# Introduction
Next handling mimetype integrity check and checksum integrity check for
s3 storage type
Always expecting a trailing end slash when deleting a folder etc
## Application
Uninstalling an application now deletes all its related files
## File storage service
Making a distincton between folder path and file path
## Validation Pipeline
Every file operation in `FileStorageService.buildOnStoragePath` runs
through `validateResourcePath`, which chains three validators in order:
**1. `validateSafeRelativePath`** -- rejects path traversal attacks
| Input | Result | Error |
|---|---|---|
| `../../../etc/passwd` | Rejected | `Resource path must not contain
path traversal (..)` |
| `/etc/passwd` | Rejected | `Resource path must be relative, not
absolute` |
| `file\0.txt` | Rejected | `Resource path contains null bytes` |
| `..\\..\\etc\\passwd` | Rejected | `Resource path must not contain
backslashes` |
| _(empty)_ | Rejected | `Resource path must not be empty` |
**2. `validateFilenameIntegrity`** -- enforces safe characters, length
limits, extension required
| Input | Result | Error |
|---|---|---|
| `my folder/file.mjs` | Rejected | `A path segment contains invalid
characters...` |
| `Makefile` | Rejected | `Filename must have an extension` |
| `aaa...(256 chars).mjs` | Rejected | `A path segment exceeds the
maximum length of 255 characters` |
| `a/b/.../file.mjs` (1025+ chars) | Rejected | `Resource path exceeds
maximum length of 1024 characters` |
| `src/handlers/index.mjs` | Accepted | -- |
| `my-app/my_file.tsx` | Accepted | -- |
| `v1.0/module.config.mjs` | Accepted | -- |
Allowed characters per segment: `a-z`, `A-Z`, `0-9`, `.`, `-`, `_`
**3. `validateResourceExtension`** -- checks extension against the
`FileFolder` allowlist
| Input | FileFolder | Result | Error |
|---|---|---|---|
| `handler.js` | `BuiltLogicFunction` | Rejected | `Invalid file
extension. Allowed extensions: .mjs` |
| `card.tsx` | `BuiltFrontComponent` | Rejected | `Invalid file
extension. Allowed extensions: .mjs` |
| `script.js` | `PublicAsset` | Rejected | `Invalid file extension.
Allowed extensions: .png, .jpg, ...` |
| `index.mjs` | `BuiltLogicFunction` | Accepted | -- |
| `app.tsx` | `Source` | Accepted | -- |
| `photo.png` | `CorePicture` | Accepted | -- (unconfigured folder,
passes through) |
## Consumers
- **`FileStorageService`** -- calls `validateResourcePath`, throws
`FileStorageException` on failure (last-resort defense)
- **Resolver (`uploadApplicationFile`)** -- calls
`validateResourcePath`, throws `ApplicationException` on failure
(user-facing)
- **Flat validators** -- call `validateResourcePath`, push the error to
`validationResult.errors` (non-throwing, collects all errors)
All error messages are translated via Lingui `t` and returned in a
discriminated union `{ isValid: true } | { isValid: false, error: string
}`, letting each consumer decide how to handle failures.
Postcard App — Twenty App Example
A rich example app showcasing all Twenty app entity types. Use this as a reference when building your own apps.
What's included
This app demonstrates every entity type available in the Twenty SDK:
| Entity | Files | What it shows |
|---|---|---|
| Application | src/application.config.ts |
App metadata, application variables, server variables |
| Objects | src/objects/ |
Custom objects with inline fields, junction tables |
| Fields | src/fields/ |
Standalone fields, relations (ONE_TO_MANY, MANY_TO_ONE), extending standard objects |
| Logic Functions | src/logic-functions/ |
HTTP routes, database event triggers, cron schedules, tool functions, install hooks |
| Front Components | src/components/ |
React components rendered inside Twenty's UI |
| Roles | src/roles/ |
Permission roles with object and field-level access control |
| Views | src/views/ |
Saved table views with column configuration |
| Navigation | src/navigation-menu-items/ |
Sidebar links targeting views |
| Skills | src/skills/ |
AI skill providing context to agents |
| Agents | src/agents/ |
AI agent with a system prompt |
| Page Layouts | src/page-layouts/ |
Custom record page with a front component widget |
Getting started
# From this directory
yarn install
yarn twenty dev