diff --git a/core/libs/prx/libc/src/Formatting.cpp b/core/libs/prx/libc/src/Formatting.cpp
index b85e0eab2..38c54e381 100644
--- a/core/libs/prx/libc/src/Formatting.cpp
+++ b/core/libs/prx/libc/src/Formatting.cpp
@@ -4,6 +4,7 @@
 #include <cstdarg>
 #include "SceTypes.hpp"
 #include "prx/libc/include/VarArgsAbi.hpp"
+#include "prx/libc/include/FileStream.hpp"
 
 #ifdef _WIN32
 #include "prx/libc/include/WindowsFormatting.hpp"
@@ -11,6 +12,37 @@
 
 extern "C" {
 
+int APS5_VABI vfprintf_nid_postfix(FileStream* stream, const char* format, VaList* args) {
+    auto* native = GetNativeStream(stream);
+#ifdef _WIN32
+    std::string buffer;
+    const int count = LibcDetail::FormatWindows(nullptr, 0, format, args, &buffer);
+    const int result = std::fwrite(buffer.data(), 1, static_cast<size_t>(count), native) ==
+        static_cast<size_t>(count) ? count : -1;
+#else
+    const int result = std::vfprintf(native, format, *reinterpret_cast<std::va_list*>(args));
+#endif
+    stream->SyncStatus();
+    return result;
+}
+
+int APS5_VABI fprintf_nid_postfix(FileStream* stream, const char* format, ...) {
+#ifdef _WIN32
+    __builtin_sysv_va_list args;
+    __builtin_sysv_va_start(args, format);
+#else
+    std::va_list args;
+    va_start(args, format);
+#endif
+    const int result = vfprintf_nid_postfix(stream, format, reinterpret_cast<VaList*>(args));
+#ifdef _WIN32
+    __builtin_sysv_va_end(args);
+#else
+    va_end(args);
+#endif
+    return result;
+}
+
 #ifdef _WIN32
 
 int APS5_VABI printf_nid_postfix(const char* format, ...) {
diff --git a/core/libs/tests/GuestStandardStreams.cpp b/core/libs/tests/GuestStandardStreams.cpp
index 3ced61b07..add7614aa 100644
--- a/core/libs/tests/GuestStandardStreams.cpp
+++ b/core/libs/tests/GuestStandardStreams.cpp
@@ -2,11 +2,15 @@
 #include "prx/libc/include/general/VabiMacros.hpp"
 #include <cstdlib>
 #include <cstring>
+#include <cstdarg>
+#include <cstdint>
 extern "C" {
 extern FileStream* __stdinp_nid_postfix;
 extern FileStream* __stdoutp_nid_postfix;
 extern FileStream* __stderrp_nid_postfix;
 extern int __isthreaded_nid_postfix;
+int APS5_VABI fprintf_nid_postfix(FileStream*, const char*, ...);
+int APS5_VABI vfprintf_nid_postfix(FileStream*, const char*, void*);
 int APS5_VABI fgetc_nid_postfix(FileStream*);
 int APS5_VABI fputc_nid_postfix(int, FileStream*);
 int APS5_VABI __srget_nid_postfix(FileStream*);
@@ -19,6 +23,22 @@ void APS5_VABI clearerr_nid_postfix(FileStream*);
 int APS5_VABI setvbuf_nid_postfix(FileStream*, char*, int, std::size_t);
 }
 static void Require(bool value) { if (!value) std::abort(); }
+static int APS5_VABI WriteFormatted(FileStream* stream, const char* format, ...) {
+#ifdef _WIN32
+    __builtin_sysv_va_list args;
+    __builtin_sysv_va_start(args, format);
+#else
+    std::va_list args;
+    va_start(args, format);
+#endif
+    const int result = vfprintf_nid_postfix(stream, format, args);
+#ifdef _WIN32
+    __builtin_sysv_va_end(args);
+#else
+    va_end(args);
+#endif
+    return result;
+}
 int main() {
     Require(__isthreaded_nid_postfix == 1);
     Require(__stdoutp_nid_postfix == &_Stdout_nid_postfix);
@@ -46,4 +66,17 @@ int main() {
     Require(!feof_nid_postfix(&stream) && !(guest.flags & 0x20));
     stream.Close();
     Require(guest.flags == 0 && guest.descriptor == -1);
+
+    FileStream formatted(std::tmpfile());
+    const char expected[] = "guest 4294967297 1.25 1 2 3 4 5 6 7 8\n";
+    Require(fprintf_nid_postfix(&formatted, "%s %ld %.2f %d %d %d %d %d %d %d %d\n",
+        "guest", std::int64_t{4294967297}, 1.25, 1, 2, 3, 4, 5, 6, 7, 8) == sizeof(expected) - 1);
+    Require(WriteFormatted(&formatted, "%*.*f:%s", 6, 2, 3.5, "end") == 10);
+    std::rewind(formatted.GetHandle());
+    char output[128]{};
+    Require(fgets_nid_postfix(output, sizeof(output), &formatted) == output);
+    Require(std::strcmp(output, expected) == 0);
+    Require(fgets_nid_postfix(output, sizeof(output), &formatted) == output);
+    Require(std::strcmp(output, "  3.50:end") == 0);
+    formatted.Close();
 }
diff --git a/docs/YAMAGI_QUAKE2.md b/docs/YAMAGI_QUAKE2.md
index 8f4d13e40..d2b86cc65 100644
--- a/docs/YAMAGI_QUAKE2.md
+++ b/docs/YAMAGI_QUAKE2.md
@@ -217,3 +217,22 @@ and closure. All fourteen suites pass and the compatibility libraries rebuild.
 
 Latest startup resolves the stream globals and stops at `8nY19bKoiZk` (`fcntl`).
 The game has not reached its entry point or displayed a frame.
+
+## Follow-up: descriptor flags and formatted stream output
+
+Added fcntl F_GETFL/F_SETFL for tracked UDP sockets. Nonblocking state is shared
+with FIONBIO ioctl and protected against concurrent mode updates. Unsupported
+flags are rejected; ordinary file descriptors and other fcntl commands are not
+implemented. The UDP test checks both APIs agree, mode transitions, and unchanged
+state after rejected flags.
+
+Added fprintf and vfprintf using the guest FileStream wrapper and the existing
+SysV variadic formatter on Windows. Tests write and read back mixed strings,
+64-bit guest long integers, floating-point values, register-overflow arguments,
+and dynamic width/precision through an explicit guest va_list. Write failure
+returns a negative result and refreshes the guest stream status.
+
+All fourteen CTest suites pass and patched compatibility libraries rebuild.
+The unchanged converted game now resolves fcntl and fprintf, and startup stops
+at `smbQukfxYJM` (`getenv`). This remains an import-resolution result: guest
+entry-point execution and a rendered frame are still unverified.