Summary

TransmitModel::setAmCarrierLevel(int level) sends the radio command but never updates its local member m_amCarrierLevel. It is the only TX setter missing the optimistic local-cache update that all its siblings perform, so transmitModel().amCarrierLevel() returns a stale value until the radio's asynchronous status echo arrives.

Location

src/models/TransmitModel.cpp, ~line 618:

void TransmitModel::setAmCarrierLevel(int level) {
    level = qBound(0, level, 100);
    emit commandReady(QString("transmit set am_carrier=%1").arg(level));   // <-- m_amCarrierLevel never set
}

Compare the sibling setters in the same file, which all cache locally before/with the signal:

• setRfPower → sets m_rfPower, then emit stateChanged()
• setMicLevel → sets m_micLevel, then emit micStateChanged()
• setDexpLevel → sets m_dexpLevel (+ m_companderLevel), then emit phoneStateChanged()

FlexLib's own Radio.cs AMCarrierLevel property setter also caches locally before SendCommand.

Impact

After the GUI (or a TCI client, or the #3646 automation bridge's get transmit) changes AM carrier level, amCarrierLevel() stays stale until the radio echoes am_carrier_level= back (parsed in applyTransmitStatus, ~line 143). Any consumer that reads the value right after a change gets the old number.

Severity: low/cosmetic — the command itself is sent correctly and the radio applies it; the model just lags behind the widget instead of being immediately consistent.

Steps to reproduce

1. Connect to a radio.
2. Change the AM carrier level via the Phone applet slider (or transmit set am_carrier=N).
3. Immediately read transmitModel().amCarrierLevel().

Observed: the value does not reflect the change until the radio's status echo arrives. Measured live on a FLEX-8400M: did not converge within a 2 s poll window, whereas RF power / mic gain / DEXP converge in ~0 ms because they update optimistically.
Expected: amCarrierLevel() reflects the new value immediately, like every other TX setpoint.

Suggested fix

Mirror the sibling pattern (AM carrier is a phone/VOX-group property, so emit phoneStateChanged()):

void TransmitModel::setAmCarrierLevel(int level) {
    level = qBound(0, level, 100);
    if (m_amCarrierLevel != level) {
        m_amCarrierLevel = level;
        emit phoneStateChanged();
    }
    emit commandReady(QString("transmit set am_carrier=%1").arg(level));
}

Notes for the fix:

• The command keyword am_carrier is correct (matches FlexLib Radio.cs:8384) — do not change it.
• Verify no GUI feedback loop is introduced: the PhoneApplet AM-carrier slider's valueChanged lambda (src/gui/PhoneApplet.cpp ~line 123) only calls setAmCarrierLevel when !m_updatingFromModel, and the model→widget sync (~line 398) uses a QSignalBlocker. Confirm a single user change does not produce repeated transmit set am_carrier commands.

How it was found

Surfaced during live QA on a FLEX-8400M using the #3646 agent automation bridge — model-level validation via get transmit caught the AM carrier slider not converging while every other TX control did.