feat(envvars): add LARKSUITE_CLI_AGENT_NAME accessor

envvars.AgentName() reads LARKSUITE_CLI_AGENT_NAME so business code can identify the agent driving the CLI. Value is sanitised (trim, reject control chars, 128-byte cap) and returns "" when unset or invalid. Local-only; not sent to the server.

internal/envvars/envvars.go

@@ -19,6 +19,7 @@ const (
 	// Content safety scanning mode
 	CliContentSafetyMode = "LARKSUITE_CLI_CONTENT_SAFETY_MODE"
 
+	CliAgentName  = "LARKSUITE_CLI_AGENT_NAME"
 	CliAgentTrace = "LARKSUITE_CLI_AGENT_TRACE"
 
 	CliProxyEnable  = "LARKSUITE_CLI_PROXY_ENABLE"

internal/envvars/read.go

@@ -0,0 +1,29 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package envvars
+
+import (
+	"os"
+	"strings"
+	"unicode"
+)
+
+const agentNameMaxLen = 128
+
+func AgentName() string {
+	return sanitizeSingleLine(os.Getenv(CliAgentName), agentNameMaxLen)
+}
+
+func sanitizeSingleLine(raw string, maxLen int) string {
+	v := strings.TrimSpace(raw)
+	if v == "" || len(v) > maxLen {
+		return ""
+	}
+	for _, r := range v {
+		if unicode.IsControl(r) {
+			return ""
+		}
+	}
+	return v
+}

internal/envvars/read_test.go

@@ -0,0 +1,52 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package envvars
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestAgentName_EmptyWhenEnvUnset(t *testing.T) {
+	t.Setenv(CliAgentName, "")
+	if got := AgentName(); got != "" {
+		t.Fatalf("AgentName() = %q, want empty when env unset", got)
+	}
+}
+
+func TestAgentName_ReturnsCleanValue(t *testing.T) {
+	t.Setenv(CliAgentName, "claude-code")
+	if got := AgentName(); got != "claude-code" {
+		t.Fatalf("AgentName() = %q, want %q", got, "claude-code")
+	}
+}
+
+func TestAgentName_TrimsWhitespace(t *testing.T) {
+	t.Setenv(CliAgentName, "  cursor  ")
+	if got := AgentName(); got != "cursor" {
+		t.Fatalf("AgentName() = %q, want %q (whitespace trimmed)", got, "cursor")
+	}
+}
+
+func TestAgentName_RejectsCRLFInjection(t *testing.T) {
+	t.Setenv(CliAgentName, "agent\r\nX-Evil: attack")
+	if got := AgentName(); got != "" {
+		t.Fatalf("AgentName() = %q, want empty for CR/LF value", got)
+	}
+}
+
+func TestAgentName_RejectsControlChar(t *testing.T) {
+	t.Setenv(CliAgentName, "agent\x01injected")
+	if got := AgentName(); got != "" {
+		t.Fatalf("AgentName() = %q, want empty for control char value", got)
+	}
+}
+
+func TestAgentName_RejectsOverlongValue(t *testing.T) {
+	longVal := strings.Repeat("a", agentNameMaxLen+1)
+	t.Setenv(CliAgentName, longVal)
+	if got := AgentName(); got != "" {
+		t.Fatalf("AgentName() returned non-empty for %d-byte value (max %d)", len(longVal), agentNameMaxLen)
+	}
+}