ctxlen 📏
A super minimal-dependency, always-fresh, project to look up the context limits (input and output tokens) of LLMs. 🤔
- 🔄 New models checked every 6 hours, and your install picks them up within the hour: no upgrade needed.
- 🪶 Just httpx and certifi as dependencies, and it still works offline, with the numbers it shipped with.
- 🧰 Just three functions.
Install
uv add ctxlen
Or with pip:
pip install ctxlen
Usage
Ask for a model's whole context window:
import ctxlen
ctxlen.ctxlen("claude-opus-5-5") # 1_000_000
ctxlen.ctxlen("gpt-6-sol") # 1_050_000
You can also put the provider in front, like litellm does:
ctxlen.ctxlen("anthropic/claude-sonnet-5-5") # 1_000_000
ctxlen.ctxlen("openai/gpt-6-luna") # 1_050_000
Or ask for the input and output limits on their own:
ctxlen.max_input("gpt-6-sol") # 922_000
ctxlen.max_output("gpt-6-sol") # 128_000
The numbers come from litellm and models.dev; their notices are in LICENSE.
Offline
ctxlen.ctxlen("gpt-6-sol", live=False) uses only the numbers that came with your version, and CTXLEN_OFFLINE=1 does that for the whole process. ctxlen asks GitHub for fresh numbers at most once an hour and keeps them in ~/.cache/ctxlen/.
1 maintainer
Metadata
1 maintainer
Release files for ctxlen 2026.10.18.2
For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.
Source distribution (sdist)
| File | Size | Uploaded | Provenance | |
|---|---|---|---|---|
| ctxlen-2026.10.18.2.tar.gz | 60.1 kB | With provenance | Details |
Built distribution (wheel)
| File | Interpreter | ABI | Platform | Reset |
|---|---|---|---|---|
| ctxlen-2026.10.18.2-py3-none-any.whl | Python 3 | none | any | Details |
Total release size: 120.9 kB
Release files / ctxlen-2026.10.18.2.tar.gz
| Download URL | ctxlen-2026.10.18.2.tar.gz |
|---|---|
| Size | 60.1 kB |
| Tags | Source |
|
SHA-256 checksum How to use checksums |
0acef1fdd60fef68518978aa5ed6b8d74b8795a0592ffe2b48a80a168eb6df5f
|
|
BLAKE2b-256 checksum How to use checksums |
76e88c67eb7df8cf1bc118e024d305d596d0efb8c3aec48bf848584eb23316b8
|
| Upload date | |
|
Uploaded using Trusted Publishing? What is trusted publishing? |
Yes |
| Uploaded via |
twine/7.0.0 CPython/3.13.14
|
Provenance
Provenance describes where a file came from. On PyPI, provenance is shared via attestations, which provide a verifiable record of the build or publishing details. View details, limitations and caveats.
PyPI Publish Attestation
PyPI verified that this artifact, at this checksum, originated from the publisher listed below.
Signed by GitHub Actions, verified by PyPI on Oct 18, 2026.
Transparency logRelease files / ctxlen-2026.10.18.2-py3-none-any.whl
| Download URL | ctxlen-2026.10.18.2-py3-none-any.whl |
|---|---|
| Size | 60.8 kB |
| Tags | Python 3 |
|
SHA-256 checksum How to use checksums |
b6fd7e74c1c2c55fee4323b76ba7bf98f369e8b9fac928f202673c54589dc58b
|
|
BLAKE2b-256 checksum How to use checksums |
4d747b08fea1b226fd40b819a2efaaa85f1d635eee75242be7b45e80b8473998
|
| Upload date | |
|
Uploaded using Trusted Publishing? What is trusted publishing? |
Yes |
| Uploaded via |
twine/7.0.0 CPython/3.13.14
|
Provenance
Provenance describes where a file came from. On PyPI, provenance is shared via attestations, which provide a verifiable record of the build or publishing details. View details, limitations and caveats.
PyPI Publish Attestation
PyPI verified that this artifact, at this checksum, originated from the publisher listed below.
Signed by GitHub Actions, verified by PyPI on Oct 18, 2026.
Transparency logSecurity for ctxlen 2026.10.18.2
Provenance
Provenance describes where a file came from. On PyPI, provenance is shared via attestations, which provide a verifiable record of the build or publishing details. View details, limitations and caveats.
Full provenance
All 2 files in this release have been uploaded with provenance metadata.
Attestation for ctxlen-2026.10.18.2.tar.gz
PyPI Publish Attestation
PyPI verified that this artifact, at this checksum, originated from the publisher listed below.
Signed by GitHub Actions, verified by PyPI on Oct 18, 2026.
Transparency logA note on package security
PyPI is a repository for distributing packages, not a service for auditing them. While third-party security researchers and our staff do their best to detect and remove malicious packages, PyPI cannot guarantee the quality, security or suitability of any given package.
