Dmitriy Vasyura

agentHost: implement resource watch and filesystem operations Extend the AHP protocol with full filesystem operation support: - Add resourceResolve, resourceMkdir, and resourceCopy methods to make efficient, single-round-trip filesystem operations - Implement createResourceWatch with lazy watcher materialization (FS watcher only created on first subscribe) - Add 30-second grace period and replay buffer for watch channel unsubscribe to support reconnections - Surface watch setup errors via onDidWatchError event for proper error propagation - Make resourceCopy, resourceResolve, resourceMkdir required (not optional) in IRemoteFilesystemConnection contract - Extend both client→server and server→client (reverse-RPC) channels with all new methods - Add comprehensive unit tests: watch lifecycle, error handling, includes pattern forwarding, copy/resolve/mkdir operations - All tests passing (37 total, 7 new), TypeScript compilation clean, layer validation clean

Add Tools to Chat Customizations (#322620)

Fix model selection issues when switching session types (#320036)

Enable BYOK in air-gapped scenarios/without GitHub auth (#317428) Air-gapped BYOK: enable chat and some other AI functionality when user is not authenticated (with or without utility models enabled).

Streamline update mode configuration and handling (#323206) Enables changing update mode without restart, allowing policy updates to cancel an in-progress update.

Refactor `galleryItemRenderer` into reusable component and add extension tools details (#322879) Refactored galleryItemRenderer into a component shared between MCP, Plugins and Tools views. Added Extension tools details pane to view tools provided by an extension from the Tools view. Fixed an issue in MCP view where installed items were rendered incorrectly

Avoid leaving detached DOM elements in Getting Started (#319128)

Handle opened and unsaved documents as attachments for Agent Host/Copilot CLI (#321591)

Filter out agent host-owned sessions from CLI session list to avoid duplicates (#320188)

Add Tools tree keyboard navigation, fix focus outline cut-off at widget edges (#323984) * Add Tools tree keyboard navigation, fix focus outline cut-off at widget edges * PR feedback

Fix session list hovers to avoid warnings and updates while a hover is active (#321596)

Harden snippet session against null decorations and selection/placeholder cardinality drift (#315206) Reconciles four telemetry issues (#233164, #233163, #196664, #193172) into clean defensive guards in OneSnippet/SnippetSession: - Capture model into a local in OneSnippet.move() and _hasPlaceholderBeenCollapsed() and null-guard getDecorationRange/_placeholderDecorations.get lookups (covers #233164, #196664). - Treat a missing decoration range on a non-empty placeholder as collapsed in _hasPlaceholderBeenCollapsed. - Add OneSnippet.activePlaceholderCount and gate SnippetSession.merge structural merge + post-merge _move on a cardinality precondition (snippets.length === sum(activePlaceholderCount)). When cursor normalization or external selection changes collapse mirrored placeholder selections, we now skip structural merge instead of crashing on others.shift() (covers #233163, #193172). Text edits still apply. - next()/prev() no-op when _move() returns no selections.

Perf: Dedupe tool-definition JSON across telemetry/OTel sites (#318477) * perf(copilot): dedupe tool-definition JSON across telemetry/OTel sites Each LLM round previously serialized the tool list multiple times (OTel inference span, OTel agent span, 'tools_available' event, GH 'request.options.tools' enhanced telemetry, and per-key 'request.option.tools' property), producing several independent multi-MB strings retained by buffered spans and telemetry queues. Add stringifyToolDefinitionsForOTel and stringifyToolsRawForTelemetry in messageFormatters: a WeakMap by-reference cache plus a single-slot content intern so identical tool lists across consecutive agent rounds collapse to one string instance. Wire all producer sites (chatMLFetcher GH telemetry + Object.entries loops, toolCallingLoop agent span and tools_available event, anthropic/gemini byok providers, genAiEvents inference event) through the helpers. * fix: leave Object.entries(request) telemetry loop untouched Those properties are sent synchronously and released; they weren't among the retained copies. The other helper sites still dedupe the long-lived strings. * perf: route tools through memoized helper in Object.entries loops with JSON.stringify fallback to preserve empty-array byte equality * Simplify comment * PR feedback

Propagate context window options from Copilot models to the picker (#320905)

Fix language model event issues (#319097) * Fix selectChatModels API * Prevent feedback loop through onChatModelsChange event Co-authored-by: Copilot <copilot@github.com> --------- Co-authored-by: Copilot <copilot@github.com>

Fix race condition involving eager createSession in chat sessions pro… (#321526) * Fix race condition involving eager createSession in chat sessions provider

Improve offline BYOK UI state management (#316579) Co-authored-by: Copilot <copilot@github.com>

Fix snippet choice trapping Shift+Tab navigation (#316822) When a snippet choice tab stop was active, the suggest widget's Shift+Tab binding (acceptAlternativeSelectedSuggestion, weight EditorContrib+90) outranked the snippet's jumpToPrevSnippetPlaceholder (weight EditorContrib+30), so Shift+Tab could not navigate back to the previous tab stop. Add an InSnippetChoice context key and register a higher-weight Shift+Tab keybinding rule for jumpToPrevSnippetPlaceholder that activates only when a snippet choice is active. Fixes #236489

BYOK: Enable Chat UI for offline scenarios (#316515) All new UI behavior is under chat.offlikeByok switch (off by default). This PR turns off sign-in requirement in chat, removes sign-in button and dialog when BYOK models are registered by the user.

Enable `Delete` command on Agent Host sessions (#320889)