Charge Grok Imagine images by official per-image tiers

[think-back]

Summary

• switch Grok Imagine image models to the official per-image pricing contract
• apply request-level resolution/quality multipliers for Imagine 2.0 and Imagine Pro/Quality
• keep unknown or auto options on the lowest official tier as a safe fallback

Official tiers

• grok-imagine-image: $0.02/image for 1K and 2K
• grok-imagine-image-2.0: $0.04 (1K low), $0.06 (2K low / 1K medium), $0.08 (2K medium)
• grok-imagine-image-pro / grok-imagine-image-quality: $0.05 (1K), $0.07 (2K)

Verification

• go test ./dto -count=1
• go test ./pkg/billingexpr -count=1
• go test ./relay/helper -count=1 (one existing timing-sensitive stream scanner test was flaky in this run; no code path from this change is involved)

[KingCesc]

🤖 OpenCodeReview · 评审 commit ffbed2cb · 共 1 条

dto/openai_image.go

• L216-223: [阻塞] grok-imagine-image-2.0 只配置了 low/medium 两档，但这里在 quality 为空或 auto 时会先回退到 modelPrices["default"]。由于该模型并没有 default 档位，qualityPrices 会是 nil，随后取价失败直接返回 1，而上游又会把图片质量设为 auto，这会导致 2.0 请求按错误倍率计费，产生明显的账单偏差。建议为该模型显式提供默认档位（按最低官方 tier）或在缺省质量时特殊映射到 low。

if quality == "" || quality == "auto" {
		if model == "grok-imagine-image-2.0" {
			quality = "low"
		} else {
			quality = "default"
		}
	}
	qualityPrices, ok := modelPrices[quality]
	if !ok {
		qualityPrices = modelPrices["default"]
	}
	if qualityPrices == nil {
		return 1
	}
	price, ok := qualityPrices[size]