Claude Code environment variables: the ones we could verify on this Mac

Of 200+ documented variables, the practical subset a solo dev is likely to actually touch.

A practical subset of 200+ variables

Per the official docs (code.claude.com/docs/en/env-vars, fetched 2026-07-29), Claude Code supports 200+ environment variables. This article picks the ones a solo dev or small team is likely to actually use, with live verification where possible.

Auth & endpoint

`ANTHROPIC_API_KEY`, `ANTHROPIC_AUTH_TOKEN`, `ANTHROPIC_BASE_URL`, `ANTHROPIC_MODEL` — common when running your own proxy/gateway or using a direct API key.

Mode-switching flags, verified live

`--safe-mode` disables CLAUDE.md, skills, plugins, hooks and MCP servers, and sets `CLAUDE_CODE_SAFE_MODE=1`. On this Mac, a CLAUDE.md instruction was honored in normal mode but not under `--safe-mode`, and `echo $CLAUDE_CODE_SAFE_MODE` returned `1`.

$ claude -p "hello"
(CLAUDE.md instruction applied)

$ claude --safe-mode -p "hello, also echo $CLAUDE_CODE_SAFE_MODE"
$CLAUDE_CODE_SAFE_MODE = 1
(CLAUDE.md instruction NOT applied)

--bare sets CLAUDE_CODE_SIMPLE

Per `claude --help`, `--bare` skips hooks/LSP/plugin sync/auto-memory/keychain reads and sets `CLAUDE_CODE_SIMPLE=1` — handy for minimal CI runs.

Bash timeouts

`BASH_DEFAULT_TIMEOUT_MS` (120000ms default), `BASH_MAX_TIMEOUT_MS` (600000ms default), `BASH_MAX_OUTPUT_LENGTH` — relevant for long builds/tests.

Detecting a subprocess

`CLAUDECODE` and `CLAUDE_CODE_CHILD_SESSION` are set to `1` in processes spawned by Claude Code — useful in your own hook scripts.

FAQ

How many environment variables exist?

200+ per the official docs (fetched 2026-07-29); this article covers a practical subset.

What does --safe-mode change?

Verified live: it sets CLAUDE_CODE_SAFE_MODE=1 and CLAUDE.md rules stop applying.

How do I adjust Bash command timeouts?

BASH_DEFAULT_TIMEOUT_MS (120000ms default) and BASH_MAX_TIMEOUT_MS (600000ms default).

How do I detect I'm running inside Claude Code?

Check whether the CLAUDECODE environment variable is 1.

Where's the full list?

The official Environment variables docs page (code.claude.com/docs/en/env-vars).

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