---
published: true
id: runtime
title: Runtime
description: Knowledge captured in João Lopes' learning graph.
tags:
- ai-engineering
- agent-design
locale: en
resource: https://joaolopes.dev.br/knowledge/concepts/en/runtime/
created: '2026-03-27'
---

# Runtime
The component of an AI agent that executes tool calls produced by the model and manages the interaction loop.

## Definition
The runtime interprets the model's response, runs the requested tools (file reads, shell commands, API calls), collects the results, and feeds them back as new context for the next turn. The runtime is not the model — the model produces text, the runtime acts on it. In Claude Code, the runtime is the harness that manages tools, permissions, context, and the turn loop.

## Source
- [Runtime system - Wikipedia](https://en.wikipedia.org/wiki/Runtime_system)
- [Claude Code overview](https://code.claude.com/docs/en/overview)

## Related
- [Tool Call](/concepts/en/tool-call.md)
- [Turn](/concepts/en/turn.md)
- [Tool](/concepts/en/tool.md)