diff --git a/python/ebook_search/protected_phrases/judge_ngrams.py b/python/ebook_search/protected_phrases/judge_ngrams.py
index b0b49e6..8afbe3f 100644
--- a/python/ebook_search/protected_phrases/judge_ngrams.py
+++ b/python/ebook_search/protected_phrases/judge_ngrams.py
@@ -5,7 +5,7 @@ from __future__ import annotations
 import asyncio
 import json
 import logging
-import re
+from dataclasses import replace
 from time import perf_counter
 from typing import TYPE_CHECKING
 
@@ -45,9 +45,6 @@ if TYPE_CHECKING:
     from python.ebook_search.protected_phrases.models import PhraseCandidate
     from python.orm.richie import EbookProtectedPhrase
 
-JSON_OBJECT_RE = re.compile(r"\{.*\}", re.DOTALL)
-
-
 logger = logging.getLogger(__name__)
 
 
@@ -262,7 +259,9 @@ async def judge_candidate_async(
     Returns:
         LLMJudgment: The parsed judgment.
     """
-    content = await request_chat_completion(client, config, build_judge_messages(candidate))
+    content = await request_chat_completion(
+        client, config, build_judge_messages(candidate), response_format={"type": "json_object"}
+    )
     return parse_llm_judgment(content, config)
 
 
@@ -287,12 +286,23 @@ async def persist_book_judgments(
     book_started_at = perf_counter()
     async with AsyncSession(engine, expire_on_commit=False) as session:
         try:
+            normalized_book_text = normalize_text(await load_book_text(session, source_id))
             protected: list[EbookProtectedPhrase] = []
             for candidate_id, candidate, judgment, promote in judged:
-                candidate_row = await save_candidate_to_db(session, source_id, None, candidate, judgment=judgment)
+                filtered_judgment = replace(
+                    judgment,
+                    aliases=tuple(
+                        alias for alias in judgment.aliases if alias_occurs_in_book(alias, normalized_book_text)
+                    ),
+                )
+                candidate_row = await save_candidate_to_db(
+                    session, source_id, None, candidate, judgment=filtered_judgment
+                )
                 if promote:
                     protected.append(
-                        await upsert_protected_phrase(session, source_id, None, candidate, judgment, candidate_row)
+                        await upsert_protected_phrase(
+                            session, source_id, None, candidate, filtered_judgment, candidate_row
+                        )
                     )
                 logger.info(
                     f"ebook_candidate_phrase_judgment_candidate_complete {source_id=} {candidate_id=} "
@@ -395,14 +405,14 @@ def parse_llm_judgment(content: str, config: EbookSearchConfig) -> LLMJudgment:
     if not isinstance(aliases, list | tuple):
         aliases = ()
     return LLMJudgment(
-        keep=bool(body.get("keep", False)),
+        keep=strict_bool(body.get("keep"), default=False),
         canonical=optional_text(body.get("canonical")),
         category=optional_text(body.get("category")),
         aliases=tuple(str(alias) for alias in aliases if isinstance(alias, str) and alias.strip()),
         confidence=clamped_float(body.get("confidence"), default=0.0),
         importance=clamped_float(body.get("importance"), default=0.5),
-        allow_nested=bool(body.get("allow_nested", config.phrase_default_allow_nested)),
-        suppress_children=bool(body.get("suppress_children", config.phrase_default_suppress_children)),
+        allow_nested=strict_bool(body.get("allow_nested"), default=config.phrase_default_allow_nested),
+        suppress_children=strict_bool(body.get("suppress_children"), default=config.phrase_default_suppress_children),
         reason=optional_text(body.get("reason")),
     )
 
@@ -419,14 +429,13 @@ def extract_json_object(content: str) -> str:
     Raises:
         ValueError: If no JSON object is found in the response.
     """
-    stripped = content.strip()
-    if stripped.startswith("{") and stripped.endswith("}"):
-        return stripped
-    match = JSON_OBJECT_RE.search(stripped)
-    if match is None:
-        msg = "LLM phrase judge response did not contain a JSON object"
-        raise ValueError(msg)
-    return match.group(0)
+    return content.strip()
+
+
+def alias_occurs_in_book(alias: str, normalized_book_text: str) -> bool:
+    """Return whether a normalized alias occurs as a complete phrase in the source book."""
+    alias_norm = normalize_text(alias)
+    return bool(alias_norm) and f" {alias_norm} " in f" {normalized_book_text} "
 
 
 def optional_text(value: object) -> str | None:
@@ -444,6 +453,11 @@ def optional_text(value: object) -> str | None:
     return stripped or None
 
 
+def strict_bool(value: object, *, default: bool) -> bool:
+    """Return a JSON boolean, falling back when the value has another type."""
+    return value if isinstance(value, bool) else default
+
+
 def clamped_float(value: object, *, default: float) -> float:
     """Coerce a JSON number into the 0.0 to 1.0 range.