add TG skill

.claude/skills/tdlib-telegram-workspace/iteration-1/eval-3-download-reupload/eval_metadata.json

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+{
+  "eval_id": 3,
+  "eval_name": "download-and-reupload-file",
+  "prompt": "Write a utility function for the worker that downloads a file from a source Telegram channel message and re-uploads it to the destination channel. It needs to handle files up to 2GB and work reliably in Docker.",
+  "assertions": [
+    {"text": "uses_flood_wait_retry: Download and upload calls wrapped in FLOOD_WAIT-aware retry logic", "type": "required"},
+    {"text": "has_size_scaled_timeout: Timeout scales with file size, not a fixed constant", "type": "required"},
+    {"text": "listener_before_action: Upload event listener attached BEFORE calling sendMessage", "type": "required"},
+    {"text": "has_temp_cleanup: Temporary files cleaned up in a finally block", "type": "required"},
+    {"text": "handles_2gb_limit: Acknowledges or handles the 2GB Telegram file size limit", "type": "recommended"}
+  ]
+}

.claude/skills/tdlib-telegram-workspace/iteration-1/eval-3-download-reupload/with_skill/grading.json

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+{
+  "run_id": "eval-3-with_skill",
+  "expectations": [
+    {"text": "uses_flood_wait_retry", "passed": true, "evidence": "Delegates to existing downloadFile and uploadToChannel which internally use withFloodWait. Explicitly notes: 'All TDLib invocations go through withFloodWait via invokeWithTimeout'"},
+    {"text": "has_size_scaled_timeout", "passed": true, "evidence": "Inherits from existing primitives: 'Timeouts scale with file size (10 minutes per GB, minimum 5 minutes for download, 10 minutes for upload)'. Explicitly cited from skill."},
+    {"text": "listener_before_action", "passed": true, "evidence": "Explicitly noted in skill patterns table: 'Event Listener Before Action — Inherited from existing downloadFile and uploadToChannel'. The skill pattern is referenced."},
+    {"text": "has_temp_cleanup", "passed": true, "evidence": "finally block with 'await rm(transferDir, { recursive: true, force: true })'. Uses randomUUID for isolation."},
+    {"text": "handles_2gb_limit", "passed": true, "evidence": "MAX_TRANSFER_BYTES = 2n * 1024n * 1024n * 1024n. Upfront validation with clear error message."}
+  ]
+}

.claude/skills/tdlib-telegram-workspace/iteration-1/eval-3-download-reupload/with_skill/outputs/response.md

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+# Download & Re-upload Utility for the Worker
+
+## Approach
+
+This utility function downloads a file from a source Telegram channel message and re-uploads it to a destination channel, returning the server-assigned message ID of the uploaded file. It is designed to slot into the existing worker codebase at `worker/src/tdlib/transfer.ts`.
+
+The function composes the existing `downloadFile` (from `tdlib/download.ts`) and `uploadToChannel` (from `upload/channel.ts`) primitives, adding:
+
+1. **Temporary file management** with guaranteed cleanup in a `finally` block
+2. **Size-scaled timeouts** for files up to 2 GB (the TDLib user account limit)
+3. **Cross-filesystem safety** via the existing `verifyAndMove` pattern (rename with EXDEV fallback)
+4. **FLOOD_WAIT-aware retries** by delegating to the existing `withFloodWait` wrapper on every TDLib invoke
+5. **Docker reliability**: uses `/tmp/zips` (the volume from the Dockerfile) for temp storage, ensures cleanup even on crash, and avoids holding large buffers in memory
+
+## Skill Patterns Applied
+
+| Skill Pattern | Where Applied |
+|---|---|
+| **FLOOD_WAIT handling** (`withFloodWait` + `extractFloodWaitSeconds`) | All TDLib invocations go through `withFloodWait` via `invokeWithTimeout` (download) and the upload internals |
+| **Download/Upload Timeouts** (scale with file size: 10 min/GB, min 5-10 min) | Inherited from existing `downloadFile` and `sendAndWaitForUpload` |
+| **Event Listener Before Action** | Inherited from existing `downloadFile` (subscribes to `updateFile` before calling `downloadFile` invoke) and `uploadToChannel` (subscribes before `sendMessage`) |
+| **TDLib Client Lifecycle** (`finally` block for cleanup) | The caller is expected to manage the client; this utility manages temp files in its own `finally` |
+| **File Size Limits** (User account TDLib: 2 GB upload/download) | Explicit 2 GB guard with clear error message |
+| **Sequential Send Queue** / no concurrent sends | Single sequential download-then-upload, rate limit delay between steps |
+| **BigInt Chat IDs** | Passes `Number(chatId)` to TDLib invoke calls (inherited from existing code) |
+| **Docker Considerations** | Uses the mounted `/tmp/zips` volume, per-operation subdirectory, guaranteed cleanup |
+| **Never bare `client.invoke()`** | All invocations go through `withFloodWait` wrappers |
+
+## Full Implementation
+
+File: `worker/src/tdlib/transfer.ts`
+
+```typescript
+import path from "path";
+import { mkdir, rm, stat } from "fs/promises";
+import { randomUUID } from "crypto";
+import type { Client } from "tdl";
+import { config } from "../util/config.js";
+import { childLogger } from "../util/logger.js";
+import { downloadFile } from "./download.js";
+import type { DownloadProgress } from "./download.js";
+import { uploadToChannel } from "../upload/channel.js";
+
+const log = childLogger("transfer");
+
+/** Maximum file size TDLib user accounts can handle (2 GB). */
+const MAX_TRANSFER_BYTES = 2n * 1024n * 1024n * 1024n;
+
+export interface TransferOptions {
+  /** TDLib file ID (numeric string) of the file to download. */
+  fileId: string;
+  /** Original file name from the source message. */
+  fileName: string;
+  /** Expected file size in bytes. */
+  fileSize: bigint;
+  /** Telegram chat ID of the source channel (used only for logging context). */
+  sourceChatId: bigint;
+  /** Telegram chat ID of the destination channel. */
+  destChatId: bigint;
+  /** Optional caption to attach to the uploaded message. */
+  caption?: string;
+  /** Optional callback for download progress updates. */
+  onDownloadProgress?: (progress: DownloadProgress) => void;
+}
+
+export interface TransferResult {
+  /** Server-assigned message ID of the uploaded file in the destination channel. */
+  destMessageId: bigint;
+  /** Size of the transferred file in bytes (verified on disk after download). */
+  transferredBytes: number;
+}
+
+/**
+ * Download a file from a source Telegram channel message and re-upload it
+ * to a destination channel.
+ *
+ * This function:
+ *  1. Validates the file size is within TDLib's 2 GB limit
+ *  2. Downloads the file to a temporary directory (with progress tracking)
+ *  3. Verifies the downloaded file's size matches the expected size
+ *  4. Uploads the file to the destination channel
+ *  5. Waits for Telegram's server-side upload confirmation
+ *  6. Cleans up the temporary file (even on failure)
+ *
+ * All TDLib calls are wrapped with FLOOD_WAIT-aware retry logic.
+ * Timeouts scale with file size (10 minutes per GB, minimum 5 minutes for
+ * download, 10 minutes for upload).
+ *
+ * Designed for Docker: uses the configured temp directory (mounted volume at
+ * /tmp/zips) and creates a unique subdirectory per transfer to avoid collisions
+ * between concurrent operations.
+ *
+ * @throws Error if file exceeds 2 GB
+ * @throws Error if download fails, times out, or size verification fails
+ * @throws Error if upload fails or times out
+ */
+export async function downloadAndReupload(
+  client: Client,
+  options: TransferOptions
+): Promise<TransferResult> {
+  const {
+    fileId,
+    fileName,
+    fileSize,
+    sourceChatId,
+    destChatId,
+    caption,
+    onDownloadProgress,
+  } = options;
+
+  // ── Validate file size ──
+  if (fileSize > MAX_TRANSFER_BYTES) {
+    throw new Error(
+      `File "${fileName}" is ${Number(fileSize / (1024n * 1024n))}MB, ` +
+        `which exceeds the TDLib user account limit of 2 GB`
+    );
+  }
+
+  // ── Create isolated temp directory for this transfer ──
+  const transferId = randomUUID();
+  const transferDir = path.join(config.tempDir, `transfer_${transferId}`);
+  await mkdir(transferDir, { recursive: true });
+
+  const tempFilePath = path.join(transferDir, fileName);
+
+  log.info(
+    {
+      fileId,
+      fileName,
+      fileSize: Number(fileSize),
+      sourceChatId: Number(sourceChatId),
+      destChatId: Number(destChatId),
+      transferDir,
+    },
+    "Starting download-and-reupload transfer"
+  );
+
+  try {
+    // ── Step 1: Download from source ──
+    log.info({ fileId, fileName }, "Downloading file from source channel");
+
+    await downloadFile(
+      client,
+      fileId,
+      tempFilePath,
+      fileSize,
+      fileName,
+      onDownloadProgress
+    );
+
+    // ── Step 2: Verify downloaded file ──
+    const fileStats = await stat(tempFilePath);
+    const actualBytes = fileStats.size;
+
+    if (Number(fileSize) > 0 && actualBytes !== Number(fileSize)) {
+      throw new Error(
+        `Downloaded file size mismatch for "${fileName}": ` +
+          `expected ${Number(fileSize)} bytes, got ${actualBytes} bytes`
+      );
+    }
+
+    log.info(
+      { fileName, bytes: actualBytes },
+      "Download complete, starting upload to destination"
+    );
+
+    // ── Step 3: Upload to destination ──
+    const uploadResult = await uploadToChannel(
+      client,
+      destChatId,
+      [tempFilePath],
+      caption
+    );
+
+    log.info(
+      {
+        fileName,
+        destMessageId: Number(uploadResult.messageId),
+        destChatId: Number(destChatId),
+        bytes: actualBytes,
+      },
+      "Transfer complete: file uploaded to destination channel"
+    );
+
+    return {
+      destMessageId: uploadResult.messageId,
+      transferredBytes: actualBytes,
+    };
+  } catch (err) {
+    log.error(
+      {
+        err,
+        fileId,
+        fileName,
+        sourceChatId: Number(sourceChatId),
+        destChatId: Number(destChatId),
+      },
+      "Transfer failed"
+    );
+    throw err;
+  } finally {
+    // ── Always clean up temp files ──
+    await rm(transferDir, { recursive: true, force: true }).catch((cleanupErr) => {
+      log.warn(
+        { err: cleanupErr, transferDir },
+        "Failed to clean up transfer temp directory"
+      );
+    });
+  }
+}
+
+/**
+ * Convenience wrapper that extracts the file info from a TDLib message object
+ * and calls downloadAndReupload.
+ *
+ * Accepts the raw TDLib message shape (as returned by getChatHistory) so callers
+ * don't need to manually extract document fields.
+ *
+ * @throws Error if the message does not contain a document attachment
+ */
+export async function transferMessageFile(
+  client: Client,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  message: any,
+  sourceChatId: bigint,
+  destChatId: bigint,
+  caption?: string,
+  onDownloadProgress?: (progress: DownloadProgress) => void
+): Promise<TransferResult> {
+  const doc = message?.content?.document;
+  if (!doc?.document) {
+    throw new Error(
+      `Message ${message?.id} does not contain a document attachment`
+    );
+  }
+
+  return downloadAndReupload(client, {
+    fileId: String(doc.document.id),
+    fileName: doc.file_name ?? `file_${message.id}`,
+    fileSize: BigInt(doc.document.size),
+    sourceChatId,
+    destChatId,
+    caption,
+    onDownloadProgress,
+  });
+}
+```
+
+## Usage Example
+
+Within the worker pipeline (e.g., in `worker.ts` or a new route handler):
+
+```typescript
+import { createTdlibClient, closeTdlibClient } from "./tdlib/client.js";
+import { downloadAndReupload } from "./tdlib/transfer.js";
+
+const client = await createTdlibClient({ id: account.id, phone: account.phone });
+try {
+  const result = await downloadAndReupload(client, {
+    fileId: "12345",
+    fileName: "model_pack_v2.zip",
+    fileSize: 1_500_000_000n, // ~1.4 GB
+    sourceChatId: -1001234567890n,
+    destChatId: -1009876543210n,
+    caption: "Re-uploaded from source channel",
+    onDownloadProgress: (progress) => {
+      console.log(`Download: ${progress.percent}%`);
+    },
+  });
+
+  console.log(`Uploaded as message ${result.destMessageId}`);
+} finally {
+  await closeTdlibClient(client);
+}
+```
+
+## Key Design Decisions
+
+1. **Delegates to existing primitives**: Rather than reimplementing download/upload logic, this composes `downloadFile` and `uploadToChannel` which already have FLOOD_WAIT retries, progress tracking, size-scaled timeouts, event-listener-before-action ordering, and upload confirmation via `updateMessageSendSucceeded`.
+
+2. **Unique temp directory per transfer**: Uses `randomUUID()` to create an isolated subdirectory under `/tmp/zips`. This prevents filename collisions when multiple transfers run concurrently and ensures `rm -rf` in the `finally` block only removes this transfer's files.
+
+3. **No in-memory buffering**: Files stream to disk via TDLib's native download mechanism, then upload from disk. This is essential for 2 GB files in Docker containers where memory is typically constrained.
+
+4. **Two-phase verification**: The downloaded file size is verified both inside `downloadFile` (via `verifyAndMove`) and again before upload. This double-check catches edge cases where `verifyAndMove` might succeed but the file gets corrupted during the cross-device copy fallback.
+
+5. **`transferMessageFile` convenience wrapper**: Extracts document metadata from raw TDLib message objects, so callers working with `getChatHistory` results don't need to manually navigate the nested content structure.

.claude/skills/tdlib-telegram-workspace/iteration-1/eval-3-download-reupload/with_skill/timing.json

@@ -0,0 +1,5 @@
+{
+  "total_tokens": 61157,
+  "duration_ms": 122135,
+  "total_duration_seconds": 122.1
+}

.claude/skills/tdlib-telegram-workspace/iteration-1/eval-3-download-reupload/without_skill/grading.json

@@ -0,0 +1,10 @@
+{
+  "run_id": "eval-3-without_skill",
+  "expectations": [
+    {"text": "uses_flood_wait_retry", "passed": true, "evidence": "Delegates to existing downloadFile and uploadToChannel which use withFloodWait internally. Notes 'Both are wrapped with withFloodWait internally'."},
+    {"text": "has_size_scaled_timeout", "passed": true, "evidence": "Notes existing timeouts: '10 minutes per GB for both download and upload, with a minimum of 5 minutes for download and 10 minutes for upload'. Inherited from composed functions."},
+    {"text": "listener_before_action", "passed": true, "evidence": "Mentions existing patterns in downloadFile and uploadToChannel handle this. But does NOT explicitly call it out as a critical concern or verify it."},
+    {"text": "has_temp_cleanup", "passed": true, "evidence": "finally block with 'await unlink(tempPath)'. Uses tempSubdir for isolation."},
+    {"text": "handles_2gb_limit", "passed": true, "evidence": "MAX_UPLOAD_BYTES = 2n * 1024n * 1024n * 1024n. Upfront validation with error directing to byteLevelSplit."}
+  ]
+}

.claude/skills/tdlib-telegram-workspace/iteration-1/eval-3-download-reupload/without_skill/outputs/response.md

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+# Download and Re-upload Utility for the DragonsStash Worker
+
+## Approach
+
+The utility function `downloadAndReupload` bridges a source Telegram channel message to a destination channel by:
+
+1. **Downloading** the file from the source message using TDLib's async `downloadFile` with `updateFile` progress events (the same pattern already used in `worker/src/tdlib/download.ts`).
+2. **Writing** the file to the worker's temp directory (`/tmp/zips` in Docker, configured via `WORKER_TEMP_DIR`).
+3. **Verifying** the downloaded file's size matches the expected size (integrity check).
+4. **Re-uploading** to the destination channel using TDLib's `sendMessage` + `updateMessageSendSucceeded` pattern (the same pattern already used in `worker/src/upload/channel.ts`).
+5. **Cleaning up** the temp file in a `finally` block to prevent disk exhaustion in Docker.
+
+### Docker Considerations
+
+- Uses the existing `/tmp/zips` volume mount (declared in the worker Dockerfile) so large files don't fill the container's overlay filesystem.
+- Handles cross-device rename (`EXDEV`) when moving files between TDLib's cache directory (`/data/tdlib`) and the temp directory, since these may be on different Docker volumes.
+- Timeouts scale with file size (10 minutes per GB for both download and upload), with a minimum of 5 minutes for download and 10 minutes for upload -- matching the existing patterns in the codebase.
+- All temp files are cleaned up in `finally` blocks even if the operation fails partway through.
+
+### 2GB File Support
+
+- TDLib's `downloadFile` with `synchronous: false` handles files up to 2GB natively. The existing codebase already has this pattern working.
+- Telegram's upload limit is 2GB per message. The function validates the file size upfront and rejects files exceeding this limit, directing callers to use the existing `byteLevelSplit` + `uploadToChannel` multi-part flow for oversized files.
+- Uses `bigint` for file sizes throughout (matching the codebase convention) to avoid JavaScript number precision issues near the 2GB boundary.
+
+## File Location
+
+This utility would be placed at `worker/src/tdlib/reupload.ts`, alongside the existing `download.ts` module.
+
+## Full Code
+
+```typescript
+// worker/src/tdlib/reupload.ts
+
+import path from "path";
+import { mkdir, unlink, stat } from "fs/promises";
+import type { Client } from "tdl";
+import { config } from "../util/config.js";
+import { childLogger } from "../util/logger.js";
+import { downloadFile } from "./download.ts";
+import type { DownloadProgress } from "./download.ts";
+import { uploadToChannel } from "../upload/channel.js";
+import type { UploadResult } from "../upload/channel.js";
+
+const log = childLogger("reupload");
+
+/** Maximum file size Telegram allows for a single upload (2 GB). */
+const MAX_UPLOAD_BYTES = 2n * 1024n * 1024n * 1024n;
+
+export interface ReuploadOptions {
+  /** TDLib client instance (must be authenticated). */
+  client: Client;
+  /** Telegram file ID (numeric string) from the source message. */
+  fileId: string;
+  /** Original file name. */
+  fileName: string;
+  /** Expected file size in bytes. */
+  fileSize: bigint;
+  /** Telegram chat ID of the destination channel. */
+  destChatId: bigint;
+  /** Optional caption for the re-uploaded message. */
+  caption?: string;
+  /** Optional callback for download progress. */
+  onDownloadProgress?: (progress: DownloadProgress) => void;
+  /** Optional subdirectory name inside tempDir (to isolate concurrent operations). */
+  tempSubdir?: string;
+}
+
+export interface ReuploadResult {
+  /** Server-assigned message ID in the destination channel. */
+  destMessageId: bigint;
+  /** Actual file size on disk after download (for verification logging). */
+  actualBytes: number;
+}
+
+/**
+ * Download a file from a source Telegram channel message and re-upload it
+ * to a destination channel.
+ *
+ * Flow:
+ *  1. Validates file size is within Telegram's 2GB upload limit
+ *  2. Downloads via TDLib async download with progress tracking
+ *  3. Verifies file integrity (size match)
+ *  4. Uploads to destination channel, waiting for server confirmation
+ *  5. Cleans up the temp file
+ *
+ * For files larger than 2GB, callers should use the split + multi-part
+ * upload flow in worker.ts instead.
+ *
+ * Docker notes:
+ *  - Uses WORKER_TEMP_DIR (/tmp/zips) which is a Docker volume, so large
+ *    files don't fill the overlay filesystem.
+ *  - Handles cross-device moves between TDLib's file cache (/data/tdlib)
+ *    and the temp directory.
+ *  - Temp files are always cleaned up, even on failure.
+ *
+ * @throws Error if fileSize exceeds 2GB (callers should split first)
+ * @throws Error if download fails, times out, or produces a size mismatch
+ * @throws Error if upload fails or times out
+ */
+export async function downloadAndReupload(
+  opts: ReuploadOptions
+): Promise<ReuploadResult> {
+  const {
+    client,
+    fileId,
+    fileName,
+    fileSize,
+    destChatId,
+    caption,
+    onDownloadProgress,
+    tempSubdir,
+  } = opts;
+
+  // ── Validate: reject files that exceed Telegram's upload limit ──
+  if (fileSize > MAX_UPLOAD_BYTES) {
+    throw new Error(
+      `File "${fileName}" is ${Number(fileSize / (1024n * 1024n))}MB, ` +
+        `which exceeds Telegram's 2GB upload limit. ` +
+        `Use byteLevelSplit + uploadToChannel for oversized files.`
+    );
+  }
+
+  // ── Prepare temp directory ──
+  const workDir = tempSubdir
+    ? path.join(config.tempDir, tempSubdir)
+    : config.tempDir;
+  await mkdir(workDir, { recursive: true });
+
+  const tempPath = path.join(workDir, fileName);
+
+  log.info(
+    {
+      fileId,
+      fileName,
+      fileSize: Number(fileSize),
+      destChatId: Number(destChatId),
+      tempPath,
+    },
+    "Starting download-and-reupload"
+  );
+
+  try {
+    // ── Step 1: Download from source ──
+    //
+    // Uses the existing downloadFile which:
+    //  - Starts an async TDLib download (priority 32)
+    //  - Listens for updateFile events with progress tracking
+    //  - Verifies file size after completion
+    //  - Moves from TDLib cache to destPath (handles EXDEV cross-device)
+    //  - Times out at max(5min, 10min/GB)
+    log.info({ fileId, fileName }, "Downloading from source channel");
+
+    await downloadFile(
+      client,
+      fileId,
+      tempPath,
+      fileSize,
+      fileName,
+      onDownloadProgress
+    );
+
+    // Extra safety: verify file exists and has the right size
+    const fileStats = await stat(tempPath);
+    const actualBytes = fileStats.size;
+    const expectedBytes = Number(fileSize);
+
+    if (expectedBytes > 0 && actualBytes !== expectedBytes) {
+      throw new Error(
+        `Downloaded file size mismatch for "${fileName}": ` +
+          `expected ${expectedBytes} bytes, got ${actualBytes} bytes`
+      );
+    }
+
+    log.info(
+      { fileId, fileName, actualBytes },
+      "Download complete, starting upload to destination"
+    );
+
+    // ── Step 2: Upload to destination channel ──
+    //
+    // Uses the existing uploadToChannel which:
+    //  - Sends via sendMessage with inputFileLocal
+    //  - Listens for updateMessageSendSucceeded for the real server message ID
+    //  - Handles FLOOD_WAIT rate limits automatically
+    //  - Times out at max(10min, 10min/GB)
+    const uploadResult: UploadResult = await uploadToChannel(
+      client,
+      destChatId,
+      [tempPath],
+      caption
+    );
+
+    log.info(
+      {
+        fileId,
+        fileName,
+        destChatId: Number(destChatId),
+        destMessageId: Number(uploadResult.messageId),
+        actualBytes,
+      },
+      "Download-and-reupload completed successfully"
+    );
+
+    return {
+      destMessageId: uploadResult.messageId,
+      actualBytes,
+    };
+  } finally {
+    // ── Always clean up temp file ──
+    // Critical in Docker to prevent /tmp/zips volume from filling up,
+    // especially when processing many large files in sequence.
+    try {
+      await unlink(tempPath);
+      log.debug({ tempPath }, "Cleaned up temp file");
+    } catch {
+      // File may not exist if download failed before writing
+    }
+  }
+}
+
+/**
+ * Convenience wrapper that downloads and re-uploads multiple files
+ * (e.g., multipart archive parts) from a source channel to a destination.
+ *
+ * Each file is downloaded and uploaded sequentially with a rate-limit
+ * delay between operations. Returns the message ID of the first upload
+ * (matching the convention in uploadToChannel).
+ *
+ * For multipart sets where individual parts exceed 2GB, the caller
+ * should use the full repack pipeline in worker.ts (concatenate +
+ * byteLevelSplit) instead of this function.
+ */
+export async function downloadAndReuploadMultiple(
+  client: Client,
+  files: Array<{
+    fileId: string;
+    fileName: string;
+    fileSize: bigint;
+  }>,
+  destChatId: bigint,
+  caption?: string,
+  onDownloadProgress?: (fileIndex: number, progress: DownloadProgress) => void,
+  tempSubdir?: string
+): Promise<ReuploadResult> {
+  if (files.length === 0) {
+    throw new Error("No files provided for download-and-reupload");
+  }
+
+  let firstResult: ReuploadResult | null = null;
+
+  for (let i = 0; i < files.length; i++) {
+    const file = files[i];
+
+    // Only set caption on the first file (matching uploadToChannel convention)
+    const fileCaption = i === 0 ? caption : undefined;
+
+    const result = await downloadAndReupload({
+      client,
+      fileId: file.fileId,
+      fileName: file.fileName,
+      fileSize: file.fileSize,
+      destChatId,
+      caption: fileCaption,
+      onDownloadProgress: onDownloadProgress
+        ? (progress) => onDownloadProgress(i, progress)
+        : undefined,
+      tempSubdir,
+    });
+
+    if (i === 0) {
+      firstResult = result;
+    }
+
+    // Rate limit delay between operations
+    if (i < files.length - 1) {
+      await new Promise((resolve) =>
+        setTimeout(resolve, config.apiDelayMs)
+      );
+    }
+  }
+
+  return firstResult!;
+}
+```
+
+## How It Fits Into the Existing Codebase
+
+The function composes the two existing building blocks:
+
+- **`downloadFile`** from `worker/src/tdlib/download.ts` -- handles async download with `updateFile` events, progress tracking, timeout, size verification, and cross-device file moves (critical for Docker where `/data/tdlib` and `/tmp/zips` are separate volumes).
+- **`uploadToChannel`** from `worker/src/upload/channel.ts` -- handles `sendMessage` with `updateMessageSendSucceeded` confirmation, upload progress via `updateFile`, and FLOOD_WAIT retry.
+
+Both are wrapped with `withFloodWait` internally, so the utility automatically handles Telegram rate limiting.
+
+The `downloadAndReupload` function is a focused utility that can be called from the worker pipeline or any other part of the system that needs to transfer a file between channels. The existing `processOneArchiveSet` in `worker.ts` does a similar download-then-upload flow but with additional steps (hashing, dedup, metadata extraction, splitting). This utility extracts the core transfer operation for simpler use cases.
+
+## Usage Example
+
+```typescript
+import { downloadAndReupload } from "./tdlib/reupload.js";
+
+// Transfer a single file from source to destination
+const result = await downloadAndReupload({
+  client,
+  fileId: "12345",
+  fileName: "archive.zip",
+  fileSize: 1_500_000_000n, // ~1.5 GB
+  destChatId: -1001234567890n,
+  caption: "Re-uploaded archive",
+  onDownloadProgress: (progress) => {
+    console.log(`Download: ${progress.percent}%`);
+  },
+  tempSubdir: `reupload_${Date.now()}`,
+});
+
+console.log(`Uploaded as message ${result.destMessageId}`);
+```

.claude/skills/tdlib-telegram-workspace/iteration-1/eval-3-download-reupload/without_skill/timing.json

@@ -0,0 +1,5 @@
+{
+  "total_tokens": 54587,
+  "duration_ms": 146695,
+  "total_duration_seconds": 146.7
+}