fix(auth): silence authlib.jose DeprecationWarning at JWT import by SarthakB11 · Pull Request #4100 · PrefectHQ/fastmcp

SarthakB11 · 2026-05-05T19:36:17Z

authlib.jose emits AuthlibDeprecationWarning at module import time, so any caller running with warnings.simplefilter("error") hits an exception just from touching FastMCP's JWT auth providers (from fastmcp.server.auth.providers.jwt import StaticTokenVerifier is enough to trigger it).

Wraps the two from authlib.jose ... imports in warnings.catch_warnings() filtering AuthlibDeprecationWarning. The filter snapshot is restored on context exit, so this stays scoped to the one import site and doesn't leak into user code. Migrating off authlib.jose to joserfc is a separate, larger change; this is the minimal patch for the warning.

from authlib.deprecate import AuthlibDeprecationWarning

with warnings.catch_warnings():
    warnings.simplefilter("ignore", AuthlibDeprecationWarning)
    from authlib.jose import JsonWebToken
    from authlib.jose.errors import JoseError

Closes #4098.

If I used an LLM, it followed the repo's contributing conventions (not generic output)

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chatgpt-codex-connector · 2026-05-05T19:38:16Z


-from authlib.jose import JsonWebToken
-from authlib.jose.errors import JoseError
+from authlib.deprecate import AuthlibDeprecationWarning


Scope the Authlib warning filter import

When this is the first authlib.deprecate import in a process, Authlib 1.7 executes warnings.simplefilter("always", AuthlibDeprecationWarning) while importing this line. Because that happens before catch_warnings(), the context snapshots the already-mutated filters and restores the global always filter on exit; a caller that had set warnings.simplefilter("error", AuthlibDeprecationWarning) can import this module, but subsequent Authlib deprecations are no longer errors. Move this import inside the catch_warnings() block before installing the ignore filter so Authlib's filter mutation is restored too.

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chatgpt-codex-connector · 2026-05-05T19:38:16Z

 import httpx
-from authlib.jose import JsonWebKey, JsonWebToken
-from authlib.jose.errors import JoseError
+from authlib.deprecate import AuthlibDeprecationWarning


Scope the Authlib warning filter import

When this is the first authlib.deprecate import in a process, Authlib 1.7 executes warnings.simplefilter("always", AuthlibDeprecationWarning) while importing this line. Because that happens before catch_warnings(), the context snapshots the already-mutated filters and restores the global always filter on exit; a caller that had set warnings.simplefilter("error", AuthlibDeprecationWarning) can import this provider, but subsequent Authlib deprecations are no longer errors. Move this import inside the catch_warnings() block before installing the ignore filter so Authlib's filter mutation is restored too.

Useful? React with 👍 / 👎.

SarthakB11 · 2026-05-05T19:42:44Z

Good catch, pushed b1c0eef. from authlib.deprecate import AuthlibDeprecationWarning is now inside the catch_warnings() block in both files, so authlib's simplefilter("always", ...) mutation gets reverted on exit and the caller's filter survives. Verified locally:

import warnings
warnings.filterwarnings('error', category=DeprecationWarning)
import fastmcp.server.auth.providers.jwt
import authlib.deprecate
authlib.deprecate.deprecate('test')   # still raises AuthlibDeprecationWarning ✓

jlowin

Thanks!

marvin-context-protocol · 2026-05-07T15:01:24Z

tl;dr: ruff check failed in the static_analysis job — it auto-fixed a missing blank line between import httpx and the with warnings.catch_warnings(): block in src/fastmcp/server/auth/providers/jwt.py. Run uv run prek run --all-files locally and push the result.

The fix is a one-line whitespace change (a blank line after import httpx on line 12, before the suppressed-warning with block). Prek would have applied it for you on commit if it were installed locally.

Log excerpt

ruff check...............................................................Failed
- hook id: ruff-check
  Found 1 error (1 fixed, 0 remaining).

diff --git a/src/fastmcp/server/auth/providers/jwt.py b/src/fastmcp/server/auth/providers/jwt.py
@@ -10,6 +10,7 @@ from dataclasses import dataclass
 from typing import Any, cast

 import httpx
+
 with warnings.catch_warnings():
     # authlib.jose emits AuthlibDeprecationWarning on import; suppress it so

Failed job

fix(auth): silence authlib.jose DeprecationWarning at JWT import

4206177

claude Bot reviewed May 5, 2026

View reviewed changes

marvin-context-protocol Bot added bug Something isn't working. Reports of errors, unexpected behavior, or broken functionality. auth Related to authentication (Bearer, JWT, OAuth, WorkOS) for client or server. labels May 5, 2026

chatgpt-codex-connector Bot reviewed May 5, 2026

View reviewed changes

fix(auth): scope authlib.deprecate import inside catch_warnings()

b1c0eef

jlowin approved these changes May 7, 2026

View reviewed changes

Add missing blank line after imports for ruff E402

e490efb

jlowin merged commit aaff924 into PrefectHQ:main May 7, 2026
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jhsmith409 mentioned this pull request May 8, 2026

Fix len(None) crash + YouTube Restricted Mode handling + markitdown[pdf] dep bump walksoda/crawl-mcp#23

Merged

5 tasks done

tseaver mentioned this pull request May 19, 2026

Migrate from authlib.jose to josefrc #4187

Closed

jlowin mentioned this pull request May 23, 2026

Migrate auth JWTs to joserfc #4221

Merged

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fix(auth): silence authlib.jose DeprecationWarning at JWT import - #4100

fix(auth): silence authlib.jose DeprecationWarning at JWT import#4100
jlowin merged 3 commits into
PrefectHQ:mainfrom
SarthakB11:fix/issue-4098

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