[BUG] Claude Code Desktop eager loading MCPs while Claude Code CLI lazy loading

Root cause for this (Desktop / Code-tab in 3p mode eager-loads MCP schemas while the standalone CLI defers): the Desktop 3p entrypoint injects CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS=1 into the runtime, and the tool-search mode resolver checks that flag before ENABLE_TOOL_SEARCH:

function _Be(){ return rt(process.env.CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS) || D1e("hipaa") }
function dPt(){
  if (_Be()) return "standard";          // tool search OFF — returns before ENABLE_TOOL_SEARCH is read
  let e = process.env.ENABLE_TOOL_SEARCH; ...
}

So on the 3p Desktop surface tool search is forced to "standard" (off) and ENABLE_TOOL_SEARCH=true is a no-op — whereas the standalone CLI (which does not set the flag) defers correctly through the same gateway, account, model and ~/.claude/settings.json. That's exactly the CLI-vs-Desktop split reported here and in the duped #67890.

Verified on macOS, runtime 2.1.181:

• the live 3p Desktop runtime process has CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS=1 and ENABLE_TOOL_SEARCH=true (the user never set the first — the host injects it);
• a headless run of the same runtime binary, --debug, ENABLE_TOOL_SEARCH=true, but without DISABLE_EXPERIMENTAL_BETAS, logs [ToolSearch:optimistic] mode=tst, ENABLE_TOOL_SEARCH=true, result=true and defers (Dynamic tool loading: 0/N deferred tools included).

Full write-up, gate-order RE and repro details: anthropics/claude-code#64311 (comment: https://github.com/anthropics/claude-code/issues/64311#issuecomment-4803852141).

The flag is the all-or-nothing experimental-betas kill switch — a defensive default for non-first-party routing — and tool search (defer_loading / the tool-search beta) is collateral. A per-beta survive-allowlist (so tool-search stays on when DISABLE_EXPERIMENTAL_BETAS=1), or simply not forcing the flag on the 3p entrypoint when the gateway forwards tool_reference blocks, would fix it. The allowlist shape was already requested in #59536.

I've encountered the same issue and hope it can be fixed. It would be great if the ToolSearch toggle could be added directly to Claude Desktop's Settings.

Same issue here : having all MCPs eagerly loading makes the desktop app pretty much unusable in terms of context window when running on Bedrock. Seems fine with the Claude API directly, so a fix would be really appreciated!

This makes the desktop app unsuable for me too.

<img width="853" height="483" alt="Image" src="https://github.com/user-attachments/assets/7bed053b-fabf-4e51-a132-196d4c901df7" />