[AztecBot]

Why

Barretenberg carries UltraStarknetFlavor, UltraStarknetZKFlavor, a stark252 curve, a Starknet Poseidon and a matching transcript, all behind STARKNET_GARAGA_FLAVORS. Garaga was the only known consumer. Its current Noir docs use --oracle_hash keccak with ultra_keccak_zk_honk, and its maintainers have confirmed they no longer need this code.

Reachability

No preset, script or CMake file defines STARKNET_GARAGA_FLAVORS; every occurrence in the tree is an #ifdef. So the flavors, their template instantiations and their test parameterizations don't compile in any build we produce, and the code goes unexercised by CI.

The guarded code had also bit-rotted. It refers to Transcript_, KeccakTranscriptParams and a single-parameter BaseTranscript. On next, Transcript_ and KeccakTranscriptParams are defined nowhere and BaseTranscript takes two template parameters, so turning the flag on should no longer compile. That comes from reading the source; I didn't try the build.

What changed

• Deleted barretenberg/cpp/src/barretenberg/ext/ and its CMake wiring. ext_starknet_crypto_poseidon is no longer linked into transcript, stdlib_poseidon2, poseidon2_bench or the barretenberg objects.
• Removed the #ifdef branches, keeping the non-Starknet side, across flavors, Oink, Ultra prover/verifier, TraceToPolynomials, SmallSubgroupIPA and the test type lists.
• Restored static_assert(Params::modulus_0 != 1) in field_declarations.hpp. It was commented out only because stark252 violates it, and modulus_minus_two underflows without it.
• Folded the custom-IV crypto::FieldSponge::hash_internal(input, iv) overload into the single-argument hash_internal. It was added for the Starknet Poseidon, which was its only outside caller. Poseidon2 output doesn't change: the IV is still in_len << 64, converted to FF the same way.
• Removed OracleHashType and parse_oracle_hash_type from bbapi_shared.hpp. They had no callers, and proof settings dispatch on the oracle_hash_type string.
• Removed starknet and starknet-no-zk from the CLI, along with the Starknet Garaga Extensions banner line, the bb.js verifierTarget values and the current docs.
• Dropped Garaga from docs/docs-words.txt, since nothing in that spellcheck's scope uses it, and pointed the Garaga link in barretenberg/docs/docs/index.md at its current URL.

Breaking changes

• bb: --verifier_target starknet, --verifier_target starknet-no-zk and --oracle_hash starknet now fail at argument parsing. Default builds already failed on these later, with Invalid proof system settings.
• bb.js: verifierTarget: 'starknet' | 'starknet-no-zk' and the deprecated starknet / starknetZK options are removed from UltraHonkBackendOptions.

Left in place

• CHANGELOG.md and versioned_docs are historical.
• barretenberg/docs/docs/index.md still cites Garaga as a third-party verifier implementation, which remains true.
• starknet stays in the root cspell.json because CHANGELOG.md still contains it and isn't in that file's ignorePaths.

Testing

Run locally on the clang20-no-avm preset with the AVM transpiler disabled:

• Built bb, ultra_honk_tests, flavor_tests, transcript_tests, crypto_poseidon2_tests, stdlib_poseidon2_tests, bbapi_tests and poseidon2_bench. flavor_tests and poseidon2_bench were built before the follow-up commit and not rebuilt after it.
• Passed: crypto_poseidon2_tests 12 of 12, stdlib_poseidon2_tests 29 of 29, transcript_tests 69 of 71 with 2 skipped (TranscriptTests/1 and /2.ProverToVerifierConversion).
• Passed before the follow-up commit: flavor_tests 28 of 28, and a filtered ultra_honk_tests subset of 63 tests (transcript, permutation, one range-constraint flavor, proof length).
• bbapi_tests has 1 failure, ChonkPinnedIvcInputsTest.AllPinnedFlows, which stops at its assertion that pinned flows exist because the inputs aren't downloaded in this checkout. I didn't read the rest of that run's output, so CI is the real result for this target.
• bb rejects both starknet spellings, and starknet no longer appears in bb or bb prove --help output.
• Ran Prettier on backend.ts with the repo's options but without the import-sort plugin, which isn't installed here.

Not run locally: ESLint, the bb.js typecheck, the wasm build and the full test suite. Those are left to CI.

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Created by claudebox · group: slackbot · requested by Sergei · Slack thread