Cut daemon and main PTY batch windows 8ms -> 2ms

At 9% pipeline utilization the DSR-under-load latency is fixed batching
windows, not queue depth (proved by the MessageChannel drain lever
moving nothing). Both hops charged an expected half-window per chunk;
2ms keeps burst coalescing at negligible IPC overhead (~500 msgs/s
worst case vs MB/s payloads).

Co-authored-by: Orca <help@stably.ai>

src/main/daemon/daemon-stream-data-batcher.ts

@@ -11,9 +11,12 @@ type PendingStreamDataBatch = {
   queuedChars: number
 }
 
-// Why: match main-process PTY IPC batching to avoid adding latency while
-// removing daemon socket writes and JSON framing during bursty output.
-const STREAM_DATA_BATCH_INTERVAL_MS = 8
+// Why 2ms: under continuous agent output every chunk waits an expected
+// half-window here AND again in main's PTY batch — at 8ms each that was
+// ~8ms of the measured ~19ms DSR-under-load latency. 2ms keeps burst
+// coalescing (~500 socket writes/s worst case, ~100B framing overhead per
+// write against MB/s payloads) while cutting the fixed latency tax 4x.
+const STREAM_DATA_BATCH_INTERVAL_MS = 2
 
 type EnqueueOptions = {
   flushImmediately?: boolean

src/main/ipc/pty.ts

@@ -1445,7 +1445,11 @@ export function registerPtyHandlers(
   let flushTimer: ReturnType<typeof setTimeout> | null = null
   let rendererInFlightTotalChars = 0
   let pendingDroppedChars = 0
-  const PTY_BATCH_INTERVAL_MS = 8
+  // Why 2ms: pairs with the daemon stream batcher (see
+  // daemon-stream-data-batcher.ts) — both hops charged an expected
+  // half-window per chunk; 2ms keeps flood coalescing at negligible IPC
+  // overhead while cutting the pipeline's fixed latency tax.
+  const PTY_BATCH_INTERVAL_MS = 2
   const PTY_BATCH_DRAIN_CONTINUE_MS = 1
   const PTY_BATCH_FLUSH_CHUNK_CHARS = 16 * 1024
   const PTY_BATCH_FLUSH_MAX_WRITES = 2

tools/benchmarks/results/terminal-pipeline-dev-msgchannel-2026-07-03T20-25-28-128Z.json

@@ -0,0 +1,116 @@
+{
+  "benchmark": "terminal-pipeline",
+  "label": "dev-msgchannel",
+  "timestamp": "2026-07-03T20:25:28.128Z",
+  "terminal": {
+    "program": "Orca",
+    "version": "1.4.120",
+    "term": "xterm-256color",
+    "cols": 282,
+    "rows": 80,
+    "tty": true
+  },
+  "machine": {
+    "platform": "darwin",
+    "arch": "arm64",
+    "cpu": "Apple M4",
+    "release": "25.2.0",
+    "node": "v26.0.0"
+  },
+  "config": {
+    "sizeMb": 3,
+    "iterations": 5,
+    "dsrCount": 200
+  },
+  "dsrIdle": {
+    "count": 200,
+    "p50": 1.0432919999999797,
+    "p90": 2.4471249999999145,
+    "p99": 45.014125000000035,
+    "max": 57.02449999999999,
+    "timeouts": 0
+  },
+  "throughput": [
+    {
+      "fixture": "ascii-log",
+      "fixtureBytes": 3145851,
+      "wallMs": {
+        "count": 5,
+        "p50": 425.00216699999964,
+        "p90": 472.5160420000002,
+        "p99": 472.5160420000002,
+        "max": 472.5160420000002
+      },
+      "mbPerSec": {
+        "count": 5,
+        "p50": 7.059063541059357,
+        "p90": 7.810209697729803,
+        "p99": 7.810209697729803,
+        "max": 7.810209697729803
+      }
+    },
+    {
+      "fixture": "cjk-emoji",
+      "fixtureBytes": 3145785,
+      "wallMs": {
+        "count": 5,
+        "p50": 331.4376660000007,
+        "p90": 383.04050000000007,
+        "p99": 383.04050000000007,
+        "max": 383.04050000000007
+      },
+      "mbPerSec": {
+        "count": 5,
+        "p50": 9.051639771793555,
+        "p90": 9.61670443426201,
+        "p99": 9.61670443426201,
+        "max": 9.61670443426201
+      }
+    },
+    {
+      "fixture": "agent-tui",
+      "fixtureBytes": 3146560,
+      "wallMs": {
+        "count": 5,
+        "p50": 328.68583300000046,
+        "p90": 357.50683300000037,
+        "p99": 357.50683300000037,
+        "max": 357.50683300000037
+      },
+      "mbPerSec": {
+        "count": 5,
+        "p50": 9.129670815569485,
+        "p90": 9.548479391576642,
+        "p99": 9.548479391576642,
+        "max": 9.548479391576642
+      }
+    },
+    {
+      "fixture": "styles-stress",
+      "fixtureBytes": 3145734,
+      "wallMs": {
+        "count": 5,
+        "p50": 753.0036249999994,
+        "p90": 770.5100000000002,
+        "p99": 770.5100000000002,
+        "max": 770.5100000000002
+      },
+      "mbPerSec": {
+        "count": 5,
+        "p50": 3.9840521644844684,
+        "p90": 4.840472273920311,
+        "p99": 4.840472273920311,
+        "max": 4.840472273920311
+      }
+    }
+  ],
+  "dsrUnderLoad": {
+    "paceBytesPerSec": 1048576,
+    "count": 50,
+    "p50": 19.011790999998993,
+    "p90": 22.73199999999997,
+    "p99": 28.13012499999968,
+    "max": 28.13012499999968,
+    "timeouts": 0
+  }
+}