Function derive_session_id

uncommon_route/session.py:15–39

Derive a session ID from the first user message (SHA-256 prefix). Used for cache key grouping, composition checkpoints, and agent/tool session continuity. Skips boilerplate user messages whose content is identical across sessions for the same workspace — notably Codex CLI's ``<

(messages: list[dict[str, Any]])

def derive_session_id(messages: list[dict[str, Any]]) -> str | None:
    """Derive a session ID from the first user message (SHA-256 prefix).

    Used for cache key grouping, composition checkpoints, and agent/tool
    session continuity.

    Skips boilerplate user messages whose content is identical across
    sessions for the same workspace — notably Codex CLI's
    ``<environment_context>`` block, which wraps cwd/shell/date and would
    otherwise collapse every Codex conversation in the same directory into
    a single session.
    """
    for msg in messages:
        if msg.get("role") != "user":
            continue
        content = msg.get("content", "")
        text = (content if isinstance(content, str) else str(content)).strip()
        if not text:
            continue
        if text.startswith("<environment_context>") and text.endswith(
            "</environment_context>"
        ):
            continue
        return hashlib.sha256(text.encode()).hexdigest()[:8]
    return None


@dataclass