MCP OAuth tokens sit in plaintext on Linux
Anthropic’s MCP documentation says authentication tokens are “stored securely”. On Linux that currently means a plain JSON file, ~/.claude/.credentials.json, protected by file permissions and nothing more.
A write-up from the SecretSpec project checked Claude Code 2.1.257 after authenticating to several remote MCP servers. The file had mode 0600, as it should, but it also carried a top-level mcpOAuth object holding the access tokens.
Codex documents auto, file and keyring backends for MCP OAuth storage, where mcp_oauth_credentials_store = “keyring” picks the system keyring. Claude Code’s public repository doesn’t include the core CLI implementation and its license is all rights reserved.
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