report.md

3 min read Original article ↗

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ CURSOR 3.0.16 — REPORT ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

App: Cursor by Anysphere, Inc. Base: VS Code 1.105.1 fork Runtime: Electron 39.8.1 (arm64) Build: 2026-04-09, Xcode 16.4 / macOS 15.5 SDK

━━ ARCHITECTURE (3 PROPRIETARY LAYERS) ━━

  1. GLASS — Complete custom UI shell (50+ services) Manages: agent panels, file trees, terminals, diffs, theming, keybindings, navigation, notifications, workspaces. Not a small overlay — it's an entire application framework.

  2. COMPOSER — AI code-generation engine (40+ services) composerService, composerAgentService, composerChatService, composerContextService, composerCheckpointService, composerPlanService, composerTerminalService, etc. Modes: agent, chat, debug, plan, project, spec, triage

  3. AGENT SYSTEM — Hierarchical architecture Local agents + Cloud agents (on cursorvm.com VMs) + Subagents 11 subagent types: Bash, BrowserUse, ComputerUse, CursorGuide, Custom, Debug, Explore, MediaReview, Shell, VmSetupHelper

━━ THE BIG FINDING: CURSOR AGENT = CLAUDE CODE ━━

The cursor-agent extension (4.1MB + 11.5MB CLI) is literally Anthropic's Claude Code / Claude Agent SDK running behind a LOCAL HTTP PROXY that:

 1. Starts on 127.0.0.1 (random port)
 2. The bundled Claude Agent SDK CLI connects to it
 3. Proxy intercepts ALL requests → routes to api2.cursor.sh
    via ConnectRPC/protobuf (InferenceService)
 4. A STRING REPLACEMENT ENGINE rewrites branding in real-time:

    "Claude Code"    → "Cursor Agent"
    "CLAUDE.md"      → "AGENTS.md"
    "claude.com"     → "cursor.com"
    "Co-Authored-By: Claude" → "Made-with: Cursor"
    "@anthropic-ai/claude-agent-sdk" → "@anysphere/cursor-agent-experimental-sdk"

 Also strips: <fast_mode_info> tags, Anthropic billing headers,
 Claude GitHub issues URLs, /sandbox references, worktree docs

━━ AI MODELS ━━

Claude: 3-haiku, 3-opus, 3-sonnet, 3.5-sonnet, 3.7-sonnet, 3.7-sonnet-finetuned-cursor-20250514-v1 (CUSTOM FINE-TUNE), 4-sonnet, 4-opus, 4.5-sonnet, 4.5-haiku, 4.5-opus-high, 4.5-opus-high-thinking, 4.6-opus-high-fast

GPT: 4, 4o, 4o-mini, 4.1-mini, o1, o1-mini, o1-preview, o3, o3-mini

Gemini: 1.5-flash, 1.5-flash-8b, 1.5-preview, 2.5-flash, 2.5-pro

━━ API INFRASTRUCTURE ━━

Primary: api2.cursor.sh, api3, api4, agent.api5.cursor.sh Auth: prod.authentication.cursor.sh Extensions: marketplace.cursorapi.com Telemetry: metrics.cursor.sh (Sentry), Statsig for feature flags

VM Fleet (cloud agents): wss://*.{us1-us7}.cursorvm.com (WebSocket to VMs) https://{us1-us7}.cursorvm-manager.com (VM lifecycle) Also: eval1-2, train1-5 (training infrastructure!)

━━ 50+ AGENT TOOLS ━━

File: edit_file, read_file, delete_file, new_file, list_dir Search: grep_search, codebase_search, semantic_search, file_search Terminal: run_terminal_command, write_shell_stdin Web: web_search, web_fetch, browser_action MCP: mcp_tool, call_mcp_tool, list/read_mcp_resources Planning: create_plan, ask_question, switch_mode, reflect Subagents: subagent_start/stop, deep_search, fix_lints SCM: pr_management, set_active_branch, fetch_rules Code Intel: read_lints, summarize_code, get_symbols, run_test Media: generate_image, computer_use, record_screen, create_diagram

━━ 58 gRPC SERVICES, 3,031 PROTOBUF TYPES ━━

All under aiserver.v1: AutopilotService, BackgroundComposerService, ChatService, CppService, InferenceService, SCMService, VmDaemonService, MCPRegistryService, and 50 more.

━━ 18 CURSOR-SPECIFIC EXTENSIONS ━━

cursor-agent Claude Code as Cursor Agent (AnthropicProxy) cursor-agent-exec Agent command execution + approvals cursor-browser-auto MCP browser automation server cursor-mcp Full Model Context Protocol support cursor-retrieval Codebase indexing/RAG (gRPC packfile upload) cursor-shadow-ws Shadow workspace for background agents cursor-resolver Cloud agent workspace resolver (+ 11 more)

Blocks: github.copilot, github.copilot-chat Replaces: remote-ssh, pylance, cpptools with Anysphere forks

━━ CLI TOOLS ━━

bin/cursor: Routes to editor CLI or cursor-agent (auto-installs from cursor.com/install) bin/cursor-tunnel: Rust binary for remote dev (tunnels, port forwarding, SSH via russh, OAuth) helpers/crepectl: Credential/process control helpers/cursorsandbox: Sandbox helper helpers/node: Bundled Node.js runtime (112MB)

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The most newsworthy finding is that "Cursor Agent" is a rebranded Claude Code running behind a local proxy with a find-and-replace engine that swaps "Claude"→"Cursor" in system prompts and messages. They bundle the full @anthropic-ai/claude-agent-sdk and @anthropic-ai/claude-code packages, plus a custom fine-tuned model (claude-3.7-sonnet-finetuned-cursor-20250514-v1).