diff --git a/.changeset/fix-deterministic-request-id.md b/.changeset/fix-deterministic-request-id.md
new file mode 100644
index 000000000..89cea3661
--- /dev/null
+++ b/.changeset/fix-deterministic-request-id.md
@@ -0,0 +1,5 @@
+---
+"openapi-fetch": patch
+---
+
+Replace `Math.random()` with a monotonic counter in `randomID()`. `Math.random()` is a non-deterministic side effect that can interfere with frameworks that cache or deduplicate `fetch()` calls (e.g. Next.js React Server Components). The counter produces unique IDs within a process while being deterministic across runs.
diff --git a/packages/openapi-fetch/src/index.js b/packages/openapi-fetch/src/index.js
index 4c7250fb0..d067fd107 100644
--- a/packages/openapi-fetch/src/index.js
+++ b/packages/openapi-fetch/src/index.js
@@ -9,12 +9,17 @@ const supportsRequestInitExt = () => {
   );
 };
 
+/** Counter for deterministic request ID generation */
+let _idCounter = 0;
+
 /**
- * Returns a cheap, non-cryptographically-secure random ID
- * Courtesy of @imranbarbhuiya (https://github.com/imranbarbhuiya)
+ * Returns a cheap, non-cryptographically-secure unique ID.
+ * Uses a monotonic counter instead of Math.random() so IDs are
+ * deterministic within a process, which is compatible with
+ * frameworks that cache or deduplicate fetch calls (e.g. Next.js).
  */
 export function randomID() {
-  return Math.random().toString(36).slice(2, 11);
+  return (++_idCounter).toString(36);
 }
 
 /**