Chronoscope

Chronoscope is a browser-first HTTP latency diagnostic tool. It measures several endpoints from the user's actual network in synchronized rounds, then shows whether latency looks healthy, isolated to one endpoint, or correlated across multiple paths.

The short version: it is a focused "is it me or them?" instrument for HTTP latency, not a synthetic cloud monitor.

What It Does Today

• Runs in the browser with no account required; optional Cloudflare Functions add an outside vantage point and short hosted report links.
• Probes enabled endpoints in synchronized rounds using Web Workers.
• Starts with region-aware default endpoints and supports custom endpoints.
• Shows three shipped views:
  • Overview: health score, causal verdicts, shared-axis endpoint comparison, and recent events.
  • Live: unified, split, and focused live latency traces.
  • Diagnose: distribution, cross-endpoint comparison, phase breakdown when browser timing data is available, and recent samples.
• Supports endpoint nicknames, reordering, enabling/disabling, regional resets, timing settings, CORS mode selection, and local persistence.
• Shares configs and result snapshots through compressed URL hashes, with optional KV-backed /r/:id hosted report permalinks on Cloudflare.
• Can compare the browser's path with a Cloudflare edge probe, then preserve that outside-vantage evidence in shared reports.
• Blocks private/local hosts from shared URLs while still allowing local testing for endpoints added directly by the current user.

Current Limits

Chronoscope's core measurement loop is still intentionally browser-first. That means it can measure HTTP fetch timing from the user's browser, but browser Resource Timing phase data is limited for cross-origin endpoints unless the target server exposes timing headers.

The optional local diagnostic companion agent adds local-only DNS, TLS, route, WiFi, and browser-history context when run by the user. The optional Cloudflare layer adds remote edge probes, short hosted report links, and a saturation endpoint; see docs/cloudflare-remote-vantage.md.

Quick Start

npm install
npm run dev

Open the Vite URL, usually http://localhost:5173.

Scripts

npm run typecheck
npm run lint
npm test
npm run build
npm run test:visual
npm run companion
npm run deploy

npm run test:visual uses Playwright and starts the Vite dev server from playwright.config.ts.

Project Map

• src/lib/engine/ - measurement engine and worker probe logic.
• src/lib/stores/ - Svelte stores for endpoints, measurements, statistics, settings, and UI state.
• src/lib/components/ - topbar, rail, views, drawers, popovers, and charts.
• src/lib/share/ - compressed share payload generation and validation.
• src/lib/remote-vantage/ - Cloudflare edge probe client, report persistence client, and browser/remote diagnosis fusion.
• functions/ - Cloudflare Pages Functions for remote probes, hosted reports, health, and saturation downloads.
• companion/ - optional signed local diagnostic companion agent.
• src/lib/security/ - URL safety checks for direct and shared endpoints.
• src/lib/regional-defaults.ts - region detection and default endpoint sets.
• tests/unit/ - Vitest unit and component coverage.
• tests/visual/ - Playwright visual, accessibility, and browser-flow checks.
• docs/vision/ - product vision and longer-term platform direction.

Development Notes

• Keep the browser-only measurement limits explicit in UI and docs.
• Treat shared URLs as untrusted input.
• Prefer deterministic sample injection in browser tests over real network timing when testing layout or visual state.
• Keep view navigation and keyboard shortcut labels in sync; visible UI should never advertise a shortcut that does something else.