---
title: Keep chat responsive under heavy load (lean hidden panels)
---

# Keep chat responsive under heavy load (lean hidden panels)

## What it is

### What it does

When you have a lot of sessions open at once, Omniscio keeps many of their chat panels
alive in the background so switching between them is instant. The cost of that
convenience: every time **any** running session sends a new chunk of output (which
happens many times a second), each of those background panels used to do a little
bit of bookkeeping work — checking whether anything it cares about had changed. With
40+ sessions open, that adds up to hundreds of tiny operations many times a second,
which can bog the app down and, in particular, make the chat **scroll land in the
wrong place** — the scroll never gets a free moment to settle where it should.

**Lean hidden panels** stops the panels you can't see from doing that work. A
hidden, non-active session is rendered as a tiny placeholder that reacts to
**nothing** — it just sits there until you click it. The result: the per-update
cost stops growing with how many sessions you have open, so scrolling stays smooth
and the chat lands in the right place no matter how many sessions are running.

This is a performance setting, not a workflow change. What you see and how switching
feels are identical; the only difference is that hidden sessions stop quietly
reacting to each other.

**It is on by default (opt-out).** It is a fully reversible layer: turn the setting
off (or use the kill switch) and Omniscio behaves exactly as it did before — every hidden
panel is mounted in full again, the off path is byte-for-byte unchanged.

## Where to find it

**Settings → Performance**, as the toggle for lean hidden panels. It is on by default, and its effect shows up as steadier scrolling once you have a lot of sessions open.

## How it behaves

### Turning it off

It is already on — there is nothing to enable. To go back to mounting every hidden
panel in full: **Settings → Performance → "Keep chat responsive under heavy load"**
and turn it off.

The toggle's own description reads: _"When you have many sessions open at once, Omniscio
stops the ones you can't see from doing background work every time another session
sends a message. This keeps scrolling smooth and the chat landing in the right place
no matter how many sessions are running. On by default; turn off to mount every
hidden session in full like before."_

No restart required — flipping it off immediately mounts hidden panels in full again;
flipping it on slims them down from your next update.

### When it applies

- The panel is **hidden** (not the session you're currently looking at).
- It is **not pre-warmed** for instant switching — i.e. not one of your pinned
  "Needs You" inbox panels (those stay fully built so switching into them is
  instant) and not a recently-viewed "frozen" panel.

In short: the session you're looking at, your inbox panels, and recent ones all stay
fully built. Everything else in the background goes lean.

### When it does NOT apply

- **The active (visible) session** — always fully built; this never touches what
  you're looking at.
- **Pre-warmed inbox ("Needs You") panels** and **recently-viewed (frozen) panels**
  — kept fully built so switching into them is still instant. Lean panels and these
  never overlap. They do **pause** their background redrawing while off-screen: a
  fully-built panel you can't see stops repainting its chat as new output arrives and
  catches up the moment you open it, so a busy background session no longer competes
  with the one you're actually reading. What you see when you click is unchanged.
- **When the feature is off** — every panel mounts in full, exactly as before.

### What you might notice

Switching **back** to a plain background _running_ session you'd visited can take a
hair longer than before — it rebuilds when you click it instead of being kept fully
alive in the background. It is work paid once, on the click (not many times a
second), and your already-loaded history makes it quick. Your pinned inbox and
recently-viewed sessions are unaffected — those stay instant.

### How it relates to the other "responsiveness" features

- The **keep-alive pool** decides which panels stay mounted in the background.
- **Lean hidden panels** (this page) decides how _cheap_ those hidden panels are —
  the ones that aren't pre-warmed render as a do-nothing placeholder.
- **Pre-render inbox sessions** and **frozen-panel retention** are the opposite end:
  they deliberately keep a small, bounded set of panels fully built so switching into
  _those_ is instant. Lean panels never touch that set.

## For agents

### The kill switch

There are **two** independent off-switches, and the kill switch always wins:

1. The **Settings toggle** above (`leanHiddenPanels`, default on).
2. An environment kill switch: launch Omniscio with **`AMC_DISABLE_LEAN_HIDDEN_PANELS=1`**
   and the feature is forced off **even if the setting is on** — the field escape
   hatch. A missing or malformed switch is treated as "not killed," so the setting
   alone governs in the normal case.

### Where it lives in code

- [src/renderer/src/features/sessions/SessionPanel.tsx](../../src/renderer/src/features/sessions/SessionPanel.tsx)
  — `SessionPanel` is `memo(SessionPanelImpl)`, where `SessionPanelImpl` is a thin
  wrapper that renders a subscription-free `SessionPanelShell` (lean + hidden) or the
  full `SessionPanelHeavy` (the former body, moved verbatim).
- [src/renderer/src/features/sessions/session-panel-heavy-gate.ts](../../src/renderer/src/features/sessions/session-panel-heavy-gate.ts)
  — `computeShouldRenderHeavy(...)`, the single shared heavy-vs-shell predicate.
- [src/renderer/src/lib/lean-hidden-panels-flag.ts](../../src/renderer/src/lib/lean-hidden-panels-flag.ts)
  — `isLeanHiddenPanelsEnabled(setting)`: setting first, then the
  `AMC_DISABLE_LEAN_HIDDEN_PANELS` kill switch wins.
- [src/preload/index.ts](../../src/preload/index.ts) — bridges the kill switch to the
  renderer before first paint.

The full engineering contract (test-locked invariants + safe-change checklist) is the
"Lean hidden panels" section of
[.claude/memory/contracts/keep-alive-pool-contract.md](../../.claude/memory/contracts/keep-alive-pool-contract.md).

## Related

- [frozen-panel-retention.md](frozen-panel-retention.md) — keeps recent sessions fully built for instant switch-back.
- [inbox-prerender.md](inbox-prerender.md) — pre-builds your inbox panels for instant switching.
- [lazy-content-load.md](lazy-content-load.md) — instant first cold-mount of a long session.