Understand any code one step at a time. Lumen AI walks you through your code with explanations lit up inline in the editor. Works with Claude Code or your own Anthropic API key.
Installation
Launch VS Code Quick Open (Ctrl+P), paste the following command, and press enter.
Understand any code, one lit-up step at a time. Select code, click the lightbulb, and Lumen AI walks you through it with explanations right in your editor. No copy-pasting into a chat window.
Features
Step-by-step walkthrough: Lumen splits your code into logical steps, highlights each one, and explains it at the end of the line and on hover.
Navigate with CodeLens: Prev, Next, Ask and Stop sit right above the current step. Alt+→ / Alt+← also move between steps, and Esc stops.
Ask follow-ups inline: click Ask to open a thread under the step and ask anything. Lumen remembers the conversation for that step.
Lightbulb entry point: select code, press Cmd+. (Ctrl+. on Windows/Linux) and choose Lumen: walk me through this selection. With no selection it walks through the whole file.
Pick your model: the status bar shows the current model. Click it to switch between Haiku (default, cheapest), Sonnet and Opus.
Quick start
Install the extension.
Open a file and select some code, or none for the whole file.
Press Cmd+Alt+E (Ctrl+Alt+E on Windows/Linux), or click the lightbulb.
Use Next to move through the steps.
Two ways to connect
Mode
When it's used
Claude Code
If the Claude Code CLI is installed and logged in, Lumen uses it. It runs as claude -p --tools "", so Claude only sees the code you send and cannot touch your files.
Anthropic API key
Otherwise Lumen asks for your own API key and stores it in VS Code's secret storage.
Force a mode with the claudeWalkthrough.mode setting (auto, cli or api).
Commands
Command
What it does
Lumen: Walk Me Through This Code
Start a walkthrough (Cmd+Alt+E)
Lumen: Next Step / Previous Step
Move between steps
Lumen: Ask About This Step
Open the inline follow-up thread
Lumen: Stop Walkthrough
End the walkthrough
Lumen: Select Model
Switch between Haiku, Sonnet, Opus or a custom model ID
Lumen: Set Anthropic API Key / Remove Anthropic API Key
Manage your stored key
Settings
Setting
Default
Description
claudeWalkthrough.mode
auto
auto, cli or api
claudeWalkthrough.model
haiku
Model alias (haiku, sonnet, opus) or a full model ID
claudeWalkthrough.level
intermediate
beginner, intermediate or expert
claudeWalkthrough.maxSteps
12
Maximum number of steps per walkthrough
claudeWalkthrough.claudePath
claude
Path to the Claude Code CLI
Privacy
The selected code (or the whole file) is sent to Claude, through your Claude Code login or the Anthropic API. Your API key stays in VS Code secret storage on your machine. Lumen collects no telemetry.
