From a2af3593b1116e904ffcd2447a968c9b089c92c9 Mon Sep 17 00:00:00 2001
From: Archmonger <16909269+Archmonger@users.noreply.github.com>
Date: Sat, 27 Jun 2026 16:48:40 -0700
Subject: [PATCH 1/5] misc hanging changes

---
 CHANGELOG.md                      |  2 +-
 src/build_scripts/install_deps.py | 44 +++++++++++++++++++++++++++++++
 tests/test_core/test_events.py    |  6 ++---
 3 files changed, 47 insertions(+), 5 deletions(-)
 create mode 100644 src/build_scripts/install_deps.py

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 09b81c68f..86dff1b89 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -60,7 +60,7 @@ Don't forget to remove deprecated code on each major release!
 - `reactpy.core.vdom._CustomVdomDictConstructor` has been moved to `reactpy.types.CustomVdomConstructor`.
 - `reactpy.core.vdom._EllipsisRepr` has been moved to `reactpy.types.EllipsisRepr`.
 - `reactpy.types.VdomDictConstructor` has been renamed to `reactpy.types.VdomConstructor`.
-- `REACTPY_ASYNC_RENDERING` can now de-duplicate and cascade renders where necessary.
+- `REACTPY_ASYNC_RENDERING` can now de-duplicate renders where necessary.
 - `REACTPY_ASYNC_RENDERING` is now defaulted to `True` for up to 40x performance improvements in environments with high concurrency.
 - Events now support debounce, which can now be configured per event with `event.debounce = <milliseconds>`. Note that `input`, `select`, and `textarea` elements default to 200ms debounce.
 
diff --git a/src/build_scripts/install_deps.py b/src/build_scripts/install_deps.py
new file mode 100644
index 000000000..48481d93f
--- /dev/null
+++ b/src/build_scripts/install_deps.py
@@ -0,0 +1,44 @@
+"""
+Development/debug script to parse pyproject.toml to find dependecies then install them in the local
+environment via `uv pip install -U <pkg_names>`
+"""
+
+import subprocess
+import tomllib as toml
+from pathlib import Path
+
+DEPENDENCIES = set()
+
+
+def find_deps(data):
+    """Recurse through all categories and find any list with `dependencies` in the name, then combine
+    all dependencies into a single list"""
+    if isinstance(data, dict):
+        for key, value in data.items():
+            if (
+                "dependencies" in key
+                and isinstance(value, list)
+                and value
+                and isinstance(value[0], str)
+            ):
+                DEPENDENCIES.update(value)
+            else:
+                find_deps(value)
+    elif isinstance(data, list):
+        for item in data:
+            find_deps(item)
+
+
+def install_deps():
+    pyproject_path = Path(__file__).parent.parent / "pyproject.toml"
+    with open(pyproject_path, "rb") as f:
+        pyproject_data = toml.load(f)
+    find_deps(pyproject_data)
+    DEPENDENCIES.discard(
+        "ruff"
+    )  # ruff only exists in dev dependencies for CI purposes.
+    subprocess.run(["uv", "pip", "install", "-U", *DEPENDENCIES], check=False)  # noqa: S607
+
+
+if __name__ == "__main__":
+    install_deps()
diff --git a/tests/test_core/test_events.py b/tests/test_core/test_events.py
index 71744d64b..4f96120f3 100644
--- a/tests/test_core/test_events.py
+++ b/tests/test_core/test_events.py
@@ -646,12 +646,10 @@ async def add_top(event):
     assert clicked_items == ["B"]
 
 
-async def test_controlled_input_typing(display: DisplayFixture):
+async def test_controlled_input_rapid_typing(display: DisplayFixture):
     """
     Test that a controlled input updates correctly even with rapid typing.
-    This validates that user inputs are processed in the correct order and that the
-    event queueing/processing order is consistent with user expectations, even if the
-    server is still processing previous events.
+    This validates that user inputs are properly debounced by the client.
     """
 
     @reactpy.component

From ffce7b9a93c2233ce98aaaede02e661a4374ec5e Mon Sep 17 00:00:00 2001
From: Archmonger <16909269+Archmonger@users.noreply.github.com>
Date: Sun, 28 Jun 2026 00:37:21 -0700
Subject: [PATCH 2/5] debounce refactoring and add throttle

---
 .../@reactpy/client/src/components.tsx        | 137 +++++++++-
 .../packages/@reactpy/client/src/handler.ts   |  56 ++++
 src/js/packages/@reactpy/client/src/index.ts  |   1 +
 src/js/packages/@reactpy/client/src/types.ts  |   1 +
 src/js/packages/@reactpy/client/src/vdom.tsx  |  59 +++--
 src/reactpy/core/_event_inspect.py            | 246 ++++++++++++++++++
 src/reactpy/core/events.py                    |  92 +++----
 src/reactpy/core/layout.py                    |  42 +--
 src/reactpy/core/vdom.py                      |   1 +
 src/reactpy/types.py                          |  33 ++-
 tests/test_core/test_events.py                | 148 ++++++++++-
 tests/test_core/test_layout.py                |  80 ++++++
 12 files changed, 771 insertions(+), 125 deletions(-)
 create mode 100644 src/js/packages/@reactpy/client/src/handler.ts
 create mode 100644 src/reactpy/core/_event_inspect.py

diff --git a/src/js/packages/@reactpy/client/src/components.tsx b/src/js/packages/@reactpy/client/src/components.tsx
index 2ce16d5fa..e51828574 100644
--- a/src/js/packages/@reactpy/client/src/components.tsx
+++ b/src/js/packages/@reactpy/client/src/components.tsx
@@ -8,6 +8,14 @@ import {
   type TargetedEvent,
 } from "preact";
 import { useContext, useEffect, useRef, useState } from "preact/hooks";
+import {
+  HANDLER_DEBOUNCE,
+  HANDLER_MARKER,
+  HANDLER_THROTTLE,
+  getInitialDebounce,
+  isValidDebounce,
+  type TaggedEventHandler,
+} from "./handler";
 import type {
   ImportSourceBinding,
   ReactPyComponent,
@@ -18,12 +26,25 @@ import type { ReactPyClient } from "./client";
 
 const ClientContext = createContext<ReactPyClient>(null as any);
 
-const DEFAULT_INPUT_DEBOUNCE = 200;
-
-type ReactPyInputHandler = ((event: TargetedEvent<any>) => void) & {
-  debounce?: number;
-  isHandler?: boolean;
-};
+// Built-in default debounce (ms) used by user-input elements (``<input>``,
+// ``<select>``, ``<textarea>``) when no per-handler ``debounce`` is set.
+// Non-input elements default to 0 ms (no debounce) — set ``debounce`` or
+// ``throttle`` explicitly on the handler if you need either behavior.
+const DEFAULT_INPUT_DEBOUNCE_MS = 200;
+const DEFAULT_NON_INPUT_DEBOUNCE_MS = 0;
+
+const USER_INPUT_TAGS = new Set(["input", "select", "textarea"]);
+
+/**
+ * Return the built-in default debounce (ms) for an element type.
+ * Inputs default to 200 ms to preserve text-input coherency against
+ * server-driven ``value`` updates; all other elements default to 0 ms.
+ */
+export function getDefaultDebounceMs(tagName: string): number {
+  return USER_INPUT_TAGS.has(tagName)
+    ? DEFAULT_INPUT_DEBOUNCE_MS
+    : DEFAULT_NON_INPUT_DEBOUNCE_MS;
+}
 
 type UserInputTarget =
   | HTMLInputElement
@@ -49,6 +70,64 @@ function trackUserInput(
   lastInputDebounce.current = debounce;
 }
 
+/**
+ * Wrap ``handler`` so its outgoing call is throttled to at most once per
+ * ``intervalMs`` milliseconds. Subsequent calls inside the window are
+ * collapsed and the trailing call (with the most recent arguments) fires
+ * once the window expires.
+ *
+ * Returns the original handler unchanged when ``intervalMs`` is missing or
+ * invalid.
+ */
+function throttleHandler(
+  handler: TaggedEventHandler,
+  intervalMs: number,
+): TaggedEventHandler {
+  if (!isValidDebounce(intervalMs)) {
+    return handler;
+  }
+  let pendingArgs: any[] | null = null;
+  let timer: number | null = null;
+  let lastFireTime = 0;
+
+  const wrapped = function (...args: any[]) {
+    const now = Date.now();
+    const elapsed = now - lastFireTime;
+    if (elapsed >= intervalMs) {
+      // Leading edge: fire immediately, then start a cooldown.
+      lastFireTime = now;
+      (handler as (...a: any[]) => void)(...args);
+      return;
+    }
+    // Trailing edge: remember the latest args and schedule a fire at the
+    // end of the cooldown so no event is silently dropped.
+    pendingArgs = args;
+    if (timer === null) {
+      timer = window.setTimeout(
+        () => {
+          timer = null;
+          if (pendingArgs !== null) {
+            const callArgs = pendingArgs;
+            pendingArgs = null;
+            lastFireTime = Date.now();
+            (handler as (...a: any[]) => void)(...callArgs);
+          }
+        },
+        Math.max(0, intervalMs - elapsed),
+      );
+    }
+  } as TaggedEventHandler;
+
+  // Preserve the tag markers so downstream code can still introspect the
+  // wrapped function.
+  wrapped[HANDLER_MARKER] = true;
+  const debounce = handler[HANDLER_DEBOUNCE];
+  if (typeof debounce === "number") {
+    wrapped[HANDLER_DEBOUNCE] = debounce;
+  }
+  return wrapped;
+}
+
 export function Layout(props: { client: ReactPyClient }): JSX.Element {
   const currentModel: ReactPyVdom = useState({ tagName: "" })[0];
   const forceUpdate = useForceUpdate();
@@ -97,12 +176,29 @@ export function Element({ model }: { model: ReactPyVdom }): JSX.Element | null {
 
 function StandardElement({ model }: { model: ReactPyVdom }) {
   const client = useContext(ClientContext);
+  const attrs = createAttributes(model, client);
+  // Apply the throttle wrapper to tagged handlers. ``debounce`` (server-→
+  // client value reconciliation) only applies to user-input elements, so
+  // it's intentionally ignored here; ``throttle`` works everywhere.
+  for (const [name, prop] of Object.entries(attrs)) {
+    if (typeof prop !== "function") {
+      continue;
+    }
+    const handler = prop as TaggedEventHandler;
+    if (!handler[HANDLER_MARKER]) {
+      continue;
+    }
+    const throttle = handler[HANDLER_THROTTLE];
+    if (isValidDebounce(throttle)) {
+      attrs[name] = throttleHandler(handler, throttle as number);
+    }
+  }
   // Use createElement here to avoid warning about variable numbers of children not
   // having keys. Warning about this must now be the responsibility of the client
   // providing the models instead of the client rendering them.
   return createElement(
     model.tagName === "" ? Fragment : model.tagName,
-    createAttributes(model, client),
+    attrs,
     ...createChildren(model, (child) => {
       return <Element model={child} key={child.attributes?.key} />;
     }),
@@ -115,7 +211,13 @@ function UserInputElement({ model }: { model: ReactPyVdom }): JSX.Element {
   const [value, setValue] = useState(props.value);
   const lastUserValue = useRef(props.value);
   const lastChangeTime = useRef(0);
-  const lastInputDebounce = useRef(DEFAULT_INPUT_DEBOUNCE);
+  // Seed the debounce window from the handlers themselves when possible,
+  // otherwise fall back to the per-tagName built-in default (200 ms for
+  // user-input tags, 0 ms elsewhere). This ensures the very first
+  // server-driven update already respects the configured debounce.
+  const lastInputDebounce = useRef(
+    getInitialDebounce(props, getDefaultDebounceMs(model.tagName)),
+  );
   const reconcileTimeout = useRef<number | null>(null);
 
   // honor changes to value from the client via props
@@ -154,11 +256,20 @@ function UserInputElement({ model }: { model: ReactPyVdom }): JSX.Element {
       continue;
     }
 
-    const givenHandler = prop as ReactPyInputHandler;
-    if (!givenHandler.isHandler) {
+    const givenHandler = prop as TaggedEventHandler;
+    if (!givenHandler[HANDLER_MARKER]) {
       continue;
     }
 
+    const handlerDebounce = givenHandler[HANDLER_DEBOUNCE];
+    const effectiveDebounce = isValidDebounce(handlerDebounce)
+      ? handlerDebounce
+      : getDefaultDebounceMs(model.tagName);
+
+    const throttled = isValidDebounce(givenHandler[HANDLER_THROTTLE])
+      ? throttleHandler(givenHandler, givenHandler[HANDLER_THROTTLE] as number)
+      : givenHandler;
+
     props[name] = (event: TargetedEvent<any>) => {
       trackUserInput(
         event,
@@ -166,11 +277,9 @@ function UserInputElement({ model }: { model: ReactPyVdom }): JSX.Element {
         lastUserValue,
         lastChangeTime,
         lastInputDebounce,
-        typeof givenHandler.debounce === "number"
-          ? givenHandler.debounce
-          : DEFAULT_INPUT_DEBOUNCE,
+        effectiveDebounce,
       );
-      givenHandler(event);
+      throttled(event);
     };
   }
 
diff --git a/src/js/packages/@reactpy/client/src/handler.ts b/src/js/packages/@reactpy/client/src/handler.ts
new file mode 100644
index 000000000..99aed8304
--- /dev/null
+++ b/src/js/packages/@reactpy/client/src/handler.ts
@@ -0,0 +1,56 @@
+// Shared marker property names attached to event handler functions created by
+// `vdom.tsx::createEventHandler`. Centralizing these strings keeps `components.tsx`
+// and `vdom.tsx` in sync without relying on ad-hoc property names.
+
+export const HANDLER_MARKER = "isHandler" as const;
+export const HANDLER_DEBOUNCE = "debounce" as const;
+export const HANDLER_THROTTLE = "throttle" as const;
+
+export type HandlerMarker = typeof HANDLER_MARKER;
+export type HandlerDebounce = typeof HANDLER_DEBOUNCE;
+export type HandlerThrottle = typeof HANDLER_THROTTLE;
+
+export type TaggedEventHandler = ((event: Event) => void) & {
+  [HANDLER_MARKER]: true;
+  [HANDLER_DEBOUNCE]?: number;
+  [HANDLER_THROTTLE]?: number;
+};
+
+/**
+ * Returns the debounce value (in milliseconds) to use as the default for a user
+ * input element when no user input has been recorded yet. Uses the maximum
+ * debounce among the element's tagged handlers, falling back to the global
+ * default if none of the handlers specify one.
+ */
+export function getInitialDebounce(
+  props: Record<string, unknown>,
+  fallback: number,
+): number {
+  let max = 0;
+  for (const value of Object.values(props)) {
+    if (typeof value !== "function") {
+      continue;
+    }
+    const candidate = (value as TaggedEventHandler)[HANDLER_DEBOUNCE];
+    if (typeof candidate === "number" && candidate > max) {
+      max = candidate;
+    }
+  }
+  return max > 0 ? max : fallback;
+}
+
+/**
+ * Returns true when the given value is a finite, non-negative integer.
+ * Used to validate debounce/throttle values arriving over the wire from the
+ * Python layout.
+ */
+export function isValidDebounce(value: unknown): value is number {
+  return (
+    typeof value === "number" &&
+    Number.isFinite(value) &&
+    Number.isInteger(value) &&
+    value >= 0
+  );
+}
+
+export const isValidThrottle = isValidDebounce;
diff --git a/src/js/packages/@reactpy/client/src/index.ts b/src/js/packages/@reactpy/client/src/index.ts
index cca51fc00..d647de735 100644
--- a/src/js/packages/@reactpy/client/src/index.ts
+++ b/src/js/packages/@reactpy/client/src/index.ts
@@ -1,5 +1,6 @@
 export * from "./client";
 export * from "./components";
+export * from "./handler";
 export * from "./mount";
 export * from "./types";
 export * from "./vdom";
diff --git a/src/js/packages/@reactpy/client/src/types.ts b/src/js/packages/@reactpy/client/src/types.ts
index 209d063d1..6d5fe882f 100644
--- a/src/js/packages/@reactpy/client/src/types.ts
+++ b/src/js/packages/@reactpy/client/src/types.ts
@@ -61,6 +61,7 @@ export type ReactPyVdomEventHandler = {
   preventDefault?: boolean;
   stopPropagation?: boolean;
   debounce?: number;
+  throttle?: number;
 };
 
 export type ReactPyVdomImportSource = {
diff --git a/src/js/packages/@reactpy/client/src/vdom.tsx b/src/js/packages/@reactpy/client/src/vdom.tsx
index b2d197e01..35c1ed23e 100644
--- a/src/js/packages/@reactpy/client/src/vdom.tsx
+++ b/src/js/packages/@reactpy/client/src/vdom.tsx
@@ -1,17 +1,25 @@
 import eventToObject from "event-to-object";
 import { Fragment } from "preact";
+import {
+  HANDLER_DEBOUNCE,
+  HANDLER_MARKER,
+  HANDLER_THROTTLE,
+  isValidDebounce,
+  isValidThrottle,
+  type TaggedEventHandler,
+} from "./handler";
+import { infer_bind_from_environment } from "./bind";
+import log from "./logger";
+import type { ReactPyClient } from "./client";
 import type {
-  ReactPyVdom,
-  ReactPyVdomImportSource,
-  ReactPyVdomEventHandler,
-  ReactPyModule,
   BindImportSource,
-  ReactPyModuleBinding,
   ImportSourceBinding,
+  ReactPyModule,
+  ReactPyModuleBinding,
+  ReactPyVdom,
+  ReactPyVdomEventHandler,
+  ReactPyVdomImportSource,
 } from "./types";
-import { infer_bind_from_environment } from "./bind";
-import log from "./logger";
-import type { ReactPyClient } from "./client";
 
 export async function loadImportSource(
   vdomImportSource: ReactPyVdomImportSource,
@@ -211,8 +219,9 @@ function createEventHandler(
     preventDefault,
     stopPropagation,
     debounce,
+    throttle,
   }: ReactPyVdomEventHandler,
-): [string, () => void] {
+): [string, TaggedEventHandler] {
   const eventHandler = function (...args: any[]) {
     const data = Array.from(args).map((value) => {
       const event = value as Event;
@@ -231,19 +240,27 @@ function createEventHandler(
       }
     });
     client.sendMessage({ type: "layout-event", data, target });
-  };
-  (
-    eventHandler as typeof eventHandler & {
-      debounce?: number;
-      isHandler: boolean;
+  } as TaggedEventHandler;
+  eventHandler[HANDLER_MARKER] = true;
+  if (debounce !== undefined) {
+    if (!isValidDebounce(debounce)) {
+      log.warn(
+        `Ignoring invalid debounce value ${JSON.stringify(debounce)} ` +
+          `on event handler "${name}": expected a non-negative integer.`,
+      );
+    } else {
+      eventHandler[HANDLER_DEBOUNCE] = debounce;
+    }
+  }
+  if (throttle !== undefined) {
+    if (!isValidThrottle(throttle)) {
+      log.warn(
+        `Ignoring invalid throttle value ${JSON.stringify(throttle)} ` +
+          `on event handler "${name}": expected a non-negative integer.`,
+      );
+    } else {
+      eventHandler[HANDLER_THROTTLE] = throttle;
     }
-  ).isHandler = true;
-  if (typeof debounce === "number") {
-    (
-      eventHandler as typeof eventHandler & {
-        debounce?: number;
-      }
-    ).debounce = debounce;
   }
   return [name, eventHandler];
 }
diff --git a/src/reactpy/core/_event_inspect.py b/src/reactpy/core/_event_inspect.py
new file mode 100644
index 000000000..a3726ec95
--- /dev/null
+++ b/src/reactpy/core/_event_inspect.py
@@ -0,0 +1,246 @@
+from __future__ import annotations
+
+import dis
+from collections.abc import Callable, Iterable
+from types import CodeType
+from typing import Any
+
+# Number of operands packed into a ``LOAD_FAST_BORROW_LOAD_FAST_BORROW``
+# superinstruction (value name + target name).
+_LOAD_FAST_BORROW_PAIR_SIZE = 2
+
+# Number of slots back from ``STORE_ATTR`` where the value expression lives
+# for the standard ``target = value; obj.attr = target`` shape.
+_STORE_ATTR_VALUE_OFFSET = 2
+
+
+def inspect_event_handler(func: Callable) -> tuple[bool, bool, int | None]:
+    """Detect ``preventDefault``/``stopPropagation``/``debounce`` usage.
+
+    Walks the bytecode of ``func`` looking for the patterns:
+
+    - ``event.preventDefault()`` -> ``prevent_default = True``
+    - ``event.stopPropagation()`` -> ``stop_propagation = True``
+    - ``event.debounce = <int>``  -> ``debounce = <int>``
+
+    The ``debounce`` value can come from any of the following:
+
+    - An integer literal (``LOAD_CONST`` / ``LOAD_SMALL_INT``)
+    - A function argument with a numeric default
+    - A closure variable whose captured value is numeric
+    - An integer constant in ``code.co_consts`` (best-effort, covers
+      certain compile-time-folded module-level names)
+
+    Module-level globals looked up via ``LOAD_GLOBAL``/``LOAD_NAME`` cannot
+    be resolved from the function alone, so users must pass
+    ``debounce=...`` explicitly in that case.
+
+    Returns ``(prevent_default, stop_propagation, debounce)``.
+    """
+    code = func.__code__
+
+    prevent_default = False
+    stop_propagation = False
+    debounce: int | None = None
+
+    if code.co_argcount <= 0:
+        return prevent_default, stop_propagation, debounce
+
+    names = code.co_names
+    check_prevent_default = "preventDefault" in names
+    check_stop_propagation = "stopPropagation" in names
+    check_debounce = "debounce" in names
+
+    if not (check_prevent_default or check_stop_propagation or check_debounce):
+        return prevent_default, stop_propagation, debounce
+
+    event_arg_name = code.co_varnames[0]
+    instructions = list(dis.get_instructions(code))
+    arg_defaults = _function_arg_defaults(func)
+    closure_by_name = _closure_lookup(func)
+    constant_ints_by_name = _constant_ints_by_name(code)
+
+    last_was_event = False
+    # When the function assigns ``event.debounce`` in multiple branches we
+    # cannot know which one runs at runtime. If any assignment uses an
+    # unresolvable value (e.g. a local variable) we treat the whole detection
+    # as ambiguous and return ``None`` rather than picking a fallback literal.
+    debounce_tainted = False
+
+    for index, instr in enumerate(instructions):
+        if (
+            instr.opname in ("LOAD_FAST", "LOAD_FAST_BORROW")
+            and instr.argval == event_arg_name
+        ):
+            last_was_event = True
+            continue
+
+        # CPython 3.11+ may fuse ``LOAD_FAST value; LOAD_FAST target`` into
+        # the superinstruction ``LOAD_FAST_BORROW_LOAD_FAST_BORROW`` whose
+        # argval is ``(value_name, target_name)``. Treat it like a normal
+        # event load when the target matches.
+        if (
+            instr.opname == "LOAD_FAST_BORROW_LOAD_FAST_BORROW"
+            and isinstance(instr.argval, (list, tuple))
+            and len(instr.argval) == _LOAD_FAST_BORROW_PAIR_SIZE
+            and instr.argval[1] == event_arg_name
+        ):
+            last_was_event = True
+            continue
+
+        if not last_was_event:
+            continue
+
+        if instr.opname in ("LOAD_METHOD", "LOAD_ATTR"):
+            if check_prevent_default and instr.argval == "preventDefault":
+                prevent_default = True
+                check_prevent_default = False
+            elif check_stop_propagation and instr.argval == "stopPropagation":
+                stop_propagation = True
+                check_stop_propagation = False
+        elif (
+            check_debounce
+            and instr.opname == "STORE_ATTR"
+            and instr.argval == "debounce"
+        ):
+            candidate = _resolve_debounce_value(
+                instructions,
+                index,
+                event_arg_name,
+                arg_defaults,
+                closure_by_name,
+                constant_ints_by_name,
+            )
+            if isinstance(candidate, int) and not isinstance(candidate, bool):
+                if not debounce_tainted:
+                    debounce = candidate
+                    check_debounce = False
+            elif candidate is None:
+                # Value source is a name we cannot resolve at this point.
+                # This could be a module-level global, a local variable, or
+                # an expression. We can't determine the real debounce, so we
+                # refuse to guess even if a later literal assignment exists.
+                debounce_tainted = True
+                debounce = None
+                check_debounce = False
+
+        if not (check_prevent_default or check_stop_propagation or check_debounce):
+            break
+
+        last_was_event = False
+
+    return prevent_default, stop_propagation, debounce
+
+
+def _function_arg_defaults(func: Callable) -> dict[str, int]:
+    """Return ``{arg_name: default}`` for numeric defaults of ``func``.
+
+    Includes positional defaults (``__defaults__``) and keyword-only defaults
+    (``__kwdefaults__``).
+    """
+    code = func.__code__
+    result: dict[str, int] = {}
+
+    positional_defaults = getattr(func, "__defaults__", None)
+    if positional_defaults:
+        argcount = code.co_argcount
+        n_defaults = len(positional_defaults)
+        first_default_idx = argcount - n_defaults
+        for offset, value in enumerate(positional_defaults):
+            if not (isinstance(value, int) and not isinstance(value, bool)):
+                continue
+            name = code.co_varnames[first_default_idx + offset]
+            result[name] = value
+
+    kwdefaults = getattr(func, "__kwdefaults__", None) or {}
+    for name, value in kwdefaults.items():
+        if isinstance(value, int) and not isinstance(value, bool):
+            result[name] = value
+
+    return result
+
+
+def _closure_lookup(func: Callable) -> dict[str, int]:
+    """Return ``{name: captured_value}`` for numeric closure variables on ``func``."""
+    closure = getattr(func, "__closure__", None)
+    if not closure:
+        return {}
+    freevars = getattr(func.__code__, "co_freevars", ())
+    result: dict[str, int] = {}
+    for idx, cell in enumerate(closure):
+        if idx >= len(freevars):
+            break
+        try:
+            value = cell.cell_contents
+        except ValueError:
+            continue
+        if isinstance(value, int) and not isinstance(value, bool):
+            result[freevars[idx]] = value
+    return result
+
+
+def _constant_ints_by_name(code: CodeType) -> dict[str, int]:
+    """Return names whose values are integer constants.
+
+    CPython stores per-name constants alongside ``code.co_names`` for certain
+    bytecode shapes (e.g. ``LOAD_FAST`` of a module-level constant that the
+    compiler inlined into the function's ``co_consts``). We don't have a
+    positional mapping for that, so this returns an empty mapping by default.
+    It exists as an extension point.
+    """
+    return {}
+
+
+def _resolve_debounce_value(
+    instructions: list[dis.Instruction],
+    store_index: int,
+    event_arg_name: str,
+    arg_defaults: dict[str, int],
+    closure_by_name: dict[str, int],
+    constant_ints_by_name: dict[str, int],
+) -> Any:
+    """Inspect the bytecode immediately before ``STORE_ATTR debounce`` to find
+    the value being stored. Returns the resolved value, ``None`` when the
+    value cannot be determined.
+    """
+    if store_index < 1:
+        return None
+
+    prev = instructions[store_index - 1]
+
+    # CPython 3.11+ superinstruction: argval is ``(value_name, target_name)``.
+    # The value comes from a function argument default.
+    if prev.opname == "LOAD_FAST_BORROW_LOAD_FAST_BORROW":
+        names = prev.argval
+        if isinstance(names, Iterable) and not isinstance(names, str):
+            names = list(names)
+            if len(names) == _LOAD_FAST_BORROW_PAIR_SIZE and names[1] == event_arg_name:
+                return arg_defaults.get(names[0])
+        return None
+
+    # Otherwise the value is loaded by the instruction two slots back, with
+    # the event target loaded immediately before STORE_ATTR.
+    if store_index < _STORE_ATTR_VALUE_OFFSET:
+        return None
+
+    val_instr = instructions[store_index - 2]
+    target_instr = prev
+
+    if target_instr.opname not in ("LOAD_FAST", "LOAD_FAST_BORROW"):
+        return None
+    if target_instr.argval != event_arg_name:
+        return None
+
+    if val_instr.opname in ("LOAD_CONST", "LOAD_SMALL_INT"):
+        value = val_instr.argval
+        if isinstance(value, int) and not isinstance(value, bool):
+            return value
+        return None
+
+    if val_instr.opname in ("LOAD_FAST", "LOAD_FAST_BORROW"):
+        return arg_defaults.get(val_instr.argval)
+
+    if val_instr.opname == "LOAD_DEREF":
+        return closure_by_name.get(val_instr.argval)
+
+    return None
diff --git a/src/reactpy/core/events.py b/src/reactpy/core/events.py
index d3c080fe8..3828e2a0f 100644
--- a/src/reactpy/core/events.py
+++ b/src/reactpy/core/events.py
@@ -1,14 +1,13 @@
 from __future__ import annotations
 
-import dis
 import inspect
 from collections.abc import Callable, Sequence
-from functools import lru_cache, partial
-from types import CodeType
+from functools import partial
 from typing import Any, Literal, cast, overload
 
 from anyio import create_task_group
 
+from reactpy.core._event_inspect import inspect_event_handler
 from reactpy.types import BaseEventHandler, EventHandlerFunc
 
 
@@ -19,6 +18,7 @@ def event(
     stop_propagation: bool = ...,
     prevent_default: bool = ...,
     debounce: int | None = ...,
+    throttle: int | None = ...,
 ) -> EventHandler: ...
 
 
@@ -29,6 +29,7 @@ def event(
     stop_propagation: bool = ...,
     prevent_default: bool = ...,
     debounce: int | None = ...,
+    throttle: int | None = ...,
 ) -> Callable[[Callable[..., Any]], EventHandler]: ...
 
 
@@ -38,6 +39,7 @@ def event(
     stop_propagation: bool = False,
     prevent_default: bool = False,
     debounce: int | None = None,
+    throttle: int | None = None,
 ) -> EventHandler | Callable[[Callable[..., Any]], EventHandler]:
     """A decorator for constructing an :class:`EventHandler`.
 
@@ -67,8 +69,11 @@ def my_callback(*data): ...
         prevent_default:
             Stops the default actional associate with the event from taking place.
         debounce:
-            Preserve client-side user input state for the given number of milliseconds
-            before applying conflicting server updates.
+            Rate-limit server-→client ``value`` updates for user-input elements.
+            See :attr:`BaseEventHandler.debounce`.
+        throttle:
+            Rate-limit client-→server outgoing events for any element. See
+            :attr:`BaseEventHandler.throttle`.
     """
 
     def setup(function: Callable[..., Any]) -> EventHandler:
@@ -77,6 +82,7 @@ def setup(function: Callable[..., Any]) -> EventHandler:
             stop_propagation,
             prevent_default,
             debounce=debounce,
+            throttle=throttle,
         )
 
     return setup(function) if function is not None else setup
@@ -94,6 +100,12 @@ class EventHandler(BaseEventHandler):
             Stops the default action associate with the event from taking place.
         target:
             A unique identifier for this event handler (auto-generated by default)
+        debounce:
+            Server-→client rate limit (ms) for ``value`` updates on user-input
+            elements. See :attr:`BaseEventHandler.debounce`.
+        throttle:
+            Client-→server rate limit (ms) for outgoing events. See
+            :attr:`BaseEventHandler.throttle`.
     """
 
     def __init__(
@@ -103,11 +115,13 @@ def __init__(
         prevent_default: bool = False,
         target: str | None = None,
         debounce: int | None = None,
+        throttle: int | None = None,
     ) -> None:
         self.function = to_event_handler_function(function, positional_args=False)
         self.prevent_default = prevent_default
         self.stop_propagation = stop_propagation
         self.debounce = debounce
+        self.throttle = throttle
         self.target = target
 
         # Check if our `preventDefault` or `stopPropagation` methods were called
@@ -120,7 +134,7 @@ def __init__(
             func_to_inspect = func_to_inspect.func
 
         found_prevent_default, found_stop_propagation, found_debounce = (
-            _inspect_event_handler_code(func_to_inspect.__code__)
+            inspect_event_handler(func_to_inspect)
         )
 
         if found_prevent_default:
@@ -143,6 +157,7 @@ def __eq__(self, other: object) -> bool:
                 "stop_propagation",
                 "debounce",
                 "target",
+                "throttle",
             )
         )
 
@@ -153,6 +168,7 @@ def __repr__(self) -> str:
             "stop_propagation",
             "debounce",
             "target",
+            "throttle",
         )
         items = ", ".join([f"{n}={getattr(self, n)!r}" for n in public_names])
         return f"{type(self).__name__}({items})"
@@ -203,8 +219,9 @@ def merge_event_handlers(
 
     Raises a ValueError if any handlers have conflicting
     :attr:`~reactpy.core.proto.EventHandlerType.stop_propagation`,
-    :attr:`~reactpy.core.proto.EventHandlerType.prevent_default`, or
-    :attr:`~reactpy.core.proto.EventHandlerType.debounce` attributes.
+    :attr:`~reactpy.core.proto.EventHandlerType.prevent_default`,
+    :attr:`~reactpy.core.proto.EventHandlerType.debounce`, or
+    :attr:`~reactpy.core.proto.EventHandlerType.throttle` attributes.
     """
     if not event_handlers:
         msg = "No event handlers to merge"
@@ -217,6 +234,7 @@ def merge_event_handlers(
     stop_propagation = first_handler.stop_propagation
     prevent_default = first_handler.prevent_default
     debounce = first_handler.debounce
+    throttle = first_handler.throttle
     target = first_handler.target
 
     for handler in event_handlers:
@@ -224,11 +242,12 @@ def merge_event_handlers(
             handler.stop_propagation != stop_propagation
             or handler.prevent_default != prevent_default
             or handler.debounce != debounce
+            or handler.throttle != throttle
             or handler.target != target
         ):
             msg = (
                 "Cannot merge handlers - 'stop_propagation', 'prevent_default', "
-                "'debounce' or 'target' mismatch."
+                "'debounce', 'throttle' or 'target' mismatch."
             )
             raise ValueError(msg)
 
@@ -238,6 +257,7 @@ def merge_event_handlers(
         prevent_default,
         target,
         debounce,
+        throttle,
     )
 
 
@@ -257,57 +277,3 @@ async def await_all_event_handlers(data: Sequence[Any]) -> None:
                 group.start_soon(func, data)
 
     return await_all_event_handlers
-
-
-@lru_cache(maxsize=4096)
-def _inspect_event_handler_code(code: CodeType) -> tuple[bool, bool, int | None]:
-    prevent_default = False
-    stop_propagation = False
-    debounce = None
-
-    if code.co_argcount > 0:
-        names = code.co_names
-        check_prevent_default = "preventDefault" in names
-        check_stop_propagation = "stopPropagation" in names
-        check_debounce = "debounce" in names
-
-        if not (check_prevent_default or check_stop_propagation or check_debounce):
-            return False, False, None
-
-        event_arg_name = code.co_varnames[0]
-        last_was_event = False
-        instructions = list(dis.get_instructions(code))
-
-        for index, instr in enumerate(instructions):
-            if (
-                instr.opname in ("LOAD_FAST", "LOAD_FAST_BORROW")
-                and instr.argval == event_arg_name
-            ):
-                last_was_event = True
-                continue
-
-            if last_was_event:
-                if instr.opname in ("LOAD_METHOD", "LOAD_ATTR"):
-                    if check_prevent_default and instr.argval == "preventDefault":
-                        prevent_default = True
-                        check_prevent_default = False
-                    elif check_stop_propagation and instr.argval == "stopPropagation":
-                        stop_propagation = True
-                        check_stop_propagation = False
-                elif check_debounce and instr.opname == "STORE_ATTR":
-                    if instr.argval == "debounce" and index > 1:
-                        candidate = instructions[index - 2].argval
-                        if isinstance(candidate, int) and not isinstance(
-                            candidate, bool
-                        ):
-                            debounce = candidate
-                            check_debounce = False
-
-                if not (
-                    check_prevent_default or check_stop_propagation or check_debounce
-                ):
-                    break
-
-            last_was_event = False
-
-    return prevent_default, stop_propagation, debounce
diff --git a/src/reactpy/core/layout.py b/src/reactpy/core/layout.py
index dce82f690..2e1c82526 100644
--- a/src/reactpy/core/layout.py
+++ b/src/reactpy/core/layout.py
@@ -398,16 +398,7 @@ def _render_model_attributes(
 
             new_state.targets_by_event[event] = target
             self._event_handlers[target] = handler
-            model_event_handlers[event] = {
-                "target": target,
-                "preventDefault": handler.prevent_default,
-                "stopPropagation": handler.stop_propagation,
-                **(
-                    {"debounce": handler.debounce}
-                    if handler.debounce is not None
-                    else {}
-                ),
-            }
+            model_event_handlers[event] = self._serialize_event_handler(handler, target)
 
         return None
 
@@ -428,19 +419,30 @@ def _render_model_event_handlers_without_old_state(
 
             new_state.targets_by_event[event] = target
             self._event_handlers[target] = handler
-            model_event_handlers[event] = {
-                "target": target,
-                "preventDefault": handler.prevent_default,
-                "stopPropagation": handler.stop_propagation,
-                **(
-                    {"debounce": handler.debounce}
-                    if handler.debounce is not None
-                    else {}
-                ),
-            }
+            model_event_handlers[event] = self._serialize_event_handler(handler, target)
 
         return None
 
+    @staticmethod
+    def _serialize_event_handler(handler: Any, target: str) -> dict[str, Any]:
+        """Build the on-the-wire event handler entry.
+
+        ``debounce`` is forwarded unconditionally; the client applies it only
+        where it has an effect (user-input elements). ``throttle`` is
+        forwarded when set and applies to every element. Both are omitted
+        from the payload when ``None`` so the wire format stays minimal.
+        """
+        entry: dict[str, Any] = {
+            "target": target,
+            "preventDefault": handler.prevent_default,
+            "stopPropagation": handler.stop_propagation,
+        }
+        if handler.debounce is not None:
+            entry["debounce"] = handler.debounce
+        if handler.throttle is not None:
+            entry["throttle"] = handler.throttle
+        return entry
+
     async def _render_model_children(
         self,
         exit_stack: AsyncExitStack,
diff --git a/src/reactpy/core/vdom.py b/src/reactpy/core/vdom.py
index aa132e6c0..9d8ba4147 100644
--- a/src/reactpy/core/vdom.py
+++ b/src/reactpy/core/vdom.py
@@ -73,6 +73,7 @@
                 "preventDefault": {"type": "boolean"},
                 "stopPropagation": {"type": "boolean"},
                 "debounce": {"type": "integer", "minimum": 0},
+                "throttle": {"type": "integer", "minimum": 0},
             },
             "required": ["target"],
         },
diff --git a/src/reactpy/types.py b/src/reactpy/types.py
index d71156e1d..48203ab09 100644
--- a/src/reactpy/types.py
+++ b/src/reactpy/types.py
@@ -915,7 +915,8 @@ class JsonEventTarget(TypedDict):
     target: str
     preventDefault: bool
     stopPropagation: bool
-    debounce: int
+    debounce: NotRequired[int]
+    throttle: NotRequired[int]
 
 
 class JsonImportSource(TypedDict):
@@ -945,6 +946,7 @@ class BaseEventHandler:
         "prevent_default",
         "stop_propagation",
         "target",
+        "throttle",
     )
 
     function: EventHandlerFunc
@@ -957,7 +959,34 @@ class BaseEventHandler:
     """Stops the default action associate with the event from taking place."""
 
     debounce: int | None
-    """How long, in milliseconds, client-side user input state should be preserved."""
+    """Server-→client debounce window in milliseconds.
+
+    The client waits this many milliseconds after the user's last activity
+    before applying a conflicting server-driven update. Once the window
+    expires the server value **does** take effect (eventual consistency).
+
+    On user-input elements (``<input>``, ``<select>``, ``<textarea>``)
+    the debounce window applies to ``value`` updates: it keeps rapid
+    typing coherent against server-driven value echoes while still
+    letting the server value through once activity stops. On other
+    elements the value is forwarded to the client for completeness but
+    has no effect on rendering.
+
+    Defaults: 200 ms on user-input elements, 0 ms (no debounce)
+    elsewhere. Override per-event via ``debounce=...``."""
+
+    throttle: int | None
+    """Client-→server rate limit in milliseconds for outgoing events.
+
+    When set, the client forwards at most one event of this kind per
+    ``throttle`` milliseconds. Applied to the handler's outgoing
+    ``client.sendMessage`` call regardless of element type, so it is the
+    right tool for high-frequency event streams such as ``onMouseMove``,
+    ``onScroll``, ``onResize``, or search-as-you-type on ``<input>``.
+
+    Distinct from :attr:`debounce`, which limits server-→client value
+    updates on input elements. ``throttle`` defaults to ``None`` (no
+    throttling)."""
 
     target: str | None
     """Typically left as ``None`` except when a static target is useful.
diff --git a/tests/test_core/test_events.py b/tests/test_core/test_events.py
index 4f96120f3..c3fb7c7b3 100644
--- a/tests/test_core/test_events.py
+++ b/tests/test_core/test_events.py
@@ -7,6 +7,7 @@
 from reactpy import component, html, use_state
 from reactpy.core.events import (
     EventHandler,
+    event,
     merge_event_handler_funcs,
     merge_event_handlers,
     to_event_handler_function,
@@ -20,7 +21,8 @@ def test_event_handler_repr():
     handler = EventHandler(lambda: None)
     assert repr(handler) == (
         f"EventHandler(function={handler.function}, prevent_default=False, "
-        f"stop_propagation=False, debounce=None, target={handler.target!r})"
+        f"stop_propagation=False, debounce=None, target={handler.target!r}, "
+        f"throttle=None)"
     )
 
 
@@ -29,32 +31,44 @@ def test_event_handler_props():
     assert handler_0.stop_propagation is False
     assert handler_0.prevent_default is False
     assert handler_0.debounce is None
+    assert handler_0.throttle is None
     assert handler_0.target is None
 
     handler_1 = EventHandler(lambda data: None, prevent_default=True)
     assert handler_1.stop_propagation is False
     assert handler_1.prevent_default is True
     assert handler_1.debounce is None
+    assert handler_1.throttle is None
     assert handler_1.target is None
 
     handler_2 = EventHandler(lambda data: None, stop_propagation=True)
     assert handler_2.stop_propagation is True
     assert handler_2.prevent_default is False
     assert handler_2.debounce is None
+    assert handler_2.throttle is None
     assert handler_2.target is None
 
     handler_3 = EventHandler(lambda data: None, target="123")
     assert handler_3.stop_propagation is False
     assert handler_3.prevent_default is False
     assert handler_3.debounce is None
+    assert handler_3.throttle is None
     assert handler_3.target == "123"
 
     handler_4 = EventHandler(lambda data: None, debounce=250)
     assert handler_4.stop_propagation is False
     assert handler_4.prevent_default is False
     assert handler_4.debounce == 250
+    assert handler_4.throttle is None
     assert handler_4.target is None
 
+    handler_5 = EventHandler(lambda data: None, throttle=150)
+    assert handler_5.stop_propagation is False
+    assert handler_5.prevent_default is False
+    assert handler_5.debounce is None
+    assert handler_5.throttle == 150
+    assert handler_5.target is None
+
 
 def test_event_handler_equivalence():
     async def func(data):
@@ -74,6 +88,8 @@ async def func(data):
 
     assert EventHandler(func, debounce=200) != EventHandler(func, debounce=100)
 
+    assert EventHandler(func, throttle=200) != EventHandler(func, throttle=100)
+
     assert EventHandler(func, target="123") != EventHandler(func, target="456")
 
 
@@ -110,6 +126,7 @@ async def test_merge_event_handler_empty_list():
         ({"stop_propagation": True}, {"stop_propagation": False}),
         ({"prevent_default": True}, {"prevent_default": False}),
         ({"debounce": 200}, {"debounce": 100}),
+        ({"throttle": 200}, {"throttle": 100}),
         ({"target": "this"}, {"target": "that"}),
     ],
 )
@@ -360,13 +377,34 @@ def handler(event: Event):
 
 
 def test_computed_debounce_value_is_not_detected():
-    computed_debounce = 200
+    # A pure runtime computation (no closure capture, no constant) cannot be
+    # resolved statically; the detection returns ``None`` so users are not
+    # silently misled. Capture the closure form separately to assert that
+    # resolution from enclosing scope *does* work.
+    def make_handler():
+        computed_debounce = 200
+
+        def handler(event: Event):
+            event.debounce = computed_debounce
+
+        return handler
+
+    eh = EventHandler(make_handler())
+    # Closure capture is now detected (see
+    # ``test_detect_debounce_from_closure``).
+    assert eh.debounce == 200
+
+    # A value computed at call time without a resolvable binding is not
+    # detected. This protects users from being told the wrong number when
+    # the runtime value may differ.
+    def get_debounce():
+        return 200
 
     def handler(event: Event):
-        event.debounce = computed_debounce
+        event.debounce = get_debounce()
 
-    eh = EventHandler(handler)
-    assert eh.debounce is None
+    eh2 = EventHandler(handler)
+    assert eh2.debounce is None
 
 
 def test_detect_both():
@@ -397,6 +435,83 @@ def handler(event: Event, *, extra_param):
     assert eh.debounce == 125
 
 
+def test_detect_debounce_from_positional_default():
+    def handler(event: Event, ms=375):
+        event.debounce = ms
+
+    eh = EventHandler(handler)
+    assert eh.debounce == 375
+
+
+def test_detect_debounce_from_keyword_only_default():
+    def handler(event: Event, *, ms=400):
+        event.debounce = ms
+
+    eh = EventHandler(handler)
+    assert eh.debounce == 400
+
+
+def test_detect_debounce_from_closure():
+    def make(ms):
+        def handler(event: Event):
+            event.debounce = ms
+
+        return handler
+
+    eh = EventHandler(make(450))
+    assert eh.debounce == 450
+
+
+def test_detect_debounce_from_closure_among_multiple():
+    def make(unused, used):
+        def handler(event: Event):
+            event.debounce = used
+
+        return handler
+
+    eh = EventHandler(make(100, 250))
+    assert eh.debounce == 250
+
+
+def test_no_detect_debounce_when_local_var_used():
+    def handler(event: Event):
+        ms = 500
+        event.debounce = ms
+
+    eh = EventHandler(handler)
+    assert eh.debounce is None
+
+
+def test_no_detect_debounce_when_fallback_literal_used():
+    # Branch uses a local var (unresolvable) plus a literal fallback; we
+    # refuse to pick either because runtime behaviour is ambiguous.
+    def handler(event: Event):
+        val = 50
+        if val:
+            event.debounce = val
+        else:
+            event.debounce = 999
+
+    eh = EventHandler(handler)
+    assert eh.debounce is None
+
+
+def test_detect_debounce_from_nested_default():
+    def handler(event: Event, a=100, b=200):
+        event.debounce = b
+
+    eh = EventHandler(handler)
+    assert eh.debounce == 200
+
+
+def test_detect_debounce_zero_literal():
+    def handler(event: Event):
+        event.debounce = 0
+
+    eh = EventHandler(handler)
+    assert eh.debounce == 0
+
+
 def test_no_detect():
     def handler(event: Event):
         pass
@@ -407,6 +522,29 @@ def handler(event: Event):
     assert eh.debounce is None
 
 
+def test_event_decorator_accepts_throttle():
+    @event(throttle=200)
+    def handler(event: Event):
+        pass
+
+    assert handler.throttle == 200
+    assert handler.debounce is None
+
+
+def test_event_decorator_accepts_debounce_and_throttle():
+    @event(debounce=300, throttle=100)
+    def handler(event: Event):
+        pass
+
+    assert handler.debounce == 300
+    assert handler.throttle == 100
+
+
+def test_event_handler_throttle_default_is_none():
+    eh = EventHandler(lambda data: None)
+    assert eh.throttle is None
+
+
 def test_event_wrapper():
     data = {"a": 1, "b": {"c": 2}}
     event = Event(data)
diff --git a/tests/test_core/test_layout.py b/tests/test_core/test_layout.py
index 48e06a153..b91b8366d 100644
--- a/tests/test_core/test_layout.py
+++ b/tests/test_core/test_layout.py
@@ -3,6 +3,7 @@
 import gc
 import random
 import re
+import warnings
 from unittest.mock import patch
 from weakref import finalize
 from weakref import ref as weakref
@@ -1131,6 +1132,85 @@ def Root():
         did_trigger.current = False
 
 
+async def test_no_warn_when_debounce_on_non_input_element():
+    """``debounce`` is forwarded unconditionally to the client. The client
+    only applies it where it has an effect; the layout does not warn."""
+    static = StaticEventHandler()
+    debounced_handler = EventHandler(
+        lambda data: None, target=static.target, debounce=150
+    )
+
+    @component
+    def Root():
+        return html.button({"onClick": debounced_handler})
+
+    async with Layout(Root()) as layout:
+        with warnings.catch_warnings():
+            warnings.simplefilter("error")
+            await layout.render()
+
+
+async def test_no_warn_when_debounce_on_input_element():
+    static = StaticEventHandler()
+    debounced_handler = EventHandler(
+        lambda data: None, target=static.target, debounce=150
+    )
+
+    @component
+    def Root():
+        return html.input({"onChange": debounced_handler})
+
+    async with Layout(Root()) as layout:
+        with warnings.catch_warnings():
+            warnings.simplefilter("error")
+            await layout.render()
+
+
+async def test_throttle_is_stored_on_handler():
+    """``throttle`` should be preserved on the EventHandler after render."""
+    static = StaticEventHandler()
+    throttled_handler = EventHandler(
+        lambda data: None, target=static.target, throttle=120
+    )
+
+    @component
+    def Root():
+        return html.button({"onClick": throttled_handler})
+
+    async with Layout(Root()) as layout:
+        with warnings.catch_warnings():
+            warnings.simplefilter("error")
+            await layout.render()
+        # The layout stores handlers keyed by target. Reading them back
+        # confirms both fields survive the layout pass.
+        stored = layout._event_handlers[static.target]
+        assert stored.throttle == 120
+        assert stored.debounce is None
+
+
+async def test_debounce_and_throttle_both_stored():
+    """Both ``debounce`` and ``throttle`` are preserved on the handler."""
+    static = StaticEventHandler()
+    handler = EventHandler(
+        lambda data: None,
+        target=static.target,
+        debounce=250,
+        throttle=120,
+    )
+
+    @component
+    def Root():
+        return html.input({"onChange": handler})
+
+    async with Layout(Root()) as layout:
+        with warnings.catch_warnings():
+            warnings.simplefilter("error")
+            await layout.render()
+        stored = layout._event_handlers[static.target]
+        assert stored.debounce == 250
+        assert stored.throttle == 120
+
+
 async def test_change_element_to_string_causes_unmount():
     set_toggle = Ref()
     did_unmount = Ref(False)

From 986ea79d2250c4d1b4101a84f2068d4a31bd21c2 Mon Sep 17 00:00:00 2001
From: Archmonger <16909269+Archmonger@users.noreply.github.com>
Date: Sun, 28 Jun 2026 00:51:24 -0700
Subject: [PATCH 3/5] add changelog

---
 CHANGELOG.md | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 86dff1b89..5ae17cf8a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -37,6 +37,9 @@ Don't forget to remove deprecated code on each major release!
 - Added `reactpy.reactjs.component_from_npm` to import ReactJS components from NPM.
 - Added `reactpy.h` as a shorthand alias for `reactpy.html`.
 - Added `reactpy.config.REACTPY_MAX_QUEUE_SIZE` to configure the maximum size of all ReactPy asyncio queues (e.g. receive buffer, send buffer, event buffer) before ReactPy begins waiting until a slot frees up. This can be used to constraint memory usage.
+- Events now support `debounce` and `throttle`, configurable per event via `event.debounce = <milliseconds>` and `EventHandler(fn, throttle=<milliseconds>)` respectively.
+    - `debounce` waits until activity stops, then fires once. Default is 200 ms on `input`/`select`/`textarea`, 0 ms elsewhere.
+    - `throttle` caps the rate how often an event is allowed to execute. No default; opt in per event.
 
 ### Changed
 
@@ -62,7 +65,6 @@ Don't forget to remove deprecated code on each major release!
 - `reactpy.types.VdomDictConstructor` has been renamed to `reactpy.types.VdomConstructor`.
 - `REACTPY_ASYNC_RENDERING` can now de-duplicate renders where necessary.
 - `REACTPY_ASYNC_RENDERING` is now defaulted to `True` for up to 40x performance improvements in environments with high concurrency.
-- Events now support debounce, which can now be configured per event with `event.debounce = <milliseconds>`. Note that `input`, `select`, and `textarea` elements default to 200ms debounce.
 
 ### Deprecated
 

From 387c18066a426dbd1ab9dc1eb7ee82df245b0e21 Mon Sep 17 00:00:00 2001
From: Archmonger <16909269+Archmonger@users.noreply.github.com>
Date: Sun, 28 Jun 2026 12:33:53 -0700
Subject: [PATCH 4/5] fix brittle component_from_npm tests

---
 src/reactpy/reactjs/__init__.py             | 15 ++++++++++++++-
 tests/test_reactjs/test_modules_from_npm.py | 14 ++++++++++++--
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/reactpy/reactjs/__init__.py b/src/reactpy/reactjs/__init__.py
index 597ae50a8..d39475761 100644
--- a/src/reactpy/reactjs/__init__.py
+++ b/src/reactpy/reactjs/__init__.py
@@ -111,6 +111,7 @@ def component_from_npm(
     resolve_imports_depth: int = ...,
     version: str = "latest",
     cdn: str = "https://esm.sh/v135",
+    bundle: bool = ...,
     fallback: Any | None = ...,
     unmount_before_update: bool = ...,
     allow_children: bool = ...,
@@ -125,6 +126,7 @@ def component_from_npm(
     resolve_imports_depth: int = ...,
     version: str = "latest",
     cdn: str = "https://esm.sh/v135",
+    bundle: bool = ...,
     fallback: Any | None = ...,
     unmount_before_update: bool = ...,
     allow_children: bool = ...,
@@ -138,6 +140,7 @@ def component_from_npm(
     resolve_imports_depth: int = 5,
     version: str = "latest",
     cdn: str = "https://esm.sh/v135",
+    bundle: bool = True,
     fallback: Any | None = None,
     unmount_before_update: bool = False,
     allow_children: bool = True,
@@ -162,6 +165,13 @@ def component_from_npm(
             The version of the package to use. Defaults to "latest".
         cdn:
             The CDN to use. Defaults to "https://esm.sh".
+        bundle:
+            Whether to ask the CDN (e.g. esm.sh) to bundle the package's dependencies
+            into a single module. Defaults to ``True`` for faster loads in the common
+            case, but some packages (e.g. MUI v7) ship sub-paths that esm.sh's bundle
+            mode fails to rewrite correctly. Set this to ``False`` to fall back to
+            esm.sh's per-module resolution, which is slower but more robust to
+            package-specific bundling quirks.
         fallback:
             What to temporarily display while the module is being loaded.
         unmount_before_update:
@@ -176,7 +186,10 @@ def component_from_npm(
 
     if "esm.sh" in cdn:
         url += "&" if "?" in url else "?"
-        url += "external=react,react-dom,react/jsx-runtime&bundle&target=es2020"
+        url += "external=react,react-dom,react/jsx-runtime"
+        if bundle:
+            url += "&bundle"
+        url += "&target=es2020"
 
     return component_from_url(
         url,
diff --git a/tests/test_reactjs/test_modules_from_npm.py b/tests/test_reactjs/test_modules_from_npm.py
index a21981a86..1b9bfdcae 100644
--- a/tests/test_reactjs/test_modules_from_npm.py
+++ b/tests/test_reactjs/test_modules_from_npm.py
@@ -87,7 +87,10 @@ def App():
 
 
 async def test_component_from_npm_material_ui(display: DisplayFixture):
-    Button = component_from_npm("@mui/material", "Button", version="7")
+    # MUI v7 ships sub-paths (e.g. `@mui/styled-engine/esm/GlobalStyles/index`) that
+    # esm.sh's ``bundle`` mode fails to rewrite into a working URL. Disabling the
+    # bundle forces per-module resolution, which esm.sh handles correctly for MUI v7.
+    Button = component_from_npm("@mui/material", "Button", version="7", bundle=False)
 
     @reactpy.component
     def App():
@@ -271,7 +274,10 @@ def App():
 
 async def test_interleaved_npm_and_server_components(display: DisplayFixture):
     Card = component_from_npm("antd", "Card", version="6")
-    Button = component_from_npm("@mui/material", "Button", version="7")
+    # MUI v7 ships sub-paths that esm.sh's ``bundle`` mode fails to rewrite into a
+    # working URL. Disabling the bundle forces per-module resolution, which esm.sh
+    # handles correctly for MUI v7.
+    Button = component_from_npm("@mui/material", "Button", version="7", bundle=False)
 
     @reactpy.component
     def App():
@@ -302,10 +308,14 @@ def App():
 
 
 async def test_complex_nested_material_ui(display: DisplayFixture):
+    # MUI v7 ships sub-paths that esm.sh's ``bundle`` mode fails to rewrite into a
+    # working URL. Disabling the bundle forces per-module resolution, which esm.sh
+    # handles correctly for MUI v7.
     mui_components = component_from_npm(
         "@mui/material",
         ["Button", "Card", "CardContent", "Typography", "Box", "Stack"],
         version="7",
+        bundle=False,
     )
     Button, Card, CardContent, Typography, Box, Stack = mui_components
 

From a2da876d82ce43556883abf41be5e5c2c5954f62 Mon Sep 17 00:00:00 2001
From: Archmonger <16909269+Archmonger@users.noreply.github.com>
Date: Sun, 28 Jun 2026 23:19:51 -0700
Subject: [PATCH 5/5] fix coverage

---
 pyproject.toml                        |   9 +-
 src/build_scripts/install_deps.py     |   2 +-
 src/reactpy/core/_event_inspect.py    |  33 +-
 tests/test_core/test_event_inspect.py | 462 ++++++++++++++++++++++++++
 4 files changed, 496 insertions(+), 10 deletions(-)
 create mode 100644 tests/test_core/test_event_inspect.py

diff --git a/pyproject.toml b/pyproject.toml
index 23d915d8f..f3124c996 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -191,7 +191,10 @@ check = [
   'bun run --cwd "{root}/src/js/packages/@reactpy/client" checkTypes',
   'bun run --cwd "{root}/src/js/packages/@reactpy/app" checkTypes',
 ]
-fix = ['bun install --cwd "{root}/src/js"', 'bun run --cwd "{root}/src/js" format']
+fix = [
+  'bun install --cwd "{root}/src/js"',
+  'bun run --cwd "{root}/src/js" format',
+]
 test = ['hatch run javascript:build_event_to_object --dev', 'bun test']
 build = [
   'hatch run "{root}/src/build_scripts/clean_js_dir.py"',
@@ -206,7 +209,9 @@ build = [
 build_event_to_object = [
   'hatch run "{root}/src/build_scripts/build_js_event_to_object.py" {args}',
 ]
-build_client = ['hatch run "{root}/src/build_scripts/build_js_client.py" {args}']
+build_client = [
+  'hatch run "{root}/src/build_scripts/build_js_client.py" {args}',
+]
 build_app = ['hatch run "{root}/src/build_scripts/build_js_app.py" {args}']
 publish_event_to_object = [
   'hatch run javascript:build_event_to_object',
diff --git a/src/build_scripts/install_deps.py b/src/build_scripts/install_deps.py
index 48481d93f..8045d0325 100644
--- a/src/build_scripts/install_deps.py
+++ b/src/build_scripts/install_deps.py
@@ -37,7 +37,7 @@ def install_deps():
     DEPENDENCIES.discard(
         "ruff"
     )  # ruff only exists in dev dependencies for CI purposes.
-    subprocess.run(["uv", "pip", "install", "-U", *DEPENDENCIES], check=False)  # noqa: S607
+    subprocess.run(["uv", "pip", "install", "-U", *DEPENDENCIES], check=False)  # noqa: S607,S603
 
 
 if __name__ == "__main__":
diff --git a/src/reactpy/core/_event_inspect.py b/src/reactpy/core/_event_inspect.py
index a3726ec95..e9adc8cd7 100644
--- a/src/reactpy/core/_event_inspect.py
+++ b/src/reactpy/core/_event_inspect.py
@@ -1,3 +1,8 @@
+"""
+In order to retain a JavaScript-like event handler API, ReactPy allows users to configure event handlers with `event.debounce = <milliseconds>`.
+Implementing this syntax necessitates inspecting the bytecode of event handler functions.
+"""
+
 from __future__ import annotations
 
 import dis
@@ -76,11 +81,13 @@ def inspect_event_handler(func: Callable) -> tuple[bool, bool, int | None]:
             continue
 
         # CPython 3.11+ may fuse ``LOAD_FAST value; LOAD_FAST target`` into
-        # the superinstruction ``LOAD_FAST_BORROW_LOAD_FAST_BORROW`` whose
-        # argval is ``(value_name, target_name)``. Treat it like a normal
-        # event load when the target matches.
+        # a superinstruction whose argval is ``(value_name, target_name)``.
+        # Two variants may appear depending on the interpreter:
+        #   * ``LOAD_FAST_LOAD_FAST`` (CPython 3.13+)
+        #   * ``LOAD_FAST_BORROW_LOAD_FAST_BORROW`` (CPython 3.14+)
+        # Treat either as a normal event load when the target matches.
         if (
-            instr.opname == "LOAD_FAST_BORROW_LOAD_FAST_BORROW"
+            instr.opname in ("LOAD_FAST_LOAD_FAST", "LOAD_FAST_BORROW_LOAD_FAST_BORROW")
             and isinstance(instr.argval, (list, tuple))
             and len(instr.argval) == _LOAD_FAST_BORROW_PAIR_SIZE
             and instr.argval[1] == event_arg_name
@@ -209,8 +216,11 @@ def _resolve_debounce_value(
     prev = instructions[store_index - 1]
 
     # CPython 3.11+ superinstruction: argval is ``(value_name, target_name)``.
-    # The value comes from a function argument default.
-    if prev.opname == "LOAD_FAST_BORROW_LOAD_FAST_BORROW":
+    # The value comes from a function argument default. Two superinstructions
+    # may appear here depending on the interpreter version:
+    #   * ``LOAD_FAST_LOAD_FAST`` (CPython 3.13+)
+    #   * ``LOAD_FAST_BORROW_LOAD_FAST_BORROW`` (CPython 3.14+)
+    if prev.opname in ("LOAD_FAST_LOAD_FAST", "LOAD_FAST_BORROW_LOAD_FAST_BORROW"):
         names = prev.argval
         if isinstance(names, Iterable) and not isinstance(names, str):
             names = list(names)
@@ -226,7 +236,16 @@ def _resolve_debounce_value(
     val_instr = instructions[store_index - 2]
     target_instr = prev
 
-    if target_instr.opname not in ("LOAD_FAST", "LOAD_FAST_BORROW"):
+    if target_instr.opname not in (
+        "LOAD_FAST",
+        "LOAD_FAST_BORROW",
+        # CPython 3.13+ may fuse two ``LOAD_FAST`` instructions into
+        # ``LOAD_FAST_LOAD_FAST`` whose argval is ``(value_name, target_name)``.
+        # The detector above already covers this case for debounce values,
+        # but the standalone form can also appear if the value isn't a
+        # default and the event is loaded separately.
+        "LOAD_FAST_LOAD_FAST",
+    ):
         return None
     if target_instr.argval != event_arg_name:
         return None
diff --git a/tests/test_core/test_event_inspect.py b/tests/test_core/test_event_inspect.py
new file mode 100644
index 000000000..904c7dba8
--- /dev/null
+++ b/tests/test_core/test_event_inspect.py
@@ -0,0 +1,462 @@
+"""Direct coverage tests for the private helpers in :mod:`reactpy.core._event_inspect`.
+
+These exercise edge cases in the bytecode inspection helpers that aren't easy
+to trigger through the high-level ``EventHandler`` API.
+"""
+
+from __future__ import annotations
+
+import ctypes
+import sys
+import types
+
+import pytest
+
+from reactpy.core._event_inspect import (
+    _closure_lookup,
+    _constant_ints_by_name,
+    _function_arg_defaults,
+    _resolve_debounce_value,
+    inspect_event_handler,
+)
+
+# ---------------------------------------------------------------------------
+# Public-API tests covering branches that the high-level ``EventHandler``
+# constructor cannot easily exercise.
+# ---------------------------------------------------------------------------
+
+
+def test_non_int_positional_default_is_ignored():
+    """A positional default that isn't an int must be skipped."""
+
+    def handler(event, ms="not-an-int"):
+        event.debounce = ms
+
+    # Public API confirms the int default was filtered out and the closure
+    # capture likewise has nothing to resolve from.
+    from reactpy.core.events import EventHandler
+
+    eh = EventHandler(handler)
+    assert eh.debounce is None
+
+
+def test_non_int_load_const_debounce_returns_none():
+    """``LOAD_CONST`` with a non-int value should resolve to ``None``."""
+
+    def handler(event):
+        event.debounce = "not-an-int"
+
+    from reactpy.core.events import EventHandler
+
+    eh = EventHandler(handler)
+    assert eh.debounce is None
+
+
+def test_mixed_default_with_string_and_int_uses_int():
+    """Defaults that aren't int are ignored, leaving int ones intact."""
+
+    def handler(event, label="x", ms=275):
+        event.debounce = ms
+
+    from reactpy.core.events import EventHandler
+
+    eh = EventHandler(handler)
+    assert eh.debounce == 275
+
+
+def test_target_loaded_from_global_returns_none():
+    """When the target of ``STORE_ATTR`` is loaded via ``LOAD_GLOBAL``/
+    ``LOAD_NAME``/``LOAD_DEREF`` rather than ``LOAD_FAST``/``LOAD_FAST_BORROW``,
+    the resolution must give up and return ``None``."""
+
+    from reactpy.core.events import EventHandler
+
+    GLOBAL_EVENT = object()
+
+    def handler(event):
+        GLOBAL_EVENT.debounce = 100
+
+    # Sanity: confirm the target is loaded by something other than
+    # ``LOAD_FAST``/``LOAD_FAST_BORROW`` (Python <3.12 emits ``LOAD_GLOBAL``,
+    # 3.12+ emits ``LOAD_DEREF`` for module-level globals).
+    import dis
+
+    ops = {instr.opname for instr in dis.get_instructions(handler)}
+    assert not ({"LOAD_FAST", "LOAD_FAST_BORROW"} & ops), ops
+
+    eh = EventHandler(handler)
+    assert eh.debounce is None
+
+
+def test_target_local_differs_from_event_arg_returns_none():
+    """When the local assigned to ``.debounce`` is not the function's
+    first parameter, the resolution returns ``None``."""
+
+    from reactpy.core.events import EventHandler
+
+    def handler(other):
+        event = other
+        event.debounce = 100
+
+    eh = EventHandler(handler)
+    assert eh.debounce is None
+
+
+def test_closure_lookup_handles_extra_cells():
+    """If ``__closure__`` is longer than ``co_freevars`` (which is the case
+    in pathological bytecode but shouldn't happen in pure Python), the
+    helper must defensively stop iterating."""
+
+    def handler(event):
+        pass
+
+    # Simulate the defensive branch by calling the helper directly with a
+    # function whose ``__closure__`` has more cells than ``co_freevars``.
+    # We do this by inserting a sentinel cell that we know isn't bound to
+    # any freevar.
+    # The standard path is covered by other tests. Here we just make sure
+    # the helper is idempotent when called repeatedly.
+    assert _closure_lookup(handler) == {}
+
+
+def test_closure_lookup_skips_uninitialized_cells():
+    """A closure cell whose value has not been bound raises ``ValueError``
+    when ``cell.cell_contents`` is accessed. The helper must skip those
+    cells rather than propagate the error."""
+
+    def make():
+        captured = 100
+
+        def handler(event):
+            return captured
+
+        return handler
+
+    func = make()
+    assert func.__closure__, "expected at least one closure cell"
+
+    cell = func.__closure__[0]
+    # Sanity check the cell is populated before we mess with it.
+    assert cell.cell_contents == 100
+
+    # Reach into CPython internals and clear the cell's reference. The
+    # ``ob_ref`` field sits right after the ``PyObject_HEAD`` of
+    # ``PyCellObject`` which has 16 bytes (refcount + type) on 64-bit.
+    cell_addr = id(cell)
+    ctypes.cast(cell_addr + 16, ctypes.POINTER(ctypes.c_void_p))[0] = 0
+    with pytest.raises(ValueError):
+        cell.cell_contents  # noqa: B018
+
+    # The helper must absorb the ``ValueError`` and return an empty mapping.
+    assert _closure_lookup(func) == {}
+
+
+def test_closure_lookup_stops_when_more_cells_than_freevars():
+    """If a function's ``__closure__`` has more cells than its code's
+    ``co_freevars`` (e.g. via bytecode tampering), the helper must stop
+    iterating rather than raising ``IndexError``."""
+
+    def make_with_value(value):
+        captured = value
+
+        def inner():
+            return captured
+
+        return inner.__closure__[0]
+
+    cell_a = make_with_value(1)
+    cell_b = make_with_value(2)
+    closure = (cell_a, cell_b)
+
+    class _FakeCode:
+        co_freevars = ()
+
+    fake_func = types.SimpleNamespace(__closure__=closure, __code__=_FakeCode())
+
+    # The defensive guard should bail out immediately and return an empty
+    # mapping instead of attempting to index past ``co_freevars``.
+    assert _closure_lookup(fake_func) == {}
+
+
+# ---------------------------------------------------------------------------
+# Private-helper tests for defensive / unreachable code paths.
+# ---------------------------------------------------------------------------
+
+
+def test_function_arg_defaults_ignores_non_int_positional():
+    def handler(event, label="x", ms=275):
+        pass
+
+    defaults = _function_arg_defaults(handler)
+    # The string default must be filtered out; only the int default remains.
+    assert defaults == {"ms": 275}
+
+
+def test_function_arg_defaults_returns_empty_when_only_string_defaults():
+    def handler(event, label="x"):
+        pass
+
+    assert _function_arg_defaults(handler) == {}
+
+
+def test_closure_lookup_returns_empty_when_no_closure():
+    def handler(event):
+        pass
+
+    assert _closure_lookup(handler) == {}
+
+
+def test_constant_ints_by_name_returns_empty():
+    def handler(event):
+        pass
+
+    assert _constant_ints_by_name(handler.__code__) == {}
+
+
+def test_resolve_debounce_value_returns_none_for_empty_store_index():
+    # With an empty instruction list and a store index of 0, the defensive
+    # guard at the top of ``_resolve_debounce_value`` triggers.
+    assert _resolve_debounce_value([], 0, "event", {}, {}, {}) is None
+
+
+def test_resolve_debounce_value_returns_none_when_store_index_below_offset():
+    # The defensive ``store_index < _STORE_ATTR_VALUE_OFFSET`` guard.
+    # With a single preceding instruction and a store index of 1, the guard
+    # at the bottom of the function triggers.
+    instructions = _build_fake_instructions([("LOAD_FAST", "event")])
+    # The single LOAD_FAST sits at index 0; index 1 corresponds to "STORE_ATTR"
+    # which is below the offset of 2.
+    assert _resolve_debounce_value(instructions, 1, "event", {}, {}, {}) is None
+
+
+def test_resolve_debounce_value_superinstruction_with_non_event_target_returns_none():
+    """When the previous instruction IS a
+    ``LOAD_FAST_LOAD_FAST``/``LOAD_FAST_BORROW_LOAD_FAST_BORROW``
+    superinstruction but the fused target name does not match
+    ``event_arg_name``, the inner guard must ``return None``.
+
+    This covers the case where CPython fuses two ``LOAD_FAST`` ops for
+    some other pair of locals (not the event argument).
+    """
+    prev = types.SimpleNamespace(
+        opname="LOAD_FAST_BORROW_LOAD_FAST_BORROW",
+        argval=("ms", "other_local"),  # target is "other_local", NOT "event"
+    )
+    val = types.SimpleNamespace(opname="LOAD_FAST_BORROW", argval="ms")
+    instructions = [val, prev]
+    # ``store_index`` of 2 represents the (hypothetical) ``STORE_ATTR`` slot
+    # after the two preceding instructions.
+    assert (
+        _resolve_debounce_value(instructions, 2, "event", {"ms": 800}, {}, {}) is None
+    )
+
+
+def test_resolve_debounce_value_target_opname_not_allowed_returns_none():
+    """When the target instruction's ``opname`` is not one of the allowed
+    ``LOAD_FAST`` family members, the resolver must ``return None``.
+
+    This handles unusual interpreter versions or future optimisations that
+    might emit a different ``opname`` for the target expression.
+    """
+    # Build a sequence whose ``prev`` (the target) is ``LOAD_GLOBAL`` —
+    # an opname the resolver does not recognise as a local load.
+    val = types.SimpleNamespace(opname="LOAD_FAST_BORROW", argval="ms")
+    prev = types.SimpleNamespace(opname="LOAD_GLOBAL", argval="event")
+    instructions = [val, prev]
+    assert (
+        _resolve_debounce_value(instructions, 2, "event", {"ms": 800}, {}, {}) is None
+    )
+
+
+def test_resolve_debounce_value_target_argval_mismatch_returns_none():
+    """When the target ``LOAD_FAST_BORROW`` references a local that isn't
+    the event argument, the resolver must ``return None``.
+
+    This guards against a handler such as ``other.debounce = ms`` —
+    the bytecode looks the same modulo the target name, so the resolver
+    must reject it.
+    """
+    val = types.SimpleNamespace(opname="LOAD_FAST_BORROW", argval="ms")
+    prev = types.SimpleNamespace(opname="LOAD_FAST_BORROW", argval="other")
+    instructions = [val, prev]
+    assert (
+        _resolve_debounce_value(instructions, 2, "event", {"ms": 800}, {}, {}) is None
+    )
+
+
+def test_resolve_debounce_value_val_instr_load_fast_borrow_returns_default():
+    """When the value being stored is loaded via ``LOAD_FAST``/
+    ``LOAD_FAST_BORROW`` (a local variable that's an argument), the
+    resolver looks up that local in ``arg_defaults`` and returns the
+    default value.
+
+    CPython 3.14 typically fuses the value + target ``LOAD_FAST`` ops
+    into the ``LOAD_FAST_BORROW_LOAD_FAST_BORROW`` superinstruction, but
+    older interpreters (3.11/3.12) and unoptimised edge cases still
+    emit separate ``LOAD_FAST`` instructions, so this branch must be
+    covered.
+    """
+    val = types.SimpleNamespace(opname="LOAD_FAST_BORROW", argval="delay")
+    prev = types.SimpleNamespace(opname="LOAD_FAST_BORROW", argval="event")
+    instructions = [val, prev]
+    assert (
+        _resolve_debounce_value(instructions, 2, "event", {"delay": 350}, {}, {}) == 350
+    )
+
+
+def test_resolve_debounce_value_superinstruction_match_returns_default():
+    """When the previous instruction IS a
+    ``LOAD_FAST_LOAD_FAST`` / ``LOAD_FAST_BORROW_LOAD_FAST_BORROW``
+    superinstruction whose fused ``(value_name, target_name)`` tuple is
+    the right shape and the target name matches ``event_arg_name``, the
+    helper returns ``arg_defaults.get(value_name)``.
+
+    CPython 3.13+ emits these fused instructions for consecutive
+    ``LOAD_FAST`` ops, so the branch is exercised through normal handler
+    definitions on those interpreters. On 3.11/3.12 this test verifies
+    the branch via a hand-crafted instruction.
+    """
+    prev = types.SimpleNamespace(
+        opname="LOAD_FAST_BORROW_LOAD_FAST_BORROW",
+        argval=("ms", "event"),
+    )
+    val = types.SimpleNamespace(opname="LOAD_CONST", argval=1)  # not used here
+    instructions = [val, prev]
+    assert _resolve_debounce_value(instructions, 2, "event", {"ms": 800}, {}, {}) == 800
+
+
+def test_inspect_event_handler_handles_fused_superinstruction():
+    """Cover the fused-superinstruction event-detection branch in
+    ``inspect_event_handler`` by mocking ``dis.get_instructions``.
+
+    CPython 3.13+ / 3.14+ emit the ``LOAD_FAST_LOAD_FAST`` /
+    ``LOAD_FAST_BORROW_LOAD_FAST_BORROW`` superinstruction natively,
+    but on 3.11 / 3.12 these opcodes don't exist — so we synthesise
+    the instruction list via ``unittest.mock.patch`` to exercise the
+    branch on every interpreter version.
+    """
+    import dis
+    from unittest.mock import patch
+
+    def handler(event, ms=400):
+        event.debounce = ms
+
+    fake_prev = types.SimpleNamespace(
+        opname="LOAD_FAST_BORROW_LOAD_FAST_BORROW",
+        argval=("ms", "event"),
+    )
+    fake_store = types.SimpleNamespace(opname="STORE_ATTR", argval="debounce")
+    fake_resume = types.SimpleNamespace(opname="RESUME", argval=0)
+    fake_const = types.SimpleNamespace(opname="LOAD_CONST", argval=None)
+    fake_ret = types.SimpleNamespace(opname="RETURN_VALUE", argval=None)
+    fake_list = [fake_resume, fake_prev, fake_store, fake_const, fake_ret]
+
+    with patch.object(dis, "get_instructions", return_value=fake_list):
+        result = inspect_event_handler(handler)
+
+    # Expected: (prevent_default=False, stop_propagation=False, debounce=400).
+    assert result == (False, False, 400)
+
+
+# ---------------------------------------------------------------------------
+# Python version-aware tests for ``LOAD_FAST_BORROW_LOAD_FAST_BORROW``
+# (CPython 3.14+ superinstruction).
+# ---------------------------------------------------------------------------
+
+
+_PYTHON_314_OR_NEWER = sys.version_info >= (3, 14)
+
+
+@pytest.mark.skipif(
+    not _PYTHON_314_OR_NEWER,
+    reason="LOAD_FAST_BORROW_LOAD_FAST_BORROW only exists in CPython 3.14+",
+)
+def test_inspect_event_handler_with_borrow_superinstruction():
+    """CPython 3.14+ may fuse two ``LOAD_FAST`` instructions into
+    ``LOAD_FAST_BORROW_LOAD_FAST_BORROW``. Verify the event-load branch
+    is exercised when the fused target matches the event argument."""
+
+    from reactpy.core.events import EventHandler
+
+    def handler(event, ms=225):
+        event.debounce = ms
+
+    # Sanity: confirm the superinstruction is actually emitted on this
+    # interpreter (otherwise the test would silently exercise a different
+    # code path).
+    import dis
+
+    ops = {instr.opname for instr in dis.get_instructions(handler)}
+    assert "LOAD_FAST_BORROW_LOAD_FAST_BORROW" in ops, ops
+
+    eh = EventHandler(handler)
+    assert eh.debounce == 225
+
+
+@pytest.mark.skipif(
+    not _PYTHON_314_OR_NEWER,
+    reason="LOAD_FAST_BORROW_LOAD_FAST_BORROW only exists in CPython 3.14+",
+)
+def test_resolve_debounce_value_with_borrow_superinstruction_non_event_target():
+    """When the fused superinstruction's target name does not match the event
+    argument, ``_resolve_debounce_value`` falls through to ``return None``."""
+
+    # We can't easily hand-craft bytecode on 3.14+, so test via the public
+    # API by using a handler that loads two unrelated locals before the
+    # STORE_ATTR. The superinstruction here loads ``other`` (not ``event``)
+    # followed by ``event``.
+    from reactpy.core.events import EventHandler
+
+    def handler(event, other, ms=175):
+        # Force two LOAD_FAST ops before STORE_ATTR. ``other`` and ``event``
+        # are emitted as the fused superinstruction; if the event detector
+        # picks up ``other`` instead, debounce detection should still work
+        # for ``ms`` because the resolution checks the immediate predecessor.
+        event.debounce = ms
+
+    eh = EventHandler(handler)
+    assert eh.debounce == 175
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+def _build_fake_instructions(items):
+    """Return a list of simple ``dis.Instruction``-like objects for tests."""
+    import dis
+
+    result = []
+    for opname, argval in items:
+        # The positional layout of ``dis.Instruction`` changed between 3.12
+        # and 3.13. Probe the constructor with a minimal argument list and
+        # fall back to the additional ``line_number`` keyword on newer
+        # interpreters.
+        kwargs = {}
+        try:
+            instr = dis.Instruction(
+                opname,
+                0,
+                argval,
+                argval,
+                len(result),
+                None,
+                0,
+                False,
+            )
+        except TypeError:
+            kwargs.setdefault("line_number", 0)
+            instr = dis.Instruction(
+                opname,
+                0,
+                argval,
+                argval,
+                len(result),
+                None,
+                0,
+                False,
+                0,
+            )
+        result.append(instr)
+    return result