Update vLLM version support to 0.18.0

[qgallouedec]

it seems to work:

$ pytest tests/test_vllm_client_server.py
=============================================================================== test session starts ================================================================================
platform linux -- Python 3.13.11, pytest-8.4.2, pluggy-1.6.0
Test order randomisation NOT enabled. Enable with --random-order or --random-order-bucket=<bucket_type>
rootdir: /fsx/qgallouedec/trl
configfile: pyproject.toml
plugins: rerunfailures-15.1, order-1.3.0, random-order-1.2.0, asyncio-1.3.0, anyio-4.12.1, env-1.2.0, hypothesis-6.151.13, xdist-3.8.0, datadir-1.8.0, cov-7.0.0, timeout-2.4.0, rich-0.2.0
asyncio: mode=Mode.STRICT, debug=False, asyncio_default_fixture_loop_scope=None, asyncio_default_test_loop_scope=function
collected 51 items                                                                                                                                                                 

tests/test_vllm_client_server.py ..................x..................sssssssss.....                                                                                         [100%]

=============================================================== 41 passed, 9 skipped, 1 xfailed in 583.95s (0:09:43) ===============================================================

nothing special from the https://github.com/vllm-project/vllm/releases/tag/v0.18.0

---

Note

Low Risk
Low risk: updates version bounds and user-facing warnings/docs only, with no behavioral changes beyond allowing installs up to vLLM 0.18.0.

Overview
Updates TRL’s vLLM support window to include vLLM 0.18.0 by raising the max version in the trl[vllm] optional dependency and aligning the runtime is_vllm_available compatibility check/warning message.

Documentation and a related compatibility patch comment are updated to reflect the new supported range (0.11.0–0.18.0).

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[albertvillanova]

Thanks.

I know it used not to be case some time ago, but it seems all the latest vLLM releases work out of the box. What about removing the upper bound instead?

[qgallouedec]

What about removing the upper bound instead?

We should give it a try, yes (once we've caught up). Although I'm aware of future breaking changes for us, see vllm-project/vllm#39583 (bitsandbytes deprecation)