revert: AuthenticationContext ambient primitive (#259)

src/celeste/__init__.py

@@ -6,15 +6,7 @@
 from pydantic import SecretStr
 
 from celeste import providers as _providers  # noqa: F401
-from celeste.auth import (
-    APIKey,
-    Authentication,
-    AuthenticationContext,
-    AuthHeader,
-    NoAuth,
-    authentication_scope,
-    resolve_authentication,
-)
+from celeste.auth import APIKey, Authentication, AuthHeader, NoAuth
 from celeste.client import ModalityClient
 from celeste.core import (
     Capability,
@@ -27,7 +19,6 @@
 from celeste.exceptions import (
     ClientNotFoundError,
     Error,
-    MissingAuthenticationError,
     ModelNotFoundError,
 )
 from celeste.io import Input, Output, Usage
@@ -196,9 +187,6 @@ def create_client(
         model: Model object, string model ID, or None for auto-selection.
         api_key: Optional API key override (string or SecretStr).
         auth: Optional Authentication object for custom auth (e.g., GoogleADC).
-            When None and api_key is also None, falls back to the ambient
-            AuthenticationContext bound by ``authentication_scope(...)`` for
-            the resolved model's provider, before the env-credential path.
         protocol: Wire format protocol for compatible APIs (e.g., "openresponses",
                   "chatcompletions"). Use with base_url for third-party compatible APIs.
         base_url: Custom base URL override. Use with protocol for compatible APIs,
@@ -211,8 +199,6 @@ def create_client(
         ModelNotFoundError: If no model found for the specified capability/provider.
         ClientNotFoundError: If no client registered for capability/provider/protocol.
         MissingCredentialsError: If required credentials are not configured.
-        MissingAuthenticationError: If an ambient AuthenticationContext is bound
-            but has no entry for the resolved model's provider.
         ValueError: If capability/operation cannot be inferred from model.
     """
     # Translation layer: convert deprecated capability to modality/operation
@@ -262,11 +248,6 @@ def create_client(
         raise ClientNotFoundError(modality=resolved_modality, provider=target)
     modality_client_class = _CLIENT_MAP[(resolved_modality, target)]
 
-    # Ambient fallback: only when neither auth nor api_key was passed and the
-    # provider is known. Explicit kwargs always win.
-    if auth is None and api_key is None and resolved_provider is not None:
-        auth = resolve_authentication(resolved_provider)
-
     # Auth resolution: BYOA for protocol path, credentials for provider path
     if resolved_protocol is not None and resolved_provider is None:
         if auth is not None:
@@ -295,14 +276,12 @@ def create_client(
 __all__ = [
     "APIKey",
     "Authentication",
-    "AuthenticationContext",
     "Capability",
     "CodeExecution",
     "Content",
     "Error",
     "Input",
     "Message",
-    "MissingAuthenticationError",
     "Modality",
     "Model",
     "Operation",
@@ -318,7 +297,6 @@ def create_client(
     "WebSearch",
     "XSearch",
     "audio",
-    "authentication_scope",
     "create_client",
     "documents",
     "get_model",

src/celeste/auth.py

@@ -1,14 +1,8 @@
 """Authentication methods for Celeste providers."""
 
 from abc import ABC, abstractmethod
-from collections.abc import Iterator, Mapping
-from contextlib import contextmanager
-from contextvars import ContextVar
 
-from pydantic import BaseModel, ConfigDict, SecretStr, field_validator
-
-from celeste.core import Provider
-from celeste.exceptions import MissingAuthenticationError
+from pydantic import BaseModel, SecretStr, field_validator
 
 # Module-level registry (same pattern as _clients and _models)
 _auth_classes: dict[str, type["Authentication"]] = {}
@@ -92,73 +86,11 @@ def get_auth_class(auth_type: str) -> type[Authentication]:
     return _auth_classes[auth_type]
 
 
-class AuthenticationContext(BaseModel):
-    """Per-provider authentication bound to an async scope."""
-
-    # Frozen: asyncio.gather siblings share the context snapshot by reference,
-    # so mutability would cause silent cross-task credential bleed.
-    model_config = ConfigDict(frozen=True, arbitrary_types_allowed=True)
-
-    entries: Mapping[Provider, Authentication]
-
-
-_current_context: ContextVar[AuthenticationContext | None] = ContextVar(
-    "celeste.auth.current_context",
-    default=None,
-)
-
-
-@contextmanager
-def authentication_scope(
-    context: AuthenticationContext | None,
-) -> Iterator[None]:
-    """Bind an authentication context for the current async scope.
-
-    Within the ``with`` block, calls to ``celeste.<modality>.<method>(...)``
-    that don't pass an explicit ``auth=`` or ``api_key=`` resolve their
-    authentication from the bound context using the resolved model's provider.
-
-    Args:
-        context: The AuthenticationContext to bind, or None to clear any
-            outer binding for the duration of the block.
-    """
-    token = _current_context.set(context)
-    try:
-        yield
-    finally:
-        _current_context.reset(token)
-
-
-def resolve_authentication(provider: Provider) -> Authentication | None:
-    """Look up the provider in the current ambient context.
-
-    Args:
-        provider: The provider to look up.
-
-    Returns:
-        The bound Authentication, or None if no ambient context is active.
-
-    Raises:
-        MissingAuthenticationError: A scope is bound but has no authentication
-            for the requested provider.
-    """
-    context = _current_context.get()
-    if context is None:
-        return None
-    auth = context.entries.get(provider)
-    if auth is None:
-        raise MissingAuthenticationError(provider)
-    return auth
-
-
 __all__ = [
     "APIKey",
     "AuthHeader",
     "Authentication",
-    "AuthenticationContext",
     "NoAuth",
-    "authentication_scope",
     "get_auth_class",
     "register_auth",
-    "resolve_authentication",
 ]

src/celeste/exceptions.py

@@ -2,8 +2,6 @@
 
 from typing import Any
 
-from celeste.core import Provider
-
 
 class Error(Exception):
     """Base exception for all Celeste errors."""
@@ -235,14 +233,6 @@ def __init__(self, provider: str) -> None:
         )
 
 
-class MissingAuthenticationError(CredentialsError):
-    """Raised when authentication cannot be resolved for a provider."""
-
-    def __init__(self, provider: Provider) -> None:
-        self.provider = provider
-        super().__init__(f"No authentication configured for provider {provider.value}")
-
-
 class InvalidToolError(ValidationError):
     """Raised when a tool item is not a Tool instance or dict."""
 
@@ -273,7 +263,6 @@ class UnsupportedParameterWarning(UserWarning):
     "ConstraintViolationError",
     "Error",
     "InvalidToolError",
-    "MissingAuthenticationError",
     "MissingCredentialsError",
     "MissingDependencyError",
     "ModalityNotFoundError",