PDF Case Review

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How Claude Code and Codex know who you are ​

This page explains the mechanism behind Use personal and school Claude accounts, and why the extension's consent dialog can name an email at all.

One directory per login ​

Claude Code keeps its login, settings and history in one directory: ~/.claude (on Windows, %USERPROFILE%\.claude). The CLAUDE_CONFIG_DIR environment variable points it at a different directory instead. Two directories, two independent logins: whichever one the variable names is the account that runs. Codex works the same way with CODEX_HOME, which relocates its ~/.codex directory (Codex does not create the directory for you; Claude Code does).

This is why switching accounts never has to mean logging out. A login is a directory, and choosing an account is choosing a directory: for one command, for one terminal, or for the whole computer.

Who reads the variable ​

The variable is read by whatever process starts the CLI, so where it is set decides who is affected:

  • Set for one command (CLAUDE_CONFIG_DIR=... claude), it affects that run only.
  • Exported in a terminal, it affects every CLI started from that terminal, including a VS Code launched from it with code ..
  • Stored at the user level (Windows) or in a shell profile (macOS and Linux), it becomes the default for the Claude Code VS Code extension and the desktop app, which read the environment they were launched with. On macOS, apps launched from the Dock or a launcher do not see shell variables, which is why the how-to launches VS Code from a terminal there.
  • PDF Case Review does not rely on any of these. When an ai.requiredAccount rule selects an ai.accounts entry, the extension sets CLAUDE_CONFIG_DIR or CODEX_HOME on the CLI it spawns, for that run only, so your terminal and the Claude Code chat panel are untouched.

The CLI stores the signed-in identity in that same directory. Before any excerpt is sent, the extension reads the email from the CLI's saved login (never by asking a model) and shows it in the consent dialog; a requiredAccount rule compares against it and refuses a mismatch with no override. The design record is ADR-0006 in Architecture decisions.