memory-leak-debug

Memory Leak Debugging

Diagnose memory leaks in the Qwen Code Node.js CLI by capturing heap snapshots and analyzing retained object sizes via chrome-devtools CLI tooling.

Prerequisites

• chrome-devtools CLI (from chrome-devtools-mcp package). If not found, install with: npm i chrome-devtools-mcp@latest -g after user confirmation. See https://github.com/ChromeDevTools/chrome-devtools-mcp/blob/main/docs/cli.md
• Node.js 22+ (for --heapsnapshot-signal support)

Step 1: Start the CLI with Snapshot Signal

Use tmux so you can interact with the TUI and trigger snapshots from another pane. Use the tmux-real-user-testing helper script:

HELPER=.qwen/skills/tmux-real-user-testing/scripts/tmux-real-user-log.sh
eval "$(bash "$HELPER" start memleak . \
  env QWEN_CODE_NO_RELAUNCH=true NODE_OPTIONS=--heapsnapshot-signal=SIGUSR2 \
  npm run dev)"
echo "SESSION=$SESSION OUTDIR=$OUTDIR"

The eval exports SESSION and OUTDIR. Note: shell environment does not persist across separate tool calls — save the session name from the output and use it explicitly in subsequent commands.

Notes:

• npm run dev runs from TypeScript source via tsx — no build step needed and changes to core/cli are reflected immediately.
• QWEN_CODE_NO_RELAUNCH=true prevents the CLI from spawning a child process, so PID management is simpler.
• NODE_OPTIONS propagates the flag through npm → tsx → node.

Get the PID of the actual node process. With npm run dev, there's a process chain (npm → node scripts/dev.js → tsx → node CLI), so walk the tree to the innermost node child:

NODE_PID=$(bash .qwen/skills/memory-leak-debug/scripts/find-leaf-node.sh "<session-name>")

To profile the production bundle instead (e.g., verifying tree-shaking): npm run bundle first, then use env QWEN_CODE_NO_RELAUNCH=true node --heapsnapshot-signal=SIGUSR2 dist/cli.js as the command. Since node is the direct pane process, PID discovery is simpler:

NODE_PID=$(tmux list-panes -t "<session-name>" -F '#{pane_pid}')