Claude Issue 769

devcontainer.json

{
  "name": "Claude Flickering Repro",
  "build": {
    "dockerfile": "Dockerfile"
  },
  "remoteUser": "vscode",
  "postCreateCommand": "echo 'Container ready. Run ./reproduce-flickering.sh to see the issue.'"
}

Dockerfile

FROM mcr.microsoft.com/devcontainers/base:ubuntu

# Basic tools
RUN apt-get update -y && \
    DEBIAN_FRONTEND=noninteractive apt-get install -y \
    curl wget jq git \
    && rm -rf /var/lib/apt/lists/*

# Install nvm and Node.js LTS
ENV NVM_DIR=/usr/local/nvm
ENV NODE_VERSION=22.12.0

RUN mkdir -p $NVM_DIR && \
    curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash && \
    . $NVM_DIR/nvm.sh && \
    nvm install $NODE_VERSION && \
    nvm alias default $NODE_VERSION && \
    nvm use default

ENV NODE_PATH=$NVM_DIR/versions/node/v$NODE_VERSION/lib/node_modules
ENV PATH=$NVM_DIR/versions/node/v$NODE_VERSION/bin:$PATH

# Install Claude Code CLI
RUN npm install -g @anthropic-ai/claude-code

# Create workspaces directory
RUN mkdir -p /workspaces && chown -R vscode:vscode /workspaces

WORKDIR /workspaces/repro

reproduce_flickering.sh

#!/bin/bash
# Reproduction script for Claude Code subagent flickering issue
#
# This script runs Claude Code with a prompt that triggers multiple
# parallel subagent spawns, which causes screen flickering in VS Code
# integrated terminal.

set -e

echo "=== Claude Code Subagent Flickering Reproduction ==="
echo ""
echo "Environment:"
echo "  Terminal: ${TERM_PROGRAM:-unknown}"
echo "  TERM: $TERM"
claude --version 2>/dev/null || echo "  Claude: not installed"
echo ""
echo "Running Claude with a prompt that spawns multiple subagents..."
echo "Watch for screen flickering as agents are spawned."
echo ""
echo "Press Ctrl+C to cancel at any time."
echo ""

# This prompt is designed to trigger multiple parallel subagent spawns
# without needing any specific codebase
claude --print "I need you to research three completely independent topics IN PARALLEL using the Task tool with subagent_type=Explore. Launch all three agents simultaneously in a single response:

1. Search the web for 'what is the Rust programming language' and summarize
2. Search the web for 'what is WebAssembly' and summarize
3. Search the web for 'what is LLVM' and summarize

IMPORTANT: You MUST launch all 3 agents in parallel (in a single message with 3 Task tool calls) to reproduce the flickering issue. Do not run them sequentially."