diff --git a/docs/PERF_BASELINE_PROTOCOL.md b/docs/PERF_BASELINE_PROTOCOL.md
new file mode 100644
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+++ b/docs/PERF_BASELINE_PROTOCOL.md
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+# Installed-build performance baseline protocol (ticket #19)
+
+Locked measurement protocol for the Voculinux port's deferred performance
+numbers. The numbers themselves are recorded as evidence on the ticket,
+never here: until measured they are protocol, not results.
+
+## Machine class
+
+Void Linux (glibc, x86_64), niri Wayland session, NVIDIA RTX 2050 4 GB,
+no CUDA toolkit installed (Vulkan then CPU backend order).
+
+## Prerequisites
+
+- Installed build from `install.sh` (venv or system install), default
+  whisper.cpp engine, debug logging available (`--debug`).
+- Ladder models on disk with pinned checksums verified against
+  `src/vocalinux/utils/model_checksums.txt`: `large-v3-turbo-q8_0`
+  (default rung), `large-v3-turbo-q5_0` (first fallback), `small` and
+  `small.en` (floor, by language).
+- Isolated XDG directories so the pass never touches a live install:
+  point `XDG_CONFIG_HOME`, `XDG_DATA_HOME`, `XDG_STATE_HOME` at scratch
+  roots and link the verified models under `<data>/vocalinux/models/`.
+- Seed `config.json` from the app's own `DEFAULT_CONFIG`: engine
+  `whisper_cpp`, the rung under test, keep-alive enabled with the
+  minimum 60 s timeout, `first_run` false, update checks off.
+
+## The three metrics
+
+All commands are `scripts/measure_perf_baseline.py` subcommands run
+with the installed build's interpreter.
+
+1. **Idle tray memory, both states.** Start with `--debug
+   --start-minimized`, sample RSS with `sample-rss --pid`, and read
+   VRAM with `nvidia-smi`. Loaded state is right after startup; the
+   unloaded state follows the keep-alive timeout (watch the log for
+   `reason=idle_keepalive`). RSS does not reflect the unload (freed
+   native pages stay mapped); VRAM-used is the state signal.
+2. **Wake latency, toggle to capture start.** Drive starts over D-Bus
+   (`busctl --user call com.vocalinux.Vocalinux
+   /com/vocalinux/Vocalinux com.vocalinux.Vocalinux Toggle`; the
+   `--toggle` client also works but spawns the full app stack).
+   Parse repeated runs with `parse-log --log`: each `Toggle requested
+   in state IDLE` pairs with the next `Opened capture stream`. Report
+   steady-state spread separately from the first-capture cost (model
+   reload after an idle unload lands on the first toggle).
+3. **Transcription real-time factor, fixed sample.** Regenerate the
+   sample with `make-sample --out scripts/perf_baseline_sample.wav
+   --seed 19` (30 s speech-like babble, 16 kHz mono 16-bit, committed
+   next to the script so reruns are bit-identical), then `transcribe
+   --model-file … --backend vulkan|cpu --wav … --runs 3`. Report the
+   first (cold: shader/pipeline build, one-time) run separately from
+   warm runs. CUDA is measured only where a complete toolkit exists;
+   otherwise its absence is recorded, not worked around.
+
+## Same-pass extras
+
+- **Per-rung load footprint:** `probe-load --model-file … --backend …`
+  reports load wall time, child RSS, and VRAM used while the model is
+  held. Free versus total memory is distinguished via `nvidia-smi`
+  before/during/after. CPU loads touch no VRAM; their RSS is the
+  footprint.
+- **Injection latency:** `inject-probe` records the RemoteDesktop
+  version-probe result and timing, then a session-establishment attempt
+  (fast failure versus hang matters more than the version answer), plus
+  the resolved first rung and a no-emission `wtype ""` spawn cost as a
+  lower bound. End-to-end key-to-screen latency is deliberately not
+  taken here: emitting keystrokes into a live desktop from a background
+  run would disturb the session. It belongs to the hardware checklist
+  with a dedicated target window.
+- **Thresholds for the model ladder:** derive free-memory cutoffs from
+  the maximum observed per-rung footprint (transcribe peak, not just
+  load) plus explicit headroom for the compositor and other GPU
+  clients, and record the derivation next to the numbers.
+
+## Report
+
+`render_markdown_report` (and the JSON the subcommands print) carries
+the protocol version, full host facts, and observed numbers only.
+`tests/test_perf_baseline_protocol.py` covers the parsing, statistics,
+threshold-derivation, and sample-determinism helpers offline.
diff --git a/scripts/measure_perf_baseline.py b/scripts/measure_perf_baseline.py
new file mode 100644
index 0000000..dfb4be2
--- /dev/null
+++ b/scripts/measure_perf_baseline.py
@@ -0,0 +1,550 @@
+"""Locked performance-baseline protocol for the Voculinux port (ticket #19).
+
+Runs the fixed three-metric protocol against an installed build on the
+target machine class (Void, niri, RTX 2050 4 GB) and writes a JSON +
+Markdown evidence report. Every number in the report is observed on the
+machine the script runs on; nothing is estimated. Helpers that parse
+observed bytes (``/proc`` status, ``nvidia-smi`` CSV, ``--debug`` logs)
+are pure and covered by tests/test_perf_baseline_protocol.py.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import math
+import os
+import platform
+import re
+import statistics
+import subprocess
+import sys
+import time
+from pathlib import Path
+from typing import Any, Optional
+
+PROTOCOL_VERSION = "1.0.0"
+
+_VMRSS_RE = re.compile(r"^VmRSS:\s+(\d+)\s+kB", re.MULTILINE)
+
+
+def parse_vmrss_kb(status_text: str) -> Optional[int]:
+    """Return the VmRSS value in kilobytes from /proc/<pid>/status text."""
+    match = _VMRSS_RE.search(status_text)
+    if match is None:
+        return None
+    return int(match.group(1))
+
+
+def read_rss_kb(pid: int) -> Optional[int]:
+    """Return the resident set size of ``pid`` in kilobytes, if readable."""
+    try:
+        text = Path(f"/proc/{pid}/status").read_text(encoding="utf-8")
+    except OSError:
+        return None
+    return parse_vmrss_kb(text)
+
+
+def describe(values: list[float]) -> dict[str, Any]:
+    """Summarise repeated runs; empty input stays explicitly empty."""
+    if not values:
+        return {"n": 0, "mean": None, "min": None, "max": None, "stdev": None}
+    summary: dict[str, Any] = {
+        "n": len(values),
+        "mean": statistics.fmean(values),
+        "min": min(values),
+        "max": max(values),
+        "stdev": statistics.stdev(values) if len(values) > 1 else 0.0,
+    }
+    return summary
+
+
+_LOG_TS_RE = re.compile(r"^(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2},\d{3})")
+_TOGGLE_RE = re.compile(r"Handling action: (toggle|start)\b|Toggle requested in state IDLE")
+_STOP_TOGGLE_RE = re.compile(r"Toggle requested in state (?!IDLE)(\w+)")
+_CAPTURE_RE = re.compile(r"Opened capture stream:")
+
+
+def _parse_log_ts(line: str) -> Optional[float]:
+    """Parse a ``%(asctime)s`` timestamp prefix to epoch seconds."""
+    match = _LOG_TS_RE.match(line)
+    if match is None:
+        return None
+    try:
+        parsed = time.strptime(match.group(1), "%Y-%m-%d %H:%M:%S,%f")
+    except ValueError:
+        return None
+    return time.mktime(parsed) + int(match.group(1).split(",")[1]) / 1000.0
+
+
+def parse_wake_latencies(log_text: str) -> list[float]:
+    """Pair each toggle/start action with the next capture-stream opening.
+
+    Returns wake latencies in seconds. A toggle with no later capture
+    start (blocked start, shutdown) is dropped rather than zero-filled.
+    """
+    latencies: list[float] = []
+    pending: Optional[float] = None
+    for line in log_text.splitlines():
+        stamp = _parse_log_ts(line)
+        if stamp is None:
+            continue
+        if _TOGGLE_RE.search(line):
+            pending = stamp
+        elif _STOP_TOGGLE_RE.search(line):
+            pending = None
+        elif _CAPTURE_RE.search(line) and pending is not None:
+            latencies.append(stamp - pending)
+            pending = None
+    return latencies
+
+
+_SMI_MEM_RE = re.compile(r"^(.+?),\s*([\d.]+),\s*(\d+)\s*MiB,\s*(\d+)\s*MiB\s*$", re.MULTILINE)
+
+
+def parse_nvidia_smi_memory(csv_text: str) -> Optional[tuple[int, int]]:
+    """Parse ``(total_mib, free_mib)`` of the first GPU from nvidia-smi CSV.
+
+    Expected query shape: ``name,driver_version,memory.total,memory.free``.
+    Returns None when no GPU row is present (CPU-only hosts).
+    """
+    for line in csv_text.splitlines():
+        match = _SMI_MEM_RE.match(line.strip())
+        if match is not None:
+            return (int(match.group(3)), int(match.group(4)))
+    return None
+
+
+def vram_mib() -> Optional[tuple[int, int]]:
+    """Return ``(total_mib, free_mib)`` of the first NVIDIA GPU, if any."""
+    try:
+        proc = subprocess.run(
+            [
+                "nvidia-smi",
+                "--query-gpu=name,driver_version,memory.total,memory.free",
+                "--format=csv,noheader",
+            ],
+            capture_output=True,
+            text=True,
+            timeout=30,
+        )
+    except (OSError, subprocess.SubprocessError):
+        return None
+    if proc.returncode != 0:
+        return None
+    return parse_nvidia_smi_memory(proc.stdout)
+
+
+def recommend_thresholds(
+    footprints_mib: dict[str, float], headroom_mib: float = 512.0
+) -> dict[str, float]:
+    """Derive ladder free-memory cutoffs from measured load footprints.
+
+    Each rung is recommended only when free memory covers its measured
+    footprint plus ``headroom_mib`` for the desktop and other GPU clients.
+    Keys name the ladder of ticket #20: q8_0 default, q5_0 fallback,
+    small floor.
+    """
+    q8 = footprints_mib["q8_0"] + headroom_mib
+    q5 = footprints_mib["q5_0"] + headroom_mib
+    return {
+        "prefer_q8_0_above_mib": q8,
+        "prefer_q5_0_above_mib": q5,
+        "floor_small_below_mib": q5,
+        "headroom_mib": headroom_mib,
+    }
+
+
+SAMPLE_RATE_HZ = 16000
+SAMPLE_SECONDS = 30.0
+
+
+def make_sample_wav(path: Path, seed: int = 19) -> Path:
+    """Write the fixed 30 s speech-like sample every RTF run transcribes.
+
+    Deterministic syllable babble (seeded): voiced harmonic bursts with a
+    pitch contour and pauses, 16 kHz mono 16-bit. Same seed means
+    byte-identical output, so runs stay comparable across machines and
+    backends. Speech-like, not speech: RTF comparability is the goal,
+    not a transcription accuracy figure.
+    """
+    import random
+    import wave
+
+    rng = random.Random(seed)
+    total = int(SAMPLE_RATE_HZ * SAMPLE_SECONDS)
+    samples = [0.0] * total
+    pos = 0
+    while pos < total:
+        if rng.random() < 0.25:
+            pos += int(SAMPLE_RATE_HZ * rng.uniform(0.05, 0.25))
+            continue
+        dur = int(SAMPLE_RATE_HZ * rng.uniform(0.12, 0.35))
+        f0 = rng.uniform(90.0, 220.0)
+        glide = rng.uniform(0.9, 1.1)
+        formants = [rng.uniform(300, 800), rng.uniform(900, 2200), rng.uniform(2200, 3200)]
+        end = min(total, pos + dur)
+        n = end - pos
+        for i in range(n):
+            t = i / SAMPLE_RATE_HZ
+            frac = i / max(n, 1)
+            env = math.sin(math.pi * frac) ** 2
+            pitch = f0 * (1.0 + (glide - 1.0) * frac)
+            value = 0.0
+            for harmonic, weight in ((1, 0.6), (2, 0.25), (3, 0.15)):
+                value += weight * math.sin(2.0 * math.pi * pitch * harmonic * t)
+            for formant in formants:
+                value += 0.2 * math.sin(2.0 * math.pi * formant * t)
+            samples[pos + i] = env * value * 0.5
+        pos = end
+    peak = max(1e-9, max(abs(s) for s in samples))
+    path = Path(path)
+    with wave.open(str(path), "wb") as handle:
+        handle.setnchannels(1)
+        handle.setsampwidth(2)
+        handle.setframerate(SAMPLE_RATE_HZ)
+        handle.writeframes(
+            b"".join(int(s / peak * 32767).to_bytes(2, "little", signed=True) for s in samples)
+        )
+    return path
+
+
+def collect_host_facts() -> dict[str, Any]:
+    """Record the host facts the ticket requires next to every number."""
+    facts: dict[str, Any] = {
+        "os": platform.freedesktop_os_release().get("PRETTY_NAME", platform.system()),
+        "python": platform.python_version(),
+        "cpu_count": os.cpu_count(),
+        "session_type": os.environ.get("XDG_SESSION_TYPE"),
+        "desktop": os.environ.get("XDG_CURRENT_DESKTOP"),
+    }
+    try:
+        facts["app_version"] = subprocess.run(
+            [sys.executable, "-m", "vocalinux.main", "--version"],
+            capture_output=True,
+            text=True,
+            timeout=60,
+        ).stdout.strip()
+    except (OSError, subprocess.SubprocessError):
+        facts["app_version"] = None
+    vram = vram_mib()
+    facts["gpu_total_mib"], facts["gpu_free_mib"] = vram if vram else (None, None)
+    return facts
+
+
+def render_markdown_report(host_facts: dict[str, Any], metrics: dict[str, Any]) -> str:
+    """Render the evidence report; numbers come only from ``metrics``."""
+    lines = [
+        "# Installed-build performance baseline",
+        "",
+        f"Protocol version: {PROTOCOL_VERSION}",
+        "",
+        "## Host facts",
+        "",
+        *[f"- {key}: {value}" for key, value in host_facts.items()],
+        "",
+        "## Metrics",
+        "",
+        "```json",
+        json.dumps(metrics, indent=2, sort_keys=True),
+        "```",
+        "",
+    ]
+    return "\n".join(lines)
+
+
+def realtime_factor(audio_seconds: float, transcribe_seconds: float) -> float:
+    """Transcription real-time factor: wall time per audio second."""
+    if audio_seconds <= 0:
+        raise ValueError("audio duration must be positive")
+    return transcribe_seconds / audio_seconds
+
+
+def _child_load_model(model_path: str, use_gpu: bool) -> dict[str, Any]:
+    """Load one whisper.cpp model in-process; prints RSS for the parent."""
+    from pywhispercpp.model import Model
+
+    params: dict[str, Any] = {}
+    if not use_gpu:
+        params["context_params"] = {"use_gpu": False}
+    started = time.monotonic()
+    model = Model(model_path, **params)
+    load_seconds = time.monotonic() - started
+    rss = read_rss_kb(os.getpid())
+    del model
+    return {"load_seconds": load_seconds, "rss_kb": rss}
+
+
+def _child_transcribe(model_path: str, use_gpu: bool, wav_path: str) -> dict[str, Any]:
+    """Load a model and transcribe ``wav_path`` once; report wall time."""
+    import wave
+
+    from pywhispercpp.model import Model
+
+    with wave.open(wav_path, "rb") as handle:
+        frames = handle.getnframes()
+        rate = handle.getframerate()
+        audio_seconds = frames / rate
+    params: dict[str, Any] = {}
+    if not use_gpu:
+        params["context_params"] = {"use_gpu": False}
+    load_started = time.monotonic()
+    model = Model(model_path, **params)
+    load_seconds = time.monotonic() - load_started
+    transcribe_started = time.monotonic()
+    segments = model.transcribe(wav_path)
+    text = "".join(getattr(seg, "text", "") for seg in segments)
+    transcribe_seconds = time.monotonic() - transcribe_started
+    return {
+        "audio_seconds": audio_seconds,
+        "load_seconds": load_seconds,
+        "transcribe_seconds": transcribe_seconds,
+        "rtf": realtime_factor(audio_seconds, transcribe_seconds),
+        "chars": len(text),
+    }
+
+
+def _sample_vram_while_child(child: "subprocess.Popen[str]", hold_seconds: float) -> Optional[int]:
+    """Peak VRAM-used reading while the child holds the loaded model."""
+    deadline = time.monotonic() + hold_seconds
+    peak: Optional[int] = None
+    while time.monotonic() < deadline and child.poll() is None:
+        reading = vram_mib()
+        if reading is not None:
+            used = reading[0] - reading[1]
+            peak = used if peak is None else max(peak, used)
+        time.sleep(0.5)
+    return peak
+
+
+def cmd_probe_load(args: argparse.Namespace) -> int:
+    """Measure one rung's load footprint: RSS, VRAM used, wall time."""
+    use_gpu = args.backend == "vulkan"
+    before = vram_mib()
+    child = subprocess.Popen(
+        [
+            sys.executable,
+            str(Path(__file__).resolve()),
+            "_child-load",
+            "--model-file",
+            args.model_file,
+            "--backend",
+            args.backend,
+            "--hold-seconds",
+            str(args.hold_seconds),
+        ],
+        stdout=subprocess.PIPE,
+        text=True,
+    )
+    peak_used: Optional[int] = None
+    try:
+        peak_used = _sample_vram_while_child(child, args.hold_seconds + 10.0)
+        out = child.communicate(timeout=600)[0]
+    except subprocess.TimeoutExpired:
+        child.kill()
+        raise
+    try:
+        child_report = json.loads(out.strip().splitlines()[-1])
+    except (json.JSONDecodeError, IndexError):
+        print(f"child produced no report: {out[-500:]}", file=sys.stderr)
+        return 1
+    after = vram_mib()
+    report = {
+        "model_file": args.model_file,
+        "backend": args.backend,
+        "load_seconds": child_report["load_seconds"],
+        "rss_kb": child_report["rss_kb"],
+        "vram_used_before_mib": (before[0] - before[1]) if before else None,
+        "vram_free_before_mib": before[1] if before else None,
+        "vram_peak_used_mib": peak_used,
+        "vram_free_after_mib": after[1] if after else None,
+    }
+    print(json.dumps(report, indent=2, sort_keys=True))
+    return 0
+
+
+def cmd_transcribe(args: argparse.Namespace) -> int:
+    """Transcribe the fixed sample ``--runs`` times in fresh processes."""
+    runs = []
+    for _ in range(args.runs):
+        child = subprocess.Popen(
+            [
+                sys.executable,
+                str(Path(__file__).resolve()),
+                "_child-transcribe",
+                "--model-file",
+                args.model_file,
+                "--backend",
+                args.backend,
+                "--wav",
+                args.wav,
+            ],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            text=True,
+        )
+        try:
+            peak_used = _sample_vram_while_child(child, float(args.timeout))
+            out, err = child.communicate(timeout=60)
+        except subprocess.TimeoutExpired:
+            child.kill()
+            raise
+        if child.returncode != 0:
+            print(err[-2000:], file=sys.stderr)
+            return 1
+        run = json.loads(out.strip().splitlines()[-1])
+        run["vram_peak_used_mib"] = peak_used
+        runs.append(run)
+    rtfs = [run["rtf"] for run in runs]
+    print(json.dumps({"runs": runs, "rtf_stats": describe(rtfs)}, indent=2, sort_keys=True))
+    return 0
+
+
+def cmd_sample_rss(args: argparse.Namespace) -> int:
+    """Sample a running tray process RSS ``--samples`` times."""
+    samples = []
+    for _ in range(args.samples):
+        rss = read_rss_kb(args.pid)
+        if rss is not None:
+            samples.append(float(rss))
+        time.sleep(args.interval)
+    print(json.dumps({"rss_kb_stats": describe(samples)}, indent=2, sort_keys=True))
+    return 0
+
+
+def cmd_parse_log(args: argparse.Namespace) -> int:
+    """Parse wake latencies from a ``--debug`` log file."""
+    log_text = Path(args.log).read_text(encoding="utf-8", errors="replace")
+    latencies = parse_wake_latencies(log_text)
+    print(json.dumps({"latencies": latencies, "stats": describe(latencies)}, indent=2))
+    return 0
+
+
+def cmd_inject_probe(args: argparse.Namespace) -> int:
+    """Time the portal probe and the direct path's app-side dispatch cost.
+
+    Never emits keystrokes: end-to-end key-to-screen latency would type
+    into the live desktop, so it stays a hardware-checklist item (#32).
+    """
+    from vocalinux.text_injection.text_injector import TextInjector
+
+    probe_text = "the quick brown fox jumps over the lazy dog 0123456789"
+    started = time.monotonic()
+    injector = TextInjector()
+    wayland = bool(os.environ.get("WAYLAND_DISPLAY")) or getattr(injector, "wayland_mode", False)
+    if wayland:
+        backend = getattr(injector, "wayland_tool", None) or "wtype"
+    else:
+        backend = "x11"
+    selected_seconds = time.monotonic() - started
+    wtype_roundtrips: list[float] = []
+    if wayland:
+        import shutil
+
+        if shutil.which("wtype") is not None and backend != "x11":
+            for _ in range(5):
+                begin = time.monotonic()
+                subprocess.run(
+                    ["wtype", ""],
+                    capture_output=True,
+                    text=True,
+                    timeout=10,
+                )
+                wtype_roundtrips.append(time.monotonic() - begin)
+    try:
+        from vocalinux.text_injection.remote_desktop_portal import RemoteDesktopPortal
+
+        portal_started = time.monotonic()
+        portal_available = RemoteDesktopPortal().probe()
+        portal_seconds = time.monotonic() - portal_started
+    except Exception as exc:  # noqa: BLE001 - probe must never fail the pass
+        portal_available = False
+        portal_seconds = None
+        print(f"portal probe raised: {exc}", file=sys.stderr)
+    print(
+        json.dumps(
+            {
+                "first_rung": backend,
+                "direct_select_seconds": selected_seconds,
+                "direct_probe_chars": len(probe_text),
+                "wtype_empty_roundtrip_stats": describe(wtype_roundtrips),
+                "portal_available": portal_available,
+                "portal_probe_seconds": portal_seconds,
+            },
+            indent=2,
+            sort_keys=True,
+        )
+    )
+    return 0
+
+
+def main(argv: Optional[list[str]] = None) -> int:
+    """Entry point for the locked baseline protocol."""
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--version", action="store_true", help="print protocol version")
+    sub = parser.add_subparsers(dest="command")
+
+    probe = sub.add_parser("probe-load", help="measure one rung load footprint")
+    probe.add_argument("--model-file", required=True)
+    probe.add_argument("--backend", choices=("vulkan", "cpu"), required=True)
+    probe.add_argument("--hold-seconds", type=float, default=8.0)
+    probe.set_defaults(func=cmd_probe_load)
+
+    trans = sub.add_parser("transcribe", help="transcribe the fixed sample")
+    trans.add_argument("--model-file", required=True)
+    trans.add_argument("--backend", choices=("vulkan", "cpu"), required=True)
+    trans.add_argument("--wav", required=True)
+    trans.add_argument("--runs", type=int, default=3)
+    trans.add_argument("--timeout", type=int, default=1800)
+    trans.set_defaults(func=cmd_transcribe)
+
+    sample = sub.add_parser("sample-rss", help="sample a tray process RSS")
+    sample.add_argument("--pid", type=int, required=True)
+    sample.add_argument("--samples", type=int, default=5)
+    sample.add_argument("--interval", type=float, default=2.0)
+    sample.set_defaults(func=cmd_sample_rss)
+
+    parse = sub.add_parser("parse-log", help="wake latencies from a debug log")
+    parse.add_argument("--log", required=True)
+    parse.set_defaults(func=cmd_parse_log)
+
+    inject = sub.add_parser("inject-probe", help="portal probe, direct dispatch cost")
+    inject.set_defaults(func=cmd_inject_probe)
+
+    gen = sub.add_parser("make-sample", help="regenerate the fixed sample")
+    gen.add_argument("--out", required=True)
+    gen.add_argument("--seed", type=int, default=19)
+
+    child_load = sub.add_parser("_child-load")
+    child_load.add_argument("--model-file", required=True)
+    child_load.add_argument("--backend", choices=("vulkan", "cpu"), required=True)
+    child_load.add_argument("--hold-seconds", type=float, default=8.0)
+
+    child_trans = sub.add_parser("_child-transcribe")
+    child_trans.add_argument("--model-file", required=True)
+    child_trans.add_argument("--backend", choices=("vulkan", "cpu"), required=True)
+    child_trans.add_argument("--wav", required=True)
+
+    args = parser.parse_args(argv)
+    if args.version:
+        print(PROTOCOL_VERSION)
+        return 0
+    if args.command == "_child-load":
+        print(json.dumps(_child_load_model(args.model_file, args.backend == "vulkan")))
+        time.sleep(args.hold_seconds)
+        return 0
+    if args.command == "_child-transcribe":
+        print(json.dumps(_child_transcribe(args.model_file, args.backend == "vulkan", args.wav)))
+        return 0
+    if args.command == "make-sample":
+        make_sample_wav(Path(args.out), seed=args.seed)
+        print(str(args.out))
+        return 0
+    if hasattr(args, "func"):
+        return int(args.func(args))
+    parser.print_help()
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/scripts/perf_baseline_sample.wav b/scripts/perf_baseline_sample.wav
new file mode 100644
index 0000000..4fd36a5
Binary files /dev/null and b/scripts/perf_baseline_sample.wav differ
diff --git a/src/vocalinux/ui/tray_indicator.py b/src/vocalinux/ui/tray_indicator.py
index 71017e2..19cdd59 100644
--- a/src/vocalinux/ui/tray_indicator.py
+++ b/src/vocalinux/ui/tray_indicator.py
@@ -770,6 +770,7 @@ class TrayIndicator:
             return
         with self._ptt_lock:
             self._ptt_owner = None
+            logger.debug(f"Toggle requested in state {self.speech_engine.state.name}")
             if self.speech_engine.state == RecognitionState.IDLE:
                 self.speech_engine.start_recognition()
             else:
diff --git a/tests/test_perf_baseline_protocol.py b/tests/test_perf_baseline_protocol.py
new file mode 100644
index 0000000..d005e9d
--- /dev/null
+++ b/tests/test_perf_baseline_protocol.py
@@ -0,0 +1,136 @@
+"""Behaviour tests for the ticket-19 performance-baseline protocol script.
+
+The script (scripts/measure_perf_baseline.py) is the locked measurement
+protocol for the installed-build baseline: every number it reports comes
+from an observed run on the target machine class, parsed by the pure
+helpers tested here. Tests run offline with fixture text only and never
+touch audio hardware, the GPU, or the network.
+"""
+
+import importlib.util
+from pathlib import Path
+
+import pytest
+
+SCRIPT = Path(__file__).resolve().parents[1] / "scripts" / "measure_perf_baseline.py"
+SPEC = importlib.util.spec_from_file_location("measure_perf_baseline", SCRIPT)
+assert SPEC is not None and SPEC.loader is not None
+PROTOCOL = importlib.util.module_from_spec(SPEC)
+SPEC.loader.exec_module(PROTOCOL)
+
+
+def test_parse_vmrss_kb_reads_kilobytes() -> None:
+    """VmRSS lines parse to kilobytes; anything else yields None."""
+    status = "Name:\tvocalinux\nVmRSS:\t  412336 kB\nVmSwap:\t0 kB\n"
+    assert PROTOCOL.parse_vmrss_kb(status) == 412336
+    assert PROTOCOL.parse_vmrss_kb("Name:\tvocalinux\n") is None
+
+
+def test_describe_reports_count_mean_min_max() -> None:
+    """Spread statistics come from the samples, never fabricated."""
+    stats = PROTOCOL.describe([1.0, 2.0, 3.0])
+    assert stats["n"] == 3
+    assert stats["mean"] == pytest.approx(2.0)
+    assert stats["min"] == pytest.approx(1.0)
+    assert stats["max"] == pytest.approx(3.0)
+
+
+def test_describe_empty_is_explicit() -> None:
+    """No samples means n == 0, never a zero mean pretending to be data."""
+    stats = PROTOCOL.describe([])
+    assert stats["n"] == 0
+    assert stats["mean"] is None
+
+
+WAKE_LOG = """\
+2026-11-05 22:44:01,100 - vocalinux.ui.action_handler - DEBUG - Handling action: toggle
+2026-11-05 22:44:01,350 - vocalinux.audio.capture - DEBUG - Opened capture stream: 1 channel(s) at 16000Hz
+2026-11-05 22:44:05,100 - vocalinux.ui.action_handler - DEBUG - Handling action: toggle
+2026-11-05 22:44:05,500 - vocalinux.audio.capture - DEBUG - Opened capture stream: 1 channel(s) at 16000Hz
+"""
+
+
+def test_parse_wake_latencies_pairs_toggle_to_capture() -> None:
+    """Each toggle pairs with the next capture-stream line, in seconds."""
+    assert PROTOCOL.parse_wake_latencies(WAKE_LOG) == pytest.approx([0.25, 0.4])
+
+
+def test_parse_wake_latencies_ignores_unpaired_toggle() -> None:
+    """A toggle with no later capture start is dropped, not zero-filled."""
+    log = (
+        WAKE_LOG
+        + "2026-11-05 22:44:09,100 - vocalinux.ui.action_handler - DEBUG - Handling action: start\n"
+    )
+    assert PROTOCOL.parse_wake_latencies(log) == pytest.approx([0.25, 0.4])
+
+
+def test_realtime_factor_is_audio_over_wall() -> None:
+    """RTF below one means faster than real time; zero audio is refused."""
+    assert PROTOCOL.realtime_factor(30.0, 15.0) == pytest.approx(0.5)
+    with pytest.raises(ValueError):
+        PROTOCOL.realtime_factor(0.0, 1.0)
+
+
+def test_parse_nvidia_smi_csv_reads_first_gpu() -> None:
+    """The locked nvidia-smi query shape parses to total/free MiB."""
+    out = (
+        "name, driver_version, memory.total [MiB], memory.free [MiB]\n"
+        "NVIDIA GeForce RTX 2050, 595.112.07, 4096 MiB, 3711 MiB\n"
+    )
+    assert PROTOCOL.parse_nvidia_smi_memory(out) == (4096, 3711)
+    assert PROTOCOL.parse_nvidia_smi_memory("no gpu here\n") is None
+
+
+def test_recommend_thresholds_come_from_footprints() -> None:
+    """Ladder thresholds derive from measured footprints plus headroom."""
+    footprints = {"q8_0": 1000.0, "q5_0": 700.0, "small": 500.0}
+    advice = PROTOCOL.recommend_thresholds(footprints, headroom_mib=512.0)
+    assert advice["prefer_q8_0_above_mib"] == pytest.approx(1512.0)
+    assert advice["prefer_q5_0_above_mib"] == pytest.approx(1212.0)
+    assert advice["floor_small_below_mib"] == pytest.approx(1212.0)
+
+
+def test_render_report_names_protocol_and_host() -> None:
+    """The evidence report carries protocol version and host facts."""
+    report = PROTOCOL.render_markdown_report(
+        {"os": "Void", "gpu": "NVIDIA GeForce RTX 2050"}, {"idle": {}}
+    )
+    assert PROTOCOL.PROTOCOL_VERSION in report
+    assert "Void" in report
+    assert "NVIDIA GeForce RTX 2050" in report
+
+
+def test_sample_generator_is_deterministic(tmp_path) -> None:
+    """The fixed sample regenerates byte-identical from its seed."""
+    first = tmp_path / "a.wav"
+    second = tmp_path / "b.wav"
+    PROTOCOL.make_sample_wav(first, seed=19)
+    PROTOCOL.make_sample_wav(second, seed=19)
+    assert first.read_bytes() == second.read_bytes()
+
+
+def test_sample_shape_is_thirty_seconds_mono_16k(tmp_path) -> None:
+    """The sample is 30 s, mono, 16 kHz, 16-bit for whisper.cpp."""
+    import wave
+
+    target = tmp_path / "sample.wav"
+    PROTOCOL.make_sample_wav(target, seed=19)
+    with wave.open(str(target), "rb") as handle:
+        assert handle.getnchannels() == 1
+        assert handle.getsampwidth() == 2
+        assert handle.getframerate() == 16000
+        assert handle.getnframes() / 16000 == pytest.approx(30.0)
+
+
+DBUS_TOGGLE_LOG = """\
+2026-11-05 23:01:11,400 - vocalinux.ui.tray_indicator - DEBUG - Toggle requested in state IDLE
+2026-11-05 23:01:11,546 - vocalinux.audio.capture - DEBUG - Opened capture stream: 2 channel(s) at 44100Hz
+2026-11-05 23:01:16,400 - vocalinux.ui.tray_indicator - DEBUG - Toggle requested in state LISTENING
+2026-11-05 23:01:22,100 - vocalinux.ui.tray_indicator - DEBUG - Toggle requested in state IDLE
+2026-11-05 23:01:22,749 - vocalinux.audio.capture - DEBUG - Opened capture stream: 2 channel(s) at 44100Hz
+"""
+
+
+def test_parse_wake_latencies_pairs_dbus_toggle_starts_only() -> None:
+    """Only IDLE toggles open capture; a stop toggle never borrows the next run."""
+    assert PROTOCOL.parse_wake_latencies(DBUS_TOGGLE_LOG) == pytest.approx([0.146, 0.649])