STATE-WP-0069 T04/T06: body metering and workplan-first state internals

Share LegacyWorkstreamIdBodyMixin across create schemas; meter POST /tasks/
and /decisions/ workstream_id bodies. State summary uses workplan flow;
NextStep dual-writes workplan_* fields alongside legacy workstream_*.

api/schemas/compat.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import uuid
+from typing import Any
 
 from pydantic import AliasChoices, Field, computed_field, model_validator
 
@@ -13,6 +14,20 @@ def workplan_id_field(*, default: uuid.UUID | None = None) -> uuid.UUID | None:
     )
 
 
+class LegacyWorkstreamIdBodyMixin:
+    """Detect POST/PUT bodies that used legacy ``workstream_id`` without ``workplan_id``."""
+
+    used_legacy_workstream_id: bool = Field(default=False, exclude=True)
+
+    @model_validator(mode="before")
+    @classmethod
+    def _detect_legacy_workstream_id(cls, data: Any) -> Any:
+        if isinstance(data, dict):
+            if data.get("workstream_id") is not None and data.get("workplan_id") is None:
+                return {**data, "used_legacy_workstream_id": True}
+        return data
+
+
 class WorkplanIdCompatMixin:
     """Accept ``workplan_id`` or legacy ``workstream_id`` on input; emit both on output."""
 
@@ -24,7 +39,7 @@ class WorkplanIdCompatMixin:
         return self.workplan_id
 
 
-class WorkplanIdCreateMixin:
+class WorkplanIdCreateMixin(LegacyWorkstreamIdBodyMixin):
     workplan_id: uuid.UUID | None = workplan_id_field(default=None)
 
     @model_validator(mode="after")

api/schemas/decision.py

@@ -4,11 +4,11 @@ from datetime import datetime
 from pydantic import BaseModel, ConfigDict, model_validator
 
 from api.models.decision import DecisionStatus, DecisionType
-from api.schemas.compat import OptionalWorkplanIdCompatMixin
+from api.schemas.compat import LegacyWorkstreamIdBodyMixin, OptionalWorkplanIdCompatMixin
 from pydantic import AliasChoices, Field
 
 
-class DecisionCreate(BaseModel):
+class DecisionCreate(LegacyWorkstreamIdBodyMixin, BaseModel):
     topic_id: uuid.UUID | None = None
     workplan_id: uuid.UUID | None = Field(
         default=None,

api/schemas/progress_event.py

@@ -2,18 +2,17 @@ import uuid
 from datetime import datetime
 from typing import Any
 
-from pydantic import AliasChoices, BaseModel, ConfigDict, Field, model_validator
+from pydantic import AliasChoices, BaseModel, ConfigDict, Field
 
-from api.schemas.compat import OptionalWorkplanIdCompatMixin
+from api.schemas.compat import LegacyWorkstreamIdBodyMixin, OptionalWorkplanIdCompatMixin
 
 
-class ProgressEventCreate(BaseModel):
+class ProgressEventCreate(LegacyWorkstreamIdBodyMixin, BaseModel):
     topic_id: uuid.UUID | None = None
     workplan_id: uuid.UUID | None = Field(
         default=None,
         validation_alias=AliasChoices("workplan_id", "workstream_id"),
     )
-    used_legacy_workstream_id: bool = Field(default=False, exclude=True)
     task_id: uuid.UUID | None = None
     decision_id: uuid.UUID | None = None
     event_type: str
@@ -22,14 +21,6 @@ class ProgressEventCreate(BaseModel):
     author: str | None = None
     session_id: str | None = None
 
-    @model_validator(mode="before")
-    @classmethod
-    def _detect_legacy_workstream_id(cls, data: Any) -> Any:
-        if isinstance(data, dict):
-            if data.get("workstream_id") is not None and data.get("workplan_id") is None:
-                return {**data, "used_legacy_workstream_id": True}
-        return data
-
 
 class ProgressEventRead(OptionalWorkplanIdCompatMixin, BaseModel):
     model_config = ConfigDict(from_attributes=True)

api/schemas/state.py

@@ -64,6 +64,9 @@ class NextStep(BaseModel):
     """
     type: str          # unblocked_task | resolved_decision | dependency_cleared
     domain: str | None = None
+    workplan_id: uuid.UUID | None = None
+    workplan_title: str | None = None
+    workplan_slug: str | None = None
     workstream_id: uuid.UUID | None = None
     workstream_title: str | None = None
     workstream_slug: str | None = None