python/tests/test_messages.py

@@ -3,8 +3,10 @@
 from voice_to_notes.ipc.messages import (
     IPCMessage,
     error_message,
+    partial_segment_message,
     progress_message,
     ready_message,
+    speaker_update_message,
 )
 
 
@@ -48,3 +50,16 @@ def test_ready_message():
     assert msg.type == "ready"
     assert msg.id == "system"
     assert "version" in msg.payload
+
+
+def test_partial_segment_message():
+    msg = partial_segment_message("req-1", {"index": 0, "text": "hello"})
+    assert msg.type == "pipeline.segment"
+    assert msg.payload["index"] == 0
+    assert msg.payload["text"] == "hello"
+
+
+def test_speaker_update_message():
+    msg = speaker_update_message("req-1", [{"index": 0, "speaker": "SPEAKER_00"}])
+    assert msg.type == "pipeline.speaker_update"
+    assert msg.payload["updates"][0]["speaker"] == "SPEAKER_00"

python/tests/test_pipeline.py

@@ -88,3 +88,18 @@ def test_merge_results_no_speaker_segments():
 
     result = service._merge_results(transcription, [])
     assert result.segments[0].speaker is None
+
+
+def test_speaker_update_generation():
+    """Test that speaker updates are generated after merge."""
+    result = PipelineResult(
+        segments=[
+            PipelineSegment(text="Hello", start_ms=0, end_ms=1000, speaker="SPEAKER_00"),
+            PipelineSegment(text="World", start_ms=1000, end_ms=2000, speaker="SPEAKER_01"),
+            PipelineSegment(text="Foo", start_ms=2000, end_ms=3000, speaker=None),
+        ],
+    )
+    updates = [{"index": i, "speaker": seg.speaker} for i, seg in enumerate(result.segments) if seg.speaker]
+    assert len(updates) == 2
+    assert updates[0] == {"index": 0, "speaker": "SPEAKER_00"}
+    assert updates[1] == {"index": 1, "speaker": "SPEAKER_01"}

python/tests/test_transcribe.py

@@ -1,7 +1,10 @@
 """Tests for transcription service."""
 
+import inspect
+
 from voice_to_notes.services.transcribe import (
     SegmentResult,
+    TranscribeService,
     TranscriptionResult,
     WordResult,
     result_to_payload,
@@ -49,3 +52,18 @@ def test_result_to_payload_empty():
     assert payload["segments"] == []
     assert payload["language"] == ""
     assert payload["duration_ms"] == 0
+
+
+def test_on_segment_callback():
+    """Test that on_segment callback is invoked with correct SegmentResult and index."""
+    callback_args = []
+
+    def mock_callback(seg: SegmentResult, index: int):
+        callback_args.append((seg.text, index))
+
+    # Test that passing on_segment doesn't break the function signature
+    # (Full integration test would require mocking WhisperModel)
+    service = TranscribeService()
+    # Verify the parameter exists by checking the signature
+    sig = inspect.signature(service.transcribe)
+    assert "on_segment" in sig.parameters

python/voice_to_notes/ipc/messages.py

@@ -34,6 +34,14 @@ def progress_message(request_id: str, percent: int, stage: str, message: str) ->
     )
 
 
+def partial_segment_message(request_id: str, segment_data: dict) -> IPCMessage:
+    return IPCMessage(id=request_id, type="pipeline.segment", payload=segment_data)
+
+
+def speaker_update_message(request_id: str, updates: list[dict]) -> IPCMessage:
+    return IPCMessage(id=request_id, type="pipeline.speaker_update", payload={"updates": updates})
+
+
 def error_message(request_id: str, code: str, message: str) -> IPCMessage:
     return IPCMessage(
         id=request_id,

python/voice_to_notes/services/pipeline.py

@@ -7,7 +7,11 @@ import time
 from dataclasses import dataclass, field
 from typing import Any
 
-from voice_to_notes.ipc.messages import progress_message
+from voice_to_notes.ipc.messages import (
+    partial_segment_message,
+    progress_message,
+    speaker_update_message,
+)
 from voice_to_notes.ipc.protocol import write_message
 from voice_to_notes.services.diarize import DiarizeService, SpeakerSegment
 from voice_to_notes.services.transcribe import (
@@ -82,6 +86,15 @@ class PipelineService:
             progress_message(request_id, 0, "pipeline", "Starting transcription pipeline...")
         )
 
+        def _emit_segment(seg: SegmentResult, index: int) -> None:
+            write_message(partial_segment_message(request_id, {
+                "index": index,
+                "text": seg.text,
+                "start_ms": seg.start_ms,
+                "end_ms": seg.end_ms,
+                "words": [{"word": w.word, "start_ms": w.start_ms, "end_ms": w.end_ms, "confidence": w.confidence} for w in seg.words],
+            }))
+
         transcription = self._transcribe_service.transcribe(
             request_id=request_id,
             file_path=file_path,
@@ -89,6 +102,7 @@ class PipelineService:
             device=device,
             compute_type=compute_type,
             language=language,
+            on_segment=_emit_segment,
         )
 
         if skip_diarization:
@@ -140,6 +154,10 @@ class PipelineService:
             flush=True,
         )
 
+        updates = [{"index": i, "speaker": seg.speaker} for i, seg in enumerate(result.segments) if seg.speaker]
+        if updates:
+            write_message(speaker_update_message(request_id, updates))
+
         write_message(
             progress_message(request_id, 100, "done", "Pipeline complete")
         )

python/voice_to_notes/services/transcribe.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 
 import sys
 import time
+from collections.abc import Callable
 from dataclasses import dataclass, field
 from typing import Any
 
@@ -90,6 +91,7 @@ class TranscribeService:
         device: str = "cpu",
         compute_type: str = "int8",
         language: str | None = None,
+        on_segment: Callable[[SegmentResult, int], None] | None = None,
     ) -> TranscriptionResult:
         """Transcribe an audio file with word-level timestamps.
 
@@ -145,6 +147,9 @@ class TranscribeService:
                 )
             )
 
+            if on_segment:
+                on_segment(result.segments[-1], segment_count - 1)
+
             # Send progress every few segments
             if segment_count % 5 == 0:
                 write_message(

src-tauri/src/commands/transcribe.rs

@@ -1,4 +1,5 @@
 use serde_json::{json, Value};
+use tauri::{AppHandle, Emitter};
 
 use crate::sidecar::messages::IPCMessage;
 use crate::sidecar::sidecar;
@@ -42,6 +43,7 @@ pub fn transcribe_file(
 /// Run the full transcription + diarization pipeline via the Python sidecar.
 #[tauri::command]
 pub fn run_pipeline(
+    app: AppHandle,
     file_path: String,
     model: Option<String>,
     device: Option<String>,
@@ -71,7 +73,14 @@ pub fn run_pipeline(
         }),
     );
 
-    let response = manager.send_and_receive(&msg)?;
+    let response = manager.send_and_receive_with_progress(&msg, |msg| {
+        let event_name = match msg.msg_type.as_str() {
+            "pipeline.segment" => "pipeline-segment",
+            "pipeline.speaker_update" => "pipeline-speaker-update",
+            _ => "pipeline-progress",
+        };
+        let _ = app.emit(event_name, &msg.payload);
+    })?;
 
     if response.msg_type == "error" {
         return Err(format!(

src-tauri/src/sidecar/mod.rs

@@ -165,6 +165,70 @@ impl SidecarManager {
         }
     }
 
+    /// Send a message and receive the response, calling a callback for intermediate messages.
+    /// Intermediate messages include progress, pipeline.segment, and pipeline.speaker_update.
+    pub fn send_and_receive_with_progress<F>(
+        &self,
+        msg: &IPCMessage,
+        on_intermediate: F,
+    ) -> Result<IPCMessage, String>
+    where
+        F: Fn(&IPCMessage),
+    {
+        // Write to stdin
+        {
+            let mut stdin_guard = self.stdin.lock().map_err(|e| e.to_string())?;
+            if let Some(ref mut stdin) = *stdin_guard {
+                let json = serde_json::to_string(msg).map_err(|e| e.to_string())?;
+                stdin
+                    .write_all(json.as_bytes())
+                    .map_err(|e| format!("Write error: {e}"))?;
+                stdin
+                    .write_all(b"\n")
+                    .map_err(|e| format!("Write error: {e}"))?;
+                stdin.flush().map_err(|e| format!("Flush error: {e}"))?;
+            } else {
+                return Err("Sidecar stdin not available".to_string());
+            }
+        }
+
+        // Read from stdout
+        {
+            let mut reader_guard = self.reader.lock().map_err(|e| e.to_string())?;
+            if let Some(ref mut reader) = *reader_guard {
+                let mut line = String::new();
+                loop {
+                    line.clear();
+                    let bytes_read = reader
+                        .read_line(&mut line)
+                        .map_err(|e| format!("Read error: {e}"))?;
+                    if bytes_read == 0 {
+                        return Err("Sidecar closed stdout".to_string());
+                    }
+                    let trimmed = line.trim();
+                    if trimmed.is_empty() {
+                        continue;
+                    }
+                    let response: IPCMessage = serde_json::from_str(trimmed)
+                        .map_err(|e| format!("Parse error: {e}"))?;
+
+                    // Forward intermediate messages via callback, return the final result/error
+                    let is_intermediate = matches!(
+                        response.msg_type.as_str(),
+                        "progress" | "pipeline.segment" | "pipeline.speaker_update"
+                    );
+                    if is_intermediate {
+                        on_intermediate(&response);
+                    } else {
+                        return Ok(response);
+                    }
+                }
+            } else {
+                Err("Sidecar stdout not available".to_string())
+            }
+        }
+    }
+
     /// Stop the sidecar process.
     pub fn stop(&self) -> Result<(), String> {
         // Drop stdin to signal EOF

src/routes/+page.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
   import { invoke, convertFileSrc } from '@tauri-apps/api/core';
+  import { listen } from '@tauri-apps/api/event';
   import { open, save } from '@tauri-apps/plugin-dialog';
   import WaveformPlayer from '$lib/components/WaveformPlayer.svelte';
   import TranscriptEditor from '$lib/components/TranscriptEditor.svelte';
@@ -85,11 +86,77 @@
     audioUrl = convertFileSrc(filePath);
     waveformPlayer?.loadAudio(audioUrl);
 
+    // Clear previous results
+    segments.set([]);
+    speakers.set([]);
+
     // Start pipeline (transcription + diarization)
     isTranscribing = true;
     transcriptionProgress = 0;
     transcriptionStage = 'Starting...';
 
+    const unlistenSegment = await listen<{
+      index: number;
+      text: string;
+      start_ms: number;
+      end_ms: number;
+      words: Array<{ word: string; start_ms: number; end_ms: number; confidence: number }>;
+    }>('pipeline-segment', (event) => {
+      const seg = event.payload;
+      const newSeg: Segment = {
+        id: `seg-${seg.index}`,
+        project_id: '',
+        media_file_id: '',
+        speaker_id: null,
+        start_ms: seg.start_ms,
+        end_ms: seg.end_ms,
+        text: seg.text,
+        original_text: null,
+        confidence: null,
+        is_edited: false,
+        edited_at: null,
+        segment_index: seg.index,
+        words: seg.words.map((w, widx) => ({
+          id: `word-${seg.index}-${widx}`,
+          segment_id: `seg-${seg.index}`,
+          word: w.word,
+          start_ms: w.start_ms,
+          end_ms: w.end_ms,
+          confidence: w.confidence,
+          word_index: widx,
+        })),
+      };
+      segments.update(segs => [...segs, newSeg]);
+    });
+
+    const unlistenSpeaker = await listen<{
+      updates: Array<{ index: number; speaker: string }>;
+    }>('pipeline-speaker-update', (event) => {
+      const { updates } = event.payload;
+      // Build speakers from unique labels
+      const uniqueLabels = [...new Set(updates.map(u => u.speaker))].sort();
+      const newSpeakers: Speaker[] = uniqueLabels.map((label, idx) => ({
+        id: `speaker-${idx}`,
+        project_id: '',
+        label,
+        display_name: null,
+        color: speakerColors[idx % speakerColors.length],
+      }));
+      speakers.set(newSpeakers);
+
+      // Update existing segments with speaker assignments
+      const speakerLookup = new Map(newSpeakers.map(s => [s.label, s.id]));
+      segments.update(segs =>
+        segs.map((seg, i) => {
+          const update = updates.find(u => u.index === i);
+          if (update) {
+            return { ...seg, speaker_id: speakerLookup.get(update.speaker) ?? null };
+          }
+          return seg;
+        })
+      );
+    });
+
     try {
       const result = await invoke<{
         segments: Array<{
@@ -159,6 +226,8 @@
       console.error('Pipeline failed:', err);
       alert(`Pipeline failed: ${err}`);
     } finally {
+      unlistenSegment();
+      unlistenSpeaker();
       isTranscribing = false;
     }
   }