Solid2
Advanced / Diagnostics & Dev Hooks

DEV

Dev tier (devtools hooks, graph traversal, console reporting): dev builds only.

Import

import { DEV } from "solid-js";

Type signature

const DEV: Dev | undefined;

Learn more

Related types

Dev

The dev tier: devtools hooks, graph traversal, and the console face of the diagnostics channel. Present only in dev builds (__DEV__).

interface Dev {
  hooks: DevHooks;
  getChildren: typeof getChildren;
  getSignals: typeof getSignals;
  getParent: typeof getParent;
  getSources: typeof getSources;
  getObservers: typeof getObservers;
  report(entry: DiagnosticEvent): void;
  guideUrl(code: DiagnosticCode): string;
}

hooks

  • Type: DevHooks

getChildren

  • Type: typeof getChildren

getSignals

  • Type: typeof getSignals

getParent

  • Type: typeof getParent

getSources

  • Type: typeof getSources

getObservers

  • Type: typeof getObservers

report

  • Type: void

Console face of an emitted event — see reportDiagnostic.

guideUrl

  • Type: string

The stable URL of code's section in the repair guide — the reactivity-diagnostics skill shipped with solid-js, one section per code. The one place the URL is built: the console footer prints it and the performance tracks' Insights link (learnMoreUrl) reads it, so both name the same section. Dev-tier: it is guidance for a developer, and a URL string on a retained object is a cost every observe build would pay.

DevHooks

interface DevHooks {
  onOwner?: (owner: Owner) => void;
  onGraph?: (value: any, owner: Owner | null) => void;
  onUpdate?: () => void;
  onStoreNodeUpdate?: (
    state: any,
    property: PropertyKey,
    value: any,
    prev: any
  ) => void;
}

onOwner

  • Type: (owner: Owner) => void

onGraph

  • Type: (value: any, owner: Owner | null) => void

onUpdate

  • Type: () => void

onStoreNodeUpdate

  • Type: (state: any, property: PropertyKey, value: any, prev: any) => void

DiagnosticCapture

interface DiagnosticCapture {
  readonly events: readonly DiagnosticEvent[];
  clear(): void;
  stop(): DiagnosticEvent[];
}

events

  • Type: readonly DiagnosticEvent[]

clear

  • Type: void

stop

  • Type: DiagnosticEvent[]

DiagnosticCode

type DiagnosticCode =
  | "STRICT_READ_UNTRACKED"
  | "PENDING_ASYNC_UNTRACKED_READ"
  | "PENDING_ASYNC_FORBIDDEN_SCOPE"
  | "REACTIVE_WRITE_IN_OWNED_SCOPE"
  | "ASYNC_STORE_SETTER"
  | "ACTION_CALLED_IN_OWNED_SCOPE"
  | "RUN_WITH_DISPOSED_OWNER"
  | "NO_OWNER_CLEANUP"
  | "CLEANUP_IN_FORBIDDEN_SCOPE"
  | "SETTLED_CLEANUP_UNOWNED"
  | "SETTLE_WALK_UNINITIALIZED_SOURCE"
  | "FLUSH_IN_EFFECT_CALLBACK"
  | "PRIMITIVE_IN_FORBIDDEN_SCOPE"
  | "PRIMITIVE_IN_EFFECT_CALLBACK"
  | "NO_OWNER_EFFECT"
  | "NO_OWNER_BOUNDARY"
  | "ASYNC_OUTSIDE_LOADING_BOUNDARY"
  | "LOADING_ON_OUTSIDE_HOLD"
  | "INVALID_REFRESH_TARGET"
  | "INVALID_AFFECTS_TARGET"
  | "MISSING_EFFECT_FN"
  | "SYNC_NODE_RECEIVED_ASYNC"
  | "UNTRACKED_READ_AFTER_AWAIT"
  | "REACTIVITY_HALTED"
  | "INVARIANT_VIOLATION"
  | "HUGE_FAN_OUT"
  | "HUGE_FAN_IN"
  | "GRAPH_GROWTH"
  | "HOT_SCOPE_RERUNS"
  | "HOT_SCOPE_TIME"
  | "WIDE_SCOPE_DEPS"
  | "UNSTABLE_MEMO_OUTPUT"
  | "WASTED_RECOMPUTE"
  | "ASYNC_WATERFALL"
  | "HOT_SCOPE_FANOUT"
  | "SILENT_HOLD"
  | "LONG_HOLD"
  | "UNTRACKED_ASYNC_HANDLER"
  | "ABANDONED_FLIGHTS"
  | "FALLBACK_FLASH"
  | "STACKED_HOLDS"
  | "OPTIMISTIC_REVERTED"
  | "EFFECT_WRITES_OWN_SOURCE"
  | "EFFECT_RELAY_TEAR"
  | "IMMUTABLE_UPDATE_IN_STORE"
  | "UNSTABLE_LIST_IDENTITY"
  // Server / SSR — emitted by the server runtimes (`solid-js`'s server
  // facade, `@solidjs/web`'s server entries) through `OBSERVE.diagnostics.emit`.
  | "SSR_RENDER_ERROR_CONTAINED"
  | "SSR_SUBTREE_ABANDONED"
  | "SSR_STREAM_ABANDONED"
  | "SSR_CLIENT_CONTENT_MASKED"
  | "LATE_HEADER_WRITE"
  | "SERVER_ERROR_SANITIZED"
  | "SSR_BOUNDARY_WATERFALL"
  | "SSR_UNDECLARED_LIVE_SOURCE"
  | "SSR_LIVE_HOLE_LATCHED"
  | "SERVER_WRITE"
  | "REVEAL_IN_RENDER_TO_STRING"
  | "LAZY_ASSET_UNMAPPED"
  | "PRELOAD_DESCRIPTOR_INVALID"
  | "HEAD_TAG_INVALID"
  | "UNRECOGNIZED_INSERT_VALUE"
  | "UNSCOPED_HOLE_ALLOCATED_IDS"
  | "LOWERCASE_EVENT_ATTRIBUTE"
  | "BINDING_SLOT_POSITION"
  | "FRAME_MARKER_CORRUPTED"
  | "DYNAMIC_ASYNC_COMPONENT";

DiagnosticEvent

interface DiagnosticEvent {
  sequence: number;
  code: DiagnosticCode;
  kind: DiagnosticKind;
  severity: DiagnosticSeverity;
  message: string;
  ownerId?: string;
  ownerName?: string;
  nodeName?: string;
  ownerPath?: string[];
  data?: Record<string, unknown>;
}

sequence

  • Type: number

code

  • Type: DiagnosticCode

kind

  • Type: DiagnosticKind

severity

  • Type: DiagnosticSeverity

message

  • Type: string

ownerId

  • Type: string

ownerName

  • Type: string

nodeName

  • Type: string

ownerPath

  • Type: string[]

Root-first chain of named owners enclosing the subject of the event — component roots as <Name>, computations by their name option (or the effect/computed default) — e.g. ["<App>", "<TodoRow>", "effect"]. Unnamed owners (plain roots) are skipped. Absent when the subject has no named owner at all (a top-level scope, or an unowned primitive — which is usually the finding itself).

data

  • Type: Record<string, unknown>

DiagnosticKind

type DiagnosticKind =
  | "strict-read"
  | "async"
  | "write"
  | "lifecycle"
  | "owner"
  | "error"
  | "perf"
  | "graph"
  | "responsiveness"
  | "ssr"
  | "head"
  | "render";

DiagnosticListener

A findings listener. subject is the live node the event is about, when the emitter located one — passed BESIDE the serializable event, the way the records channel passes live — for an in-process consumer that goes from a finding to the scope (devtools, a console task lookup); undefined for an event with no location, or a host event whose owners are not signals' owners.

type DiagnosticListener = (
  event: DiagnosticEvent,
  subject: DiagnosticSubject | undefined
) => void;

Diagnostics

interface Diagnostics {
  subscribe(listener: DiagnosticListener): () => void;
  capture(): DiagnosticCapture;
  emit(
    event: Omit<DiagnosticEvent, "sequence">,
    subject?: DiagnosticSubject | null
  ): DiagnosticEvent;
}

subscribe

  • Type: () => void

capture

  • Type: DiagnosticCapture

emit

  • Type: DiagnosticEvent

Records an event on the channel from outside the reactive core — a host runtime reporting its own findings (hydration mismatches, server render faults) so consumers see one stream. subject locates it like the internal sites do; a host whose owners are not signals' owners passes ownerPath on the event instead and it is used as-is.

DiagnosticSeverity

info is the advisory tier: a structural fact worth surfacing that is not presumptively a bug (e.g. a 2-deep sequential fetch chain, which may be an intrinsic data dependency). Budget/assertion consumers should treat only warn/error as failures unless they opt in to info.

type DiagnosticSeverity = "info" | "warn" | "error";

DiagnosticSubject

Anything a diagnostic can be about: an owner (root, computed, effect) or a signal.

type DiagnosticSubject = Owner | Signal<any> | Computed<any>;
Last updated: 10/15/26, 9:29 AMEdit this pageReport an issue with this page