diff --git a/scripts/convert-openrouter-models.ts b/scripts/convert-openrouter-models.ts
index e5967a975..5c20f6558 100644
--- a/scripts/convert-openrouter-models.ts
+++ b/scripts/convert-openrouter-models.ts
@@ -130,12 +130,30 @@ function generateModelMetaString(model: OpenRouterModel): string {
   const outputModalities = model.architecture.output_modalities
     .map(mapInputModality)
     .filter((m): m is InputModality => m !== null)
+  // OpenRouter uses `~prefix/name` to denote routing aliases (e.g.
+  // `~anthropic/claude-haiku-latest`). The model ID itself is preserved as a
+  // string literal so users can pass it to `chat({ model: ... })`. The leading
+  // `~` is mapped to `_` only for the derived constant name so it's a valid
+  // JavaScript identifier.
   const constName = model.id
+    .replaceAll('~', '_')
     .replaceAll('/', '-')
     .replaceAll('-', '_')
     .replaceAll('.', '_')
     .replaceAll(':', '_')
     .toUpperCase()
+  // Safety net: if a future OpenRouter ID quirk produces a non-identifier
+  // constant name, fail loudly here instead of letting prettier choke on the
+  // generated file later in the pipeline.
+  if (!/^[A-Z_][A-Z0-9_]*$/.test(constName)) {
+    throw new Error(
+      `Generated constant name is not a valid JS identifier: ${JSON.stringify(
+        constName,
+      )} (from OpenRouter model.id ${JSON.stringify(
+        model.id,
+      )}). Extend the constName sanitiser to handle this case.`,
+    )
+  }
   // Ensure at least 'text' is present
   if (!inputModalities.includes('text')) {
     inputModalities.unshift('text')