diff --git a/esphome/components/bluetooth_connection/__init__.py b/esphome/components/bluetooth_connection/__init__.py
index 9dd6ac7099..25aea88812 100644
--- a/esphome/components/bluetooth_connection/__init__.py
+++ b/esphome/components/bluetooth_connection/__init__.py
@@ -117,31 +117,31 @@ _PLATFORM_BACKENDS: dict[str, _PlatformBackend] = {
 GATT_CLIENT_PLATFORMS = list(_PLATFORM_BACKENDS)
 
 
-def _backend_entry() -> _PlatformBackend:
-    if (entry := _PLATFORM_BACKENDS.get(CORE.target_platform)) is None:
-        raise cv.Invalid(
-            f"no GATT client backend is registered for {CORE.target_platform}"
-        )
+def _backend_entry(platform: str | None = None) -> _PlatformBackend:
+    key = platform if platform is not None else CORE.target_platform
+    if (entry := _PLATFORM_BACKENDS.get(key)) is None:
+        raise cv.Invalid(f"no GATT client backend is registered for {key}")
     return entry
 
 
-def gatt_client_schema() -> cv.Schema:
+def gatt_client_schema(platform: str | None = None) -> cv.Schema:
     """Schema fragment for one GATT backend instance: its generated id plus
-    the platform-stack reference new_gatt_backend() resolves. Platform
-    dispatch happens at call time, so call this from inside a validator or a
-    per-platform schema builder, never at module import.
+    the platform-stack reference new_gatt_backend() resolves.
+
+    Defaults to the platform being validated; pass `platform` explicitly when
+    building a schema outside validation (the language-schema dumper calls
+    per-platform builders under arbitrary CORE platforms).
     """
-    entry = _backend_entry()
+    entry = _backend_entry(platform)
     return entry.schema_fragment().extend(
         {cv.GenerateID(CONF_BACKEND_ID): cv.declare_id(entry.backend_class)}
     )
 
 
-def hub_connection_schema() -> cv.Schema:
+def hub_connection_schema(platform: str | None = None) -> cv.Schema:
     """Per-slot schema for the proxy's connection wrappers: the wrapper id on
-    top of the backend fragment. Same call-time constraint as
-    gatt_client_schema()."""
-    return gatt_client_schema().extend(
+    top of the backend fragment. Same platform rules as gatt_client_schema()."""
+    return gatt_client_schema(platform).extend(
         {cv.GenerateID(): cv.declare_id(HubBluetoothConnection)}
     )
 
diff --git a/esphome/components/bluetooth_proxy/__init__.py b/esphome/components/bluetooth_proxy/__init__.py
index b30ea275c4..8f8a0da1bc 100644
--- a/esphome/components/bluetooth_proxy/__init__.py
+++ b/esphome/components/bluetooth_proxy/__init__.py
@@ -4,7 +4,13 @@ import logging
 import esphome.codegen as cg
 from esphome.components import ble_device_base, bluetooth_connection
 import esphome.config_validation as cv
-from esphome.const import CONF_ACTIVE, CONF_ID, PLATFORM_LN882X, PLATFORM_RP2
+from esphome.const import (
+    CONF_ACTIVE,
+    CONF_ID,
+    PLATFORM_ESP32,
+    PLATFORM_LN882X,
+    PLATFORM_RP2,
+)
 from esphome.core import CORE
 from esphome.schema_extractors import SCHEMA_EXTRACT, schema_extractor
 from esphome.types import ConfigType
@@ -84,7 +90,7 @@ def _esp32_config_schema() -> cv.All:
             f"update _IDF_MAX_CONNECTIONS in bluetooth_proxy/__init__.py"
         )
 
-    CONNECTION_SCHEMA = bluetooth_connection.hub_connection_schema()
+    CONNECTION_SCHEMA = bluetooth_connection.hub_connection_schema(PLATFORM_ESP32)
 
     def validate_connections(config):
         if CONF_CONNECTIONS in config:
@@ -147,7 +153,7 @@ def _rp2_config_schema() -> cv.All:
     """Full proxy on the rp2 BLE hub: active connections through the BTstack
     GATT client backend in bluetooth_connection. The slot limit comes from the
     prebuilt BTstack library (one connection today); the code is built for N."""
-    connection_schema = bluetooth_connection.hub_connection_schema()
+    connection_schema = bluetooth_connection.hub_connection_schema(PLATFORM_RP2)
 
     def populate_connections(config: ConfigType) -> ConfigType:
         # One wrapper + backend pair per slot, declared during validation so
diff --git a/tests/component_tests/bluetooth_proxy/test_outer_schema_mirror.py b/tests/component_tests/bluetooth_proxy/test_outer_schema_mirror.py
index 0054b2226c..765b2e48d4 100644
--- a/tests/component_tests/bluetooth_proxy/test_outer_schema_mirror.py
+++ b/tests/component_tests/bluetooth_proxy/test_outer_schema_mirror.py
@@ -14,15 +14,11 @@ import voluptuous as vol
 
 from esphome import config_validation as cv
 from esphome.components.bluetooth_proxy import CONFIG_SCHEMA, _esp32_config_schema
-from esphome.const import KEY_CORE, KEY_TARGET_PLATFORM, PLATFORM_ESP32
-from esphome.core import CORE
 
 
 def _esp32_schema_keys() -> dict[str, object]:
-    # The builder resolves the backend schema through the platform-dispatched
-    # bluetooth_connection.gatt_client_schema(), so the platform must be set
-    # (conftest's autouse reset restores CORE after each test).
-    CORE.data.setdefault(KEY_CORE, {})[KEY_TARGET_PLATFORM] = PLATFORM_ESP32
+    # The builder names its platform explicitly, so no CORE state is needed
+    # (this also mirrors how the language-schema dumper calls it).
     return _keys(_schema_of(_esp32_config_schema()))