fix: fetch upstream models

[seefs001]

fix #2389

Summary by CodeRabbit

• Refactor
  • Improved request header computation logic for upstream model fetching operations, enhancing maintainability and error handling consistency.

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[coderabbitai]

Walkthrough

A new helper function buildFetchModelsHeaders is added to controller/channel.go to consolidate header computation logic for the FetchUpstreamModels operation. This function applies channel-type-specific headers and header overrides, ensuring header override configurations are properly applied to upstream model fetch requests.

Changes

Cohort / File(s)	Summary
Header Processing Helper controller/channel.go	Added buildFetchModelsHeaders(channel *model.Channel, key string) function to compute request headers based on channel type and header overrides; integrated into FetchUpstreamModels to replace inline header logic and enable header override application.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

• Verify the new buildFetchModelsHeaders function correctly prioritizes and merges channel-type-specific headers with header override configurations
• Confirm proper error handling and propagation within the function
• Validate integration with FetchUpstreamModels and GetResponseBody call sites

Possibly related PRs

• feat: add GetClaudeAuthHeader function and update FetchUpstreamModels to support Anthropic channel type #1984: Also modifies how FetchUpstreamModels constructs request headers, introducing a dedicated header helper for channel-type-specific (Anthropic/Claude) authentication logic.

Poem

🐰 A header helper hops to the rescue,
Cloudflare's auth now flows through the channel,
Overrides cascade like morning dew,
No more silent failures to unravels—
Requests rise with proper care! ✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: fetch upstream models' is concise and clearly relates to the main change in the pull request, which addresses the FetchUpstreamModels function to apply request header overrides.
Linked Issues check	✅ Passed	The pull request adds the buildFetchModelsHeaders function to apply request header overrides in FetchUpstreamModels, directly addressing issue #2389's requirement to support custom headers like cf-aig-authorization.
Out of Scope Changes check	✅ Passed	All changes focus on the FetchUpstreamModels functionality and header handling, which are directly aligned with the linked issue #2389 objectives.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 3ebc713 and c7539d1.

📒 Files selected for processing (1)

• controller/channel.go (2 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

controller/channel.go (3)

model/channel.go (1)

• Channel (21-58)

constant/channel.go (1)

• ChannelTypeAnthropic (18-18)

controller/channel-billing.go (3)

• GetClaudeAuthHeader (132-137)
• GetAuthHeader (125-129)
• GetResponseBody (139-167)

🔇 Additional comments (2)

controller/channel.go (2)

168-190: Excellent implementation that solves the header override issue.

The function correctly:

• Applies channel-type-specific headers (Anthropic vs. default Bearer token)
• Iterates through header overrides and validates that values are strings
• Replaces {api_key} placeholders dynamically
• Returns clear error messages for invalid configurations

The use of headers.Set() properly implements override semantics, ensuring custom headers like cf-aig-authorization will be applied when fetching upstream models.

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250-256: Correct integration that fixes the missing header override application.

The refactored code properly builds headers with overrides applied before making the upstream request. This directly addresses issue #2389.

However, manual verification is required to confirm:

• The buildFetchModelsHeaders function correctly applies header overrides
• The GetResponseBody call properly utilizes the constructed headers
• The error handling flow matches the intended behavior

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