diff --git a/CHANGELOG.md b/CHANGELOG.md
index a2de081..4c3f8aa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,16 @@
 # Hermes Web UI -- Changelog
 
+## [Unreleased]
+
+### Added
+- **Workspace path autocomplete in Spaces** — the "Add workspace path" field in
+  the Spaces panel now suggests trusted directories as you type, supports
+  keyboard navigation plus `Tab` completion, and keeps hidden directories out of
+  the list unless the current path segment starts with `.`. Suggestions are
+  limited to trusted roots (home, saved workspaces, and the boot default
+  workspace subtree) and never enumerate blocked system roots. (`api/routes.py`,
+  `api/workspace.py`, `static/panels.js`, `static/style.css`) (partial for #616)
+
 ## [v0.50.161] — 2026-04-23
 
 ### Fixed
diff --git a/api/routes.py b/api/routes.py
index 5dad0a7..ca5c78e 100644
--- a/api/routes.py
+++ b/api/routes.py
@@ -300,6 +300,7 @@ from api.workspace import (
     get_last_workspace,
     set_last_workspace,
     list_dir,
+    list_workspace_suggestions,
     read_file_content,
     safe_resolve_ws,
     resolve_trusted_workspace,
@@ -711,6 +712,17 @@ def handle_get(handler, parsed) -> bool:
             handler, {"workspaces": load_workspaces(), "last": get_last_workspace()}
         )
 
+    if parsed.path == "/api/workspaces/suggest":
+        qs = parse_qs(parsed.query)
+        prefix = qs.get("prefix", [""])[0]
+        return j(
+            handler,
+            {
+                "suggestions": list_workspace_suggestions(prefix),
+                "prefix": prefix,
+            },
+        )
+
     if parsed.path == "/api/sessions/search":
         return _handle_sessions_search(handler, parsed)
 
diff --git a/api/workspace.py b/api/workspace.py
index dddae29..b66b42f 100644
--- a/api/workspace.py
+++ b/api/workspace.py
@@ -219,6 +219,141 @@ def set_last_workspace(path: str) -> None:
         logger.debug("Failed to set last workspace")
 
 
+def _workspace_blocked_roots() -> tuple[Path, ...]:
+    return (
+        # Linux / macOS
+        Path('/etc'),
+        Path('/usr'),
+        Path('/var'),
+        Path('/bin'),
+        Path('/sbin'),
+        Path('/boot'),
+        Path('/proc'),
+        Path('/sys'),
+        Path('/dev'),
+        Path('/lib'),
+        Path('/lib64'),
+        Path('/opt/homebrew'),
+    )
+
+
+def _is_within(path: Path, root: Path) -> bool:
+    try:
+        path.relative_to(root)
+        return True
+    except ValueError:
+        return False
+
+
+def _trusted_workspace_roots() -> list[Path]:
+    roots: list[Path] = []
+
+    def add(candidate: str | Path | None) -> None:
+        if candidate in (None, ""):
+            return
+        try:
+            p = Path(candidate).expanduser().resolve()
+        except Exception:
+            return
+        if not p.exists() or not p.is_dir():
+            return
+        if any(_is_within(p, blocked) for blocked in _workspace_blocked_roots()):
+            return
+        if p not in roots:
+            roots.append(p)
+
+    add(Path.home())
+    add(_BOOT_DEFAULT_WORKSPACE)
+    for w in load_workspaces():
+        add(w.get("path"))
+    roots.sort(key=lambda p: len(str(p)))
+    return roots
+
+
+def list_workspace_suggestions(prefix: str = "", limit: int = 12) -> list[str]:
+    """Return workspace path suggestions under trusted roots only.
+
+    Suggestions are limited to directories under one of:
+      - Path.home()
+      - the boot default workspace
+      - already-saved workspace roots
+
+    Arbitrary system prefixes return an empty list rather than an error so the
+    UI can safely autocomplete while the user types.
+    """
+    roots = _trusted_workspace_roots()
+    if not roots:
+        return []
+
+    raw = (prefix or "").strip()
+    if not raw:
+        return [str(p) for p in roots[:limit]]
+
+    if raw.startswith("~"):
+        target = Path(raw).expanduser()
+    elif Path(raw).is_absolute():
+        target = Path(raw)
+    else:
+        target = Path.home() / raw
+
+    normalized = str(target)
+    normalized_lower = normalized.lower()
+    suggestions: list[str] = []
+
+    def add(path: Path) -> None:
+        value = str(path)
+        if value not in suggestions:
+            suggestions.append(value)
+
+    # If the user is typing a partial trusted root like /Users/xuef..., suggest
+    # the matching trusted roots without scanning arbitrary system parents.
+    for root in roots:
+        if str(root).lower().startswith(normalized_lower):
+            add(root)
+
+    in_root = [
+        root
+        for root in roots
+        if normalized == str(root) or normalized.startswith(str(root) + os.sep)
+    ]
+    if not in_root:
+        return suggestions[:limit]
+
+    anchor_root = max(in_root, key=lambda p: len(str(p)))
+    ends_with_sep = raw.endswith(os.sep) or raw.endswith('/')
+    parent = target if ends_with_sep else target.parent
+    leaf = '' if ends_with_sep else target.name
+    show_hidden = leaf.startswith('.')
+
+    try:
+        parent_resolved = parent.expanduser().resolve()
+    except Exception:
+        return suggestions[:limit]
+
+    if not parent_resolved.exists() or not parent_resolved.is_dir():
+        return suggestions[:limit]
+    if not _is_within(parent_resolved, anchor_root):
+        return suggestions[:limit]
+
+    leaf_lower = leaf.lower()
+    try:
+        children = sorted(parent_resolved.iterdir(), key=lambda p: p.name.lower())
+    except OSError:
+        return suggestions[:limit]
+
+    for child in children:
+        if not child.is_dir():
+            continue
+        if child.name.startswith('.') and not show_hidden:
+            continue
+        if leaf_lower and not child.name.lower().startswith(leaf_lower):
+            continue
+        add(child.resolve())
+        if len(suggestions) >= limit:
+            break
+    return suggestions[:limit]
+
+
 def resolve_trusted_workspace(path: str | Path | None = None) -> Path:
     """Resolve and validate a workspace path.
 
@@ -240,13 +375,6 @@ def resolve_trusted_workspace(path: str | Path | None = None) -> Path:
     None/empty path falls back to the boot-time DEFAULT_WORKSPACE, which is always
     trusted (it was validated at server startup).
     """
-    _BLOCKED_SYSTEM_ROOTS = {
-        # Linux / macOS
-        Path('/etc'), Path('/usr'), Path('/var'), Path('/bin'), Path('/sbin'),
-        Path('/boot'), Path('/proc'), Path('/sys'), Path('/dev'),
-        Path('/lib'), Path('/lib64'), Path('/opt/homebrew'),
-    }
-
     if path in (None, ""):
         return Path(_BOOT_DEFAULT_WORKSPACE).expanduser().resolve()
 
@@ -258,7 +386,7 @@ def resolve_trusted_workspace(path: str | Path | None = None) -> Path:
         raise ValueError(f"Path is not a directory: {candidate}")
 
     # Block known system roots and their children
-    for blocked in _BLOCKED_SYSTEM_ROOTS:
+    for blocked in _workspace_blocked_roots():
         try:
             candidate.relative_to(blocked)
             raise ValueError(f"Path points to a system directory: {candidate}")
diff --git a/static/panels.js b/static/panels.js
index 3f25cb4..0edd1a0 100644
--- a/static/panels.js
+++ b/static/panels.js
@@ -536,6 +536,94 @@ async function submitMemorySave() {
 
 // ── Workspace management ──
 let _workspaceList = [];  // cached from /api/workspaces
+let _wsSuggestTimer = null;
+let _wsSuggestReq = 0;
+let _wsSuggestIndex = -1;
+
+function closeWorkspacePathSuggestions(){
+  const box=$('wsAddSuggestions');
+  if(box){
+    box.innerHTML='';
+    box.style.display='none';
+  }
+  _wsSuggestIndex=-1;
+}
+
+function _applyWorkspaceSuggestion(path){
+  const input=$('wsAddInput');
+  const next=(path||'').endsWith('/')?(path||''):`${path||''}/`;
+  if(input){
+    input.value=next;
+    input.focus();
+    input.setSelectionRange(next.length, next.length);
+  }
+  scheduleWorkspacePathSuggestions();
+}
+
+function _highlightWorkspaceSuggestion(idx){
+  const box=$('wsAddSuggestions');
+  if(!box)return;
+  const items=[...box.querySelectorAll('.ws-suggest-item')];
+  items.forEach((el,i)=>{
+    const active=i===idx;
+    el.classList.toggle('active', active);
+    if(active) el.scrollIntoView({block:'nearest'});
+  });
+}
+
+function _renderWorkspacePathSuggestions(paths){
+  const box=$('wsAddSuggestions');
+  if(!box)return;
+  box.innerHTML='';
+  if(!paths || !paths.length){
+    box.style.display='none';
+    _wsSuggestIndex=-1;
+    return;
+  }
+  paths.forEach((path, idx)=>{
+    const pathParts=(path||'').split('/').filter(Boolean);
+    const leaf=pathParts[pathParts.length-1]||path;
+    const parent=pathParts.length>1?`/${pathParts.slice(0,-1).join('/')}`:'/';
+    const item=document.createElement('button');
+    item.type='button';
+    item.className='ws-suggest-item';
+    item.innerHTML=`<span class="ws-suggest-leaf">${esc(leaf)}</span><span class="ws-suggest-parent">${esc(parent)}</span>`;
+    item.dataset.path=path;
+    item.onmouseenter=()=>{_wsSuggestIndex=idx;_highlightWorkspaceSuggestion(idx);};
+    item.onmousedown=(e)=>{e.preventDefault();_applyWorkspaceSuggestion(path);};
+    box.appendChild(item);
+  });
+  box.style.display='block';
+  _wsSuggestIndex=0;
+  _highlightWorkspaceSuggestion(_wsSuggestIndex);
+}
+
+async function _loadWorkspacePathSuggestions(prefix){
+  const reqId=++_wsSuggestReq;
+  try{
+    const qs=new URLSearchParams({prefix:prefix||''}).toString();
+    const data=await api(`/api/workspaces/suggest?${qs}`);
+    if(reqId!==_wsSuggestReq)return;
+    _renderWorkspacePathSuggestions(data.suggestions||[]);
+  }catch(_){
+    if(reqId!==_wsSuggestReq)return;
+    closeWorkspacePathSuggestions();
+  }
+}
+
+function scheduleWorkspacePathSuggestions(){
+  const input=$('wsAddInput');
+  if(!input)return;
+  const prefix=input.value.trim();
+  if(!prefix){
+    closeWorkspacePathSuggestions();
+    return;
+  }
+  if(_wsSuggestTimer) clearTimeout(_wsSuggestTimer);
+  _wsSuggestTimer=setTimeout(()=>{
+    _loadWorkspacePathSuggestions(prefix);
+  }, 120);
+}
 
 function getWorkspaceFriendlyName(path){
   // Look up the friendly name from the workspace list cache, fallback to last path segment
@@ -719,13 +807,70 @@ function renderWorkspacesPanel(workspaces){
   }
   const addRow=document.createElement('div');addRow.className='ws-add-row';
   addRow.innerHTML=`
-    <input id="wsAddInput" placeholder="${esc(t('workspace_add_path_placeholder'))}" style="flex:1;background:rgba(255,255,255,.06);border:1px solid var(--border2);border-radius:7px;color:var(--text);padding:7px 10px;font-size:12px;outline:none;">
+    <div class="ws-add-input-wrap">
+      <input id="wsAddInput" placeholder="${esc(t('workspace_add_path_placeholder'))}" autocomplete="off" style="width:100%;background:rgba(255,255,255,.06);border:1px solid var(--border2);border-radius:7px;color:var(--text);padding:7px 10px;font-size:12px;outline:none;">
+    </div>
     <button class="ws-action-btn" onclick="addWorkspace()">${li('plus',12)} ${esc(t('add'))}</button>`;
   panel.appendChild(addRow);
+  const suggestBox=document.createElement('div');
+  suggestBox.id='wsAddSuggestions';
+  suggestBox.className='ws-suggestions';
+  suggestBox.style.display='none';
+  panel.appendChild(suggestBox);
   const hint=document.createElement('div');
   hint.style.cssText='font-size:11px;color:var(--muted);padding:4px 0 8px';
   hint.textContent=t('workspace_paths_validated_hint');
   panel.appendChild(hint);
+  const input=$('wsAddInput');
+  if(input){
+    input.oninput=()=>scheduleWorkspacePathSuggestions();
+    input.onfocus=()=>{
+      if(input.value.trim()) scheduleWorkspacePathSuggestions();
+      else closeWorkspacePathSuggestions();
+    };
+    input.onkeydown=(e)=>{
+      const box=$('wsAddSuggestions');
+      const items=box?[...box.querySelectorAll('.ws-suggest-item')]:[];
+      if(!items.length){
+        if(e.key==='Enter'){
+          e.preventDefault();
+          addWorkspace();
+        }
+        return;
+      }
+      if(e.key==='ArrowDown'){
+        e.preventDefault();
+        _wsSuggestIndex=Math.min(items.length-1,Math.max(-1,_wsSuggestIndex)+1);
+        _highlightWorkspaceSuggestion(_wsSuggestIndex);
+        return;
+      }
+      if(e.key==='ArrowUp'){
+        e.preventDefault();
+        _wsSuggestIndex=_wsSuggestIndex<=0?0:_wsSuggestIndex-1;
+        _highlightWorkspaceSuggestion(_wsSuggestIndex);
+        return;
+      }
+      if(e.key==='Escape'){
+        e.preventDefault();
+        closeWorkspacePathSuggestions();
+        return;
+      }
+      if(e.key==='Enter'){
+        e.preventDefault();
+        if(_wsSuggestIndex>=0 && items[_wsSuggestIndex]){
+          _applyWorkspaceSuggestion(items[_wsSuggestIndex].dataset.path||'');
+        }else{
+          addWorkspace();
+        }
+        return;
+      }
+      if(e.key==='Tab' && _wsSuggestIndex>=0 && items[_wsSuggestIndex]){
+        e.preventDefault();
+        _applyWorkspaceSuggestion(items[_wsSuggestIndex].dataset.path||'');
+        return;
+      }
+    };
+  }
 }
 
 async function addWorkspace(){
@@ -737,10 +882,15 @@ async function addWorkspace(){
     _workspaceList=data.workspaces;
     renderWorkspacesPanel(data.workspaces);
     if(input)input.value='';
+    closeWorkspacePathSuggestions();
     showToast(t('workspace_added'));
   }catch(e){setStatus(t('add_failed')+e.message);}
 }
 
+document.addEventListener('click',e=>{
+  if(!e.target.closest('.ws-add-input-wrap')) closeWorkspacePathSuggestions();
+});
+
 async function removeWorkspace(path){
   const _rmWs=await showConfirmDialog({title:t('workspace_remove_confirm_title'),message:t('workspace_remove_confirm_message',path),confirmLabel:t('remove'),danger:true,focusCancel:true});
   if(!_rmWs) return;
diff --git a/static/style.css b/static/style.css
index b11733b..d9158b6 100644
--- a/static/style.css
+++ b/static/style.css
@@ -874,6 +874,15 @@
 .cmd-item-badge-skill{color:var(--accent-text);background:var(--accent-bg);border-color:var(--accent-bg-strong);}
 .ws-action-btn.danger:hover{background:rgba(239,83,80,.1);color:var(--error);border-color:var(--error);}
 .ws-add-row{display:flex;gap:8px;align-items:center;padding:10px 0 4px;}
+.ws-add-input-wrap{flex:1;min-width:0;}
+.ws-suggestions{margin:0 0 6px;background:var(--bg2);border:1px solid var(--border2);border-radius:8px;box-shadow:0 10px 24px rgba(0,0,0,.22);max-height:220px;overflow:auto;}
+.ws-suggest-item{display:flex;flex-direction:column;gap:2px;width:100%;padding:8px 10px;border:0;background:transparent;color:var(--text);text-align:left;font-size:12px;cursor:pointer;}
+.ws-suggest-item:hover{background:rgba(255,255,255,.08);}
+.ws-suggest-item.active{background:var(--accent-bg);outline:1px solid var(--accent-bg-strong);outline-offset:-1px;box-shadow:inset 0 0 0 1px rgba(255,255,255,.04);}
+.ws-suggest-leaf{font-size:13px;font-weight:600;color:var(--text);}
+.ws-suggest-parent{font-size:11px;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis;}
+.ws-suggest-item.active .ws-suggest-leaf{color:var(--accent-text);}
+.ws-suggest-item.active .ws-suggest-parent{color:var(--text);}
 /* ── Message action buttons (copy, edit, retry) ── */
 .msg-actions{display:flex;align-items:center;gap:2px;opacity:0;transition:opacity .15s;margin-left:auto;}
 .msg-row:hover .msg-actions{opacity:1;}
diff --git a/tests/test_issue616.py b/tests/test_issue616.py
new file mode 100644
index 0000000..b19d148
--- /dev/null
+++ b/tests/test_issue616.py
@@ -0,0 +1,17 @@
+import pathlib
+
+
+def test_workspace_suggest_endpoint_is_wired():
+    src = pathlib.Path("api/routes.py").read_text(encoding="utf-8")
+    assert '"/api/workspaces/suggest"' in src
+
+
+def test_spaces_panel_uses_workspace_suggest_autocomplete():
+    src = pathlib.Path("static/panels.js").read_text(encoding="utf-8")
+    assert "/api/workspaces/suggest" in src
+    assert "wsAddSuggestions" in src
+    assert "scheduleWorkspacePathSuggestions" in src
+    assert "if(!prefix)" in src
+    assert "dataset.path" in src
+    assert "scrollIntoView" in src
+    assert "_wsSuggestIndex=0" in src
diff --git a/tests/test_sprint5.py b/tests/test_sprint5.py
index 620f11c..dee6779 100644
--- a/tests/test_sprint5.py
+++ b/tests/test_sprint5.py
@@ -1,5 +1,5 @@
 """Sprint 5 tests: workspace CRUD, file save, session index, JS serving."""
-import json, pathlib, uuid, urllib.request, urllib.error
+import json, pathlib, uuid, urllib.request, urllib.error, urllib.parse
 import os
 
 from tests._pytest_port import BASE
@@ -80,6 +80,34 @@ def test_workspace_add_requires_path():
     result, status = post("/api/workspaces/add", {})
     assert status == 400
 
+def test_workspace_suggest_returns_trusted_directories(cleanup_test_sessions):
+    _, ws = make_session_tracked(cleanup_test_sessions)
+    child = make_workspace_child(ws, f"workspace-suggest-{uuid.uuid4().hex[:6]}")
+    nested = make_workspace_child(child, "nested")
+    prefix = str(child.parent / child.name[:12])
+    data, status = get(f"/api/workspaces/suggest?prefix={urllib.parse.quote(prefix)}")
+    assert status == 200
+    assert str(child) in data["suggestions"]
+    assert all(not pathlib.Path(p).name.startswith('.') for p in data["suggestions"])
+
+def test_workspace_suggest_hides_untrusted_system_prefix():
+    data, status = get("/api/workspaces/suggest?prefix=/etc")
+    assert status == 200
+    assert data["suggestions"] == []
+
+def test_workspace_suggest_hidden_dirs_only_when_requested(cleanup_test_sessions):
+    _, ws = make_session_tracked(cleanup_test_sessions)
+    hidden = make_workspace_child(ws, ".workspace-hidden")
+    visible = make_workspace_child(ws, "workspace-visible")
+    base = str(ws) + "/"
+    data, status = get(f"/api/workspaces/suggest?prefix={urllib.parse.quote(base)}")
+    assert status == 200
+    assert str(visible) in data["suggestions"]
+    assert str(hidden) not in data["suggestions"]
+    data2, status2 = get(f"/api/workspaces/suggest?prefix={urllib.parse.quote(base + '.w')}")
+    assert status2 == 200
+    assert str(hidden) in data2["suggestions"]
+
 def test_workspace_remove(cleanup_test_sessions):
     _, ws = make_session_tracked(cleanup_test_sessions)
     child = make_workspace_child(ws, f"workspace-remove-{uuid.uuid4().hex[:6]}")