diff --git a/.gitignore b/.gitignore
index 2b0e83ef2..17e3ebe60 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,3 +13,6 @@ supabase/.temp/
 .idea
 eval/reports/
 eval/data/world-v1/world.html
+
+# BrainBench amara-life-v1 Opus cache (regenerate via eval:generate-amara-life)
+eval/data/amara-life-v1/_cache/
diff --git a/eval/generators/amara-life-gen.ts b/eval/generators/amara-life-gen.ts
index 055a254cb..66ce23ccc 100644
--- a/eval/generators/amara-life-gen.ts
+++ b/eval/generators/amara-life-gen.ts
@@ -79,7 +79,10 @@ const SCHEMA_VERSION = 1;         // bump invalidates cache wholesale
 const MODEL_PARAMS = {
   max_tokens: 1500,
   temperature: 1.0,
-  top_p: 1.0,
+  // top_p omitted: current Opus rejects temperature + top_p together.
+  // top_p=1.0 is a no-op (no nucleus truncation), so dropping it has no
+  // semantic effect. Cache-key field still hashed; old cache entries
+  // (none in v1 yet) would invalidate cleanly on this change.
 };
 
 const CORPUS_ROOT = 'eval/data/amara-life-v1';
@@ -320,7 +323,6 @@ async function callOpus(
     model: MODEL,
     max_tokens: MODEL_PARAMS.max_tokens,
     temperature: MODEL_PARAMS.temperature,
-    top_p: MODEL_PARAMS.top_p,
     messages: [{ role: 'user', content: prompt }],
   });