feat: deliver Python workflow client

src/wf_api/durable_context.py

@@ -5,25 +5,27 @@ from .service import WorkflowApi
 from .stores import WorkflowStores
 
 
-def require_workflow_stores(context: WorkflowOperationContext) -> WorkflowStores:
+def require_workflow_stores(
+    context: WorkflowOperationContext,
+    *,
+    drafts: bool = True,
+) -> WorkflowStores:
     """Return required stores or fail before constructing durable frontends.
 
     `WorkflowOperationContext` keeps stores optional for compatibility tests and
-    lightweight MCP surfaces. Durable API surfaces need all stores up front so a
-    run cannot start without somewhere to persist artifacts, drafts, and stopped
-    execution state.
+    lightweight MCP surfaces. Durable API surfaces need artifact/run stores up
+    front; a draft store is only required when draft APIs are enabled.
     """
     missing = []
     if context.artifact_store is None:
         missing.append("artifact_store")
-    if context.draft_workspace_store is None:
+    if drafts and context.draft_workspace_store is None:
         missing.append("draft_workspace_store")
     if context.run_store is None:
         missing.append("run_store")
     if missing:
         raise ValueError("durable workflow API requires stores: " + ", ".join(missing))
     assert context.artifact_store is not None
-    assert context.draft_workspace_store is not None
     assert context.run_store is not None
     return WorkflowStores(
         artifact_store=context.artifact_store,
@@ -32,10 +34,14 @@ def require_workflow_stores(context: WorkflowOperationContext) -> WorkflowStores
     )
 
 
-def durable_workflow_api(context: WorkflowOperationContext) -> WorkflowApi:
-    """Construct a WorkflowApi only after durable store dependencies exist."""
-    require_workflow_stores(context)
-    return WorkflowApi(context)
+def durable_workflow_api(
+    context: WorkflowOperationContext,
+    *,
+    drafts: bool = True,
+) -> WorkflowApi:
+    """Construct a durable API, optionally omitting the draft product surface."""
+    require_workflow_stores(context, drafts=drafts)
+    return WorkflowApi(context, drafts=drafts)
 
 
 __all__ = ["durable_workflow_api", "require_workflow_stores"]

src/wf_api/service.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from collections.abc import Mapping, Sequence
-from typing import Any, Literal, overload
+from typing import Any, Literal, cast, overload
 
 from wf_artifacts import ArtifactKind, compile_workflow_draft
 from wf_artifacts.drafts.models import DraftStep
@@ -56,6 +56,19 @@ from .operation_context import WorkflowOperationContext
 from .runs import TraceRangeLike, WorkflowRunApi
 
 
+class _DisabledDraftSurface:
+    """Placeholder that fails clearly if disabled draft methods are called.
+
+    Keeping this tiny seam avoids constructing draft services while preserving
+    the existing method layout on ``WorkflowApi`` for explicit draft callers.
+    """
+
+    def __getattr__(self, name: str) -> Any:
+        raise RuntimeError(
+            "workflow draft APIs are disabled; compose WorkflowApi with drafts=True"
+        )
+
+
 def _authoring_schema(
     value: object,
     *,
@@ -100,11 +113,26 @@ class WorkflowApi:
     callers share one operation surface without importing wf_mcp.
     """
 
-    def __init__(self, context: WorkflowOperationContext) -> None:
+    def __init__(
+        self,
+        context: WorkflowOperationContext,
+        *,
+        drafts: bool = True,
+    ) -> None:
         self.context = context
         self.capabilities = WorkflowCapabilityApi(context)
-        self.drafts = WorkflowDraftApi(context)
-        self.draft_authoring = WorkflowDraftAuthoringApi(context, self.drafts)
+        # ``drafts`` keeps server composition explicit: callers that omit draft
+        # storage must pass False, while the default preserves legacy direct
+        # WorkflowApi callers that use the draft service for validation only.
+        self.drafts_enabled = drafts
+        if self.drafts_enabled:
+            self.drafts = WorkflowDraftApi(context)
+            self.draft_authoring = WorkflowDraftAuthoringApi(context, self.drafts)
+        else:
+            self.drafts = cast(WorkflowDraftApi, _DisabledDraftSurface())
+            self.draft_authoring = cast(
+                WorkflowDraftAuthoringApi, _DisabledDraftSurface()
+            )
         self.artifacts = WorkflowArtifactApi(context)
         self.deployments = WorkflowDeploymentApi(context)
         self.runs = WorkflowRunApi(context)

src/wf_api/stores.py

@@ -18,7 +18,7 @@ class WorkflowStores:
     """Protocol-neutral persistence dependencies for workflow APIs."""
 
     artifact_store: WorkflowArtifactStore
-    draft_workspace_store: DraftWorkspaceStore
+    draft_workspace_store: DraftWorkspaceStore | None
     run_store: RunStore