Iteration Nodes

Available Iteration Nodes:

Loop Node - Execute a toolkit repeatedly based on task instructions
Loop from Tool Node - Generate a list dynamically and process each item
Router Node (for Loops) - Create custom loop structures with conditional routing

Iteration nodes are powerful but can be complex. They allow you to process multiple items (files, records, tasks) in a single pipeline execution, making them essential for automation and batch processing workflows. You can also create custom loops using Router nodes for more precise control over iteration logic.

Loop Node

The Loop Node executes a selected toolkit repeatedly, creating input for each iteration based on task instructions. It’s designed for scenarios where you know what needs to be iterated over and can describe how to create inputs for each iteration.

Purpose

Use the Loop Node to:

Process lists of items where you define iteration logic in the Task field
Execute the same action repeatedly with different inputs
Automate batch operations across multiple entities
Iterate through data extracted from state or previous nodes
Repeat toolkit execution until all items are processed

Parameters

Parameter	Purpose	Type Options & Examples
Toolkit	Select the toolkit type that will be executed in each loop iteration	Options: - Toolkits - ELITEA toolkits (e.g., GitHub, Jira, Confluence) - MCPs - Model Context Protocol servers - Agents - ELITEA agents - Pipelines - Other pipeline executions Toolkit Selection Behavior: - When you select Toolkits or MCPs: A Tool dropdown appears; you must select a specific tool - When you select Agents or Pipelines: No additional dropdown; the toolkit is executed directly Example - Toolkit with Tool: `toolkit: "llm-node"` `tool: "createFile"` Example - Agent: `toolkit: "Code Documentation Agent"`
Tool	Select the specific tool from the chosen toolkit or MCP	Availability: Only appears when Toolkit is set to Toolkits or MCPs Example: `toolkit: "GitHub Expert"` `tool: "createFile"` Tool Selection: - Dropdown shows all available tools from the selected toolkit/MCP - Each toolkit provides different tools - Tool parameters are configured through the Task field and input mapping
Task	Provide instructions on how to formulate the input for each iteration of the loop	Format: Natural language instructions describing how to extract or create input data from the current state or chat history Example Task: `task: \|` `Formulate ALL file paths from chat_history as a list of inputs.` `For each file path, create input as:` `- "task": the file path` `- "chat_history": the entire conversation history` Common Task Patterns: - Extract from Chat History - Process State Variable List - Generate Range - Parse JSON Array How Task Works: The Loop Node uses the Task instructions with an internal LLM to analyze the current state, identify items to iterate over, generate a list of inputs, and execute the toolkit for each input
Input	Specify which state variables the Loop Node reads when executing the Task instructions	Options: - Default states: `input`, `messages` - Custom states: Any state variables you’ve defined Example: `input: ["messages", "file_list", "project_id"]` Usage in Task: The Loop Node uses these input variables to extract items to iterate over, provide context for iteration logic, and access data needed for each iteration
Output	Specify state variable names to store the results from all loop iterations	Options: - Single output: Results concatenated as string - Multiple outputs: Different aspects of results Example: `output: ["documentation_results", "processed_count"]` Output Accumulation: All iteration results joined into one string; results from each iteration are appended; final output contains complete results from all iterations
Structured Output	Enable structured output parsing for loop results	Options: - Enabled (toggle on): Parse toolkit responses as structured data - Disabled (toggle off): Treat responses as plain text When to Enable: - Toolkit returns JSON or structured data - You need to extract specific fields from results - Results will be used in subsequent nodes with structured input Example: `structured_output: true`

YAML Configuration

- id: "process_files"
  type: "loop"
  toolkit: "Code Documentation Agent"
  task: |
    Formulate ALL file paths from chat_history as a list of inputs.
    For each file path, create input as:
    - "task": the file path
    - "chat_history": the entire conversation history
  input: ["messages"]
  output: ["documentation"]
  structured_output: false
  transition: "END"

Be specific in your Task instructions. The clearer you are about what to extract and how to format it, the more reliably the Loop Node will execute.

Only enable structured output if the toolkit being called actually returns structured data (JSON, dict). Otherwise, parsing may fail.

Each iteration executes the toolkit, which may involve LLM calls, API requests, or external tool execution. For large lists (100+ items), consider batching, pagination, or implementing error handling.

Best Practices

Write Clear Task Instructions: Provide explicit, step-by-step instructions on what to extract and how to format inputs.
Specify Input Variables: List all state variables the Task needs to access for iteration logic.
Use Structured Output When Appropriate: Enable structured output for JSON-returning toolkits.
Provide Clear Output Names: Name outputs to indicate what they contain (e.g., “documentation_results” not “result”).
Consider Performance: Be mindful of iteration count; test with small lists first before scaling up.
Test with Small Lists First: Start with 2-3 items to verify logic, then scale to full list.
Handle Empty Lists: Account for scenarios with no items; ensure Task returns empty list if nothing found.
Use Descriptive Toolkit Names: Select toolkits with clear purposes for maintainability.
Document Expected Input Format: Comment on what the Task expects (e.g., “Expects messages to contain file paths”).
Plan Transition After Loop: Ensure next node handles loop output properly.

Loop from Tool Node

The Loop from Tool Node is a two-stage iteration mechanism: first, it executes a toolkit to generate a list of items, then it processes each item in that list using a second toolkit. This is ideal for dynamic iteration where the list of items isn’t known beforehand.

Purpose

Use the Loop from Tool Node to:

Dynamically generate iteration lists using a toolkit
Process items from tool outputs (e.g., files from a directory, tickets from Jira)
Chain two toolkits where first generates inputs for second
Automate discovery and processing workflows
Handle variable-length lists determined at runtime

Parameters

Parameter	Purpose	Type Options & Examples
Toolkit (List Generator)	Select the toolkit that will generate the list of items to iterate over	Options: - Toolkits - ELITEA toolkits - MCPs - Model Context Protocol servers - Agents - ELITEA agents - Pipelines - Other pipelines First-Stage Toolkit: This toolkit is executed once at the beginning to generate the list - For Toolkits/MCPs: Must select a specific Tool - For Agents/Pipelines: Toolkit is executed directly Example: `toolkit: "GitHub Expert"` `tool: "getFilesFromDirectory"`
Tool (List Generator Tool)	Select the specific tool that generates the item list	Availability: Only appears when Toolkit is set to Toolkits or MCPs Example: `toolkit: "GitHub Expert"` `tool: "getFilesFromDirectory"` Tool Output Requirements: The tool must return structured data (list or array)
Loop Toolkit (Item Processor)	Select the toolkit that will process each item in the generated list	Options: - Toolkits - ELITEA toolkits - MCPs - Model Context Protocol servers - Agents - ELITEA agents - Pipelines - Other pipelines Second-Stage Toolkit: This toolkit is executed for each item in the list - For Toolkits/MCPs: Must select a specific Loop Tool - For Agents/Pipelines: Toolkit is executed directly Example: `loop_toolkit: "llm-node"` `loop_tool: "createFile"`
Loop Tool (Item Processor Tool)	Select the specific tool that processes each item	Availability: Only appears when Loop Toolkit is set to Toolkits or MCPs Example: `loop_toolkit: "llm-node"` `loop_tool: "createFile"` Loop Tool Input: The loop tool receives input from Variables Mapping for each item
Variables Mapping	Map output fields from the list-generating tool to input parameters of the item-processing tool	Critical Component: This is the most important configuration for Loop from Tool nodes Format: `variables_mapping:` `<output_field>: <input_parameter>` Example: `variables_mapping:` `file_path: "task"` `file_content: "source_code"` `bucket_name: "BUCKET_NAME"` Mapping Types: - Type: Fixed - Direct mapping - Type: F-String - Format string - Type: Variable - Combine variables
Task	Optional instructions for the list-generating toolkit (first stage)	Usage: Provide context or instructions to the tool that generates the list Example: `task: "Get all Python files from the src directory"` When to Use Task: - List-generating toolkit needs specific instructions - You want to filter or customize the list generation - Agent or LLM-based toolkit requires context
Input	Specify state variables needed by the list-generating toolkit	Example: `input: ["repository_name", "directory_path", "file_extension"]` Input Usage: The first-stage toolkit uses these inputs to generate the list
Output	Specify state variable names to store accumulated results from all loop iterations	Example: `output: ["documentation_results", "file_count"]` Output Accumulation: Results from each iteration of the loop tool are accumulated; all loop tool responses combined into single output; final output contains results from processing all items
Structured Output	Enable structured output parsing for the list-generating tool	When to Enable: - List tool returns JSON or structured data - You need to parse array of objects - Variables Mapping depends on structured fields Example: `structured_output: true`

YAML Configuration

- id: "document_github_files"
  type: "loop_from_tool"
  toolkit: "GitHub Expert"
  tool: "getFilesFromDirectory"
  loop_toolkit: "Code Documentation Agent"
  variables_mapping:
    file_path: "task"
    file_content: "source_code"
  input: ["repository_name"]
  output: ["documentation"]
  structured_output: true
  transition: "create_readme"

Almost always enable structured_output: true for Loop from Tool nodes, since the list tool must return an array or list of items to iterate over.

Variables Mapping is mandatory for Loop from Tool nodes. Without it, the loop tool won’t know how to receive data from the list tool.

Loop from Tool executes loop toolkit for each item in the list. Large lists can result in many iterations. Test with small lists first and consider rate limits.

Best Practices

Ensure List Tool Returns Structured Data: The first toolkit must return an array of objects with consistent fields.
Map All Required Loop Tool Parameters: Include all necessary mappings for the item processor tool.
Enable Structured Output: Always enable for list generation since the tool must return an array.
Test List Generation First: Verify the list tool works before adding loop processing; check field names in output.
Use Descriptive Variable Names: Clear mapping names improve readability (e.g., “customer_id” not “id”).
Handle Empty Lists: Ensure list tool returns empty array [] not null; loop skips execution if list is empty.
Consider List Size Limits: Be aware of iteration count; test with small subsets first.
Provide Input for List Tool: Ensure list tool has needed context (repository name, directory path, etc.).
Use Task for Additional Context: Provide instructions to list tool (e.g., “Get only Python files modified in last 7 days”).
Document Mapping Expectations: Comment expected structure from list tool and what loop tool expects.
Plan for Failures: Consider what happens if list tool fails; test with empty repositories, missing directories.
Chain Outputs Properly: Ensure accumulated output is usable by next node.

Router Node (for Loops)

The Router Node, typically used for conditional branching, can also create custom loop structures by routing execution back to previous nodes. This approach provides more precise control over loop conditions and iteration logic compared to dedicated Loop nodes.

Purpose

Use the Router Node for loops to:

Create custom iteration logic with explicit loop control conditions
Route back to previous nodes to repeat execution
Control loop termination using state variables (counters, flags, conditions)
Implement complex loop patterns that Loop and Loop from Tool nodes don’t support
Combine conditional logic with iteration in a single node

How It Works

Router-based loops follow this pattern:

Initialize: Set up loop control variables (counter, list index, continuation flag) in state
Process: Execute processing nodes (LLM, Function, Tool, Code nodes)
Update State: Modify loop control variables (increment counter, update flag, process next item)
Route Decision: Router evaluates loop condition:
- Continue Loop: Routes back to processing node if condition met (e.g., counter < max)
- Exit Loop: Routes to next node or END if loop should terminate
Repeat: Steps 2-4 repeat until exit condition is met

Configuration Pattern

Basic Loop Structure:

nodes:
  - id: InitializeLoop
    type: state_modifier
    template: "{{ 0 }}"  # Initialize counter
    output:
      - loop_counter
    transition: ProcessItem
    
  - id: ProcessItem
    type: llm
    # Processing logic here
    transition: UpdateCounter
    
  - id: UpdateCounter
    type: code
    code:
      type: fixed
      value: |
        counter = alita_state.get('loop_counter', 0)
        max_iterations = alita_state.get('max_iterations', 10)
        return {
          "loop_counter": counter + 1,
          "continue_loop": counter + 1 < max_iterations
        }
    input:
      - loop_counter
      - max_iterations
    output:
      - loop_counter
      - continue_loop
    structured_output: true
    transition: LoopRouter
    
  - id: LoopRouter
    type: router
    condition: |
      {% if continue_loop %}
      ProcessItem
      {% else %}
      END
      {% endif %}
    routes:
      - ProcessItem
      - END
    input:
      - continue_loop
    default_output: END

state:
  loop_counter:
    type: int
    value: 0
  max_iterations:
    type: int
    value: 10
  continue_loop:
    type: bool
    value: true

Loop Patterns

Counter-Based Loop:

Initialize counter to 0
Process item
Increment counter
Router checks if counter < max_iterations
Routes back to process or exits

List Processing Loop:

Initialize list index to 0
Process current item at index
Increment index
Router checks if index < list length
Routes back to process next item or exits

Condition-Based Loop:

Initialize continuation flag
Process and update state
Code node sets flag based on condition (e.g., task complete, error occurred)
Router checks flag
Routes back to process or exits

Best Practices

Initialize Loop Variables: Always set up counters, flags, or indices before entering the loop.
Prevent Infinite Loops: Include explicit termination conditions (max iterations, completion flag) to ensure loops exit.
Use State Variables for Control: Track loop state with dedicated variables (loop_counter, current_index, continue_flag).
Update State Between Iterations: Use Code or State Modifier nodes to update loop control variables after each iteration.
Route Explicitly: Define both continue and exit paths clearly in Router condition.
Set Maximum Iterations: Always include a max iteration limit as a safety measure.
Test Loop Termination: Verify loops exit correctly under all conditions (normal completion, error, max iterations).
Document Loop Logic: Comment YAML to explain loop purpose, termination condition, and iteration count.
Consider Performance: Router-based loops execute synchronously; for large iteration counts, consider Loop or Loop from Tool nodes.
Use Descriptive Variable Names: Name loop control variables clearly (loop_counter not i, continue_processing not flag).

When to Use Router for Loops

Choose Router-based loops when you:

Need custom loop termination logic not supported by Loop nodes
Want explicit control over every iteration
Require complex conditional logic combined with iteration
Need to route to different processing paths within the loop
Have simple iteration requirements (< 20 iterations typically)

Use dedicated Loop nodes when you:

Processing large lists (20+ items)
Loop logic fits Loop or Loop from Tool patterns
Performance is critical (dedicated Loop nodes are optimized)
Iteration logic is straightforward (process each item in a list)

Iteration Nodes Comparison

Feature	Loop Node	Loop from Tool Node	Router Node (for Loops)
Purpose	Execute toolkit repeatedly based on task instructions	Generate list dynamically, then process each item	Create custom loop structures with conditional routing
Input Source	Task instructions describe how to extract/create inputs	First toolkit generates the list of inputs	State variables (counters, flags, conditions)
Iteration Logic	Defined in Task field using natural language	Defined by output of list-generating toolkit	Defined by Router condition template
Toolkit Selection	Single toolkit (Toolkits/MCPs/Agents/Pipelines)	Two toolkits: list generator + item processor	N/A (uses other nodes for processing)
Tool Selection	Optional (for Toolkits/MCPs only)	Two tools: list tool + loop tool (for Toolkits/MCPs)	N/A
Variables Mapping	Not applicable	Required - maps list tool outputs to loop tool inputs	Not applicable (uses state variables)
Loop Control	Internal (LLM-based from Task)	Internal (list length)	Explicit (Router condition evaluates state)
Configuration Complexity	Medium (Task instructions)	High (two toolkits + variables mapping)	Medium-High (multiple nodes + state management)
Use When	You can describe iteration logic in Task	You need to dynamically discover items to process	You need custom loop control logic
List Generation	Internal (from Task + LLM)	External (from toolkit execution)	Manual (via state variables)
Example Use Case	Process file paths mentioned in chat	Get files from GitHub directory and process each	Counter-based loop, process until condition met
Performance	Task execution + N toolkit calls	List tool call + N loop toolkit calls	N iterations through pipeline nodes
Termination Control	Task-defined or list exhaustion	List exhaustion	Explicit condition in Router
Output	Accumulated results from all iterations	Accumulated results from all loop iterations	Accumulated via state updates
Flexibility	Medium	Medium	Very High (complete control)
Best For	Simple iteration with natural language	Dynamic list discovery + processing	Custom loop logic, complex conditions

When to Use Each Node

Loop Node ✅

Choose Loop Node when you:

Can describe iteration logic in natural language
Know what items to process (from state or chat history)
Want simple configuration with task instructions
Don’t need dynamic list discovery
Prefer LLM-based input generation

Example: Process file paths mentioned in chat, iterate through known list of tasks, generate reports for ID range 1-100.

Loop from Tool Node ✅

Choose Loop from Tool Node when you:

Need to dynamically discover items at runtime
Items come from external source (GitHub, Jira, database)
List generation requires toolkit execution
Want to chain two toolkits (discovery + processing)
Need structured mapping between tools

Example: Get all files from GitHub directory then document each, list Confluence pages then process each, discover Jira tickets then update each.

Router Node (for Loops) ✅

Choose Router Node for loops when you:

Need custom loop termination conditions
Want explicit control over iteration logic
Require complex conditional routing within loops
Have simple iteration requirements (< 20 iterations)
Need to combine branching and iteration logic

Example: Process items until condition met, retry operation with counter limit, iterate through workflow steps with conditional branching.

Nodes Overview - Understand all available node types
Execution Nodes - Function, Tool, Code nodes for task execution
Control Flow Nodes - Router, Condition, Decision nodes
States - Manage data flow through pipeline state
Connections - Link nodes together
YAML Configuration - See complete node syntax examples

Help & Support

Migration & Upgrade

Archived Documentation

Loop Node

Purpose

Parameters

Best Practices

Loop from Tool Node

Purpose

Parameters

Best Practices

Router Node (for Loops)

Purpose

How It Works

Configuration Pattern

Loop Patterns

Best Practices

When to Use Router for Loops

Iteration Nodes Comparison

When to Use Each Node

Loop Node ✅

Loop from Tool Node ✅

Router Node (for Loops) ✅

​Loop Node

​Purpose

​Parameters

​Best Practices

​Loop from Tool Node

​Purpose

​Parameters

​Best Practices

​Router Node (for Loops)

​Purpose

​How It Works

​Configuration Pattern

​Loop Patterns

​Best Practices

​When to Use Router for Loops

​Iteration Nodes Comparison

​When to Use Each Node

​Loop Node ✅

​Loop from Tool Node ✅

​Router Node (for Loops) ✅

Loop Node

Purpose

Parameters

Best Practices

Loop from Tool Node

Purpose

Parameters

Best Practices

Router Node (for Loops)

Purpose

How It Works

Configuration Pattern

Loop Patterns

Best Practices

When to Use Router for Loops

Iteration Nodes Comparison

When to Use Each Node

Loop Node ✅

Loop from Tool Node ✅

Router Node (for Loops) ✅