diff --git a/hermes_cli/dashboard_procs.py b/hermes_cli/dashboard_procs.py
index 35a047f6f1..84bd48573e 100644
--- a/hermes_cli/dashboard_procs.py
+++ b/hermes_cli/dashboard_procs.py
@@ -144,6 +144,153 @@ def _scan_dashboard_processes(
         ]
     return dashboard_processes
 
+
+def _hermes_home_for_pid(pid: int) -> str | None:
+    """Best-effort ``HERMES_HOME`` from *pid*'s environment."""
+    try:
+        import psutil
+
+        home = psutil.Process(pid).environ().get("HERMES_HOME")
+        if home:
+            return home
+    except Exception:
+        pass
+    try:
+        raw = Path(f"/proc/{pid}/environ").read_bytes()
+    except (OSError, PermissionError):
+        return None
+    for part in raw.split(b"\x00"):
+        if part.startswith(b"HERMES_HOME="):
+            return part.split(b"=", 1)[1].decode("utf-8", errors="replace") or None
+    return None
+
+
+def _is_ephemeral_port_zero_backend(argv: list[str]) -> bool:
+    """True for Desktop-style ``serve|dashboard --port 0`` backends (#78821).
+
+    Ephemeral-port backends are owned by Hermes Desktop (or become PPID-1
+    orphans after a prior update respawn).  Replaying them after
+    ``hermes update`` multiplies listening backends because ``--port 0``
+    always binds a fresh free port.  Covers both ``serve`` and the legacy
+    ``dashboard --no-open`` fallback older Desktop runtimes use.
+    """
+    if _dashboard_subcommand_index(argv) is None:
+        return False
+    for i, tok in enumerate(argv):
+        if tok == "--port" and i + 1 < len(argv) and str(argv[i + 1]) == "0":
+            return True
+        if tok.startswith("--port=") and tok.split("=", 1)[1].strip() == "0":
+            return True
+    return False
+
+
+def _dashboard_subcommand_index(argv: list[str]) -> int | None:
+    for i, tok in enumerate(argv):
+        if tok in ("serve", "dashboard"):
+            return i
+    return None
+
+
+def _normalize_dashboard_cmdline(argv: list[str]) -> tuple[str, ...]:
+    """Collapse argv to profile flags + serve/dashboard tail for dedupe."""
+    idx = _dashboard_subcommand_index(argv)
+    if idx is None:
+        return tuple(argv)
+    prefix: list[str] = []
+    i = 0
+    while i < idx:
+        tok = argv[i]
+        if tok in ("--profile", "-p") and i + 1 < idx:
+            prefix.extend([tok, argv[i + 1]])
+            i += 2
+            continue
+        if tok.startswith("--profile="):
+            prefix.append(tok)
+        i += 1
+    return tuple(prefix + list(argv[idx:]))
+
+
+def _profile_key_for_respawn(
+    argv: list[str], hermes_home: str | None = None
+) -> str:
+    """Stable owner key: ``HERMES_HOME`` when known, else ``--profile`` / ``-p``.
+
+    ``HERMES_HOME`` ending in ``profiles/<name>`` is normalized to
+    ``profile:<name>`` so it shares a cap with an explicit ``--profile``
+    flag for the same profile (#78821).  Non-profile homes (including
+    distinct ``…/.hermes`` roots) keep a resolved ``home:`` key so
+    unrelated installs do not collapse together.
+    """
+    profile_name: str | None = None
+    for i, tok in enumerate(argv):
+        if tok in ("--profile", "-p") and i + 1 < len(argv):
+            profile_name = argv[i + 1]
+            break
+        if tok.startswith("--profile="):
+            profile_name = tok.split("=", 1)[1]
+            break
+
+    if hermes_home:
+        try:
+            home_path = Path(hermes_home).resolve()
+        except (OSError, RuntimeError, ValueError):
+            home_path = Path(hermes_home)
+        parts = home_path.parts
+        if len(parts) >= 2 and parts[-2] == "profiles" and parts[-1]:
+            return f"profile:{parts[-1]}"
+        try:
+            return f"home:{os.path.normcase(str(home_path))}"
+        except (OSError, RuntimeError, ValueError):
+            return f"home:{os.path.normcase(hermes_home)}"
+
+    if profile_name:
+        return f"profile:{profile_name}"
+    return "profile:default"
+
+
+def _filter_dashboard_respawn_candidates(
+    candidates: list[tuple[int, list[str], str | None]],
+) -> list[list[str]]:
+    """Select which killed manual backends to respawn after ``hermes update``.
+
+    Each candidate is ``(pid, argv, hermes_home)``.
+
+    Rules (#78821):
+    1. Never resurrect Desktop ephemeral ``serve|dashboard --port 0``
+       backends — Desktop (``HERMES_DESKTOP_CHILD_PID``) owns their
+       lifecycle.  These are also the PPID-1 orphans that previously
+       multiplied across updates because ``--port 0`` always binds a
+       fresh free port.
+    2. Dedupe by normalized cmdline (identical argv → one respawn).
+    3. Cap at most one managed backend per profile / ``HERMES_HOME``.
+
+    Intentionally does **not** blanket-skip every PPID-1 process: a prior
+    ``hermes update`` respawn detaches with ``start_new_session=True``, so
+    fixed-port manual backends are reparented to init and must still be
+    eligible for the next update's #40449 restart.
+    """
+    selected: list[list[str]] = []
+    seen_cmdlines: set[tuple[str, ...]] = set()
+    seen_profiles: set[str] = set()
+
+    for _pid, argv, hermes_home in candidates:
+        if not argv:
+            continue
+        if _is_ephemeral_port_zero_backend(argv):
+            continue
+        norm = _normalize_dashboard_cmdline(argv)
+        if norm in seen_cmdlines:
+            continue
+        profile_key = _profile_key_for_respawn(argv, hermes_home)
+        if profile_key in seen_profiles:
+            continue
+        seen_cmdlines.add(norm)
+        seen_profiles.add(profile_key)
+        selected.append(list(argv))
+
+    return selected
+
+
 def _kill_stale_dashboard_processes(
     reason: str = "the running backend no longer matches the updated frontend",
     *,
@@ -210,6 +357,7 @@ def _kill_stale_dashboard_processes(
     pid_cgroup: dict[int, str | None] = {}
     pid_service: dict[int, str | None] = {}
     pid_cmdline: dict[int, list[str]] = {}
+    pid_home: dict[int, str | None] = {}
     if restart_managed and sys.platform != "win32":
         for pid in pids:
             cg_path = _m()._get_pid_cgroup_path(pid)
@@ -218,9 +366,12 @@ def _kill_stale_dashboard_processes(
             if not pid_service[pid]:
                 # Manually-started process: preserve its exact argv so we
                 # can respawn it after the update (#40449, #68934).
+                # Snapshot HERMES_HOME before the kill so per-profile caps
+                # still work after the process is gone (#78821).
                 cmdline = _m()._dashboard_cmdline_for_pid(pid)
                 if cmdline:
                     pid_cmdline[pid] = cmdline
+                    pid_home[pid] = _hermes_home_for_pid(pid)
 
     killed: list[int] = []
     failed: list[tuple[int, str]] = []
@@ -294,12 +445,14 @@ def _kill_stale_dashboard_processes(
     #    back after our clean SIGTERM, and the Desktop can't reconnect (#68934).
     #  - manually-started PIDs: respawn the argv captured before the kill
     #    (#40449) — detached, headless, logged to logs/dashboard-restart.log.
+    #    Filtered so Desktop ``serve|dashboard --port 0`` backends are not
+    #    resurrected and duplicates collapse to one per profile (#78821).
     restarted_services: list[str] = []
     unrecovered: list[int] = []
     if killed and restart_managed:
         failed_restarts: list[tuple[str, str]] = []
         seen_services: set[str] = set()
-        respawn_cmds: list[list[str]] = []
+        respawn_candidates: list[tuple[int, list[str], str | None]] = []
         for pid in killed:
             svc_name = pid_service.get(pid)
             if svc_name:
@@ -312,7 +465,9 @@ def _kill_stale_dashboard_processes(
                     failed_restarts.append((svc_name, "systemctl restart returned non-zero"))
                     unrecovered.append(pid)
             elif pid in pid_cmdline:
-                respawn_cmds.append(pid_cmdline[pid])
+                respawn_candidates.append(
+                    (pid, pid_cmdline[pid], pid_home.get(pid))
+                )
             else:
                 unrecovered.append(pid)
 
@@ -321,6 +476,7 @@ def _kill_stale_dashboard_processes(
         for svc, err in failed_restarts:
             print(f"    ⚠ {svc}: {err}")
 
+        respawn_cmds = _filter_dashboard_respawn_candidates(respawn_candidates)
         if respawn_cmds:
             failed_cmds = _m()._respawn_dashboard_processes(respawn_cmds)
             if failed_cmds:
diff --git a/hermes_cli/main.py b/hermes_cli/main.py
index 58eac00527..22ea6e5972 100644
--- a/hermes_cli/main.py
+++ b/hermes_cli/main.py
@@ -7561,6 +7561,7 @@ def cmd_gui(args: argparse.Namespace):
 # monkeypatches on hermes_cli.main.<name> keep resolving unchanged.
 from hermes_cli.dashboard_procs import (  # noqa: F401
     _detect_concurrent_hermes_instances,
+    _filter_dashboard_respawn_candidates,
     _kill_stale_dashboard_processes,
     _scan_dashboard_processes,
 )
@@ -7889,6 +7890,10 @@ def _respawn_dashboard_processes(commands: list[list[str]]) -> list[list[str]]:
     Spawns each recovered argv detached (new session, output to the profile's
     ``logs/dashboard-restart.log``).  Returns the commands that failed to
     spawn; the caller prints the manual hint for those.
+
+    Callers must pre-filter via ``_filter_dashboard_respawn_candidates`` so
+    Desktop ``serve|dashboard --port 0`` backends are not replayed and
+    duplicates are capped per profile (#78821).
     """
     from hermes_constants import get_hermes_home
 
diff --git a/tests/hermes_cli/test_update_stale_dashboard.py b/tests/hermes_cli/test_update_stale_dashboard.py
index 547b4f887a..c1caf89815 100644
--- a/tests/hermes_cli/test_update_stale_dashboard.py
+++ b/tests/hermes_cli/test_update_stale_dashboard.py
@@ -91,6 +91,7 @@ class TestFindStaleDashboardPids:
 
 
 
+    @pytest.mark.skipif(sys.platform == "win32", reason="ps-based scan path")
     def test_self_pid_excluded(self):
         with patch("subprocess.run") as mock_run:
             mock_run.return_value = MagicMock(
@@ -289,6 +290,7 @@ class TestWindowsWmicEncoding:
         )
 
 
+@pytest.mark.skipif(sys.platform == "win32", reason="POSIX kill + systemd restart")
 class TestSupervisedBackendRestart:
     """After the kill, systemd-supervised PIDs get their owning unit
     restarted (#68934) — SIGTERM reads as a clean stop to systemd, so
@@ -333,6 +335,7 @@ class TestManualBackendRespawn:
         return sys.modules["hermes_cli.main"]
 
 
+    @pytest.mark.skipif(sys.platform == "win32", reason="POSIX cmdline capture + respawn")
     def test_argv_capture_failure_falls_back_to_hint(self, capsys):
         live = self._live()
 
@@ -354,6 +357,85 @@ class TestManualBackendRespawn:
         out = capsys.readouterr().out
         assert "Restart anything not auto-restarted" in out
 
+    @pytest.mark.skipif(sys.platform == "win32", reason="POSIX cmdline capture + respawn")
+    def test_non_orphan_fixed_port_still_respawns(self, capsys):
+        """A supervised-by-shell dashboard with a fixed port is still restarted."""
+        live = self._live()
+        argv = ["hermes", "dashboard", "--port", "8300"]
+
+        def fake_kill(pid, sig):
+            if sig == 0:
+                raise ProcessLookupError
+
+        with patch.object(live, "_restart_managed_dashboard_service", return_value=False), \
+             patch.object(live, "_find_stale_dashboard_pids", return_value=[6001]), \
+             patch.object(live, "_get_pid_cgroup_path", return_value=None), \
+             patch.object(live, "_get_systemd_service_for_pid", return_value=None), \
+             patch.object(live, "_dashboard_cmdline_for_pid", return_value=argv), \
+             patch("hermes_cli.dashboard_procs._hermes_home_for_pid", return_value=None), \
+             patch.object(live, "_respawn_dashboard_processes", return_value=[]) as respawn, \
+             patch("os.kill", side_effect=fake_kill), \
+             patch("time.sleep"):
+            _kill_stale_dashboard_processes(restart_managed=True)
+
+        respawn.assert_called_once_with([argv])
+        assert "when you're ready" not in capsys.readouterr().out
+
+    @pytest.mark.skipif(sys.platform == "win32", reason="POSIX cmdline capture + respawn")
+    def test_port_zero_serves_killed_without_respawn(self, capsys):
+        """``serve --port 0`` backends are stopped but not resurrected (#78821)."""
+        live = self._live()
+        argv = [
+            "python", "-m", "hermes_cli.main",
+            "serve", "--host", "127.0.0.1", "--port", "0",
+        ]
+
+        def fake_kill(pid, sig):
+            if sig == 0:
+                raise ProcessLookupError
+
+        with patch.object(live, "_restart_managed_dashboard_service", return_value=False), \
+             patch.object(live, "_find_stale_dashboard_pids",
+                          return_value=[7001, 7002, 7003]), \
+             patch.object(live, "_get_pid_cgroup_path", return_value=None), \
+             patch.object(live, "_get_systemd_service_for_pid", return_value=None), \
+             patch.object(live, "_dashboard_cmdline_for_pid", return_value=argv), \
+             patch("hermes_cli.dashboard_procs._hermes_home_for_pid", return_value=None), \
+             patch.object(live, "_respawn_dashboard_processes") as respawn, \
+             patch("os.kill", side_effect=fake_kill), \
+             patch("time.sleep"):
+            result = _kill_stale_dashboard_processes(restart_managed=True)
+
+        respawn.assert_not_called()
+        assert sorted(result["killed"]) == [7001, 7002, 7003]
+        # Intentional skips are not "unrecovered" — no noisy manual hint.
+        assert result["unrecovered"] == []
+        assert "when you're ready" not in capsys.readouterr().out
+
+    @pytest.mark.skipif(sys.platform == "win32", reason="POSIX cmdline capture + respawn")
+    def test_detached_fixed_port_still_respawns_after_prior_update(self, capsys):
+        """PPID-1 fixed-port backends (prior start_new_session respawn) stay eligible."""
+        live = self._live()
+        argv = ["hermes", "dashboard", "--port", "8300"]
+
+        def fake_kill(pid, sig):
+            if sig == 0:
+                raise ProcessLookupError
+
+        with patch.object(live, "_restart_managed_dashboard_service", return_value=False), \
+             patch.object(live, "_find_stale_dashboard_pids", return_value=[8001]), \
+             patch.object(live, "_get_pid_cgroup_path", return_value=None), \
+             patch.object(live, "_get_systemd_service_for_pid", return_value=None), \
+             patch.object(live, "_dashboard_cmdline_for_pid", return_value=argv), \
+             patch("hermes_cli.dashboard_procs._hermes_home_for_pid", return_value=None), \
+             patch.object(live, "_respawn_dashboard_processes", return_value=[]) as respawn, \
+             patch("os.kill", side_effect=fake_kill), \
+             patch("time.sleep"):
+            _kill_stale_dashboard_processes(restart_managed=True)
+
+        respawn.assert_called_once_with([argv])
+        assert "when you're ready" not in capsys.readouterr().out
+
     def test_respawn_adds_no_open_to_dashboard_commands(self, tmp_path, monkeypatch):
         """Respawned `dashboard` argv gains --no-open; `serve` argv untouched."""
         live = self._live()
@@ -386,12 +468,140 @@ class TestManualBackendRespawn:
         assert "✗ failed to restart" in out
 
 
+class TestFilterDashboardRespawnCandidates:
+    """Unit tests for respawn filtering / dedupe / orphan skip (#78821)."""
+
+    def test_skips_serve_port_zero(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        argv = [
+            "python", "-m", "hermes_cli.main",
+            "--profile", "mini-cat",
+            "serve", "--host", "127.0.0.1", "--port", "0",
+        ]
+        assert _filter_dashboard_respawn_candidates([
+            (42, argv, "/home/u/.hermes/profiles/mini-cat"),
+        ]) == []
+
+    def test_skips_legacy_dashboard_port_zero(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        argv = [
+            "hermes", "--profile", "coder",
+            "dashboard", "--no-open", "--host", "127.0.0.1", "--port", "0",
+        ]
+        assert _filter_dashboard_respawn_candidates([(7, argv, None)]) == []
+
+    def test_skips_serve_port_equals_zero(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        argv = ["hermes", "serve", "--port=0"]
+        assert _filter_dashboard_respawn_candidates([(1, argv, None)]) == []
+
+    def test_keeps_ppid1_fixed_port_for_repeat_update(self):
+        """Detached prior-update respawns (PPID 1) must remain restartable (#40449)."""
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        argv = ["hermes", "dashboard", "--port", "9119"]
+        assert _filter_dashboard_respawn_candidates([(10, argv, None)]) == [argv]
+
+    def test_dedupes_identical_normalized_cmdlines(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        a = ["/usr/bin/python3", "-m", "hermes_cli.main", "dashboard", "--port", "8300"]
+        b = ["/other/python", "-m", "hermes_cli.main", "dashboard", "--port", "8300"]
+        out = _filter_dashboard_respawn_candidates([
+            (1, a, None),
+            (2, b, None),
+        ])
+        assert out == [a]
+
+    def test_caps_one_per_profile(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        a = ["hermes", "--profile", "coder", "dashboard", "--port", "8300"]
+        b = ["hermes", "--profile", "coder", "dashboard", "--port", "8301"]
+        c = ["hermes", "--profile", "writer", "dashboard", "--port", "8302"]
+        out = _filter_dashboard_respawn_candidates([
+            (1, a, None),
+            (2, b, None),
+            (3, c, None),
+        ])
+        assert out == [a, c]
+
+    def test_caps_one_per_hermes_home(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        home = "/tmp/hermes-home-a"
+        a = ["hermes", "dashboard", "--port", "8300"]
+        b = ["hermes", "dashboard", "--port", "8301"]
+        out = _filter_dashboard_respawn_candidates([
+            (1, a, home),
+            (2, b, home),
+        ])
+        assert out == [a]
+
+    def test_profile_flag_and_profiles_home_share_cap(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        a = ["hermes", "--profile", "coder", "dashboard", "--port", "8300"]
+        b = ["hermes", "dashboard", "--port", "8301"]
+        out = _filter_dashboard_respawn_candidates([
+            (1, a, None),
+            (2, b, "/home/u/.hermes/profiles/coder"),
+        ])
+        assert out == [a]
+
+    def test_default_profile_same_root_home_caps(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        a = ["hermes", "--profile", "default", "dashboard", "--port", "8300"]
+        b = ["hermes", "dashboard", "--port", "8301"]
+        home = "/home/u/.hermes"
+        out = _filter_dashboard_respawn_candidates([
+            (1, a, home),
+            (2, b, home),
+        ])
+        assert out == [a]
+
+    def test_distinct_dot_hermes_homes_do_not_share_cap(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        a = ["hermes", "dashboard", "--port", "8300"]
+        b = ["hermes", "dashboard", "--port", "8301"]
+        out = _filter_dashboard_respawn_candidates([
+            (1, a, "/home/u/.hermes"),
+            (2, b, "/work/project/.hermes"),
+        ])
+        assert out == [a, b]
+
+    def test_keeps_fixed_port_serve(self):
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        argv = ["hermes", "serve", "--host", "0.0.0.0", "--port", "9119"]
+        assert _filter_dashboard_respawn_candidates([
+            (9, argv, None),
+        ]) == [argv]
+
+    def test_seventeen_port_zero_orphans_collapse_to_zero(self):
+        """The reported accumulation case: many identical serve --port 0 → none."""
+        from hermes_cli.dashboard_procs import _filter_dashboard_respawn_candidates
+
+        argv = [
+            "python", "-m", "hermes_cli.main",
+            "serve", "--host", "127.0.0.1", "--port", "0",
+        ]
+        candidates = [(i, argv, None) for i in range(17)]
+        assert _filter_dashboard_respawn_candidates(candidates) == []
+
+
 class TestCmdlineCapture:
     """_dashboard_cmdline_for_pid reads /proc on Linux, ps on macOS."""
 
     def _live(self):
         return sys.modules["hermes_cli.main"]
 
+    @pytest.mark.skipif(sys.platform == "win32", reason="POSIX /proc cmdline path")
     def test_reads_proc_cmdline_when_available(self, tmp_path, monkeypatch):
         live = self._live()
         proc_file = tmp_path / "cmdline"
@@ -417,6 +627,7 @@ class TestCmdlineCapture:
 
         assert argv == ["/usr/bin/python3", "-m", "hermes_cli.main", "serve"]
 
+    @pytest.mark.skipif(sys.platform == "win32", reason="POSIX ps cmdline fallback")
     def test_falls_back_to_ps_without_proc(self, monkeypatch):
         live = self._live()