Exceptions¶

All shield exceptions inherit from GuardrailError.

GuardrailError¶

Base exception for all shield violations.

InputBlocked¶

Raised when input fails validation. Thrown by InputGuard, PromptInjection, PiiDetector, BlockedKeywords.

Python

from pydantic_ai_shields import InputBlocked

try:
    result = await agent.run("bad input")
except InputBlocked as e:
    print(f"Blocked: {e}")

OutputBlocked¶

Raised when output fails validation. Thrown by OutputGuard, SecretRedaction, NoRefusals.

Python

from pydantic_ai_shields import OutputBlocked

try:
    result = await agent.run("prompt")
except OutputBlocked as e:
    print(f"Output blocked: {e}")

ToolBlocked¶

Raised when a tool call is denied. Thrown by ToolGuard.

Python

from pydantic_ai_shields import ToolBlocked

try:
    result = await agent.run("execute rm -rf /")
except ToolBlocked as e:
    print(f"Tool '{e.tool_name}' blocked: {e.reason}")

BudgetExceededError¶

Raised when cumulative cost exceeds the budget. Thrown by CostTracking.

Python

from pydantic_ai_shields import BudgetExceededError

try:
    result = await agent.run("expensive query")
except BudgetExceededError as e:
    print(f"Over budget: ${e.total_cost:.4f} > ${e.budget:.4f}")