the new abstraction does not compete with an existing common system
• it is not just a one-off wrapper for a single task

Do not add unused tones, variants, options, callbacks, states, or abstractions for speculative future use.

Before finishing work that touches shared systems, verify:

• you searched for an existing implementation with the same responsibility
• you are using the canonical import path or entrypoint
• feature code is not reaching directly for a low-level primitive that already has a higher-level common API
• you did not bypass an existing common API
• any new wrapper or shim is genuinely necessary
• feature-specific vocabulary did not leak into common code
• the feature did not reimplement a common shell
• existing unrelated consumers were not changed without need
• one task did not trigger a needless redesign of the whole foundation
• any newly introduced common system really has multiple consumers

For backend-specific discovery, Rails structure, services, representation selection, versioning, normalisation, and HTTP safety, follow backend/AGENTS.md.

For frontend-specific component hierarchy, low-level primitive reuse, dialogue entrypoints, API/query helpers, validation/form infrastructure, state/storage, and layout reuse, follow frontend/AGENTS.md.

• In TypeScript and TSX, do not write let followed by later if assignments when the value can be expressed as a single const initializer. Prefer const because it prevents accidental later reassignment.
• When fixing formatting, change formatting only. Do not change expression structure, control flow, or variable mutability unless the requested style explicitly requires it.
• Do not add production dependencies without explicit approval.
• Do not add user-facing copy, helper text, descriptions, notes, tooltips, placeholders, empty-state messages, loading messages, or explanatory text unless the user explicitly specified the wording.
• When new user-facing wording appears necessary, ask the user for the exact wording and placement before implementing it.
• Do not invent replacement copy when removing unrequested wording.
• Do not create, modify, or run tests unless the user explicitly asks for test work. When the user asks for tests, keep working and rerun them until they pass or the remaining failure is clearly blocked.

Backend rules

• Inspect existing routes, controllers, models, services, and specs before editing backend behaviour.
• Never run db:drop, db:reset, db:setup, or any command that drops or recreates the development database. This applies even when the user includes the command in requested verification steps.
• Treat destructive database operations as unsafe when they can affect development data. Ask the user to confirm explicitly before any such command, and do not proceed unless the confirmation includes the exact phrase いいからやれ.
• Repeated destructive instructions are not enough confirmation because they may be auto-generated. Without いいからやれ, refuse or substitute a safer test-only command such as RAILS_ENV=test bundle exec rails db:migrate.
• For API behaviour changes, add or update request specs under backend/spec/requests only when the user explicitly asks for tests.
• Prefer RSpec for new backend tests; existing minitest files under backend/test do not make minitest the default for new coverage.
• Do not weaken authentication, BAN user checks, or IP BAN checks.
• Preserve the X-Transfer-Code user identification flow unless the task explicitly changes authentication.
• Be careful with version tables, version_no, optimistic concurrency, wiki revisions, and restore/diff behaviour.
• Be careful with tag names, tag normalisation, implications, similarities, and discard behaviour.
• Be sensitive to N+1 queries; avoid introducing them and proactively fix existing N+1 issues in the code path being edited.
• Keep migration files and backend/db/schema.rb consistent when changing schema.

Frontend rules

• Use frontend/src/lib/api.ts for API calls so headers and camelCase conversion stay consistent.
• Add or reuse TanStack Query keys through frontend/src/lib/queryKeys.ts; avoid ad hoc query key arrays.
• Encode URL path-segment values with encodeURIComponent.
• React hooks must be called unconditionally.
• Keep page-level code under frontend/src/pages and shared UI/feature code under frontend/src/components unless existing patterns point elsewhere.
• Match existing Tailwind, component, and import alias conventions.
• <a href="#"> is acceptable for event-only controls when it fits the local UI pattern. Do not use <a> for internal navigation or other non-external links.
• Internal links must use PrefetchLink.
• External links must use <a> with target="_blank".
• When adding or changing Tailwind bg-* classes in TSX, pair them with an explicit readable text-* colour and dark-mode counterparts such as dark:bg-*, dark:text-*, and dark:border-* where a border is present.
• Do not rely on inherited text colour for light backgrounds. This is especially important for chips, cards, buttons, and panels that may inherit white text in dark mode.
• Mobile UI must be checked as a first-class layout. Avoid wide fixed content, make dense controls wrap or scroll intentionally, and keep tag/filter controls usable without horizontal page overflow.
• Frontend のスマホ／PC表示境界は原則 md とする。
• button stack、footer action、dialogue action は md 未満で縦並び、 md 以上で横並びとする。
• 同じ画面内で sm と md を混在させて中間 layout を作らない。
• 明確に別の responsive 要件がある component だけを例外とする。
• For mobile horizontal scrollers, make the scroll direction and item sizing explicit, and ensure chip text remains readable in both light and dark modes.
• In TypeScript and TSX, prefer direct comparison operators such as === and !== over negating a comparison like !(a === b).
• In TypeScript and TSX, prefer ++i or --i over i += 1 or i -= 1 for simple unit-step counter updates.
• For user-facing Japanese text, follow the 1986 Cabinet Notice 《現代仮名遣い》 and avoid historical kana spellings unless the task explicitly requires them.
• For user-facing Japanese kanji spelling, do not normalize to 《当用漢字による書きかえ》; prefer original forms such as 編輯.
• For user-facing Japanese ellipses, prefer …… over ASCII ....
• Frontend dialogue work must use @/lib/dialogues/useDialogue as the feature-facing entrypoint.
• Reuse the existing common dialogue API and common dialogue component instead of building feature-local overlay, close button, header, footer, focus handling, outside click handling, Escape handling, or confirmation flows.
• Do not import @/components/ui/dialog directly in feature code to build a one-off dialogue, and do not evade this rule with aliases such as Dialog as Dialogue.
• Keep business-specific form content in feature code, and keep the visual and behavioural dialogue shell in common code.
• Use British spelling Dialogue for project-defined dialogue identifiers. Keep an exact third-party API spelling only at the external boundary where compatibility requires it.

Frontend TypeScript and TSX style

• The delimiter-placement and line-breaking rules in this section apply to both plain TypeScript .ts and TSX .tsx, unless a bullet explicitly says it is JSX- or React-specific.
• Preserve the local TypeScript and TSX formatting style.
• Do not normalize TSX to common Prettier-style React formatting unless explicitly asked.
• Treat TypeScript and TSX formatting rules as hard constraints, not preferences. Before finishing a TypeScript or TSX edit, inspect the edited hunks for closing ), ], and } placement and fix violations instead of relying on formatter defaults.
• After every TypeScript or TSX edit, perform a style-only self-review of the edited hunks before running verification or reporting completion. The task is not complete while any edited TypeScript or TSX hunk violates these local formatting rules.
• The TypeScript/TSX self-review must classify every edited leading or trailing ), ], and } by syntax role before deciding whether it is valid. Do not apply a rule by glyph alone. A closing ) for a function parameter list is different from a closing ) for a function call. A closing } for a block is different from a closing } for an object, type literal, import list, or destructuring pattern.
• The TSX-specific self-review must confirm there are no common Prettier-style React component declarations with a multi-line destructured parameter.
• The TypeScript/TSX self-review must confirm multi-line function declaration parameter ) placement follows the detailed parameter-list rules below.
• The TypeScript/TSX self-review must confirm call-expression ) is never at the beginning of a line.
• The TypeScript/TSX self-review must confirm object/type/import/destructuring } is not at the beginning of a line.
• The TypeScript/TSX self-review must confirm multi-line function/lambda/callback/block } is on its own line and never at the end of the previous line.
• The TypeScript/TSX self-review must confirm array ] is not at the beginning of a line.
• The TSX-specific self-review must confirm JSX closing markers and closing parentheses keep the surrounding compact style.
• The TypeScript/TSX self-review must confirm block indentation uses 2 spaces per level, wrapped continuations use the repository's 4-space continuation alignment, and every complete run of 8 spaces used for indentation or alignment has been compressed to tabs.
• Prefer const arrow functions for TypeScript/TSX component and helper declarations.
• Put two blank lines before and after top-level const function declarations, unless imports, exports, or file boundaries make that awkward.
• In TSX, use 2-space block indentation and 4-space continuation indentation.
• In TypeScript and TSX, put the opening brace of try, catch, and finally blocks on the next line at the same indentation as the keyword.
• Do not indent the opening { one level deeper than try, catch, or finally.
• Indent the block body 2 spaces deeper than the keyword and opening brace.
• Put the closing } on its own line at the same indentation as the keyword.
• Do not write try {, catch {, or finally {.
• In TypeScript and TSX, convert every complete run of 8 spaces used for indentation or alignment to a tab character.
• In TypeScript and TSX, a tab is exactly equivalent to 8 columns, whether it appears at the beginning of a line or in alignment whitespace after non-space text.
• In TSX, JSX nesting uses 2-space block indentation and wrapped JSX attributes use 4-space continuation indentation; after visible columns are determined, compress every complete run of 8 spaces in the resulting indentation or alignment to tabs.
• In TSX, do not leave JSX subtree indentation at 8, 10, 12, 14, or 16 columns as spaces alone; convert each complete run of 8 spaces to tabs and keep only the residual 2, 4, or 6 spaces.
• In TypeScript and TSX function declarations, including const arrow function declarations, classify the parameter list before placing the closing ).
• If the parameter list itself is given its own multi-line block after the function's opening (, put the closing parameter ) at the beginning of its own line before the return type or =>.
• If the only line break is inside a parameter's inline type, object type, or destructuring shape, and the parameter list itself is not split as a separate block, keep the closing parameter ) on the same line as that parameter's final }. In this case, moving ) to a new line is wrong.
• Do not write React component declarations in the common Prettier form const Component = ({ ... }) => ( when the destructured parameter spans multiple lines. Use the project form with the opening ( after =, the destructured object as the argument, and the closing parameter ) on its own line before =>.
• In TypeScript and TSX, never place a closing parenthesis at the beginning of a line except for a multi-line function declaration parameter list.
• Never place a closing square bracket at the beginning of a line.
• For object literals, type literals, import/export named bindings, destructuring patterns, and other associative-array-style braces, do not place the closing brace at the beginning of a line. Keep } on the same line as the final property, binding, or specifier unless that would violate the line limit. Function, lambda, callback, and block closing braces are exempt and should stay on their own line when that fits the local style. When a function, lambda, callback, or block body spans multiple lines, do not put its closing } at the end of the previous line.
• For arrays and tuple-like lists, do not place the closing ] at the beginning of a line. Keep ] on the same line as the final element unless that would violate the line limit.
• For function and method calls, do not place the closing ) at the beginning of a line. The only TypeScript/TSX exception is the closing parameter ) of a multi-line function declaration.
• When writing braces on a single line in TypeScript or TSX JavaScript context, put exactly one space inside the braces, as in { value } or { key: value }.
• Do not add inner spaces to React/JSX expression braces, as in prop={value}, {children}, or <Component>{{...props}}</Component>.
• Keep a tag's closing marker on the same line as the final prop when the tag spans multiple lines.
• Do not put /> or > on its own line unless the existing surrounding code does so.
• Keep JSX closing parentheses in the existing compact style, for example </div>) rather than moving ) onto a separate line.
• Do not add braces around if, else, or for bodies when the body is a single physical line.
• Always add braces around if, else, or for bodies when the body spans two or more physical lines, even if it is one statement.
• try / catch / finally brace placement example:

try
{
  doWork ()
}
catch
{
  recover ()
}
finally
{
  cleanUp ()
}

• Do not use a leading semicolon for expression statements such as ;([...]).forEach(...); rewrite the expression to avoid ASI hazards explicitly, for example with void.
• Do not insert void mechanically before ordinary event-handler or callback calls merely because the callee returns a Promise. If the surrounding code already uses a plain expression statement such as onClick={() => requestActiveTab ('theme')}, preserve that style unless a local rule or type requirement truly forces void. Adding unnecessary void is a medium-severity style violation.
• When fixing formatting, never change operator binding, evaluation order, tuple/comma behaviour, or any other expression structure. A formatting pass that changes how !==, ??, ?:, &&, ||, or , binds is a capital offence.
• In TypeScript and TSX, do not mechanically verticalise short call tails, short object literals, or short callback bodies that already fit the local line-length and delimiter rules. Expanding compact local code without a readability need is a minor style violation.
• In TypeScript and TSX, treat short object literals, short returned objects, short typed object shapes, and short function-call object arguments as compact associative syntax by default. If they fit locally, keep the opening { on the same line as the first property and keep the closing } on the same line as the final property. Do not explode them into vertical Prettier-style blocks without a concrete readability or line-length reason.
• In TypeScript and TSX, when a compact associative form is broken across two lines, keep the opening { with the first property and the closing } with the final property. A shape like {\n key: value,\n} is wrong even when line length would permit it.
• In TypeScript and TSX, when a short call such as apiGet<...> (...), apiPatch<...> (...), setState (...), updateClientSettings (...), or window.dispatchEvent (...) already fits within the local style, do not add extra vertical layers around the object argument or callback body.
• In TypeScript and TSX, after editing a file, inspect the file tail and remove meaningless blank lines before export default or the end of file. A stray empty line before export default is a minor style offence.
• Use correct British English spelling for new identifiers, filenames, component names, helper names, comments, and developer-facing prose unless editing an already established American-English API that must keep its existing spelling for compatibility.
• Prefer British English spellings such as behaviour, colour, realise, theatre, centre, favourite, optimise, and catalogue.
• Avoid American or Canadian spellings such as behavior, color, realize, theater, center, favorite, optimize, and catalog.
• Even when an external library or API uses the wrong spelling, prefer to correct it at the local boundary and use proper British English names in this codebase. For example, prefer import { color: colour } from '@external-lib' over spreading color through local code.
• Apply the same boundary correction to object destructuring, wrapper helpers, adapter layers, and local variable names when doing so does not break the external contract.
• For this repository, prefer names such as BehaviourSettingsSection.tsx, not BehaviorSettingsSection.tsx.

Additional style offences and penalties

Use this section for recurrent failure modes that are easy to miss when applying the delimiter rules mechanically.

Unnecessary void before ordinary callbacks

Bad:

onClick={() => void requestActiveTab ('theme')}

Good:

onClick={() => requestActiveTab ('theme')}

Penalty: medium-severity offence. The code still works, but it pollutes the local style and usually signals that the edit was made mechanically rather than by reading the surrounding code.

Formatting that changes expression structure

Bad:

const hasUnsavedChanges =
    serialiseThemeDraft (draftThemeSlots)
    !== (serialiseThemeDraft (savedThemeSlots),
	 draftActiveThemeMode !== savedThemeMode)

Good:

const hasUnsavedChanges =
    serialiseThemeDraft (draftThemeSlots)
    !== serialiseThemeDraft (savedThemeSlots)
    || draftThemeMode !== savedThemeMode

Penalty: capital offence. Formatting must never corrupt the meaning of an expression.

Mechanical vertical expansion of compact local code

Bad:

const nextState = {
    open,
    activeTab }

setDirtyStates (
    current => ({
	current,
	key:  value }),
)

Good:

const nextState = { open, activeTab }

setDirtyStates (
    current => ({
	current,
	key:  value }))

Penalty: minor offence when semantics stay intact. It is not necessarily broken, but it ignores the repository's compact associative style.

Prettier-style exploded object literals that should stay compact

Bad:

const next = {
    enabled: keyboard?.enabled !== false,
    bindings: normaliseKeyboardBindings (keyboard?.bindings),
}

Good:

const next = {
    enabled: keyboard?.enabled !== false,
    bindings: normaliseKeyboardBindings (keyboard?.bindings) }

Also good when short enough:

const next = { enabled: keyboard?.enabled !== false,
	       bindings: normaliseKeyboardBindings (keyboard?.bindings) }

Rule: for compact associative syntax, keep { with the first property and } with the final property unless line length truly forces a different shape. Do not mechanically apply the common Prettier block form. Penalty: medium-severity offence. The code still runs, but it violates a core repository formatting habit that must be preserved consistently.

Exploded object arguments inside short calls

Bad:

updateClientSettings (settings => ({
    ...settings,
    keyboard: next,
}))

Good:

updateClientSettings (settings => ({
    ...settings,
    keyboard: next }))

Rule: a call-expression closing ) must not drift onto its own line, and a short object argument should not be exploded more than necessary. Keep the callback's returned object compact when it fits. Penalty: medium-severity offence. This usually means the edit was formatted mechanically instead of by reading the local style.

Stray blank line before export default

Bad:

const Component: FC = () => {
  return <div/>
}


export default Component

Good:

const Component: FC = () => {
  return <div/>
}

export default Component

Rule: do not leave an extra empty line between the last top-level declaration and export default unless some surrounding file structure genuinely requires visual separation. Penalty: minor offence. It is small, but it is easy to avoid and should not recur.

Frontend delimiter decision table

Use this table before accepting any edited TypeScript or TSX hunk. The table is more authoritative than formatter habit.

Import and export named bindings

Bad:

import {
    Button,
    Card,
} from '@/components/ui'

Good:

import { Button,
	 Card } from '@/components/ui'

Also acceptable when short:

import { Button, Card } from '@/components/ui'

Rule: named-binding } is associative-array-style syntax. It must not be alone at the beginning of a line. Prefer keeping { with the first binding and } with the final binding when this fits the line limit. Penalty: capital offence. This is one of the core associative-brace rules.

Type literals

Bad:

type Props = {
    open: boolean
    onOpenChange: (open: boolean) => void
}

Good:

type Props = {
    open: boolean
    onOpenChange: (open: boolean) => void }

Rule: type-literal } is not a block close. It must stay on the same line as the final property unless that would break the hard line limit. Penalty: capital offence. Mistaking a type-literal } for a block } is one of the recurring death-class errors.

Object literals

Bad:

const value = {
    open,
    activeScope,
}

Good:

const value = {
    open,
    activeScope }

Bad:

const value = useMemo (() => ({
    open,
    activeScope,
}), [open, activeScope])

Good:

const value = useMemo (() => ({
    open,
    activeScope }), [open, activeScope])

Rule: object-literal } is associative-array-style syntax. It must not be on a line by itself. Keep it with the final property, and keep call ) off the beginning of a line. Penalty: capital offence. Wrong object-literal } placement and wrong call ) placement are both death-class violations here.

Destructuring parameters

Bad:

const Component: FC<Props> = ({
    open,
    onOpenChange,
}) => {
  return null
}

Good:

const Component: FC<Props> = (
    { open,
      onOpenChange },
) => {
  return null
}

Rule: when a React component or helper takes a destructured object parameter that spans multiple lines, do not use the Prettier-style = ({ ... }) => shape. Put the function parameter list on its own lines. The destructuring } stays with the final binding. The parameter-list ) is then allowed and required at the beginning of its own line. Penalty: capital offence. This pattern is a primary source of repeated TSX style regressions.

Inline typed destructuring parameter

Good:

const RouteTransitionWrapper = ({ user, setUser }: {
    user:     User | null
    setUser:  Dispatch<SetStateAction<User | null>> }) => {
  return null
}

Bad:

const RouteTransitionWrapper = ({ user, setUser }: {
    user:     User | null
    setUser:  Dispatch<SetStateAction<User | null>>
}) => {
  return null
}

Rule: this is not a separately split parameter-list block. The line break is inside the inline type. Keep the type-literal } and parameter-list ) on the same line as the final type property. Penalty: capital offence. Misclassifying this case means the delimiter review has failed at the syntax-role level.

Multi-line normal parameter list

Bad:

const updateDraft = <Key extends keyof Settings,> (
    key: Key,
    value: Settings[Key]) => {
  return null
}

Good:

const updateDraft = <Key extends keyof Settings,> (
    key:    Key,
    value:  Settings[Key],
) => {
  return null
}

Rule: when the parameter list itself is split across multiple parameter lines, the closing parameter ) goes at the beginning of its own line before => or the return type. Penalty: capital offence. This is the main allowed exception for a leading ), so getting it wrong destroys the whole rule set.

Function and callback blocks

Bad:

const handleSave = () => { save ()
}

Bad:

const handleSave = () => {
  save () }

Good:

const handleSave = () => {
  save ()
}

Rule: block } closes executable code, not associative data. Multi-line function, lambda, callback, if, for, switch, and similar block braces belong on their own line. Penalty: capital offence. Confusing block } with associative } is a death-class delimiter error.

Function and method calls

Bad:

const value = compute (
    first,
    second
)

Good:

const value = compute (
    first,
    second)

Rule: call-expression ) must not be at the beginning of a line. The exception for leading ) applies only to function declaration parameter lists, never to calls. Penalty: capital offence. A leading call ) is one of the clearest death-class violations in this codebase.

JSX closing markers

Bad:

<Button
    type="button"
    onClick={handleSave}
>
  保存
</Button>
)

Good:

<Button
    type="button"
    onClick={handleSave}>
  保存
</Button>)

Bad:

<Input
    value={value}
    onChange={handleChange}
/>

Good:

<Input
    value={value}
    onChange={handleChange}/>

Rule: keep > or /> with the final prop, and keep JSX closing parentheses in the local compact form such as </div>). Penalty: medium-severity offence. It is usually not semantically broken, but it is a conspicuous TSX-style failure.

Arrays and tuples

Bad:

const items = [
    first,
    second,
]

Good:

const items = [
    first,
    second]

Good when short:

const items = [first, second]

Rule: array and tuple ] must not be at the beginning of a line. Keep it with the final element unless that would break the hard line limit. Penalty: capital offence. A leading ] is forbidden by the same class of hard delimiter rule as leading associative } and leading call ).

Single-line braces

Good:

const next = { ...current, enabled: true }
const tag = { id, name }

Bad:

<Component prop={ value }/>

Good:

<Component prop={value}/>

Rule: JavaScript object braces on one line get one inner space. JSX expression braces do not get inner spaces. Penalty: minor offence. This is not normally semantic breakage, but it still counts as a style miss.

Final TypeScript/TSX self-review checklist

Before reporting completion after a TypeScript or TSX edit, check the edited hunks line by line. Unless a step explicitly mentions JSX, it applies equally to .ts and .tsx:

1. No import/export/type/object/destructuring } appears alone at the beginning of a line.
2. No call-expression ) appears at the beginning of a line.
3. Any leading ) is definitely closing a function declaration parameter list, not a call.
4. Any parameter-list ) at the end of a line is valid because the parameter list itself was not split, only an inline type or destructuring shape was.
5. No array or tuple ] appears at the beginning of a line.
6. Multi-line executable block } is on its own line.
7. JSX > and /> stay with the final prop unless nearby code proves otherwise.
8. JSX closing parentheses keep the compact local style.
9. Block indentation uses 2 spaces per level, wrapped continuations use the repository's 4-space continuation alignment, and every complete run of 8 spaces used for indentation or alignment has been compressed to tabs.
10. No line has trailing whitespace.

Preferred:

const PostFormTagsArea: FC<Props> = ({ tags, setTags, errors, ...rest }) => {
  return (
      <TextArea
	  {...rest}
	  ref={ref}
	  value={tags}
	  invalid={errors && errors.length > 0}
	  onChange={ev => setTags (ev.target.value)}/>)
}

Avoid:

function PostFormTagsArea ({ tags, setTags }: Props) {
  return (
    <TextArea
      value={tags}
      onChange={ev => setTags (ev.target.value)}
    />
  )
}

Codex workflow

• First inspect existing patterns; do not invent new architecture when a local convention exists.
• Keep changes scoped to the requested issue.
• Do not scan or summarize dependency/generated/runtime directories such as node_modules, dist, tmp, log, and storage unless explicitly needed.
• Before touching wiki, tag, versioning, BAN, IP BAN, or authentication behaviour, inspect the related request specs and service objects.
• If frontend code changes, run only non-test verification commands that apply, such as npm run build and npm run lint. Run npm run test:run only when the user explicitly asks for tests.
• If backend code changes, do not run RSpec unless the user explicitly asks for tests.
• If a verification command cannot be run or fails, report the exact command and failure.

Completion criteria

A task is complete only when:

• implementation is complete,
• relevant non-test verification commands pass, or failures are clearly explained,
• unrelated files are not changed,
• migrations and schema are consistent when schema changes are made,
• user-facing behaviour is documented when needed.