The esp32/s3/c3 MicroPython bins were v1.20.0 (April 2023) — built by
micropython.org on IDF 4.4, three IDF generations behind the compile
pipeline and the engines' own validation corpus (both IDF 5.5), and two
behind the C6 bin (already v1.28). That drift is what broke I2C on the
S3: the engines decode the IDF 5.x driver sequences, and the v1.20 image
drove them the 4.4 way.
All four families now ship v1.28.0 (2026-04-06, IDF 5.x). Remote URLs
and cache keys move together, so a browser holding the old bin in
IndexedDB misses the new key and fetches v1.28 on its own. The new
images all declare 4 MB flash — padToFlashSize's floor exactly (the old
S3 bin declared 8 MB).
Validated cold on each engine (boot -> REPL, i2c.scan finds an attached
slave, WLAN scan/connect/DHCP; S3 additionally quad-PSRAM with a
multi-MB heap) and in the app (scan [60] on esp32/s3/c3, the ssd1306
gallery example drawing). Companion engine release: esp32s3js v1.16.0
(I2C interrupts on both cores, quad-PSRAM data plane). Pin.toggle() and
three years of upstream fixes come along; the v1.20 Pin.toggle note in
the editor seed is now history only.
Residual risk, flagged not fixed: the OSS QEMU self-host path (no JS
engines) now boots v1.28 under QEMU — unvalidated here, velxio.dev does
not exercise it.
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