Roo Code, The Cline Fork With Modes And Custom Agents

What you'll build

Roo Code installed in VS Code, signed in with an Anthropic API key, with a custom mode (a "Reviewer" agent) added on top of the stock four. Roughly 15 minutes.

Caption: Roo's mode picker, four stock modes plus my custom Reviewer.

Prerequisites

• VS Code 1.95+ on Linux, Mac, or Windows
• An Anthropic API key (Roo also supports OpenAI, Ollama, and OpenRouter)
• A project to test against
• 8GB RAM (16GB if you also run Ollama for the local model path)

If you are coming from stock Cline, you can run both side by side; the extensions do not conflict.

Step 1, install Roo

In VS Code, open Extensions (Ctrl+Shift+X), search "Roo Code", install. The official one is RooVeterinaryInc.roo-cline.

The activity-bar icon is a kangaroo. Click it; the Roo panel opens with a model-provider prompt.

Step 2, configure the model

In Roo's settings panel, choose Anthropic as the provider, paste your API key, pick claude-sonnet-4-6 as the default model.

For the inline tools (autocomplete, tab-suggest), Roo uses the same model by default. You can override in settings if you want a faster model for inline.

Step 3, explore the four stock modes

Roo ships with four modes:

• Code: edits files (the default Cline behaviour)
• Architect: plans without editing, useful for big-picture decisions
• Ask: read-only Q&A about the code, no edits
• Debug: runs and reads errors, doesn't write fixes unless you confirm

Switch modes via the panel dropdown.

I find Architect the most useful addition; it gives you a plan you can refine before any code is touched.

Step 4, write a custom mode

The custom-mode story is where Roo extends past Cline. Open Roo settings → Modes → New, define a Reviewer mode:

name: Reviewer
description: Reviews diffs without editing, focused on bugs and security
system_prompt: |
  You are a senior code reviewer. Read the staged diff and give:
  1. A list of concrete bugs with line numbers.
  2. Security concerns (SQL injection, secret leaks, race conditions).
  3. Style nits (one section, optional).
  Do not edit the files. Output as a markdown report.
permissions:
  - read_file
  - run_command  # for git diff

Save. The new mode shows up in the dropdown alongside the four stock ones.

Step 5, run the Reviewer mode

Stage some changes (git add -p), open Roo, switch to Reviewer mode, prompt:

> review the staged diff for bugs and security issues

Roo runs git diff --cached, reads the output, returns a structured review without touching any files.

First run

A typical mixed session for me:

[Architect mode]
You: I want to add streaming responses to my FastAPI Claude wrapper

Roo: Plan:
1. Switch endpoint from POST to GET with SSE
2. Use StreamingResponse from FastAPI
3. Iterate over the Anthropic stream object
4. Handle disconnect cleanly

[I review the plan, agree]

[Switch to Code mode]
You: implement that plan against src/api/chat.py

Roo: [edits the file with the plan as guide]
[shows diff, I approve]

[Switch to Reviewer mode]
You: review my staged change

Roo: [reads diff, returns review with one bug found]

The mode switch keeps the conversation context; you do not lose history when switching.

What broke for me

Two issues. First, the custom-mode YAML schema is undocumented in the visible UI. I had to read the Roo source to figure out which fields the parser accepts. The settings UI accepts the YAML but silently drops fields it does not recognise. The fix is checking the Roo logs in ~/.config/Code/logs/ after saving a custom mode; any dropped fields show up as warnings.

Second, Roo's tool-permission model is per-mode but not per-project. A custom mode that allows run_command allows it everywhere, including in projects where you would rather it did not. There is no per-project override. I worked around this by keeping run_command only on modes I trust, and using the Ask-mode for any project where I do not want shell execution.

What it costs

A normal Roo session is comparable to Cline on cost. The custom-mode and Architect-first workflow does not change the API spend meaningfully.

When NOT to use this

Skip Roo if you only want the stock Cline behaviour. The maintainer overhead of two similar extensions is real; pick one.

Skip if you do not need custom modes. The four stock modes are useful but if Code mode covers your work, the upgrade does not justify the switch from Cline.

Indian operator angle

The Architect mode is the underrated win for Indian dev shops doing client work. Many gigs need a written plan before any code is touched (the client wants a deliverable before kickoff). Architect mode produces exactly that, in a format you can paste into a doc and send. It saved me a half-hour of write-up on the last small client project I did.

Forex billing is the same as the other Anthropic API paths. The Roo extension itself is free and Apache-licensed; for an Indian startup wanting to ship an internal coding-assistant fork, Roo is a cleaner base than stock Cline because the mode system gives you somewhere to add company-specific guardrails.

Related

• Cline VS Code extension with local LLM
• Continue.dev in VS Code and JetBrains
• Cursor 0.42 setup with Claude