chat: stop agent host config update loop across windows

[roblourens]

Fix #320011

Problem

The local agent host's root config is shared across all VS Code windows. AgentHostTerminalContribution pushes a couple of host-managed values into defaultShell and and listened torootState.onDidChange to re-push them.disableCustomTerminalTool it

The bug: that listener re-pushed on every root-state change, including value changes made by other windows. So two windows with different terminal settings would ping-pong root/configChanged actions forever, each forcing its own value back over the other's.

Captured agent-host protocol logs show ~8000 root/configChanged dispatches in 25s, alternating between two windows:

Window	disableCustomTerminalTool	defaultShell
79ed98fd	false	PowerShell 7 (pwsh.exe)
d551eb09	true	Windows PowerShell v1.0

Fix

The rootState.onDidChange re-push only ever needed to do one thing: retry the initial push once the host's root-config schema hydrates (the first push from _reconcile() can race an undefined rootState.value). It was never meant to react to value changes.

present**, tracked via a Set<AgentHostConfigKey>. Value-only changes (another window writing a different value) are ignored, which breaks the loop. The existing value-equality guard still prevents redundant self-dispatches.

Refactor

While here, the two managed keys are now a data-driven table (IManagedRootConfigKey[]). The schema gate, value-equality guard, dispatch, and hydration-retry are shared in a single generic _push(entry). Adding a new managed root-config key is now one table no new fields, no copy/pasted push logic.entry

Notes for reviewers

• One existing test (re-dispatches disableCustomTerminalTool when the enabled setting changes) gained an await flush() because the push pipeline is now uniformly async (computeValue may be async). The dispatch simply lands a microtask behavior is otherwise unchanged.later
• Added 2 regression tests asserting a value-only root-state change from another window does not trigger a re-dispatch.
• This stops windows from fighting. The underlying design multiple windows share one singleton root config, so it's last-writer- is unchanged; reconciling divergent per-window settings would be a larger design change.wins reality

Type-check (tsgo), ESLint, and all 15 tests pass.

(Written by Copilot)

[Copilot]

Pull request overview

This PR fixes an infinite cross-window update loop where AgentHostTerminalContribution re-pushed agent-host root-config values on every rootState change, causing multiple VS Code windows with differing terminal settings to “fight” via repeated root/configChanged dispatches. The new approach only re-pushes when a managed key’s schema first appears (hydration), and consolidates the managed-key logic into a single data-driven pipeline.

Changes:

• Refactors managed agent-host root-config pushes into a declarative _managedKeys table and a shared async _push(entry) pipeline.
• Changes the rootState.onDidChange behavior to re-push only on schema appearance (hydration), ignoring value-only changes to prevent cross-window ping-pong.
• Updates/extends tests with flush() usage and adds regressions ensuring value-only root-state updates don’t trigger re-dispatch.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/agentHostTerminalContribution.ts	Implements schema-seen gating to prevent cross-window config wars; refactors pushes into a shared managed-key pipeline.
src/vs/workbench/contrib/chat/test/browser/agentSessions/agentHostTerminalContribution.test.ts	Adds regression coverage for value-only root-state changes and adjusts timing with await flush() for async push behavior.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 1