Cline

Cline is an open-source VS Code extension that runs a large language model as an autonomous coding agent directly in your editor sidebar. Built by Saoud Rizwan and released in mid-2024 under the MIT license, it grew from a single-model experiment called Claude Dev into a model-agnostic platform with 5 million installs, 61,000 GitHub stars, and recognition from GitHub's Octoverse 2025 as the second fastest-growing open-source project on the platform that year. The extension is free; users connect their own API keys from Anthropic, OpenAI, Google Gemini, AWS Bedrock, Azure, local Ollama models, or any OpenAI-compatible endpoint.

The core loop: you describe a task in natural language, Cline reads your codebase, proposes a structured plan, and then executes file edits, terminal commands, and browser interactions one step at a time with your explicit approval at every stage. Key features include Plan/Act mode (introduced in v3.2, January 21, 2025), which separates architectural planning from code execution; MCP Marketplace integration (v3.4, February 2025) for connecting over 150 third-party tools including CI/CD platforms, database clients, and cloud monitoring services; built-in browser automation via Anthropic's Computer Use capability; workspace checkpoints for diffing and reverting changes; and real-time per-session cost tracking so you can see exactly what each task costs in API tokens.

What Cline actually does in April 2026

Cline is not an inline completion engine. It does not suggest code as you type. Instead it operates as a multi-step agent in a sidebar panel: you give it a goal, it researches your codebase using AST search and file reading, generates a structured plan, and then works through the plan file by file, showing you a full diff before applying each change and requesting approval before running any terminal command.

As of April 2026, the current stable release is v3.81.0, available from the VS Code Marketplace at 3.75 million installs with a 4-star rating across 283 reviews (marketplace numbers lag total installs, which span VS Code, JetBrains, and CLI). The extension supports:

• Plan/Act mode: Plan mode locks Cline to read-only codebase exploration and strategy discussion. No files are modified, no commands run. Switching to Act mode carries the full plan context forward and unlocks execution. Each mode can run a different model, which Saoud Rizwan's recommended workflow exploits: use a cheaper reasoning model for planning, a more capable one for execution.
• MCP Marketplace: Over 150 Model Context Protocol servers are installable with one click. Cline reads the server's setup instructions, prompts for required API keys, and configures everything automatically. Categories include GitHub, Jira, Slack, PostgreSQL, AWS, Datadog, and Figma integrations.
• Browser automation: Leverages Claude's Computer Use feature to open URLs, click buttons, fill forms, and capture screenshots. Used primarily for end-to-end testing and reading live documentation.
• Context tools: @url, @file, @folder, and @problems references inject specific content into the agent's context window without requiring manual copy-paste.
• Checkpoints: Workspace snapshots taken before each task let you compare current state against any prior checkpoint or restore a full rollback.
• Subagents (v3.58): Parallel agents each get their own context window. Intermediate exploration stays isolated, and only final results flow back to the main session.
• CLI (v2.0, February 2026): A full terminal rebuild adds headless CI/CD mode and parallel execution, extending Cline beyond VS Code into pipeline automation.

The extension works inside VS Code, VS Code Insiders, Cursor, and Windsurf. JetBrains support is in early access.

Where Cline sits versus Cursor Composer and Aider

Cline vs. Cursor Composer

Cursor is a proprietary VS Code fork built by Anysphere. Its Composer multi-file agent runs inside the same closed IDE, using Cursor's own model routing infrastructure. Cursor Pro costs $20/month; its background agents run on Anysphere-managed cloud VMs using git worktrees, enabling up to eight parallel agents with no API key management required. The tradeoff: you cannot substitute your own model at the API level, vendor lock-in is structural, and the closed codebase cannot be audited or forked.

Cline is an extension you layer onto VS Code without replacing it. Every model call goes directly from your machine to your chosen provider using your own API key. No data transits Cline's servers. The MCP layer lets you extend the agent's capabilities with tools Cursor does not support. Cursor has inline tab completions that predict code as you type; Cline does not. For teams comparing costs, Cursor Teams runs $40/user/month; Cline's Enterprise tier adds SSO and centralized billing at custom pricing, but the baseline extension is free regardless of team size.

Cline vs. Aider

Aider is a terminal-native CLI tool (39,000+ GitHub stars). Its most structurally distinctive feature is a two-model pipeline: an "architect" model proposes a solution, then a cheaper "editor" model translates that proposal into specific file edits, optimizing cost without sacrificing reasoning quality. Aider treats Git as a first-class citizen, auto-committing every AI change with conventional commit messages and enabling undo via standard git revert. Watch mode monitors files for AI comments and responds automatically, and auto-testing re-prompts the agent on test failures.

Cline's approach is inverted: every change requires human approval before commit, and Git management stays with the developer. Aider operates entirely in a terminal without a GUI diff view; Cline shows a visual diff with inline highlighting before any file is modified. Aider's native environment is the shell; Cline's is the VS Code sidebar. Neither is objectively superior. Aider suits developers who want Git-automated, terminal-first workflows. Cline suits those who want granular visual control over every agent action inside their existing editor.

"The 'act' mode is a game changer for me. It's just.. amazing." - remuskaos, Hacker News, February 2025

What the Plan/Act workflow reality looks like

The January 21, 2025 v3.2.0 release formalized the workflow that experienced Cline users had already been approximating by hand. The release notes describe the goal directly: "PLANNING > PROMPTING."

In practice, a typical Plan/Act session looks like this: you paste a feature request into the chat in Plan mode. Cline reads the relevant files, asks two or three clarifying questions, and outputs a numbered task list with the specific files it will touch and why. You adjust the plan in natural language, confirm, then flip to Act mode. From that point, Cline executes each step in sequence, pausing for approval before each file write and each terminal command. When a build fails, it reads the error output, proposes a fix, and asks before applying it.

Addy Osmani, Chrome engineering lead at Google, published a detailed write-up in January 2025 summarizing his daily use:

"If you're building complex systems and want AI assistance that respects engineering principles, Cline is worth serious consideration." - Addy Osmani, Substack (addyo.substack.com), January 30, 2025

Osmani specifically called out Cline's model flexibility as enabling hybrid cost strategies: using DeepSeek-R1 for planning and Claude Sonnet for execution, which he described as cutting costs "by up to 97% while improving overall output quality."

The rename from Claude Dev to Cline happened alongside the v2.0 release in October 2024. Saoud Rizwan announced it on X: "Introducing Cline (formerly Claude Dev), an AI assistant that can use your CLI aNd Editor. v2.0 brings exciting updates: responses are now streamed into your editor, a cancel button for better control over tasks, a new XML-based tool calling prompt resulting in ~40% fewer requests per task." The name change reflected the tool's shift from a Claude-specific experiment to a model-agnostic platform. The extension's VS Code marketplace ID, saoudrizwan.claude-dev, was kept unchanged to preserve continuity for existing users.

Then in February 2025, Cline launched the MCP Marketplace, and the tool's scope changed again: it became a coordination layer for the broader developer toolchain, not just a coding agent. A single click installs a configured MCP server that lets Cline open GitHub issues, query a Postgres database, push to Slack, or trigger a Datadog alert, all from within the same chat session.

Who Cline is built for

Cline rewards a specific kind of developer workflow: you are comfortable reviewing diffs, you understand enough about what the agent is doing to catch errors, and you want full control over model selection and API costs without ceding those decisions to a vendor.

It works especially well for:

• Mid-complexity feature work across multiple files in a React, Next.js, or TypeScript codebase
• Developers who switch models depending on task type, running planning on a cheaper model and execution on a more capable one
• Teams on tight budgets where Cursor's per-seat subscription cost is a real constraint
• Self-hosted or air-gapped environments where all model calls run through Ollama or a local endpoint
• Developers who need MCP extensibility to connect their coding agent to external systems

Damian Arnsdorff, a career-switching developer who attended his first hackathon after learning to use Cline, described the experience: "It's like having a senior dev you can ask on call 24/7 that isn't gonna scoff at you." (Cline blog, November 2025.) GitHub's Octoverse 2025 report documented 4,704% year-over-year contributor growth for the Cline repository, the second largest of any project on the platform that year.

What Cline is not

Cline is not a tab completion tool. It will not autocomplete a function signature as you type. If that is the primary thing you want from an AI coding assistant, GitHub Copilot, Cursor's Tab feature, or Continue are better fits.

It is not a managed service. API costs are unpredictable without discipline: forum threads and GitHub issues document users spending $30 to $200 per month depending on usage intensity, with some heavy users reporting daily costs climbing to $50 on complex multi-file projects. The extension provides real-time token cost tracking per session, but there are no budget caps or spending alerts built in. Users who want a predictable monthly bill should look at Cursor Pro ($20/month flat) or GitHub Copilot ($10/month flat) instead.

Context window degradation is a recurring frustration. After 15 to 20 conversation turns, the model's performance typically degrades, and users report having to start a fresh task to recover quality. A context condensing feature added in a 2025 update caused significant user complaints (GitHub issue #5616) by creating an aggressive "analyzing" cycle that broke workflows mid-task. The team acknowledged the issue but context management remains a known friction point.

It is not a one-click magic button. Users who are not comfortable reading code or reviewing diffs will find the approval loop tedious rather than reassuring, and the agent will occasionally make changes that require judgment to evaluate. The tool works best when you can catch a mistake before it propagates across ten files.

Cline is also not the only open-source VS Code agent in this space. Roo Code (a Cline fork) and Kilo Code are active alternatives drawing from the same community, and the ecosystem is actively fragmenting as the space matures.