What changed?

Replace three type-specific guardrail decorators (@pii_detection_guardrail, @prompt_injection_guardrail, @deterministic_guardrail) with a single unified @guardrail(validator=..., action=..., name=..., stage=...) decorator using the strategy pattern.

New API:

@guardrail(validator=PromptInjectionValidator(threshold=0.5), action=BlockAction(), name="LLM Prompt Injection", stage=GuardrailExecutionStage.PRE)
@guardrail(validator=PIIValidator(entities=[PIIDetectionEntity(PIIDetectionEntityType.EMAIL, 0.5)]), action=LogAction(), name="LLM PII")
def create_llm():
    return UiPathChat(model="gpt-4o")

Key changes:

• Add decorators/validators/ package with GuardrailValidatorBase, PIIValidator, PromptInjectionValidator, DeterministicValidator
• Validators carry what to check (entities, threshold, rules); decorator carries how to respond (action, name, stage)
• A single validator instance can be reused across multiple @guardrail decorators with different actions or stages
• Scope/stage validation at decoration time via validate_scope() / validate_stage()
• Remove old type-specific decorator files (pii_detection.py, prompt_injection.py, deterministic.py) — 100% parity replacement, no backward compat shims
• Fix double POST guardrail application on sync StructuredTool: StructuredTool.ainvoke (no coroutine) delegates to self.invoke via run_in_executor; overriding ainvoke in _GuardedTool caused POST to fire twice (words++++ → words++)
• Run ruff check --fix + ruff format

Files:

• src/uipath_langchain/guardrails/decorators/guardrail.py — new unified decorator
• src/uipath_langchain/guardrails/decorators/validators/ — 4 new files
• src/uipath_langchain/guardrails/decorators/{pii_detection,prompt_injection,deterministic}.py — deleted
• src/uipath_langchain/guardrails/{__init__,decorators/__init__}.py — updated exports
• samples/joke-agent-decorator/graph.py — rewritten to use new API

How has this been tested?

• End-to-end run with uv run uipath run agent '{"topic": "money"}' — verified all 3 scopes (AGENT, LLM, TOOL) fire correctly, words++ filter applies exactly once
• End-to-end run with uv run uipath run agent '{"topic": "joke about Andrei Petraru"}' — verified Agent PII (PERSON) blocks with AgentRuntimeError
• uv run pytest — all tests pass (2 pre-existing failures for missing botocore/google optional deps, unrelated)
• uv run ruff check src/uipath_langchain/guardrails/ — clean
• uv run ruff format — 4 files reformatted

Are there any breaking changes?

• Under Feature Flag
• None
• DB migrations required
• API/interface removals or renames
• Other

Old decorator names (pii_detection_guardrail, prompt_injection_guardrail, deterministic_guardrail) are removed. This branch replaces them entirely — callers must migrate to @guardrail(validator=...). No other public API is affected.

Ticket

AL-288