Tracing the Data Flow: A Read Operation in the PSProve PoRep Debugging Journey

Message Overview

In message [msg 1666] of this opencode coding session, the assistant performs a targeted read of a single file — /tmp/czk/tasks/proofshare/task_prove.go — focusing on the computeProof function at line 244. The message is deceptively simple: a lone read tool call with no accompanying analysis, commentary, or follow-up action. Yet this read sits at a critical juncture in an intense debugging session, representing the assistant's systematic effort to trace the complete data flow of a failing PoRep (Proof of Replication) SNARK computation in the PSProve/proofshare system.

To understand why this seemingly mundane file read matters, we must situate it within the broader investigation. The session has been consumed by a deep-rooted bug: when the PSProve/proofshare system generates a PoRep SNARK via the CuZK GPU proving engine, the resulting proof fails ffi.VerifySeal on the Go side. Yet the exact same proof type works flawlessly when generated through the normal CuZK path (cuzk_funcs.go). The only apparent difference between the working and failing paths is the source of the "vanilla proof" JSON — the Phase1 output that serves as input to the SNARK generation. The working path uses raw bytes from ffi.SealCommitPhase1() (Rust-generated JSON), while the failing path uses Go-re-serialized JSON via json.Marshal(Commit1OutRaw{...}).

The Investigation Context

By the time the assistant issues this read, it has already conducted an exhaustive multi-threaded investigation spanning several subagent tasks and numerous direct file reads. The investigation has systematically ruled out a series of plausible hypotheses:

  1. Enum mappings: The RegisteredSealProof enum values were traced across Go, C, and Rust code, confirming they are identical across all three languages. Not the bug.
  2. JSON struct field parity: Every field in the Go Commit1OutRaw struct was compared against the Rust SealCommitPhase1Output struct, confirming structural parity. Not the bug.
  3. Prover ID derivation: The CuZK Rust make_prover_id function (which uses LEB128/varint encoding) was compared against the Go FFI toProverID function (which uses address.NewIDAddress), and both produce identical 32-byte prover IDs. Confirmed by an explicit test with miner_id=1000. Not the bug.
  4. Data flow integrity: The proofshare client upload path was traced end-to-end, confirming no data corruption occurs during transmission. Not the bug.
  5. fr32 seed masking: The user suggested that powsrv does not apply the standard seed[31] &= 0x3f truncation, but analysis of the Rust challenge derivation code showed the seed is used as raw bytes for SHA256, not directly as an Fr element, ruling this out as the root cause of the intermittent failure. With these hypotheses eliminated, the investigation has narrowed to a single remaining suspect: the JSON round-trip. The assistant suspects that when Go serializes the Commit1OutRaw struct to JSON and then CuZK's Rust code deserializes it, some subtle byte-level discrepancy may cause CuZK to generate a SNARK with different public inputs than what the Go-side verification expects.

What This Message Actually Does

The computeProof function at line 244 is a straightforward dispatcher:

func computeProof(ctx context.Context, taskID harmonytask.TaskID, request common.ProofData, cuzkClient *cuzk.Client) ([]byte, error) {
    if request.PoRep != nil {
        if request.SectorID == nil {
            return nil, xerrors.Errorf("sector id is required")
        }
        return computePoRep(ctx, request.PoRep, *request.SectorID, cuzkClient)
    }
    if request.Snap != nil {
        if requ...

The function checks whether the ProofData contains a PoRep or Snap request, validates that the required SectorID is present, and delegates to the appropriate handler. For PoRep proofs, it calls computePoRep with the PoRep data, the sector ID, and the CuZK client.

The Reasoning Behind This Read

Why is the assistant reading this particular function at this point in the investigation? The answer lies in the assistant's debugging methodology. After spending considerable effort analyzing the computePoRep function (the actual proof computation logic), the assistant is now working backward to understand how computePoRep is invoked. This is a classic debugging technique: when you've identified a potential point of failure, you trace the data flow both forward (from input to the failure point) and backward (from the failure point to the input) to ensure you haven't missed any intermediate transformations.

In the previous message ([msg 1665]), the assistant read the Do() method of TaskProvideSnark to understand how sectorID is derived from the database. Now, in this message, the assistant reads computeProof — the function that sits between the task dispatch and the actual proof computation. This function is the "glue" that connects the task execution framework to the proof generation logic.

The assistant is essentially asking: "Is there any data transformation happening in computeProof that could alter the Commit1OutRaw data before it reaches computePoRep?" If computeProof simply passes through the data unchanged, then the bug must lie deeper in computePoRep or in the CuZK deserialization. But if computeProof somehow modifies the data (e.g., by re-serializing or copying fields), that could be the source of the discrepancy.## Input Knowledge Required

To fully understand this message, one needs substantial context about the PSProve/proofshare architecture. The ProofData struct is the central data type that carries proof requests from the proofshare queue to the computation engine. It contains optional fields for different proof types (PoRep, Snap, etc.), and the SectorID field identifies the specific sector being proven. The cuzkClient is a gRPC client that communicates with the CuZK GPU proving service, which generates Groth16 SNARKs for Filecoin proofs.

The reader must also understand that computePoRep (called at line 250) is the function that serializes the Commit1OutRaw to JSON and sends it to CuZK. The assistant has already read this function in detail in earlier messages and knows that the critical line is vproof, err := json.Marshal(request) — the Go JSON serialization that is the prime suspect in the investigation.

Output Knowledge Created

This read operation produces a subtle but important piece of knowledge: the computeProof function is a pure dispatcher with no data transformation. The function takes the request.PoRep pointer (a *proof.Commit1OutRaw) and passes it directly to computePoRep along with the dereferenced SectorID. There is no re-serialization, no field copying, no intermediate data structure that could introduce a discrepancy.

This is a negative finding — it eliminates one more potential source of the bug. The assistant now knows that the data entering computePoRep is exactly the data that was retrieved from the proofshare queue and stored in the ProofData struct. The JSON serialization at line 266 of computePoRep is the first and only point where the data is converted to a byte stream for transmission to CuZK.

The Thinking Process Visible in Reasoning

While this message contains no explicit reasoning text (it is a bare read tool call), the reasoning is evident from the sequence of messages leading up to it. The assistant has been systematically narrowing down the bug location using a process of elimination:

  1. Identify the symptom: PSProve PoRep SNARK fails verification; normal CuZK PoRep works.
  2. Identify the difference: The source of the vanilla proof JSON (Rust-generated vs. Go-re-serialized).
  3. Eliminate structural differences: Enum mappings, struct fields, prover ID derivation all match.
  4. Trace the data flow: Follow the data from the proofshare queue through every transformation until it reaches CuZK.
  5. Isolate the first transformation: The first point where the data is converted to a byte stream is json.Marshal(request) in computePoRep. The read of computeProof is step 4b in this process — verifying that no transformation occurs in the dispatch layer. The assistant is being methodical, checking every intermediate function to ensure no hidden data mutation exists.

Assumptions Made

The assistant makes several assumptions in this read:

  1. That the computeProof function is the correct entry point for PoRep proofs. This is confirmed by the Do() method of TaskProvideSnark, which calls computeProof with the ProofData from the database.
  2. That the SectorID pointer is valid. The function checks for nil and returns an error if so, but assumes that if non-nil, it contains the correct sector identifier.
  3. That the cuzkClient is properly initialized. The function assumes the client is ready to accept gRPC connections to the CuZK service.
  4. That the request.PoRep pointer contains a complete Commit1OutRaw struct. The function does not validate the contents of the PoRep data beyond checking for nil.
  5. That the data flow is linear and synchronous. The assistant assumes that computePoRep is called and completes before any verification happens, which is correct for this codebase.

Potential Mistakes or Incorrect Assumptions

One potential oversight: the assistant does not check whether computeProof could be called from multiple paths. If there are other callers of computeProof that prepare the ProofData differently, the bug could be in one of those preparation paths rather than in the serialization. However, the assistant has already traced the Do() method and confirmed the data originates from the proofshare queue, so this concern is partially addressed.

Another subtle point: the assistant assumes that json.Marshal(request) produces the same JSON regardless of the Go runtime environment. But Go's JSON marshaling can be affected by architecture-specific behavior (e.g., endianness for integer arrays) or by custom marshalers that depend on global state. The assistant has previously noted the testMarshal variable in merkle.go (line 5), which controls whether Sha256Domain uses a different marshaling path. If testMarshal is set to true in the production environment but false in test, the JSON output could differ. This is a genuine risk that the assistant has not fully explored.

Broader Significance

This message exemplifies a critical phase in debugging complex distributed systems: the point where the investigation shifts from broad hypothesis testing to fine-grained data flow analysis. The assistant has eliminated all structural and configuration-level explanations and is now focused on the exact byte-level behavior of the JSON serialization. The read of computeProof is a checkpoint — confirming that the data path is clean up to the serialization point, so the remaining investigation can focus entirely on the json.Marshal / json.Unmarshal round-trip and the CuZK Rust deserialization code.

The next logical steps, which the assistant pursues in subsequent messages, are to add diagnostic logging to capture the exact byte streams and to extend the 2KiB roundtrip test to cover the full CuZK wrapper and FFI C2 verification path. These actions directly target the remaining hypothesis: that the Go JSON round-trip produces byte-level differences that cause CuZK to generate a SNARK with mismatched public inputs.

In summary, message [msg 1666] is a quiet but essential step in a methodical debugging process — a data point that confirms the absence of a bug in one layer, allowing the investigation to press deeper into the remaining suspect.