feat(guardrails): add llm_as_judge middleware and @guardrail re-export [AL-470]

[apetraru-uipath]

What changed?

Adds llm_as_judge support to both coded-agent guardrail paths in uipath-langchain.

• Middleware: UiPathLLMAsJudgeMiddleware (AGENT/LLM/TOOL scopes) builds a
  BuiltInValidatorGuardrail(validator_type="llm_as_judge") and wires the PRE/POST hooks;
  demonstrated in the joke-agent (middleware) sample. Works with the currently published
  uipath-platform.
• Decorator: re-export LLMAsJudgeValidator from uipath.platform.guardrails.decorators
  (added in the paired uipath-python PR, AL-470); demonstrated in the joke-agent-decorator
  sample.

How has this been tested?

• Middleware unit tests: construction, hook wiring per scope/stage, block/log/filter actions,
  async tool path.
• Guarded decorator re-export test (skips until the installed uipath-platform ships
  LLMAsJudgeValidator).
• ruff + mypy clean; full guardrails suite + circular-import tests pass locally.
• Both samples validated end-to-end against the real validate endpoint (judge fires at POST;
  forced an off-topic rule to confirm the block/log verdict).

⚠️ Cross-repo dependency (expected red CI until merged)

The decorator re-export in guardrails/__init__.py is a hard import of LLMAsJudgeValidator,
which is not in a published uipath-platform yet — it ships in the paired uipath-python PR
(AL-470). CI here will fail on that import until uipath-platform is released; the guarded
re-export test skips in the meantime. Merge after the uipath-python PR releases.

Are there any breaking changes?

• None
• Under Feature Flag
• UiPath CLI Runtime changes

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds LLM-as-judge guardrail support to the uipath_langchain guardrails integration via a new middleware and a decorator-path re-export, with accompanying unit tests and updated samples.

Changes:

• Introduces UiPathLLMAsJudgeMiddleware to build a BuiltInValidatorGuardrail(validator_type="llm_as_judge") and wire PRE/POST hooks across AGENT/LLM/TOOL scopes.
• Re-exports LLMAsJudgeValidator via uipath_langchain.guardrails and adds a guarded test for the re-export.
• Updates both “joke-agent” samples (middleware + decorator) to demonstrate usage.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/guardrails/test_llm_as_judge_validator.py	Adds a guarded test for the LLMAsJudgeValidator re-export and expected built-in guardrail shape.
tests/guardrails/middlewares/test_llm_as_judge.py	Adds unit tests for middleware construction, hook wiring, actions, and async tool path.
src/uipath_langchain/guardrails/middlewares/llm_as_judge.py	Implements the new LLM-as-judge middleware and built-in guardrail construction.
src/uipath_langchain/guardrails/middlewares/init.py	Exposes UiPathLLMAsJudgeMiddleware from the middleware package.
src/uipath_langchain/guardrails/init.py	Re-exports LLMAsJudgeValidator and exposes the new middleware at the top-level guardrails module.
samples/joke-agent/graph.py	Demonstrates middleware-based LLM-as-judge guardrail at AGENT/POST.
samples/joke-agent-decorator/graph.py	Demonstrates decorator-based LLM-as-judge guardrail at POST.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
96.1% Coverage on New Code
0.7% Duplication on New Code

See analysis details on SonarQube Cloud