Here's what each does:

target.h — declares meck_audio_route_amp() and meck_audio_codec_init() in the bridge (54-55), guarded by HAS_ES8311_AUDIO, ready for the alarm/voice paths to reuse later.
target.cpp — includes ES8311.h (6) and defines both helpers where board and the codec driver are visible: route+amp (100-102), and the once-only es8311_init_44100_16bit() (108-110).
Audiobookplayerscreen.h — forward-declares both (54-55); ensureI2SInit() now does route+amp and the 5-arg setPinout with MCLK on MAX (268-270); and meck_audio_codec_init() runs right after connecttoFS (1142). The Pro path is untouched.

examples/companion_radio/ui-new/Audiobookplayerscreen.h

@@ -48,6 +48,13 @@
 // Forward declarations
 class UITask;
 
+#ifdef HAS_ES8311_AUDIO
+// Defined in target.cpp (where the board object + ES8311 driver are visible).
+// Forward-declared here so this UI header doesn't need the heavy target.h.
+void meck_audio_route_amp();
+void meck_audio_codec_init();
+#endif
+
 // ============================================================================
 // Configuration
 // ============================================================================
@@ -253,10 +260,20 @@ private:
 
   void ensureI2SInit() {
     if (!_i2sInitialized && _audio) {
+#ifdef HAS_ES8311_AUDIO
+      // MAX: route to the ES8311 + enable the speaker amp, then configure I2S
+      // WITH MCLK (the ES8311 is clock slave and needs MCLK on BOARD_I2S_MCLK).
+      // The codec registers are initialised after connecttoFS starts the clocks
+      // (see meck_audio_codec_init() in startPlayback).
+      meck_audio_route_amp();
+      bool ok = _audio->setPinout(BOARD_I2S_BCLK, BOARD_I2S_LRC, BOARD_I2S_DOUT,
+                                  I2S_PIN_NO_CHANGE, BOARD_I2S_MCLK);
+#else
       bool ok = _audio->setPinout(BOARD_I2S_BCLK, BOARD_I2S_LRC, BOARD_I2S_DOUT, 0);
       if (!ok) {
         ok = _audio->setPinout(BOARD_I2S_BCLK, BOARD_I2S_LRC, BOARD_I2S_DOUT);
       }
+#endif
       if (!ok) Serial.println("AB: setPinout FAILED");
       _i2sInitialized = true;
     }
@@ -1118,6 +1135,12 @@ private:
 
     // Connect to file — library parses headers asynchronously via loop()
     _audio->connecttoFS(SD, fullPath.c_str());
+#ifdef HAS_ES8311_AUDIO
+    // MAX: I2S clocks are now running, so initialise the ES8311 codec (once;
+    // idempotent). Without this, audiobook/music output is silent until a
+    // notification tone happens to bring the codec up.
+    meck_audio_codec_init();
+#endif
     _audio->setVolume(_volume);
 
     // DON'T seek immediately — the library hasn't parsed headers yet.

variants/lilygo_tdeck_max/target.cpp

@@ -2,6 +2,10 @@
 #include "variant.h"
 #include "target.h"
 
+#ifdef HAS_ES8311_AUDIO
+  #include "ES8311.h"   // MAX: native ES8311 codec init (Arduino Wire)
+#endif
+
 TDeckProMaxBoard board;
 
 #if defined(P_LORA_SCLK)
@@ -89,3 +93,20 @@ mesh::LocalIdentity radio_new_identity() {
 void radio_reset_agc() {
   radio.setRxBoostedGainMode(true);
 }
+
+#ifdef HAS_ES8311_AUDIO
+// Route audio to the ES8311 and enable the speaker amp. Safe to call any time
+// (just XL9555 GPIO writes); the outputs latch, so repeat calls are harmless.
+void meck_audio_route_amp() {
+  board.selectAudioES8311();   // XL9555 AUDIO_SEL low -> ES8311
+  board.amplifierEnable();     // XL9555 AMPLIFIER high -> NS4150B on
+}
+
+// One-time ES8311 codec init. Must be called after the I2S clocks are running
+// (after connecttoFS) so the codec can lock to MCLK/BCLK. Idempotent: the
+// static guard means the register init runs at most once per boot.
+void meck_audio_codec_init() {
+  static bool es8311_ready = false;
+  if (!es8311_ready) es8311_ready = es8311_init_44100_16bit();
+}
+#endif

variants/lilygo_tdeck_max/target.h

@@ -45,3 +45,12 @@ void radio_set_params(float freq, float bw, uint8_t sf, uint8_t cr);
 void radio_set_tx_power(uint8_t dbm);
 mesh::LocalIdentity radio_new_identity();
 void radio_reset_agc();
+
+#ifdef HAS_ES8311_AUDIO
+// Audio hardware bring-up (MAX/ES8311), shared across playback paths.
+// route_amp: select ES8311 output + enable the speaker amp (safe any time).
+// codec_init: one-time ES8311 register init; call AFTER the I2S clocks are
+// running (i.e. after connecttoFS), since the codec locks to MCLK/BCLK.
+void meck_audio_route_amp();
+void meck_audio_codec_init();
+#endif