[HTTPXodus] Consider migrating from `httpx` to `httpx2` (the actively maintained fork)

[HTTPXodus] Consider migrating from httpx to httpx2 (the actively maintained fork)

️ This issue is part of HTTPXodus — a community effort to help major Python projects plan their path off the stalled httpx stable line onto httpx2, the actively maintained fork by Pydantic Services. One coordinated issue per project — no spam, no drive-by PRs.

Background — what happened to httpx

• The last stable release is 0.28.1 (2024-12) — 21+ months ago.
• 1.0.dev4–dev6 shipped Aug 2026; no committed date for stable 1.0.
• httpx2 (fork by Pydantic Services, Tom Christie involved) has been releasing weekly since 2026-05, currently at 2.12.0. Public API is compatible (Client, AsyncClient, Limits, Response, HTTPError).

Meanwhile, the ecosystem has adopted httpx2: Starlette, FastAPI, OpenAI SDK, Anthropic SDK, MCP Python SDK, and AutoGPT, mem0, FastChat, reflex, chroma, flet, python-telegram-bot, instructor (HTTPXodus campaign, all in flight).

Usage in promptflow

• src/promptflow-core/.../_http_connection_provider.py
• src/promptflow-azure/.../_asset_client.py
• src/promptflow-azure/.../_run_history_client.py
• src/promptflow-azure/.../_artifact_client.py
• src/promptflow-azure/.../_metrics_client.py
• src/promptflow-azure/.../_async_run_downloader.py
• src/promptflow-devkit/.../_base_executor_proxy.py
• httpx = ">=0.25.1" in src/promptflow-devkit/pyproject.toml (devkit owns the dep; other sub-packages inherit via the workspace)

All call sites are async HTTP and treat httpx as a transport implementation detail — no httpx.Response is re-exported in a public signature.

Migration options

• Option A — dual import (recommended for libraries / framework SDKs): try: import httpx2 as httpx; except ImportError: import httpx. python_version >= "3.10" marker on the new dep keeps 3.9 working.
• Option B — hard switch: drop httpx entirely. Cleaner, but drops 3.9.

Notes

• ⚠️ TLS behaviour change: httpx2 verifies against the OS trust store instead of certifi. Worth a changelog line for Azure Stack / private CA users.
• No existing httpx2 PR or issue in this repo (verified 2026-09-04).
• Happy to revise / close per maintainer direction.