diff --git a/lix/libstore/build/derivation-goal.cc b/lix/libstore/build/derivation-goal.cc
index d364e1bf9..856ad16d5 100644
--- a/lix/libstore/build/derivation-goal.cc
+++ b/lix/libstore/build/derivation-goal.cc
@@ -121,7 +121,6 @@ DerivationGoal::~DerivationGoal() noexcept(false)
 void DerivationGoal::killChild()
 {
     hook.reset();
-    builderOutFD = nullptr;
 }
 
 
@@ -796,15 +795,12 @@ void replaceValidPath(const Path & storePath, const Path & tmpPath)
 
 int DerivationGoal::getChildStatus()
 {
-    builderOutFD = nullptr;
     return hook->pid.kill();
 }
 
-
 void DerivationGoal::closeReadPipes()
 {
     hook->fromHook.reset();
-    builderOutFD = nullptr;
 }
 
 void DerivationGoal::cleanupHookFinally()
@@ -1205,81 +1201,14 @@ Goal::WorkResult DerivationGoal::tooMuchLogs()
             getName(), settings.maxLogSize));
 }
 
-kj::Promise<Result<std::optional<Goal::WorkResult>>>
-DerivationGoal::handleBuilderOutput(AsyncInputStream & in) noexcept
+kj::Promise<Result<std::optional<Goal::WorkResult>>> DerivationGoal::handleRawChildStream() noexcept
 try {
-    LogLineSplitter splitter;
+    assert(hook);
 
-    auto flushLine = [&](const std::string & line) {
-        if (const auto state =
-                handleJSONLogMessage(line, *act, builderActivities, "the derivation builder"))
-        {
-            return *state;
-        } else {
-            logTail.push_back(line);
-            if (logTail.size() > settings.logLines) {
-                logTail.pop_front();
-            }
-
-            return act->result(resBuildLogLine, line);
-        }
-    };
-
-    auto buf = kj::heapArray<char>(4096);
-    while (true) {
-        std::string_view data;
-        try {
-            if (const auto got = TRY_AWAIT(in.read(buf.begin(), buf.size()))) {
-                data = {buf.begin(), *got};
-            } else {
-                co_return std::nullopt;
-            }
-        } catch (SysError & e) {
-            // the builder output stream may be a pty fd, and closing one pty
-            // endpoint sends EIO to the other endpoint. this is a good exit.
-            if (e.errNo == EIO) {
-                data = {};
-            } else {
-                throw;
-            }
-        }
-        lastChildActivity = AIO().provider.getTimer().now();
-
-        if (data.empty()) {
-            if (auto left = splitter.finish(); !left.empty()) {
-                if (flushLine(left) == Logger::BufferState::NeedsFlush) {
-                    TRY_AWAIT(act->getLogger().flush());
-                }
-            }
-            co_return std::nullopt;
-        }
-
-        logSize += data.size();
-        if (settings.maxLogSize && logSize > settings.maxLogSize) {
-            co_return tooMuchLogs();
-        }
-
-        if (logSink) {
-            (*logSink)(data);
-        }
-
-        while (!data.empty()) {
-            if (auto line = splitter.feed(data)) {
-                if (flushLine(*line) == Logger::BufferState::NeedsFlush) {
-                    TRY_AWAIT(act->getLogger().flush());
-                }
-            }
-        }
-    }
-} catch (...) {
-    co_return result::current_exception();
-}
-
-kj::Promise<Result<std::optional<Goal::WorkResult>>>
-DerivationGoal::handleHookOutput(AsyncInputStream & in) noexcept
-try {
     std::string currentHookLine;
 
+    AsyncFdIoStream in(AsyncFdIoStream::shared_fd{}, hook->fromHook.get());
+
     auto buf = kj::heapArray<char>(4096);
     while (true) {
         const auto got = TRY_AWAIT(in.read(buf.begin(), buf.size()));
@@ -1337,19 +1266,16 @@ try {
 
 kj::Promise<Result<std::optional<Goal::WorkResult>>> DerivationGoal::handleChildOutput() noexcept
 try {
-    kj::Own<AsyncInputStream> builderIn, hookIn;
-    if (builderOutFD) {
-        builderIn = kj::heap<AsyncFdIoStream>(AsyncFdIoStream::shared_fd{}, builderOutFD->get());
-    }
-    if (hook) {
-        hookIn = kj::heap<AsyncFdIoStream>(AsyncFdIoStream::shared_fd{}, hook->fromHook.get());
-    }
+    lastChildActivity = AIO().provider.getTimer().now();
 
-    auto handlers = handleChildStreams(builderIn.get(), hookIn.get())
-                        .attach(std::move(builderIn), std::move(hookIn));
+    auto handler = handleRawChildStream();
+
+    if (respectsTimeouts() && settings.maxSilentTime != 0) {
+        handler = handler.exclusiveJoin(monitorForSilence());
+    }
 
     if (respectsTimeouts() && settings.buildTimeout != 0) {
-        handlers = handlers.exclusiveJoin(
+        handler = handler.exclusiveJoin(
             AIO()
                 .provider.getTimer()
                 .afterDelay(settings.buildTimeout.get() * kj::SECONDS)
@@ -1361,7 +1287,7 @@ try {
         );
     }
 
-    co_return TRY_AWAIT(handlers);
+    co_return TRY_AWAIT(handler);
 } catch (...) {
     co_return result::current_exception();
 }
@@ -1380,40 +1306,6 @@ kj::Promise<Result<std::optional<Goal::WorkResult>>> DerivationGoal::monitorForS
     }
 }
 
-kj::Promise<Result<std::optional<Goal::WorkResult>>>
-DerivationGoal::handleChildStreams(AsyncInputStream * builderIn, AsyncInputStream * hookIn) noexcept
-{
-    assert(builderIn || hookIn);
-
-    lastChildActivity = AIO().provider.getTimer().now();
-
-    auto handlers = kj::joinPromisesFailFast([&] {
-        kj::Vector<kj::Promise<Result<std::optional<WorkResult>>>> parts{2};
-
-        if (builderIn) {
-            parts.add(handleBuilderOutput(*builderIn));
-        }
-        if (hookIn) {
-            parts.add(handleHookOutput(*hookIn));
-        }
-
-        return parts.releaseAsArray();
-    }());
-
-    if (respectsTimeouts() && settings.maxSilentTime != 0) {
-        handlers = handlers.exclusiveJoin(monitorForSilence().then([](auto r) {
-            return kj::arr(std::move(r));
-        }));
-    }
-
-    for (auto r : co_await handlers) {
-        if (r) {
-            co_return r;
-        }
-    }
-    co_return std::nullopt;
-}
-
 kj::Promise<Result<OutputPathMap>> DerivationGoal::queryDerivationOutputMap()
 try {
     OutputPathMap res;
diff --git a/lix/libstore/build/derivation-goal.hh b/lix/libstore/build/derivation-goal.hh
index 3becd9d3d..af885a1f7 100644
--- a/lix/libstore/build/derivation-goal.hh
+++ b/lix/libstore/build/derivation-goal.hh
@@ -206,13 +206,6 @@ struct DerivationGoal : public Goal
      */
     std::unique_ptr<HookInstance> hook;
 
-    /**
-      * Builder output is pulled from this file descriptor when not null.
-      * Owned by the derivation goal or subclass, must not be reset until
-      * the build has finished and no more output must be processed by us
-      */
-    AutoCloseFD * builderOutFD = nullptr;
-
     /**
      * The sort of derivation we are building.
      */
@@ -313,11 +306,7 @@ protected:
     kj::TimePoint lastChildActivity = kj::minValue;
 
     kj::Promise<Result<std::optional<WorkResult>>> handleChildOutput() noexcept;
-    kj::Promise<Result<std::optional<WorkResult>>>
-    handleChildStreams(AsyncInputStream * builderIn, AsyncInputStream * hookIn) noexcept;
-    kj::Promise<Result<std::optional<WorkResult>>> handleBuilderOutput(AsyncInputStream & in
-    ) noexcept;
-    kj::Promise<Result<std::optional<WorkResult>>> handleHookOutput(AsyncInputStream & in) noexcept;
+    virtual kj::Promise<Result<std::optional<WorkResult>>> handleRawChildStream() noexcept;
     kj::Promise<Result<std::optional<WorkResult>>> monitorForSilence() noexcept;
     WorkResult tooMuchLogs();
 
diff --git a/lix/libstore/build/local-derivation-goal.cc b/lix/libstore/build/local-derivation-goal.cc
index 852c70333..e446c58d9 100644
--- a/lix/libstore/build/local-derivation-goal.cc
+++ b/lix/libstore/build/local-derivation-goal.cc
@@ -1,4 +1,5 @@
 #include "lix/libstore/build/local-derivation-goal.hh"
+#include "build/derivation-goal.hh"
 #include "lix/libutil/async-io.hh"
 #include "lix/libutil/async.hh"
 #include "lix/libutil/error.hh"
@@ -337,7 +338,6 @@ void LocalDerivationGoal::closeReadPipes()
         DerivationGoal::closeReadPipes();
     } else {
         builderOutPTY.close();
-        builderOutFD = nullptr;
     }
 }
 
@@ -789,9 +789,9 @@ try {
 
     /* Create a pseudoterminal to get the output of the builder. */
     builderOutPTY = AutoCloseFD{posix_openpt(O_RDWR | O_NOCTTY)};
-    if (!builderOutPTY)
+    if (!builderOutPTY) {
         throw SysError("opening pseudoterminal master");
-    builderOutFD = &builderOutPTY;
+    }
 
     // FIXME: not thread-safe, use ptsname_r
     std::string slaveName = ptsname(builderOutPTY.get());
@@ -2689,5 +2689,79 @@ StorePath LocalDerivationGoal::makeFallbackPath(const StorePath & path)
         Hash(HashType::SHA256), path.name());
 }
 
+kj::Promise<Result<std::optional<Goal::WorkResult>>>
+LocalDerivationGoal::handleRawChildStream() noexcept
+try {
+    if (hook) {
+        co_return TRY_AWAIT(DerivationGoal::handleRawChildStream());
+    }
 
+    AsyncFdIoStream in(AsyncFdIoStream::shared_fd{}, builderOutPTY.get());
+
+    LogLineSplitter splitter;
+
+    auto flushLine = [&](const std::string & line) {
+        if (const auto state =
+                handleJSONLogMessage(line, *act, builderActivities, "the derivation builder"))
+        {
+            return *state;
+        } else {
+            logTail.push_back(line);
+            if (logTail.size() > settings.logLines) {
+                logTail.pop_front();
+            }
+
+            return act->result(resBuildLogLine, line);
+        }
+    };
+
+    auto buf = kj::heapArray<char>(4096);
+    while (true) {
+        std::string_view data;
+        try {
+            if (const auto got = TRY_AWAIT(in.read(buf.begin(), buf.size()))) {
+                data = {buf.begin(), *got};
+            } else {
+                co_return std::nullopt;
+            }
+        } catch (SysError & e) {
+            // the builder output stream may be a pty fd, and closing one pty
+            // endpoint sends EIO to the other endpoint. this is a good exit.
+            if (e.errNo == EIO) {
+                data = {};
+            } else {
+                throw;
+            }
+        }
+        lastChildActivity = AIO().provider.getTimer().now();
+
+        if (data.empty()) {
+            if (auto left = splitter.finish(); !left.empty()) {
+                if (flushLine(left) == Logger::BufferState::NeedsFlush) {
+                    TRY_AWAIT(act->getLogger().flush());
+                }
+            }
+            co_return std::nullopt;
+        }
+
+        logSize += data.size();
+        if (settings.maxLogSize && logSize > settings.maxLogSize) {
+            co_return tooMuchLogs();
+        }
+
+        if (logSink) {
+            (*logSink)(data);
+        }
+
+        while (!data.empty()) {
+            if (auto line = splitter.feed(data)) {
+                if (flushLine(*line) == Logger::BufferState::NeedsFlush) {
+                    TRY_AWAIT(act->getLogger().flush());
+                }
+            }
+        }
+    }
+} catch (...) {
+    co_return result::current_exception();
+}
 }
diff --git a/lix/libstore/build/local-derivation-goal.hh b/lix/libstore/build/local-derivation-goal.hh
index 3d1c04722..284a3cb0b 100644
--- a/lix/libstore/build/local-derivation-goal.hh
+++ b/lix/libstore/build/local-derivation-goal.hh
@@ -324,6 +324,8 @@ protected:
      */
     virtual Pid startChild(std::function<void()> openSlave);
 
+    kj::Promise<Result<std::optional<WorkResult>>> handleRawChildStream() noexcept override;
+
     /**
      * Set up the system call filtering required for the sandbox.
      * This currently only has an effect on Linux.