@@ -16,13 +16,11 @@ const {
   ObjectDefineProperties,
   ObjectKeys,
   PromisePrototypeThen,
-  PromiseResolve,
   PromiseWithResolvers,
   SafeSet,
   Symbol,
   SymbolAsyncDispose,
   SymbolAsyncIterator,
-  SymbolDispose,
   SymbolIterator,
   TypedArrayPrototypeGetByteLength,
   Uint8Array,
@@ -133,16 +131,9 @@ const {
 } = require('internal/blob');
 
 const {
-  drainableProtocol,
   kValidatedSource,
 } = require('internal/streams/iter/types');
 
-const {
-  convertChunks,
-  getWriterSignal,
-  toWriterUint8Array,
-} = require('internal/streams/iter/utils');
-
 const {
   from: streamFrom,
   fromSync: streamFromSync,
@@ -231,6 +222,10 @@ const {
   QuicStreamState,
 } = require('internal/quic/state');
 
+const {
+  getWriter,
+} = require('internal/quic/writer');
+
 const assert = require('internal/assert');
 
 const {
@@ -1551,328 +1546,6 @@ function isSyncIterable(obj) {
   return obj != null && typeof obj[SymbolIterator] === 'function';
 }
 
-function getWriter(obj) {
-  const {
-    setDrainCallback,
-    setStopSendingCallback,
-    writeDesiredSize,
-    writeEnded,
-    writeChunks,
-    resetStream,
-    endWrite,
-    nonWritableStream,
-    initStreamingSource,
-  } = obj;
-  // TODO, if this is not an internal function,
-  // the input should be checked for types
-  let closed = false;
-  let ending = false;
-  let errored = false;
-  let error = null;
-  let totalBytesWritten = 0;
-  let drainWakeup = null;
-  let pendingWrite = null;
-  let pendingEnd = null;
-
-  function raceWithSignal(promise, signal) {
-    if (signal === undefined) return promise;
-    signal.throwIfAborted();
-
-    const deferred = PromiseWithResolvers();
-    const onAbort = () => deferred.reject(signal.reason);
-    signal.addEventListener('abort', onAbort, {
-      __proto__: null,
-      once: true,
-    });
-    PromisePrototypeThen(
-      promise,
-      (value) => {
-        signal.removeEventListener('abort', onAbort);
-        deferred.resolve(value);
-      },
-      (reason) => {
-        signal.removeEventListener('abort', onAbort);
-        deferred.reject(reason);
-      });
-    return deferred.promise;
-  }
-
-  function waitForDrain(signal) {
-    drainWakeup ??= PromiseWithResolvers();
-    return raceWithSignal(drainWakeup.promise, signal);
-  }
-
-  // Drain callback - The implementation C++/js fires this when send buffer has space
-  setDrainCallback(() => {
-    if (drainWakeup) {
-      drainWakeup.resolve(true);
-      drainWakeup = null;
-    }
-  });
-
-  setStopSendingCallback((reason) => {
-    if (!closed && !errored) {
-      errored = true;
-      error = reason;
-      if (drainWakeup != null) {
-        markPromiseAsHandled(drainWakeup.promise);
-        drainWakeup.reject(error);
-        drainWakeup = null;
-      }
-    }
-  });
-
-  // A note on backpressure handling: per the stream/iter spec, the default
-  // backpressure policy for writers is strict. One async write may wait for
-  // capacity; additional writes are rejected until it settles.
-
-  function writeConvertedSync(chunk, token) {
-    const isPending = pendingWrite === token && token !== undefined;
-    // If the stream is closed, errored, or write-ended, we cannot accept
-    // more data. Refuse the sync write.
-    if (closed || errored || writeEnded() ||
-        (ending && !isPending) ||
-        (pendingWrite !== null && !isPending)) {
-      return false;
-    }
-    const len = TypedArrayPrototypeGetByteLength(chunk);
-    if (len === 0) return true;
-    // Refuse the write only when there is no available capacity at
-    // all. If we can write we allow the write even if the
-    // chunk is larger than the remaining capacity -- the source
-    // will accept the data into the underlying queues e.g. DataQueue and
-    // UpdateWriteDesiredSize() will drop writeDesiredSize toward 0,
-    // at which point the standard drain mechanism takes over.
-    // This follows the iter-streams model where writes beyond the
-    // budget succeed and backpressure applies to *subsequent* writes.
-    if (writeDesiredSize() === 0) return false;
-    const result = writeChunks([chunk]);
-    if (result === undefined) return false;
-    totalBytesWritten += len;
-    return true;
-  }
-
-  function writeSync(chunk) {
-    return writeConvertedSync(toWriterUint8Array(chunk));
-  }
-
-  function write(chunk, options = kEmptyObject) {
-    chunk = toWriterUint8Array(chunk);
-    const signal = getWriterSignal(options);
-    return writeAsync(chunk, signal);
-  }
-
-  async function writeAsync(chunk, signal) {
-    if (errored) throw error;
-    if (closed || ending || writeEnded()) {
-      throw new ERR_INVALID_STATE('Writer is closed');
-    }
-    signal?.throwIfAborted();
-
-    if (writeConvertedSync(chunk)) return;
-    await writeWhenDrained(chunk, writeConvertedSync, signal);
-  }
-
-  async function writeWhenDrained(chunks, writeConverted, signal) {
-    if (pendingWrite !== null) {
-      throw new ERR_INVALID_STATE.RangeError(
-        'Backpressure violation: too many pending writes. ' +
-        'Await each write() call to respect backpressure.');
-    }
-    if (writeDesiredSize() !== 0) {
-      throw new ERR_INVALID_STATE('Stream write buffer is full');
-    }
-
-    const done = PromiseWithResolvers();
-    const token = { __proto__: null, done };
-    pendingWrite = token;
-    try {
-      while (true) {
-        await waitForDrain(signal);
-        if (errored) throw error;
-        if (closed || writeEnded()) {
-          throw new ERR_INVALID_STATE('Writer is closed');
-        }
-        signal?.throwIfAborted();
-        if (writeConverted(chunks, token)) return;
-        if (writeDesiredSize() !== 0) {
-          throw new ERR_INVALID_STATE('Stream write buffer is full');
-        }
-      }
-    } finally {
-      if (pendingWrite === token) pendingWrite = null;
-      done.resolve();
-    }
-  }
-
-  function writevConvertedSync(chunks, token) {
-    const isPending = pendingWrite === token && token !== undefined;
-    if (closed || errored || writeEnded() ||
-        (ending && !isPending) ||
-        (pendingWrite !== null && !isPending)) {
-      return false;
-    }
-    let len = 0;
-    for (const c of chunks) len += TypedArrayPrototypeGetByteLength(c);
-    if (len === 0) return true;
-    if (writeDesiredSize() === 0) return false;
-    const result = writeChunks(chunks);
-    if (result === undefined) return false;
-    totalBytesWritten += len;
-    return true;
-  }
-
-  function writevSync(chunks) {
-    return writevConvertedSync(convertChunks(chunks));
-  }
-
-  function writev(chunks, options = kEmptyObject) {
-    chunks = convertChunks(chunks);
-    const signal = getWriterSignal(options);
-    return writevAsync(chunks, signal);
-  }
-
-  async function writevAsync(chunks, signal) {
-    if (errored) throw error;
-    if (closed || ending || writeEnded()) {
-      throw new ERR_INVALID_STATE('Writer is closed');
-    }
-    signal?.throwIfAborted();
-
-    if (writevConvertedSync(chunks)) return;
-    await writeWhenDrained(chunks, writevConvertedSync, signal);
-  }
-
-  function endSync() {
-    // Per the streams/iter spec, endSync and end follow a try-fallback
-    // pattern. That is, callers should try endSync first and if it returns
-    // -1, then they should call and await end(). This is a signal that sync
-    // end is not currently possible. However, we always support sync end
-    // here unless the stream is already errored.
-    if (errored) return -1;
-
-    // If we're already closed, just return the total bytes written.
-    if (closed) return totalBytesWritten;
-
-    // Accepted writes and existing drain waiters must settle before ending.
-    if (ending || pendingWrite !== null || drainWakeup !== null) return -1;
-
-    // Fantastic, we can end synchronously!
-    endWrite();
-    closed = true;
-    return totalBytesWritten;
-  }
-
-  function end(options = kEmptyObject) {
-    const signal = getWriterSignal(options);
-    return endAsync(signal);
-  }
-
-  async function endAsync(signal) {
-    if (errored) throw error;
-    if (closed) return totalBytesWritten;
-    signal?.throwIfAborted();
-
-    // Per the streams/iter spec, endSync and end follow a try-fallback
-    // pattern. That is, callers should try endSync first and if it returns
-    // -1, then they should call and await end(). This is a signal that sync
-    // end is not currently possible. However, we always support sync end
-    // here unless the stream is already errored.
-    // While the user should have already called endSync, we call it again
-    // here to actually process the end request. At worst it's called twice.
-    const n = endSync();
-
-    // A return value of -1 indicates that endSync was not yet able to
-    // process the end request, either because we are errored or because we
-    // are awaiting drain. If we're errored, throw the error. If we're waiting
-    // for drain, await it and then try ending again.
-
-    if (n >= 0) return n;
-    if (errored) throw error;
-
-    if (pendingEnd === null) {
-      ending = true;
-      pendingEnd = finishEnd();
-    }
-    return raceWithSignal(pendingEnd, signal);
-  }
-
-  async function finishEnd() {
-    if (pendingWrite !== null) {
-      await pendingWrite.done.promise;
-    }
-    if (errored) throw error;
-
-    if (drainWakeup !== null) {
-      await drainWakeup.promise;
-    }
-    if (errored) throw error;
-
-    if (!writeEnded()) endWrite();
-    closed = true;
-    ending = false;
-    return totalBytesWritten;
-  }
-
-  function fail(reason) {
-    if (closed || errored) return;
-    errored = true;
-    error = reason;
-    resetStream(error);
-    if (drainWakeup != null) {
-      markPromiseAsHandled(drainWakeup.promise);
-      drainWakeup.reject(error);
-      drainWakeup = null;
-    }
-  }
-
-  const writer = {
-    __proto__: null,
-    get canWrite() {
-      if (closed || ending || errored || writeEnded()) {
-        return null;
-      }
-      return writeDesiredSize() > 0;
-    },
-    writeSync,
-    write,
-    writevSync,
-    writev,
-    endSync,
-    end,
-    fail,
-    [drainableProtocol]() {
-      if (closed || ending || errored) return null;
-      // If a drain is already pending, return the existing promise.
-      if (drainWakeup != null) return drainWakeup.promise;
-      if (writeDesiredSize() > 0) return null;
-      drainWakeup = PromiseWithResolvers();
-      return drainWakeup.promise;
-    },
-    [SymbolAsyncDispose]() {
-      if (ending) return pendingEnd;
-      if (!closed && !errored) fail();
-      return PromiseResolve();
-    },
-    [SymbolDispose]() {
-      if (!closed && !errored) fail();
-    },
-  };
-
-  // Non-writable stream - return a pre-closed writer.
-  // A remote unidirectional stream is read-only and has no writable
-  // side. isLocal distinguishes locally-initiated (writable) from
-  // remotely-initiated (read-only) uni streams.
-  if (nonWritableStream() || writeEnded()) {
-    closed = true;
-    return writer;
-  }
-
-  // Initialize the outbound DataQueue for streaming writes
-  initStreamingSource();
-  return writer;
-}
-
 // Functions used specifically for internal or assertion purposes only.
 let getQuicStreamState;
 let getQuicSessionState;