puter/AGENTS.md

AGENTS.md

Guidance for AI coding agents working in this repository, and the source of truth for how we write code, tests, and docs here. Read it before making changes. FOLLOW GUIDANCE AS CLOSELY AS POSSIBLE. If you think a rule is wrong, raise an issue or flag a maintainer instead of doing what you think is right.

Documentation Index

Use these as the source of truth before exploring further:

• README.md — project overview and quickstart.
• doc/architecture.md — backend layered stack (controllers → drivers → services → stores → clients), PuterServer wiring, Context (ALS), actors, and extensions.
• doc/contributing-apis.md — adding and maintaining public APIs end to end (backend surface → puter.js → types → docs → tests). Follow it for any API work.
• doc/pagination.md — the one pagination convention for list APIs (limit/cursor/offset/includeTotal, envelope shape, cursor semantics).
• doc/alarms.md — raising alarms and picking a severity (what pages, what only gets recorded), plus the config that routes them.
• doc/self-hosting.md — running Puter outside hosted infra.
• CONTRIBUTING.md — contributor entry point and PR conventions.
• SECURITY.md — how to report vulnerabilities (do not file them publicly).
• BUG-BOUNTY.md — bounty program scope.
• TRADEMARK.md — trademark usage.

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Repo-wide conventions

These apply everywhere — backend, puter.js, and GUI.

Language & files

• Write ES modules, not CommonJS — we transpile and build as needed.
• TypeScript preferred for new files in the backend and extensions; convert existing JS there opportunistically when you're already touching a file. The GUI and puter.js are plain JavaScript — don't introduce TypeScript files in them.
• In plain-JS files, typing with JSDoc (@type/@param/@returns, @typedef for shared shapes, using the TypeScript type system) is encouraged. API types must not be unknown or untyped ...args: spell out the real parameter and return shapes, unless the value passes through transparently to an upstream layer that owns its type. puter.js has stricter rules (below).
• Make new types findable: descriptive PascalCase names, exported from the obvious entry point. A type used from many places goes in the owning module's types.ts (e.g. src/backend/controllers/types.ts); a type with a single consumer can stay next to it.
• Naming: camelCase for variables and functions, PascalCase for classes and files containing a class (AuthService.ts). Prefer camelCase for all new code, including parameters and internal object properties. snake_case is reserved for external contracts that already use it: wire/JSON keys, stable API error codes, public option names that already ship as snake_case, and established puter_* namespaced fields. Don't rename those (it's a breaking change), and don't add new snake_case beside them; a camelCase local can carry a value into a wire key ({ operation_id: operationId }).

Comments

Prefer self-documenting code. Comment only when the why is non-obvious or a usage detail would trip the next reader. A comment is a sentence or two: one or two lines of //, a few of /** ... */ JSDoc. State the constraint and stop. Don't restate the code, narrate history ("used to swallow the failure, which meant…"), argue the design, or explain parameters the signature already shows. Reasoning that needs paragraphs belongs in a design doc.

Don't reference the current task, PR, or version; those rot. No ticket references (PUT-1234, // fix for FOO-99) in code, comments, or test names: describe the why in domain terms. Section dividers use plain ASCII (// -- Section --), never box-drawing characters.

Security & privacy

Before opening a PR, scan the diff for:

• Logs, error messages, or responses leaking internal paths, secrets, tokens, env vars, or other users' data.
• Debug routes, test credentials, commented-out auth checks.
• Endpoints returning more than the caller actually needs.

When in doubt, return less. Auth-, permission-, or data-export-related changes deserve an explicit callout in the PR description.

Commit messages and PR descriptions never credit anyone or mention a bug report. For security fixes, state what the change does mechanically ("scoped tokens do xyz now"), not the vulnerability or how it could be abused.

Reuse and abstraction

• Search before you build. Before writing a type, helper, cache/TTL map, retry, lock, pagination, validator, serializer, error mapper, host/email normalizer, or provider adapter, grep src/backend/util/, the owning layer, and extensions/ for one that exists, and extend it instead of adding a parallel copy. If you find two copies, consolidate them or flag it. Before opening the PR, check the diff for new helpers that duplicate existing ones.
• One path per operation. Single-item variants call the batch version. Legacy and v2 endpoints share one service method. A second entry point (OIDC, WebDAV, admin, cron) calls the same service as the first instead of re-implementing it.
• No abstraction without a second caller. No base class, interface, factory, registry, decorator, or option bag with one implementation. No wrappers that only forward, no interface methods nobody calls, no methods only tests call.
• Variants are data. Providers or models that differ only in constants (base URL, prices, key names) are entries in a table read by one implementation, not one file each.

Hot paths

• No per-row queries or awaits in loops: use the store's batch method (add one if missing) or src/backend/util/concurrency.ts.
• Bound everything: queries get LIMIT/pagination, in-memory maps get eviction, outbound calls get a timeout and a size cap.
• Build clients, catalogs, and config-derived lookups once, not per request.
• Listeners on fleet-wide events (fs.write.file, route lifecycle) return before any I/O for requests they don't concern.

Working rules of thumb

• Run it, don't just compile it. "It type-checks" is not "it works." Exercise the code path end-to-end at least once.
• Read the neighbors before writing. Match the shape of similar things already in the tree. If you think the existing pattern is wrong, raise it — don't quietly diverge.
• Test new behavior. Every new function, endpoint, driver method, or logic branch gets a test; every bug fix gets a regression test that fails before the fix. If something is genuinely hard to test, skip it but say so in the PR.
• Boy Scout Rule, proportional to the change. In files you're already touching, fix the typo, the dead import, the missing test, the bit you had to read twice. Don't ride a refactor along with a bug fix.
• Understand what you commit. AI assistance is fine; shipping code you couldn't have written, debugged, or defended in review is not.
• A limit change is not done until the docs change with it. Every rate limit, concurrency cap, quota, and allowance in the code is published in src/docs/src/rate-limits-and-quotas.md — an undisclosed limit is one developers discover as a service failure. If a PR moves any of these numbers, the same PR updates that page. The numbers live in src/backend/controllers/fs/limits.ts (filesystem), src/backend/drivers/util/aiLimits.ts (all AI drivers), per-driver rateLimit/concurrent configs, and src/backend/data/subPolicies/ (free-tier allowances).

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Local development

To test a local Docker build, use the gitignored docker-compose.override.yml described in Self-Hosting → Building from source. Keep local build settings there, not in docker-compose.yml.

When budget checks block unrelated local API tests, you may set "unlimitedMetering": true without further approval. Merge it into the gitignored config.json (npm start) or puter/config/config.json (Docker) and restart Puter. It covers every account on that instance, guests included, and usage is still recorded. Keep normal settings when testing budget or subscription enforcement, and leave shared defaults unchanged.

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Backend

Controllers → drivers (optional) → services → stores → clients, all configured from IConfig. Each layer depends only on the layers beneath it and receives them through its constructor; PuterServer (src/backend/server.ts) wires them. doc/architecture.md is the full reference.

A public API can be a controller or a driver. Prefer a controller when you need fine-grained control over routes and gates; doc/contributing-apis.md has the decision guide.

Layer rules:

• Don't reach across layers. Controllers don't poke clients; services don't register routes; lower layers never import from controllers. If you want to, the abstraction is wrong; fix the abstraction.
• Gates run at the edge. Controllers and drivers validate input and apply auth gates; services assume the caller is already authenticated and authorized.
• Don't call sideways within a layer for code reuse. Two services needing the same logic means a util/helper, not a service-to-service dependency.
• A table's store owns every query against it. Services, controllers, and extensions don't run raw SQL/redis against a table that has a store; add the store method so cache invalidation stays with the write.
• Drivers and controllers stay thin. Domain rules a second entry point needs (signup, app CRUD, worker deploy, AI routing/billing) live in a service, not in the first driver or controller that needed them.
• Prefer explicit arguments over Context (ALS). Use it only for request-scoped values that would otherwise thread through many layers; today that's mostly actor and req.

Extensions

extensions/ is for non-crucial parts of the system: Puter must still work with the extension removed. If core needs to call it, it belongs in core (whoami is the cautionary example). Inside an extension, follow the same layered structure, unless it only needs a few route handlers, in which case the extension.get/post/... helpers are enough on their own. The extension API is in doc/architecture.md.

Backend tests

• Vitest; test files sit next to the code they test (*.test.ts / *.test.js). Run with npm run test:backend.
• Mock data, not methods. Stub inputs (fixtures, fake rows, payloads), not the function under test or the layer beneath it — over-mocking produces tests that pass while production breaks. If you must mock, mock at a real boundary (a client/external service).
• Prefer the test server over mocking deps. setupPuterTestEnv() in src/backend/testUtil.ts boots a fully in-memory backend; hit a real database/client shape where reasonable — integration shapes catch what mocked unit tests miss.
• Test code, not docs. Never write a test that reads a file under src/docs/ and asserts on its wording or numbers. Docs are kept in step by the PR (see the limits rule above) and checked in review; a test that greps a markdown page fails on every rewording and verifies nothing about behavior.

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puter.js (the SDK)

src/puter-js/ is the public SDK. It ships live from https://js.puter.com/v2/ with no version pinning, so every change reaches every existing app at once; see Rule zero.

Layout: SDK modules in src/puter-js/src/modules/ (one file or directory per area — FileSystem/, kv/, ai/, …), shared plumbing in src/puter-js/src/lib/, generated (gitignored) type declarations in src/puter-js/types/, API tests in src/puter-js/tests/api/, UI e2e tests in src/puter-js/tests/e2e/, developer docs in src/docs/.

Every SDK change carries all five of these, or the PR is incomplete. doc/contributing-apis.md has the steps for each.

1. Backward compatibility, unless a maintainer explicitly signs off on a break (rules).
2. Tests in the cross-platform API suite, or the Playwright harness for desktop-rendered puter.ui.* (steps).
3. Docs in src/docs/src/ that match the implementation exactly (steps).
4. Types, per the rules below.
5. Error handling: { message, code } with stable snake_case codes, as in modules/kv/ (steps).

Types

puter.js source is plain JavaScript typed via JSDoc, and the JSDoc is the source of truth for the SDK's types. src/puter-js/types/ is tsc --emitDeclarationOnly output: the SDK build (npm run build in src/puter-js) generates it, the npm tarball ships it, and git ignores it. Never commit or hand-edit it. npm run check:puterjs:types generates it and type-checks the result without skipLibCheck; run it after any type change. The one hand-written declaration file is src/puter-js/index.d.ts: it decides what is public and re-exports the generated names, so name a new type there if consumers should be able to import it.

• Public (exposed) methods carry JSDoc types for parameters and return value, with one @overload block per accepted call form; those overloads are the published signature. Typing private helpers is at your discretion; annotate where it helps the next reader.
• Tag members @internal, not @private, to strip them from the generated declarations.
• Declarations must match runtime behavior exactly. A wrong type is worse than a missing one.

Declare a shape where it belongs and reference it elsewhere with an import(...) type. A shape more than one file needs lives in the module's types.js; one shared across modules lives in src/puter-js/src/lib/types.js; one with a single consumer can stay next to it:

/** @typedef {import('./types.js').KVOptConfig} KVOptConfig */

Use @typedef {Object} + @property for any shape whose fields need documenting; it's the only JSDoc form that carries a per-field doc comment into the generated declarations. Use the inline form for small internal shapes with nothing to say per field, and prefer unknown over *:

/** @typedef {{ key: string; value: unknown }} KVEntry */

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GUI

src/gui/ is the Puter desktop: deliberately plain JavaScript + jQuery with HTML-string templates. Don't introduce a UI framework or a new rendering pattern.

Conformity over novelty: match the existing design and code structure even where you'd choose differently. A visually or structurally divergent addition is a defect even when it works.

• Reuse existing UI primitives before writing new ones. Windows and dialogs are UIWindow* functions in src/gui/src/UI/; generic pieces already exist (UIAlert, UIPrompt, UIContextMenu, UINotification, UIPopover, widgets in UI/Components/). A new window should read like its neighbors: an async function taking an options object, composing an HTML string, wiring behavior with jQuery, delegating to UIWindow(...).
• Match the visual language. Use existing CSS classes (button, button-primary, window chrome, form styles) and copy the layout patterns of neighboring windows; new styles go in src/gui/src/css/ following existing conventions. Verify anything positional (menus, overlays, z-index) on both desktop and mobile viewports.
• i18n every user-facing string. No hardcoded UI text — use i18n('key') and add the key to src/gui/src/i18n/translations/en.js. Run npm run check-translations before opening the PR.
• Shared logic goes in helpers/services. Reusable non-UI logic belongs in src/gui/src/helpers/ or src/gui/src/services/, not copy-pasted between windows.
• Tests. Vitest is wired for the GUI (src/**/*.test.js; see appOrder.test.js for the shape). Extract pure logic into functions and test those. Desktop behavior driven through puter.js (puter.ui.*) is covered by the Playwright harness in src/puter-js/tests/e2e/ — add a spec there when you change how the desktop renders SDK-driven UI.