# Barretenberg 0.82.0 Migration Notes

This is a list of changes made to the `bb` CLI and the `@aztec/bb.js` package between `v0.76.0` and `v0.82.2`.
This is useful if you are upgrading your Noir version to `v1.0.0.beta2+`, as it works well with `bb v0.82.2+`.

# Summary of `bb` CLI Changes
- UltraHonk is now the default proving scheme. UltraPlonk is being deprecated.
- Subcommands specific to a proving scheme, like `prove_ultra_honk`, have been removed. Instead, a `--scheme` argument is used (defaulting to `ultra_honk`), keeping the subcommands uniform (`prove`, `verify`, `write_vk`, etc.).
- `bb contract` has been renamed to `bb write_solidity_verifier`.
- Added `bb --help` to list available commands and options.
- The `-o` output flag now specifies the directory to write the output file (proof, vk) instead of the path to the file, in `prove` and `write_vk` command.
- The proof output from `bb prove` has public inputs at the beginning of the proof (except for the first 4 bytes which contain the proof size). This is relevant when [splitting the proof](https://noir-lang.org/docs/dev/how_to/how-to-solidity-verifier) for the Solidity verifier.
- The `--scheme` flag can be set using the `BB_SCHEME` environment variable to avoid specifying `--scheme ultra_honk` repeatedly.

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## UltraHonk

### Generate Proof

**Before**: `bb prove_ultra_honk -b ./circuit.json -w ./witness.gz -o ./proof`
**Now**: `bb prove --scheme ultra_honk -b ./circuit.json -w ./witness.gz -o ./`

### Write Verification Key

**Before**: `bb write_vk_ultra_honk -b ./circuit.json -o ./vk`
**Now**: `bb write_vk --scheme ultra_honk -b ./circuit.json -o ./`

### Verify Proof

**Before**: `bb verify_ultra_honk -k ./vk -p ./proof`
**Now**: `bb verify --scheme ultra_honk -k ./vk -p ./proof`

### Solidity Verifier

**Before**: `bb contract_ultra_honk -k ./vk -o ./Verifier.sol`
**Now**: `bb write_solidity_verifier --scheme ultra_honk -k ./vk -o ./Verifier.sol`

As before, only proofs generated with the `keccak` hash can be verified in Solidity. You can use the `--oracle_hash keccak` flag with the `prove`, `verify`, and `write_vk` commands to use the `keccak` hashing scheme instead of `Poseidon`.

### Gates

`bb gates --scheme ultra_honk -b ./circuit.json`

Note: `bb gates` now prints `gates_per_opcode` only when using the `--include_gates_per_opcode` flag (producing cleaner output by default).

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## UltraPlonk

UltraPlonk is usable as-is with the `OLD_API` flag:

bb OLD_API prove -b ./circuit.json -w ./witness.gz -o ./proof
bb OLD_API write_vk -b ./target/hello_world.json -o ./target/vk
bb OLD_API verify -k ./target/vk -p ./target/proof
bb OLD_API contract -k ./vk -b ./circuit.json -o ./Verifier.sol

- The UltraPlonk scheme is not available with new APIs under the `--scheme` flag. You must use `OLD_API` for UltraPlonk.

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# `@aztec/bb.js` Changes

- The `proof` returned from `UltraHonkBackend.generatedProof()` no longer has the proof size in the first 4 bytes.
- You can directly use this proof with a Solidity verifier without doing `proof.slice(4)`.

# Upcoming changes

There is ongoing work on the CLI to save `proof` and `public-inputs` as separate files when running the `bb prove` command.

This will be part of an upcoming version.