Read-only Windows MCP server cuts vision tokens 72% with delta canvas
Right-Mushroom6802 · reddit · 2026-11-15
A developer released super-computer-agent, a read-only Windows MCP server with 28 tools and zero input injection, tackling the token cost of full-screen PNGs in screen-using agents. Four observation layers are forced cheapest-first:
- Delta canvas: full keyframe only on scene change, then compact deltas (PATCH/SCROLL/MOVE/DC); RECALL cache makes alt-tabbing back cost 3–15 tokens. In tests, 9 canvas steps used 3,256 tokens vs 11,800 for full images.
- Live pixel grid: screen encoded as colored characters; UIA tree indices fused onto tiles so models see both shape and control identity. Background thread watches pixel changes plus SetWinEventHook events; verifyaction confirms clicks landed by comparing real pixels and OS events.
- UI tree: UI Automation as JSON, hiding password managers/banking/UAC, capped at 500 nodes.
- Screenshot: last resort, requires a valid-reason parameter.
Anti-default measures (priority tags in tool descriptions, NEXT hints, polling warnings) stop models from falling back to full screenshots. Caveats: beta, primary monitor only. Delta engines are closed-source .pyd gated by offline Ed25519 license (24h trial via email); the rest is AGPL-3.0.
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