The Fix
pip install urllib3==2.6.0
Based on closed urllib3/urllib3 issue #3638 · PR/commit linked
Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.
@@ -0,0 +1 @@
@@ -0,0 +1 @@
+Ensured successful urllib3 builds by setting Hatchling requirement to >= 1.27.0.
\ No newline at end of file
diff --git a/pyproject.toml b/pyproject.toml
[sdist]
dist/urllib3-2.5.1.dev5.tar.gz
[wheel]
dist/urllib3-2.5.1.dev5-py3-none-any.whl
Re-run the minimal reproduction on your broken version, then apply the fix and re-run.
Option A — Upgrade to fixed release\npip install urllib3==2.6.0\nWhen NOT to use: This fix is not applicable if using a hatchling version outside the specified range.\n\n
Why This Fix Works in Production
- Trigger: TypeError: Field `project.license-files` must be a table
- Mechanism: The hatchling version requirement was incorrectly set, causing build failures
- Why the fix works: Updated the hatchling version requirements to ensure successful builds. (first fixed release: 2.6.0).
- If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.
Why This Breaks in Prod
- Shows up under Python 3.13.4 in real deployments (not just unit tests).
- The hatchling version requirement was incorrectly set, causing build failures
- Surfaces as: TypeError: Field `project.license-files` must be a table
Proof / Evidence
- GitHub issue: #3638
- Fix PR: https://github.com/urllib3/urllib3/pull/3639
- First fixed release: 2.6.0
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.78
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“### Subject The hatchling>=1.6.0,<2 version requirement is incorrect and results in build failures with any hatchling version between 1.6.0 and 1.27.0 excluded. The error is as follow: This is due to this change being required to address an”
Failure Signature (Search String)
- TypeError: Field `project.license-files` must be a table
Error Message
Stack trace
Error Message
-------------
TypeError: Field `project.license-files` must be a table
Minimal Reproduction
[sdist]
dist/urllib3-2.5.1.dev5.tar.gz
[wheel]
dist/urllib3-2.5.1.dev5-py3-none-any.whl
Environment
- Python: 3.13.4
- urllib3: 2.5.1
Why It Broke
The hatchling version requirement was incorrectly set, causing build failures
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install urllib3==2.6.0
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Fix reference: https://github.com/urllib3/urllib3/pull/3639
First fixed release: 2.6.0
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- This fix is not applicable if using a hatchling version outside the specified range.
Verify Fix
Re-run the minimal reproduction on your broken version, then apply the fix and re-run.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Add a CI check that diffs key outputs after upgrades (OpenAPI schema snapshots, JSON payload shapes, CLI output).
- Upgrade behind a canary and run integration tests against the canary before 100% rollout.
- Add a TLS smoke test that performs a real handshake in CI (include CA bundle validation and hostname checks).
- Alert on handshake failures by error string and endpoint to catch cert/CA changes quickly.
Version Compatibility Table
| Version | Status |
|---|---|
| 2.6.0 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.