87}87}
88```88```
89 89
90Claude Code copies these values into its environment as written. No shell processes them, so shorthand such as `~` or `$HOME` stays as typed. For a variable that takes a path, such as `CLAUDE_CONFIG_DIR`, write the absolute path: `"CLAUDE_CONFIG_DIR": "/home/you/.claude-work"`.
91
90The file you choose controls who the variables apply to:92The file you choose controls who the variables apply to:
91 93
92| File | Applies to |94| File | Applies to |
214| `CLAUDE_CODE_AUTO_COMPACT_WINDOW` | Set the [auto-compact window](/docs/en/model-config#set-the-auto-compact-window) in tokens, from `100000` to `1000000`. Accepts a plain integer such as `500000` only: a value like `500k` reads as `500` and clamps to the 100K minimum. The effective window is also capped at the model's context window. Takes precedence over the `/autocompact` command, the `--autocompact` flag, and the `autoCompactWindow` setting. The status line's `used_percentage` always measures against the model's full context window, so once this variable is set, that percentage no longer indicates when compaction will run |216| `CLAUDE_CODE_AUTO_COMPACT_WINDOW` | Set the [auto-compact window](/docs/en/model-config#set-the-auto-compact-window) in tokens, from `100000` to `1000000`. Accepts a plain integer such as `500000` only: a value like `500k` reads as `500` and clamps to the 100K minimum. The effective window is also capped at the model's context window. Takes precedence over the `/autocompact` command, the `--autocompact` flag, and the `autoCompactWindow` setting. The status line's `used_percentage` always measures against the model's full context window, so once this variable is set, that percentage no longer indicates when compaction will run |
215| `CLAUDE_CODE_AUTO_CONNECT_IDE` | Override automatic [IDE connection](/docs/en/vs-code). By default, Claude Code connects automatically when launched inside a supported IDE's integrated terminal. Set to `false` to prevent this. Set to `true` to force a connection attempt when auto-detection fails, such as when tmux obscures the parent terminal. Takes precedence over the [`autoConnectIde`](/docs/en/settings-reference#autoconnectide) global config setting |217| `CLAUDE_CODE_AUTO_CONNECT_IDE` | Override automatic [IDE connection](/docs/en/vs-code). By default, Claude Code connects automatically when launched inside a supported IDE's integrated terminal. Set to `false` to prevent this. Set to `true` to force a connection attempt when auto-detection fails, such as when tmux obscures the parent terminal. Takes precedence over the [`autoConnectIde`](/docs/en/settings-reference#autoconnectide) global config setting |
216| `CLAUDE_CODE_AUTO_MODE_SERVER` | Controls whether Claude Code asks the server to [review auto mode actions](/docs/en/permission-modes#server-side-classifier-review). Set to `0` to use Claude Code's own classifier requests instead. On a direct connection to the Anthropic API, requires v2.1.281 or later. The linked section lists which sessions ask the server when the variable is unset, and from which version. Requires Claude Code v2.1.271 or later |218| `CLAUDE_CODE_AUTO_MODE_SERVER` | Controls whether Claude Code asks the server to [review auto mode actions](/docs/en/permission-modes#server-side-classifier-review). Set to `0` to use Claude Code's own classifier requests instead. On a direct connection to the Anthropic API, requires v2.1.281 or later. The linked section lists which sessions ask the server when the variable is unset, and from which version. Requires Claude Code v2.1.271 or later |
217| `CLAUDE_CODE_AWS_CHAIN_RESOLVE_TIMEOUT_MS` | Time in milliseconds Claude Code waits for the AWS default credential provider chain to produce credentials before the request fails with [`AWS default-chain credential resolve timed out`](/docs/en/errors#aws-default-chain-credential-resolve-timed-out) (default: `60000`). Raise it when a step in your chain legitimately needs longer, such as a browser-based SSO sign-in with MFA through a wrapper like `aws-vault`. Applies wherever Claude Code signs with the default chain: [Amazon Bedrock](/docs/en/amazon-bedrock#credential-caching-and-resolution-timeout), [Claude Platform on AWS](/docs/en/claude-platform-on-aws), and the [Mantle endpoint](/docs/en/amazon-bedrock#use-the-mantle-endpoint). Requires Claude Code v2.1.207 or later |219| `CLAUDE_CODE_AWS_CHAIN_RESOLVE_TIMEOUT_MS` | Time in milliseconds Claude Code waits for the AWS default credential provider chain to produce credentials before the request fails with [`AWS default-chain credential resolve timed out`](/docs/en/errors#aws-default-chain-credential-resolve-timed-out) (default: `60000`). Raise it when a step in your chain legitimately needs longer, such as a browser-based SSO sign-in with MFA through a wrapper like `aws-vault`. Applies on Amazon Bedrock, [Claude Platform on AWS](/docs/en/claude-platform-on-aws), and the [Mantle endpoint](/docs/en/amazon-bedrock#use-the-mantle-endpoint). See [credential caching and resolution timeout](/docs/en/amazon-bedrock#credential-caching-and-resolution-timeout). Requires Claude Code v2.1.207 or later |
218| `CLAUDE_CODE_BASH_EDIT_DIFF` | Set to `0` to turn off the [diff of the files that changed while a Bash command ran](/docs/en/hooks#bash), or `1` to record it in every permission mode. Takes precedence over the [`bashEditDiffEnabled`](/docs/en/settings-reference#basheditdiffenabled) setting. Requires Claude Code v2.1.269 or later |220| `CLAUDE_CODE_BASH_EDIT_DIFF` | Set to `0` to turn off the [diff of the files that changed while a Bash command ran](/docs/en/hooks#bash), or `1` to record it in every permission mode. Takes precedence over the [`bashEditDiffEnabled`](/docs/en/settings-reference#basheditdiffenabled) setting. Requires Claude Code v2.1.269 or later |
219| `CLAUDE_CODE_BG_TASKS_REPORT_RUNNING` | Set to `0` to make a non-interactive session report an idle status to its host at every turn end, even while background work is still running. By default, the session keeps reporting a running status past turn end while background work such as a background agent or a [workflow](/docs/en/workflows) run is still live. This keeps a host that watches the status, such as a remote session list, from announcing that Claude is waiting for your input mid-work. Background shell commands, such as a dev server, don't hold the running status. The running-status default and the `0` opt-out require Claude Code v2.1.269 or later; on earlier versions, set `1` to hold the running status |221| `CLAUDE_CODE_BG_TASKS_REPORT_RUNNING` | Set to `0` to make a non-interactive session report an idle status to its host at every turn end, even while background work is still running. By default, the session keeps reporting a running status past turn end while background work such as a background agent or a [workflow](/docs/en/workflows) run is still live. This keeps a host that watches the status, such as a remote session list, from announcing that Claude is waiting for your input mid-work. Background shell commands, such as a dev server, don't hold the running status. The running-status default and the `0` opt-out require Claude Code v2.1.269 or later; on earlier versions, set `1` to hold the running status |
220| `CLAUDE_CODE_BRIDGE_SESSION_ID` | Set automatically in Bash tool and [hook command](/docs/en/hooks) subprocesses while the session has an active [Remote Control](/docs/en/remote-control) connection, and removed when the connection ends. The value is the session's ID in `session_` form, the same identifier that appears in the session's `claude.ai/code` URL, so a script can link back to the session that ran it. Requires Claude Code v2.1.199 or later. In [cloud sessions](/docs/en/claude-code-on-the-web), read `CLAUDE_CODE_REMOTE_SESSION_ID` instead |222| `CLAUDE_CODE_BRIDGE_SESSION_ID` | Set automatically in Bash tool and [hook command](/docs/en/hooks) subprocesses while the session has an active [Remote Control](/docs/en/remote-control) connection, and removed when the connection ends. The value is the session's ID in `session_` form, the same identifier that appears in the session's `claude.ai/code` URL, so a script can link back to the session that ran it. Requires Claude Code v2.1.199 or later. In [cloud sessions](/docs/en/claude-code-on-the-web), read `CLAUDE_CODE_REMOTE_SESSION_ID` instead |
228| `CLAUDE_CODE_DEBUG_LOGS_DIR` | Override the debug log file path. Despite the name, this is a file path, not a directory. Requires debug mode to be enabled separately via `--debug`, `/debug`, or the `DEBUG` environment variable: setting this variable alone does not enable logging. The [`--debug-file`](/docs/en/cli-reference#cli-flags) flag does both at once. Defaults to `~/.claude/debug/<session-id>.txt` |230| `CLAUDE_CODE_DEBUG_LOGS_DIR` | Override the debug log file path. Despite the name, this is a file path, not a directory. Requires debug mode to be enabled separately via `--debug`, `/debug`, or the `DEBUG` environment variable: setting this variable alone does not enable logging. The [`--debug-file`](/docs/en/cli-reference#cli-flags) flag does both at once. Defaults to `~/.claude/debug/<session-id>.txt` |
229| `CLAUDE_CODE_DEBUG_LOG_LEVEL` | Minimum log level written to the debug log file. Values: `verbose`, `debug` (default), `info`, `warn`, `error`. Set to `verbose` to include high-volume diagnostics like full status line command output, or raise to `error` to reduce noise |231| `CLAUDE_CODE_DEBUG_LOG_LEVEL` | Minimum log level written to the debug log file. Values: `verbose`, `debug` (default), `info`, `warn`, `error`. Set to `verbose` to include high-volume diagnostics like full status line command output, or raise to `error` to reduce noise |
230| `CLAUDE_CODE_DISABLE_1M_CONTEXT` | Set to `1` to disable [1M context window](/docs/en/model-config#extended-context) support. When set, 1M model variants are unavailable in the model picker, and Claude Code holds sessions on models with a native 1M window, such as [Sonnet 5.5](/docs/en/model-config#sonnet-5-5-and-sonnet-5-context-window) and the Fable models, to a 200K window; see [Extended context](/docs/en/model-config#extended-context) for how the hold is enforced. Useful for enterprise environments with compliance requirements. For its role in correcting the window for an unrecognized `[1m]` model ID, see [Correct the window for a gateway or custom model ID](/docs/en/model-config#correct-the-window-for-a-gateway-or-custom-model-id) |232| `CLAUDE_CODE_DISABLE_1M_CONTEXT` | Set to `1` to disable [1M context window](/docs/en/model-config#extended-context) support. When set, 1M model variants are unavailable in the model picker, and Claude Code holds sessions on models with a native 1M window, such as [Sonnet 5.5](/docs/en/model-config#sonnet-5-5-and-sonnet-5-context-window) and the Fable models, to a 200K window; see [Extended context](/docs/en/model-config#extended-context) for how the hold is enforced. Useful for enterprise environments with compliance requirements. For its role in correcting the window for an unrecognized `[1m]` model ID, see [Correct the window for a gateway or custom model ID](/docs/en/model-config#correct-the-window-for-a-gateway-or-custom-model-id) |
231| `CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING` | Set to `1` to disable [adaptive reasoning](/docs/en/model-config#adjust-effort-level) on Opus 4.6 and Sonnet 4.6 and fall back to the fixed thinking budget controlled by `MAX_THINKING_TOKENS`. Has no effect on [Fable models](/docs/en/model-config#extended-thinking), Sonnet 5 and later, or Opus 4.7 and later, which always use adaptive reasoning |233| `CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING` | Set to `1` to disable [adaptive reasoning](/docs/en/model-config#adjust-effort-level) on Opus 4.6 and Sonnet 4.6 and fall back to the fixed thinking budget controlled by `MAX_THINKING_TOKENS`. Has no effect on [Fable models](/docs/en/model-config#extended-thinking), Sonnet 5 and later, Haiku 5.5, or Opus 4.7 and later, which always use adaptive reasoning |
232| `CLAUDE_CODE_DISABLE_ADMIN_ENV_UNION` | Set to `1` to stop Claude Code from merging [managed settings](/docs/en/managed-settings#precedence-within-the-managed-tier) `env` blocks per key across admin sources, so only the highest-priority source's whole `env` block applies, as before v2.1.223. Set it in the environment that launches Claude Code, since Claude Code ignores a copy delivered through a settings `env` block. Requires Claude Code v2.1.223 or later |234| `CLAUDE_CODE_DISABLE_ADMIN_ENV_UNION` | Set to `1` to stop Claude Code from merging [managed settings](/docs/en/managed-settings#precedence-within-the-managed-tier) `env` blocks per key across admin sources, so only the highest-priority source's whole `env` block applies, as before v2.1.223. Set it in the environment that launches Claude Code, since Claude Code ignores a copy delivered through a settings `env` block. Requires Claude Code v2.1.223 or later |
233| `CLAUDE_CODE_DISABLE_ADVISOR_TOOL` | Set to `1` to disable the [advisor tool](/docs/en/advisor). The `/advisor` command becomes unavailable, any configured `advisorModel` is ignored, and the `--advisor` flag is accepted but has no effect, so existing scripts that pass it continue to work without errors |235| `CLAUDE_CODE_DISABLE_ADVISOR_TOOL` | Set to `1` to disable the [advisor tool](/docs/en/advisor). The `/advisor` command becomes unavailable, any configured `advisorModel` is ignored, and the `--advisor` flag is accepted but has no effect, so existing scripts that pass it continue to work without errors |
234| `CLAUDE_CODE_DISABLE_AGENT_VIEW` | Set to `1` to turn off [background agents and agent view](/docs/en/agent-view): `claude agents`, `--bg`, `/background`, and the on-demand supervisor. Equivalent to the [`disableAgentView`](/docs/en/settings-reference#disableagentview) setting |236| `CLAUDE_CODE_DISABLE_AGENT_VIEW` | Set to `1` to turn off [background agents and agent view](/docs/en/agent-view): `claude agents`, `--bg`, `/background`, and the on-demand supervisor. Equivalent to the [`disableAgentView`](/docs/en/settings-reference#disableagentview) setting |
270| `CLAUDE_CODE_DISABLE_STRUCTURED_OUTPUTS` | Set to `1` to stop Claude Code from sending the structured-output `output_config.format` field and the `anthropic-beta` value that pairs with it, for an [LLM gateway](/docs/en/llm-gateway-protocol#feature-pass-through) whose upstream rejects them. This leaves on the other pre-release capabilities that [`CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS`](/docs/en/llm-gateway-protocol#disable-pre-release-capabilities) turns off. Requires Claude Code v2.1.288 or later |272| `CLAUDE_CODE_DISABLE_STRUCTURED_OUTPUTS` | Set to `1` to stop Claude Code from sending the structured-output `output_config.format` field and the `anthropic-beta` value that pairs with it, for an [LLM gateway](/docs/en/llm-gateway-protocol#feature-pass-through) whose upstream rejects them. This leaves on the other pre-release capabilities that [`CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS`](/docs/en/llm-gateway-protocol#disable-pre-release-capabilities) turns off. Requires Claude Code v2.1.288 or later |
271| `CLAUDE_CODE_DISABLE_SUBSTITUTION_RM_PROMPT` | Set to `1` to turn off the [critical-path](/docs/en/permission-modes#critical-paths) check for a recursive `rm` whose target is entirely the output of a command substitution, such as `rm -rf "$(pwd)"`. The other critical-path checks keep running. Set it in the environment that launches Claude Code, since Claude Code ignores a copy delivered through a settings `env` block. Requires Claude Code v2.1.281 or later |273| `CLAUDE_CODE_DISABLE_SUBSTITUTION_RM_PROMPT` | Set to `1` to turn off the [critical-path](/docs/en/permission-modes#critical-paths) check for a recursive `rm` whose target is entirely the output of a command substitution, such as `rm -rf "$(pwd)"`. The other critical-path checks keep running. Set it in the environment that launches Claude Code, since Claude Code ignores a copy delivered through a settings `env` block. Requires Claude Code v2.1.281 or later |
272| `CLAUDE_CODE_DISABLE_TERMINAL_TITLE` | Set to `1` to disable automatic terminal title updates based on conversation context. This also skips the background small/fast-model request that [generates a session title](/docs/en/sessions#name-your-sessions) |274| `CLAUDE_CODE_DISABLE_TERMINAL_TITLE` | Set to `1` to disable automatic terminal title updates based on conversation context. This also skips the background small/fast-model request that [generates a session title](/docs/en/sessions#name-your-sessions) |
273| `CLAUDE_CODE_DISABLE_THINKING` | Set to `1` to omit the `thinking` parameter from API requests entirely. This is a compatibility option for proxies and gateways that reject the parameter. On models that think by default, omitting the parameter means the model may still think. To explicitly disable [extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking) on the Anthropic API, use `MAX_THINKING_TOKENS=0` instead. Neither variable turns thinking off on Opus 5.5, Sonnet 5.5, or the Fable models, which can't have thinking turned off. On [third-party providers](/docs/en/third-party-integrations), `MAX_THINKING_TOKENS=0` likewise omits the parameter, so the two variables behave the same there |275| `CLAUDE_CODE_DISABLE_THINKING` | Set to `1` to omit the `thinking` parameter from API requests entirely. This is a compatibility option for proxies and gateways that reject the parameter. On models that think by default, omitting the parameter means the model may still think. To explicitly disable [extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking) on the Anthropic API, use `MAX_THINKING_TOKENS=0` instead. Neither variable turns thinking off on Opus 5.5, Sonnet 5.5, Haiku 5.5, or the Fable models, which can't have thinking turned off. On [third-party providers](/docs/en/third-party-integrations), `MAX_THINKING_TOKENS=0` likewise omits the parameter, so the two variables behave the same there |
274| `CLAUDE_CODE_DISABLE_UNKNOWN_MODEL_WINDOW_ENFORCEMENT` | Set to `1` to skip proactive [auto-compaction](/docs/en/costs#reduce-token-usage) when Claude Code doesn't recognize the model ID, such as an [LLM gateway](/docs/en/llm-gateway) alias. Without this variable, Claude Code compacts at the context window it assumes for the ID. `CLAUDE_CODE_MAX_CONTEXT_TOKENS` can correct the assumed window instead; see [Correct the window for a gateway or custom model ID](/docs/en/model-config#correct-the-window-for-a-gateway-or-custom-model-id) for when each variable applies. Requires Claude Code v2.1.223 or later |276| `CLAUDE_CODE_DISABLE_UNKNOWN_MODEL_WINDOW_ENFORCEMENT` | Set to `1` to skip proactive [auto-compaction](/docs/en/costs#reduce-token-usage) when Claude Code doesn't recognize the model ID, such as an [LLM gateway](/docs/en/llm-gateway) alias. Without this variable, Claude Code compacts at the context window it assumes for the ID. `CLAUDE_CODE_MAX_CONTEXT_TOKENS` can correct the assumed window instead; see [Correct the window for a gateway or custom model ID](/docs/en/model-config#correct-the-window-for-a-gateway-or-custom-model-id) for when each variable applies. Requires Claude Code v2.1.223 or later |
275| `CLAUDE_CODE_DISABLE_VIRTUAL_SCROLL` | Set to `1` to disable virtual scrolling in [fullscreen rendering](/docs/en/fullscreen) and render every message in the transcript. Use this if scrolling in fullscreen mode shows blank regions where messages should appear |277| `CLAUDE_CODE_DISABLE_VIRTUAL_SCROLL` | Set to `1` to disable virtual scrolling in [fullscreen rendering](/docs/en/fullscreen) and render every message in the transcript. Use this if scrolling in fullscreen mode shows blank regions where messages should appear |
276| `CLAUDE_CODE_DISABLE_WEB_FETCH` | Set to `1` to turn off the [WebFetch](/docs/en/tools-reference#webfetch-tool-behavior) tool. The [WebSearch](/docs/en/tools-reference#websearch-tool-behavior) tool stays available. Requires Claude Code v2.1.285 or later |278| `CLAUDE_CODE_DISABLE_WEB_FETCH` | Set to `1` to turn off the [WebFetch](/docs/en/tools-reference#webfetch-tool-behavior) tool. The [WebSearch](/docs/en/tools-reference#websearch-tool-behavior) tool stays available. Requires Claude Code v2.1.285 or later |
326| `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 |328| `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 |
327| `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 |329| `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 |
328| `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. On native Windows, Claude Code requires this line and closes any connection that doesn't open with a valid one. The [own-child rules](/docs/en/cross-session-messaging#the-sessions-inbox-socket) say when Claude Code consults the token. 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 |330| `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. On native Windows, Claude Code requires this line and closes any connection that doesn't open with a valid one. The [own-child rules](/docs/en/cross-session-messaging#the-sessions-inbox-socket) say when Claude Code consults the token. 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 |
329| `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 |331| `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. Setting `0` reads the same as leaving the variable unset, so it doesn't bring the drawn block back in a session where the terminal's own cursor is already on |
330| `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 |332| `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 |
331| `CLAUDE_CODE_NONBLOCKING_STDOUT` | Set to `1` to write terminal output through a second non-blocking file descriptor, so a terminal that stops reading, such as a paused tmux control-mode pane or a stalled SSH connection, can't freeze Claude Code mid-session. Applies on macOS, Linux, and WSL when stdout is a terminal. Requires Claude Code v2.1.261 or later |333| `CLAUDE_CODE_NONBLOCKING_STDOUT` | Set to `1` to write terminal output through a second non-blocking file descriptor, so a terminal that stops reading, such as a paused tmux control-mode pane or a stalled SSH connection, can't freeze Claude Code mid-session. Applies on macOS, Linux, and WSL when stdout is a terminal. Requires Claude Code v2.1.261 or later |
332| `CLAUDE_CODE_NONSTREAMING_TIMEOUT_RETRIES` | Limit how many times Claude Code re-sends a [non-streaming request](/docs/en/errors#streaming-response-ended-before-any-complete-data-was-received) that times out. With `0`, the request fails on the first timeout. Unset by default, so `CLAUDE_CODE_MAX_RETRIES` limits these re-sends. See [Tune retry behavior](/docs/en/errors#tune-retry-behavior) for the timeout. Requires Claude Code v2.1.285 or later |334| `CLAUDE_CODE_NONSTREAMING_TIMEOUT_RETRIES` | Limit how many times Claude Code re-sends a [non-streaming request](/docs/en/errors#streaming-response-ended-before-any-complete-data-was-received) that times out. With `0`, the request fails on the first timeout. Unset by default, so `CLAUDE_CODE_MAX_RETRIES` limits these re-sends. See [Tune retry behavior](/docs/en/errors#tune-retry-behavior) for the timeout. Requires Claude Code v2.1.285 or later |
344| `CLAUDE_CODE_PERFORCE_MODE` | Set to `1` to enable Perforce-aware write protection. When set, Edit, Write, and NotebookEdit fail with a `p4 edit <file>` hint if the target file lacks the owner-write bit, which Perforce clears on synced files until `p4 edit` opens them. This prevents Claude Code from bypassing Perforce change tracking |346| `CLAUDE_CODE_PERFORCE_MODE` | Set to `1` to enable Perforce-aware write protection. When set, Edit, Write, and NotebookEdit fail with a `p4 edit <file>` hint if the target file lacks the owner-write bit, which Perforce clears on synced files until `p4 edit` opens them. This prevents Claude Code from bypassing Perforce change tracking |
345| `CLAUDE_CODE_PLUGIN_CACHE_DIR` | Override the plugins root directory. Despite the name, this sets the parent directory, not the cache itself: marketplaces and the plugin cache live in subdirectories under this path. Defaults to `~/.claude/plugins` |347| `CLAUDE_CODE_PLUGIN_CACHE_DIR` | Override the plugins root directory. Despite the name, this sets the parent directory, not the cache itself: marketplaces and the plugin cache live in subdirectories under this path. Defaults to `~/.claude/plugins` |
346| `CLAUDE_CODE_PLUGIN_DIRS` | Plugin directories to load for the session, each loaded the way a [`--plugin-dir`](/docs/en/plugins/cli-reference#flags-that-load-a-plugin-for-one-session) flag loads it. Separate multiple paths with `:` on Unix or `;` on Windows. Give each path as an absolute path or start it with `~`, because Claude Code skips relative paths. Requires Claude Code v2.1.280 or later. See [Load a plugin for one session](/docs/en/plugins/create#load-a-directory-or-archive-for-one-session) |348| `CLAUDE_CODE_PLUGIN_DIRS` | Plugin directories to load for the session, each loaded the way a [`--plugin-dir`](/docs/en/plugins/cli-reference#flags-that-load-a-plugin-for-one-session) flag loads it. Separate multiple paths with `:` on Unix or `;` on Windows. Give each path as an absolute path or start it with `~`, because Claude Code skips relative paths. Requires Claude Code v2.1.280 or later. See [Load a plugin for one session](/docs/en/plugins/create#load-a-directory-or-archive-for-one-session) |
349| `CLAUDE_CODE_PLUGIN_DIR_WATCH` | Controls whether Claude Code reloads a [mod](/docs/en/plugins/mods/overview) when the mod's files change. Reloading applies to a mod you load from a directory with `--plugin-dir`, and it's on by default in interactive sessions. Set to `1` to turn it on in non-interactive sessions as well, or `0` to turn it off in every session. Requires Claude Code v2.1.287 or later. See [mod settings and environment variables](/docs/en/plugins/mods/reference#settings-and-environment-variables) |
347| `CLAUDE_CODE_PLUGIN_GIT_TIMEOUT_MS` | Timeout in milliseconds for cloning or refreshing a plugin marketplace (default: 120000). Increase this value for large repositories or slow network connections. See [Git clone timed out](/docs/en/plugins/troubleshooting#git-clone-timed-out-after-120s) |350| `CLAUDE_CODE_PLUGIN_GIT_TIMEOUT_MS` | Timeout in milliseconds for cloning or refreshing a plugin marketplace (default: 120000). Increase this value for large repositories or slow network connections. See [Git clone timed out](/docs/en/plugins/troubleshooting#git-clone-timed-out-after-120s) |
348| `CLAUDE_CODE_PLUGIN_KEEP_MARKETPLACE_ON_FAILURE` | Set to `1` to skip the re-clone attempt and keep using the existing marketplace checkout when a marketplace refresh can't reach or authenticate to the remote. Useful in offline or airgapped environments where re-cloning would fail the same way. See [Marketplace updates fail in offline environments](/docs/en/plugins/troubleshooting#marketplace-updates-keep-failing-offline) |351| `CLAUDE_CODE_PLUGIN_KEEP_MARKETPLACE_ON_FAILURE` | Set to `1` to skip the re-clone attempt and keep using the existing marketplace checkout when a marketplace refresh can't reach or authenticate to the remote. Useful in offline or airgapped environments where re-cloning would fail the same way. See [Marketplace updates fail in offline environments](/docs/en/plugins/troubleshooting#marketplace-updates-keep-failing-offline) |
349| `CLAUDE_CODE_PLUGIN_PREFER_HTTPS` | Set to `1` to clone GitHub `owner/repo` shorthand sources over HTTPS instead of SSH. Applies to plugin install and update, and to `/plugin marketplace add` and `update`. Useful in CI runners, containers, or any environment without a configured SSH key for `github.com` |352| `CLAUDE_CODE_PLUGIN_PREFER_HTTPS` | Set to `1` to clone GitHub `owner/repo` shorthand sources over HTTPS instead of SSH. Applies to plugin install and update, and to `/plugin marketplace add` and `update`. Useful in CI runners, containers, or any environment without a configured SSH key for `github.com` |
391| `CLAUDE_CODE_SUBPROCESS_ENV_SCRUB` | Set to `1` to strip credentials from the environments of the subprocesses Claude Code starts, such as Bash commands, hooks, and stdio MCP servers. The scrub recognizes a credential by its variable name or its value, and it leaves GitHub tokens and proxy settings in place. See [What the subprocess environment scrub removes](#what-the-subprocess-environment-scrub-removes). `claude-code-action` sets this automatically when `allowed_non_write_users` is configured |394| `CLAUDE_CODE_SUBPROCESS_ENV_SCRUB` | Set to `1` to strip credentials from the environments of the subprocesses Claude Code starts, such as Bash commands, hooks, and stdio MCP servers. The scrub recognizes a credential by its variable name or its value, and it leaves GitHub tokens and proxy settings in place. See [What the subprocess environment scrub removes](#what-the-subprocess-environment-scrub-removes). `claude-code-action` sets this automatically when `allowed_non_write_users` is configured |
392| `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 |395| `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 |
393| `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 |396| `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 |
394| `CLAUDE_CODE_SYNC_SKILLS` | Set to `1` in non-interactive mode with the `-p` flag to make Claude Code download the skills enabled for your claude.ai account in that run and wait for the list of them, up to `CLAUDE_CODE_SYNC_SKILLS_WAIT_TIMEOUT_MS`, before it runs the first query. The downloads themselves finish in the background, and Claude waits for a skill's download when it invokes that skill. Requires claude.ai authentication. Terminal sessions where you sign in with your claude.ai account [download these skills](/docs/en/skills#where-synced-skills-load) into `~/.claude/skills/synced/` and resync about every 10 minutes without this variable, so set it only when a `-p` run needs your current skills on its first query. Before v2.1.273, terminal sessions downloaded them only in a `-p` run with this variable set. 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. 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 |397| `CLAUDE_CODE_SYNC_SKILLS` | Set to `1` in non-interactive mode with the `-p` flag to make Claude Code download the skills enabled for your claude.ai account in that run and wait for the list of them, up to `CLAUDE_CODE_SYNC_SKILLS_WAIT_TIMEOUT_MS`, before it runs the first query. Requires claude.ai authentication. Terminal sessions where you sign in with your claude.ai account [sync these skills](/docs/en/skills#where-synced-skills-load) without this variable, so set it only when a `-p` run needs your current skills on its first query |
395| `CLAUDE_CODE_SYNC_SKILLS_INSTALL_TIMEOUT_MS` | Timeout in milliseconds for the skills resync that runs mid-session when an app built on the [Agent SDK](/docs/en/agent-sdk/typescript#query-object) reloads skills (default: 30000). When exceeded, the reload continues with whichever skills have arrived, and the remaining downloads finish in the background |398| `CLAUDE_CODE_SYNC_SKILLS_INSTALL_TIMEOUT_MS` | Timeout in milliseconds for the skills resync that runs mid-session when an app built on the [Agent SDK](/docs/en/agent-sdk/typescript#query-object) reloads skills (default: 30000). When exceeded, the reload continues with whichever skills have arrived, and the remaining downloads finish in the background |
396| `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 |399| `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 |
397| `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-reference#syntaxhighlightingdisabled) setting |400| `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-reference#syntaxhighlightingdisabled) setting |
415| `CLAUDE_CODE_WORKER_CHECKIN_SCHEDULE` | When `CLAUDE_AUTO_BACKGROUND_TASKS` is set to `1`, how long Claude Code waits before each reminder to Claude to check on [background subagents](/docs/en/sub-agents#run-subagents-in-foreground-or-background) that are still running. Takes one or more comma-separated waits in whole seconds from `1` to `86400`, such as `600` or `600,1800,3600`. Each value is the wait before the next reminder, and the last value repeats. Takes plain digits only; any other value or spelling reads as unset. When unset, there are no reminders. Requires Claude Code v2.1.283 or later |418| `CLAUDE_CODE_WORKER_CHECKIN_SCHEDULE` | When `CLAUDE_AUTO_BACKGROUND_TASKS` is set to `1`, how long Claude Code waits before each reminder to Claude to check on [background subagents](/docs/en/sub-agents#run-subagents-in-foreground-or-background) that are still running. Takes one or more comma-separated waits in whole seconds from `1` to `86400`, such as `600` or `600,1800,3600`. Each value is the wait before the next reminder, and the last value repeats. Takes plain digits only; any other value or spelling reads as unset. When unset, there are no reminders. Requires Claude Code v2.1.283 or later |
416| `CLAUDE_CODE_WORKFLOW_MAX_CONCURRENT_AGENTS` | How many agents a single [workflow](/docs/en/workflows) run executes at once, from `1` to `256`. By default, a run executes up to 16 agents at once, fewer when Claude Code has fewer CPUs available; queued `agent()` calls wait for a free slot. Each running agent's transcript stays in Claude Code's memory, so higher values raise memory use. Takes plain digits only; out-of-range values and other spellings keep the default. Requires Claude Code v2.1.269 or later |419| `CLAUDE_CODE_WORKFLOW_MAX_CONCURRENT_AGENTS` | How many agents a single [workflow](/docs/en/workflows) run executes at once, from `1` to `256`. By default, a run executes up to 16 agents at once, fewer when Claude Code has fewer CPUs available; queued `agent()` calls wait for a free slot. Each running agent's transcript stays in Claude Code's memory, so higher values raise memory use. Takes plain digits only; out-of-range values and other spellings keep the default. Requires Claude Code v2.1.269 or later |
417| `CLAUDE_CODE_WORKFLOW_PREFIX_STAGGER_MS` | Upper bound in milliseconds on how long a [workflow](/docs/en/workflows) agent waits for a same-prefix sibling's first response to begin before sending its own first request. When a fan-out starts several agents that share a [prompt-cache prefix](/docs/en/workflows#prompt-caching-in-a-fan-out), Claude Code holds all but the first agent for up to this long so the rest read the cached prefix instead of each processing it uncached. Default `5000`. Set to `0` to disable the wait. When `DISABLE_PROMPT_CACHING` is set, agents never wait. Requires Claude Code v2.1.229 or later |420| `CLAUDE_CODE_WORKFLOW_PREFIX_STAGGER_MS` | Upper bound in milliseconds on how long a [workflow](/docs/en/workflows) agent waits for a same-prefix sibling's first response to begin before sending its own first request. When a fan-out starts several agents that share a [prompt-cache prefix](/docs/en/workflows#prompt-caching-in-a-fan-out), Claude Code holds all but the first agent for up to this long so the rest read the cached prefix instead of each processing it uncached. Default `5000`. Set to `0` to disable the wait. When `DISABLE_PROMPT_CACHING` is set, agents never wait. Requires Claude Code v2.1.229 or later |
418| `CLAUDE_CONFIG_DIR` | Override the configuration directory (default: `~/.claude`). All settings, session history, and plugins are stored under this path. For credentials, see [where Claude Code stores credentials](/docs/en/authentication#credential-management). Useful for running multiple accounts side by side: for example, `alias claude-work='CLAUDE_CONFIG_DIR=~/.claude-work claude'`. Set it in your shell, user settings, or managed settings. Ignored in [project and local settings](/docs/en/settings-reference#variables-claude-code-ignores-in-env) |421| `CLAUDE_CONFIG_DIR` | Override the configuration directory (default: `~/.claude`). All settings, session history, and plugins are stored under this path. For credentials, see [where Claude Code stores credentials](/docs/en/authentication#credential-management). Useful for running multiple accounts side by side: for example, `alias claude-work='CLAUDE_CONFIG_DIR=~/.claude-work claude'`. Set it in your shell, user settings, or managed settings. In a settings file, write the [absolute path](#in-settings-files). Ignored in [project and local settings](/docs/en/settings-reference#variables-claude-code-ignores-in-env) |
419| `CLAUDE_DISABLE_ADOPT` | Set to `1` to stop in-flight background work instead of carrying it over when you background a session by pressing `←` or with [`/background`](/docs/en/agent-view#from-inside-a-session). Claude Code asks you to confirm before backgrounding, then stops the tasks that would otherwise carry over. Requires Claude Code v2.1.195 or later |422| `CLAUDE_DISABLE_ADOPT` | Set to `1` to stop in-flight background work instead of carrying it over when you background a session by pressing `←` or with [`/background`](/docs/en/agent-view#from-inside-a-session). Claude Code asks you to confirm before backgrounding, then stops the tasks that would otherwise carry over. Requires Claude Code v2.1.195 or later |
420| `CLAUDE_EFFORT` | Set automatically in Bash tool subprocesses and hook commands to the [effort level](/docs/en/model-config#adjust-effort-level) in effect when the subprocess starts: `low`, `medium`, `high`, `xhigh`, or `max`. Matches the `effort.level` field passed to [hooks](/docs/en/hooks). Only set when the current model supports the effort parameter |423| `CLAUDE_EFFORT` | Set automatically in Bash tool subprocesses and hook commands to the [effort level](/docs/en/model-config#adjust-effort-level) in effect when the subprocess starts: `low`, `medium`, `high`, `xhigh`, or `max`. Matches the `effort.level` field passed to [hooks](/docs/en/hooks). Only set when the current model supports the effort parameter |
421| `CLAUDE_ENABLE_BYTE_WATCHDOG` | Set to `1` to force-enable the byte-level streaming idle watchdog, or set to `0` to force-disable it. `0` also turns off the [first-byte deadline](/docs/en/network-config#streaming-idle-watchdogs) on the connections where that deadline runs. When unset, the watchdog is enabled by default for direct Anthropic API and [Claude Platform on AWS](/docs/en/claude-platform-on-aws) connections, and for streaming responses on [gateway](/docs/en/gateways) connections reached through `ANTHROPIC_BASE_URL` or `ANTHROPIC_AWS_BASE_URL`; before v2.1.222 it didn't run on those gateway connections, so the event-level watchdog could report a stall there even while keep-alive pings were arriving. For timeouts and how the timers interact, see [Streaming idle watchdogs](/docs/en/network-config#streaming-idle-watchdogs) |424| `CLAUDE_ENABLE_BYTE_WATCHDOG` | Set to `1` to force-enable the byte-level streaming idle watchdog, or set to `0` to force-disable it. `0` also turns off the [first-byte deadline](/docs/en/network-config#streaming-idle-watchdogs) on the connections where that deadline runs. When unset, the watchdog is enabled by default for direct Anthropic API and [Claude Platform on AWS](/docs/en/claude-platform-on-aws) connections, and for streaming responses on [gateway](/docs/en/gateways) connections reached through `ANTHROPIC_BASE_URL` or `ANTHROPIC_AWS_BASE_URL`; before v2.1.222 it didn't run on those gateway connections, so the event-level watchdog could report a stall there even while keep-alive pings were arriving. For timeouts and how the timers interact, see [Streaming idle watchdogs](/docs/en/network-config#streaming-idle-watchdogs) |
466| `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 |469| `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 |
467| `MAX_MCP_OUTPUT_TOKENS` | Maximum number of tokens allowed in MCP tool responses (default: 25000). 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. A successful text result longer than 50,000 characters from a tool without that annotation is [saved to a file](/docs/en/mcp#mcp-output-limits-and-warnings) regardless of this variable |470| `MAX_MCP_OUTPUT_TOKENS` | Maximum number of tokens allowed in MCP tool responses (default: 25000). 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. A successful text result longer than 50,000 characters from a tool without that annotation is [saved to a file](/docs/en/mcp#mcp-output-limits-and-warnings) regardless of this variable |
468| `MAX_STRUCTURED_OUTPUT_RETRIES` | Number of attempts Claude Code allows 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; after that many failed attempts with no valid output, the run fails. The same cap applies when a [workflow](/docs/en/workflows) subagent's structured output fails validation. Defaults to 5, a first attempt plus four retries |471| `MAX_STRUCTURED_OUTPUT_RETRIES` | Number of attempts Claude Code allows 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; after that many failed attempts with no valid output, the run fails. The same cap applies when a [workflow](/docs/en/workflows) subagent's structured output fails validation. Defaults to 5, a first attempt plus four retries |
469| `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 Opus 5.5, Sonnet 5.5, and the Fable models, which can't have thinking turned off. On [third-party providers](/docs/en/third-party-integrations), `0` omits the `thinking` parameter instead. With thinking turned off on the Anthropic API, Claude Code sends effort `high` instead of a higher level to models it knows [don't accept that combination](/docs/en/errors#effort-isnt-available-with-thinking-turned-off), such as Opus 5. For a positive value, Claude Code ignores the number itself on adaptive reasoning models, except when `CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING` turns adaptive reasoning off |472| `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 Opus 5.5, Sonnet 5.5, Haiku 5.5, and the Fable models, which can't have thinking turned off. On [third-party providers](/docs/en/third-party-integrations), `0` omits the `thinking` parameter instead. With thinking turned off on the Anthropic API, Claude Code sends effort `high` instead of a higher level to models it knows [don't accept that combination](/docs/en/errors#effort-isnt-available-with-thinking-turned-off), such as Opus 5. For a positive value, Claude Code ignores the number itself on adaptive reasoning models, except when `CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING` turns adaptive reasoning off |
470| `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` |473| `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` |
471| `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. Set to `0` to make Claude Code wait for servers to connect before the first query. 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#server-status-detail), since their tools must be present when the first prompt is built. In non-interactive mode (`-p`) without `--input-format stream-json`, Claude Code also waits for still-pending servers before the first turn regardless of this variable. When you pass [`--mcp-config`](/docs/en/cli-reference#cli-flags) explicitly, the wait has a longer deadline; see that flag's entry for the cached-server exception |474| `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. Set to `0` to make Claude Code wait for servers to connect before the first query. 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#server-status-detail), since their tools must be present when the first prompt is built. In non-interactive mode (`-p`) without `--input-format stream-json`, Claude Code also waits for still-pending servers before the first turn regardless of this variable. When you pass [`--mcp-config`](/docs/en/cli-reference#cli-flags) explicitly, the wait has a longer deadline; see that flag's entry for the cached-server exception |
472| `MCP_CONNECT_TIMEOUT_MS` | How long blocking MCP startup waits, in milliseconds, for the connection batch before snapshotting the tool list (default: 5000). Applies when `MCP_CONNECTION_NONBLOCKING=0` or for servers marked [`alwaysLoad: true`](/docs/en/mcp#exempt-a-server-from-deferral). Servers still pending at the deadline keep connecting in the background. Distinct from `MCP_TIMEOUT`, which bounds an individual server's connect attempt |475| `MCP_CONNECT_TIMEOUT_MS` | How long blocking MCP startup waits, in milliseconds, for the connection batch before snapshotting the tool list (default: 5000). Applies when `MCP_CONNECTION_NONBLOCKING=0` or for servers marked [`alwaysLoad: true`](/docs/en/mcp#exempt-a-server-from-deferral). Servers still pending at the deadline keep connecting in the background. Distinct from `MCP_TIMEOUT`, which bounds an individual server's connect attempt |
517| `VERTEX_REGION_CLAUDE_FABLE_5` | Override region for Claude Fable 5 when using Google Cloud's Agent Platform. Added in v2.1.170 |520| `VERTEX_REGION_CLAUDE_FABLE_5` | Override region for Claude Fable 5 when using Google Cloud's Agent Platform. Added in v2.1.170 |
518| `VERTEX_REGION_CLAUDE_FABLE_5_1` | Override region for Claude Fable 5.1 when using Google Cloud's Agent Platform. Added in v2.1.257 |521| `VERTEX_REGION_CLAUDE_FABLE_5_1` | Override region for Claude Fable 5.1 when using Google Cloud's Agent Platform. Added in v2.1.257 |
519| `VERTEX_REGION_CLAUDE_HAIKU_4_5` | Override region for Claude Haiku 4.5 when using Google Cloud's Agent Platform |522| `VERTEX_REGION_CLAUDE_HAIKU_4_5` | Override region for Claude Haiku 4.5 when using Google Cloud's Agent Platform |
523| `VERTEX_REGION_CLAUDE_HAIKU_5_5` | Override region for Claude Haiku 5.5 when using Google Cloud's Agent Platform. Added in v2.1.293 |
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521Standard 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.525Standard 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.
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