13* [Set environment variables](#set-environment-variables) in your shell or in a settings file13* [Set environment variables](#set-environment-variables) in your shell or in a settings file
14* [Check which value applies](#precedence) when a behavior can be set more than one way14* [Check which value applies](#precedence) when a behavior can be set more than one way
15* [Look up the variables Claude Code reads](#variables)15* [Look up the variables Claude Code reads](#variables)
16* [See which features stop working](#features-that-need-feature-flag-fetching) when a variable turns feature-flag fetching off
16 17
17## Set environment variables18## Set environment variables
18 19
143| `ANTHROPIC_BEDROCK_REGION_PREFIX` | Cross-region inference profile prefix (`us`, `eu`, `apac`, `jp`, `au`, or `global`) Claude Code tries first instead of the one derived from the AWS region. Ignored in AWS GovCloud regions. Requires Claude Code v2.1.224 or later. See [Amazon Bedrock](/docs/en/amazon-bedrock#cross-region-inference-profile-prefixes) |144| `ANTHROPIC_BEDROCK_REGION_PREFIX` | Cross-region inference profile prefix (`us`, `eu`, `apac`, `jp`, `au`, or `global`) Claude Code tries first instead of the one derived from the AWS region. Ignored in AWS GovCloud regions. Requires Claude Code v2.1.224 or later. See [Amazon Bedrock](/docs/en/amazon-bedrock#cross-region-inference-profile-prefixes) |
144| `ANTHROPIC_BEDROCK_SERVICE_TIER` | Amazon Bedrock [service tier](https://docs.aws.amazon.com/bedrock/latest/userguide/service-tiers-inference.html) (`default`, `flex`, or `priority`). Sent as the `X-Amzn-Bedrock-Service-Tier` header. See [Amazon Bedrock](/docs/en/amazon-bedrock#service-tiers) |145| `ANTHROPIC_BEDROCK_SERVICE_TIER` | Amazon Bedrock [service tier](https://docs.aws.amazon.com/bedrock/latest/userguide/service-tiers-inference.html) (`default`, `flex`, or `priority`). Sent as the `X-Amzn-Bedrock-Service-Tier` header. See [Amazon Bedrock](/docs/en/amazon-bedrock#service-tiers) |
145| `ANTHROPIC_BETAS` | Comma-separated list of additional `anthropic-beta` header values to include in API requests. Claude Code already sends the beta headers it needs; use this to opt into an [Anthropic API beta](https://platform.claude.com/docs/en/api/beta-headers) before Claude Code adds native support. Unlike the [`--betas` flag](/docs/en/cli-reference#cli-flags), which requires API key authentication, this variable works with all auth methods including Claude.ai subscription |146| `ANTHROPIC_BETAS` | Comma-separated list of additional `anthropic-beta` header values to include in API requests. Claude Code already sends the beta headers it needs; use this to opt into an [Anthropic API beta](https://platform.claude.com/docs/en/api/beta-headers) before Claude Code adds native support. Unlike the [`--betas` flag](/docs/en/cli-reference#cli-flags), which requires API key authentication, this variable works with all auth methods including Claude.ai subscription |
146| `ANTHROPIC_CUSTOM_HEADERS` | Custom headers to add to requests (`Name: Value` format, newline-separated for multiple headers) |147| `ANTHROPIC_CUSTOM_HEADERS` | Custom headers to add to requests (`Name: Value` format, newline-separated for multiple headers). If a name or value contains a character an HTTP header can't carry, such as a curly quote or a zero-width space, Claude Code fails the request with an error that identifies the pair by position. Requires Claude Code v2.1.227 or later. [Invalid request header value](/docs/en/errors#invalid-request-header-value) lists the exact character set and where the check runs |
147| `ANTHROPIC_CUSTOM_MODEL_OPTION` | Model ID to add as a custom entry in the `/model` picker. Use this to make a non-standard or gateway-specific model selectable without replacing built-in aliases. See [Model configuration](/docs/en/model-config#add-a-custom-model-option) |148| `ANTHROPIC_CUSTOM_MODEL_OPTION` | Model ID to add as a custom entry in the `/model` picker. Use this to make a non-standard or gateway-specific model selectable without replacing built-in aliases. See [Model configuration](/docs/en/model-config#add-a-custom-model-option) |
148| `ANTHROPIC_CUSTOM_MODEL_OPTION_DESCRIPTION` | Display description for the custom model entry in the `/model` picker. Defaults to `Custom model (<model-id>)` when not set |149| `ANTHROPIC_CUSTOM_MODEL_OPTION_DESCRIPTION` | Display description for the custom model entry in the `/model` picker. Defaults to `Custom model (<model-id>)` when not set |
149| `ANTHROPIC_CUSTOM_MODEL_OPTION_NAME` | Display name for the custom model entry in the `/model` picker. Defaults to the model ID when not set |150| `ANTHROPIC_CUSTOM_MODEL_OPTION_NAME` | Display name for the custom model entry in the `/model` picker. Defaults to the model ID when not set |
193| `CLAUDE_AUTOCOMPACT_PCT_OVERRIDE` | Set the percentage (1-100) of the auto-compact window at which auto-compaction triggers. Use lower values like `50` to compact earlier; the variable can't raise the threshold, so values above the default percentage are ignored. It applies only in sessions that [compact before the model's context limit](/docs/en/model-config#context-window-and-auto-compaction). Applies to both main conversations and subagents |194| `CLAUDE_AUTOCOMPACT_PCT_OVERRIDE` | Set the percentage (1-100) of the auto-compact window at which auto-compaction triggers. Use lower values like `50` to compact earlier; the variable can't raise the threshold, so values above the default percentage are ignored. It applies only in sessions that [compact before the model's context limit](/docs/en/model-config#context-window-and-auto-compaction). Applies to both main conversations and subagents |
194| `CLAUDE_AUTO_BACKGROUND_TASKS` | Set to `1` to force-enable automatic backgrounding of long-running agent tasks. When enabled, subagents are moved to the background after running for approximately two minutes. Also enables [automatic backgrounding of long MCP tool calls](/docs/en/mcp#automatic-backgrounding-of-long-tool-calls) in non-interactive mode on Claude Code v2.1.212 or later |195| `CLAUDE_AUTO_BACKGROUND_TASKS` | Set to `1` to force-enable automatic backgrounding of long-running agent tasks. When enabled, subagents are moved to the background after running for approximately two minutes. Also enables [automatic backgrounding of long MCP tool calls](/docs/en/mcp#automatic-backgrounding-of-long-tool-calls) in non-interactive mode on Claude Code v2.1.212 or later |
195| `CLAUDE_AX_SCREEN_READER` | Set to `1` to render screen-reader friendly output: flat text without decorative borders or animations. Set to `0` to force screen-reader mode off even when [`axScreenReader`](/docs/en/settings#available-settings) is `true`. The [`--ax-screen-reader`](/docs/en/cli-reference#cli-flags) flag takes precedence. Requires Claude Code v2.1.181 or later |196| `CLAUDE_AX_SCREEN_READER` | Set to `1` to render screen-reader friendly output: flat text without decorative borders or animations. Set to `0` to force screen-reader mode off even when [`axScreenReader`](/docs/en/settings#available-settings) is `true`. The [`--ax-screen-reader`](/docs/en/cli-reference#cli-flags) flag takes precedence. Requires Claude Code v2.1.181 or later |
197| `CLAUDE_AX_STARTUP_QUIET_MS` | In [screen reader mode](/docs/en/accessibility), how many milliseconds Claude Code holds the first interface render after the startup confirmation line, so your screen reader can speak the line in full before new output interrupts it. Default `3000`. Set `0` to render immediately. Claude Code caps the hold at `600000` (10 minutes). Your first keystroke ends the hold early. Requires Claude Code v2.1.217 or later |
196| `CLAUDE_BASH_MAINTAIN_PROJECT_WORKING_DIR` | Return to the original working directory after each Bash or PowerShell command in the main session |198| `CLAUDE_BASH_MAINTAIN_PROJECT_WORKING_DIR` | Return to the original working directory after each Bash or PowerShell command in the main session |
197| `CLAUDE_BYTE_STREAM_IDLE_TIMEOUT_MS` | Timeout in milliseconds for the byte-level streaming idle watchdog only; when set, it takes precedence over `CLAUDE_STREAM_IDLE_TIMEOUT_MS` for that watchdog and leaves the event-level watchdog unchanged. Claude Code clamps this variable to between 10 seconds and 30 minutes. Requires Claude Code v2.1.210 or later |199| `CLAUDE_BYTE_STREAM_IDLE_TIMEOUT_MS` | Timeout in milliseconds for the byte-level streaming idle watchdog only; when set, it takes precedence over `CLAUDE_STREAM_IDLE_TIMEOUT_MS` for that watchdog and leaves the event-level watchdog unchanged. Claude Code clamps this variable to between 10 seconds and 30 minutes. Requires Claude Code v2.1.210 or later |
198| `CLAUDE_CLIENT_PRESENCE_FILE` | Path to a file that an external tool, such as a screen-lock listener, creates when you unlock your screen and deletes when you lock it. While the file exists, Claude Code skips [Remote Control mobile push notifications](/docs/en/remote-control#mobile-push-notifications), so you stop getting pushes while you are actively using the computer. When the file is absent or unreadable, notifications are sent as normal. Claude Code checks the file once per push-triggering event rather than polling it. Requires Claude Code v2.1.181 or later |200| `CLAUDE_CLIENT_PRESENCE_FILE` | Path to a file that an external tool, such as a screen-lock listener, creates when you unlock your screen and deletes when you lock it. While the file exists, Claude Code skips [Remote Control mobile push notifications](/docs/en/remote-control#mobile-push-notifications), so you stop getting pushes while you are actively using the computer. When the file is absent or unreadable, notifications are sent as normal. Claude Code checks the file once per push-triggering event rather than polling it. Requires Claude Code v2.1.181 or later |
229| `CLAUDE_CODE_DISABLE_BG_EXIT_HANDOFF` | Set to `1` to stop a [background session's](/docs/en/agent-view) running background shell commands, dynamic workflows, and, as of v2.1.198, background subagents when the [supervisor](/docs/en/agent-view#the-supervisor-process) stops, restarts, or updates that session's process, instead of handing them to the session's next process. Affects only that handoff: backgrounding a session with `←` or [`/background`](/docs/en/agent-view#from-inside-a-session) still carries in-flight work over, and `CLAUDE_DISABLE_ADOPT` turns off both. Requires Claude Code v2.1.196 or later |231| `CLAUDE_CODE_DISABLE_BG_EXIT_HANDOFF` | Set to `1` to stop a [background session's](/docs/en/agent-view) running background shell commands, dynamic workflows, and, as of v2.1.198, background subagents when the [supervisor](/docs/en/agent-view#the-supervisor-process) stops, restarts, or updates that session's process, instead of handing them to the session's next process. Affects only that handoff: backgrounding a session with `←` or [`/background`](/docs/en/agent-view#from-inside-a-session) still carries in-flight work over, and `CLAUDE_DISABLE_ADOPT` turns off both. Requires Claude Code v2.1.196 or later |
230| `CLAUDE_CODE_DISABLE_BG_SHELL_PRESSURE_REAP` | Set to `1` to stop Claude Code from terminating [background shell commands](/docs/en/interactive-mode#background-bash-commands) when the operating system reports memory pressure. By default, on macOS and Linux, Claude Code terminates a background shell started in the main session on a memory-pressure signal once the session has been idle for 30 minutes and no turn or subagent is running. Windows has no memory-pressure signal, so this variable has no effect there. Requires Claude Code v2.1.193 or later |232| `CLAUDE_CODE_DISABLE_BG_SHELL_PRESSURE_REAP` | Set to `1` to stop Claude Code from terminating [background shell commands](/docs/en/interactive-mode#background-bash-commands) when the operating system reports memory pressure. By default, on macOS and Linux, Claude Code terminates a background shell started in the main session on a memory-pressure signal once the session has been idle for 30 minutes and no turn or subagent is running. Windows has no memory-pressure signal, so this variable has no effect there. Requires Claude Code v2.1.193 or later |
231| `CLAUDE_CODE_DISABLE_BUNDLED_SKILLS` | Set to `1` to disable the [skills](/docs/en/skills) and workflows included with Claude Code: bundled skills and workflows are removed entirely, while built-in commands like `/init` stay typable but are hidden from the model. `/doctor` stays typable like the built-in commands; hide it with `DISABLE_DOCTOR_COMMAND` instead. Skills from plugins, `.claude/skills/`, and `.claude/commands/` are unaffected. Equivalent to the [`disableBundledSkills`](/docs/en/settings#available-settings) setting |233| `CLAUDE_CODE_DISABLE_BUNDLED_SKILLS` | Set to `1` to disable the [skills](/docs/en/skills) and workflows included with Claude Code: bundled skills and workflows are removed entirely, while built-in commands like `/init` stay typable but are hidden from the model. `/doctor` stays typable like the built-in commands; hide it with `DISABLE_DOCTOR_COMMAND` instead. Skills from plugins, `.claude/skills/`, and `.claude/commands/` are unaffected. Equivalent to the [`disableBundledSkills`](/docs/en/settings#available-settings) setting |
232| `CLAUDE_CODE_DISABLE_CLAUDE_MDS` | Set to `1` to prevent loading any CLAUDE.md memory files into context, including user, project, and auto-memory files |234| `CLAUDE_CODE_DISABLE_CLAUDE_MDS` | Set to `1` to prevent loading any CLAUDE.md memory files into context, including user, project, and auto memory files |
233| `CLAUDE_CODE_DISABLE_CRON` | Set to `1` to disable [scheduled tasks](/docs/en/scheduled-tasks). The `/loop` skill and cron tools become unavailable and any already-scheduled tasks stop firing, including tasks that are already running mid-session |235| `CLAUDE_CODE_DISABLE_CRON` | Set to `1` to disable [scheduled tasks](/docs/en/scheduled-tasks). The `/loop` skill and cron tools become unavailable and any already-scheduled tasks stop firing, including tasks that are already running mid-session |
234| `CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS` | Set to `1` to strip Anthropic-specific `anthropic-beta` request headers and beta tool-schema fields (such as `defer_loading` and `eager_input_streaming`) from API requests. Use this when a proxy gateway rejects requests with errors like "Unexpected value(s) for the `anthropic-beta` header" or "Extra inputs are not permitted". Standard fields (`name`, `description`, `input_schema`, `cache_control`) are preserved. [MCP tool search](/docs/en/mcp#scale-with-mcp-tool-search) is disabled and all MCP tools load upfront, even when you set `ENABLE_TOOL_SEARCH`. On Claude Code v2.1.227 or later, [managed settings](/docs/en/settings#settings-files) can keep tool search on. [Disable pre-release capabilities](/docs/en/llm-gateway-protocol#disable-pre-release-capabilities) covers where the override applies |236| `CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS` | Set to `1` to strip Anthropic-specific `anthropic-beta` request headers and beta tool-schema fields (such as `defer_loading` and `eager_input_streaming`) from API requests. Use this when a proxy gateway rejects requests with errors like "Unexpected value(s) for the `anthropic-beta` header" or "Extra inputs are not permitted". Standard fields (`name`, `description`, `input_schema`, `cache_control`) are preserved. [MCP tool search](/docs/en/mcp#scale-with-mcp-tool-search) is disabled and all MCP tools load upfront, even when you set `ENABLE_TOOL_SEARCH`. On Claude Code v2.1.227 or later, [managed settings](/docs/en/settings#settings-files) can keep tool search on. [Disable pre-release capabilities](/docs/en/llm-gateway-protocol#disable-pre-release-capabilities) covers where the override applies |
235| `CLAUDE_CODE_DISABLE_EXPLORE_PLAN_AGENTS` | Set to `1` to disable the built-in [Explore and Plan subagents](/docs/en/sub-agents#built-in-subagents). Claude explores with its search tools or the general-purpose subagent instead, and [plan mode](/docs/en/permission-modes#analyze-before-you-edit-with-plan-mode) reads files directly rather than launching Explore and Plan agents. Custom subagents named `Explore` or `Plan` are unaffected. To remove every built-in subagent type in the Agent SDK or non-interactive mode, use `CLAUDE_AGENT_SDK_DISABLE_BUILTIN_AGENTS` instead. Requires Claude Code v2.1.198 or later |237| `CLAUDE_CODE_DISABLE_EXPLORE_PLAN_AGENTS` | Set to `1` to disable the built-in [Explore and Plan subagents](/docs/en/sub-agents#built-in-subagents). Claude explores with its search tools or the general-purpose subagent instead, and [plan mode](/docs/en/permission-modes#analyze-before-you-edit-with-plan-mode) reads files directly rather than launching Explore and Plan agents. Custom subagents named `Explore` or `Plan` are unaffected. To remove every built-in subagent type in the Agent SDK or non-interactive mode, use `CLAUDE_AGENT_SDK_DISABLE_BUILTIN_AGENTS` instead. Requires Claude Code v2.1.198 or later |
240| `CLAUDE_CODE_DISABLE_LEGACY_MODEL_REMAP` | Set to `1` to prevent automatic remapping of Opus 4.0 and 4.1 to the current Opus version on the Anthropic API. Use when you intentionally want to pin an older model. The remap does not run on Amazon Bedrock, Google Cloud's Agent Platform, or Microsoft Foundry |242| `CLAUDE_CODE_DISABLE_LEGACY_MODEL_REMAP` | Set to `1` to prevent automatic remapping of Opus 4.0 and 4.1 to the current Opus version on the Anthropic API. Use when you intentionally want to pin an older model. The remap does not run on Amazon Bedrock, Google Cloud's Agent Platform, or Microsoft Foundry |
241| `CLAUDE_CODE_DISABLE_MOUSE` | Set to `1` to disable mouse tracking in [fullscreen rendering](/docs/en/fullscreen). Keyboard scrolling with `PgUp` and `PgDn` still works. Use this to keep your terminal's native copy-on-select behavior |243| `CLAUDE_CODE_DISABLE_MOUSE` | Set to `1` to disable mouse tracking in [fullscreen rendering](/docs/en/fullscreen). Keyboard scrolling with `PgUp` and `PgDn` still works. Use this to keep your terminal's native copy-on-select behavior |
242| `CLAUDE_CODE_DISABLE_MOUSE_CLICKS` | Set to `1` to disable click, drag, and hover handling in [fullscreen rendering](/docs/en/fullscreen) while keeping mouse-wheel scrolling. Use this when you want wheel scroll to work inside Claude Code but don't want clicks to position the cursor, expand tool output, or open links. `CLAUDE_CODE_DISABLE_MOUSE` takes precedence when both are set. Requires Claude Code v2.1.195 or later |244| `CLAUDE_CODE_DISABLE_MOUSE_CLICKS` | Set to `1` to disable click, drag, and hover handling in [fullscreen rendering](/docs/en/fullscreen) while keeping mouse-wheel scrolling. Use this when you want wheel scroll to work inside Claude Code but don't want clicks to position the cursor, expand tool output, or open links. `CLAUDE_CODE_DISABLE_MOUSE` takes precedence when both are set. Requires Claude Code v2.1.195 or later |
243| `CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC` | Set to any non-empty value, such as `1`, to disable nonessential network traffic: auto-updates, telemetry, error reporting, the `/feedback` command, release notes, [gateway model discovery](/docs/en/llm-gateway-connect#add-gateway-models-to-the-model-picker) refreshes, and availability checks such as the [fast mode](/docs/en/fast-mode#use-fast-mode-behind-proxies-and-llm-gateways) check. **Setting it to `0` or `false` still disables this traffic**, unlike most on/off variables; unset the variable to allow it again. Also disables feature-flag fetching, which makes [Remote Control](/docs/en/remote-control#requirements) and [cross-session messaging](/docs/en/cross-session-messaging#availability) unavailable. Official plugin marketplace auto-install isn't covered; disable it with `CLAUDE_CODE_DISABLE_OFFICIAL_MARKETPLACE_AUTOINSTALL` |245| `CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC` | Set to any non-empty value, such as `1`, to disable nonessential network traffic: auto-updates, telemetry, error reporting, the `/feedback` command, release notes, [gateway model discovery](/docs/en/llm-gateway-connect#add-gateway-models-to-the-model-picker) refreshes, and availability checks such as the [fast mode](/docs/en/fast-mode#use-fast-mode-behind-proxies-and-llm-gateways) check. **Setting it to `0` or `false` still disables this traffic**, unlike most on/off variables; unset the variable to allow it again. Also disables feature-flag fetching, which makes [Remote Control](/docs/en/remote-control#requirements) and the other [features that need feature-flag fetching](#features-that-need-feature-flag-fetching) unavailable. Official plugin marketplace auto-install isn't covered; disable it with `CLAUDE_CODE_DISABLE_OFFICIAL_MARKETPLACE_AUTOINSTALL` |
244| `CLAUDE_CODE_DISABLE_NONSTREAMING_FALLBACK` | Set to `1` to disable the non-streaming fallback when a streaming request fails mid-stream. Streaming errors propagate to the retry layer instead. Useful when a proxy or gateway causes the fallback to produce duplicate tool execution |246| `CLAUDE_CODE_DISABLE_NONSTREAMING_FALLBACK` | Set to `1` to disable the non-streaming fallback when a streaming request fails mid-stream. Streaming errors propagate to the retry layer instead. Useful when a proxy or gateway causes the fallback to produce duplicate tool execution |
245| `CLAUDE_CODE_DISABLE_NOTIFICATION_PRESENCE_CHECK` | Set to `1` to send the `PushNotification` tool's desktop notification even while you are typing in or focused on the terminal. By default the tool skips both the desktop notification and the [mobile push](/docs/en/remote-control#mobile-push-notifications) when it detects recent keyboard activity or terminal focus. This variable disables only that local check, so the server can still suppress the mobile push when it detects that you are active. Requires Claude Code v2.1.193 or later |247| `CLAUDE_CODE_DISABLE_NOTIFICATION_PRESENCE_CHECK` | Set to `1` to send the `PushNotification` tool's desktop notification even while you are typing in or focused on the terminal. By default the tool skips both the desktop notification and the [mobile push](/docs/en/remote-control#mobile-push-notifications) when it detects recent keyboard activity or terminal focus. This variable disables only that local check, so the server can still suppress the mobile push when it detects that you are active. Requires Claude Code v2.1.193 or later |
246| `CLAUDE_CODE_DISABLE_OFFICIAL_MARKETPLACE_AUTOINSTALL` | Set to `1` to disable automatic registration of the official plugin marketplace. Claude Code reads the variable when it is about to register the marketplace, usually during a machine's first interactive launch. If the variable is set at that point, Claude Code skips the registration permanently. Unsetting the variable later doesn't undo the skip. Run `claude plugin marketplace add anthropics/claude-plugins-official` to register the marketplace at any time |248| `CLAUDE_CODE_DISABLE_OFFICIAL_MARKETPLACE_AUTOINSTALL` | Set to `1` to disable automatic registration of the official plugin marketplace. Claude Code reads the variable when it is about to register the marketplace, usually during a machine's first interactive launch. If the variable is set at that point, Claude Code skips the registration permanently. Unsetting the variable later doesn't undo the skip. Run `claude plugin marketplace add anthropics/claude-plugins-official` to register the marketplace at any time |
291| `CLAUDE_CODE_MCP_ALLOWLIST_ENV` | Set to `1` to spawn stdio MCP servers with only a safe baseline environment plus the server's configured `env`, instead of inheriting your shell environment |293| `CLAUDE_CODE_MCP_ALLOWLIST_ENV` | Set to `1` to spawn stdio MCP servers with only a safe baseline environment plus the server's configured `env`, instead of inheriting your shell environment |
292| `CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS` | Elapsed time in milliseconds before a still-running MCP tool call [moves to a background task](/docs/en/mcp#automatic-backgrounding-of-long-tool-calls) (default: 120000, or 2 minutes). Set to `0` to turn automatic backgrounding off. Requires Claude Code v2.1.212 or later |294| `CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS` | Elapsed time in milliseconds before a still-running MCP tool call [moves to a background task](/docs/en/mcp#automatic-backgrounding-of-long-tool-calls) (default: 120000, or 2 minutes). Set to `0` to turn automatic backgrounding off. Requires Claude Code v2.1.212 or later |
293| `CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT` | Idle timeout in milliseconds for MCP tool calls. When a stdio, HTTP, SSE, WebSocket, or [claude.ai connector](/docs/en/mcp#use-mcp-servers-from-claude-ai) MCP server sends no response and no progress notification for this long, the tool call aborts with an error instead of waiting for the overall `MCP_TOOL_TIMEOUT`. Overrides the per-transport defaults of 300000 (5 minutes) for network servers and 1800000 (30 minutes) for stdio servers. Set to `0` to disable the idle check. Values below 1000 are raised to one second, and the value is capped at the effective `MCP_TOOL_TIMEOUT`. A per-server `timeout` in `.mcp.json` of at least 1000 raises that server's idle window to at least the `timeout` value. Doesn't apply to IDE servers or SDK in-process servers. Requires Claude Code v2.1.187 or later. Before v2.1.203, stdio servers were exempt from the idle timeout |295| `CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT` | Idle timeout in milliseconds for MCP tool calls. When a stdio, HTTP, SSE, WebSocket, or [claude.ai connector](/docs/en/mcp#use-mcp-servers-from-claude-ai) MCP server sends no response and no progress notification for this long, the tool call aborts with an error instead of waiting for the overall `MCP_TOOL_TIMEOUT`. Overrides the per-transport defaults of 300000 (5 minutes) for network servers and 1800000 (30 minutes) for stdio servers. Set to `0` to disable the idle check. Values below 1000 are raised to one second, and the value is capped at the effective `MCP_TOOL_TIMEOUT`. A per-server `timeout` in `.mcp.json` of at least 1000 raises that server's idle window to at least the `timeout` value. Doesn't apply to IDE servers or SDK in-process servers. Requires Claude Code v2.1.187 or later. Before v2.1.203, stdio servers were exempt from the idle timeout |
294| `CLAUDE_CODE_MESSAGING_SOCKET` | Set by Claude Code, not by you: in sessions that bind an [inbox socket](/docs/en/cross-session-messaging#the-sessions-inbox-socket), Claude Code exports that socket's path to hooks and Bash commands before any hook runs. Other sessions on the machine deliver messages to this path. Each session exports its own socket rather than one inherited from a parent, and messages arriving on it go through the session's [inbound controls](/docs/en/cross-session-messaging#control-inbound-messages). Settings `env` blocks can't set it. Requires Claude Code v2.1.224 or later |296| `CLAUDE_CODE_MESSAGING_SOCKET` | Set by Claude Code, not by you: in sessions that bind an [inbox socket](/docs/en/cross-session-messaging#the-sessions-inbox-socket), Claude Code exports that socket's path to hooks and Bash commands when it binds the socket. In a session that starts with messaging on, Claude Code binds the socket before any hook runs. Other sessions on the machine deliver messages to this path. Each session exports its own socket rather than one inherited from a parent, and messages arriving on it go through the session's [inbound controls](/docs/en/cross-session-messaging#control-inbound-messages). Settings `env` blocks can't set it. Requires Claude Code v2.1.224 or later |
297| `CLAUDE_CODE_MESSAGING_TOKEN` | Set by Claude Code, not by you: in sessions that bind an [inbox socket](/docs/en/cross-session-messaging#the-sessions-inbox-socket), Claude Code exports this per-session token to hooks and Bash commands alongside `CLAUDE_CODE_MESSAGING_SOCKET`. A script posting to the socket can send `{"type":"auth","token":"<token>"}` as its first line to prove it belongs to the session. The [own-child rules](/docs/en/cross-session-messaging#the-sessions-inbox-socket) say when Claude Code consults it. Each session exports its own token, never one inherited from a parent session. Settings `env` blocks can't set it. Requires Claude Code v2.1.228 or later |
295| `CLAUDE_CODE_NATIVE_CURSOR` | Set to `1` to show the terminal's own cursor at the input caret instead of a drawn block. The cursor respects the terminal's blink, shape, and focus settings |298| `CLAUDE_CODE_NATIVE_CURSOR` | Set to `1` to show the terminal's own cursor at the input caret instead of a drawn block. The cursor respects the terminal's blink, shape, and focus settings |
296| `CLAUDE_CODE_NEW_INIT` | Set to `1` to make `/init` run an interactive setup flow. The flow asks which files to generate, including CLAUDE.md, skills, and hooks, before exploring the codebase and writing them. Without this variable, `/init` generates a CLAUDE.md automatically without prompting |299| `CLAUDE_CODE_NEW_INIT` | Set to `1` to make `/init` run an interactive setup flow. The flow asks which files to generate, including CLAUDE.md, skills, and hooks, before exploring the codebase and writing them. Without this variable, `/init` generates a CLAUDE.md automatically without prompting |
297| `CLAUDE_CODE_NO_FLICKER` | Set to `1` to enable [fullscreen rendering](/docs/en/fullscreen), a research preview that reduces flicker and keeps memory flat in long conversations. Equivalent to the [`tui`](/docs/en/settings#available-settings) setting; you can also switch with `/tui fullscreen` |300| `CLAUDE_CODE_NO_FLICKER` | Set to `1` to enable [fullscreen rendering](/docs/en/fullscreen), a research preview that reduces flicker and keeps memory flat in long conversations. Equivalent to the [`tui`](/docs/en/settings#available-settings) setting; you can also switch with `/tui fullscreen` |
298| `CLAUDE_CODE_OAUTH_REFRESH_TOKEN` | OAuth refresh token for Claude.ai authentication. When set, `claude auth login` exchanges this token directly instead of opening a browser. Requires `CLAUDE_CODE_OAUTH_SCOPES`. Useful for provisioning authentication in automated environments |301| `CLAUDE_CODE_OAUTH_REFRESH_TOKEN` | OAuth refresh token for Claude.ai authentication. When set, `claude auth login` exchanges this token directly instead of opening a browser. Requires `CLAUDE_CODE_OAUTH_SCOPES`. Useful for provisioning authentication in automated environments |
299| `CLAUDE_CODE_OAUTH_SCOPES` | Space-separated OAuth scopes the refresh token was issued with, such as `"user:profile user:inference user:sessions:claude_code"`. Required when `CLAUDE_CODE_OAUTH_REFRESH_TOKEN` is set |302| `CLAUDE_CODE_OAUTH_SCOPES` | Space-separated OAuth scopes the refresh token was issued with, such as `"user:profile user:inference user:sessions:claude_code"`. Required when `CLAUDE_CODE_OAUTH_REFRESH_TOKEN` is set |
300| `CLAUDE_CODE_OAUTH_TOKEN` | OAuth access token for Claude.ai authentication. Alternative to `/login` for SDK and automated environments. Takes precedence over keychain-stored credentials. Generate one with [`claude setup-token`](/docs/en/authentication#generate-a-long-lived-token) |303| `CLAUDE_CODE_OAUTH_TOKEN` | OAuth access token for Claude.ai authentication. Alternative to `/login` for SDK and automated environments. Takes precedence over keychain-stored credentials. Generate one with [`claude setup-token`](/docs/en/authentication#generate-a-long-lived-token). Claude Code uses the token you set for the whole session. To replace an expired token, generate a new one and restart |
301| `CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE` | Removed in v2.1.160 and now a no-op. Previously pinned [fast mode](/docs/en/fast-mode) to Claude Opus 4.6 instead of the current default. Opus 4.6 no longer supports fast mode |304| `CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE` | Removed in v2.1.160 and now a no-op. Previously pinned [fast mode](/docs/en/fast-mode) to Claude Opus 4.6 instead of the current default. Opus 4.6 no longer supports fast mode |
302| `CLAUDE_CODE_OTEL_CONTENT_MAX_LENGTH` | Maximum length of content-bearing OpenTelemetry attributes (model responses, tool content, system prompts, raw API bodies), truncation marker included, in UTF-16 code units (default: 61440, i.e. 60 KB). Raise it only if your telemetry backend accepts attribute values larger than 64 KB, or lower it to cut telemetry volume. Requires Claude Code v2.1.214 or later. See [Monitoring](/docs/en/monitoring-usage) |305| `CLAUDE_CODE_OTEL_CONTENT_MAX_LENGTH` | Maximum length of content-bearing OpenTelemetry attributes (model responses, tool content, system prompts, raw API bodies), truncation marker included, in UTF-16 code units (default: 61440, i.e. 60 KB). Raise it only if your telemetry backend accepts attribute values larger than 64 KB, or lower it to cut telemetry volume. Requires Claude Code v2.1.214 or later. See [Monitoring](/docs/en/monitoring-usage) |
303| `CLAUDE_CODE_OTEL_DIAG_STDERR` | Set to `1` to write OpenTelemetry exporter diagnostic errors to stderr. By default these errors only appear with `--debug`, so a misconfigured exporter such as a Prometheus port collision otherwise fails silently. Requires Claude Code v2.1.179 or later. See [Monitoring](/docs/en/monitoring-usage) |306| `CLAUDE_CODE_OTEL_DIAG_STDERR` | Set to `1` to write OpenTelemetry exporter diagnostic errors to stderr. By default these errors only appear with `--debug`, so a misconfigured exporter such as a Prometheus port collision otherwise fails silently. Requires Claude Code v2.1.179 or later. See [Monitoring](/docs/en/monitoring-usage) |
323| `CLAUDE_CODE_RESUME_INTERRUPTED_TURN_MAX_AGE_MS` | Maximum age in milliseconds of the last transcript message for a session that ended mid-turn to continue automatically on resume. When the last message is older than this bound, Claude Code skips both the `CLAUDE_CODE_RESUME_INTERRUPTED_TURN` automatic resume and the injected `CLAUDE_CODE_RESUME_PROMPT` continuation message, and the session starts idle so you continue explicitly. Unset or `0` means no bound; a negative or non-numeric value applies a one-hour bound. Spawn scripts for long-running agents can set this so a restart against an old transcript doesn't re-run a stale prompt. Claude Code sets a one-hour bound itself when it restarts a crashed [agent view](/docs/en/agent-view) session that inherited its conversation from an interactive session. Requires Claude Code v2.1.211 or later |326| `CLAUDE_CODE_RESUME_INTERRUPTED_TURN_MAX_AGE_MS` | Maximum age in milliseconds of the last transcript message for a session that ended mid-turn to continue automatically on resume. When the last message is older than this bound, Claude Code skips both the `CLAUDE_CODE_RESUME_INTERRUPTED_TURN` automatic resume and the injected `CLAUDE_CODE_RESUME_PROMPT` continuation message, and the session starts idle so you continue explicitly. Unset or `0` means no bound; a negative or non-numeric value applies a one-hour bound. Spawn scripts for long-running agents can set this so a restart against an old transcript doesn't re-run a stale prompt. Claude Code sets a one-hour bound itself when it restarts a crashed [agent view](/docs/en/agent-view) session that inherited its conversation from an interactive session. Requires Claude Code v2.1.211 or later |
324| `CLAUDE_CODE_RESUME_PROMPT` | Override the continuation message injected when resuming a session that ended mid-turn. Defaults to `Continue from where you left off.`. Spawn scripts for long-running agents can set this to a more directive boot message. An empty string uses the default |327| `CLAUDE_CODE_RESUME_PROMPT` | Override the continuation message injected when resuming a session that ended mid-turn. Defaults to `Continue from where you left off.`. Spawn scripts for long-running agents can set this to a more directive boot message. An empty string uses the default |
325| `CLAUDE_CODE_RETRY_WATCHDOG` | Set to `1` for unattended sessions such as eval harnesses, CI jobs, or remote workers. Retries `429` and `529` capacity errors indefinitely instead of failing after `CLAUDE_CODE_MAX_RETRIES` attempts. The watchdog backs off up to 5 minutes between attempts, or until the limit resets when the response carries a rate-limit reset time, so a session that hits a usage limit waits out the remaining window. As of v2.1.199 it also raises the default retry count for other transient errors, such as server errors, timeouts, and dropped connections, to 300, roughly three hours of backoff, and removes the cap of 15 on `CLAUDE_CODE_MAX_RETRIES` if you set that variable explicitly. Requires Claude Code v2.1.186 or later |328| `CLAUDE_CODE_RETRY_WATCHDOG` | Set to `1` for unattended sessions such as eval harnesses, CI jobs, or remote workers. Retries `429` and `529` capacity errors indefinitely instead of failing after `CLAUDE_CODE_MAX_RETRIES` attempts. The watchdog backs off up to 5 minutes between attempts, or until the limit resets when the response carries a rate-limit reset time, so a session that hits a usage limit waits out the remaining window. As of v2.1.199 it also raises the default retry count for other transient errors, such as server errors, timeouts, and dropped connections, to 300, roughly three hours of backoff, and removes the cap of 15 on `CLAUDE_CODE_MAX_RETRIES` if you set that variable explicitly. Requires Claude Code v2.1.186 or later |
326| `CLAUDE_CODE_SAFE_MODE` | Set to `1` to start in safe mode: CLAUDE.md, skills, plugins, hooks, MCP servers, custom commands and agents, output styles, workflows, custom themes, custom keybindings, status line and file-suggestion commands, LSP servers, and auto-memory do not load, for troubleshooting a broken configuration. Managed settings policy still applies, including policy-configured hooks, status line, and file-suggestion commands; managed plugins, managed skills, managed CLAUDE.md, and policy-configured MCP servers do not. Equivalent to passing [`--safe-mode`](/docs/en/cli-reference#cli-flags). Directly spawned child processes inherit the variable |329| `CLAUDE_CODE_SAFE_MODE` | Set to `1` to start in safe mode: CLAUDE.md, skills, plugins, hooks, MCP servers, custom commands and agents, output styles, workflows, custom themes, custom keybindings, status line and file-suggestion commands, LSP servers, and auto memory do not load, for troubleshooting a broken configuration. Managed settings policy still applies, including policy-configured hooks, status line, and file-suggestion commands; managed plugins, managed skills, managed CLAUDE.md, and policy-configured MCP servers do not. Equivalent to passing [`--safe-mode`](/docs/en/cli-reference#cli-flags). Directly spawned child processes inherit the variable |
327| `CLAUDE_CODE_SCRIPT_CAPS` | JSON object limiting how many times specific scripts may be invoked per session when `CLAUDE_CODE_SUBPROCESS_ENV_SCRUB` is set. Keys are substrings matched against the command text; values are integer call limits. For example, `{"deploy.sh": 2}` allows `deploy.sh` to be called at most twice. Matching is substring-based so shell-expansion tricks like `./scripts/deploy.sh $(evil)` still count against the cap. Runtime fan-out via `xargs` or `find -exec` is not detected; this is a defense-in-depth control |330| `CLAUDE_CODE_SCRIPT_CAPS` | JSON object limiting how many times specific scripts may be invoked per session when `CLAUDE_CODE_SUBPROCESS_ENV_SCRUB` is set. Keys are substrings matched against the command text; values are integer call limits. For example, `{"deploy.sh": 2}` allows `deploy.sh` to be called at most twice. Matching is substring-based so shell-expansion tricks like `./scripts/deploy.sh $(evil)` still count against the cap. Runtime fan-out via `xargs` or `find -exec` is not detected; this is a defense-in-depth control |
328| `CLAUDE_CODE_SCROLL_SPEED` | Set the mouse wheel scroll multiplier in [fullscreen rendering](/docs/en/fullscreen#mouse-wheel-scrolling). Accepts any positive value up to 20, including fractional values below 1 such as `0.5` to slow accelerated trackpad and wheel scrolling in terminals that already amplify wheel events. Set to `3` to match `vim` if your terminal sends one wheel event per notch without amplification. Ignored in the JetBrains IDE terminal, where Claude Code uses its own scroll handling |331| `CLAUDE_CODE_SCROLL_SPEED` | Set the mouse wheel scroll multiplier in [fullscreen rendering](/docs/en/fullscreen#mouse-wheel-scrolling). Accepts any positive value up to 20, including fractional values below 1 such as `0.5` to slow accelerated trackpad and wheel scrolling in terminals that already amplify wheel events. Set to `3` to match `vim` if your terminal sends one wheel event per notch without amplification. Ignored in the JetBrains IDE terminal, where Claude Code uses its own scroll handling |
329| `CLAUDE_CODE_SESSIONEND_HOOKS_TIMEOUT_MS` | Override the time budget in milliseconds for [SessionEnd](/docs/en/hooks#sessionend) hooks. Applies to session exit, `/clear`, and switching sessions via interactive `/resume`. By default the budget is 1.5 seconds, automatically raised to the highest per-hook `timeout` configured in settings files, up to 60 seconds. Timeouts on plugin-provided hooks do not raise the budget |332| `CLAUDE_CODE_SESSIONEND_HOOKS_TIMEOUT_MS` | Override the time budget in milliseconds for [SessionEnd](/docs/en/hooks#sessionend) hooks. Applies to session exit, `/clear`, and switching sessions via interactive `/resume`. By default the budget is 1.5 seconds, automatically raised to the highest per-hook `timeout` configured in settings files, up to 60 seconds. Timeouts on plugin-provided hooks do not raise the budget |
346| `CLAUDE_CODE_SUBPROCESS_ENV_SCRUB` | Set to `1` to strip Anthropic and cloud provider credentials from subprocess environments (Bash tool, hooks, MCP stdio servers). The parent Claude process keeps these credentials for API calls, but child processes cannot read them, reducing exposure to prompt injection attacks that attempt to exfiltrate secrets via shell expansion. On Linux, this also runs Bash subprocesses in an isolated PID namespace so they cannot read host process environments via `/proc`; as a side effect, `ps`, `pgrep`, and `kill` cannot see or signal host processes. `claude-code-action` sets this automatically when `allowed_non_write_users` is configured |349| `CLAUDE_CODE_SUBPROCESS_ENV_SCRUB` | Set to `1` to strip Anthropic and cloud provider credentials from subprocess environments (Bash tool, hooks, MCP stdio servers). The parent Claude process keeps these credentials for API calls, but child processes cannot read them, reducing exposure to prompt injection attacks that attempt to exfiltrate secrets via shell expansion. On Linux, this also runs Bash subprocesses in an isolated PID namespace so they cannot read host process environments via `/proc`; as a side effect, `ps`, `pgrep`, and `kill` cannot see or signal host processes. `claude-code-action` sets this automatically when `allowed_non_write_users` is configured |
347| `CLAUDE_CODE_SYNC_PLUGIN_INSTALL` | Set to `1` in non-interactive mode (the `-p` flag) to wait for plugin installation to complete before the first query. Without this, plugins install in the background and may not be available on the first turn. Combine with `CLAUDE_CODE_SYNC_PLUGIN_INSTALL_TIMEOUT_MS` to bound the wait |350| `CLAUDE_CODE_SYNC_PLUGIN_INSTALL` | Set to `1` in non-interactive mode (the `-p` flag) to wait for plugin installation to complete before the first query. Without this, plugins install in the background and may not be available on the first turn. Combine with `CLAUDE_CODE_SYNC_PLUGIN_INSTALL_TIMEOUT_MS` to bound the wait |
348| `CLAUDE_CODE_SYNC_PLUGIN_INSTALL_TIMEOUT_MS` | Timeout in milliseconds for synchronous plugin installation. When exceeded, Claude Code proceeds without plugins and logs an error. No default: without this variable, synchronous installation waits until complete |351| `CLAUDE_CODE_SYNC_PLUGIN_INSTALL_TIMEOUT_MS` | Timeout in milliseconds for synchronous plugin installation. When exceeded, Claude Code proceeds without plugins and logs an error. No default: without this variable, synchronous installation waits until complete |
349| `CLAUDE_CODE_SYNC_SKILLS` | Set to `1` to download your enabled claude.ai skills into `~/.claude/skills/synced/` before the first query and resync every 10 minutes. The `synced` folder name is [reserved for this download](/docs/en/skills#where-skills-live). Before v2.1.227, the skills downloaded into `~/.claude/skills/` directly. Applies only in non-interactive mode with the `-p` flag. Requires claude.ai authentication. [Claude Code on the web](/docs/en/claude-code-on-the-web) sessions receive your enabled claude.ai skills automatically; you don't need to set this there |352| `CLAUDE_CODE_SYNC_SKILLS` | Set to `1` to download your enabled claude.ai skills into `~/.claude/skills/synced/` and resync every 10 minutes. Before it runs the first query, Claude Code waits up to `CLAUDE_CODE_SYNC_SKILLS_WAIT_TIMEOUT_MS` for the list of your skills. The downloads themselves finish in the background, and Claude waits for a skill's download when it invokes that skill. The `synced` folder name is [reserved for this download](/docs/en/skills#where-skills-live). Before v2.1.227, the skills downloaded into `~/.claude/skills/` directly. Applies only in non-interactive mode with the `-p` flag. Requires claude.ai authentication. [Claude Code on the web](/docs/en/claude-code-on-the-web) sessions receive your enabled claude.ai skills automatically; you don't need to set this there. Claude Code applies [extra rules to the downloaded skills](/docs/en/skills#how-synced-skills-behave), such as not running their `!` commands on your machine |
350| `CLAUDE_CODE_SYNC_SKILLS_INSTALL_TIMEOUT_MS` | Timeout in milliseconds for a mid-session skills resync when `CLAUDE_CODE_SYNC_SKILLS` is set (default: 30000). Bounds the download triggered when the host requests a skill reload during the session. When exceeded, the resync stops and remaining downloads continue in the background |353| `CLAUDE_CODE_SYNC_SKILLS_INSTALL_TIMEOUT_MS` | Timeout in milliseconds for a mid-session skills resync when `CLAUDE_CODE_SYNC_SKILLS` is set (default: 30000). Bounds the download triggered when the host requests a skill reload during the session. When exceeded, the resync stops and remaining downloads continue in the background |
351| `CLAUDE_CODE_SYNC_SKILLS_WAIT_TIMEOUT_MS` | Timeout in milliseconds for the first query to wait on the initial skills sync when `CLAUDE_CODE_SYNC_SKILLS` is set (default: 5000). When exceeded, the query proceeds and remaining skill downloads continue in the background |354| `CLAUDE_CODE_SYNC_SKILLS_WAIT_TIMEOUT_MS` | Timeout in milliseconds for the first query to wait for the initial skill list when `CLAUDE_CODE_SYNC_SKILLS` is set (default: 5000). When exceeded, the first query runs with whichever skills have arrived. The downloads finish in the background either way, and Claude waits for a skill's download when it invokes that skill |
352| `CLAUDE_CODE_SYNTAX_HIGHLIGHT` | Set to `false` to disable syntax highlighting in diff output. Useful when colors interfere with your terminal setup. To also disable highlighting in code blocks and file previews, use the [`syntaxHighlightingDisabled`](/docs/en/settings) setting |355| `CLAUDE_CODE_SYNTAX_HIGHLIGHT` | Set to `false` to disable syntax highlighting in diff output. Useful when colors interfere with your terminal setup. To also disable highlighting in code blocks and file previews, use the [`syntaxHighlightingDisabled`](/docs/en/settings) setting |
353| `CLAUDE_CODE_TASK_LIST_ID` | Share a task list across sessions. Set the same ID in multiple Claude Code instances to coordinate on a shared task list. See [Task list](/docs/en/interactive-mode#task-list) |356| `CLAUDE_CODE_TASK_LIST_ID` | Share a task list across sessions. Set the same ID in multiple Claude Code instances to coordinate on a shared task list. See [Task list](/docs/en/interactive-mode#task-list) |
354| `CLAUDE_CODE_TEAM_TEARDOWN_PARK_TIMEOUT_MS` | Override, in milliseconds, how long a non-interactive session waits at exit for its [agent team](/docs/en/agent-teams) to finish tearing down. Accepts 1000 to 60000; an out-of-range value is ignored and the default of 10000 applies. Requires Claude Code v2.1.206 or later |357| `CLAUDE_CODE_TEAM_TEARDOWN_PARK_TIMEOUT_MS` | Override, in milliseconds, how long a non-interactive session waits at exit for its [agent team](/docs/en/agent-teams) to finish tearing down. Accepts 1000 to 60000; an out-of-range value is ignored and the default of 10000 applies. Requires Claude Code v2.1.206 or later |
355| `CLAUDE_CODE_TMPDIR` | Override the temp directory used for internal temp files. Claude Code appends `/claude-{uid}/` on Unix or `/claude/` on Windows to this path. Default: `/tmp` on macOS, `os.tmpdir()` on Linux and Windows. As of v2.1.161, on macOS and Linux, [sandboxed](/docs/en/sandboxing) Bash subprocesses receive a short fallback `$TMPDIR` under the system default when your override is a long path, since some tools fail when temp paths get too long. Unsandboxed Bash commands inherit your shell's `$TMPDIR` unchanged. Claude Code's own temp files always use your override |358| `CLAUDE_CODE_TMPDIR` | Override the temp directory used for internal temp files. Claude Code appends `/claude-{uid}/` on Unix or `/claude/` on Windows to this path. Default: `/tmp` on macOS, `os.tmpdir()` on Linux and Windows. As of v2.1.161, on macOS and Linux, [sandboxed](/docs/en/sandboxing) Bash subprocesses receive a short fallback `$TMPDIR` under the system default when your override is a long path, since some tools fail when temp paths get too long. Unsandboxed Bash commands inherit your shell's `$TMPDIR` unchanged. Claude Code's own temp files always use your override |
356| `CLAUDE_CODE_TMUX_TRUECOLOR` | Set to any non-empty value, such as `1`, to allow 24-bit truecolor output inside tmux. **Setting it to `0` or `false` still allows truecolor**, unlike most on/off variables; unset the variable to restore the 256-color clamp. By default, Claude Code clamps to 256 colors when `$TMUX` is set because tmux does not pass through truecolor escape sequences unless configured to. Set this after adding `set -ga terminal-overrides ',*:Tc'` to your `~/.tmux.conf`. See [Terminal configuration](/docs/en/terminal-config) for other tmux settings |359| `CLAUDE_CODE_TMUX_TRUECOLOR` | Set to any non-empty value, such as `1`, to allow 24-bit truecolor output inside tmux. **Setting it to `0` or `false` still allows truecolor**, unlike most on/off variables; unset the variable to restore the 256-color clamp. By default, Claude Code clamps to 256 colors when `$TMUX` is set because tmux does not pass through truecolor escape sequences unless configured to. Set this after adding `set -ga terminal-overrides ',*:Tc'` to your `~/.tmux.conf`. See [Terminal configuration](/docs/en/terminal-config) for other tmux settings |
357| `CLAUDE_CODE_USER_DIALOG_TIMEOUT_MS` | Deadline in milliseconds for dialogs Claude Code forwards to a remote client, such as a [Remote Control](/docs/en/remote-control) or SDK host, and for a [held cross-session message](/docs/en/cross-session-messaging#control-inbound-messages) awaiting approval, before Claude Code cancels the dialog or drops the default-held message; permission prompts and `AskUserQuestion` questions use their own flows and aren't governed by it. Overrides the [`dialogExpiry`](/docs/en/settings#available-settings) setting; `0` or a negative value disables the deadline |360| `CLAUDE_CODE_USER_DIALOG_TIMEOUT_MS` | Deadline in milliseconds for dialogs Claude Code forwards to a remote client, such as a [Remote Control](/docs/en/remote-control) or SDK host, and for the approval dialog for a [held cross-session message](/docs/en/cross-session-messaging#control-inbound-messages), before Claude Code cancels them; permission prompts and `AskUserQuestion` questions use their own flows and aren't governed by it. [Control inbound messages](/docs/en/cross-session-messaging#control-inbound-messages) and [non-interactive sessions](/docs/en/cross-session-messaging#non-interactive-sessions) cover the full held-message expiry rules, including the cases where the deadline doesn't apply. Overrides the [`dialogExpiry`](/docs/en/settings#available-settings) setting; `0` or a negative value disables the deadline |
358| `CLAUDE_CODE_USE_ANTHROPIC_AWS` | Use [Claude Platform on AWS](/docs/en/claude-platform-on-aws) |361| `CLAUDE_CODE_USE_ANTHROPIC_AWS` | Use [Claude Platform on AWS](/docs/en/claude-platform-on-aws) |
359| `CLAUDE_CODE_USE_BEDROCK` | Use [Amazon Bedrock](/docs/en/amazon-bedrock) |362| `CLAUDE_CODE_USE_BEDROCK` | Use [Amazon Bedrock](/docs/en/amazon-bedrock) |
360| `CLAUDE_CODE_USE_FOUNDRY` | Use [Microsoft Foundry](/docs/en/microsoft-foundry) |363| `CLAUDE_CODE_USE_FOUNDRY` | Use [Microsoft Foundry](/docs/en/microsoft-foundry) |
372| `CLAUDE_PID` | Claude Code sets this to its own process ID in the subprocesses it spawns: Bash and PowerShell tool commands and hook commands. On Linux, the Bash tool's shell integration uses it to refuse a `pkill` pattern that would match the Claude Code process itself; see [the error reference](/docs/en/errors#pkill-pattern-matches-the-claude-code-process). Read it from your own scripts to identify or signal the parent Claude Code process deliberately. Requires Claude Code v2.1.214 or later |375| `CLAUDE_PID` | Claude Code sets this to its own process ID in the subprocesses it spawns: Bash and PowerShell tool commands and hook commands. On Linux, the Bash tool's shell integration uses it to refuse a `pkill` pattern that would match the Claude Code process itself; see [the error reference](/docs/en/errors#pkill-pattern-matches-the-claude-code-process). Read it from your own scripts to identify or signal the parent Claude Code process deliberately. Requires Claude Code v2.1.214 or later |
373| `CLAUDE_REMOTE_CONTROL_SESSION_NAME_PREFIX` | Prefix for auto-generated [Remote Control](/docs/en/remote-control) session names when no explicit name is provided. Defaults to your machine's hostname, producing names like `myhost-graceful-unicorn`. The `--remote-control-session-name-prefix` CLI flag sets the same value for a single invocation |376| `CLAUDE_REMOTE_CONTROL_SESSION_NAME_PREFIX` | Prefix for auto-generated [Remote Control](/docs/en/remote-control) session names when no explicit name is provided. Defaults to your machine's hostname, producing names like `myhost-graceful-unicorn`. The `--remote-control-session-name-prefix` CLI flag sets the same value for a single invocation |
374| `CLAUDE_STREAM_IDLE_TIMEOUT_MS` | Timeout in milliseconds before the event- and byte-level streaming idle watchdogs close a stalled connection. When you set this variable explicitly, the minimum is `300000` (5 minutes); lower values are silently clamped to absorb extended thinking pauses and proxy buffering, and the byte-level watchdog caps the value at 30 minutes. `CLAUDE_BYTE_STREAM_IDLE_TIMEOUT_MS` takes precedence over this variable for the byte-level watchdog. For the per-watchdog unset defaults, see [Streaming idle watchdogs](/docs/en/network-config#streaming-idle-watchdogs) |377| `CLAUDE_STREAM_IDLE_TIMEOUT_MS` | Timeout in milliseconds before the event- and byte-level streaming idle watchdogs close a stalled connection. When you set this variable explicitly, the minimum is `300000` (5 minutes); lower values are silently clamped to absorb extended thinking pauses and proxy buffering, and the byte-level watchdog caps the value at 30 minutes. `CLAUDE_BYTE_STREAM_IDLE_TIMEOUT_MS` takes precedence over this variable for the byte-level watchdog. For the per-watchdog unset defaults, see [Streaming idle watchdogs](/docs/en/network-config#streaming-idle-watchdogs) |
375| `CLAUDE_SUBAGENT_BG_SHELL_MAX_MS` | Maximum lifetime in milliseconds for a [background shell command](/docs/en/interactive-mode#background-bash-commands) that a [subagent](/docs/en/sub-agents) started. Default `3600000` (60 minutes). When you set `0`, Claude Code applies the default instead of removing the cap. Claude Code doesn't cap main-session background commands this way; see [How backgrounding works](/docs/en/interactive-mode#how-backgrounding-works) for the memory-pressure limit that covers them |378| `CLAUDE_SUBAGENT_BG_SHELL_MAX_MS` | Maximum lifetime in milliseconds for a [background shell command](/docs/en/interactive-mode#background-bash-commands) that a [subagent](/docs/en/sub-agents) started. Default `3600000` (60 minutes). When you set `0`, Claude Code applies the default instead of removing the cap. When the subagent runs in the foreground, Claude Code also ends the command when that subagent gives its final response, regardless of this cap. See [the background command lifetime rules](/docs/en/tools-reference#background-commands). Claude Code doesn't cap main-session background commands this way. For the memory-pressure limit that covers them, see [How backgrounding works](/docs/en/interactive-mode#how-backgrounding-works) |
376| `DEBUG` | Set to `1` to enable debug mode, equivalent to launching with [`--debug`](/docs/en/cli-reference#cli-flags). Debug logs are written to `~/.claude/debug/<session-id>.txt`, or to the path set by `CLAUDE_CODE_DEBUG_LOGS_DIR`. Only the truthy values `1`, `true`, `yes`, and `on` enable debug mode, so namespace patterns like `DEBUG=express:*` set for other tools do not trigger it |379| `DEBUG` | Set to `1` to enable debug mode, equivalent to launching with [`--debug`](/docs/en/cli-reference#cli-flags). Debug logs are written to `~/.claude/debug/<session-id>.txt`, or to the path set by `CLAUDE_CODE_DEBUG_LOGS_DIR`. Only the truthy values `1`, `true`, `yes`, and `on` enable debug mode, so namespace patterns like `DEBUG=express:*` set for other tools do not trigger it |
377| `DISABLE_AUTOUPDATER` | Set to `1` to disable automatic background updates. Manual `claude update` still works. Use `DISABLE_UPDATES` to block both |380| `DISABLE_AUTOUPDATER` | Set to `1` to disable automatic background updates. Manual `claude update` still works. Use `DISABLE_UPDATES` to block both |
378| `DISABLE_AUTO_COMPACT` | Set to `1` to disable automatic compaction when approaching the context limit. The manual `/compact` command remains available. Use when you want explicit control over when compaction occurs. Overrides the [`autoCompactEnabled`](/docs/en/settings#available-settings) setting |381| `DISABLE_AUTO_COMPACT` | Set to `1` to disable automatic compaction when approaching the context limit. The manual `/compact` command remains available. Use when you want explicit control over when compaction occurs. Overrides the [`autoCompactEnabled`](/docs/en/settings#available-settings) setting |
382| `DISABLE_ERROR_REPORTING` | Set to any non-empty value, such as `1`, to opt out of error reporting. **Setting it to `0` or `false` still opts out**, unlike most on/off variables; unset the variable to turn error reporting back on |385| `DISABLE_ERROR_REPORTING` | Set to any non-empty value, such as `1`, to opt out of error reporting. **Setting it to `0` or `false` still opts out**, unlike most on/off variables; unset the variable to turn error reporting back on |
383| `DISABLE_EXTRA_USAGE_COMMAND` | Set to `1` to hide the `/usage-credits` command that lets users purchase additional usage beyond rate limits |386| `DISABLE_EXTRA_USAGE_COMMAND` | Set to `1` to hide the `/usage-credits` command that lets users purchase additional usage beyond rate limits |
384| `DISABLE_FEEDBACK_COMMAND` | Set to `1` to disable the `/feedback` command. Also disables `/bug` and `/share`, which report through the same path; before v2.1.212 they were aliases of `/feedback`, so the command was disabled under every name. The older name `DISABLE_BUG_COMMAND` is also accepted |387| `DISABLE_FEEDBACK_COMMAND` | Set to `1` to disable the `/feedback` command. Also disables `/bug` and `/share`, which report through the same path; before v2.1.212 they were aliases of `/feedback`, so the command was disabled under every name. The older name `DISABLE_BUG_COMMAND` is also accepted |
385| `DISABLE_GROWTHBOOK` | Set to `1` to disable GrowthBook feature-flag fetching and use code defaults for every flag. This makes [Remote Control](/docs/en/remote-control#requirements) and [cross-session messaging](/docs/en/cross-session-messaging#availability) unavailable. Telemetry event logging stays on unless `DISABLE_TELEMETRY` is also set |388| `DISABLE_GROWTHBOOK` | Set to `1` to disable GrowthBook feature-flag fetching and use code defaults for every flag. This makes [Remote Control](/docs/en/remote-control#requirements) and the other [features that need feature-flag fetching](#features-that-need-feature-flag-fetching) unavailable. Telemetry event logging stays on unless `DISABLE_TELEMETRY` is also set |
386| `DISABLE_INSTALLATION_CHECKS` | Set to `1` to disable installation warnings. Use only when manually managing the installation location, as this can mask issues with standard installations |389| `DISABLE_INSTALLATION_CHECKS` | Set to `1` to disable installation warnings. Use only when manually managing the installation location, as this can mask issues with standard installations |
387| `DISABLE_INSTALL_GITHUB_APP_COMMAND` | Set to `1` to hide the `/install-github-app` command. Already hidden when using third-party providers (Amazon Bedrock, Google Cloud's Agent Platform, or Microsoft Foundry) |390| `DISABLE_INSTALL_GITHUB_APP_COMMAND` | Set to `1` to hide the `/install-github-app` command. Already hidden when using third-party providers (Amazon Bedrock, Google Cloud's Agent Platform, or Microsoft Foundry) |
388| `DISABLE_INTERLEAVED_THINKING` | Set to `1` to prevent sending the interleaved-thinking beta header. Useful when your LLM gateway or provider does not support [interleaved thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking#interleaved-thinking) |391| `DISABLE_INTERLEAVED_THINKING` | Set to `1` to prevent sending the interleaved-thinking beta header. Useful when your LLM gateway or provider does not support [interleaved thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking#interleaved-thinking) |
393| `DISABLE_PROMPT_CACHING_HAIKU` | Set to `1` to disable prompt caching for Haiku models |396| `DISABLE_PROMPT_CACHING_HAIKU` | Set to `1` to disable prompt caching for Haiku models |
394| `DISABLE_PROMPT_CACHING_OPUS` | Set to `1` to disable prompt caching for Opus models |397| `DISABLE_PROMPT_CACHING_OPUS` | Set to `1` to disable prompt caching for Opus models |
395| `DISABLE_PROMPT_CACHING_SONNET` | Set to `1` to disable prompt caching for Sonnet models |398| `DISABLE_PROMPT_CACHING_SONNET` | Set to `1` to disable prompt caching for Sonnet models |
396| `DISABLE_TELEMETRY` | Set to any non-empty value, such as `1`, to opt out of telemetry. **Setting it to `0` or `false` still opts out**, unlike most on/off variables; unset the variable to turn telemetry back on. Telemetry events do not include user data like code, file paths, or bash commands. Also disables feature-flag fetching with the same effect as `DISABLE_GROWTHBOOK`, which makes [Remote Control](/docs/en/remote-control#requirements) and [cross-session messaging](/docs/en/cross-session-messaging#availability) unavailable |399| `DISABLE_TELEMETRY` | Set to any non-empty value, such as `1`, to opt out of telemetry. **Setting it to `0` or `false` still opts out**, unlike most on/off variables; unset the variable to turn telemetry back on. Telemetry events do not include user data like code, file paths, or bash commands. Also disables feature-flag fetching with the same effect as `DISABLE_GROWTHBOOK`, which makes [Remote Control](/docs/en/remote-control#requirements) and the other [features that need feature-flag fetching](#features-that-need-feature-flag-fetching) unavailable |
397| `DISABLE_UPDATES` | Set to `1` to block all updates including manual `claude update` and `claude install`. Stricter than `DISABLE_AUTOUPDATER`. Use when distributing Claude Code through your own channels and users should not self-update |400| `DISABLE_UPDATES` | Set to `1` to block all updates including manual `claude update` and `claude install`. Stricter than `DISABLE_AUTOUPDATER`. Use when distributing Claude Code through your own channels and users should not self-update |
398| `DISABLE_UPGRADE_COMMAND` | Set to `1` to hide the `/upgrade` command |401| `DISABLE_UPGRADE_COMMAND` | Set to `1` to hide the `/upgrade` command |
399| `DO_NOT_TRACK` | Set to `1` to opt out of telemetry, with the same effect as `DISABLE_TELEMETRY`, including making [Remote Control](/docs/en/remote-control#requirements) and [cross-session messaging](/docs/en/cross-session-messaging#availability) unavailable. Claude Code reads this variable as a standard boolean, so `0` leaves telemetry on, and honors it as the cross-tool convention recognized by many developer CLIs |402| `DO_NOT_TRACK` | Set to `1` to opt out of telemetry, with the same effect as `DISABLE_TELEMETRY`, including making [Remote Control](/docs/en/remote-control#requirements) and the other [features that need feature-flag fetching](#features-that-need-feature-flag-fetching) unavailable. Claude Code reads this variable as a standard boolean, so `0` leaves telemetry on, and honors it as the cross-tool convention recognized by many developer CLIs |
400| `ENABLE_CLAUDEAI_MCP_SERVERS` | Set to `false` to disable [claude.ai MCP servers](/docs/en/mcp#use-mcp-servers-from-claude-ai) in Claude Code. Enabled by default for logged-in users. To disable per-project or per-org, set [`disableClaudeAiConnectors`](/docs/en/settings#available-settings) in settings instead |403| `ENABLE_CLAUDEAI_MCP_SERVERS` | Set to `false` to disable [claude.ai MCP servers](/docs/en/mcp#use-mcp-servers-from-claude-ai) in Claude Code. Enabled by default for logged-in users. To disable per-project or per-org, set [`disableClaudeAiConnectors`](/docs/en/settings#available-settings) in settings instead |
401| `ENABLE_PROMPT_CACHING_1H` | Set to `1` to request a 1-hour [prompt cache TTL](/docs/en/prompt-caching#cache-lifetime) instead of the default 5 minutes. Intended for API key, [Amazon Bedrock](/docs/en/amazon-bedrock), [Google Cloud's Agent Platform](/docs/en/google-vertex-ai), [Microsoft Foundry](/docs/en/microsoft-foundry), and [Claude Platform on AWS](/docs/en/claude-platform-on-aws) users. Subscription users within included usage receive 1-hour TTL automatically. Subscription users drawing on [usage credits](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) can set it to keep the 1-hour TTL. 1-hour cache writes are billed at a higher rate |404| `ENABLE_PROMPT_CACHING_1H` | Set to `1` to request a 1-hour [prompt cache TTL](/docs/en/prompt-caching#cache-lifetime) instead of the default 5 minutes. Intended for API key, [Amazon Bedrock](/docs/en/amazon-bedrock), [Google Cloud's Agent Platform](/docs/en/google-vertex-ai), [Microsoft Foundry](/docs/en/microsoft-foundry), and [Claude Platform on AWS](/docs/en/claude-platform-on-aws) users. Subscription users within included usage receive 1-hour TTL automatically. Subscription users drawing on [usage credits](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) can set it to keep the 1-hour TTL. 1-hour cache writes are billed at a higher rate |
402| `ENABLE_PROMPT_CACHING_1H_BEDROCK` | Deprecated. Use `ENABLE_PROMPT_CACHING_1H` instead |405| `ENABLE_PROMPT_CACHING_1H_BEDROCK` | Deprecated. Use `ENABLE_PROMPT_CACHING_1H` instead |
403| `ENABLE_TOOL_SEARCH` | Controls [MCP tool search](/docs/en/mcp#scale-with-mcp-tool-search). Unset, Claude Code defers all MCP tools by default. It still loads them upfront on Google Cloud's Agent Platform models earlier than the Claude 4.5 generation, on a Microsoft Foundry deployment hosted on Azure, and when `ANTHROPIC_BASE_URL` points to a non-first-party host. `true` always defers and sends the beta header, except on those same Agent Platform models and Microsoft Foundry deployments; requests fail on proxies that don't support `tool_reference`. `auto` loads upfront when tool definitions fit within 10% of context. `auto:N` sets a custom threshold, such as `auto:5` for 5%. `false` loads all tools upfront. A value you set yourself is ignored when `CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS` is set. Before v2.1.221, Claude Code disabled tool search for all models on Google Cloud's Agent Platform unless you set this variable to `true` |406| `ENABLE_TOOL_SEARCH` | Controls [MCP tool search](/docs/en/mcp#scale-with-mcp-tool-search). Unset, Claude Code defers all MCP tools by default. It still loads them upfront on Google Cloud's Agent Platform models earlier than the Claude 4.5 generation, on a Microsoft Foundry deployment hosted on Azure, and when `ANTHROPIC_BASE_URL` points to a non-first-party host. `true` always defers and sends the beta header, except on those same Agent Platform models and Microsoft Foundry deployments; requests fail on proxies that don't support `tool_reference`. `auto` loads upfront when tool definitions fit within 10% of context. `auto:N` sets a custom threshold, such as `auto:5` for 5%. `false` loads all tools upfront. A value you set yourself is ignored when `CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS` is set. Before v2.1.221, Claude Code disabled tool search for all models on Google Cloud's Agent Platform unless you set this variable to `true` |
404| `FALLBACK_FOR_ALL_PRIMARY_MODELS` | Set to any non-empty value, such as `1`, to make every model stop retrying with a repeated-overload error when no fallback model is configured. **Setting it to `0` or `false` still enables this**, unlike most on/off variables; unset the variable to restore the default retry behavior. Without it, models Claude Code recognizes as Opus, Fable 5, or Mythos models stop retrying this way when you authenticate with an API key or a [third-party provider](/docs/en/third-party-integrations) rather than a Claude subscription. As of v2.1.160, a configured [fallback model chain](/docs/en/model-config#fallback-model-chains) triggers on repeated overload errors for any primary model, so this variable does not affect switching to a fallback model |407| `FALLBACK_FOR_ALL_PRIMARY_MODELS` | Set to any non-empty value, such as `1`, to make every model stop retrying with a repeated-overload error when no fallback model is configured. **Setting it to `0` or `false` still enables this**, unlike most on/off variables; unset the variable to restore the default retry behavior. Without it, models Claude Code recognizes as Opus, Fable 5, or Mythos models stop retrying this way when you authenticate with an API key or a [third-party provider](/docs/en/third-party-integrations) rather than a Claude subscription. As of v2.1.160, a configured [fallback model chain](/docs/en/model-config#fallback-model-chains) triggers on repeated overload errors for any primary model, so this variable does not affect switching to a fallback model |
405| `FORCE_AUTOUPDATE_PLUGINS` | Set to `1` to force plugin auto-updates even when the main auto-updater is disabled via `DISABLE_AUTOUPDATER` |408| `FORCE_AUTOUPDATE_PLUGINS` | Set to `1` to force plugin auto-updates even when the main auto-updater is disabled via `DISABLE_AUTOUPDATER` |
406| `FORCE_HYPERLINK` | Set to `1` to enable clickable OSC 8 hyperlinks when your terminal supports them but isn't auto-detected, or `0` to disable them. Claude Code parses this value as a number, not a boolean, so word spellings such as `false`, `no`, or `off` enable hyperlinks rather than disabling them |409| `FORCE_HYPERLINK` | Set to `1` to enable clickable OSC 8 hyperlinks when your terminal supports them but isn't auto-detected, or `0` to disable them. When unset, Claude Code enables hyperlinks only when it detects terminal support. Claude Code parses this value as a number, not a Boolean, so a value such as `false`, `no`, or `off` enables hyperlinks rather than disabling them. Claude Code renders the footer PR badge as a hyperlink even when it can't detect terminal support, such as over SSH. Set `0` to render the badge as plain text |
407| `FORCE_PROMPT_CACHING_5M` | Set to `1` to force the 5-minute prompt cache TTL even when 1-hour TTL would otherwise apply. Overrides `ENABLE_PROMPT_CACHING_1H` |410| `FORCE_PROMPT_CACHING_5M` | Set to `1` to force the 5-minute prompt cache TTL even when 1-hour TTL would otherwise apply. Overrides `ENABLE_PROMPT_CACHING_1H` |
408| `HTTP_PROXY` | Specify HTTP proxy server for network connections |411| `HTTP_PROXY` | Specify HTTP proxy server for network connections |
409| `HTTPS_PROXY` | Specify HTTPS proxy server for network connections |412| `HTTPS_PROXY` | Specify HTTPS proxy server for network connections |
410| `IS_DEMO` | Set to any non-empty value, such as `1`, to enable demo mode: hides your email and organization name from the header and `/status` output, and skips onboarding. **Setting it to `0` or `false` still enables demo mode**, unlike most on/off variables; unset the variable to turn it off. Useful when streaming or recording a session |413| `IS_DEMO` | Set to any non-empty value, such as `1`, to enable demo mode: hides your email and organization name from the header and `/status` output, and skips onboarding. **Setting it to `0` or `false` still enables demo mode**, unlike most on/off variables; unset the variable to turn it off. Useful when streaming or recording a session |
411| `MAX_MCP_OUTPUT_TOKENS` | Maximum number of tokens allowed in MCP tool responses. Claude Code displays a warning when output exceeds 10,000 tokens. Tools that declare [`anthropic/maxResultSizeChars`](/docs/en/mcp#raise-the-limit-for-a-specific-tool) use that character limit for text content instead, but image content from those tools is still subject to this variable (default: 25000) |414| `MAX_MCP_OUTPUT_TOKENS` | Maximum number of tokens allowed in MCP tool responses. Claude Code displays a warning when output exceeds 10,000 tokens. Tools that declare [`anthropic/maxResultSizeChars`](/docs/en/mcp#raise-the-limit-for-a-specific-tool) use that character limit for text content instead, but image content from those tools is still subject to this variable (default: 25000) |
412| `MAX_STRUCTURED_OUTPUT_RETRIES` | Number of times to retry when the model's response fails validation against the [`--json-schema`](/docs/en/cli-reference#cli-flags) in non-interactive mode (the `-p` flag). Defaults to 5 |415| `MAX_STRUCTURED_OUTPUT_RETRIES` | Number of times Claude Code retries when the model's response fails validation against the [`--json-schema`](/docs/en/cli-reference#cli-flags) in non-interactive mode with the `-p` flag. The same retry count applies when a [workflow](/docs/en/workflows) subagent's structured output fails validation. Defaults to 5 |
413| `MAX_THINKING_TOKENS` | Fixed token budget for [extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking). Claude Code caps it at one token below the request's max output tokens and never below 1,024; see `CLAUDE_CODE_MAX_OUTPUT_TOKENS` for how that limit is set. When unset and thinking is enabled, models with [adaptive reasoning](/docs/en/model-config#adjust-effort-level) choose their own thinking depth, and other models use the cap. Set to `0` to disable thinking on the Anthropic API, except on Fable 5, which cannot have thinking turned off; on [third-party providers](/docs/en/third-party-integrations), `0` omits the `thinking` parameter instead. Nonzero values are ignored on adaptive reasoning models unless `CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING` is set |416| `MAX_THINKING_TOKENS` | Fixed token budget for [extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking). Claude Code caps it at one token below the request's max output tokens and never below 1,024; see `CLAUDE_CODE_MAX_OUTPUT_TOKENS` for how that limit is set. When unset and thinking is enabled, models with [adaptive reasoning](/docs/en/model-config#adjust-effort-level) choose their own thinking depth, and other models use the cap. Set to `0` to disable thinking on the Anthropic API, except on Fable 5, which cannot have thinking turned off; on [third-party providers](/docs/en/third-party-integrations), `0` omits the `thinking` parameter instead. Nonzero values are ignored on adaptive reasoning models unless `CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING` is set |
414| `MCP_CLIENT_SECRET` | OAuth client secret for MCP servers that require [pre-configured credentials](/docs/en/mcp#use-pre-configured-oauth-credentials). Avoids the interactive prompt when adding a server with `--client-secret` |417| `MCP_CLIENT_SECRET` | OAuth client secret for MCP servers that require [pre-configured credentials](/docs/en/mcp#use-pre-configured-oauth-credentials). Avoids the interactive prompt when adding a server with `--client-secret` |
415| `MCP_CONNECTION_NONBLOCKING` | Controls whether startup waits for MCP servers to connect before the first query. MCP startup is non-blocking by default: servers connect in the background and their tools become available as they finish; before v2.1.142, the blocking wait was the default. Set to `0` to restore the blocking 5-second connection wait. Servers configured with [`alwaysLoad: true`](/docs/en/mcp#exempt-a-server-from-deferral) still make startup wait regardless, except when served from the [discovery cache](/docs/en/mcp#managing-your-servers), since their tools must be present when the first prompt is built. In non-interactive mode (`-p`), Claude Code also waits for still-pending servers before the first turn regardless of this variable, with a longer deadline when you pass [`--mcp-config`](/docs/en/cli-reference#cli-flags) explicitly; see that flag's entry for the cached-server exception |418| `MCP_CONNECTION_NONBLOCKING` | Controls whether startup waits for MCP servers to connect before the first query. MCP startup is non-blocking by default: servers connect in the background and their tools become available as they finish; before v2.1.142, the blocking wait was the default. Set to `0` to restore the blocking 5-second connection wait. Servers configured with [`alwaysLoad: true`](/docs/en/mcp#exempt-a-server-from-deferral) still make startup wait regardless, except when served from the [discovery cache](/docs/en/mcp#managing-your-servers), since their tools must be present when the first prompt is built. In non-interactive mode (`-p`), Claude Code also waits for still-pending servers before the first turn regardless of this variable, with a longer deadline when you pass [`--mcp-config`](/docs/en/cli-reference#cli-flags) explicitly; see that flag's entry for the cached-server exception |
417| `MCP_DISCOVERY_CACHE` | Set to `0` to turn off the cross-process MCP discovery cache, so every server connects at startup instead of showing the [`connects on first use` cached status](/docs/en/mcp#managing-your-servers) and connecting on its first tool call. The cached status requires Claude Code v2.1.221 or later |420| `MCP_DISCOVERY_CACHE` | Set to `0` to turn off the cross-process MCP discovery cache, so every server connects at startup instead of showing the [`connects on first use` cached status](/docs/en/mcp#managing-your-servers) and connecting on its first tool call. The cached status requires Claude Code v2.1.221 or later |
418| `MCP_OAUTH_CALLBACK_PORT` | Fixed port for the OAuth redirect callback, as an alternative to `--callback-port` when adding an MCP server with [pre-configured credentials](/docs/en/mcp#use-pre-configured-oauth-credentials) |421| `MCP_OAUTH_CALLBACK_PORT` | Fixed port for the OAuth redirect callback, as an alternative to `--callback-port` when adding an MCP server with [pre-configured credentials](/docs/en/mcp#use-pre-configured-oauth-credentials) |
419| `MCP_REMOTE_SERVER_CONNECTION_BATCH_SIZE` | Maximum number of remote MCP servers (HTTP/SSE) to connect in parallel during startup (default: 20) |422| `MCP_REMOTE_SERVER_CONNECTION_BATCH_SIZE` | Maximum number of remote MCP servers (HTTP/SSE) to connect in parallel during startup (default: 20) |
423| `MCP_SDK_GENERATION` | Pin which MCP client runtime this process uses, the implementation behind [MCP server connections](/docs/en/mcp), while Claude Code migrates from its v1 runtime to v2. Set `v1` to stay on the current runtime or `v2` to opt in early. Without the variable, a gradual rollout decides, and defaults to v1. On Claude Code v2.1.221 or later, the v2 runtime checks the issuer an MCP OAuth server returns in its authorization response and fails the sign-in with an error that begins `Issuer mismatch in authorization response` when it doesn't match. The v1 runtime doesn't run this check. If you set an unrecognized value, Claude Code ignores it and writes a warning to the debug log. Claude Code reads the value once per process. Requires Claude Code v2.1.218 or later |
420| `MCP_SERVER_CONNECTION_BATCH_SIZE` | Maximum number of local MCP servers (stdio) to connect in parallel during startup (default: 3) |424| `MCP_SERVER_CONNECTION_BATCH_SIZE` | Maximum number of local MCP servers (stdio) to connect in parallel during startup (default: 3) |
421| `MCP_TIMEOUT` | Timeout in milliseconds for MCP server startup (default: 30000, or 30 seconds) |425| `MCP_TIMEOUT` | Timeout in milliseconds for MCP server startup (default: 30000, or 30 seconds) |
422| `MCP_TOOL_TIMEOUT` | Timeout in milliseconds for MCP tool execution (default: 100000000, about 28 hours). For an HTTP, SSE, or claude.ai connector server, each request also times out after 60 seconds by default; set this variable, or the per-server `timeout`, above 60000 to raise that per-request limit. A lower value still shortens the overall tool-execution timeout but leaves the per-request limit at 60 seconds. Stdio and WebSocket servers have no per-request timer. A per-server `timeout` field in `.mcp.json` overrides this for that server. A per-server `timeout` of at least 1000 also sets the minimum idle window for that server's tool calls, so `CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT` never aborts them sooner; this floor requires Claude Code v2.1.203 or later. For the env variable, values below 1000 are floored to one second; for the per-server field, values below 1000 are ignored |426| `MCP_TOOL_TIMEOUT` | Timeout in milliseconds for MCP tool execution (default: 100000000, about 28 hours). For an HTTP, SSE, or claude.ai connector server, each request also times out after 60 seconds by default; set this variable, or the per-server `timeout`, above 60000 to raise that per-request limit. A lower value still shortens the overall tool-execution timeout but leaves the per-request limit at 60 seconds. Stdio and WebSocket servers have no per-request timer. A per-server `timeout` field in `.mcp.json` overrides this for that server. A per-server `timeout` of at least 1000 also sets the minimum idle window for that server's tool calls, so `CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT` never aborts them sooner; this floor requires Claude Code v2.1.203 or later. For the env variable, values below 1000 are floored to one second; for the per-server field, values below 1000 are ignored |
454 458
455Standard OpenTelemetry exporter variables (`OTEL_METRICS_EXPORTER`, `OTEL_LOGS_EXPORTER`, `OTEL_EXPORTER_OTLP_ENDPOINT`, `OTEL_EXPORTER_OTLP_PROTOCOL`, `OTEL_EXPORTER_OTLP_HEADERS`, `OTEL_METRIC_EXPORT_INTERVAL`, `OTEL_RESOURCE_ATTRIBUTES`, and signal-specific variants) are also supported. See [Monitoring](/docs/en/monitoring-usage) for configuration details.459Standard OpenTelemetry exporter variables (`OTEL_METRICS_EXPORTER`, `OTEL_LOGS_EXPORTER`, `OTEL_EXPORTER_OTLP_ENDPOINT`, `OTEL_EXPORTER_OTLP_PROTOCOL`, `OTEL_EXPORTER_OTLP_HEADERS`, `OTEL_METRIC_EXPORT_INTERVAL`, `OTEL_RESOURCE_ATTRIBUTES`, and signal-specific variants) are also supported. See [Monitoring](/docs/en/monitoring-usage) for configuration details.
456 460
461## Features that need feature-flag fetching
462
463Claude Code turns some features on through feature flags it fetches from Anthropic. `DISABLE_GROWTHBOOK`, `DISABLE_TELEMETRY`, `DO_NOT_TRACK`, and `CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC` all turn flag fetching off when set to a value that disables them, and each variable's row says which values do that. A session running with fetching off can't use:
464
465* [Remote Control](/docs/en/remote-control#requirements)
466* [Cross-session messaging](/docs/en/cross-session-messaging#availability)
467* [`claude import` and the `/import` command](/docs/en/cli-reference#cli-commands)
468* [The `/schedule` command](/docs/en/routines#troubleshooting) for creating routines from the CLI
469* [The advisor tool](/docs/en/advisor#requirements)
470* [`/loop` self-pacing](/docs/en/scheduled-tasks#let-claude-choose-the-interval), so a `/loop` prompt with no interval runs on the fixed 10-minute schedule instead
471* [The built-in `/loop` maintenance prompt](/docs/en/scheduled-tasks#run-the-built-in-maintenance-prompt), so `/loop` with no prompt shows the usage message instead
472
473In such a session you can still type `/code-review` yourself, but [Claude can't start the review on its own, and a scheduled `/code-review` reaches Claude as plain text](/docs/en/code-review#let-claude-start-the-review) instead of running the review.
474
475### First session after an install or upgrade
476
477A feature in this list can be missing from your first session after you install Claude Code, or after you upgrade to a version that adds the feature, even with none of these variables set. Claude Code fetches the flags during that session, so a feature that's otherwise available to you is there in your next session. Two features work differently in that first session:
478
479* Claude Code [binds the session's inbox socket](/docs/en/cross-session-messaging#the-sessions-inbox-socket) and exports the messaging variables partway through the session, as soon as the fetch completes, so other sessions can message it before you restart.
480* Claude Code checks the `claude import` flag before it starts a session, so if `claude import` is the first thing you run after installing, it prints [`claude import is not yet available in this build`](/docs/en/errors#claude-import-is-not-yet-available-in-this-build). Start a session, then run it again.
481
457## See also482## See also
458 483
459* [Settings](/docs/en/settings): all `settings.json` configuration, including the `env` key484* [Settings](/docs/en/settings): all `settings.json` configuration, including the `env` key
