diff --git a/frontend/src/utils/tags.ts b/frontend/src/utils/tags.ts
index 8c79cd3..2474319 100644
--- a/frontend/src/utils/tags.ts
+++ b/frontend/src/utils/tags.ts
@@ -1,5 +1,5 @@
 const CODE_FENCE_RE = /```[\s\S]*?```|`[^`\n]+`/g;
-const TAG_RE = /(?<!\w)(?<!&)#([\w]+(?:\/[\w]+)*)/g;
+const TAG_RE = /(?<!\w)(?<!&)#([\w][\w-]*(?:\/[\w][\w-]*)*)/g;
 
 function escapeHtmlAttr(s: string): string {
   return s.replace(/&/g, "&amp;").replace(/"/g, "&quot;").replace(/</g, "&lt;").replace(/>/g, "&gt;");
diff --git a/src/fabledassistant/routes/notes.py b/src/fabledassistant/routes/notes.py
index f06b384..0d5dd9e 100644
--- a/src/fabledassistant/routes/notes.py
+++ b/src/fabledassistant/routes/notes.py
@@ -120,7 +120,7 @@ async def suggest_tags_route():
 async def append_tag_route(note_id: int):
     uid = get_current_user_id()
     data = await request.get_json()
-    tag = data.get("tag", "").strip()
+    tag = data.get("tag", "").strip().replace(" ", "-")
     if not tag:
         return jsonify({"error": "tag is required"}), 400
 
diff --git a/src/fabledassistant/services/llm.py b/src/fabledassistant/services/llm.py
index 3a204e8..b3ae613 100644
--- a/src/fabledassistant/services/llm.py
+++ b/src/fabledassistant/services/llm.py
@@ -337,6 +337,7 @@ async def build_context(
         tool_lines.append("When the user says 'remind me' with a time before an event, use the reminder_minutes parameter.")
         tool_lines.append("Use search_todos to find a specific CalDAV todo by keyword when list_todos would return too many results.")
     tool_lines.append("For relative dates like 'Friday' or 'next week', resolve them to YYYY-MM-DD format.")
+    tool_lines.append("When writing #tags in note bodies, use hyphens for multi-word tags (e.g. #science-fiction, #space-travel). Never use spaces inside a tag.")
     tool_lines.append(
         "Use update_note to edit/expand an existing note OR to update a task's status/priority/due_date. "
         "Use create_note ONLY for genuinely new notes with a different title. "
diff --git a/src/fabledassistant/services/tag_suggestions.py b/src/fabledassistant/services/tag_suggestions.py
index 7cc6cff..6b428ac 100644
--- a/src/fabledassistant/services/tag_suggestions.py
+++ b/src/fabledassistant/services/tag_suggestions.py
@@ -33,8 +33,10 @@ async def suggest_tags(user_id: int, title: str, body: str) -> list[str]:
             "content": (
                 "You are a tag suggestion assistant. Given a note's title and body, "
                 "suggest 3-5 relevant tags. Prefer reusing existing tags when they fit, "
-                "but you may suggest new ones too. Reply with ONLY a JSON array of tag "
-                'strings (without # prefix). Example: ["meeting", "project/alpha", "followup"]\n\n'
+                "but you may suggest new ones too. "
+                "Tags must use hyphens for multi-word names (e.g. science-fiction, space-travel) — never spaces. "
+                "Reply with ONLY a JSON array of tag strings (without # prefix). "
+                'Example: ["meeting", "project/alpha", "science-fiction"]\n\n'
                 f"Existing tags: {existing_list}"
             ),
         },
@@ -64,10 +66,13 @@ def _parse_tag_list(response: str) -> list[str]:
     text = response.strip()
 
     # Try direct JSON parse
+    def _clean(tag: str) -> str:
+        return str(tag).strip().lstrip("#").replace(" ", "-")
+
     try:
         parsed = json.loads(text)
         if isinstance(parsed, list):
-            return [str(t).strip().lstrip("#") for t in parsed if t]
+            return [_clean(t) for t in parsed if t]
     except json.JSONDecodeError:
         pass
 
@@ -77,7 +82,7 @@ def _parse_tag_list(response: str) -> list[str]:
         try:
             parsed = json.loads(match.group())
             if isinstance(parsed, list):
-                return [str(t).strip().lstrip("#") for t in parsed if t]
+                return [_clean(t) for t in parsed if t]
         except json.JSONDecodeError:
             pass
 
diff --git a/src/fabledassistant/utils/tags.py b/src/fabledassistant/utils/tags.py
index a436f75..b0373e4 100644
--- a/src/fabledassistant/utils/tags.py
+++ b/src/fabledassistant/utils/tags.py
@@ -1,7 +1,7 @@
 import re
 
 _CODE_FENCE_RE = re.compile(r"```[\s\S]*?```|`[^`\n]+`")
-_TAG_RE = re.compile(r"(?<!\w)#([\w]+(?:/[\w]+)*)")
+_TAG_RE = re.compile(r"(?<!\w)#([\w][\w-]*(?:/[\w][\w-]*)*)")
 
 
 def extract_tags(body: str) -> list[str]: