| """会话指纹：基于 system prompt + 首条 user 消息计算 SHA-256 指纹。 | |
| 同一逻辑对话（相同 system + 相同首条 user）的指纹恒定， | |
| 不同对话指纹不同，杜绝上下文污染。 | |
| """ | |
| import hashlib | |
| from core.api.schemas import OpenAIMessage | |
| def _norm_content(content: str | list | None) -> str: | |
| if content is None: | |
| return "" | |
| if isinstance(content, str): | |
| return content.strip() | |
| # list[OpenAIContentPart] | |
| parts: list[str] = [] | |
| for p in content: | |
| if hasattr(p, "type") and p.type == "text" and p.text: | |
| parts.append(p.text.strip()) | |
| return " ".join(parts) | |
| def compute_conversation_fingerprint(messages: list[OpenAIMessage]) -> str: | |
| """sha256(system_prompt + first_user_message)[:16] | |
| Returns empty string if no user message found. | |
| """ | |
| system_text = "" | |
| first_user_text = "" | |
| for m in messages: | |
| if m.role == "system" and not system_text: | |
| system_text = _norm_content(m.content) | |
| elif m.role == "user" and not first_user_text: | |
| first_user_text = _norm_content(m.content) | |
| break | |
| if not first_user_text: | |
| return "" | |
| raw = f"{system_text}\n{first_user_text}" | |
| return hashlib.sha256(raw.encode()).hexdigest()[:16] | |