Summary

Migrates all bb-prover server-side proving and verification from spawning bb/bb-avm binaries via child_process.spawn() to using the bb.js TypeScript API (Barretenberg class via NativeUnixSocket backend). This eliminates temporary file I/O (writing/reading bytecode, witnesses, proofs, VKs to disk) and stdout-based result parsing. A fresh bb process is still spawned per proof to maintain parallelism, but communication happens via Unix socket instead of files.

What was migrated

Key changes

• New BBJsInstance / BBJsProverFactory (bb_js_backend.ts): Adapter layer wrapping the Barretenberg class with typed methods for all proof operations
• New DebugBBJsInstance (bb_js_debug.ts): Debug wrapper that writes inputs/outputs to disk and logs equivalent CLI commands (see debug section below)
• C++ AVM msgpack commands (bbapi_avm.hpp/cpp): Three new bbapi command structs (AvmProve, AvmVerify, AvmCheckCircuit) with in-memory function implementations in vm2/api_avm.cpp and stub implementations in vm2_stub/api_avm.cpp
• Chonk proof splitting (splitChonkProofToStructured): Converts flat Fr[] proof arrays to structured ChonkProof format expected by chonkVerify, using sub-proof sizes inlined from C++ static_assert values
• Removed ~415 lines from execute.ts (6 dead functions)

Debug workflow with BB_DEBUG_OUTPUT_DIR

Set the BB_DEBUG_OUTPUT_DIR environment variable to enable file-based debugging. When set, DebugBBJsInstance wraps all bb.js calls and:

1. Writes all inputs (bytecode, witness, VK, proof, etc.) to numbered subdirectories under the debug dir
2. Writes a command.sh script with the equivalent bb CLI command that can be re-run manually
3. Writes outputs (proof files, verification results) after each operation

Example:

BB_DEBUG_OUTPUT_DIR=/tmp/bb-debug yarn workspace @aztec/prover-client test
# Then inspect /tmp/bb-debug/0001_prove_MyCircuit/, /tmp/bb-debug/0002_verify_MyCircuit/, etc.

Each subdirectory contains the input files and a command.sh that reproduces the operation using the bb CLI binary, useful for isolating failures outside of the TypeScript stack.

Test plan

• CI green on all checks
• Chonk integration tests pass
• AVM proving tests pass
• E2E block building tests pass

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