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Date: Tue, 11 Aug 2026 00:16:46 +0900
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- 기존 "DO NOT GUESS" 는 Strategy 3(가격)에 국한돼 있었고, 빈 셸 환각 사고(에이블리 mobile.*, 15회 중 8회 창작)에서 flash-lite 가 이 지시를 절반가량만 따르는 것이 실측됐다. 극한(빈 입력)은 #26 게이트가 결정론으로 막았으므로, 이 규칙은 남은 표면 - 내용이 일부 있는 페이지에서 없는 필드를 채워 넣는 창작 - 을 겨냥한다
- 전역 규칙을 프롬프트 서두에 승격: 모든 출력 값은 제공된 HTML 에 존재해야 하고, 없으면 null(상품 자체가 없으면 isProductPage=false). 기억·유사 상품에서 회상한 값 생성을 명시적으로 금지하고 "창작이 null 보다 엄격히 나쁘다"는 우선순위를 박는다
- imageUrl 필드에도 개별 강화: URL(또는 resolve 전 상대경로)이 HTML 에 실재해야 하며 조립·축약 금지. 사고에서 창작된 이미지가 전부 NXDOMAIN/403 이었던 것의 직접 대응이며, 보류 중인 출력 대조(grounding 검증) PR 이 들어오기 전까지의 확률적 방어층이다
- 효과 측정은 dev 모델 실험(gemini-3.6-flash, extraction_models)과 함께 via=llm 대비 UNTRUSTWORTHY_VALUE·INCOMPLETE_SNAPSHOT 비율로 본다
---
 .../extraction/gemini/GeminiExtractionRequest.java       | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/main/java/com/depromeet/piki/extractor/extraction/gemini/GeminiExtractionRequest.java b/src/main/java/com/depromeet/piki/extractor/extraction/gemini/GeminiExtractionRequest.java
index ffb3fbf..6ffd506 100644
--- a/src/main/java/com/depromeet/piki/extractor/extraction/gemini/GeminiExtractionRequest.java
+++ b/src/main/java/com/depromeet/piki/extractor/extraction/gemini/GeminiExtractionRequest.java
@@ -56,6 +56,13 @@ static JsonSchema ofNullableType(String type) {
             You are a product information extractor. Given the URL and the HTML of a product page,
             extract information for the MAIN product of the page.
 
+            **Grounding rule (highest priority, applies to every field)**:
+            Every value you output MUST be taken from the provided HTML. If a value is not present
+            in the HTML, return null for that field (or isProductPage=false if the page shows no
+            product at all). NEVER invent, guess, or recall values from memory or from similar
+            products you have seen elsewhere. A fabricated value is the worst possible outcome —
+            strictly worse than null.
+
             **Input**:
             - URL: the product page URL
             - HTML: raw HTML content of that page (may include <script type="application/ld+json"> JSON-LD,
@@ -79,6 +86,8 @@ static JsonSchema ofNullableType(String type) {
             4. currency (string): ISO 4217 code (KRW, USD, JPY, EUR, etc.). Infer from page language/locale if ambiguous.
             5. imageUrl (string): ABSOLUTE URL of the primary product image. Prefer og:image meta tag,
                fallback to the main product image. Resolve relative URLs against the page URL.
+               The URL (or the relative path you resolve) must appear in the HTML — do not construct
+               or abbreviate image URLs. If no product image URL appears in the HTML, return null.
 
             **Price rules**:
             - Single price, no discount indicator → that price is currentPrice.