Agent Architecture

GitHub Copilot CLI

GitHub Copilot CLI is a background-capable local terminal agent that can be launched from VS Code, used directly from the terminal, remote-controlled from GitHub or mobile, customized with hooks, MCP, skills, custom agents, plugins, and run in worktree or folder isolation.

Source reviewed #6Checked 2026-07-06

Setup guide Source

Run type

CLI

Adapter

json-stdio

Source

Closed / product homepage

Stars

Frontier

Archive Context

This page is one host entry inside the full architecture archive and keeps multi-surface products visible instead of collapsing them into a single run type.

42 host archive

Host page

copilot-cli

Run cohort

CLI: 30

Archive route

/agents

Host Surface Perspectives

The host is the primary architecture boundary. Each runnable surface below separates what the host owns from what agent-connector can safely install for GitHub Copilot CLI.

1 surface entry

CLI

cli

Host entry: A terminal command owns the process, current working directory, stdin/stdout, shell environment, and project file discovery.
Host owns: The CLI host owns agent loop timing, approval prompts, tool execution, session files, and how hook or MCP subprocesses are launched.
Connector role: agent-connector can only write the host's documented CLI config, prompt, memory, hook, MCP, or package files and point them at the home binary. Current wired connector surfaces: MCP server, Hooks, Skills, Subagents, Memory.
Implementation consequence: A CLI surface is byte-addressable and smoke-testable from a temporary HOME, but terminal UI behavior still belongs to the host process. No visible host-native gap is currently tracked for this surface.

Verified Architecture

Source-checked on 2026-07-06. These notes are intentionally separate from the generated surface matrix below.

Sequence #6

Source pass

Current source review findings are kept as the first architecture section so readers can separate external evidence from the generated local coverage model.

GitHub Copilot CLI is a terminal-native coding agent, so the architecture page keeps it separate from the VS Code extension row.
The repository states that the CLI uses GitHub workflow context and ships with GitHub's MCP server by default, with custom MCP servers as an extension point.
Action approval is a host-native control surface, but agent-connector should not infer generic lifecycle hooks or subagent folders from that approval model.

Runtime boundary

The adapter target is the Copilot CLI agent harness. VS Code can install, launch, monitor, and hand off to it, but the CLI sessions run outside the editor and can continue in the background after the editor window closes.

Sessions can use worktree isolation or folder isolation.
VS Code surfaces progress, approvals, and chat steering for the background CLI.
The terminal command is a distinct host row from VS Code Copilot and JetBrains Copilot.

MCP registration

Copilot CLI has a documented customization path for adding MCP servers, but VS Code documents an important limitation: Copilot CLI sessions can currently access local MCP servers that do not require authentication.

MCP support should be documented as CLI-specific, not inherited from VS Code local agents.
Authentication limitations matter for plugin developers packaging MCP servers.
MCP setup belongs beside permissions, isolation, and remote-control constraints.

Hook bridge

GitHub documents Copilot CLI hooks as a customization feature, and VS Code lists hooks among slash-command surfaced CLI capabilities. agent-connector can therefore model a CLI hook bridge while keeping event details tied to GitHub's current hook docs.

The CLI also supports `/compact`, `/research`, `/yolo`, and `/autoApprove` as chat commands.
Hook semantics should not be copied from VS Code preview hooks or Copilot SDK hooks without checking CLI docs.

Content surfaces

Copilot CLI content includes custom instructions, agent skills, custom agents, plugins, LSP servers, research mode, session data, and remote-control state. These surfaces are CLI-owned even when launched from an editor.

Custom agents can be selected for Copilot CLI sessions from VS Code when enabled.
Session data can sync to remote control surfaces such as GitHub and GitHub Mobile.
Worktree commits and rollback behavior are part of the host's operating model.

Marketplace and host-only affordances

The host-only affordance is GitHub ecosystem reach: Actions automation, GitHub task pages, mobile remote control, custom agents, plugins, LSP servers, and cloud/local sandbox integration around one CLI agent harness.

Remote control mirrors status, tool activity, and approvals across VS Code and GitHub.
GitHub Actions automation and scheduled prompts are workflow surfaces, not local hook events.

Host-specific shape

GitHub Copilot CLI is terminal-native but narrower than Copilot in editors: MCP, hooks, skills, subagents, memory, and marketplace driver support are tracked, while user slash commands remain absent.

Form factor: CLI.
Native surfaces: MCP server, Hooks, Skills, Subagents, Memory.
Wired surfaces: MCP server, Hooks, Skills, Subagents, Memory.
Visible gaps: none.

Hooks

Hooks enter through a host-launched command that exchanges event JSON over stdio.

MCP

The adapter writes this host's native MCP registration dialect, including its root key, scope, transport fields, and environment syntax.

Memory

Managed memory text is written into the rules or memory file this host actually reads, with ownership markers for reversible uninstall.

Marketplace and affordances

A marketplace or plugin-driver path is wired, so install/update/uninstall can be driven rather than only emitted as files.

Runtime handlers: none.
User-visible affordances: Users see managed skills + subagents + memory surfaces after install; runtime-only surfaces stay behind the host boundary..

Known Limits

Do not treat VS Code local-agent extension tools as available to Copilot CLI.
MCP authentication limitations should stay visible until GitHub changes the CLI docs.
Remote control is a GitHub session feature, not a generic connector transport.

Evidence checked

VS Code Copilot CLI sessions GitHub Copilot CLI overview GitHub Copilot CLI MCP GitHub Copilot CLI hooks github/copilot-cli repository

Architecture Diagram

Host-specific flow for the CLI surface.

json-stdio

1
Entry point: CLI
Terminal agent process reads user/project config and invokes the connector home binary for runtime callbacks.
2
Connector package
defineConnector package declares server, hooks, content, memory, and actions.
3
Adapter module: copilot-cli
json-stdio renderer at src/adapters/copilot-cli/index.ts.
4
Native host artifacts
Adapter writes MCP config + hook config + content files + memory/rules + marketplace bundle through this host's native file, package, or marketplace surface.
5
Runtime boundary
host launches JSON-stdio hook command
6
User-visible surface
Users see managed skills + subagents + memory surfaces after install; runtime-only surfaces stay behind the host boundary.
7
Coverage ceiling
5/5 native surfaces wired. No visible host-native gap in the current coverage matrix.

Component Diagram

Static parts of the GitHub Copilot CLI integration and which side owns each one.

GitHub Copilot CLI host
CLI surface owns the model loop, UI shell, config discovery, and native lifecycle for this integration.
agent-connector package
Normalizes connector declarations into MCP, hook, memory, content, and action payloads before delegating to a host adapter.
copilot-cli adapter
Implements the json-stdio translation layer in src/adapters/copilot-cli/index.ts.
Native artifacts
Adapter writes MCP config + hook config + content files + memory/rules + marketplace bundle through this host's native file, package, or marketplace surface.
Runtime bridge
host launches JSON-stdio hook command
User-visible surface
Users see managed skills + subagents + memory surfaces after install; runtime-only surfaces stay behind the host boundary.

Runtime Sequence Flow

Message order from install to runtime for the CLI surface.

1 · User / project
Choose host adapter
Install or update starts against GitHub Copilot CLI; the selected surface is CLI.
2 · agent-connector
Resolve connector declaration
The package reads connector metadata and routes it to the copilot-cli adapter instead of exposing a generic host contract.
3 · copilot-cli adapter
Render host-native shape
Adapter writes MCP config + hook config + content files + memory/rules + marketplace bundle through this host's native file, package, or marketplace surface.
4 · GitHub Copilot CLI
Host loads artifacts
host launches JSON-stdio hook command
5 · Agent runtime
Run through host boundary
Users see managed skills + subagents + memory surfaces after install; runtime-only surfaces stay behind the host boundary.
6 · Coverage matrix
Expose remaining ceiling
5/5 native surfaces wired. No visible host-native gap in the current coverage matrix.

Architecture Archive

The same five study axes are rendered for every host: runtime shape, hooks, MCP, memory, and host-only affordances.

Host-specific shape

GitHub Copilot CLI is terminal-native but narrower than Copilot in editors: MCP, hooks, skills, subagents, memory, and marketplace driver support are tracked, while user slash commands remain absent.

Form factor: CLI.
Native surfaces: MCP server, Hooks, Skills, Subagents, Memory.
Wired surfaces: MCP server, Hooks, Skills, Subagents, Memory.
Visible gaps: none.

Hooks

Hooks enter through a host-launched command that exchanges event JSON over stdio.

MCP

The adapter writes this host's native MCP registration dialect, including its root key, scope, transport fields, and environment syntax.

Memory

Managed memory text is written into the rules or memory file this host actually reads, with ownership markers for reversible uninstall.

Marketplace and affordances

A marketplace or plugin-driver path is wired, so install/update/uninstall can be driven rather than only emitted as files.

Runtime handlers: none.
User-visible affordances: Users see managed skills + subagents + memory surfaces after install; runtime-only surfaces stay behind the host boundary..

Special Feature Inventory

Host-specific capabilities separated from the generic surface matrix: lifecycle hooks, MCP registration, memory/rules, marketplace delivery, and UI or content affordances owned by the host.

Lifecycle hooks

Wired

Hooks enter through a host-launched command that exchanges event JSON over stdio.

MCP registration

Wired

The adapter writes this host's native MCP registration dialect, including its root key, scope, transport fields, and environment syntax.

Memory and rules

Wired

Managed memory text is written into the rules or memory file this host actually reads, with ownership markers for reversible uninstall.

Marketplace delivery

Driver wired

A marketplace or plugin-driver path is wired, so install/update/uninstall can be driven rather than only emitted as files.

Host-only affordances

2/2 wired

Wired host affordances: Skills, Subagents. Host-native gaps: none. Not confirmed: Commands, Statusline handler, Action affordances.

Source Review Notes

Latest source pass for host-specific architecture details. This is separate from generated adapter coverage and local drift guards.

Checked 2026-07-06Open review source

github/copilot-cli repository

GitHub Copilot CLI is a terminal-native coding agent, so the architecture page keeps it separate from the VS Code extension row.
The repository states that the CLI uses GitHub workflow context and ships with GitHub's MCP server by default, with custom MCP servers as an extension point.
Action approval is a host-native control surface, but agent-connector should not infer generic lifecycle hooks or subagent folders from that approval model.

Evidence Map

Each host page ties public source evidence to the local adapter and drift guards that keep the rendered archive aligned with code.

Product source

Official product homepage or public tracker used when no open product repository is confirmed.

external

Open source

Local adapter implementation

Defines the install/uninstall behavior, native config rendering, capability flags, and any runtime parse/format bridge for this host.

local

src/adapters/copilot-cli/index.ts

Platform metadata and host-native matrix

Records the form factor, public source target, ranking source, native host surfaces, and current agent-connector coverage cells.

local

site/src/platform-data.ts

Architecture drift guard

Asserts that every registered host has a page, diagram, host-specific brief, source link, form-factor band, and adapter-aligned surface data.

local

tests/docs/platform-drift.test.ts

Marketplace driver registry

Shows this host has a drivable package/plugin install path beyond direct native-file writes.

local

src/core/marketplace-drivers/registry.ts

Runtime Shape

Hooks are dispatched through a host-launched command. The adapter parses host JSON, calls the connector handler, and formats the reply back to the host contract.

MCP registration: Wired through this adapter
Hook bridge: Wired

Connector Surfaces

Static content

MCP server, Hooks, Skills, Subagents, Memory

Runtime handlers

No runtime handler surfaces wired

Surface Matrix

Wired means agent-connector installs it now. Host native marks support we know about but have not wired yet.

SurfaceStatus

MCP server

Static content

agent-connector installs this surface today.

Wired

Hooks

Static content

agent-connector installs this surface today.

Wired

Commands

Static content

No confirmed host-native surface.

N/A

Skills

Static content

agent-connector installs this surface today.

Wired

Subagents

Static content

agent-connector installs this surface today.

Wired

Memory

Static content

agent-connector installs this surface today.

Wired

Statusline handler

Runtime handler

No confirmed host-native surface.

N/A

Action affordances

Runtime handler

No confirmed host-native surface.

N/A