Fix IPC stdout corruption, dark window background, overlay timing

- Redirect sys.stdout to stderr in Python sidecar so library print()
  calls don't corrupt the JSON-line IPC stream
- Save real stdout fd for exclusive IPC use via init_ipc()
- Skip non-JSON lines in Rust reader instead of failing with parse error
- Set Tauri window background color to match dark theme (#0a0a23)
- Add inline dark background on html/body to prevent white flash
- Use Svelte tick() to ensure progress overlay renders before invoke
- Improve ProgressOverlay with spinner, better styling, z-index 9999

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

python/tests/test_protocol.py

@@ -5,16 +5,23 @@ import json
 
 from voice_to_notes.ipc.messages import IPCMessage
 from voice_to_notes.ipc.protocol import read_message, write_message
+import voice_to_notes.ipc.protocol as protocol
 
 
-def test_write_message(capsys):
-    msg = IPCMessage(id="req-1", type="pong", payload={"ok": True})
-    write_message(msg)
-    captured = capsys.readouterr()
-    parsed = json.loads(captured.out.strip())
-    assert parsed["id"] == "req-1"
-    assert parsed["type"] == "pong"
-    assert parsed["payload"]["ok"] is True
+def test_write_message():
+    buf = io.StringIO()
+    # Temporarily replace the IPC output stream
+    old_out = protocol._ipc_out
+    protocol._ipc_out = buf
+    try:
+        msg = IPCMessage(id="req-1", type="pong", payload={"ok": True})
+        write_message(msg)
+        parsed = json.loads(buf.getvalue().strip())
+        assert parsed["id"] == "req-1"
+        assert parsed["type"] == "pong"
+        assert parsed["payload"]["ok"] is True
+    finally:
+        protocol._ipc_out = old_out
 
 
 def test_read_message(monkeypatch):

python/voice_to_notes/ipc/protocol.py

@@ -1,13 +1,53 @@
-"""JSON-line protocol reader/writer over stdin/stdout."""
+"""JSON-line protocol reader/writer over stdin/stdout.
+
+IMPORTANT: stdout is reserved exclusively for IPC messages.
+At init time we save the real stdout, then redirect sys.stdout → stderr
+so that any rogue print() calls from libraries don't corrupt the IPC stream.
+"""
 
 from __future__ import annotations
 
+import io
 import json
+import os
 import sys
 from typing import Any
 
 from voice_to_notes.ipc.messages import IPCMessage
 
+# Save the real stdout fd for IPC before any library can pollute it.
+# Then redirect sys.stdout to stderr so library prints go to stderr.
+_ipc_out: io.TextIOWrapper | None = None
+
+
+def init_ipc() -> None:
+    """Capture real stdout for IPC and redirect sys.stdout to stderr.
+
+    Must be called once at sidecar startup, before importing any ML libraries.
+    """
+    global _ipc_out
+    if _ipc_out is not None:
+        return  # already initialised
+
+    # Duplicate the real stdout fd so we keep it even after redirect
+    real_stdout_fd = os.dup(sys.stdout.fileno())
+    _ipc_out = io.TextIOWrapper(
+        io.BufferedWriter(io.FileIO(real_stdout_fd, "w")),
+        encoding="utf-8",
+        line_buffering=True,
+    )
+
+    # Redirect sys.stdout → stderr so print() from libraries goes to stderr
+    sys.stdout = sys.stderr
+
+
+def _get_ipc_out() -> io.TextIOWrapper:
+    """Return the IPC output stream, falling back to sys.__stdout__."""
+    if _ipc_out is not None:
+        return _ipc_out
+    # Fallback if init_ipc() was never called (e.g. in tests)
+    return sys.__stdout__
+
 
 def read_message() -> IPCMessage | None:
     """Read a single JSON-line message from stdin. Returns None on EOF."""
@@ -29,17 +69,19 @@ def read_message() -> IPCMessage | None:
 
 
 def write_message(msg: IPCMessage) -> None:
-    """Write a JSON-line message to stdout."""
+    """Write a JSON-line message to the IPC channel (real stdout)."""
+    out = _get_ipc_out()
     line = json.dumps(msg.to_dict(), separators=(",", ":"))
-    sys.stdout.write(line + "\n")
-    sys.stdout.flush()
+    out.write(line + "\n")
+    out.flush()
 
 
 def write_dict(data: dict[str, Any]) -> None:
-    """Write a raw dict as a JSON-line message to stdout."""
+    """Write a raw dict as a JSON-line message to the IPC channel."""
+    out = _get_ipc_out()
     line = json.dumps(data, separators=(",", ":"))
-    sys.stdout.write(line + "\n")
-    sys.stdout.flush()
+    out.write(line + "\n")
+    out.flush()
 
 
 def _log(message: str) -> None:

python/voice_to_notes/main.py

@@ -5,7 +5,13 @@ from __future__ import annotations
 import signal
 import sys
 
-from voice_to_notes.ipc.handlers import (
+# CRITICAL: Capture real stdout for IPC *before* importing any ML libraries
+# that might print to stdout and corrupt the JSON-line protocol.
+from voice_to_notes.ipc.protocol import init_ipc
+
+init_ipc()
+
+from voice_to_notes.ipc.handlers import (  # noqa: E402
     HandlerRegistry,
     hardware_detect_handler,
     make_ai_chat_handler,
@@ -15,8 +21,8 @@ from voice_to_notes.ipc.handlers import (
     make_transcribe_handler,
     ping_handler,
 )
-from voice_to_notes.ipc.messages import ready_message
-from voice_to_notes.ipc.protocol import read_message, write_message
+from voice_to_notes.ipc.messages import ready_message  # noqa: E402
+from voice_to_notes.ipc.protocol import read_message, write_message  # noqa: E402
 
 
 def create_registry() -> HandlerRegistry:

src-tauri/src/lib.rs

@@ -4,6 +4,9 @@ pub mod llama;
 pub mod sidecar;
 pub mod state;
 
+use tauri::window::Color;
+use tauri::Manager;
+
 use commands::ai::{ai_chat, ai_configure, ai_list_providers};
 use commands::export::export_transcript;
 use commands::project::{create_project, get_project, list_projects};
@@ -20,6 +23,13 @@ pub fn run() {
         .plugin(tauri_plugin_opener::init())
         .plugin(tauri_plugin_dialog::init())
         .manage(app_state)
+        .setup(|app| {
+            // Set the webview background to match the app's dark theme
+            if let Some(window) = app.get_webview_window("main") {
+                let _ = window.set_background_color(Some(Color(10, 10, 35, 255)));
+            }
+            Ok(())
+        })
         .invoke_handler(tauri::generate_handler![
             create_project,
             get_project,

src-tauri/src/sidecar/mod.rs

@@ -107,8 +107,9 @@ impl SidecarManager {
                         return Ok(());
                     }
                 }
-                // Non-ready message: something is wrong
-                break;
+                // Non-JSON or non-ready line — skip and keep waiting
+                eprintln!("[sidecar-rs] Skipping pre-ready line: {}", &trimmed[..trimmed.len().min(200)]);
+                continue;
             }
         }
         Err("Sidecar did not send ready message".to_string())
@@ -160,8 +161,14 @@ impl SidecarManager {
                     if trimmed.is_empty() {
                         continue;
                     }
-                    let response: IPCMessage = serde_json::from_str(trimmed)
-                        .map_err(|e| format!("Parse error: {e}"))?;
+                    // Skip non-JSON lines (library output that leaked to stdout)
+                    let response: IPCMessage = match serde_json::from_str(trimmed) {
+                        Ok(msg) => msg,
+                        Err(_) => {
+                            eprintln!("[sidecar-rs] Skipping non-JSON line: {}", &trimmed[..trimmed.len().min(200)]);
+                            continue;
+                        }
+                    };
 
                     if response.msg_type == "progress" {
                         on_progress(&response);

src-tauri/tauri.conf.json

@@ -16,7 +16,9 @@
         "width": 1200,
         "height": 800,
         "minWidth": 800,
-        "minHeight": 600
+        "minHeight": 600,
+        "decorations": true,
+        "transparent": false
       }
     ],
     "security": {

src/app.html

@@ -1,5 +1,5 @@
 <!doctype html>
-<html lang="en">
+<html lang="en" style="margin:0;padding:0;background:#0a0a23;height:100%;">
   <head>
     <meta charset="utf-8" />
     <link rel="icon" href="%sveltekit.assets%/favicon.png" />
@@ -7,7 +7,7 @@
     <title>Voice to Notes</title>
     %sveltekit.head%
   </head>
-  <body data-sveltekit-preload-data="hover">
+  <body data-sveltekit-preload-data="hover" style="margin:0;padding:0;background:#0a0a23;overflow:hidden;">
     <div style="display: contents">%sveltekit.body%</div>
   </body>
 </html>

src/routes/+page.svelte

@@ -11,7 +11,7 @@
   import { segments, speakers } from '$lib/stores/transcript';
   import { settings, loadSettings } from '$lib/stores/settings';
   import type { Segment, Speaker } from '$lib/types/transcript';
-  import { onMount } from 'svelte';
+  import { onMount, tick } from 'svelte';
 
   let waveformPlayer: WaveformPlayer;
   let audioUrl = $state('');
@@ -87,12 +87,15 @@
     audioUrl = convertFileSrc(filePath);
     waveformPlayer?.loadAudio(audioUrl);
 
-    // Start pipeline (transcription + diarization)
+    // Start pipeline — show overlay immediately before heavy processing
     isTranscribing = true;
     transcriptionProgress = 0;
     transcriptionStage = 'Starting...';
     transcriptionMessage = 'Initializing pipeline...';
 
+    // Flush DOM so the progress overlay renders before the blocking invoke
+    await tick();
+
     // Listen for progress events from the sidecar
     const unlisten = await listen<{
       percent: number;