I write these notes the same way I write calibrations: plain, first-person, and from the bench.
Custom OS started on GM P59 — that is where this work began — and it still runs through E38, E90 and E99. Expect unlock workflow, OS work, checksum and signature quirks, and the small decisions that decide whether a flash sticks. No marketing copy — just what we actually did.
If you are a shop sending reads, this is also where I will call out tools, gotchas, and what to send with the file so turnaround stays short.