Vibe Coding an OS: What to Build & Verify

Updated 6 November 2026 · Standard formula, shown below

Vibe coding an operating system means using an AI assistant to generate most of the code, and the first thing you should build is a simple, text-based kernel that can boot and print to the screen; you verify it by running it in an emulator like QEMU and checking that it outputs the expected text without crashing. This article explains what to build, in what order, and how to test each piece so you don’t end up with a pile of code that looks impressive but never runs.

Why Vibe Coding an OS Is Different

An OS is not a single program; it’s a collection of layers that depend on each other: the bootloader, the kernel, memory management, process scheduler, device drivers, and a filesystem. Unlike a web app, you can’t just refresh the browser to see if it works. A single wrong byte in a linker script or a misaligned stack pointer will cause a silent hang or a reboot loop. Vibe coding amplifies this because the AI doesn’t know the exact state of your toolchain, your hardware, or your previous changes. It will happily generate code that looks correct but references a function that doesn’t exist in your project.

That’s why the “verify” part is not an afterthought—it’s the core of the workflow. You need a fast, repeatable test loop: edit code, build, run in an emulator, observe output, and check for specific markers. If you can’t run the OS in under 10 seconds, you’ll lose patience and stop verifying, which is when the real trouble starts.

What to Build First: A Minimal Bootable Kernel

Start with the smallest possible thing that boots and does something visible. The standard path is:

Bootloader: Use an existing one like GRUB or Limine rather than writing your own. They handle the messy hardware initialization and load your kernel into memory. You just need a multiboot header or a limine protocol header in your kernel binary.
Kernel entry point: A function written in C (or Rust) that the bootloader calls. It should disable interrupts, set up a stack, and then call a simple print function.
Text output: Write to the VGA text buffer at memory address 0xB8000. Each character cell is two bytes: the ASCII code and an attribute byte for color. A simple loop that writes “Hello, OS!” to the buffer is enough.

Verify: Boot it in QEMU with qemu-system-x86_64 -kernel your_kernel.bin (if using the multiboot protocol) and look for the string on the screen. Also check that the emulator doesn’t report a triple fault (it will show “Guest has not initialized the display” or just reboot in a loop).

How to Verify Each Layer (Not Just “It Boots”)

“It boots” is the bare minimum. You need to verify each subsystem independently:

GDT and IDT: Load a Global Descriptor Table and an Interrupt Descriptor Table. Verify by triggering a software interrupt (e.g., int 0x80) and seeing if your handler prints a message. If it triple-faults, your IDT entry is wrong.
Memory detection: Use BIOS or UEFI calls to get the memory map. Print the number of regions and the total memory. Verify it matches what QEMU reports (e.g., 128 MB if you set that).
Paging: Enable paging with a simple identity map for the first 4 GB. Test by reading and writing to a known address. If you get a page fault, your page tables are wrong.
Timer interrupt: Program the PIT (Programmable Interval Timer) to fire at 100 Hz. In the interrupt handler, increment a counter and print it periodically. Verify the counter increases roughly 100 times per second.
Keyboard input: Read from port 0x60 and print the scancode. Press a key in QEMU and see the scancode appear. This confirms your IRQ routing works.

Each of these tests is a small, observable behavior. If you can’t see the expected output, you know exactly which layer is broken.

Common Mistakes When Vibe Coding an OS

Assuming the AI knows your toolchain: The AI might generate code that uses __attribute__((section(".text"))) but your linker script doesn’t include that section. Always check the linker script and the build flags.
Not using a cross-compiler: On a 64-bit host, a normal gcc will produce 64-bit code by default. If you’re writing a 32-bit kernel, you need gcc -m32 and the corresponding libc. The AI might not specify this. Always build with -ffreestanding -nostdlib -fno-stack-protector.
Forgetting to disable interrupts: Before setting up your own IDT, the CPU might have interrupts enabled. A stray IRQ will jump to a random address and crash. The first thing in your kernel should be cli (clear interrupt flag).
Stack issues: The bootloader sets a stack for you, but it’s small and may be in a weird location. Set up your own stack in the BSS section and point ESP/RSP to it before calling any C function.
Trusting the AI’s memory addresses: The VGA buffer at 0xB8000 is correct for legacy VGA text mode, but if you boot in UEFI with a framebuffer, that address won’t work. You need to use the framebuffer provided by the bootloader. The AI might not know which mode you’re using.

Verification Tooling: Emulators, Logs, and Debuggers

QEMU is your best friend. It can emulate a full PC and gives you a serial port that you can use for logging. Add a simple serial_print function that writes to COM1 (port 0x3F8). Then in QEMU, use -serial stdio to see the logs. This is far more reliable than the VGA text buffer because it works even if the display is broken.

For deeper debugging, use QEMU’s -d int,cpu_reset to log interrupts and resets, or connect GDB with -s -S and step through the code. You can set breakpoints in your kernel source if you compile with -g. The AI won’t help you debug—it will just generate more code that might make it worse. You need to understand the basics of assembly and the x86 architecture to interpret the logs.

What Not to Build (Yet)

Resist the urge to build a GUI, a network stack, or a filesystem. These require thousands of lines of code and deep hardware knowledge. The AI will happily generate a 2000-line ext2 driver that won’t work because it doesn’t know your specific disk layout. Instead, focus on the core that makes an OS an OS: interrupts, memory management, and a scheduler. Once you have those, you can run a simple shell that reads from the keyboard and prints to the screen. That’s a complete, verifiable OS.

Costs and Alternatives

Vibe coding an OS is free in terms of money (QEMU and gcc are open-source), but it costs time—lots of it. Each iteration of “generate code, build, run, debug” can take 10-30 minutes, and you’ll do dozens of iterations. The alternative is to follow a structured tutorial like the OSDev Wiki’s “Bare Bones” or write the code yourself from a textbook. That’s slower at first but builds understanding that the AI can’t give you. A hybrid approach works well: use the AI to generate boilerplate (linker scripts, headers, Makefiles) and write the core logic yourself.

Frequently Asked Questions

Can I really build an OS without knowing assembly?

You need at least a basic understanding of assembly to read the generated code and debug crashes. The AI will write the assembly for you, but when something goes wrong (and it will), you’ll need to read the disassembly in GDB. Spend a weekend learning the basics of x86 assembly—it’s worth it.

Why does my kernel boot in QEMU but not on real hardware?

QEMU is forgiving. Real hardware has different timings, memory layouts, and devices. Common issues: your kernel doesn’t handle the A20 line, your GDT is not properly aligned, or your interrupt handlers are too slow. Test on real hardware only after it works perfectly in QEMU with -cpu max.

Should I use a microkernel or a monolithic kernel?

For a hobby OS, start monolithic. It’s simpler: everything runs in kernel mode, and you don’t need inter-process communication. Microkernels are a research topic; they require careful design and are hard to get right.

How do I know if my kernel is actually stable?

Run it for an hour under QEMU with a stress test: create a process that allocates memory, writes to it, and frees it in a loop. If it doesn’t crash, your memory management is probably sound. Also run with -d int to see if any unexpected interrupts occur.

Can I use Rust instead of C?

Yes, Rust is great for OS development because of its memory safety. But you’ll need to write a few assembly files for the bootstrapping, and the AI might generate unsafe code that bypasses Rust’s guarantees. Stick with C for your first OS to keep the toolchain simple.

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