# Session Log — 2026-07-05

## Completed
- **DAG refactoring** (`scratchpad/dag.c`): Decoupled PrGraph from PrNodeManager.
  Graph tracks its own active vertices (`vertex_count`, `max_vertex_ever`, `b8 active`).
  `prGraphAddEdge`, `prGraphTopologicalSort` no longer take `PrNodeManager*`.
  Kahn's algorithm integrated into `prGraphAddEdge` for cycle detection with rollback.
  Output verified matching baseline.
- **RHI research document** written to `documents/research/rendering-hardware-interface.md`.
  Covers 8 reference RHIs, architecture patterns, core API surface, Vulkan-specific
  considerations, Slang integration, and proposed directory layout / lifecycle design.
- Added NVRHI to `documents/resources.md`.
- **RHI API surface** (`scratchpad/rhi/pr_rhi.h`, `pr_rhi_types.h`): Full RHI API
  designed with compile-time alias dispatch, by-value desc structs, wapp array types
  for pointer+count replacement, `PrRhiSwapchainResult` enum, surface capabilities,
  compute pipeline support, all primitive topologies, and aligned function declarations
  grouped by subsystem section.
- **Initial opencode setup** (opencode.json, justfile, skills, trimmed AGENTS.md).

## Key Decisions
- Graph API is self-contained — no graphics or node-manager dependencies.
- RHI will use compile-time alias dispatch (`#define prRhiCreateDevice prRhiCreateDeviceVk`)
  over vtbl — zero runtime overhead, dead-stripping, separate builds per backend.
- `justfile` (Just) as task runner.
- Object lifecycle: `prRhiCreate*` / `prRhiDestroy*` with explicit `WpAllocator*`.
- All GPU state explicit (no hidden pipeline state).
- Per-frame command pools and descriptor pools, arena-allocated scratch.
- `#version-macro` convention removed from Slang files; `__slang` define used instead.
- Desc structs passed by value (not `const *`) for simpler caller ergonomics.
- Array aliases grouped: opaque handles (`**`) first, value types (`*`) second, separated
  by blank line — element types before array aliases before desc structs.

## Next Steps
- Begin Vulkan backend implementation starting with `pr_rhi_vk_device.c` (instance/device/surface/swapchain creation).
- Implement Slang shader compilation + reflection integration.
- Wire up per-frame lifecycle (command pool reset, descriptor pool reset, scratch reset).
