claude CLI 2.x enables dynamic tool loading ("tool search") by default,
which defers MCP tools behind the built-in ToolSearch tool instead of
presenting them directly. Combined with our `--tools ""` (which also
removes ToolSearch), the model could not reach the loopback tools and
fabricated `<tool_call>` text instead of real `tool_use` blocks, breaking
single- and multi-turn tool use.

Spawn `claude -p` with:
- ENABLE_TOOL_SEARCH=false — present MCP tools to the model directly.
- CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1 — skip background prefetches
  (e.g. the haiku session-title request) we never use.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>