diff --git a/esphome/components/zigbee_proxy/__init__.py b/esphome/components/zigbee_proxy/__init__.py
index ba421e3221..6f73f5544d 100644
--- a/esphome/components/zigbee_proxy/__init__.py
+++ b/esphome/components/zigbee_proxy/__init__.py
@@ -1,7 +1,7 @@
 import esphome.codegen as cg
 from esphome.components import serial_proxy
 import esphome.config_validation as cv
-from esphome.const import CONF_BUFFER_SIZE, CONF_ID, CONF_POWER_SAVE_MODE, CONF_WIFI
+from esphome.const import CONF_ID, CONF_POWER_SAVE_MODE, CONF_WIFI
 import esphome.final_validate as fv
 from esphome.types import ConfigType
 
@@ -31,11 +31,6 @@ CONFIG_SCHEMA = cv.Schema(
     {
         cv.GenerateID(): cv.declare_id(ZigbeeProxy),
         cv.Required(CONF_SERIAL_PROXY_ID): cv.use_id(serial_proxy.SerialProxy),
-        cv.Optional(CONF_BUFFER_SIZE): cv.SplitDefault(
-            cv.int_range(min=256, max=2048),
-            esp8266=512,
-            default=1024,
-        ),
     }
 ).extend(cv.COMPONENT_SCHEMA)
 
@@ -50,7 +45,3 @@ async def to_code(config: ConfigType) -> None:
     cg.add_define("USE_ZIGBEE_PROXY")
     # Compiles the tap interface into serial_proxy; without it the port is a plain byte pipe
     cg.add_define("USE_SERIAL_PROXY_TAP")
-
-    # Set buffer size via define for compile-time allocation
-    if (buffer_size := config.get(CONF_BUFFER_SIZE)) is not None:
-        cg.add_define("ZIGBEE_PROXY_BUFFER_SIZE", buffer_size)
diff --git a/esphome/components/zigbee_proxy/ash_protocol.h b/esphome/components/zigbee_proxy/ash_protocol.h
index c3d513c338..0891b439f8 100644
--- a/esphome/components/zigbee_proxy/ash_protocol.h
+++ b/esphome/components/zigbee_proxy/ash_protocol.h
@@ -1,7 +1,5 @@
 #pragma once
 
-#include "esphome/core/defines.h"
-
 #include <cstddef>
 #include <cstdint>
 
@@ -31,16 +29,12 @@ inline bool ash_is_reserved(uint8_t byte) {
 // 0x7E framing, so Spinel frames systematically fail this check.
 uint16_t ash_crc16(const uint8_t *data, size_t length, uint16_t init = 0xFFFF);
 
-// Buffer size configuration
-#ifdef ZIGBEE_PROXY_BUFFER_SIZE
-static constexpr size_t MAX_ASH_FRAME_SIZE = ZIGBEE_PROXY_BUFFER_SIZE;
-#else
-#ifdef USE_ESP8266
-static constexpr size_t MAX_ASH_FRAME_SIZE = 512;  // Limited RAM on ESP8266
-#else
-static constexpr size_t MAX_ASH_FRAME_SIZE = 1024;  // Full buffer on ESP32/RP2040
-#endif
-#endif
+// ASH bounds a frame's Data Field at 128 bytes, so the largest body a scanner has to
+// hold is that field plus the control byte and the two CRC bytes ahead of the closing
+// delimiter. Byte stuffing happens on the wire only and is undone as bytes arrive, so it
+// does not enlarge this.
+static constexpr size_t ASH_MAX_DATA_FIELD_SIZE = 128;
+static constexpr size_t MAX_ASH_FRAME_SIZE = 1 + ASH_MAX_DATA_FIELD_SIZE + 2;
 
 // Protocol limits
 static constexpr uint8_t ASH_MAX_SEQUENCE = 7;    // 3-bit sequence number (0-7)
diff --git a/esphome/components/zigbee_proxy/zigbee_proxy.cpp b/esphome/components/zigbee_proxy/zigbee_proxy.cpp
index 4f9260a684..c5cf71786e 100644
--- a/esphome/components/zigbee_proxy/zigbee_proxy.cpp
+++ b/esphome/components/zigbee_proxy/zigbee_proxy.cpp
@@ -10,13 +10,7 @@ static const char *const TAG = "zigbee_proxy";
 
 void ZigbeeProxy::setup() { this->parent_->set_tap(this); }
 
-void ZigbeeProxy::dump_config() {
-  ESP_LOGCONFIG(TAG,
-                "Zigbee Proxy:\n"
-                "  Port: %s\n"
-                "  Buffer Size: %u bytes",
-                this->parent_->get_name(), MAX_ASH_FRAME_SIZE);
-}
+void ZigbeeProxy::dump_config() { ESP_LOGCONFIG(TAG, "Zigbee Proxy:\n  Port: %s", this->parent_->get_name()); }
 
 void ZigbeeProxy::on_device_rx(const uint8_t *data, size_t len) {
   for (size_t i = 0; i < len; i++) {
diff --git a/tests/components/zigbee_proxy/test.esp32-idf.yaml b/tests/components/zigbee_proxy/test.esp32-idf.yaml
index 6c4c86a9a4..4c27e96efd 100644
--- a/tests/components/zigbee_proxy/test.esp32-idf.yaml
+++ b/tests/components/zigbee_proxy/test.esp32-idf.yaml
@@ -9,7 +9,3 @@ esp32:
 
 zigbee_proxy:
   serial_proxy_id: zigbee_serial
-  buffer_size: 1024
-  initial_timeout: 1600
-  min_timeout: 400
-  max_timeout: 3200
diff --git a/tests/components/zigbee_proxy/test.esp8266-ard.yaml b/tests/components/zigbee_proxy/test.esp8266-ard.yaml
index 9c970b37d8..f08b9eee94 100644
--- a/tests/components/zigbee_proxy/test.esp8266-ard.yaml
+++ b/tests/components/zigbee_proxy/test.esp8266-ard.yaml
@@ -9,4 +9,3 @@ esp8266:
 
 zigbee_proxy:
   serial_proxy_id: zigbee_serial
-  buffer_size: 512