Quarterly longitudinal panel of GitHub engineering-velocity signals across 55 venture-backed startups in 20 sectors, spanning 5 quarters from Q2 2025 through Q2 2026 (219 startup-period observations). Collected by VC Deal Flow Signal from the public GitHub REST API.Each observation records rolling 14-day commit velocity, unique-contributor count, new-repository creation, and a deterministic classification into one of four acceleration patterns: framework migration, engineering hiring burst, infrastructure buildout, and deploy frequency spike.Live data: signals.gitdealflow.com/api/signals.csv (refreshed weekly).Kaggle mirror: kaggle.com/datasets/thedatanerd2026/vc-deal-flow-signal.Data.world mirror: data.world/thedatanerd2026/vc-deal-flow-signal-startup-engineering-acceleration.Full methodology: signals.gitdealflow.com/methodology.Designed for venture-capital deal sourcing, academic research on alternative data in VC, and predictive modeling of startup funding events. Released under CC BY 4.0 — free to reuse with attribution.