Merge pull request 'Post translation via Interpreter (milestone 143)' (#201) from dev into main

alembic/versions/0083_post_translation.py

@@ -0,0 +1,73 @@
+"""post-text translation via Interpreter (milestone 143) — Post columns + settings
+
+Post gains the translated title/description + the detected source language,
+Interpreter engine_version (cache key), and translated_at — filled by the
+translate sweep. ImportSettings gains translation_enabled (OFF by default),
+interpreter_base_url (EMPTY — the operator sets their own, behind a reverse
+proxy), and translation_target_lang (en).
+
+Revision ID: 0083
+Revises: 0082
+Create Date: 2026-07-07
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0083"
+down_revision: Union[str, None] = "0082"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "post", sa.Column("post_title_translated", sa.Text(), nullable=True)
+    )
+    op.add_column(
+        "post", sa.Column("description_translated", sa.Text(), nullable=True)
+    )
+    op.add_column(
+        "post",
+        sa.Column("translated_source_lang", sa.String(8), nullable=True),
+    )
+    op.add_column(
+        "post",
+        sa.Column("translation_engine_version", sa.String(128), nullable=True),
+    )
+    op.add_column(
+        "post",
+        sa.Column("translated_at", sa.DateTime(timezone=True), nullable=True),
+    )
+    op.add_column(
+        "import_settings",
+        sa.Column(
+            "translation_enabled", sa.Boolean(), nullable=False,
+            server_default=sa.text("false"),
+        ),
+    )
+    op.add_column(
+        "import_settings",
+        sa.Column(
+            "interpreter_base_url", sa.Text(), nullable=False, server_default="",
+        ),
+    )
+    op.add_column(
+        "import_settings",
+        sa.Column(
+            "translation_target_lang", sa.Text(), nullable=False,
+            server_default="en",
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("import_settings", "translation_target_lang")
+    op.drop_column("import_settings", "interpreter_base_url")
+    op.drop_column("import_settings", "translation_enabled")
+    op.drop_column("post", "translated_at")
+    op.drop_column("post", "translation_engine_version")
+    op.drop_column("post", "translated_source_lang")
+    op.drop_column("post", "description_translated")
+    op.drop_column("post", "post_title_translated")

backend/app/api/settings.py

@@ -1,12 +1,23 @@
 """Settings API: import filters, system stats."""
 
+import asyncio
 import secrets
 
 from quart import Blueprint, jsonify, request
-from sqlalchemy import func, select
+from sqlalchemy import func, or_, select
 
 from ..extensions import get_session
-from ..models import AppSetting, Artist, ImageRecord, ImportBatch, ImportSettings, ImportTask, Tag
+from ..models import (
+    AppSetting,
+    Artist,
+    ImageRecord,
+    ImportBatch,
+    ImportSettings,
+    ImportTask,
+    Post,
+    Tag,
+)
+from ..services import interpreter_client as ic
 
 settings_bp = Blueprint("settings", __name__, url_prefix="/api")
 
@@ -32,6 +43,9 @@ _EDITABLE_FIELDS = (
     "extdl_mediafire_enabled",
     "extdl_dropbox_enabled",
     "extdl_pixeldrain_enabled",
+    "translation_enabled",
+    "interpreter_base_url",
+    "translation_target_lang",
 )
 
 # Per-host external-download toggles — all plain booleans, validated uniformly.
@@ -69,6 +83,9 @@ async def get_import_settings():
         "extdl_mediafire_enabled": row.extdl_mediafire_enabled,
         "extdl_dropbox_enabled": row.extdl_dropbox_enabled,
         "extdl_pixeldrain_enabled": row.extdl_pixeldrain_enabled,
+        "translation_enabled": row.translation_enabled,
+        "interpreter_base_url": row.interpreter_base_url,
+        "translation_target_lang": row.translation_target_lang,
     })
 
 
@@ -128,6 +145,15 @@ async def update_import_settings():
     for tog in _EXTDL_TOGGLE_FIELDS:
         if tog in body and not isinstance(body[tog], bool):
             return jsonify({"error": f"{tog} must be a boolean"}), 400
+    # Translation (#143): base URL may be empty (feature off until set — no
+    # default host; the operator points it at their own Interpreter proxy).
+    if "translation_enabled" in body and not isinstance(
+        body["translation_enabled"], bool
+    ):
+        return jsonify({"error": "translation_enabled must be a boolean"}), 400
+    for key in ("interpreter_base_url", "translation_target_lang"):
+        if key in body and not isinstance(body[key], str):
+            return jsonify({"error": f"{key} must be a string"}), 400
     if "series_suggest_threshold" in body:
         v = body["series_suggest_threshold"]
         if not isinstance(v, (int, float)) or isinstance(v, bool) or v < 0 or v > 1:
@@ -270,3 +296,58 @@ async def rotate_extension_api_key():
             row.value = new_value
         await session.commit()
     return jsonify({"key": new_value})
+
+
+# --- Translation (#143): live status + manual "Translate now" --------------
+
+
+@settings_bp.route("/settings/translation/status", methods=["GET"])
+async def translation_status():
+    """For the Settings card: is it on, is a URL set, is the service reachable,
+    and how many posts still await translation. Health runs the sync client in a
+    thread so the event loop isn't blocked."""
+    async with get_session() as session:
+        cfg = await ImportSettings.load(session)
+        untranslated = (await session.execute(
+            select(func.count(Post.id))
+            .where(Post.translated_source_lang.is_(None))
+            .where(or_(
+                Post.post_title.is_not(None), Post.description.is_not(None),
+            ))
+        )).scalar_one()
+    base_url = (cfg.interpreter_base_url or "").strip()
+    healthy = await asyncio.to_thread(ic.health, base_url) if base_url else False
+    return jsonify({
+        "enabled": cfg.translation_enabled,
+        "base_url_set": bool(base_url),
+        "healthy": healthy,
+        "untranslated_count": int(untranslated),
+    })
+
+
+@settings_bp.route("/settings/translation/test", methods=["POST"])
+async def translation_test():
+    """On-demand reachability check for a GIVEN Interpreter base URL (the Settings
+    'Test connection' button) — pings /v1/health without saving, so the operator
+    can verify a URL before enabling. Health runs in a thread (sync client)."""
+    body = await request.get_json()
+    base_url = ""
+    if isinstance(body, dict):
+        base_url = (body.get("base_url") or "").strip()
+    healthy = await asyncio.to_thread(ic.health, base_url) if base_url else False
+    return jsonify({"healthy": healthy})
+
+
+@settings_bp.route("/settings/translation/run", methods=["POST"])
+async def translation_run():
+    """Enqueue the translate sweep now (the Settings 'Translate now' button)."""
+    async with get_session() as session:
+        cfg = await ImportSettings.load(session)
+    if not cfg.translation_enabled or not (cfg.interpreter_base_url or "").strip():
+        return jsonify(
+            {"error": "translation is disabled or no base URL is set"}
+        ), 400
+    from ..tasks.translation import translate_posts
+
+    r = translate_posts.delay()
+    return jsonify({"celery_task_id": r.id}), 202

backend/app/celery_app.py

@@ -35,6 +35,7 @@ def make_celery() -> Celery:
             "backend.app.tasks.backup",
             "backend.app.tasks.admin",
             "backend.app.tasks.library_audit",
+            "backend.app.tasks.translation",
         ],
     )
     app.conf.update(
@@ -63,6 +64,9 @@ def make_celery() -> Celery:
             "backend.app.tasks.backup.*": {"queue": "maintenance_long"},
             "backend.app.tasks.admin.*": {"queue": "maintenance_long"},
             "backend.app.tasks.library_audit.*": {"queue": "maintenance_long"},
+            # Translation backfill hits the LLM (~1–6s/item) → the long lane so it
+            # never starves the quick self-healing sweeps (#143).
+            "backend.app.tasks.translation.*": {"queue": "maintenance_long"},
         },
         # Heavy ML tasks need fair dispatch — see ImageRepo's precedent.
         task_acks_late=True,
@@ -161,6 +165,10 @@ def make_celery() -> Celery:
                 "task": "backend.app.tasks.ml.prune_presentation_reviews",
                 "schedule": 86400.0,  # retention: drop resolved review flags >30d
             },
+            "translate-posts-daily": {
+                "task": "backend.app.tasks.translation.translate_posts",
+                "schedule": 86400.0,  # no-op unless translation configured + healthy
+            },
             "snapshot-head-metrics-daily": {
                 "task": "backend.app.tasks.maintenance.snapshot_head_metrics",
                 "schedule": 86400.0,

backend/app/models/import_settings.py

@@ -92,6 +92,21 @@ class ImportSettings(Base):
         Boolean, nullable=False, default=True, server_default="true",
     )
 
+    # -- Post-text translation via the Interpreter LAN service (milestone 143).
+    # Off by default with NO default host — it needs a reachable Interpreter
+    # service (the operator's, behind a reverse proxy), which not every install
+    # has; the operator sets the URL and flips it on. Empty base_url OR disabled
+    # → the translate sweep no-ops.
+    translation_enabled: Mapped[bool] = mapped_column(
+        Boolean, nullable=False, default=False, server_default="false",
+    )
+    interpreter_base_url: Mapped[str] = mapped_column(
+        Text, nullable=False, default="", server_default="",
+    )
+    translation_target_lang: Mapped[str] = mapped_column(
+        Text, nullable=False, default="en", server_default="en",
+    )
+
     @classmethod
     async def load(cls, session) -> ImportSettings:
         """The singleton settings row (id=1), via an async session."""

backend/app/models/post.py

@@ -47,6 +47,24 @@ class Post(Base):
     description: Mapped[str | None] = mapped_column(Text, nullable=True)
     attachment_count: Mapped[int | None] = mapped_column(Integer, nullable=True)
 
+    # -- Post-text translation (milestone 143). Filled by the translate_posts
+    # sweep via the Interpreter LAN service so viewing is instant.
+    # translated_source_lang is the DETECTED original language; "en" (or a
+    # passthrough) means nothing to translate and the *_translated columns stay
+    # NULL. engine_version keys the Interpreter cache — re-runs are ~1ms and a
+    # model upgrade re-translates instead of serving stale.
+    post_title_translated: Mapped[str | None] = mapped_column(Text, nullable=True)
+    description_translated: Mapped[str | None] = mapped_column(Text, nullable=True)
+    translated_source_lang: Mapped[str | None] = mapped_column(
+        String(8), nullable=True
+    )
+    translation_engine_version: Mapped[str | None] = mapped_column(
+        String(128), nullable=True
+    )
+    translated_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
+
     downloaded_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()
     )

backend/app/services/interpreter_client.py

@@ -0,0 +1,88 @@
+"""Interpreter translation client (milestone 143) — a thin SYNC wrapper over the
+self-hosted Interpreter LAN service (LibreTranslate-compatible `/v1/translate`).
+
+Sync (requests) because the only caller is the sync celery translate sweep, and
+it mirrors FC's other platform clients. The service knows nothing about Curator —
+all Curator logic stays here. base_url is operator-configured (empty until set;
+behind a reverse proxy). Full API contract: Scribe note #1347.
+"""
+from __future__ import annotations
+
+import requests
+
+
+class InterpreterUnavailable(Exception):
+    """The translation engine is down / unreachable (HTTP 503 or a connection
+    error) — retry later, don't drop the item."""
+
+
+class InterpreterBadRequest(Exception):
+    """Bad request params (HTTP 400)."""
+
+
+def _url(base_url: str, path: str) -> str:
+    return f"{base_url.rstrip('/')}{path}"
+
+
+def health(base_url: str, *, timeout: float = 5.0) -> bool:
+    """True iff the Interpreter LLM engine is up. Any error (unset URL, network,
+    non-200, engine down) → False, so the sweep just no-ops rather than raising."""
+    if not base_url:
+        return False
+    try:
+        r = requests.get(_url(base_url, "/v1/health"), timeout=timeout)
+    except requests.RequestException:
+        return False
+    if r.status_code != 200:
+        return False
+    engines = (r.json() or {}).get("engines") or {}
+    return bool(engines.get("llm"))
+
+
+def translate(
+    texts: list[str], *, base_url: str, target: str = "en",
+    source: str = "auto", timeout: float = 120.0,
+) -> dict:
+    """Translate a batch. Returns::
+
+        {"translations": [str, ...],   # SAME order & length as `texts`
+         "detected_lang": str | None,  # aggregate: describes the FIRST item
+         "engine": str | None,
+         "engine_version": str | None}
+
+    Interpreter batch metadata is aggregate (first item only) — fine for one
+    post's ``[title, description]`` batch since they share a language. Passthrough
+    items (already target-language / emoji-only) come back UNCHANGED in their
+    slot. Raises InterpreterUnavailable on 503 / connection error (retry later),
+    InterpreterBadRequest on 400. (Scribe note #1347.)
+    """
+    if not texts:
+        return {"translations": [], "detected_lang": None,
+                "engine": None, "engine_version": None}
+    try:
+        r = requests.post(
+            _url(base_url, "/v1/translate"),
+            json={"q": list(texts), "source": source,
+                  "target": target, "engine": "auto"},
+            timeout=timeout,
+        )
+    except requests.RequestException as e:
+        raise InterpreterUnavailable(str(e)) from e
+    if r.status_code == 503:
+        raise InterpreterUnavailable("interpreter engine unavailable")
+    if r.status_code == 400:
+        raise InterpreterBadRequest((r.json() or {}).get("error", "bad request"))
+    r.raise_for_status()
+    body = r.json() or {}
+    out = body.get("translatedText")
+    # q was an array → translatedText is an array (same order & length). Guard a
+    # scalar reply just in case (shouldn't happen for an array q).
+    if not isinstance(out, list):
+        out = [out]
+    interp = body.get("interpreter") or {}
+    return {
+        "translations": out,
+        "detected_lang": (body.get("detectedLanguage") or {}).get("language"),
+        "engine": interp.get("engine"),
+        "engine_version": interp.get("engine_version"),
+    }

backend/app/services/post_feed_service.py

@@ -200,6 +200,8 @@ class PostFeedService:
         atts_map = await self._attachments_for([post.id])
         item = self._to_dict(post, artist, source, thumbs_map, atts_map)
         item["description_full"] = html_to_plain(post.description)
+        # Full (uncapped) translated description for the detail view (#143).
+        item["description_translated_full"] = post.description_translated
         # Sanitized HTML body for faithful (semantic) rendering in the post view;
         # detail-only (the feed list stays lightweight plain text). None when the
         # post has no body. Inline `<img>` sources are remapped to locally-served
@@ -371,6 +373,12 @@ class PostFeedService:
             description_plain, truncated = None, False
         else:
             description_plain, truncated = truncate_at_word(plain_full, DESCRIPTION_LIMIT)
+        # Translation (#143): the stored translated description is already plain
+        # text; truncate it the same way for the card.
+        desc_trans = post.description_translated
+        desc_trans_short = (
+            truncate_at_word(desc_trans, DESCRIPTION_LIMIT)[0] if desc_trans else None
+        )
         thumbs_entry = thumbs_map.get(post.id, {"thumbs": [], "more": 0})
         # `source` is null for filesystem-imported posts with no live
         # subscription (alembic 0030). Frontend renders that as a
@@ -384,6 +392,11 @@ class PostFeedService:
             "downloaded_at": post.downloaded_at.isoformat(),
             "description_plain": description_plain,
             "description_truncated": truncated,
+            # Translation-forward fields (#143): shown by default when present;
+            # UI toggles back to the originals above. Source lang labels the toggle.
+            "post_title_translated": post.post_title_translated,
+            "description_translated": desc_trans_short,
+            "translated_source_lang": post.translated_source_lang,
             "artist": {"id": artist.id, "name": artist.name, "slug": artist.slug},
             "source": (
                 {"id": source.id, "platform": source.platform}

backend/app/services/provenance_service.py

@@ -29,6 +29,12 @@ def _post_dict(p: Post) -> dict:
         "date": p.post_date.isoformat() if p.post_date else None,
         "description_html": sanitize_post_html(p.description),
         "attachment_count": p.attachment_count,
+        # Translation (#143): the English title/description shown by default when
+        # a translation exists; the UI toggles to the original. Source lang labels
+        # the original.
+        "title_translated": p.post_title_translated,
+        "description_translated": p.description_translated,
+        "translated_source_lang": p.translated_source_lang,
     }
 
 

backend/app/tasks/translation.py

@@ -0,0 +1,101 @@
+"""Post-text translation Celery task (milestone 143).
+
+Backfills non-English post title/description to the target language via the
+self-hosted Interpreter LAN service, storing the result + engine_version so
+viewing is instant and re-runs are cache-fast. Sync (Celery workers are sync),
+same pattern as the other backfill sweeps. No-op unless translation is enabled,
+a base URL is set, and the service is healthy.
+"""
+import logging
+from datetime import UTC, datetime
+
+from celery.exceptions import SoftTimeLimitExceeded
+from sqlalchemy import or_, select
+
+from ..celery_app import celery
+from ..models import ImportSettings, Post
+from ..services import interpreter_client as ic
+from ..utils.text import html_to_plain
+from ._sync_engine import sync_session_factory as _sync_session_factory
+
+log = logging.getLogger(__name__)
+
+# Bound one run's work so it commits progress rather than dying at the time
+# limit; the rest resumes next cycle (idempotent — only untranslated posts are
+# picked, so an interrupted run just re-runs = rule-89 recovery).
+_MAX_POSTS_PER_RUN = 300
+
+
+@celery.task(
+    name="backend.app.tasks.translation.translate_posts",
+    soft_time_limit=1800, time_limit=2100,
+)
+def translate_posts() -> str:
+    """Translate untranslated non-English post title/description (default target
+    en) via Interpreter. Per-post [title, description] batch → per-post detected
+    language. Passthrough / already-target posts are marked handled (source ==
+    target) with no stored translation. 503 or a connection error interrupts the
+    run (retry next cycle); 400 stops it (fix config); posts done so far stay
+    committed. No-op unless configured + healthy. Returns a summary string."""
+    SessionLocal = _sync_session_factory()
+    with SessionLocal() as session:
+        cfg = ImportSettings.load_sync(session)
+        if not cfg.translation_enabled or not cfg.interpreter_base_url.strip():
+            return "disabled"
+        base_url = cfg.interpreter_base_url.strip()
+        target = (cfg.translation_target_lang or "en").strip() or "en"
+        if not ic.health(base_url):
+            return "interpreter unavailable"
+
+        posts = session.execute(
+            select(Post)
+            .where(Post.translated_source_lang.is_(None))
+            .where(or_(
+                Post.post_title.is_not(None), Post.description.is_not(None),
+            ))
+            .limit(_MAX_POSTS_PER_RUN)
+        ).scalars().all()
+
+        translated = 0
+        try:
+            for post in posts:
+                translated += _translate_one(session, post, base_url, target)
+                session.commit()   # per-post → an interrupted run keeps progress
+        except ic.InterpreterUnavailable:
+            session.rollback()
+            return f"interrupted (service down) — translated={translated}"
+        except ic.InterpreterBadRequest as e:
+            session.rollback()
+            log.warning("translate_posts bad request: %s", e)
+            return f"stopped (bad request) — translated={translated}"
+        except SoftTimeLimitExceeded:
+            return f"time limit — translated={translated}"
+    return f"translated={translated} scanned={len(posts)}"
+
+
+def _translate_one(session, post, base_url: str, target: str) -> int:
+    """Translate one post's title/description in place. Returns 1 if it stored a
+    translation, 0 for passthrough/empty (which still marks the post handled)."""
+    title = (post.post_title or "").strip()
+    desc = (html_to_plain(post.description) if post.description else "") or ""
+    desc = desc.strip()
+    fields: list[tuple[str, str]] = []
+    if title:
+        fields.append(("title", title))
+    if desc:
+        fields.append(("desc", desc))
+    if not fields:
+        post.translated_source_lang = target   # nothing to translate → handled
+        return 0
+    res = ic.translate([t for _, t in fields], base_url=base_url, target=target)
+    detected = res["detected_lang"] or target
+    if detected == target or res["engine"] == "none":
+        post.translated_source_lang = target   # already target language → handled
+        return 0
+    by_field = {f: res["translations"][i] for i, (f, _) in enumerate(fields)}
+    post.post_title_translated = by_field.get("title")
+    post.description_translated = by_field.get("desc")
+    post.translated_source_lang = detected
+    post.translation_engine_version = res["engine_version"]
+    post.translated_at = datetime.now(UTC)
+    return 1

frontend/src/components/modal/ProvenancePanel.vue

@@ -42,13 +42,23 @@
             · {{ e.post.attachment_count }} files
           </span>
         </div>
+        <div v-if="hasTranslation(e)" class="fc-prov__actions">
+          <a
+            href="#" @click.prevent="toggleOrig(e.provenance_id)"
+          >{{ showOrig[e.provenance_id] ? 'Show translation' : `Show original${langLabel(e)}` }}</a>
+        </div>
         <div v-if="e.post.description_html" class="fc-prov__actions">
           <a
             href="#" @click.prevent="toggleDesc(e.provenance_id)"
           >{{ expanded[e.provenance_id] ? 'Hide description ▴' : 'Show description ▾' }}</a>
         </div>
+        <!-- Translated body = plain text; original = sanitized HTML (#143). -->
+        <p
+          v-if="showTranslated(e) && expanded[e.provenance_id] && e.post.description_translated"
+          class="fc-prov__desc"
+        >{{ e.post.description_translated }}</p>
         <div
-          v-if="e.post.description_html && expanded[e.provenance_id]"
+          v-else-if="e.post.description_html && expanded[e.provenance_id]"
           class="fc-prov__desc" v-html="e.post.description_html"
         />
       </article>
@@ -117,8 +127,12 @@ const effectiveImage = computed(() => props.image ?? modal.current)
 // 2026-05-28. Reset when the viewed image changes.
 const expanded = reactive({})
 function toggleDesc(id) { expanded[id] = !expanded[id] }
+// Per-entry "show the original (untranslated) text" toggle (#143).
+const showOrig = reactive({})
+function toggleOrig(id) { showOrig[id] = !showOrig[id] }
 watch(() => effectiveId.value, () => {
   for (const k of Object.keys(expanded)) delete expanded[k]
+  for (const k of Object.keys(showOrig)) delete showOrig[k]
 })
 
 watch(
@@ -157,10 +171,23 @@ const show = computed(() => {
 const attachments = computed(() => state.value?.attachments || [])
 
 function postDate(e) { return formatPostDate(e.post.date) }
+// Translation-forward (#143): show the English by default when present.
+function hasTranslation(e) {
+  return !!(e.post.title_translated || e.post.description_translated)
+}
+function showTranslated(e) {
+  return hasTranslation(e) && !showOrig[e.provenance_id]
+}
+function langLabel(e) {
+  return e.post.translated_source_lang ? ` (${e.post.translated_source_lang})` : ''
+}
 function postTitle(e) {
   // Titles can arrive as stored HTML (e.g. "<strong>…</strong>"); render
   // as plain text (the CSS makes it bold).
-  return toPlainText(e.post.title) || `Post ${e.post.external_post_id}`
+  const t = showTranslated(e) && e.post.title_translated
+    ? e.post.title_translated
+    : e.post.title
+  return toPlainText(t) || `Post ${e.post.external_post_id}`
 }
 
 function openPost(postId, artistId) {

frontend/src/components/posts/PostCard.vue

@@ -58,16 +58,23 @@
       </div>
 
       <div class="fc-post-card__text">
-        <h3 v-if="plainTitle" class="fc-post-card__title">{{ plainTitle }}</h3>
+        <h3 v-if="displayTitle" class="fc-post-card__title">{{ displayTitle }}</h3>
         <h3 v-else class="fc-post-card__title fc-post-card__title--missing">
           Post {{ post.external_post_id }}
         </h3>
+        <!-- Translation toggle (#143): English shown by default; reveal the
+             original, labelled with its detected language. -->
+        <button
+          v-if="hasTranslation" type="button" class="fc-post-card__lang"
+          :title="showOriginal ? 'Show the English translation' : `Show the original${sourceLangLabel} text`"
+          @click.stop="showOriginal = !showOriginal"
+        >{{ showOriginal ? 'Show translation' : `Show original${sourceLangLabel}` }}</button>
 
         <!-- Faithful (semantic) body render once expanded: backend-sanitized
              HTML (headings, lists, links, inline images). Collapsed and the
              no-detail fallback stay plain text. -->
         <div
-          v-if="hasDescription && descExpanded && descHtml"
+          v-if="hasDescription && showHtmlBody"
           class="fc-post-card__desc fc-post-card__desc--html"
           v-html="descHtml"
         />
@@ -75,7 +82,7 @@
           v-else-if="hasDescription" ref="descEl"
           class="fc-post-card__desc"
           :class="{ 'fc-post-card__desc--clamped': !descExpanded }"
-        >{{ descText }}</p>
+        >{{ descTextDisplay }}</p>
         <p v-else class="fc-post-card__desc fc-post-card__desc--missing">
           (no description)
         </p>
@@ -231,6 +238,32 @@ const canExpand = computed(
   () => props.post.description_truncated === true || cssOverflow.value,
 )
 
+// --- translation-forward (#143): the English is shown by default when a
+// translation exists; a per-card toggle reveals the original. Translations are
+// plain text, so showTranslated also decides HTML-vs-plain body rendering.
+const showOriginal = ref(false)
+const hasTranslation = computed(
+  () => !!(props.post.post_title_translated || props.post.description_translated),
+)
+const showTranslated = computed(() => hasTranslation.value && !showOriginal.value)
+const sourceLangLabel = computed(() =>
+  props.post.translated_source_lang ? ` (${props.post.translated_source_lang})` : '',
+)
+const displayTitle = computed(() =>
+  showTranslated.value && props.post.post_title_translated
+    ? toPlainText(props.post.post_title_translated)
+    : plainTitle.value,
+)
+const descTextDisplay = computed(() => {
+  if (!showTranslated.value) return descText.value
+  return descExpanded.value
+    ? (detail.value?.description_translated_full || props.post.description_translated)
+    : props.post.description_translated
+})
+const showHtmlBody = computed(
+  () => !showTranslated.value && descExpanded.value && !!descHtml.value,
+)
+
 function measureOverflow () {
   const el = descEl.value
   cssOverflow.value = !!el && el.scrollHeight > el.clientHeight + 1
@@ -467,6 +500,19 @@ function formatBytes (n) {
   font-size: 0.85rem; font-weight: 600;
 }
 .fc-post-card__more:hover { text-decoration: underline; }
+/* Translation toggle (#143) — quiet secondary affordance under the title. */
+.fc-post-card__lang {
+  display: block; margin: 2px 0 6px; padding: 0;
+  background: none; border: 0; cursor: pointer;
+  color: rgb(var(--v-theme-on-surface-variant));
+  font-size: 0.75rem; font-weight: 600;
+}
+.fc-post-card__lang:hover {
+  text-decoration: underline; color: rgb(var(--v-theme-accent));
+}
+.fc-post-card__lang:focus-visible {
+  outline: 2px solid rgb(var(--v-theme-accent)); outline-offset: 1px;
+}
 
 .fc-post-card__atts {
   display: flex; flex-wrap: wrap; gap: 8px;

frontend/src/components/settings/MaintenancePanel.vue

@@ -13,6 +13,7 @@
       </p>
       <div class="fc-tile-stack">
         <ImportFiltersForm />
+        <TranslationCard />
       </div>
     </section>
 
@@ -69,6 +70,7 @@
 import { onMounted, onUnmounted } from 'vue'
 
 import ImportFiltersForm from './ImportFiltersForm.vue'
+import TranslationCard from './TranslationCard.vue'
 import MLBackfillCard from './MLBackfillCard.vue'
 import ThumbnailBackfillCard from './ThumbnailBackfillCard.vue'
 import ArchiveReextractCard from './ArchiveReextractCard.vue'

frontend/src/components/settings/TranslationCard.vue

@@ -0,0 +1,162 @@
+<template>
+  <MaintenanceTile
+    icon="mdi-translate"
+    title="Post translation (Interpreter)"
+    blurb="Translate non-English post titles + descriptions to English via your self-hosted Interpreter service, so archived posts read naturally."
+  >
+    <div class="d-flex align-center mb-3" style="gap: 10px;">
+      <span class="fc-section-h">Enabled</span>
+      <v-switch
+        v-model="enabled" :loading="busy" hide-details density="compact"
+        color="success" class="ml-auto" @update:model-value="onToggle"
+      />
+    </div>
+    <p class="fc-muted text-body-2 mb-3">
+      Point this at your Interpreter service. It stays off until a URL is set, and
+      only translates posts whose text isn't already in the target language — the
+      English is shown by default on post cards, with a toggle back to the original.
+    </p>
+
+    <v-text-field
+      v-model="baseUrl" label="Interpreter base URL"
+      placeholder="http://interpreter.your-domain/" density="compact"
+      hide-details class="mb-3" :disabled="busy" @change="onSave"
+    />
+    <v-text-field
+      v-model="targetLang" label="Target language" density="compact"
+      hide-details style="max-width: 160px;" class="mb-3" :disabled="busy"
+      @change="onSave"
+    />
+
+    <div class="d-flex align-center flex-wrap mb-3" style="gap: 8px;">
+      <v-icon size="12" :color="statusColor">mdi-circle</v-icon>
+      <span class="fc-muted text-body-2">{{ statusText }}</span>
+      <v-btn
+        size="x-small" variant="tonal" rounded="pill" class="ml-2"
+        :loading="testing" :disabled="!baseUrl" @click="onTest"
+      >Test connection</v-btn>
+      <span
+        v-if="testResult !== null" class="text-caption"
+        :class="testResult ? 'text-success' : 'text-error'"
+      >{{ testResult ? '✓ reachable' : '✗ unreachable' }}</span>
+    </div>
+
+    <div class="d-flex align-center flex-wrap" style="gap: 10px;">
+      <v-btn
+        size="small" variant="flat" color="accent" rounded="pill"
+        prepend-icon="mdi-translate" :loading="running"
+        :disabled="!enabled || !baseUrl" @click="onRun"
+      >Translate now</v-btn>
+      <span v-if="status" class="fc-muted text-caption">
+        {{ status.untranslated_count }}
+        post{{ status.untranslated_count === 1 ? '' : 's' }} awaiting translation
+      </span>
+    </div>
+
+    <v-alert
+      v-if="err" type="error" variant="tonal" density="compact"
+      class="mt-3" closable @click:close="err = null"
+    >{{ err }}</v-alert>
+  </MaintenanceTile>
+</template>
+
+<script setup>
+import { computed, onMounted, ref } from 'vue'
+import { toast } from '../../utils/toast.js'
+import { useApi } from '../../composables/useApi.js'
+import { useImportStore } from '../../stores/import.js'
+import MaintenanceTile from '../common/MaintenanceTile.vue'
+
+const api = useApi()
+const store = useImportStore()
+
+const enabled = ref(false)
+const baseUrl = ref('')
+const targetLang = ref('en')
+const busy = ref(false)
+const running = ref(false)
+const testing = ref(false)
+const testResult = ref(null)   // null = not tested this session; true/false = last result
+const status = ref(null)
+const err = ref(null)
+
+const statusColor = computed(() => {
+  if (!enabled.value || !baseUrl.value) return 'grey'
+  return status.value?.healthy ? 'success' : 'error'
+})
+const statusText = computed(() => {
+  if (!enabled.value) return 'Off'
+  if (!baseUrl.value) return 'No base URL set'
+  if (status.value == null) return 'Checking…'
+  return status.value.healthy ? 'Interpreter reachable' : 'Interpreter unreachable'
+})
+
+async function loadStatus() {
+  try { status.value = await api.get('/api/settings/translation/status') }
+  catch { status.value = null }
+}
+
+async function onTest() {
+  // Ping /v1/health for the CURRENTLY-typed URL (not the saved one), so a new
+  // URL can be verified before enabling. Also reflects in the status dot.
+  testing.value = true
+  err.value = null
+  testResult.value = null
+  try {
+    const r = await api.post('/api/settings/translation/test', {
+      body: { base_url: baseUrl.value.trim() },
+    })
+    testResult.value = !!r.healthy
+    if (status.value) status.value.healthy = !!r.healthy
+  } catch (e) {
+    err.value = e.message
+  } finally {
+    testing.value = false
+  }
+}
+
+onMounted(async () => {
+  try {
+    await store.loadSettings()
+    const s = store.settings || {}
+    enabled.value = !!s.translation_enabled
+    baseUrl.value = s.interpreter_base_url || ''
+    targetLang.value = s.translation_target_lang || 'en'
+  } catch { /* non-fatal */ }
+  await loadStatus()
+})
+
+async function save(patch) {
+  busy.value = true
+  err.value = null
+  try { await store.patchSettings(patch) }
+  catch (e) { err.value = e.message }
+  finally { busy.value = false }
+}
+
+async function onToggle(val) {
+  await save({ translation_enabled: !!val })
+  toast({ text: val ? 'Translation on' : 'Translation off', type: 'success' })
+  await loadStatus()
+}
+async function onSave() {
+  await save({
+    interpreter_base_url: baseUrl.value.trim(),
+    translation_target_lang: (targetLang.value || 'en').trim() || 'en',
+  })
+  await loadStatus()
+}
+async function onRun() {
+  running.value = true
+  err.value = null
+  try {
+    await api.post('/api/settings/translation/run')
+    toast({ text: 'Translation sweep started', type: 'success' })
+  } catch (e) {
+    err.value = e.message
+  } finally {
+    running.value = false
+    setTimeout(loadStatus, 1500)   // let the sweep make a dent, then refresh
+  }
+}
+</script>

tests/test_api_settings.py

@@ -28,6 +28,75 @@ async def test_patch_import_settings(client):
     assert body["transparency_threshold"] == 0.7
 
 
+@pytest.mark.asyncio
+async def test_translation_settings_defaults_and_patch(client):
+    # #143: translation is OFF by default with NO default host — the operator
+    # points it at their own Interpreter proxy and enables it.
+    body = await (await client.get("/api/settings/import")).get_json()
+    assert body["translation_enabled"] is False
+    assert body["interpreter_base_url"] == ""
+    assert body["translation_target_lang"] == "en"
+
+    ok = await client.patch("/api/settings/import", json={
+        "translation_enabled": True,
+        "interpreter_base_url": "http://interpreter.lan",
+    })
+    assert ok.status_code == 200
+    out = await ok.get_json()
+    assert out["translation_enabled"] is True
+    assert out["interpreter_base_url"] == "http://interpreter.lan"
+
+    # Type validation.
+    assert (await client.patch(
+        "/api/settings/import", json={"translation_enabled": "yes"})).status_code == 400
+    assert (await client.patch(
+        "/api/settings/import", json={"interpreter_base_url": 123})).status_code == 400
+
+
+@pytest.mark.asyncio
+async def test_translation_status_defaults(client):
+    # Off + no URL → no network health call, healthy False (#143).
+    body = await (await client.get("/api/settings/translation/status")).get_json()
+    assert body["enabled"] is False
+    assert body["base_url_set"] is False
+    assert body["healthy"] is False
+    assert "untranslated_count" in body
+
+
+@pytest.mark.asyncio
+async def test_translation_run_requires_config(client):
+    resp = await client.post("/api/settings/translation/run")
+    assert resp.status_code == 400   # disabled / no base URL
+
+
+@pytest.mark.asyncio
+async def test_translation_test_connection(client, monkeypatch):
+    # Tests a GIVEN url (not the saved one) without persisting anything.
+    monkeypatch.setattr("backend.app.api.settings.ic.health", lambda *a, **k: True)
+    resp = await client.post(
+        "/api/settings/translation/test", json={"base_url": "http://i.lan"})
+    assert resp.status_code == 200
+    assert (await resp.get_json())["healthy"] is True
+    # Empty URL → False, no health call.
+    empty = await client.post(
+        "/api/settings/translation/test", json={"base_url": ""})
+    assert (await empty.get_json())["healthy"] is False
+
+
+@pytest.mark.asyncio
+async def test_translation_run_enqueues_when_configured(client, monkeypatch):
+    monkeypatch.setattr(
+        "backend.app.tasks.translation.translate_posts.delay",
+        lambda *a, **k: type("R", (), {"id": "t1"})(),
+    )
+    await client.patch("/api/settings/import", json={
+        "translation_enabled": True, "interpreter_base_url": "http://i.lan",
+    })
+    resp = await client.post("/api/settings/translation/run")
+    assert resp.status_code == 202
+    assert (await resp.get_json())["celery_task_id"] == "t1"
+
+
 @pytest.mark.asyncio
 async def test_patch_rejects_non_object(client):
     resp = await client.patch("/api/settings/import", json=[1, 2, 3])

tests/test_interpreter_client.py

@@ -0,0 +1,108 @@
+"""Interpreter translation client (#143) — unit tests with mocked HTTP (no DB,
+no real network)."""
+import pytest
+
+from backend.app.services import interpreter_client as ic
+
+
+class _Resp:
+    def __init__(self, status_code=200, payload=None):
+        self.status_code = status_code
+        self._payload = payload or {}
+
+    def json(self):
+        return self._payload
+
+    def raise_for_status(self):
+        if self.status_code >= 400:
+            raise ic.requests.HTTPError(f"status {self.status_code}")
+
+
+def test_translate_maps_batch_in_order(monkeypatch):
+    captured = {}
+
+    def fake_post(url, json, timeout):
+        captured["json"] = json
+        return _Resp(200, {
+            "translatedText": ["The cat is cute", "Blonde gal!"],
+            "detectedLanguage": {"language": "ja", "confidence": 0.98},
+            "interpreter": {"engine": "llm", "engine_version": "ollama:x:12b"},
+        })
+
+    monkeypatch.setattr(ic.requests, "post", fake_post)
+    out = ic.translate(["ねこが可愛い", "金髪ギャル！"], base_url="http://i.lan")
+    assert out["translations"] == ["The cat is cute", "Blonde gal!"]
+    assert out["detected_lang"] == "ja"
+    assert out["engine_version"] == "ollama:x:12b"
+    assert captured["json"]["q"] == ["ねこが可愛い", "金髪ギャル！"]
+    assert captured["json"]["target"] == "en"
+
+
+def test_translate_passthrough_unchanged(monkeypatch):
+    # Already-English items come back unchanged in their slot (engine "none").
+    monkeypatch.setattr(ic.requests, "post", lambda *a, **k: _Resp(200, {
+        "translatedText": ["already english"],
+        "detectedLanguage": {"language": "en"},
+        "interpreter": {"engine": "none", "engine_version": None},
+    }))
+    out = ic.translate(["already english"], base_url="http://i.lan")
+    assert out["translations"] == ["already english"]
+    assert out["detected_lang"] == "en"
+    assert out["engine"] == "none"
+
+
+def test_translate_503_raises_unavailable(monkeypatch):
+    monkeypatch.setattr(ic.requests, "post", lambda *a, **k: _Resp(503, {}))
+    with pytest.raises(ic.InterpreterUnavailable):
+        ic.translate(["x"], base_url="http://i.lan")
+
+
+def test_translate_connection_error_raises_unavailable(monkeypatch):
+    def boom(*a, **k):
+        raise ic.requests.ConnectionError("refused")
+
+    monkeypatch.setattr(ic.requests, "post", boom)
+    with pytest.raises(ic.InterpreterUnavailable):
+        ic.translate(["x"], base_url="http://i.lan")
+
+
+def test_translate_400_raises_bad_request(monkeypatch):
+    monkeypatch.setattr(
+        ic.requests, "post", lambda *a, **k: _Resp(400, {"error": "bad target"})
+    )
+    with pytest.raises(ic.InterpreterBadRequest):
+        ic.translate(["x"], base_url="http://i.lan")
+
+
+def test_translate_empty_is_noop(monkeypatch):
+    def boom(*a, **k):
+        raise AssertionError("should not call the service for an empty batch")
+
+    monkeypatch.setattr(ic.requests, "post", boom)
+    assert ic.translate([], base_url="http://i.lan")["translations"] == []
+
+
+def test_health_true_when_llm_up(monkeypatch):
+    monkeypatch.setattr(
+        ic.requests, "get", lambda *a, **k: _Resp(200, {"engines": {"llm": True}})
+    )
+    assert ic.health("http://i.lan") is True
+
+
+def test_health_false_when_engine_down(monkeypatch):
+    monkeypatch.setattr(
+        ic.requests, "get", lambda *a, **k: _Resp(200, {"engines": {"llm": False}})
+    )
+    assert ic.health("http://i.lan") is False
+
+
+def test_health_false_on_error(monkeypatch):
+    def boom(*a, **k):
+        raise ic.requests.ConnectionError("refused")
+
+    monkeypatch.setattr(ic.requests, "get", boom)
+    assert ic.health("http://i.lan") is False
+
+
+def test_health_false_when_url_empty():
+    assert ic.health("") is False

tests/test_post_feed_service.py

@@ -283,6 +283,30 @@ async def test_scroll_item_shape_minimal(db):
     assert "description_full" not in item
 
 
+@pytest.mark.asyncio
+async def test_scroll_surfaces_translation_fields(db):
+    # #143: a translated post exposes the translated title/description + source
+    # lang, with the originals still present for the toggle.
+    artist = await _seed_artist(db, "alice-tr")
+    src = await _seed_source(db, artist.id, "pixiv", "https://p/alice-tr")
+    p = await _seed_post(
+        db, src.id, external_id="TR", post_date=datetime.now(UTC),
+        title="ねこ", description="<p>かわいい</p>",
+    )
+    p.post_title_translated = "cat"
+    p.description_translated = "cute"
+    p.translated_source_lang = "ja"
+    await db.commit()
+
+    page = await PostFeedService(db).scroll(cursor=None, limit=10)
+    item = page["items"][0]
+    assert item["post_title_translated"] == "cat"
+    assert item["description_translated"] == "cute"
+    assert item["translated_source_lang"] == "ja"
+    assert item["post_title"] == "ねこ"           # original kept for the toggle
+    assert item["description_plain"] == "かわいい"
+
+
 @pytest.mark.asyncio
 async def test_scroll_description_truncates_long_text(db):
     artist = await _seed_artist(db, "alice-long")

tests/test_translate_posts.py

@@ -0,0 +1,127 @@
+"""translate_posts sweep (#143) — integration, with a stubbed Interpreter client
+and the task's session factory pointed at the test's db_sync."""
+import pytest
+from sqlalchemy import select
+
+from backend.app.models import Artist, ImportSettings, Post
+from backend.app.tasks.translation import translate_posts
+
+pytestmark = pytest.mark.integration
+
+
+class _Ctx:
+    def __init__(self, s):
+        self.s = s
+
+    def __enter__(self):
+        return self.s
+
+    def __exit__(self, *a):
+        return False
+
+
+def _sf(db_sync):
+    class _SM:
+        def __call__(self):
+            return _Ctx(db_sync)
+
+    return _SM()
+
+
+def _artist(db):
+    a = Artist(name="A", slug="a")
+    db.add(a)
+    db.flush()
+    return a
+
+
+def _post(db, artist_id, *, title=None, desc=None, ext="p1"):
+    p = Post(
+        artist_id=artist_id, external_post_id=ext,
+        post_title=title, description=desc,
+    )
+    db.add(p)
+    db.flush()
+    return p
+
+
+def _enable(db, url="http://i.lan"):
+    cfg = db.execute(
+        select(ImportSettings).where(ImportSettings.id == 1)
+    ).scalar_one()
+    cfg.translation_enabled = True
+    cfg.interpreter_base_url = url
+    db.flush()
+
+
+def _patch(monkeypatch, db_sync):
+    monkeypatch.setattr(
+        "backend.app.tasks.translation._sync_session_factory",
+        lambda: _sf(db_sync),
+    )
+
+
+def test_translate_posts_stores_translation(db_sync, monkeypatch):
+    _patch(monkeypatch, db_sync)
+    monkeypatch.setattr("backend.app.tasks.translation.ic.health", lambda *a, **k: True)
+    monkeypatch.setattr(
+        "backend.app.tasks.translation.ic.translate",
+        lambda texts, **k: {
+            "translations": [f"EN:{t}" for t in texts],
+            "detected_lang": "ja", "engine": "llm", "engine_version": "v1",
+        },
+    )
+    a = _artist(db_sync)
+    p = _post(db_sync, a.id, title="ねこ", desc="かわいい")
+    _enable(db_sync)
+    db_sync.commit()
+
+    assert "translated=1" in translate_posts()
+    db_sync.refresh(p)
+    assert p.post_title_translated == "EN:ねこ"
+    assert p.description_translated == "EN:かわいい"
+    assert p.translated_source_lang == "ja"
+    assert p.translation_engine_version == "v1"
+
+
+def test_translate_posts_passthrough_english_marks_handled(db_sync, monkeypatch):
+    _patch(monkeypatch, db_sync)
+    monkeypatch.setattr("backend.app.tasks.translation.ic.health", lambda *a, **k: True)
+    monkeypatch.setattr(
+        "backend.app.tasks.translation.ic.translate",
+        lambda texts, **k: {
+            "translations": list(texts), "detected_lang": "en",
+            "engine": "none", "engine_version": None,
+        },
+    )
+    a = _artist(db_sync)
+    p = _post(db_sync, a.id, title="hello world", ext="p2")
+    _enable(db_sync)
+    db_sync.commit()
+
+    translate_posts()
+    db_sync.refresh(p)
+    assert p.translated_source_lang == "en"     # marked handled...
+    assert p.post_title_translated is None       # ...but nothing to show
+
+
+def test_translate_posts_disabled_is_noop(db_sync, monkeypatch):
+    _patch(monkeypatch, db_sync)
+    a = _artist(db_sync)
+    p = _post(db_sync, a.id, title="ねこ", ext="p3")
+    db_sync.commit()   # translation_enabled defaults False
+    assert translate_posts() == "disabled"
+    db_sync.refresh(p)
+    assert p.translated_source_lang is None
+
+
+def test_translate_posts_service_down_leaves_untranslated(db_sync, monkeypatch):
+    _patch(monkeypatch, db_sync)
+    monkeypatch.setattr("backend.app.tasks.translation.ic.health", lambda *a, **k: False)
+    a = _artist(db_sync)
+    p = _post(db_sync, a.id, title="ねこ", ext="p4")
+    _enable(db_sync)
+    db_sync.commit()
+    assert translate_posts() == "interpreter unavailable"
+    db_sync.refresh(p)
+    assert p.translated_source_lang is None       # will retry next run