# Behavior traces — vuejs/core > Canonical page: https://codevetter.com/unpack/vue/behavior-traces # Behavior traces — vuejs/core Scanned commit 4ab865a848a1da3d10fb674f857e5fff13094644 (2026-09-18). Generated by codevetter codevetter 1.12.0 on 2026-09-22. Three flows carry most of the system's weight: browser app startup, a reactive state change producing a re-render, and SFC compilation as invoked by a bundler plugin. A fourth, hydration, forks off startup at `createSSRApp`. The call chains below were read in order through runtime-dom → apiCreateApp → renderer → component → scheduler. - Startup step 1: `createApp(RootComponent)` in runtime-dom calls `ensureRenderer()` (memoising a single module-level renderer created from `rendererOptions`), then in dev injects `isNativeTag` and the `compilerOptions` getter warnings before wrapping `app.mount`. — [packages/runtime-dom/src/index.ts#L80-L113](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-dom/src/index.ts#L80-L113) [packages/runtime-dom/src/index.ts#L185-L232](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-dom/src/index.ts#L185-L232) - Startup step 2: the wrapped `app.mount` calls `normalizeContainer` (a `document.querySelector` for string selectors, with a dev warning for closed ShadowRoots), copies `container.innerHTML` into `component.template` when the component has neither render nor template, clears `container.textContent`, calls the inner mount, then sets `data-v-app` and removes `v-cloak`. — [packages/runtime-dom/src/index.ts#L111-L148](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-dom/src/index.ts#L111-L148) [packages/runtime-dom/src/index.ts#L234-L258](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-dom/src/index.ts#L234-L258) - Startup step 3: the inner `mount` in apiCreateApp creates the root vnode via `createVNode(rootComponent, rootProps)`, stamps `vnode.appContext = context`, installs a dev-only `context.reload` HMR hook that re-renders a cloned vnode with `el = null`, then calls `render(vnode, rootContainer, namespace)` and finally sets `rootContainer.__vue_app__ = app` and calls `devtoolsInitApp`. — [packages/runtime-core/src/apiCreateApp.ts#L356-L420](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/apiCreateApp.ts#L356-L420) - Startup step 4: the renderer's `render` dispatches to `patch(container._vnode || null, vnode, ...)`, records `container._vnode = vnode`, and then — guarded by an `isFlushing` latch — drains `flushPreFlushCbs` and `flushPostFlushCbs` synchronously. — [packages/runtime-core/src/renderer.ts#L2449-L2476](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/renderer.ts#L2449-L2476) - Startup step 5: `patch` switches on vnode type (Text/Comment/Static/Fragment) and otherwise on `shapeFlag`, routing ELEMENT → `processElement`, COMPONENT → `processComponent`, TELEPORT → `TeleportImpl.process(..., internals)` and (under `__FEATURE_SUSPENSE__`) SUSPENSE → `SuspenseImpl.process(..., internals)`. — [packages/runtime-core/src/renderer.ts#L420-L500](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/renderer.ts#L420-L500) - Startup step 6: `mountComponent` calls `createComponentInstance`, registers HMR when `instance.type.__hmrId` exists, injects `internals` into the ctx when the vnode is a KeepAlive, calls `setupComponent(instance, false, optimized)`, and either registers the instance with the parent Suspense (when `instance.asyncDep` is set, inserting a Comment placeholder) or calls `setupRenderEffect`. — [packages/runtime-core/src/renderer.ts#L1215-L1290](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/renderer.ts#L1215-L1290) - Startup step 7: `setupComponent` runs `initProps` then `initSlots`, and for stateful components `setupStatefulComponent` creates `instance.accessCache`, wraps `instance.ctx` in `new Proxy(instance.ctx, PublicInstanceProxyHandlers)`, pauses tracking, and invokes `setup(props, setupContext)` through `callWithErrorHandling` with `ErrorCodes.SETUP_FUNCTION`. — [packages/runtime-core/src/component.ts#L809-L880](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/component.ts#L809-L880) - Startup step 8: `finishComponentSetup` performs on-the-fly compilation only when `!isSSR && compile && !Component.render`, merging app-level `compilerOptions`, component-level `compilerOptions` and `delimiters` into `finalCompilerOptions`, then installs the `RuntimeCompiledPublicInstanceProxyHandlers` proxy for `with`-block render functions and finally runs `applyOptions(instance)` when `__FEATURE_OPTIONS_API__`. — [packages/runtime-core/src/component.ts#L998-L1080](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/component.ts#L998-L1080) - Startup step 9: `setupRenderEffect`'s `componentUpdateFn` on first run fires `bm` hooks, then either hydrates (when `el && hydrateNode`, optionally deferring through `type.__asyncHydrate` for lazy-hydrated async components) or calls `renderComponentRoot(instance)` and patches; on completion it queues `onVnodeMounted`/`m`/`a` hooks via `queuePostRenderEffect`, sets `instance.isMounted = true` and nulls `initialVNode`/`container`/`anchor` to avoid mount-only memory leaks (#2458). — [packages/runtime-core/src/renderer.ts#L1329-L1490](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/renderer.ts#L1329-L1490) - Update trace: a reactive write calls `Dep.trigger` → subscriber `notify()` → `batch(sub)` unless the effect is already RUNNING without ALLOW_RECURSE; the component's effect scheduler calls `queueJob`, `queueFlush` schedules `flushJobs` on the microtask queue, and `flushJobs` re-enters `componentUpdateFn` on the update branch which resolves `next`, runs `bu`, re-renders and patches, then queues `u`. — [packages/reactivity/src/effect.ts#L148-L162](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/reactivity/src/effect.ts#L148-L162) [packages/runtime-core/src/scheduler.ts#L99-L123](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/scheduler.ts#L99-L123) [packages/runtime-core/src/renderer.ts#L1487-L1530](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/renderer.ts#L1487-L1530) - Hydration trace: `createSSRApp` → `ensureHydrationRenderer()` → `createHydrationRenderer(rendererOptions)` → `baseCreateRenderer(options, createHydrationFunctions)`, whose returned `[hydrate, hydrateNode]` pair is wired to the internals; `app.mount(container, true, ...)` then routes to `hydrate(vnode, rootContainer)` instead of `render`, and any structural divergence calls `logMismatchError()`. — [packages/runtime-dom/src/index.ts#L87-L170](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-dom/src/index.ts#L87-L170) [packages/runtime-core/src/renderer.ts#L2494-L2500](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/renderer.ts#L2494-L2500) [packages/runtime-core/src/hydration.ts#L59-L140](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/runtime-core/src/hydration.ts#L59-L140) - Full-build template trace: `compileToFunction` short-circuits on `compileCache[key]`, resolves a `#id` selector to `el.innerHTML` (annotated `__UNSAFE__`), defaults `isCustomElement` to `tag => !!customElements.get(tag)`, calls `compile(template, opts)`, then evaluates the generated code with `new Function('Vue', code)(runtimeDom)` and tags the result `_rc = true`. — [packages/vue/src/index.ts#L30-L105](https://github.com/vuejs/core/blob/4ab865a848a1da3d10fb674f857e5fff13094644/packages/vue/src/index.ts#L30-L105) - SFC trace: a bundler plugin calls `parse()` (LRU-cached) → `compileScript(descriptor, options)` for `