That makes sense because it goes through serial for that device, which uses circuitpython-repl-js. It needs to be more reliable because this is the favored way to open files.

I don't think this is the correct fix because in certain situations, you want the text to be returned only and not the raw file. I need to look further, but the correct fix likely needs to be in https://github.com/adafruit/circuitpython-repl-js with mechanisms to only look for >>> in the right situations.

I traced this to the raw REPL response parser and opened adafruit/circuitpython-repl-js#25 with a fix and regression tests.

_checkCodeRunning() was calling _detectCurrentMode() before parsing each raw response. Since mode detection searches the accumulated serial buffer for >>> and other prompt strings, text printed as raw stdout could be mistaken for a mode transition. The new PR keeps an active raw response under the documented OK / stdout / Ctrl-D / stderr / Ctrl-D / > framing and also handles OK split across serial chunks.

With that fixed in the library, this web-editor change should not need to route all text reads through the binary/base64 path and Blob.text().

Closing in favor of adafruit/circuitpython-repl-js#25 and #561.

The root-cause fix should be live in a couple minutes if you'd like to give it a test.