cli: 100% CPU on one core while a shell tool command runs #51926

Summary

On Windows 11, opencode-cli.exe (OpenCode Desktop 2.0.18) pins ~100% of one CPU core for the entire time a shell tool command is running — even when the command only sleeps and produces no output. Memory use is ~0.7 GB. The sleeping child process itself uses ~0% CPU.

Environment

• opencode version: 2.0.18 (opencode-cli.exe --version → opencode v2.0.18; desktop-bundled CLI, not on PATH)
• OS: Microsoft Windows [Version 10.0.26200.9457] (Windows 11)
• Terminal: OpenCode Desktop app (Electron); TERM=xterm-256color, TERM_PROGRAM and COLORTERM unset
• Shell: C:\WINDOWS\system32\cmd.exe
• Install/channel: OpenCode Desktop release, latest (updater reports "Update for version 2.0.18 is not available"); CLI at %APPDATA%\ai.opencode.desktop\cli\2.0.18\opencode-cli.exe
• Active plugins: none found (checked opencode.json/opencode.jsonc in the workspace and ~/.config/opencode/, plus plugin/plugins directories). MCP servers are configured in ~/.config/opencode/opencode.jsonc, all with "disabled": true

Reproduction

1. On Windows 11, run OpenCode Desktop 2.0.18 and use a session for a while (in my case ~3.5 h of history with many tool calls).
2. Have the agent run a shell command that takes a while without output, e.g. powershell -NoProfile -Command "Start-Sleep -Seconds 60".
3. While the command runs, watch opencode-cli.exe CPU in Process Explorer / Task Manager.

Expected Behavior

The CLI process should be near-idle while waiting for the child process. Only the child command should consume resources (it used ~0%).

Actual Behavior

opencode-cli.exe consumes ~100% of one CPU core for the whole duration of the command:

• foreground command, 20 s window: 20.16 s of CPU time in 20 s wall clock (100.8% of one core);
• background command, 60 s window, sampled every 5 s (% of one core): 101.2, 98.1, 101.2, 99.7, 99.1, 99.7, 99.4, 99.4, 99.7, 100, 101.6, 100 — average 99.9%;
• process memory: Private Bytes ~765 MB, Working Set ~440 MB (CLI process alone).

During one measured 60 s window the CLI wrote no log lines and spawned no subprocesses (~/.local/share/opencode/log/opencode.log), so the busy loop is silent.

Additional Context

• Working directory is a local git workspace containing a large .venv (~60k files), a models\ folder (~1.3 GB) and an output\ folder with six ~60 MB WAV files. This may matter for the watcher/snapshot subsystem (cf. fff watcher: GitStatusCache loops even after file changes stop, resulting in 100% cpu usage #42557 "GitStatusCache loops"), but the CPU is burned inside the CLI process, and during the measured idle window no git.exe child was spawned.
• Desktop renderer.log has 1145 ResizeObserver loop completed with undelivered notifications. errors since launch (bursts of layout loops on updates) — probably related to [Desktop] UI freezes after agent turns finish — renderer stuck in ResizeObserver loop; only force-quit + relaunch recovers #43355, though in my case the UI does not freeze.
• Possibly related: TUI: main thread burns ~100% CPU continuously redrawing a spinner (~15fps writev to tty) with no active output #42306 (TUI spinner burns ~100% CPU with no active output), fff watcher: GitStatusCache loops even after file changes stop, resulting in 100% cpu usage #42557, [Desktop] UI freezes after agent turns finish — renderer stuck in ResizeObserver loop; only force-quit + relaunch recovers #43355, Desktop (macOS, Electron): high CPU usage during active use, CHROME_HEADLESS=1 works around it, but silently disables all window shadows #48120.
• Not tried yet: restarting the app, a fresh short session, a small/empty workspace, or closing the app (closing should free the core).
• Workaround: none found yet.
• A Process Explorer screenshot from the reporter is available.