feat(pm): ignore sub-threshold voice transmissions (STT noise gate)

Whisper hallucinates short real words ("Test", "Thank you", "Okay") on
near-silent or noisy audio. Unfiltered these reached the backend as a wrong
readback attempt — counting toward the 3x-skip — and triggered paid
LLM-router calls. Drop voice (PTT) transcripts below NUXT_PUBLIC_PTT_MIN_WORDS
(default 2); text input is exempt so deliberate short commands still work.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.env.example

@@ -27,6 +27,12 @@ ROUTER_LLM_MODEL=gpt-5-mini
 # disabled (the backend falls back to deterministic bad_next routing).
 SERVICE_SECRET=CHANGE_ME
 
+# PM radio training
+# Minimum word count for a voice (PTT) transmission to be used; shorter
+# transcripts are treated as STT noise/hallucination and ignored. Set to 1 to
+# disable. See the "STT MINIMUM-WORD GATE" in app/pages/pm.vue.
+NUXT_PUBLIC_PTT_MIN_WORDS=2
+
 # ATC audio generation
 ATC_OUT_DIR=./storage/atc
 FLIGHTLAB_TTS_CACHE_DIR=./.cache/flightlab-tts

app/pages/pm.vue

@@ -3365,6 +3365,20 @@ const handlePilotTransmission = async (message: string, source: 'text' | 'ptt' =
   // ("roger", "wilco") still contains letters/digits and passes.
   if (!transcript || !/[a-z0-9]/i.test(transcript)) return
 
+  // STT MINIMUM-WORD GATE — search here if a spoken transmission was ignored.
+  // Voice (PTT) only: drop transcripts shorter than the configured minimum.
+  // Whisper hallucinates short real words ("Test", "Thank you", "Okay") on
+  // near-silent or noisy audio; left unfiltered those reach the backend as a
+  // (wrong) readback attempt — counting toward the 3x-skip — and now also
+  // trigger a paid LLM-router call. Text input is exempt so deliberate short
+  // commands still work. Threshold is the NUXT_PUBLIC_PTT_MIN_WORDS env var
+  // (default 2); set it to 1 to effectively disable the gate.
+  const minPttWords = Number(config.public.pttMinWords ?? 2)
+  if (source === 'ptt' && transcript.split(/\s+/).filter(Boolean).length < minPttWords) {
+    pmLog.info(`IGNORED short PTT transcript (<${minPttWords} words):`, transcript)
+    return
+  }
+
   const prefix = source === 'ptt' ? 'Pilot (PTT)' : 'Pilot'
   setLastTransmission(`${prefix}: ${transcript}`)
 

nuxt.config.ts

@@ -58,6 +58,10 @@ export default defineNuxtConfig({
         public: {
             apiDocumentationUrl: '/api-docs',
             radioBackendUrl: process.env.NUXT_PUBLIC_RADIO_BACKEND_URL || 'http://127.0.0.1:8000',
+            // Minimum word count for a voice (PTT) transmission to be used. Below
+            // this the transcript is treated as STT noise/hallucination and
+            // ignored. See the "STT MINIMUM-WORD GATE" in pages/pm.vue.
+            pttMinWords: Number(process.env.NUXT_PUBLIC_PTT_MIN_WORDS || 2),
         },
     },
     vuetify: {