Frozen Qwen Code Session Diagnosis

/stuck — diagnose frozen/slow Qwen Code sessions

The user thinks another Qwen Code session on this machine is frozen, stuck, or very slow. Investigate and present a diagnostic report.

What to look for

Scan for other Qwen Code processes (excluding the current one — exclude the PID you see running this prompt). Since Qwen Code is a Node.js CLI (#!/usr/bin/env node), the process name (comm column) is always node (or bun if run with Bun). Identify Qwen Code sessions by looking at the command column for a script path inside a directory whose name starts with qwen-code (matches qwen-code/, qwen-code-dev/, worktree clones, etc.) — anchored to the start of the path or after / so unrelated names like analyze-qwen-code/ don't false-match — or a bin invocation ending in /qwen (the global symlink). Avoid loose qwen-code substring matching: it false-positives on plugin brokers that merely pass a qwen-code path as --cwd.

Signs of a stuck session:

• High CPU (>=90%) sustained — likely an infinite loop. Sample twice, 1-2s apart, to confirm it's not a transient spike.
• Process state D / U (uninterruptible sleep) — often an I/O hang. Linux uses D, macOS/BSD uses U. The state column in ps output; first character matters (ignore modifiers like +, s, <).
• Process state T (stopped) — user probably hit Ctrl+Z by accident.
• Process state Z (zombie) — parent isn't reaping.
• Very high RSS (>=4GB) — possible memory leak making the session sluggish.
• State S with low CPU — the most common hang signature: a hung HTTPS request to the model API. Not a process-level red flag on its own, but combined with the user reporting "stuck", treat it as a strong signal to run the network check in step 3.
• Stuck child process — a hung git, node, or shell subprocess can freeze the parent. Check pgrep -P <pid> (then ps -p for state — see step 3) for each session.

Argument validation

If the user gave an argument, treat it as a PID only if it consists entirely of digits 0-9. Anything else — letters, whitespace, punctuation — fails the check, in which case treat it as a free-text symptom description (guidance for the report only, never substituted into shell commands). The strict digit-only whitelist is safer than enumerating shell metacharacters.

Investigation steps

Preamble — resolve the runtime base directory. Required for both paths below (sidecar enumeration in step 1, debug log lookup in step 3, and the PID fast path). The base directory is taken from (in priority order): QWEN_RUNTIME_DIR env var, the advanced.runtimeOutputDir setting, QWEN_HOME env var, and finally ~/.qwen.

RUNTIME_DIR="${QWEN_RUNTIME_DIR:-}"
[ -z "$RUNTIME_DIR" ] && command -v jq >/dev/null && RUNTIME_DIR=$(jq -r '.advanced.runtimeOutputDir // empty' "${QWEN_HOME:-$HOME/.qwen}/settings.json" 2>/dev/null)
# `advanced.runtimeOutputDir` may be `~/...` or relative; mirror Storage.resolvePath() before using in globs
[ -n "$RUNTIME_DIR" ] && RUNTIME_DIR="${RUNTIME_DIR/#\~/$HOME}"
[ -n "$RUNTIME_DIR" ] && case "$RUNTIME_DIR" in /*) ;; *) RUNTIME_DIR="$(cd "$RUNTIME_DIR" 2>/dev/null && pwd)" || RUNTIME_DIR="" ;; esac
RUNTIME_DIR="${RUNTIME_DIR:-${QWEN_HOME:-$HOME/.qwen}}"

(If jq isn't installed, the settings layer is silently skipped — the env-var / default fallback covers the common case.)

Fast path for targeted diagnosis — if a digit-only PID argument was given, skip step 1 enumeration. Validate that the PID is a live current-user Qwen Code process before dumping any details:

kill -0 <pid> 2>/dev/null || { echo "PID <pid> is dead, or owned by another user"; exit 0; }
ps -p <pid> -o command= -ww 2>/dev/null | grep -qE '((^|/)qwen-code[^ /]*/[^ ]*\.(js|ts|mjs|cjs)( |$)|/qwen( |$))' || { echo "PID <pid> is yours but is not a Qwen Code process — refusing to dump details"; exit 0; }

If either guard prints, stop the diagnostic and surface the message verbatim. Otherwise, gather stats and the sidecar mapping, then jump to step 3:

ps -p <pid> -o pid=,pcpu=,rss=,etime=,state=,comm=,command= -ww
grep -El '"pid"[[:space:]]*:[[:space:]]*<pid>\b' "$RUNTIME_DIR"/projects/*/chats/*.runtime.json 2>/dev/null

Note: as in step 2, the command= column may include credentials passed as CLI args (e.g., --openai-api-key=sk-…). Redact such values to *** before quoting them in the report.

-E is required so \b is interpreted as word boundary (BSD grep without -E treats \b as a backspace character, silently returning nothing on macOS). The -l flag returns the matching sidecar file path; the basename (stripped of .runtime.json) is the session ID for step 3's debug log read. If multiple sidecars match (rare — happens only after PID reuse leaves a stale file), prefer the most recently modified one: ls -t <matches> | head -n 1.

Otherwise (no arg, or symptom-only arg), run the general path below:

1. Enumerate live sessions via the runtime sidecar (preferred, reliable):

   Qwen Code writes a runtime.json sidecar for each interactive session at "$RUNTIME_DIR"/projects/<sanitized-cwd>/chats/<sessionId>.runtime.json. Each file contains {schema_version, pid, session_id, work_dir, hostname, started_at, qwen_version} — the authoritative source of (pid, session_id, work_dir) mappings.

   Filter to live (pid, sidecar-path) pairs in one shot. Use Node (guaranteed available — qwen-code requires it) instead of jq (often missing on default macOS / minimal Linux) so this path doesn't silently degrade:

   node -e 'const fs=require("fs"); for (const f of process.argv.slice(1)) { try { const p=JSON.parse(fs.readFileSync(f,"utf8")).pid; if (p) { try { process.kill(p,0); console.log(p+" "+f); } catch {} } } catch {} }' "$RUNTIME_DIR"/projects/*/chats/*.runtime.json 2>/dev/null

   PID reuse is rare but possible — when you cross-reference with ps in step 2, skip pairs whose live PID's command line no longer looks like a Qwen Code process.

   If the command emits nothing (no sidecars, or no live PIDs), fall through to step 2 — ps is the working fallback.

2. List Qwen Code processes via ps (macOS/Linux) — used to enrich each live session with CPU/RSS/state/uptime, and to catch sessions that may have started before the sidecar feature existed:

   ps -xo pid=,pcpu=,rss=,etime=,state=,comm=,command= -u "$(id -u)" -ww | grep -E '((^|/)qwen-code[^ /]*/[^ ]*\.(js|ts|mjs|cjs)( |$)|/qwen( |$))' | grep -v grep

   -u "$(id -u)" restricts the scan to the current user — on shared hosts this avoids exposing other users' Qwen process paths/arguments into the chat. -ww disables column truncation so long "qwen" paths aren't cut off. The comm column will be node or bun, not qwen; filter to rows where the command column contains a qwen path (e.g., qwen-code/dist/cli.js, or a bin symlink ending in /qwen). Cross-reference with the PIDs from step 1.

   Note: ps reports rss in kilobytes on both macOS and Linux. To report in MB, divide by 1024; to report in GB, divide by 1048576. The 4GB threshold is 4194304 KB — compare the raw rss value against that, or compare the GB value against 4. Do not divide once and then compare against 4; that would flag every process >4MB as "very high RSS".

   Note: full command lines may contain credentials passed as CLI args (e.g., --openai-api-key=sk-…). Redact such values to *** before quoting them in the report.

3. For anything suspicious, gather more context. If the process state alone explains the problem (T = accidentally stopped, Z = parent not reaping), skip directly to the report — child / log / stack inspection adds nothing. Otherwise:

   • Child processes (with state, so a hung git / node shows up): CHILDREN=$(pgrep -P <pid> | tr '\n' ',' | sed 's/,$//'); [ -n "$CHILDREN" ] && ps -p "$CHILDREN" -o pid=,ppid=,pcpu=,state=,etime=,command= -ww. Single ps call (avoids forking one per child) and -ww so long child command lines aren't truncated.
   • If high CPU: sample again after 1-2s to confirm it's sustained
   • Network hang — if CPU is low and state is S despite the user reporting "stuck", the most likely cause is a hung HTTPS request to the model API. macOS: lsof -nP -i -p <pid> 2>/dev/null | head -20 (the -nP flags skip reverse-DNS and port lookups, which can themselves hang). If lsof itself feels slow, prefix with timeout 10 (or gtimeout 10 on macOS with Homebrew coreutils). Linux: ss -tnp 2>/dev/null | grep "pid=<pid>,". Note that ss -tnp's -p requires root or CAP_NET_ADMIN — without it, the PID column shows - and the grep returns empty. If you see no matches but ss -t 2>/dev/null does show ESTABLISHED sockets, fall back to lsof -nP -i -p <pid> rather than reporting "no connections". A long-lived ESTABLISHED connection to a model host (dashscope, openai, anthropic, etc.) with no recent traffic is the smoking gun.
   • Debug log — start with "$RUNTIME_DIR"/debug/latest (symlink to the most recent session); if it matches the suspicious PID's session, that's usually the right one. Otherwise infer the session ID from the sidecar and read "$RUNTIME_DIR"/debug/<session-id>.txt. Bound the read with tail -n 200 <path> — debug logs can be GB-sized. The last few hundred lines typically show what the session was doing before hanging. Debug logs may contain prompts, file contents, or tokens from other sessions — paste only lines relevant to the hang, and never quote secrets/API keys you happen to see.

4. Consider a stack dump for a truly frozen process (advanced, optional):

   • macOS: sample <pid> 3 gives a 3-second native stack sample. If sample itself seems to hang (the target's Mach task port may be wedged on a kernel-level freeze), wrap it: timeout 15 sample <pid> 3 (or gtimeout 15 ... on Homebrew coreutils). Stack frames may include function arguments containing API keys or tokens held in memory — redact such values to *** before including the dump in the report.
   • Linux: cat /proc/<pid>/stack for kernel stack (read-only, no ptrace permissions needed). Avoid strace -p for this purpose: it requires CAP_SYS_PTRACE (often denied under kernel.yama.ptrace_scope=1), and strace -c blocks until the target exits — it would hang on the very kind of stuck process you are diagnosing.
   • This is big — only grab it if the process is clearly hung and you want to know why