feat: add OpenAI base URL override for regional endpoints

[MichaelFBA]

Summary

• add support for overriding OpenAI API base URL via OPENAI_BASE_URL
• add a new CLI flag --openai-base-url for explicit endpoint selection
• default to https://api.openai.com/v1 to preserve existing behavior
• apply override to both OpenAI call paths used by tests (agent-to-agent goal evaluation and similarity validation)
• document the new option in authentication docs with EU endpoint example

Why

Some environments require region-specific OpenAI endpoints (for example https://eu.api.openai.com/v1).
Without a base URL override, voiceflow-cli always calls https://api.openai.com/v1/chat/completions, which can fail under geography constraints.

Test plan

• run go test ./...
• manual verification with defaults (no override): existing behavior remains unchanged
• manual verification with override:
  • voiceflow test execute <suite> --openai-base-url https://eu.api.openai.com/v1
  • or OPENAI_BASE_URL=https://eu.api.openai.com/v1 voiceflow test execute <suite>

Made with Cursor

Summary by CodeRabbit

• New Features

  • Added support for configuring a custom OpenAI API base URL via the --openai-base-url flag or OPENAI_BASE_URL environment variable (defaults to https://api.openai.com/v1 if not provided).

• Documentation

  • Updated authentication guide with instructions for overriding the OpenAI API base URL.

[coderabbitai]

Walkthrough

This pull request introduces a configurable OpenAI base URL feature. A new global variable, command-line flag (--openai-base-url), and environment variable support (OPENAI_BASE_URL) are added, with two new functions managing the URL lifecycle. Hardcoded OpenAI API URLs are replaced with dynamic lookups across the codebase.

Changes

Cohort / File(s)	Summary
Configuration Setup cmd/root.go, internal/global/vars.go	Introduces persistent flag --openai-base-url and new global variable OpenAIBaseURL to store the configured base URL.
URL Management internal/openai/authentication.go	Adds SetOpenAIBaseURL() to initialize base URL from environment or use default (https://api.openai.com/v1), and GetChatCompletionsURL() to return the full chat completions endpoint.
URL Endpoint Consolidation pkg/openai/similarity.go, pkg/test/common.go	Replaces hardcoded OpenAI API URLs with centralized calls to GetChatCompletionsURL().
Execution Integration cmd/test/execute.go	Calls SetOpenAIBaseURL() during test execution to initialize the configured base URL.
Documentation docs/docs/overview/authentication.md	Documents the new --openai-base-url flag and OPENAI_BASE_URL environment variable with usage examples and default behavior.

Sequence Diagram(s)

sequenceDiagram
    actor User
    participant CLI as cmd/root.go
    participant Global as global vars
    participant Auth as openai/auth
    participant Client as API Client
    
    User->>CLI: Provides --openai-base-url flag<br/>(or OPENAI_BASE_URL env var)
    CLI->>Global: Stores in global.OpenAIBaseURL
    Note over CLI,Global: Flag parsed & bound during init()
    
    CLI->>Auth: Calls SetOpenAIBaseURL()
    Auth->>Global: Reads global.OpenAIBaseURL
    Alt Env var set
        Auth->>Auth: Use OPENAI_BASE_URL value
    Else Env var unset
        Auth->>Auth: Default to https://api.openai.com/v1
    End
    Auth->>Auth: Trim trailing slashes
    Auth->>Global: Update global.OpenAIBaseURL
    
    CLI->>Client: Calls API function (similarity/common)
    Client->>Auth: GetChatCompletionsURL()
    Auth->>Auth: Return base + /chat/completions
    Auth-->>Client: Full endpoint URL
    Client->>Client: Make HTTP request to configured URL

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 Whiskers twitch with glee,
Base URLs now flow so free,
Flags and env vars align,
Config magic, oh so fine!
OpenAI calls centralized with care. 🌟

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ 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%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and concisely describes the main feature addition: enabling OpenAI base URL overrides for regional endpoints.
Merge Conflict Detection	✅ Passed	✅ No merge conflicts detected when merging into main

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

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

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@docs/docs/overview/authentication.md`:
- Line 13: Fix the typo in the markdown heading by replacing the incorrect
heading text "## Open AI PI Key" with the corrected "## OpenAI API Key" so the
section title reads properly; locate the heading string "## Open AI PI Key" in
the docs/overview/authentication.md content and update it to "## OpenAI API
Key".

🧹 Nitpick comments (1)

internal/openai/authentication.go (1)

30-33: Getter with side-effect: GetChatCompletionsURL() mutates global state.

GetChatCompletionsURL() calls SetOpenAIBaseURL() on every invocation, which writes to global.OpenAIBaseURL. While harmless in a single-threaded CLI and consistent with the existing SetOpenAIAPIKey() pattern, a reader might not expect a Get* function to mutate global state. Consider guarding the set with a sync.Once or just documenting the lazy-init behavior with a brief comment.

Not blocking — just a readability note.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Typo in section heading: "Open AI PI Key" → "OpenAI API Key".

Pre-existing typo, but worth fixing since you're already editing this section.

📝 Proposed fix

-## Open AI PI Key
+## OpenAI API Key

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	## Open AI PI Key
	## OpenAI API Key

🤖 Prompt for AI Agents

In `@docs/docs/overview/authentication.md` at line 13, Fix the typo in the
markdown heading by replacing the incorrect heading text "## Open AI PI Key"
with the corrected "## OpenAI API Key" so the section title reads properly;
locate the heading string "## Open AI PI Key" in the
docs/overview/authentication.md content and update it to "## OpenAI API Key".