Skip to main content

Overview

Every Canvas deploy produces a detailed build log — from downloading your bundle through validation, asset upload, and completion. Logs stream in real time via Server-Sent Events (SSE) and persist in the deploy record for later review.

Streaming logs

Subscribe to live build output during a deploy:
The response is an SSE stream (text/event-stream). Each event contains a JSON log entry:

Consuming in JavaScript

Use fetch + ReadableStream instead of EventSource — fetch supports Authorization headers, while EventSource does not.

Reconnecting mid-deploy

If you disconnect and reconnect, the SSE endpoint replays all previously emitted log lines (from MongoDB) before switching to live streaming. No log lines are lost on reconnect.

Log lifecycle

After a deploy reaches a terminal state (complete or failed), the full log is persisted in the deploy record and can be retrieved at any time.

Git deploy logs

Deploys triggered via GitHub push include additional log lines from the build process:
Real npm ci and npm run build output is streamed line-by-line, so you see the same output you’d see locally.

Studio

In the App details page, the Deploy panel shows a terminal-style log viewer during active deploys. Logs auto-scroll as new lines arrive and remain viewable after completion.