Did I brick my ESP8266 ESP01 on Pico?

Oh wow, ok. So it would seem that the firmware update process does workbut your module is the 512k variant, so it's uploading the wrong firmware.

I'm sorry about this - I checked with a Pico+ESP01 I had on my desk here assuming it was the same and it worked, but it must have been a 1M variant and I got confused between 0.5M/1M and 4M ones.

I just had a quick google and found this tidbit:

if the PCB is blue, the flashsize is 512KB if the PCB is black the flashsize is 1MB

And it looks like I must have supplied the blue 512KB ones with the KickStarter campaign (at least that's what is in the picture on http://www.espruino.com/ESP8266)

Sorry - it's possible I was aware at one point but in the years since this I must have forgotten.

I did manage to find this though: https://www.sevarg.net/2016/11/20/instal­ling-latest-at-firmware-on-4mbit/

It seems to imply that you can use AT firmware 1.3.0.0 with 'noboot' - the firmware link doesn't work now, but this seems to be the new one: https://github.com/espressif/ESP8266_NON­OS_SDK/releases/tag/v2.0.0

I checked and v2.1.0 and later don't have 'noboot' so I guess that really is the last available firmware. Still, I guess it's a decent step up over 0.25.0.0