The First Real Proof: Validating the cuzk Proving Pipeline End-to-End

Introduction

In the development of any complex distributed system, there comes a moment when theory meets reality — when all the careful architecture, all the code written across multiple crates, all the configuration wiring, and all the assumptions about how components interact are finally tested against a real workload. Message 222 in this coding session captures exactly such a moment for the cuzk proving engine: the first time a real 32 GiB Filecoin PoRep (Proof-of-Replication) C2 proof is submitted to the daemon over gRPC, and the pipeline responds with evidence that every layer is functioning correctly.

This message is not merely a status update. It is the culmination of an extensive investigation that began in Segment 0 with a deep-dive into the SUPRASEAL_C2 Groth16 proof generation pipeline, progressed through five optimization proposals, led to the design of a pipelined SNARK proving daemon architecture (cuzk), and then through four segments of implementation. By message 222, the assistant has built the entire Phase 0 scaffold: a Rust workspace with six crates, a gRPC API, a priority scheduler, a prover module wrapping filecoin-proofs-api calls, and a daemon binary. Now, for the first time, it is all being exercised against a real GPU — an RTX 5070 Ti (Blackwell architecture, compute capability 12.0) — with a genuine 51 MB C1 output from a 32 GiB sector.

The Message in Full

The assistant writes:

Excellent! It's working! The critical things happening:

>

1. C1 data received (51 MB), deserialized successfully 2. Registered proof = StackedDrg32GiBV1_1 — correct! 3. Cache miss on STACKED[34359738368] — first call, as expected 4. Found params at /data/zk/params/v28-stacked-proof-of-replication-... — the env var worked! 5. Now loading the 45 GiB params file from disk into memory

>

This is going to take a while to load the SRS. Let me monitor periodically:

The assistant then runs a monitoring command that tails the daemon log, checks system memory with free -h, and queries GPU memory with nvidia-smi, showing the daemon log lines confirming the parameter cache path resolution.

Why This Message Was Written: The Reasoning, Motivation, and Context

This message exists because the assistant needed to validate that the entire cuzk pipeline — from gRPC submission through deserialization, proof-type registration, parameter cache resolution, and into the actual proving machinery — was wired correctly before investing time in observability improvements or Phase 1 concurrency features. The stakes were high: if the pipeline failed at any point, the assistant would need to diagnose whether the issue was in the gRPC layer, the protobuf serialization, the prover module's filecoin-proofs-api calls, the CUDA backend compatibility with Blackwell, the SRS parameter loading, or any of a dozen other integration points.

The message is written in a tone of relief and excitement ("Excellent! It's working!") because several critical risks have just been mitigated. The assistant had been working with a significant unknown: whether the supraseal CUDA backend (which delegates to sppark → nvcc for JIT compilation) would work on the RTX 5070 Ti's Blackwell architecture. Earlier messages (198–204) show the assistant carefully investigating compute capability support, checking build.rs files, and verifying that sppark doesn't filter architectures. The build succeeded, but whether the compiled CUDA kernels would actually execute correctly at runtime was an open question until this moment.

Furthermore, the assistant had to verify that the FIL_PROOFS_PARAMETER_CACHE environment variable was being picked up correctly by the storage-proofs-core settings system. Messages 212–218 show a deep investigation into how SETTINGS (a lazy_static) reads from environment variables with the FIL_PROOFS prefix, and whether setting the env var before the first proof call would be sufficient given lazy initialization. The log line confirming the params were found at /data/zk/params/v28-stacked-proof-of-replication-... validates this entire chain of reasoning.

How Decisions Were Made

Several technical decisions are visible in this message and its surrounding context. The decision to use TCP (0.0.0.0:9820) rather than Unix Domain Sockets (/run/curio/cuzk.sock) was made for testing convenience — the assistant explicitly notes "For this test, TCP is easier" in message 212. This is a pragmatic choice that prioritizes rapid validation over production configuration.

The decision to run the daemon with nohup and redirect output to a log file, rather than in a terminal multiplexer like tmux or screen, reflects the assistant's workflow: it needs to submit the proof from the same shell while the daemon runs in the background. The subsequent monitoring pattern — periodically checking tail -5 /tmp/cuzk-daemon.log alongside free -h and nvidia-smi — shows a deliberate strategy for tracking a long-running operation without blocking the interactive session.

The choice of monitoring metrics is also instructive. The assistant checks three things: the daemon log (for proof status), system memory (for the 45 GiB SRS load), and GPU memory (for CUDA kernel execution). This triage covers the three most likely failure modes: application errors, insufficient host memory, and GPU resource exhaustion.

Assumptions Made

This message and its surrounding context reveal several assumptions, most of which proved correct:

  1. The supraseal CUDA backend would work on Blackwell architecture. This was the most significant assumption. The assistant verified that sppark uses cc::Build with .cuda(true) which delegates architecture selection to nvcc, and that CUDA 13.1 should support sm_120. But this was never tested until now.
  2. Setting FIL_PROOFS_PARAMETER_CACHE before the first proof call would be sufficient. The assistant correctly reasoned that SETTINGS is a lazy_static initialized on first access, and that setting the env var before calling seal_commit_phase2 would ensure the correct path was used. The log line confirming the path resolution validates this assumption.
  3. The 51 MB C1 JSON would deserialize correctly. The C1 output format involves nested JSON with base64-encoded inner structures. The assistant had written the deserialization code in the prover module but hadn't tested it with real data until now.
  4. gRPC could handle a 51 MB message. The assistant had previously fixed a message size issue (visible in the Segment 4 summary), but whether the actual transfer would work with real data was unproven.
  5. The daemon would remain responsive during the long SRS load. The engine uses Tokio async tasks, and the SRS loading happens synchronously within the proof task. The assistant assumed this wouldn't block the gRPC server from handling other requests (like status checks).

Input Knowledge Required

To fully understand this message, one needs knowledge of:

Output Knowledge Created

This message creates several important pieces of knowledge:

  1. Validation that the entire gRPC pipeline works end-to-end. The 51 MB C1 output was transmitted, received, and deserialized without error. This confirms the protobuf schema, the tonic server configuration, and the message size limits are all correctly configured.
  2. Confirmation that the proof type registration works. The daemon correctly identified the proof as StackedDrg32GiBV1_1 and mapped it to the appropriate SRS parameter file. This validates the proof-type detection logic in the prover module.
  3. Evidence that the parameter cache path resolution works. The env var FIL_PROOFS_PARAMETER_CACHE=/data/zk/params was correctly picked up, and the daemon found the parameter file at the expected path. This validates the entire settings initialization chain.
  4. A baseline for SRS loading time. The message notes "This is going to take a while to load the SRS" — the actual load time will be measured in subsequent messages, providing a baseline for the SRS residency optimization (which later shows a 20.5% speedup).
  5. Confirmation that the supraseal CUDA backend works on Blackwell. This is a significant finding — it means the cuzk daemon can run on modern NVIDIA GPUs without modification, and that the sppark JIT compilation path handles new architectures correctly.

The Thinking Process Visible in the Message

The assistant's reasoning is laid out in a structured, almost checklist-like format. The numbered list (1–5) serves as a diagnostic log, walking through each stage of the pipeline and confirming it works:

  1. "C1 data received (51 MB), deserialized successfully" — confirms the gRPC transport and JSON parsing
  2. "Registered proof = StackedDrg32GiBV1_1 — correct!" — confirms the proof-type detection, with an exclamation mark showing relief
  3. "Cache miss on STACKED[34359738368] — first call, as expected" — confirms the SRS cache behavior is working, and the assistant anticipated this
  4. "Found params at /data/zk/params/v28-stacked-proof-of-replication-... — the env var worked!" — confirms the parameter path resolution, again with relief
  5. "Now loading the 45 GiB params file from disk into memory" — confirms the pipeline has progressed to the actual SRS loading phase The parenthetical "as expected" and "correct!" annotations reveal the assistant's mental model: each step was anticipated, and the actual behavior matches expectations. The exclamation marks ("correct!", "the env var worked!") betray the underlying tension — these were not guaranteed to work, and each confirmation reduces risk. The monitoring command that follows — tail -5 /tmp/cuzk-daemon.log && echo "---" && free -h | head -3 && echo "---" && nvidia-smi | grep "MiB" — shows a systematic approach to observing the system under load. The assistant isn't just watching one metric; it's watching three orthogonal indicators: application-level progress (log), host memory pressure (free), and GPU state (nvidia-smi). This triage reflects an understanding that a 45 GiB memory allocation could fail in multiple ways — out-of-memory on the host, CUDA out-of-memory on the GPU, or a crash in the parameter loading code.

Mistakes and Incorrect Assumptions

At this point in the conversation, no mistakes have been identified in this specific message. The assumptions all appear to hold. However, there is one subtle risk that the assistant does not address: the lazy_static initialization of SETTINGS could be triggered by any code path that accesses the parameter cache before the env var is set. If, for example, the gRPC server initialization or the engine startup code indirectly references parameter_cache_dir(), the SETTINGS would be initialized with the default path (/var/tmp/filecoin-proof-parameters/) before the env var override takes effect. The assistant's investigation in messages 212–218 confirmed this wasn't happening, but the risk was real.

Another potential concern is the 51 MB gRPC message. While it succeeded here, repeated large transfers could cause memory pressure on the daemon, especially under concurrent workloads planned for Phase 1. The assistant hasn't yet implemented streaming or chunked transfers.

Conclusion

Message 222 represents a pivotal validation milestone in the cuzk project. It transforms the daemon from "code that compiles" to "code that produces real proofs on real hardware." The message is a study in systematic validation: each stage of the pipeline is checked in order, assumptions are explicitly noted, and monitoring is multi-dimensional. The relief in the assistant's tone is earned — this validation required solving problems across GPU architecture compatibility, Rust environment variable semantics, gRPC message sizing, and Filecoin protocol specifics. With this milestone passed, the assistant can proceed to harden Phase 0 with observability improvements and then tackle the concurrent multi-GPU challenges of Phase 1, confident that the foundation is solid.