Agent Fallback

Automatically recover from script failures with AI agents

Agent Fallback automatically spawns an AI agent when deterministic script execution fails, providing intelligent error recovery without manual intervention.

Overview

When executing session actions, failures can occur due to:

• Elements not found
• Unexpected page changes
• Timing issues
• Dynamic content

Agent Fallback catches these failures and uses an agent to recover:

agent_fallback.py

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Add item to cart") as fb:
        # Try deterministic actions
        session.execute(type="click", selector="#add-to-cart")
        session.execute(type="click", selector="#checkout")

        # If any action fails, agent takes over automatically

    if fb.success:
        print("Task completed!")
    if fb.agent_invoked:
        print("Agent helped recover from failure")

How It Works

1. Normal Execution

Actions execute normally when they succeed:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Submit form") as fb:
        session.execute(type="fill", selector="input[name='email']", value="[e-mail]")
        session.execute(type="click", selector="button[type='submit']")

    # No agent spawned if all actions succeed
    print(f"Agent invoked: {fb.agent_invoked}")  # False

2. Automatic Recovery

When an action fails, the agent spawns:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Add to cart") as fb:
        # This selector is wrong - action will fail
        session.execute(type="click", selector="#wrong-selector")

        # Agent automatically:
        # 1. Sees the failure
        # 2. Understands the task ("Add to cart")
        # 3. Finds the correct button
        # 4. Completes the action

    print(f"Agent invoked: {fb.agent_invoked}")  # True
    print(f"Success: {fb.success}")  # True (agent recovered)

3. Continuation

After agent recovery, remaining actions are skipped:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Complete checkout") as fb:
        session.execute(type="click", selector="#step1")  # Success
        session.execute(type="click", selector="#step2")  # Fails - agent spawned
        session.execute(type="click", selector="#step3")  # Skipped (agent already handled task)

Use Cases

1. Fragile Selectors

Handle pages with frequently changing selectors:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Click the submit button") as fb:
        # Try specific selector first (fast and cheap)
        session.execute(type="click", selector="button#submit-btn")

        # If selector changed, agent finds the button (slower but works)

2. Dynamic Content

Handle dynamically loaded content:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Click the popup close button") as fb:
        # Try clicking without waiting
        session.execute(type="click", selector=".popup-close")

        # If popup not loaded yet, agent waits and retries

3. A/B Testing

Handle pages with multiple variations:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Click continue button") as fb:
        # Try variant A
        session.execute(type="click", selector="#continue-a")

        # If user got variant B, agent adapts

4. Graceful Degradation

Start with fast scripts, fall back to AI when needed:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Navigate to pricing") as fb:
        # Fast path - direct navigation
        session.execute(type="click", selector="nav a[href='/pricing']")

        # Slow path - agent finds the pricing link if layout changed

Configuration

Task Description

The task guides the agent when it’s invoked:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    # Clear task description helps agent understand goal
    with client.AgentFallback(session, task="Add the first product to cart") as fb:
        session.execute(type="click", selector=".add-to-cart")

Agent Parameters

Pass agent configuration:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(
        session,
        task="Complete signup",
        max_steps=15,  # Agent parameters
        reasoning_model="anthropic/claude-3.5-sonnet",
        use_vision=True
    ) as fb:
        session.execute(type="click", selector="#signup")

Vault and Persona

Provide credentials to the agent:

from notte_sdk import NotteClient

client = NotteClient()

vault = client.Vault(vault_id="vault_123")

with client.Session() as session:
    with client.AgentFallback(
        session,
        task="Login and navigate to settings",
        vault=vault
    ) as fb:
        # Try logging in with deterministic actions
        session.execute(type="fill", selector="#email", value="[e-mail]")
        session.execute(type="fill", selector="#password", value="password123")
        session.execute(type="click", selector="#login")

        # If login flow changed, agent uses vault credentials

Fallback Properties

Access information about the fallback execution:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Complete task") as fb:
        # Execute actions
        session.execute(type="click", selector="#button")

    # Check what happened
    print(f"All succeeded: {fb.success}")
    print(f"Agent was invoked: {fb.agent_invoked}")

    if fb.agent_response:
        print(f"Agent result: {fb.agent_response}")

Success

Whether the task was completed successfully:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Task") as fb:
        session.execute(type="click", selector="#button")

    if fb.success:
        print("Task completed successfully!")
    else:
        print("Task failed even after agent intervention")

Agent Response

Details from the agent if it was invoked:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Extract data") as fb:
        session.execute(type="click", selector="#button")

    if fb.agent_invoked:
        print(f"Agent answer: {fb.agent_response.answer}")
        print(f"Agent steps: {len(fb.agent_response.steps)}")

Inspecting Individual Steps

Access detailed information about each execution attempt:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Task") as fb:
        session.execute(type="click", selector="#btn1")
        session.execute(type="click", selector="#btn2")  # Fails

    for step in fb.steps:
        print(f"Action: {step.action}")    # The action type and parameters
        print(f"Success: {step.success}")  # Whether this step succeeded
        if not step.success:
            print(f"Error: {step.message}")  # Error message if failed

This is useful for debugging which specific action triggered the agent fallback.

Best Practices

1. Use for Brittle Workflows

Ideal for pages that change frequently:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    # Good use case - page layout changes often
    with client.AgentFallback(session, task="Click pricing link") as fb:
        session.execute(type="click", selector="a[href='/pricing']")

2. Be Specific in Tasks

Clear tasks help the agent understand what to do:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    # Good - specific task
    with client.AgentFallback(session, task="Add the blue XL t-shirt to cart") as fb:
        session.execute(type="click", selector="#add-to-cart")

    # Less clear - vague task
    with client.AgentFallback(session, task="Do something") as fb:
        session.execute(type="click", selector="#button")

3. Try Fast Path First

Put cheap, fast actions inside the fallback:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    with client.AgentFallback(session, task="Navigate to dashboard") as fb:
        # Fast path - direct click
        session.execute(type="click", selector="a[href='/dashboard']")

        # Agent only invoked if fast path fails

4. Don’t Use for Complex Logic

Fallback is for single-goal recovery, not complex workflows:

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    # Bad - too complex for fallback
    with client.AgentFallback(session, task="Complete entire checkout process") as fb:
        session.execute(type="click", selector="#cart")
        session.execute(type="click", selector="#checkout")
        session.execute(type="fill", selector="#address", value="123 Main St")
        # ... many more steps

    # Better - break into smaller fallbacks
    with client.AgentFallback(session, task="Click cart") as fb:
        session.execute(type="click", selector="#cart")

    with client.AgentFallback(session, task="Proceed to checkout") as fb:
        session.execute(type="click", selector="#checkout")

5. Monitor Fallback Rate

Track how often agents are invoked:

from notte_sdk import NotteClient

client = NotteClient()
fallback_invoked_count = 0
total_runs = 0

for _ in range(100):
    with client.Session() as session:
        with client.AgentFallback(session, task="Task") as fb:
            session.execute(type="click", selector="#button")

    total_runs += 1
    if fb.agent_invoked:
        fallback_invoked_count += 1

fallback_rate = fallback_invoked_count / total_runs
print(f"Agent fallback rate: {fallback_rate:.1%}")

# If rate is high, consider:
# - Updating selectors
# - Using agents directly
# - Improving page stability

Limitations

Not Supported

Agent Fallback does not support:

• session.scrape() calls
• raise_on_failure=True on actions
• Multiple nested fallbacks

from notte_sdk import NotteClient

client = NotteClient()

with client.Session() as session:
    # This will raise an error
    with client.AgentFallback(session, task="Task") as fb:
        data = session.scrape()  # Not allowed

    # This will raise an error
    with client.AgentFallback(session, task="Task") as fb:
        session.execute(type="click", selector="#btn", raise_on_failure=True)  # Not allowed

When Not to Use

Don’t use Agent Fallback for:

• Tasks that always fail (fix the script instead)
• Complex multi-step workflows (use full agent)
• Scraping/data extraction (use session.scrape or agents)
• When you need structured output (use agent with response_format)

Error Handling

Handle failures gracefully:

from notte_sdk import NotteClient

client = NotteClient()

try:
    with client.Session() as session:
        with client.AgentFallback(session, task="Critical task") as fb:
            session.execute(type="click", selector="#button")

        if not fb.success:
            # Even agent couldn't complete the task
            alert_failure(f"Task failed: {fb.steps[-1].message}")
except Exception as e:
    # Unexpected error
    logging.error(f"Fallback exception: {e}")

Next Steps

Lifecycle

Understand agent execution modes

Configuration

Configure agent parameters

Session Actions

Learn about session actions

Best Practices

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