When a Fix Doesn't Fix: The Moment of Verification in Production Debugging

The Message

[user] seems still bad id - 2026-03-13T10:10:25.968225Z  INFO cuzk_core::pipeline: GPU prove complete (split) proof_count=1 proof_bytes=192 gpu_ms=16491
TIMELINE,2260853,GPU_END,ps-porep-1000-1,worker=1,partition=5,gpu_ms=16491
2026-03-13T10:10:25.968370Z  INFO cuzk_core::engine: partition GPU prove complete job_id=ps-porep-1000-1 partition=5 gpu_ms=16491 filled=0
CUZK_TIMING: async_dealloc_ms=485 ?

This message, sent by the user in the midst of a high-stakes production debugging session, is a masterclass in concise, evidence-driven communication. In just five lines—four of them verbatim log output—the user communicates a devastating finding: the carefully crafted fix that was just deployed has not taken effect. The job_id in the cuzk engine logs still reads ps-porep-1000-1, the exact same format that caused the catastrophic "partition 0 already inserted" panic and rendered all ten PoRep partitions invalid. The fix, which was supposed to append the harmony task ID to create ps-porep-%d-%d-%d, simply isn't there.

Context: The Battle Against Job ID Collision

To understand the weight of this message, one must appreciate the debugging marathon that preceded it. The ProofShare system in Curio is a distributed proving pipeline where multiple concurrent tasks generate GPU-based proofs for Filecoin sectors. The cuzk engine, a Rust-based GPU proving library, uses a job_id string as a key in its internal JobTracker.assemblers HashMap. This HashMap collects partition results from GPU workers and assembles them into complete proofs.

The problem emerged because ProofShare challenges, issued by an external service (cusvc/powsrv), all target the same sector: miner=1000, sector=1. This is a bench/testing sector used for all challenges. When multiple PSProve tasks ran concurrently, they all sent the identical job_id = "ps-porep-1000-1" to cuzk. The engine's partition assembler, keying on this job_id, would mix partition results from different proofs together. The symptom was unmistakable: a panic reading "partition 0 already inserted", followed by all ten partitions reporting INVALID during verification.

The assistant traced the root cause to the RequestId generation in task_prove.go:338, which used fmt.Sprintf("ps-porep-%d-%d", sectorID.Miner, sectorID.Number). The fix was conceptually simple: add the harmony task ID to make the identifier unique per invocation, matching the pattern already used by the computeSnap path. The code was edited, the binary was rebuilt inside a Docker CUDA environment, and it was deployed to the remote vast GPU host with a version tag of _psfix2.

The Devastating Verification

The user's message arrives after that deployment. It is a single sentence—"seems still bad id"—followed by raw log output. The evidence is damning:

• GPU_END,ps-porep-1000-1,worker=1,partition=5: The timeline event still shows the old job_id format. No task ID suffix.
• job_id=ps-porep-1000-1 partition=5 gpu_ms=16491 filled=0: The engine log confirms the job_id is unchanged. The filled=0 field is particularly telling—it suggests the partition assembler slot is empty or mismatched, a likely consequence of the ongoing collision.
• async_dealloc_ms=485 ?: The trailing question mark is the user's own annotation, a subtle signal of confusion or suspicion. Something is off. The user does not need to spell out the conclusion. The logs speak for themselves. The fix that was supposed to change the format string from ps-porep-%d-%d to ps-porep-%d-%d-%d has produced a binary that still emits the old two-field format. Either the code change was not compiled into the binary, or the running process is not the new binary, or the cuzk daemon is processing stale jobs from before the restart. Any of these possibilities represents a failure in the deployment pipeline.

Assumptions Embedded in the Message

The user makes several assumptions, all of which are reasonable given the context:

1. The assistant will immediately recognize the problem. The user does not explain why ps-porep-1000-1 is wrong. They assume the assistant remembers that the fix was to add a third field (the task ID). This is a safe assumption given the intense, collaborative debugging session.
2. The log evidence is sufficient proof. The user does not ask the assistant to verify the binary or check the version string. They present the raw evidence and let it speak. This reflects a shared understanding that log output from the running system is the ultimate source of truth.
3. The fix was conceptually correct but the deployment failed. The user does not question the logic of adding a unique identifier. They implicitly accept that the fix is right but something went wrong in the build or deploy step. This assumption turns out to be correct—the Go build cache in Docker prevented the modified source files from being recompiled.
4. The assistant can and should debug this further. The message is not a complaint or a resignation. It is a handoff: "Here's the evidence, figure out why." The user trusts the assistant to trace the gap between the intended fix and the deployed binary.

The Hidden Complexity: Docker Build Caching

What the user's message does not show—but what the subsequent investigation reveals—is the subtle failure mode of Docker-based Go builds. The assistant had used docker run --volumes-from curio-rebuild2 to build the binary. This approach mounts the builder container's filesystem, including the Go module cache. When the assistant copied the modified source files into the container using docker cp, the Go compiler saw that the source files had changed and should have recompiled them. However, Go's build cache is sophisticated: if the compiler determines that the object files are still valid (based on content hashes of dependencies), it may skip recompilation even when source files are modified. The --volumes-from approach, combined with the way docker cp updates files, apparently did not trigger a full rebuild.

The result was a binary that carried the _psfix2 version tag (because that was set via -ldflags and always gets written) but contained the old format string ps-porep-%d-%d in the compiled code. The version tag was a false positive—it suggested the fix was present when it was not.

Input Knowledge Required

To fully understand this message, a reader needs:

• Knowledge of the ProofShare architecture: That PSProve tasks generate PoRep proofs using the cuzk GPU engine, that the engine uses job_id as a HashMap key for partition assembly, and that concurrent tasks with identical job_ids cause partition mixing.
• Knowledge of the previous fix: That the assistant changed the RequestId format from ps-porep-%d-%d to ps-porep-%d-%d-%d by adding the harmony task ID, and that this was deployed as binary version _psfix2.
• Knowledge of the crash symptom: The "partition 0 already inserted" panic and the 0/10 valid verification result.
• Knowledge of the deployment pipeline: That binaries are built inside Docker containers using a curio-builder:latest image, copied out to /tmp, and SCP'd to the remote host.
• Familiarity with Go build caching: The subtle behavior where modified source files may not trigger recompilation if the Go compiler's content hashing decides the object files are still valid.

Output Knowledge Created

This message creates critical knowledge that ripples forward through the rest of the session:

1. The fix is not deployed correctly. This invalidates the assistant's previous conclusion and forces a deeper investigation into the build pipeline itself.
2. Version tags are not reliable indicators of code content. The _psfix2 binary had the correct version string but the old format string. This is a painful but valuable lesson about trusting build metadata.
3. Docker build caching is a liability for hotfixes. The --volumes-from approach, while convenient, does not guarantee that modified source files are recompiled. The subsequent fix (in the next chunk) switches to direct bind mounts (-v) for the source files, which forces a full recompile.
4. The debugging methodology must extend to the deployment pipeline. When a fix doesn't work, the first question should not be "is the code wrong?" but "is the deployed binary actually the fixed binary?" The user's message implicitly teaches this lesson.
5. Log output is the ultimate verification mechanism. No amount of version checking, hash comparison, or "it compiled fine" can substitute for seeing the actual behavior in production logs. The user's insistence on checking the logs after deployment is what caught this failure.

The Thinking Process Visible in the Message

The user's thinking is compressed into a few characters but is remarkably rich:

• "seems still bad id": The user has checked the logs, spotted the familiar ps-porep-1000-1 pattern, and formed a hypothesis: the fix didn't work. The word "seems" conveys appropriate caution—they are presenting evidence, not a definitive conclusion.
• The log selection: The user chose four specific log lines that together tell the complete story. The GPU_END line shows the job_id in the timeline event. The partition GPU prove complete line shows the job_id in the structured log. The filled=0 field hints at the ongoing assembly problem. The async_dealloc_ms=485 ? with the question mark suggests the user noticed something anomalous about the timing or is questioning whether this is expected.
• The question mark: This is the most human element in the message. It is not part of the log output—it is the user's own annotation. It could mean "why is this only 485ms?" or "is this normal?" or simply "something is wrong here." It invites the assistant to investigate further.

Conclusion

Message 1997 is a pivotal moment in the production debugging session. It is the point where a seemingly successful fix is revealed to be ineffective, forcing the team to look beyond the code change itself and examine the deployment pipeline. The user's concise, evidence-driven communication style—four log lines and a question mark—demonstrates a deep understanding of the system and a trust in the assistant's ability to interpret the evidence correctly. The message creates a turning point: the debugging effort shifts from "what is the bug?" to "why isn't the fix deployed?"—a subtle but crucial distinction that ultimately leads to the discovery of Docker build caching as the culprit. In the broader narrative of the session, this message is the moment of verification that separates a theoretical fix from an actual one, and it underscores the cardinal rule of production debugging: trust the logs, not the version string.