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fix(calldata): always emit DECIMALS in PARAM_UNIT - #353
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app-ethereum >= 1.22.4 rejects PARAM_UNIT structs without DECIMALS (6a80), although its spec documents the tag as optional with a default of 0. Unit fields without decimals (e.g. opencover "Cover duration") therefore fall back to blind signing on released devices. Always serialize DECIMALS, defaulting to 0, which is byte-for-byte the value the app is specified to assume. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
ckorchane-ledger
approved these changes
Oct 9, 2026
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Problem
app-ethereum commit
21d2695f(shipped since 1.22.4) madeDECIMALSmandatory inPARAM_UNIT, while the app's own spec documents it as optional with a default of0. python-erc7730 only emitted the tag whendecimalswas set, so anyunitfield without decimals is rejected with6a80and the whole transaction falls back to blind signing on released devices (e.g. opencover's "Cover duration").Fix
Always serialize
DECIMALSintlv_param_unit, defaulting to0— the exact value the app is specified to assume when the tag is absent, so display is unchanged. The calldata model (decimals: int | None) is left as is.The app-side check should still be relaxed (or the spec updated) so other descriptor producers don't hit the same issue.
Tests
test_convert_unit_always_serializes_decimals(unset →0, set → value); the unset case fails without the fix.prek run --all-filesandpytest testspass locally.🤖 Generated with Claude Code