refactor(settings): deprecate SAGEMAKER_* and drop two unused settings

SAGEMAKER_REGION, SAGEMAKER_ACCESS_KEY and SAGEMAKER_SECRET_KEY survive
only as a fallback for the S3_* credentials. They carry
Field(deprecated=...) now, so any read emits a DeprecationWarning naming
the replacement and the generated reference shows the notice. The S3
store is the one sanctioned reader; it silences that warning locally
because it already logs its own operator-facing one when the fallback
is actually used.

DEFAULT_MAX_HISTORY was referenced nowhere. RETRIEVERS_ENABLED was read by
no code at all, while two docs pages described it as an enforced
allow-list; both the setting and those claims are removed.

docsgpt/core/settings/agents.py

@@ -13,7 +13,6 @@ class AgentSettings(SettingsGroup):
     """What an agent may do per turn and how its context is kept within budget."""
 
     AGENT_NAME: str = Field(default="classic", description="Default agent type for agentless chats.")
-    DEFAULT_MAX_HISTORY: int = Field(default=150, description="Default number of history messages kept.")
     DEFAULT_AGENT_LIMITS: dict[str, int] = Field(
         default={"token_limit": 50000, "request_limit": 500},
         description="Per-agent default quotas: tokens and requests.",

docsgpt/core/settings/retrieval.py

@@ -15,13 +15,6 @@ class RetrievalSettings(SettingsGroup):
     VECTOR_STORE: Literal["faiss", "elasticsearch", "mongodb", "qdrant", "milvus", "pgvector"] = Field(
         default="faiss", description="Vector store backend."
     )
-    RETRIEVERS_ENABLED: list[str] = Field(
-        default=["classic", "default"],
-        description=(
-            "Retriever keys an agent may use; must match RetrieverCreator.retrievers registry keys, NOT the "
-            "legacy classic_rag label which never matched the registry."
-        ),
-    )
     RETRIEVAL_MAX_PARALLEL_SOURCES: int = Field(
         default=4,
         ge=1,

docsgpt/core/settings/storage.py

@@ -34,14 +34,17 @@ class StorageSettings(SettingsGroup):
     # Legacy AWS credentials from the retired SageMaker provider.
     SAGEMAKER_REGION: Optional[str] = Field(
         default=None,
+        deprecated="Set S3_REGION instead; the SAGEMAKER_* fallback will be removed.",
         description="Legacy AWS region from the retired SageMaker provider; deprecated fallback for S3_REGION.",
     )
     SAGEMAKER_ACCESS_KEY: Optional[str] = Field(
         default=None,
+        deprecated="Set S3_ACCESS_KEY_ID instead; the SAGEMAKER_* fallback will be removed.",
         description="Legacy AWS access key from the retired SageMaker provider; deprecated fallback for S3_ACCESS_KEY_ID.",
     )
     SAGEMAKER_SECRET_KEY: Optional[str] = Field(
         default=None,
+        deprecated="Set S3_SECRET_ACCESS_KEY instead; the SAGEMAKER_* fallback will be removed.",
         description=(
             "Legacy AWS secret key from the retired SageMaker provider; deprecated fallback for "
             "S3_SECRET_ACCESS_KEY."

docsgpt/storage/s3.py

@@ -4,6 +4,7 @@ import io
 import logging
 import os
 import posixpath
+import warnings
 from typing import BinaryIO, Callable, List, Optional, Tuple
 
 import boto3
@@ -30,9 +31,13 @@ class S3Storage(BaseStorage):
         secret_key = settings.S3_SECRET_ACCESS_KEY
         region = settings.S3_REGION
 
-        legacy_access = getattr(settings, "SAGEMAKER_ACCESS_KEY", None)
-        legacy_secret = getattr(settings, "SAGEMAKER_SECRET_KEY", None)
-        legacy_region = getattr(settings, "SAGEMAKER_REGION", None)
+        # The SAGEMAKER_* fields are marked deprecated on the model and warn on every read;
+        # this is the one sanctioned reader, and it raises its own operator-facing warning.
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
+            legacy_access = settings.SAGEMAKER_ACCESS_KEY
+            legacy_secret = settings.SAGEMAKER_SECRET_KEY
+            legacy_region = settings.SAGEMAKER_REGION
 
         used_legacy = (
             (not access_key and legacy_access)