AX-Copilot/docs/claude-code-docs-main/en/configuration/environment-variables.md

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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

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-..."

Alternative authentication token. Used in contexts where `ANTHROPIC_API_KEY` is not applicable. 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-specific API base URL override. Takes precedence over `ANTHROPIC_BASE_URL` when set. Base URL for AWS Bedrock API access. Set this when routing Claude Code through a Bedrock endpoint. Google Cloud project ID for Vertex AI access. Required when using Claude Code through Google Cloud's Vertex AI platform. Set to `1` or `true` to use AWS Bedrock as the API provider. Set to `1` or `true` to use Anthropic Foundry as the API provider. OAuth access token to use for authentication directly, bypassing the interactive login flow. Useful for automated environments.

Configuration paths

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"

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

Model selection

Default model to use. Overridden by the `model` setting in settings files and by explicit `--model` flags. 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. Model to use when running in auto mode. Defaults to the main session model when not specified.

Behavior toggles

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

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. 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

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

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

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

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

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

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"

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

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

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

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