diff --git a/changelog.d/11028-passthrough-subclass.md b/changelog.d/11028-passthrough-subclass.md
new file mode 100644
index 0000000000..1f39b18791
--- /dev/null
+++ b/changelog.d/11028-passthrough-subclass.md
@@ -0,0 +1,5 @@
+### Fixed
+
+- Honor `_transform` overrides on classes derived from `node:stream`'s
+  `PassThrough`, including aliased, dynamic, and indirect inheritance forms,
+  while preserving the default identity transform.
diff --git a/crates/perry-codegen/src/codegen/helpers.rs b/crates/perry-codegen/src/codegen/helpers.rs
index 584ba953f8..a1553d9dab 100644
--- a/crates/perry-codegen/src/codegen/helpers.rs
+++ b/crates/perry-codegen/src/codegen/helpers.rs
@@ -927,6 +927,7 @@ pub(super) fn node_stream_parent_kind(
             "Readable" => return Some("readable"),
             "Duplex" => return Some("duplex"),
             "Transform" => return Some("transform"),
+            "PassThrough" => return Some("passthrough"),
             _ => {}
         }
         cur = classes
diff --git a/crates/perry-codegen/src/codegen/method.rs b/crates/perry-codegen/src/codegen/method.rs
index 0e77806ec2..94665e9bbf 100644
--- a/crates/perry-codegen/src/codegen/method.rs
+++ b/crates/perry-codegen/src/codegen/method.rs
@@ -900,6 +900,7 @@ pub(super) fn compile_method(
                 Some("Writable") => Some("js_node_stream_writable_subclass_init"),
                 Some("Duplex") => Some("js_node_stream_duplex_subclass_init"),
                 Some("Transform") => Some("js_node_stream_transform_subclass_init"),
+                Some("PassThrough") => Some("js_node_stream_passthrough_subclass_init"),
                 _ => None,
             };
             let mut effective_parent: Option<&str> = if builtin_parent_runtime.is_some() {
@@ -936,7 +937,8 @@ pub(super) fn compile_method(
             // inline path for dynamic-parent classes.
             if let Some(pname) = effective_parent.filter(|_| dynamic_parent_owner.is_none()) {
                 let pname_owned = pname.to_string();
-                let node_stream_kind = if pname_owned == "Readable" {
+                let node_stream_kind = if matches!(pname_owned.as_str(), "Readable" | "PassThrough")
+                {
                     node_stream_parent_kind(ctx.classes, class)
                 } else {
                     None
@@ -958,6 +960,7 @@ pub(super) fn compile_method(
                         "readable" => "js_node_stream_readable_subclass_init",
                         "duplex" => "js_node_stream_duplex_subclass_init",
                         "transform" => "js_node_stream_transform_subclass_init",
+                        "passthrough" => "js_node_stream_passthrough_subclass_init",
                         _ => unreachable!("node stream parent kind {}", kind),
                     };
                     ctx.block().call(
diff --git a/crates/perry-codegen/src/expr/this_super_call.rs b/crates/perry-codegen/src/expr/this_super_call.rs
index f0d5af3d44..0c4d74d0d7 100644
--- a/crates/perry-codegen/src/expr/this_super_call.rs
+++ b/crates/perry-codegen/src/expr/this_super_call.rs
@@ -623,6 +623,7 @@ pub(crate) fn lower(ctx: &mut FnCtx<'_>, expr: &Expr) -> Result<String> {
                             | "Writable"
                             | "Duplex"
                             | "Transform"
+                            | "PassThrough"
                             | "ReadableStream"
                             | "WritableStream"
                             | "TransformStream"
@@ -785,6 +786,7 @@ pub(crate) fn lower(ctx: &mut FnCtx<'_>, expr: &Expr) -> Result<String> {
                         "Writable" => Some("writable"),
                         "Duplex" => Some("duplex"),
                         "Transform" => Some("transform"),
+                        "PassThrough" => Some("passthrough"),
                         _ => None,
                     };
                     if let Some(kind) = node_stream_kind {
@@ -851,6 +853,7 @@ pub(crate) fn lower(ctx: &mut FnCtx<'_>, expr: &Expr) -> Result<String> {
                         "Writable" => Some("writable"),
                         "Duplex" => Some("duplex"),
                         "Transform" => Some("transform"),
+                        "PassThrough" => Some("passthrough"),
                         _ => None,
                     };
                     if let Some(kind) = node_stream_kind {
diff --git a/crates/perry-codegen/src/expr/write_barrier.rs b/crates/perry-codegen/src/expr/write_barrier.rs
index a1b6c65c82..2036188faf 100644
--- a/crates/perry-codegen/src/expr/write_barrier.rs
+++ b/crates/perry-codegen/src/expr/write_barrier.rs
@@ -1202,6 +1202,7 @@ pub(crate) fn lower_node_stream_super_init(
         "writable" => "js_node_stream_writable_subclass_init",
         "duplex" => "js_node_stream_duplex_subclass_init",
         "transform" => "js_node_stream_transform_subclass_init",
+        "passthrough" => "js_node_stream_passthrough_subclass_init",
         _ => unreachable!(
             "lower_node_stream_super_init: unexpected Node stream kind {}",
             kind
diff --git a/crates/perry-codegen/src/lower_call/new.rs b/crates/perry-codegen/src/lower_call/new.rs
index ab8ed03fdf..2b641a2f1a 100644
--- a/crates/perry-codegen/src/lower_call/new.rs
+++ b/crates/perry-codegen/src/lower_call/new.rs
@@ -1092,6 +1092,7 @@ fn lower_new_impl_inner<'a>(
             Some("Writable") => Some("js_node_stream_writable_subclass_init"),
             Some("Duplex") => Some("js_node_stream_duplex_subclass_init"),
             Some("Transform") => Some("js_node_stream_transform_subclass_init"),
+            Some("PassThrough") => Some("js_node_stream_passthrough_subclass_init"),
             _ => None,
         }
     } else {
@@ -1390,6 +1391,7 @@ fn lower_new_impl_inner<'a>(
                     "readable" => "js_node_stream_readable_subclass_init",
                     "duplex" => "js_node_stream_duplex_subclass_init",
                     "transform" => "js_node_stream_transform_subclass_init",
+                    "passthrough" => "js_node_stream_passthrough_subclass_init",
                     _ => unreachable!("node stream parent kind {}", kind),
                 };
                 ctx.block().call(
diff --git a/crates/perry-codegen/src/lower_call/new_helpers.rs b/crates/perry-codegen/src/lower_call/new_helpers.rs
index 3ed72efe24..043124c67a 100644
--- a/crates/perry-codegen/src/lower_call/new_helpers.rs
+++ b/crates/perry-codegen/src/lower_call/new_helpers.rs
@@ -620,6 +620,7 @@ pub(super) fn node_stream_parent_kind(
             "Readable" => return Some("readable"),
             "Duplex" => return Some("duplex"),
             "Transform" => return Some("transform"),
+            "PassThrough" => return Some("passthrough"),
             _ => {}
         }
         if ctx.imported_class_ctors.contains_key(name) {
diff --git a/crates/perry-codegen/src/runtime_decls/stdlib_ffi/streams_events.rs b/crates/perry-codegen/src/runtime_decls/stdlib_ffi/streams_events.rs
index 9b7c51395c..bc4cfba3a0 100644
--- a/crates/perry-codegen/src/runtime_decls/stdlib_ffi/streams_events.rs
+++ b/crates/perry-codegen/src/runtime_decls/stdlib_ffi/streams_events.rs
@@ -47,6 +47,11 @@ pub(crate) fn declare_streams_events(module: &mut LlModule) {
         &[DOUBLE, DOUBLE],
     );
     module.declare_function("js_node_stream_passthrough_new", DOUBLE, &[DOUBLE]);
+    module.declare_function(
+        "js_node_stream_passthrough_subclass_init",
+        DOUBLE,
+        &[DOUBLE, DOUBLE],
+    );
     module.declare_function("js_node_stream_readable_from", DOUBLE, &[DOUBLE]);
     module.declare_function(
         "js_node_stream_readable_from_options",
diff --git a/crates/perry-hir/src/lower/tests.rs b/crates/perry-hir/src/lower/tests.rs
index 7ad4e18935..75adeb6b7b 100644
--- a/crates/perry-hir/src/lower/tests.rs
+++ b/crates/perry-hir/src/lower/tests.rs
@@ -1986,5 +1986,6 @@ mod subclass_ctor_inherited_method;
 mod ui_widget_add_child;
 
 mod issue_10623_require_destructured_native_super;
+mod issue_10745_passthrough_heritage;
 
 mod hoisted_sibling_in_later_closure;
diff --git a/crates/perry-hir/src/lower/tests/issue_10745_passthrough_heritage.rs b/crates/perry-hir/src/lower/tests/issue_10745_passthrough_heritage.rs
new file mode 100644
index 0000000000..ebf11535ed
--- /dev/null
+++ b/crates/perry-hir/src/lower/tests/issue_10745_passthrough_heritage.rs
@@ -0,0 +1,28 @@
+//! #10745: `PassThrough` is a classic `node:stream` native parent just like
+//! `Transform`. Both class-lowering paths must retain that identity so codegen
+//! can initialize the derived object in place and honor its `_transform`.
+
+#[test]
+fn passthrough_import_alias_is_a_native_parent_for_decls_and_expressions() {
+    let source = r#"
+        import { PassThrough as PT } from "node:stream";
+        class Decl extends PT { _transform(chunk, enc, cb) { cb(null, chunk); } }
+        const Expr = class extends PT { _transform(chunk, enc, cb) { cb(null, chunk); } };
+    "#;
+    let module = perry_parser::parse_typescript(source, "t.ts").expect("source parses");
+    let hir = super::lower_module(&module, "t", "t.ts").expect("source lowers");
+
+    for name in ["Decl", "Expr"] {
+        let class = hir
+            .classes
+            .iter()
+            .find(|class| class.name == name)
+            .unwrap_or_else(|| panic!("{name} is lowered"));
+        assert_eq!(class.extends_name.as_deref(), Some("PassThrough"));
+        assert_eq!(
+            class.native_extends,
+            Some(("node_stream".to_string(), "PassThrough".to_string()))
+        );
+        assert!(class.extends_expr.is_none());
+    }
+}
diff --git a/crates/perry-hir/src/lower_decl/class_decl.rs b/crates/perry-hir/src/lower_decl/class_decl.rs
index 56c34a7975..05de5e433c 100644
--- a/crates/perry-hir/src/lower_decl/class_decl.rs
+++ b/crates/perry-hir/src/lower_decl/class_decl.rs
@@ -12,7 +12,10 @@ use crate::lower_types::*;
 /// imports are registered under the local binding while preserving this export.
 fn canonical_native_parent_name<'a>(ctx: &'a LoweringContext, name: &str) -> Option<&'a str> {
     match ctx.lookup_native_module(name) {
-        Some(("stream", Some(class @ ("Readable" | "Writable" | "Duplex" | "Transform"))))
+        Some((
+            "stream",
+            Some(class @ ("Readable" | "Writable" | "Duplex" | "Transform" | "PassThrough")),
+        ))
         | Some(("events", Some(class @ ("EventEmitter" | "EventEmitterAsyncResource"))))
         | Some(("async_hooks", Some(class @ ("AsyncLocalStorage" | "AsyncResource"))))
         | Some(("ws", Some(class @ "WebSocketServer")))
@@ -30,10 +33,16 @@ fn canonical_native_parent_name<'a>(ctx: &'a LoweringContext, name: &str) -> Opt
 /// minified local binding such as `Readable as ut`.
 fn is_genuine_node_stream_parent(ctx: &LoweringContext, name: &str) -> bool {
     match ctx.lookup_native_module(name) {
-        Some(("stream", Some("Readable" | "Writable" | "Duplex" | "Transform"))) => true,
+        Some((
+            "stream",
+            Some("Readable" | "Writable" | "Duplex" | "Transform" | "PassThrough"),
+        )) => true,
         // Preserve the historical name-based treatment of a namespace/default
         // binding whose local name itself is a classic stream constructor.
-        Some(("stream", None)) => matches!(name, "Readable" | "Writable" | "Duplex" | "Transform"),
+        Some(("stream", None)) => matches!(
+            name,
+            "Readable" | "Writable" | "Duplex" | "Transform" | "PassThrough"
+        ),
         _ => false,
     }
 }
@@ -236,7 +245,7 @@ pub fn lower_class_decl(
                 // so a userland stream-shim binding (readable-stream's
                 // `Transform`, winston) falls through to the dynamic
                 // `extends_expr` parent path and runs its real constructor.
-                "Readable" | "Writable" | "Duplex" | "Transform"
+                "Readable" | "Writable" | "Duplex" | "Transform" | "PassThrough"
                     if is_genuine_node_stream_parent(ctx, &parent_name) =>
                 {
                     Some(("node_stream".to_string(), canonical_parent_name.clone()))
diff --git a/crates/perry-hir/src/lower_decl/class_decl/from_ast.rs b/crates/perry-hir/src/lower_decl/class_decl/from_ast.rs
index cf9f617a4b..6b3c554583 100644
--- a/crates/perry-hir/src/lower_decl/class_decl/from_ast.rs
+++ b/crates/perry-hir/src/lower_decl/class_decl/from_ast.rs
@@ -117,7 +117,7 @@ pub(crate) fn lower_class_from_ast(
                 // `is_genuine_node_stream_parent` so a userland stream-shim
                 // binding (readable-stream's `Transform`) falls through to the
                 // dynamic `extends_expr` parent path.
-                "Readable" | "Writable" | "Duplex" | "Transform"
+                "Readable" | "Writable" | "Duplex" | "Transform" | "PassThrough"
                     if is_genuine_node_stream_parent(ctx, &parent_name) =>
                 {
                     Some(("node_stream".to_string(), canonical_parent_name.clone()))
diff --git a/crates/perry-runtime/src/node_stream_constructors.rs b/crates/perry-runtime/src/node_stream_constructors.rs
index 1dae81e4f5..50bf98b33a 100644
--- a/crates/perry-runtime/src/node_stream_constructors.rs
+++ b/crates/perry-runtime/src/node_stream_constructors.rs
@@ -363,10 +363,11 @@ pub use builders::{
     js_array_subclass_init, js_event_emitter_async_resource_subclass_init,
     js_event_emitter_subclass_init, js_node_stream_duplex_new, js_node_stream_duplex_subclass_init,
     js_node_stream_legacy_subclass_init, js_node_stream_passthrough_new,
-    js_node_stream_readable_from, js_node_stream_readable_from_options,
-    js_node_stream_readable_new, js_node_stream_readable_subclass_init,
-    js_node_stream_transform_new, js_node_stream_transform_subclass_init,
-    js_node_stream_writable_new, js_node_stream_writable_subclass_init,
+    js_node_stream_passthrough_subclass_init, js_node_stream_readable_from,
+    js_node_stream_readable_from_options, js_node_stream_readable_new,
+    js_node_stream_readable_subclass_init, js_node_stream_transform_new,
+    js_node_stream_transform_subclass_init, js_node_stream_writable_new,
+    js_node_stream_writable_subclass_init,
 };
 
 pub use introspection::{
diff --git a/crates/perry-runtime/src/node_stream_constructors/builders.rs b/crates/perry-runtime/src/node_stream_constructors/builders.rs
index 0f9a5bff6a..5f2cbc7a08 100644
--- a/crates/perry-runtime/src/node_stream_constructors/builders.rs
+++ b/crates/perry-runtime/src/node_stream_constructors/builders.rs
@@ -566,6 +566,24 @@ pub extern "C" fn js_node_stream_passthrough_new(opts: f64) -> f64 {
     passthrough
 }
 
+/// Initialize `class X extends PassThrough` without replacing the derived
+/// instance. A subclass-provided `_transform` wins; otherwise retain
+/// PassThrough's identity transform instead of falling into Transform's
+/// missing-method error.
+#[no_mangle]
+pub extern "C" fn js_node_stream_passthrough_subclass_init(this: f64, opts: f64) -> f64 {
+    let passthrough = js_node_stream_transform_subclass_init(this, opts);
+    if transform_hidden_callback(passthrough).is_none() {
+        set_hidden_value(
+            passthrough,
+            hidden_transform_passthrough_key(),
+            f64::from_bits(TAG_TRUE),
+        );
+    }
+    init_constructor(passthrough, "PassThrough");
+    passthrough
+}
+
 /// `Readable.from(iterable)` — Node's static factory. Returns a
 /// Readable object and retains simple iterable chunks so
 /// `node:stream/consumers` can drain the current stub stream surface.
diff --git a/crates/perry-runtime/src/node_stream_keepalive.rs b/crates/perry-runtime/src/node_stream_keepalive.rs
index 9c1654d74f..b168bc121e 100644
--- a/crates/perry-runtime/src/node_stream_keepalive.rs
+++ b/crates/perry-runtime/src/node_stream_keepalive.rs
@@ -196,6 +196,10 @@ static KEEP_NS_TRANSFORM_NEW: extern "C" fn(f64) -> f64 = super::js_node_stream_
 static KEEP_NS_PASSTHROUGH_NEW: extern "C" fn(f64) -> f64 = super::js_node_stream_passthrough_new;
 #[cfg(feature = "keepalive-anchors")]
 #[used(compiler)]
+static KEEP_NS_PASSTHROUGH_SUBCLASS_INIT: extern "C" fn(f64, f64) -> f64 =
+    super::js_node_stream_passthrough_subclass_init;
+#[cfg(feature = "keepalive-anchors")]
+#[used(compiler)]
 static KEEP_NS_READABLE_FROM: extern "C" fn(f64) -> f64 = super::js_node_stream_readable_from;
 #[cfg(feature = "keepalive-anchors")]
 #[used(compiler)]
diff --git a/crates/perry-runtime/src/node_stream_state_tests.rs b/crates/perry-runtime/src/node_stream_state_tests.rs
index 4cc4fb0547..1e61ec2241 100644
--- a/crates/perry-runtime/src/node_stream_state_tests.rs
+++ b/crates/perry-runtime/src/node_stream_state_tests.rs
@@ -116,6 +116,39 @@ fn stream_object_mode_flags_default_false_and_follow_options() {
     );
 }
 
+#[test]
+fn passthrough_subclass_uses_override_or_identity_transform() {
+    crate::closure::js_register_closure_arity(super::tests::noop_listener as *const u8, 0);
+    let callback =
+        box_pointer(js_closure_alloc(super::tests::noop_listener as *const u8, 0) as *const u8);
+
+    let overridden_obj = crate::object::js_object_alloc(0, 1);
+    js_object_set_field_by_name(overridden_obj, hidden_key(b"_transform"), callback);
+    let overridden = js_node_stream_passthrough_subclass_init(
+        box_pointer(overridden_obj as *const u8),
+        f64::from_bits(TAG_UNDEFINED),
+    );
+    assert_eq!(
+        transform_hidden_callback(overridden).map(f64::to_bits),
+        Some(callback.to_bits())
+    );
+    assert!(!has_truthy_hidden(
+        overridden,
+        hidden_transform_passthrough_key()
+    ));
+
+    let default_obj = crate::object::js_object_alloc(0, 0);
+    let default = js_node_stream_passthrough_subclass_init(
+        box_pointer(default_obj as *const u8),
+        f64::from_bits(TAG_UNDEFINED),
+    );
+    assert!(transform_hidden_callback(default).is_none());
+    assert!(has_truthy_hidden(
+        default,
+        hidden_transform_passthrough_key()
+    ));
+}
+
 #[test]
 fn stream_dynamic_instanceof_follows_node_stream_inheritance() {
     let readable = crate::object::bound_native_callable_export_value("stream", "Readable");
diff --git a/crates/perry-runtime/src/object/global_this/fetch_globals.rs b/crates/perry-runtime/src/object/global_this/fetch_globals.rs
index 745c2b8d87..7ae27ab868 100644
--- a/crates/perry-runtime/src/object/global_this/fetch_globals.rs
+++ b/crates/perry-runtime/src/object/global_this/fetch_globals.rs
@@ -790,14 +790,6 @@ pub unsafe extern "C" fn js_fetch_or_value_super(
     // `lower_node_stream_super_init`), so every heritage shape installs the
     // override onto `this` identically.
     //
-    // `PassThrough` is deliberately NOT handled here: HIR never recognizes
-    // it as a node:stream native parent at all, even via a bare import
-    // (`canonical_native_parent_name` lists Readable/Writable/Duplex/
-    // Transform but not PassThrough), so the hidden `_transform` field this
-    // shim reads is never pre-seeded for ANY `PassThrough` heritage shape —
-    // that's a separate, deeper HIR-level gap needing its own fix; adding an
-    // arm here alone was confirmed (empirically) to change nothing.
-    //
     // #10798: `Stream` (the legacy `node:stream` base that `Readable` and
     // friends themselves derive from) is a DIFFERENT shape than
     // `PassThrough`: it carries no hidden per-instance state at all — in
@@ -840,6 +832,9 @@ pub unsafe extern "C" fn js_fetch_or_value_super(
                 "Transform" => Some(crate::node_stream::js_node_stream_transform_subclass_init(
                     this_box, opts,
                 )),
+                "PassThrough" => Some(
+                    crate::node_stream::js_node_stream_passthrough_subclass_init(this_box, opts),
+                ),
                 "Stream" => Some(crate::node_stream::js_node_stream_legacy_subclass_init(
                     this_box,
                 )),
diff --git a/test-files/test_gap_10745_passthrough_subclass.ts b/test-files/test_gap_10745_passthrough_subclass.ts
new file mode 100644
index 0000000000..d4d645338b
--- /dev/null
+++ b/test-files/test_gap_10745_passthrough_subclass.ts
@@ -0,0 +1,54 @@
+import { PassThrough, PassThrough as PT } from "node:stream";
+
+class Direct extends PassThrough {
+  _transform(chunk: any, _encoding: string, callback: any) {
+    callback(null, "direct:" + String(chunk).toUpperCase());
+  }
+}
+
+class ImportedAlias extends PT {
+  _transform(chunk: any, _encoding: string, callback: any) {
+    callback(null, "import-alias:" + String(chunk).toUpperCase());
+  }
+}
+
+const LocalAlias = PassThrough;
+const ClassExpression = class extends LocalAlias {
+  _transform(chunk: any, _encoding: string, callback: any) {
+    callback(null, "class-expr:" + String(chunk).toUpperCase());
+  }
+};
+
+class Middle extends PassThrough {}
+class Indirect extends Middle {
+  _transform(chunk: any, _encoding: string, callback: any) {
+    callback(null, "indirect:" + String(chunk).toUpperCase());
+  }
+}
+
+class DefaultPassThrough extends PassThrough {}
+
+function run(name: string, Constructor: any): Promise<void> {
+  return new Promise((resolve) => {
+    const stream = new Constructor();
+    let output = "";
+    stream.on("data", (chunk: any) => (output += String(chunk)));
+    stream.on("error", (error: any) => {
+      console.log(name, "error", error.code || error.message);
+      resolve();
+    });
+    stream.on("end", () => {
+      console.log(name, JSON.stringify(output));
+      resolve();
+    });
+    stream.end("ab");
+  });
+}
+
+(async () => {
+  await run("direct", Direct);
+  await run("import-alias", ImportedAlias);
+  await run("class-expr", ClassExpression);
+  await run("indirect", Indirect);
+  await run("default", DefaultPassThrough);
+})();