[KV Connector] Remove compat support for pre-v0.12.0 constructor signatures without `KVCacheConfig` by yewentao256 · Pull Request #39832 · vllm-project/vllm

yewentao256 · 2026-04-14T20:38:00Z

The v0.12.0 release contained initial support for HMA in KV Connectors. As part of these changes, a KVCacheConfig argument was added to KV connector constructors.

Backwards compatibility support for out-of-tree connectors was included in this change, with a very prominent warning:

if self._kv_cache_config is None:
            logger.warning(
                "KVConnectorBase_V1 initialized without kv_cache_config. "
                "This is deprecated - please update your connector to accept "
                "kv_cache_config as the third constructor argument and pass it "
                "to super().__init__()."
            )

See #25712 and #27887

Since the warning has been around for over 5 months, I think we can safely remove the support of it. The compatibility test can be removed safely as well.

Signed-off-by: yewentao256 <zhyanwentao@126.com>

gemini-code-assist

Code Review

This pull request removes various deprecated tests and compatibility layers across the codebase, specifically targeting pooling tasks, weight utilities, argparse utilities, and KV connector integrations. However, feedback indicates that several tests—including those for deprecated KV scale mapping, argparse back-compatibility for the --model flag, and LMCache integration contracts—are being removed while the underlying implementation logic remains active in the repository, resulting in a significant loss of test coverage.

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tests/model_executor/test_weight_utils.py (105-110)

The test test_deprecated_kv_scale is being removed, but the corresponding compatibility logic in vllm/model_executor/model_loader/weight_utils.py (lines 1521-1538) is still present in the codebase. Removing tests for features that are still active and supported (even if deprecated) increases the risk of regressions. It is recommended to retain these tests until the underlying code is actually removed from the repository.

tests/utils_/test_argparse_utils.py (279-321)

This PR removes the test coverage for the --model argument back-compatibility in vllm serve. However, the remapping logic and the associated warning are still present in vllm/utils/argparse_utils.py (lines 185-217). Furthermore, the commented-out test block intended for when compatibility ends is also being deleted. It is safer to keep these tests active as long as the code they verify remains in the repository, or to update the code to the final state (raising an error) and update the tests accordingly to ensure the transition is correctly enforced.

tests/v1/kv_connector/unit/test_lmcache_integration.py (1-229)

Removing test_lmcache_integration.py eliminates critical contract tests that ensure vLLM's internal changes do not break the LMCache integration. These tests verify that key attributes and methods on classes like VllmConfig, ModelConfig, and Request remain stable. Unless the LMCache integration is also being removed or these tests have been moved to a different suite, this represents a significant loss in integration testing coverage for a major external component.

Signed-off-by: yewentao256 <zhyanwentao@126.com>

noooop · 2026-04-15T02:36:33Z

For pooling-related tests, please wait for #37861 to land in v0.20.0.

These tests are important before this, please do not remove them.

Signed-off-by: yewentao256 <zhyanwentao@126.com>

yewentao256

CC @noooop

noooop · 2026-04-26T06:12:11Z

cc @ApostaC @orozery

orozery · 2026-04-26T06:36:12Z

@yewentao256 If we remove this test it means we no longer support old style connectors.
So let's change all connectors (and base.py as well):

kv_cache_config: "KVCacheConfig",

instead of:

kv_cache_config: "KVCacheConfig | None" = None,

Signed-off-by: yewentao256 <zhyanwentao@126.com>

mergify · 2026-04-26T22:47:36Z

Documentation preview: https://vllm--39832.org.readthedocs.build/en/39832/

yewentao256

@orozery OK updated, thanks for the feedback!

orozery

LGTM!
cc @NickLucche

orozery · 2026-04-27T06:05:53Z

+        if kv_cache_config is None:
+            raise ValueError("kv_cache_config must be set for KVConnectorBase_V1")


Is this check necessary given the type annotation of kv_cache_config?

Nice catch, fixed

NickLucche

I think we're mixing retro-compat with ci optimizations.
We can't just crash on OOT connectors after we went through the trouble of ensuring backward compatibility without raising a warning at least a version earlier.

Also as importantly, I don't understand what kind of savings are we getting from deleting cpu-only tests that work against the interface. Tbh this is the kind of unit tests I'd like to see more of.

We should:

mark tests as cpu only
raise a warning that the old api is deprecated and the eventually apply this PR

cc @markmc that added this in case he has a different opinion on this.

yewentao256 · 2026-04-27T18:41:24Z

Thanks @NickLucche for the review!

    if self._kv_cache_config is None:
            logger.warning(
                "KVConnectorBase_V1 initialized without kv_cache_config. "
                "This is deprecated - please update your connector to accept "
                "kv_cache_config as the third constructor argument and pass it "
                "to super().__init__()."
            )

The warning has been added in #27887 and lasts for around 6 months, I think we can safely remove the support of it.

As we remove the support of None param, the compatibility test can be removed safely as well.

The previous PR description is kind of misleading so I also updated that.

Signed-off-by: yewentao256 <zhyanwentao@126.com>

markmc · 2026-04-28T09:27:46Z

Ok, I had to page this context back in, so here it is:

[Core][Hybrid allocator + kv connector 1/n] Enable hybrid allocator + KV cache connector #25712 merged initial HMA support, but it did some weird stuff to pass KVCacheConfig into HMA-supporting connectors to avoid breaking old connectors. See https://github.com/vllm-project/vllm/pull/25712/changes#r2447539735
[KV Connector] Make KVCacheConfig an explicit constructor argument #27887 achieved this a different way - add a KVCacheConfig argument to in-tree connector constructors, retain compat support for out-of-tree connectors constructor that haven't been updated, and make a visible enough warning that hopefully would encourage owners of those connectors to update

So this warning has been in place since v0.12.0, released 5 months ago. The warning didn't specify how long we would retain backwards compat support, but IMO it would be unreasonable to expect it to be retained any longer than this.

markmc

Generally lgtm, couple of small suggestions

Signed-off-by: yewentao256 <zhyanwentao@126.com>

…atures without `KVCacheConfig` (vllm-project#39832) The v0.12.0 release contained initial support for HMA in KV Connectors. As part of these changes, a KVCacheConfig argument was added to KV connector constructors. Backwards compatibility support for out-of-tree connectors was included in this change, with a very prominent warning. See vllm-project#25712 and vllm-project#27887. Since the warning has been around for over 5 months, we can safely remove the support of it. Signed-off-by: yewentao256 <zhyanwentao@126.com>

…atures without `KVCacheConfig` (vllm-project#39832) The v0.12.0 release contained initial support for HMA in KV Connectors. As part of these changes, a KVCacheConfig argument was added to KV connector constructors. Backwards compatibility support for out-of-tree connectors was included in this change, with a very prominent warning. See vllm-project#25712 and vllm-project#27887. Since the warning has been around for over 5 months, we can safely remove the support of it. Signed-off-by: yewentao256 <zhyanwentao@126.com> Signed-off-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>

…atures without `KVCacheConfig` (vllm-project#39832) The v0.12.0 release contained initial support for HMA in KV Connectors. As part of these changes, a KVCacheConfig argument was added to KV connector constructors. Backwards compatibility support for out-of-tree connectors was included in this change, with a very prominent warning. See vllm-project#25712 and vllm-project#27887. Since the warning has been around for over 5 months, we can safely remove the support of it. Signed-off-by: yewentao256 <zhyanwentao@126.com>

remove out-dated unit tests

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Signed-off-by: yewentao256 <zhyanwentao@126.com>

yewentao256 requested review from ApostaC, noooop and orozery as code owners April 14, 2026 20:38

yewentao256 added the ready ONLY add when PR is ready to merge/full CI is needed label Apr 14, 2026

mergify Bot added v1 kv-connector labels Apr 14, 2026

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add back

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Merge branch 'main' into remove-outdated-unit-tests

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Merge branch 'main' into remove-outdated-unit-tests

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remove support of None kv_cache_config

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Signed-off-by: yewentao256 <zhyanwentao@126.com>

yewentao256 requested review from NickLucche and xuechendi as code owners April 26, 2026 22:46

mergify Bot added the documentation Improvements or additions to documentation label Apr 26, 2026

yewentao256 changed the title ~~[Tests] Remove deprecated and compatibility-only coverage~~ [Refactor] Deprecate kv_cache_config None support Apr 26, 2026

yewentao256 commented Apr 26, 2026

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orozery approved these changes Apr 27, 2026

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update

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Signed-off-by: yewentao256 <zhyanwentao@126.com>

markmc changed the title ~~[Refactor] Deprecate kv_cache_config None support~~ [KV Connector] Remove compat support for pre-v0.12.0 constructor signatures without KVCacheConfig Apr 28, 2026

markmc requested changes Apr 28, 2026

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Comment thread vllm/distributed/kv_transfer/kv_connector/factory.py Outdated

Comment thread vllm/distributed/kv_transfer/kv_connector/factory.py

update

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Signed-off-by: yewentao256 <zhyanwentao@126.com>

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markmc enabled auto-merge (squash) April 28, 2026 16:05

Merge branch 'main' into remove-outdated-unit-tests

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yewentao256 and others added 9 commits April 29, 2026 08:46

Merge branch 'main' into remove-outdated-unit-tests

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Signed-off-by: yewentao256 <zhyanwentao@126.com>

Merge branch 'main' into remove-outdated-unit-tests

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markmc merged commit ea0e501 into main May 9, 2026
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markmc deleted the remove-outdated-unit-tests branch May 9, 2026 23:39

richardsliu mentioned this pull request May 11, 2026

Fix upstream vllm integration break for KVCacheConfig vllm-project/tpu-inference#2580

Merged

		if kv_cache_config is None:
		raise ValueError("kv_cache_config must be set for KVConnectorBase_V1")

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tests/model_executor/test_weight_utils.py (105-110)

tests/utils_/test_argparse_utils.py (279-321)

tests/v1/kv_connector/unit/test_lmcache_integration.py (1-229)

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yewentao256 commented Apr 14, 2026 •

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