SERVER_WRITE
Signal/store/optimistic setter ran during a server render; inert, will throw (dev; once per category).
What you saw
- Kind:
write - Severity:
warn(code that works but is structurally wrong or expensive)
The console report opens with [SERVER_WRITE] and the message, then an in line naming the owners that enclose the subject, root first, and an at line with the source location when the code was compiled with one.
In a captured artifact the same finding is an event with code: "SERVER_WRITE", ownerPath, and loc.
Diagnostics explains each line.
Why it fires
A signal, store or optimistic setter ran during a server render. Server render is pure — state enters through async sources, never setters — so the write landed as inert data and will throw in a later release.
The server runtime reports on the same channel, with the same in <App> › <Page> line.
Two groups.
Findings (SSR_RENDER_ERROR_CONTAINED, SSR_SUBTREE_ABANDONED, SSR_STREAM_ABANDONED, LATE_HEADER_WRITE, DYNAMIC_ASYNC_COMPONENT, SERVER_ERROR_SANITIZED, FRAME_MARKER_CORRUPTED) are facts about a render that exist in observe builds too — an APM sees them in production; in dev they print.
Checks (the rest, SSR_BOUNDARY_WATERFALL and SSR_CLIENT_CONTENT_MASKED included) are dev-only guidance.
A captured artifact from a server render carries both.
How to fix it
Derive the state (createStore(fn, seed), a memo over the promise); if the write bridges a subscription, make the subscription the async source itself.
In tests
captureArtifact from @solidjs/diagnostics runs a scenario with the diagnostics channel open and returns the events it saw.
expectNoDiagnostics(artifact) fails while SERVER_WRITE is among them, with the events as evidence; after the fix, the code is gone from artifact.diagnostics.
Check for regressions in tests shows the loop and the Vitest matcher form.
Learn more
- Diagnostics: every code, with its kind, severity, and trigger.
- Debugging reactivity: how to read a report and what each group of codes points at.