Why wasn't SP1 included in Kaspa's initial zero-knowledge implementation?

Kaspa's KIP-0016 passed over SP1 as its initial zkVM primarily because of maturity concerns at the time of evaluation. A security vulnerability discovered in early 2025 by LambdaClass and 3MI Labs — though responsibly disclosed and patched — raised questions about SP1's relative maturity. Additionally, questions about SP1's benchmark methodology, specifically around the use of a FRI blowup factor of 2 versus the industry-standard factor of 4, led to an a16z analysis suggesting a roughly 1.5× performance advantage that may not reflect real-world costs once recursion is fully implemented. The KIP explicitly leaves the door open for SP1 integration in the future as the system matures and more independent evaluation occurs. For a beginner, the key point is that Kaspa chose a more battle-tested starting point rather than a faster-moving but less proven alternative.