diff --git a/apps/api/src/services/SegmentService.ts b/apps/api/src/services/SegmentService.ts
index 6c1a7224..9d8040f3 100644
--- a/apps/api/src/services/SegmentService.ts
+++ b/apps/api/src/services/SegmentService.ts
@@ -818,7 +818,10 @@ export class SegmentService {
     value: unknown,
     unit?: 'days' | 'hours' | 'minutes',
   ): Prisma.ContactWhereInput {
-    const path = jsonPath.split('.');
+    // Use the entire jsonPath as a single path element.
+    // Contact data is a flat JSON object, so field names like "prefix.key"
+    // must be treated as literal keys, not nested paths.
+    const path = [jsonPath];
 
     switch (operator) {
       case 'equals':
diff --git a/apps/api/src/services/WorkflowExecutionService.ts b/apps/api/src/services/WorkflowExecutionService.ts
index a418c815..8426c85d 100644
--- a/apps/api/src/services/WorkflowExecutionService.ts
+++ b/apps/api/src/services/WorkflowExecutionService.ts
@@ -1111,7 +1111,15 @@ export class WorkflowExecutionService {
       normalizedField = field.substring(8); // Remove "contact." prefix, leaving "data.X"
     }
 
-    const parts = normalizedField.split('.');
+    // Split only on the first dot to separate the top-level field (e.g., "data")
+    // from the custom field name. This preserves dots in custom field names
+    // (e.g., "data.prefix.key" → ["data", "prefix.key"]).
+    const firstDotIndex = normalizedField.indexOf('.');
+    const parts =
+      firstDotIndex === -1
+        ? [normalizedField]
+        : [normalizedField.substring(0, firstDotIndex), normalizedField.substring(firstDotIndex + 1)];
+
     let value: unknown = data;
 
     for (const part of parts) {
diff --git a/packages/shared/src/template.ts b/packages/shared/src/template.ts
index b1198b24..9abdce7b 100644
--- a/packages/shared/src/template.ts
+++ b/packages/shared/src/template.ts
@@ -13,13 +13,24 @@ export function renderTemplate(template: string, variables: Record<string, unkno
     const [mainKey, defaultValue] = key.split('??').map((s: string) => s.trim());
 
     // Handle nested property access (e.g., data.firstName)
+    // Uses recursive first-dot splitting so that literal dots in custom field
+    // names (e.g., "prefix.key") are resolved correctly: direct key lookup is
+    // tried before descending into nested objects.
     const getValue = (obj: Record<string, unknown>, path: string): unknown => {
-      return path.split('.').reduce((current: Record<string, unknown> | unknown, key) => {
-        if (current && typeof current === 'object' && !Array.isArray(current)) {
-          return (current as Record<string, unknown>)[key];
-        }
+      if (path in obj) {
+        return obj[path];
+      }
+      const firstDotIndex = path.indexOf('.');
+      if (firstDotIndex === -1) {
         return undefined;
-      }, obj);
+      }
+      const firstKey = path.substring(0, firstDotIndex);
+      const rest = path.substring(firstDotIndex + 1);
+      const next = obj[firstKey];
+      if (next && typeof next === 'object' && !Array.isArray(next)) {
+        return getValue(next as Record<string, unknown>, rest);
+      }
+      return undefined;
     };
 
     // Try multiple lookup strategies