fix(desktop): stream the transcript while the window is backgrounded#42399
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The chat transcript reaches the screen through a requestAnimationFrame-gated flush (useSessionStateCache). The main BrowserWindow never set backgroundThrottling, so Chromium paused rAF and clamped timers whenever the window was blurred or occluded -- the live answer would stall until the window regained focus or the user refreshed. In practice this bit any time Hermes wasn't the focused window mid-turn (typing in your editor while the agent replies, detached devtools, another window on top), presenting as "thinking, no text, have to refresh." Opt the renderer out of background throttling so a streaming chat app actually streams in the background: - backgroundThrottling: false on the main window (matches the secondary windows that already set it) - disable-renderer-backgrounding / disable-backgrounding-occluded-windows / disable-background-timer-throttling at the process level for the occlusion case Latent since the desktop app landed (#20059), not a recent regression.
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wachoo
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Jun 10, 2026
…ousResearch#42399) The chat transcript reaches the screen through a requestAnimationFrame-gated flush (useSessionStateCache). The main BrowserWindow never set backgroundThrottling, so Chromium paused rAF and clamped timers whenever the window was blurred or occluded -- the live answer would stall until the window regained focus or the user refreshed. In practice this bit any time Hermes wasn't the focused window mid-turn (typing in your editor while the agent replies, detached devtools, another window on top), presenting as "thinking, no text, have to refresh." Opt the renderer out of background throttling so a streaming chat app actually streams in the background: - backgroundThrottling: false on the main window (matches the secondary windows that already set it) - disable-renderer-backgrounding / disable-backgrounding-occluded-windows / disable-background-timer-throttling at the process level for the occlusion case Latent since the desktop app landed (NousResearch#20059), not a recent regression.
changman
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Jun 10, 2026
…ousResearch#42399) The chat transcript reaches the screen through a requestAnimationFrame-gated flush (useSessionStateCache). The main BrowserWindow never set backgroundThrottling, so Chromium paused rAF and clamped timers whenever the window was blurred or occluded -- the live answer would stall until the window regained focus or the user refreshed. In practice this bit any time Hermes wasn't the focused window mid-turn (typing in your editor while the agent replies, detached devtools, another window on top), presenting as "thinking, no text, have to refresh." Opt the renderer out of background throttling so a streaming chat app actually streams in the background: - backgroundThrottling: false on the main window (matches the secondary windows that already set it) - disable-renderer-backgrounding / disable-backgrounding-occluded-windows / disable-background-timer-throttling at the process level for the occlusion case Latent since the desktop app landed (NousResearch#20059), not a recent regression.
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Summary
The desktop chat transcript reaches the screen through a
requestAnimationFrame-gated flush (useSessionStateCache). The mainBrowserWindownever setbackgroundThrottling, so Chromium paused rAF and clamped timers whenever the window was blurred or occluded — the live answer stalled until the window regained focus or the user refreshed.In practice this bit any time Hermes wasn't the focused window mid-turn (typing in your editor while the agent replies, detached devtools, another window covering it), presenting as the recurring "thinking, no text, have to refresh" report. It resolves the instant you tab back, because rAF resumes on focus.
This is latent since the desktop app first landed (#20059) — not a regression from any recent PR. Backend event emission and renderer event routing were both verified correct (headless RPC probe + in-renderer event trace); the only broken hop was the final paint, throttled by Chromium.
Changes
apps/desktop/electron/main.cjs:backgroundThrottling: falseon the main window — matches the secondary windows in this same file that already set it.disable-renderer-backgrounding,disable-backgrounding-occluded-windows,disable-background-timer-throttling.Test plan
npm run type-checkcleanCmd+N, send a prompt, immediately click into another window; the reply streams in live while Hermes is unfocused (no refresh, no tab-back)