fix(azure): preserve deployment routing across copy/with_options

[hsusul]

• I understand that this repository is auto-generated and my pull request may not be merged

Changes being requested

Fixes a routing regression in AzureOpenAI / AsyncAzureOpenAI after .copy() / .with_options().

This change is in hand-maintained code — src/openai/lib/azure.py has no File generated from our OpenAPI spec by Stainless header, and copy()/with_options() there is custom Azure logic, so it is not affected by codegen.

Problem

AzureOpenAI.copy() (aliased as with_options()) delegates to the base OpenAI.copy(), which reconstructs the client from base_url and does not pass azure_endpoint / azure_deployment back to AzureOpenAI.__init__. Because _azure_endpoint and _azure_deployment are only set from those constructor arguments, they get reset to None on the copied client.

_prepare_url() uses those attributes to bypass the deployment path for non-deployment endpoints:

if self._azure_deployment and self._azure_endpoint and url not in _deployments_endpoints:
    # -> {endpoint}/openai/{url}   (no /deployments/<name>/)

Once they are None, that bypass no longer runs, so a client configured with azure_deployment starts routing non-deployment endpoints (e.g. /models) under the deployment path, which 404s.

Reproduction (no network / key required)

from openai import AzureOpenAI

c = AzureOpenAI(
    azure_endpoint="https://example.openai.azure.com",
    azure_deployment="my-deploy",
    api_version="2024-06-01",
    azure_ad_token="fake-token",
)
print(c._prepare_url("/models"))
# https://example.openai.azure.com/openai/models        ✅

c2 = c.with_options(timeout=30)
print(c2._azure_endpoint, c2._azure_deployment)          # None None
print(c2._prepare_url("/models"))
# https://example.openai.azure.com/openai/deployments/my-deploy/models   ❌ (404)

Fix

Preserve _azure_endpoint / _azure_deployment on the copied client, unless the caller overrides base_url in the copy (in which case the old endpoint context is intentionally not carried over). Applied symmetrically to the sync and async clients.

Why minimal

• Only copy() in each of the two Azure clients changes; two guarded lines each.
• Public API, credential handling, and the mutually-exclusive base_url / azure_endpoint constructor contract are untouched (the fix deliberately avoids passing azure_endpoint alongside base_url).
• Deployment endpoints (e.g. /chat/completions) are unaffected — base_url already encodes the deployment and _build_request continues to guard on "/deployments" in base_url.path.

Tests

Added test_copy_preserves_deployment_routing in tests/lib/test_azure.py (sync + async × copy / with_options), asserting that after a copy:

• /models → {endpoint}/openai/models (not nested under /deployments/<name>/), and
• /chat/completions still keeps the deployment path.

Fails on main (wrong /models URL), passes with this change.

Validation

• rye run pytest tests/lib/test_azure.py → 63 passed
• rye run pytest tests/lib/ → all pass except a pre-existing, unrelated failure (test_bedrock_auth_conformance.py::test_retry_signing_fixture, which fails identically on clean main in this environment)
• ruff check / ruff format clean on both files
• pyright and mypy clean on src/openai/lib/azure.py

Compatibility

No public API change; behavior only changes for the previously-broken post-copy case. Copies that override base_url keep their current behavior.

Additional context & links

Discovered by auditing sibling copy/state-preservation logic; no existing issue or PR covers this. .with_options() is a common pattern (per-request timeouts/headers), so Azure users combining it with azure_deployment are likely to hit this.