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

sdk/python/packages/flet/src/flet/auth/authorization_service.py と関連する oauth_provider.py および oauth_token.py ファイルから始め、リンクされている httpx2 の移行ガイドを読んでください。デュアルサポートと完全な切り替えのどちらにするかを決定し、依存関係マーカー platform_system != "Emscripten" は維持してください。OAuth AsyncClient フローがサポート対象で動作し、トラストストアの動作が文書化されていれば完了です。

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

Background — what happened to httpx

httpx is one of the most important HTTP clients in the Python ecosystem (370k+ dependent repositories). However:

• The last stable release is 0.28.1 (December 2024) — over 20 months ago.
• For most of 2025 the repository was dormant; maintenance trackers (e.g. Snyk) now flag it as inactive.
• Encouragingly, the project has recently resumed activity: 1.0.dev4–dev6 shipped between 2026-08-19 and 2026-08-31. A 1.0 is clearly in the works, but there is no committed date for a stable 1.0, and the dev line carries breaking changes.

Meanwhile, the ecosystem has already begun moving. Projects that have adopted httpx2:

Project	Stars	Status
Starlette	12.5k+	✅ Migrated
FastAPI	102k+	✅ Dual support (httpx2 test dependency)
OpenAI Python SDK	31.5k+	✅ Migrated
Anthropic Python SDK	3.9k+	✅ Migrated in v1.0
MCP Python SDK	24k+	✅ Migrated in v2.0

What is httpx2

httpx2 is a fork of httpx 0.28.1 maintained by Pydantic Services Inc., with Tom Christie involved. It is actively released (v2.0.0 → v2.12.0 since May 2026) and keeps a compatible public API:

import httpx2
r = httpx2.get("https://example.org")

Why migrate — the benefits

1. Active maintenance — regular releases, reviewed PRs, and a funded maintainer team, versus an uncertain stable-release timeline.
2. Modern TLS by default — certificates are verified against the OS trust store instead of the bundled certifi, removing a common source of stale-CA issues.
3. New capabilities — built-in Server-Sent Events (client.sse()) and WebSocket support (httpx2[ws]), without extra dependencies.
4. Ecosystem alignment — as frameworks and SDKs migrate, staying on httpx increasingly means duplicate HTTP stacks in one dependency tree.

Risks of staying on httpx

• Security exposure: no stable-line releases means no stable-line security fixes. If a CVE lands in 0.28.x today, there is no maintained branch to patch it.
• Dependency conflicts: packages that pin httpx<1.0 already conflict with migrated peers; the longer the wait, the worse the resolver pain for downstream users.
• Compounding migration cost: the gap between 0.28.x and whatever 1.0 becomes keeps growing; migrating to httpx2 now is a small, well-documented step (official migration guide: https://pydantic.dev/docs/httpx2/get-started/migration/).

What migration could look like here

Flet is published to PyPI (pip install flet), so it is a library — whichever HTTP client it depends on is inherited by every downstream app. That makes the choice worth making deliberately.

httpx is a genuine runtime dependency of the core flet package, and it is already unpinned at the top:

Requires-Dist: httpx>=0.28.1; platform_system != "Emscripten"

an open floor (>=0.28.1, no <1.0 upper bound), excluded only on the web target (platform_system != "Emscripten", i.e. Pyodide/WebAssembly) where there is no socket support anyway.

Where it is actually used — the OAuth / authentication feature:

• sdk/python/packages/flet/src/flet/auth/authorization_service.py uses httpx (and oauthlib) inside its OAuth 2.0 flow — exchanging the authorization code for tokens and fetching the user profile / groups over async HTTP (httpx.AsyncClient). It backs the AuthorizationService / page.login() API, alongside flet/auth/oauth_provider.py, oauth_token.py, and the built-in GitHub / Google / Azure / Auth0 providers. The httpx import itself is lazy (inside the methods, not a top-level line), which is why the web build could drop it — and that is exactly what happened: once httpx was excluded on Pyodide, flet build web crashed (#6258, now closed). That incident is the concrete proof that httpx is a real runtime dependency, not a dev/optional extra.
• The desktop/mobile client↔server protocol itself runs over WebSockets (via flet-web / FastAPI), not httpx — httpx's role in the SDK is specifically these OAuth HTTP calls.

Two viable paths, depending on your compatibility goals:

• Option A — dual support (recommended for libraries): prefer httpx2 when available, fall back to httpx:

  try:
      import httpx2 as httpx
  except ModuleNotFoundError:
      import httpx
  

  with httpx2; python_version >= "3.10" added as an extra/optional dependency. Either way, keep the platform_system != "Emscripten" marker on whichever package is declared — httpx2, like httpx, cannot run under Pyodide/wasm, so the web exclusion must carry over.

• Option B — hard switch: replace the dependency outright and switch the import to import httpx2 as httpx. This is unusually clean here: Flet already declares requires-python >=3.10, which satisfies httpx2's Python ≥ 3.10 floor, so no supported interpreter is dropped — and with a 1.0 on the way, a small dependency swap fits naturally into the release notes.

⚠️ One caveat worth calling out: httpx2's move to the OS trust store can change behavior in containers and corporate-proxy environments that relied on certifi. For Flet this mostly affects self-hosted desktop/server deployments; worth a note in your changelog either way.

Notes

• No existing httpx2-related issue or PR in this repo as of 2026-09-02 (checked via GitHub search).
• Dependency constraint: httpx>=0.28.1 — an open floor with no <1.0 pin, so there is no resolver conflict to untangle. The only special handling is the platform_system != "Emscripten" marker (web/Pyodide exclusion), which a migration must replicate for httpx2.
• Python floor: requires-python >=3.10 already satisfies httpx2's ≥ 3.10 requirement, so even a hard switch drops no currently-supported Python.
• Timing: Flet is on the road to 1.0 (1.0 Beta shipped 2025-12; recent releases ~0.8x), an ideal window if you would rather fold this into a major than carry it as a compat shim.
• The public API surface relevant here (AsyncClient, Response.raise_for_status(), HTTPStatusError) behaves the same in httpx2, so the OAuth code path should need no logic changes beyond the import.

Happy to open a PR for either option if the maintainers are interested — and equally happy to close this if you'd rather wait for httpx 1.0 stable. No pressure; the goal is just to make sure the decision is an informed one. 🙏