Agent sub-process leaks `toolCallResults` into parent scope

[nikku]

Describe the Bug

Agentic sub-process "leaks" toolCallResults variable into parent scope:

This is surprising to me as a user, as I expect that the agent works isolated, does not "leak" a variable, beyond the agent variable that I have to explicitly output map. It can also be an issue, when agents run in parallel to each other, or nested inside of each other.

Steps to Reproduce

1. Run ai-agent-chat-with-tools
2. Observe global toolCallResults variable, populated with results of last agent run

Expected Behavior

• Agent is self-contained and does not leak any variable not explicitly specified.

Environment

• OS: Ubuntu 24
• Library version: 8.8, 8.9-alpha3
• Camunda version: 8.8, 8.9

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Related to camunda/camunda#46530
Related to this discussion

[nikku]

Attaching two examples that I'd expect to "just work", without the variable leak:

Nested agent execution

Side-by-side agent execution