diff --git a/docs/adr/0003-pioarduino-idf55.md b/docs/adr/0003-pioarduino-idf55.md
index cb06ae1..96fbc8b 100644
--- a/docs/adr/0003-pioarduino-idf55.md
+++ b/docs/adr/0003-pioarduino-idf55.md
@@ -13,8 +13,8 @@ We moved every firmware env from `espressif32 @ 6.13.0` (Arduino 2.0.17 on ESP-I
 - **Firmware size.** The ESP32 image grows from 1,382,640 bytes (v3.0.14) to 1,555,472 at `CORE_DEBUG_LEVEL=2`, leaving 17 KB of the 1.5 MB OTA slot. At level 3 it doesn't fit, so release envs build at level 2 (warnings and errors) and debug envs stay at 3. PlatformIO's "Flash:" figure counts ELF sections, not the image, and reads about 45 KB low, so CI checks `firmware.bin` against the app partition and fails under 8 KB free (`.github/size_check.py`).
 - **No more C3 builds.** Its image grows by 214 KB to 1,651,216 bytes, 76.5 KB over the OTA slot even at level 2. C3 boards stay on the 3.0.x releases.
 
-  > **Amended in 4.0.0.** The C3 builds again. Without the old API (ports 8080 and 8081), its image is 1,498,512 bytes at level 2 and leaves 72.6 KB of the OTA slot.
+  > **Amended by [ADR 0006](0006-two-security-modes-eleven-http-routes.md) (4.0.0).** The C3 builds again. Without the old API (ports 8080 and 8081), its image is 1,498,512 bytes at level 2 and leaves 72.6 KB of the OTA slot. It runs on chip revision v0.3 or later only: the framework's C3 libraries are built with `CONFIG_ESP32C3_REV_MIN_3`. Its default radio pins moved off GPIO 12-17, which hold the SPI flash.
 - **Ethernet PHY ids are ours.** Arduino 3.x renumbered `eth_phy_type_t` (`ETH_PHY_GENERIC` is 0). NVS, backups and the web UI keep the Arduino 2.x numbers as `eth_phy_id_t` (`src/EthPhy.h`), translated by name when Ethernet starts. Never cast a stored id to the framework enum.
-- **Ethernet only on the original ESP32.** Arduino 3.x has the RMII MAC API only where `CONFIG_ETH_USE_ESP32_EMAC` is set. S3 and C6 build without Ethernet.
+- **Ethernet only on the original ESP32.** Arduino 3.x has the RMII MAC API only where `CONFIG_ETH_USE_ESP32_EMAC` is set. S3, C3 and C6 build without Ethernet.
 - **Updates roll back until proven.** We override the core's `verifyRollbackLater()` hook to return true, and `loop()` marks the new firmware valid once it has run 60 s and the network is up. A reset before then boots the previous firmware. The LittleFS image an update wrote stays, so the old firmware runs with the new web UI.
 - **Tooling.** pioarduino needs its own Core fork (`pip install pioarduino`, the pioarduino IDE extension in VS Code), which it installs into `~/.platformio/penv` in place of PlatformIO Core.
diff --git a/src/Transceiver.cpp b/src/Transceiver.cpp
index 9f10d2b..48ca4cf 100644
--- a/src/Transceiver.cpp
+++ b/src/Transceiver.cpp
@@ -474,12 +474,14 @@ void transceiver_config_t::load() {
         this->CSNPin = 34;
         break;
       case esp_chip_model_t::CHIP_ESP32C3:
-        this->TXPin = 13;
-        this->RXPin = 12;
-        this->MOSIPin = 16;
-        this->MISOPin = 17;
-        this->SCKPin = 15;
-        this->CSNPin = 14;
+        // The framework's default SPI pins (variants/esp32c3).  12-17 hold the
+        // SPI flash, and 2, 8 and 9 are strapping pins.
+        this->TXPin = 10;
+        this->RXPin = 3;
+        this->MOSIPin = 6;
+        this->MISOPin = 5;
+        this->SCKPin = 4;
+        this->CSNPin = 7;
         break;
 #ifdef CONFIG_IDF_TARGET_ESP32C6
       case esp_chip_model_t::CHIP_ESP32C6: