ScreenshotRunner

Captures the game's framebuffer for the take_screenshot tool.

The render thread's whole contribution is one pixel-array copy; scaling and encoding run on the calling (HTTP) thread, so a screenshot costs the game a texture readback and nothing else. The hop over is vanilla's own Minecraft#execute rather than a lane — there is no tick affinity to respect here, just a thread requirement.

JPEG at a fixed size and quality, with nothing exposed to the caller: both are questions only whoever consumes the image can answer, and that is a model with no idea what resolution it can actually see. The cost of getting them wrong is ours, so the numbers are ours.

Loads only when the client path is actually taken, so it never touches client classes on a dedicated server. Minecraft.getInstance() is non-null from mod init on, but half-built until its constructor returns — the execute hop is what makes that safe, not Lanes.RENDER.isReady, which is a physical-side constant and would not catch a render-state read placed ahead of it.