A Milestone Confirmed: Validating Phase 1 of the cuzk Proving Engine

The Message

All output files are valid JSON arrays of base64-encoded proof bytes. The format matches what cuzk-bench single --vanilla expects.

This short, declarative sentence — message [msg 386] in the opencode session — is the quiet culmination of an intense implementation sprint. The assistant has just finished running all three proof types (WinningPoSt, WindowPoSt, and SnapDeals) through the newly built gen-vanilla command against real 32 GiB sector data, and the verdict is clear: everything works. The output files are valid, the format is compatible, and Phase 1 of the cuzk proving engine is complete.

The message is terse, almost anticlimactic after the dozens of tool calls, compilation cycles, and debugging iterations that preceded it. But that terseness is itself a signal. The assistant is not discovering problems or iterating on fixes — it is confirming that the system behaves exactly as intended. The todo list that follows the message tells the story: every single task under the gen-vanilla umbrella, from reviewing upstream APIs to implementing the three subcommands, is marked completed. The milestone has been reached.

The Journey to This Point

To understand why this message matters, one must understand what it took to get here. The cuzk project is a pipelined SNARK proving daemon for Filecoin, designed to address the memory and throughput bottlenecks identified in earlier analysis of the supraseal-c2 Groth16 proof generation pipeline. Phase 0 established the core engine architecture with gRPC API, priority scheduling, and end-to-end proof submission. Phase 1 extended that foundation by implementing all four Filecoin proof types (WinningPoSt, WindowPoSt, SnapDeals, and the existing PC1/PC2/C1/C2 pipeline) and adding multi-GPU worker pool support.

But one critical piece remained: the gen-vanilla command. Vanilla proofs are the CPU-only Merkle inclusion proofs that serve as input to the GPU-accelerated Groth16 proving phase. In the existing Curio architecture, these are generated by the Go-based task layer and passed through FFI into the Rust proof system. For cuzk to operate as an independent proving daemon — accepting proof requests from upstream task systems — it needed the ability to generate these vanilla proofs from scratch, reading sealed sector data directly from disk.

The implementation required several careful engineering decisions. First, the assistant needed to understand how Filecoin commitment CIDs (strings like bagboea4b5abc...) decode to raw 32-byte commitment arrays. This was investigated in a dedicated subagent task ([msg 357]) that traced through the multibase, CID, and multihash specifications. Second, the assistant had to decide whether to pull in the cid crate as a dependency or implement manual parsing. After checking the dependency tree and finding no existing cid crate in the lockfile, the assistant initially considered a manual approach but ultimately chose to add the cid crate — a pragmatic decision that favored correctness and maintainability over minimalism.

Third, the assistant designed the feature-gating strategy. Since gen-vanilla is a CPU-only utility that doesn't need GPU dependencies, it was placed behind a gen-vanilla feature flag in cuzk-bench/Cargo.toml, with filecoin-proofs-api and cid as optional dependencies. This kept the base build lean while allowing the full tooling when needed.

What the Message Actually Confirms

The assistant's validation went beyond a simple "it compiled" check. After building a release binary, the assistant ran three separate commands against the golden test data at /data/32gbench/ — the same data used by the existing Curio system for end-to-end testing.

For WinningPoSt, the command produced a single vanilla proof of 164,064 bytes (66 challenges against 1 sector), serialized as a 218 KB JSON array containing one base64-encoded entry. For WindowPoSt, the output was a 24,960-byte proof (10 challenges) in a 33 KB JSON file. For SnapDeals, the result was 16 partition proofs of 561,768 bytes each, totaling 12 MB of JSON output.

But the assistant didn't stop at generation. The message references a crucial second validation step: verifying that the output files are "valid JSON arrays of base64-encoded proof bytes" whose format "matches what cuzk-bench single --vanilla expects." This was done in the preceding message ([msg 385]) using a Python script that parsed each JSON file, decoded the base64 entries, and confirmed the byte lengths matched expectations. This two-stage validation — generation succeeds and output is consumable by the downstream tool — is what gives the message its weight.

Why This Is a Milestone

The gen-vanilla command is the last deliverable of Phase 1. With its completion, the cuzk proving engine now has:

  1. A working daemon that accepts gRPC proof requests and dispatches them to GPU workers
  2. Support for all four Filecoin proof types (WinningPoSt, WindowPoSt, SnapDeals, and the existing pipeline)
  3. A multi-GPU worker pool with CUDA_VISIBLE_DEVICES isolation and priority scheduling
  4. Observability through tracing spans, Prometheus metrics, and timing breakdowns
  5. Test data generation for vanilla proofs, enabling offline benchmarking and validation The message at [msg 386] is the moment where the assistant, having built all of this, takes a step back and confirms that the pieces fit together. The gen-vanilla output format matches what cuzk-bench single --vanilla expects — meaning the bench tool can now generate its own test data rather than relying on pre-existing golden files. This closes the loop for the development workflow.

Assumptions and Their Validity

The assistant made several assumptions in this message, all of which proved correct:

That the golden test data is representative. The assistant assumed that generating proofs against the /data/32gbench/ dataset would produce outputs valid for the real proving pipeline. This assumption was justified by the fact that this same data is used by Curio's own test infrastructure. The successful generation and format validation confirmed it.

That JSON + base64 is the right interchange format. The assistant assumed that serializing proofs as base64-encoded bytes within a JSON array would be compatible with the existing --vanilla flag. This was validated by the Python script that confirmed the decoded byte lengths matched expectations.

That the filecoin-proofs-api CPU-only functions would work without GPU context. The assistant assumed that vanilla proof generation (Merkle inclusion proofs) doesn't require GPU acceleration and can run purely on CPU. This is correct by design — vanilla proofs are intentionally CPU-only in the Filecoin proof architecture.

That the cid crate would resolve correctly. The assistant assumed that adding cid as a dependency would work without version conflicts. The clean compilation confirmed this, though it required adding 12 new packages to the lockfile (including multibase, multihash, unsigned-varint, and others).

What Comes Next

The message at [msg 386] is not just an endpoint — it is a launchpad. The very next message ([msg 387]) shows the assistant committing the work to the feat/cuzk branch with a 399-line diff across four files. And immediately after that, the assistant pivots to Phase 2: a deep analysis of bellperson's internal architecture, the creation of a minimal fork to expose synthesis/GPU split APIs, and the design of a per-partition pipeline strategy that reduces intermediate state from 136 GiB to 13.6 GiB.

The gen-vanilla command, now validated, becomes the test data generation backbone for all subsequent development. Every optimization in Phase 2 — the pipelined prover, the SRS manager, the memory budget analysis — will be tested against vanilla proofs produced by this tool. The message at [msg 386] is the foundation on which that work rests.

Conclusion

Message [msg 386] is a study in understatement. In 21 words, the assistant confirms that an entire phase of development — spanning multiple days, dozens of tool calls, and hundreds of lines of code — has reached its intended conclusion. The todo list that follows is the real story: every checkbox filled, every task complete. The message is the period at the end of a long sentence, the moment when the assistant allows itself to state what it has accomplished before turning to the next challenge.

For a reader who has followed the conversation from the beginning, this message carries the weight of everything that came before it. For a reader encountering it in isolation, it is a testament to the discipline of incremental validation: build, test, confirm, commit, move on. The assistant does not celebrate or elaborate — it simply states the facts and updates the task list. The work speaks for itself.