Reconnect to in-progress remote agent host chat sessions

[roblourens]

When opening a remote agent host session that has an active (in-progress) turn, the chat UI now reconnects to it and streams ongoing progress instead of only showing completed turns as history.

Changes

agentHostSessionHandler.ts

• AgentHostChatSession: Accepts initialProgress for reconnection. Sets isCompleteObs=false and seeds progressObs when reconnecting. Exposes appendProgress() and complete() for the reconnect flow. interruptActiveResponseCallback is mutable so reconnection can replace it with a real cancel callback.
• provideChatSessionContent: Detects sessionState.activeTurn, includes the active turn's request in history with an empty response placeholder, generates initial progress via activeTurnToProgress(), and calls _reconnectToActiveTurn().
• _reconnectToActiveTurn() (new): Streams incremental state changes into progressObs. Extracts live ChatToolInvocation objects from initialProgress (same instances the chat UI holds). Handles text/reasoning deltas, tool call lifecycle, permission resolution, turn completion/error. Dispatches session/turnCancelled on interrupt. Immediately reconciles after listener registration to close the snapshot-to-listener race.
• _wireUpPermissionConfirmation() (new): Shared helper for interactive permission confirmation with CancellationTokenSource cleanup.

stateToProgressAdapter.ts

• activeTurnToProgress(): Converts an IActiveTurn's accumulated state (reasoning, streaming text, tool calls, permissions) into IChatProgress[] items suitable for initial replay.

Tests

• 7 new tests for activeTurnToProgress in stateToProgressAdapter.test.ts
• 10 new reconnection integration tests in agentHostChatContribution.test.ts covering: history loading, progressObs/isCompleteObs state, interrupt callback dispatch, live streaming, turn completion, tool calls, permissions, reasoning, and no-active-turn baseline

(Written by Copilot)

[Copilot]

Pull request overview

This PR enables the chat UI to reconnect to an in-progress remote agent host session turn, replaying accumulated partial output and then continuing to stream live progress (text/reasoning/tool activity/permissions) instead of showing only completed turns.

Changes:

• Added activeTurnToProgress() to convert an IActiveTurn snapshot into replayable IChatProgress[] (including live ChatToolInvocations where applicable).
• Updated AgentHostSessionHandler.provideChatSessionContent and session plumbing to seed progressObs/isCompleteObs when an active turn exists and to attach a reconnection listener that streams incremental state changes.
• Added unit tests for activeTurnToProgress and integration tests for reconnection behavior (history seeding, streaming deltas, cancellation dispatch, tool calls, permissions, reasoning).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/vs/workbench/contrib/chat/test/browser/agentSessions/stateToProgressAdapter.test.ts	Adds unit tests covering activeTurnToProgress behavior and ordering.
src/vs/workbench/contrib/chat/test/browser/agentSessions/agentHostChatContribution.test.ts	Adds integration tests validating reconnection to an active turn and live streaming behavior.
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/stateToProgressAdapter.ts	Introduces activeTurnToProgress() to replay active turn state into chat progress items.
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/agentHostSessionHandler.ts	Implements reconnection flow: seeds session observables, streams live state updates, and wires permission confirmation + cancellation for active turns.

[rzhao271]

Looks like an actual build error.
Error: [core-ci ] src/vs/workbench/contrib/chat/test/browser/agentSessions/agentHostChatContribution.test.ts(1730,6): error TS2353: Object literal may only specify known properties, and 'confirmed' does not exist in type 'IToolCallPendingConfirmationState'.

[roblourens]

lmao thanks