Gemini APIの設定ドリフトを止める — モデルID・安全設定をコード化して環境差を検出する

# snapshot.py
from google import genai
from google.genai import types
from gemini_config import GeminiConfig, SafetyThreshold
import hashlib
 
def snapshot_effective_config(
    app_id: str,
    environment: str,
    model_id: str,
    gen_config: types.GenerateContentConfig,
    system_instruction: str,
) -> GeminiConfig:
    """実際にリクエストへ渡している設定を、検証可能なスナップショットに変換する。"""
    safety = [
        SafetyThreshold(category=s.category.name, threshold=s.threshold.name)
        for s in (gen_config.safety_settings or [])
    ]
    instr_sha = hashlib.sha256(
        system_instruction.encode("utf-8")
    ).hexdigest()[:16]
 
    return GeminiConfig(
        app_id=app_id,
        environment=environment,
        model_id=model_id,
        api_version="v1",
        max_output_tokens=gen_config.max_output_tokens,
        temperature=gen_config.temperature,
        top_p=gen_config.top_p,
        thinking_budget=(
            gen_config.thinking_config.thinking_budget
            if gen_config.thinking_config else 0
        ),
        safety_settings=safety,
        system_instruction_sha=instr_sha,
    )

# detect.py
import json, glob
from gemini_config import GeminiConfig
 
def load_desired() -> dict[str, GeminiConfig]:
    out = {}
    for path in glob.glob("configs/*.json"):
        with open(path, encoding="utf-8") as f:
            cfg = GeminiConfig(**json.load(f))
        out[f"{cfg.app_id}:{cfg.environment}"] = cfg
    return out
 
def diff_configs(desired: GeminiConfig, effective: GeminiConfig) -> list[str]:
    """あるべき姿と実効設定の差分を、項目名のリストで返す。"""
    drifts = []
    a = desired.model_dump(exclude={"app_id", "environment"})
    b = effective.model_dump(exclude={"app_id", "environment"})
    for key in a:
        if a[key] != b[key]:
            drifts.append(f"{key}: desired={a[key]!r} effective={b[key]!r}")
    return drifts

# ci_gate.py
import sys
from detect import load_desired, diff_configs
 
def main() -> int:
    desired = load_desired()
    failed = False
    apps = {k.split(":")[0] for k in desired}
 
    for app in sorted(apps):
        prod = desired.get(f"{app}:production")
        stg = desired.get(f"{app}:staging")
        if not (prod and stg):
            continue
        # api_version 以外は staging と production で一致すべき
        if prod.fingerprint() != stg.fingerprint():
            print(f"DRIFT [{app}] staging != production")
            for line in diff_configs(prod, stg):
                print(f"  {line}")
            failed = True
 
    if failed:
        print("Config drift detected. Align environments before merge.")
        return 1
    print("No config drift. All environments aligned.")
    return 0
 
if __name__ == "__main__":
    sys.exit(main())