Implement agentHost process (#296627)

* agent host init

* Agent host: Copilot SDK integration with chat UI

* Agent host: direct MessagePort, logging, SDK wrapper, env fix

* Refactoring and cleanup

* Copilot-authored message: Agent-host tool rendering, protocol, and session fixes

Tool invocation rendering:
- Emit tool_start/tool_complete as ChatToolInvocation (not progressMessage)
- Shell tools (bash/powershell) render as terminal command blocks with
  IChatTerminalToolInvocationData, output, and exit codes
- Non-shell tools render via invocationMessage/pastTenseMessage (markdown)
- Filter out report_intent (hidden internal tool)

Agent-agnostic protocol:
- IPC events carry display-ready fields (displayName, invocationMessage,
  pastTenseMessage, toolInput, toolOutput, toolKind, language)
- All Copilot CLI-specific logic in copilotToolDisplay.ts with typed
  interfaces for known tools (CopilotToolName enum, parameter types)
- Renderer never references specific SDK tool names

Session fixes:
- Resumed sessions show tool invocations in history (getSessionMessages
  now returns tool events alongside messages)
- Fixed 'already has a pending request' on resumed sessions by
  conditionally providing interruptActiveResponseCallback
- Fixed event filtering for resumed sessions (sessionId override in
  _trackSession)

Documentation:
- Split parity.md into design.md (decisions) and backlog.md (tasks)
- Updated architecture.md, sessions.md with cross-references
- Added maintenance notes to all docs

* Copilot-authored message: Model picker, session class, DI and test cleanup

* Cleanups

* stuff

* add diagram

* Add claude agent

* Clean up

* Copy some build script changes from #295817

* Simplify

* Update docs

* Register agent-host via chatSessions contribution API, reduce peripheral diff

* Cleanup

* Don't ship stuff in stable

* Dynamic agent discovery via listAgents() IPC

Replace hardcoded per-provider contributions with a single
AgentHostContribution that discovers available agents from the
agent host process at startup. Each IAgent backend now exposes
an IAgentDescriptor with display metadata and auth requirements.

- Add IAgentDescriptor interface and listAgents() to IPC contract
- CopilotAgent/ClaudeAgent return descriptors via getDescriptor()
- Single AgentHostContribution discovers + registers dynamically
- Remove agentHostConstants.ts (no more hardcoded session types)
- AgentHostSessionListController/LMProvider take params instead
- Rename AgentSessionProviders.AgentHost -> AgentHostCopilot
- Update architecture.md, sessions.md, backlog.md

(Written by Copilot)

* Fix review findings: proxy, disposal, filtering, tests

- Add listAgents() forwarding to AgentHostServiceClient
- Guard async discovery against disposal race
- Add provider field to IAgentModelInfo for per-provider filtering
- Filter models and sessions by provider in LM provider and list
  controller
- Update tests for new dynamic API and agent-host-copilot scheme

(Written by Copilot)

* Use DI for AgentHostLanguageModelProvider

(Written by Copilot)

* Strip @img/sharp native binaries from builds

sharp is a transitive dependency of the Claude Agent SDK used for
image processing. Its native .node binaries cause dpkg-shlibdeps
errors during Debian packaging due to $ORIGIN RPATH references.
Strip all @img/sharp-* platform packages since the agent host
doesn't need image processing at runtime.

(Written by Copilot)

* Strip Claude SDK vendored ripgrep binaries

The Claude Agent SDK bundles ripgrep binaries for all platforms
under vendor/ripgrep/. Wrong-architecture binaries cause macOS
Mach-O verification to fail. Strip them entirely via .moduleignore
(VS Code has its own ripgrep) and add to verify-macho skip list.

(Written by Copilot)

* Add tests for AgentSession, AgentService dispatcher, and workbench agent host components

(Written by Copilot)

* Add trace logging, IPC output channel, tool permissions, and attachment context

- Add Agent Host IPC output channel (only registered at trace log level) that
  logs all IPC method calls, results, and progress events with full JSON payloads
- Add trace-level logging in AgentService dispatcher for all method calls
- Add trace-level logging in session handler for all progress events and session
  resolution
- Wire up onPermissionRequest handler on CopilotClient.createSession and
  resumeSession to auto-approve tool permission requests
- Add IAgentAttachment type to IPC contract and thread attachments from chat
  variables (file, directory, selection) through sendMessage to the Copilot SDK

(Written by Copilot)

* Add tests for attachment context conversion and threading

(Written by Copilot)

* Add gap analysis docs for Copilot and Claude SDK implementations

(Written by Copilot)

* Sanitize env vars for Copilot CLI subprocess

Strip VSCODE_*, ELECTRON_* (except ELECTRON_RUN_AS_NODE), NODE_OPTIONS, and
other debug-related env vars that can interfere with the Node.js process the
SDK spawns. Matches the env sanitization from the extension implementation.
Also set useStdio and autoStart for proper CLI communication.

(Written by Copilot)

* Add error, usage, and title_changed event types to IPC contract

Add IAgentErrorEvent, IAgentUsageEvent, and IAgentTitleChangedEvent to the
progress event union. Wire up session.error and assistant.usage events from
the Copilot SDK to fire as IPC events instead of only logging. Handle error
events in the renderer session handler by rendering the error message. Usage
and title_changed events are logged at trace level.

(Written by Copilot)

* Add abortSession IPC method for proper cancellation

Add abortSession(session) to the IPC contract, implemented across AgentService,
CopilotAgent (calls session.abort()), ClaudeAgent (no-op, uses AbortController),
and the renderer proxy. Wire up cancellation in the session handler to call
abortSession before finishing, so the SDK actually stops processing.

(Written by Copilot)

* Address reviewer feedback: error finishes request, Claude abort, tests

- Error events now call finish() so the request doesn't hang if the SDK
  doesn't send idle after an error
- ClaudeAgent.abortSession calls ClaudeSession.abort() which signals the
  AbortController and creates a new one for future turns
- Add test: cancellation calls abortSession on the agent host service
- Add test: error event renders message and finishes the request
- Remove stale TODO in interruptActiveResponseCallback
- Use timeout() helper instead of raw setTimeout in test
- Update gap docs to reflect completed work

(Written by Copilot)

* Add permission request IPC round-trip (Written by Copilot)

* Remove Claude agent from agent-host process

Strip the Claude Agent SDK integration from the agent-host utility process
to focus on the Copilot SDK path.

- Delete src/vs/platform/agent/node/claude/ (claudeAgent, claudeSession, claudeToolDisplay)
- Remove @anthropic-ai/claude-agent-sdk from package.json
- Remove AgentHostClaude enum member and all switch cases
- Remove Claude command registration in electron-browser chat.contribution
- Clean up build scripts (.moduleignore, verify-macho, gulpfile.vscode)
- Narrow AgentProvider type to just 'copilot'
- Update tests and documentation

(Written by Copilot)

* Wire up permission confirmation UI with ChatToolInvocation (Written by Copilot)

* Fix reviewer feedback: safe permission serialization, deny on abort/dispose (Written by Copilot)

* Forward reasoning events as thinking blocks (Written by Copilot)

* Pass workspace folder as workingDirectory to Copilot SDK (Written by Copilot)

* Store and pass workingDirectory on session resume, update gap docs (Written by Copilot)

* Fix permission rendering, session-scoped permissions, and test gaps (Written by Copilot)

* Auto-approve read permissions inside workspace folder (Written by Copilot)

* Move read auto-approve into CopilotAgent where permission policy belongs (Written by Copilot)

* Update gap docs (Written by Copilot)

* Use log language for IPC output channel, add trace prefix (Written by Copilot)

* Add tool rendering gaps to docs (Written by Copilot)

* Stringify URIs in IPC output channel for readability (Written by Copilot)

* Fix IPC output channel: use log languageId with non-log channel for proper append + syntax highlighting (Written by Copilot)

* Fix build errors: add URI import, fix test mock types (Written by Copilot)

* Don't localize agent host provider strings (Written by Copilot)

* Remove claude-agent-sdk from eslint allowed imports (Written by Copilot)

* fix test

* initial thoughts

* Rename folder to agentHost

* Fix paths

* Fixes

* Fixes for copilot

* Fix moduleignore

* first working protocol version

align more closely with protocol

json rpc and some gaps

* cleanup

* Fix copilot pty.node packaging

* Fix test

* prebuild packaging

* Agenthost server fixes

* Update monaco.d.ts

* Update docs

* Fixes

* Build fix

* Fix build issues

* reduce duplication in side effecting code

* fix model switching not working

* reduce mock duplication

* Build fixes

* Copy vscode's node.pty

* And ripgrep

* And thsi

* Ripgrep goes to non-SDK

* Skip copy for stable build

* Remove outdated script

* Build fixes for asar

* fix

* Add some logging

* Fix for windows

* Fix

* Logs

* build: add glob diagnostic for copyCopilotNativeDeps

* build: check both node_modules/ and .asar.unpacked/ for source binaries

* Fix

* Remove excalidraw

---------

Co-authored-by: Connor Peet <[email protected]>
Co-authored-by: Connor Peet <[email protected]>