Starting in WebAssembly/component-model#263 the component model binary specification was updated in a technically breaking way to encode binaries differently. This was intended to be rolled out in a manner that minimized breakage however so bytecodealliance/wasm-tools#1262 implemented validation where the prefix byte which changed was actually ignored if it was 0 or 1. The encoder at the time still emitted 1 as the prefix byte, however. The intention was that once the validator had percolated enough the encoder would switch to using 0.
Unfortunately this change was basically forgotten about until now with WebAssembly/component-model#391, but now's probably "enough time passed" so the encoder is updated to emit a 0x00 leading byte in this situation instead of the historical 0x01 byte. This will start the transition period to eventually removing the validator's acceptance of the 0x01 byte.
Starting in WebAssembly/component-model#263 the component model binary specification was updated in a technically breaking way to encode binaries differently. This was intended to be rolled out in a manner that minimized breakage however so bytecodealliance/wasm-tools#1262 implemented validation where the prefix byte which changed was actually ignored if it was 0 or 1. The encoder at the time still emitted 1 as the prefix byte, however. The intention was that once the validator had percolated enough the encoder would switch to using 0.
Unfortunately this change was basically forgotten about until now with WebAssembly/component-model#391, but now's probably "enough time passed" so the encoder is updated to emit a 0x00 leading byte in this situation instead of the historical 0x01 byte. This will start the transition period to eventually removing the validator's acceptance of the 0x01 byte.