diff --git a/changelog.d/10392-fetch-json-key-order.md b/changelog.d/10392-fetch-json-key-order.md
new file mode 100644
index 0000000000..23a793a7be
--- /dev/null
+++ b/changelog.d/10392-fetch-json-key-order.md
@@ -0,0 +1,5 @@
+### Fixed
+
+- `Request.json()` and `Response.json()` now preserve JSON document order for
+  non-index object keys while retaining JavaScript's numeric-key ordering
+  (#10392, PR #11049).
diff --git a/crates/perry-stdlib/src/fetch/mod.rs b/crates/perry-stdlib/src/fetch/mod.rs
index c98dbc2e0e..a72f82bcbc 100644
--- a/crates/perry-stdlib/src/fetch/mod.rs
+++ b/crates/perry-stdlib/src/fetch/mod.rs
@@ -3,10 +3,7 @@
 //! Native implementation of the 'node-fetch' npm package using reqwest.
 //! Provides fetch() function for making HTTP requests.
 
-use perry_runtime::{
-    js_array_alloc, js_array_push, js_object_alloc, js_object_set_field, js_object_set_keys,
-    js_string_from_bytes, JSValue, StringHeader,
-};
+use perry_runtime::{js_string_from_bytes, JSValue, StringHeader};
 use std::cell::Cell;
 use std::collections::HashMap;
 use std::sync::Mutex;
@@ -1100,47 +1097,14 @@ pub unsafe extern "C" fn js_fetch_response_text(handle: f64) -> *mut perry_runti
     promise
 }
 
-/// Convert serde_json::Value to JSValue
-unsafe fn json_value_to_jsvalue(value: &serde_json::Value) -> JSValue {
-    match value {
-        serde_json::Value::Null => JSValue::null(),
-        serde_json::Value::Bool(b) => JSValue::bool(*b),
-        serde_json::Value::Number(n) => {
-            if let Some(f) = n.as_f64() {
-                JSValue::number(f)
-            } else if let Some(i) = n.as_i64() {
-                JSValue::number(i as f64)
-            } else {
-                JSValue::number(0.0)
-            }
-        }
-        serde_json::Value::String(s) => {
-            let ptr = js_string_from_bytes(s.as_ptr(), s.len() as u32);
-            JSValue::string_ptr(ptr)
-        }
-        serde_json::Value::Array(arr) => {
-            let js_arr = js_array_alloc(arr.len() as u32);
-            for item in arr {
-                js_array_push(js_arr, json_value_to_jsvalue(item));
-            }
-            JSValue::object_ptr(js_arr as *mut u8)
-        }
-        serde_json::Value::Object(obj) => {
-            let js_obj = js_object_alloc(0, obj.len() as u32);
-            // Create keys array for property names
-            let keys_arr = js_array_alloc(obj.len() as u32);
-            for (idx, (key, val)) in obj.iter().enumerate() {
-                // Add key to keys array
-                let key_ptr = js_string_from_bytes(key.as_ptr(), key.len() as u32);
-                js_array_push(keys_arr, JSValue::string_ptr(key_ptr));
-                // Set field value
-                js_object_set_field(js_obj, idx as u32, json_value_to_jsvalue(val));
-            }
-            // Associate keys with object
-            js_object_set_keys(js_obj, keys_arr);
-            JSValue::object_ptr(js_obj as *mut u8)
-        }
-    }
+/// Parse a Fetch body with the runtime's `JSON.parse` implementation. Besides
+/// matching JavaScript number and error semantics, this preserves document
+/// order for non-index object keys; `serde_json::Value` uses a sorted map in
+/// this build and silently reordered them (#10392).
+unsafe fn parse_json_body(body: &[u8]) -> Result<JSValue, f64> {
+    let text = String::from_utf8_lossy(body);
+    let text_ptr = js_string_from_bytes(text.as_ptr(), text.len() as u32);
+    perry_runtime::json::js_json_parse_result(text_ptr)
 }
 
 /// Get response body as JSON (parses and returns proper JS object)
@@ -1161,19 +1125,15 @@ pub unsafe extern "C" fn js_fetch_response_json(handle: f64) -> *mut perry_runti
         }
     };
 
-    // Convert body to string and parse as JSON. Resolve the promise
-    // synchronously — see comment on `js_fetch_response_text`.
-    let text = String::from_utf8_lossy(&body).to_string();
-    match serde_json::from_str::<serde_json::Value>(&text) {
-        Ok(json_value) => {
-            let js_value = json_value_to_jsvalue(&json_value);
+    // Parse and resolve synchronously — see comment on
+    // `js_fetch_response_text`.
+    match parse_json_body(&body) {
+        Ok(js_value) => {
             let result_nan = f64::from_bits(js_value.bits());
             perry_runtime::js_promise_resolve(promise, result_nan);
         }
-        Err(e) => {
-            let err_msg = format!("JSON parse error: {}", e);
-            let err_nan = f64::from_bits(fetch_error_bits(&err_msg));
-            perry_runtime::js_promise_reject(promise, err_nan);
+        Err(error) => {
+            perry_runtime::js_promise_reject(promise, error);
         }
     }
 
@@ -1918,15 +1878,12 @@ pub unsafe extern "C" fn js_request_json(handle: f64) -> *mut perry_runtime::Pro
             return promise;
         }
     };
-    let text = String::from_utf8_lossy(&body).to_string();
-    match serde_json::from_str::<serde_json::Value>(&text) {
-        Ok(json_value) => {
-            let js_value = json_value_to_jsvalue(&json_value);
+    match parse_json_body(&body) {
+        Ok(js_value) => {
             perry_runtime::js_promise_resolve(promise, f64::from_bits(js_value.bits()));
         }
-        Err(e) => {
-            let err_nan = f64::from_bits(fetch_error_bits(&format!("JSON parse error: {}", e)));
-            perry_runtime::js_promise_reject(promise, err_nan);
+        Err(error) => {
+            perry_runtime::js_promise_reject(promise, error);
         }
     }
     promise
diff --git a/crates/perry-stdlib/src/fetch/tests.rs b/crates/perry-stdlib/src/fetch/tests.rs
index 11b5fa23e6..2139a8b90e 100644
--- a/crates/perry-stdlib/src/fetch/tests.rs
+++ b/crates/perry-stdlib/src/fetch/tests.rs
@@ -1,5 +1,20 @@
 use super::*;
 
+#[test]
+fn fetch_json_preserves_document_key_order() {
+    let source = br#"{"title":"t","permission":[],"zeta":1,"10":"ten","2":"two"}"#;
+    let parsed = unsafe { parse_json_body(source) }.expect("valid JSON body");
+    let output =
+        unsafe { perry_runtime::json::js_json_stringify(f64::from_bits(parsed.bits()), 0) };
+    assert!(!output.is_null());
+    let output = unsafe { perry_ffi::JsString::from_raw(output.cast::<perry_ffi::StringHeader>()) };
+    let bytes = perry_ffi::read_bytes(output).expect("JSON.stringify returned a string");
+    assert_eq!(
+        bytes,
+        br#"{"2":"two","10":"ten","title":"t","permission":[],"zeta":1}"#
+    );
+}
+
 /// #8546: Coop hosts each in-process deployment on its own dedicated Perry
 /// thread. The Fetch scanner registry is thread-local, so a process-global
 /// registration latch makes the first Next application safe and leaves the
diff --git a/scripts/unrooted_local_shape_baseline.json b/scripts/unrooted_local_shape_baseline.json
index bc1153f514..1a216a0ea3 100644
--- a/scripts/unrooted_local_shape_baseline.json
+++ b/scripts/unrooted_local_shape_baseline.json
@@ -34,7 +34,6 @@
     "crates/perry-stdlib/src/events/module_helpers.rs": 1,
     "crates/perry-stdlib/src/events/once_helpers.rs": 1,
     "crates/perry-stdlib/src/events/warnings.rs": 1,
-    "crates/perry-stdlib/src/fetch/mod.rs": 6,
     "crates/perry-stdlib/src/lodash.rs": 21,
     "crates/perry-stdlib/src/querystring.rs": 2,
     "crates/perry-stdlib/src/readline/mod.rs": 4,
@@ -65,5 +64,5 @@
     "crates/perry-stdlib/src/zlib.rs": 3
   },
   "schema_version": 3,
-  "total": 390
+  "total": 384
 }
diff --git a/test-files/test_gap_10392_fetch_json_key_order.ts b/test-files/test_gap_10392_fetch_json_key_order.ts
new file mode 100644
index 0000000000..9250c83dfc
--- /dev/null
+++ b/test-files/test_gap_10392_fetch_json_key_order.ts
@@ -0,0 +1,12 @@
+const body = '{"title":"t","permission":[],"zeta":1,"10":"ten","2":"two"}';
+
+const request = await new Request("http://example.com/", {
+  method: "POST",
+  body,
+}).json();
+console.log("request json", JSON.stringify(request));
+console.log("request keys", JSON.stringify(Object.keys(request)));
+
+const response = await new Response(body).json();
+console.log("response json", JSON.stringify(response));
+console.log("response keys", JSON.stringify(Object.keys(response)));