Bohdan Triapitsyn
3b8ed8fc36
Token-by-token streaming mutates the trailing paragraph in place on every tick: words rewrap, the last line jitters, and the whole reply reads as flicker. Streamed text now commits only up to the last complete line — prose arrives a paragraph at a time (a markdown paragraph is one logical line), code fences reveal line by line, tables row by row — and a shown block never changes again. A paragraph that runs long without a newline releases at the last sentence (then word) boundary so the stream never stalls. Applies to assistant text and reasoning; tool output keeps its raw tail. With growth arriving in block steps, the end follow switches to the list's animated mode so each step is a glide — reveal and scroll read as one continuous motion. The gesture opt-out now measures at-end from the live list state instead of the cached flag, which the animated glide deliberately leaves stale while trailing the edge; without that, a drag during a glide could leave the scroll-to-bottom pill unshown. Measured: end-following holds at distance 0 for the whole stream, and the mobile drag opt-out shows the pill in three of three runs. The continuous glide costs ~15% more main-thread time per streamed character than the instant follow — the price of the motion.
40 lines
1.4 KiB
TypeScript
40 lines
1.4 KiB
TypeScript
import { describe, expect, test } from 'bun:test';
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import { commitStreamedText } from './streamTextCommit';
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describe('commitStreamedText', () => {
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test('holds an incomplete short paragraph entirely', () => {
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expect(commitStreamedText('An unfinished thought abo')).toBe('');
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});
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test('commits up to the last complete line', () => {
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expect(commitStreamedText('First paragraph.\n\nSecond par')).toBe('First paragraph.\n\n');
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});
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test('reveals code fences line by line', () => {
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const text = '```py\nprint("a")\nprint("b';
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expect(commitStreamedText(text)).toBe('```py\nprint("a")\n');
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});
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test('releases a long held paragraph at the last sentence boundary', () => {
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const sentence = 'A finished sentence lives here. ';
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const text = sentence.repeat(12) + 'and an unfinished trail';
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expect(commitStreamedText(text)).toBe(sentence.repeat(12));
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});
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test('falls back to the last word boundary without sentences', () => {
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const words = 'word '.repeat(70);
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const text = words + 'unfinishe';
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expect(commitStreamedText(text)).toBe(words);
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});
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test('keeps unbreakable runs intact rather than splitting them', () => {
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const run = 'x'.repeat(400);
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expect(commitStreamedText(run)).toBe(run);
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});
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test('empty input stays empty', () => {
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expect(commitStreamedText('')).toBe('');
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});
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});
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