Build Log

First Horizon Spike: Disappearing Platform, End to End

August 3, 2026

Delivered the exact vertical slice nextItems[4] of the 2026-08-01 scaffold session called for: a child picks a timing, previews it in plain language, the app builds one disappearing platform in a real Roblox Studio session via a fixed Luau template, playtests it, and reports success or failure in plain English, with one-click rollback.

Game BuilderExperimentRoblox MCP

1 of 1

nextItems deliverable from the 2026-08-01 scaffold session's acceptance criteria fully met

new/changed source files (roblox-mcp.ts expanded from a stub, mcp-client.ts new, DisappearingPlatformCockpit.tsx new) plus 1 new API route

live Roblox Studio MCP round-trips verified in this retro pass — no Studio session was available to test against; see gate_checks

Timeline

Unknown

Actual build session — timeline not recoverable

No commits, no session JSON, no transcript reference exist for the session that wrote this code. See provenance_note.

2026-08-03

Found, read, committed

Discovered as uncommitted working-tree state during an unrelated medinaCHF session; read in full, tsc-verified, committed as 48baa8a; this retro written after the fact.

What shipped

experiments/game-builder/lib/roblox-mcp.ts — expanded from the 2026-08-01 stub ('Not implemented.') into two real functions: addDisappearingPlatform() and undoLastDisappearingPlatform(), each sending exactly one fixed, hand-written Luau template to a real MCP client's executeLuau(), with only a validated numeric timingSeconds interpolated in

experiments/game-builder/lib/mcp-client.ts (new) — a real StdioClientTransport connection to the Roblox Studio MCP bridge (@modelcontextprotocol/sdk), separate from any Claude Code MCP connection, wrapping execute_luau/start_stop_play/get_console_output

experiments/game-builder/app/api/workpiece/disappearing-platform/route.ts (new) — server-side POST handler for build/playtest/undo actions, keeping the real MCP client off the browser

experiments/game-builder/app/DisappearingPlatformCockpit.tsx (new) — the child-facing step UI: ask timing -> preview in plain language -> build -> built (playtest/undo) -> playtesting -> done/error, each state its own screen

experiments/game-builder/package.json — added @modelcontextprotocol/sdk as a real dependency (not a stub import)