diff --git a/app.go b/app.go
index b63cb91..e7e2ffc 100644
--- a/app.go
+++ b/app.go
@@ -14533,6 +14533,14 @@ func (a *App) IcomSetSplit(on bool) error {
 	return a.cat.IcomDo(func(ic cat.IcomController) error { return ic.SetIcomSplit(on) })
 }
 
+// IcomSetATU puts the internal tuner in or out of line.
+func (a *App) IcomSetATU(on bool) error {
+	if a.cat == nil {
+		return fmt.Errorf("cat not initialized")
+	}
+	return a.cat.IcomDo(func(ic cat.IcomController) error { return ic.SetATU(on) })
+}
+
 // IcomSetSplitOffset turns split on with a chosen TX offset (Hz) — the
 // console's +1/+5/+10 kHz buttons.
 func (a *App) IcomSetSplitOffset(hz int64) error {
diff --git a/changelog.json b/changelog.json
index 48e2968..d7bc2cd 100644
--- a/changelog.json
+++ b/changelog.json
@@ -31,7 +31,8 @@
       "Icom network: a radio in standby keeps its session and the console’s ON button — the quiet-CI-V recovery was tearing the session down every 15 s, so a radio that was off when OpsLog started could never be powered on.",
       "Icom console: the MOX button carries your microphone on a network station, and engaging split aligns the TX VFO’s mode with the main.",
       "Icom console: the spectrum scope is removed. Every model streams its waveform differently — and on the IC-7760 enabling it killed the whole CI-V link, audio included. The radio’s own scope does it better.",
-      "Icom: any leftover waveform stream is switched off at connect — the scope flag lives in the radio and survived sessions, and its flood is what was killing the IC-7760’s CI-V link."
+      "Icom: any leftover waveform stream is switched off at connect — the scope flag lives in the radio and survived sessions, and its flood is what was killing the IC-7760’s CI-V link.",
+      "Icom console: an ATU chip beside SPLIT engages or DISENGAGES the internal tuner — TUNE started a cycle but could never take the tuner back out of line."
     ],
     "fr": [
       "Console Elecraft : le S-mètre est calibré sur un vrai K3 — S9 et les +dB correspondent désormais à l’affichage de la radio (il lisait environ deux points S trop bas).",
@@ -62,7 +63,8 @@
       "Réseau Icom : une radio en veille garde sa session et le bouton ON de la console — la récupération du CI-V muet détruisait la session toutes les 15 s, donc une radio éteinte au lancement d’OpsLog ne pouvait jamais être allumée.",
       "Console Icom : le bouton MOX emporte votre micro sur une station réseau, et activer le split aligne le mode du VFO TX sur le main.",
       "Console Icom : le scope spectral est retiré. Chaque modèle streame sa forme d’onde différemment — et sur l’IC-7760 son activation tuait tout le lien CI-V, audio compris. Le scope de la radio fait ça mieux.",
-      "Icom : tout flux waveform résiduel est coupé à la connexion — le drapeau scope vit dans la radio et survivait aux sessions, et son flot est ce qui tuait le lien CI-V de l’IC-7760."
+      "Icom : tout flux waveform résiduel est coupé à la connexion — le drapeau scope vit dans la radio et survivait aux sessions, et son flot est ce qui tuait le lien CI-V de l’IC-7760.",
+      "Console Icom : une puce ATU à côté de SPLIT engage ou DÉSENGAGE le tuner interne — TUNE lançait un cycle mais ne pouvait jamais remettre le tuner hors ligne."
     ]
   },
   {
diff --git a/frontend/src/components/IcomPanel.tsx b/frontend/src/components/IcomPanel.tsx
index 05cd022..11bc9ad 100644
--- a/frontend/src/components/IcomPanel.tsx
+++ b/frontend/src/components/IcomPanel.tsx
@@ -5,7 +5,7 @@ import {
   IcomSetAFGain, IcomSetRFGain, IcomSetNB, IcomSetNBLevel, IcomSetNR, IcomSetNRLevel,
   IcomSetANF, IcomSetAPF, IcomSetAGC, IcomSetPreamp, IcomSetAtt, IcomSetFilter,
   AudioMonitorActive, AudioStartMonitor, AudioStopMonitor,
-  IcomSetRFPower, IcomSetMicGain, IcomSetSplit, IcomTune, IcomConsolePTT,
+  IcomSetRFPower, IcomSetMicGain, IcomSetSplit, IcomTune, IcomSetATU, IcomConsolePTT,
   GetCATState, SetCATFrequency, SetCATMode,
   IcomSetRIT, IcomSetRITOn, IcomSetXITOn,
   IcomSetAntenna, IcomSetPBTInner, IcomSetPBTOuter, IcomSetManualNotch, IcomSetNotchPos,
@@ -20,7 +20,7 @@ import { ShiftRow } from '@/components/ShiftRow';
 
 type IcomState = {
   available: boolean; model?: string; mode?: string;
-  transmitting: boolean; split: boolean; sub_hz?: number;
+  transmitting: boolean; split: boolean; sub_hz?: number; atu_on?: boolean;
   s_meter: number; power_meter: number; swr_meter: number;
   rf_power: number; mic_gain: number;
   af_gain: number; rf_gain: number;
@@ -585,6 +585,9 @@ export function IcomPanel({ onReportRST, isNetwork = false }: { onReportRST?: (r
             {tx ? 'TX ON' : 'MOX'}
           </button>
           <Chip label="SPLIT" on={st.split} onClick={() => set({ split: !st.split }, () => IcomSetSplit(!st.split))} />
+          {/* Tuner IN/OUT — TUNE below starts a cycle but could never take the
+              tuner back out of line. */}
+          <Chip label="ATU" on={!!st.atu_on} onClick={() => set({ atu_on: !st.atu_on } as any, () => IcomSetATU(!st.atu_on))} />
           <button type="button" onClick={tune} disabled={tuning}
             className={cn('w-14 shrink-0 px-2 py-1.5 rounded-md text-[11px] font-bold border transition-colors',
               tuning ? 'bg-warning border-warning text-warning-foreground animate-pulse' : 'bg-card text-foreground border-border hover:bg-muted')}>
diff --git a/frontend/wailsjs/go/main/App.d.ts b/frontend/wailsjs/go/main/App.d.ts
index 033be14..9eca5fa 100644
--- a/frontend/wailsjs/go/main/App.d.ts
+++ b/frontend/wailsjs/go/main/App.d.ts
@@ -646,6 +646,8 @@ export function IcomSetANF(arg1:boolean):Promise<void>;
 
 export function IcomSetAPF(arg1:boolean):Promise<void>;
 
+export function IcomSetATU(arg1:boolean):Promise<void>;
+
 export function IcomSetAntenna(arg1:number):Promise<void>;
 
 export function IcomSetAntiVOX(arg1:number):Promise<void>;
diff --git a/frontend/wailsjs/go/main/App.js b/frontend/wailsjs/go/main/App.js
index 59553af..46e9f88 100644
--- a/frontend/wailsjs/go/main/App.js
+++ b/frontend/wailsjs/go/main/App.js
@@ -1230,6 +1230,10 @@ export function IcomSetAPF(arg1) {
   return window['go']['main']['App']['IcomSetAPF'](arg1);
 }
 
+export function IcomSetATU(arg1) {
+  return window['go']['main']['App']['IcomSetATU'](arg1);
+}
+
 export function IcomSetAntenna(arg1) {
   return window['go']['main']['App']['IcomSetAntenna'](arg1);
 }
diff --git a/frontend/wailsjs/go/models.ts b/frontend/wailsjs/go/models.ts
index e8ec81b..80d7964 100644
--- a/frontend/wailsjs/go/models.ts
+++ b/frontend/wailsjs/go/models.ts
@@ -1007,6 +1007,7 @@ export namespace cat {
 	    att: number;
 	    filter: number;
 	    antenna: number;
+	    atu_on: boolean;
 	    pbt_inner: number;
 	    pbt_outer: number;
 	    manual_notch: boolean;
@@ -1055,6 +1056,7 @@ export namespace cat {
 	        this.att = source["att"];
 	        this.filter = source["filter"];
 	        this.antenna = source["antenna"];
+	        this.atu_on = source["atu_on"];
 	        this.pbt_inner = source["pbt_inner"];
 	        this.pbt_outer = source["pbt_outer"];
 	        this.manual_notch = source["manual_notch"];
diff --git a/internal/cat/cat.go b/internal/cat/cat.go
index 2643ed6..edec835 100644
--- a/internal/cat/cat.go
+++ b/internal/cat/cat.go
@@ -602,7 +602,8 @@ type IcomTXState struct {
 	Att     int    `json:"att"`           // dB attenuation, 0=off
 	Filter  int    `json:"filter"`        // 1 | 2 | 3 (FIL1/2/3)
 	// Antenna (IC-7610 = ANT1/ANT2).
-	Antenna int `json:"antenna"` // 1 | 2 (0 = unknown)
+	Antenna int  `json:"antenna"` // 1 | 2 (0 = unknown)
+	ATUOn   bool `json:"atu_on"`  // internal tuner engaged
 	// Filter fine controls: Twin PBT + manual notch (0-100, 50 = centre).
 	PBTInner    int  `json:"pbt_inner"`
 	PBTOuter    int  `json:"pbt_outer"`
@@ -641,6 +642,7 @@ type IcomController interface {
 	SetMicGain(int) error
 	SetIcomSplit(bool) error
 	SetIcomSplitOffset(bool, int64) error
+	SetATU(bool) error
 	TuneATU() error
 	SetScope(bool) error              // enable/disable the spectrum-scope waveform stream
 	SetScopeMode(bool) error          // true = fixed span, false = center-on-VFO
diff --git a/internal/cat/icomserial.go b/internal/cat/icomserial.go
index 604de58..884da73 100644
--- a/internal/cat/icomserial.go
+++ b/internal/cat/icomserial.go
@@ -530,6 +530,13 @@ func (b *IcomSerial) refreshFrontPanel() {
 			b.dsp.Filter = int(f)
 			b.dspMu.Unlock()
 		}
+	case 2:
+		// Tuner in/out — the radio's own TUNER button changes it mid-session.
+		if v, ok := b.readSwitchSub(civ.CmdATU, civ.SubATU); ok {
+			b.dspMu.Lock()
+			b.dsp.ATUOn = v == 1
+			b.dspMu.Unlock()
+		}
 	}
 }
 
@@ -2041,6 +2048,17 @@ func (b *IcomSerial) TuneATU() error {
 	return b.exec(civ.CmdATU, civ.SubATU, 0x02)
 }
 
+// SetATU engages or DISENGAGES the internal tuner (0x1C 0x01: 1 = in line,
+// 0 = through). Tune existed without this, which meant a tuner once engaged
+// could not be taken out of line again from the console.
+func (b *IcomSerial) SetATU(on bool) error {
+	if err := b.exec(civ.CmdATU, civ.SubATU, boolByte(on)); err != nil {
+		return err
+	}
+	b.setCache(func(s *IcomTXState) { s.ATUOn = on })
+	return nil
+}
+
 func (b *IcomSerial) setCache(fn func(*IcomTXState)) {
 	b.dspMu.Lock()
 	fn(&b.dsp)