Codex quickstart: check what changed in your code

Install the plugin or the server

We suggest the plugin. It adds the MCP server plus four skills that tell Codex when to check. Add our marketplace from your shell:

codex plugin marketplace add since-dev/mcp

Then run /plugins in Codex and install Since.dev, or run codex plugin add since-dev@since-dev. It asks you to sign in as it installs. Start a new session afterwards so Codex loads its skills and tools (Codex plugin docs).

For the server alone:

codex mcp add since --url https://api.since.dev/mcp
codex mcp login since

Codex saves the server to ~/.codex/config.toml, which the CLI, the IDE extension and the desktop app share (Codex MCP docs).

Sign in with OAuth

codex mcp add starts the sign-in on its own when a server supports OAuth, as ours does, and codex mcp login since runs it again whenever you need to. In your browser, sign in to Since.dev (a free account works) and approve Codex for one workspace. No key is stored in a file.

• On a machine with no browser, add --no-browser to the login, open the printed URL elsewhere and paste the redirect URL back.
• In the IDE extension, open the gear menu and select MCP servers. In the desktop app, a server that needs sign-in shows Authenticate.
• In the CLI, /mcp lists your active servers. Ask Codex to list the since tools: whats_changed, check_code and fix_code.

Three things to ask first

The plugin suggests three starters, and they're good first asks. Every answer cites its source.

Check this repo's dependencies with Since.dev before we upgrade anything.

Codex sends the lockfile, or the manifest, to check_code. Each finding has a state, severity, file and line, days left, replacement and source. affected means your code uses the thing that changed. Fix those before the upgrade.

Which AI models in this code are retiring, and what replaces them?

Codex sends each file that names a model to check_code. OpenAI's API, Azure, Amazon Bedrock and Google Vertex AI each set their own dates, so the answer gives the date for the platform your code calls. A shortened example:

src/agent.py line 8: gpt-5
  status: deprecated
  shuts down: 2026-12-11 on OpenAI's API
  replacement: gpt-5.6-sol
  Azure: a later date

What changed in this package since my training cutoff?

Codex calls whats_changed with the package and since set to a date, a version or cutoff:<model>. You get each renamed or removed function, changed parameter and deprecation since then, linked to the publisher's page, so the code Codex writes matches the version you have.

Treat needs_review and unknown as not settled, never as safe.

What the plugin's skills add

Codex chooses a skill when your task matches its description, so checks happen without you asking. Run /skills or type $ to use one by name (Codex skills docs).

Approvals and fixes

fix_code writes. With a snippet it returns the patch, on Team and up. With a connected repository it opens fix pull requests, on Business and Platform. Fixes count against the month's fix pull requests, not credits.

If you added the server with codex mcp add, set its approval mode to writes. Codex then asks only before tools not marked read-only, which here means fix_code:

[mcp_servers.since]
url = "https://api.since.dev/mcp"
default_tools_approval_mode = "writes"

Use an API key for CI and headless runs

OAuth needs a browser. For CI, or codex exec where nobody can sign in, use a workspace API key:

1. In app.since.dev, pick the workspace, open API keys and choose Create API key. It starts with sc_live_ and is shown once.
2. Store it as a secret named SINCE_DEV_KEY and tell Codex to send it:

[mcp_servers.since]
url = "https://api.since.dev/mcp"
bearer_token_env_var = "SINCE_DEV_KEY"
required = true

Codex reads the key from the environment, so it stays out of the file. With required = true, codex exec stops with an error if the server can't start, instead of running without it (non-interactive mode). A key reaches only its own workspace. Never commit one.

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.

fix_code costs what its check costs, and a call that fails costs nothing (credits). Check a lockfile once, then ask about single packages. Prices change, see since.dev/#pricing.

Troubleshooting

• codex mcp list shows the servers you've configured. If since is missing, add it again.
• Calls fail with a sign-in error: run codex mcp login since. A 401 means the sign-in expired or the key isn't valid.
• The plugin's skills or tools don't appear: start a new session.
• With an API key, check that SINCE_DEV_KEY is set in the environment Codex runs in.
• 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, no sign-in needed.
• See every OpenAI date on the OpenAI retirement calendar.

Connect GitHub and, on Team and up, it opens fix pull requests for people to review. Nothing merges or deploys.

Questions

Does it work in the Codex IDE extension and desktop app?

Yes. The CLI, the IDE extension and the ChatGPT desktop app share one MCP config, so a server you add once shows up in all three.

Should I install the plugin or only the server?

The plugin. It adds the same server plus four skills, so Codex checks before upgrades, model changes and CI edits without being asked.

Can I use it with codex exec in CI?

Yes. Point bearer_token_env_var at a workspace API key and set required = true, so the run stops if the server can't connect.

Do I need a paid plan to use Since.dev in Codex?

No. whats_changed and check_code work on every plan, Free included. Fixes start on Team.

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