fix: Fr::from_u64 big-endian encoding to match C++ msgpack format#22233
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ludamad merged 1 commit intomerge-train/barretenbergfrom Apr 6, 2026
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fix: Fr::from_u64 big-endian encoding to match C++ msgpack format#22233ludamad merged 1 commit intomerge-train/barretenbergfrom
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…ormat Fr::from_u64 was storing values in little-endian, but the C++ field::msgpack_unpack expects big-endian (network byte order). This was masked before because the C++ side silently reduced non-canonical values via to_montgomery_form_reduced(). After #22311 added strict non-canonical field validation (throwing for values >= modulus), values like Fr::from_u64(123) produce 0x7B<<248 which exceeds the BN254 Fr modulus (0x30...) and cause a C++ exception that propagates through the FFI boundary, aborting the Rust test process.
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…nical field encoding (#22333) ## Summary Fixes CI failure in `merge-train/barretenberg` caused by the interaction of #22233 (Fr::from_u64 big-endian encoding) and #22311 (strict non-canonical field validation). The `corruptProofFields()` test helper was flipping high-order bytes (indices 0,1) of field elements, creating values exceeding the BN254 Fr modulus. The strict validation now rejects these at deserialization time with `non-canonical encoding (value >= modulus)` before they reach the verifier. **Fix**: Flip low-order bytes (indices 30,31) instead — still corrupts the proof but keeps field values canonical. ## Test plan - [x] `batch_verifier.test.ts` — all 4 tests pass locally (previously 1 failing) ClaudeBox log: https://claudebox.work/s/e5146dc92fea29dd?run=1
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BEGIN_COMMIT_OVERRIDE fix: reject VK with log_circuit_size=0 in UltraKeccak verifier (#22319) chore: merkle tree audit 2 (#21475) fix: graceful failures in verifier code paths + other fixes (#22311) fix: Fr::from_u64 big-endian encoding to match C++ msgpack format (#22233) fix: corrupt low-order bytes in batch verifier test to avoid non-canonical field encoding (#22333) fix: skip MsgpackRejectsNonCanonical test in WASM builds (#22335) END_COMMIT_OVERRIDE
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Summary
Fixes bb-rs test failure introduced by #22311 (graceful failures in verifier code paths).
Fr::from_u64was storing values in little-endian, but the C++field::msgpack_unpackexpects big-endian (network byte order). This was masked before because the C++ side silently reduced non-canonical values viato_montgomery_form_reduced(). After #22311 added strict non-canonical field validation (throwing for values >= modulus), values likeFr::from_u64(123)produce0x7B<<248which exceeds the BN254 Fr modulus (0x30644e72...) and cause a C++ exception that propagates through the FFI boundary, aborting the Rust test process with "Rust cannot catch foreign exceptions".Fix
One-line change: store the u64 value in bytes 24..32 as big-endian instead of bytes 0..8 as little-endian.
Test plan
test_pedersen_commit_deterministiccrashes with SIGABRT./bootstrap.sh cirunning