agentHost: subagents by roblourens · Pull Request #308592 · microsoft/vscode

roblourens · 2026-04-08T19:27:12Z

No description provided.

Copilot

Pull request overview

Adds “subagent” support to the Agent Host protocol + VS Code chat UI so that a tool call can spawn a child (subagent) session, and the client can subscribe to/stream that child session (including inner tool calls) grouped under the parent subagent invocation.

Changes:

Extend the AHP protocol/state model with ToolResultContentType.Subagent and subagent session URI helpers (/subagent/{toolCallId}), plus new mapping for subagent.started events.
Update the renderer/session handler and progress adapters to detect subagent content, propagate subAgentInvocationId, and observe/stream child sessions into parent progress.
Add unit + integration coverage for subagent content mapping, reconnection, and child-session streaming behavior.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/test/browser/agentSessions/stateToProgressAdapter.test.ts	Adds tests for subagent toolSpecificData extraction + update notification behavior.
src/vs/workbench/contrib/chat/test/browser/agentSessions/agentHostSubagent.integrationTest.ts	New integration tests covering snapshot restore, reconnection, and streaming updates for subagent sessions.
src/vs/workbench/contrib/chat/common/model/chatProgressTypes/chatToolInvocation.ts	Adds a mechanism to notify observers when `toolSpecificData` changes (non-observable field).
src/vs/workbench/contrib/chat/browser/widget/chatContentParts/chatSubagentContentPart.ts	Updates UI part to re-read metadata when subagent toolSpecificData is updated after initial render.
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/stateToProgressAdapter.ts	Adds subagent content detection/serialization, `subAgentInvocationId` plumbing, and running toolSpecificData updates.
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/agentHostSessionHandler.ts	Observes subagent child sessions and forwards child tool calls into parent progress grouped by `subAgentInvocationId`.
src/vs/platform/agentHost/test/node/sessionStateManager.test.ts	Adds tests for subagent URI helper functions.
src/vs/platform/agentHost/test/node/mapSessionEvents.test.ts	Adds test ensuring SDK `subagent.started` maps to `subagent_started`.
src/vs/platform/agentHost/test/node/agentSideEffects.test.ts	Adds tests for creating/routing/completing/cancelling/removing subagent sessions.
src/vs/platform/agentHost/test/node/agentEventMapper.test.ts	Tests extracting subagent metadata from tool arguments into `_meta`.
src/vs/platform/agentHost/node/sessionStateManager.ts	Adds prefix-based session URI discovery to support cleanup of subagent sessions.
src/vs/platform/agentHost/node/copilot/mapSessionEvents.ts	Maps `subagent.started` SDK events to protocol `subagent_started` events.
src/vs/platform/agentHost/node/copilot/copilotToolDisplay.ts	Classifies subagent-spawning tools via `getToolKind(...): 'subagent'`.
src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts	Emits `subagent_started` progress events from the SDK wrapper.
src/vs/platform/agentHost/node/copilot/copilotAgent.ts	Updates session message typing to include subagent-start events.
src/vs/platform/agentHost/node/agentSideEffects.ts	Creates/routs events into subagent sessions; injects subagent content into parent tool call; cleans up on cancel/dispose.
src/vs/platform/agentHost/node/agentService.ts	Restores subagent sessions on subscribe and injects subagent content into completed tool calls during turn reconstruction.
src/vs/platform/agentHost/node/agentEventMapper.ts	Populates `_meta` with subagent metadata parsed from tool arguments for early UI rendering.
src/vs/platform/agentHost/common/state/sessionState.ts	Adds subagent content extraction helper + subagent session URI helpers.
src/vs/platform/agentHost/common/state/sessionReducers.ts	Extends `getToolKind` to include `'subagent'`.
src/vs/platform/agentHost/common/state/protocol/version/registry.ts	Updates protocol action version registry (includes SessionDiffsChanged mapping).
src/vs/platform/agentHost/common/state/protocol/state.ts	Adds `ToolResultContentType.Subagent` and `IToolResultSubagentContent` to tool result union.
src/vs/platform/agentHost/common/state/protocol/reducers.ts	Handles `SessionDiffsChanged` in the protocol session reducer.
src/vs/platform/agentHost/common/state/protocol/actions.ts	Adds `SessionDiffsChanged` action type and interface (generated).
src/vs/platform/agentHost/common/state/protocol/action-origin.generated.ts	Updates action unions and dispatchability table (generated).
src/vs/platform/agentHost/common/state/protocol/.ahp-version	Bumps synced AHP protocol version hash.
src/vs/platform/agentHost/common/agentService.ts	Extends agent progress event types with `IAgentSubagentStartedEvent` and toolKind `'subagent'`.

Copilot's findings

Files reviewed: 27/27 changed files
Comments generated: 2

…ld sessions instead Inner tool calls from subagent sessions are no longer stored in the parent turn with _meta.parentToolCallId. Instead: - Server: _buildTurnsFromMessages skips inner events (parentToolCallId), _restoreSubagentSession builds child session turns from raw messages - Client: _enrichHistoryWithSubagentCalls subscribes to child sessions during history restore, injects serialized inner tool calls with subAgentInvocationId set Also fixes hygiene: replace 'in' operator with hasKey in agentSideEffects.test.ts, exclude .jsonl from copyright filter.

github-actions · 2026-04-10T02:44:45Z

Screenshot Changes

Base: 6df6bbde Current: ef5851df

Changed (12)

agentSessionsViewer/CompletedRead/Dark

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agentSessionsViewer/CompletedRead/Light

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agentSessionsViewer/FailedWithoutDuration/Dark

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agentSessionsViewer/FailedWithoutDuration/Light

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agentSessionsViewer/WithFileChangesList/Dark

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agentSessionsViewer/WithFileChangesList/Light

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agentSessionsViewer/WithBadgeAndDiff/Dark

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agentSessionsViewer/WithBadgeAndDiff/Light

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agentSessionsViewer/BackgroundProvider/Dark

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agentSessionsViewer/BackgroundProvider/Light

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agentSessionsViewer/ClaudeProvider/Dark

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agentSessionsViewer/ClaudeProvider/Light

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…ogressAdapter completedToolCallToSerialized and toolCallStateToInvocation were not detecting terminal tools via ToolResultContentType.Terminal content blocks or setting terminalCommandUri/terminalToolSessionId, causing 6 test failures in CI.

Copilot

Pull request overview

Adds end-to-end “subagent” support to the Agent Host pipeline so a tool call that spawns a subagent creates/targets a child session, and the UI can render/group inner tool calls under the parent subagent widget (including restore-from-history behavior).

Changes:

Extend agent/protocol and Copilot event mapping to emit/handle subagent_started, create subagent sessions, and route parentToolCallId events into the child session.
Update chat progress adaptation/session handler to surface subagent tool invocations and splice child-session tool calls into parent history/progress (via subAgentInvocationId).
Add/expand unit tests and fixtures validating subagent session creation, routing, history restore, and UI metadata updates.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/test/browser/agentSessions/stateToProgressAdapter.test.ts	Adds test coverage for subagent tool metadata and `updateRunningToolSpecificData`.
src/vs/workbench/contrib/chat/common/model/chatProgressTypes/chatToolInvocation.ts	Adds a helper to notify observers when `toolSpecificData` changes.
src/vs/workbench/contrib/chat/browser/widget/chatContentParts/chatSubagentContentPart.ts	Adjusts subagent title rendering and updates title when tool metadata arrives late.
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/stateToProgressAdapter.ts	Teaches progress/history conversion about subagent tool calls and `subAgentInvocationId`; updates terminal/subagent handling.
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/agentHostSessionHandler.ts	Observes child subagent sessions, enriches history with inner tool calls, and forwards child progress into the parent session.
src/vs/platform/agentHost/test/node/test-cases/subagent-session.jsonl	Adds a JSONL fixture representing a real subagent session event stream.
src/vs/platform/agentHost/test/node/mockAgent.ts	Expands mock agent message types to include subagent-start events.
src/vs/platform/agentHost/test/node/mapSessionEvents.test.ts	Verifies raw SDK `subagent.started` maps to protocol `subagent_started`.
src/vs/platform/agentHost/test/node/agentSideEffects.test.ts	Adds tests for subagent session creation, routing, cancellation/completion, and content preservation.
src/vs/platform/agentHost/test/node/agentService.test.ts	Adds restore tests for subagent sessions (including fixture-based restore).
src/vs/platform/agentHost/test/node/agentHostStateManager.test.ts	Adds tests for subagent session URI helper utilities.
src/vs/platform/agentHost/test/node/agentEventMapper.test.ts	Tests extracting subagent metadata from `toolArguments` into `_meta`.
src/vs/platform/agentHost/node/copilot/mapSessionEvents.ts	Maps SDK `subagent.started` into agent-host `subagent_started` events.
src/vs/platform/agentHost/node/copilot/copilotToolDisplay.ts	Classifies `task` as a `subagent` toolKind for renderer hints.
src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts	Forwards SDK subagent-start events through the session progress stream.
src/vs/platform/agentHost/node/copilot/copilotAgent.ts	Updates message typing to include subagent-start events.
src/vs/platform/agentHost/node/agentSideEffects.ts	Manages subagent session lifecycle and routes `parentToolCallId` progress into child sessions.
src/vs/platform/agentHost/node/agentService.ts	Builds/restores parent turns without inner subagent events; restores child sessions on subscribe.
src/vs/platform/agentHost/node/agentHostStateManager.ts	Adds helper to list session URIs by prefix (used for subagent cleanup).
src/vs/platform/agentHost/node/agentEventMapper.ts	Injects subagent metadata into `_meta` from tool arguments at `tool_start`.
src/vs/platform/agentHost/common/state/sessionState.ts	Adds subagent content extraction and subagent session URI helper functions.
src/vs/platform/agentHost/common/state/sessionReducers.ts	Adds helpers to read VS Code-specific `_meta` fields (`toolKind`, `language`).
src/vs/platform/agentHost/common/agentService.ts	Extends agent event types to include `subagent_started` and `toolKind: 'subagent'`.
extensions/copilot/src/extension/prompts/node/agent/openai/hiddenModelBPrompt.tsx	Formatting-only bullet indentation change in prompt text.
build/filters.ts	Excludes `*.jsonl` from copyright header filtering.

Copilot's findings

Files reviewed: 24/25 changed files
Comments generated: 7

Co-authored-by: Copilot <copilot@github.com>

agentHost: subagents

6a81728

Copilot AI review requested due to automatic review settings April 8, 2026 19:27

roblourens self-assigned this Apr 8, 2026

Copilot started reviewing on behalf of roblourens April 8, 2026 19:28 View session

Copilot AI reviewed Apr 8, 2026

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Comment thread src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/stateToProgressAdapter.ts

Comment thread src/vs/platform/agentHost/node/agentService.ts

austindyoung mentioned this pull request Apr 8, 2026

[mirror] microsoft/vscode#308592 agentHost: subagents austindyoung/vscode-driftfence-mirror-fork#1324

Open

roblourens added 2 commits April 9, 2026 18:55

Merge origin/main into roblou/only-crow

2e71f5e

roblourens requested a review from Copilot April 10, 2026 02:55

nongkibki mentioned this pull request Apr 10, 2026

Can't add anything to right panel #307830

Closed

Copilot started reviewing on behalf of roblourens April 10, 2026 02:57 View session

Copilot AI reviewed Apr 10, 2026

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roblourens and others added 2 commits April 9, 2026 20:28

comments

93c5f7e

Co-authored-by: Copilot <copilot@github.com>

revert diff

459f5ea

roblourens marked this pull request as ready for review April 10, 2026 04:02

roblourens enabled auto-merge (squash) April 10, 2026 04:02

bhavyaus approved these changes Apr 10, 2026

View reviewed changes

roblourens merged commit a4f5119 into main Apr 10, 2026
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roblourens deleted the roblou/only-crow branch April 10, 2026 04:56

vs-code-engineering Bot added this to the 1.116.0 milestone Apr 10, 2026

vs-code-engineering Bot mentioned this pull request Apr 14, 2026

[Unhandled Error] potential listener LEAK detected, dominated #309906

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agentHost: subagents#308592

agentHost: subagents#308592
roblourens merged 6 commits intomainfrom
roblou/only-crow

roblourens commented Apr 8, 2026

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edited

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roblourens commented Apr 8, 2026

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