[VSCode Extension] Parallel Agent and MCP tool calls silently rejected

Description

When running in the VSCode extension, parallel tool calls (Agent, MCP tools) are silently rejected after the first one. The error message says "The user doesn't want to proceed with this tool use" but no permission prompt is ever shown to the user. The user never declined anything.

Steps to Reproduce

1. Open Claude Code in VSCode extension
2. Give a prompt that triggers multiple parallel Agent tool calls (e.g., "spawn 4 research agents to analyze these files")
3. First Agent launches successfully
4. Remaining Agents are immediately rejected with "The user doesn't want to proceed"
5. No permission dialog is ever shown

Same behavior observed with parallel MCP tool calls (e.g., Stitch generate_screen_from_text).

Expected Behavior

All parallel tool calls should either:

• Execute in parallel (as the CLI does), or
• Show individual permission prompts for each, or
• Queue and execute sequentially with a single approval

Actual Behavior

First call succeeds. All subsequent parallel calls are silently auto-rejected. The "user doesn't want to proceed" message is misleading — it implies user action that never happened.

Environment

• Claude Code VSCode Extension (latest as of 2026-03-26)
• macOS (Apple Silicon)
• Affects: Agent tool, MCP tools (Stitch confirmed)
• Does NOT affect: Read, Write, Edit, Glob, Grep (these work in parallel)

Impact

This blocks a key power-user workflow: running parallel sub-agents for research, code review, or expert analysis. A task that takes 3 minutes with 4 parallel agents takes 12+ minutes sequentially. The CLI handles this correctly, so the limitation is VSCode-extension-specific.

Related

• #24131 (parallel Write/Edit, closed as Not Planned — but this is about Agent/MCP, not Write/Edit)
• #29159 (VSCode ignores permission settings)