fix(ios): start incremental speech at soft boundaries (#33305)

Merged via squash.

Prepared head SHA: d1acf72317
Co-authored-by: mbelinky <132747814+mbelinky@users.noreply.github.com>
Co-authored-by: mbelinky <132747814+mbelinky@users.noreply.github.com>
Reviewed-by: @mbelinky

apps/ios/Sources/Voice/TalkModeManager.swift

@@ -1682,6 +1682,8 @@ final class TalkModeManager: NSObject {
 }
 
 private struct IncrementalSpeechBuffer {
+    private static let softBoundaryMinChars = 72
+
     private(set) var latestText: String = ""
     private(set) var directive: TalkDirective?
     private var spokenOffset: Int = 0
@@ -1774,8 +1776,9 @@ private struct IncrementalSpeechBuffer {
             }
 
             if !inCodeBlock {
-                buffer.append(chars[idx])
-                if Self.isBoundary(chars[idx]) {
+                let currentChar = chars[idx]
+                buffer.append(currentChar)
+                if Self.isBoundary(currentChar) || Self.isSoftBoundary(currentChar, bufferedChars: buffer.count) {
                     lastBoundary = idx + 1
                     bufferAtBoundary = buffer
                     inCodeBlockAtBoundary = inCodeBlock
@@ -1802,6 +1805,10 @@ private struct IncrementalSpeechBuffer {
     private static func isBoundary(_ ch: Character) -> Bool {
         ch == "." || ch == "!" || ch == "?" || ch == "\n"
     }
+
+    private static func isSoftBoundary(_ ch: Character, bufferedChars: Int) -> Bool {
+        bufferedChars >= Self.softBoundaryMinChars && ch.isWhitespace
+    }
 }
 
 extension TalkModeManager {

apps/ios/Tests/TalkModeIncrementalSpeechBufferTests.swift

@@ -0,0 +1,28 @@
+import Testing
+@testable import OpenClaw
+
+@MainActor
+@Suite struct TalkModeIncrementalSpeechBufferTests {
+    @Test func emitsSoftBoundaryBeforeTerminalPunctuation() {
+        let manager = TalkModeManager(allowSimulatorCapture: true)
+        manager._test_incrementalReset()
+
+        let partial =
+            "We start speaking earlier by splitting this long stream chunk at a whitespace boundary before punctuation arrives"
+        let segments = manager._test_incrementalIngest(partial, isFinal: false)
+
+        #expect(segments.count == 1)
+        #expect(segments[0].count >= 72)
+        #expect(segments[0].count < partial.count)
+    }
+
+    @Test func keepsShortChunkBufferedWithoutPunctuation() {
+        let manager = TalkModeManager(allowSimulatorCapture: true)
+        manager._test_incrementalReset()
+
+        let short = "short chunk without punctuation"
+        let segments = manager._test_incrementalIngest(short, isFinal: false)
+
+        #expect(segments.isEmpty)
+    }
+}