diff --git a/src/pyra/daemon/service.py b/src/pyra/daemon/service.py
new file mode 100644
index 0000000..6bb0f58
--- /dev/null
+++ b/src/pyra/daemon/service.py
@@ -0,0 +1,212 @@
+"""OS-specific service file generation and install/uninstall for the Pyra daemon."""
+
+from __future__ import annotations
+
+import platform
+import shutil
+import subprocess
+import sys
+from pathlib import Path
+from typing import Literal
+
+from pyra.utils.paths import safe_chmod
+
+
+def detect_platform() -> Literal["macos", "linux", "windows"]:
+    s = platform.system()
+    if s == "Darwin":
+        return "macos"
+    if s == "Linux":
+        return "linux"
+    if s == "Windows":
+        return "windows"
+    raise RuntimeError(f"Unsupported platform: {s}")
+
+
+def find_pyra_executable() -> str:
+    """Return the full path to the active pyra executable.
+
+    Tries, in order:
+    1. shutil.which("pyra") — works when pyra is on PATH (activated venv)
+    2. sys.executable's sibling "pyra" script — covers editable installs
+    3. Fallback: sys.executable -m pyra
+    """
+    found = shutil.which("pyra")
+    if found:
+        return found
+
+    sibling = Path(sys.executable).parent / "pyra"
+    if sibling.exists():
+        return str(sibling)
+
+    return f"{sys.executable} -m pyra"
+
+
+# ── Template generators ───────────────────────────────────────────────────────
+
+def render_launchd_plist(exe: str, log_file: str, pid_file: str) -> str:
+    log = str(Path(log_file).expanduser())
+    return f"""<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
+    "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+    <key>Label</key>
+    <string>com.pyra.daemon</string>
+    <key>ProgramArguments</key>
+    <array>
+        <string>{exe}</string>
+        <string>daemon</string>
+        <string>run</string>
+    </array>
+    <key>RunAtLoad</key>
+    <true/>
+    <key>KeepAlive</key>
+    <true/>
+    <key>StandardOutPath</key>
+    <string>{log}</string>
+    <key>StandardErrorPath</key>
+    <string>{log}</string>
+    <key>ProcessType</key>
+    <string>Background</string>
+</dict>
+</plist>
+"""
+
+
+def render_systemd_unit(exe: str, log_file: str) -> str:
+    log = str(Path(log_file).expanduser())
+    return f"""[Unit]
+Description=Pyra Personal AI Assistant Daemon
+After=default.target
+
+[Service]
+Type=simple
+ExecStart={exe} daemon run
+Restart=on-failure
+RestartSec=5s
+StandardOutput=append:{log}
+StandardError=append:{log}
+
+[Install]
+WantedBy=default.target
+"""
+
+
+def render_schtasks_xml(exe: str) -> str:
+    return f"""<?xml version="1.0" encoding="UTF-16"?>
+<Task version="1.2" xmlns="http://schemas.microsoft.com/windows/2004/02/mit/task">
+  <RegistrationInfo>
+    <Description>Pyra Personal AI Assistant Daemon</Description>
+  </RegistrationInfo>
+  <Triggers>
+    <LogonTrigger>
+      <Enabled>true</Enabled>
+    </LogonTrigger>
+  </Triggers>
+  <Settings>
+    <MultipleInstancesPolicy>IgnoreNew</MultipleInstancesPolicy>
+    <DisallowStartIfOnBatteries>false</DisallowStartIfOnBatteries>
+    <StopIfGoingOnBatteries>false</StopIfGoingOnBatteries>
+    <ExecutionTimeLimit>PT0S</ExecutionTimeLimit>
+    <RestartOnFailure>
+      <Interval>PT1M</Interval>
+      <Count>999</Count>
+    </RestartOnFailure>
+  </Settings>
+  <Actions Context="Author">
+    <Exec>
+      <Command>{exe}</Command>
+      <Arguments>daemon run</Arguments>
+    </Exec>
+  </Actions>
+</Task>
+"""
+
+
+# ── Install / uninstall ───────────────────────────────────────────────────────
+
+def install_service() -> None:
+    """Generate and register the OS service for the current platform."""
+    from pyra.config.manager import load_config
+
+    cfg = load_config()
+    exe = find_pyra_executable()
+    plat = detect_platform()
+
+    if plat == "macos":
+        _install_launchd(exe, cfg.daemon.log_file, cfg.daemon.pid_file)
+    elif plat == "linux":
+        _install_systemd(exe, cfg.daemon.log_file)
+    else:
+        _install_windows(exe)
+
+
+def uninstall_service() -> None:
+    """Deregister the OS service for the current platform."""
+    plat = detect_platform()
+    if plat == "macos":
+        _uninstall_launchd()
+    elif plat == "linux":
+        _uninstall_systemd()
+    else:
+        _uninstall_windows()
+
+
+# ── macOS launchd ─────────────────────────────────────────────────────────────
+
+_PLIST_PATH = Path.home() / "Library" / "LaunchAgents" / "com.pyra.daemon.plist"
+
+
+def _install_launchd(exe: str, log_file: str, pid_file: str) -> None:
+    _PLIST_PATH.parent.mkdir(parents=True, exist_ok=True)
+    _PLIST_PATH.write_text(render_launchd_plist(exe, log_file, pid_file))
+    safe_chmod(_PLIST_PATH, 0o644)  # launchd requires 644, not 600
+    subprocess.run(["launchctl", "load", str(_PLIST_PATH)], check=True)
+
+
+def _uninstall_launchd() -> None:
+    if _PLIST_PATH.exists():
+        subprocess.run(["launchctl", "unload", str(_PLIST_PATH)], check=False)
+        _PLIST_PATH.unlink()
+
+
+# ── Linux systemd ─────────────────────────────────────────────────────────────
+
+_SYSTEMD_UNIT = Path.home() / ".config" / "systemd" / "user" / "pyra.service"
+
+
+def _install_systemd(exe: str, log_file: str) -> None:
+    _SYSTEMD_UNIT.parent.mkdir(parents=True, exist_ok=True)
+    _SYSTEMD_UNIT.write_text(render_systemd_unit(exe, log_file))
+    subprocess.run(["systemctl", "--user", "daemon-reload"], check=True)
+    subprocess.run(["systemctl", "--user", "enable", "pyra"], check=True)
+
+
+def _uninstall_systemd() -> None:
+    subprocess.run(
+        ["systemctl", "--user", "disable", "--now", "pyra"], check=False
+    )
+    if _SYSTEMD_UNIT.exists():
+        _SYSTEMD_UNIT.unlink()
+    subprocess.run(["systemctl", "--user", "daemon-reload"], check=False)
+
+
+# ── Windows Task Scheduler ────────────────────────────────────────────────────
+
+def _install_windows(exe: str) -> None:
+    from pyra.utils.paths import pyra_home
+
+    xml_path = pyra_home() / "daemon_task.xml"
+    # schtasks /Create /XML requires UTF-16 encoding
+    xml_path.write_text(render_schtasks_xml(exe), encoding="utf-16")
+    subprocess.run(
+        ["schtasks", "/Create", "/TN", "PyraAssistant", "/XML", str(xml_path), "/F"],
+        check=True,
+    )
+
+
+def _uninstall_windows() -> None:
+    subprocess.run(
+        ["schtasks", "/Delete", "/TN", "PyraAssistant", "/F"], check=False
+    )
diff --git a/tests/unit/test_daemon_service.py b/tests/unit/test_daemon_service.py
new file mode 100644
index 0000000..0dc951a
--- /dev/null
+++ b/tests/unit/test_daemon_service.py
@@ -0,0 +1,189 @@
+"""Unit tests for daemon service file generation and platform detection."""
+
+from __future__ import annotations
+
+import subprocess
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from pyra.daemon.service import (
+    detect_platform,
+    find_pyra_executable,
+    render_launchd_plist,
+    render_systemd_unit,
+    render_schtasks_xml,
+)
+
+
+# ── Template rendering ────────────────────────────────────────────────────────
+
+def test_render_launchd_plist_contains_exe() -> None:
+    xml = render_launchd_plist("/usr/local/bin/pyra", "~/.pyra/daemon.log", "~/.pyra/daemon.pid")
+    assert "/usr/local/bin/pyra" in xml
+    assert "<string>daemon</string>" in xml
+    assert "<string>run</string>" in xml
+    assert "com.pyra.daemon" in xml
+    assert "<true/>" in xml  # KeepAlive and RunAtLoad
+
+
+def test_render_launchd_plist_expands_log_tilde() -> None:
+    xml = render_launchd_plist("/bin/pyra", "~/.pyra/daemon.log", "~/.pyra/daemon.pid")
+    assert "~" not in xml
+
+
+def test_render_systemd_unit_contains_exe() -> None:
+    unit = render_systemd_unit("/usr/local/bin/pyra", "~/.pyra/daemon.log")
+    assert "ExecStart=/usr/local/bin/pyra daemon run" in unit
+    assert "Restart=on-failure" in unit
+    assert "Type=simple" in unit
+    assert "WantedBy=default.target" in unit
+
+
+def test_render_systemd_unit_expands_log_tilde() -> None:
+    unit = render_systemd_unit("/bin/pyra", "~/.pyra/daemon.log")
+    assert "~" not in unit
+
+
+def test_render_schtasks_xml_contains_exe() -> None:
+    xml = render_schtasks_xml("C:\\Users\\test\\pyra.exe")
+    assert "C:\\Users\\test\\pyra.exe" in xml
+    assert "LogonTrigger" in xml
+    assert "daemon run" in xml
+    assert "IgnoreNew" in xml
+
+
+def test_render_schtasks_xml_no_time_limit() -> None:
+    xml = render_schtasks_xml("pyra.exe")
+    assert "PT0S" in xml  # ExecutionTimeLimit=PT0S means unlimited
+
+
+# ── Platform detection ────────────────────────────────────────────────────────
+
+def test_detect_platform_returns_known_value() -> None:
+    result = detect_platform()
+    assert result in ("macos", "linux", "windows")
+
+
+@pytest.mark.parametrize("system,expected", [
+    ("Darwin", "macos"),
+    ("Linux", "linux"),
+    ("Windows", "windows"),
+])
+def test_detect_platform_maps_correctly(system: str, expected: str) -> None:
+    with patch("platform.system", return_value=system):
+        assert detect_platform() == expected
+
+
+def test_detect_platform_raises_on_unknown() -> None:
+    with patch("platform.system", return_value="FreeBSD"):
+        with pytest.raises(RuntimeError, match="Unsupported platform"):
+            detect_platform()
+
+
+# ── Executable detection ──────────────────────────────────────────────────────
+
+def test_find_pyra_executable_returns_string() -> None:
+    result = find_pyra_executable()
+    assert isinstance(result, str)
+    assert len(result) > 0
+
+
+def test_find_pyra_executable_uses_which_when_available(tmp_path: Path) -> None:
+    fake_pyra = tmp_path / "pyra"
+    fake_pyra.touch()
+    with patch("shutil.which", return_value=str(fake_pyra)):
+        assert find_pyra_executable() == str(fake_pyra)
+
+
+def test_find_pyra_executable_falls_back_to_sibling(tmp_path: Path) -> None:
+    fake_python = tmp_path / "python3"
+    fake_pyra = tmp_path / "pyra"
+    fake_pyra.touch()
+    with patch("shutil.which", return_value=None):
+        with patch("sys.executable", str(fake_python)):
+            assert find_pyra_executable() == str(fake_pyra)
+
+
+def test_find_pyra_executable_falls_back_to_module(tmp_path: Path) -> None:
+    fake_python = tmp_path / "python3"
+    with patch("shutil.which", return_value=None):
+        with patch("sys.executable", str(fake_python)):
+            result = find_pyra_executable()
+            assert result == f"{fake_python} -m pyra"
+
+
+# ── Install / uninstall (subprocess mocked) ───────────────────────────────────
+
+@pytest.mark.skipif(sys.platform == "win32", reason="launchd install is macOS-only")
+def test_install_launchd_writes_plist_and_calls_launchctl(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    import pyra.daemon.service as svc
+
+    plist_path = tmp_path / "Library" / "LaunchAgents" / "com.pyra.daemon.plist"
+    monkeypatch.setattr(svc, "_PLIST_PATH", plist_path)
+
+    calls: list[list[str]] = []
+    monkeypatch.setattr(subprocess, "run", lambda cmd, **kw: calls.append(cmd))
+
+    svc._install_launchd("/usr/local/bin/pyra", "~/.pyra/daemon.log", "~/.pyra/daemon.pid")
+
+    assert plist_path.exists()
+    assert "com.pyra.daemon" in plist_path.read_text()
+    assert any("launchctl" in c[0] for c in calls)
+
+
+@pytest.mark.skipif(sys.platform == "win32", reason="systemd install is Linux-only")
+def test_install_systemd_writes_unit_and_calls_systemctl(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    import pyra.daemon.service as svc
+
+    unit_path = tmp_path / ".config" / "systemd" / "user" / "pyra.service"
+    monkeypatch.setattr(svc, "_SYSTEMD_UNIT", unit_path)
+
+    calls: list[list[str]] = []
+    monkeypatch.setattr(subprocess, "run", lambda cmd, **kw: calls.append(cmd))
+
+    svc._install_systemd("/usr/local/bin/pyra", "~/.pyra/daemon.log")
+
+    assert unit_path.exists()
+    assert "ExecStart" in unit_path.read_text()
+    assert any("systemctl" in c[0] for c in calls)
+
+
+@pytest.mark.skipif(sys.platform == "win32", reason="launchd uninstall is macOS-only")
+def test_uninstall_launchd_removes_plist(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    import pyra.daemon.service as svc
+
+    plist_path = tmp_path / "Library" / "LaunchAgents" / "com.pyra.daemon.plist"
+    plist_path.parent.mkdir(parents=True)
+    plist_path.write_text("<plist/>")
+    monkeypatch.setattr(svc, "_PLIST_PATH", plist_path)
+    monkeypatch.setattr(subprocess, "run", lambda cmd, **kw: None)
+
+    svc._uninstall_launchd()
+
+    assert not plist_path.exists()
+
+
+@pytest.mark.skipif(sys.platform == "win32", reason="systemd uninstall is Linux-only")
+def test_uninstall_systemd_removes_unit(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    import pyra.daemon.service as svc
+
+    unit_path = tmp_path / ".config" / "systemd" / "user" / "pyra.service"
+    unit_path.parent.mkdir(parents=True)
+    unit_path.write_text("[Service]")
+    monkeypatch.setattr(svc, "_SYSTEMD_UNIT", unit_path)
+    monkeypatch.setattr(subprocess, "run", lambda cmd, **kw: None)
+
+    svc._uninstall_systemd()
+
+    assert not unit_path.exists()