sessions: recover empty Agent Host session list after a failed initial refresh

[roblourens]

Problem

In the Agents app, the local Agent Host session list could stay empty on the list just stayed blank. Starting a new local session would "unstick" it and make all the existing sessions appear.launch

Root cause

The provider's session cache is one-shot. BaseAgentHostSessionsProvider._refreshSessions() ran once (guarded by _cacheInitialized), but its blanket catch {} could not distinguish two very different outcomes:

• listSessions() ** e.g. the agent throws AHP_AUTH_REQUIRED before its token is effective server-side, or a transient offline/network error.threw**
• listSessions() ** a genuinely empty, valid result.returned []**

Both collapsed to an empty cache marked initialized, and nothing retried until an unrelated AHP event (SessionTurnComplete / notify/sessionAdded) forced a re-fetch. That's exactly why starting a new whose turn completes and fires made the whole list suddenly populate.SessionTurnComplete session

Fix

• _refreshSessions now owns _cacheInitialized and sets it true only on a successful list.
  30s, reset on success), so a transient startup failure self-heals on its own without any user action.
• An empty successful list is still treated as a valid result: it marks the cache initialized and arms no retry.
• Listing sessions still never pops a sign-in AHP_AUTH_REQUIRED is retried silently in the background.dialog
• The local provider's auth autorun and the remote provider's setConnection no longer pre-set _cacheInitialized; clearConnection cancels any pending retry.

Tests

Three new tests in localAgentHostSessionsProvider.test.ts (via a listSessions failure-injection hook on the mock):

• recovers an empty list when the initial listSessions fails, without needing a new session
• a successful empty listSessions arms no retry
• retries with backoff until listSessions succeeds

Verified: browser unit suite 78 passing (incl. the 3 new tests), full test-node 10640 passing, eslint + hygiene clean.

(Written by Copilot)

[Copilot]

Pull request overview

This PR updates Agent Host session cache refresh behavior so a failed initial listSessions() call does not permanently leave the Agents app session list empty.

Changes:

• Moves _cacheInitialized ownership into successful _refreshSessions() completion.
• Adds silent retry with exponential backoff for failed session list refreshes.
• Updates local/remote providers and adds tests for retry and empty-list behavior.

Show a summary per file

File	Description
src/vs/sessions/contrib/providers/agentHost/browser/baseAgentHostSessionsProvider.ts	Adds retry/backoff handling and successful-list cache initialization semantics.
src/vs/sessions/contrib/providers/agentHost/browser/localAgentHostSessionsProvider.ts	Stops pre-marking the cache initialized before eager local refresh.
src/vs/sessions/contrib/providers/remoteAgentHost/browser/remoteAgentHostSessionsProvider.ts	Lets refresh own cache initialization and cancels pending retry on connection clear.
src/vs/sessions/contrib/providers/agentHost/test/browser/localAgentHostSessionsProvider.test.ts	Adds mock failure injection and tests around failed initial refresh recovery.

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 3