Senior TypeScript / Three.js Engineer for Browser Runtime Proof

I am looking for an experienced TypeScript and browser-runtime engineer to complete a small, tightly bounded technical proof involving a browser-based 3D runtime. This is not a website-design, game-art, 3D-modelling, animation or general full-stack role. The work requires careful separation of authoritative application state from browser presentation, strict fail-closed input validation, atomic state transitions, genuine WebGL renderer lifecycle testing and a precise evidence-backed handover. You should have direct, personally implemented experience with: * TypeScript and modern browser APIs * Three.js and genuine WebGL rendering * Vite and Vitest, or comparable reproducible tooling * Strict schema, event and state validation * Hostile or malformed JavaScript object handling * Atomic in-memory state transitions * Renderer and scene creation, destruction and reconstruction * Adversarial and failure-path testing * Chrome DevTools memory or performance profiling * Clean Git commits and reproducible project exports The successful freelancer will build a fresh and independent implementation in an assigned private Git repository. You will receive a detailed private technical brief and acceptance matrix after shortlisting, confidentiality confirmation and agreement to complete the work personally. The implementation must be completed personally by the hired freelancer. No subcontracting, team transfer, undisclosed collaborator access or disclosure of confidential project material to third parties or external AI services is permitted without prior written approval through Upwork. This is one bounded Candidate / Unapproved technical proof. It is not a production system, final engine selection, permanent development appointment or authorization for broader follow-on work. The final delivery will be independently reviewed. Written assurances, screenshots, videos or passing unit tests alone will not establish completion. The repository, exact final commit, exported ZIP, automated tests, production build, real-browser evidence, raw logs, profiling artifacts and documentation must agree and be independently reproducible. Required delivery will include: * Complete source code, tests, package manifest and dependency lockfile * Reproducible clean-install, test and production-build commands * One exact final Git commit and a clean ZIP exported from it * A genuine browser harness using a real Three.js WebGL renderer * Renderer and scene destruction/reconstruction testing * Adversarial validation and atomic-failure testing * Raw browser measurements and profiling evidence * Concise architecture, limitation and failure notes * A file-by-file reconciliation before final submission Commercial terms: * Fixed price: USD $125 * Delivery: 10 calendar days after written start authorization * Required midweek evidence checkpoint * Communication and file exchange through Upwork and the assigned private repository * Independent verification before milestone acceptance Accepting an offer will not authorize work to begin. Work begins only after the Upwork contract is active, the milestone is funded, confidentiality requirements are complete, the private brief has been acknowledged, repository access is ready and I issue separate written start authorization through Upwork. Please begin your proposal with the words BROWSER RUNTIME FOUNDATION so I know you have read the complete post. Answer every screening question directly. Clearly distinguish work you personally implemented from work completed by a team, work you only reviewed and claims that cannot currently be verified. Generic proposals will not be considered. APPLICATION QUESTIONS Please answer all five questions directly. Generic or incomplete proposals will not be considered. 1. Provide one or two examples of browser-based TypeScript and Three.js/WebGL work that you personally implemented. State exactly which parts were your own work and provide verifiable evidence where possible. 2. How would you prove that a real THREE.WebGLRenderer, canvas, scene and associated resources can be deliberately destroyed and reconstructed without using a mock renderer or leaving stale canvases, listeners or resources behind? State what reproducible evidence you would provide. 3. Describe your experience with strict, fail-closed TypeScript validation. Include how you test inherited properties, prototype manipulation, getters, caller mutation after validation, malformed input, unsafe integers and stale revisions. How would you prove that rejected input caused no partial state mutation? 4. Describe a project where you personally implemented an atomic in-memory state transition, snapshot import or transaction boundary. What failure cases did you test, and how did you prevent older or arbitrary state from being installed? Do not propose persistence, IndexedDB, browser recovery, sleep/resume or multi-tab coordination. 5. Confirm whether you personally accept the following terms: USD $125 fixed price; delivery within 10 calendar days after separate written start authorization; required Day 5 checkpoint; Upwork-only communication; no subcontracting; confidentiality; no unauthorized third-party or external AI disclosure; and independent acceptance review. Also provide the exact Node.js, package-manager, operating-system and browser versions you would use. Clearly distinguish work you personally implemented from work completed by a team, work you only reviewed and claims that cannot currently be verified.