Streaming Input

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Understanding the two input modes for the Claude Code Elixir SDK and when to use each.

Official Documentation: This guide is based on the official Claude Agent SDK documentation. Examples are adapted for Elixir.

Overview

The Claude Agent SDK supports two distinct input modes for interacting with agents:

  • Streaming Input Mode (Default & Recommended) - A persistent, interactive session
  • Single Message Input - One-shot queries that use session state and resuming

This guide explains the differences, benefits, and use cases for each mode to help you choose the right approach for your application.

Streaming input mode is the preferred way to use the Claude Agent SDK. It provides full access to the agent's capabilities and enables rich, interactive experiences.

It allows the agent to operate as a long-lived process that takes in user input, handles interruptions, surfaces permission requests, and handles session management.

How It Works

sequenceDiagram
    participant App as Your Application
    participant Agent as Claude Agent
    participant Tools as Tools/Hooks
    participant FS as Environment/<br/>File System

    App->>Agent: start_link(options)
    activate Agent

    App->>Agent: stream("Message 1")
    Agent->>Tools: Execute tools
    Tools->>FS: Read files
    FS-->>Tools: File contents
    Tools->>FS: Write/Edit files
    FS-->>Tools: Success/Error
    Agent-->>App: Stream partial response
    Agent-->>App: Stream more content...
    Agent->>App: Complete Message 1

    App->>Agent: stream("Message 2")
    Agent->>Tools: Process & execute
    Tools->>FS: Access filesystem
    FS-->>Tools: Operation results
    Agent-->>App: Stream response 2

    App->>Agent: stream("Message 3")
    App->>Agent: Interrupt/Cancel
    Agent->>App: Handle interruption

    Note over App,Agent: Session stays alive
    Note over Tools,FS: Persistent file system<br/>state maintained

    deactivate Agent

Benefits

  • Queued Messages - Send multiple messages that process sequentially, with ability to interrupt
  • Tool Integration - Full access to all tools and custom MCP servers during the session
  • Hooks Support - Use lifecycle hooks to customize behavior at various points
  • Real-time Feedback - See responses as they're generated, not just final results
  • Context Persistence - Maintain conversation context across multiple turns naturally

Implementation Example

# Start a persistent session with tools
{:ok, session} = ClaudeCode.start_link(
  allowed_tools: ["Read", "Grep"]
)

# First message
session
|> ClaudeCode.stream("Analyze this codebase for security issues")
|> ClaudeCode.Stream.text_content()
|> Enum.each(&IO.write/1)

# Wait for conditions or user input
Process.sleep(2000)

# Follow-up message - context is maintained
session
|> ClaudeCode.stream("Now check the authentication module specifically")
|> ClaudeCode.Stream.text_content()
|> Enum.each(&IO.write/1)

# Clean shutdown
ClaudeCode.stop(session)

Single Message Input

Single message input is simpler but more limited.

When to Use Single Message Input

Use single message input when:

  • You need a one-shot response
  • You do not need hooks, real-time streaming, etc.
  • You need to operate in a stateless environment, such as a lambda function

Limitations

Single message input mode does **not** support: - Dynamic message queueing - Real-time interruption - Hook integration - Natural multi-turn conversations (requires explicit session management)

Implementation Example

# Simple one-shot query
result =
  ClaudeCode.query("Explain the authentication flow",
    allowed_tools: ["Read", "Grep"]
  )

case result do
  {:ok, response} -> IO.puts(response.result)
  {:error, reason} -> IO.puts("Error: #{inspect(reason)}")
end

# Continue conversation with session management
result =
  ClaudeCode.query("Now explain the authorization process",
    continue: true
  )

case result do
  {:ok, response} -> IO.puts(response.result)
  {:error, reason} -> IO.puts("Error: #{inspect(reason)}")
end

Next Steps