Adding the same custom strategy multiple times on a feature flag does not evaluate all instances (last one wins)

[kanishka-shashan]

Describe the bug

When adding the same custom strategy implementation multiple times to a single feature flag (with different parameters), only one of the strategy instances appears to be evaluated effectively.

The observed behavior is that the last-added instance determines the final evaluation result, while earlier instances are ignored.

Note

Only if we upgrade unleash-client-java from 11.1.1 to 11.2.1.

Steps to reproduce the bug

1. Implement a custom strategy in Java.
2. Add the same custom strategy to a feature flag multiple times.
3. Configure different parameters for each instance.
4. Evaluate the flag with a context that should match one of the earlier instances.
5. Observe that only the last-added strategy instance is effectively applied.

Reordering the strategies changes the outcome.

Expected behavior

Unleash documentation states that:

If a feature flag has multiple activation strategies, the flag is enabled if any strategy evaluates to true.

Therefore, when the same custom strategy is added multiple times to a feature flag:

• Each strategy instance should be evaluated independently.
• Each instance should receive its own parameters.
• The flag should be enabled if any of the strategy instances evaluate to true.

Logs, error output, etc.

Screenshots

No response

Additional context

Technical Context

There is a related commit in yggdrasil-bindings that introduces indexed internal strategy identifiers:

[https://github.com/Unleash/yggdrasil-bindings/commit/f8794cfd072644c500385fbaa769ccca8b702e78](Unleash/yggdrasil-bindings@f8794cf

This appears to address potential result key collisions.

However, stacking the same custom strategy multiple times still results in only one instance being respected during evaluation.

Questions

• Is stacking the same custom strategy multiple times on a single feature flag officially supported?
• If supported, should each instance be evaluated independently?
• If not supported, should this limitation be documented?

Environment

Unleash Server version: Tested on 5.6.9, 6.10.1, 7.4.1
unleash-client-java version: 11.2.1
yggdrasil-engine version: 0.4.4
Java version: 25
Deployment: Docker

Unleash version

6.10.1

Subscription type

Open source

Hosting type

Self-hosted

SDK information (language and version)

unleash-client-java 11.2.0 onwards

[chriswk]

Hi @kanishka-shashan, thanks for reporting this. This definitely sounds like a bug.

Is stacking the same custom strategy multiple times on a single feature flag officially supported?
Yes, it should work
If supported, should each instance be evaluated independently?
Yes, and if any returns true, the flag should be evaluated to true

So you've found a bug. We'll write some tests confirming the behaviour, and then make them run green, and then publish a new version

[kanishka-shashan]

So you've found a bug. We'll write some tests confirming the behaviour, and then make them run green, and then publish a new version

@chriswk Thank you for confirming and taking a look at this.

[chriswk]

For interest: Unleash/yggdrasil-bindings#86 . We'll start the release train