{"version":"2.1.315","anchor":"header-env-var-expansion-only-builds-its-blank-list-when-a-v","canonical_anchor":"header-env-var-expansion-only-builds-its-blank-list-when-a-v","heading":"Header variable expansion does less work","tier":"internal","area":"MCP","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.315\/e\/header-env-var-expansion-only-builds-its-blank-list-when-a-v","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.315","markdown":"### Header variable expansion does less work\n\nClaude Code now only prepares variable expansion for MCP and remote headers whose value contains `${`, with no change to the result\n\n**What**\n\nWhen Claude Code fills in environment variables in headers for MCP and remote connections, it now does the setup only for header values that contain `${`, instead of on every call.\n\n**Why**\n\nHeader processing does less work, and the headers that come out are the same.\n\n- Area: MCP\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 0\/5\n- Scope: individual\n- Heads-up: no"}