fix: force HTTPS for image downloads and add base64 response format

[nguyenngothuong]

Problem

The mmx image generate command fails with Network request failed when trying to download generated images from certain regions (confirmed from Vietnam, likely affects others).

Root Cause

The MiniMax Image Generation API returns image URLs using HTTP (e.g. http://hailuo-image-*.oss-us-east-1.aliyuncs.com/...), but the Alibaba Cloud OSS US East CDN blocks HTTP traffic, causing fetch() to fail.

❌ http://hailuo-image-*.oss-us-east-1.aliyuncs.com/... → "fetch failed"
✅ https://hailuo-image-*.oss-us-east-1.aliyuncs.com/... → 200 OK

Solution

1. Force HTTPS in download.ts

Auto-convert http:// → https:// before fetching, with retry logic (3 attempts, exponential backoff).

2. Add --response-format base64 flag

The API supports response_format: base64 which returns base64-encoded images directly, completely bypassing the CDN download step. This is useful as a fallback when CDN URLs are unreachable.

Changes

File	Description
src/files/download.ts	Force HTTPS conversion + retry logic
src/commands/image/generate.ts	Add `--response-format <url
src/types/api.ts	Add response_format and image_base64 types

Test Results

# Default mode (HTTP→HTTPS fix)
mmx image "A sunset over mountains" --out-dir ./out/
# ✅ Saved: ./out/image_001.jpg (290KB, 1024x1024 JPEG)

# Base64 mode (bypasses CDN entirely)
mmx image "A cat wearing sunglasses" --response-format base64 --out-dir ./out/
# ✅ Saved: ./out/image_001.jpg (571KB, 1024x1024 JPEG)

Related

• Issue: Fix: image download fails — API returns HTTP URLs but OSS CDN requires HTTPS #93