Hotspot

Hotspot keeps a per-minute record of CPU, memory and macOS thermal pressure, and charges the load to the BB threads whose processes caused it. When the fans spin up, you see which agent's dev server, build or test run is responsible, and you can stop it from BB.

What you get

• A footer readout. A flame that turns amber or red with the heat, plus CPU and memory figures, updated every 2 seconds while a BB window is on screen.
• A popover with the answer. Click the footer for a verdict such as "Running hot since 2:13 PM, mostly Run e2e test suite", a numbers row (heat, CPU, memory with swap, load per core, each with a line for the last hour), the busiest threads with their CPU and memory under a BB total row, and your recent hot spells.
• A drill-down for each thread. Unfold a thread to see its five busiest processes. Stop its running turn, kill all its work processes, or kill one process with its × button. Each kill first lists what gets stopped and what is spared.
• An Activity Monitor button for the load that comes from outside BB.
• A Hotspot page with a 24-hour or 7-day timeline of CPU and thermal pressure, hot spells shaded, a memory plot on the same time axis, and the list of hot spells. Open a spell to see the threads that used the most CPU during it, each with its busiest processes.
• A toast when the Mac starts running hot, naming the thread responsible.
• Answers for agents and terminals. Ask an agent "why was my Mac hot at 3pm?" and it reads the hotspot_history tool. bb hotspot status and bb hotspot episodes answer the same question in a terminal.

How it works

Hotspot stores one sample a minute from ps, notifyutil, vm_stat and sysctl, and keeps seven days of history in its own database on the BB server. Three hot minutes in a row (thermal pressure above nominal, or CPU at 80% of all cores) open a hot spell, and three normal minutes close it. The 2-second live readings are never stored. Sampling only reads, and it needs no account, root access or network service.

A kill targets only a thread's own work: the dev servers, builds, test runners and headless browsers its shells started. It never signals the thread's agent or its MCP servers, BB, your apps or system processes. Agents get no tool to kill processes or stop turns. Set allowKill to false to remove the kill actions.

Requirements

Hotspot is built for macOS. On Linux it records CPU, memory and threads, but it has no thermal reading, so only the CPU rule opens a hot spell, and memory has no pressure level. The Activity Monitor button opens GNOME's or KDE's system monitor there. Windows is not supported.