fix(riva): preserve long-dictation leading segments on interim divergence

apps/sotto/internal/riva/client.go

@@ -41,14 +41,15 @@ type Stream struct {
 
 	recvDone chan struct{}
 
-	mu                   sync.Mutex
-	segments             []string // committed transcript segments (final results and sealed interim chains)
-	lastInterim          string
-	lastInterimAge       int
-	lastInterimStability float32
-	recvErr              error
-	closedSend           bool
-	debugSinkJSON        io.Writer
+	mu                        sync.Mutex
+	segments                  []string // committed transcript segments (final results and sealed interim chains)
+	lastInterim               string
+	lastInterimAge            int
+	lastInterimStability      float32
+	lastInterimAudioProcessed float32
+	recvErr                   error
+	closedSend                bool
+	debugSinkJSON             io.Writer
 }
 
 // DialStream establishes a stream, sends config, and starts the receive loop.

apps/sotto/internal/riva/client_test.go

@@ -106,6 +106,54 @@ func TestRecordResponseCommitsStableSingleInterimOnDivergence(t *testing.T) {
 	require.Equal(t, []string{"first phrase", "second phrase"}, segments)
 }
 
+func TestRecordResponseCommitsOneShotInterimOnAudioAdvance(t *testing.T) {
+	s := &Stream{}
+
+	s.recordResponse(&asrpb.StreamingRecognizeResponse{
+		Results: []*asrpb.StreamingRecognitionResult{{
+			IsFinal:        false,
+			AudioProcessed: 1.0,
+			Alternatives:   []*asrpb.SpeechRecognitionAlternative{{Transcript: "first phrase has enough words"}},
+		}},
+	})
+
+	s.recordResponse(&asrpb.StreamingRecognizeResponse{
+		Results: []*asrpb.StreamingRecognitionResult{{
+			IsFinal:        false,
+			AudioProcessed: 2.0,
+			Alternatives:   []*asrpb.SpeechRecognitionAlternative{{Transcript: "second phrase continues now"}},
+		}},
+	})
+
+	require.Equal(t, []string{"first phrase has enough words"}, s.segments)
+	segments := collectSegments(s.segments, s.lastInterim)
+	require.Equal(t, []string{"first phrase has enough words", "second phrase continues now"}, segments)
+}
+
+func TestRecordResponseKeepsOneShotInterimWhenAudioAdvanceIsSmall(t *testing.T) {
+	s := &Stream{}
+
+	s.recordResponse(&asrpb.StreamingRecognizeResponse{
+		Results: []*asrpb.StreamingRecognitionResult{{
+			IsFinal:        false,
+			AudioProcessed: 1.0,
+			Alternatives:   []*asrpb.SpeechRecognitionAlternative{{Transcript: "first phrase has enough words"}},
+		}},
+	})
+
+	s.recordResponse(&asrpb.StreamingRecognizeResponse{
+		Results: []*asrpb.StreamingRecognitionResult{{
+			IsFinal:        false,
+			AudioProcessed: 1.2,
+			Alternatives:   []*asrpb.SpeechRecognitionAlternative{{Transcript: "second phrase continues now"}},
+		}},
+	})
+
+	require.Empty(t, s.segments)
+	segments := collectSegments(s.segments, s.lastInterim)
+	require.Equal(t, []string{"second phrase continues now"}, segments)
+}
+
 func TestRecordResponseCommitsInterimChainOnDivergence(t *testing.T) {
 	s := &Stream{}
 
@@ -244,11 +292,13 @@ func TestInterimHelpers(t *testing.T) {
 		})
 	}
 
-	require.False(t, shouldCommitInterimBoundary("", 5, 0.9))
-	require.False(t, shouldCommitInterimBoundary("first phrase", 1, 0.1))
-	require.True(t, shouldCommitInterimBoundary("first phrase", 2, 0.1))
-	require.True(t, shouldCommitInterimBoundary("first phrase", 1, 0.9))
-	require.True(t, shouldCommitInterimBoundary("done.", 1, 0.0))
+	require.False(t, shouldCommitInterimBoundary("", 5, 0.9, 1.0, 2.0))
+	require.False(t, shouldCommitInterimBoundary("first phrase", 1, 0.1, 1.0, 1.2))
+	require.True(t, shouldCommitInterimBoundary("first phrase", 2, 0.1, 1.0, 1.1))
+	require.True(t, shouldCommitInterimBoundary("first phrase", 1, 0.9, 1.0, 1.1))
+	require.True(t, shouldCommitInterimBoundary("done.", 1, 0.0, 1.0, 1.1))
+	require.True(t, shouldCommitInterimBoundary("first phrase has enough words", 1, 0.1, 1.0, 2.0))
+	require.False(t, shouldCommitInterimBoundary("too short", 1, 0.1, 1.0, 2.0))
 }
 
 func TestDialStreamEndToEndWithDebugSinkAndSpeechContexts(t *testing.T) {

apps/sotto/internal/riva/stream_receive.go

@@ -55,23 +55,33 @@ func (s *Stream) recordResponse(resp *asrpb.StreamingRecognizeResponse) {
 			s.lastInterim = ""
 			s.lastInterimAge = 0
 			s.lastInterimStability = 0
+			s.lastInterimAudioProcessed = 0
 			continue
 		}
 
+		currentAudioProcessed := result.GetAudioProcessed()
 		if s.lastInterim != "" {
 			if isInterimContinuation(s.lastInterim, transcript) {
 				s.lastInterim = transcript
 				s.lastInterimAge++
 				s.lastInterimStability = result.GetStability()
+				s.lastInterimAudioProcessed = currentAudioProcessed
 				continue
 			}
-			if shouldCommitInterimBoundary(s.lastInterim, s.lastInterimAge, s.lastInterimStability) {
+			if shouldCommitInterimBoundary(
+				s.lastInterim,
+				s.lastInterimAge,
+				s.lastInterimStability,
+				s.lastInterimAudioProcessed,
+				currentAudioProcessed,
+			) {
 				s.segments = appendSegment(s.segments, s.lastInterim)
 			}
 		}
 
 		s.lastInterim = transcript
 		s.lastInterimAge = 1
 		s.lastInterimStability = result.GetStability()
+		s.lastInterimAudioProcessed = currentAudioProcessed
 	}
 }

apps/sotto/internal/riva/transcript_segments.go

@@ -3,8 +3,10 @@ package riva
 import "strings"
 
 const (
-	minInterimChainUpdates         = 2
-	stableInterimBoundaryThreshold = 0.85
+	minInterimChainUpdates             = 2
+	stableInterimBoundaryThreshold     = 0.85
+	interimBoundaryAudioAdvanceSeconds = 0.75
+	minInterimWordsForAudioBoundary    = 3
 )
 
 // collectSegments appends a valid trailing interim segment when needed.
@@ -80,7 +82,13 @@ func isInterimContinuation(previous string, current string) bool {
 
 // shouldCommitInterimBoundary returns true when a divergent interim chain looks
 // established enough to preserve as a committed segment.
-func shouldCommitInterimBoundary(previous string, chainUpdates int, stability float32) bool {
+func shouldCommitInterimBoundary(
+	previous string,
+	chainUpdates int,
+	stability float32,
+	previousAudioProcessed float32,
+	currentAudioProcessed float32,
+) bool {
 	previous = cleanSegment(previous)
 	if previous == "" {
 		return false
@@ -91,7 +99,23 @@ func shouldCommitInterimBoundary(previous string, chainUpdates int, stability fl
 	if stability >= stableInterimBoundaryThreshold {
 		return true
 	}
-	return endsWithSentencePunctuation(previous)
+	if endsWithSentencePunctuation(previous) {
+		return true
+	}
+	return advancedAudioBoundary(previous, previousAudioProcessed, currentAudioProcessed)
+}
+
+func advancedAudioBoundary(previous string, previousAudioProcessed float32, currentAudioProcessed float32) bool {
+	if previousAudioProcessed <= 0 || currentAudioProcessed <= 0 {
+		return false
+	}
+	if currentAudioProcessed <= previousAudioProcessed {
+		return false
+	}
+	if currentAudioProcessed-previousAudioProcessed < interimBoundaryAudioAdvanceSeconds {
+		return false
+	}
+	return len(strings.Fields(previous)) >= minInterimWordsForAudioBoundary
 }
 
 func endsWithSentencePunctuation(text string) bool {