fix: the Flex panel DAX button now toggles the TRANSMIT-bar DAX (transmit set dax=), not the slice RX DAX channel — this is the button that routes TX audio through DAX (WSJT-X); state follows changes made in SmartSDR too

internal/cat/cat.go

@@ -319,6 +319,7 @@ type FlexTXState struct {
 	NRFLevel     int  `json:"nrf_level"`
 	DSPV4        bool `json:"dsp_v4"`
 	DAXCh        int  `json:"dax_ch"` // DAX audio channel of the active slice (0 = off, 1-8)
+	TXDAX        bool `json:"tx_dax"` // DAX is the TX audio source (SmartSDR transmit-bar DAX button)
 	// RIT/XIT — offsets applied to the active slice's RX / TX frequency without
 	// moving the slice. The offset survives the switch being turned off, so
 	// re-enabling restores it, exactly like the radio's own knob.
@@ -412,7 +413,8 @@ type FlexController interface {
 	SetANFT(bool) error
 	SetNRF(bool) error
 	SetNRFLevel(int) error
-	SetDAX(int) error // DAX channel 0 (off) - 8
+	SetDAX(int) error    // slice RX DAX channel 0 (off) - 8
+	SetTXDAX(bool) error // TX audio from DAX (transmit set dax=)
 	SetRIT(bool) error
 	SetRITFreq(int) error
 	SetXIT(bool) error

internal/cat/flex.go

@@ -134,8 +134,9 @@ type flexTX struct {
 	mon          bool
 	monLevel     int
 	micLevel     int
-	filterLow    int // TX filter low cut (Hz)
-	filterHigh   int // TX filter high cut (Hz)
+	filterLow    int  // TX filter low cut (Hz)
+	filterHigh   int  // TX filter high cut (Hz)
+	dax          bool // TX audio comes from DAX (SmartSDR's transmit-bar DAX button)
 	atuStatus    string
 	atuMemories  bool
 	// CW keyer params (set via the top-level "cw" commands).
@@ -447,6 +448,8 @@ func (f *Flex) handleStatus(payload string) {
 					f.tx.tunePower = atoiDefault(val, f.tx.tunePower)
 				case "tune":
 					f.tx.tune = val == "1"
+				case "dax":
+					f.tx.dax = val == "1"
 				case "vox_enable":
 					f.tx.voxEnable = val == "1"
 				case "vox_level":
@@ -1312,6 +1315,7 @@ func (f *Flex) FlexState() FlexTXState {
 		MicLevel:     f.tx.micLevel,
 		TXFilterLow:  f.tx.filterLow,
 		TXFilterHigh: f.tx.filterHigh,
+		TXDAX:        f.tx.dax,
 		MicProfile:   f.micProfile,
 		MicProfiles:  f.micProfiles,
 		ATUStatus:    f.tx.atuStatus,
@@ -1635,6 +1639,12 @@ func (f *Flex) SetDAX(ch int) error {
 	}
 	return f.sendSlice("dax", ch)
 }
+
+// SetTXDAX toggles DAX as the TRANSMIT audio source — SmartSDR's transmit-bar
+// DAX button ("transmit set dax="), the one used to send WSJT-X audio.
+func (f *Flex) SetTXDAX(on bool) error {
+	return f.txSet("transmit set dax="+boolFlex(on), "dax", func(t *flexTX) { t.dax = on })
+}
 func (f *Flex) SetWNB(on bool) error    { return f.sendSlice("wnb", boolFlex(on)) }
 func (f *Flex) SetWNBLevel(l int) error { return f.sendSlice("wnb_level", clampLevel(l)) }