[bfullam]

Explanation

On mid-tier Android, the first streamed quote reaches controller state well before it reaches the screen. The stream reader processes the rest of the buffered burst (parsing, validation, fees, and a state update for each quote, roughly 75–120ms each) back to back on the JS thread. The client's Redux flush and render only run once that work is done.

This PR adds an optional getShouldYieldAfterFirstQuote constructor option. When it returns true, the quote stream handler awaits one macrotask (setTimeout(0)) right after the first valid quote is written to state, so the client can flush and render it before the rest of the burst is processed. It's a getter, like getUseAssetsControllerForRates, so clients can A/B it behind a remote flag that's read at fetch time. When the option is omitted or returns false, behavior is unchanged.

Only the first valid quote of each stream triggers a yield, so it costs at most one task tick per fetch. Grouping later quote updates into fewer state writes is out of scope.

References

• Mobile: perf(bridge): flush first quote to Redux without batch delay metamask-mobile#38220 flushes the first quote to Redux without the batch wait. This change lets that flush render before the rest of the burst is processed.

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

  

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Note

Low Risk
Opt-in constructor flag with a single macrotask pause on the first quote only; default behavior is unchanged when the option is not used.

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@MetaMask/swaps-engineers (3 files)

• packages/bridge-controller/CHANGELOG.md
• packages/bridge-controller/src/bridge-controller.sse.test.ts
• packages/bridge-controller/src/bridge-controller.ts

ℹ️ Files co-owned by @MetaMask/core-platform (expand for more)

[!NOTE]
For convenience in maintaining this repo, @MetaMask/core-platform co-owns
the following files. It is not required to seek approval from
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• packages/bridge-controller/CHANGELOG.md

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

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[cursor]

Stale quotes written after yield

Medium Severity

After the first quote is written, the handler yields with setTimeout and then keeps processing the rest of the buffered burst with no abort check. A newer fetch that cancels this stream during that gap can still receive the remaining old quotes in state.quotes.

 

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