feat: add EagerEval dataclass for frontend-side node evaluation

Add EagerEval to the V3 API schema, enabling nodes to declare
frontend-evaluated JSONata expressions. The frontend uses this to
display computation results as badges without a backend round-trip.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

comfy_api/latest/_io.py

@@ -1347,6 +1347,7 @@ class NodeInfoV1:
     price_badge: dict | None = None
     search_aliases: list[str]=None
     essentials_category: str=None
+    eager_eval: dict | None = None
 
 
 @dataclass
@@ -1413,6 +1414,35 @@ class PriceBadge:
         }
 
 
+@dataclass
+class EagerEval:
+    """Frontend-evaluated expression badge for pure-computation nodes.
+
+    When declared, the frontend evaluates the JSONata expression against
+    widget values whenever they change, displaying the result as a badge
+    without a backend round-trip.
+    """
+    expr: str | None = None
+    """Static JSONata expression (e.g. "a + b")."""
+    expr_widget: str | None = None
+    """Name of a widget whose value is the dynamic expression."""
+    engine: str = field(default="jsonata")
+
+    def validate(self) -> None:
+        if self.engine != "jsonata":
+            raise ValueError(f"Unsupported EagerEval.engine '{self.engine}'. Only 'jsonata' is supported.")
+        if not self.expr and not self.expr_widget:
+            raise ValueError("EagerEval requires either 'expr' or 'expr_widget'.")
+
+    def as_dict(self) -> dict[str, Any]:
+        d: dict[str, Any] = {"engine": self.engine}
+        if self.expr is not None:
+            d["expr"] = self.expr
+        if self.expr_widget is not None:
+            d["expr_widget"] = self.expr_widget
+        return d
+
+
 @dataclass
 class Schema:
     """Definition of V3 node properties."""
@@ -1470,6 +1500,8 @@ class Schema:
     """When True, all inputs from the prompt will be passed to the node as kwargs, even if not defined in the schema."""
     essentials_category: str | None = None
     """Optional category for the Essentials tab. Path-based like category field (e.g., 'Basic', 'Image Tools/Editing')."""
+    eager_eval: EagerEval | None = None
+    """Optional frontend-evaluated expression badge for pure-computation nodes."""
 
     def validate(self):
         '''Validate the schema:
@@ -1498,6 +1530,8 @@ class Schema:
             output.validate()
         if self.price_badge is not None:
             self.price_badge.validate()
+        if self.eager_eval is not None:
+            self.eager_eval.validate()
 
     def finalize(self):
         """Add hidden based on selected schema options, and give outputs without ids default ids."""
@@ -1577,6 +1611,7 @@ class Schema:
             price_badge=self.price_badge.as_dict(self.inputs) if self.price_badge is not None else None,
             search_aliases=self.search_aliases if self.search_aliases else None,
             essentials_category=self.essentials_category,
+            eager_eval=self.eager_eval.as_dict() if self.eager_eval is not None else None,
         )
         return info
 
@@ -2225,6 +2260,7 @@ __all__ = [
     "ImageCompare",
     "PriceBadgeDepends",
     "PriceBadge",
+    "EagerEval",
     "BoundingBox",
     "NodeReplace",
 ]