diff --git a/AGENTS.md b/AGENTS.md
index 98e1b57..826e374 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -35,6 +35,7 @@ Keep it stable. Prefer pointers to canonical sources over copied structure, file
 - First split intent into broad error classes: what can go wrong, and what outcome must hold.
 - Test the largest risky classes before narrow examples.
 - Add adversarial tests for malformed, hostile, ambiguous, missing, duplicated, and boundary inputs.
+- When changing generated lowering, prove dynamic rendered attributes at the consumer boundary; literal lowering fixtures alone are insufficient.
 - Do not over-codify existing behavior while direction is still moving.
 - Add narrow concrete tests only after requirements converge into a stable direction.
 
diff --git a/REQUIREMENTS.md b/REQUIREMENTS.md
index 9f5f29e..05c7d84 100644
--- a/REQUIREMENTS.md
+++ b/REQUIREMENTS.md
@@ -320,7 +320,7 @@ resources. Concrete runtime targets are addressed through `ResourceRef`
 
 004	Without a key, hemx-addressable nodes inside a loop are rejected at build time. Keyed identity is `ResourceRef { resource: ResourceId, scope: Some(ScopeKey::KeyValue(...)) }`. [north_star]
 
-002	Slots inside a keyed loop receive a composite identity. hemplate records `key_expr` in the Surface; hemx implements keyed slot lookups. [north_star]
+002	Slots inside a keyed loop receive a composite identity. hemplate records `key_expr` in the Surface; hemx implements keyed slot lookups and lowers rendered `h-key` identity to its private `data-key` runtime marker. [north_star]
 
 003	Generated helpers for keyed slots are `append(view)`, `prepend(view)`, `replace(view)`, and `remove(key_or_view)` when the template and view type provide an unambiguous `h-key`. [north_star]
 
diff --git a/hemx-build/src/lib.rs b/hemx-build/src/lib.rs
index 8799dd2..8f89e17 100644
--- a/hemx-build/src/lib.rs
+++ b/hemx-build/src/lib.rs
@@ -1072,6 +1072,7 @@ fn __hemx_lower_html(html: &str, table: &[(&str, &str, u32)]) -> ::std::string::
         out = __hemx_replace_attr(out, attr, name, runtime_attr, *id);
     }
     out = __hemx_lower_static_attr(out, "data-hemx-key", "data-key");
+    out = __hemx_lower_static_attr(out, "h-key", "data-key");
     __hemx_inject_handle_inputs(out)
 }
 
@@ -4586,11 +4587,11 @@ mod hemplate {{
 }}
 {generated}
 fn main() {{
-    let html = todo::lower_html(r#"<form data-hemx-handle="create"><input name="title"></form><li data-hemx-slot="row" data-hemx-key="7"></li>"#);
+    let html = todo::lower_html(r#"<form data-hemx-handle="create"><input name="title"></form><li data-hemx-slot="row" h-key="7"></li>"#);
     assert!(html.contains(r#"data-hid="#));
     assert!(html.contains(r#"name="__h""#));
-    assert!(html.contains(r#"data-key="7""#));
-    assert!(!html.contains("data-hemx-key"));
+    assert!(html.contains(r#"data-key="7""#)); // req: list/002 test
+    assert!(!html.contains("h-key"));
 }}
 "###,
         );