zstd decoding complete frame in read stream halts stream

### Version v26.5.0 ### Platform ```text Darwin Mac.lan 24.6.0 Darwin Kernel Version 24.6.0: Tue Apr 21 20:19:12 PDT 2026; root:xnu-11417.140.69.710.16~1/RELEASE_ARM64_T6041 arm64 ``` ### Subsystem _No response_ ### What steps will reproduce the bug? ```js import { Buffer } from 'node:buffer'; import * as consumers from 'node:stream/consumers'; import * as zlib from 'node:zlib'; function consume(codec, writes) { const inflate = codec.createDecompress(); const result = consumers.buffer(inflate); writes.forEach(write => inflate.write(write)); inflate.end(); return result; } function describe(buffer) { const aa = buffer.includes(0x41); const bb = buffer.includes(0x42); const which = function() { if (aa && bb) { return 'frameA + frameB'; } else if (aa) { return 'frameA only'; } else if (bb) { return 'frameB only'; } else { return 'nothing'; } }(); return `${buffer.length} bytes (${which})`; } async function attempt(codec, writes) { try { return describe(await consume(codec, writes)); } catch (error) { return `threw: ${error.message}`; } } const tests = [ { name: 'zstd', compress: buffer => zlib.zstdCompressSync(buffer), createDecompress: () => zlib.createZstdDecompress(), }, { name: 'gzip', compress: buffer => zlib.gzipSync(buffer), createDecompress: () => zlib.createGunzip(), } ]; console.log(`node ${process.version}`); for (const codec of tests) { // 'A' / 'B' const frameA = codec.compress(Buffer.alloc(2000, 0x41)); const frameB = codec.compress(Buffer.alloc(2000, 0x42)); const concatenated = Buffer.concat([ frameA, frameB ]); // BUG: both frames in a single write — the boundary between them falls inside one input buffer. const bug = await attempt(codec, [ concatenated ]); // COUNTER-EXAMPLE: the same two frames, one per write — the boundary lands at a write boundary. const counter = await attempt(codec, [ frameA, frameB ]); console.log(`${codec.name}:`); console.log(` stream, both frames in ONE write -> ${bug}…