Stability

This page explains which Quater APIs you can rely on during the pre-release period.

Prerequisites

Read Public API. This page matters when you decide what to import, wrap, or extend in application code.

Current Promise

Quater is pre-release. The project can still fix names, defaults, and contracts before they become stable. The documented top-level imports are the API you should try first.

from quater import Quater, Request, Resource, RouteGroup

Prefer that style over importing implementation modules:

from quater.app import Quater

The second form may work today, but it is not the path the docs promise for application code.

Public Import Boundary

Use names exported from quater and documented in the Reference:

• application objects: Quater, RouteGroup, AppConfig, CORSConfig
• request and state: Request, State
• binding markers: Path, Query, Body, Header, Cookie
• responses: Response, JSONResponse, TextResponse, HTMLResponse, BytesResponse, StreamResponse, RedirectResponse, EmptyResponse
• auth and security: AuthRequest, AuthContext, ApprovalRequest, ActionApproval, HTTPError, ImproperlyConfigured, SignedCookieSigner
• resources: Resource
• observability: AccessLogEvent, AccessLogHook, ToolAuditEvent
• testing: TestClient, MCPTestClient, TestResponse

Some compatibility modules exist for advanced cases, but the top-level import should be enough for normal apps.

Internal Modules

Treat these as internal unless a guide points you there:

• quater.app
• quater.router
• quater.actions
• quater.protocol
• quater.docs
• quater.tools.registry
• quater.params
• quater.datastructures

They exist so Quater can keep its implementation structured. They are not stable extension points yet.

Remote Action Protocol

The CLI uses:

• /.well-known/quater-actions.json
• /__quater__/actions/call

Those endpoints exist for the Quater CLI. Do not build third-party clients directly on them yet. Use quater actions ... and quater call ....

Changelog And Migration

Quater release notes live in Changelog / Release Notes. While the project is pre-release, pin the exact version you test:

python -m pip install quater

If you use uv, pin with uv add quater instead.

When a release contains a breaking change, the release note should include a before-and-after snippet.

What Can Go Wrong

Loaded object is not a Quater application : You pointed the CLI at an object that is not a Quater instance.

App factory target is not callable : You passed --factory, but the import target is not a function.

ConfigurationError still exists in quater.exceptions : Use ImproperlyConfigured in new app code. ConfigurationError remains for compatibility with older internal names.

Also See

• Public API: what application code should import.
• Reference: exact signatures.
• Known Limitations: current pre-release gaps.
• Deployment: direct server risks and production checks.