diff --git a/.gitea/workflows/deploy.yml b/.gitea/workflows/deploy.yml
index bd1ebdd..3be766e 100644
--- a/.gitea/workflows/deploy.yml
+++ b/.gitea/workflows/deploy.yml
@@ -92,6 +92,20 @@ jobs:
           rm -f /tmp/backend-deploy.tar.gz
           REMOTE
 
+      - name: Free disk on deploy host (docker prune)
+        run: |
+          ssh deploy-target bash -s <<REMOTE
+          set -euo pipefail
+          PRUNE="${REMOTE_BACKEND}/scripts/docker-prune.sh"
+          if [[ -x "\${PRUNE}" ]]; then
+            bash "\${PRUNE}"
+          else
+            sudo docker builder prune -af || true
+            sudo docker system prune -af || true
+            df -h /
+          fi
+          REMOTE
+
       - name: Rebuild and restart API container
         run: |
           ssh deploy-target bash -s <<REMOTE
diff --git a/internal/handlers/post_text.go b/internal/handlers/post_text.go
index acd63da..802b626 100644
--- a/internal/handlers/post_text.go
+++ b/internal/handlers/post_text.go
@@ -36,8 +36,57 @@ func requestLangCode(r *http.Request) string {
 	return translateNormalizePostLang(raw)
 }
 
-func (t postTextI18n) pick(r *http.Request) string {
-	return pickLangField(r, t.TextZh, t.TextEn, t.TextJa, t.TextKo, t.TextVi, t.TextId, t.TextMs)
+// textForLang returns body text stored for the post's source language only.
+func (t postTextI18n) textForLang(lang string) string {
+	switch translateNormalizePostLang(lang) {
+	case "en":
+		return strings.TrimSpace(t.TextEn)
+	case "ja":
+		return strings.TrimSpace(t.TextJa)
+	case "ko":
+		return strings.TrimSpace(t.TextKo)
+	case "vi":
+		return strings.TrimSpace(t.TextVi)
+	case "id":
+		return strings.TrimSpace(t.TextId)
+	case "ms":
+		return strings.TrimSpace(t.TextMs)
+	default:
+		return strings.TrimSpace(t.TextZh)
+	}
+}
+
+func postTextI18nFromSingle(lang, text string) postTextI18n {
+	lang = translateNormalizePostLang(lang)
+	text = strings.TrimSpace(text)
+	var t postTextI18n
+	switch lang {
+	case "en":
+		t.TextEn = text
+	case "ja":
+		t.TextJa = text
+	case "ko":
+		t.TextKo = text
+	case "vi":
+		t.TextVi = text
+	case "id":
+		t.TextId = text
+	case "ms":
+		t.TextMs = text
+	default:
+		t.TextZh = text
+	}
+	return t
+}
+
+func normalizePostSourceLang(lang string) string {
+	lang = translateNormalizePostLang(strings.TrimSpace(lang))
+	switch lang {
+	case "zh", "en", "ja", "ko", "vi", "id", "ms":
+		return lang
+	default:
+		return "zh"
+	}
 }
 
 func (t postTextI18n) anyNonEmpty() bool {
diff --git a/internal/handlers/posts_common.go b/internal/handlers/posts_common.go
index dd1796a..9fd70db 100644
--- a/internal/handlers/posts_common.go
+++ b/internal/handlers/posts_common.go
@@ -34,7 +34,7 @@ type PostDTO struct {
 	Language       string                       `json:"language"` // UI locale from ?lang= (matches text selection)
 	SourceLanguage string                       `json:"sourceLanguage,omitempty"` // DB source metadata (admin input language)
 	Text           string                       `json:"text,omitempty"`
-	Localizations  map[string]postLocalePayload `json:"localizations"`
+	Localizations  map[string]postLocalePayload `json:"localizations,omitempty"`
 	Attachments    []AttachmentDTO              `json:"attachments"`
 	IsRecommended  bool            `json:"isRecommended"`
 	PublishedAt    string          `json:"publishedAt"`
@@ -439,10 +439,10 @@ func scanPostRow(r *http.Request, row pgx.Row) (PostDTO, postTextI18n, error) {
 	if slug != nil {
 		dto.CategorySlug = *slug
 	}
-	dto.SourceLanguage = sourceLang
-	dto.Language = requestLangCode(r)
-	dto.Text = texts.pick(r)
-	dto.Localizations = texts.toLocalizations()
+	src := normalizePostSourceLang(sourceLang)
+	dto.SourceLanguage = src
+	dto.Language = src
+	dto.Text = texts.textForLang(src)
 	if pub != nil {
 		dto.PublishedAt = pub.UTC().Format(time.RFC3339)
 	} else if created != nil {
diff --git a/internal/handlers/posts_public.go b/internal/handlers/posts_public.go
index b9019a9..ed96bee 100644
--- a/internal/handlers/posts_public.go
+++ b/internal/handlers/posts_public.go
@@ -127,6 +127,9 @@ func listPostsQuery(w http.ResponseWriter, r *http.Request, searchMode bool) {
 		typ = "all"
 	}
 	langFilter := strings.TrimSpace(r.URL.Query().Get("language"))
+	if langFilter == "" {
+		langFilter = strings.TrimSpace(r.URL.Query().Get("lang"))
+	}
 
 	base := postSelectBase() + ` WHERE ` + publicPostWhere
 	args := []any{}
diff --git a/scripts/docker-prune.sh b/scripts/docker-prune.sh
new file mode 100755
index 0000000..4e2c695
--- /dev/null
+++ b/scripts/docker-prune.sh
@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+# Free disk before docker compose build (build cache is the usual culprit for Go OOM / no space).
+# Safe on deploy hosts: does NOT use --volumes (keeps named DB volumes).
+set -euo pipefail
+
+docker_cmd() {
+  if docker info >/dev/null 2>&1; then
+    docker "$@"
+  elif sudo docker info >/dev/null 2>&1; then
+    sudo docker "$@"
+  else
+    echo "docker not available — skip prune" >&2
+    return 1
+  fi
+}
+
+echo "==> disk before prune"
+df -h / 2>/dev/null || true
+if [[ -d /var/lib/docker ]]; then
+  df -h /var/lib/docker 2>/dev/null || true
+fi
+
+if ! docker info >/dev/null 2>&1 && ! sudo docker info >/dev/null 2>&1; then
+  echo "docker not available — skip prune" >&2
+  exit 0
+fi
+
+echo "==> docker builder prune (build cache)"
+docker_cmd builder prune -af || true
+
+echo "==> docker system prune (unused images, stopped containers, networks)"
+docker_cmd system prune -af || true
+
+echo "==> disk after prune"
+df -h / 2>/dev/null || true
+if [[ -d /var/lib/docker ]]; then
+  df -h /var/lib/docker 2>/dev/null || true
+fi