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Harness detection

detectHarness() reads environment variables that each harness sets on the processes it spawns. Every rule rests on a vendor source recorded in .research/harness-detection, and every piece of evidence it returns names the research claim behind it.

What each harness sets

Section titled “What each harness sets”

A harness does not set the same variables everywhere it runs code. Your code can run in three places: a command the agent runs in a shell or terminal, a hook the harness fires, or an MCP server the harness starts. The table shows what identifies each harness in each place. A dash means no rule applies there, so detection reports unknown.

Harness Commands the agent runs Hooks MCP servers
Claude Code CLAUDECODE=1 with CLAUDE_CODE_CHILD_SESSION=1 or CLAUDE_CODE_SESSION_ID Same as commands; also the status line CLAUDECODE=1 with CLAUDE_CODE_SESSION_ID (stdio servers)
Cursor CURSOR_AGENT=1 CURSOR_VERSION with CURSOR_PROJECT_DIR —
Codex CODEX_THREAD_ID — —
GitHub Copilot CLI COPILOT_CLI=1 or COPILOT_AGENT_SESSION_ID COPILOT_PLUGIN_ROOT (plugin hooks) COPILOT_CLI=1 or COPILOT_AGENT_SESSION_ID
OpenCode OPENCODE=1 with OPENCODE_PID — OPENCODE=1 with OPENCODE_PID
Kilo Code KILO=1 with KILO_PID — KILO=1 with KILO_PID
Gemini CLI GEMINI_CLI=1 — GEMINI_CLI=1
Qwen Code QWEN_CODE=1 — —
GitHub Copilot in VS Code COPILOT_AGENT=1 — —
Cline CLINE_ACTIVE=true (VS Code extension only) — —
Crush CRUSH=1 CRUSH=1 —
OpenHands AI_AGENT=openhands (SDK 1.40.1 and later; not the OpenHands CLI 1.16.0) AI_AGENT=openhands, or OPENHANDS_EVENT_TYPE with OPENHANDS_PROJECT_DIR —
Auggie CLI — AUGMENT_HOOK_EVENT with AUGMENT_PROJECT_DIR —

When the answer is unknown

Section titled “When the answer is unknown”

The library reports unknown rather than guess:

  • CLAUDECODE=1 on its own. Claude Code’s IDE extensions set it in their integrated terminals, where a person, not the agent, runs commands.
  • Borrowed names. Codex, Copilot CLI, and Cursor pass CLAUDE_PLUGIN_ROOT, CLAUDE_PLUGIN_DATA, or CLAUDE_PROJECT_DIR to hooks for compatibility, so those names prove nothing.
  • Shared names. OpenCode and Kilo Code set AGENT=1, and VS Code, Claude Code, and Crush set AI_AGENT. These say that some agent is running, not which one. The one exception is AI_AGENT=openhands, a value no other harness uses. OpenHands fills it in only when AI_AGENT is unset, so OpenHands started under another harness keeps the outer value and is seen only in its hooks. The OpenHands CLI 1.16.0 bundles an SDK older than that variable, so it too is seen only in its hooks.
  • Nested harnesses. A harness started from another harness’s shell inherits the outer harness’s variables. With signals from two harnesses present, the environment cannot say which one is innermost. candidates lists both.
  • Contexts with no marker of their own. Codex, Gemini CLI, and Qwen Code hooks, Qwen Code, Crush, OpenHands, and Auggie MCP servers, Auggie shell commands, Copilot in VS Code hooks and MCP servers, and the Cline CLI carry no variable that names the harness.
  • Harnesses with no verified signal. Goose documents GOOSE_TERMINAL=1, but its shell tool does not set it. Antigravity, Rovo Dev, Kiro, Amp, Factory Droid, Devin Desktop, and Warp have no variable that could be verified from outside. The library does not detect them.

Forks

Section titled “Forks”

A fork inherits its parent’s code, and sometimes its variables. Kilo Code still sets OpenCode’s OPENCODE=1, but not OPENCODE_PID, which OpenCode’s rule requires, so Kilo Code is read as Kilo Code. Kilo Code started from an OpenCode shell carries both, which is nesting and gives unknown. Qwen Code renamed Gemini CLI’s variable to QWEN_CODE, so the two never overlap.

Beyond detection

Section titled “Beyond detection”

The same research backs the harness queries:

  • managedPolicyLocations() lists the managed-policy files, MDM domains, registry keys, and server-side sources for each harness.
  • pluginStorage() returns where plugins are installed and where the enabled record lives.
  • enabledPlugins() reads the enabled record for Claude Code, Codex, and Copilot CLI, and names the policy sources it cannot read. The other harnesses keep no record it can resolve: Auggie’s enabledPlugins merges only its true entries across scopes, and OpenHands keeps enabled state in per-plugin install metadata.
  • installedPlugins() maps each installed plugin to the folder it is loaded from, for Claude Code, Codex, and Copilot CLI. Codex keeps no install record, so it applies Codex’s own rule for which cached version is active.
  • skillInvocation() returns what a user types to run a plugin skill, or undefined where the model loads skills itself: Gemini CLI, Qwen Code, Crush, and OpenHands. It also returns undefined for the Auggie CLI, where the typed form of a plugin skill is not confirmed.
  • skillsDirectories() returns the project and user directories a harness reads skills from, or undefined where they are not confirmed: Qwen Code, Crush, and OpenHands.