feat(im): add recovery hint for cross-identity message resources

internal/output/lark_errors.go

@@ -49,6 +49,9 @@ const (
 	// caller already holds the requested permission, or the target type does
 	// not accept apply operations).
 	LarkErrDrivePermApplyNotApplicable = 1063007
+
+	// IM resource ownership mismatch.
+	LarkErrOwnershipMismatch = 231205
 )
 
 // ClassifyLarkError maps a Lark API error code + message to (exitCode, errType, hint).
@@ -98,6 +101,9 @@ func ClassifyLarkError(code int, msg string) (int, string, string) {
 	case LarkErrDrivePermApplyNotApplicable:
 		return ExitAPI, "invalid_params",
 			"this document does not accept a permission-apply request (common causes: the document is configured to disallow access requests, the caller already holds the permission, or the target type does not support apply); contact the owner directly"
+
+	case LarkErrOwnershipMismatch:
+		return ExitAPI, "ownership_mismatch", buildOwnershipRecoveryHint()
 	}
 
 	return ExitAPI, "api_error", ""

internal/output/lark_errors_test.go

@@ -61,6 +61,13 @@ func TestClassifyLarkError_DriveCreateShortcutConstraints(t *testing.T) {
 			wantType:     "invalid_params",
 			wantHint:     "does not accept a permission-apply request",
 		},
+		{
+			name:         "ownership mismatch",
+			code:         LarkErrOwnershipMismatch,
+			wantExitCode: ExitAPI,
+			wantType:     "ownership_mismatch",
+			wantHint:     "messages-resources-download",
+		},
 	}
 
 	for _, tt := range tests {

internal/output/ownership_recovery.go

@@ -0,0 +1,8 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package output
+
+func buildOwnershipRecoveryHint() string {
+	return "This resource belongs to another user — you can't send it directly. Download it with 'im +messages-resources-download --output <output_path>', then send the local file via 'im +send..'. For post or interactive, upload first and use the new image_key or file_key."
+}

internal/output/ownership_recovery_test.go

@@ -0,0 +1,71 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package output
+
+import (
+	"strings"
+	"testing"
+)
+
+func checkOwnershipRecoveryHint(t *testing.T, hint string) {
+	t.Helper()
+
+	for _, part := range []string{
+		"im +messages-resources-download",
+		"--output <output_path>",
+		"This resource belongs to another user",
+		"download",
+		"send",
+		"image_key",
+		"file_key",
+	} {
+		if !strings.Contains(hint, part) {
+			t.Fatalf("hint %q missing %q", hint, part)
+		}
+	}
+	if len(hint) > 360 {
+		t.Fatalf("hint is too long: %d bytes", len(hint))
+	}
+	for _, noisy := range []string{
+		"Step 1",
+		"Step 2",
+		"Step 3",
+		"--message-id <message_id>",
+		"--file-key <resource_key>",
+		"--type <image|file>",
+		"identity",
+		"do not keep retrying alternative download methods",
+		"POST /open-apis",
+	} {
+		if strings.Contains(hint, noisy) {
+			t.Fatalf("hint %q should not contain noisy phrase %q", hint, noisy)
+		}
+	}
+}
+
+func TestBuildOwnershipRecoveryHint(t *testing.T) {
+	checkOwnershipRecoveryHint(t, buildOwnershipRecoveryHint())
+}
+
+func TestErrAPI_OwnershipMismatch(t *testing.T) {
+	upstreamMessage := "Bot or User is NOT the owner of the uat resource."
+	err := ErrAPI(LarkErrOwnershipMismatch, upstreamMessage, map[string]any{"log_id": "test-log"})
+
+	if err.Code != ExitAPI {
+		t.Fatalf("exit code = %d, want %d", err.Code, ExitAPI)
+	}
+	if err.Detail == nil {
+		t.Fatal("expected detail")
+	}
+	if err.Detail.Type != "ownership_mismatch" {
+		t.Fatalf("type = %q, want %q", err.Detail.Type, "ownership_mismatch")
+	}
+	if got, want := err.Detail.Message, upstreamMessage; got != want {
+		t.Fatalf("message = %q, want %q", got, want)
+	}
+	checkOwnershipRecoveryHint(t, err.Detail.Hint)
+	if err.Detail.Detail == nil {
+		t.Fatal("expected upstream detail to be preserved")
+	}
+}