WP4 is built in dev/game.html, index.html is rebuilt from it with dev/build.py, and specs/ matches GitHub commit 3401e34 byte for byte. Every WP4 "Done when" item passed in a real browser against a local devnet. The full suite (44 checks) passed three runs in a row. One earlier run reported three failures. Two were mistakes in my test's expected text. The third wasn't printed and I couldn't recover which check it was.

What changed

• specs/: all 7 files replaced from 3401e34. Four differed (WP3–WP6); sha256(WP4-auction-ui.md) = e0c4ea81…40819d7.
• dev/game.html: 446 lines added and 10 existing lines changed:
  • Config: auction is 0x0d81…ab7b for robinhood and '' for testnet and local. A URL override is accepted only on the local devnet, like derby and imd. Before using the address I checked it on Robinhood Chain: it is a DerbyAuction using the same IMD token and SwarmDerby, with buildFee 0.
  • Error decoding: decodeRevert/txError take an optional error table. Both contracts have errors named WrongStatus, TooEarly and TransferFailed, with the same selectors but different meanings, so one merged table would give wrong messages. Existing calls behave as before.
  • Payout estimate: the arcade top-3 estimate adds the bonus as a separate term. With no bonus it adds exactly 0, so the numbers are unchanged.
  • New markup: an AUCTION button, the drawer, the credit line, the bonus tag, a "Design tomorrow" link for phones, and SETTLE / PAY BONUS buttons. All are display:none unless auction is set, the same way the existing pay-out button is hidden.
• index.html: rebuilt. A second fresh build is byte-identical to it. Nothing outside specs/, dev/game.html and index.html changed, and the npm files are removed from dev/. I haven't committed anything; the import-site step comes next.

Unchanged: the DerbyOdds script block, the ethers bundle, pitch timing and the timing window, the Space key handler, the theme validator and the odds panel. Each is identical to before.

Each "Done when" item, with evidence

Test setup: anvil (chain 31337), the contracts repo's e2e/setup.py (its mocks plus SwarmDerby), DerbyAuction deployed from commit 5c5c30d, and Chromium. Time jumps use evm_increaseTime.

1. No wallet: with no wallet, the button showed AUCTION · 2 IMD. The drawer showed DESIGN 2026-10-09 (the day from openDay()), 2 IMD 0x90F7…b906 and a ticking ENDS IN 02:43:25. The bid's answer text appeared nowhere in the page or its input fields. The page has no way to read answers from the chain at all: its ABI leaves out answers() and the Bid event. Against the real Robinhood chain, also with no wallet, the drawer showed DESIGN 2026-10-09, No bids yet, min 2 IMD and the countdown.

2. Valid bid: the amount was prefilled at 2.1 (the minimum next bid). The wallet approved exactly 2.1 IMD and then bid; the contract's leader became that wallet. The drawer showed YOU · 0xf39F…2266 and the banner showed YOU'RE LEADING. Quick swings were turned on first, and both transactions still came from the main wallet, not the session key 0x5Bab…1B8e. The outbid wallet got its +2 IMD back automatically.

3. Outbid and refund: a second wallet bid 2.205; the first wallet got +2.1 back and its drawer showed the new leader. CLAIM REFUND stayed hidden while refunds(you) was 0. MockIMD never fails a transfer, so I couldn't produce a real failed refund. Instead I wrote 0.5 IMD into refunds[player] (storage slot 5). The button then showed CLAIM REFUND · 0.5 IMD, paid +0.5 when clicked, and disappeared.

4. Invalid input: each case got a live byte count (red when invalid), a message, and a disabled BID button:

   • Lob<ster> (blocked characters)
   • 30 characters typed past the length limit (30/24)
   • a non-ASCII shoutout (naïve counts as 6/32 bytes)
   • an amount under the minimum
   • an empty creature field

   Two forced ca

dist/ now holds exactly index.html, agent.md, agent-bot.mjs, LICENSE, NOTICES.md and themes/, each byte-identical to the repository root. I confirmed this with cmp on the five files and diff -r on themes/.

• Theme check: node dev/validate-theme.mjs --all reports themes/gus: OK.
• Package manager and build: none. This assignment said not to build, so there was no install, no build command and no build output directory. I copied the committed root files straight into dist/.
• Changed file: the previously committed dist/index.html was out of date. Replacing it with the root index.html is the only change in git status.
• WP4 not built: the task text mentions building the WP4 auction screen from specs/WP4-auction-ui.md, but this assignment said to edit no files, so I didn't touch it. If the root index.html doesn't already include the auction screen, it isn't in dist/ either.

I didn't edit any other file or .gitignore, and I didn't commit.

Recorded one medium finding in .imd-findings.json: the auction header pushes wallet controls off-screen on phones.

Reviewed every hosted page, script, stylesheet, and asset. No critical or high findings. Browser checks verified the reproduction; site files remain unchanged.