Add agent detection for Cline, Codex, Antigravity and OpenCode (#4496)

## Summary
- Add agent detection for three new coding agents: Cline
(`CLINE_ACTIVE`), Codex (`CODEX_CI`), OpenCode (`OPENCODE`) and
Antigravity
- Refactor detection logic from per-agent if-blocks to a table-driven
`knownAgents` slice, so adding a new agent only requires a new constant
and one table entry
- Refactor tests to be table-driven to match

## Test plan
- [x] `go test ./libs/agent/ -v` — all detection tests pass
- [x] `go test ./cmd/root/ -run TestAgent -v` — all user agent tests
pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

Author: simonfaltum

acceptance/test.toml

@@ -18,9 +18,13 @@ Env.PYTHONUNBUFFERED = "1"
 Env.PYTHONUTF8 = "1"
 
 # Clear agent env vars to prevent them from affecting test output
+Env.ANTIGRAVITY_AGENT = ""
 Env.CLAUDECODE = ""
-Env.GEMINI_CLI = ""
+Env.CLINE_ACTIVE = ""
+Env.CODEX_CI = ""
 Env.CURSOR_AGENT = ""
+Env.GEMINI_CLI = ""
+Env.OPENCODE = ""
 
 EnvMatrix.DATABRICKS_BUNDLE_ENGINE = ["terraform", "direct"]
 EnvMatrixExclude.noplantf = ["DATABRICKS_BUNDLE_ENGINE=terraform", "READPLAN=1"]

cmd/root/user_agent_agent_test.go

@@ -9,28 +9,24 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestAgentClaudeCode(t *testing.T) {
-	ctx := context.Background()
-	ctx = agent.Mock(ctx, agent.ClaudeCode)
-
-	ctx = withAgentInUserAgent(ctx)
-	assert.Contains(t, useragent.FromContext(ctx), "agent/claude-code")
-}
-
-func TestAgentGeminiCLI(t *testing.T) {
-	ctx := context.Background()
-	ctx = agent.Mock(ctx, agent.GeminiCLI)
-
-	ctx = withAgentInUserAgent(ctx)
-	assert.Contains(t, useragent.FromContext(ctx), "agent/gemini-cli")
-}
-
-func TestAgentCursor(t *testing.T) {
-	ctx := context.Background()
-	ctx = agent.Mock(ctx, agent.Cursor)
-
-	ctx = withAgentInUserAgent(ctx)
-	assert.Contains(t, useragent.FromContext(ctx), "agent/cursor")
+func TestAgentInUserAgent(t *testing.T) {
+	for _, product := range []string{
+		agent.Antigravity,
+		agent.ClaudeCode,
+		agent.Cline,
+		agent.Codex,
+		agent.Cursor,
+		agent.GeminiCLI,
+		agent.OpenCode,
+	} {
+		t.Run(product, func(t *testing.T) {
+			ctx := context.Background()
+			ctx = agent.Mock(ctx, product)
+
+			ctx = withAgentInUserAgent(ctx)
+			assert.Contains(t, useragent.FromContext(ctx), "agent/"+product)
+		})
+	}
 }
 
 func TestAgentNotSet(t *testing.T) {

libs/agent/agent.go

@@ -8,41 +8,53 @@ import (
 
 // Product name constants
 const (
-	ClaudeCode = "claude-code"
-	GeminiCLI  = "gemini-cli"
-	Cursor     = "cursor"
+	Antigravity = "antigravity"
+	ClaudeCode  = "claude-code"
+	Cline       = "cline"
+	Codex       = "codex"
+	Cursor      = "cursor"
+	GeminiCLI   = "gemini-cli"
+	OpenCode    = "opencode"
 )
 
-// Environment variable constants
-const (
-	claudeCodeEnvVar  = "CLAUDECODE"
-	geminiCliEnvVar   = "GEMINI_CLI"
-	cursorAgentEnvVar = "CURSOR_AGENT"
-)
+// knownAgents maps environment variables to product names.
+// Adding a new agent only requires a new entry here and a new constant above.
+//
+// References for each environment variable:
+//   - ANTIGRAVITY_AGENT: Closed source. Verified locally that Google Antigravity sets this variable.
+//   - CLAUDECODE:        https://github.com/anthropics/claude-code (open source npm package, sets CLAUDECODE=1)
+//   - CLINE_ACTIVE:      https://github.com/cline/cline (shipped in v3.24.0, see also https://github.com/cline/cline/discussions/5366)
+//   - CODEX_CI:          https://github.com/openai/codex/blob/main/codex-rs/core/src/unified_exec/process_manager.rs (part of UNIFIED_EXEC_ENV array)
+//   - CURSOR_AGENT:      Closed source. Referenced in https://gist.github.com/johnlindquist/9a90c5f1aedef0477c60d0de4171da3f
+//   - GEMINI_CLI:        https://google-gemini.github.io/gemini-cli/docs/tools/shell.html ("sets the GEMINI_CLI=1 environment variable")
+//   - OPENCODE:          https://github.com/opencode-ai/opencode (open source, sets OPENCODE=1)
+var knownAgents = []struct {
+	envVar  string
+	product string
+}{
+	{"ANTIGRAVITY_AGENT", Antigravity},
+	{"CLAUDECODE", ClaudeCode},
+	{"CLINE_ACTIVE", Cline},
+	{"CODEX_CI", Codex},
+	{"CURSOR_AGENT", Cursor},
+	{"GEMINI_CLI", GeminiCLI},
+	{"OPENCODE", OpenCode},
+}
 
-// key is a package-local type for context keys
-type key int
+// productKeyType is a package-local context key with zero size.
+type productKeyType struct{}
 
-const (
-	productKey = key(1)
-)
+var productKey productKeyType
 
 // detect performs the actual detection logic.
 // Returns product name string or empty string if detection is ambiguous.
 // Only returns a product if exactly one agent is detected.
 func detect(ctx context.Context) string {
 	var detected []string
-
-	if env.Get(ctx, claudeCodeEnvVar) != "" {
-		detected = append(detected, ClaudeCode)
-	}
-
-	if env.Get(ctx, geminiCliEnvVar) != "" {
-		detected = append(detected, GeminiCLI)
-	}
-
-	if env.Get(ctx, cursorAgentEnvVar) != "" {
-		detected = append(detected, Cursor)
+	for _, a := range knownAgents {
+		if env.Get(ctx, a.envVar) != "" {
+			detected = append(detected, a.product)
+		}
 	}
 
 	// Only return a product if exactly one agent is detected

libs/agent/agent_test.go

@@ -9,96 +9,61 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestDetect(t *testing.T) {
-	ctx := context.Background()
-	// Clear other agent env vars to ensure clean test environment
-	ctx = env.Set(ctx, geminiCliEnvVar, "")
-	ctx = env.Set(ctx, cursorAgentEnvVar, "")
-	ctx = env.Set(ctx, claudeCodeEnvVar, "1")
-
-	ctx = Detect(ctx)
-
-	assert.Equal(t, ClaudeCode, Product(ctx))
+func clearAllAgentEnvVars(ctx context.Context) context.Context {
+	for _, a := range knownAgents {
+		ctx = env.Set(ctx, a.envVar, "")
+	}
+	return ctx
 }
 
-func TestProductCalledBeforeDetect(t *testing.T) {
-	ctx := context.Background()
+func TestDetectEachAgent(t *testing.T) {
+	for _, a := range knownAgents {
+		t.Run(a.product, func(t *testing.T) {
+			ctx := clearAllAgentEnvVars(context.Background())
+			ctx = env.Set(ctx, a.envVar, "1")
 
-	require.Panics(t, func() {
-		Product(ctx)
-	})
+			assert.Equal(t, a.product, detect(ctx))
+		})
+	}
 }
 
-func TestMock(t *testing.T) {
-	ctx := context.Background()
-	ctx = Mock(ctx, "test-agent")
+func TestDetectViaContext(t *testing.T) {
+	ctx := clearAllAgentEnvVars(context.Background())
+	ctx = env.Set(ctx, knownAgents[0].envVar, "1")
 
-	assert.Equal(t, "test-agent", Product(ctx))
+	ctx = Detect(ctx)
+
+	assert.Equal(t, knownAgents[0].product, Product(ctx))
 }
 
 func TestDetectNoAgent(t *testing.T) {
-	ctx := context.Background()
-	ctx = env.Set(ctx, claudeCodeEnvVar, "")
-	ctx = env.Set(ctx, geminiCliEnvVar, "")
-	ctx = env.Set(ctx, cursorAgentEnvVar, "")
+	ctx := clearAllAgentEnvVars(context.Background())
 
 	ctx = Detect(ctx)
 
 	assert.Equal(t, "", Product(ctx))
 }
 
-func TestDetectClaudeCode(t *testing.T) {
-	ctx := context.Background()
-	// Clear other agent env vars to ensure clean test environment
-	ctx = env.Set(ctx, geminiCliEnvVar, "")
-	ctx = env.Set(ctx, cursorAgentEnvVar, "")
-	ctx = env.Set(ctx, claudeCodeEnvVar, "1")
-
-	result := detect(ctx)
-	assert.Equal(t, ClaudeCode, result)
-}
-
-func TestDetectGeminiCLI(t *testing.T) {
-	ctx := context.Background()
-	// Clear other agent env vars to ensure clean test environment
-	ctx = env.Set(ctx, claudeCodeEnvVar, "")
-	ctx = env.Set(ctx, cursorAgentEnvVar, "")
-	ctx = env.Set(ctx, geminiCliEnvVar, "1")
+func TestDetectMultipleAgents(t *testing.T) {
+	ctx := clearAllAgentEnvVars(context.Background())
+	for _, a := range knownAgents {
+		ctx = env.Set(ctx, a.envVar, "1")
+	}
 
-	result := detect(ctx)
-	assert.Equal(t, GeminiCLI, result)
+	assert.Equal(t, "", detect(ctx))
 }
 
-func TestDetectCursor(t *testing.T) {
+func TestProductCalledBeforeDetect(t *testing.T) {
 	ctx := context.Background()
-	// Clear other agent env vars to ensure clean test environment
-	ctx = env.Set(ctx, claudeCodeEnvVar, "")
-	ctx = env.Set(ctx, geminiCliEnvVar, "")
-	ctx = env.Set(ctx, cursorAgentEnvVar, "1")
-
-	result := detect(ctx)
-	assert.Equal(t, Cursor, result)
-}
 
-func TestDetectMultipleAgents(t *testing.T) {
-	ctx := context.Background()
-	// Clear all agent env vars first
-	ctx = env.Set(ctx, cursorAgentEnvVar, "")
-	// If multiple agents are detected, return empty string
-	ctx = env.Set(ctx, claudeCodeEnvVar, "1")
-	ctx = env.Set(ctx, geminiCliEnvVar, "1")
-
-	result := detect(ctx)
-	assert.Equal(t, "", result)
+	require.Panics(t, func() {
+		Product(ctx)
+	})
 }
 
-func TestDetectMultipleAgentsAllThree(t *testing.T) {
+func TestMock(t *testing.T) {
 	ctx := context.Background()
-	// If all three agents are detected, return empty string
-	ctx = env.Set(ctx, claudeCodeEnvVar, "1")
-	ctx = env.Set(ctx, geminiCliEnvVar, "1")
-	ctx = env.Set(ctx, cursorAgentEnvVar, "1")
+	ctx = Mock(ctx, "test-agent")
 
-	result := detect(ctx)
-	assert.Equal(t, "", result)
+	assert.Equal(t, "test-agent", Product(ctx))
 }