Error codes#

Every error the SignalX runtime throws carries a unique code, SIGX001 through SIGX999. Production builds print that code with a link back to this reference:

SIGX101 "#app" — see https://sigx.dev/errors/SIGX101/

Follow the link for the code you hit, or find it in the table below.

Dev builds vs production builds#

The two builds report the same error differently, and each is tuned for where you read it.

Development gives you the full message plus a suggestion naming the fix:

Mount target "#app" not found.

Production gives you the code, the runtime detail, and this URL. The human-readable messages and suggestions are stripped — they sit behind a compile-time __DEV__ branch that folds away during the build, so those strings never reach your production bundle. That is what keeps the runtime small, and it is why this page exists: in production the link is the message.

Handling errors in code#

Every runtime error is a SigxError, so you can branch on code rather than matching message text:

TypeScript

import { SigxError } from 'sigx';

try {
    app.mount('#app');
} catch (e) {
    if (e instanceof SigxError && e.code === 'SIGX101') {
        // the mount target isn't in the document yet
    }
}

Property	Type	Notes
`code`	`string`	The `SIGX###` code — stable across dev and production
`message`	`string`	Full text in dev; code + detail + docs link in production
`suggestion`	`string \| undefined`	The fix hint. Dev builds only
`cause`	`Error \| undefined`	The underlying error, when there is one
`name`	`string`	Always `'SigxError'`

code is the only field worth branching on. Treat message and suggestion as diagnostics for humans, not as a contract.

Two codes that aren't SigxErrors#

Most coded failures are thrown SigxErrors. Two are not, because the packages that raise them sit outside that class:

Code	Shape
SIGX500	A plain `Error` — `@sigx/reactivity` sits below `SigxError` and takes no dependency on it. No `error.code`.
SIGX700	Not thrown at all — `@sigx/cache` logs it with `console.error` and degrades. Nothing to catch.

Both still print the same SIGX### — see … line in production, so the code is how you find them; you just can't instanceof-narrow to them.

Every code#

Codes are grouped into ranges by subsystem, so the number alone tells you roughly where to look.

App lifecycle · 001–099#

Code	Meaning
SIGX001	No mount function provided and no default set

Rendering & mounting · 100–199#

Code	Meaning
SIGX100	Render target not found
SIGX101	Mount target not found
SIGX102	Async setup is SSR-only
SIGX103	`errorScope()` called outside setup

Dependency injection · 200–299#

Code	Meaning
SIGX200	`defineProvide` called outside setup
SIGX201	`defineProvide` called with something that isn't an injectable
SIGX202	A required injectable was never provided
SIGX203	`defineFactory` setup returned a primitive

Hooks & async · 300–399#

Code	Meaning
SIGX300	A hook was called outside setup

Messaging · 400–499#

Code	Meaning
SIGX400	Subscribed to a destroyed topic
SIGX401	Created a topic on a destroyed group

Reactivity · 500–599#

Code	Meaning
SIGX500	`toSignal` wrote to a read-only property

Server rendering · 600–699#

Code	Meaning
SIGX600	`hydrate()` could not find its container
SIGX601	`hydrate()` found no root component on the app
SIGX602	`renderDocument` found no outlet marker in the template

Cache · 700–799#

Code	Meaning
SIGX700	The `@sigx/cache` revalidation trigger threw while subscribing

Error handling — errorScope and app.onError, the value-first error model
App & plugins — providing injectables before mount