tui: animated session tabs cause high CPU/GPU use and slow other apps #57462

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1. opencode-agent commented on Oct 20, 2026

   

   opencode-agentBot

   on Oct 20, 2026 – with OpenCode Agent

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   Thanks for the detailed measurements. I could reproduce this in kind on 2.0.32 and on the latest release, 2.1.1. The sandbox can't measure terminal or GPU load, so I measured only the OpenCode process.

   What I did: I opened a session with the tab strip on and a long transcript, then held a turn open for 25 s with a simulated model and sampled the TUI process's CPU and terminal output:

   • 2.1.1, animations on: about 9.4% CPU and a constant ~37.5 KiB/s of terminal output.
   • 2.1.1, animations off: about 0.9% CPU and no output.
   • 2.0.32: 6.6% with animations on, 0.8% with them off, and 4.6% with animations on but tabs off.

   The absolute numbers are much lower than yours because the sandbox has a fast CPU and no real terminal or GPU. The pattern matches what you describe, though: while a session is busy, the animations keep the whole UI re-rendering and writing frames to the terminal, which your terminal then has to redraw. The screenshot below shows the busy tab spinner during the measurement, and the script below reproduces it.

   I couldn't run the current dev branch from source here, so this was checked against the 2.1.1 release. I also didn't test your idle-selected-tab case. Until this is looked at, "animations": false in cli.json remains the workaround. Related: #39681 (an earlier tab pulse frame-rate fix) and #42306.

   

   Reproduction script (drive.ts)

   // Measures CPU of the OpenCode TUI process while a session is working (simulated model holds
   // the response open), with animations on vs off, and tabs on vs off.
   // Variants run sequentially in the same script; each launches a fresh TUI.
   import { Effect } from "effect"
   import { Llm, OpenCodeDriver } from "opencode-drive"
   import { readFileSync, readdirSync } from "node:fs"
   
   const ticks = () => {
     const out = new Map<number, { cmd: string; t: number; w: number }>()
     for (const d of readdirSync("/proc")) {
       if (!/^\d+$/.test(d)) continue
       try {
         const cmd = readFileSync(`/proc/${d}/cmdline`, "utf8").replace(/\0/g, " ")
         if (!/opencode|packages\/cli\/src\/index\.ts/.test(cmd) || /opencode-drive|drive\.ts/.test(cmd)) continue
         const st = readFileSync(`/proc/${d}/stat`, "utf8").split(") ")[1]!.split(" ")
         let w = 0
         try { w = +(readFileSync(`/proc/${d}/io`, "utf8").match(/wchar: (\d+)/)?.[1] ?? 0) } catch {}
         out.set(+d, { cmd: cmd.slice(0, 90), t: +st[11]! + +st[12]!, w })
       } catch {}
     }
     return out
   }
   const sample = (label: string, secs: number) =>
     Effect.gen(function* () {
       const a = ticks()
       yield* Effect.sleep(secs * 1000)
       const b = ticks()
       for (const [pid, v] of b) {
         const pct = ((v.t - (a.get(pid)?.t ?? v.t)) / 100 / secs) * 100
         const kbs = (v.w - (a.get(pid)?.w ?? v.w)) / 1024 / secs
         if (pct > 0.5) yield* Effect.log(`[${label}] pid ${pid} ${pct.toFixed(1)}% CPU ${kbs.toFixed(1)} KiB/s written  ${v.cmd}`)
       }
     })
   
   const long = Array.from({ length: 30 }, (_, i) => `Line ${i}: ` + "lorem ipsum dolor sit amet ".repeat(4)).join("\n\n")
   
   const variant = process.env.VARIANT ?? "animations-on"
   const cfgs: Record<string, any> = {
     "animations-on": { animations: true, tabs: { mode: "on" } },
     "animations-off": { animations: false, tabs: { mode: "on" } },
     "anim-on-tabs-off": { animations: true, tabs: { mode: "off" } },
   }
   
   export default OpenCodeDriver.use(
     {
       ...(process.env.OC_DEV ? { opencode: { dev: process.env.OC_DEV } } : {}),
       tuiConfig: cfgs[variant],
       tui: { recording: true, viewport: { cols: 160, rows: 45 } },
     },
     ({ ui, llm }) =>
       Effect.gen(function* () {
         // a long transcript first, then a turn held open for 25 s (session "working")
         yield* llm.queue(Llm.text(long))
         yield* ui.submit("Write a long answer")
         yield* Effect.sleep(8000)
         yield* Effect.sleep(1500)
         yield* sample(`${variant} after-first-turn-idle`, 5)
         yield* llm.queue(Llm.text("Starting..."), Llm.pause(25000), Llm.text("Done working."))
         yield* ui.submit("Keep working for a while")
         yield* Effect.sleep(3000)
         yield* ui.screenshot(`${variant}-working`)
         yield* sample(`${variant} working`, 10)
         yield* Effect.sleep(14000)
       }),
   )

   Run it with opencode-drive: opencode-drive run ./drive.ts. It drives opencode from your PATH; set OC_DEV to the path of an OpenCode checkout to run that from source instead.
2. opencode-agent

   added

   reproduced

   on Oct 20, 2026
3. opencode-agent commented on Oct 20, 2026

   

   opencode-agentBot

   on Oct 20, 2026 – with OpenCode Agent

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