Greptile Summary

This PR correctly fixes a regression introduced in #49543 where all *.services.ai.azure.com (Azure AI Foundry) custom providers were forced onto the openai-responses API path, breaking chat-completions–based Foundry models. The fix splits the old isAzureUrl helper into isAzureFoundryUrl and isAzureOpenAiUrl, and threads the more-specific predicates into the two affected code paths — the verification probe endpoint selection and the persisted api field in config.

Key changes:

• *.openai.azure.com (classic Azure OpenAI) → continues to use the Responses API (openai-responses) and probes against the /responses endpoint.
• *.services.ai.azure.com (Azure AI Foundry) → now respects the user-selected compatibility, defaulting to openai-completions and probing against chat/completions.
• Azure-wide concerns (auth-header suppression, api-key headers, larger context-window defaults, reasoning-model detection) are correctly preserved for both URL families via the combined isAzureUrl guard.
• A new integration test validates the Foundry probe URL, headers, and body shape; a renamed unit test confirms the persisted config shape.

Confidence Score: 5/5

• This PR is safe to merge — it is a targeted, well-tested bug fix with no risk of regressions to the classic Azure OpenAI path.
• The change is minimal and surgical: a single boolean predicate is split into two, and the correct specialised predicate is used in each of the two affected call sites. Existing tests for classic Azure OpenAI still pass unchanged, and two new tests directly cover the Foundry regression. The only finding is a stale code comment, which does not affect runtime behaviour.
• No files require special attention.

This is a comment left during a code review.
Path: src/commands/onboard-custom.ts
Line: 22-24

Comment:
**Stale comment on Azure defaults constants**

The comment says "Azure OpenAI uses the Responses API which supports larger defaults", but `AZURE_DEFAULT_CONTEXT_WINDOW` and `AZURE_DEFAULT_MAX_TOKENS` are now applied to both classic `*.openai.azure.com` **and** Foundry `*.services.ai.azure.com` URLs (since the `isAzure` guard on line 648 still covers both). The comment is now misleading because Foundry endpoints aren't on the Responses API path.

```suggestion
// Both Azure OpenAI and Azure AI Foundry use larger context defaults
const AZURE_DEFAULT_CONTEXT_WINDOW = 400_000;
const AZURE_DEFAULT_MAX_TOKENS = 16_384;
```

How can I resolve this? If you propose a fix, please make it concise.

_{Last reviewed commit: "fix: add changelog a..."}

Landed on main.

• Landed source commit: 6134aad
• Merge commit: f1e4f8e