.

Author: TooTallNate

packages/core/src/observability.ts

@@ -48,42 +48,20 @@ const hydrateStepIO = <
 >(
   step: T
 ): T => {
-  // Handle both old format (array) and new format (object with args and closureVars)
-  let hydratedInput = step.input;
-
-  if (step.input) {
-    if (Array.isArray(step.input) && step.input.length) {
-      // Old format: input is an array of arguments
-      hydratedInput = hydrateStepArguments(
+  const hydratedInput = step.input
+    ? hydrateStepArguments(
         step.input,
         [],
         step.runId as string,
         globalThis,
         streamPrintRevivers
-      );
-    } else if (
-      typeof step.input === 'object' &&
-      'args' in step.input &&
-      Array.isArray(step.input.args) &&
-      step.input.args.length
-    ) {
-      // New format: input is { args: [...], closureVars: {...} }
-      hydratedInput = {
-        ...step.input,
-        args: hydrateStepArguments(
-          step.input.args,
-          [],
-          step.runId as string,
-          globalThis,
-          streamPrintRevivers
-        ),
-      };
-    }
-  }
+      )
+    : step.input;
 
   return {
     ...step,
-    input: hydratedInput,
+    input: 'args' in hydratedInput ? hydratedInput.args : hydratedInput,
+    // TODO: should we also render the closure vars for o11y?
     output: step.output
       ? hydrateStepReturnValue(step.output, globalThis, streamPrintRevivers)
       : step.output,

packages/core/src/runtime.ts

@@ -680,23 +680,7 @@ export const stepEntrypoint =
               workflowRunId
             );
 
-            // Handle both new format { args, closureVars } and legacy format (just args array)
-            let args: any[];
-            let closureVars: Record<string, any>;
-
-            if (
-              hydratedInput &&
-              typeof hydratedInput === 'object' &&
-              'args' in hydratedInput
-            ) {
-              // New format: { args, closureVars }
-              args = hydratedInput.args;
-              closureVars = hydratedInput.closureVars || {};
-            } else {
-              // Legacy format: just args array
-              args = hydratedInput;
-              closureVars = {};
-            }
+            const args = hydratedInput.args;
 
             span?.setAttributes({
               ...Attribute.StepArgumentsCount(args.length),
@@ -719,9 +703,9 @@ export const stepEntrypoint =
                     : `http://localhost:${port ?? 3000}`,
                 },
                 ops,
-                closureVars,
+                closureVars: hydratedInput.closureVars,
               },
-              () => stepFn(...args)
+              () => stepFn.apply(null, args)
             );
 
             result = dehydrateStepReturnValue(result, ops, workflowRunId);