pyTincture

Overview

pyTincture is a Python framework for browser interfaces with Python backends. Pyodide is the default browser runtime. This feature branch adds opt-in portable bundles for Pyodide and MicroPython. Engine and delivery mode are independent; see configuration and migration and the portable Python profile.

Development toward a stable 1.0 release is tracked in the Pytincture 1.0 roadmap and the Pytincture 1.0 GitHub milestone.

The proposed 1.0 stability contract is documented in the public API reference, compatibility matrix, BFF v1 contract, and appcode.pyt v1 contract. CI checks the machine-readable API inventory for accidental contract drift. Typed service settings and create_app() are documented in the configuration guide. Deterministic browser startup stages, errors, and callbacks are described in the browser lifecycle guide. The real Pyodide browser matrix and local commands are in the end-to-end testing guide. Backend ownership and dependency boundaries are described in the backend architecture guide. Production topology, probes, monitoring, secret rotation, backup, and rollback are covered by the production deployment runbook.

Start with the five-minute quickstart, then choose the service or standalone guide. Task guides cover BFFs, browser packaging and dynamic imports, authentication, and troubleshooting. Upgrades are documented from 0.9 to 0.10 and 0.10 to 1.0. Project policies and operations are in the changelog, security policy, contribution guide, and release procedure. The RC qualification record shows the current 1.0 go/no-go state and the evidence still required before publication. The performance budgets define and retain regression evidence for browser startup, package generation, health, and BFF calls.

Features

• Pyodide Integration: Seamlessly bring Python to the web via Pyodide.
• GUI Library Support: Simplify the creation and management of GUI components in Python.
• Browser-safe Code Packaging: Package the application entrypoint, reachable local imports, and explicitly configured browser files.
• Widgetset Stub Generation: Automatically generate frontend stub classes using the @backend_for_frontend decorator.
• Streaming BFF Calls: Enable true streaming responses with the @bff_stream decorator.
• Authentication & Sessions: Supports Google and Microsoft OAuth2, SAML 2.0 SSO, verified email/password login, key rotation, CSRF protection, and revocable signed sessions.
• Redis Integration: Optionally expose the legacy shared USER_SESSION_DICT through Upstash; authentication does not require Redis.
• Cross-Platform Compatibility: Works on any platform where Pyodide is supported.
• Easy to Use: Provides a user-friendly API to streamline GUI development.
• Production Launcher: Includes a uvicorn-based launcher for deploying the service.
• PyPI Distribution: Easily installable via pip from PyPI.

Installation

From PyPI:

pip install pytincture

The base install serves unauthenticated applications and local development without pulling optional identity-provider, Redis, or MCP stacks. Install only the features a deployment enables:

pip install "pytincture[password]"  # Argon2/bcrypt local login
pip install "pytincture[oauth]"     # Google/Microsoft OAuth
pip install "pytincture[saml]"      # SAML 2.0
pip install "pytincture[redis]"     # shared Upstash state
pip install "pytincture[mcp]"       # MCP endpoint
pip install "pytincture[dev]"       # contributors: all features and test/build tools

From Source:

1. Clone the repository:

git clone https://github.com/yourusername/pyTincture.git
cd pyTincture

2. Install dependencies:

pip install ".[dev]"

(Alternatively, follow the instructions in pyproject.toml.)

Environment Variables

Browser capabilities are opt-in. All four settings below default to false:

• PYTINCTURE_ALLOW_MICROPHONE=true: Allow same-origin microphone requests, for example for voice input.
• PYTINCTURE_ALLOW_CAMERA=true: Allow same-origin camera requests.
• PYTINCTURE_ALLOW_GEOLOCATION=true: Allow same-origin geolocation requests.
• PYTINCTURE_ALLOW_PAYMENT=true: Allow same-origin Payment Request API use.

Set these in the service environment or launch_service(env_vars={...}) before startup. Browser consent and secure-context requirements still apply. See browser permissions for examples, configuration precedence, and service-wide scope.

• MODULES_PATH: Directory containing module files used for dynamic packaging. This is set automatically from modules_folder when launch_service starts; overriding it via env vars is usually unnecessary.
• USE_REDIS_INSTANCE: Set to "true" to back the legacy USER_SESSION_DICT with Upstash. Authentication does not read or write this dictionary.
• ALLOWED_EMAILS: An optional comma-separated authorization allowlist. It is not a password verifier. example: "some@email.com,joe@email.com"
• ENABLE_USER_LOGIN: Enable verified local email/password login. This route is rejected when the flag is false.
• AUTH_PASSWORD_HASHES: JSON object mapping normalized email addresses to Argon2id or bcrypt hashes. example: {"user@example.com":"$argon2id$..."}
• AUTH_USER_CLAIMS: Optional JSON user list or email-to-claims object used to hydrate verified local users with application profile fields. Password and token fields are always discarded. When unset, DEFAULT_APP_USERS is read as a compatibility fallback after password verification succeeds.
• AUTH_SESSION_CLAIM_KEYS: Optional comma-separated names of additional trusted claims to retain in the signed session. id, role, plan, next_billing, theme, and sidebar are retained by default; passwords, hashes, secrets, and tokens are never retained.
• AUTH_USER_AUTHENTICATOR: Optional dotted path to a sync or async callable accepting email, password, and request. It must return trusted user claims, True, or False.
• ENABLE_DEV_EMAIL_LOGIN: Allow a non-empty ALLOWED_EMAILS list without password verification only when the actual client peer is loopback. The launcher automatically binds this mode to 127.0.0.1 and rejects routable bind hosts. This is intentionally unsafe and must only be set to true for local development.
• PYTINCTURE_ALLOWED_HOSTS / PYTINCTURE_CANONICAL_ORIGIN: Required exact hostnames and one HTTPS external origin when production authentication is enabled. Wildcard or request-derived production auth origins are rejected.
• PYTINCTURE_ALLOW_DEVELOPMENT_AUTH_ORIGIN: Permit request-derived auth origins only for local HTTP testing. Also set AUTH_SESSION_HTTPS_ONLY=false; the supported launcher binds this mode to loopback and rejects routable bind hosts.
• LOGIN_HELP_TEXT: Optional plain-text guidance displayed below the login-page introduction. It is HTML-escaped and is suitable for demo credentials or environment-specific login instructions. Do not expose real production passwords. example: "Demo login: demo@example.com / demo-password"
• ENABLE_GOOGLE_AUTH: Enable the respective authentication mechanisms. example: "true"
• ENABLE_MICROSOFT_AUTH: Enable Microsoft OAuth2 authentication for one explicitly configured Entra tenant. example: "true"
• GOOGLE_CLIENT_ID: OAuth client ID for Google.
• GOOGLE_CLIENT_SECRET: OAuth client secret for Google.
• MICROSOFT_CLIENT_ID: OAuth client ID for Microsoft Azure AD / Microsoft identity platform.
• MICROSOFT_CLIENT_SECRET: OAuth client secret for Microsoft Azure AD / Microsoft identity platform.
• MICROSOFT_TENANT_ID: Required Entra tenant ID. The shared common issuer is not accepted.
• ENABLE_SAML_AUTH: Enable SAML 2.0 authentication. example: "true"
• SAML_EMAIL_ATTRIBUTE: Attribute name used to extract the user email from the SAML assertion. example: "email"
• SAML_NAME_ATTRIBUTE: Optional attribute for the display name. example: "givenName"
• SAML_LOGIN_LABEL: Optional label for the single-provider SAML login button. example: "Login with Contoso"
• SAML_LOGO_URL: Optional image URL for the single-provider SAML login button. example: "/appcode/contoso-logo.svg"
• SAML_SECRET_KEY: Required whenever any production authentication method is enabled. Use at least 32 random characters, keep it stable across deployments, and provide the same value to every replica. Generate one with python -c "import secrets; print(secrets.token_urlsafe(32))". Loopback development login may use an ephemeral generated key.
• AUTH_SESSION_PREVIOUS_SECRET_KEYS: JSON list (or comma-separated list) of prior strong signing keys accepted during rotation. Cookies accepted with an old key are re-signed with the current key.
• AUTH_SESSION_MAX_AGE_SECONDS: Signed authentication cookie idle lifetime in seconds. Defaults to 28800 (8 hours).
• AUTH_SESSION_ABSOLUTE_MAX_AGE_SECONDS: Absolute authenticated-session lifetime that cannot be extended by activity. Defaults to 86400 (24 hours) and must be at least the idle lifetime.
• AUTH_SESSION_HTTPS_ONLY: Require HTTPS for authentication and CSRF cookies. Defaults to true; loopback development login defaults it to false unless explicitly overridden.
• AUTH_SESSION_SAME_SITE: Cookie SameSite policy: lax, strict, or none. Defaults to lax.
• AUTH_SESSION_MAX_CLAIM_COUNT / AUTH_SESSION_MAX_IDENTITY_BYTES / AUTH_SESSION_MAX_COOKIE_BYTES: Fail-closed limits for retained identity keys, canonical identity JSON, and the final signed browser-session cookie. Defaults are 32, 2048, and 3800 bytes.
• AUTH_LOGIN_CSRF_TTL_SECONDS: Lifetime of the one-time, application-bound password-login transaction. Defaults to 600 seconds. JSON clients obtain a token from GET /{application}/auth/mcp before posting credentials and that token to the same URL.
• SAML_RELAY_STATE_TTL_SECONDS: Maximum browser-bound, one-time SAML login transaction age in seconds. Defaults to 600 (10 minutes).
• SAML_DEFAULT_REDIRECT: Optional redirect path or URL template after SAML login (defaults to /{application} when unset). example: "/{application}"
• SAML_SP_ENTITY_ID: Optional template for the SP entity ID (supports {application}, {base_url}, {host}); defaults to /{application}/auth/saml/metadata.
• SAML_SP_ASSERTION_CONSUMER_SERVICE_URL: Optional template for the ACS endpoint (supports placeholders like {application}).
• SAML_SP_X509_CERT: Service Provider certificate in PEM format. Encrypted assertions are currently rejected before toolkit processing; configure the IdP for signed plaintext assertions.
• SAML_SP_PRIVATE_KEY: Service Provider private key in PEM format matching the SP certificate. It does not opt the service into encrypted assertions.
• SAML_IDP_ENTITY_ID: Identity Provider entity ID.
• SAML_IDP_SSO_URL: Identity Provider SSO URL.
• SAML_IDP_SLO_URL: Optional Identity Provider SLO URL.
• SAML_IDP_X509_CERT: Identity Provider certificate in PEM format.
• SAML_REQUESTED_AUTHN_CONTEXT: Include RequestedAuthnContext in SAML authentication requests. Defaults to false; set to true for identity providers that require it.
• SAML_PROVIDERS: Optional JSON configuration for multiple named SAML providers. When set, the login page renders one SAML button per provider and uses provider-specific login routes such as /{application}/auth/saml/{provider_id}/login. By default, providers share the standard SP entity ID and ACS URLs (/{application}/auth/saml/metadata and /{application}/auth/saml/acs) so existing IdP app registrations do not need new reply URLs. Provider entries may override these with sp_entity_id and sp_assertion_consumer_service_url when per-provider SP URLs are required. example:

  [
     {
        "id": "company-a",
        "label": "Login with Company A",
        "logo_url": "/appcode/company-a.svg",
        "idp_entity_id": "https://idp-a.example.com/metadata",
        "idp_sso_url": "https://idp-a.example.com/sso",
        "idp_x509_cert": "-----BEGIN CERTIFICATE-----..."
     },
     {
        "id": "company-b",
        "label": "Login with Company B",
        "logo_url": "/appcode/company-b.svg",
        "idp_entity_id": "https://idp-b.example.com/metadata",
        "idp_sso_url": "https://idp-b.example.com/sso",
        "idp_x509_cert": "-----BEGIN CERTIFICATE-----..."
     }
  ]
  

  Provider entries may also override `sp_entity_id`, `sp_assertion_consumer_service_url`, `sp_x509_cert`, `sp_private_key`, `idp_slo_url`, `default_redirect`, `allowed_roles`, and `role_attribute_keys`. If `SAML_PROVIDERS` is not set, the existing single-provider `SAML_*` variables continue to work.
  

• SAML_DEBUG: Enable verbose SAML logging.
• ALLOWED_NOAUTH_CLASSCALLS example: [{"application": "portal", "file": "services/somefile.py", "class": "SomeClass", "function": "somefunction"}]
• GOOGLE_CLIENT_ID
• GOOGLE_CLIENT_SECRET
• SECRET_KEY: Legacy fallback signing key used only when SAML_SECRET_KEY is unset.
• REDIS_UPSTASH_INSTANCE_URL: Optional URL for an Upstash Redis instance. Remote endpoints must use HTTPS; HTTP is accepted only for a literal loopback development IP. Redis is not required for sessions or load balancing. example: "http://127.0.0.1:16379"
• REDIS_UPSTASH_INSTANCE_TOKEN: Redis Upstash token
• DATABASE_URL: Database connection string example: "sqlite:////absolute/path/to/database.db"
• PYTINCTURE_BROWSER_FILES: JSON list or comma-separated globs for extra files to include in the browser package. Python entrypoints and reachable local imports are discovered automatically.
• PYTINCTURE_PUBLIC_ASSET_PATHS: Explicit globs for files that may be served from /{application}/appcode/ in addition to standard image, font, media, CSS, and JavaScript assets. Python and configuration files are denied by default. A root-level wheel is served automatically only when its distribution and version match the requested application's widgetset or its explicit development-wheel fallback; unrelated/stale wheels remain private.
• PYTINCTURE_DEV_WHEEL_VERSION: Explicit backend development-widget fallback version (99.99.99 by default). The runtime requests the declared real version first.
• MAX_REQUEST_BODY_BYTES: Maximum request body size. Defaults to 2 MiB.
• BFF_CALL_TIMEOUT_SECONDS: Maximum non-streaming BFF execution time. Defaults to 30 seconds.
• BFF_RESULT_MAX_BYTES / BFF_RESULT_MAX_DEPTH / BFF_RESULT_MAX_ITEMS: Bound ordinary serialized BFF responses before they are returned. Defaults to 10 MiB, 32 levels, and 10,000 aggregate items.
• BFF_EXECUTION_MODE: trusted-thread by default. Set isolated-process only when non-streaming BFFs need a killable child-process boundary; configure BFF_ISOLATED_MAX_CONCURRENCY, BFF_ISOLATED_MAX_PER_USER, BFF_ISOLATED_CPU_SECONDS, and BFF_ISOLATED_MEMORY_BYTES for that mode.
• BFF_STREAM_MAX_SECONDS: Maximum BFF stream duration. Defaults to 300 seconds.
• BFF_STREAM_MAX_BYTES: Maximum BFF stream output. Defaults to 10 MiB.
• BFF_POLICY_HOOK_PATH: Dotted path to a sync or async policy hook. This is the recommended launcher configuration because the hook must be available before application modules are imported or constructed. Return True or None to allow, False to deny, or raise an HTTP exception with an explicit status.
• ENABLE_BFF_REPLAY_TOKENS: Opt-in one-time request proofs for authenticated BFF calls. Generated browser stubs automatically obtain, consume, and refill an in-memory token pool. Defaults to false.
• BFF_REPLAY_TOKEN_BATCH_SIZE: Number of one-time proofs returned in each opaque refill. Defaults to 12.
• BFF_REPLAY_TOKEN_LOW_WATERMARK: Refill the browser-side pool when this many proofs remain. Defaults to 3.
• BFF_REPLAY_TOKEN_TTL_SECONDS: Lifetime of an unused proof. Defaults to 300 seconds.
• ENABLE_MCP: Enable the authenticated, stateless MCP mount. Disabled by default.
• MCP_TOOLS: JSON list mapping purpose-built tool names and scopes to exact @backend_for_frontend methods. Generic HTTP/BFF dispatchers cannot be exported.
• MCP_ALLOWED_HOSTS / MCP_ALLOWED_ORIGINS: Non-empty JSON lists of exact transport hosts and origins; wildcards are rejected.
• MCP_JWT_JWKS_URI (or MCP_JWT_PUBLIC_KEY), MCP_JWT_ISSUER, and MCP_JWT_AUDIENCE: Mandatory bearer-token verification policy.
• PYTINCTURE_LOG_LEVEL: Structured Pytincture application log level (DEBUG, INFO, WARNING, ERROR, or CRITICAL). Defaults to INFO.

Authenticated browser cookies contain only stable identity claims plus opaque session and CSRF identifiers. Passwords, complete SAML attributes, SAML assertions, and changing SAML session indexes are not stored in the cookie. Browser logout is a CSRF-protected POST that clears the signed cookie. The default remains fully stateless across replicas; an explicitly enabled shared store adds cross-browser revocation and fails closed if that store is unavailable.

When ENABLE_BFF_REPLAY_TOKENS=true, each authenticated .pyt download receives a random, short-lived client decoder and an opaque session-bound capsule. Token refills return an authenticated opaque payload rather than a visible JSON token list. The capsule is recoverable after backend restarts as long as SAML_SECRET_KEY remains stable. Without Upstash, already-issued tokens are intentionally invalidated by a backend restart and generated stubs transparently refill them. This feature makes copied completed BFF requests fail and adds a reverse-engineering barrier; it is not a security boundary against a user who controls the browser, WASM memory, or application archive.

Running the Service with your application

Development Mode:

Use the service from your application:

if __name__=="__main__":
    from pytincture import launch_service
    launch_service(
        modules_folder=".",  # point to your modules directly
        default_application="py_ui",  # optional: redirect / to /py_ui
        favicon_folder="branding/favicon",  # optional; relative to modules_folder
        env_vars={
            "ENABLE_USER_LOGIN": "true",
            "ENABLE_DEV_EMAIL_LOGIN": "true",
            "ALLOWED_EMAILS": "developer@example.com",
            "AUTH_SESSION_HTTPS_ONLY": "false",
        }
    )

For one application, place the complete favicon set in a conventional favicon directory under modules_folder:

favicon/
  favicon.ico
  favicon-16x16.png
  favicon-32x32.png
  apple-touch-icon.png
  android-chrome-192x192.png
  android-chrome-512x512.png
  site.webmanifest

pyTincture scans the directory and emits the icon, size, Apple touch icon, mask icon, and web-manifest declarations browsers need. Browsers do not enumerate favicon directories themselves.

Set favicon_folder on launch_service to use a different directory. Relative paths are resolved from modules_folder, and absolute paths are supported, including paths outside the modules directory.

For multiple applications, use one directory per application, such as favicon/py_ui/ and favicon/admin/. This also works under a launcher-configured directory. An application can override both the launcher setting and the convention with either APP_FAVICON = "branding/icons" or APP_CONFIG = {"favicon": "branding/icons"}; the value may point to a directory or a single icon file under modules_folder.

Testing

Tests are written using pytest and cover endpoints, helper functions, and the launcher. Run all tests with:

python -m pytest

Tests include:

• tests/test_app.py: Endpoint tests and service logic.
• tests/test_dataclass.py: Tests for stub generation, decorators, and helper functions.
• tests/test_launcher.py: Tests for the uvicorn launcher and process management.

Container status

This repository does not currently publish or support a Pytincture container image. Install the verified Python release from PyPI, or build a deployment-owned image from an exact Pytincture version and your application. Do not treat a mutable container tag as a production pin. A future official image must be tied to a protected release, published by digest, accompanied by an SBOM, and signed or attested before it is documented here.

Standalone pytincture.js build

The file under pytincture/frontend/pytincture.js can be bundled as a standalone runtime for static sites that only need a <script> tag plus embedded Python. Production sites should use the verified self-hosted asset export documented in standalone mode.

Building the bundle

1. Install the JS tooling once:

   cd pytincture/frontend
   npm install
   

2. Produce distributable artifacts (this automatically syncs package.json's version to the Python framework’s pytincture/__init__.py):

   npm run build
   

   The dist/ folder will contain:
   • pytincture.js (IIFE build for script tags)
   • pytincture.min.js (minified IIFE)
   • pytincture.esm.js (ES module build)

You can run npm run build:watch while editing pytincture/frontend/pytincture.js to regenerate the bundles automatically.

Packaging the runtime

The frontend directory is wired like a normal npm package (name: @pytincture/runtime). To inspect the package locally:

cd pytincture/frontend
npm run build
npm pack --dry-run

The build synchronizes the npm and browser runtime versions with the Python framework version. Official npm publication occurs from the validated GitHub release artifacts described below. An exact npm release may be used for controlled demos only when its SRI is copied from the trusted release integrity manifest, for example:

<script src="https://cdn.jsdelivr.net/npm/@pytincture/runtime@1.0.0-rc.12/dist/pytincture.min.js" integrity="sha384-<trusted-manifest-value>" crossorigin="anonymous"></script>

Using pytincture.js standalone

With the runtime script on the page, Pytincture auto-detects any <script type="text/python"> blocks and runs them once Pyodide is ready. Optional helpers:

• Add window.pytinctureAutoStartConfig = { widgetlib: "dhxpyt==0.9.18", libsSelector: "#micropip-libs" } before loading the script to override defaults.
• Set window.pytinctureAutoStartDisabled = true if you prefer to call runTinctureApp({...}) manually.
• Extra Python wheels can be listed in <script type="text/json" id="micropip-libs">["faker==37.0.0"]</script>.

Errors are rendered inside #maindiv (if present) and logged to the console, making it easy to host pure-static demos without the full framework.

Backend-for-Frontend access policies

Only classes marked with @backend_for_frontend and their public methods/attributes are registered. Unknown targets are rejected from a static manifest before application code is imported or constructed. Methods default to POST.

Use @bff_http_methods to declare a parameterless, read-only, repeatable GET method or to select PUT, PATCH, or DELETE:

from pytincture.dataclass import backend_for_frontend, bff_http_methods

@backend_for_frontend
class Reports:
    @bff_http_methods("GET")
    def status(self):
        return {"ready": True}

Policy metadata must use literal values so it can be read without importing the module. Hooks may be synchronous or asynchronous and run before module import, construction, or attribute access:

1. Tag the method with @bff_policy(...) to describe whatever metadata you need (roles, scopes, tenants, etc.):

   from pytincture.dataclass import backend_for_frontend, bff_policy
   
   @backend_for_frontend
   class Reports:
       @bff_policy(role="manager", scopes=["reports:view"])
       def export(self):
           ...
   

2. Register a server-side hook that runs before every call. The hook receives the authenticated user (from OAuth/SAML/local login), the policy metadata, the class/method names, and the request. It can raise HTTPException to block the call:

   from fastapi import HTTPException
   from pytincture.backend.app import set_bff_policy_hook
   
   def my_policy_hook(user, policy, **kwargs):
       roles = set(user.get("roles", []))
       required = policy.get("role")
       if required and required not in roles:
           raise HTTPException(status_code=403, detail="Forbidden")
   
   set_bff_policy_hook(my_policy_hook)
   

Because the authorization decision lives on the server, even an authenticated user who opens the browser console can’t call methods they don’t have rights to. Policy-bearing exports fail application startup unless a hook is configured. Pytincture also enforces the standard application, auth_provider/provider, issuer, tenant, role/roles, and operation predicates before calling the hook. Cookie-authenticated state-changing calls require the CSRF token automatically sent by generated browser stubs.

0.10 security migration

Version 0.10 intentionally removes insecure legacy behavior:

• configure a strong SAML_SECRET_KEY before enabling authentication;
• configure AUTH_PASSWORD_HASHES or AUTH_USER_AUTHENTICATOR for local login, or use ENABLE_DEV_EMAIL_LOGIN only on loopback during development;
• decorate every remotely callable class with @backend_for_frontend;
• change manually issued GET method calls to POST or declare @bff_http_methods("GET");
• explicitly list extra browser package files and public assets;
• explicitly opt in to MCP operations;
• update custom cookie-based clients to echo the pytincture_csrf cookie in X-CSRF-Token for POST, PUT, PATCH, and DELETE.

Pytincture does not currently provide rate limiting. Production deployments should enforce suitable login and request rates at the application gateway or reverse proxy.

CI/CD release flow

Publishing a GitHub release runs the complete CI workflow. CI builds the wheel, source distribution, and npm tarball once; verifies their contents, versions, and hashes; clean-installs every optional feature; and publishes those exact validated files only after the Python, JavaScript, browser, and production gates pass. Manual publish workflows are intentionally not provided.

Required GitHub secrets:

• PYPI_PASSWORD: a PyPI API token (formatted pypi-***) with publish rights to pytincture.
• NPM_TOKEN: an npm access token with publish rights to @pytincture/runtime.

The artifact contract and local verification command are documented in the release artifact guide.

License

pyTincture is licensed under the MIT License.