feat(worker): use TDLib remote.unique_id as zero-false-positive dedup signal

The fileName + size repost detection from ff4e150 works but has a
theoretical false-positive: two unrelated files in the same channel
with identical names and identical total sizes get treated as duplicates.

TDLib's document.remote.unique_id is a stable identifier per file
content — every repost of the exact same file across messages keeps
the same unique_id. Using it as the first dedup check eliminates the
false-positive risk entirely.

Schema:
  - Package.remoteUniqueId (nullable, since existing rows lack it)
  - Index on (sourceChannelId, remoteUniqueId)

Pipeline:
  1. Capture remoteUniqueId in getChannelMessages + getTopicMessages
  2. Pass through TelegramMessage type
  3. processOneArchiveSet checks findPackageByRemoteUniqueId FIRST
     (before packageExistsBySourceMessage / findRepostedPackage)
  4. createPackageStub stores it on the new Package row

Existing 19,952 Packages have remoteUniqueId = NULL — they fall through
to the existing checks (source-msg-id, name+size, content-hash). New
ingestions populate it and benefit from the strong signal immediately.
Old Packages get backfilled organically when their content is
re-encountered and a new Package would otherwise be created.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

prisma/migrations/20260524000000_package_remote_unique_id/migration.sql

@@ -0,0 +1,10 @@
+-- AlterTable: capture TDLib's stable per-content identifier for new packages.
+-- Existing rows are NULL; they fall through to the other dedup checks until
+-- they're re-encountered organically.
+ALTER TABLE "packages" ADD COLUMN "remoteUniqueId" TEXT;
+
+-- CreateIndex: scoped to source channel because we want to dedup
+-- per-channel (the same file appearing in two different channels is still
+-- worth indexing twice — they're different ingestion sources).
+CREATE INDEX "packages_sourceChannelId_remoteUniqueId_idx"
+  ON "packages"("sourceChannelId", "remoteUniqueId");

prisma/schema.prisma

@@ -472,6 +472,11 @@ model Package {
   sourceChannelId String
   sourceMessageId BigInt
   sourceTopicId   BigInt?
+  /// TDLib's `remote.unique_id` for the FIRST part's file. Stable across
+  /// reposts of identical content in the same channel — used as the
+  /// strongest pre-download dedup signal (no false positives unlike
+  /// fileName + size matching).
+  remoteUniqueId  String?
   destChannelId   String?
   destMessageId   BigInt?
   destMessageIds  BigInt[]    @default([])
@@ -503,6 +508,7 @@ model Package {
   @@index([archiveType])
   @@index([creator])
   @@index([packageGroupId])
+  @@index([sourceChannelId, remoteUniqueId])
   @@map("packages")
 }
 

worker/src/archive/multipart.ts

@@ -11,8 +11,11 @@ export interface TelegramMessage {
   fileSize: bigint;
   date: Date;
   mediaAlbumId?: string;
-  replyToMessageId?: bigint;  // NEW
-  caption?: string;            // NEW
+  replyToMessageId?: bigint;
+  caption?: string;
+  /** TDLib's `remote.unique_id` for the file — stable across reposts of
+   *  the exact same content. Empty string if the message didn't expose it. */
+  remoteUniqueId?: string;
 }
 
 export interface ArchiveSet {

worker/src/db/queries.ts

@@ -82,6 +82,8 @@ export interface CreatePackageStubInput {
   sourceChannelId: string;
   sourceMessageId: bigint;
   sourceTopicId?: bigint | null;
+  /** TDLib remote.unique_id of the first part — for future dedup. */
+  remoteUniqueId?: string | null;
   destChannelId: string;
   destMessageId: bigint;
   destMessageIds: bigint[];
@@ -111,6 +113,7 @@ export async function createPackageStub(
       sourceChannelId: input.sourceChannelId,
       sourceMessageId: input.sourceMessageId,
       sourceTopicId: input.sourceTopicId ?? undefined,
+      remoteUniqueId: input.remoteUniqueId ?? undefined,
       destChannelId: input.destChannelId,
       destMessageId: input.destMessageId,
       destMessageIds: input.destMessageIds,
@@ -189,6 +192,34 @@ export async function packageExistsBySourceMessage(
   return pkg !== null;
 }
 
+/**
+ * Strongest pre-download dedup signal: a Package in this channel already
+ * has a matching TDLib remote.unique_id. The unique_id is stable across
+ * reposts of the exact same file content, so a hit is a guaranteed
+ * (lossless) duplicate. No false positives.
+ *
+ * Falls back to the older findRepostedPackage (name + size) for packages
+ * that were ingested before we started capturing remote.unique_id.
+ */
+export async function findPackageByRemoteUniqueId(
+  sourceChannelId: string,
+  remoteUniqueId: string
+): Promise<{
+  id: string;
+  destMessageId: bigint | null;
+  sourceTopicId: bigint | null;
+} | null> {
+  return db.package.findFirst({
+    where: {
+      sourceChannelId,
+      remoteUniqueId,
+      destMessageId: { not: null },
+    },
+    orderBy: { sourceTopicId: { sort: "desc", nulls: "last" } },
+    select: { id: true, destMessageId: true, sourceTopicId: true },
+  });
+}
+
 /**
  * Detect a likely repost: same source channel + same fileName + same total
  * fileSize already exists with destMessageId set. Used to skip downloads

worker/src/tdlib/download.ts

@@ -51,6 +51,10 @@ interface TdMessage {
           path?: string;
           is_downloading_completed?: boolean;
         };
+        remote?: {
+          /** Stable identifier across reposts of the same file content. */
+          unique_id?: string;
+        };
       };
     };
     photo?: {
@@ -231,6 +235,7 @@ export async function getChannelMessages(
             mediaAlbumId: msg.media_album_id && msg.media_album_id !== "0" ? msg.media_album_id : undefined,
             replyToMessageId: msg.reply_to_message_id ? BigInt(msg.reply_to_message_id) : undefined,
             caption: msg.content?.caption?.text || undefined,
+            remoteUniqueId: doc.document.remote?.unique_id || undefined,
           });
           continue;
         }

worker/src/tdlib/topics.ts

@@ -210,6 +210,7 @@ export async function getTopicMessages(
             document?: {
               id: number;
               size: number;
+              remote?: { unique_id?: string };
             };
           };
           photo?: {
@@ -257,6 +258,7 @@ export async function getTopicMessages(
           fileSize: BigInt(doc.document.size),
           date: new Date(msg.date * 1000),
           mediaAlbumId: msg.media_album_id && msg.media_album_id !== "0" ? msg.media_album_id : undefined,
+          remoteUniqueId: doc.document.remote?.unique_id || undefined,
         });
         continue;
       }

worker/src/worker.ts

@@ -32,6 +32,7 @@ import {
   deleteSkippedPackage,
   getCappedSkippedMessageIds,
   findRepostedPackage,
+  findPackageByRemoteUniqueId,
   getRetryableSkippedMessageIds,
   updatePackageTopicContext,
 } from "./db/queries.js";
@@ -1240,6 +1241,38 @@ async function processOneArchiveSet(
 
   const archiveName = archiveSet.parts[0].fileName;
 
+  // ── Earliest skip: remote.unique_id match ──
+  // TDLib reports a stable unique_id per file content. If we already have a
+  // Package in this channel with the same unique_id, it's the exact same
+  // file content reposted at a new message ID — zero false positives.
+  const firstRemoteUniqueId = archiveSet.parts[0].remoteUniqueId;
+  if (firstRemoteUniqueId) {
+    const match = await findPackageByRemoteUniqueId(channel.id, firstRemoteUniqueId);
+    if (match) {
+      counters.zipsDuplicate++;
+      accountLog.info(
+        {
+          fileName: archiveSet.parts[0].fileName,
+          sourceMessageId: Number(archiveSet.parts[0].id),
+          remoteUniqueId: firstRemoteUniqueId,
+          existingPackageId: match.id,
+          existingDestMessageId: match.destMessageId ? Number(match.destMessageId) : null,
+        },
+        "Skipping — remote.unique_id matches an existing Package in this channel"
+      );
+      await updateRunActivity(runId, {
+        currentActivity: `Skipped ${archiveSet.parts[0].fileName} (already ingested by unique_id)`,
+        currentStep: "deduplicating",
+        currentChannel: channelTitle,
+        currentFile: archiveSet.parts[0].fileName,
+        currentFileNum: setIdx + 1,
+        totalFiles: totalSets,
+        zipsDuplicate: counters.zipsDuplicate,
+      });
+      return null;
+    }
+  }
+
   // ── Early skip: check if this archive set was already ingested ──
   // This avoids re-downloading large archives that were processed in a prior run.
   const alreadyIngested = await packageExistsBySourceMessage(
@@ -1705,6 +1738,7 @@ async function processOneArchiveSet(
         sourceChannelId: channel.id,
         sourceMessageId: archiveSet.parts[0].id,
         sourceTopicId,
+        remoteUniqueId: archiveSet.parts[0].remoteUniqueId ?? null,
         destChannelId,
         destMessageId: destResult.messageId,
         destMessageIds: destResult.messageIds,