diff --git a/AGENTS.md b/AGENTS.md
index e4aeb68d0..3191c72fc 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -238,7 +238,7 @@ Release commits are the exception: keep using `Release v0.x.y`.
 ## Code conventions
 
 - Do not place code or tests ad hoc. Before adding or moving files, inspect the existing folder structure and nearby patterns, then put changes in the established domain-specific location. If no proper location exists, create one deliberately and update docs/conventions as needed.
-- Architecture boundaries are enforced by Steiger (`bun run check:arch`). App code must use public workspace package exports, workspace packages must not import app `src/` code, package-local aliases (`#core`, `#vue`, `#cli`, `#mcp`) are only for their owning package, core must stay framework-agnostic, app service/domain code (`src/app/**`) must not import app component/view layers, components must not import views, shared UI (`src/components/ui/**`) must not import app services/stores, property-panel internals must stay inside the property panel, canvas/editor overlay code must not import property-panel internals, committed code must not import scratch/generated/vendor internals, and durable docs belong under `packages/docs/**` unless the root Markdown allowlist is deliberately updated.
+- Architecture boundaries are enforced by Steiger (`bun run check:arch`). App code must use public workspace package exports, workspace packages must not import app `src/` code, package-local aliases (`#core`, `#vue`, `#cli`, `#mcp`) are only for their owning package, core must stay framework-agnostic, app service/domain code (`src/app/**`) must not import app component/view layers, components must not import views, shared UI (`src/components/ui/**`) must not import app services/stores, property-panel internals must stay inside the property panel, canvas/editor overlay code must not import property-panel internals, Vue components must not use `<style>` blocks, code outside core editor internals must not assign `editor.state.selectedIds` or `editor.state.activeTool` directly, committed code must not import scratch/generated/vendor internals, and durable docs belong under `packages/docs/**` unless the root Markdown allowlist is deliberately updated.
 - Test placement is strict and enforced by Steiger: app E2E tests live under `tests/e2e/**` and use `*.spec.ts`; Figma automation tests live under `tests/figma/**` and use `*.spec.ts`; engine/unit tests live under `tests/engine/**` and use `*.test.ts` (with `helpers.ts`, `*.bench.ts`, and `visual-*` support scripts allowed); shared test utilities live under `tests/helpers/**`. Do not commit temporary/profile specs (`*.tmp.*`, `*.profile.*`). Do not put store-only/internal-state assertions in E2E. If a test drives the UI like a user and verifies visible behavior, it can be E2E; if it creates nodes through internals and asserts graph state, it belongs in engine/unit coverage.
 
 ### File and folder naming
diff --git a/scripts/steiger-rules.ts b/scripts/steiger-rules.ts
index e1d007572..74160ce5d 100644
--- a/scripts/steiger-rules.ts
+++ b/scripts/steiger-rules.ts
@@ -230,6 +230,27 @@ const noE2EImportsInEngineTests = createImportRule(
   }
 )
 
+const noVueStyleBlocks = createFileRule('open-pencil/no-vue-style-blocks', (sourceRel) => {
+  if (!sourceRel.endsWith('.vue')) return null
+  if (!sourceRel.startsWith('src/') && !sourceRel.startsWith('packages/vue/src/')) return null
+  const content = readFileSync(path.resolve(sourceRel), 'utf8')
+  return /<style\b/i.test(content)
+    ? 'Vue components must not use <style> blocks. Use Tailwind utilities or global app.css tokens.'
+    : null
+})
+
+const noDirectSelectionOrToolStateMutation = createFileRule(
+  'open-pencil/no-direct-selection-tool-state-mutation',
+  (sourceRel) => {
+    if (!sourceRel.endsWith('.ts') && !sourceRel.endsWith('.vue')) return null
+    if (sourceRel.startsWith('packages/core/src/editor/')) return null
+    const content = readFileSync(path.resolve(sourceRel), 'utf8')
+    return /\.state\.(selectedIds|activeTool)\s*=(?!=)/.test(content)
+      ? 'Do not assign editor.state.selectedIds or editor.state.activeTool directly. Use editor selection/tool actions.'
+      : null
+  }
+)
+
 const noRootMarkdownClutter = createFileRule('open-pencil/no-root-markdown-clutter', (sourceRel) => {
   if (sourceRel.includes('/')) return null
   if (!sourceRel.endsWith('.md')) return null
@@ -397,6 +418,8 @@ export const openPencilArchitecturePlugin = {
   meta: { name: 'open-pencil-architecture', version: '0.0.0' },
   ruleDefinitions: [
     preferDomainFoldersOverFilenamePrefixes,
+    noVueStyleBlocks,
+    noDirectSelectionOrToolStateMutation,
     strictTestFilePlacement,
     noEngineOnlyAssertionsInE2E,
     noE2EImportsInEngineTests,
diff --git a/src/app.css b/src/app.css
index 6b445fada..c3bf3d9ac 100644
--- a/src/app.css
+++ b/src/app.css
@@ -109,6 +109,32 @@ body {
   -webkit-user-select: none;
 }
 
+.code-highlight .token.tag {
+  color: var(--color-code-tag);
+}
+
+.code-highlight .token.attr-name {
+  color: var(--color-code-attribute);
+}
+
+.code-highlight .token.attr-value,
+.code-highlight .token.string {
+  color: var(--color-code-string);
+}
+
+.code-highlight .token.number,
+.code-highlight .token.boolean {
+  color: var(--color-code-number);
+}
+
+.code-highlight .token.punctuation {
+  color: var(--color-code-punctuation);
+}
+
+.code-highlight .token.keyword {
+  color: var(--color-code-attribute);
+}
+
 input[type='number'] {
   appearance: textfield;
   -moz-appearance: textfield;
diff --git a/src/components/CodePanel.vue b/src/components/CodePanel.vue
index 8d8c9cc72..d3404b084 100644
--- a/src/components/CodePanel.vue
+++ b/src/components/CodePanel.vue
@@ -92,7 +92,7 @@ function copyReference() {
     </div>
 
     <ScrollAreaRoot class="min-h-0 flex-1">
-      <ScrollAreaViewport class="size-full">
+      <ScrollAreaViewport class="code-highlight size-full">
         <div class="p-3">
           <div v-for="(html, i) in highlightedLines" :key="i" class="flex text-xs leading-5">
             <span
@@ -113,27 +113,3 @@ function copyReference() {
   </div>
 </template>
 
-<style scoped>
-.token.tag {
-  color: var(--color-code-tag);
-}
-.token.attr-name {
-  color: var(--color-code-attribute);
-}
-.token.attr-value,
-.token.string {
-  color: var(--color-code-string);
-}
-.token.number {
-  color: var(--color-code-number);
-}
-.token.punctuation {
-  color: var(--color-code-punctuation);
-}
-.token.boolean {
-  color: var(--color-code-number);
-}
-.token.keyword {
-  color: var(--color-code-attribute);
-}
-</style>
diff --git a/steiger.config.ts b/steiger.config.ts
index 1e137d73b..f149a3611 100644
--- a/steiger.config.ts
+++ b/steiger.config.ts
@@ -22,6 +22,8 @@ export default defineConfig([
   {
     rules: {
       'open-pencil/prefer-domain-folders-over-filename-prefixes': 'error',
+      'open-pencil/no-vue-style-blocks': 'error',
+      'open-pencil/no-direct-selection-tool-state-mutation': 'error',
       'open-pencil/strict-test-file-placement': 'error',
       'open-pencil/no-engine-only-assertions-in-e2e': 'error',
       'open-pencil/no-e2e-imports-in-engine-tests': 'error',
diff --git a/tests/e2e/color-picker/demo-card.spec.ts b/tests/e2e/color-picker/demo-card.spec.ts
index 30aa1670f..96c01de74 100644
--- a/tests/e2e/color-picker/demo-card.spec.ts
+++ b/tests/e2e/color-picker/demo-card.spec.ts
@@ -39,8 +39,7 @@ async function selectDemoCard(page: Parameters<typeof test>[0]['page'], canvas:
           .map((n) => `${n.name}:${n.type}`)
           .join(', ')}`
       )
-    store.state.selectedIds = new Set([card.id])
-    store.requestRender()
+    store.select([card.id])
   })
   await canvas.waitForRender()
 
diff --git a/tests/e2e/stroke-picker/basic.spec.ts b/tests/e2e/stroke-picker/basic.spec.ts
index 33ec30c5e..e598eb962 100644
--- a/tests/e2e/stroke-picker/basic.spec.ts
+++ b/tests/e2e/stroke-picker/basic.spec.ts
@@ -103,8 +103,7 @@ test('stroke picker hsb saturation and brightness sliders update stroke color on
       align: 'INSIDE'
     }
     store.updateNodeWithUndo(card.id, { strokes: [stroke] }, 'Add demo card stroke')
-    store.state.selectedIds = new Set([card.id])
-    store.requestRender()
+    store.select([card.id])
   })
   await canvas.waitForRender()