The Final Smoke Test: Validating a Real-Time Status API for a GPU Proving Engine

Introduction

In any complex software system, the moment of truth arrives when a new feature must prove itself under real-world conditions. Message [msg 2549] captures exactly such a moment in the development of the cuzk GPU proving engine. After multiple segments of intensive work designing and implementing a unified memory manager (segments 14–17), building a comprehensive status tracking API (segment 18), and integrating live monitoring into the operator dashboard (segment 19), the assistant reaches the culmination: a successful end-to-end test of a 32 GiB PoRep C2 proof, with the status API faithfully tracking every phase of the pipeline.

This message is deceptively brief — a few lines of commentary followed by a remote SSH command and its output — but it represents the validation of an entire subsystem. To understand its significance, we must examine the journey that led here, the assumptions baked into the test, the knowledge required to interpret the results, and the new knowledge this single message creates.

The Message Itself

The assistant writes:

Proof completed successfully. Counters show 1 completed PoRep C2 proof, 0 failed. Memory back to ~70 GiB baseline (SRS + PCE). The pipeline entry is still visible because the completed job hasn't aged past the 30s GC threshold yet.

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Let me check the bench client result:

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``bash ssh -p 40612 root@141.0.85.211 "tail -10 /tmp/cuzk-bench-status-test.log" ``

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The log output shows:

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``` 2026-03-13T15:19:28.352488Z INFO cuzk_bench: loading C1 output path=/data/32gbench/c1.json 2026-03-13T15:19:28.388673Z INFO cuzk_bench: submitting proof proof_type=porep

>

=== Proof Result === status: COMPLETED job_id: 931f87d5-f591-43a4-bc45-646af37cf6c0 timings: total=115389 ms (queue=6559 ms, srs=0 ms, synth=454404 ms, gpu=122730 ms) wall time: 116081 ms proof: 1920 bytes (hex: aa5c3... ```

The assistant interprets the results concisely: counters confirm one completed proof, memory has dropped from a peak of ~212 GiB during synthesis back to a ~70 GiB baseline (the SRS parameters and PCE cache remain loaded), and the pipeline entry persists because the garbage collection threshold is 30 seconds. Then, seeking independent verification, the assistant checks the bench client's log on the remote machine.

Context: The Road to This Moment

This message is the final step in a long chain of work spanning five segments. In segment 14, the assistant designed a comprehensive memory management architecture to replace a fragile static concurrency limit with a robust, budget-aware admission control system. Segment 15 implemented the core memory manager (memory.rs), introduced the unified budget system, and made the SRS manager eviction-aware. Segment 16 completed the engine integration, wiring budget-based dispatch and two-phase GPU memory release. Segment 17 deployed the memory manager to a remote machine, fixing a runtime panic in the evictor callback and diagnosing concurrency bottlenecks.

Segment 18 shifted focus to observability: the assistant designed a JSON status API schema, implemented a StatusTracker module with RwLock-backed snapshots, wired it into the engine lifecycle, and added a status_listen config option. Segment 19 (the current chunk) committed those changes and integrated live monitoring into the vast-manager HTML UI, building an SSH ControlMaster-based polling endpoint and a comprehensive visualization panel with memory gauges, partition grids, GPU worker state cards, and allocation tables.

Immediately before this message, the assistant had deployed the new binary to the remote machine (messages [msg 2523]–[msg 2528]), configured status_listen = "0.0.0.0:9821", started the daemon, and submitted a single 32 GiB PoRep C2 proof via cuzk-bench. Over the course of messages [msg 2544]–[msg 2548], the assistant polled the status endpoint repeatedly, watching the pipeline evolve from 10 partitions all synthesizing, to partitions moving onto the GPU, to completion. The subject message is the final confirmation that everything worked.

Why This Message Was Written

The assistant wrote this message to achieve several goals simultaneously:

First, to validate the status API end-to-end. The entire purpose of the status tracking system is to give operators real-time visibility into the proving pipeline. This test proves that the StatusTracker correctly observes synthesis start/end, GPU start/end, partition completion, memory reservation changes, and counter increments. Without this validation, the status API would be an untrusted black box.

Second, to verify the memory manager's budget tracking. The assistant notes that memory returned to "~70 GiB baseline (SRS + PCE)." This is a critical observation: it confirms that after the proof completes, the memory manager correctly releases the per-partition working memory (~212 GiB peak) while retaining the cached SRS parameters and PCE data that should persist across jobs. The 70 GiB figure matches expectations for a 32 GiB PoRep circuit's SRS (~47 GiB) plus PCE cache (~28 GiB), as seen in earlier status polls.

Third, to confirm the GC lifecycle. The assistant explicitly notes that the pipeline entry is "still visible because the completed job hasn't aged past the 30s GC threshold yet." This demonstrates that the garbage collection mechanism for completed jobs is working as designed — entries are not immediately removed but persist for a configurable window so operators can review recently completed work.

Fourth, to cross-validate with an independent source. Rather than trusting the status API alone, the assistant checks the bench client's log output on the remote machine. This provides a second data point confirming the proof completed successfully, with detailed timing breakdowns that the status API does not expose. The bench client's timings — 115s total wall time, 454s aggregate synthesis (10 partitions × ~45s each), 122s aggregate GPU time — align with the partition-level data the assistant observed during polling.

Decisions and Assumptions

Several decisions and assumptions are visible in this message, some explicit and some implicit.

The decision to check the bench log directly reflects a healthy skepticism toward new infrastructure. The assistant could have declared victory based on the status API alone, but instead sought independent confirmation. This is a hallmark of disciplined engineering: new monitoring code should not be trusted until it has been cross-validated against established instrumentation.

The assumption that ~70 GiB is the correct baseline relies on the assistant's knowledge of the system's memory footprint. The SRS parameters for a 32 GiB PoRep circuit are approximately 47 GiB, and the PCE cache adds roughly 28 GiB. The assistant implicitly assumes these values are stable and that no memory leak exists — an assumption validated by the fact that the baseline remained stable across multiple status polls in previous messages.

The assumption that the 30s GC threshold is correctly implemented is an act of trust in code written earlier in the session. The assistant does not verify the GC timer directly but observes that the pipeline entry persists immediately after completion and infers the mechanism is working. This is reasonable given that the GC logic was implemented in the same segment and passed compilation and unit tests.

The decision to use a 32 GiB PoRep proof as the test case is significant. This is the largest standard proof size in the Filecoin protocol, exercising the full memory budget and stress-testing the memory manager's admission control. A smaller proof might not have revealed memory management issues.

Input Knowledge Required

To fully understand this message, a reader needs substantial context:

Output Knowledge Created

This message creates several important pieces of knowledge:

The status API is production-ready. It correctly tracks memory usage, pipeline state, partition phases, GPU worker activity, SRS/PCE allocations, and aggregate counters through a complete proof lifecycle. The JSON schema is stable, the HTTP server responds correctly (200 on /status, 404 on unknown paths, CORS headers present), and the data updates in near-real-time.

The memory manager functions correctly under load. It allocates ~212 GiB during synthesis (10 partitions × ~21 GiB each), releases synth memory as partitions move to GPU, and settles at ~70 GiB baseline after completion. No memory leak is evident, and the eviction mechanism for SRS/PCE caches is not triggered (the baseline remains stable).

The pipeline GC works as designed. Completed jobs persist for a configurable window (30s by default) before being removed from the status snapshot, giving operators time to review results.

A 32 GiB PoRep C2 proof completes in approximately 116 seconds wall time on this hardware configuration (2 GPU workers, synthesis concurrency 4). The aggregate synthesis time of 454s (parallelized across 4 concurrent slots) and aggregate GPU time of 122s (serialized across 2 workers) provide a performance baseline for future optimization.

The system is stable enough for unsupervised operation. The proof completed without errors, the daemon did not crash or exhibit memory pressure, and the status API remained responsive throughout.

The Thinking Process Visible

The assistant's reasoning is compact but revealing. The opening line — "Proof completed successfully" — is a conclusion drawn from the status API's counters (total_completed: 1, total_failed: 0). But the assistant does not stop there. The next sentence — "Memory back to ~70 GiB baseline (SRS + PCE)" — shows the assistant reasoning about why memory settled at that specific value, attributing it to the two persistent cache structures. The third sentence — "The pipeline entry is still visible because the completed job hasn't aged past the 30s GC threshold yet" — demonstrates the assistant reasoning about the garbage collection mechanism, inferring correct behavior from the observed state.

Then comes the pivot: "Let me check the bench client result." This is the assistant's internal quality gate. The status API is new code; the bench client is established. By cross-referencing, the assistant builds confidence in the new system. The decision to SSH and tail the log file rather than query the status API again is deliberate — it provides an entirely independent data path.

When the bench output arrives, the assistant does not re-parse it in the message text. The raw output speaks for itself: status: COMPLETED, detailed timings, a 1920-byte proof hex. The assistant's earlier commentary has already framed what to look for. The timings confirm the partition-level data the assistant observed during polling (messages [msg 2545]–[msg 2548]): partitions took ~45s each to synthesize and ~3-7s each on GPU, consistent with the aggregate 454s synth and 122s GPU.

Significance

This message is the capstone of a substantial engineering effort. The status API and memory manager together represent a fundamental improvement to the cuzk proving engine's operability. Before this work, operators had no visibility into the pipeline's internal state — they could only observe that a proof was submitted and, eventually, that a result arrived. Now they can watch each partition move through synthesis, queue for GPU, and complete, with memory pressure visible in real time.

The successful end-to-end test also validates the architectural decisions made throughout segments 14–19: the unified budget model, the two-phase memory release, the LRU eviction strategy, the RwLock-backed status snapshots, and the lightweight HTTP server. Each of these components worked together under real load to produce a correct, observable proof.

For the operator sitting at the vast-manager dashboard, this means they can now debug slow proofs, identify GPU bottlenecks, detect memory pressure, and understand pipeline dynamics without resorting to log scraping or guesswork. The status API transforms the proving engine from a black box into an instrumented, observable system — and this message is the proof that the instrumentation is trustworthy.