From a0fb802bd2490713fbe0f5cd0823bb85fe7165df Mon Sep 17 00:00:00 2001
From: coyaSONG <66289470+coyaSONG@users.noreply.github.com>
Date: Sat, 18 Jul 2026 00:41:54 +0900
Subject: [PATCH] fix: serialize bigint values in stringifyCircular

---
 .changeset/tidy-bigint-inspection.md     | 5 +++++
 packages/effect/src/Inspectable.ts       | 2 ++
 packages/effect/test/Inspectable.test.ts | 6 ++++++
 3 files changed, 13 insertions(+)
 create mode 100644 .changeset/tidy-bigint-inspection.md

diff --git a/.changeset/tidy-bigint-inspection.md b/.changeset/tidy-bigint-inspection.md
new file mode 100644
index 00000000000..4d687ef8af4
--- /dev/null
+++ b/.changeset/tidy-bigint-inspection.md
@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+Handle bigint values in circular JSON serialization.
diff --git a/packages/effect/src/Inspectable.ts b/packages/effect/src/Inspectable.ts
index 9bab2d1e9c4..61f28482bd9 100644
--- a/packages/effect/src/Inspectable.ts
+++ b/packages/effect/src/Inspectable.ts
@@ -229,6 +229,8 @@ export const stringifyCircular = (obj: unknown, whitespace?: number | string | u
           : cache.push(value) && (redactableState.fiberRefs !== undefined && isRedactable(value)
             ? value[symbolRedactable](redactableState.fiberRefs)
             : value)
+        : typeof value === "bigint"
+        ? String(value) + "n"
         : value,
     whitespace
   )
diff --git a/packages/effect/test/Inspectable.test.ts b/packages/effect/test/Inspectable.test.ts
index 2170415c4e1..a1a9e2f227b 100644
--- a/packages/effect/test/Inspectable.test.ts
+++ b/packages/effect/test/Inspectable.test.ts
@@ -151,6 +151,12 @@ describe("Inspectable", () => {
     })
   })
 
+  describe("stringifyCircular", () => {
+    it("serializes bigint values", () => {
+      strictEqual(Inspectable.stringifyCircular({ value: 123n }), `{"value":"123n"}`)
+    })
+  })
+
   describe("toString", () => {
     it("primitives", () => {
       strictEqual(Inspectable.format(null), "null")