I used cursor with a mix of Gemini 3.1 and opus 4.6.

It referenced the Amiga ROM Kernel Reference Manual, appendix C to create a boot block in assembly. It's a raw sector-mapped image, the build process creates a blank adf, which then writes everything at it's fixed offsets and we go back with another tool to patch the bootblock with the right checksum so the kernel accepts it.

I copied that adf to the A1200 so I can then write it to a real floppy.