Sessions frequently hang/get stuck on large repos

Description

Claude Code sessions repeatedly get stuck and become unresponsive. User had to recreate new sessions 5+ times. The issue is persistent across new sessions — not a one-off hang.

Environment

• macOS (Darwin 25.3.0)
• Claude Code with Opus 4.6 (1M context)
• Repo size: ~2.5 GB on disk (2.1 GB Flutter build/ dir + 164 MB node_modules/, both gitignored)
• swift-lsp plugin enabled
• Custom skills (session-start, session-close, checkpoint) defined

Observed behavior

• New sessions hang/lag repeatedly
• No specific tool call or command identified as the trigger — sessions just stop responding
• Happens even after starting fresh sessions

Possible contributing factors

• Large gitignored directories on disk (build/, node_modules/) may be getting scanned despite being in .gitignore
• swift-lsp plugin indexing a large repo
• Session-start skill reads multiple files + runs gh commands in parallel

Expected behavior

Sessions should start and remain responsive regardless of repo size, especially when large directories are already gitignored.