agent
An AI assistant that can read files, write code, run commands, and perform tasks on your behalf. OpenCode's built-in agents include "build" (for making changes) and "plan" (for thinking through problems without making changes). You can also create custom agents for specialized tasks.
AGENTS.md
A plain text file containing custom instructions that OpenCode reads at the start of every session. Think of it as a set of standing orders for the AI. Can exist globally (~/.config/opencode/AGENTS.md) or per-project (in the project root). The global one is personal to you; the project one is typically committed to Git and shared with your team.
CLI
Command-Line Interface. A way to interact with software by typing text commands. OpenCode has a CLI for running one-off tasks, like opencode run "explain this function". Unlike the TUI, the CLI runs a single command and exits.
command
A slash-prefixed action you can run inside OpenCode, like /models to switch AI models, /share to share a conversation, or /undo to revert the last change. You can also create custom commands for repetitive tasks.
config
Short for configuration. A file (usually opencode.json) where you define preferences for how OpenCode behaves — which model to use, what permissions to grant, which MCP servers to connect, and more. Config files can be global (applying to all sessions) or per-project.
context window
The amount of text a model can "see" at once during a conversation. Measured in tokens (roughly ¾ of a word). A model with a 128K context window can work with about 128,000 tokens of combined input and output — including your messages, file contents, tool results, and the model's own responses. Larger context windows let the model handle bigger codebases and longer conversations without losing track of earlier details.
GUI
Graphical User Interface. A visual interface with windows, buttons, and menus that you interact with using a mouse and keyboard. OpenCode Desktop is a GUI. Compare with TUI and CLI.
Homebrew
A package manager for macOS (and Linux) that lets you install software from the command line. Run brew install <package> to install something, brew update to update Homebrew itself, and brew upgrade to update installed packages. OpenCode Desktop can be installed with brew install --cask opencode-desktop. See brew.sh.
LLM
Large Language Model. A type of AI that works like a fancy version of autocomplete — it takes existing text and guesses the next likely words to follow it. Feed it the beginning of a sentence and it predicts how to continue. Feed it a question and it predicts what an answer would look like. Feed it code with a bug and it predicts what a fix would look like.
LLMs are trained on vast amounts of text and code from the internet, which is how they "learn" patterns of language, reasoning, and programming. They power tools like OpenCode — when you type a prompt, it's an LLM that reads it and generates a response. Examples include Claude (by Anthropic), GPT (by OpenAI), and Gemini (by Google).
For a deeper understanding of how LLMs work, watch Intro to Large Language Models by Andrej Karpathy — a clear, non-technical explainer covering how these models are built, how to think about them, and how to get the most out of them.
LM Studio
A desktop application for downloading and running LLMs locally on your computer. It provides a GUI for browsing models, managing downloads, and running a local API server that OpenCode can connect to as a provider. See lmstudio.ai.
Markdown
A plaintext format preferred by developers for writing content. Unlike formats tied to specific programs (like .docx for Microsoft Word or .pages for Apple Pages), Markdown is lightweight and not associated with any particular program, company, or technology. Files end in .md and use simple characters for formatting: # for headings, ** for bold, - for bullet lists, and [text](url) for links.
Markdown is also the preferred text format used by LLMs — both for reading input and generating output. Many of the files you'll work with in OpenCode are Markdown, including AGENTS.md and the lesson files in this course.
To learn the Markdown format interactively, check out Markdown Live Preview.
MCP
Model Context Protocol. An open standard that lets OpenCode connect to external tools and services. For example, you can add an MCP server that gives OpenCode access to your GitHub issues, Sentry error logs, or documentation search. MCP servers can be local (running on your machine) or remote (hosted on the internet).
mode
OpenCode has different operating modes. Build mode lets the agent make changes to your files. Plan mode restricts it to only reading and suggesting — useful for thinking through a problem before committing to changes. Switch between them with the Tab key in the TUI, or through the mode selector in Desktop.
model
The AI brain that powers OpenCode. Models are created by companies like Anthropic (Claude), OpenAI (GPT), and Google (Gemini). Different models have different strengths, speeds, and costs. You choose which model to use, and you can switch between them at any time.
Ollama
A CLI tool for downloading and running LLMs locally on your computer. It works like a package manager for AI models — run ollama pull llama3 to download a model and ollama run llama3 to start chatting with it. OpenCode can connect to Ollama as a local provider. See ollama.com.
permissions
Rules that control what OpenCode is allowed to do on your machine. Each action can be set to allow (run without asking), ask (prompt for approval), or deny (block entirely). For example, you might allow file reads but require approval before deleting files.
prompt
The message or instruction you type into OpenCode. A good prompt gives the AI enough context to do what you want. For example: "Add a dark mode toggle to the settings page" or "Explain how authentication works in this project."
provider
A company or service that hosts AI models. Anthropic, OpenAI, and Google are providers. OpenCode supports 75+ providers, including self-hosted options like Ollama for running models locally.
session
A single conversation with OpenCode. Each session has its own context and history. You can run multiple sessions in parallel, and you can share sessions with others using the /share command.
skill
A reusable set of instructions packaged as a SKILL.md file. Skills are loaded on-demand by OpenCode when they're relevant to the current task. Think of them as specialized knowledge packs — for example, a skill that knows how to draft release notes or set up a new React component.
text editor
A program for writing and editing plain text files. You'll need one for viewing and editing OpenCode's config files, though OpenCode itself handles most file creation and editing.
A few popular cross-platform editors (all free): VS Code, Cursor, Zed, and Windsurf. If you don't want to install anything extra, your operating system includes one: TextEdit on macOS (set it to plain text mode in Settings), Notepad on Windows, or gedit/Kate/nano on Linux.
tool
A capability that OpenCode's AI agent can use. Built-in tools include reading files, editing code, running shell commands, searching the web, and more. MCP servers can add additional tools from external services.
TUI
Terminal User Interface. A text-based interface that runs inside your terminal. OpenCode's TUI looks like a chat app but runs entirely in the terminal — no mouse needed. It's the original way to use OpenCode, and it's popular with developers who are comfortable in the terminal. Compare with GUI and CLI.