From a2d0b7af189069ce962e6ba72e828ca8831e9094 Mon Sep 17 00:00:00 2001
From: "Claude (sandbox)" <claude@sandbox.local>
Date: Mon, 13 Jul 2026 11:11:20 +0000
Subject: [PATCH] feat(causal): fidelity footer in render_summary
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

One unconditional footer line whenever there are results:
"note: impacts are lower bounds — undershoot grows with speedup pct;
rankings unaffected" — surfacing the RFC 007 Validation fidelity statement
where users actually look, instead of only in the RFC. Wording pinned by
the summary test.
---
 src/causal.rs   | 11 +++++++++++
 tests/causal.rs |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/src/causal.rs b/src/causal.rs
index b9a413e..751ed9b 100644
--- a/src/causal.rs
+++ b/src/causal.rs
@@ -582,6 +582,11 @@ mod inner {
     /// each virtual speedup and the change relative to that site's own 0%
     /// baseline. A near-zero column across speedups means: optimising this
     /// site buys you nothing — the RFC's headline answer.
+    ///
+    /// Ends with a one-line fidelity note (RFC 007 Validation): reported
+    /// impacts are conservative — the controller undershoots ideal injection
+    /// at high speedup pcts, so gains are lower bounds; site *rankings* are
+    /// unaffected.
     pub fn render_summary(results: &[ExperimentResult]) -> String {
         use std::fmt::Write;
         let mut s = String::new();
@@ -612,6 +617,12 @@ mod inner {
                 }
             }
         }
+        if !results.is_empty() {
+            let _ = writeln!(
+                s,
+                "note: impacts are lower bounds — undershoot grows with speedup pct; rankings unaffected"
+            );
+        }
         s
     }
 
diff --git a/tests/causal.rs b/tests/causal.rs
index 653700b..e857337 100644
--- a/tests/causal.rs
+++ b/tests/causal.rs
@@ -330,6 +330,10 @@ fn controller_produces_report() {
         let summary = smarm::causal::render_summary(&results);
         assert!(summary.contains("stage-x"), "summary: {summary}");
         assert!(summary.contains("items"), "summary: {summary}");
+        assert!(
+            summary.contains("impacts are lower bounds"),
+            "fidelity footer missing: {summary}"
+        );
 
         let coz = smarm::causal::render_coz(&results);
         assert!(coz.contains("experiment\tselected=stage-x"), "coz: {coz}");