# What changed in miniflare

> 18 changes in miniflare 4 from its official release notes, upgrade guides and advisories: 6 new APIs and options. Each one cited. Sources checked 2026-10-20. HTML: https://unstale.sh/npm/miniflare/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## miniflare 4

### New APIs and options

- The endpoint accepts ?format=json to return the email handler result as JSON, while requests without it retain the existing text outcome. (4.20260730.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260730.0)
- Adds a local S3-compatible HTTP API for R2 buckets configured with `s3Credentials`, supporting AWS Signature Version 4 authentication and the listed S3 operations. (4.20260722.1) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.1)
- Remote VPC Network and VPC Service bindings now support raw TCP connections through `binding.connect(address)` in local development; the feature is experimental and requires no new configuration. (4.20260722.1) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.1)
- Passes space-separated V8 flags to workerd, allowing developers to raise the heap limit and keep long development sessions alive. (4.20260722.1) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.1)
- A read-only SQL endpoint lets tools query the spans and logs tables. (4.20260722.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.0)
- Set this environment variable to enable local observability while it is off by default during testing. (4.20260722.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.0)

### Behavior and default changes

- When enabled, local observability captures Workflows invocations so workflow runs appear in the Local Explorer's Observability view with traces, spans, and logs. (4.20260730.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260730.0)
- The updated sharp no longer requires explicit build approval in package managers that block dependency build scripts by default. (4.20260722.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.0)

### Tooling

- Local Worker invocations can be traced across worker and Durable Object boundaries, capturing spans, logs, and console output. (4.20260722.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.0)
- A new Observability tab provides Traces and Events views for exploring local invocation data. (4.20260722.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.0)

### Fixes and other changes

- Local Images binding transforms now respect the fit, gravity, and background options, matching production behavior instead of always letterboxing with black bars. (4.20260730.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260730.0)
- The idle keep-alive timeout is disabled to prevent pooled workerd connections from failing with `Network connection lost` during local development. (4.20260730.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260730.0)
- Preserves metadata when stored KV values are falsy, such as an empty string or `"0"`; missing keys still return null metadata. (4.20260722.1) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.1)
- On Windows, hides the workerd console window when the parent process has no console, preventing a visible, focus-stealing window for background or detached parents. (4.20260722.1) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.1)
- AVIF inputs are now correctly reported as image/avif rather than as an unsupported or unknown type. (4.20260722.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.0)
- The error now reports the enforced 288000-byte maximum instead of the incorrect 256000-byte limit. (4.20260722.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.0)
- The Cloudflare Vite plugin restarts the Vite development server after workerd recovers, recreating its environments, hot channels, and module runners. (4.20260722.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.0)
- Miniflare restarts workerd after post-startup crashes so local development can serve subsequent requests; startup crashes remain fatal. (4.20260722.0) — [release notes](https://github.com/cloudflare/workers-sdk/releases/tag/miniflare%404.20260722.0)