--- title: "Claude Code Quickstart: MCP Server and Plugin | Since.dev" description: "Add Since.dev to Claude Code with the plugin or one command, sign in with OAuth, and ask what changed in your packages, AI models and runtimes." canonical_url: https://since.dev/guides/claude-code-quickstart last_updated: 2026-11-04 --- # Claude Code quickstart: check what changed in your code Install the Since.dev plugin or add the MCP server with one command, sign in through your browser, and Claude Code can check your packages, AI models and runtimes against what changed, down to the file and line. Updated November 4, 2026 ## Install the plugin or the server We suggest the plugin. It adds the MCP server plus four skills that tell Claude when to check. Run these in a Claude Code session: ``` /plugin marketplace add since-dev/mcp /plugin install since-dev@since-dev ``` The install opens the plugin's details, where you pick who gets it: you, everyone on this repository, or you in this repository only ([Claude Code plugin docs](https://code.claude.com/docs/en/discover-plugins)). If the summary asks you to, run `/reload-plugins`. For the server alone, run this in your shell: ``` claude mcp add --transport http since \ https://api.since.dev/mcp ``` Add `--scope user` for every project, or `--scope project` to share it through `.mcp.json` ([Claude Code MCP docs](https://code.claude.com/docs/en/mcp)). ## Sign in with OAuth 1. Run `/mcp` in Claude Code and pick the Since.dev server. 2. In your browser, sign in to Since.dev (a free account works) and approve Claude Code for one workspace. 3. Back in Claude Code, `/mcp` shows the server connected, with three tools: `whats_changed`, `check_code` and `fix_code`. No key goes in a file, and Claude Code refreshes the sign-in for you. To use another workspace, choose Clear authentication in the `/mcp` menu and sign in again ([MCP reference](https://since.dev/docs.md#mcp)). ## Three things to ask first Ask in plain words. Claude picks the tool, and every answer cites its source. ### Which AI models in this repo are retiring? Claude sends the files that call a model to `check_code`. Each model comes back with its status, its date on the platform your code calls, the days left and the replacement. A shortened example: ``` src/llm.ts line 1: claude-sonnet-4-5-20250929 status: deprecated retires: 2026-11-30 on the Claude API replacement: claude-sonnet-5-5 ``` ### What breaks if I upgrade this package? Claude checks your lockfile, then asks `whats_changed` with `since` set to your version. You get each breaking change, deprecation and advisory since then, with what to use instead. Have it check the files that use the package too, and you get the lines. An example, for a made-up package: ``` acme-sdk: 3.2.0 installed, 4.1.0 latest removed in 4.0.0: Client.send use instead: Client.request source: the 4.0.0 release notes ``` ### What changed since you were trained? Before Claude writes code against a library it learned in training, have it call `whats_changed` with `since` set to a date or `cutoff:`. You get renamed and removed functions, changed parameters and retired models, each linked to the publisher's page. Treat `needs_review` and `unknown` as not settled, never as safe. Read the cited source or decide yourself. ## What the plugin's skills add The skills tell Claude when to check, so you don't have to ask. Claude loads one when your task matches its description, or you can run one, such as `/since-dev:since-before-upgrading` ([skills docs](https://code.claude.com/docs/en/skills)). The four skills in the Since.dev plugin | Skill | Used when | Checks | | ----------------------- | --------------------------------------------- | -------------------------------------- | | since-before-upgrading | You change a dependency, manifest or lockfile | What the new version breaks | | since-model-retirements | Code names an AI model ID | Status, date per platform, replacement | | since-what-changed | Claude writes against something from training | What changed since its cutoff | | since-ci-and-runtimes | You edit CI, a Dockerfile or a version file | Runtime, image and runner end of life | ## Fixes, with your approval `fix_code` writes, so Claude Code asks before it runs. Give it a snippet and it returns the patch, on Team and up. Give it a connected repository and it opens fix pull requests, on Business and Platform. Fixes count against the month's fix pull requests, not credits. To skip approving the two read tools, allow `mcp__since__whats_changed` and `mcp__since__check_code` with `/permissions`. The plugin's names start with `mcp__plugin_since-dev_since__` ([permission rules](https://code.claude.com/docs/en/permissions)). ## Use an API key for CI and headless runs OAuth needs a browser. For CI or `claude -p` where nobody can sign in, use a workspace API key: 1. In [app.since.dev](https://app.since.dev), pick the workspace, open [API keys](https://app.since.dev/api-keys) and choose Create API key. It starts with `sc_live_` and is shown once. 2. Store it as a CI secret, such as `SINCE_DEV_KEY`, and add the server with it as a header: ``` claude mcp add --transport http since \ https://api.since.dev/mcp \ --header "Authorization: Bearer $SINCE_DEV_KEY" ``` A key reaches only its own workspace. Never commit one, and revoke it under API keys when you're done. Without an agent, the [HTTP API](https://since.dev/docs.md#api) takes the same arguments. ## What calls cost Calls spend credits from your workspace's monthly allowance. Every plan includes some, Free too, and every response says how many are left. Credits per call, from Since.dev pricing as of Nov 4, 2026 | Call | With | Credits | | ------------- | ------------------------------------ | --------------------------------- | | whats_changed | Any read | 1, plus 1 per 10 changes returned | | check_code | A model, package, surface or snippet | 2 | | check_code | A manifest, lockfile or repository | 20 | `fix_code` costs what its check costs. A call that fails costs nothing, and so do a check's later pages read with `nextCursor` within 15 minutes ([credits](https://since.dev/docs.md#api-credits)). Prices change, see [since.dev/#pricing](https://since.dev/index.md#pricing). ## Troubleshooting - `claude mcp list` shows each server's health. For Failed to connect, `claude mcp get since` gives the reason. - Needs authentication: run `/mcp` and sign in. If no browser opens, copy the URL Claude Code shows. - No skills after the plugin install: run `/reload-plugins`. - A 401 means the sign-in expired or the key isn't valid. Sign in again or make a new key. - `credits_exhausted` means the month's credits are spent. They reset monthly. ## Where Since.dev fits Since.dev tracks breaking releases, deprecations, model retirements and end-of-life dates, and matches each one to the file and line it hits. - [Scan any public GitHub repository](https://since.dev/scan.md), no sign-in needed. - See every Claude model date on the [Claude retirement calendar](https://since.dev/calendar/anthropic.md). Connect GitHub and, on Team and up, it opens [fix pull requests](https://since.dev/docs.md#repairs) for people to review. Nothing merges or deploys. ## Questions ### Do I need a paid plan to use Since.dev in Claude Code? No. `whats_changed` and `check_code` work on every plan, Free included. Fixes start on Team. ### Should I install the plugin or only the server? The plugin. It adds the same server plus four skills, so Claude checks before upgrades, model changes and CI edits without being asked. ### What does Claude Code send to Since.dev? Only what the tool call holds, such as a model ID, a lockfile or a snippet. Code is read to analyze it, then deleted. ### Can I use it in CI? Yes. Add the server with a workspace API key as a bearer header, or call the HTTP API directly. Keep the key in CI secrets. ## Related guides ### Migration guides - [Claude Sonnet 4.5 retires on November 30, 2026: how to move off it](https://since.dev/guides/claude-sonnet-4-5-retirement.md)claude-sonnet-4-5-20250929 stops working on the Claude API on November 30, 2026. The date on each platform, how to find every use, and what to test. ### Quickstarts - [Cursor quickstart: check what changed in your code](https://since.dev/guides/cursor-quickstart.md)Add Since.dev to Cursor in one click, sign in with OAuth, and have the agent check dependency, AI model and runtime changes before it edits them. - [Codex quickstart: check what changed in your code](https://since.dev/guides/codex-quickstart.md)Add Since.dev to Codex with the plugin or codex mcp add, sign in with OAuth, and check your packages, AI models and runtimes for breaking changes. ## Put your code on continuous management. Scan a public repository now, or give your agent one line. ### See how out of date your code is. [Scan a repository](https://since.dev/scan.md). Any public GitHub repository. No sign-in. ### Tell your agent what changed since it was trained. `claude mcp add --transport http since https://api.since.dev/mcp` --- Every page on this site as Markdown: https://since.dev/sitemap.md. For agents: https://since.dev/llms.txt.