The Strategic Reconnaissance: Reading Four Files to Bridge Phase 1 and Phase 2 of the cuzk Proving Engine

Introduction

In the development of complex systems, the moments between phases are often the most revealing. They expose the engineer's mental model, their assumptions about what matters, and the implicit architecture that guides their next steps. Message 354 of this opencode session captures exactly such a transitional moment: an AI assistant, having just completed the core of Phase 1 for the cuzk proving engine, pauses to read four critical files before implementing the final Phase 1 deliverable — the gen-vanilla command.

This message is not about writing code. It is about preparing to write code. It is a reconnaissance mission, a deliberate gathering of the current state before making changes. The assistant reads four files in rapid succession, each chosen to answer a specific question about the system's current configuration. Understanding why these four files were selected, what the assistant expected to find, and how this reading sets up the subsequent implementation reveals a deeply methodical approach to software engineering — one that prioritizes understanding over action, and context over speed.

The Context: Phase 1's Last Deliverable

The cuzk project is a pipelined SNARK proving engine for Filecoin proof generation, built as a Rust workspace in extern/cuzk/. By message 354, the assistant has already completed Phase 0 (scaffold with gRPC API, PoRep C2 proving, priority scheduler) and the bulk of Phase 1 (multi-GPU worker pool, all four proof types — PoRep C2, WinningPoSt, WindowPoSt, SnapDeals). One deliverable remains: the gen-vanilla command.

The gen-vanilla command is a test data generation utility. It produces "vanilla proofs" — the intermediate cryptographic evidence that gets aggregated into a final Groth16 proof. For WinningPoSt and WindowPoSt, these are per-sector proofs generated from sealed sector data on disk. For SnapDeals, they are per-partition proofs. The command is essential because the team has golden test data for PoRep C2 (the c1.json file at /data/32gbench/) but no vanilla proof files for the other proof types. Without these, the newly implemented WinningPoSt, WindowPoSt, and SnapDeals provers cannot be end-to-end tested.

The assistant's plan is to add filecoin-proofs-api as an optional dependency to cuzk-bench (behind a feature flag), then implement three sub-subcommands: winning-post, window-post, and snap-prove. Each will call CPU-only functions from filecoin-proofs-api to generate vanilla proofs from real sector data on disk.

The Four Files: A Strategic Reading

The assistant reads four files in a single round, dispatching all reads in parallel. This parallelism is significant — it reveals that the assistant already knows exactly which files it needs and is not iteratively discovering them. Each file answers a specific question.

File 1: cuzk-bench/src/main.rs — The CLI Surface

The first read targets the bench tool's main entry point. The assistant needs to understand the current CLI structure: how commands are organized (clap-based subcommands), how arguments are parsed, and what patterns to follow when adding the new gen-vanilla subcommand. The file's doc comment reveals the existing commands: single, batch, status, preload, metrics. The assistant needs to add a sixth command — gen-vanilla — with its own sub-subcommands.

By reading this file, the assistant learns the code conventions: the use of anyhow for error handling, the pattern of #[derive(clap::Subcommand)] for command dispatch, and the overall structure of the main() function. This is the template the new code must follow.

File 2: cuzk-bench/Cargo.toml — The Dependency Boundary

The second read is the bench tool's manifest. This is arguably the most critical file because it defines the dependency boundary. Currently, cuzk-bench is a thin gRPC client — it depends only on cuzk-proto, tonic, tokio, and clap. It does not depend on filecoin-proofs-api, which is the library that contains the vanilla proof generation functions.

The assistant needs to add filecoin-proofs-api as a dependency, but it must do so carefully. The bench tool is meant to remain lightweight for normal use; the heavy proving library should only be linked when generating vanilla proofs. The solution is an optional dependency behind a feature flag — gen-vanilla — that pulls in filecoin-proofs-api only when needed. This pattern preserves the bench tool's small binary size for its primary use case (sending gRPC requests to the daemon) while enabling the test data generation capability.

Reading this file also reveals the workspace dependency structure: cuzk-proto is a workspace dependency, tonic is a workspace dependency, etc. The assistant needs to check whether filecoin-proofs-api is already declared as a workspace dependency (it is, in cuzk-core's dependencies) and whether it can be reused.

File 3: Cargo.toml (Workspace Root) — The Shared Dependency Catalog

The third read is the workspace root manifest. This is the catalog of all shared dependencies. The assistant needs to verify that filecoin-proofs-api is declared as a workspace dependency (it is, because cuzk-core uses it) and understand how feature flags propagate through the workspace.

The workspace root also defines the member crates. The assistant can confirm that cuzk-bench is a workspace member (it is, at line 8) and that no other crates need to be added. The commented-out cuzk-ffi member (line 9) serves as a reminder of future plans.

File 4: cuzk-core/src/prover.rs — The Reference Implementation

The fourth read is the prover module in cuzk-core. This is the reference implementation for how filecoin-proofs-api functions are called. The assistant has already written this code (it was part of Phase 1's core implementation). By re-reading it, the assistant refreshes its context on:

• How seal_commit_phase2 is called for PoRep C2
• How generate_winning_post_with_vanilla is called for WinningPoSt
• How generate_single_window_post_with_vanilla is called for WindowPoSt
• How generate_empty_sector_update_proof_with_vanilla is called for SnapDeals
• The enum conversion functions (registered_post_proof_from_u64, registered_update_proof_from_u64)
• The helper functions (to_array32, make_prover_id) The gen-vanilla command will need to call different functions from filecoin-proofs-api — the vanilla proof generation functions rather than the proof aggregation functions. Specifically, it needs generate_fallback_sector_challenges, generate_single_vanilla_proof, and generate_partition_proofs. But the patterns for type conversion, error handling, and parameter construction will be similar. The prover module serves as both a reference and a reminder of the API's conventions.

The Assistant's Reasoning Process

The assistant's thinking is visible in the sequence and selection of these reads. It is working through a checklist:

1. What does the bench tool currently look like? (Read main.rs) — Understand the CLI structure I need to extend.
2. What dependencies does it have? (Read Cargo.toml) — Understand what I need to add and how.
3. Can I use the workspace dependency? (Read workspace Cargo.toml) — Check if filecoin-proofs-api is already declared at workspace level.
4. How did I call the API before? (Read prover.rs) — Refresh on the patterns used in the existing prover code. This is a classic "read before write" pattern. The assistant is loading context into its working memory before making any changes. It is not making decisions yet — it is gathering the information needed to make informed decisions in the next round. The parallelism of the reads is notable. All four files are read simultaneously, which means the assistant already knew exactly which files it needed before starting. This is not exploratory browsing — it is targeted information retrieval. The assistant has a clear mental model of the system's structure and knows precisely where to look for each piece of information.

Assumptions and Knowledge Boundaries

This message reveals several assumptions the assistant is making:

Assumption 1: The workspace dependency structure is sufficient. The assistant assumes that adding filecoin-proofs-api as a dependency to cuzk-bench (behind a feature flag) will work without version conflicts. It assumes that the version already used by cuzk-core (19.0.0) is compatible and that no additional dependency resolution issues will arise.

Assumption 2: The CLI pattern is extensible. The assistant assumes that adding a gen-vanilla subcommand with its own sub-subcommands fits cleanly into the existing clap-based structure. It assumes that the existing main.rs pattern — a single #[derive(clap::Parser)] struct with subcommands — can accommodate the new command without refactoring.

Assumption 3: The upstream API is sufficient. The assistant assumes that filecoin-proofs-api's vanilla proof generation functions (generate_fallback_sector_challenges, generate_single_vanilla_proof, generate_partition_proofs) are callable with the data available at /data/32gbench/. It assumes that PrivateReplicaInfo::new() can be constructed from the sealed sector data and cache directory paths.

Assumption 4: The test data paths are valid. The assistant assumes that /data/32gbench/sealed, /data/32gbench/cache/, /data/32gbench/update, and /data/32gbench/updatecache/ contain valid sector data that will produce correct vanilla proofs. It assumes the commitment values in commdr.txt and update-commdr.txt correspond to these sectors.

These assumptions are reasonable given the assistant's extensive prior investigation (documented in the session summaries), but they remain unverified until the code is written and tested.

The Bridge to Phase 2

This reconnaissance message is also a bridge between Phase 1 and Phase 2. The assistant is not just reading files for the gen-vanilla implementation — it is also refreshing its understanding of the system before the much larger Phase 2 work begins.

Phase 2 will involve forking bellperson to expose internal synthesis/GPU split APIs, implementing a pipelined prover that streams partitions sequentially (reducing peak memory from ~200 GiB to ~13.6 GiB), and building an SRS manager with tiered memory. This is architecturally far more complex than anything in Phase 1. The assistant's methodical approach in this message — reading before writing, verifying before acting — is the same discipline that will be essential for the Phase 2 work.

By reading cuzk-core/src/prover.rs, the assistant is also implicitly reviewing the API surface it will need to modify in Phase 2. The current prover module calls filecoin-proofs-api directly, which internally handles both synthesis (CPU) and proving (GPU) as a single monolithic operation. Phase 2 will split these into separate steps, with the bellperson fork exposing synthesize_circuits_batch() and prove_from_assignments() as distinct API calls. The current prover module's structure — where each proof type has its own function — will need to be refactored to support the new pipeline architecture.

Conclusion

Message 354 is a masterclass in strategic reading. The assistant reads exactly four files, each chosen to answer a specific question about the system's current state. It does not read the entire codebase — it reads the minimal set needed to proceed. This targeted approach reveals a deep understanding of the system's architecture and a clear mental model of what needs to change.

The message also reveals the assistant's engineering philosophy: understand before acting, verify before modifying, and always maintain context on the system's current state. In a project as complex as a pipelined SNARK proving engine — with its intricate dependency chains, multi-GPU scheduling, and memory-aware pipeline design — this discipline is not optional. It is essential.

The gen-vanilla command that follows from this reconnaissance will complete Phase 1 and unlock end-to-end testing for all four proof types. But more importantly, the methodical approach demonstrated in this message — the careful reading, the targeted information gathering, the verification of assumptions — will carry forward into Phase 2 and beyond, where the real architectural challenges await.