feat(journal): closeout system prompt with structured-field guard

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/fabledassistant/services/journal_closeout.py

@@ -38,3 +38,19 @@ def _build_transcript(messages) -> str:
     return "\n".join(
         f"{m.role.upper()}: {m.content[:_CONTENT_CAP]}" for m in tail
     )
+
+
+SYSTEM_PROMPT = (
+    "You are reviewing a day's journal conversation to extract preference "
+    "observations the USER revealed about themselves.\n\n"
+    "Rules:\n"
+    "- Only extract patterns, habits, recurring frustrations, or contextual "
+    "facts the user said or demonstrated.\n"
+    "- DO NOT restate facts that belong in structured fields: name, job title, "
+    "industry, expertise level, response style, tone, interests. Those are "
+    "handled separately.\n"
+    "- DO NOT extract anything from the ASSISTANT turns about the user — only "
+    "what the user themselves stated or demonstrated by their choices.\n"
+    "- Write 2-5 short bullet points. Be specific and factual.\n"
+    "- If nothing notable, output only: (nothing to note)"
+)

tests/test_journal_closeout.py

@@ -51,3 +51,14 @@ def test_build_transcript_keeps_only_last_20_messages():
     # Newest 20 means msg-10 through msg-29
     assert lines[0] == "USER: msg-10"
     assert lines[-1] == "USER: msg-29"
+
+
+def test_system_prompt_lists_structured_fields_to_exclude():
+    """The prompt must explicitly tell the LLM not to restate structured
+    fields, so the freeform learned_summary stays a narrow lane."""
+    from fabledassistant.services.journal_closeout import SYSTEM_PROMPT
+
+    text = SYSTEM_PROMPT.lower()
+    for field in ("name", "job title", "industry", "expertise", "response style", "tone", "interests"):
+        assert field in text, f"system prompt should mention '{field}'"
+    assert "(nothing to note)" in SYSTEM_PROMPT