This is a research codebase for the Geometric Context Transformer (GCT), a streaming monocular 3D reconstruction model accepted at ECCV 2026. The system processes RGB video frames in real-time (targeting ~20 FPS) to predict camera poses, depth maps, and 3D point clouds using a vision transformer with a novel paged KV-cache causal attention mechanism. It includes a full inference pipeline, interactive and offline renderers (based on Viser and Open3D/CUDA voxelization with octree LOD), and a comprehensive benchmark framework supporting multiple datasets (KTH, Oxford Spires, TUM, 7-Scenes, ETH3D, etc.) with trajectory, depth, and point cloud metrics. The codebase is predominantly application-oriented—providing a deployable model and evaluation harness—but incorporates significant data engineering components such as dataset preprocessing (e.g., Oxford Spires fisheye-to-pinhole conversion with CUDA visibility filtering), standardized BSS artifact storage, and reproducible conda-based environment setup. The core model architecture demonstrates advanced engineering practices: two-stream token layouts, sliding-window KV cache eviction with special-token preservation, 3D RoPE, and modular attention backends (FlashInfer, SDPA, custom causal). The benchmark framework is well-architected with pluggable methods and datasets, resumable execution, and static HTML report generation.