diff --git a/shortcuts/sheets/csv_put_guard_test.go b/shortcuts/sheets/csv_put_guard_test.go
new file mode 100644
index 000000000..5191e45ee
--- /dev/null
+++ b/shortcuts/sheets/csv_put_guard_test.go
@@ -0,0 +1,58 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package sheets
+
+import (
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/larksuite/cli/internal/cmdutil"
+	_ "github.com/larksuite/cli/internal/vfs/localfileio"
+	"github.com/larksuite/cli/shortcuts/common"
+	"github.com/spf13/cobra"
+)
+
+func newCSVGuardRuntime(csvVal string) *common.RuntimeContext {
+	cmd := &cobra.Command{Use: "test"}
+	cmd.Flags().String("csv", "", "")
+	cmd.ParseFlags(nil)
+	cmd.Flags().Set("csv", csvVal)
+	return &common.RuntimeContext{Cmd: cmd}
+}
+
+// TestGuardCSVValueIsNotFilePath verifies the guard flags a bare --csv value
+// only when it names a real file (a forgotten @), while leaving genuine inline
+// content alone — including the case the old name-shape heuristic got wrong:
+// prose that merely ends in or mentions a filename.
+func TestGuardCSVValueIsNotFilePath(t *testing.T) {
+	dir := t.TempDir()
+	cmdutil.TestChdir(t, dir)
+	if err := os.WriteFile("data.csv", []byte("a,b\n1,2\n"), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	// Bare value naming an existing file → guarded with a fix-it hint.
+	err := guardCSVValueIsNotFilePath(newCSVGuardRuntime("data.csv"))
+	if err == nil {
+		t.Fatal("expected guard error when --csv names an existing file")
+	}
+	if !strings.Contains(err.Error(), "existing file") || !strings.Contains(err.Error(), "@data.csv") {
+		t.Errorf("error should flag the file and suggest @data.csv, got: %v", err)
+	}
+
+	// Content that is not a real file must pass through unchanged.
+	for _, v := range []string{
+		"改完记得更新config.json",           // prose ending in a filename — not a real file
+		"remember to update data.csv", // mentions the real file but isn't its name
+		"a,b\n1,2",                    // multi-cell CSV
+		"hello world",
+		"nope.csv", // path-shaped but no such file
+		"",
+	} {
+		if err := guardCSVValueIsNotFilePath(newCSVGuardRuntime(v)); err != nil {
+			t.Errorf("content %q must pass through, got: %v", v, err)
+		}
+	}
+}
diff --git a/shortcuts/sheets/lark_sheet_write_cells.go b/shortcuts/sheets/lark_sheet_write_cells.go
index 07768614f..9cb51fbae 100644
--- a/shortcuts/sheets/lark_sheet_write_cells.go
+++ b/shortcuts/sheets/lark_sheet_write_cells.go
@@ -219,7 +219,12 @@ var CsvPut = common.Shortcut{
 		}
 		cmd.MarkFlagsOneRequired("start-cell", "range")
 	},
-	Validate: validateViaInput(csvPutInput),
+	Validate: func(ctx context.Context, runtime *common.RuntimeContext) error {
+		if err := guardCSVValueIsNotFilePath(runtime); err != nil {
+			return err
+		}
+		return validateViaInput(csvPutInput)(ctx, runtime)
+	},
 	DryRun: func(ctx context.Context, runtime *common.RuntimeContext) *common.DryRunAPI {
 		token, _ := resolveSpreadsheetToken(runtime)
 		sheetID, sheetName, _ := resolveSheetSelector(runtime)
@@ -295,6 +300,36 @@ func csvPutWriteRangeFromInput(input map[string]interface{}) (string, bool) {
 	return fmt.Sprintf("%s:%s%d", anchor, endCol, endRow), true
 }
 
+// guardCSVValueIsNotFilePath catches the common slip of passing a CSV file path
+// to --csv without the "@" that reads it (e.g. `--csv data.csv` instead of
+// `--csv @data.csv`). Because any string is a valid one-cell CSV, the mistake
+// would otherwise be written silently as the literal text "data.csv". It runs
+// in +csv-put's Validate, after resolveInputFlags — so an @file / stdin value is
+// already its contents (a real CSV blob, never a path) and only a bare value
+// reaches here unchanged. It flags the value only when it actually names an
+// existing file in the cwd subtree; checking real existence (not name shape)
+// means inline content that merely ends in a filename ("see config.json") is
+// never misjudged. Fails open: any Stat error or a directory leaves the value
+// untouched. Scoped to --csv only — no other flag is affected.
+func guardCSVValueIsNotFilePath(runtime *common.RuntimeContext) error {
+	raw := strings.TrimSpace(runtime.Str("csv"))
+	if raw == "" {
+		return nil
+	}
+	fio := runtime.FileIO()
+	if fio == nil {
+		return nil
+	}
+	info, err := fio.Stat(raw)
+	if err != nil || info == nil || info.IsDir() {
+		return nil //nolint:nilerr // fail-open: a missing/unreadable path is treated as inline content, not a forgotten @
+	}
+	return common.FlagErrorf(
+		"--csv value %q is an existing file, not inline CSV; to read it use --csv @%s, or pass the literal text via stdin (--csv -)",
+		raw, raw,
+	)
+}
+
 func csvPutInput(runtime flagView, token, sheetID, sheetName string) (map[string]interface{}, error) {
 	if err := requireSheetSelector(sheetID, sheetName); err != nil {
 		return nil, err