ETHOnline backup: Uniswap sdks #720 (DCA EIP-712)

Read-only prep. No SDK or UniswapX source edits and no PR until the ETHOnline window is open (4 Sep 2026 16:00 UTC). This is the Uniswap Foundation “Best Uniswap Stack Contribution” path ($1,000 × 3 Start Fresh): an improvement to an official Uniswap repo plus FEEDBACK.md and the hackathon feedback form.

Rechecked: 3 September 2026 ~03:40 UTC

Fact	Evidence
Issue	https://github.com/Uniswap/sdks/issues/720 — `open`, 0 comments, opened 2026-09-02 by `gomesalexandre`. No linked PR. GitHub search for `DCAIntent` / `hashDCAIntent` / `FeedInfo` in that repo returns only this issue.
Prize page	https://ethglobal.com/events/ethonline2026/prizes/uniswap-foundation (HTTP 200). Qualification: public GitHub repo, `FEEDBACK.md`, feedback form link. README must point at the changed files. Continuity-track $2k is a separate prize — do not enter this as Continuity.
SDK tree	local clone `/tmp/uniswap-sdks` at `35c4e35` (“chore(sdks): Version Packages (#719)”).
Contract tree	local clone `/tmp/uniswapx` at `fd60225`. Authoritative hasher is `src/v4/hooks/dca/DCALib.sol`.
Competing PR	0. Recheck immediately before coding.

Do not copy this note into either Uniswap repo.

What is wrong (verified against the clones)

sdks/uniswapx-sdk/src/order/v4/hashing.ts hashes DCA intents four ways that DCALib.sol does not. A signature built with the published SDK will not be accepted by DCAHook.

Axis	Contract (`DCALib.sol`)	SDK (`hashing.ts`)
`FeedInfo` shape	`FeedInfo(FeedTemplate feedTemplate, address feedAddress, string feedType)` plus nested `FeedTemplate` (`DCALib.sol:25-27`, `DCAStructs.sol:6-18`)	`FeedInfo(bytes32 feedId, address feed_address, string feedType)` (`hashing.ts:287-288`). `FeedTemplate` does not exist in the SDK.
Referenced-struct order in `DCA_INTENT_TYPE`	`FeedInfo`, `FeedTemplate`, `OutputAllocation`, `PrivateIntent` (`DCALib.sol:37-41`)	`OutputAllocation` then `PrivateIntent` (which already appends old `FeedInfo`) (`hashing.ts:407-426`)
`string feedType`	`keccak256(bytes(feeds[i].feedType))` (`DCALib.sol:78`)	`defaultAbiCoder.encode(..., "string", feed.feedType)` (`hashing.ts:317-323`) — encodes the string, not its hash
Struct-array hashing	`keccak256(abi.encodePacked(hashes))` (`DCALib.sol:81, 90`)	`defaultAbiCoder.encode(["bytes32[]"], [hashes])` (`hashing.ts:331-336, 397-402`) — adds offset + length words

The same file already does the right thing elsewhere: hashHybridOutputs / hashPriceCurve use ethers.utils.solidityPack (hashing.ts:196-214). DCA_COSIGNER_DATA_TYPE matches the contract byte-for-byte (hashing.ts:495-496 vs DCALib.sol:44-45). Only the DCA intent path is stale (landed 2025-12-19 as SDK PR #432 against the pre-#351 FeedInfo).

File-level map — open these first on 4 Sep

SDK (the PR)

File	Why
`sdks/uniswapx-sdk/src/order/v4/types.ts`	Replace `FeedInfo` (`~198`) with `FeedTemplate` + `feedAddress` (camelCase, matching the contract). Keep `DCAIntent` / `PrivateIntent` / `OutputAllocation` field order.
`sdks/uniswapx-sdk/src/order/v4/hashing.ts`	Rewrite `FEED_INFO_TYPE`, add `FEED_TEMPLATE_TYPE`, fix `PRIVATE_INTENT_TYPE` and `DCA_INTENT_TYPE` suffix order (alphabetical referenced structs). Hash strings with `keccak256(toUtf8Bytes(...))`. Hash arrays with `solidityPack` of `bytes32` hashes, not `defaultAbiCoder.encode(["bytes32[]"])`. Export `hashFeedTemplate` if tests need it. Leave `hashDCACosignerData` alone.
`sdks/uniswapx-sdk/src/order/v4/index.ts`	Re-export any new types / hash helpers used by tests.
`sdks/uniswapx-sdk/src/order/v4/hashing.test.ts` (new)	There is no DCA hash test today (only `HybridOrder.test.ts`). Add fixtures that match `DCALib.hash` / `hashPrivateIntent` / `_hashFeedInfoArray`. Prefer Foundry FFI or a checked-in Solidity fixture if `FFISignDCAIntent.sol` is present on the UniswapX tip after a full clone; otherwise compute expected hashes with a tiny `forge` script against `DCALib` and paste them. Cover: empty arrays, one feed, two feeds, empty vs non-empty `feedType`, nested `FeedTemplate` string arrays.
`sdks/uniswapx-sdk/src/order/index.ts`	Only if the public barrel currently exports the old `FeedInfo` shape — update the export, do not silently break Hybrid types.

Do not bump the published package version in this PR unless maintainers ask. Do not change Hybrid hashing.

Contract (read-only reference, do not PR unless a fixture is missing)

File	Why
`src/v4/hooks/dca/DCALib.sol`	Source of truth for type strings and `_hashFeedTemplate` / `_hashFeedInfoArray` / `_hashOutputAllocations` / `hash` / `hashWithInnerHash`.
`src/v4/hooks/dca/DCAStructs.sol`	`FeedTemplate`, `FeedInfo`, `DCAIntent`, `PrivateIntent`.
`src/v4/hooks/dca/DCAHook.sol`	Confirm the hook calls `DCALib.hash` / `hashWithInnerHash` on the signed digest. Do not change it.

Acceptance

hashDCAIntent + hashPrivateIntent on a fixture equal DCALib.hash / hashPrivateIntent for the same struct.
Array hashing matches abi.encodePacked (empty array → keccak256("")).
Existing Hybrid tests still pass.
Issue #720 is referenced in the PR body.
After the window opens: commit in small steps, add FEEDBACK.md in the ETHOnline submission repo (not in Uniswap/sdks unless they want it), and file the Uniswap feedback form with that link.

Human blockers

ETHGlobal hacker application + 0.01 ETH stake.
A GitHub account that can open a PR on a fork of Uniswap/sdks. Optional GITHUB_FORK_TOKEN so this agent can push the branch.
Public repo for the ETHOnline submission that points at the Uniswap PR.

No UniswapX / sdks code before 4 Sep 16:00 UTC.