🤖 feat: sliding window audio waveform for voice recording (#862)

_Generated with `mux`_

Replaces the static animated bars with a custom sliding window waveform
that shows the last 10 seconds of audio amplitude - similar to ChatGPT's
recording UI.

### Features
- **10-second sliding window**: Shows audio history with new samples
appearing on the right and sliding left
- **Mode-colored**: Visualization uses plan (blue) or exec (purple)
based on current mode
- **Full-width responsive**: Bars dynamically fill the container at any
viewport size
- **Smooth visualization**: RMS amplitude calculation with 50ms sampling
interval

### Technical
- Custom `SlidingWaveform` component using canvas and Web Audio API
- `AnalyserNode` for real-time audio amplitude sampling
- `ResizeObserver` for responsive container measurement
- Exposed `MediaRecorder` from `useVoiceInput` hook

Author: ammar-agent

src/browser/components/ChatInput/RecordingOverlay.tsx

@@ -0,0 +1,262 @@
+/**
+ * Recording overlay - shows live audio visualization during voice recording.
+ * Replaces the chat textarea when voice input is active.
+ */
+
+import React, { useRef, useState, useLayoutEffect, useEffect, useCallback } from "react";
+import { Loader2 } from "lucide-react";
+import { cn } from "@/common/lib/utils";
+import { formatKeybind, KEYBINDS } from "@/browser/utils/ui/keybinds";
+import type { UIMode } from "@/common/types/mode";
+import type { VoiceInputState } from "@/browser/hooks/useVoiceInput";
+
+/** Canvas fill colors for the waveform (slightly lighter than CSS vars for visibility) */
+const MODE_COLORS: Record<UIMode, string> = {
+  plan: "hsl(210, 70%, 55%)",
+  exec: "hsl(268, 94%, 65%)",
+};
+
+/** Tailwind classes for recording state, keyed by mode */
+const RECORDING_CLASSES: Record<UIMode, string> = {
+  plan: "cursor-pointer border-plan-mode bg-plan-mode/10",
+  exec: "cursor-pointer border-exec-mode bg-exec-mode/10",
+};
+
+const TEXT_CLASSES: Record<UIMode, string> = {
+  plan: "text-plan-mode-light",
+  exec: "text-exec-mode-light",
+};
+
+// Waveform shows last 10 seconds of audio, sampled every 50ms (200 samples)
+const WINDOW_DURATION_MS = 10_000;
+const SAMPLE_INTERVAL_MS = 50;
+const NUM_SAMPLES = WINDOW_DURATION_MS / SAMPLE_INTERVAL_MS;
+
+interface RecordingOverlayProps {
+  state: VoiceInputState;
+  mode: UIMode;
+  mediaRecorder: MediaRecorder | null;
+  onStop: () => void;
+}
+
+export const RecordingOverlay: React.FC<RecordingOverlayProps> = (props) => {
+  const isRecording = props.state === "recording";
+  const isTranscribing = props.state === "transcribing";
+
+  const containerClasses = cn(
+    "mb-1 flex w-full flex-col items-center justify-center gap-1 rounded-md border px-3 py-2 transition-all focus:outline-none",
+    isRecording ? RECORDING_CLASSES[props.mode] : "cursor-wait border-amber-500 bg-amber-500/10"
+  );
+
+  return (
+    <button
+      type="button"
+      onClick={isRecording ? props.onStop : undefined}
+      disabled={isTranscribing}
+      className={containerClasses}
+      aria-label={isRecording ? "Stop recording" : "Transcribing..."}
+    >
+      <div className="flex h-8 w-full items-center justify-center">
+        {isRecording && props.mediaRecorder ? (
+          <SlidingWaveform
+            mediaRecorder={props.mediaRecorder}
+            color={MODE_COLORS[props.mode]}
+            height={32}
+          />
+        ) : (
+          <Loader2 className="h-5 w-5 animate-spin text-amber-500" />
+        )}
+      </div>
+
+      <span
+        className={cn(
+          "text-xs font-medium",
+          isRecording ? TEXT_CLASSES[props.mode] : "text-amber-500"
+        )}
+      >
+        {isRecording ? <RecordingHints /> : "Transcribing..."}
+      </span>
+    </button>
+  );
+};
+
+/** Keyboard hint display for recording state */
+const RecordingHints: React.FC = () => (
+  <>
+    <span className="opacity-70">space</span> send ·{" "}
+    <span className="opacity-70">{formatKeybind(KEYBINDS.TOGGLE_VOICE_INPUT)}</span> review ·{" "}
+    <span className="opacity-70">esc</span> cancel
+  </>
+);
+
+// =============================================================================
+// SlidingWaveform - Canvas-based amplitude visualization
+// =============================================================================
+
+interface SlidingWaveformProps {
+  mediaRecorder: MediaRecorder;
+  color: string;
+  height: number;
+}
+
+/**
+ * Renders a sliding window of audio amplitude over time.
+ * New samples appear on the right and scroll left as time passes.
+ * Falls back to a simple pulsing indicator if Web Audio API fails.
+ */
+const SlidingWaveform: React.FC<SlidingWaveformProps> = (props) => {
+  const canvasRef = useRef<HTMLCanvasElement>(null);
+  const containerRef = useRef<HTMLDivElement>(null);
+  const [containerWidth, setContainerWidth] = useState(600);
+  const [audioError, setAudioError] = useState(false);
+
+  // Audio analysis state (refs to avoid re-renders)
+  const audioContextRef = useRef<AudioContext | null>(null);
+  const analyserRef = useRef<AnalyserNode | null>(null);
+  const samplesRef = useRef<number[]>(new Array<number>(NUM_SAMPLES).fill(0));
+  const animationFrameRef = useRef<number>(0);
+  const lastSampleTimeRef = useRef<number>(0);
+
+  // Track container width for responsive canvas
+  useLayoutEffect(() => {
+    const container = containerRef.current;
+    if (!container) return;
+
+    const observer = new ResizeObserver((entries) => {
+      for (const entry of entries) {
+        setContainerWidth(entry.contentRect.width);
+      }
+    });
+    observer.observe(container);
+    setContainerWidth(container.offsetWidth);
+
+    return () => observer.disconnect();
+  }, []);
+
+  // Initialize Web Audio API analyser
+  useEffect(() => {
+    const stream = props.mediaRecorder.stream;
+    if (!stream) return;
+
+    try {
+      const audioContext = new AudioContext();
+      const analyser = audioContext.createAnalyser();
+      analyser.fftSize = 256;
+      analyser.smoothingTimeConstant = 0.3;
+
+      const source = audioContext.createMediaStreamSource(stream);
+      source.connect(analyser);
+
+      audioContextRef.current = audioContext;
+      analyserRef.current = analyser;
+      samplesRef.current = new Array<number>(NUM_SAMPLES).fill(0);
+      lastSampleTimeRef.current = performance.now();
+
+      return () => {
+        void audioContext.close();
+        audioContextRef.current = null;
+        analyserRef.current = null;
+      };
+    } catch (err) {
+      console.error("Failed to initialize audio visualization:", err);
+      setAudioError(true);
+    }
+  }, [props.mediaRecorder]);
+
+  // Animation loop: sample audio amplitude and render bars
+  const draw = useCallback(() => {
+    const canvas = canvasRef.current;
+    const analyser = analyserRef.current;
+    if (!canvas || !analyser) return;
+
+    const ctx = canvas.getContext("2d");
+    if (!ctx) return;
+
+    // Sample audio at fixed intervals
+    const now = performance.now();
+    if (now - lastSampleTimeRef.current >= SAMPLE_INTERVAL_MS) {
+      const dataArray = new Uint8Array(analyser.frequencyBinCount);
+      analyser.getByteTimeDomainData(dataArray);
+
+      // Calculate RMS (root mean square) amplitude
+      let sum = 0;
+      for (const sample of dataArray) {
+        const normalized = (sample - 128) / 128;
+        sum += normalized * normalized;
+      }
+      const rms = Math.sqrt(sum / dataArray.length);
+
+      samplesRef.current.shift();
+      samplesRef.current.push(rms);
+      lastSampleTimeRef.current = now;
+    }
+
+    // Render bars
+    ctx.clearRect(0, 0, canvas.width, canvas.height);
+
+    const samples = samplesRef.current;
+    const numBars = samples.length;
+    // Bar sizing: bars fill full width with 40% gap ratio
+    const barWidth = canvas.width / (1.4 * numBars - 0.4);
+    const gap = barWidth * 0.4;
+    const centerY = canvas.height / 2;
+
+    ctx.fillStyle = props.color;
+
+    for (let i = 0; i < numBars; i++) {
+      const scaledAmplitude = Math.min(1, samples[i] * 3); // Boost for visibility
+      const barHeight = Math.max(2, scaledAmplitude * canvas.height * 0.9);
+      const x = i * (barWidth + gap);
+      const y = centerY - barHeight / 2;
+
+      ctx.beginPath();
+      // roundRect fallback for older browsers (though Electron 38+ supports it)
+      if (ctx.roundRect) {
+        ctx.roundRect(x, y, barWidth, barHeight, 1);
+      } else {
+        ctx.rect(x, y, barWidth, barHeight);
+      }
+      ctx.fill();
+    }
+
+    animationFrameRef.current = requestAnimationFrame(draw);
+  }, [props.color]);
+
+  // Run animation loop
+  useEffect(() => {
+    if (audioError) return;
+    animationFrameRef.current = requestAnimationFrame(draw);
+    return () => cancelAnimationFrame(animationFrameRef.current);
+  }, [draw, audioError]);
+
+  // Fallback: simple pulsing indicator if Web Audio API unavailable
+  if (audioError) {
+    return (
+      <div className="flex h-full w-full items-center justify-center gap-1">
+        {[0, 1, 2, 3, 4].map((i) => (
+          <div
+            key={i}
+            className="animate-pulse rounded-full"
+            style={{
+              width: 4,
+              height: 12 + (i % 3) * 4,
+              backgroundColor: props.color,
+              animationDelay: `${i * 100}ms`,
+            }}
+          />
+        ))}
+      </div>
+    );
+  }
+
+  return (
+    <div ref={containerRef} className="flex h-full w-full items-center justify-center">
+      <canvas
+        ref={canvasRef}
+        width={containerWidth}
+        height={props.height}
+        style={{ width: containerWidth, height: props.height }}
+      />
+    </div>
+  );
+};

src/browser/components/ChatInput/VoiceInputButton.tsx

@@ -9,6 +9,7 @@ import { TooltipWrapper, Tooltip } from "../Tooltip";
 import { formatKeybind, KEYBINDS } from "@/browser/utils/ui/keybinds";
 import { cn } from "@/common/lib/utils";
 import type { VoiceInputState } from "@/browser/hooks/useVoiceInput";
+import type { UIMode } from "@/common/types/mode";
 
 interface VoiceInputButtonProps {
   state: VoiceInputState;
@@ -17,29 +18,43 @@ interface VoiceInputButtonProps {
   requiresSecureContext: boolean;
   onToggle: () => void;
   disabled?: boolean;
+  mode: UIMode;
 }
 
-const STATE_CONFIG: Record<VoiceInputState, { label: string; colorClass: string }> = {
-  idle: { label: "Voice input", colorClass: "text-muted/50 hover:text-muted" },
-  recording: { label: "Stop recording", colorClass: "text-blue-500 animate-pulse" },
-  transcribing: { label: "Transcribing...", colorClass: "text-amber-500" },
+/** Color classes for each voice input state */
+const STATE_COLORS: Record<VoiceInputState, string> = {
+  idle: "text-muted/50 hover:text-muted",
+  recording: "", // Set dynamically based on mode
+  transcribing: "text-amber-500",
 };
 
+const RECORDING_COLORS: Record<UIMode, string> = {
+  plan: "text-plan-mode-light animate-pulse",
+  exec: "text-exec-mode-light animate-pulse",
+};
+
+function getColorClass(state: VoiceInputState, mode: UIMode): string {
+  return state === "recording" ? RECORDING_COLORS[mode] : STATE_COLORS[state];
+}
+
 export const VoiceInputButton: React.FC<VoiceInputButtonProps> = (props) => {
   if (!props.shouldShowUI) return null;
 
   const needsHttps = props.requiresSecureContext;
   const needsApiKey = !needsHttps && !props.isApiKeySet;
-  const isDisabledReason = needsHttps || needsApiKey;
+  const isDisabled = needsHttps || needsApiKey;
+
+  const label = isDisabled
+    ? needsHttps
+      ? "Voice input (requires HTTPS)"
+      : "Voice input (requires OpenAI API key)"
+    : props.state === "recording"
+      ? "Stop recording"
+      : props.state === "transcribing"
+        ? "Transcribing..."
+        : "Voice input";
 
-  const { label, colorClass } = isDisabledReason
-    ? {
-        label: needsHttps
-          ? "Voice input (requires HTTPS)"
-          : "Voice input (requires OpenAI API key)",
-        colorClass: "text-muted/50",
-      }
-    : STATE_CONFIG[props.state];
+  const colorClass = isDisabled ? "text-muted/50" : getColorClass(props.state, props.mode);
 
   const Icon = props.state === "transcribing" ? Loader2 : Mic;
   const isTranscribing = props.state === "transcribing";
@@ -49,7 +64,7 @@ export const VoiceInputButton: React.FC<VoiceInputButtonProps> = (props) => {
       <button
         type="button"
         onClick={props.onToggle}
-        disabled={(props.disabled ?? false) || isTranscribing || isDisabledReason}
+        disabled={(props.disabled ?? false) || isTranscribing || isDisabled}
         aria-label={label}
         aria-pressed={props.state === "recording"}
         className={cn(