diff --git a/.github/workflows/pr_check.yml b/.github/workflows/pr_check.yml
index d8b061db3..164112974 100644
--- a/.github/workflows/pr_check.yml
+++ b/.github/workflows/pr_check.yml
@@ -22,10 +22,10 @@ jobs:
         with:
           python-version: '3.13'
 
-      - name: Install PlatformIO
+      - name: Install pioarduino
         run: |
           pip install wheel
-          pip install -U platformio
+          pip install -U "pioarduino==6.2.0"
 
       - name: Run unit tests
         run: |
diff --git a/.github/workflows/stable_release.yml b/.github/workflows/stable_release.yml
index c96af1acb..7d2c174ce 100644
--- a/.github/workflows/stable_release.yml
+++ b/.github/workflows/stable_release.yml
@@ -38,10 +38,10 @@ jobs:
           version=`grep -E '^#define EMSESP_APP_VERSION' ./src/emsesp_version.h | awk -F'"' '{print $2}'`
           echo "VERSION=$version" >> $GITHUB_OUTPUT
 
-      - name: Install PlatformIO
+      - name: Install pioarduino
         run: |
           python -m pip install --upgrade pip
-          pip install -U platformio
+          pip install -U "pioarduino==6.2.0"
           python -m pip install intelhex
 
       - name: Build webUI
diff --git a/.github/workflows/test_release.yml b/.github/workflows/test_release.yml
index cc46c6a2c..efc1b31d5 100644
--- a/.github/workflows/test_release.yml
+++ b/.github/workflows/test_release.yml
@@ -39,10 +39,10 @@ jobs:
           version=`grep -E '^#define EMSESP_APP_VERSION' ./src/emsesp_version.h | awk -F'"' '{print $2}'`
           echo "VERSION=$version" >> $GITHUB_OUTPUT
 
-      - name: Install PlatformIO
+      - name: Install pioarduino
         run: |
           python -m pip install --upgrade pip
-          pip install -U platformio
+          pip install -U "pioarduino==6.2.0"
           python -m pip install intelhex
 
       - name: Build webUI
diff --git a/CHANGELOG_LATEST.md b/CHANGELOG_LATEST.md
index d6faa85c1..e2caf3112 100644
--- a/CHANGELOG_LATEST.md
+++ b/CHANGELOG_LATEST.md
@@ -74,5 +74,5 @@ This release is based on the latest Espressif/Arduino core version 3. It brings
 - failed versions.json fetches back off from 5 up to 160 minutes instead of retrying every 5 minutes, as each attempt blocks the main loop for as long as the DNS, connect and read timeouts allow
 - optimized the LED library to support WS2812B V5 and the newer V6 RGB LEDs
 - hold Tx while a K30RF/KM200 gateway is syncing [#3094](https://github.com/emsesp/EMS-ESP32/issues/3094)
-- Tasmota platform 2026.05.50 (Arduino 3.3.8 / IDF 5.5.4) to 2026.09.50 (Arduino 3.3.12 / IDF 5.5.5)
+- Tasmota platform 2026.05.50 (Arduino 3.3.8 / IDF 5.5.4) to 2026.09.50 (Arduino 3.3.12 / IDF 5.5.5). Building that platform needs PlatformIO Core ≥6.2.0; install `pioarduino==6.2.0` (official `platformio` is still 6.1.19). See CONTRIBUTING.md
 - CI dev-release firmware jobs run in parallel (webUI, firmware targets, standalone) instead of one serial job
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 04d99e530..41ab1ee29 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -10,6 +10,40 @@ Everybody is welcome and invited to contribute to the EMS-ESP Project by:
 
 This document describes rules that are in effect for this repository, meant for handling issues by contributors in the issue tracker and PRs.
 
+## Building the firmware
+
+Arduino/IDF 3.3.12 (Tasmota platform `2026.09.50` in `platformio.ini`) needs **PlatformIO Core ≥6.2.0**. The official `platformio` package on PyPI is still 6.1.19, so `pio upgrade` and `pip install -U platformio` stay on 6.1.19 and you get:
+
+`IncompatiblePlatform: Development platform 'espressif32' is not compatible with PlatformIO Core v6.1.19 and depends on PlatformIO Core >=6.2.0.`
+
+Install **pioarduino** 6.2.0 (drop-in Core fork). It provides the same `pio` / `platformio` commands.
+
+**VS Code / Cursor** (PlatformIO IDE uses `~/.platformio/penv`):
+
+Linux / macOS:
+
+```bash
+~/.platformio/penv/bin/pip install -U "pioarduino==6.2.0"
+~/.platformio/penv/bin/pio --version
+```
+
+Windows (PowerShell):
+
+```powershell
+& "$env:USERPROFILE\.platformio\penv\Scripts\pip.exe" install -U "pioarduino==6.2.0"
+& "$env:USERPROFILE\.platformio\penv\Scripts\pio.exe" --version
+```
+
+You should see `PlatformIO Core, version 6.2.0`. Reload the window (or restart the IDE), then build again.
+
+**CLI-only / CI:**
+
+```bash
+pip install -U "pioarduino==6.2.0"
+# or: uv pip install --system pioarduino==6.2.0
+platformio --version
+```
+
 ## Opening New Issues
 
 1. Opening an issue means that a problem exists in the code and should be addressed by the project contributors.
diff --git a/pio_local.ini_bak b/pio_local.ini_bak
new file mode 100644
index 000000000..54dbfc56f
--- /dev/null
+++ b/pio_local.ini_bak
@@ -0,0 +1,109 @@
+; example custom platformio ini file for EMS-ESP
+
+[common]
+; custom build flags to use in my_build_flags
+;  -DEMSESP_UART_DEBUG ; debugging UART
+;  -DEMSESP_DEBUG ; enables DEBUG to the log. Will generate a lot of extra traffic on Console and Syslog
+;  -DEMSESP_DEFAULT_BOARD_PROFILE=\"NODEMCU\" ; hard code the default board name
+;  -DEMSESP_DEBUG_SENSOR ; additional debug for the sensors
+;  -DCORE_DEBUG_LEVEL=5 ; verbose core level debugging 5=verbose, 4=debug, 3=info
+;  -DEMSESP_TEST ; enable the tests. EN language only
+;  -DEMSESP_DE_ONLY ; only DE translated entity names
+;  -DEMSESP_EN_ONLY ; only EN translated entity names
+;  -DEMSESP_PINGTEST ; send log message every 1/2 second
+
+; my_build_flags = -DEMSESP_TEST -DEMSESP_DEBUG
+; my_build_flags = -DEMSESP_DEBUG -DEMSESP_TEST -DEMSESP_PINGTEST
+; my_build_flags = -DEMSESP_DEBUG -DCORE_DEBUG_LEVEL=5
+; my_build_flags = -DEMSESP_EN_ONLY -DEMSESP_TEST -DCORE_DEBUG_LEVEL=5 -DARDUINO_USB_CDC_ON_BOOT=1
+; my_build_flags = -DEMSESP_EN_ONLY
+; my_build_flags = -DEMSESP_DEBUG
+; my_build_flags =
+;   -D EMSESP_GATEWAY_TX_HOLD ; hold Tx while a K30RF/KM200 gateway is syncing, see issue #3094
+;   -D EMSESP_TX_PRE_DELAY=1000 ; wait this many us before each Tx so we don't overlap the master's break, see issue #3094
+
+my_build_flags = 
+
+[platformio]
+default_envs = s_16M_P ; BBQKees E32V2
+; default_envs = s_16M_P_custom ; BBQKees E32V2 with custom Arduino/IDF libs
+; default_envs = recovery_s_16M_P ; recovery
+; default_envs = crashtest_s_16M_P ; crash test
+; default_envs = build-webUI ; build the web interface only
+; default_envs = s3_16M_P ; BBQKees S3
+; default_envs = s_4M ; BBQKees older S32, 4MB no psram
+; default_envs = s_16M ; BBQKees newer S32 V2, 16MB no psram
+; default_envs = c6 ; XIAO ESP32C
+; default_envs = debug
+
+; default_envs = core3
+; default_envs = core2
+
+[env]
+
+; uncomment if you want to upload the firmware via OTA (must have upload_protocol = custom)
+extra_scripts =
+ post:scripts/rename_fw.py ; renames the firmware .bin file
+ scripts/upload.py ; optionally upload the firmware via OTA (must have upload_protocol = custom)
+
+; set the username and password for the admin account (default password is admin)
+custom_username = admin
+custom_password = admin
+
+; ** upload settings **
+; for direct USB, which is the default you can set an optional port for example:
+; upload_port = /dev/ttyUSB0
+; upload_port = /dev/ttyACM0
+
+; CH340G bridge tops out here reliably; drop back to 460800 if uploads fail
+; upload_speed = 921600
+upload_speed = 2000000
+
+; for direct via HTTP (OTA) set:
+;  upload_protocol = custom
+;  custom_emsesp_ip = <ip address> or ems-esp.local
+
+upload_protocol = custom
+
+; custom_emsesp_ip = ems-esp.local ; E32V2.2 (test)
+; custom_emsesp_ip = 192.168.1.39 ; E32V2.2 (test)
+; custom_emsesp_ip = 192.168.1.75 ; E32V2.2 (test) v3.8.4
+
+custom_emsesp_ip = ems-espP.local ; E32V2.2 (prod)
+; custom_emsesp_ip = 10.10.10.202 ; E32V2.2 (prod)
+
+; custom_emsesp_ip = ems-esps32.local ; S32, 4MB no psramS32
+; custom_emsesp_ip = ems-espS3.local ; ems-espS3
+; custom_emsesp_ip = 10.10.10.175 ; Wemos Lolin S3
+
+; lib_deps =
+;   bblanchon/ArduinoJson @ 7.4.3
+;   ESP32Async/AsyncTCP @ 3.4.10
+;   ESP32Async/ESPAsyncWebServer @ 3.11.0
+;   https://github.com/mobizt/ReadyMail.git @ 0.4.0
+;   https://github.com/mobizt/ESP_SSLClient.git @ 3.1.3
+  ; https://github.com/emsesp/EMS-ESP-Modules.git @ 1.0.8
+;   ; file://${PROJECT_DIR}/../modules/EMS-ESP-Modules
+
+; ** debug settings **
+; to be used with an ESP32-S3 which has an onboard JTAG, connect the OTG USB port to the PC
+; if using an external JTAG board like the ESP-PROG set debug_tool = esp-prog, and use zadig to set the correct driver for the USB port
+; see https://docs.platformio.org/en/stable/projectconf/sections/env/options/debug/debug_init_break.html for settings
+; use with my_build_flags = -DEMSESP_EN_ONLY -DEMSESP_TEST -DCORE_DEBUG_LEVEL=5 -DARDUINO_USB_CDC_ON_BOOT=1
+[env:debug]
+board = esp32-s3-devkitc-1
+framework = arduino
+platform = espressif32@6.12.0 ; Arduino Core v2.0.17 / IDF v4.4.7
+board_build.partitions = partitions/esp32_partition_16M.csv
+board_upload.flash_size = 16MB
+board_build.app_partition_name = app0
+board_build.filesystem = littlefs
+upload_protocol = esptool
+build_type = debug
+monitor_raw = no
+monitor_filters = colorize, esp32_exception_decoder
+debug_tool = esp-builtin
+debug_init_break = 
+upload_speed = 2000000
+monitor_speed = 115200
+extra_scripts =
diff --git a/platformio.ini b/platformio.ini
index 67c440f4a..f02f21474 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -6,6 +6,8 @@
 ;   For example: EMS-ESP-3_7_0-dev_31-esp32-16MB+.bin
 ;
 ; boards can be found in https://github.com/pioarduino/platform-espressif32/tree/main/boards
+; Tasmota platform 2026.09.50 needs PlatformIO Core >=6.2.0. Official platformio is still
+; 6.1.19 — install pioarduino instead (see CONTRIBUTING.md). `pio upgrade` will not get 6.2.0.
 
 [platformio]
 ; build all supported targets. Use pio_local.ini to override and build specific targets.
@@ -63,18 +65,11 @@ unbuild_flags =
 [espressif32_base_4M]
 framework = arduino
 board_build.partitions = partitions/esp32_partition_4M.csv
-board_upload.flash_size = 4MB
-board_build.app_partition_name = app0
-platform = https://github.com/tasmota/platform-espressif32/releases/download/2026.09.50/platform-espressif32.zip ; Arduino Core 3.3.12 based on IDF 5.5.5
 
 ; 16MB Flash variants
 [espressif32_base_16M]
 framework = arduino
 board_build.partitions = partitions/esp32_partition_16M.csv
-board_upload.flash_size = 16MB
-board_build.app_partition_name = app0
-platform = https://github.com/tasmota/platform-espressif32/releases/download/2026.09.50/platform-espressif32.zip ; Arduino Core 3.3.12 based on IDF 5.5.5
-platform_packages = framework-arduinoespressif32 @ https://github.com/emsesp/esp32-arduino-lib-builder/releases/download/0910-1604-5.5.5/framework-arduinoespressif32-v5.5.5-a63b839f.tar.xz
 build_flags =
   ${common.build_flags}
   -D EMSESP_HAS_RECOVERY ; installs and falls back to the recovery firmware in the factory partition
@@ -84,11 +79,10 @@ build_flags =
 [espressif32_base_32M]
 framework = arduino
 board_build.partitions = partitions/esp32_partition_32M.csv
-board_upload.flash_size = 32MB
-board_build.app_partition_name = app0
-platform = https://github.com/tasmota/platform-espressif32/releases/download/2026.09.50/platform-espressif32.zip ; Arduino Core 3.3.12 based on IDF 5.5.5
 
 [env]
+platform = https://github.com/tasmota/platform-espressif32/releases/download/2026.09.50/platform-espressif32.zip ; Arduino Core 3.3.12 based on IDF 5.5.5
+platform_packages = framework-arduinoespressif32 @ https://github.com/emsesp/esp32-arduino-lib-builder/releases/download/0910-1604-5.5.5/framework-arduinoespressif32-v5.5.5-a63b839f.tar.xz
 build_flags =
   ${common.build_flags}
 build_unflags =