Uniswap swap regression — release blocker for 0.0.28

[BitHighlander]

Status

🔴 Blocking release of 0.0.28 (PR #51).

Symptom

User signs Permit2 typed-data successfully on the device, but the Uniswap swap then fails:

POST https://trading-api-labs.interface.gateway.uniswap.org/v1/swap 404 (Not Found)
TransactionStepFailedError: SwapTransactionAsync failed during swap

Reproduces against ETH mainnet on 0x141D9959cAe3853b035000490C03991eB70Fc4aC. User confirms this is a real regression — not Uniswap quote expiry.

Full retro + handoff

See RETRO_uniswap_swap_release_blocker.md on develop for:

• Hypothesis table (what was tried, what was ruled out, what's still open)
• Test scaffolding built (keepkey-vault-v11/projects/keepkey-sdk/tests/evm-eip712/uniswap-permit-prod.js + fixtures)
• Concrete next steps in priority order

Quick triage path

1. Capture /v1/swap 404 response body in DevTools Network tab — most likely collapses 3+ hypotheses
2. Run node tests/evm-eip712/uniswap-permit-prod.js against local vault — proves vault EIP-712 path or rules it out
3. Then narrow to BEX layer (MetaMask masking shim, side-panel/popup merge, EIP-1193 emit timing)

Do not

• Merge PR release: 0.0.29 — dApp resilience pass + MetaMask masking default ON #51 until this is closed
• Cut a tag for 0.0.28

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