diff --git a/src/workerd/api/container.c++ b/src/workerd/api/container.c++
index 394fdc6cfe0..b47206e390a 100644
--- a/src/workerd/api/container.c++
+++ b/src/workerd/api/container.c++
@@ -760,7 +760,9 @@ class Container::TcpPortOutgoingFactory final: public Fetcher::OutgoingFactory {
 
   kj::Own<WorkerInterface> newSingleUseClient(kj::Maybe<kj::String> cfStr) override {
     // At present we have no use for `cfStr`.
-    return kj::heap<TcpPortWorkerInterface>(byteStreamFactory, entropySource, headerTable, port);
+    return IoContext::current().getSubrequestNoChecks([&](auto& tracing, auto& channelFactory) {
+      return kj::heap<TcpPortWorkerInterface>(byteStreamFactory, entropySource, headerTable, port);
+    }, {.inHouse = false, .wrapMetrics = false});
   }
 
  private:
diff --git a/src/workerd/api/http.c++ b/src/workerd/api/http.c++
index ffb9ac613bd..71e1a4dfe3e 100644
--- a/src/workerd/api/http.c++
+++ b/src/workerd/api/http.c++
@@ -2434,12 +2434,15 @@ Fetcher::ClientWithTracing Fetcher::getClientWithTracing(
       return ClientWithTracing{kj::mv(client), kj::mv(traceContext)};
     }
     KJ_CASE_ONEOF(outgoingFactory, IoOwn<OutgoingFactory>) {
-      // For outgoing factories, no trace context needed
+      // Outgoing factories are responsible for routing through getSubrequestNoChecks() (or
+      // getSubrequest()) internally if they create HTTP connections, to ensure external memory
+      // adjustment and other subrequest accounting are applied.
       auto client = outgoingFactory->newSingleUseClient(kj::mv(cfStr));
       return ClientWithTracing{kj::mv(client), kj::none};
     }
     KJ_CASE_ONEOF(outgoingFactory, kj::Own<CrossContextOutgoingFactory>) {
-      // For cross-context outgoing factories, no trace context needed
+      // Same as OutgoingFactory above -- the factory is responsible for routing through
+      // getSubrequestNoChecks() internally.
       auto client = outgoingFactory->newSingleUseClient(ioContext, kj::mv(cfStr));
       return ClientWithTracing{kj::mv(client), kj::none};
     }
diff --git a/src/workerd/api/http.h b/src/workerd/api/http.h
index efbdb670349..df9f1a4c4f9 100644
--- a/src/workerd/api/http.h
+++ b/src/workerd/api/http.h
@@ -280,6 +280,10 @@ class Fetcher: public JsRpcClientProvider {
   // Used by Fetchers that use ad-hoc, single-use WorkerInterface instances, such as ones
   // created for Actors.
   //
+  // Implementations that create HTTP connections should route through
+  // IoContext::getSubrequestNoChecks() (or getSubrequest()) internally, to ensure external memory
+  // adjustment and other subrequest accounting are applied.
+  //
   // TODO(cleanup): Consider removing this in favor of `IoChannelFactory::SubrequestChannel`, which
   //   is almost the same thing.
   class OutgoingFactory {
@@ -297,6 +301,9 @@ class Fetcher: public JsRpcClientProvider {
   // Used by Fetchers that obtain their HttpClient in a custom way, but which aren't tied
   // to a specific I/O context. The factory object moves with the isolate across threads and
   // contexts, and must work from any context.
+  //
+  // Same as OutgoingFactory: implementations that create HTTP connections should route through
+  // IoContext::getSubrequestNoChecks() internally.
   class CrossContextOutgoingFactory {
    public:
     virtual kj::Own<WorkerInterface> newSingleUseClient(
diff --git a/src/workerd/api/sockets.c++ b/src/workerd/api/sockets.c++
index ebfcd6b4ccb..985fd6cc794 100644
--- a/src/workerd/api/sockets.c++
+++ b/src/workerd/api/sockets.c++
@@ -8,6 +8,7 @@
 #include "streams/standard.h"
 #include "system-streams.h"
 
+#include <workerd/io/io-context.h>
 #include <workerd/io/worker-interface.h>
 #include <workerd/jsg/exception.h>
 #include <workerd/jsg/url.h>
@@ -636,8 +637,11 @@ class StreamWorkerInterface final: public WorkerInterface {
 kj::Own<WorkerInterface> StreamOutgoingFactory::newSingleUseClient(kj::Maybe<kj::String> cfStr) {
   JSG_ASSERT(stream.get() != nullptr, Error,
       "Fetcher created from internalNewHttpClient can only be used once");
-  // Create a WorkerInterface that wraps the stream
-  return kj::heap<StreamWorkerInterface>(kj::addRef(*this));
+  // Create a WorkerInterface that wraps the stream, routing through getSubrequestNoChecks to apply
+  // external memory adjustment for GC pressure.
+  return IoContext::current().getSubrequestNoChecks([&](auto& tracing, auto& channelFactory) {
+    return kj::heap<StreamWorkerInterface>(kj::addRef(*this));
+  }, {.inHouse = false, .wrapMetrics = false});
 }
 
 jsg::Promise<jsg::Ref<Fetcher>> SocketsModule::internalNewHttpClient(
diff --git a/src/workerd/io/io-context.h b/src/workerd/io/io-context.h
index 25a18596c38..38756f59d30 100644
--- a/src/workerd/io/io-context.h
+++ b/src/workerd/io/io-context.h
@@ -758,6 +758,10 @@ class IoContext final: public kj::Refcounted, private kj::TaskSet::ErrorHandler
     kj::Maybe<TraceContext&> existingTraceContext;
   };
 
+  // Wraps a WorkerInterface factory with subrequest accounting: tracing, optional metrics wrapping,
+  // and an external memory adjustment to pressure V8's GC. All code paths that create HTTP
+  // connections (including those built from capnp capabilities via getHttpOverCapnpFactory())
+  // should route through this function or getSubrequest().
   kj::Own<WorkerInterface> getSubrequestNoChecks(
       kj::FunctionParam<kj::Own<WorkerInterface>(TraceContext&, IoChannelFactory&)> func,
       SubrequestOptions options);
@@ -834,6 +838,11 @@ class IoContext final: public kj::Refcounted, private kj::TaskSet::ErrorHandler
   // TODO(cleanup): Make it the caller's job to call asHttpClient() on the result of
   //   getSubrequest*().
 
+  // Get a raw Cap'n Proto capability for the given channel. This is appropriate for pure RPC use
+  // cases (e.g. actor operations, email dispatch) that don't create HTTP connections. If you're
+  // converting the capability to an HTTP service via getHttpOverCapnpFactory(), use
+  // getSubrequestNoChecks() instead and call channelFactory.getCapability() from the callback,
+  // so that the external memory adjustment and other subrequest accounting are applied.
   capnp::Capability::Client getCapnpChannel(uint channel) {
     return getIoChannelFactory().getCapability(channel);
   }