From 6146e625dd6e466ab150e9030dad4d04b75334d3 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 8 Sep 2026 14:12:09 +0200
Subject: [PATCH] Gate RP2 gzip on the core version, log an inflate overrun,
 document the window aliasing

---
 esphome/components/esphome/ota/ota_esphome.cpp       |  4 +++-
 esphome/components/esphome/ota/ota_esphome_inflate.h |  4 +++-
 esphome/components/ota/ota_backend_arduino_rp2.h     | 12 ++++++++----
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/esphome/components/esphome/ota/ota_esphome.cpp b/esphome/components/esphome/ota/ota_esphome.cpp
index 68e048eeed..e724490b08 100644
--- a/esphome/components/esphome/ota/ota_esphome.cpp
+++ b/esphome/components/esphome/ota/ota_esphome.cpp
@@ -824,8 +824,10 @@ ota::OTAResponseTypes ESPHomeOTAComponent::inflate_flush_(InflateSession &sessio
   const size_t pending = produced - session.flushed;
   if (pending == 0)
     return ota::OTA_RESPONSE_OK;
-  if (pending > session.image_size - session.written)
+  if (pending > session.image_size - session.written) {
+    ESP_LOGW(TAG, "Inflate overrun");
     return ota::OTA_RESPONSE_ERROR_UNKNOWN;
+  }
   ota::OTAResponseTypes result = this->write_flash_(session.window + session.flushed, pending);
   if (result != ota::OTA_RESPONSE_OK)
     return result;
diff --git a/esphome/components/esphome/ota/ota_esphome_inflate.h b/esphome/components/esphome/ota/ota_esphome_inflate.h
index 197e20e42d..5d9f268f73 100644
--- a/esphome/components/esphome/ota/ota_esphome_inflate.h
+++ b/esphome/components/esphome/ota/ota_esphome_inflate.h
@@ -56,7 +56,9 @@ struct OtaInflateState {
 
 /* dict must cover the encoder's window (its largest back reference) */
 void ota_inflate_init(struct OtaInflateState *d, unsigned char *dict, unsigned int dict_len);
-/* Fills dest up to dest_limit (OK) or to the end of the stream (DONE) */
+/* Fills dest up to dest_limit (OK) or to the end of the stream (DONE). dest may
+   alias dict only if dest_limit - dest == dict_len and dest is reset to dict
+   exactly when a call returns OK, so the ring index and dest stay in lockstep */
 int ota_inflate(struct OtaInflateState *d);
 
 #ifdef __cplusplus
diff --git a/esphome/components/ota/ota_backend_arduino_rp2.h b/esphome/components/ota/ota_backend_arduino_rp2.h
index fd72685823..a9716c5d30 100644
--- a/esphome/components/ota/ota_backend_arduino_rp2.h
+++ b/esphome/components/ota/ota_backend_arduino_rp2.h
@@ -6,6 +6,8 @@
 #include "esphome/core/defines.h"
 #include "esphome/core/macros.h"
 
+#include <RP2040Version.h>
+
 namespace esphome::ota {
 
 class ArduinoRP2OTABackend final {
@@ -15,10 +17,12 @@ class ArduinoRP2OTABackend final {
   OTAResponseTypes write(uint8_t *data, size_t len);
   OTAResponseTypes end();
   void abort();
-  // The core's OTA stub inflates a staged gzip image at reboot (arduino-pico
-  // 2.4.0, RP2350 4.0.3; ESPHome pins 6.0.0). begin() only sees the gzip
-  // size; the inflated size is known when the stub reads the trailer.
-  static constexpr bool supports_compression() { return true; }
+  // The core's OTA stub inflates a staged gzip image at reboot, on every chip
+  // from 4.0.3 (ESPHome pins 6.0.0). begin() only sees the gzip size; the
+  // inflated size is known when the stub reads the trailer.
+  static constexpr bool supports_compression() {
+    return VERSION_CODE(ARDUINO_PICO_MAJOR, ARDUINO_PICO_MINOR, ARDUINO_PICO_REVISION) >= VERSION_CODE(4, 0, 3);
+  }
 
  private:
   bool md5_set_{false};