fanbox
FanBox is a free, open-source macOS terminal app that pairs an xterm terminal with a live diff viewer and an agent-control API
FanBox's agent-control API is the unusual part: a running coding agent can read output from and send keys to sibling terminal windows under a per-session token, which most terminal apps simply don't offer. The v2.16.x line shows a project shipping quickly — in-app one-click updates, ⌘K full-text search with PDF and screenshot OCR, ⌘⇧M maximize — and it is free and open source, so there is no pricing argument to have. Contributors outside the maintainer are filing real pull requests (#51, #53, #46, #58). Just don't buy it for collaboration, Windows, or Linux; none of those exist. If you want an IDE with debugging and refactoring, look at a full IDE instead.
Verified 8d ago · liveness 67/100 · cite: rightaichoice.com/tools/fanbox
- macOS solo developers who prompt coding agents in a shell
- Vibe coders who want terminal, file browser, and live diff in one window
- Hobbyists and open-source contributors who want a free alternative to a full IDE
- Developers who need one agent to read or drive sibling terminal windows
- Windows and Linux users — FanBox ships as a macOS app only
- Teams that need shared workspaces, collaboration, or code review integrations
- Enterprise deployments requiring managed authentication or compliance controls
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Skip FanBox if you're on Windows or Linux, if your team needs shared workspaces and code review integrations, or if you want a debugger and plugin ecosystem from your editor.
FanBox is $0 — free and open source, with no paid tier listed in the repo or the release notes, so there is no per-seat or usage cost to model. The real costs are time and platform: a manual, non-notarized install, a macOS machine, and the maintenance risk of depending on a roughly 1k-star project for your agent workflow. Paid peers bundle collaboration, code review, and IDE tooling that FanBox does not attempt.
In short
fanbox — FanBox is a free, open-source macOS terminal app that pairs an xterm terminal with a live diff viewer and an agent-control API. Best for macOS solo developers who prompt coding agents in a shell, Vibe coders who want terminal, file browser, and live diff in one window, Hobbyists and open-source contributors who want a free alternative to a full IDE. Free to use.
What's new in fanbox
Checked 8 days agoAcross the latest 5 updates: 4 feature updates and 1 changelog entry.
v2.16.1 · 修 2.16.0「更新」按钮显示不对的竞态
Fixes a race where the in-app update button rendered as "download update" because the auto-install probe had not finished before the renderer painted. Installing this version is still manual; automatic updates take effect from it onward.
应用内一键更新：后台下载、重启即换好 (#26)
electron-updater downloads the current-architecture zip in the background with a percentage pill, then Squirrel.Mac installs it in place on restart, falling back to a dmg download when no compatible build or latest-mac.yml exists.Release assets now include zip, blockmap, and late
⌘K 里全文搜索改成一键开关 (PR #51, @jhoncao)
A "▤ 搜内容" pill next to the search box switches ⌘K into full-text search over PDFs and screenshot OCR without typing the "内容:" prefix; the prefix syntax still works.
⌘⇧M 一键铺满 / 还原终端 (PR #53, @jhoncao)
⌘⇧M maximizes and restores the terminal window, including while an agent is typing in the focused terminal; Ctrl+Shift+M is left available for TUIs inside the terminal.
.jsonl 按文本打开和编辑 (PR #46, @ajia1206)
Claude Code and Codex session logs plus other NDJSON files now open with JSON syntax highlighting and are served as application/x-ndjson instead of being treated as unknown binaries.
What people actually say about fanbox — is it worth it?
We ran a structured research pass across product reviews, community discussions, and post-purchase forum threads to surface the patterns vendors won't publish themselves. Below: the recurring strengths, the hidden costs people mention most, and the cohort that consistently regrets adopting this tool.
8 mentions across 5 sources (Hacker News, YouTube, App Store, GitHub, Lemmy), 32 more we could not attribute · researched Sep 15, 2026.
Weighted by the 40 posts each of 5 sources contributed.
- +Completely free and open source, with no subscription, seat pricing, or feature gates
- +Three-panel layout keeps files, terminal, and live diff visible without IDE clutter
- +Agent Control API lets a terminal agent list, read, and drive sibling windows programmatically
- +v2.14.0 isolates the backend in a utilityProcess so terminal echo stays responsive during scans
- +Maintainer closes GitHub issues the same day they are filed — verifiable in the tracker
- −macOS only — no Windows or Linux build exists, ruling out mixed-OS teams
- −Community discussion volume for this specific tool is genuinely low
- −Custom agent support for pi, codebuddy and similar remains unresolved since 2026-09-04
- −Being an Electron app means a heavier footprint than a native terminal or TUI
- −No collaboration, shared workspaces, or code review integrations of any kind
- • No monetary costs, but the maintainer's time is the real constraint — there is no paid support tier to escalate to
- • Agent orchestration implies API usage with your model provider, which is billed by them, not by FanBox
Viability Score
How well maintained and how widely used is fanbox? Built from what the vendor actually publishes (docs, changelog, tutorials, integrations, pricing), whether the site is live, and how much real users discuss it. How we calculate this
Last calculated: October 2026
How we score →Key Features
- Live diff viewer that highlights code changes in real time as files are written
- WebGL-accelerated xterm 6.0.0 terminal emulator with a toggleable DOM fallback
- Agent Control API (/api/agent/*): list terminals, read output, send keystrokes, open windows, long-poll
- Per-session random security token (FANBOX_CTL_TOKEN / FANBOX_TERM_ID / FANBOX_CTL) scoped to the FanBox process tree
- ⚡ badge on tabs that are under agent control
- One-click "Agent 互控" skill installer that writes curl-based skills to ~/.claude/skills
- In-app one-click updates: background zip download, restart-and-install via Squirrel.Mac (v2.16.0)
- Fallback dmg download when a release has no latest-mac.yml or no current-architecture build
- ⌘K full-text search toggle covering PDF text and screenshot OCR (v2.16.0)
- ⌘⇧M one-key terminal maximize and restore (v2.16.0)
- Preview and edit .jsonl / NDJSON session logs with JSON highlighting, served as application/x-ndjson (v2.16.0)
- Skills view detects nested skill-collection repos one level deep, e.g. skills/*/SKILL.md (v2.16.0)
- Backend runs in a separate utilityProcess so terminal input doesn't queue behind file scans (v2.14.0)
- File follow mode that watches the file a running script is writing
- Thumbnail-based image loading in the markdown editor (v2.14.0)
About fanbox
FanBox is a free, open-source macOS desktop app from the GitHub project alchaincyf/fanbox. It puts a WebGL-accelerated xterm 6.0.0 terminal (with a DOM fallback if WebGL is unavailable) side by side with a live diff viewer and a file browser, so you can prompt a coding agent in a shell, watch its commands run, and see the resulting file changes highlighted in real time. The repo currently shows about 1k stars and 148 forks. The headline capability is the Agent Control Interface: a REST-like API under /api/agent/* that lets an agent running in one terminal list sibling terminals, read their ANSI-stripped output, send keystrokes with bracketed paste, open new windows with autorun scripts, and long-poll for completion by idle shell, output silence, or regex match. A per-session random token (FANBOX_TERM_ID, FANBOX_CTL, FANBOX_CTL_TOKEN) scopes that access to the FanBox process tree, controlled tabs show a lightning-bolt badge, and a one-click "Agent 互控" installer adds curl-based skills to ~/.claude/skills. Recent releases pack in everyday conveniences: v2.16.0 added in-app one-click updates (background download, then restart-and-install via Squirrel.Mac with a fallback to a plain dmg download), a one-tap full-text search toggle in ⌘K covering PDF and screenshot OCR, ⌘⇧M terminal maximize, .jsonl files opening as highlighted JSON, and Skills detection for nested skill-collection repos. v2.16.1 fixes a race where the update button showed "download update" instead of "update" — as that release note spells out, installing 2.16.1 is still a manual step, and fully automatic updates start from 2.16.1 onward. The app is Developer ID signed and notarized since 2.4.1. It suits solo Mac developers who want agent orchestration without IDE baggage. It is not for teams that need collaboration, shared workspaces, or code review integrations, and there is no Windows or Linux build.
Behind the Verdict
What FanBox is actually good at: staying out of the way while an agent works. The window combines three things you usually alt-tab between — a real terminal (xterm 6.0.0, WebGL-accelerated with a toggleable DOM fallback and CJK rendering from the xterm 6 upgrade), a file browser, and a live diff viewer that highlights changes as files are written. Version 2.14.0 moved the backend into a separate utilityProcess so terminal input doesn't queue behind file scans, which matters when an agent is churning through files. The differentiator is the Agent Control Interface. /api/agent/* exposes list-terminals, ANSI-stripped output reads, keystroke sends with bracketed paste, window opening with autorun scripts, and long-poll completion detection triggered by an idle shell, output silence, or a regex match. Access is scoped by a per-session random token (FANBOX_TERM_ID, FANBOX_CTL, FANBOX_CTL_TOKEN) to the FanBox process tree, and controlled tabs flash a ⚡ badge so you can see which window an agent is driving. The one-click "Agent 互控" installer writes curl-based skills into ~/.claude/skills, which is a neat bridge from Claude Code into the app. Housekeeping has improved steadily. v2.16.0 shipped in-app one-click updates: electron-updater pulls the current-architecture zip in the background (the pill on screen shows a percentage), then Squirrel.Mac swaps the package in place on restart, and if you never click it the next app quit installs it anyway. When a release has no latest-mac.yml or no build for your architecture (an arm64 build on an Intel Mac doesn't count), it falls back to downloading the dmg to your Downloads folder. v2.16.1 fixed a race in that flow where the button rendered as "download update" because the auto-install probe hadn't finished before the renderer painted — installing 2.16.1 itself is still manual; automatic updates begin with 2.16.1. Also in 2.16.0: a "▤ 搜内容" toggle in ⌘K switches to full-text search over PDFs and screenshot OCR without typing the "内容:" prefix, ⌘⇧M maximizes and restores the terminal (⌘ only — Ctrl+Shift+M is left for TUIs), .jsonl session logs from Claude Code and Codex open with JSON highlighting and are served as application/x-ndjson, and the Skills view now detects nested skill-collection repos like superpowers by scanning one level down to skills/*/SKILL.md. Note the release note is explicit that Claude Code itself does not recursively load those nested directories — FanBox only lists them. Where it stops: it is macOS-only and ships without notarized release assets, so manual installation involves a Gatekeeper step even though the app has been Developer ID signed and notarized since 2.4.1. There is no team collaboration, no shared workspaces, no code review integration, and deliberately no IDE depth — no debugger, no refactoring engine, no plugin ecosystem. The Agent Control API is token-scoped to the FanBox process tree, so cross-process or remote orchestration isn't supported as-is. The community is
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Real-world workflow fit
Concrete scenarios for the personas fanbox actually fits — and what changes day-one when you adopt it.
You start a coding agent in one FanBox terminal, prompt it, and keep the diff viewer open beside it. As the agent writes files the diff updates live; when you want to inspect a change you open the file in the browser pane instead of alt-tabbing to an IDE.
Outcome: You review agent edits as they happen and catch a wrong change seconds after it lands, without leaving the window.
An agent in window A uses the Agent Control API (with FANBOX_CTL_TOKEN set) to open window B with an autorun script, then long-polls for the build to finish by watching for an idle shell or a regex match in B's output.
Outcome: Multi-step work runs across windows while you watch the ⚡ badge on the tabs the agent controls, and you get control back when the poll resolves.
You open a Claude Code or Codex .jsonl session log in FanBox, which now renders it as highlighted JSON, and search across it with the ⌘K full-text toggle — which also covers PDFs and screenshot OCR.
Outcome: You find the exact tool call or screenshot that produced a bad edit without leaving the app.
Use Cases
- Prompt a coding agent in one terminal and watch its file edits light up in the diff viewer without switching apps
- Let an agent read ANSI-stripped output from a sibling window and wait for completion via idle shell, silence, or a regex match
- Search PDFs, screenshots, and JSONL session logs from ⌘K inside the terminal app
- Follow a file that a long-running script is writing to catch changes as they land
- Open Claude Code or Codex .jsonl session logs as highlighted JSON to debug what an agent actually did
- Hide the macOS Dock icon and keep background terminals alive while you work elsewhere
- Run a build or test command in a second window while you keep typing in the first
Limitations
- FanBox is macOS-only.
- The latest release asset you download is not notarized, so the install is a manual step (the app itself has been Developer ID signed and notarized since 2.4.1).
- Installing v2.16.1 is still manual — the release note states automatic updates take effect from 2.16.1 onward.
- There is no team collaboration, no shared workspaces, and no code review integration.
- IDE depth is deliberately absent: no debugger, no refactoring engine, no plugin ecosystem.
- The Agent Control API requires a per-session token and is scoped to the FanBox process tree, so cross-process or remote orchestration isn't supported as-is.
- Nested skill-collection repos are only listed by the Skills view — the release note is explicit that Claude Code does not recursively load them.
- The project is small (roughly 1k stars, 148 forks) relative to mainstream terminals and IDEs.
as of 2026-09-30
Verification history
We have re-verified fanbox 8 times since . Each pass re-reads the vendor's own pages and re-checks every listed field against that evidence; passes where nothing had changed are marked as such.
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
Showing the 6 most recent of 8 verification passes.
Free to cite with attribution — this page re-verifies continuously.
12-month cost
Project the real annual outlay, including the implied monthly cost when only an annual tier is published.
Vendor list price only. Add-on usage, seat overages, and contract minimums are surfaced under Hidden costs & gotchas.
Plans compared
For each published fanbox tier: who it actually fits, and what it adds vs. the previous tier. Cross-reference the cost calculator above for projected annual outlay.
Free
$0
Ideal for
Solo macOS developers and hobbyists who want a terminal, live diff viewer, and agent-control API at zero cost.
What this tier adds
Starting tier — the only tier. Everything the project ships, including the Agent Control API and in-app updates, at $0.
Where the pricing makes sense
The company stage and team size where fanbox's pricing actually pencils out — and where peers do it cheaper.
FanBox is $0 — free and open source, with no paid tier listed in the repo or the release notes, so there is no per-seat or usage cost to model. The real costs are time and platform: a manual, non-notarized install, a macOS machine, and the maintenance risk of depending on a roughly 1k-star project for your agent workflow. Paid peers bundle collaboration, code review, and IDE tooling that FanBox does not attempt.
Setup time & first value
How long it actually takes to get something useful out of fanbox — broken out by persona, not the marketing-page minute.
Solo Mac user: download the release from the GitHub project page, drag it to Applications, and clear the Gatekeeper prompt — expect a few minutes, longer if you have to work around the notarization warning. Configuring the Agent Control API for an agent is roughly 10-15 minutes: set the token environment variables and, if you use Claude, run the one-click "Agent 互控" installer to write skills into
Switching to or from fanbox
How to bring data in from common predecessors and how to get it back out — written for the switcher, not the buyer.
- →From a plain macOS Terminal or iTerm2 session: if you only need a shell, keep what you have — FanBox adds the diff viewer and agent API rather than replacing a terminal's raw speed and profile tooling.
- →From a full IDE for agent-driven edits: move your prompt-and-review loop into FanBox's terminal plus diff viewer, and keep the IDE open only for debugging and refactoring.
- →From a Claude Code skill setup: run the one-click "Agent 互控" installer to add curl-based skills to ~/.claude/skills so your agent can call /api/agent/*.
- ↗To a full IDE (for example JetBrains or VS Code): export your project as normal, then rebuild the debugging, refactoring, and plugin workflows FanBox deliberately omits.
- ↗To a team collaboration or code review platform: expect to redo review flow, shared workspaces, and permissions from scratch — FanBox has none of these.
- ↗To a cross-platform terminal: if you move to Windows or Linux, your FanBox window layout and the Agent Control API have no equivalent to port to.
Resources & Guides
Tutorials & Learning
YouTube returned 6 videos for “fanbox”, and we withheld 6: 6 could not be judged, because “fanbox” is a single word that other videos use for other things. We are showing none, because we could not prove any of them are about fanbox.
Official links
Tools that pair well with fanbox
Common stack mates teams adopt alongside fanbox, with the specific reason each pairing earns its keep.
Crush
Open-source agentic coding assistant that runs inside your terminal and wires any LLM into your CLI workflow.
Cline
Open-source coding agent that reads your repo, edits files, and runs terminal commands across VS Code, JetBrains, CLI, and a desktop app.
DevoxxGenieIDEAPlugin
Free, open-source AI code assistant plugin for JetBrains IDEs with spec-driven development and agent mode
Featured Head-to-Head Comparisons
Fanbox vs Cognition Ai
Cognition AI is for enterprise teams that need an autonomous AI engineer handling complex, multi-step tasks across large codebases, with a $10M productivity guarantee. Fanbox is for solo developers on macOS who want a free, open-source vibe coding cockpit with live diffs and a terminal—no cloud dependency or team features. Choose based on whether you need an enterprise-grade autonomous agent or a lightweight local diff viewer.
Fanbox vs Bito
Choose Bito if you lead a team wrestling with microservices across dozens of repos and need AI that understands service topology, dependencies, and architecture — it's an enterprise-grade context layer that plugs into your existing coding agents. Pick FanBox if you're a solo macOS developer who wants a free, open-source, distraction-free terminal with live diff feedback for rapid vibe coding. They serve orthogonal needs; your repo count and collaboration requirements decide.
Fanbox vs Poolside Ai
Poolside AI is built for enterprises needing secure, custom AI agents in regulated environments, while fanbox is a free, individual-focused tool for rapid, visual coding on Mac. Unless you have enterprise requirements and budget, fanbox offers immediate, no-cost value for solo developers on Apple Silicon. Choose Poolside only if you need on-prem deployment, governance, and multi-step agent capabilities.
Fanbox vs Replit Agent
Fanbox is a free, open-source macOS terminal with live diff and agent control for solo developers who want a minimal vibe-coding cockpit. Replit Agent is a browser-based freemium platform that generates and deploys full-stack apps from natural language, now with voice mode, Slack integration, and reduced cloud prices. Choose Fanbox if you own a Mac and crave a lightweight, hackable terminal; choose Replit Agent if you need rapid prototyping, deployment, and team collaboration.
Fanbox vs Marvin
Marvin and fanbox serve entirely different needs. If you're a Python developer embedding LLM logic into your codebase with decorators, Marvin is the clear choice. If you're a macOS solo developer seeking a lightweight, real-time diff environment for AI-assisted coding, fanbox is purpose-built for that. They're not competitors; pick based on whether you need a library or a desktop app for vibe coding.
Alternatives to fanbox
View all
Crush
Open-source agentic coding assistant that runs inside your terminal and wires any LLM into your CLI workflow.
Cline
Open-source coding agent that reads your repo, edits files, and runs terminal commands across VS Code, JetBrains, CLI, and a desktop app.
DevoxxGenieIDEAPlugin
Free, open-source AI code assistant plugin for JetBrains IDEs with spec-driven development and agent mode
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