fix: optimistic session creation for instant UI feedback#252
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In local (Persistent/Embedded) mode, CreateSessionAsync blocked the UI during the slow SDK call. The session only appeared in the sidebar after the SDK finished, causing a noticeable delay. Apply the same optimistic UI pattern already used for remote mode: - Add a placeholder AgentSessionInfo with IsCreating=true immediately - Fire OnStateChanged so the sidebar and chat view update instantly - Complete the SDK session creation in the background - On success: update the state with the real CopilotSession - On failure: clean up the placeholder and re-throw Also adds a guard in SendPromptAsync to reject prompts to sessions that are still being created. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
- Dispose existing session before overwriting in _sessions[name] to prevent leaking the old CopilotSession when a name collision occurs - Save previousActiveSessionName before optimistic add and restore it in the catch block so _activeSessionName is not left dangling after a failed SDK session creation Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
If a session is closed while awaiting SDK creation, the returned CopilotSession would be assigned to an orphaned state object and leak permanently (with a dangling event handler). Now checks _sessions.ContainsKey after the await and disposes the SDK session if it was removed during creation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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✅ Multi-model consensus review (5 models × 2 rounds)
Previous Findings -- All Fixed
| Finding | Status |
|---|---|
🔴 CRITICAL -- Dangling _activeSessionName after SDK creation failure |
✅ FIXED -- previousActiveSessionName saved/restored in catch block |
🔴 CRITICAL -- Silent overwrite of _sessions[name] leaks CopilotSession |
✅ FIXED -- Existing session disposed before overwrite |
| 🟡 MODERATE -- Close-during-create race leaks SDK session | ✅ FIXED -- !_sessions.ContainsKey(name) guard after await CreateSessionAsync, disposes orphaned session |
Summary
Three fix commits address all consensus findings from two review rounds:
fix: optimistic session creation for instant UI feedback-- original featureFix session overwrite leak and dangling _activeSessionName-- fixes both CRITICALsGuard against close-during-create race-- fixes the MODERATE race condition
The IsCreating flag correctly guards SendPromptAsync (line 1825) to prevent prompts during creation. CloseSessionCoreAsync handles null! Session via is not null check. Tests pass (1666/1667, 1 pre-existing).
Action: ✅ Approve
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Problem
When creating a session in local (Persistent/Embedded) mode, the UI blocked during the slow SDK call (
_client.CreateSessionAsync). The session only appeared in the sidebar after the SDK finished creating it, causing a noticeable delay where the user had no visual feedback.Fix
Apply the same optimistic UI pattern already used for remote mode to local mode:
AgentSessionInfowithIsCreating = trueand add it to_sessionsbefore the SDK callOnStateChangedand set_activeSessionNameso the sidebar and chat view update immediatelyCopilotSession, setIsCreating = false_sessionsand Organization, re-throwAlso adds:
IsCreatingproperty onAgentSessionInfoto signal creating state to the UISendPromptAsyncto reject prompts to sessions still being createdSessionState.Sessionchanged frominittosetto allow updating after optimistic addTests Added
IsCreating_DefaultsToFalse— model property testIsCreating_CanBeSetAndCleared— model property testCreateSessionAsync_DemoMode_IsCreatingIsFalse— demo path doesn't use IsCreatingCreateSessionAsync_DemoMode_SessionActiveImmediately— session is immediately activeCreateSession_BeforeInitialize_NoOptimisticAdd— no placeholder on init failureCreateSessionAsync_EmptyName_Throws— validation before optimistic addAll 1666 tests pass (1 pre-existing unrelated failure in PlatformHelperTests).