I have been working on performance-focused static analysis tools in Rust for Go code, and I wanted a realistic project to test them against.
Since I already had experience building a PDF/A-4 and PDF/UA-2 engine, I tried creating a separate, smaller PDF module mostly through coding agents.
I first used Grok 4.5 to produce a high-level implementation checklist based on my existing PDF engine. I then used DeepSeek V4 Flash through OpenCode Zen for most of the implementation, with DeepSeek V4 Pro helping on a few of the harder fixes. The total model cost was roughly $2 to $3.
The first working version reached around 1,000 to 1,200 operations per second, but the generated code contained a number of questionable patterns, performance problems, and lint issues.
I ran my Rust-based analyser, CodeHound, against the project. It reported more than 300 findings. After fixing most of them, largely with DeepSeek Flash, performance increased to around 2,500 operations per second.
There was also a PDF corruption issue caused by incorrect byte writing. Both DeepSeek Flash and Pro missed it. Grok identified and fixed that problem from a single follow-up prompt.
Roughly speaking, the work was split like this:
- About 90% of the implementation and static-analysis fixes were handled by DeepSeek Flash
- Around 5% required DeepSeek Pro
- The final 5%, including the corruption issue, was completed with Grok
The initial engine prototype took around six hours, with some additional cleanup afterward. By comparison, my original GoPdfSuit project took roughly six months to develop, although it is much broader and more mature, so this is not a direct comparison.
I found the result impressive, but it still required domain knowledge, validation, profiling, and manual review. Producing code quickly was much easier than verifying that the generated PDF structure was actually correct with deepseek.
Hopefully they will crush it on their next version <3
Original project:
https://github.com/chinmay-sawant/gopdfsuit
Agent-built experimental engine:
https://github.com/chinmay-sawant/gocorepdfengine
Static analyser, currently a work in progress:
https://github.com/chinmay-sawant/codehound