fix(sessions): keep streaming live when the window is backgrounded

[posthog]

Problem

When the agent enters a waiting/looping state (e.g. "Loop over this PR until all checks succeed" → "I'll check back in ~10 min once CI finishes"), the conversation appears to hang. The messages the agent produces afterward stay hidden and then appear all at once the moment the user sends a follow-up.

The streamed events are not lost — they are buffered in the renderer and committed to the conversation store on a short setTimeout flush (a frame-sized coalescing window that keeps streaming from re-rendering per token). Chromium clamps, and once the window is occluded/hidden effectively freezes, renderer timers when the window is backgrounded. Backgrounding the app is exactly what you do during a 10-minute CI wait, so the flush timer stops firing: buffered events pile up and only drain in a burst when the timer thaws on refocus (sending a follow-up focuses the window). This matches the reported "hidden messages appear the instant a follow-up is sent."

Changes

Set backgroundThrottling: false on the main BrowserWindow so the renderer keeps running at full speed while backgrounded. This keeps the streamed-event flush (and other timer/rAF-driven UI) working during long-running agent runs, so a waiting/looping agent no longer looks hung.

How did you test this?

I traced the full local streaming path (agent stream tap → tRPC subscription → renderer flush → zustand store → conversation view) and confirmed the only deferral point is the renderer setTimeout flush in SessionService; every other hop delivers immediately. backgroundThrottling was unset (defaults to true), and SessionService (which owns the flush) is bound in the renderer container, so the flush timer is subject to Chromium background throttling — the mechanism behind the symptom.

I was not able to run the live multi-minute backgrounded repro in this headless environment, so this has not been verified end-to-end in a running app; the fix is the standard Electron remedy for a backgrounded renderer batching updates until refocus.

Automatic notifications

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Created with PostHog Code from an inbox report.

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit fffce79.}