starknet_transaction_prover: relay opaque additional_data on proveTransaction response

[avi-starkware]

ProveTransactionResult gains an optional additional_data field carrying the opaque object the blocking check relayed. The prover passes it through verbatim (omitted from the JSON response when absent) and never interprets its contents — a screened deposit's signature lives under additional_data.signature, but that is the screening/wallet domain's concern, not the prover's. additional_data must be a JSON object; a non-object value maps to Inconclusive (fail-open policy). A transaction allowed via fail-open carries none.

Follow-up (separate change, not in this stack): document additional_data as an opaque/open object on the starknet_proveTransaction result in the external starknet-specs proving-api OpenRPC (starkware-libs/starknet-specs#389), then bump resources/starknet_specs_rev.txt. The committed mock fixture intentionally omits additional_data, so the pinned-spec validation is unaffected; the opaque relay is covered by serde tests.

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com

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[avi-starkware]

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• starknet_transaction_prover: bump starknet_specs rev for additional_data #14421
• starknet_transaction_prover: relay opaque additional_data on proveTransaction response #14411 👈 (View in Graphite)
• starknet_transaction_prover: relay opaque additional_data from check response #14410
• main-v0.14.3

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PR Summary

Medium Risk
Touches prove RPC response shape and blocking-check integration; behavior is pass-through only, but clients may now depend on additional_data for screening workflows.

Overview
ProveTransactionResult now includes an optional additional_data JSON object that is relayed unchanged from the external blocking check’s allow response into the prove RPC result (e.g. screening signature). The prover does not read or validate that payload; it is omitted from JSON when absent.

When a blocking check runs in parallel with proving, prove_with_blocking_check copies additional_data only on an explicit Allowed outcome. Fail-open paths (inconclusive check or timeout) still allow proving but set additional_data to None.

Tests cover an allow response with additional_data, verbatim serde round-trip, and omission when the field is empty.

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[remollemo]

@remollemo reviewed 2 files and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on ittaysw and Yoni-Starkware).

[Yoni-Starkware]

@Yoni-Starkware reviewed all commit messages and made 1 comment.
Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on avi-starkware, ittaysw, and remollemo).

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crates/starknet_transaction_prover/src/proving/blocking_check_integration_test.rs line 182 at r2 (raw file):

    let json = serde_json::to_value(&result).unwrap();
    assert!(json.get("additional_data").is_none());

How can you distinguish between "missing" and "additional_data": null?
Can you check contains or something? similar?

Code quote:

assert!(json.get("additional_data").is_none());