fix(THU-537): advertise host-reachable PowerSync URL in local docker-compose#982
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- POWERSYNC_URL is echoed to the browser in the /v1/powersync/token response, so the internal `powersync:8080` Docker hostname can't resolve there and leaves the SharedWorker stuck offline - Use the host port mapping (localhost:POWERSYNC_PORT) instead
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Updated Fri, 12 Jun 2026 19:35:22 GMT · run #1881 |
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Problem
In the local
deploy/docker-compose.ymlstack, Cloud Sync never establishes — the panel sits on "Changes will sync when back online".POWERSYNC_URLwas set to the internal Docker hostnamehttp://powersync:8080. The backend echoes that value back to the browser in/v1/powersync/token(backend/src/api/powersync.ts), and the frontend SharedWorker then tries to connect tohttp://powersync:8080/...— which only resolves inside the Docker network. Browser DNS fails silently → SharedWorker stays offline.Fix
Point
POWERSYNC_URLat the host-reachable URL via the existing port mapping:(
powersyncalready maps${POWERSYNC_PORT:-8080}:8080to the host.) Added a comment contrasting this withOIDC_DISCOVERY_URLright above it, which intentionally does use the internal hostname (backend-only, never sent to the browser).Note vs. ticket
The ticket suggested port 8081, but the actual host mapping in this file defaults to 8080 (
${POWERSYNC_PORT:-8080}:8080). Used 8080 to match the real mapping — 8081 would point at nothing.Testing
Config-only. With this change the backend advertises
http://localhost:8080, which the browser can reach, so the SharedWorker connects. (Out of scope: preview-env PowerSync architecture — separate/larger issue.)🤖 Generated with Claude Code
Note
Low Risk
Single local dev compose env change with no application code or production config impact.
Overview
Fixes local Docker Cloud Sync staying offline by changing backend
POWERSYNC_URLfrom the internal service URL (http://powersync:8080) tohttp://localhost:${POWERSYNC_PORT:-8080}, matching the published host port on thepowersyncservice.That value is returned to the browser (e.g.
/v1/powersync/token), so the client must use a host-resolvable URL—not a Docker-only hostname. A short comment was added next to the env var to contrast this withOIDC_DISCOVERY_URL, which correctly stays on an internal hostname because only the backend uses it.Reviewed by Cursor Bugbot for commit cd0615e. Bugbot is set up for automated code reviews on this repo. Configure here.