httpx Passing 'timeout=None' should always result in no

The Fix

Upgrade to version 0.13.0 or later.

Based on closed encode/httpx issue #433 · 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%.

Jump to Verify Open PR/Commit

@@ -12,6 +12,7 @@
     CertTypes,
     PoolLimits,
+    Timeout,
     TimeoutTypes,
     VerifyTypes,

repro.py

import httpx

url = "https://httpbin.org/delay/10"

# (1)
httpx.get(url, timeout=None)  # Times out after 5s

# (2)
client = httpx.Client(timeout=None)
client.get(url)  # Does not timeout, returns after 10s

# (3)
client = httpx.Client()
client.get(url, timeout=None)  # Times out after 5s

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 0.13.0 or later.\nWhen NOT to use: Do not use this fix if the behavior of timeout=None is intended to be different in specific contexts.\n\n

Why This Fix Works in Production

Trigger: Passing 'timeout=None' should always result in no timeout
Mechanism: Passing None to the timeout parameter leads to inconsistent timeout behavior across request entrypoints
Why the fix works: Differentiates between `timeout=None` and `timeout=UNSET`, ensuring consistent timeout behavior across the library. (first fixed release: 0.13.0).

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

Passing None to the timeout parameter leads to inconsistent timeout behavior across request entrypoints
Production symptom (often without a traceback): Passing 'timeout=None' should always result in no timeout

Proof / Evidence

GitHub issue: #433
Fix PR: https://github.com/encode/httpx/pull/592
First fixed release: 0.13.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.72

Discussion

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

Jump to Sources Open on GitHub

“@florimondmanca I don't understand the reason to use the sentinel value”

@jcugat · 2019-10-03 · source

“This issue is more subtle than I initially thought it would be and will require to go through various places of the code base. Still…”

@florimondmanca · 2019-10-04 · source

“@florimondmanaca can you assign it to me please?”

@gdhameeja · 2019-10-04 · source

“Ok, so if I got it right, in summary we want: - [x] Client instance: leave default DEFAULT_TIMEOUT_CONFIG - [ ] client .request(...) methods: change…”

@jcugat · 2019-10-04 · source

Failure Signature (Search String)

Passing 'timeout=None' should always result in no timeout
Currently, the behavior of passing `None` to the `timeout` parameter in the various request entrypoints is not consistent:

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Passing 'timeout=None' should always result in no timeout
Currently, the behavior of passing `None` to the `timeout` parameter in the various request entrypoints is not consistent:

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Passing 'timeout=None' should always result in no timeout
Currently, the behavior of passing `None` to the `timeout` parameter in the various request entrypoints is not consistent:

Minimal Reproduction

repro.py

import httpx

url = "https://httpbin.org/delay/10"

# (1)
httpx.get(url, timeout=None)  # Times out after 5s

# (2)
client = httpx.Client(timeout=None)
client.get(url)  # Does not timeout, returns after 10s

# (3)
client = httpx.Client()
client.get(url, timeout=None)  # Times out after 5s

What Broke

Users experience unexpected timeouts or delays when using timeout=None in requests.

Why It Broke

Passing None to the timeout parameter leads to inconsistent timeout behavior across request entrypoints

Fix Options (Details)

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

Upgrade to version 0.13.0 or later.

When NOT to use: Do not use this fix if the behavior of timeout=None is intended to be different in specific contexts.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Option D — Guard side-effects with OnceOnly Guardrail for side-effects

Mitigate duplicate external side-effects under retries/timeouts/agent loops by gating the operation before calling external systems.

Place OnceOnly between your code/agent and real side-effects (Stripe, emails, CRM, APIs).
Use a stable key per side-effect (e.g., customer_id + action + idempotency_key).
Fail-safe: configure fail-open vs fail-closed based on blast radius and spend risk.

Show example snippet (optional)

onceonly.py

from onceonly import OnceOnly
import os

once = OnceOnly(api_key=os.environ["ONCEONLY_API_KEY"], fail_open=True)

# Stable idempotency key per real side-effect.
# Use a request id / job id / webhook delivery id / Stripe event id, etc.
event_id = "evt_..."  # replace
key = f"stripe:webhook:{event_id}"

res = once.check_lock(key=key, ttl=3600)
if res.duplicate:
    return {"status": "already_processed"}

# Safe to execute the side-effect exactly once.
handle_event(event_id)

See OnceOnly SDK

When NOT to use: Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.

Fix reference: https://github.com/encode/httpx/pull/592

First fixed release: 0.13.0

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

When NOT to Use This Fix

Do not use this fix if the behavior of timeout=None is intended to be different in specific contexts.
Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.

Verify Fix

verify

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.
Track RSS + object counts after deployments; alert on monotonic growth and GC pressure.
Add a long-running test that repeats the failing call path and asserts stable memory.

Version Compatibility Table

Version	Status
0.13.0	Fixed

Related Issues

No related fixes found.

Cluster: httpx:configuration-error All hubs All clusters

Related clusters: Data consistency Other Timeout

Sources

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

httpx Passing 'timeout=None' should always result in no timeout (Fix)