Environment variables

Environment variables that Claude Code reads to configure authentication, API access, behavior, and runtime options.

Claude Code reads environment variables at startup. These variables let you configure authentication, point to custom API endpoints, tune runtime behavior, and control which features are active — without modifying settings files.

Authentication

ANTHROPIC_API_KEY · string

API key for authenticating directly with the Anthropic API. When set, Claude Code uses this key instead of (or in addition to) OAuth credentials. Takes priority over OAuth when present in most contexts.

export ANTHROPIC_API_KEY="sk-ant-..."

ANTHROPIC_AUTH_TOKEN · string

Alternative authentication token. Used in contexts where ANTHROPIC_API_KEY is not applicable.

ANTHROPIC_BASE_URL · string

Override the Anthropic API base URL. Useful for pointing Claude Code at a proxy, staging environment, or compatible third-party endpoint.

export ANTHROPIC_BASE_URL="https://my-proxy.example.com"

CLAUDE_CODE_API_BASE_URL · string

Claude Code-specific API base URL override. Takes precedence over ANTHROPIC_BASE_URL when set.

ANTHROPIC_BEDROCK_BASE_URL · string

Base URL for AWS Bedrock API access. Set this when routing Claude Code through a Bedrock endpoint.

ANTHROPIC_VERTEX_PROJECT_ID · string

Google Cloud project ID for Vertex AI access. Required when using Claude Code through Google Cloud’s Vertex AI platform.

CLAUDE_CODE_USE_BEDROCK · string

Set to 1 or true to use AWS Bedrock as the API provider.

CLAUDE_CODE_USE_FOUNDRY · string

Set to 1 or true to use Anthropic Foundry as the API provider.

CLAUDE_CODE_OAUTH_TOKEN · string

OAuth access token to use for authentication directly, bypassing the interactive login flow. Useful for automated environments.

Configuration paths

CLAUDE_CONFIG_DIR · string · default: "~/.claude"

Override the directory where Claude Code stores its configuration, settings, and transcripts. Defaults to ~/.claude in your home directory.

export CLAUDE_CONFIG_DIR="/opt/claude-config"

CLAUDE_CODE_MANAGED_SETTINGS_PATH · string

Override the path to the managed settings file. Useful in enterprise environments where the default platform path is not appropriate.

Model selection

ANTHROPIC_MODEL · string

Default model to use. Overridden by the model setting in settings files and by explicit --model flags.

CLAUDE_CODE_SUBAGENT_MODEL · string

Model to use for sub-agent tasks spawned by the main agent. When not set, sub-agents use the same model as the main session.

CLAUDE_CODE_AUTO_MODE_MODEL · string

Model to use when running in auto mode. Defaults to the main session model when not specified.

Behavior toggles

CLAUDE_CODE_REMOTE · string

Set to 1 or true to enable remote/container mode. In this mode, Claude Code adjusts its behavior for non-interactive environments — extended API timeouts (120s vs. 300s), suppressed interactive prompts, and adapted output formatting.

export CLAUDE_CODE_REMOTE=1

CLAUDE_CODE_SIMPLE · string

Set to 1 or true (or pass --bare) to run in bare mode. Bare mode skips hooks, LSP integration, plugin sync, skill directory walks, attribution, background prefetches, and all keychain/credential reads. Authentication must be provided via ANTHROPIC_API_KEY or apiKeyHelper in --settings. Useful for lightweight scripted use.

DISABLE_AUTO_COMPACT · string

Set to 1 or true to disable automatic context compaction. When set, Claude Code will not compact the conversation context even when it approaches the model’s context limit.

export DISABLE_AUTO_COMPACT=1

CLAUDE_CODE_DISABLE_BACKGROUND_TASKS · boolean

Set to 1 or true to disable background task execution. When enabled, the run_in_background parameter is removed from Bash and PowerShell tools, and Claude cannot run shell commands as background processes.

CLAUDE_CODE_DISABLE_THINKING · string

Set to 1 or true to disable extended thinking for all API calls, regardless of model support.

CLAUDE_CODE_DISABLE_AUTO_MEMORY · string

Set to 1 or true to disable automatic memory. When disabled, Claude does not read from or write to the auto-memory directory. Set to 0 or false to explicitly enable it (useful when other conditions would disable it, such as bare mode).

Auto-memory is also disabled automatically in bare mode (CLAUDE_CODE_SIMPLE) and remote mode (CLAUDE_CODE_REMOTE) unless explicitly enabled.

CLAUDE_CODE_DISABLE_CLAUDE_MDS · string

Set to 1 or true to completely disable loading of all CLAUDE.md memory files. Claude will not read any CLAUDE.md, CLAUDE.local.md, or .claude/rules/*.md files.

CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC · string

Set to 1 or true to suppress analytics, telemetry, and other non-essential network requests.

CLAUDE_CODE_ADDITIONAL_DIRECTORIES_CLAUDE_MD · string

Set to 1 or true to load CLAUDE.md files from directories added via --add-dir. By default, additional directories do not have their CLAUDE.md files loaded.

CLAUDE_BASH_MAINTAIN_PROJECT_WORKING_DIR · string

Set to 1 or true to reset the working directory back to the original project root after each Bash command. Prevents one command from changing the CWD for subsequent commands.

Resource limits

CLAUDE_CODE_MAX_OUTPUT_TOKENS · number

Override the maximum number of output tokens per API response. When not set, Claude Code uses the model’s default maximum. Useful for controlling costs in automated workflows.

export CLAUDE_CODE_MAX_OUTPUT_TOKENS=4096

CLAUDE_CODE_MAX_CONTEXT_TOKENS · number

Override the maximum context window size. When set, Claude Code uses this value instead of the model’s reported context limit.

BASH_MAX_OUTPUT_LENGTH · number

Maximum number of characters captured from Bash command output. Output exceeding this limit is truncated. Useful for preventing very large command outputs from consuming context.

export BASH_MAX_OUTPUT_LENGTH=50000

API_TIMEOUT_MS · number

Override the API request timeout in milliseconds. Defaults to 300,000ms (5 minutes) for standard mode and 120,000ms (2 minutes) in remote mode.

export API_TIMEOUT_MS=60000

Telemetry and observability

CLAUDE_CODE_ENABLE_TELEMETRY · string

Set to 1 or true to enable OpenTelemetry export of traces, metrics, and logs. Requires additional OTEL configuration (endpoint, headers, etc.) to be set via standard OpenTelemetry environment variables.

export CLAUDE_CODE_ENABLE_TELEMETRY=1
export OTEL_EXPORTER_OTLP_ENDPOINT="https://otel.example.com"

CLAUDE_CODE_JSONL_TRANSCRIPT · string

Path to a file where Claude Code writes a JSONL transcript of the session. Each line is a JSON object representing a conversation event.

export CLAUDE_CODE_JSONL_TRANSCRIPT="/tmp/session.jsonl"

Node.js runtime

NODE_OPTIONS · string

Standard Node.js options passed to the runtime. Claude Code reads this to detect flags like --max-old-space-size and adjusts its behavior accordingly. Claude Code itself sets this internally to configure heap size for large sessions.

export NODE_OPTIONS="--max-old-space-size=4096"

Avoid setting NODE_OPTIONS to values that include code execution flags. Claude Code validates shell environments and treats some NODE_OPTIONS values as requiring confirmation before running Bash commands.

Host platform override

CLAUDE_CODE_HOST_PLATFORM · string

Override the reported host platform for analytics. Accepts "win32", "darwin", or "linux". Useful when Claude Code runs in a container (where process.platform reports the container OS) but the actual host platform differs.

export CLAUDE_CODE_HOST_PLATFORM=darwin

Cloud provider region overrides

Claude Code supports per-model Vertex AI region overrides. Set the corresponding environment variable to route a specific model to a different region.

Model prefix	Environment variable
claude-haiku-4-5	VERTEX_REGION_CLAUDE_HAIKU_4_5
claude-3-5-haiku	VERTEX_REGION_CLAUDE_3_5_HAIKU
claude-3-5-sonnet	VERTEX_REGION_CLAUDE_3_5_SONNET
claude-3-7-sonnet	VERTEX_REGION_CLAUDE_3_7_SONNET
claude-opus-4-1	VERTEX_REGION_CLAUDE_4_1_OPUS
claude-opus-4	VERTEX_REGION_CLAUDE_4_0_OPUS
claude-sonnet-4-6	VERTEX_REGION_CLAUDE_4_6_SONNET
claude-sonnet-4-5	VERTEX_REGION_CLAUDE_4_5_SONNET
claude-sonnet-4	VERTEX_REGION_CLAUDE_4_0_SONNET

# Route Opus 4 to a specific Vertex region
export VERTEX_REGION_CLAUDE_4_0_OPUS="us-central1"

The default Vertex region is controlled by CLOUD_ML_REGION (defaults to us-east5).

AWS credentials

For Bedrock access, Claude Code respects standard AWS credential environment variables:

AWS_REGION · string

AWS region for Bedrock API calls. Falls back to AWS_DEFAULT_REGION, then defaults to us-east-1.

AWS_DEFAULT_REGION · string

Fallback AWS region when AWS_REGION is not set.

Setting environment variables for all sessions

You can set environment variables that apply to every Claude Code session using the env field in your settings file, rather than setting them in your shell profile:

{
  "env": {
    "DISABLE_AUTO_COMPACT": "1",
    "BASH_MAX_OUTPUT_LENGTH": "30000"
  }
}

See Settings for documentation on the env field.