diff --git a/builder/frameworks/espidf.py b/builder/frameworks/espidf.py
index aee61611c..2983387a3 100644
--- a/builder/frameworks/espidf.py
+++ b/builder/frameworks/espidf.py
@@ -26,7 +26,6 @@
 import sys
 import shutil
 import os
-import pkg_resources
 import platform as sys_platform
 
 import click
@@ -1149,9 +1148,7 @@ def _get_installed_pip_packages(python_exe_path):
 
         # A special "esp-windows-curses" python package is required on Windows
         # for Menuconfig on IDF <5
-        if not IDF5 and "esp-windows-curses" not in {
-            pkg.key for pkg in pkg_resources.working_set
-        }:
+        if not IDF5 and "esp-windows-curses" not in installed_packages:
             env.Execute(
                 env.VerboseAction(
                     '"%s" -m pip install "file://%s/tools/kconfig_new/esp-windows-curses"'
diff --git a/builder/main.py b/builder/main.py
index 0374fe8b6..8c9e5dd42 100644
--- a/builder/main.py
+++ b/builder/main.py
@@ -211,7 +211,7 @@ def __fetch_fs_size(target, source, env):
 board = env.BoardConfig()
 mcu = board.get("build.mcu", "esp32")
 toolchain_arch = "xtensa-%s" % mcu
-filesystem = board.get("build.filesystem", "spiffs")
+filesystem = board.get("build.filesystem", "littlefs")
 if mcu in ("esp32c2", "esp32c3", "esp32c6", "esp32h2"):
     toolchain_arch = "riscv32-esp"
 
@@ -256,20 +256,8 @@ def __fetch_fs_size(target, source, env):
     ],
     ERASECMD='"$PYTHONEXE" "$OBJCOPY" $ERASEFLAGS erase_flash',
 
-    # mkspiffs package contains two different binaries for IDF and Arduino
-    MKFSTOOL="mk%s" % filesystem
-    + (
-        (
-            "_${PIOPLATFORM}_"
-            + (
-                "espidf"
-                if "espidf" in env.subst("$PIOFRAMEWORK")
-                else "${PIOFRAMEWORK}"
-            )
-        )
-        if filesystem == "spiffs"
-        else ""
-    ),
+    MKFSTOOL="mk%s" % filesystem,
+
     # Legacy `ESP32_SPIFFS_IMAGE_NAME` is used as the second fallback value for
     # backward compatibility
     ESP32_FS_IMAGE_NAME=env.get(
@@ -310,7 +298,7 @@ def __fetch_fs_size(target, source, env):
                             "-b",
                             "$FS_BLOCK",
                         ]
-                        if filesystem in ("spiffs", "littlefs")
+                        if filesystem in ("littlefs")
                         else []
                     )
                     + ["$TARGET"]
@@ -363,9 +351,6 @@ def __fetch_fs_size(target, source, env):
         env.VerboseAction(
             lambda source, target, env: _update_max_upload_size(env),
             "Retrieving maximum program size $SOURCES"))
-# remove after PIO Core 3.6 release
-elif set(["checkprogsize", "upload"]) & set(COMMAND_LINE_TARGETS):
-    _update_max_upload_size(env)
 
 #
 # Target: Print binary size
diff --git a/platform.json b/platform.json
index eed7f76d8..4a4fb3de5 100644
--- a/platform.json
+++ b/platform.json
@@ -112,12 +112,6 @@
       "owner": "platformio",
       "version": "~2.1100.0"
     },
-    "tool-mkspiffs": {
-      "type": "uploader",
-      "optional": true,
-      "owner": "platformio",
-      "version": "~2.230.0"
-    },
     "tool-mklittlefs": {
       "type": "uploader",
       "owner": "tasmota",
diff --git a/platform.py b/platform.py
index b22a1a2a1..7462bac2c 100644
--- a/platform.py
+++ b/platform.py
@@ -51,8 +51,6 @@ def configure_default_packages(self, variables, targets):
                 self.packages["tool-mklittlefs"]["optional"] = False
             elif filesystem == "fatfs":
                 self.packages["tool-mkfatfs"]["optional"] = False
-            else:
-                self.packages["tool-mkspiffs"]["optional"] = False
         if variables.get("upload_protocol"):
             self.packages["tool-openocd-esp32"]["optional"] = False
         if os.path.isdir("ulp"):