The single-file app grew to ~57KB; CircuitPython compiling it at boot fragments the
RP2040 heap so badly that the fonts can't get a contiguous block (161KB free, yet a
~16KB alloc fails). Fix: precompile to app.mpy (Adafruit mpy-cross for CP 10.2.1, emits
CircuitPython mpy v6) so the device loads bytecode without compiling -> no fragmentation.
- build.sh precompiles pico-cp/app.py -> dist/app.mpy via tools/mpy-cross (gitignored
binary); the bundle ships app.mpy (NOT app.py); serves pico-cp-app.mpy + pico-cp-app.py
(the .py only for the editor's version regex + as readable reference).
- Loader (code.py) imports app.mpy and rolls back app.bak as .mpy.
- One-click updater now pushes the .mpy: editor base64-encodes it and sends it over the
existing flow-controlled chunked transport (512-char = mult-of-4 chunks); the device
base64-decodes each chunk to /app.new and verifies the CircuitPython .mpy header
(magic 'C', v6, >=4KB) before the A/B install. Version still read from the served .py.
Verified: mpy-cross emits magic 'C'/v6; build produces a 21.8KB app.mpy; editing-logic
harness + scene render still pass; and a simulated push (base64 -> 57 chunks -> a2b_base64)
reassembles the .mpy byte-exact and passes the device's header check.
One-time recovery: delete app.py from the drive, copy app.mpy + code.py from the new zip.
After that, updates are one-click again (and can't brick: header check + A/B rollback).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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