[hryhoriiK97]

What/Why?

streamingAnimation sounds like a fade, but it switches on everything streaming does:

• the streaming session: held-back tables, code blocks and media, and repaired inline syntax;
• the pending code block header;
• every arrival animation.

There was no way to stream without the fade, and the name hid what the prop is for.

This is the fifth PR of the streaming stack, stacked on #1149. It renames the prop to streaming and adds streamingConfig.animation.

The streaming stack

1. feat: rebuild markdown streaming and add a streaming API #1140: measure and schedule.
2. feat(core): prepare streamed markdown in one core session #1141: the core streaming session.
3. perf: render only the tail of a streamed text segment #1146: render only the tail.
4. perf(ios): draw only the part of a long document near the screen #1149: iOS memory, drawing only the part of a long document near the screen.
5. This PR: streaming and streamingConfig.animation.
6. The stream object: createMarkdownStream() with append / end / reset, text fed to a C++ buffer without a React render per token.
7. Custom streaming animations: the 'gradient' preset and the animation object.

How

streaming replaces streamingAnimation in the types, the codegen specs and both platforms. streamingAnimation stays as a deprecated alias: streaming ?? streamingAnimation ?? false, so streaming wins when both are set. There's no runtime warning: react-native-streamdown sets streamingAnimation on every view, so a warning would reach all its users. The @deprecated tag marks it in editors.

streamingConfig.animation: 'fade' (default) or 'none'.

• 'none' turns off the arrival animations:
  • the text tail fade;
  • block and table row fades;
  • the grow-in of blocks drawn by renderers.
• Streaming itself keeps working: the held-back blocks, the repaired syntax and the pending code block header follow streaming as before.
• Switching to 'none' mid-stream, or turning streaming off, shows what is still fading at once on both platforms. On Android, the segmented host now keeps one text fade animator per text view, as iOS does, so it can stop them.
• animation changes no layout, so it isn't part of the measurement keys (iOS ENRMStreamingRenderEqual, Android stream-update hash).

Ending a stream: turning streaming off gives one unfiltered render, as before. The docs now say to do it.

onStreamingEnd: called when the view stops streaming, once streaming turns false. It fires once per stream, from where each host ends streaming, and not when the view unmounts mid-stream. iOS and Android only, like streaming. Later in the stack it also fires when a stream ends (#1151), and with smooth pacing only once the last words have appeared (#1159).

Testing

Unit tests:

• Jest: streaming and animation reach the native view, animation defaults to 'fade', streamingAnimation alone arrives as streaming, and streaming={false} overrides streamingAnimation. onStreamingEnd reaches the callback.
• Results: Jest 1,814 of 1,814, iOS 95 of 95, Android 119 of 119; ktlint and typecheck clean.

Devices: Release build on an iPhone 15 Pro (iOS 26.6.1). The 80 KB github "forest" and 66 KB commonmark "chat" streams from #1146 were each streamed three ways. A scratch counter logged the text tail fades started and the frames with an opacity animation on screen.

Stream	Prop	Updates shown	Text fades	Frames animating	Final height = static
github forest	streamingAnimation	1,315	1,125	5,808	yes
github forest	streaming	1,312	1,121	5,529	yes
github forest	streaming, animation: 'none'	1,313	0	0	yes
commonmark chat	streamingAnimation	1,100	1,099	0	yes
commonmark chat	streaming	1,100	1,099	0	yes
commonmark chat	streaming, animation: 'none'	1,100	0	0	yes

The old and new props behave the same. 'none' starts no fade, and every stream still shows every update and ends at the static height.

onStreamingEnd, added later: iOS and Android build at this PR. At the top of the stack, checked with Argent on the iOS simulator and the Pixel 9 emulator: it fires once per stream in both flavors, with smooth pacing on and off, and when smooth is turned off during the final reveal.

On a Pixel 9 emulator (Android 16, Release build), the github forest stream through the deprecated streamingAnimation (sent to native as streaming) ends at 75,660.58, the same height as mounting the document in one go.

Docs

• The API reference, the streaming guide and docs-md describe streaming, the deprecated alias and animation.
• The prop's example is renamed with it and now stops streaming once the text is complete.
• The reference said streamingConfig only works with flavor="github"; it works in both flavors.
• onStreamingEnd has its reference entry and a line in the guide's Reference list.
• check-examples, check-llms and yarn build pass.

Changes after review

• Deprecation. react-native-streamdown is deprecated: this package holds back incomplete blocks and repairs half-written syntax natively. streamingAnimation logs a one-time development warning pointing to streaming. While it is on it also holds back incomplete blocks and repairs syntax, so turn it off when the stream ends. Migration notes are in both streaming guides, BREAKING_CHANGES.md and the README.
• iOS stops a block's fade (tables included) without relying on UIKit's animation key. Android hashes only the streaming modes in the stream-update key.
• The Jest mock calls onStreamingEnd when streaming turns off.
• Docs: the docs-md streaming guide matches the Docusaurus guide; JSDoc, web tables and examples are updated, and the example app uses streaming.

Checked on the whole stack after these changes: core suite and fuzzing, Jest (1,838), Android unit tests (134), iOS unit tests (118), ktlint; streams on an iPhone 15 Pro and a Galaxy A16 call onStreamingEnd once and end at the static height, with CPU level or lower; the 106 Maestro flows give the same results and screenshots as before.

PR Checklist

• Code compiles and runs on iOS
• Code compiles and runs on Android
• Updated documentation/README if applicable
• Ran example app to verify changes
• E2E tests are passing (not run)
• Required E2E tests have been added (if applicable): Jest tests

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