ai

import { convertArrayToReadableStream } from '@ai-sdk/provider-utils/test'; import { smoothStream } from './smooth-stream'; import { TextStreamPart } from './stream-text-result'; import { ToolSet } from './tool-set'; import { beforeEach, describe, expect, it } from 'vitest'; describe('smoothStream', () => { let events: any[] = []; beforeEach(() => { events = []; }); async function consumeStream(stream: ReadableStream<any>) { const reader = stream.getReader(); while (true) { const { done, value } = await reader.read(); if (done) break; events.push(value); } } function delay(delayInMs: number | null) { events.push(`delay ${delayInMs}`); return Promise.resolve(); } describe('throws error if chunking option is invalid', async () => { it('throws error if chunking strategy is invalid', async () => { expect(() => { smoothStream({ chunking: 'foo' as any, }); }).toThrowError(); }); it('throws error if chunking option is null', async () => { expect(() => { smoothStream({ chunking: null as any, }); }).toThrowError(); }); }); describe('word chunking', () => { it('should combine partial words', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello', type: 'text-delta', id: '1' }, { text: ', ', type: 'text-delta', id: '1' }, { text: 'world!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "Hello, ", "type": "text-delta", }, { "id": "1", "text": "world!", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should split larger text chunks', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello, World! This is an example text.', type: 'text-delta', id: '1', }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "Hello, ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "World! ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "This ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "is ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "an ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "example ", "type": "text-delta", }, { "id": "1", "text": "text.", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should keep longer whitespace sequences together', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'First line', type: 'text-delta', id: '1' }, { text: ' \n\n', type: 'text-delta', id: '1' }, { text: ' ', type: 'text-delta', id: '1' }, { text: ' Multiple spaces', type: 'text-delta', id: '1' }, { text: '\n Indented', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toEqual([ { id: '1', type: 'text-start' }, 'delay 10', { id: '1', text: 'First ', type: 'text-delta', }, 'delay 10', { id: '1', text: 'line \n\n', type: 'text-delta', }, 'delay 10', { // note: leading whitespace is included here // because it is part of the new chunk: id: '1', text: ' Multiple ', type: 'text-delta', }, 'delay 10', { id: '1', text: 'spaces\n ', type: 'text-delta', }, { id: '1', text: 'Indented', type: 'text-delta', }, { id: '1', type: 'text-end' }, ]); }); it('should send remaining text buffer before tool call starts', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'I will check the', type: 'text-delta', id: '1' }, { text: ' weather in Lon', type: 'text-delta', id: '1' }, { text: 'don.', type: 'text-delta', id: '1' }, { type: 'tool-call', toolCallId: '1', toolName: 'weather', input: { city: 'London' }, }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "I ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "will ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "check ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "the ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "weather ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "in ", "type": "text-delta", }, { "id": "1", "text": "London.", "type": "text-delta", }, { "input": { "city": "London", }, "toolCallId": "1", "toolName": "weather", "type": "tool-call", }, { "id": "1", "type": "text-end", }, ] `); }); it('should send remaining text buffer before tool call starts and tool call streaming is enabled', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { type: 'text-delta', id: '1', text: 'I will check the' }, { type: 'text-delta', id: '1', text: ' weather in Lon' }, { type: 'text-delta', id: '1', text: 'don.' }, { type: 'tool-input-start', toolName: 'weather', id: '2', }, { type: 'tool-input-delta', id: '2', delta: '{ city: "London" }' }, { type: 'tool-input-end', id: '2' }, { type: 'tool-call', toolCallId: '1', toolName: 'weather', input: { city: 'London' }, }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "I ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "will ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "check ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "the ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "weather ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "in ", "type": "text-delta", }, { "id": "1", "text": "London.", "type": "text-delta", }, { "id": "2", "toolName": "weather", "type": "tool-input-start", }, { "delta": "{ city: "London" }", "id": "2", "type": "tool-input-delta", }, { "id": "2", "type": "tool-input-end", }, { "input": { "city": "London", }, "toolCallId": "1", "toolName": "weather", "type": "tool-call", }, { "id": "1", "type": "text-end", }, ] `); }); it(`doesn't return chunks with just spaces`, async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { type: 'text-delta', id: '1', text: ' ' }, { type: 'text-delta', id: '1', text: ' ' }, { type: 'text-delta', id: '1', text: ' ' }, { type: 'text-delta', id: '1', text: 'foo' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, { "id": "1", "text": " foo", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); }); describe('line chunking', () => { it('should split text by lines when using line chunking mode', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'First line\nSecond line\nThird line with more text\n', type: 'text-delta', id: '1', }, { text: 'Partial line', type: 'text-delta', id: '1' }, { text: ' continues\nFinal line\n', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, chunking: 'line', _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "First line ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "Second line ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "Third line with more text ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "Partial line continues ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "Final line ", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should handle text without line endings in line chunking mode', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Text without', type: 'text-delta', id: '1' }, { text: ' any line', type: 'text-delta', id: '1' }, { text: ' breaks', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: 'line', _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, { "id": "1", "text": "Text without any line breaks", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); }); describe('custom chunking', () => { it(`should return correct result for regexes that don't match from the exact start onwards`, async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello_, world!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: /_/, delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "Hello_", "type": "text-delta", }, { "id": "1", "text": ", world!", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should support custom chunking regexps (character-level)', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello, world!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: /./, delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "H", "type": "text-delta", }, "delay 10", { "id": "1", "text": "e", "type": "text-delta", }, "delay 10", { "id": "1", "text": "l", "type": "text-delta", }, "delay 10", { "id": "1", "text": "l", "type": "text-delta", }, "delay 10", { "id": "1", "text": "o", "type": "text-delta", }, "delay 10", { "id": "1", "text": ",", "type": "text-delta", }, "delay 10", { "id": "1", "text": " ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "w", "type": "text-delta", }, "delay 10", { "id": "1", "text": "o", "type": "text-delta", }, "delay 10", { "id": "1", "text": "r", "type": "text-delta", }, "delay 10", { "id": "1", "text": "l", "type": "text-delta", }, "delay 10", { "id": "1", "text": "d", "type": "text-delta", }, "delay 10", { "id": "1", "text": "!", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); }); describe('custom callback chunking', () => { it('should support custom chunking callback', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'He_llo, ', type: 'text-delta', id: '1' }, { text: 'w_orld!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: buffer => /[^_]*_/.exec(buffer)?.[0], _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "He_", "type": "text-delta", }, "delay 10", { "id": "1", "text": "llo, w_", "type": "text-delta", }, { "id": "1", "text": "orld!", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); describe('throws errors if the chunking function invalid matches', async () => { it('throws empty match error', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello, world!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: () => '', _internal: { delay } })({ tools: {}, }), ); await expect( consumeStream(stream), ).rejects.toThrowErrorMatchingInlineSnapshot( `[Error: Chunking function must return a non-empty string.]`, ); }); it('throws match prefix error', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello, world!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: () => 'world', _internal: { delay } })({ tools: {}, }), ); await expect( consumeStream(stream), ).rejects.toThrowErrorMatchingInlineSnapshot( `[Error: Chunking function must return a match that is a prefix of the buffer. Received: "world" expected to start with "Hello, world!"]`, ); }); }); }); describe('delay', () => { it('should default to 10ms', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello, world!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "Hello, ", "type": "text-delta", }, { "id": "1", "text": "world!", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should support different number of milliseconds delay', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello, world!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 20, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 20", { "id": "1", "text": "Hello, ", "type": "text-delta", }, { "id": "1", "text": "world!", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should support null delay', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello, world!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: null, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay null", { "id": "1", "text": "Hello, ", "type": "text-delta", }, { "id": "1", "text": "world!", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); }); describe('text part id changes', () => { it('should change the id when the text part id changes', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { type: 'text-start', id: '2' }, { text: 'I will check the', type: 'text-delta', id: '1' }, { text: ' weather in Lon', type: 'text-delta', id: '1' }, { text: 'don.', type: 'text-delta', id: '1' }, { text: 'I will check the', type: 'text-delta', id: '2' }, { text: ' weather in Lon', type: 'text-delta', id: '2' }, { text: 'don.', type: 'text-delta', id: '2' }, { type: 'text-end', id: '1' }, { type: 'text-end', id: '2' }, ]).pipeThrough( smoothStream({ _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, { "id": "2", "type": "text-start", }, "delay 10", { "id": "1", "text": "I ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "will ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "check ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "the ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "weather ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "in ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "London.", "type": "text-delta", }, "delay 10", { "id": "2", "text": "I ", "type": "text-delta", }, "delay 10", { "id": "2", "text": "will ", "type": "text-delta", }, { "id": "2", "text": "check ", "type": "text-delta", }, "delay 10", { "id": "2", "text": "the ", "type": "text-delta", }, "delay 10", { "id": "2", "text": "weather ", "type": "text-delta", }, "delay 10", { "id": "2", "text": "in ", "type": "text-delta", }, { "id": "2", "text": "London.", "type": "text-delta", }, { "id": "1", "type": "text-end", }, { "id": "2", "type": "text-end", }, ] `); }); }); describe('reasoning smoothing', () => { it('should combine partial reasoning words', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'reasoning-start', id: '1' }, { text: 'Let', type: 'reasoning-delta', id: '1' }, { text: ' me ', type: 'reasoning-delta', id: '1' }, { text: 'think...', type: 'reasoning-delta', id: '1' }, { type: 'reasoning-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "reasoning-start", }, "delay 10", { "id": "1", "text": "Let ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "me ", "type": "reasoning-delta", }, { "id": "1", "text": "think...", "type": "reasoning-delta", }, { "id": "1", "type": "reasoning-end", }, ] `); }); it('should split larger reasoning chunks', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'reasoning-start', id: '1' }, { text: 'First I need to analyze the problem. Then I will solve it.', type: 'reasoning-delta', id: '1', }, { type: 'reasoning-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "reasoning-start", }, "delay 10", { "id": "1", "text": "First ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "I ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "need ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "to ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "analyze ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "the ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "problem. ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "Then ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "I ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "will ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "solve ", "type": "reasoning-delta", }, { "id": "1", "text": "it.", "type": "reasoning-delta", }, { "id": "1", "type": "reasoning-end", }, ] `); }); it('should flush reasoning buffer before tool call', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'reasoning-start', id: '1' }, { text: 'I should check the', type: 'reasoning-delta', id: '1' }, { text: ' weather', type: 'reasoning-delta', id: '1' }, { type: 'tool-call', toolCallId: '1', toolName: 'weather', input: { city: 'London' }, }, { type: 'reasoning-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "reasoning-start", }, "delay 10", { "id": "1", "text": "I ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "should ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "check ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "the ", "type": "reasoning-delta", }, { "id": "1", "text": "weather", "type": "reasoning-delta", }, { "input": { "city": "London", }, "toolCallId": "1", "toolName": "weather", "type": "tool-call", }, { "id": "1", "type": "reasoning-end", }, ] `); }); it('should use line chunking for reasoning', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'reasoning-start', id: '1' }, { text: 'Step 1: Analyze\nStep 2: Solve\n', type: 'reasoning-delta', id: '1', }, { type: 'reasoning-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, chunking: 'line', _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "reasoning-start", }, "delay 10", { "id": "1", "text": "Step 1: Analyze ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "Step 2: Solve ", "type": "reasoning-delta", }, { "id": "1", "type": "reasoning-end", }, ] `); }); }); describe('interleaved text and reasoning', () => { it('should flush text buffer when switching to reasoning', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { type: 'reasoning-start', id: '2' }, { text: 'Hello ', type: 'text-delta', id: '1' }, { text: 'world', type: 'text-delta', id: '1' }, { text: 'Let me', type: 'reasoning-delta', id: '2' }, { text: ' think', type: 'reasoning-delta', id: '2' }, { type: 'text-end', id: '1' }, { type: 'reasoning-end', id: '2' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, { "id": "2", "type": "reasoning-start", }, "delay 10", { "id": "1", "text": "Hello ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "world", "type": "text-delta", }, { "id": "2", "text": "Let ", "type": "reasoning-delta", }, "delay 10", { "id": "2", "text": "me ", "type": "reasoning-delta", }, { "id": "2", "text": "think", "type": "reasoning-delta", }, { "id": "1", "type": "text-end", }, { "id": "2", "type": "reasoning-end", }, ] `); }); it('should flush reasoning buffer when switching to text', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'reasoning-start', id: '1' }, { type: 'text-start', id: '2' }, { text: 'Thinking ', type: 'reasoning-delta', id: '1' }, { text: 'hard', type: 'reasoning-delta', id: '1' }, { text: 'The answer', type: 'text-delta', id: '2' }, { text: ' is 42', type: 'text-delta', id: '2' }, { type: 'reasoning-end', id: '1' }, { type: 'text-end', id: '2' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "reasoning-start", }, { "id": "2", "type": "text-start", }, "delay 10", { "id": "1", "text": "Thinking ", "type": "reasoning-delta", }, "delay 10", { "id": "1", "text": "hard", "type": "reasoning-delta", }, { "id": "2", "text": "The ", "type": "text-delta", }, "delay 10", { "id": "2", "text": "answer ", "type": "text-delta", }, "delay 10", { "id": "2", "text": "is ", "type": "text-delta", }, { "id": "2", "text": "42", "type": "text-delta", }, { "id": "1", "type": "reasoning-end", }, { "id": "2", "type": "text-end", }, ] `); }); it('should handle multiple switches between text and reasoning', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'reasoning-start', id: 'r1' }, { type: 'text-start', id: 't1' }, { text: 'Think ', type: 'reasoning-delta', id: 'r1' }, { text: 'Hello ', type: 'text-delta', id: 't1' }, { text: 'more ', type: 'reasoning-delta', id: 'r1' }, { text: 'world ', type: 'text-delta', id: 't1' }, { type: 'reasoning-end', id: 'r1' }, { type: 'text-end', id: 't1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "r1", "type": "reasoning-start", }, { "id": "t1", "type": "text-start", }, "delay 10", { "id": "r1", "text": "Think ", "type": "reasoning-delta", }, "delay 10", { "id": "t1", "text": "Hello ", "type": "text-delta", }, "delay 10", { "id": "r1", "text": "more ", "type": "reasoning-delta", }, "delay 10", { "id": "t1", "text": "world ", "type": "text-delta", }, { "id": "r1", "type": "reasoning-end", }, { "id": "t1", "type": "text-end", }, ] `); }); }); describe('providerMetadata preservation', () => { it('should preserve providerMetadata on reasoning-delta chunks (signature for Anthropic thinking)', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'reasoning-start', id: '1' }, { text: 'I am', type: 'reasoning-delta', id: '1' }, { text: ' thinking...', type: 'reasoning-delta', id: '1' }, // signature as an empty delta with providerMetadata { text: '', type: 'reasoning-delta', id: '1', providerMetadata: { anthropic: { signature: 'sig_abc123' }, }, }, { type: 'reasoning-end', id: '1' }, { type: 'text-start', id: '2' }, { text: 'Hello!', type: 'text-delta', id: '2' }, { type: 'text-end', id: '2' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); // Find the last reasoning-delta chunk const reasoningDeltas = events.filter( (e: any) => e.type === 'reasoning-delta', ); const lastReasoningDelta = reasoningDeltas[reasoningDeltas.length - 1]; expect(lastReasoningDelta).toHaveProperty('providerMetadata'); expect(lastReasoningDelta.providerMetadata).toEqual({ anthropic: { signature: 'sig_abc123' }, }); }); it('should preserve providerMetadata on reasoning-start for redacted thinking', async () => { const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'reasoning-start', id: '1', providerMetadata: { anthropic: { redactedData: 'redacted-thinking-data' }, }, }, { type: 'reasoning-end', id: '1' }, ]).pipeThrough( smoothStream({ delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); // reasoning-start should pass through unchanged with providerMetadata const reasoningStart = events.find( (e: any) => e.type === 'reasoning-start', ); expect(reasoningStart).toHaveProperty('providerMetadata'); expect(reasoningStart.providerMetadata).toEqual({ anthropic: { redactedData: 'redacted-thinking-data' }, }); }); }); describe('Intl.Segmenter chunking', () => { it('should segment English text using Intl.Segmenter', async () => { const segmenter = new Intl.Segmenter('en', { granularity: 'word' }); const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello, world!', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: segmenter, delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "Hello", "type": "text-delta", }, "delay 10", { "id": "1", "text": ",", "type": "text-delta", }, "delay 10", { "id": "1", "text": " ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "world", "type": "text-delta", }, "delay 10", { "id": "1", "text": "!", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should segment Japanese text using Intl.Segmenter', async () => { const segmenter = new Intl.Segmenter('ja', { granularity: 'word' }); const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'こんにちは世界', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: segmenter, delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "こんにちは", "type": "text-delta", }, "delay 10", { "id": "1", "text": "世界", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should segment Chinese text using Intl.Segmenter', async () => { const segmenter = new Intl.Segmenter('zh', { granularity: 'word' }); const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: '你好世界', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: segmenter, delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "你好", "type": "text-delta", }, "delay 10", { "id": "1", "text": "世界", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should handle mixed CJK and Latin content', async () => { const segmenter = new Intl.Segmenter('ja', { granularity: 'word' }); const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'Hello こんにちは World', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: segmenter, delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "Hello", "type": "text-delta", }, "delay 10", { "id": "1", "text": " ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "こんにちは", "type": "text-delta", }, "delay 10", { "id": "1", "text": " ", "type": "text-delta", }, "delay 10", { "id": "1", "text": "World", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should combine partial chunks with Intl.Segmenter', async () => { const segmenter = new Intl.Segmenter('ja', { granularity: 'word' }); const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: 'こんに', type: 'text-delta', id: '1' }, { text: 'ちは', type: 'text-delta', id: '1' }, { text: '世界', type: 'text-delta', id: '1' }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: segmenter, delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); // Note: Intl.Segmenter segments hiragana character-by-character when // the full word isn't available in the buffer expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "こん", "type": "text-delta", }, "delay 10", { "id": "1", "text": "に", "type": "text-delta", }, "delay 10", { "id": "1", "text": "ち", "type": "text-delta", }, "delay 10", { "id": "1", "text": "は", "type": "text-delta", }, "delay 10", { "id": "1", "text": "世界", "type": "text-delta", }, { "id": "1", "type": "text-end", }, ] `); }); it('should segment longer Japanese sentence with mixed content', async () => { const segmenter = new Intl.Segmenter('ja', { granularity: 'word' }); const stream = convertArrayToReadableStream<TextStreamPart<ToolSet>>([ { type: 'text-start', id: '1' }, { text: '東京は日本の首都です。人口は約1400万人で、世界最大の都市圏の一つです。美しい桜の季節には多くの観光客が訪れます。', type: 'text-delta', id: '1', }, { type: 'text-end', id: '1' }, ]).pipeThrough( smoothStream({ chunking: segmenter, delayInMs: 10, _internal: { delay }, })({ tools: {} }), ); await consumeStream(stream); expect(events).toMatchInlineSnapshot(` [ { "id": "1", "type": "text-start", }, "delay 10", { "id": "1", "text": "東京", "type": "text-delta", }, "delay 10", { "id": "1", "text": "は", "type": "text-delta", }, "delay 10", { "id": "1", "text": "日本", "type": "text-delta", }, "delay 10", { "id": "1", "text": "の", "type": "text-delta", }, "delay 10", { "id": "1", "text": "首都", "type": "text-delta", }, "delay 10", { "id": "1", "text": "です", "type": "text-delta", }, "delay 10", { "id": "1", "text": "。", "type": "text-delta", }, "delay 10", { "id": "1", "text": "人口", "type": "text-delta", }, "delay 10", { "id": "1", "text": "は", "type": "text-delta", }, "delay 10", { "id": "1", "text": "約", "type": "text-delta", }, "delay 10", { "id": "1", "text": "1400", "type": "text-delta", }, "delay 10", { "id": "1", "text": "万人", "type": "text-delta", }, "delay 10", { "id": "1", "text": "で", "type": "text-delta",