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Merged
pranaygp merged 3 commits into from
May 28, 2026
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[world-local] Reduce stream metadata I/O #2139

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[world-local] Reduce stream metadata I/O
pranaygp May 28, 2026
e8b7c17
Merge branch 'main' into pranaygp/codex/world-local-stream-metadata-io
pranaygp May 28, 2026
21bfb77
[world-local] Address stream metadata review feedback
pranaygp May 28, 2026
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5 changes: 5 additions & 0 deletions .changeset/quieter-stream-metadata.md
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@workflow/world-local': patch
---

Reduce local stream metadata and pagination I/O by reading only EOF marker bytes and scanning chunk files once.
16 changes: 16 additions & 0 deletions packages/world-local/src/fs.test.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -18,6 +18,7 @@ import { z } from 'zod';
import {
assertSafeEntityId,
paginatedFileSystemQuery,
readFirstByte,
readJSONWithFallback,
resolveWithinBase,
taggedPath,
Expand DownExpand Up@@ -97,6 +98,21 @@ describe('fs utilities', () => {
});
});

describe('readFirstByte', () => {
it('reads only the marker value and handles empty files', async () => {
const dataPath = path.join(testDir, 'chunk.bin');
const nonEofPath = path.join(testDir, 'non-eof-chunk.bin');
const emptyPath = path.join(testDir, 'empty.bin');
await fs.writeFile(dataPath, Buffer.from([1, 2, 3]));
await fs.writeFile(nonEofPath, Buffer.from([0, 2, 3]));
await fs.writeFile(emptyPath, Buffer.alloc(0));

expect(await readFirstByte(dataPath)).toBe(1);
expect(await readFirstByte(nonEofPath)).toBe(0);
expect(await readFirstByte(emptyPath)).toBeUndefined();
});
});

describe('paginatedFileSystemQuery', () => {
// Simple getCreatedAt function that strips .json and tries to parse as ULID
const getCreatedAt = (filename: string): Date | null => {
Expand Down
13 changes: 13 additions & 0 deletions packages/world-local/src/fs.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -375,6 +375,19 @@ export async function readBuffer(filePath: string): Promise<Buffer> {
return content;
}

export async function readFirstByte(
filePath: string
): Promise<number | undefined> {
const file = await fs.open(filePath, 'r');
try {
const byte = Buffer.allocUnsafe(1);
const { bytesRead } = await file.read(byte, 0, 1, 0);
return bytesRead === 0 ? undefined : byte[0];
} finally {
await file.close();
}
}

export async function deleteJSON(filePath: string): Promise<void> {
try {
await fs.unlink(filePath);
Expand Down
34 changes: 34 additions & 0 deletions packages/world-local/src/streamer.test.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -909,6 +909,40 @@ describe('streamer', () => {
expect(page2.done).toBe(true);
});

it('prefers tagged chunks over untagged and legacy files', async () => {
const { testDir } = await setupStreamer();
const streamName = 'mixed-format-stream';
const taggedStreamer = createStreamer(testDir, 'vitest-0');
const chunksDir = path.join(testDir, 'streams', 'chunks');
await fs.mkdir(chunksDir, { recursive: true });

const writeChunk = (fileName: string, text: string, eof = false) =>
fs.writeFile(
path.join(chunksDir, fileName),
serializeChunk({ chunk: Buffer.from(text), eof })
);

await Promise.all([
writeChunk(`${streamName}-chnk_01.json`, 'legacy-shadowed'),
writeChunk(`${streamName}-chnk_01.bin`, 'untagged-shadowed'),
writeChunk(`${streamName}-chnk_01.vitest-0.bin`, 'tagged'),
writeChunk(`${streamName}-chnk_02.json`, 'legacy-shadowed'),
writeChunk(`${streamName}-chnk_02.bin`, 'untagged'),
writeChunk(`${streamName}-chnk_03.json`, 'legacy'),
writeChunk(`${streamName}-chnk_04.vitest-0.bin`, '', true),
]);

const result = await taggedStreamer.streams.getChunks(
TEST_RUN_ID,
streamName
);

expect(
result.data.map((chunk) => Buffer.from(chunk.data).toString())
).toEqual(['tagged', 'untagged', 'legacy']);
expect(result.done).toBe(true);
});

it('should return done=false for in-progress stream', async () => {
const { streamer } = await setupStreamer();
const streamName = 'in-progress';
Expand Down
92 changes: 60 additions & 32 deletions packages/world-local/src/streamer.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
import { EventEmitter } from 'node:events';
import fs from 'node:fs/promises';
import path from 'node:path';
import type {
GetChunksOptions,
Expand All@@ -10,8 +11,8 @@ import { monotonicFactory } from 'ulid';
import { z } from 'zod';
import {
assertSafeEntityId,
listFilesByExtension,
readBuffer,
readFirstByte,
readJSONWithFallback,
taggedPath,
write,
Expand DownExpand Up@@ -39,23 +40,52 @@ export interface Chunk {
chunk: Buffer;
}

const EOF_MARKER = 1;

function isEofByte(byte: number | undefined): boolean {
return byte === EOF_MARKER;
}

export function serializeChunk(chunk: Chunk) {
const eofByte = Buffer.from([chunk.eof ? 1 : 0]);
const eofByte = Buffer.from([chunk.eof ? EOF_MARKER : 0]);
return Buffer.concat([eofByte, chunk.chunk]);
}

/** Check only the EOF flag byte without copying chunk payload. */
export function isEofChunk(serialized: Buffer): boolean {
return serialized[0] === 1;
return isEofByte(serialized[0]);
}

export function deserializeChunk(serialized: Buffer) {
const eof = serialized[0] === 1;
const eof = isEofChunk(serialized);
// Create a copy instead of a view to prevent ArrayBuffer detachment
const chunk = Buffer.from(serialized.subarray(1));
return { eof, chunk };
}

async function listChunkEntries(chunksDir: string): Promise<string[]> {
try {
return await fs.readdir(chunksDir);
} catch (error) {
if ((error as NodeJS.ErrnoException).code === 'ENOENT') return [];
throw error;
}
}

function addChunkFilesByExtension(
extMap: Map<string, string>,
entries: string[],
sourceExtension: string,
fileExtension = sourceExtension,
include: (file: string) => boolean = () => true
): void {
for (const entry of entries) {
if (!entry.endsWith(sourceExtension)) continue;
const file = entry.slice(0, -sourceExtension.length);
if (include(file)) extMap.set(file, fileExtension);
}
}

/**
* List chunk files for a stream, sorted chronologically (ULID order).
* Returns both the sorted file names and a map of file → extension for
Expand All@@ -68,25 +98,21 @@ async function listChunkFilesForStream(
): Promise<{ files: string[]; extMap: Map<string, string> }> {
// Name is used as a filename prefix below; validate it can't escape chunksDir.
assertSafeEntityId('streamName', name);
const listPromises: Promise<string[]>[] = [
listFilesByExtension(chunksDir, '.bin'),
listFilesByExtension(chunksDir, '.json'),
];
if (tag) {
listPromises.push(listFilesByExtension(chunksDir, `.${tag}.bin`));
}
const [binFiles, jsonFiles, ...taggedResults] =
await Promise.all(listPromises);
const taggedBinFiles = taggedResults[0] ?? [];

const entries = await listChunkEntries(chunksDir);
const extMap = new Map<string, string>();
for (const f of jsonFiles) extMap.set(f, '.json');
const tagSfx = tag ? `.${tag}` : '';
for (const f of binFiles) {
if (tag && f.endsWith(tagSfx)) continue;
extMap.set(f, '.bin');
addChunkFilesByExtension(extMap, entries, '.json');
Comment thread
pranaygp marked this conversation as resolved.
addChunkFilesByExtension(
extMap,
entries,
'.bin',
'.bin',
tag ? (file) => !file.endsWith(`.${tag}`) : undefined
);

if (tag) {
const taggedExtension = `.${tag}.bin`;
addChunkFilesByExtension(extMap, entries, taggedExtension);
}
for (const f of taggedBinFiles) extMap.set(f, `.${tag}.bin`);

const files = [...extMap.keys()]
.filter((file) => file.startsWith(`${name}-`))
Expand DownExpand Up@@ -333,7 +359,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

// Before the cursor: only need to check EOF (1 byte), skip content
if (dataIndex < startIndex) {
if (isEofChunk(await readBuffer(filePath))) {
if (isEofByte(await readFirstByte(filePath))) {
streamDone = true;
break;
}
Expand All@@ -343,7 +369,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

// Collected enough data chunks — peek at the next file for EOF/hasMore
if (resultChunks.length >= limit) {
if (isEofChunk(await readBuffer(filePath))) {
if (isEofByte(await readFirstByte(filePath))) {
streamDone = true;
} else {
// More data files exist beyond this page
Expand DownExpand Up@@ -386,14 +412,15 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
const { files: chunkFiles, extMap: fileExtMap } =
await listChunkFilesForStream(chunksDir, name, tag);

// Only read the first byte of each file to check EOF — no full
// deserialization needed since we just need a count.
// Read only the EOF marker byte because metadata never needs payloads.
let streamDone = false;
let dataCount = 0;
for (const file of chunkFiles) {
const ext = fileExtMap.get(file) ?? '.bin';
if (
isEofChunk(await readBuffer(path.join(chunksDir, `${file}${ext}`)))
isEofByte(
await readFirstByte(path.join(chunksDir, `${file}${ext}`))
)
) {
streamDone = true;
break;
Expand DownExpand Up@@ -494,12 +521,13 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
) {
const lastFile = chunkFiles[chunkFiles.length - 1];
const lastExt = fileExtMap.get(lastFile) ?? '.bin';
// Note: this incurs an extra disk read to check the EOF marker.
// Acceptable since negative startIndex is not a hot path.
const lastChunk = deserializeChunk(
await readBuffer(path.join(chunksDir, `${lastFile}${lastExt}`))
);
if (lastChunk?.eof === true) {
if (
isEofByte(
await readFirstByte(
path.join(chunksDir, `${lastFile}${lastExt}`)
)
)
) {
dataChunkCount--;
}
}
Expand Down
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
 blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
[world-local] Reduce stream metadata I/O by pranaygp · Pull Request #2139 · vercel/workflow · GitHub
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[world-local] Reduce stream metadata I/O#2139

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 Merged

pranaygp
merged 3 commits into

from

May 28, 2026
 Merged


[world-local] Reduce stream metadata I/O
#2139
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7156bb7

[world-local] Reduce stream metadata I/O


pranaygp May 28, 2026
e8b7c17

Merge branch 'main' into pranaygp/codex/world-local-stream-metadata-io


pranaygp May 28, 2026
21bfb77

[world-local] Address stream metadata review feedback


pranaygp May 28, 2026

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5 changes: 5 additions & 0 deletions
.changeset/quieter-stream-metadata.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@workflow/world-local': patch
---

Reduce local stream metadata and pagination I/O by reading only EOF marker bytes and scanning chunk files once.

16 changes: 16 additions & 0 deletions
packages/world-local/src/fs.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -18,6 +18,7 @@ import { z } from 'zod';
import {
 assertSafeEntityId,
 paginatedFileSystemQuery,
 readFirstByte,
 readJSONWithFallback,
 resolveWithinBase,
 taggedPath,
Expand DownExpand Up@@ -97,6 +98,21 @@ describe('fs utilities', () => {
 });
 });

 describe('readFirstByte', () => {
 it('reads only the marker value and handles empty files', async () => {
 const dataPath = path.join(testDir, 'chunk.bin');
 const nonEofPath = path.join(testDir, 'non-eof-chunk.bin');
 const emptyPath = path.join(testDir, 'empty.bin');
 await fs.writeFile(dataPath, Buffer.from([1, 2, 3]));
 await fs.writeFile(nonEofPath, Buffer.from([0, 2, 3]));
 await fs.writeFile(emptyPath, Buffer.alloc(0));

 expect(await readFirstByte(dataPath)).toBe(1);
 expect(await readFirstByte(nonEofPath)).toBe(0);
 expect(await readFirstByte(emptyPath)).toBeUndefined();
 });
 });

 describe('paginatedFileSystemQuery', () => {
 // Simple getCreatedAt function that strips .json and tries to parse as ULID
 const getCreatedAt = (filename: string): Date | null => {
Expand Down

13 changes: 13 additions & 0 deletions
packages/world-local/src/fs.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -375,6 +375,19 @@ export async function readBuffer(filePath: string): Promise<Buffer> {
 return content;
}

export async function readFirstByte(
 filePath: string
): Promise<number | undefined> {
 const file = await fs.open(filePath, 'r');
 try {
 const byte = Buffer.allocUnsafe(1);
 const { bytesRead } = await file.read(byte, 0, 1, 0);
 return bytesRead === 0 ? undefined : byte[0];
 } finally {
 await file.close();
 }
}

export async function deleteJSON(filePath: string): Promise<void> {
 try {
 await fs.unlink(filePath);
Expand Down

34 changes: 34 additions & 0 deletions
packages/world-local/src/streamer.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -909,6 +909,40 @@ describe('streamer', () => {
 expect(page2.done).toBe(true);
 });

 it('prefers tagged chunks over untagged and legacy files', async () => {
 const { testDir } = await setupStreamer();
 const streamName = 'mixed-format-stream';
 const taggedStreamer = createStreamer(testDir, 'vitest-0');
 const chunksDir = path.join(testDir, 'streams', 'chunks');
 await fs.mkdir(chunksDir, { recursive: true });

 const writeChunk = (fileName: string, text: string, eof = false) =>
 fs.writeFile(
 path.join(chunksDir, fileName),
 serializeChunk({ chunk: Buffer.from(text), eof })
 );

 await Promise.all([
 writeChunk(`${streamName}-chnk_01.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_01.bin`, 'untagged-shadowed'),
 writeChunk(`${streamName}-chnk_01.vitest-0.bin`, 'tagged'),
 writeChunk(`${streamName}-chnk_02.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_02.bin`, 'untagged'),
 writeChunk(`${streamName}-chnk_03.json`, 'legacy'),
 writeChunk(`${streamName}-chnk_04.vitest-0.bin`, '', true),
 ]);

 const result = await taggedStreamer.streams.getChunks(
 TEST_RUN_ID,
 streamName
 );

 expect(
 result.data.map((chunk) => Buffer.from(chunk.data).toString())
 ).toEqual(['tagged', 'untagged', 'legacy']);
 expect(result.done).toBe(true);
 });

 it('should return done=false for in-progress stream', async () => {
 const { streamer } = await setupStreamer();
 const streamName = 'in-progress';
Expand Down

92 changes: 60 additions & 32 deletions
packages/world-local/src/streamer.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
import { EventEmitter } from 'node:events';
import fs from 'node:fs/promises';
import path from 'node:path';
import type {
 GetChunksOptions,
Expand All@@ -10,8 +11,8 @@ import { monotonicFactory } from 'ulid';
import { z } from 'zod';
import {
 assertSafeEntityId,
 listFilesByExtension,
 readBuffer,
 readFirstByte,
 readJSONWithFallback,
 taggedPath,
 write,
Expand DownExpand Up@@ -39,23 +40,52 @@ export interface Chunk {
 chunk: Buffer;
}

const EOF_MARKER = 1;

function isEofByte(byte: number | undefined): boolean {
 return byte === EOF_MARKER;
}

export function serializeChunk(chunk: Chunk) {
 const eofByte = Buffer.from([chunk.eof ? 1 : 0]);
 const eofByte = Buffer.from([chunk.eof ? EOF_MARKER : 0]);
 return Buffer.concat([eofByte, chunk.chunk]);
}

/** Check only the EOF flag byte without copying chunk payload. */
export function isEofChunk(serialized: Buffer): boolean {
 return serialized[0] === 1;
 return isEofByte(serialized[0]);
}

export function deserializeChunk(serialized: Buffer) {
 const eof = serialized[0] === 1;
 const eof = isEofChunk(serialized);
 // Create a copy instead of a view to prevent ArrayBuffer detachment
 const chunk = Buffer.from(serialized.subarray(1));
 return { eof, chunk };
}

async function listChunkEntries(chunksDir: string): Promise<string[]> {
 try {
 return await fs.readdir(chunksDir);
 } catch (error) {
 if ((error as NodeJS.ErrnoException).code === 'ENOENT') return [];
 throw error;
 }
}

function addChunkFilesByExtension(
 extMap: Map<string, string>,
 entries: string[],
 sourceExtension: string,
 fileExtension = sourceExtension,
 include: (file: string) => boolean = () => true
): void {
 for (const entry of entries) {
 if (!entry.endsWith(sourceExtension)) continue;
 const file = entry.slice(0, -sourceExtension.length);
 if (include(file)) extMap.set(file, fileExtension);
 }
}

/**
 * List chunk files for a stream, sorted chronologically (ULID order).
 * Returns both the sorted file names and a map of file → extension for
Expand All@@ -68,25 +98,21 @@ async function listChunkFilesForStream(
): Promise<{ files: string[]; extMap: Map<string, string> }> {
 // Name is used as a filename prefix below; validate it can't escape chunksDir.
 assertSafeEntityId('streamName', name);
 const listPromises: Promise<string[]>[] = [
 listFilesByExtension(chunksDir, '.bin'),
 listFilesByExtension(chunksDir, '.json'),
 ];
 if (tag) {
 listPromises.push(listFilesByExtension(chunksDir, `.${tag}.bin`));
 }
 const [binFiles, jsonFiles, ...taggedResults] =
 await Promise.all(listPromises);
 const taggedBinFiles = taggedResults[0] ?? [];

 const entries = await listChunkEntries(chunksDir);
 const extMap = new Map<string, string>();
 for (const f of jsonFiles) extMap.set(f, '.json');
 const tagSfx = tag ? `.${tag}` : '';
 for (const f of binFiles) {
 if (tag && f.endsWith(tagSfx)) continue;
 extMap.set(f, '.bin');
 addChunkFilesByExtension(extMap, entries, '.json');
Comment thread
pranaygp marked this conversation as resolved.

 addChunkFilesByExtension(
 extMap,
 entries,
 '.bin',
 '.bin',
 tag ? (file) => !file.endsWith(`.${tag}`) : undefined
 );

 if (tag) {
 const taggedExtension = `.${tag}.bin`;
 addChunkFilesByExtension(extMap, entries, taggedExtension);
 }
 for (const f of taggedBinFiles) extMap.set(f, `.${tag}.bin`);

 const files = [...extMap.keys()]
 .filter((file) => file.startsWith(`${name}-`))
Expand DownExpand Up@@ -333,7 +359,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Before the cursor: only need to check EOF (1 byte), skip content
 if (dataIndex < startIndex) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 break;
 }
Expand All@@ -343,7 +369,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Collected enough data chunks — peek at the next file for EOF/hasMore
 if (resultChunks.length >= limit) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 } else {
 // More data files exist beyond this page
Expand DownExpand Up@@ -386,14 +412,15 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 const { files: chunkFiles, extMap: fileExtMap } =
 await listChunkFilesForStream(chunksDir, name, tag);

 // Only read the first byte of each file to check EOF — no full
 // deserialization needed since we just need a count.
 // Read only the EOF marker byte because metadata never needs payloads.
 let streamDone = false;
 let dataCount = 0;
 for (const file of chunkFiles) {
 const ext = fileExtMap.get(file) ?? '.bin';
 if (
 isEofChunk(await readBuffer(path.join(chunksDir, `${file}${ext}`)))
 isEofByte(
 await readFirstByte(path.join(chunksDir, `${file}${ext}`))
 )
 ) {
 streamDone = true;
 break;
Expand DownExpand Up@@ -494,12 +521,13 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 ) {
 const lastFile = chunkFiles[chunkFiles.length - 1];
 const lastExt = fileExtMap.get(lastFile) ?? '.bin';
 // Note: this incurs an extra disk read to check the EOF marker.
 // Acceptable since negative startIndex is not a hot path.
 const lastChunk = deserializeChunk(
 await readBuffer(path.join(chunksDir, `${lastFile}${lastExt}`))
 );
 if (lastChunk?.eof === true) {
 if (
 isEofByte(
 await readFirstByte(
 path.join(chunksDir, `${lastFile}${lastExt}`)
 )
 )
 ) {
 dataChunkCount--;
 }
 }
Expand Down
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var style = document.createElement('style');
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color-scheme: dark light;
}
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var __m = "*";
var __re = new RegExp('^' + ".*" + '
[world-local] Reduce stream metadata I/O by pranaygp · Pull Request #2139 · vercel/workflow · GitHub
Skip to content
[world-local] Reduce stream metadata I/O#2139

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 Merged

pranaygp
merged 3 commits into

from

May 28, 2026
 Merged


[world-local] Reduce stream metadata I/O
#2139
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7156bb7

[world-local] Reduce stream metadata I/O


pranaygp May 28, 2026
e8b7c17

Merge branch 'main' into pranaygp/codex/world-local-stream-metadata-io


pranaygp May 28, 2026
21bfb77

[world-local] Address stream metadata review feedback


pranaygp May 28, 2026

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5 changes: 5 additions & 0 deletions
.changeset/quieter-stream-metadata.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@workflow/world-local': patch
---

Reduce local stream metadata and pagination I/O by reading only EOF marker bytes and scanning chunk files once.

16 changes: 16 additions & 0 deletions
packages/world-local/src/fs.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -18,6 +18,7 @@ import { z } from 'zod';
import {
 assertSafeEntityId,
 paginatedFileSystemQuery,
 readFirstByte,
 readJSONWithFallback,
 resolveWithinBase,
 taggedPath,
Expand DownExpand Up@@ -97,6 +98,21 @@ describe('fs utilities', () => {
 });
 });

 describe('readFirstByte', () => {
 it('reads only the marker value and handles empty files', async () => {
 const dataPath = path.join(testDir, 'chunk.bin');
 const nonEofPath = path.join(testDir, 'non-eof-chunk.bin');
 const emptyPath = path.join(testDir, 'empty.bin');
 await fs.writeFile(dataPath, Buffer.from([1, 2, 3]));
 await fs.writeFile(nonEofPath, Buffer.from([0, 2, 3]));
 await fs.writeFile(emptyPath, Buffer.alloc(0));

 expect(await readFirstByte(dataPath)).toBe(1);
 expect(await readFirstByte(nonEofPath)).toBe(0);
 expect(await readFirstByte(emptyPath)).toBeUndefined();
 });
 });

 describe('paginatedFileSystemQuery', () => {
 // Simple getCreatedAt function that strips .json and tries to parse as ULID
 const getCreatedAt = (filename: string): Date | null => {
Expand Down

13 changes: 13 additions & 0 deletions
packages/world-local/src/fs.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -375,6 +375,19 @@ export async function readBuffer(filePath: string): Promise<Buffer> {
 return content;
}

export async function readFirstByte(
 filePath: string
): Promise<number | undefined> {
 const file = await fs.open(filePath, 'r');
 try {
 const byte = Buffer.allocUnsafe(1);
 const { bytesRead } = await file.read(byte, 0, 1, 0);
 return bytesRead === 0 ? undefined : byte[0];
 } finally {
 await file.close();
 }
}

export async function deleteJSON(filePath: string): Promise<void> {
 try {
 await fs.unlink(filePath);
Expand Down

34 changes: 34 additions & 0 deletions
packages/world-local/src/streamer.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -909,6 +909,40 @@ describe('streamer', () => {
 expect(page2.done).toBe(true);
 });

 it('prefers tagged chunks over untagged and legacy files', async () => {
 const { testDir } = await setupStreamer();
 const streamName = 'mixed-format-stream';
 const taggedStreamer = createStreamer(testDir, 'vitest-0');
 const chunksDir = path.join(testDir, 'streams', 'chunks');
 await fs.mkdir(chunksDir, { recursive: true });

 const writeChunk = (fileName: string, text: string, eof = false) =>
 fs.writeFile(
 path.join(chunksDir, fileName),
 serializeChunk({ chunk: Buffer.from(text), eof })
 );

 await Promise.all([
 writeChunk(`${streamName}-chnk_01.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_01.bin`, 'untagged-shadowed'),
 writeChunk(`${streamName}-chnk_01.vitest-0.bin`, 'tagged'),
 writeChunk(`${streamName}-chnk_02.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_02.bin`, 'untagged'),
 writeChunk(`${streamName}-chnk_03.json`, 'legacy'),
 writeChunk(`${streamName}-chnk_04.vitest-0.bin`, '', true),
 ]);

 const result = await taggedStreamer.streams.getChunks(
 TEST_RUN_ID,
 streamName
 );

 expect(
 result.data.map((chunk) => Buffer.from(chunk.data).toString())
 ).toEqual(['tagged', 'untagged', 'legacy']);
 expect(result.done).toBe(true);
 });

 it('should return done=false for in-progress stream', async () => {
 const { streamer } = await setupStreamer();
 const streamName = 'in-progress';
Expand Down

92 changes: 60 additions & 32 deletions
packages/world-local/src/streamer.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
import { EventEmitter } from 'node:events';
import fs from 'node:fs/promises';
import path from 'node:path';
import type {
 GetChunksOptions,
Expand All@@ -10,8 +11,8 @@ import { monotonicFactory } from 'ulid';
import { z } from 'zod';
import {
 assertSafeEntityId,
 listFilesByExtension,
 readBuffer,
 readFirstByte,
 readJSONWithFallback,
 taggedPath,
 write,
Expand DownExpand Up@@ -39,23 +40,52 @@ export interface Chunk {
 chunk: Buffer;
}

const EOF_MARKER = 1;

function isEofByte(byte: number | undefined): boolean {
 return byte === EOF_MARKER;
}

export function serializeChunk(chunk: Chunk) {
 const eofByte = Buffer.from([chunk.eof ? 1 : 0]);
 const eofByte = Buffer.from([chunk.eof ? EOF_MARKER : 0]);
 return Buffer.concat([eofByte, chunk.chunk]);
}

/** Check only the EOF flag byte without copying chunk payload. */
export function isEofChunk(serialized: Buffer): boolean {
 return serialized[0] === 1;
 return isEofByte(serialized[0]);
}

export function deserializeChunk(serialized: Buffer) {
 const eof = serialized[0] === 1;
 const eof = isEofChunk(serialized);
 // Create a copy instead of a view to prevent ArrayBuffer detachment
 const chunk = Buffer.from(serialized.subarray(1));
 return { eof, chunk };
}

async function listChunkEntries(chunksDir: string): Promise<string[]> {
 try {
 return await fs.readdir(chunksDir);
 } catch (error) {
 if ((error as NodeJS.ErrnoException).code === 'ENOENT') return [];
 throw error;
 }
}

function addChunkFilesByExtension(
 extMap: Map<string, string>,
 entries: string[],
 sourceExtension: string,
 fileExtension = sourceExtension,
 include: (file: string) => boolean = () => true
): void {
 for (const entry of entries) {
 if (!entry.endsWith(sourceExtension)) continue;
 const file = entry.slice(0, -sourceExtension.length);
 if (include(file)) extMap.set(file, fileExtension);
 }
}

/**
 * List chunk files for a stream, sorted chronologically (ULID order).
 * Returns both the sorted file names and a map of file → extension for
Expand All@@ -68,25 +98,21 @@ async function listChunkFilesForStream(
): Promise<{ files: string[]; extMap: Map<string, string> }> {
 // Name is used as a filename prefix below; validate it can't escape chunksDir.
 assertSafeEntityId('streamName', name);
 const listPromises: Promise<string[]>[] = [
 listFilesByExtension(chunksDir, '.bin'),
 listFilesByExtension(chunksDir, '.json'),
 ];
 if (tag) {
 listPromises.push(listFilesByExtension(chunksDir, `.${tag}.bin`));
 }
 const [binFiles, jsonFiles, ...taggedResults] =
 await Promise.all(listPromises);
 const taggedBinFiles = taggedResults[0] ?? [];

 const entries = await listChunkEntries(chunksDir);
 const extMap = new Map<string, string>();
 for (const f of jsonFiles) extMap.set(f, '.json');
 const tagSfx = tag ? `.${tag}` : '';
 for (const f of binFiles) {
 if (tag && f.endsWith(tagSfx)) continue;
 extMap.set(f, '.bin');
 addChunkFilesByExtension(extMap, entries, '.json');
Comment thread
pranaygp marked this conversation as resolved.

 addChunkFilesByExtension(
 extMap,
 entries,
 '.bin',
 '.bin',
 tag ? (file) => !file.endsWith(`.${tag}`) : undefined
 );

 if (tag) {
 const taggedExtension = `.${tag}.bin`;
 addChunkFilesByExtension(extMap, entries, taggedExtension);
 }
 for (const f of taggedBinFiles) extMap.set(f, `.${tag}.bin`);

 const files = [...extMap.keys()]
 .filter((file) => file.startsWith(`${name}-`))
Expand DownExpand Up@@ -333,7 +359,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Before the cursor: only need to check EOF (1 byte), skip content
 if (dataIndex < startIndex) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 break;
 }
Expand All@@ -343,7 +369,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Collected enough data chunks — peek at the next file for EOF/hasMore
 if (resultChunks.length >= limit) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 } else {
 // More data files exist beyond this page
Expand DownExpand Up@@ -386,14 +412,15 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 const { files: chunkFiles, extMap: fileExtMap } =
 await listChunkFilesForStream(chunksDir, name, tag);

 // Only read the first byte of each file to check EOF — no full
 // deserialization needed since we just need a count.
 // Read only the EOF marker byte because metadata never needs payloads.
 let streamDone = false;
 let dataCount = 0;
 for (const file of chunkFiles) {
 const ext = fileExtMap.get(file) ?? '.bin';
 if (
 isEofChunk(await readBuffer(path.join(chunksDir, `${file}${ext}`)))
 isEofByte(
 await readFirstByte(path.join(chunksDir, `${file}${ext}`))
 )
 ) {
 streamDone = true;
 break;
Expand DownExpand Up@@ -494,12 +521,13 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 ) {
 const lastFile = chunkFiles[chunkFiles.length - 1];
 const lastExt = fileExtMap.get(lastFile) ?? '.bin';
 // Note: this incurs an extra disk read to check the EOF marker.
 // Acceptable since negative startIndex is not a hot path.
 const lastChunk = deserializeChunk(
 await readBuffer(path.join(chunksDir, `${lastFile}${lastExt}`))
 );
 if (lastChunk?.eof === true) {
 if (
 isEofByte(
 await readFirstByte(
 path.join(chunksDir, `${lastFile}${lastExt}`)
 )
 )
 ) {
 dataChunkCount--;
 }
 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[world-local] Reduce stream metadata I/O by pranaygp · Pull Request #2139 · vercel/workflow · GitHub
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pranaygp
merged 3 commits into

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May 28, 2026
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[world-local] Reduce stream metadata I/O
#2139
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7156bb7

[world-local] Reduce stream metadata I/O


pranaygp May 28, 2026
e8b7c17

Merge branch 'main' into pranaygp/codex/world-local-stream-metadata-io


pranaygp May 28, 2026
21bfb77

[world-local] Address stream metadata review feedback


pranaygp May 28, 2026

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5 changes: 5 additions & 0 deletions
.changeset/quieter-stream-metadata.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@workflow/world-local': patch
---

Reduce local stream metadata and pagination I/O by reading only EOF marker bytes and scanning chunk files once.

16 changes: 16 additions & 0 deletions
packages/world-local/src/fs.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -18,6 +18,7 @@ import { z } from 'zod';
import {
 assertSafeEntityId,
 paginatedFileSystemQuery,
 readFirstByte,
 readJSONWithFallback,
 resolveWithinBase,
 taggedPath,
Expand DownExpand Up@@ -97,6 +98,21 @@ describe('fs utilities', () => {
 });
 });

 describe('readFirstByte', () => {
 it('reads only the marker value and handles empty files', async () => {
 const dataPath = path.join(testDir, 'chunk.bin');
 const nonEofPath = path.join(testDir, 'non-eof-chunk.bin');
 const emptyPath = path.join(testDir, 'empty.bin');
 await fs.writeFile(dataPath, Buffer.from([1, 2, 3]));
 await fs.writeFile(nonEofPath, Buffer.from([0, 2, 3]));
 await fs.writeFile(emptyPath, Buffer.alloc(0));

 expect(await readFirstByte(dataPath)).toBe(1);
 expect(await readFirstByte(nonEofPath)).toBe(0);
 expect(await readFirstByte(emptyPath)).toBeUndefined();
 });
 });

 describe('paginatedFileSystemQuery', () => {
 // Simple getCreatedAt function that strips .json and tries to parse as ULID
 const getCreatedAt = (filename: string): Date | null => {
Expand Down

13 changes: 13 additions & 0 deletions
packages/world-local/src/fs.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -375,6 +375,19 @@ export async function readBuffer(filePath: string): Promise<Buffer> {
 return content;
}

export async function readFirstByte(
 filePath: string
): Promise<number | undefined> {
 const file = await fs.open(filePath, 'r');
 try {
 const byte = Buffer.allocUnsafe(1);
 const { bytesRead } = await file.read(byte, 0, 1, 0);
 return bytesRead === 0 ? undefined : byte[0];
 } finally {
 await file.close();
 }
}

export async function deleteJSON(filePath: string): Promise<void> {
 try {
 await fs.unlink(filePath);
Expand Down

34 changes: 34 additions & 0 deletions
packages/world-local/src/streamer.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -909,6 +909,40 @@ describe('streamer', () => {
 expect(page2.done).toBe(true);
 });

 it('prefers tagged chunks over untagged and legacy files', async () => {
 const { testDir } = await setupStreamer();
 const streamName = 'mixed-format-stream';
 const taggedStreamer = createStreamer(testDir, 'vitest-0');
 const chunksDir = path.join(testDir, 'streams', 'chunks');
 await fs.mkdir(chunksDir, { recursive: true });

 const writeChunk = (fileName: string, text: string, eof = false) =>
 fs.writeFile(
 path.join(chunksDir, fileName),
 serializeChunk({ chunk: Buffer.from(text), eof })
 );

 await Promise.all([
 writeChunk(`${streamName}-chnk_01.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_01.bin`, 'untagged-shadowed'),
 writeChunk(`${streamName}-chnk_01.vitest-0.bin`, 'tagged'),
 writeChunk(`${streamName}-chnk_02.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_02.bin`, 'untagged'),
 writeChunk(`${streamName}-chnk_03.json`, 'legacy'),
 writeChunk(`${streamName}-chnk_04.vitest-0.bin`, '', true),
 ]);

 const result = await taggedStreamer.streams.getChunks(
 TEST_RUN_ID,
 streamName
 );

 expect(
 result.data.map((chunk) => Buffer.from(chunk.data).toString())
 ).toEqual(['tagged', 'untagged', 'legacy']);
 expect(result.done).toBe(true);
 });

 it('should return done=false for in-progress stream', async () => {
 const { streamer } = await setupStreamer();
 const streamName = 'in-progress';
Expand Down

92 changes: 60 additions & 32 deletions
packages/world-local/src/streamer.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
import { EventEmitter } from 'node:events';
import fs from 'node:fs/promises';
import path from 'node:path';
import type {
 GetChunksOptions,
Expand All@@ -10,8 +11,8 @@ import { monotonicFactory } from 'ulid';
import { z } from 'zod';
import {
 assertSafeEntityId,
 listFilesByExtension,
 readBuffer,
 readFirstByte,
 readJSONWithFallback,
 taggedPath,
 write,
Expand DownExpand Up@@ -39,23 +40,52 @@ export interface Chunk {
 chunk: Buffer;
}

const EOF_MARKER = 1;

function isEofByte(byte: number | undefined): boolean {
 return byte === EOF_MARKER;
}

export function serializeChunk(chunk: Chunk) {
 const eofByte = Buffer.from([chunk.eof ? 1 : 0]);
 const eofByte = Buffer.from([chunk.eof ? EOF_MARKER : 0]);
 return Buffer.concat([eofByte, chunk.chunk]);
}

/** Check only the EOF flag byte without copying chunk payload. */
export function isEofChunk(serialized: Buffer): boolean {
 return serialized[0] === 1;
 return isEofByte(serialized[0]);
}

export function deserializeChunk(serialized: Buffer) {
 const eof = serialized[0] === 1;
 const eof = isEofChunk(serialized);
 // Create a copy instead of a view to prevent ArrayBuffer detachment
 const chunk = Buffer.from(serialized.subarray(1));
 return { eof, chunk };
}

async function listChunkEntries(chunksDir: string): Promise<string[]> {
 try {
 return await fs.readdir(chunksDir);
 } catch (error) {
 if ((error as NodeJS.ErrnoException).code === 'ENOENT') return [];
 throw error;
 }
}

function addChunkFilesByExtension(
 extMap: Map<string, string>,
 entries: string[],
 sourceExtension: string,
 fileExtension = sourceExtension,
 include: (file: string) => boolean = () => true
): void {
 for (const entry of entries) {
 if (!entry.endsWith(sourceExtension)) continue;
 const file = entry.slice(0, -sourceExtension.length);
 if (include(file)) extMap.set(file, fileExtension);
 }
}

/**
 * List chunk files for a stream, sorted chronologically (ULID order).
 * Returns both the sorted file names and a map of file → extension for
Expand All@@ -68,25 +98,21 @@ async function listChunkFilesForStream(
): Promise<{ files: string[]; extMap: Map<string, string> }> {
 // Name is used as a filename prefix below; validate it can't escape chunksDir.
 assertSafeEntityId('streamName', name);
 const listPromises: Promise<string[]>[] = [
 listFilesByExtension(chunksDir, '.bin'),
 listFilesByExtension(chunksDir, '.json'),
 ];
 if (tag) {
 listPromises.push(listFilesByExtension(chunksDir, `.${tag}.bin`));
 }
 const [binFiles, jsonFiles, ...taggedResults] =
 await Promise.all(listPromises);
 const taggedBinFiles = taggedResults[0] ?? [];

 const entries = await listChunkEntries(chunksDir);
 const extMap = new Map<string, string>();
 for (const f of jsonFiles) extMap.set(f, '.json');
 const tagSfx = tag ? `.${tag}` : '';
 for (const f of binFiles) {
 if (tag && f.endsWith(tagSfx)) continue;
 extMap.set(f, '.bin');
 addChunkFilesByExtension(extMap, entries, '.json');
Comment thread
pranaygp marked this conversation as resolved.

 addChunkFilesByExtension(
 extMap,
 entries,
 '.bin',
 '.bin',
 tag ? (file) => !file.endsWith(`.${tag}`) : undefined
 );

 if (tag) {
 const taggedExtension = `.${tag}.bin`;
 addChunkFilesByExtension(extMap, entries, taggedExtension);
 }
 for (const f of taggedBinFiles) extMap.set(f, `.${tag}.bin`);

 const files = [...extMap.keys()]
 .filter((file) => file.startsWith(`${name}-`))
Expand DownExpand Up@@ -333,7 +359,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Before the cursor: only need to check EOF (1 byte), skip content
 if (dataIndex < startIndex) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 break;
 }
Expand All@@ -343,7 +369,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Collected enough data chunks — peek at the next file for EOF/hasMore
 if (resultChunks.length >= limit) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 } else {
 // More data files exist beyond this page
Expand DownExpand Up@@ -386,14 +412,15 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 const { files: chunkFiles, extMap: fileExtMap } =
 await listChunkFilesForStream(chunksDir, name, tag);

 // Only read the first byte of each file to check EOF — no full
 // deserialization needed since we just need a count.
 // Read only the EOF marker byte because metadata never needs payloads.
 let streamDone = false;
 let dataCount = 0;
 for (const file of chunkFiles) {
 const ext = fileExtMap.get(file) ?? '.bin';
 if (
 isEofChunk(await readBuffer(path.join(chunksDir, `${file}${ext}`)))
 isEofByte(
 await readFirstByte(path.join(chunksDir, `${file}${ext}`))
 )
 ) {
 streamDone = true;
 break;
Expand DownExpand Up@@ -494,12 +521,13 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 ) {
 const lastFile = chunkFiles[chunkFiles.length - 1];
 const lastExt = fileExtMap.get(lastFile) ?? '.bin';
 // Note: this incurs an extra disk read to check the EOF marker.
 // Acceptable since negative startIndex is not a hot path.
 const lastChunk = deserializeChunk(
 await readBuffer(path.join(chunksDir, `${lastFile}${lastExt}`))
 );
 if (lastChunk?.eof === true) {
 if (
 isEofByte(
 await readFirstByte(
 path.join(chunksDir, `${lastFile}${lastExt}`)
 )
 )
 ) {
 dataChunkCount--;
 }
 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
[world-local] Reduce stream metadata I/O by pranaygp · Pull Request #2139 · vercel/workflow · GitHub
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[world-local] Reduce stream metadata I/O#2139

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pranaygp
merged 3 commits into

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May 28, 2026
 Merged


[world-local] Reduce stream metadata I/O
#2139
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7156bb7

[world-local] Reduce stream metadata I/O


pranaygp May 28, 2026
e8b7c17

Merge branch 'main' into pranaygp/codex/world-local-stream-metadata-io


pranaygp May 28, 2026
21bfb77

[world-local] Address stream metadata review feedback


pranaygp May 28, 2026

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5 changes: 5 additions & 0 deletions
.changeset/quieter-stream-metadata.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@workflow/world-local': patch
---

Reduce local stream metadata and pagination I/O by reading only EOF marker bytes and scanning chunk files once.

16 changes: 16 additions & 0 deletions
packages/world-local/src/fs.test.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -18,6 +18,7 @@ import { z } from 'zod';
import {
 assertSafeEntityId,
 paginatedFileSystemQuery,
 readFirstByte,
 readJSONWithFallback,
 resolveWithinBase,
 taggedPath,
Expand DownExpand Up@@ -97,6 +98,21 @@ describe('fs utilities', () => {
 });
 });

 describe('readFirstByte', () => {
 it('reads only the marker value and handles empty files', async () => {
 const dataPath = path.join(testDir, 'chunk.bin');
 const nonEofPath = path.join(testDir, 'non-eof-chunk.bin');
 const emptyPath = path.join(testDir, 'empty.bin');
 await fs.writeFile(dataPath, Buffer.from([1, 2, 3]));
 await fs.writeFile(nonEofPath, Buffer.from([0, 2, 3]));
 await fs.writeFile(emptyPath, Buffer.alloc(0));

 expect(await readFirstByte(dataPath)).toBe(1);
 expect(await readFirstByte(nonEofPath)).toBe(0);
 expect(await readFirstByte(emptyPath)).toBeUndefined();
 });
 });

 describe('paginatedFileSystemQuery', () => {
 // Simple getCreatedAt function that strips .json and tries to parse as ULID
 const getCreatedAt = (filename: string): Date | null => {
Expand Down

13 changes: 13 additions & 0 deletions
packages/world-local/src/fs.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -375,6 +375,19 @@ export async function readBuffer(filePath: string): Promise<Buffer> {
 return content;
}

export async function readFirstByte(
 filePath: string
): Promise<number | undefined> {
 const file = await fs.open(filePath, 'r');
 try {
 const byte = Buffer.allocUnsafe(1);
 const { bytesRead } = await file.read(byte, 0, 1, 0);
 return bytesRead === 0 ? undefined : byte[0];
 } finally {
 await file.close();
 }
}

export async function deleteJSON(filePath: string): Promise<void> {
 try {
 await fs.unlink(filePath);
Expand Down

34 changes: 34 additions & 0 deletions
packages/world-local/src/streamer.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -909,6 +909,40 @@ describe('streamer', () => {
 expect(page2.done).toBe(true);
 });

 it('prefers tagged chunks over untagged and legacy files', async () => {
 const { testDir } = await setupStreamer();
 const streamName = 'mixed-format-stream';
 const taggedStreamer = createStreamer(testDir, 'vitest-0');
 const chunksDir = path.join(testDir, 'streams', 'chunks');
 await fs.mkdir(chunksDir, { recursive: true });

 const writeChunk = (fileName: string, text: string, eof = false) =>
 fs.writeFile(
 path.join(chunksDir, fileName),
 serializeChunk({ chunk: Buffer.from(text), eof })
 );

 await Promise.all([
 writeChunk(`${streamName}-chnk_01.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_01.bin`, 'untagged-shadowed'),
 writeChunk(`${streamName}-chnk_01.vitest-0.bin`, 'tagged'),
 writeChunk(`${streamName}-chnk_02.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_02.bin`, 'untagged'),
 writeChunk(`${streamName}-chnk_03.json`, 'legacy'),
 writeChunk(`${streamName}-chnk_04.vitest-0.bin`, '', true),
 ]);

 const result = await taggedStreamer.streams.getChunks(
 TEST_RUN_ID,
 streamName
 );

 expect(
 result.data.map((chunk) => Buffer.from(chunk.data).toString())
 ).toEqual(['tagged', 'untagged', 'legacy']);
 expect(result.done).toBe(true);
 });

 it('should return done=false for in-progress stream', async () => {
 const { streamer } = await setupStreamer();
 const streamName = 'in-progress';
Expand Down

92 changes: 60 additions & 32 deletions
packages/world-local/src/streamer.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
import { EventEmitter } from 'node:events';
import fs from 'node:fs/promises';
import path from 'node:path';
import type {
 GetChunksOptions,
Expand All@@ -10,8 +11,8 @@ import { monotonicFactory } from 'ulid';
import { z } from 'zod';
import {
 assertSafeEntityId,
 listFilesByExtension,
 readBuffer,
 readFirstByte,
 readJSONWithFallback,
 taggedPath,
 write,
Expand DownExpand Up@@ -39,23 +40,52 @@ export interface Chunk {
 chunk: Buffer;
}

const EOF_MARKER = 1;

function isEofByte(byte: number | undefined): boolean {
 return byte === EOF_MARKER;
}

export function serializeChunk(chunk: Chunk) {
 const eofByte = Buffer.from([chunk.eof ? 1 : 0]);
 const eofByte = Buffer.from([chunk.eof ? EOF_MARKER : 0]);
 return Buffer.concat([eofByte, chunk.chunk]);
}

/** Check only the EOF flag byte without copying chunk payload. */
export function isEofChunk(serialized: Buffer): boolean {
 return serialized[0] === 1;
 return isEofByte(serialized[0]);
}

export function deserializeChunk(serialized: Buffer) {
 const eof = serialized[0] === 1;
 const eof = isEofChunk(serialized);
 // Create a copy instead of a view to prevent ArrayBuffer detachment
 const chunk = Buffer.from(serialized.subarray(1));
 return { eof, chunk };
}

async function listChunkEntries(chunksDir: string): Promise<string[]> {
 try {
 return await fs.readdir(chunksDir);
 } catch (error) {
 if ((error as NodeJS.ErrnoException).code === 'ENOENT') return [];
 throw error;
 }
}

function addChunkFilesByExtension(
 extMap: Map<string, string>,
 entries: string[],
 sourceExtension: string,
 fileExtension = sourceExtension,
 include: (file: string) => boolean = () => true
): void {
 for (const entry of entries) {
 if (!entry.endsWith(sourceExtension)) continue;
 const file = entry.slice(0, -sourceExtension.length);
 if (include(file)) extMap.set(file, fileExtension);
 }
}

/**
 * List chunk files for a stream, sorted chronologically (ULID order).
 * Returns both the sorted file names and a map of file → extension for
Expand All@@ -68,25 +98,21 @@ async function listChunkFilesForStream(
): Promise<{ files: string[]; extMap: Map<string, string> }> {
 // Name is used as a filename prefix below; validate it can't escape chunksDir.
 assertSafeEntityId('streamName', name);
 const listPromises: Promise<string[]>[] = [
 listFilesByExtension(chunksDir, '.bin'),
 listFilesByExtension(chunksDir, '.json'),
 ];
 if (tag) {
 listPromises.push(listFilesByExtension(chunksDir, `.${tag}.bin`));
 }
 const [binFiles, jsonFiles, ...taggedResults] =
 await Promise.all(listPromises);
 const taggedBinFiles = taggedResults[0] ?? [];

 const entries = await listChunkEntries(chunksDir);
 const extMap = new Map<string, string>();
 for (const f of jsonFiles) extMap.set(f, '.json');
 const tagSfx = tag ? `.${tag}` : '';
 for (const f of binFiles) {
 if (tag && f.endsWith(tagSfx)) continue;
 extMap.set(f, '.bin');
 addChunkFilesByExtension(extMap, entries, '.json');
Comment thread
pranaygp marked this conversation as resolved.

 addChunkFilesByExtension(
 extMap,
 entries,
 '.bin',
 '.bin',
 tag ? (file) => !file.endsWith(`.${tag}`) : undefined
 );

 if (tag) {
 const taggedExtension = `.${tag}.bin`;
 addChunkFilesByExtension(extMap, entries, taggedExtension);
 }
 for (const f of taggedBinFiles) extMap.set(f, `.${tag}.bin`);

 const files = [...extMap.keys()]
 .filter((file) => file.startsWith(`${name}-`))
Expand DownExpand Up@@ -333,7 +359,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Before the cursor: only need to check EOF (1 byte), skip content
 if (dataIndex < startIndex) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 break;
 }
Expand All@@ -343,7 +369,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Collected enough data chunks — peek at the next file for EOF/hasMore
 if (resultChunks.length >= limit) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 } else {
 // More data files exist beyond this page
Expand DownExpand Up@@ -386,14 +412,15 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 const { files: chunkFiles, extMap: fileExtMap } =
 await listChunkFilesForStream(chunksDir, name, tag);

 // Only read the first byte of each file to check EOF — no full
 // deserialization needed since we just need a count.
 // Read only the EOF marker byte because metadata never needs payloads.
 let streamDone = false;
 let dataCount = 0;
 for (const file of chunkFiles) {
 const ext = fileExtMap.get(file) ?? '.bin';
 if (
 isEofChunk(await readBuffer(path.join(chunksDir, `${file}${ext}`)))
 isEofByte(
 await readFirstByte(path.join(chunksDir, `${file}${ext}`))
 )
 ) {
 streamDone = true;
 break;
Expand DownExpand Up@@ -494,12 +521,13 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 ) {
 const lastFile = chunkFiles[chunkFiles.length - 1];
 const lastExt = fileExtMap.get(lastFile) ?? '.bin';
 // Note: this incurs an extra disk read to check the EOF marker.
 // Acceptable since negative startIndex is not a hot path.
 const lastChunk = deserializeChunk(
 await readBuffer(path.join(chunksDir, `${lastFile}${lastExt}`))
 );
 if (lastChunk?.eof === true) {
 if (
 isEofByte(
 await readFirstByte(
 path.join(chunksDir, `${lastFile}${lastExt}`)
 )
 )
 ) {
 dataChunkCount--;
 }
 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[world-local] Reduce stream metadata I/O by pranaygp · Pull Request #2139 · vercel/workflow · GitHub
Skip to content
[world-local] Reduce stream metadata I/O#2139

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 Merged

pranaygp
merged 3 commits into

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May 28, 2026
 Merged


[world-local] Reduce stream metadata I/O
#2139
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7156bb7

[world-local] Reduce stream metadata I/O


pranaygp May 28, 2026
e8b7c17

Merge branch 'main' into pranaygp/codex/world-local-stream-metadata-io


pranaygp May 28, 2026
21bfb77

[world-local] Address stream metadata review feedback


pranaygp May 28, 2026

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5 changes: 5 additions & 0 deletions
.changeset/quieter-stream-metadata.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@workflow/world-local': patch
---

Reduce local stream metadata and pagination I/O by reading only EOF marker bytes and scanning chunk files once.

16 changes: 16 additions & 0 deletions
packages/world-local/src/fs.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -18,6 +18,7 @@ import { z } from 'zod';
import {
 assertSafeEntityId,
 paginatedFileSystemQuery,
 readFirstByte,
 readJSONWithFallback,
 resolveWithinBase,
 taggedPath,
Expand DownExpand Up@@ -97,6 +98,21 @@ describe('fs utilities', () => {
 });
 });

 describe('readFirstByte', () => {
 it('reads only the marker value and handles empty files', async () => {
 const dataPath = path.join(testDir, 'chunk.bin');
 const nonEofPath = path.join(testDir, 'non-eof-chunk.bin');
 const emptyPath = path.join(testDir, 'empty.bin');
 await fs.writeFile(dataPath, Buffer.from([1, 2, 3]));
 await fs.writeFile(nonEofPath, Buffer.from([0, 2, 3]));
 await fs.writeFile(emptyPath, Buffer.alloc(0));

 expect(await readFirstByte(dataPath)).toBe(1);
 expect(await readFirstByte(nonEofPath)).toBe(0);
 expect(await readFirstByte(emptyPath)).toBeUndefined();
 });
 });

 describe('paginatedFileSystemQuery', () => {
 // Simple getCreatedAt function that strips .json and tries to parse as ULID
 const getCreatedAt = (filename: string): Date | null => {
Expand Down

13 changes: 13 additions & 0 deletions
packages/world-local/src/fs.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -375,6 +375,19 @@ export async function readBuffer(filePath: string): Promise<Buffer> {
 return content;
}

export async function readFirstByte(
 filePath: string
): Promise<number | undefined> {
 const file = await fs.open(filePath, 'r');
 try {
 const byte = Buffer.allocUnsafe(1);
 const { bytesRead } = await file.read(byte, 0, 1, 0);
 return bytesRead === 0 ? undefined : byte[0];
 } finally {
 await file.close();
 }
}

export async function deleteJSON(filePath: string): Promise<void> {
 try {
 await fs.unlink(filePath);
Expand Down

34 changes: 34 additions & 0 deletions
packages/world-local/src/streamer.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -909,6 +909,40 @@ describe('streamer', () => {
 expect(page2.done).toBe(true);
 });

 it('prefers tagged chunks over untagged and legacy files', async () => {
 const { testDir } = await setupStreamer();
 const streamName = 'mixed-format-stream';
 const taggedStreamer = createStreamer(testDir, 'vitest-0');
 const chunksDir = path.join(testDir, 'streams', 'chunks');
 await fs.mkdir(chunksDir, { recursive: true });

 const writeChunk = (fileName: string, text: string, eof = false) =>
 fs.writeFile(
 path.join(chunksDir, fileName),
 serializeChunk({ chunk: Buffer.from(text), eof })
 );

 await Promise.all([
 writeChunk(`${streamName}-chnk_01.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_01.bin`, 'untagged-shadowed'),
 writeChunk(`${streamName}-chnk_01.vitest-0.bin`, 'tagged'),
 writeChunk(`${streamName}-chnk_02.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_02.bin`, 'untagged'),
 writeChunk(`${streamName}-chnk_03.json`, 'legacy'),
 writeChunk(`${streamName}-chnk_04.vitest-0.bin`, '', true),
 ]);

 const result = await taggedStreamer.streams.getChunks(
 TEST_RUN_ID,
 streamName
 );

 expect(
 result.data.map((chunk) => Buffer.from(chunk.data).toString())
 ).toEqual(['tagged', 'untagged', 'legacy']);
 expect(result.done).toBe(true);
 });

 it('should return done=false for in-progress stream', async () => {
 const { streamer } = await setupStreamer();
 const streamName = 'in-progress';
Expand Down

92 changes: 60 additions & 32 deletions
packages/world-local/src/streamer.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
import { EventEmitter } from 'node:events';
import fs from 'node:fs/promises';
import path from 'node:path';
import type {
 GetChunksOptions,
Expand All@@ -10,8 +11,8 @@ import { monotonicFactory } from 'ulid';
import { z } from 'zod';
import {
 assertSafeEntityId,
 listFilesByExtension,
 readBuffer,
 readFirstByte,
 readJSONWithFallback,
 taggedPath,
 write,
Expand DownExpand Up@@ -39,23 +40,52 @@ export interface Chunk {
 chunk: Buffer;
}

const EOF_MARKER = 1;

function isEofByte(byte: number | undefined): boolean {
 return byte === EOF_MARKER;
}

export function serializeChunk(chunk: Chunk) {
 const eofByte = Buffer.from([chunk.eof ? 1 : 0]);
 const eofByte = Buffer.from([chunk.eof ? EOF_MARKER : 0]);
 return Buffer.concat([eofByte, chunk.chunk]);
}

/** Check only the EOF flag byte without copying chunk payload. */
export function isEofChunk(serialized: Buffer): boolean {
 return serialized[0] === 1;
 return isEofByte(serialized[0]);
}

export function deserializeChunk(serialized: Buffer) {
 const eof = serialized[0] === 1;
 const eof = isEofChunk(serialized);
 // Create a copy instead of a view to prevent ArrayBuffer detachment
 const chunk = Buffer.from(serialized.subarray(1));
 return { eof, chunk };
}

async function listChunkEntries(chunksDir: string): Promise<string[]> {
 try {
 return await fs.readdir(chunksDir);
 } catch (error) {
 if ((error as NodeJS.ErrnoException).code === 'ENOENT') return [];
 throw error;
 }
}

function addChunkFilesByExtension(
 extMap: Map<string, string>,
 entries: string[],
 sourceExtension: string,
 fileExtension = sourceExtension,
 include: (file: string) => boolean = () => true
): void {
 for (const entry of entries) {
 if (!entry.endsWith(sourceExtension)) continue;
 const file = entry.slice(0, -sourceExtension.length);
 if (include(file)) extMap.set(file, fileExtension);
 }
}

/**
 * List chunk files for a stream, sorted chronologically (ULID order).
 * Returns both the sorted file names and a map of file → extension for
Expand All@@ -68,25 +98,21 @@ async function listChunkFilesForStream(
): Promise<{ files: string[]; extMap: Map<string, string> }> {
 // Name is used as a filename prefix below; validate it can't escape chunksDir.
 assertSafeEntityId('streamName', name);
 const listPromises: Promise<string[]>[] = [
 listFilesByExtension(chunksDir, '.bin'),
 listFilesByExtension(chunksDir, '.json'),
 ];
 if (tag) {
 listPromises.push(listFilesByExtension(chunksDir, `.${tag}.bin`));
 }
 const [binFiles, jsonFiles, ...taggedResults] =
 await Promise.all(listPromises);
 const taggedBinFiles = taggedResults[0] ?? [];

 const entries = await listChunkEntries(chunksDir);
 const extMap = new Map<string, string>();
 for (const f of jsonFiles) extMap.set(f, '.json');
 const tagSfx = tag ? `.${tag}` : '';
 for (const f of binFiles) {
 if (tag && f.endsWith(tagSfx)) continue;
 extMap.set(f, '.bin');
 addChunkFilesByExtension(extMap, entries, '.json');
Comment thread
pranaygp marked this conversation as resolved.

 addChunkFilesByExtension(
 extMap,
 entries,
 '.bin',
 '.bin',
 tag ? (file) => !file.endsWith(`.${tag}`) : undefined
 );

 if (tag) {
 const taggedExtension = `.${tag}.bin`;
 addChunkFilesByExtension(extMap, entries, taggedExtension);
 }
 for (const f of taggedBinFiles) extMap.set(f, `.${tag}.bin`);

 const files = [...extMap.keys()]
 .filter((file) => file.startsWith(`${name}-`))
Expand DownExpand Up@@ -333,7 +359,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Before the cursor: only need to check EOF (1 byte), skip content
 if (dataIndex < startIndex) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 break;
 }
Expand All@@ -343,7 +369,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Collected enough data chunks — peek at the next file for EOF/hasMore
 if (resultChunks.length >= limit) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 } else {
 // More data files exist beyond this page
Expand DownExpand Up@@ -386,14 +412,15 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 const { files: chunkFiles, extMap: fileExtMap } =
 await listChunkFilesForStream(chunksDir, name, tag);

 // Only read the first byte of each file to check EOF — no full
 // deserialization needed since we just need a count.
 // Read only the EOF marker byte because metadata never needs payloads.
 let streamDone = false;
 let dataCount = 0;
 for (const file of chunkFiles) {
 const ext = fileExtMap.get(file) ?? '.bin';
 if (
 isEofChunk(await readBuffer(path.join(chunksDir, `${file}${ext}`)))
 isEofByte(
 await readFirstByte(path.join(chunksDir, `${file}${ext}`))
 )
 ) {
 streamDone = true;
 break;
Expand DownExpand Up@@ -494,12 +521,13 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 ) {
 const lastFile = chunkFiles[chunkFiles.length - 1];
 const lastExt = fileExtMap.get(lastFile) ?? '.bin';
 // Note: this incurs an extra disk read to check the EOF marker.
 // Acceptable since negative startIndex is not a hot path.
 const lastChunk = deserializeChunk(
 await readBuffer(path.join(chunksDir, `${lastFile}${lastExt}`))
 );
 if (lastChunk?.eof === true) {
 if (
 isEofByte(
 await readFirstByte(
 path.join(chunksDir, `${lastFile}${lastExt}`)
 )
 )
 ) {
 dataChunkCount--;
 }
 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[world-local] Reduce stream metadata I/O by pranaygp · Pull Request #2139 · vercel/workflow · GitHub
Skip to content
[world-local] Reduce stream metadata I/O#2139

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privacy statement. We’ll occasionally send you account related emails.

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Sign in
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 Merged

pranaygp
merged 3 commits into

from

May 28, 2026
 Merged


[world-local] Reduce stream metadata I/O
#2139
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7156bb7

[world-local] Reduce stream metadata I/O


pranaygp May 28, 2026
e8b7c17

Merge branch 'main' into pranaygp/codex/world-local-stream-metadata-io


pranaygp May 28, 2026
21bfb77

[world-local] Address stream metadata review feedback


pranaygp May 28, 2026

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5 changes: 5 additions & 0 deletions
.changeset/quieter-stream-metadata.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@workflow/world-local': patch
---

Reduce local stream metadata and pagination I/O by reading only EOF marker bytes and scanning chunk files once.

16 changes: 16 additions & 0 deletions
packages/world-local/src/fs.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -18,6 +18,7 @@ import { z } from 'zod';
import {
 assertSafeEntityId,
 paginatedFileSystemQuery,
 readFirstByte,
 readJSONWithFallback,
 resolveWithinBase,
 taggedPath,
Expand DownExpand Up@@ -97,6 +98,21 @@ describe('fs utilities', () => {
 });
 });

 describe('readFirstByte', () => {
 it('reads only the marker value and handles empty files', async () => {
 const dataPath = path.join(testDir, 'chunk.bin');
 const nonEofPath = path.join(testDir, 'non-eof-chunk.bin');
 const emptyPath = path.join(testDir, 'empty.bin');
 await fs.writeFile(dataPath, Buffer.from([1, 2, 3]));
 await fs.writeFile(nonEofPath, Buffer.from([0, 2, 3]));
 await fs.writeFile(emptyPath, Buffer.alloc(0));

 expect(await readFirstByte(dataPath)).toBe(1);
 expect(await readFirstByte(nonEofPath)).toBe(0);
 expect(await readFirstByte(emptyPath)).toBeUndefined();
 });
 });

 describe('paginatedFileSystemQuery', () => {
 // Simple getCreatedAt function that strips .json and tries to parse as ULID
 const getCreatedAt = (filename: string): Date | null => {
Expand Down

13 changes: 13 additions & 0 deletions
packages/world-local/src/fs.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -375,6 +375,19 @@ export async function readBuffer(filePath: string): Promise<Buffer> {
 return content;
}

export async function readFirstByte(
 filePath: string
): Promise<number | undefined> {
 const file = await fs.open(filePath, 'r');
 try {
 const byte = Buffer.allocUnsafe(1);
 const { bytesRead } = await file.read(byte, 0, 1, 0);
 return bytesRead === 0 ? undefined : byte[0];
 } finally {
 await file.close();
 }
}

export async function deleteJSON(filePath: string): Promise<void> {
 try {
 await fs.unlink(filePath);
Expand Down

34 changes: 34 additions & 0 deletions
packages/world-local/src/streamer.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -909,6 +909,40 @@ describe('streamer', () => {
 expect(page2.done).toBe(true);
 });

 it('prefers tagged chunks over untagged and legacy files', async () => {
 const { testDir } = await setupStreamer();
 const streamName = 'mixed-format-stream';
 const taggedStreamer = createStreamer(testDir, 'vitest-0');
 const chunksDir = path.join(testDir, 'streams', 'chunks');
 await fs.mkdir(chunksDir, { recursive: true });

 const writeChunk = (fileName: string, text: string, eof = false) =>
 fs.writeFile(
 path.join(chunksDir, fileName),
 serializeChunk({ chunk: Buffer.from(text), eof })
 );

 await Promise.all([
 writeChunk(`${streamName}-chnk_01.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_01.bin`, 'untagged-shadowed'),
 writeChunk(`${streamName}-chnk_01.vitest-0.bin`, 'tagged'),
 writeChunk(`${streamName}-chnk_02.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_02.bin`, 'untagged'),
 writeChunk(`${streamName}-chnk_03.json`, 'legacy'),
 writeChunk(`${streamName}-chnk_04.vitest-0.bin`, '', true),
 ]);

 const result = await taggedStreamer.streams.getChunks(
 TEST_RUN_ID,
 streamName
 );

 expect(
 result.data.map((chunk) => Buffer.from(chunk.data).toString())
 ).toEqual(['tagged', 'untagged', 'legacy']);
 expect(result.done).toBe(true);
 });

 it('should return done=false for in-progress stream', async () => {
 const { streamer } = await setupStreamer();
 const streamName = 'in-progress';
Expand Down

92 changes: 60 additions & 32 deletions
packages/world-local/src/streamer.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
import { EventEmitter } from 'node:events';
import fs from 'node:fs/promises';
import path from 'node:path';
import type {
 GetChunksOptions,
Expand All@@ -10,8 +11,8 @@ import { monotonicFactory } from 'ulid';
import { z } from 'zod';
import {
 assertSafeEntityId,
 listFilesByExtension,
 readBuffer,
 readFirstByte,
 readJSONWithFallback,
 taggedPath,
 write,
Expand DownExpand Up@@ -39,23 +40,52 @@ export interface Chunk {
 chunk: Buffer;
}

const EOF_MARKER = 1;

function isEofByte(byte: number | undefined): boolean {
 return byte === EOF_MARKER;
}

export function serializeChunk(chunk: Chunk) {
 const eofByte = Buffer.from([chunk.eof ? 1 : 0]);
 const eofByte = Buffer.from([chunk.eof ? EOF_MARKER : 0]);
 return Buffer.concat([eofByte, chunk.chunk]);
}

/** Check only the EOF flag byte without copying chunk payload. */
export function isEofChunk(serialized: Buffer): boolean {
 return serialized[0] === 1;
 return isEofByte(serialized[0]);
}

export function deserializeChunk(serialized: Buffer) {
 const eof = serialized[0] === 1;
 const eof = isEofChunk(serialized);
 // Create a copy instead of a view to prevent ArrayBuffer detachment
 const chunk = Buffer.from(serialized.subarray(1));
 return { eof, chunk };
}

async function listChunkEntries(chunksDir: string): Promise<string[]> {
 try {
 return await fs.readdir(chunksDir);
 } catch (error) {
 if ((error as NodeJS.ErrnoException).code === 'ENOENT') return [];
 throw error;
 }
}

function addChunkFilesByExtension(
 extMap: Map<string, string>,
 entries: string[],
 sourceExtension: string,
 fileExtension = sourceExtension,
 include: (file: string) => boolean = () => true
): void {
 for (const entry of entries) {
 if (!entry.endsWith(sourceExtension)) continue;
 const file = entry.slice(0, -sourceExtension.length);
 if (include(file)) extMap.set(file, fileExtension);
 }
}

/**
 * List chunk files for a stream, sorted chronologically (ULID order).
 * Returns both the sorted file names and a map of file → extension for
Expand All@@ -68,25 +98,21 @@ async function listChunkFilesForStream(
): Promise<{ files: string[]; extMap: Map<string, string> }> {
 // Name is used as a filename prefix below; validate it can't escape chunksDir.
 assertSafeEntityId('streamName', name);
 const listPromises: Promise<string[]>[] = [
 listFilesByExtension(chunksDir, '.bin'),
 listFilesByExtension(chunksDir, '.json'),
 ];
 if (tag) {
 listPromises.push(listFilesByExtension(chunksDir, `.${tag}.bin`));
 }
 const [binFiles, jsonFiles, ...taggedResults] =
 await Promise.all(listPromises);
 const taggedBinFiles = taggedResults[0] ?? [];

 const entries = await listChunkEntries(chunksDir);
 const extMap = new Map<string, string>();
 for (const f of jsonFiles) extMap.set(f, '.json');
 const tagSfx = tag ? `.${tag}` : '';
 for (const f of binFiles) {
 if (tag && f.endsWith(tagSfx)) continue;
 extMap.set(f, '.bin');
 addChunkFilesByExtension(extMap, entries, '.json');
Comment thread
pranaygp marked this conversation as resolved.

 addChunkFilesByExtension(
 extMap,
 entries,
 '.bin',
 '.bin',
 tag ? (file) => !file.endsWith(`.${tag}`) : undefined
 );

 if (tag) {
 const taggedExtension = `.${tag}.bin`;
 addChunkFilesByExtension(extMap, entries, taggedExtension);
 }
 for (const f of taggedBinFiles) extMap.set(f, `.${tag}.bin`);

 const files = [...extMap.keys()]
 .filter((file) => file.startsWith(`${name}-`))
Expand DownExpand Up@@ -333,7 +359,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Before the cursor: only need to check EOF (1 byte), skip content
 if (dataIndex < startIndex) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 break;
 }
Expand All@@ -343,7 +369,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Collected enough data chunks — peek at the next file for EOF/hasMore
 if (resultChunks.length >= limit) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 } else {
 // More data files exist beyond this page
Expand DownExpand Up@@ -386,14 +412,15 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 const { files: chunkFiles, extMap: fileExtMap } =
 await listChunkFilesForStream(chunksDir, name, tag);

 // Only read the first byte of each file to check EOF — no full
 // deserialization needed since we just need a count.
 // Read only the EOF marker byte because metadata never needs payloads.
 let streamDone = false;
 let dataCount = 0;
 for (const file of chunkFiles) {
 const ext = fileExtMap.get(file) ?? '.bin';
 if (
 isEofChunk(await readBuffer(path.join(chunksDir, `${file}${ext}`)))
 isEofByte(
 await readFirstByte(path.join(chunksDir, `${file}${ext}`))
 )
 ) {
 streamDone = true;
 break;
Expand DownExpand Up@@ -494,12 +521,13 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 ) {
 const lastFile = chunkFiles[chunkFiles.length - 1];
 const lastExt = fileExtMap.get(lastFile) ?? '.bin';
 // Note: this incurs an extra disk read to check the EOF marker.
 // Acceptable since negative startIndex is not a hot path.
 const lastChunk = deserializeChunk(
 await readBuffer(path.join(chunksDir, `${lastFile}${lastExt}`))
 );
 if (lastChunk?.eof === true) {
 if (
 isEofByte(
 await readFirstByte(
 path.join(chunksDir, `${lastFile}${lastExt}`)
 )
 )
 ) {
 dataChunkCount--;
 }
 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
[world-local] Reduce stream metadata I/O by pranaygp · Pull Request #2139 · vercel/workflow · GitHub
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pranaygp
merged 3 commits into

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May 28, 2026
 Merged


[world-local] Reduce stream metadata I/O
#2139
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7156bb7

[world-local] Reduce stream metadata I/O


pranaygp May 28, 2026
e8b7c17

Merge branch 'main' into pranaygp/codex/world-local-stream-metadata-io


pranaygp May 28, 2026
21bfb77

[world-local] Address stream metadata review feedback


pranaygp May 28, 2026

File filter

Filter by extension
Filter by extension
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5 changes: 5 additions & 0 deletions
.changeset/quieter-stream-metadata.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@workflow/world-local': patch
---

Reduce local stream metadata and pagination I/O by reading only EOF marker bytes and scanning chunk files once.

16 changes: 16 additions & 0 deletions
packages/world-local/src/fs.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -18,6 +18,7 @@ import { z } from 'zod';
import {
 assertSafeEntityId,
 paginatedFileSystemQuery,
 readFirstByte,
 readJSONWithFallback,
 resolveWithinBase,
 taggedPath,
Expand DownExpand Up@@ -97,6 +98,21 @@ describe('fs utilities', () => {
 });
 });

 describe('readFirstByte', () => {
 it('reads only the marker value and handles empty files', async () => {
 const dataPath = path.join(testDir, 'chunk.bin');
 const nonEofPath = path.join(testDir, 'non-eof-chunk.bin');
 const emptyPath = path.join(testDir, 'empty.bin');
 await fs.writeFile(dataPath, Buffer.from([1, 2, 3]));
 await fs.writeFile(nonEofPath, Buffer.from([0, 2, 3]));
 await fs.writeFile(emptyPath, Buffer.alloc(0));

 expect(await readFirstByte(dataPath)).toBe(1);
 expect(await readFirstByte(nonEofPath)).toBe(0);
 expect(await readFirstByte(emptyPath)).toBeUndefined();
 });
 });

 describe('paginatedFileSystemQuery', () => {
 // Simple getCreatedAt function that strips .json and tries to parse as ULID
 const getCreatedAt = (filename: string): Date | null => {
Expand Down

13 changes: 13 additions & 0 deletions
packages/world-local/src/fs.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -375,6 +375,19 @@ export async function readBuffer(filePath: string): Promise<Buffer> {
 return content;
}

export async function readFirstByte(
 filePath: string
): Promise<number | undefined> {
 const file = await fs.open(filePath, 'r');
 try {
 const byte = Buffer.allocUnsafe(1);
 const { bytesRead } = await file.read(byte, 0, 1, 0);
 return bytesRead === 0 ? undefined : byte[0];
 } finally {
 await file.close();
 }
}

export async function deleteJSON(filePath: string): Promise<void> {
 try {
 await fs.unlink(filePath);
Expand Down

34 changes: 34 additions & 0 deletions
packages/world-local/src/streamer.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -909,6 +909,40 @@ describe('streamer', () => {
 expect(page2.done).toBe(true);
 });

 it('prefers tagged chunks over untagged and legacy files', async () => {
 const { testDir } = await setupStreamer();
 const streamName = 'mixed-format-stream';
 const taggedStreamer = createStreamer(testDir, 'vitest-0');
 const chunksDir = path.join(testDir, 'streams', 'chunks');
 await fs.mkdir(chunksDir, { recursive: true });

 const writeChunk = (fileName: string, text: string, eof = false) =>
 fs.writeFile(
 path.join(chunksDir, fileName),
 serializeChunk({ chunk: Buffer.from(text), eof })
 );

 await Promise.all([
 writeChunk(`${streamName}-chnk_01.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_01.bin`, 'untagged-shadowed'),
 writeChunk(`${streamName}-chnk_01.vitest-0.bin`, 'tagged'),
 writeChunk(`${streamName}-chnk_02.json`, 'legacy-shadowed'),
 writeChunk(`${streamName}-chnk_02.bin`, 'untagged'),
 writeChunk(`${streamName}-chnk_03.json`, 'legacy'),
 writeChunk(`${streamName}-chnk_04.vitest-0.bin`, '', true),
 ]);

 const result = await taggedStreamer.streams.getChunks(
 TEST_RUN_ID,
 streamName
 );

 expect(
 result.data.map((chunk) => Buffer.from(chunk.data).toString())
 ).toEqual(['tagged', 'untagged', 'legacy']);
 expect(result.done).toBe(true);
 });

 it('should return done=false for in-progress stream', async () => {
 const { streamer } = await setupStreamer();
 const streamName = 'in-progress';
Expand Down

92 changes: 60 additions & 32 deletions
packages/world-local/src/streamer.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
import { EventEmitter } from 'node:events';
import fs from 'node:fs/promises';
import path from 'node:path';
import type {
 GetChunksOptions,
Expand All@@ -10,8 +11,8 @@ import { monotonicFactory } from 'ulid';
import { z } from 'zod';
import {
 assertSafeEntityId,
 listFilesByExtension,
 readBuffer,
 readFirstByte,
 readJSONWithFallback,
 taggedPath,
 write,
Expand DownExpand Up@@ -39,23 +40,52 @@ export interface Chunk {
 chunk: Buffer;
}

const EOF_MARKER = 1;

function isEofByte(byte: number | undefined): boolean {
 return byte === EOF_MARKER;
}

export function serializeChunk(chunk: Chunk) {
 const eofByte = Buffer.from([chunk.eof ? 1 : 0]);
 const eofByte = Buffer.from([chunk.eof ? EOF_MARKER : 0]);
 return Buffer.concat([eofByte, chunk.chunk]);
}

/** Check only the EOF flag byte without copying chunk payload. */
export function isEofChunk(serialized: Buffer): boolean {
 return serialized[0] === 1;
 return isEofByte(serialized[0]);
}

export function deserializeChunk(serialized: Buffer) {
 const eof = serialized[0] === 1;
 const eof = isEofChunk(serialized);
 // Create a copy instead of a view to prevent ArrayBuffer detachment
 const chunk = Buffer.from(serialized.subarray(1));
 return { eof, chunk };
}

async function listChunkEntries(chunksDir: string): Promise<string[]> {
 try {
 return await fs.readdir(chunksDir);
 } catch (error) {
 if ((error as NodeJS.ErrnoException).code === 'ENOENT') return [];
 throw error;
 }
}

function addChunkFilesByExtension(
 extMap: Map<string, string>,
 entries: string[],
 sourceExtension: string,
 fileExtension = sourceExtension,
 include: (file: string) => boolean = () => true
): void {
 for (const entry of entries) {
 if (!entry.endsWith(sourceExtension)) continue;
 const file = entry.slice(0, -sourceExtension.length);
 if (include(file)) extMap.set(file, fileExtension);
 }
}

/**
 * List chunk files for a stream, sorted chronologically (ULID order).
 * Returns both the sorted file names and a map of file → extension for
Expand All@@ -68,25 +98,21 @@ async function listChunkFilesForStream(
): Promise<{ files: string[]; extMap: Map<string, string> }> {
 // Name is used as a filename prefix below; validate it can't escape chunksDir.
 assertSafeEntityId('streamName', name);
 const listPromises: Promise<string[]>[] = [
 listFilesByExtension(chunksDir, '.bin'),
 listFilesByExtension(chunksDir, '.json'),
 ];
 if (tag) {
 listPromises.push(listFilesByExtension(chunksDir, `.${tag}.bin`));
 }
 const [binFiles, jsonFiles, ...taggedResults] =
 await Promise.all(listPromises);
 const taggedBinFiles = taggedResults[0] ?? [];

 const entries = await listChunkEntries(chunksDir);
 const extMap = new Map<string, string>();
 for (const f of jsonFiles) extMap.set(f, '.json');
 const tagSfx = tag ? `.${tag}` : '';
 for (const f of binFiles) {
 if (tag && f.endsWith(tagSfx)) continue;
 extMap.set(f, '.bin');
 addChunkFilesByExtension(extMap, entries, '.json');
Comment thread
pranaygp marked this conversation as resolved.

 addChunkFilesByExtension(
 extMap,
 entries,
 '.bin',
 '.bin',
 tag ? (file) => !file.endsWith(`.${tag}`) : undefined
 );

 if (tag) {
 const taggedExtension = `.${tag}.bin`;
 addChunkFilesByExtension(extMap, entries, taggedExtension);
 }
 for (const f of taggedBinFiles) extMap.set(f, `.${tag}.bin`);

 const files = [...extMap.keys()]
 .filter((file) => file.startsWith(`${name}-`))
Expand DownExpand Up@@ -333,7 +359,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Before the cursor: only need to check EOF (1 byte), skip content
 if (dataIndex < startIndex) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 break;
 }
Expand All@@ -343,7 +369,7 @@ export function createStreamer(basedir: string, tag?: string): Streamer {

 // Collected enough data chunks — peek at the next file for EOF/hasMore
 if (resultChunks.length >= limit) {
 if (isEofChunk(await readBuffer(filePath))) {
 if (isEofByte(await readFirstByte(filePath))) {
 streamDone = true;
 } else {
 // More data files exist beyond this page
Expand DownExpand Up@@ -386,14 +412,15 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 const { files: chunkFiles, extMap: fileExtMap } =
 await listChunkFilesForStream(chunksDir, name, tag);

 // Only read the first byte of each file to check EOF — no full
 // deserialization needed since we just need a count.
 // Read only the EOF marker byte because metadata never needs payloads.
 let streamDone = false;
 let dataCount = 0;
 for (const file of chunkFiles) {
 const ext = fileExtMap.get(file) ?? '.bin';
 if (
 isEofChunk(await readBuffer(path.join(chunksDir, `${file}${ext}`)))
 isEofByte(
 await readFirstByte(path.join(chunksDir, `${file}${ext}`))
 )
 ) {
 streamDone = true;
 break;
Expand DownExpand Up@@ -494,12 +521,13 @@ export function createStreamer(basedir: string, tag?: string): Streamer {
 ) {
 const lastFile = chunkFiles[chunkFiles.length - 1];
 const lastExt = fileExtMap.get(lastFile) ?? '.bin';
 // Note: this incurs an extra disk read to check the EOF marker.
 // Acceptable since negative startIndex is not a hot path.
 const lastChunk = deserializeChunk(
 await readBuffer(path.join(chunksDir, `${lastFile}${lastExt}`))
 );
 if (lastChunk?.eof === true) {
 if (
 isEofByte(
 await readFirstByte(
 path.join(chunksDir, `${lastFile}${lastExt}`)
 )
 )
 ) {
 dataChunkCount--;
 }
 }
Expand Down
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