feat: Enhance agent host session management with custom agent support - #317398
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Pull request overview
This PR extends the Agent Host–backed sessions stack (protocol → agent host implementation → sessions provider adapters → sessions UI) to support selecting a custom agent per session, including persistence/fallback behavior and surfacing an Agent picker in the Sessions UI.
Changes:
- Added protocol + metadata plumb‑through for session-level custom agent selection (
SessionAgentChanged,agentonSessionSummary,CreateSessionParams.agent). - Extended sessions-layer APIs/providers to expose and set per-session custom agents (
ISessionAgentRef,ISessionsProvider.setAgent?,IAgentHostSessionsProvider.getCustomAgents+ change event). - Implemented custom agent discovery/advertisement from plugins (YAML frontmatter support) and added UI/tests for effective-agent resolution and picker behavior.
Show a summary per file
| File | Description |
|---|---|
| src/vs/sessions/services/sessions/common/sessionsProvider.ts | Adds optional setAgent hook for providers to set/clear a session’s custom agent. |
| src/vs/sessions/services/sessions/common/session.ts | Introduces ISessionAgentRef and adds optional agent observables to ISession/IChat. |
| src/vs/sessions/services/sessions/browser/sessionsManagementService.ts | Exposes agent on the active session wrapper. |
| src/vs/sessions/contrib/providers/remoteAgentHost/browser/remoteAgentHost.contribution.ts | Wires in the Agent picker contribution for remote agent hosts. |
| src/vs/sessions/contrib/providers/agentHost/test/browser/localAgentHostSessionsProvider.test.ts | Adds tests for setAgent, custom agent merging, and change events. |
| src/vs/sessions/contrib/providers/agentHost/test/browser/agentHostAgents.test.ts | Adds unit tests for effective-agent merging/deduping/sorting. |
| src/vs/sessions/contrib/providers/agentHost/test/browser/agentHostAgentPicker.test.ts | Adds unit tests for stored-vs-session agent resolution and storage key formation. |
| src/vs/sessions/contrib/providers/agentHost/browser/baseAgentHostSessionsProvider.ts | Implements setAgent, caches root/session state for agent merging, and exposes getCustomAgents + change event. |
| src/vs/sessions/contrib/providers/agentHost/browser/agentHostAgents.ts | New helper to compute the merged effective custom-agent list. |
| src/vs/sessions/contrib/providers/agentHost/browser/agentHostAgentPicker.ts | New UI contribution to render/persist an Agent picker and dispatch setAgent. |
| src/vs/sessions/common/agentHostSessionsProvider.ts | Extends IAgentHostSessionsProvider with getCustomAgents + onDidChangeCustomAgents. |
| src/vs/platform/agentPlugins/common/pluginParsers.ts | Adds agent frontmatter parsing for name/description via readAgentComponents. |
| src/vs/platform/agentHost/test/node/copilotPluginConverters.test.ts | Expands test coverage for agent frontmatter parsing and tool allow-list behavior. |
| src/vs/platform/agentHost/node/protocolServerHandler.ts | Passes agent through to createSession. |
| src/vs/platform/agentHost/node/copilot/copilotPluginConverters.ts | Parses agent frontmatter for SDK config and projects agents into protocol CustomizationAgentRef. |
| src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts | Adds SDK calls to select/deselect a custom agent on a live session. |
| src/vs/platform/agentHost/node/copilot/copilotAgent.ts | Persists agent selection in session metadata, includes it in create/resume paths, and advertises agents on customizations. |
| src/vs/platform/agentHost/node/agentSideEffects.ts | Applies SessionAgentChanged via agent.changeAgent side-effect hook. |
| src/vs/platform/agentHost/node/agentService.ts | Includes agent in created/listed session summary metadata. |
| src/vs/platform/agentHost/common/state/sessionState.ts | Re-exports new protocol types (AgentSelection, CustomizationAgentRef). |
| src/vs/platform/agentHost/common/state/sessionActions.ts | Re-exports new SessionAgentChangedAction type alias. |
| src/vs/platform/agentHost/common/state/protocol/version/registry.ts | Declares protocol introduction version for SessionAgentChanged. |
| src/vs/platform/agentHost/common/state/protocol/common/actions.ts | Adds ActionType.SessionAgentChanged to unions. |
| src/vs/platform/agentHost/common/state/protocol/channels-session/state.ts | Adds SessionSummary.agent, defines AgentSelection, and introduces CustomizationAgentRef + CustomizationRef.agents. |
| src/vs/platform/agentHost/common/state/protocol/channels-session/reducer.ts | Updates session reducer to apply SessionAgentChanged. |
| src/vs/platform/agentHost/common/state/protocol/channels-session/commands.ts | Adds CreateSessionParams.agent. |
| src/vs/platform/agentHost/common/state/protocol/channels-session/actions.ts | Defines SessionAgentChangedAction. |
| src/vs/platform/agentHost/common/state/protocol/action-origin.generated.ts | Updates generated unions/dispatchability map to include SessionAgentChanged. |
| src/vs/platform/agentHost/common/state/protocol/.ahp-version | Bumps protocol sync/version reference. |
| src/vs/platform/agentHost/common/agentService.ts | Extends common agent interfaces to carry/accept agent selection and changeAgent?. |
Copilot's findings
- Files reviewed: 30/30 changed files
- Comments generated: 4
Don Jayamanne (DonJayamanne)
requested review from
Connor Peet (connor4312) and
roblourens
and removed request for
Connor Peet (connor4312) and
roblourens
May 20, 2026 00:48
Don Jayamanne (DonJayamanne)
marked this pull request as ready for review
May 20, 2026 00:48
Contributor
📬 CODENOTIFYThe following users are being notified based on files changed in this PR: Ladislau Szomoru (@lszomoru)Matched files:
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roblourens
previously requested changes
May 20, 2026
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I think we should land the AHP PR first
Sandeep Somavarapu (sandy081)
previously requested changes
May 20, 2026
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Implementation looks generally OK to me |
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- Introduced ISessionAgentRef interface to represent custom agent references in session management. - Updated AgentHostSessionAdapter to handle agent selection and state updates. - Implemented setAgent method in BaseAgentHostSessionsProvider to manage agent changes and dispatch relevant actions. - Enhanced session-related interfaces and types to include agent properties. - Added tests for agent selection, effective agent resolution, and custom agent handling in various scenarios. - Integrated agent host agent picker into remote agent host contributions.
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
…ng plugin agent is found
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…ion customizations
Don Jayamanne (DonJayamanne)
requested a review
from Sandeep Somavarapu (sandy081)
May 21, 2026 00:21
Don Jayamanne (DonJayamanne)
requested review from
Connor Peet (connor4312) and
roblourens
May 21, 2026 00:21
Don Jayamanne (DonJayamanne)
enabled auto-merge (squash)
May 21, 2026 00:21
Justin Chen (justschen)
approved these changes
May 21, 2026
Don Jayamanne (DonJayamanne)
dismissed stale reviews from Sandeep Somavarapu (sandy081) and roblourens
May 21, 2026 00:50
Resolved the feedback
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For #316169