fix: skip estimated tokens for abnormal streams without usage (#4168)

[cat0825]

⚠️ 提交说明 / PR Notice

Important

• 请提供人工撰写的简洁摘要，避免直接粘贴未经整理的 AI 输出。

📝 变更描述 / Description

当流式请求异常结束（client_gone/timeout 等）且上游未返回 usage 时，不再使用估算 prompt tokens 结算扣费。正常结束或上游提供 usage 的路径保持不变，避免误伤。

This PR was AI-assisted and manually reviewed before submission.

🚀 变更类型 / Type of change

• 🐛 Bug 修复 (Bug fix) - 请关联对应 Issue，避免将设计取舍、理解偏差或预期不一致直接归类为 bug
• ✨ 新功能 (New feature) - 重大特性建议先通过 Issue 沟通
• ⚡ 性能优化 / 重构 (Refactor)
• 📝 文档更新 (Documentation)

🔗 关联任务 / Related Issue

• Closes bug: stream 失败（client_gone/timeout）且 completion_tokens=0 时仍按 prompt_tokens 扣费 #4168

✅ 提交前检查项 / Checklist

• 人工确认: 我已亲自整理并撰写此描述，没有直接粘贴未经处理的 AI 输出。
• 非重复提交: 我已搜索现有的 Issues 与 PRs，确认不是重复提交。
• Bug fix 说明: 若此 PR 标记为 Bug fix，我已提交或关联对应 Issue，且不会将设计取舍、预期不一致或理解偏差直接归类为 bug。
• 变更理解: 我已理解这些更改的工作原理及可能影响。
• 范围聚焦: 本 PR 未包含任何与当前任务无关的代码改动。
• 本地验证: 已在本地运行并通过测试或手动验证，维护者可以据此复核结果。
• 安全合规: 代码中无敏感凭据，且符合项目代码规范。

📸 运行证明 / Proof of Work

docker run --rm -v "$PWD":/work -w /work -e GOMODCACHE=/gomod -e GOCACHE=/gocache golang:1.25.1 go test ./service -run 'TestCalculateTextQuotaSummary'
ok  	github.com/QuantumNous/new-api/service	0.021s

Summary by CodeRabbit

• Bug Fixes
  • Prevented quota deductions when a streaming response ends abnormally and upstream usage data is unavailable.
  • Preserved estimated token usage for normally completed streams without upstream usage data.
  • Improved quota reporting to accurately reflect zero usage in applicable abnormal termination cases.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 81e5207a-9749-4a7e-b4ef-c9b6df464294

📥 Commits

Reviewing files that changed from the base of the PR and between ad900bb and b04b7f9.

📒 Files selected for processing (2)

• service/text_quota.go
• service/text_quota_test.go

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Walkthrough

Streaming quota calculation now skips estimated prompt tokens when a stream ends abnormally without upstream usage. Billing metadata records the skipped deduction, while normal completed streams retain estimated usage. Tests cover both behaviors.

Changes

Streaming quota handling

Layer / File(s)	Summary
Abnormal stream usage and validation service/text_quota.go, service/text_quota_test.go	Abnormal streams without upstream usage use zero tokens and quota, append a skipped-billing reason, and are tested against normal completed streams that continue using estimates.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related issues

• Issue 5235: The changes implement its objective of avoiding estimated usage and zeroing quota when streaming ends abnormally without upstream billing information.

Poem

I’m a bunny guarding tokens tonight,
No usage? Then charges take flight.
A broken stream gets zero to pay,
While normal streams keep estimates in play.
Hop, hop—billing’s clear and right!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: skipping estimated tokens for abnormal streams without upstream usage.
Linked Issues check	✅ Passed	The changes address #4168 by avoiding estimated prompt-token charging on abnormal stream endings when usage is missing.
Out of Scope Changes check	✅ Passed	The diff stays focused on text quota billing logic and matching tests, with no obvious unrelated changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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