diff --git a/apps/web/src/services/ai/__tests__/model-profiles-element-tools.test.ts b/apps/web/src/services/ai/__tests__/model-profiles-element-tools.test.ts
index f2b988665..adb1280d7 100644
--- a/apps/web/src/services/ai/__tests__/model-profiles-element-tools.test.ts
+++ b/apps/web/src/services/ai/__tests__/model-profiles-element-tools.test.ts
@@ -8,7 +8,7 @@ import type { ModelProfile } from '../model-profiles';
  * Contract (per plan §3.1 — openpencil-docs
  * superpowers/plans/2026-04-21-element-tools-orchestrator-integration.md):
  *   needsElementTools(p) === true
- *     iff  ENABLE_ELEMENT_TOOLS_IN_ORCHESTRATOR env var is truthy
+ *     iff  VITE_ENABLE_ELEMENT_TOOLS env var is truthy
  *     AND  p.tier is 'basic' or 'standard'
  *
  * Why the tier gate: A/B v1 showed ceiling regression on the one
@@ -17,7 +17,7 @@ import type { ModelProfile } from '../model-profiles';
  * by default even when the global flag is on.
  */
 
-const FLAG = 'ENABLE_ELEMENT_TOOLS_IN_ORCHESTRATOR';
+const FLAG = 'VITE_ENABLE_ELEMENT_TOOLS';
 
 function profile(tier: ModelProfile['tier']): ModelProfile {
   return { match: '', tier, label: `Test ${tier}` };
diff --git a/apps/web/src/services/ai/model-profiles.ts b/apps/web/src/services/ai/model-profiles.ts
index 816b876f0..987ccc5f4 100644
--- a/apps/web/src/services/ai/model-profiles.ts
+++ b/apps/web/src/services/ai/model-profiles.ts
@@ -110,13 +110,22 @@ export function needsSimplifiedPrompt(profile: ModelProfile): boolean {
  * unchanged until the flag is explicitly flipped. Any truthy value
  * (`"1"`, `"true"`, `"yes"`, case-insensitive) enables the feature.
  *
+ * Name MUST start with `VITE_` — the sub-agent that reads this helper
+ * runs inside the Vite browser bundle, and Vite's default `envPrefix`
+ * only exposes `VITE_`-prefixed variables to `import.meta.env`. A
+ * bare name (e.g. `ENABLE_ELEMENT_TOOLS_IN_ORCHESTRATOR`) would be
+ * inlined as `undefined` at build time for the client, silently
+ * defeating the rollout flip. Server-side `process.env` reads work
+ * fine with any name, so this dual-compatible name is an alias that
+ * functions on both sides of the SSR boundary.
+ *
  * Rollout per plan §4 (openpencil-docs
  * superpowers/plans/2026-04-21-element-tools-orchestrator-integration.md):
  *   Phase 1: ship with flag off (scaffolding only, zero behavior change)
  *   Phase 2: flip on for basic + standard tiers in a canary env
  *   Phase 3: remove the flag once stable across a monitoring window
  */
-const ELEMENT_TOOLS_FLAG_ENV = 'ENABLE_ELEMENT_TOOLS_IN_ORCHESTRATOR';
+const ELEMENT_TOOLS_FLAG_ENV = 'VITE_ENABLE_ELEMENT_TOOLS';
 
 /**
  * Read the element-tools feature flag from env in a way that's safe
diff --git a/apps/web/src/services/ai/orchestrator-sub-agent.ts b/apps/web/src/services/ai/orchestrator-sub-agent.ts
index e88359001..6be893ab1 100644
--- a/apps/web/src/services/ai/orchestrator-sub-agent.ts
+++ b/apps/web/src/services/ai/orchestrator-sub-agent.ts
@@ -363,7 +363,7 @@ async function executeSubAgent(
   const hasDesignMdContent = designMdContent.length > 0;
 
   // Feature-flagged gate for N-tool element-surface integration.
-  // Only fires when ENABLE_ELEMENT_TOOLS_IN_ORCHESTRATOR env var is
+  // Only fires when VITE_ENABLE_ELEMENT_TOOLS env var is
   // truthy AND the model is in the basic/standard tier; full-tier
   // models stay on the legacy path per A/B v1 ceiling-effect finding
   // (Kimi K2.5 Δ M1 -12.5pp). Default production state is off, so
@@ -517,8 +517,8 @@ async function executeSubAgent(
           error:
             `Element-tool output detected (${detectedName}) but the ` +
             `apply pipeline is not yet wired into the embedded ` +
-            `orchestrator. Set ENABLE_ELEMENT_TOOLS_IN_ORCHESTRATOR=0 ` +
-            `to fall back to the legacy JSONL path, or wait for ` +
+            `orchestrator. Unset VITE_ENABLE_ELEMENT_TOOLS (or set ` +
+            `it to 0) to fall back to the legacy JSONL path, or wait for ` +
             `integration plan §3.5 (openpencil-docs ` +
             `superpowers/plans/2026-04-21-element-tools-orchestrator-integration.md).`,
         };