Architecture

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apps/desktop  (Electron + React + Monaco)   packages/cli  (testpion)   testpion mcp-server
      │  IPC → backend (production guard)            │                          │
      ▼                                              ▼                          ▼
             packages/core — the single execution engine
  protocols (HTTP · GraphQL · gRPC · WebSocket · Socket.IO · MQTT · Kafka · MCP) │ AI providers · agent loop
  variables · scripts (QuickJS/WASM) · checks & evaluators · tracer
  runner (streaming, bounded concurrency, retries, checkpoints, flows) · reports
  storage (workspace files · SQLite metadata · secret stores) · importers

The desktop backend, the CLI and the MCP server (testpion mcp-server, or the installed app with --mcp-server) call the same engine, so test execution logic is not duplicated.
An environment marked as production is guarded in one place per host: the desktop backend checks every RPC call that sends or runs before its handler runs and the window asks once; the CLI takes --allow-production; the MCP server needs --allow-production and allowProduction: true per call. The engine refuses data-changing steps without that consent (Production, Design).
Every CLI --json output is one envelope, { schema_version, command, status, data, errors, warnings, metrics }, written by packages/cli/src/output.ts; --jsonl streams events as { type, data } lines (JSON output).
The React renderer never performs network or test execution. It sends RPC calls to the backend and receives batched events, throttled to about 50–100 ms, so high-frequency streams don't cause excessive renders.
Electron uses contextIsolation, a sandboxed renderer and a strict CSP. The preload exposes only an RPC bridge.
The UI is React 19 with Tailwind CSS v4 and Radix UI primitives, in the shadcn/ui style. Colours are OKLCH design tokens in apps/desktop/src/styles.css, with the TestPion blue → violet brand as the accent, and surfaces layered as chrome (top bar, navigation rail, status bar) → sidebars → work area → popovers. Dark and light themes share the same tokens. New UI reuses the primitives in apps/desktop/src/components/ui.tsx (Button, Tabs, Badge, Modal, Menu, Empty, Split with sidebar …).

Storage

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workspace/
  workspace.json  (schemaVersion 1.0)   database.sqlite (history · runs · traces index)
  collections/  environments/  tests/  datasets/  providers.json  mcp-servers.json
  traces/  payloads/  runs/<runId>/{results.jsonl,summary.json,reports}  baselines/

Large payloads, traces and results are separate files and are never stored in SQLite rows. Writes are atomic (temp file, fsync, rename). A corrupted JSON file is preserved as *.corrupt-<ts> and reported instead of crashing. Workspace format migrations run on open, and the pre-migration file is backed up.

See execution engine and plugin system.

Architecture ​

Storage ​

Architecture

Storage