cd

Fast, private file handoffs at cd.yash0.in.

CD supports two focused flows:

• Browsers exchange one or more files directly over WebRTC.
• Agents and terminals run cdx send <file> and produce one browser link.

Files are never intentionally stored by CD. The orange CD interface is the receiver for both flows.

Send a file from an agent or terminal

Install cdx with Go:

go install github.com/YashasVM/cd/cmd/cdx@latest

Or install the latest checksum-verified release on Linux or macOS:

curl -fsSL https://raw.githubusercontent.com/YashasVM/cd/main/scripts/install.sh | sh

Then send one regular file:

cdx send ./app.apk

The binary is named cdx because cd is already the shell's change-directory command.

Standard output contains only the private share URL:

https://cd.yash0.in/s/3JgrxJIKt2cqd2V0aTDQyQ#v1.<private-key>

Send that complete URL to the receiver. Keep cdx running while they accept and download the file. Progress is written to standard error; exit status 0 means the receiver verified the complete byte count. Use --json when a tool needs structured output.

The URL fragment holds the encryption key. Browsers do not send fragments to the server, and the relay receives encrypted records only. A receiver must also prove knowledge of a token derived from that key before joining. Treat the full URL as a temporary secret.

Repository agents should follow AGENTS.md and the reusable CD file-sharing skill.

Browser-to-browser sharing

Open cd.yash0.in, choose files, and share the displayed 128-bit private code, link, or QR code. The private code is placed in the URL fragment so it is not sent in HTTP requests. Keep both tabs open until the WebRTC transfer finishes. CD coordinates the connection through its own cd.yash0.in Worker; file bytes travel over the encrypted WebRTC data channel. WebRTC may use public STUN servers for NAT discovery, but they do not receive file bytes. This remains separate from the agent relay.

Develop locally

Requirements: Node.js 24+, npm, and Go 1.26.8+.

npm ci
npm run dev

Build the local CLI with make cdx; it is written to bin/cdx. Run the full production checks with:

npm test
npm run test:cli
npm run typecheck
npm run verify:agent
npm run deploy:dry
cd android && ./gradlew testDebugUnitTest lintDebug assembleDebug

verify:agent starts a local Worker, builds the real Go sender, and drives the built receiver page in Chromium. It checks admission failures, duplicate participants, multi-chunk flow control, Unicode filenames, the downloaded bytes, visible CD branding, and the sender's completion status. Set CHROMIUM_PATH if Chromium is installed outside the common system paths.

To exercise the browser receiver locally:

npx wrangler dev
CD_RELAY_URL=ws://127.0.0.1:8787/ws/v1 \
CD_PUBLIC_URL=http://127.0.0.1:8787 \
./bin/cdx send ./README.md

Architecture

Browser sender  ── CD signaling ── WebRTC ── Browser receiver

cdx sender ── encrypted WebSocket records ── CD relay ── Browser receiver
                 key remains in URL fragment

The Cloudflare Worker uses one Durable Object room per random 128-bit transfer identifier. Rooms admit one sender and one authorized receiver, bound memory and frame sizes, expire automatically, and retain no file contents. The sender uses 64 KiB chunks with an acknowledged 1 MiB window. The browser streams to the File System Access API where available, stages to the Origin Private File System next, and otherwise offers a Blob download (capped at 256 MiB on WebKit receivers, where large blob downloads crash real devices).

The exact protocol and trust boundaries are documented in Agent transfer protocol v1. Operational recovery notes are in Production recovery.

Repository layout

cmd/cdx/                  Go sender CLI
src/                      Browser UI and transfer protocols
worker/                   Cloudflare Worker and Durable Object relay
scripts/verify-agent.mjs  Deterministic end-to-end verification
android/                  Android shell for the browser P2P flow
skills/                   Instructions for AI agents

Deploy and release

npm run build && npx wrangler deploy publishes the Worker and assets using wrangler.jsonc. Pushing a v* tag runs the release workflow, cross-compiles cdx, publishes SHA-256 checksums, and creates a GitHub release.

After deployment, run CD_VERIFY_URL=https://cd.yash0.in node scripts/verify-p2p.mjs to verify that two browsers can transfer and save the exact file bytes through production signaling. This check sends a generated test file through both disk staging and the memory fallback, including unavailable disk storage. Run CD_VERIFY_URL=https://cd.yash0.in node scripts/verify-agent.mjs to verify the encrypted CLI transfer and downloaded bytes against production as well.

See SECURITY.md before reporting vulnerabilities. CD is available under the MIT License.