diff --git a/.changeset/brown-laws-rest.md b/.changeset/brown-laws-rest.md
new file mode 100644
index 0000000000..757ba89d87
--- /dev/null
+++ b/.changeset/brown-laws-rest.md
@@ -0,0 +1,5 @@
+---
+"@trigger.dev/core": patch
+---
+
+Fix: Handle circular references in flattenAttributes function
diff --git a/packages/core/src/v3/utils/flattenAttributes.ts b/packages/core/src/v3/utils/flattenAttributes.ts
index 7ef0a20d12..545b0184e6 100644
--- a/packages/core/src/v3/utils/flattenAttributes.ts
+++ b/packages/core/src/v3/utils/flattenAttributes.ts
@@ -1,10 +1,12 @@
 import { Attributes } from "@opentelemetry/api";
 
 export const NULL_SENTINEL = "$@null((";
+export const CIRCULAR_REFERENCE_SENTINEL = "$@circular((";
 
 export function flattenAttributes(
   obj: Record<string, unknown> | Array<unknown> | string | boolean | number | null | undefined,
-  prefix?: string
+  prefix?: string ,
+  seen: WeakSet<object> = new WeakSet()
 ): Attributes {
   const result: Attributes = {};
 
@@ -38,13 +40,25 @@ export function flattenAttributes(
     return result;
   }
 
+  // Check for circular reference
+  if (obj !== null && typeof obj === "object" && seen.has(obj)) {
+    result[prefix || ""] = CIRCULAR_REFERENCE_SENTINEL;
+    return result;
+  }
+
+  // Add object to seen set
+  if (obj !== null && typeof obj === "object") {
+    seen.add(obj);
+  }
+
+
   for (const [key, value] of Object.entries(obj)) {
     const newPrefix = `${prefix ? `${prefix}.` : ""}${Array.isArray(obj) ? `[${key}]` : key}`;
     if (Array.isArray(value)) {
       for (let i = 0; i < value.length; i++) {
         if (typeof value[i] === "object" && value[i] !== null) {
           // update null check here as well
-          Object.assign(result, flattenAttributes(value[i], `${newPrefix}.[${i}]`));
+          Object.assign(result, flattenAttributes(value[i], `${newPrefix}.[${i}]`,seen));
         } else {
           if (value[i] === null) {
             result[`${newPrefix}.[${i}]`] = NULL_SENTINEL;
@@ -55,7 +69,7 @@ export function flattenAttributes(
       }
     } else if (isRecord(value)) {
       // update null check here
-      Object.assign(result, flattenAttributes(value, newPrefix));
+      Object.assign(result, flattenAttributes(value, newPrefix, seen));
     } else {
       if (typeof value === "number" || typeof value === "string" || typeof value === "boolean") {
         result[newPrefix] = value;
@@ -135,8 +149,10 @@ export function unflattenAttributes(
     }
 
     const lastPart = parts[parts.length - 1];
+
     if (lastPart !== undefined) {
-      current[lastPart] = rehydrateNull(value);
+      current[lastPart] = rehydrateNull(rehydrateCircular(value));
+
     }
   }
 
@@ -153,6 +169,13 @@ export function unflattenAttributes(
   return result;
 }
 
+function rehydrateCircular(value: any): any {
+  if (value === CIRCULAR_REFERENCE_SENTINEL) {
+    return "[Circular Reference]";
+  }
+  return value;
+}
+
 export function primitiveValueOrflattenedAttributes(
   obj: Record<string, unknown> | Array<unknown> | string | boolean | number | undefined,
   prefix: string | undefined
diff --git a/packages/core/test/flattenAttributes.test.ts b/packages/core/test/flattenAttributes.test.ts
index 139d2311e3..4b00995163 100644
--- a/packages/core/test/flattenAttributes.test.ts
+++ b/packages/core/test/flattenAttributes.test.ts
@@ -156,6 +156,29 @@ describe("flattenAttributes", () => {
 
     expect(flattenAttributes(obj, "retry.byStatus")).toEqual(expected);
   });
+
+   it("handles circular references correctly", () => {
+    const user = { name: "Alice" };
+    user["blogPosts"] = [{ title: "Post 1", author: user }]; // Circular reference
+
+    const result = flattenAttributes(user);
+    expect(result).toEqual({
+      "name": "Alice",
+      "blogPosts.[0].title": "Post 1",
+      "blogPosts.[0].author": "$@circular((",
+    });
+  });
+
+  it("handles nested circular references correctly", () => {
+    const user = { name: "Bob" };
+    user["friends"] = [user]; // Circular reference
+
+    const result = flattenAttributes(user);
+    expect(result).toEqual({
+      "name": "Bob",
+      "friends.[0]": "$@circular((",
+    });
+  });
 });
 
 describe("unflattenAttributes", () => {
@@ -223,4 +246,18 @@ describe("unflattenAttributes", () => {
     };
     expect(unflattenAttributes(flattened)).toEqual(expected);
   });
+  
+  it("rehydrates circular references correctly", () => {
+    const flattened = {
+      "name": "Alice",
+      "blogPosts.[0].title": "Post 1",
+      "blogPosts.[0].author": "$@circular((",
+    };
+
+    const result = unflattenAttributes(flattened);
+    expect(result).toEqual({
+      name: "Alice",
+      blogPosts: [{ title: "Post 1", author: "[Circular Reference]" }],
+    });
+  });
 });