diff --git a/packages/open-workflow-diagram-editor/src/core/schemaToFormFields.ts b/packages/open-workflow-diagram-editor/src/core/schemaToFormFields.ts
index 8c089b1c..7ab078b3 100644
--- a/packages/open-workflow-diagram-editor/src/core/schemaToFormFields.ts
+++ b/packages/open-workflow-diagram-editor/src/core/schemaToFormFields.ts
@@ -15,6 +15,7 @@
  */
 
 import type { DereferencedSchema } from "./schemaFilter";
+import type { ContentFormat } from "./workflowSdk";
 
 /**
  * A single form field descriptor produced by walking a task's JSON Schema.
@@ -107,7 +108,7 @@ export interface MapField extends FieldBase {
 
 export interface JsonField extends FieldBase {
   kind: "json";
-  format: "json" | "yaml";
+  format: ContentFormat;
 }
 
 export interface OneOfField extends FieldBase {
@@ -313,7 +314,7 @@ export function schemaToFormFields(
   defs?: Record<string, unknown>,
   requiredSet?: Set<string>,
   path = "",
-  format: "json" | "yaml" = "yaml",
+  format: ContentFormat = "yaml",
 ): FormFieldDescriptor[] {
   const fields: FormFieldDescriptor[] = [];
 
@@ -636,7 +637,7 @@ function buildOneOfVariants(
   candidates: unknown[],
   defs: Record<string, unknown> | undefined,
   parentPath: string,
-  format: "json" | "yaml" = "yaml",
+  format: ContentFormat = "yaml",
 ): OneOfVariant[] {
   const leafPath = parentPath || "__leaf__";
 
diff --git a/packages/open-workflow-diagram-editor/src/core/schemaWalker.ts b/packages/open-workflow-diagram-editor/src/core/schemaWalker.ts
index 5a78968c..d299560b 100644
--- a/packages/open-workflow-diagram-editor/src/core/schemaWalker.ts
+++ b/packages/open-workflow-diagram-editor/src/core/schemaWalker.ts
@@ -17,6 +17,7 @@
 import { GraphNodeType } from "@openworkflowspec/sdk";
 import { getSchemaForDefinition } from "./schemaFilter";
 import { schemaToFormFields, FormFieldDescriptor } from "./schemaToFormFields";
+import type { ContentFormat } from "./workflowSdk";
 
 // ---------------------------------------------------------------------------
 // Node-type → schema definition-name mapping
@@ -60,7 +61,7 @@ const _fieldCache = new Map<string, FormFieldDescriptor[]>();
  */
 export function getFormFieldsForNodeType(
   nodeType: string,
-  format: "json" | "yaml" = "yaml",
+  format: ContentFormat = "yaml",
 ): FormFieldDescriptor[] {
   const cacheKey = `${nodeType}:${format}`;
   const cached = _fieldCache.get(cacheKey);
diff --git a/packages/open-workflow-diagram-editor/src/side-panel/forms/customFields/StringControl.tsx b/packages/open-workflow-diagram-editor/src/side-panel/forms/customFields/StringControl.tsx
index a0a27ab7..febc13d0 100644
--- a/packages/open-workflow-diagram-editor/src/side-panel/forms/customFields/StringControl.tsx
+++ b/packages/open-workflow-diagram-editor/src/side-panel/forms/customFields/StringControl.tsx
@@ -15,7 +15,7 @@
  */
 
 import * as React from "react";
-import { Controller, useFormContext, useFormState } from "react-hook-form";
+import { Controller } from "react-hook-form";
 import { Input } from "../ui/input";
 import type { StringField } from "../../../core/schemaToFormFields";
 import { useTaskFormContext } from "../taskFormContext";
@@ -41,70 +41,32 @@ export function StringControl({ field, id }: StringControlProps) {
 }
 
 function SingleLineStringControl({ field, id }: StringControlProps) {
-  const { control, getValues, getFieldState } = useFormContext<Record<string, unknown>>();
   const { isReadOnly } = useTaskFormContext();
   const errorMessage = useFieldError(field.path);
-  const { defaultValues } = useFormState({ control });
 
   const placeholder = field.placeholder ?? (field.isRuntimeExpression ? "${...}" : undefined);
 
-  // Compute the initial display value.
-  const [inputValue, setInputValue] = React.useState<string>(() => {
-    const live = getValues(field.path as never) as unknown;
-    const wasDirtied = getFieldState(field.path as never).isDirty;
-    // Stale defaultValues restoration after a kind-boundary switch
-    if (typeof live === "string" && !wasDirtied) {
-      const isRe = /^\s*\$\{.+\}\s*$/.test(live);
-      if (isRe !== field.isRuntimeExpression) {
-        return "";
-      }
-    }
-    // Show the live string value, or empty if not a string.
-    return typeof live === "string" ? live : "";
-  });
-
-  // Reset when the task changes (defaultValues identity) or path/isRuntimeExpression changes.
-  const prevDefaultValuesRef = React.useRef(defaultValues);
-  const prevPathRef = React.useRef(field.path);
-  const prevIsReRef = React.useRef(field.isRuntimeExpression);
-  React.useEffect(() => {
-    const pathOrKindChanged =
-      field.path !== prevPathRef.current || field.isRuntimeExpression !== prevIsReRef.current;
-    if (defaultValues === prevDefaultValuesRef.current && !pathOrKindChanged) return;
-    prevDefaultValuesRef.current = defaultValues;
-    prevPathRef.current = field.path;
-    prevIsReRef.current = field.isRuntimeExpression;
-    // Re-derive from the new task state — same logic as the useState initialiser.
-    const live = getValues(field.path as never) as unknown;
-    const wasDirtied = getFieldState(field.path as never).isDirty;
-    if (typeof live === "string" && !wasDirtied) {
-      const isRe = /^\s*\$\{.+\}\s*$/.test(live);
-      if (isRe !== field.isRuntimeExpression) {
-        setInputValue("");
-        return;
-      }
-    }
-    setInputValue(typeof live === "string" ? live : "");
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [defaultValues, field.path, field.isRuntimeExpression]);
-
   return (
     <Controller
       name={field.path}
-      control={control}
-      render={({ field: rhfField }) => {
-        const handleChange = (e: React.ChangeEvent<HTMLInputElement>) => {
-          const val = e.target.value;
-          setInputValue(val);
-          rhfField.onChange(val);
-        };
+      render={({ field: rhfField, fieldState }) => {
+        const live = rhfField.value as unknown;
+        let inputValue = typeof live === "string" ? live : "";
+
+        if (typeof live === "string" && !fieldState.isDirty) {
+          const isRuntimeExpression = /^\s*\$\{.+\}\s*$/.test(live);
+
+          if (isRuntimeExpression !== field.isRuntimeExpression) {
+            inputValue = "";
+          }
+        }
 
         return (
           <FieldWithError errorMessage={errorMessage}>
             <Input
               id={id}
               value={inputValue}
-              onChange={handleChange}
+              onChange={rhfField.onChange}
               onBlur={rhfField.onBlur}
               disabled={isReadOnly}
               readOnly={isReadOnly}
diff --git a/packages/open-workflow-diagram-editor/src/side-panel/forms/customFields/StructuredValueField.tsx b/packages/open-workflow-diagram-editor/src/side-panel/forms/customFields/StructuredValueField.tsx
index 1b9bd5ce..77aae1be 100644
--- a/packages/open-workflow-diagram-editor/src/side-panel/forms/customFields/StructuredValueField.tsx
+++ b/packages/open-workflow-diagram-editor/src/side-panel/forms/customFields/StructuredValueField.tsx
@@ -19,6 +19,7 @@ import { Controller, useFormContext, useFormState } from "react-hook-form";
 import { dump, load } from "js-yaml";
 import { Textarea } from "../ui/textarea";
 import type { JsonField } from "../../../core/schemaToFormFields";
+import type { ContentFormat } from "../../../core/workflowSdk";
 import { useTaskFormContext, getNestedValue } from "../taskFormContext";
 import { useFieldError, FieldWithError } from "./fieldHelpers";
 
@@ -31,7 +32,7 @@ export type StructuredValueFieldProps = {
   id?: string | undefined;
 };
 
-function valueToText(value: unknown, format: "json" | "yaml"): string {
+function valueToText(value: unknown, format: ContentFormat): string {
   if (value === undefined || value === null) return "";
   if (typeof value === "string") return value;
   try {
@@ -43,7 +44,7 @@ function valueToText(value: unknown, format: "json" | "yaml"): string {
   }
 }
 
-function parseText(text: string, format: "json" | "yaml"): unknown {
+function parseText(text: string, format: ContentFormat): unknown {
   if (format === "json") {
     return JSON.parse(text);
   }
@@ -104,6 +105,12 @@ export function StructuredValueField({ field, id }: StructuredValueFieldProps) {
       return;
     }
     setText(valueToText(fromDefault, field.format));
+    // The effect intentionally reads `prevDefaultValuesRef`, `prevFormatRef`,
+    // and `prevPathRef` as mutable ref containers — refs are stable objects and
+    // must NOT be in the dependency array (they never change identity, so adding
+    // them would not trigger the effect; and their `.current` mutations are the
+    // side-effect, not the trigger). The deps are exactly the reactive values
+    // that should re-run the effect: `defaultValues`, `field.format`, `field.path`.
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [defaultValues, field.format, field.path]);