diff --git a/AGENTS.md b/AGENTS.md
index f37bbc7..60a44a1 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -52,27 +52,27 @@ LVGL timers).
   `examples/esp-idf/` — notably `08_lvgl_demo_v9` (display), `06_I2SCodec` (audio),
   `04_wifistation` (Wi-Fi via ESP-Hosted). When wiring a new peripheral, check the
   official example first; do not guess pin mappings.
-- ⚠️ **Unverified scaffold**: the BSP API calls in `desklock_main.c` and the
-  `sdkconfig.defaults` values were written before the first successful build. Validate
-  against the official examples on first bring-up, then delete this warning.
-
 ```bash
-# One-time: install ESP-IDF (not yet installed on tower-of-joy)
-git clone -b v5.5 --recursive https://github.com/espressif/esp-idf.git ~/esp-idf
-~/esp-idf/install.sh esp32p4
-
-# Every shell:
+# ESP-IDF v5.5 is installed at ~/esp-idf. Every shell:
 source ~/esp-idf/export.sh
 
-# Build / flash / monitor (device is on USB-C; check `ls /dev/ttyACM*`)
+# Build / flash (device on USB-C at /dev/ttyACM0, CH343 bridge)
 cd firmware
-idf.py set-target esp32p4        # once
 idf.py build
-idf.py -p /dev/ttyACM0 flash monitor   # Ctrl+] exits monitor
+sg dialout -c "bash -lc 'source ~/esp-idf/export.sh >/dev/null && idf.py -p /dev/ttyACM0 flash'"
 ```
 
-Flashing requires the `dialout` group (or run with sudo once and fix the group). If the
-device doesn't enumerate, hold BOOT while pressing RESET to enter download mode.
+- `sg dialout -c '…'` is needed because the login session predates the user's dialout
+  membership; a plain `idf.py flash` works after any re-login.
+- **PSRAM must run at 200 MHz** or the 800×800 MIPI-DSI framebuffer underruns
+  (`lcd.dsi.dpi: can't fetch data…` spam, LVGL lock never frees, task watchdog).
+  `CONFIG_SPIRAM_SPEED_200M` only takes effect together with
+  `CONFIG_IDF_EXPERIMENTAL_FEATURES=y` — otherwise it is **silently dropped** and you
+  get 20 MHz. `sdkconfig.defaults` mirrors the official `08_lvgl_demo_v9` config.
+- Non-interactive boot-log capture (avoid `idf.py monitor`, it's interactive): open
+  `/dev/ttyACM0` at 115200 with pyserial, pulse RTS to reset, read ~8 s. Verified boot
+  is ~1.6 s from reset to `desklock: DeskLock up`.
+- If the device doesn't enumerate, hold BOOT while pressing RESET for download mode.
 
 ## Gateway (`gateway/`)
 
diff --git a/CLAUDE.md b/CLAUDE.md
index 781a3d5..5717899 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -28,11 +28,14 @@ make lint typecheck
 
 ## Gotchas
 
-- **ESP-IDF is not yet installed on this machine** — install instructions in AGENTS.md.
-- The firmware scaffold has never been built; treat BSP calls and sdkconfig as
-  provisional until first successful `idf.py build` (see warning in AGENTS.md).
-- The device flashes over USB-C on this server, but it doesn't currently enumerate
-  (`/dev/ttyACM*` empty) and this user lacks the `dialout` group — resolve both before
-  attempting to flash.
+- ESP-IDF v5.5 lives at `~/esp-idf` (`source ~/esp-idf/export.sh`). Flash via
+  `sg dialout -c …` (see AGENTS.md) — the login session predates dialout membership.
+- **PSRAM 200 MHz requires `CONFIG_IDF_EXPERIMENTAL_FEATURES=y`** — without it the
+  option silently degrades to 20 MHz and the DSI display underruns into a watchdog
+  loop. Details in AGENTS.md.
 - Gateway speech deps are optional extras; `make setup` alone runs the app and tests
-  without GPU/ML packages.
+  without GPU/ML packages. `make setup` uses `python3.12` (system python3 is 3.8).
+- Tatlock replies open with a `<think>` block — always strip via
+  `tatlock.strip_reasoning()` before TTS or display.
+- Low power is a prime user requirement: see "Power management" in
+  docs/architecture.md before touching the face/render loop.
diff --git a/docs/architecture.md b/docs/architecture.md
index 8c19942..cd3b561 100644
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -164,6 +164,54 @@ WebSocket disconnected → `error` (quiet, persistent); otherwise `idle`.
   The `rage` frames additionally need `╯ ︵ ┻ ━ ┬ ─ ノ ° □ º` in the subset.
 - The sim's text glow (`text-shadow`) is browser flair — the device renders flat glyphs.
 
+## Power management (prime concern)
+
+User requirement: the device idles on a wall 95%+ of its life — low power when nothing
+is happening is a first-class design goal, not a phase-5 nicety. The face state machine
+is therefore built around a **power ladder** from day one:
+
+| Power state | Backlight | Rendering | CPU | Entered when |
+|-------------|-----------|-----------|-----|--------------|
+| `active` | 100% | full animation | full clock | conversation in progress (listening→speaking) |
+| `ambient` | ~35% | idle face, sparse rain | DFS enabled | idle, but activity in the last few minutes |
+| `dormant` | off (or ≤5%) | **no redraws** — render loop parked | min clock via DFS | no voice/touch for N min (default 10) |
+| `night` | off, panel sleep | none | min clock | schedule or "goodnight" command |
+
+Levers, in order of impact:
+
+1. **Backlight** — this is an IPS LCD: black pixels still burn backlight (unlike OLED),
+   so brightness is the dominant lever. `bsp_display_brightness_set()` drives it.
+2. **Render idleness** — rain off and animations parked means LVGL stops producing
+   frames, which is what lets DFS actually reach its floor.
+3. **DFS / power management** (`CONFIG_PM_ENABLE`) — automatic frequency scaling when
+   tasks are quiet. Note the MIPI-DSI constraint below.
+4. **Radio** — the C6 runs Wi-Fi modem power-save; the gateway WebSocket widens its
+   ping interval when the device reports `dormant`.
+
+Wake triggers (any → `ambient`/`active`): wake word (phase 5), touch (from phase 2),
+local VAD "someone is speaking" pre-warm, a gateway-initiated event (butler wants to
+say something), scheduled morning end of `night`.
+
+**Hard edges — what limits how low we can go:**
+
+- **The hands-free promise sets the power floor.** Wake word requires mics + the AFE
+  pipeline running continuously; deep sleep is permanently off the table while the
+  device promises to answer its name. The floor is "CPU lightly loaded at min clock,
+  radios in power-save, backlight off."
+- **DSI needs clocks while the panel is active** — the deepest CPU savings only unlock
+  in `dormant`/`night` when the panel stops being refreshed (panel sleep / blank).
+- **Wake latency budget: ≤ ~300 ms** from trigger to visible face (backlight ramp +
+  first render). Anything slower reads as "it's off," which kills the butler illusion.
+- **Touch stays powered** in all states except possibly `night` — its idle draw is
+  negligible and tap-to-wake must always work.
+- **No invented numbers**: actual draw gets measured with a USB power meter at each
+  phase; working target is `dormant` ≤ ⅓ of `active`. (Always-on device: every watt
+  saved ≈ 9 kWh/year.)
+
+Implementation order: backlight dimming + `dormant` timeout + touch wake land in
+**phase 2** with the face state machine (timeout-driven); voice-linked triggers upgrade
+it in phase 5.
+
 ## Latency budget & streaming
 
 Measured/known numbers that shape the design (Tatlock figures per tatlock CLAUDE.md,
diff --git a/firmware/main/desklock_main.c b/firmware/main/desklock_main.c
index c266dd2..c222dee 100644
--- a/firmware/main/desklock_main.c
+++ b/firmware/main/desklock_main.c
@@ -6,25 +6,55 @@
  *   2. Wi-Fi up via ESP32-C6 (ESP-Hosted over SDIO)
  *   3. WebSocket connection to the DeskLock gateway
  *   4. Face state machine: idle / listening / thinking / speaking
+ *
+ * Current stage: bring-up — display + a placeholder face.
  */
 
 #include "esp_log.h"
 #include "bsp/esp-bsp.h"
+#include "lvgl.h"
 
 static const char *TAG = "desklock";
 
+static void show_placeholder_face(void)
+{
+    bsp_display_lock(0);
+
+    lv_obj_t *scr = lv_screen_active();
+    lv_obj_set_style_bg_color(scr, lv_color_black(), 0);
+
+    lv_obj_t *eyes = lv_label_create(scr);
+    lv_label_set_text(eyes, "-   -");
+    lv_obj_set_style_text_color(eyes, lv_color_hex(0xADFFC8), 0);
+    lv_obj_set_style_text_font(eyes, &lv_font_montserrat_48, 0);
+    lv_obj_align(eyes, LV_ALIGN_CENTER, 0, -80);
+
+    lv_obj_t *mouth = lv_label_create(scr);
+    lv_label_set_text(mouth, "\\_/");
+    lv_obj_set_style_text_color(mouth, lv_color_hex(0xADFFC8), 0);
+    lv_obj_set_style_text_font(mouth, &lv_font_montserrat_48, 0);
+    lv_obj_align(mouth, LV_ALIGN_CENTER, 0, 40);
+
+    lv_obj_t *tag = lv_label_create(scr);
+    lv_label_set_text(tag, "DESKLOCK");
+    lv_obj_set_style_text_color(tag, lv_color_hex(0x2F7A4B), 0);
+    lv_obj_align(tag, LV_ALIGN_CENTER, 0, 160);
+
+    bsp_display_unlock();
+}
+
 void app_main(void)
 {
     ESP_LOGI(TAG, "DeskLock starting");
 
     bsp_display_start();
     bsp_display_backlight_on();
+    show_placeholder_face();
 
-    /* TODO(bring-up): render placeholder face via LVGL
-     * TODO(bring-up): Wi-Fi via ESP-Hosted (C6)
-     * TODO(voice): mic capture (ES7210) -> WebSocket upstream
-     * TODO(voice): gateway PCM downstream -> ES8311 playback
+    ESP_LOGI(TAG, "DeskLock up (placeholder face)");
+
+    /* TODO(face): full LVGL face state machine per docs/architecture.md
+     * TODO(net): Wi-Fi via ESP-Hosted (C6), WebSocket to gateway
+     * TODO(voice): ES7210 capture upstream, ES8311 playback downstream
      */
-
-    ESP_LOGI(TAG, "DeskLock up (display only)");
 }
diff --git a/firmware/sdkconfig.defaults b/firmware/sdkconfig.defaults
index f58aa73..67a23b8 100644
--- a/firmware/sdkconfig.defaults
+++ b/firmware/sdkconfig.defaults
@@ -5,10 +5,19 @@ CONFIG_IDF_TARGET="esp32p4"
 CONFIG_ESPTOOLPY_FLASHSIZE_32MB=y
 CONFIG_PARTITION_TABLE_SINGLE_APP_LARGE=y
 
-# 32 MB in-package PSRAM (hex mode) — LVGL frame buffers live here
+# PSRAM at 200 MHz — REQUIRED for the 800x800 MIPI-DSI framebuffer.
+# 200 MHz is gated behind IDF_EXPERIMENTAL_FEATURES; without it the build
+# silently falls back to 20 MHz and the DSI underruns (mirrors the official
+# 08_lvgl_demo_v9 example config).
 CONFIG_SPIRAM=y
-CONFIG_SPIRAM_MODE_HEX=y
+CONFIG_IDF_EXPERIMENTAL_FEATURES=y
 CONFIG_SPIRAM_SPEED_200M=y
+CONFIG_SPIRAM_XIP_FROM_PSRAM=y
+CONFIG_CACHE_L2_CACHE_256KB=y
+CONFIG_CACHE_L2_CACHE_LINE_128B=y
 
 CONFIG_COMPILER_OPTIMIZATION_PERF=y
 CONFIG_FREERTOS_HZ=1000
+
+# LVGL font for the bring-up placeholder face
+CONFIG_LV_FONT_MONTSERRAT_48=y