> ## Documentation Index
> Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Environment variables
> Reference for environment variables that control Claude Code behavior.
Environment variables can control Claude Code behavior such as model selection, authentication, request routing, and feature toggles. Many of the same behaviors can also be configured through a [settings file](/docs/en/settings) field, a [CLI flag](/docs/en/cli-reference), or an in-session command like `/model`.
This page covers how to:
* [Set environment variables](#set-environment-variables) in your shell or in a settings file
* [Check which value applies](#precedence) when a behavior can be set more than one way
* [Look up the variables Claude Code reads](#variables)
## Set environment variables
A variable you set in your shell lasts for that terminal session, while a variable in a settings file applies every time `claude` runs.
### In your shell
Set the variable before launching `claude`:
```bash theme={null}
export API_TIMEOUT_MS="1200000"
claude
```
To set it for every session, add the `export` line to `~/.bashrc`, `~/.zshrc`, or your shell's profile file.
```powershell theme={null}
$env:API_TIMEOUT_MS = "1200000"
claude
```
To set it for every session, run `[Environment]::SetEnvironmentVariable("API_TIMEOUT_MS", "1200000", "User")` and open a new terminal.
```batch theme={null}
set API_TIMEOUT_MS=1200000
claude
```
To set it for every session, run `setx API_TIMEOUT_MS "1200000"` and open a new terminal.
The assignment line prints nothing on success, so confirm the variable is set by printing it in the same shell before you run `claude`:
```bash theme={null}
echo $API_TIMEOUT_MS
```
```powershell theme={null}
echo $env:API_TIMEOUT_MS
```
```batch theme={null}
echo %API_TIMEOUT_MS%
```
### In settings files
Add variables under the `env` key in a `settings.json` file, creating the file if it doesn't exist. Claude Code reads them directly from the file, so they take effect no matter how `claude` was launched. A running session applies new and changed values to its environment when you save the file, but a feature that reads its variables once at startup, such as [OpenTelemetry monitoring](/docs/en/monitoring-usage), keeps its startup values until you relaunch. Removing a variable from the file doesn't unset it in a running session; the removal takes effect the next time you launch `claude`.
```json ~/.claude/settings.json theme={null}
{
"env": {
"API_TIMEOUT_MS": "1200000",
"BASH_DEFAULT_TIMEOUT_MS": "300000"
}
}
```
The file you choose controls who the variables apply to:
| File | Applies to |
| :---------------------------- | :------------------------------------------------------------------------------------------------------------------------------ |
| `~/.claude/settings.json` | You, in every project |
| `.claude/settings.json` | Everyone working in the project, checked into source control |
| `.claude/settings.local.json` | You, in this project only, gitignored when Claude Code saves a setting to it; add it to your gitignore if you create it by hand |
| Managed settings | Everyone in your organization, deployed by an admin |
See [Settings files](/docs/en/settings#settings-files) for where each file lives and [Settings precedence](/docs/en/settings#settings-precedence) for how they combine when more than one sets the same variable.
## Precedence
Some behaviors have both an environment variable and a dedicated settings key. If you set both, the environment variable takes precedence. For example, `ANTHROPIC_MODEL` overrides the `model` setting, and `CLAUDE_CODE_AUTO_CONNECT_IDE` overrides `autoConnectIde`. Claude Code uses the settings key only when the environment variable is unset.
When the same variable is set in both your shell and a settings file `env` block, the settings file value applies. Claude Code writes each `env` entry into the process environment at startup and again when the file changes, replacing the value inherited from the shell. A few variables are special-cased; the [`env` setting](/docs/en/settings#available-settings) lists the exceptions.
In a settings file you can set a variable but you can't remove one. To override a variable you can't unset, such as a stale `CLAUDE_CODE_USE_VERTEX` exported by a shell profile you don't control, set it to an empty string in the `env` block: `"CLAUDE_CODE_USE_VERTEX": ""`. Claude Code treats the empty value as unset for provider selection. Subprocesses still inherit the empty value.
Between settings files, `env` values follow [settings precedence](/docs/en/settings#settings-precedence), so a managed settings entry overrides the same variable in user or project settings.
How an environment variable interacts with CLI flags and in-session commands varies per feature: `--model` and `/model` override `ANTHROPIC_MODEL`, while `CLAUDE_CODE_EFFORT_LEVEL` overrides `/effort`. When a variable interacts with another configuration source, its row in the [Variables](#variables) list states the precedence or links to the page that documents it.
Claude Code reads shell environment variables at startup, so changes to them take effect the next time you launch `claude`. Variables set under the `env` key in settings files are reapplied to a running session when the file changes, with the startup-only exception described in [In settings files](#in-settings-files).
## Variables
Numeric variables such as timeouts, token budgets, and retry counts accept scientific notation and digit-separator spellings in addition to plain digits, except where a variable's row notes it takes plain digits only. For example, Claude Code reads `2e3` as 2000 and `64_000` as 64000. Before v2.1.211, these spellings could silently set a much smaller value, such as `1e6` setting a timeout to 1.
For variables that turn a behavior on or off, set `1` or `true` to turn it on and `0` or `false` to turn it off, in any casing.
Some variables read only whether you set them at all, so any non-empty value including `0` turns the behavior on, and you turn the behavior off by unsetting the variable or setting it to an empty value. These variables work that way:
* `CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC`
* `DISABLE_TELEMETRY`
* `DISABLE_ERROR_REPORTING`
* `CLAUDE_CODE_TMUX_TRUECOLOR`
* `FALLBACK_FOR_ALL_PRIMARY_MODELS`
* `IS_DEMO`
One other variable has its own rule: `FORCE_HYPERLINK` reads a number, so only `0` turns it off. Each variable's row also states its own rule.
| Variable | Purpose |
| :------------------------------------------------------ | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `ANTHROPIC_API_KEY` | API key sent as `X-Api-Key` header. When set, this key is used instead of your Claude Pro, Max, Team, or Enterprise subscription even if you are logged in. In non-interactive mode (`-p`), the key is always used when present. In interactive mode, you are prompted to approve the key once before it overrides your subscription. To use your subscription instead, run `unset ANTHROPIC_API_KEY` |
| `ANTHROPIC_AUTH_TOKEN` | Custom value for the `Authorization` header (the value you set here will be prefixed with `Bearer `) |
| `ANTHROPIC_AWS_API_KEY` | Workspace API key for [Claude Platform on AWS](/docs/en/claude-platform-on-aws), generated in the AWS Console. Sent as `x-api-key` and takes precedence over AWS SigV4 |
| `ANTHROPIC_AWS_BASE_URL` | Override the [Claude Platform on AWS](/docs/en/claude-platform-on-aws) endpoint URL. Use for custom regions or when routing through an [LLM gateway](/docs/en/llm-gateway). Defaults to `https://aws-external-anthropic.{AWS_REGION}.api.aws` |
| `ANTHROPIC_AWS_WORKSPACE_ID` | Required for [Claude Platform on AWS](/docs/en/claude-platform-on-aws). Sent on every request as the `anthropic-workspace-id` header |
| `ANTHROPIC_BASE_URL` | Override the API endpoint to route requests through a proxy or gateway. When set to a non-first-party host, [MCP tool search](/docs/en/mcp#scale-with-mcp-tool-search) is disabled by default. Set `ENABLE_TOOL_SEARCH=true` if your proxy forwards `tool_reference` blocks. As of v2.1.196, [Remote Control](/docs/en/remote-control#requirements) is disabled when this points at a host other than `api.anthropic.com`, matching its behavior on Amazon Bedrock, Google Cloud's Agent Platform, and Microsoft Foundry |
| `ANTHROPIC_BEDROCK_BASE_URL` | Override the Amazon Bedrock endpoint URL. Use for custom Amazon Bedrock endpoints or when routing through an [LLM gateway](/docs/en/llm-gateway). See [Amazon Bedrock](/docs/en/amazon-bedrock) |
| `ANTHROPIC_BEDROCK_MANTLE_BASE_URL` | Override the Amazon Bedrock Mantle endpoint URL. See [Mantle endpoint](/docs/en/amazon-bedrock#use-the-mantle-endpoint) |
| `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) |
| `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 |
| `ANTHROPIC_CUSTOM_HEADERS` | Custom headers to add to requests (`Name: Value` format, newline-separated for multiple headers) |
| `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) |
| `ANTHROPIC_CUSTOM_MODEL_OPTION_DESCRIPTION` | Display description for the custom model entry in the `/model` picker. Defaults to `Custom model ()` when not set |
| `ANTHROPIC_CUSTOM_MODEL_OPTION_NAME` | Display name for the custom model entry in the `/model` picker. Defaults to the model ID when not set |
| `ANTHROPIC_CUSTOM_MODEL_OPTION_SUPPORTED_CAPABILITIES` | Comma-separated list of [capabilities](/docs/en/model-config#customize-pinned-model-display-and-capabilities) the custom model supports, for example `effort,thinking`. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_FABLE_MODEL` | Model ID that the `fable` alias resolves to, and the ID Claude Code recognizes as Fable 5 for [automatic model fallback](/docs/en/model-config#automatic-model-fallback) on third-party providers. See [Model configuration](/docs/en/model-config#environment-variables) |
| `ANTHROPIC_DEFAULT_FABLE_MODEL_DESCRIPTION` | Display description for the pinned Fable model in the `/model` picker. Defaults to `Custom Fable model` when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_FABLE_MODEL_NAME` | Display name for the pinned Fable model in the `/model` picker. Defaults to the model ID when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_FABLE_MODEL_SUPPORTED_CAPABILITIES` | Comma-separated list of [capabilities](/docs/en/model-config#customize-pinned-model-display-and-capabilities) the pinned Fable model supports, for example `effort,thinking`. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_HAIKU_MODEL` | Model ID that the `haiku` alias resolves to, also used for [background functionality](/docs/en/costs#background-token-usage). See [Model configuration](/docs/en/model-config#environment-variables) |
| `ANTHROPIC_DEFAULT_HAIKU_MODEL_DESCRIPTION` | Display description for the pinned Haiku model in the `/model` picker. Defaults to `Custom Haiku model` when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_HAIKU_MODEL_NAME` | Display name for the pinned Haiku model in the `/model` picker. Defaults to the model ID when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_HAIKU_MODEL_SUPPORTED_CAPABILITIES` | Comma-separated list of [capabilities](/docs/en/model-config#customize-pinned-model-display-and-capabilities) the pinned Haiku model supports, for example `effort,thinking`. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_OPUS_MODEL` | Model ID that the `opus` alias resolves to, and that `opusplan` uses while Plan Mode is active. See [Model configuration](/docs/en/model-config#environment-variables) |
| `ANTHROPIC_DEFAULT_OPUS_MODEL_DESCRIPTION` | Display description for the pinned Opus model in the `/model` picker. When not set, defaults to `Custom Opus model`, or `Custom Opus model (1M context)` if the pinned model ID has the `[1m]` suffix and `CLAUDE_CODE_DISABLE_1M_CONTEXT` isn't turned on. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_OPUS_MODEL_NAME` | Display name for the pinned Opus model in the `/model` picker. Defaults to the model ID when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_OPUS_MODEL_SUPPORTED_CAPABILITIES` | Comma-separated list of [capabilities](/docs/en/model-config#customize-pinned-model-display-and-capabilities) the pinned Opus model supports, for example `effort,thinking`. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_SONNET_MODEL` | Model ID that the `sonnet` alias resolves to, and that `opusplan` uses when Plan Mode is not active. See [Model configuration](/docs/en/model-config#environment-variables) |
| `ANTHROPIC_DEFAULT_SONNET_MODEL_DESCRIPTION` | Display description for the pinned Sonnet model in the `/model` picker. When not set, defaults to `Custom Sonnet model`, or `Custom Sonnet model (1M context)` if the pinned model ID has the `[1m]` suffix and `CLAUDE_CODE_DISABLE_1M_CONTEXT` isn't turned on. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_SONNET_MODEL_NAME` | Display name for the pinned Sonnet model in the `/model` picker. Defaults to the model ID when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_DEFAULT_SONNET_MODEL_SUPPORTED_CAPABILITIES` | Comma-separated list of [capabilities](/docs/en/model-config#customize-pinned-model-display-and-capabilities) the pinned Sonnet model supports, for example `effort,thinking`. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) |
| `ANTHROPIC_FOUNDRY_API_KEY` | API key for Microsoft Foundry authentication (see [Microsoft Foundry](/docs/en/microsoft-foundry)) |
| `ANTHROPIC_FOUNDRY_AUTH_TOKEN` | Bearer token for Microsoft Foundry authentication, such as a Microsoft Entra access token. Claude Code sends it as the `Authorization: Bearer` header. Takes precedence over `ANTHROPIC_FOUNDRY_API_KEY` and over the Azure default credential chain. See [Microsoft Foundry](/docs/en/microsoft-foundry). Requires Claude Code v2.1.203 or later |
| `ANTHROPIC_FOUNDRY_BASE_URL` | Full base URL for the Microsoft Foundry resource (for example, `https://my-resource.services.ai.azure.com/anthropic`). Alternative to `ANTHROPIC_FOUNDRY_RESOURCE` (see [Microsoft Foundry](/docs/en/microsoft-foundry)) |
| `ANTHROPIC_FOUNDRY_RESOURCE` | Microsoft Foundry resource name (for example, `my-resource`). Required if `ANTHROPIC_FOUNDRY_BASE_URL` is not set (see [Microsoft Foundry](/docs/en/microsoft-foundry)) |
| `ANTHROPIC_MODEL` | Name of the model setting to use (see [Model Configuration](/docs/en/model-config#environment-variables)) |
| `ANTHROPIC_SMALL_FAST_MODEL` | \[DEPRECATED] Name of [Haiku-class model for background tasks](/docs/en/costs) |
| `ANTHROPIC_SMALL_FAST_MODEL_AWS_REGION` | Override AWS region for the Haiku-class model when using Amazon Bedrock or Amazon Bedrock Mantle. On Amazon Bedrock, this only takes effect when `ANTHROPIC_DEFAULT_HAIKU_MODEL` or the deprecated `ANTHROPIC_SMALL_FAST_MODEL` is also set, since Amazon Bedrock otherwise runs background tasks on the [default Sonnet model or the primary model](/docs/en/amazon-bedrock#4-pin-model-versions) in the session region |
| `ANTHROPIC_VERTEX_BASE_URL` | Override Google Cloud's Agent Platform endpoint URL. Use for custom Google Cloud's Agent Platform endpoints or when routing through an [LLM gateway](/docs/en/llm-gateway). See [Google Cloud's Agent Platform](/docs/en/google-vertex-ai) |
| `ANTHROPIC_VERTEX_PROJECT_ID` | GCP project ID for Google Cloud's Agent Platform requests. Overridden by `GCLOUD_PROJECT`, `GOOGLE_CLOUD_PROJECT`, or the project in your `GOOGLE_APPLICATION_CREDENTIALS` credential file. See [Google Cloud's Agent Platform](/docs/en/google-vertex-ai) |
| `ANTHROPIC_WORKSPACE_ID` | Workspace ID for [workload identity federation](https://platform.claude.com/docs/en/manage-claude/workload-identity-federation). Set this when your federation rule is scoped to more than one workspace so the token exchange knows which workspace to target |
| `API_FORCE_IDLE_TIMEOUT` | Override the 5-minute body idle timeout that aborts a streaming model response when no bytes arrive. Set to `0` to turn the timeout off, for example when a slow [gateway](/docs/en/llm-gateway) or local model pauses longer than 5 minutes between chunks, or `1` to keep it on for every provider. When unset, the timeout is active on providers other than the direct Anthropic API and [Claude Platform on AWS](/docs/en/claude-platform-on-aws). The [stream watchdogs](/docs/en/network-config#streaming-idle-watchdogs) run independently of it and abort a long silent pause even when you set `0` here. Requires Claude Code v2.1.169 or later |
| `API_TIMEOUT_MS` | Timeout for API requests in milliseconds (default: 600000, or 10 minutes; maximum: 2147483647). Increase this when requests time out on slow networks or when routing through a proxy. Values above the maximum overflow the underlying timer and cause requests to fail immediately |
| `AWS_BEARER_TOKEN_BEDROCK` | Amazon Bedrock API key for authentication (see [Amazon Bedrock API keys](https://aws.amazon.com/blogs/machine-learning/accelerate-ai-development-with-amazon-bedrock-api-keys/)) |
| `BASH_DEFAULT_TIMEOUT_MS` | Default timeout for long-running bash commands (default: 120000, or 2 minutes) |
| `BASH_MAX_OUTPUT_LENGTH` | Maximum number of characters of bash output that Claude Code reads back into a command's result (default: 30000; maximum: 150000). See [Output limits](/docs/en/tools-reference#output-limits) |
| `BASH_MAX_TIMEOUT_MS` | Maximum timeout the model can set for long-running bash commands (default: 600000, or 10 minutes). The effective ceiling is the larger of this and `BASH_DEFAULT_TIMEOUT_MS` |
| `CCR_FORCE_BUNDLE` | Set to `1` to force [`claude --cloud`](/docs/en/claude-code-on-the-web#send-local-repositories-without-github) to bundle and upload your local repository even when GitHub access is available |
| `CLAUDECODE` | Set to `1` in subprocesses Claude Code spawns (Bash and PowerShell tools, tmux sessions, [hook](/docs/en/hooks) commands, [status line](/docs/en/statusline) commands, stdio [MCP server](/docs/en/mcp) subprocesses). IDE extensions also set this in their integrated terminals. Use to detect when a script is running inside a subprocess spawned by Claude Code. To check whether the current process was spawned directly by a tool call or hook, rather than inside a stdio MCP server that Claude Code started, use `CLAUDE_CODE_CHILD_SESSION` instead |
| `CLAUDE_AFK_COUNTDOWN_MS` | How many milliseconds before auto-continue the on-screen countdown appears on an unanswered [`AskUserQuestion`](/docs/en/tools-reference) dialog. Default `20000` (20 seconds), capped at the auto-continue timeout. Has no effect unless auto-continue is on; see the [`askUserQuestionTimeout`](/docs/en/settings#available-settings) setting and `CLAUDE_AFK_TIMEOUT_MS`. Requires Claude Code v2.1.198 or later |
| `CLAUDE_AFK_TIMEOUT_MS` | How many milliseconds of idle time before an unanswered [`AskUserQuestion`](/docs/en/tools-reference) dialog auto-continues without you. Auto-continue is off by default; opt in with the [`askUserQuestionTimeout`](/docs/en/settings#available-settings) setting. This variable is an override for demos and automated tests: when set, it takes precedence over that setting and turns auto-continue on even when the setting is unset or `never`. Setting `0` doesn't turn the timeout off; it closes the dialog immediately. In v2.1.198 and v2.1.199, auto-continue was on by default with a `60000` (60 seconds) timeout. Requires Claude Code v2.1.198 or later |
| `CLAUDE_AGENT_SDK_DISABLE_BUILTIN_AGENTS` | Set to `1` to disable all built-in [subagent](/docs/en/sub-agents) types such as Explore and Plan. Only applies in non-interactive mode (the `-p` flag). Useful for SDK users who want a blank slate |
| `CLAUDE_AGENT_SDK_MCP_NO_PREFIX` | Set to `1` to skip the `mcp____` prefix on tool names from SDK-created MCP servers. Tools use their original names. SDK usage only |
| `CLAUDE_ASYNC_AGENT_STALL_TIMEOUT_MS` | Stall timeout in milliseconds for background subagents. Default `600000` (10 minutes). The timer resets on each streaming progress event; if no progress arrives within the window, the subagent is aborted and the task is marked failed, surfacing any partial result to the parent |
| `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/context-window#set-the-auto-compact-window). Applies to both main conversations and subagents |
| `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 |
| `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 |
| `CLAUDE_BASH_MAINTAIN_PROJECT_WORKING_DIR` | Return to the original working directory after each Bash or PowerShell command in the main session |
| `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 |
| `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 |
| `CLAUDE_CODE_ACCESSIBILITY` | Set to `1` to keep the native terminal cursor visible and disable the inverted-text cursor indicator. Allows screen magnifiers like macOS Zoom to track cursor position |
| `CLAUDE_CODE_ADDITIONAL_DIRECTORIES_CLAUDE_MD` | Set to `1` to load memory files from directories specified with `--add-dir`. Loads `CLAUDE.md`, `.claude/CLAUDE.md`, `.claude/rules/*.md`, and `CLAUDE.local.md`. By default, additional directories do not load memory files |
| `CLAUDE_CODE_ALT_SCREEN_FULL_REPAINT` | Set to `1` to repaint the entire screen on every frame in [fullscreen rendering](/docs/en/fullscreen) instead of sending incremental updates. Use this if fullscreen mode shows stale or misplaced text fragments. Claude Code enables this automatically for background sessions and [agent view](/docs/en/agent-view) on Windows |
| `CLAUDE_CODE_ALWAYS_ENABLE_EFFORT` | Set to `1` to send the [effort](/docs/en/model-config#adjust-effort-level) parameter with every request, even when Claude Code does not recognize the model ID as effort-capable. Use this when routing through an [LLM gateway](/docs/en/llm-gateway) or third-party provider that serves models under custom identifiers. Models that reject the effort parameter at the API, including Claude 3 models, Sonnet 4.0 and 4.5, Opus 4.0 and 4.1, and Haiku 4.5, are still excluded so requests do not fail |
| `CLAUDE_CODE_API_KEY_HELPER_TTL_MS` | Interval in milliseconds at which credentials should be refreshed (when using [`apiKeyHelper`](/docs/en/settings#available-settings)) |
| `CLAUDE_CODE_ARTIFACT_AUTO_OPEN` | Set to `0` to stop Claude Code from opening the browser automatically when a new [artifact](/docs/en/artifacts) is published. Republishing an existing artifact does not open the browser regardless of this setting |
| `CLAUDE_CODE_ATTRIBUTION_HEADER` | Set to `0` to omit the [attribution block](/docs/en/llm-gateway-protocol#system-prompt-attribution-block), which carries the client version and a prompt fingerprint, from the start of the system prompt. Caching on a direct connection to the Anthropic API is unaffected either way. Before v2.1.181 the block included a per-request token on custom base URLs and Microsoft Foundry connections, so on those versions set it to `0` when your [LLM gateway](/docs/en/llm-gateway) caches on the request body or forwards requests to a third-party provider, or when you connect to Microsoft Foundry directly |
| `CLAUDE_CODE_AUTO_COMPACT_WINDOW` | Set the [auto-compact window](/docs/en/context-window#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. 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 |
| `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#global-config-settings) global config setting |
| `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 |
| `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 |
| `CLAUDE_CODE_CERT_STORE` | Comma-separated list of CA certificate sources for TLS connections. `bundled` is the Mozilla CA set shipped with Claude Code. `system` is the operating system trust store, read only on runtimes with `tls.getCACertificates`: the native binary, or Node 22.15 or later for npm installs. See [CA certificate store](/docs/en/network-config#ca-certificate-store). Default is `bundled,system` |
| `CLAUDE_CODE_CHILD_SESSION` | Set to `1` in subprocesses Claude Code spawns via the Bash, PowerShell, and Monitor tools, [hook](/docs/en/hooks) commands, and [status line](/docs/en/statusline) commands. Not set for stdio [MCP server](/docs/en/mcp) subprocesses, which are long-lived and outlive the session that spawned them. Unlike `CLAUDECODE`, this is only set by Claude Code itself when it launches a subprocess and not by IDE extensions, so it reliably distinguishes a nested session from a top-level `claude` launched in an IDE-integrated terminal. A nested interactive `claude` TUI started this way is automatically excluded from `--resume`, `--continue`, up-arrow history, and the `claude agents` list. Non-interactive `claude -p` sessions still persist. Set `CLAUDE_CODE_FORCE_SESSION_PERSISTENCE=1` to override this exclusion. Requires Claude Code v2.1.172 or later |
| `CLAUDE_CODE_CLIENT_CERT` | Path to client certificate file for mTLS authentication |
| `CLAUDE_CODE_CLIENT_KEY` | Path to client private key file for mTLS authentication |
| `CLAUDE_CODE_CLIENT_KEY_PASSPHRASE` | Passphrase for encrypted CLAUDE\_CODE\_CLIENT\_KEY (optional) |
| `CLAUDE_CODE_CONNECT_TIMEOUT_MS` | Removed in v2.1.186 and now a no-op. Previously set a separate timeout for the connect, TLS, and response-header phase of a streaming API request. Use `API_TIMEOUT_MS` for the per-request timeout |
| `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/.txt` |
| `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 |
| `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 [Sonnet 5](/docs/en/model-config#sonnet-5-context-window) sessions are treated as having a 200K window. Useful for enterprise environments with compliance requirements |
| `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 5, Sonnet 5, or Opus 4.7 and later, which always use adaptive reasoning |
| `CLAUDE_CODE_DISABLE_ADMIN_ENV_UNION` | Set to `1` to stop Claude Code from merging [managed settings](/docs/en/settings#settings-precedence) `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 |
| `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 |
| `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#available-settings) setting |
| `CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN` | Set to `1` to disable [fullscreen rendering](/docs/en/fullscreen) and use the classic main-screen renderer. The conversation stays in your terminal's native scrollback so `Cmd+f` and tmux copy mode work as usual. Takes precedence over `CLAUDE_CODE_NO_FLICKER` and the [`tui`](/docs/en/settings#available-settings) setting. You can also switch with `/tui default`. Does not apply to background sessions opened from [agent view](/docs/en/agent-view), which always use fullscreen rendering |
| `CLAUDE_CODE_DISABLE_ARTIFACT` | Set to `1` to disable the [Artifact](/docs/en/artifacts) tool, which publishes session output as a private web page on claude.ai. Equivalent to the [`disableArtifact`](/docs/en/settings#available-settings) setting |
| `CLAUDE_CODE_DISABLE_ATTACHMENTS` | Set to `1` to disable attachment processing. File mentions with `@` syntax are sent as plain text instead of being expanded into file content |
| `CLAUDE_CODE_DISABLE_AUTO_MEMORY` | Set to `1` to disable [auto memory](/docs/en/memory#auto-memory). Set to `0` to force auto memory on even when `--bare` mode or [`autoMemoryEnabled: false`](/docs/en/settings#available-settings) would otherwise disable it. When disabled, Claude does not create or load auto memory files |
| `CLAUDE_CODE_DISABLE_BACKGROUND_TASKS` | Set to `1` to disable all background task functionality, including the `run_in_background` parameter on Bash and subagent tools, auto-backgrounding, and the Ctrl+B shortcut |
| `CLAUDE_CODE_DISABLE_BEDROCK_CONTENT_TYPE_GUARD` | Set to `1` to skip the check that an [Amazon Bedrock](/docs/en/amazon-bedrock) streaming response carries the `application/vnd.amazon.eventstream` content-type. Without this variable, a response with a different content-type fails with an error naming that content-type, which means a [gateway or proxy is transforming the response](/docs/en/amazon-bedrock#streaming-errors-behind-a-gateway-or-proxy). Set it only when the gateway rewrites the `Content-Type` header but passes the binary event-stream body through unmodified; if the body itself was transformed, requests fail with `Truncated event message received` instead. Requires Claude Code v2.1.208 or later |
| `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 |
| `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 |
| `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 |
| `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 |
| `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 |
| `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 `ENABLE_TOOL_SEARCH` is set |
| `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 |
| `CLAUDE_CODE_DISABLE_FAST_MODE` | Set to `1` to disable [fast mode](/docs/en/fast-mode) |
| `CLAUDE_CODE_DISABLE_FEEDBACK_SURVEY` | Set to `1` to disable the "How is Claude doing?" session quality surveys. Surveys are also disabled when `DISABLE_TELEMETRY`, `DO_NOT_TRACK`, or `CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC` is set, unless `CLAUDE_CODE_ENABLE_FEEDBACK_SURVEY_FOR_OTEL` opts back in. To set a sample rate instead of disabling outright, use the [`feedbackSurveyRate`](/docs/en/settings#available-settings) setting. See [Session quality surveys](/docs/en/data-usage#session-quality-surveys) |
| `CLAUDE_CODE_DISABLE_FILE_CHECKPOINTING` | Set to `1` to disable file [checkpointing](/docs/en/checkpointing). The `/rewind` command will not be able to restore code changes. Overrides the [`fileCheckpointingEnabled`](/docs/en/settings#available-settings) setting |
| `CLAUDE_CODE_DISABLE_GIT_INSTRUCTIONS` | Set to `1` to remove built-in commit and PR workflow instructions and the git status snapshot from Claude's system prompt. Useful when using your own git workflow skills. Takes precedence over the [`includeGitInstructions`](/docs/en/settings#available-settings) setting when set |
| `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 |
| `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 |
| `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 |
| `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) unavailable. Official plugin marketplace auto-install isn't covered; disable it with `CLAUDE_CODE_DISABLE_OFFICIAL_MARKETPLACE_AUTOINSTALL` |
| `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 |
| `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 |
| `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 |
| `CLAUDE_CODE_DISABLE_POLICY_SKILLS` | Set to `1` to skip loading skills from the system-wide managed skills directory. Useful for container or CI sessions that should not load operator-provisioned skills |
| `CLAUDE_CODE_DISABLE_TERMINAL_TITLE` | Set to `1` to disable automatic terminal title updates based on conversation context. In Agent SDK and `claude -p` sessions, this also skips the background small/fast-model request that generates the session title |
| `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. The variable's behavior is unchanged from earlier versions; 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, which is also ineffective on Fable 5 since it cannot have thinking turned off. On [third-party providers](/docs/en/third-party-integrations), `0` likewise omits the parameter, so the two variables behave the same there |
| `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 |
| `CLAUDE_CODE_DISABLE_WORKFLOWS` | Set to `1` to disable [workflows](/docs/en/workflows#turn-workflows-off). Equivalent to the [`disableWorkflows`](/docs/en/settings#available-settings) setting |
| `CLAUDE_CODE_EFFORT_LEVEL` | Set the effort level for supported models. Values: `low`, `medium`, `high`, `xhigh`, `max`, or `auto` to use the model default. Available levels depend on the model. Takes precedence over `/effort` and the `effortLevel` setting. See [Adjust effort level](/docs/en/model-config#adjust-effort-level) |
| `CLAUDE_CODE_ENABLE_APPEND_SUBAGENT_PROMPT` | Set to `1` to enable appending extra text to the end of every [subagent](/docs/en/sub-agents)'s system prompt. The [`--append-subagent-system-prompt`](/docs/en/cli-reference#cli-flags) flag supplies the appended text and sets this variable automatically, so you don't need to set it yourself. Requires Claude Code v2.1.205 or later |
| `CLAUDE_CODE_ENABLE_AUTO_MODE` | Accepted for compatibility with older releases and has no effect. Auto mode is available by default on every provider, including Amazon Bedrock, Google Cloud's Agent Platform, Microsoft Foundry, and signed-in [Claude apps gateway](/docs/en/claude-apps-gateway) sessions. In v2.1.158 through v2.1.206, setting this to `1` was required to make [auto mode](/docs/en/permission-modes#eliminate-prompts-with-auto-mode) available on those providers |
| `CLAUDE_CODE_ENABLE_AWAY_SUMMARY` | Override [session recap](/docs/en/interactive-mode#session-recap) availability. Set to `0` to force recaps off regardless of the `/config` toggle. Set to `1` to force recaps on when [`awaySummaryEnabled`](/docs/en/settings#available-settings) is `false`. Takes precedence over the setting and `/config` toggle |
| `CLAUDE_CODE_ENABLE_BACKGROUND_PLUGIN_REFRESH` | Set to `1` to refresh plugin state at turn boundaries in [non-interactive mode](/docs/en/headless) after a background install completes. Off by default because the refresh changes the system prompt mid-session, which invalidates [prompt caching](/docs/en/prompt-caching) for that turn |
| `CLAUDE_CODE_ENABLE_FEEDBACK_SURVEY_FOR_OTEL` | Set to `1` to route the "How is Claude doing?" session quality survey to your own [OpenTelemetry collector](/docs/en/monitoring-usage) when Anthropic-bound nonessential traffic is blocked. Survey ratings are emitted only as OTEL events to your configured collector. No survey data is sent to Anthropic in this mode. Applies when `CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC`, `DISABLE_TELEMETRY`, or `DO_NOT_TRACK` is set, and has no effect otherwise. `CLAUDE_CODE_DISABLE_FEEDBACK_SURVEY` and the organization product feedback policy take precedence |
| `CLAUDE_CODE_ENABLE_FINE_GRAINED_TOOL_STREAMING` | Controls whether tool call inputs stream from the API as Claude generates them. With this off, a large tool input such as a long file write arrives only after Claude finishes generating it, which can look like it's hanging. Enabled by default on the Anthropic API. On Amazon Bedrock and Google Cloud's Agent Platform, enabled per model where the deployed container supports it. Set to `0` to opt out. Set to `1` to force on when routing through a proxy via `ANTHROPIC_BASE_URL`, `ANTHROPIC_VERTEX_BASE_URL`, or `ANTHROPIC_BEDROCK_BASE_URL`. Off by default on Microsoft Foundry and [gateway](/docs/en/llm-gateway) connections |
| `CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY` | Set to `1` to populate the `/model` picker from your gateway's `/v1/models` endpoint when `ANTHROPIC_BASE_URL` points at an Anthropic-compatible gateway such as LiteLLM, Kong, or an internal proxy. Off by default because gateways backed by a shared API key would otherwise show every user every model the key can access. Discovered models are still filtered by an [`availableModels`](/docs/en/settings#available-settings) allowlist the session receives; deliver the list through [MDM or a managed settings file](/docs/en/settings#settings-files), since [server-managed delivery is not available on gateway configurations](/docs/en/server-managed-settings#platform-availability) |
| `CLAUDE_CODE_ENABLE_OPUS_4_7_FAST_MODE` | Removed in v2.1.142, when the [fast mode](/docs/en/fast-mode) default moved from Opus 4.6 to Opus 4.7 |
| `CLAUDE_CODE_ENABLE_PROMPT_SUGGESTION` | Set to `false` to disable prompt suggestions (the "Prompt suggestions" toggle in `/config`). These are the grayed-out predictions that appear in your prompt input after Claude responds. See [Prompt suggestions](/docs/en/interactive-mode#prompt-suggestions) |
| `CLAUDE_CODE_ENABLE_TASKS` | Controls whether sessions use the structured Task tools (`TaskCreate`, `TaskUpdate`, `TaskGet`, `TaskList`) or the legacy `TodoWrite` tool. As of Claude Code v2.1.142, Task tools are the default in all modes. Set to `0` to revert to `TodoWrite`. See [Task list](/docs/en/interactive-mode#task-list) and [Migrate to Task tools](/docs/en/agent-sdk/todo-tracking#migrate-to-task-tools) |
| `CLAUDE_CODE_ENABLE_TELEMETRY` | Set to `1` to enable OpenTelemetry data collection for metrics and logging. Required before configuring OTel exporters. See [Monitoring](/docs/en/monitoring-usage) |
| `CLAUDE_CODE_EXIT_AFTER_STOP_DELAY` | Time in milliseconds to wait after the query loop becomes idle before automatically exiting. Useful for automated workflows and scripts using SDK mode |
| `CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS` | Set to `1` to enable [agent teams](/docs/en/agent-teams). Agent teams are experimental and disabled by default |
| `CLAUDE_CODE_EXTRA_BODY` | JSON object to merge into the top level of every API request body. Useful for passing provider-specific parameters that Claude Code doesn't expose directly. A value exported in your shell also applies to the [background sessions](/docs/en/agent-view) you dispatch with `claude agents` or `--bg`. Before v2.1.206, background sessions ignored a shell-exported value and used whatever copy the background supervisor process inherited |
| `CLAUDE_CODE_FILE_READ_MAX_OUTPUT_TOKENS` | Override the default token limit for file reads. Useful when you need to read larger files in full |
| `CLAUDE_CODE_FORCE_SESSION_PERSISTENCE` | Set to `1` to force transcript persistence, prompt history, and `claude agents` registration even when this `claude` was launched from inside another Claude Code session. Use when an inherited `CLAUDE_CODE_CHILD_SESSION` value, for example from a `screen` session or a background launcher first started by Claude Code's Bash tool, causes a genuine top-level session to be misclassified as nested. As of v2.1.178, Claude Code detects the tmux case automatically and ignores the inherited marker, so tmux no longer needs this variable. Also honored on v2.1.169 and earlier; has no effect on v2.1.170 and v2.1.171, where the nested-session detection it overrides was removed |
| `CLAUDE_CODE_FORCE_STRIKETHROUGH` | Set to `1` to force strikethrough rendering for `~~text~~` in Claude's responses when your terminal supports it but is not auto-detected, such as over SSH without `TERM_PROGRAM` forwarded. Without this, undetected terminals show the literal `~~` markers instead of rendering the text as strikethrough. Requires Claude Code v2.1.186 or later |
| `CLAUDE_CODE_FORCE_SYNC_OUTPUT` | Set to `1` to force-enable DEC private mode 2026 [synchronized output](https://gist.github.com/christianparpart/d8a62cc1ab659194337d73e399004036) when your terminal supports it but is not auto-detected. Useful for emulators such as Emacs `eat` that implement BSU/ESU but do not reply to the capability probe. Has no effect under tmux. Unlike `CLAUDE_CODE_NO_FLICKER`, which switches to [fullscreen rendering](/docs/en/fullscreen), this doesn't change the renderer |
| `CLAUDE_CODE_FORK_SUBAGENT` | Set to `1` to let Claude spawn [forked subagents](/docs/en/sub-agents#fork-the-current-conversation), or `0` to disable them, overriding any server-side rollout. When enabled, Claude can request the `fork` subagent type to spawn a fork, a subagent that inherits the full conversation context instead of starting fresh. When Claude doesn't request a subagent type, it still gets the general-purpose subagent, and every subagent runs in the background. The explicit [`/subtask`](/docs/en/commands#all-commands) command, named `/fork` on v2.1.161 through v2.1.211, works without this variable; on v2.1.117 through v2.1.160, `/fork` is the forked-subagent command only when this variable is set to `1` or a server-side rollout enabled it. Works in interactive mode and via the SDK or `claude -p`. When [agent view is turned off](/docs/en/agent-view#turn-off-agent-view), `/subtask` isn't available and the command stays `/fork` |
| `CLAUDE_CODE_FORWARD_SUBAGENT_TEXT` | Set to `1` to emit [subagent](/docs/en/sub-agents) text and thinking blocks in `claude -p --output-format stream-json` output, the same behavior as the [`--forward-subagent-text`](/docs/en/cli-reference#cli-flags) flag. Use the variable when a harness invokes `claude` and can't pass the flag itself. Unlike the flag, which exits with an error outside non-interactive mode with stream-json output, the variable is ignored there so that nested invocations keep working when it's set process-wide. Requires Claude Code v2.1.211 or later |
| `CLAUDE_CODE_GIT_BASH_PATH` | Windows only: path to the Git Bash executable (`bash.exe`). Use when Git Bash is installed but not in your PATH. If the path doesn't exist or the file isn't named `bash.exe`, `sh.exe`, `bash`, or `sh`, Claude Code ignores the variable and auto-detects Git Bash as if it were unset, logging a warning visible with `--debug`. Before v2.1.219, Claude Code exited at startup when the path didn't exist, and used any existing file as the shell without checking that it was bash or sh. See [Windows setup](/docs/en/setup#set-up-on-windows) |
| `CLAUDE_CODE_GLOB_HIDDEN` | Set to `false` to exclude dotfiles from results when Claude invokes the [Glob tool](/docs/en/tools-reference#glob-tool-behavior). Included by default. Does not affect `@` file autocomplete, `ls`, Grep, or Read |
| `CLAUDE_CODE_GLOB_NO_IGNORE` | Set to `false` to make the [Glob tool](/docs/en/tools-reference#glob-tool-behavior) respect `.gitignore` patterns. By default, Glob returns all matching files including gitignored ones. Does not affect `@` file autocomplete, which has its own [`respectGitignore` setting](/docs/en/settings#available-settings) |
| `CLAUDE_CODE_GLOB_TIMEOUT_SECONDS` | Timeout in seconds for Glob tool file discovery. Defaults to 20 seconds on most platforms and 60 seconds on WSL |
| `CLAUDE_CODE_HIDE_CWD` | Set to `1` to hide the working directory in the startup logo. Useful for screenshares or recordings where the path exposes your OS username |
| `CLAUDE_CODE_IDE_HOST_OVERRIDE` | Override the host address used to connect to the IDE extension. By default Claude Code auto-detects the correct address, including WSL-to-Windows routing |
| `CLAUDE_CODE_IDE_SKIP_AUTO_INSTALL` | Set to `1` to skip auto-installation of IDE extensions. Equivalent to setting [`autoInstallIdeExtension`](/docs/en/settings#global-config-settings) to `false` |
| `CLAUDE_CODE_IDE_SKIP_VALID_CHECK` | Set to `1` to skip validation of IDE lockfile entries during connection. Use when auto-connect fails to find your IDE despite it running |
| `CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS` | How many [subagents](/docs/en/sub-agents#concurrent-subagent-limit) can be running in one session before the Agent tool refuses to spawn another (default: 20). Accepts a positive whole number in plain digits; anything else is ignored, so the variable can adjust the cap but can't disable it. Requires Claude Code v2.1.217 or later |
| `CLAUDE_CODE_MAX_CONTEXT_TOKENS` | Override the context window size Claude Code assumes for the active model. As of v2.1.193, applied directly for model names Claude Code does not recognize as a Claude model; for recognized Claude models it only takes effect when `DISABLE_COMPACT` is also set. Use this when routing to a model through `ANTHROPIC_BASE_URL` whose context window does not match the built-in size for its name |
| `CLAUDE_CODE_MAX_OUTPUT_TOKENS` | Set the maximum number of output tokens for most requests. Defaults and caps vary by model; see [max output tokens](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison). Claude Code defaults to 32000 for model IDs it doesn't recognize, such as gateway-specific names, and lowers values above a model's cap to the cap. Increasing this value reduces the effective context window available before [auto-compaction](/docs/en/costs#reduce-token-usage) triggers |
| `CLAUDE_CODE_MAX_RETRIES` | Override the number of times to retry failed API requests (default: 10). Capped at 15 as of v2.1.186; as of v2.1.199, `CLAUDE_CODE_RETRY_WATCHDOG` raises the default and removes the cap. For unattended sessions that need to wait through longer outages, set `CLAUDE_CODE_RETRY_WATCHDOG` instead |
| `CLAUDE_CODE_MAX_SUBAGENTS_PER_SESSION` | Removed in v2.1.224 and now a no-op. Previously capped the total number of [subagents](/docs/en/sub-agents) Claude could spawn with the Agent tool in one session (default: 200); spawning past the cap failed with `Subagent spawn limit reached`. The [concurrent subagent limit](/docs/en/sub-agents#concurrent-subagent-limit) and the [depth limit](/docs/en/sub-agents#let-subagents-spawn-their-own-subagents) still apply |
| `CLAUDE_CODE_MAX_SUBAGENT_SPAWN_DEPTH` | Number of [subagent layers](/docs/en/sub-agents#let-subagents-spawn-their-own-subagents) allowed below the main conversation (default: 3). At the default, subagents can spawn their own subagents, and a subagent at the third layer can't spawn further; set `1` to turn nesting off. In v2.1.217 through v2.1.218, the default was 1, so a subagent couldn't spawn its own unless you raised the limit; v2.1.219 raised the default to 3. Accepts a positive whole number in plain digits; anything else is ignored, so the limit can be adjusted but not removed. Requires Claude Code v2.1.217 or later |
| `CLAUDE_CODE_MAX_TOOL_USE_CONCURRENCY` | Maximum number of read-only tools and subagents that can execute in parallel (default: 10). Higher values increase parallelism but consume more resources |
| `CLAUDE_CODE_MAX_TURNS` | Cap the number of agentic turns when no explicit limit is passed. Equivalent to passing [`--max-turns`](/docs/en/cli-reference#cli-flags), which takes precedence when both are set. A value that is not a positive integer is rejected at startup with an error rather than treated as no cap |
| `CLAUDE_CODE_MAX_WEB_SEARCHES_PER_SESSION` | Cap on the total number of [WebSearch](/docs/en/tools-reference#websearch-tool-behavior) calls one session can make (default: 200). When Claude reaches the cap, further WebSearch calls return a notice telling it to continue with the information it already gathered. Accepts a positive whole number with no upper bound. Anything else is ignored and the default applies, so the cap can be raised but not turned off. Requires Claude Code v2.1.212 or later |
| `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 |
| `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 |
| `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 |
| `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 |
| `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 |
| `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` |
| `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 |
| `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 |
| `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_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 |
| `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) |
| `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) |
| `CLAUDE_CODE_OTEL_FLUSH_TIMEOUT_MS` | Timeout in milliseconds for flushing pending OpenTelemetry spans (default: 5000). See [Monitoring](/docs/en/monitoring-usage) |
| `CLAUDE_CODE_OTEL_HEADERS_HELPER_DEBOUNCE_MS` | Interval for refreshing dynamic OpenTelemetry headers in milliseconds (default: 1740000 / 29 minutes). See [Dynamic headers](/docs/en/monitoring-usage#dynamic-headers) |
| `CLAUDE_CODE_OTEL_SHUTDOWN_TIMEOUT_MS` | Timeout in milliseconds for the OpenTelemetry exporter to finish on shutdown (default: 2000). Increase if metrics are dropped at exit. See [Monitoring](/docs/en/monitoring-usage) |
| `CLAUDE_CODE_PACKAGE_MANAGER_AUTO_UPDATE` | Set to `1` to let Claude Code run your package manager's upgrade command in the background when a new version is available. Applies to Homebrew and WinGet installations. Other package managers continue to show the upgrade command without running it. See [Auto updates](/docs/en/setup#auto-updates) |
| `CLAUDE_CODE_PERFORCE_MODE` | Set to `1` to enable Perforce-aware write protection. When set, Edit, Write, and NotebookEdit fail with a `p4 edit ` 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 |
| `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` |
| `CLAUDE_CODE_PLUGIN_GIT_TIMEOUT_MS` | Timeout in milliseconds for git operations when installing or updating plugins (default: 120000). Increase this value for large repositories or slow network connections. See [Git operations time out](/docs/en/plugin-marketplaces#git-operations-time-out) |
| `CLAUDE_CODE_PLUGIN_KEEP_MARKETPLACE_ON_FAILURE` | Set to `1` to skip the re-clone attempt and keep using the existing marketplace cache when a `git pull` fails. Useful in offline or airgapped environments where re-cloning would fail the same way. See [Marketplace updates fail in offline environments](/docs/en/plugin-marketplaces#marketplace-updates-fail-in-offline-environments) |
| `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` |
| `CLAUDE_CODE_PLUGIN_SEED_DIR` | Path to one or more read-only plugin seed directories, separated by `:` on Unix or `;` on Windows. Use this to bundle a pre-populated plugins directory into a container image. Claude Code registers marketplaces from these directories at startup and uses pre-cached plugins without re-cloning. See [Pre-populate plugins for containers](/docs/en/plugin-marketplaces#pre-populate-plugins-for-containers) |
| `CLAUDE_CODE_POWERSHELL_RESPECT_EXECUTION_POLICY` | Set to `1` to stop Claude Code from passing `-ExecutionPolicy Bypass` when spawning PowerShell for tool calls, hooks, and status line commands, and respect the machine's effective execution policy instead. By default Claude Code bypasses execution policy at process scope so `.ps1` scripts and module imports work on default-Restricted Windows installs. Process-scope bypass never overrides Group Policy `MachinePolicy` or `UserPolicy` regardless of this setting |
| `CLAUDE_CODE_PRINT_BG_WAIT_CEILING_MS` | Maximum time in milliseconds that [non-interactive mode](/docs/en/headless#background-tasks-at-exit) with the `-p` flag waits after the final turn for background subagents and workflows whose result is part of the output. Default: `600000`, or 10 minutes. When the cap is exceeded, remaining background tasks are terminated and the process exits. Set to `0` to wait indefinitely. This cap is separate from the five-second grace period that applies to plain background shells |
| `CLAUDE_CODE_PROCESS_WRAPPER` | Launch the processes Claude Code starts from its own binary, such as the background service that hosts [agent view](/docs/en/agent-view) sessions, through a corporate launcher given as an argv prefix like `/opt/corp/launcher`. Set it in the `env` block of user or [managed settings](/docs/en/permissions#managed-settings), not as a shell export, so the detached background service inherits it; project and local settings can't set it. Equivalent to the [`processWrapper` setting](/docs/en/settings#available-settings), which requires Claude Code v2.1.210 or later; this variable takes precedence when both are set. The VS Code extension configures its own launcher separately through its `claudeProcessWrapper` setting. Ignored on Windows. See [Run Claude Code behind a corporate launcher](/docs/en/corporate-launcher) for the value format, what the launcher covers, and the contract the launcher must satisfy. Requires Claude Code v2.1.208 or later |
| `CLAUDE_CODE_PROPAGATE_TRACEPARENT` | Set to `1` to propagate W3C trace context when `ANTHROPIC_BASE_URL` points at a custom proxy. Propagation covers the `traceparent` header on model and HTTP MCP requests and the `TRACEPARENT` environment variable for Bash, PowerShell, and hook subprocesses. By default, propagation is enabled only when connected directly to the Anthropic API. Added in v2.1.152. See [Traces (beta)](/docs/en/monitoring-usage#traces-beta) |
| `CLAUDE_CODE_PROVIDER_MANAGED_BY_HOST` | Set by host platforms that embed Claude Code and manage model provider routing on its behalf. When set, Claude Code ignores provider-selection, endpoint, and authentication variables such as `CLAUDE_CODE_USE_BEDROCK`, `ANTHROPIC_BASE_URL`, and `ANTHROPIC_API_KEY` in settings files, so user settings can't override the host's routing. Claude Code also ignores model-selection keys such as `model`, `fallbackModel`, and `modelOverrides` in [managed settings](/docs/en/permissions#managed-settings), whichever managed source delivers them, so the host's model configuration takes precedence over an out-of-date managed model pin; an [`availableModels`](/docs/en/model-config#restrict-model-selection) allowlist in managed settings still applies unless the host supplies its own. Claude Code also skips the automatic telemetry opt-out for Amazon Bedrock, Google Cloud's Agent Platform, and Microsoft Foundry, so telemetry follows the standard `DISABLE_TELEMETRY` opt-out. See [Default behaviors by API provider](/docs/en/data-usage#default-behaviors-by-api-provider) |
| `CLAUDE_CODE_PROXY_RESOLVES_HOSTS` | Set to `1` to allow the proxy to perform DNS resolution instead of the caller. Opt-in for environments where the proxy should handle hostname resolution |
| `CLAUDE_CODE_REMOTE` | Set automatically to `true` when Claude Code is running as a [cloud session](/docs/en/claude-code-on-the-web). Read this from a hook or setup script to detect whether you are in a cloud session |
| `CLAUDE_CODE_REMOTE_SESSION_ID` | Set automatically in [cloud sessions](/docs/en/claude-code-on-the-web) to the current session's ID. Read this to construct a link back to the session transcript. See [Link output back to the session](/docs/en/cloud-environments#link-output-back-to-the-session) |
| `CLAUDE_CODE_RESUME_INTERRUPTED_TURN` | Set to `1` to automatically resume if the previous session ended mid-turn. Used in SDK mode so the model continues without requiring the SDK to re-send the prompt. To turn this off, unset the variable or set it to `0`. Before v2.1.221, Claude Code ignored `0` and other falsy values, so setting `0` still triggered the resume in non-interactive mode and unsetting the variable was the only way to turn it off |
| `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 |
| `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 |
| `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 |
| `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 |
| `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 |
| `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 |
| `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 |
| `CLAUDE_CODE_SESSION_ID` | Set automatically to the current session ID in Bash and PowerShell tool subprocesses, [hook command](/docs/en/hooks) subprocesses, and stdio [MCP server](/docs/en/mcp) subprocesses. For Bash, PowerShell, and hooks this matches the `session_id` field in the hook JSON input and is updated on `/clear`. An MCP server subprocess retains the ID it was spawned with. On `--resume ` it receives the resumed ID, matching hooks and Bash. On `--continue` or `--resume` without an explicit ID it may receive the initial startup ID instead. Use to correlate scripts and external tools with the Claude Code session that launched them |
| `CLAUDE_CODE_SHELL` | Set the shell Claude Code uses to run Bash tool commands. Accepts a path to a `bash` or `zsh` binary, for example `/opt/homebrew/bin/bash`. Other shells such as `fish` are not supported. If the value is not a working `bash` or `zsh` path, Claude Code ignores it and falls back to auto-detection. Auto-detection uses your `$SHELL` when it points to `bash` or `zsh`, otherwise it picks the first working `zsh` then `bash` found on your `PATH` and standard install locations |
| `CLAUDE_CODE_SHELL_PREFIX` | Command prefix that wraps shell commands Claude Code spawns: Bash tool calls, [hook](/docs/en/hooks) commands, [status line](/docs/en/statusline) commands, and stdio [MCP server](/docs/en/mcp) startup commands. PowerShell hooks and exec-form hooks run without the prefix. Useful for logging or auditing. Setting a bare executable path such as `/path/to/logger.sh` runs each command as `/path/to/logger.sh ''`. The wrapper receives the command line as a single shell-quoted argument in `$1`, so the wrapper must re-evaluate `$1` with a shell, for example `exec bash -c "$1"`. Treating `$1` as a bare executable path breaks stdio MCP servers that pass arguments such as `npx -y `. For Bash tool calls, `$1` contains the full shell invocation Claude Code assembles, including environment setup, not only the command Claude ran |
| `CLAUDE_CODE_SIMPLE` | Set to `1` to run with a minimal system prompt and only the Bash, file read, and file edit tools. MCP tools from `--mcp-config` are still available. Disables auto-discovery of hooks, skills, plugins, MCP servers, auto memory, and CLAUDE.md. OAuth tokens and keychain credentials are not read, so Anthropic authentication must come from `ANTHROPIC_API_KEY` or an `apiKeyHelper` in `--settings`. Equivalent to passing [`--bare`](/docs/en/headless#start-faster-with-bare-mode) |
| `CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT` | Set to `1` to use a shorter system prompt and abbreviated tool descriptions on any model. Set to `0`, `false`, `no`, or `off` to opt out even on models where the experiment or server configuration would otherwise enable it. The full tool set, hooks, MCP servers, and CLAUDE.md discovery remain enabled |
| `CLAUDE_CODE_SKIP_ANTHROPIC_AWS_AUTH` | Skip client-side authentication for [Claude Platform on AWS](/docs/en/claude-platform-on-aws), for gateways that sign requests themselves |
| `CLAUDE_CODE_SKIP_AWS_CRED_CACHE` | Set to `1` to turn off the in-process cache of credentials resolved from the AWS default credential provider chain, so Claude Code resolves the chain on every API request. With the cache off, an SSO-backed profile requests credentials from IAM Identity Center on every request. See [credential caching and resolution timeout](/docs/en/amazon-bedrock#credential-caching-and-resolution-timeout). Requires Claude Code v2.1.207 or later |
| `CLAUDE_CODE_SKIP_BEDROCK_AUTH` | Skip AWS authentication for Amazon Bedrock (for example, when using an LLM gateway) |
| `CLAUDE_CODE_SKIP_FAST_MODE_NETWORK_ERRORS` | Set to `1` to treat a failed [fast mode](/docs/en/fast-mode#use-fast-mode-behind-proxies-and-llm-gateways) availability check as available, for networks that block the check's direct request to `api.anthropic.com`. Claude Code still honors a "disabled by your organization" response |
| `CLAUDE_CODE_SKIP_FAST_MODE_ORG_CHECK` | Set to `1` to skip the client-side [fast mode](/docs/en/fast-mode#use-fast-mode-behind-proxies-and-llm-gateways) availability check, for proxies that intercept the check's request rather than refuse it. The API still rejects fast mode requests when your organization has fast mode disabled |
| `CLAUDE_CODE_SKIP_FOUNDRY_AUTH` | Skip Azure authentication for Microsoft Foundry, for a proxy or gateway that injects its own `Authorization` header. Claude Code sends requests without an Azure credential and preserves the `Authorization` header you supply, for example through `ANTHROPIC_CUSTOM_HEADERS`. Ignored when `ANTHROPIC_FOUNDRY_API_KEY` or `ANTHROPIC_FOUNDRY_AUTH_TOKEN` is set. Before v2.1.203, this variable left the Microsoft Foundry client unable to send requests unless an API key was also set |
| `CLAUDE_CODE_SKIP_MANTLE_AUTH` | Skip AWS authentication for Amazon Bedrock Mantle (for example, when using an LLM gateway) |
| `CLAUDE_CODE_SKIP_PROMPT_HISTORY` | Set to `1` to skip writing prompt history and session transcripts to disk. Sessions started with this variable set do not appear in `--resume`, `--continue`, or up-arrow history. Useful for ephemeral scripted sessions |
| `CLAUDE_CODE_SKIP_VERTEX_AUTH` | Skip Google authentication for Google Cloud's Agent Platform (for example, when using an LLM gateway) |
| `CLAUDE_CODE_STOP_HOOK_BLOCK_CAP` | Maximum number of consecutive times a [Stop](/docs/en/hooks#stop) or [SubagentStop](/docs/en/hooks#subagentstop) hook may block the turn from ending before Claude Code overrides it and ends the turn anyway (default: 8). Set to `0` to disable the cap. Raise this if your hook legitimately needs more iterations to resolve |
| `CLAUDE_CODE_SUBAGENT_MODEL` | The model Claude Code uses for all [subagents](/docs/en/sub-agents#choose-a-model), [agent teams](/docs/en/agent-teams), and agents in a [workflow](/docs/en/workflows). Accepts an alias such as `haiku` or a full model name, and takes precedence over the per-invocation `model` parameter and the subagent definition's `model` frontmatter. See [Model configuration](/docs/en/model-config#environment-variables). Setting it to `inherit` is the same as leaving it unset; before v2.1.196, `inherit` was an override that forced every subagent onto the main conversation's model |
| `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 |
| `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 |
| `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 |
| `CLAUDE_CODE_SYNC_SKILLS` | Set to `1` to download your enabled claude.ai skills into `~/.claude/skills/` before the first query and resync every 10 minutes. 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_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 |
| `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 |
| `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 |
| `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) |
| `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 |
| `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 `$TMPDIR` unchanged. Claude Code's own temp files always use your override |
| `CLAUDE_CODE_TMUX_TRUECOLOR` | Set to any non-empty value, such as `1`, to allow 24-bit truecolor output inside tmux. **Setting it to `0` or `false` still allows truecolor**, unlike most on/off variables; unset the variable to restore the 256-color clamp. By default, Claude Code clamps to 256 colors when `$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 |
| `CLAUDE_CODE_USE_ANTHROPIC_AWS` | Use [Claude Platform on AWS](/docs/en/claude-platform-on-aws) |
| `CLAUDE_CODE_USE_BEDROCK` | Use [Amazon Bedrock](/docs/en/amazon-bedrock) |
| `CLAUDE_CODE_USE_FOUNDRY` | Use [Microsoft Foundry](/docs/en/microsoft-foundry) |
| `CLAUDE_CODE_USE_MANTLE` | Use the Amazon Bedrock [Mantle endpoint](/docs/en/amazon-bedrock#use-the-mantle-endpoint) |
| `CLAUDE_CODE_USE_NATIVE_FILE_SEARCH` | Set to `1` to discover custom commands, subagents, and output styles using Node.js file APIs instead of ripgrep. Set this if the bundled ripgrep binary is unavailable or blocked in your environment. Does not affect the Grep or file search tools |
| `CLAUDE_CODE_USE_POWERSHELL_TOOL` | Controls the PowerShell tool. On Windows without Git Bash, the tool is enabled automatically; set to `0` to disable it. On Windows with Git Bash installed, the tool is rolling out progressively: set to `1` to opt in or `0` to opt out. On Linux, macOS, and WSL, set to `1` to enable it, which requires `pwsh` on your `PATH`. When enabled on Windows, Claude can run PowerShell commands natively instead of routing through Git Bash. See [PowerShell tool](/docs/en/tools-reference#powershell-tool) |
| `CLAUDE_CODE_USE_VERTEX` | Use [Google Cloud's Agent Platform](/docs/en/google-vertex-ai) |
| `CLAUDE_CONFIG_DIR` | Override the configuration directory (default: `~/.claude`). All settings, session history, and plugins are stored under this path, as are credentials on Linux and Windows; on macOS, credentials are in the system Keychain. Useful for running multiple accounts side by side: for example, `alias claude-work='CLAUDE_CONFIG_DIR=~/.claude-work claude'` |
| `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 |
| `CLAUDE_EFFORT` | Set automatically in Bash tool subprocesses and hook commands to the active [effort level](/docs/en/model-config#adjust-effort-level) for the turn: `low`, `medium`, `high`, `xhigh`, or `max`. Ultracode is not a distinct level and reports as `xhigh`. Matches the `effort.level` field passed to [hooks](/docs/en/hooks). Only set when the current model supports the effort parameter |
| `CLAUDE_ENABLE_BYTE_WATCHDOG` | Set to `1` to force-enable the byte-level streaming idle watchdog, or set to `0` to force-disable it. 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) |
| `CLAUDE_ENABLE_BYTE_WATCHDOG_BEDROCK` | Set to `1` to enable the byte-level streaming idle watchdog on Amazon Bedrock `vnd.amazon.eventstream` responses. Off by default. Configure the timeout with `CLAUDE_STREAM_IDLE_TIMEOUT_MS` |
| `CLAUDE_ENABLE_STREAM_WATCHDOG` | Set to `0` to force-disable the event-level streaming idle watchdog, or set to `1` to force-enable it. When unset, the watchdog is on by default for all providers. Before v2.1.196, the unset default was server-controlled on the direct Anthropic API and off on other providers. Configure the timeout with `CLAUDE_STREAM_IDLE_TIMEOUT_MS`; for the other stall timers that run alongside this one, see [Streaming idle watchdogs](/docs/en/network-config#streaming-idle-watchdogs) |
| `CLAUDE_ENV_FILE` | Path to a shell script whose contents Claude Code runs before each Bash command in the same shell process, so exports in the file are visible to the command. Use to persist virtualenv or conda activation across commands. Also populated dynamically by [SessionStart](/docs/en/hooks#persist-environment-variables), [Setup](/docs/en/hooks#setup), [CwdChanged](/docs/en/hooks#cwdchanged), and [FileChanged](/docs/en/hooks#filechanged) hooks |
| `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 |
| `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 |
| `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) |
| `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/.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 |
| `DISABLE_AUTOUPDATER` | Set to `1` to disable automatic background updates. Manual `claude update` still works. Use `DISABLE_UPDATES` to block both |
| `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 |
| `DISABLE_COMPACT` | Set to `1` to disable all compaction: both automatic compaction and the manual `/compact` command |
| `DISABLE_COST_WARNINGS` | Set to `1` to disable cost warning messages |
| `DISABLE_DOCTOR_COMMAND` | Set to `1` to hide the [`/doctor`](/docs/en/commands#all-commands) setup checkup skill and its `/checkup` alias. Useful for managed deployments where users shouldn't run setup diagnostics from a session. Doesn't affect the `claude doctor` terminal command. Before v2.1.205, this variable hid the `/doctor` diagnostics screen command |
| `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 |
| `DISABLE_EXTRA_USAGE_COMMAND` | Set to `1` to hide the `/usage-credits` command that lets users purchase additional usage beyond rate limits |
| `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 |
| `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) unavailable. Telemetry event logging stays on unless `DISABLE_TELEMETRY` is also set |
| `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 |
| `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) |
| `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) |
| `DISABLE_LOGIN_COMMAND` | Set to `1` to hide the `/login` command. Useful when authentication is handled externally via API keys or `apiKeyHelper` |
| `DISABLE_LOGOUT_COMMAND` | Set to `1` to hide the `/logout` command |
| `DISABLE_PROMPT_CACHING` | Set to `1` to disable [prompt caching](/docs/en/prompt-caching#disable-prompt-caching) for all models (takes precedence over per-model settings) |
| `DISABLE_PROMPT_CACHING_FABLE` | Set to `1` to disable prompt caching for Fable models |
| `DISABLE_PROMPT_CACHING_HAIKU` | Set to `1` to disable prompt caching for Haiku models |
| `DISABLE_PROMPT_CACHING_OPUS` | Set to `1` to disable prompt caching for Opus models |
| `DISABLE_PROMPT_CACHING_SONNET` | Set to `1` to disable prompt caching for Sonnet models |
| `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) unavailable |
| `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 |
| `DISABLE_UPGRADE_COMMAND` | Set to `1` to hide the `/upgrade` command |
| `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) 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 |
| `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 |
| `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. 1-hour cache writes are billed at a higher rate |
| `ENABLE_PROMPT_CACHING_1H_BEDROCK` | Deprecated. Use `ENABLE_PROMPT_CACHING_1H` instead |
| `ENABLE_TOOL_SEARCH` | Controls [MCP tool search](/docs/en/mcp#scale-with-mcp-tool-search). Unset: all MCP tools deferred by default, but loaded upfront on Google Cloud's Agent Platform models earlier than the Claude 4.5 generation, when `ANTHROPIC_BASE_URL` points to a non-first-party host, or on a Microsoft Foundry deployment hosted on Azure. Values: `true` (always defer and send the beta header, except on a Microsoft Foundry deployment hosted on Azure and on Google Cloud's Agent Platform models earlier than the Claude 4.5 generation, where Claude Code still loads tools upfront; requests fail on proxies that don't support `tool_reference`), `auto` (threshold mode: load upfront if tools fit within 10% of context), `auto:N` (custom threshold, e.g., `auto:5` for 5%), `false` (load all upfront). Ignored when `CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS` is set, which forces all tools to load upfront. 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` |
| `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 |
| `FORCE_AUTOUPDATE_PLUGINS` | Set to `1` to force plugin auto-updates even when the main auto-updater is disabled via `DISABLE_AUTOUPDATER` |
| `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 |
| `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` |
| `HTTP_PROXY` | Specify HTTP proxy server for network connections |
| `HTTPS_PROXY` | Specify HTTPS proxy server for network connections |
| `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 |
| `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) |
| `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 |
| `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 |
| `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` |
| `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 |
| `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 |
| `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 |
| `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) |
| `MCP_REMOTE_SERVER_CONNECTION_BATCH_SIZE` | Maximum number of remote MCP servers (HTTP/SSE) to connect in parallel during startup (default: 20) |
| `MCP_SERVER_CONNECTION_BATCH_SIZE` | Maximum number of local MCP servers (stdio) to connect in parallel during startup (default: 3) |
| `MCP_TIMEOUT` | Timeout in milliseconds for MCP server startup (default: 30000, or 30 seconds) |
| `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 |
| `NO_PROXY` | List of domains and IPs to which requests will be directly issued, bypassing proxy |
| `OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT` | Standard OpenTelemetry SDK limit on attribute value length. Claude Code caps content-bearing telemetry attributes at the smaller of this and `CLAUDE_CODE_OTEL_CONTENT_MAX_LENGTH`, so the truncation marker stays within the SDK limit. Claude Code reads the `OTEL_LOGRECORD_ATTRIBUTE_VALUE_LENGTH_LIMIT` and `OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT` variants the same way, and the smallest set value applies to all signals. Requires Claude Code v2.1.214 or later. See [Monitoring](/docs/en/monitoring-usage#common-configuration-variables) |
| `OTEL_LOG_ASSISTANT_RESPONSES` | Set to `1` to include the model's response text on `assistant_response` OpenTelemetry log events. When unset, the value of `OTEL_LOG_USER_PROMPTS` is used instead. Set to `0` to keep responses redacted even when `OTEL_LOG_USER_PROMPTS` is set. Requires Claude Code v2.1.193 or later. See [Monitoring](/docs/en/monitoring-usage#assistant-response-event) |
| `OTEL_LOG_RAW_API_BODIES` | Emit Anthropic Messages API request and response JSON as `api_request_body` / `api_response_body` log events. Set to `1` for inline bodies truncated at the content limit, or `file:` to write untruncated bodies to disk and emit a `body_ref` path instead. `CLAUDE_CODE_OTEL_CONTENT_MAX_LENGTH` configures the content limit, 60 KB by default. Disabled by default; bodies include the entire conversation history. See [Monitoring](/docs/en/monitoring-usage#api-request-body-event) |
| `OTEL_LOG_TOOL_CONTENT` | Set to `1` to include tool input and output content in OpenTelemetry span events. Disabled by default to protect sensitive data. See [Monitoring](/docs/en/monitoring-usage) |
| `OTEL_LOG_TOOL_DETAILS` | Set to `1` to include tool input arguments, MCP server names, user-authored workflow names, raw error strings on tool failures, the refusal `category` on `api_refusal` events, and other tool details in OpenTelemetry traces and logs. Disabled by default to protect PII. See [Monitoring](/docs/en/monitoring-usage) |
| `OTEL_LOG_USER_PROMPTS` | Set to `1` to include user prompt text in OpenTelemetry traces and logs. Disabled by default (prompts are redacted). See [Monitoring](/docs/en/monitoring-usage) |
| `OTEL_METRICS_INCLUDE_ACCOUNT_UUID` | Set to `false` to exclude account UUID from metrics attributes (default: included). See [Monitoring](/docs/en/monitoring-usage) |
| `OTEL_METRICS_INCLUDE_ENTRYPOINT` | Set to `true` to include the session entrypoint in metrics attributes (default: excluded). Added in v2.1.152. See [Monitoring](/docs/en/monitoring-usage) |
| `OTEL_METRICS_INCLUDE_RESOURCE_ATTRIBUTES` | As of v2.1.161, Claude Code attaches `OTEL_RESOURCE_ATTRIBUTES` keys to metric datapoint labels. Set to `false` to exclude them (default: included). See [Monitoring](/docs/en/monitoring-usage#multi-team-organization-support) |
| `OTEL_METRICS_INCLUDE_SESSION_ID` | Set to `false` to exclude session ID from metrics attributes (default: included). See [Monitoring](/docs/en/monitoring-usage) |
| `OTEL_METRICS_INCLUDE_VERSION` | Set to `true` to include Claude Code version in metrics attributes (default: excluded). See [Monitoring](/docs/en/monitoring-usage) |
| `SLASH_COMMAND_TOOL_CHAR_BUDGET` | Override the character budget for skill metadata shown to the [Skill tool](/docs/en/skills#control-who-invokes-a-skill). The budget scales dynamically at 1% of the context window, with a fallback of 8,000 characters. Legacy name kept for backwards compatibility |
| `TASK_MAX_OUTPUT_LENGTH` | Maximum number of characters in [subagent](/docs/en/sub-agents) output before truncation (default: 32000, maximum: 160000). When truncated, the full output is saved to disk and the path is included in the truncated response |
| `USE_BUILTIN_RIPGREP` | Set to `0` to use system-installed `rg` instead of `rg` included with Claude Code |
| `VERTEX_REGION_CLAUDE_3_5_HAIKU` | Override region for Claude 3.5 Haiku when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_3_5_SONNET` | Override region for Claude 3.5 Sonnet when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_3_7_SONNET` | Override region for Claude 3.7 Sonnet when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_4_0_OPUS` | Override region for Claude 4.0 Opus when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_4_0_SONNET` | Override region for Claude 4.0 Sonnet when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_4_1_OPUS` | Override region for Claude 4.1 Opus when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_4_5_OPUS` | Override region for Claude Opus 4.5 when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_4_5_SONNET` | Override region for Claude Sonnet 4.5 when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_4_6_OPUS` | Override region for Claude Opus 4.6 when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_4_6_SONNET` | Override region for Claude Sonnet 4.6 when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_4_7_OPUS` | Override region for Claude Opus 4.7 when using Google Cloud's Agent Platform |
| `VERTEX_REGION_CLAUDE_4_8_OPUS` | Override region for Claude Opus 4.8 when using Google Cloud's Agent Platform. Added in v2.1.154 |
| `VERTEX_REGION_CLAUDE_5_OPUS` | Override region for Claude Opus 5 when using Google Cloud's Agent Platform. Added in v2.1.219 |
| `VERTEX_REGION_CLAUDE_5_SONNET` | Override region for Claude Sonnet 5 when using Google Cloud's Agent Platform. Added in v2.1.197 |
| `VERTEX_REGION_CLAUDE_FABLE_5` | Override region for Claude Fable 5 when using Google Cloud's Agent Platform. Added in v2.1.170 |
| `VERTEX_REGION_CLAUDE_HAIKU_4_5` | Override region for Claude Haiku 4.5 when using Google Cloud's Agent Platform |
Standard 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.
## See also
* [Settings](/docs/en/settings): all `settings.json` configuration, including the `env` key
* [CLI reference](/docs/en/cli-reference): launch-time flags
* [Network configuration](/docs/en/network-config): proxy and TLS setup
* [Monitoring](/docs/en/monitoring-usage): OpenTelemetry configuration