The Fix
pip install fastapi==0.128.4
Based on closed fastapi/fastapi issue #12017 · 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%.
@@ -462,7 +462,7 @@ When you install FastAPI with `pip install "fastapi[standard]"` it comes the `st
Used by Pydantic:
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Option A — Upgrade to fixed release\npip install fastapi==0.128.4\nWhen NOT to use: This fix should not be applied if the documentation structure is fundamentally changed.\n\n
Why This Fix Works in Production
- Trigger: 👷🏻 Recently, the CI is failing due to docs building failures
- Mechanism: A regression in the CI caused document building checks to fail due to missing files
- Why the fix works: Updated configurations for MkDocs to resolve CI failures related to document building checks. (first fixed release: 0.128.4).
- 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
- A regression in the CI caused document building checks to fail due to missing files
- Production symptom (often without a traceback): 👷🏻 Recently, the CI is failing due to docs building failures
Proof / Evidence
- GitHub issue: #12017
- Fix PR: https://github.com/fastapi/fastapi/pull/11515
- First fixed release: 0.128.4
- Reproduced locally: No (not executed)
- Last verified: 2026-02-08
- Confidence: 0.75
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.61
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“This was handled in https://github.com/fastapi/fastapi/pull/12016 :rocket:”
Failure Signature (Search String)
- 👷🏻 Recently, the CI is failing due to docs building failures
- Recently, PRs have started failing the CI due to failing some of the document building checks. It looks like a regression may have been introduced on `master` causing this.
Copy-friendly signature
Failure Signature
-----------------
👷🏻 Recently, the CI is failing due to docs building failures
Recently, PRs have started failing the CI due to failing some of the document building checks. It looks like a regression may have been introduced on `master` causing this.
Error Message
Signature-only (no traceback captured)
Error Message
-------------
👷🏻 Recently, the CI is failing due to docs building failures
Recently, PRs have started failing the CI due to failing some of the document building checks. It looks like a regression may have been introduced on `master` causing this.
What Broke
CI builds are failing due to missing documentation assets, leading to build errors.
Why It Broke
A regression in the CI caused document building checks to fail due to missing files
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install fastapi==0.128.4
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Fix reference: https://github.com/fastapi/fastapi/pull/11515
First fixed release: 0.128.4
Last verified: 2026-02-08. Validate in your environment.
When NOT to Use This Fix
- This fix should not be applied if the documentation structure is fundamentally changed.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Capture the exact failing error string in logs and tests so you can reproduce via a minimal script.
- Pin production dependencies and upgrade only with a reproducible test that hits the failing path.
Version Compatibility Table
| Version | Status |
|---|---|
| 0.128.4 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.