diff --git a/apps/backend/internal/agentctl/server/process/shell_test.go b/apps/backend/internal/agentctl/server/process/shell_test.go
index 5c0c12c8e8..bdfab3c741 100644
--- a/apps/backend/internal/agentctl/server/process/shell_test.go
+++ b/apps/backend/internal/agentctl/server/process/shell_test.go
@@ -18,11 +18,14 @@ func TestDefaultShellCommand_EmptyPreferred(t *testing.T) {
 	if len(cmd) == 0 {
 		t.Fatal("expected non-empty command")
 	}
-	// On Unix, should fall back to $SHELL or /bin/sh with -l flag
-	// On Windows, should fall back to %COMSPEC% or powershell.exe
+	// On Unix the shell must be invoked WITHOUT -l so /etc/profile doesn't
+	// reset PATH (which would drop /data/.npm-global/bin where agent CLIs
+	// installed via the Settings → Agents install button live).
 	if runtime.GOOS != "windows" {
-		if cmd[len(cmd)-1] != "-l" {
-			t.Errorf("expected login flag -l on Unix, got %v", cmd)
+		for _, a := range cmd[1:] {
+			if a == "-l" {
+				t.Errorf("expected no -l flag on Unix shell, got %v", cmd)
+			}
 		}
 	}
 }
diff --git a/apps/backend/internal/agentctl/server/process/shell_unix.go b/apps/backend/internal/agentctl/server/process/shell_unix.go
index ea75687f5e..5443e64994 100644
--- a/apps/backend/internal/agentctl/server/process/shell_unix.go
+++ b/apps/backend/internal/agentctl/server/process/shell_unix.go
@@ -8,8 +8,11 @@ import (
 	"strings"
 )
 
-// defaultShellCommand returns the command and args for starting an interactive login shell.
-// On Unix, uses $SHELL (or /bin/sh) with the -l (login) flag.
+// defaultShellCommand returns the command and args for starting an interactive shell.
+// On Unix, uses $SHELL (or /bin/sh) with no extra flags — the shell is interactive
+// via the attached PTY. We deliberately do NOT pass -l: Debian's /etc/profile
+// (and /etc/profile.d/*) can overwrite PATH, dropping container-set entries like
+// /data/.npm-global/bin where agent CLIs (claude, codex, ...) are installed.
 func defaultShellCommand(preferredShell string) []string {
 	shell := resolveShellPath(preferredShell)
 	if shell == "" {
@@ -18,7 +21,7 @@ func defaultShellCommand(preferredShell string) []string {
 	if shell == "" {
 		shell = "/bin/sh"
 	}
-	return []string{shell, "-l"}
+	return []string{shell}
 }
 
 func resolveShellPath(value string) string {
diff --git a/apps/backend/internal/agentctl/server/shell/session.go b/apps/backend/internal/agentctl/server/shell/session.go
index 1165856bc9..21a86346fa 100644
--- a/apps/backend/internal/agentctl/server/shell/session.go
+++ b/apps/backend/internal/agentctl/server/shell/session.go
@@ -95,10 +95,13 @@ func detectShell() (string, []string) {
 
 	// Unix-like systems (Linux, macOS)
 	// Check $SHELL but only use it if the shell actually exists
-	// (host's $SHELL may not be installed in Docker containers)
+	// (host's $SHELL may not be installed in Docker containers).
+	// No -l flag: Debian's /etc/profile (and /etc/profile.d/*) can overwrite
+	// PATH, dropping container-set entries like /data/.npm-global/bin where
+	// agent CLIs (claude, codex, ...) are installed.
 	if shell := os.Getenv("SHELL"); shell != "" {
 		if _, err := exec.LookPath(shell); err == nil {
-			return shell, []string{"-l"} // Login shell
+			return shell, nil
 		}
 	}
 
@@ -106,7 +109,7 @@ func detectShell() (string, []string) {
 	shells := []string{"/bin/bash", "/bin/zsh", "/bin/sh"}
 	for _, sh := range shells {
 		if _, err := os.Stat(sh); err == nil {
-			return sh, []string{"-l"}
+			return sh, nil
 		}
 	}
 
@@ -152,7 +155,7 @@ func defaultShellArgs(shellCommand string) []string {
 		}
 		return nil
 	}
-	return []string{"-l"}
+	return nil
 }
 
 // start initializes and starts the shell process
diff --git a/apps/backend/internal/agentctl/server/shell/session_test.go b/apps/backend/internal/agentctl/server/shell/session_test.go
index 0d40a765d7..aef37eb358 100644
--- a/apps/backend/internal/agentctl/server/shell/session_test.go
+++ b/apps/backend/internal/agentctl/server/shell/session_test.go
@@ -55,9 +55,12 @@ func assertUnixShell(t *testing.T, shell string, args []string) {
 	if _, err := os.Stat(shell); err != nil && shell != os.Getenv("SHELL") {
 		t.Logf("Warning: detected shell %q may not exist: %v", shell, err)
 	}
-	// Unix shells should have -l flag for login shell
-	if len(args) > 0 && args[0] != "-l" {
-		t.Errorf("expected Unix shell args to contain '-l', got %v", args)
+	// No -l flag: login mode lets /etc/profile reset PATH and lose the
+	// container-set entries needed to find agent CLIs.
+	for _, a := range args {
+		if a == "-l" {
+			t.Errorf("expected no -l flag in Unix shell args, got %v", args)
+		}
 	}
 }
 
@@ -91,8 +94,10 @@ func TestDetectShellWithSHELLEnv(t *testing.T) {
 	if shell != "/bin/sh" {
 		t.Errorf("expected shell from SHELL env (/bin/sh), got %q", shell)
 	}
-	if len(args) == 0 || args[0] != "-l" {
-		t.Errorf("expected args to contain '-l', got %v", args)
+	for _, a := range args {
+		if a == "-l" {
+			t.Errorf("expected no -l flag, got %v", args)
+		}
 	}
 }