diff --git a/CHANGELOG.md b/CHANGELOG.md
index d2738e444c..3f7364fc48 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
 - macOS: cache VM regions for FP validation in the new unwinder. ([#1634](https://github.com/getsentry/sentry-native/pull/1634))
 - Linux: remove dependency on `stdio` in the unwinder pointer validation code to reduce exposure to async-signal-unsafe functions. ([#1637](https://github.com/getsentry/sentry-native/pull/1637))
 - macOS: replace sandbox-incompatible IPC primitives (`sem_open`, `shm_open`, `fork`) with sandbox-safe alternatives (`pthread_mutex`, file-backed `mmap`, `posix_spawn`) so the native backend works inside App Sandbox. ([#1644](https://github.com/getsentry/sentry-native/pull/1644))
+- Fix minidump UUID byte order (swap GUID fields to match RSDS format) and use `int64` for image sizes to support modules larger than 2 GB. ([#1651](https://github.com/getsentry/sentry-native/pull/1651))
 
 ## 0.13.6
 
diff --git a/src/backends/native/minidump/sentry_minidump_macos.c b/src/backends/native/minidump/sentry_minidump_macos.c
index ee28419305..bde715c795 100644
--- a/src/backends/native/minidump/sentry_minidump_macos.c
+++ b/src/backends/native/minidump/sentry_minidump_macos.c
@@ -1,4 +1,5 @@
 #include "sentry_boot.h"
+#include "sentry_utils.h"
 
 #if defined(SENTRY_PLATFORM_MACOS)
 
@@ -243,8 +244,11 @@ write_cv_record(
     cv_record->cv_signature = CV_SIGNATURE_RSDS;
     cv_record->age = 0; // Not used for Mach-O
 
-    // Copy UUID
+    // Copy UUID with byte-swap for GUID format.
+    // Mach-O LC_UUID is big-endian (RFC 4122), but the RSDS CV record uses
+    // Windows GUID layout where the first 3 fields are little-endian.
     memcpy(cv_record->signature, uuid, 16);
+    sentry__uuid_swap_guid_bytes(cv_record->signature);
 
     // Copy module path
     memcpy(cv_record->pdb_file_name, module_path, path_len + 1);
diff --git a/src/backends/native/sentry_crash_daemon.c b/src/backends/native/sentry_crash_daemon.c
index fea4fe03a7..6fcbd0af6a 100644
--- a/src/backends/native/sentry_crash_daemon.c
+++ b/src/backends/native/sentry_crash_daemon.c
@@ -29,7 +29,6 @@
 #include <time.h>
 
 #if defined(SENTRY_PLATFORM_UNIX)
-#    include <arpa/inet.h>
 #    include <dirent.h>
 #    include <dlfcn.h>
 #    include <errno.h>
@@ -1171,13 +1170,7 @@ capture_modules_from_proc_maps(sentry_crash_context_t *ctx)
             mod->name, mod->uuid, sizeof(mod->uuid));
 
         // Convert to little-endian GUID format for Sentry debug_id
-        // (same byte swapping as sentry_modulefinder_linux.c)
-        uint32_t *a = (uint32_t *)mod->uuid;
-        *a = htonl(*a);
-        uint16_t *b = (uint16_t *)(mod->uuid + 4);
-        *b = htons(*b);
-        uint16_t *c = (uint16_t *)(mod->uuid + 6);
-        *c = htons(*c);
+        sentry__uuid_swap_guid_bytes(mod->uuid);
 
         SENTRY_DEBUGF("Captured module: %s base=0x%llx size=0x%llx", mod->name,
             (unsigned long long)mod->base_address,
@@ -2092,9 +2085,8 @@ build_native_crash_event(
             sentry_value_set_by_key(
                 image, "image_addr", sentry_value_new_string(addr_buf));
 
-            // Set image_size as int32 (modules > 2GB are extremely rare)
             sentry_value_set_by_key(image, "image_size",
-                sentry_value_new_int32((int32_t)mod->size));
+                sentry_value_new_int64((int64_t)mod->size));
 
 #if defined(SENTRY_PLATFORM_WINDOWS)
             // Set code_id for PE modules (TimeDateStamp + SizeOfImage)
diff --git a/src/modulefinder/sentry_modulefinder_linux.c b/src/modulefinder/sentry_modulefinder_linux.c
index a826bb7bf3..8219d0cf72 100644
--- a/src/modulefinder/sentry_modulefinder_linux.c
+++ b/src/modulefinder/sentry_modulefinder_linux.c
@@ -10,7 +10,6 @@
 #include "sentry_utils.h"
 #include "sentry_value.h"
 
-#include <arpa/inet.h>
 #include <elf.h>
 #include <fcntl.h>
 #include <string.h>
@@ -493,13 +492,7 @@ sentry__procmaps_read_ids_from_elf(
     // https://getsentry.github.io/symbolicator/advanced/symbol-server-compatibility/#identifiers
     // in particular, the debug_id is a `little-endian GUID`, so we have
     // to do appropriate byte-flipping
-    char *uuid_bytes = uuid.bytes;
-    uint32_t *a = (uint32_t *)uuid_bytes;
-    *a = htonl(*a);
-    uint16_t *b = (uint16_t *)(uuid_bytes + 4);
-    *b = htons(*b);
-    uint16_t *c = (uint16_t *)(uuid_bytes + 6);
-    *c = htons(*c);
+    sentry__uuid_swap_guid_bytes(uuid.bytes);
 
     sentry_value_set_by_key(value, "debug_id", sentry__value_new_uuid(&uuid));
     return true;
diff --git a/src/sentry_utils.h b/src/sentry_utils.h
index 75ea87d4c5..c74c293b4a 100644
--- a/src/sentry_utils.h
+++ b/src/sentry_utils.h
@@ -24,6 +24,34 @@
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
 #define MAX(a, b) ((a) > (b) ? (a) : (b))
 
+/**
+ * Byte-swap the first three GUID fields (Data1, Data2, Data3) of a 16-byte
+ * UUID in place.  This converts between RFC 4122 (big-endian) and Windows
+ * mixed-endian GUID layout, which is used by RSDS CodeView records and Sentry
+ * debug-id strings.
+ */
+static inline void
+sentry__uuid_swap_guid_bytes(void *uuid)
+{
+    uint8_t *p = (uint8_t *)uuid;
+    uint8_t t;
+    // Swap Data1 (4 bytes)
+    t = p[0];
+    p[0] = p[3];
+    p[3] = t;
+    t = p[1];
+    p[1] = p[2];
+    p[2] = t;
+    // Swap Data2 (2 bytes)
+    t = p[4];
+    p[4] = p[5];
+    p[5] = t;
+    // Swap Data3 (2 bytes)
+    t = p[6];
+    p[6] = p[7];
+    p[7] = t;
+}
+
 #if defined(_MSC_VER) && !defined(__clang__)
 #    define UNREACHABLE(reason) assert(!reason)
 #else