{"version":"2.1.281","anchor":"new-env-vars-claude-code-tether-live-and-claude-code-mcp-app","canonical_anchor":"new-env-vars-claude-code-tether-live-and-claude-code-mcp-app","heading":"New env vars CLAUDE_CODE_TETHER_LIVE and CLAUDE_CODE_MCP_APPS_HOST added to the protected env-key set","tier":"internal","area":"Settings","url":"https:\/\/changelogs.core-directive.com\/v\/2.1.281\/e\/new-env-vars-claude-code-tether-live-and-claude-code-mcp-app","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.281","markdown":"### New env vars CLAUDE_CODE_TETHER_LIVE and CLAUDE_CODE_MCP_APPS_HOST added to the protected env-key set\n\nCLAUDE_CODE_TETHER_LIVE and CLAUDE_CODE_MCP_APPS_HOST join Claude Code's protected set of environment variables\n\n**Unclear.** The finding does not confirm that being in the protected set stops settings `env` blocks from setting these variables.\n\n**What**\n\nAn environment variable is a named value set outside Claude Code, for example in your shell. Claude Code keeps a protected set of these names that it checks separately, alongside ones such as `CLAUDE_CODE_SYNC_PLUGINS`. Two names are added to that set:\n\n- `CLAUDE_CODE_TETHER_LIVE`\n\n- `CLAUDE_CODE_MCP_APPS_HOST`\n\n`CLAUDE_CODE_MCP_APPS_HOST` is also added to a second list, and is only treated as set when its value is exactly true.\n\n`CLAUDE_CODE_TETHER_LIVE` used to fall back to the `tengu_curious_tower` gate when it was not set, and that fallback defaulted to off in the earlier code. That fallback pattern is replaced here. For that gate, the flag server has returned on for this site's account and for an anonymous account, first seen on 2026-09-17.\n\n**Why**\n\nThe protected set exists to stop certain variables from being set where Claude Code does not accept them. The likely effect is that an `env` block in a settings file, the section that sets environment variables for Claude Code, cannot set these two.\n\n- Flag `tengu_curious_tower`: Off by default, switched on for this account (read for one account on one subscription tier against v2.1.281; this account: on, anonymous baseline: on, compiled default: off) These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.\n- Area: Settings\n- Names: `CLAUDE_CODE_MCP_APPS_HOST`\n- Tier: Under the hood\n- Useful: 3\/5\n- Signal: 4\/5"}