User Guide

Core Concepts

• Runnable: a unit with invoke + pipe.
• Chain: composition of runnables into deterministic pipelines.
• PromptTemplate: runtime prompt formatting using named placeholders.
• OutputParser: conversion from raw model text into structured outputs.
• Agent Runtime: iterative loop that can execute tools and continue until final response.

Choosing the Right Primitive

• Use RunnableLambda for custom transformation logic.
• Use RunnableMap when one input needs multiple named derived values.
• Use RunnableParallel for independent branches that can run concurrently.
• Use RunnablePassthrough when downstream stage needs the original input unchanged.
• Use ModelRunnable when adapting a provider model into runnable pipelines.

Error Handling Pattern

The framework exposes explicit error types:

• ModelError
• ToolNotFoundError
• ToolValidationError
• MaxStepsExceededError
• PromptTemplateError
• OutputParserError

Recommended pattern:

1. catch framework errors at application boundary
2. map to user-safe messages
3. log full error and cause for diagnostics

Testing Recommendations

• Unit test each runnable in isolation.
• Add contract tests for chain behavior and parser guarantees.
• Keep one golden-path example that always compiles and runs.