urllib3 Should BaseHTTPResponse.readable() return False?

The Fix

pip install urllib3==1.26.13

Based on closed urllib3/urllib3 issue #2765 · 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%.

Open PR/Commit

@@ -301,10 +301,6 @@ def json(self) -> Any:
         raise NotImplementedError()
 
-    @property
-    def closed(self) -> bool:
-        raise NotImplementedError()

fix.md

Option A — Upgrade to fixed release\npip install urllib3==1.26.13\nWhen NOT to use: Do not use this fix if the implementation requires readable() to return True.\n\n

Why This Fix Works in Production

Trigger: To match with the `io` module we'll return `False` here. `io.IOBase` doesn't define `read` but does define `readable` which returns `False`.
Mechanism: Modifies the BaseHTTPResponse class to align its readable() method with the io.IOBase interface, returning False when read() is not implemented.
Why the fix works: Modifies the BaseHTTPResponse class to align its readable() method with the io.IOBase interface, returning False when read() is not implemented. (first fixed release: 1.26.13).

Production impact:

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

Production symptom (often without a traceback): To match with the `io` module we'll return `False` here. `io.IOBase` doesn't define `read` but does define `readable` which returns `False`.

Proof / Evidence

GitHub issue: #2765
Fix PR: https://github.com/urllib3/urllib3/pull/2766
First fixed release: 1.26.13
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.76

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“For the record, IOBase does mention read: > Even though IOBase does not declare read() or write() because their signatures will vary, implementations and clients…”

@pquentin · 2022-11-07 · source

“To match with the io module we'll return False here. io.IOBase doesn't define read but does define readable which returns False.”

@sethmlarson · 2022-11-07 · source

Failure Signature (Search String)

To match with the `io` module we'll return `False` here. `io.IOBase` doesn't define `read` but does define `readable` which returns `False`.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
To match with the `io` module we'll return `False` here. `io.IOBase` doesn't define `read` but does define `readable` which returns `False`.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
To match with the `io` module we'll return `False` here. `io.IOBase` doesn't define `read` but does define `readable` which returns `False`.

Environment

urllib3: 2.0

What Broke

Unexpected behavior when checking if BaseHTTPResponse is readable, leading to potential misuse.

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install urllib3==1.26.13

When NOT to use: Do not use this fix if the implementation requires readable() to return True.

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/2766

First fixed release: 1.26.13

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

Do not use this fix if the implementation requires readable() to return True.

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.

Version Compatibility Table

Version	Status
1.26.13	Fixed

Related Issues

No related fixes found.

Cluster: urllib3:configuration-error urllib3 hub urllib3 best practices All hubs All clusters

Related clusters: Data consistency SSL handshake Other

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

urllib3 Should BaseHTTPResponse.readable() return False? (Fix)