6.6 Complete Environment Variable Reference

Based on exhaustive process.env.* scan from source. 70+ environment variables, grouped by function.

Usage

# one-shot
ANTHROPIC_MODEL=claude-opus-4-5 claude

# persistent shell config
echo 'export CLAUDE_CODE_DISABLE_THINKING=1' >> ~/.zshrc

# project-level .env
echo 'ANTHROPIC_BASE_URL=http://my-proxy.com' > .env

1) Core API config

Env varDescriptionExample
ANTHROPIC_API_KEYAnthropic API keysk-ant-...
ANTHROPIC_BASE_URLoverride API base URL (proxy/private deployment)https://my-proxy.com
ANTHROPIC_MODELoverride default modelclaude-opus-4-5
CLAUDE_CODE_API_BASE_URLoverride Files API base URLhttps://api.anthropic.com

2) Model and reasoning controls

Env varDescriptionDefault
CLAUDE_CODE_MAX_OUTPUT_TOKENSmaximum output tokensmodel limit
CLAUDE_CODE_DISABLE_THINKINGdisable Extended Thinkingfalse
CLAUDE_CODE_DISABLE_ADAPTIVE_THINKINGdisable adaptive thinking budgetfalse
CLAUDE_CODE_DISABLE_NONSTREAMING_FALLBACKdisable non-stream fallbackfalse
MAX_THINKING_TOKENSmax thinking tokens (ant-only)none
CLAUDE_CODE_DISABLE_FAST_MODEdisable fast modefalse

3) Functional mode switches

Env varDescription
CLAUDE_CODE_PROACTIVEenable Proactive mode (--proactive)
CLAUDE_CODE_COORDINATOR_MODEenable Coordinator mode
CLAUDE_CODE_BRIEFenable Brief mode (KAIROS)
CLAUDE_CODE_SIMPLESimple Worker mode (Coordinator)
CLAUDE_CODE_EMIT_TOOL_USE_SUMMARIESemit tool-use summaries
CLAUDE_CODE_ENABLE_PROMPT_SUGGESTIONprompt suggestion toggle (false disables)

4) Cloud provider integrations

Env varDescription
CLAUDE_CODE_USE_BEDROCKuse AWS Bedrock provider
CLAUDE_CODE_SKIP_BEDROCK_AUTHskip Bedrock auth checks
CLAUDE_CODE_USE_VERTEXuse Google Vertex AI
CLAUDE_CODE_SKIP_VERTEX_AUTHskip Vertex auth checks
CLAUDE_CODE_USE_FOUNDRYuse Foundry
CLAUDE_CODE_SKIP_FOUNDRY_AUTHskip Foundry auth checks
ANTHROPIC_FOUNDRY_API_KEYFoundry API key

5) Context compaction controls

Env varDescriptionDefault
CLAUDE_AUTOCOMPACT_PCT_OVERRIDEAutoCompact threshold override (%)auto (~85%)
CLAUDE_CODE_AUTO_COMPACT_WINDOWAutoCompact token window limitmodel limit
CLAUDE_NO_SESSION_PERSISTENCEdisable session persistencefalse

6) API extension and metadata

Env varDescriptionExample
CLAUDE_CODE_EXTRA_BODYappend JSON fields to request body{"betas":["..."]}
CLAUDE_CODE_EXTRA_METADATAappend request metadata JSON{"session_type":"dev"}
CLAUDE_CODE_ATTRIBUTION_HEADERattribution header contentarbitrary string
CLAUDE_CODE_ADDITIONAL_PROTECTIONenable additional safety headerstrue
CLAUDE_CODE_TAGStelemetry tagsproject=foo,env=dev
CLAUDE_AGENT_SDK_CLIENT_APPSDK client app identifierarbitrary string

7) Identity and authentication

Env varDescription
CLAUDE_CODE_OAUTH_TOKENprovide OAuth access token directly
CLAUDE_CODE_OAUTH_REFRESH_TOKENOAuth refresh token
CLAUDE_CODE_ACCOUNT_UUIDforce account UUID
CLAUDE_CODE_ORGANIZATION_UUIDforce organization UUID
CLAUDE_CODE_CUSTOM_OAUTH_URLcustom OAuth server URL

8) Performance and limits

Env varDescriptionDefault
CLAUDE_CODE_MAX_TOOL_USE_CONCURRENCYmax concurrent tool executions10
CLAUDE_CODE_IDLE_THRESHOLD_MINUTESidle timeout threshold75
CLAUDE_CODE_UNATTENDED_RETRYunattended auto-retry (UNATTENDED_RETRY gated)false

9) Memory and data

Env varDescription
CLAUDE_CODE_DISABLE_AUTO_MEMORYdisable EXTRACT_MEMORIES auto memory extraction
CLAUDE_CODE_CLIENT_CERTclient TLS cert path (enterprise mTLS)

10) UI and display

Env varDescriptionExample
CLAUDE_CODE_SYNTAX_HIGHLIGHTterminal syntax themeDracula
BAT_THEMEfallback highlight theme (bat)Monokai Extended
CLAUDE_CODE_USE_POWERSHELL_TOOLuse PowerShell tool (Windows)true/false

11) Telemetry and observability

Env varDescription
CLAUDE_CODE_DATADOG_FLUSH_INTERVAL_MSDataDog flush interval (ms)
CLAUDE_CODE_REMOTEmark remote runtime (adjust timeout profile)
CLAUDE_CODE_REMOTE_ENVIRONMENT_TYPEremote environment type
CLAUDE_CODE_REMOTE_SESSION_IDremote session ID
CLAUDE_CODE_CONTAINER_IDcontainer ID
CLAUDE_CODE_HOST_PLATFORMoverride host platform (darwin/linux/win32)
CLAUDE_CODE_COWORKER_TYPEcoworker type telemetry marker
CLAUDE_CODE_ACTIONmark as Claude Code Action run
GITHUB_ACTIONSstandard GitHub Actions marker
CLAUBBITinternal Claubbit marker

12) Runtime entrypoint and mode

Env varDescriptionValues
CLAUDE_CODE_ENTRYPOINTruntime entrypoint markercli / local-agent / sdk
CLAUDE_JOB_DIRjob directory for stop-hook task classifierpath

13) Sub-agent and multi-agent

Env varDescription
CLAUDE_CODE_PARENT_SESSION_IDparent session ID for sub-agents
CLAUDE_CODE_MESSAGING_SOCKET_PATHUnix Domain Socket path (UDS_INBOX)

14) Internal-only (USER_TYPE=ant)

Env varDescription
USER_TYPEuser type (external in public build, ant internal)
CLAUDE_INTERNAL_FC_OVERRIDESGrowthBook override JSON
CLAUDE_CODE_GB_BASE_URLoverride GrowthBook API base URL
ULTRAPLAN_PROMPT_FILEoverride Ultraplan prompt file path
SESSION_INGRESS_URLoverride session ingress URL
IS_DEMOdemo mode marker
CLAUBBITinternal Claubbit marker

15) Standard third-party env vars consumed by Claude Code

Env varDescription
ANTHROPIC_BASE_URLAnthropic SDK standard base URL
NODE_ENVruntime environment
HOME / USERPROFILEhome directory resolution
SHELLshell detection
TERMterminal capability detection

Env vars vs CLI flags

Some env vars correspond to CLI flags:

Env varEquivalent CLI
CLAUDE_CODE_PROACTIVE=1--proactive
CLAUDE_CODE_COORDINATOR_MODE=1no direct flag (env-only)
CLAUDE_NO_SESSION_PERSISTENCE=1--no-session-persistence (where available)
ANTHROPIC_MODEL=xxx--model xxx
ANTHROPIC_BASE_URL=xxx--base-url xxx (selected contexts)

Common debugging combinations

# switch to Opus and disable thinking
ANTHROPIC_MODEL=claude-opus-4-5 CLAUDE_CODE_DISABLE_THINKING=1 claude

# use proxy + larger output budget
ANTHROPIC_BASE_URL=http://localhost:8080 CLAUDE_CODE_MAX_OUTPUT_TOKENS=8192 claude

# fully disable persistence (headless testing)
CLAUDE_NO_SESSION_PERSISTENCE=1 claude -p "hello"

# internal GB override
CLAUDE_INTERNAL_FC_OVERRIDES='{"tengu_kairos": true}' claude

# use AWS Bedrock
CLAUDE_CODE_USE_BEDROCK=1 ANTHROPIC_MODEL=us.anthropic.claude-opus-4-5-20251101-v1:0 claude

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