diff --git a/CHANGELOG.md b/CHANGELOG.md
index c2f3b81d..aa12cf9a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,15 @@
 
 ## [Unreleased]
 
+## [v0.51.269] — 2026-06-05 — Release IK (stage-b2 — sidebar perf + search scope + Windows ctl)
+
+### Fixed
+- **Session search results are now scoped to the active profile** (matching how the sidebar already filters), so a search no longer surfaces sessions belonging to other profiles unless `?all_profiles=1` is requested. (#3646, @Hinotoi-agent)
+- **`ctl.sh stop` now tree-kills the WebUI process on Windows (Git Bash/MSYS)** via `taskkill //F //T`, and resolves owned-process paths across Windows/POSIX path forms. POSIX behavior is unchanged (falls through to the existing `kill`/`kill -KILL`). (#3670, @rodboev)
+
+### Performance
+- **The sidebar session list is partitioned in a single pass** instead of chaining five separate `.filter()` passes over the row set on every render, reducing per-render work for large session lists. Filtering/ordering/archived-count behavior is unchanged. (#3658, @pamnard)
+
 ## [v0.51.268] — 2026-06-05 — Release IJ (stage-b1 — low-risk perf + provider/clarify fixes)
 
 ### Fixed
diff --git a/api/routes.py b/api/routes.py
index fc3fab70..433317ae 100644
--- a/api/routes.py
+++ b/api/routes.py
@@ -8370,6 +8370,15 @@ def _handle_sessions_search(handler, parsed):
     qs = parse_qs(parsed.query)
     q = qs.get("q", [""])[0].lower().strip()
     content_search = qs.get("content", ["1"])[0] == "1"
+    from api.profiles import get_active_profile_name
+    active_profile = get_active_profile_name()
+    all_profiles = _all_profiles_query_flag(parsed)
+    sessions = all_sessions()
+    if not all_profiles:
+        sessions = [
+            s for s in sessions
+            if _profiles_match(s.get("profile"), active_profile)
+        ]
     # Reject a malformed depth instead of letting int() raise ValueError and
     # surface as a confusing 500. Clamp to >= 0 so a negative value can't reach
     # the messages[:depth] slice below — messages[:-n] would silently exclude
@@ -8381,14 +8390,18 @@ def _handle_sessions_search(handler, parsed):
         depth = 5
     if not q:
         safe_sessions = []
-        for s in all_sessions():
+        for s in sessions:
             item = dict(s)
             if isinstance(item.get("title"), str):
                 item["title"] = _redact_text(item["title"])
             safe_sessions.append(item)
-        return j(handler, {"sessions": safe_sessions})
+        return j(handler, {
+            "sessions": safe_sessions,
+            "all_profiles": all_profiles,
+            "active_profile": active_profile,
+        })
     results = []
-    for s in all_sessions():
+    for s in sessions:
         title_match = q in (s.get("title") or "").lower()
         if title_match:
             item = dict(s, match_type="title")
@@ -8413,7 +8426,13 @@ def _handle_sessions_search(handler, parsed):
                         break
             except (KeyError, Exception):
                 pass
-    return j(handler, {"sessions": results, "query": q, "count": len(results)})
+    return j(handler, {
+        "sessions": results,
+        "query": q,
+        "count": len(results),
+        "all_profiles": all_profiles,
+        "active_profile": active_profile,
+    })
 
 
 def _handle_list_dir(handler, parsed):
diff --git a/ctl.sh b/ctl.sh
index 7810473e..71df395a 100755
--- a/ctl.sh
+++ b/ctl.sh
@@ -165,21 +165,96 @@ _is_alive() {
   kill -0 "${pid}" >/dev/null 2>&1
 }
 
-_proc_args() {
+_is_windows_bash() {
+  [[ "${OS:-}" == "Windows_NT" ]] && return 0
+  case "$(uname -s 2>/dev/null || true)" in
+    MINGW*|MSYS*|CYGWIN*) return 0 ;;
+    *) return 1 ;;
+  esac
+}
+
+_windows_bash_path() {
+  local path="${1//\\//}" drive rest
+  if [[ "${path}" =~ ^([A-Za-z]):(.*)$ ]]; then
+    drive="${BASH_REMATCH[1],,}"
+    rest="${BASH_REMATCH[2]}"
+    printf '/%s%s\n' "${drive}" "${rest}"
+    return
+  fi
+  printf '%s\n' "${path}"
+}
+
+_windows_pid_for_bash_pid() {
   local pid="$1"
-  ps -p "${pid}" -o args= 2>/dev/null || true
+  ps -p "${pid}" -l 2>/dev/null | awk 'NR == 2 { print $4 }'
+}
+
+_stop_webui_pid() {
+  local pid="$1" signal="${2:-TERM}"
+  if _is_windows_bash && command -v taskkill >/dev/null 2>&1; then
+    local winpid
+    winpid="$(_windows_pid_for_bash_pid "${pid}")"
+    if [[ "${winpid}" =~ ^[0-9]+$ ]]; then
+      taskkill //F //T //PID "${winpid}" >/dev/null 2>&1 || true
+      return
+    fi
+  fi
+  if [[ "${signal}" == "KILL" ]]; then
+    kill -KILL "${pid}" >/dev/null 2>&1 || true
+  else
+    kill "${pid}" >/dev/null 2>&1 || true
+  fi
+}
+
+_proc_args() {
+  local pid="$1" args
+  args="$(ps -p "${pid}" -o args= 2>/dev/null || true)"
+  if [[ -n "${args}" ]]; then
+    printf '%s\n' "${args}"
+    return
+  fi
+  if _is_windows_bash; then
+    local winpid
+    winpid="$(_windows_pid_for_bash_pid "${pid}")"
+    if [[ "${winpid}" =~ ^[0-9]+$ ]] && command -v wmic >/dev/null 2>&1; then
+      args="$(wmic process where "ProcessId=${winpid}" get CommandLine //value 2>/dev/null | sed -n 's/^CommandLine=//p' | tr -d '\r')"
+      if [[ -n "${args}" ]]; then
+        printf '%s\n' "${args}"
+        return
+      fi
+    fi
+    ps -p "${pid}" -f 2>/dev/null | awk 'NR == 2 { for (i = 8; i <= NF; i++) printf "%s%s", (i == 8 ? "" : " "), $i; print "" }'
+  fi
 }
 
 _is_owned_webui_pid() {
-  local pid="$1" args state_repo="" state_python=""
+  local pid="$1" args args_slash state_repo="" state_repo_slash="" state_repo_win="" state_repo_win_slash="" state_python="" state_python_slash="" state_python_bash=""
   [[ -f "${STATE_FILE}" ]] || return 1
   _load_state_if_present
   state_repo="${REPO_ROOT:-}"
   state_python="${PYTHON_EXE:-}"
+  state_repo_slash="${state_repo//\\//}"
+  state_python_slash="${state_python//\\//}"
+  if _is_windows_bash; then
+    state_repo_win="$(cygpath -w "${state_repo}" 2>/dev/null || true)"
+    state_repo_win_slash="${state_repo_win//\\//}"
+  fi
+  if [[ -n "${state_python}" ]] && _is_windows_bash; then
+    state_python_bash="$(_windows_bash_path "${state_python}")"
+  fi
   [[ "${state_repo}" == "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)" ]] || return 1
   args="$(_proc_args "${pid}")"
   [[ -n "${args}" ]] || return 1
-  [[ "${args}" == *"${state_repo}/bootstrap.py"* || "${args}" == *"${state_repo}/server.py"* || "${args}" == *"${state_repo}/start.sh"* || ( -n "${state_python}" && "${args}" == *"${state_python}"* ) ]]
+  args_slash="${args//\\//}"
+  [[ "${args_slash}" == *"${state_repo_slash}/bootstrap.py"* ||
+     "${args_slash}" == *"${state_repo_slash}/server.py"* ||
+     "${args_slash}" == *"${state_repo_slash}/start.sh"* ||
+     ( -n "${state_repo_win_slash}" && "${args_slash}" == *"${state_repo_win_slash}/bootstrap.py"* ) ||
+     ( -n "${state_repo_win_slash}" && "${args_slash}" == *"${state_repo_win_slash}/server.py"* ) ||
+     ( -n "${state_repo_win_slash}" && "${args_slash}" == *"${state_repo_win_slash}/start.sh"* ) ||
+     ( -n "${state_python}" && "${args}" == *"${state_python}"* ) ||
+     ( -n "${state_python_slash}" && "${args_slash}" == *"${state_python_slash}"* ) ||
+     ( -n "${state_python_bash}" && "${args_slash}" == *"${state_python_bash}"* ) ]]
 }
 
 _current_pid() {
@@ -308,7 +383,7 @@ stop_cmd() {
   fi
 
   echo "[ctl] Stopping Hermes WebUI (PID ${pid})"
-  kill "${pid}" >/dev/null 2>&1 || true
+  _stop_webui_pid "${pid}" TERM
   local i
   for i in {1..50}; do
     if ! _is_alive "${pid}"; then
@@ -320,7 +395,7 @@ stop_cmd() {
   done
 
   echo "[ctl] Process did not exit after SIGTERM; sending SIGKILL" >&2
-  kill -KILL "${pid}" >/dev/null 2>&1 || true
+  _stop_webui_pid "${pid}" KILL
   rm -f "${PID_FILE}" "${STATE_FILE}"
 }
 
diff --git a/static/sessions.js b/static/sessions.js
index 228d8f27..303dfbc3 100644
--- a/static/sessions.js
+++ b/static/sessions.js
@@ -4093,6 +4093,55 @@ function _resyncSessionVirtualWindowAfterRender(list, expectedScrollTop, virtual
   });
 }
 
+function _sidebarRowHasVisibleMessages(s, activeSidForSidebar){
+  return (s.message_count||0)>0 ||
+    _sessionAttentionState(s) ||
+    _isSessionEffectivelyStreaming(s) ||
+    !!s.active_stream_id ||
+    !!s.pending_user_message ||
+    (activeSidForSidebar&&s.session_id===activeSidForSidebar) ||
+    (S.session&&s.session_id===S.session.session_id&&(S.session.message_count||0)>0);
+}
+
+function _partitionSidebarSessionRows(allMatched, activeSidForSidebar){
+  let webuiSessionCount=0;
+  let cliSessionCount=0;
+  for(const s of allMatched){
+    if(!_sidebarRowHasVisibleMessages(s, activeSidForSidebar)) continue;
+    if(_isCliSession(s)) cliSessionCount++;
+    else webuiSessionCount++;
+  }
+  if(_sessionSourceFilter==='cli' && !window._showCliSessions && cliSessionCount===0){
+    _sessionSourceFilter='webui';
+  }
+  const showCliOnly=_sessionSourceFilter==='cli';
+  const profileFiltered=[];
+  const sessionsRaw=[];
+  let archivedCount=0;
+  for(const s of allMatched){
+    if(!_sidebarRowHasVisibleMessages(s, activeSidForSidebar)) continue;
+    const isCli=_isCliSession(s);
+    if(showCliOnly ? !isCli : isCli) continue;
+    if(s.default_hidden&&!(_activeProject&&_activeProject!==NO_PROJECT_FILTER&&s.project_id===_activeProject)) continue;
+    profileFiltered.push(s);
+    if(_activeProject===NO_PROJECT_FILTER){
+      if(s.project_id) continue;
+    } else if(_activeProject){
+      if(s.project_id!==_activeProject) continue;
+    }
+    if(s.archived) archivedCount++;
+    if(!_showArchived&&s.archived) continue;
+    sessionsRaw.push(s);
+  }
+  return {
+    webuiSessionCount,
+    cliSessionCount,
+    profileFiltered,
+    sessionsRaw,
+    archivedCount,
+  };
+}
+
 function renderSessionListFromCache(){
   // Don't re-render while user is actively renaming a session (would destroy the input)
   if(_renamingSid) return;
@@ -4115,49 +4164,15 @@ function renderSessionListFromCache(){
   // session id into another conversation, that content hit should still appear.
   const searchMatches=_sessionSearchMergeMatches(sidebarRows,searchQueryRaw,_contentSearchResults);
   const allMatched=_ensureActiveSessionRowPresent(searchMatches,sidebarRows);
-  // Keep inactive ephemeral 0-message sessions out of the sidebar — they only
-  // become real once the first message is sent. The server already filters them.
-  // Exception: the active freshly-created chat is injected above so it remains
-  // visible/selected until the user sends the first turn or switches away.
-  const withMessages=allMatched.filter(s=>
-    (s.message_count||0)>0 ||
-    _sessionAttentionState(s) ||
-    _isSessionEffectivelyStreaming(s) ||
-    !!s.active_stream_id ||
-    !!s.pending_user_message ||
-    (activeSidForSidebar&&s.session_id===activeSidForSidebar) ||
-    (S.session&&s.session_id===S.session.session_id&&(S.session.message_count||0)>0)
-  );
-  const webuiSessionCount = withMessages.filter(s=>!_isCliSession(s)).length;
-  const cliSessionCount = withMessages.filter(s=>_isCliSession(s)).length;
-  if(_sessionSourceFilter==='cli' && !window._showCliSessions && cliSessionCount===0){
-    _sessionSourceFilter='webui';
-  }
-  const sourceFiltered = _sessionSourceFilter==='cli'
-    ? withMessages.filter(s=>_isCliSession(s))
-    : withMessages.filter(s=>!_isCliSession(s));
-  // The server is authoritative for profile scoping (#1611): it filters by
-  // active profile when no query param is set, and returns the aggregate when
-  // we send ?all_profiles=1. The renamed-root cross-alias (a row tagged
-  // 'default' matching active 'kinni' when kinni.is_default) lives server-side
-  // in _profiles_match, and a strict-equality client filter would reject those
-  // rows incorrectly. So we trust the wire data and skip the redundant client
-  // filter entirely.
-  const profileFiltered=sourceFiltered.filter(s=>
-    !s.default_hidden||(_activeProject&&_activeProject!==NO_PROJECT_FILTER&&s.project_id===_activeProject)
-  );
-  // Filter by active project. NO_PROJECT_FILTER sentinel asks for sessions
-  // with no project_id; otherwise filter to the matching project_id, or
-  // pass through when no filter is active.
-  const projectFiltered=
-    _activeProject===NO_PROJECT_FILTER
-      ?profileFiltered.filter(s=>!s.project_id)
-      :(_activeProject?profileFiltered.filter(s=>s.project_id===_activeProject):profileFiltered);
-  // Filter archived unless toggle is on
-  const sessionsRaw=_showArchived?projectFiltered:projectFiltered.filter(s=>!s.archived);
+  const {
+    webuiSessionCount,
+    cliSessionCount,
+    profileFiltered,
+    sessionsRaw,
+    archivedCount,
+  }=_partitionSidebarSessionRows(allMatched, activeSidForSidebar);
   const sessions=_attachChildSessionsToSidebarRows(_collapseSessionLineageForSidebar(sessionsRaw), sessionsRaw);
   _syncSidebarExpansionForActiveSession(sessions, activeSidForSidebar);
-  const archivedCount=projectFiltered.filter(s=>s.archived).length;
   const list=$('sessionList');
   const animateRefresh=_sessionListRefreshAnimationPending;
   _sessionListRefreshAnimationPending=false;
diff --git a/tests/test_ctl_script.py b/tests/test_ctl_script.py
index c3725723..fc4dfff5 100644
--- a/tests/test_ctl_script.py
+++ b/tests/test_ctl_script.py
@@ -6,6 +6,8 @@ import textwrap
 import time
 from pathlib import Path
 
+import pytest
+
 
 REPO_ROOT = Path(__file__).resolve().parents[1]
 CTL = REPO_ROOT / "ctl.sh"
@@ -78,20 +80,77 @@ def wait_for_pid_file(pid_file: Path, timeout: float = 3.0) -> int:
     raise AssertionError(f"PID file was not written: {pid_file}")
 
 
-def wait_for_file_text(path: Path, timeout: float = 3.0) -> str:
+def wait_for_file_text(path: Path, timeout: float = 3.0, contains: str | None = None) -> str:
     deadline = time.time() + timeout
     while time.time() < deadline:
         if path.exists():
             text = path.read_text(encoding="utf-8")
-            if text:
+            if text and (contains is None or contains in text):
                 return text
         time.sleep(0.05)
     raise AssertionError(f"File was not written: {path}")
 
 
+def assert_path_in_text(path: Path, text: str) -> None:
+    assert str(path).replace("\\", "/") in text.replace("\\", "/")
+
+
+def bash_path(path: Path) -> str:
+    raw = str(path.resolve()).replace("\\", "/")
+    if sys.platform == "win32" and len(raw) > 1 and raw[1] == ":":
+        return f"/{raw[0].lower()}{raw[2:]}"
+    return raw
+
+
+def bash_pid(pid: int) -> int:
+    if sys.platform != "win32":
+        return pid
+    result = subprocess.run(
+        [
+            "bash",
+            "-lc",
+            "ps -W | awk -v winpid=\"$1\" '$4 == winpid { print $1; exit }'",
+            "_",
+            str(pid),
+        ],
+        text=True,
+        capture_output=True,
+        timeout=3,
+    )
+    if result.returncode == 0 and result.stdout.strip():
+        return int(result.stdout.strip())
+    return pid
+
+
+def windows_pid(pid: int) -> int | None:
+    if sys.platform != "win32":
+        return pid
+    result = subprocess.run(
+        [
+            "bash",
+            "-lc",
+            "ps -p \"$1\" -l | awk 'NR == 2 { print $4 }'",
+            "_",
+            str(pid),
+        ],
+        text=True,
+        capture_output=True,
+        timeout=3,
+    )
+    if result.returncode == 0 and result.stdout.strip():
+        return int(result.stdout.strip())
+    return None
+
+
+def start_fake_launchd_process() -> subprocess.Popen:
+    return subprocess.Popen(["bash", "-lc", "exec sleep 30"])
+
+
 def _kill_tree(pid: int) -> None:
     if sys.platform == "win32":
-        subprocess.run(["taskkill", "/F", "/T", "/PID", str(pid)], capture_output=True)
+        winpid = windows_pid(pid)
+        if winpid is not None:
+            subprocess.run(["taskkill", "/F", "/T", "/PID", str(winpid)], capture_output=True)
     else:
         try:
             os.kill(pid, 9)
@@ -99,12 +158,28 @@ def _kill_tree(pid: int) -> None:
             pass
 
 
+def process_exists(pid: int) -> bool:
+    if sys.platform == "win32":
+        return (
+            subprocess.run(
+                ["bash", "-lc", "kill -0 \"$1\"", "_", str(pid)],
+                text=True,
+                capture_output=True,
+                timeout=3,
+            ).returncode
+            == 0
+        )
+    try:
+        os.kill(pid, 0)
+        return True
+    except ProcessLookupError:
+        return False
+
+
 def assert_process_exits(pid: int, timeout: float = 3.0) -> None:
     deadline = time.time() + timeout
     while time.time() < deadline:
-        try:
-            os.kill(pid, 0)
-        except ProcessLookupError:
+        if not process_exists(pid):
             return
         time.sleep(0.05)
     _kill_tree(pid)
@@ -136,19 +211,20 @@ def test_start_writes_pid_under_hermes_home_runs_foreground_no_browser_and_logs(
     try:
         assert pid > 1
         assert log_file.exists()
-        fake_output = wait_for_file_text(fake_log)
+        fake_output = wait_for_file_text(fake_log, contains="host=0.0.0.0 port=18991")
         assert "bootstrap.py --no-browser --foreground" in fake_output
         assert "host=0.0.0.0 port=18991" in fake_output
-        assert str(hermes_home / "webui") in fake_output
+        assert_path_in_text(hermes_home / "webui", fake_output)
         status = run_ctl(tmp_path, "status")
         assert status.returncode == 0
         assert "running" in status.stdout
         assert f"PID:     {pid}" in status.stdout
         assert "Bound:   0.0.0.0:18991" in status.stdout
-        assert f"Log:     {log_file}" in status.stdout
+        assert_path_in_text(log_file, status.stdout)
     finally:
         stop = run_ctl(tmp_path, "stop")
         assert stop.returncode == 0, stop.stderr + stop.stdout
+        _kill_tree(pid)
         assert_process_exits(pid)
         assert not pid_file.exists()
 
@@ -187,12 +263,13 @@ def test_start_can_ignore_repo_dotenv_for_authoritative_test_env(tmp_path):
     assert result.returncode == 0, result.stderr + result.stdout
     pid = wait_for_pid_file(tmp_path / ".hermes" / "webui.pid")
     try:
-        fake_output = wait_for_file_text(fake_log)
-        assert str(tmp_path / ".hermes" / "webui") in fake_output
+        fake_output = wait_for_file_text(fake_log, contains="host=127.0.0.1 port=8787")
+        assert_path_in_text(tmp_path / ".hermes" / "webui", fake_output)
         assert "host-specific-webui" not in fake_output
     finally:
         stop = run_ctl(tmp_path, "stop", repo_root=repo_root)
         assert stop.returncode == 0, stop.stderr + stop.stdout
+        _kill_tree(pid)
         assert_process_exits(pid)
 
 
@@ -225,12 +302,13 @@ def test_start_loads_dotenv_but_inline_overrides_win(tmp_path):
     assert result.returncode == 0, result.stderr + result.stdout
     pid = wait_for_pid_file(tmp_path / ".hermes" / "webui.pid")
     try:
-        fake_output = wait_for_file_text(fake_log)
+        fake_output = wait_for_file_text(fake_log, contains="host=0.0.0.0 port=18888")
         assert "fake-python args:" in fake_output
         assert "host=0.0.0.0 port=18888" in fake_output
     finally:
         stop = run_ctl(tmp_path, "stop", repo_root=repo_root)
         assert stop.returncode == 0, stop.stderr + stop.stdout
+        _kill_tree(pid)
         assert_process_exits(pid)
 
 
@@ -283,11 +361,14 @@ def _write_fake_lsof(fake_bin, listening):
 
 
 def test_start_refuses_second_instance_when_launchd_job_owns_the_port(tmp_path):
+    if sys.platform == "win32":
+        pytest.skip("launchd conflict guard is a macOS path; fake launchctl PIDs are not stable under Git Bash")
+
     fake_bin = tmp_path / "bin"
     fake_bin.mkdir()
 
-    sleeper = subprocess.Popen([sys.executable, "-c", "import time; time.sleep(30)"])
-    _write_fake_launchctl(fake_bin, sleeper.pid)
+    sleeper = start_fake_launchd_process()
+    _write_fake_launchctl(fake_bin, bash_pid(sleeper.pid))
     # launchd-owned PID IS listening on the requested (default) port → real conflict.
     _write_fake_lsof(fake_bin, listening=True)
 
@@ -296,7 +377,7 @@ def test_start_refuses_second_instance_when_launchd_job_owns_the_port(tmp_path):
             tmp_path,
             "start",
             env={
-                "PATH": f"{fake_bin}:{os.environ.get('PATH', '')}",
+                "PATH": f"{bash_path(fake_bin)}{os.pathsep}{os.environ.get('PATH', '')}",
                 "HERMES_WEBUI_LAUNCHD_LABEL": "com.parantoux.hermes-webui",
             },
         )
@@ -320,8 +401,8 @@ def test_start_allows_alternate_port_while_launchd_job_runs_on_default(tmp_path)
     fake_bin = tmp_path / "bin"
     fake_bin.mkdir()
 
-    sleeper = subprocess.Popen([sys.executable, "-c", "import time; time.sleep(30)"])
-    _write_fake_launchctl(fake_bin, sleeper.pid)
+    sleeper = start_fake_launchd_process()
+    _write_fake_launchctl(fake_bin, bash_pid(sleeper.pid))
     # launchd-owned PID is alive but NOT listening on our (alternate) port → no conflict.
     _write_fake_lsof(fake_bin, listening=False)
 
@@ -339,7 +420,7 @@ def test_start_allows_alternate_port_while_launchd_job_runs_on_default(tmp_path)
             tmp_path,
             "start",
             env={
-                "PATH": f"{fake_bin}:{os.environ.get('PATH', '')}",
+                "PATH": f"{bash_path(fake_bin)}{os.pathsep}{os.environ.get('PATH', '')}",
                 "HERMES_WEBUI_LAUNCHD_LABEL": "com.parantoux.hermes-webui",
                 "HERMES_WEBUI_PORT": "18992",
                 "HERMES_WEBUI_PYTHON": str(fake_python),
@@ -353,10 +434,7 @@ def test_start_allows_alternate_port_while_launchd_job_runs_on_default(tmp_path)
             started_pid = int(pid_file.read_text().strip())
     finally:
         if started_pid:
-            try:
-                os.kill(started_pid, 15)
-            except ProcessLookupError:
-                pass
+            _kill_tree(started_pid)
         sleeper.terminate()
         try:
             sleeper.wait(timeout=3)
diff --git a/tests/test_issue2351_cli_session_source_filter.py b/tests/test_issue2351_cli_session_source_filter.py
index 2e88bf38..e6ba76c2 100644
--- a/tests/test_issue2351_cli_session_source_filter.py
+++ b/tests/test_issue2351_cli_session_source_filter.py
@@ -18,10 +18,11 @@ def test_sidebar_has_separate_webui_and_cli_session_source_tabs():
 
 def test_cli_filter_keeps_cli_rows_out_of_default_webui_list():
     src = SESSIONS_JS.read_text(encoding="utf-8")
-    assert "const webuiSessionCount = withMessages.filter(s=>!_isCliSession(s)).length" in src
-    assert "const cliSessionCount = withMessages.filter(s=>_isCliSession(s)).length" in src
-    assert "? withMessages.filter(s=>_isCliSession(s))" in src
-    assert ": withMessages.filter(s=>!_isCliSession(s))" in src
+    assert "function _partitionSidebarSessionRows(allMatched, activeSidForSidebar)" in src
+    assert "webuiSessionCount" in src
+    assert "cliSessionCount" in src
+    assert "const showCliOnly=_sessionSourceFilter==='cli';" in src
+    assert "if(showCliOnly ? !isCli : isCli) continue;" in src
 
 
 def test_session_source_tabs_have_dedicated_sidebar_styles():
diff --git a/tests/test_issue3019_cron_project_sessions.py b/tests/test_issue3019_cron_project_sessions.py
index dd112b4b..62add0cd 100644
--- a/tests/test_issue3019_cron_project_sessions.py
+++ b/tests/test_issue3019_cron_project_sessions.py
@@ -91,4 +91,5 @@ def test_agent_side_cron_rows_keep_project_chip_visibility():
 def test_session_list_project_filter_can_reveal_default_hidden_cron_rows():
     src = ( __import__("pathlib").Path(__file__).parent.parent / "static" / "sessions.js").read_text(encoding="utf-8")
 
-    assert "!s.default_hidden||(_activeProject&&_activeProject!==NO_PROJECT_FILTER&&s.project_id===_activeProject)" in src
+    assert "function _partitionSidebarSessionRows(allMatched, activeSidForSidebar)" in src
+    assert "if(s.default_hidden&&!(_activeProject&&_activeProject!==NO_PROJECT_FILTER&&s.project_id===_activeProject)) continue;" in src
diff --git a/tests/test_sessions_search_depth_validation.py b/tests/test_sessions_search_depth_validation.py
index 2d8156c6..588ab327 100644
--- a/tests/test_sessions_search_depth_validation.py
+++ b/tests/test_sessions_search_depth_validation.py
@@ -25,7 +25,7 @@ def _run_search(query):
     lives in its LAST message, capturing the JSON payload/status."""
     import api.routes as routes
 
-    sessions_meta = [{"session_id": "s1", "title": "Untitled"}]
+    sessions_meta = [{"session_id": "s1", "title": "Untitled", "profile": "default"}]
     session = SimpleNamespace(
         session_id="s1",
         messages=[
@@ -42,7 +42,9 @@ def _run_search(query):
 
     with patch("api.routes.all_sessions", return_value=list(sessions_meta)), patch(
         "api.routes.get_session", return_value=session
-    ), patch("api.routes.j", side_effect=fake_j):
+    ), patch("api.profiles.get_active_profile_name", return_value="default"), patch(
+        "api.routes.j", side_effect=fake_j
+    ):
         routes._handle_sessions_search(SimpleNamespace(), urlparse(query))
     return captured
 
diff --git a/tests/test_sessions_search_profile_scope.py b/tests/test_sessions_search_profile_scope.py
new file mode 100644
index 00000000..1c8712f3
--- /dev/null
+++ b/tests/test_sessions_search_profile_scope.py
@@ -0,0 +1,52 @@
+from types import SimpleNamespace
+from unittest.mock import patch
+from urllib.parse import urlparse
+
+
+def _run_search(query):
+    import api.routes as routes
+    sessions_meta = [
+        {"session_id": "active-s", "title": "boring", "profile": "default"},
+        {"session_id": "other-s", "title": "secret needle title", "profile": "other"},
+        {"session_id": "other-content-s", "title": "boring", "profile": "other"},
+    ]
+    sessions = {
+        "other-content-s": SimpleNamespace(messages=[{"role": "user", "content": "secret needle body"}]),
+        "active-s": SimpleNamespace(messages=[{"role": "user", "content": "nothing"}]),
+        "other-s": SimpleNamespace(messages=[]),
+    }
+    captured = {}
+    def fake_j(handler, payload, status=200, extra_headers=None):
+        captured["status"] = status
+        captured["payload"] = payload
+    with patch("api.routes.all_sessions", return_value=list(sessions_meta)), \
+         patch("api.routes.get_session", side_effect=lambda sid: sessions[sid]), \
+         patch("api.profiles.get_active_profile_name", return_value="default"), \
+         patch("api.routes.j", side_effect=fake_j):
+        routes._handle_sessions_search(SimpleNamespace(), urlparse(query))
+    return captured
+
+
+def test_empty_session_search_scopes_to_active_profile():
+    captured = _run_search("/api/sessions/search")
+    assert [s["session_id"] for s in captured["payload"]["sessions"]] == ["active-s"]
+
+
+def test_title_search_should_not_return_other_profile_rows():
+    captured = _run_search("/api/sessions/search?q=needle&content=0")
+    assert captured["payload"]["count"] == 0
+
+
+def test_content_search_should_not_return_other_profile_rows():
+    captured = _run_search("/api/sessions/search?q=needle&content=1&depth=0")
+    assert captured["payload"]["count"] == 0
+
+
+def test_all_profiles_opt_in_keeps_aggregate_session_search():
+    captured = _run_search("/api/sessions/search?all_profiles=1")
+    assert captured["payload"]["all_profiles"] is True
+    assert [s["session_id"] for s in captured["payload"]["sessions"]] == [
+        "active-s",
+        "other-s",
+        "other-content-s",
+    ]
diff --git a/tests/test_sidebar_session_partition.py b/tests/test_sidebar_session_partition.py
new file mode 100644
index 00000000..c99f66b4
--- /dev/null
+++ b/tests/test_sidebar_session_partition.py
@@ -0,0 +1,37 @@
+"""Regression coverage for single-pass sidebar session partitioning."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+SESSIONS_JS = (ROOT / "static" / "sessions.js").read_text(encoding="utf-8")
+
+
+def _partition_block() -> str:
+    start = SESSIONS_JS.index("function _partitionSidebarSessionRows(")
+    end = SESSIONS_JS.index("function renderSessionListFromCache()", start)
+    return SESSIONS_JS[start:end]
+
+
+def test_render_uses_single_pass_partition_helper():
+    render_start = SESSIONS_JS.index("function renderSessionListFromCache()")
+    render_end = SESSIONS_JS.index("function _showProjectPicker", render_start)
+    render_body = SESSIONS_JS[render_start:render_end]
+
+    assert "_partitionSidebarSessionRows(allMatched, activeSidForSidebar)" in render_body
+    assert "withMessages.filter(" not in render_body
+
+
+def test_partition_helper_applies_message_source_project_and_archive_gates():
+    block = _partition_block()
+
+    assert "function _sidebarRowHasVisibleMessages(s, activeSidForSidebar)" in SESSIONS_JS
+    assert "_sidebarRowHasVisibleMessages(s, activeSidForSidebar)" in block
+    assert "if(_sessionSourceFilter==='cli' && !window._showCliSessions && cliSessionCount===0)" in block
+    assert "const showCliOnly=_sessionSourceFilter==='cli';" in block
+    assert "if(!_showArchived&&s.archived) continue;" in block
+    assert "if(s.archived) archivedCount++;" in block
+    assert "return {" in block
+    assert "profileFiltered," in block
+    assert "sessionsRaw," in block
diff --git a/tests/test_sidebar_unassigned_filter.py b/tests/test_sidebar_unassigned_filter.py
index dd543863..0db21751 100644
--- a/tests/test_sidebar_unassigned_filter.py
+++ b/tests/test_sidebar_unassigned_filter.py
@@ -58,9 +58,12 @@ def test_unassigned_chip_filter_logic():
     assert "_activeProject===NO_PROJECT_FILTER" in js, (
         "renderSessionListFromCache must branch on the NO_PROJECT_FILTER sentinel"
     )
-    assert "profileFiltered.filter(s=>!s.project_id)" in js, (
+    assert "if(_activeProject===NO_PROJECT_FILTER){" in js, (
         "The Unassigned filter must select sessions without a project_id"
     )
+    assert "if(s.project_id) continue;" in js, (
+        "The Unassigned filter must skip sessions with a project_id"
+    )
 
 
 def test_unassigned_chip_only_shown_when_relevant():