Smooth Concierge draft streaming

[inimaga]

Explanation of Change

Adds a frontend pacing buffer for live Concierge draft events so server-delivered chunks are rendered progressively instead of snapping in as received. The draft provider now stores the latest server body as the target, reveals visible text character by character with catch-up/complete acceleration, preserves draft state across remounts, and keeps existing markdown cleanup so partial markdown does not render broken syntax.

Fixed Issues

$#89857
PROPOSAL: N/A

Tests

• Verify that no errors appear in the JS console

1. Login with an Expensifail account (Or with an account that is added to the explicit streaming beta)
2. Start a 1-on-1 DM with Concierge
3. Send it a message, ex: "How do I export a report?"
4. Observe that the streamed answer is streamed smoothly character by character

Offline tests

N/A

QA Steps

Same as manual test steps above

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
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  • The assets load correctly across all supported platforms.
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
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• If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
• I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
• I verified that similar component doesn't exist in the codebase
• I verified that all props are defined accurately and each prop has a /** comment above it */
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• I verified that all JSX used for rendering exists in the render method
• I verified that each component has the minimum amount of code necessary for its purpose, and it is broken down into smaller components in order to separate concerns and functions

Screenshots/Videos

Letter.by.letter.streaming.demo.mp4

[melvin-bot]

@dmkt9 Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

[github-actions]

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[github-actions]

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[codecov]

Codecov Report

❌ Looks like you've decreased code coverage for some files. Please write tests to increase, or at least maintain, the existing level of code coverage. See our documentation here for how to interpret this table.

Files with missing lines	Coverage Δ
src/pages/inbox/ConciergeDraftContext.tsx	96.29% <100.00%> (+62.20%)	⬆️
src/pages/inbox/conciergeDraftState.ts	94.85% <94.11%> (-0.11%)	⬇️
src/pages/inbox/usePusherDraftPacing.ts	74.17% <74.17%> (ø)
... and 28 files with indirect coverage changes

[inimaga]

@dmkt9 This is ready for review

[dmkt9]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 6e48f1ed1b

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[chatgpt-codex-connector]

Process empty started updates to advance stream session

Do not return early on started/updated events with empty bodyMarkdown while a previous draft is active. This early return skips switching the active streamSessionID, so if the new stream then emits failed or completed before sending a non-empty update, isStalePusherDraftEvent() treats those terminal events as stale (because currentDraftRef still points to the old stream) and drops them. In that sequence, the old synthetic draft can remain stuck instead of being cleared or finalized.

Useful? React with 👍 / 👎.

[dmkt9]

Hi @inimaga, do I need a specific account? I noticed that streaming data does not seem to occur with my test account.

2026-05-20.16-01-30.mp4

[inimaga]

@dmkt9 Yes, you need to login with an Expensifail account (Or with an account that is added to the explicit streaming beta). Could you dm me your account and I'll add it to the Beta?