NextTurn

Private bidding rounds for savings groups that choose each payout by bidding. Members offer to take less than the pot in exchange for receiving it this round. Offers stay hidden until opening, and the result can be checked against the original rules. The group still collects contributions and pays members itself.

Built for ZECATHON 2026 · Private Markets. The original procurement framing is preserved in project history.

Previously called Sealed Tender. The checkout path, native tender-verify command and existing file/protocol formats keep their names for compatibility.

Public practice demo: https://nextturn-pro.vercel.app/
Source: https://github.com/Daveboss123/next-turn

Current checkpoint: 27 October 2026

Implemented:

• Separate white/black/forest-green landing page and Open app workspace.
• NextTurn branding, locally hosted Manrope, adapted Illos free illustrations and a grouped footer. Asset sources and licences.
• A scroll-away landing header, faint background footer wordmark and scroll-only fade-and-slide entrances that repeat on viewport re-entry. Bars grow and the pot ring draws when reached, not on page load. Reduced motion is respected; no scroll hijack or external animation library.
• Original local SVG charts using clearly labelled example rounds, not live data.
• Responsive hero: the illustration sits beside the hero text at reduced size on tablets and is hidden on phone widths. Checked from 360 px to 1280 px with no horizontal overflow.
• Editable Round settings for participants, pot, maximum discount and deadlines. They open before an offer, collapse after applying, and lock once a bid exists. Starting a new round keeps the settings and reopens the panel.
• Practice flow: offer → save private bid file → close → open → check result.
• A wrong-winner demonstration and separate public-result import/export.
• A bid-file download acknowledgement that survives navigation within the app, without browser storage or accounts.
• Rules-bound salted commitments, strict memo/address validation and integer-only money handling.
• Version-2 bids bind a fresh Ed25519 proof key; local winner signing/checking and public challenge/proof files. Version-1 rules remain readable, without claiming ownership verification. The Ownership check button shows a spinner with Checking ownership… while pending, and the spinner stays still under reduced motion. Ownership and limits.
• Testnet round-file and wallet request builders, including local QR codes, exact fields for manual Zingo entry, and fresh/stale local chain-tip gates.
• Safe dedicated receiver creation: secret files stay local and only the public address is printed. Private files are never added to public exports.
• Rejected file replacements clear older inputs; accepted challenges cannot be reused in the same page. This is not durable replay/payout enforcement.
• Incoming-only native reading for Sapling, Orchard and Ironwood; independent result verification with fail-closed full-window retrieval.
• No accounts, analytics, remote fonts, bid API or transaction relay. Production CSP blocks application network connections.

Build and public practice demo prepared for final review. The 120-second, captioned practice-only demo video is rendered and verified locally: 1920×1080, 30 fps, H.264 High, AAC stereo 48 kHz, exactly 120.000 s, with a "Try it yourself" end card. It shows the public practice flow with locally generated narration; the save acknowledgement is explicitly labelled as simulated. It is not embedded in or deployed with the app. David uploads it separately, and its public URL, registration/team, eligibility and final submission confirmation remain. A dedicated security review and genuine user feedback have not been completed. The current live checks confirm testnet connectivity, a funded Zingo wallet and one valid rules anchor; they are not proof of a completed sealed-offer round. The full two-offer wallet round has been set aside for the quick submission path. The public practice experience is simulation, not two real participants or a real savings group's use. Do not claim otherwise.

Run locally

Use Node 24 or newer. On Windows, use npm.cmd so PowerShell's script policy does not block npm. Do not change system security settings to run the project.

npm.cmd install
npm.cmd run dev

Open the URL Vite prints. The site starts with the landing page; Open app starts a local practice round. No wallet or real money is needed.

Production preview:

npm.cmd run build
npm.cmd run preview -- --host 127.0.0.1 --port 4173

Practice and unsaved bid data are held only in memory. Refreshing or leaving the workspace clears them. Save the private bid file before paying or leaving; anyone with that file can read the amount and control its bid-proof key. Never publish it or share it with the organiser.

The single download my bid file button opens Save As when supported. If the picker cannot open, that same button uses the browser's normal download flow; check that the file is accessible and tick I have this bid file saved locally. A download request alone does not unlock the next step. Embedded Review-browser downloads may stay in its own file panel rather than Windows Downloads. No file contents are copied to a clipboard or uploaded by the app.

Verify the build

npm.cmd test
npm.cmd run lint
npm.cmd run build

For the Rust tool, run from verifier/:

cargo test --locked
cargo build --locked

On David's machine the existing build cache is outside the repo:

$env:CARGO_TARGET_DIR = 'C:\Users\David\.builds\sealed-tender'
cargo test --locked
cargo build --locked

Compare the independent TypeScript and Rust outcome implementations from the project root:

node tests/cross-language.ts 'C:\Users\David\.builds\sealed-tender\debug\tender-verify.exe'

These tests use generated public practice records, never local wallet files.

Local desktop/phone UI screenshots on Windows can be repeated with:

node scripts/capture-ui.mjs http://127.0.0.1:4173/

This uses a fresh temporary Edge profile at 1280px, 768px, 390px and 360px. It checks overflow, header/footer behaviour, repeatable entrances and reduced-motion cancellation. Entrances repeat after fully leaving/re-entering view; initial content does not fade on page load. It never uses your normal browser profile or wallet files.

Production file/signature/wallet-request flow checks:

node scripts/check-flows.mjs http://127.0.0.1:4173/
node scripts/check-flows.mjs https://nextturn-pro.vercel.app/
node scripts/check-local-files.mjs
node scripts/check-release.ts

The flow uses generated fixtures and holds private downloads in browser memory, not Downloads or storage. The local-file guard probes only a new harmless canary, never actual keys. The release checker uses source/distribution filenames and the reviewed public licence inventory. None deploys or proves a real-wallet round.

Builds reject unreviewed public/ files, redirected output directories and stale licence inventories. Vite copies public/ without filtering, so this explicit allowlist is intentional: new public assets must be reviewed first. The release check rejects private-looking git candidates and extra distribution artifacts without opening them. Filename checks are not a complete secret-content audit.

Independent checks

The browser and node audit.ts result.json check supplied records only. An imported JSON file cannot prove that the organiser included every bid.

The native verifier independently retrieves the full round from a public light-client server. It needs the public round file and the organiser's published incoming viewing key, not a recovery phrase or spending key:

tender-verify verify https://testnet.zec.rocks:443 incoming-key.txt round.json --out result.json

Add a winning commitment as an optional argument to check a declaration, or none to check a no-winner declaration. --out writes UTF-8 and refuses to overwrite an existing file. tender-verify check result.json is an offline file check, not independent chain retrieval.

For the first rules transaction only:

tender-verify check-anchor https://testnet.zec.rocks:443 incoming-key.txt round.json transaction-id

This retrieves and checks the anchor's recipient, fixed payment, shielded source, memo and timing without printing keys or unexpected memo text. It does not check the full bidding window. The receiver key stays local and unpublished until the commitment deadline has passed.

The light-client server is still a trust assumption. This is not full-node consensus validation. See the protocol and threat model.

Ownership against supplied results:

tender-verify check-claim result.json expected-challenge.json public-winner-proof.json

The checker must issue a fresh nonce. Reusing an accepted challenge is not a new ownership check. The browser's in-memory consumption history is lost on refresh; native file verification has no persistent consumption or payout state.

Preparing a controlled testnet round

Follow the live-demo procedure. Use a dedicated receiver, never your funded wallet's viewing key. New local receiver files can be created without printing secret material:

tender-verify receiver-init test --out-dir .local/round-receiver-1
tender-verify tip-json test https://testnet.zec.rocks:443 --out .local/tip-1.json

Use new filenames/folders; these commands refuse overwrites. private/seed.bin and private/incoming-key.txt remain private. Only public/receiver.json is needed to prepare rules. The seed is not used for reading a round. Never copy private files into public/, which Vite copies directly into the build.

Privacy and scope

• Every revealed amount becomes public after incoming-key disclosure, including losing offers. Bid memos do not contain names; permanent anonymity against network metadata or identifying patterns is not promised.
• Publish only a dedicated incoming viewing key, after bidding closes. Never publish a seed, recovery phrase, full viewing key or private bid file.
• The native checker rejects transparent-source bids. The browser refuses transparent fallback receivers and unsupported address formats.
• Membership, planted bids below the member count, collusion, missed payouts, custody, eligibility, local regulation and disputes are outside this MVP.
• A static host can see page requests and IPs. A compromised frontend can read what you type. CSP and passing tests are not a substitute for a security audit.
• No mainnet financial use. Example payout splits do not enforce a group's actual financial arrangements.

Third-party libraries are React/Vite/TypeScript, qrcode, @noble/hashes for address decoding, the pinned librustzcash ecosystem and ed25519-compact for native bid-key signatures. Illos free SVG artwork and Manrope are incorporated under their own licences and served locally. The charts and NextTurn mark are original. No reference-site runtime, hosted widget, telemetry hook or remote font loader is embedded. See asset credits.

Hackathon release checklist

Follow the verified official requirements. Deadline: 28 October 2026, 23:59 UTC. The submission form requires both a usable demo link and a two-minute video, a repository public at submission, and exactly one track. Publishing and wallet use require David's approval.

No real user feedback has been collected. Record consented observations in the feedback log; never invent validation or participation.

The source repository was approved for publication and verified public on 25 October 2026: https://github.com/Daveboss123/next-turn. The public practice demo is deployed at https://nextturn-pro.vercel.app/. The required two-minute video is rendered and checked locally; David uploads it and supplies the public URL. It is not part of the app deployment. This repository being public does not mean the hackathon entry is submitted.

Continue later

For public project context, read the protocol and submission draft. Internal builder notes are kept locally, not released. Wallet sends remain user-controlled; an unfinished live flow is never presented as completed.

Licence

Original project code is MIT-licensed; David confirmed that choice on 25 October 2026. See LICENSE and THIRD_PARTY_NOTICES.md. Third-party artwork, fonts and dependencies retain their own terms. The reviewed inventory and original licence texts are under docs/licences/reviewed/; the frontend build carries project, browser-library and font notices. Native CI artifacts are configured to include their notice bundle. This is a notice inventory, not a completed legal audit.

The description/video plan is in docs/SUBMISSION.md. Source and static demo publication were approved; no hackathon submission or wallet spending is automatic.