From b9d60e9f856eb53a1ff8a5a9c5de9f4112684302 Mon Sep 17 00:00:00 2001
From: dawn <90008@klbr.net>
Date: Wed, 5 Aug 2026 18:24:13 +0300
Subject: [PATCH] [config] reject ephemeral backlinks builds

backlinks hooks are compiled into every record mutation and
enable_backlinks does not disable them at runtime; without its own
retention machinery an ephemeral window would leak stale backlink
entries. validate() now rejects HYDRANT_EPHEMERAL when the backlinks
feature is compiled in, and relay mode rejects only_index_links.

issue: hydrant-die
---
 src/config.rs | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/src/config.rs b/src/config.rs
index d320e37..8b6d7a3 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -434,6 +434,16 @@ impl Config {
             ));
         }
 
+        // backlinks hooks are compiled directly into every record mutation;
+        // `enable_backlinks` does not disable them at runtime. without its own
+        // retention machinery an ephemeral window would leak stale entries.
+        #[cfg(feature = "backlinks")]
+        if self.ephemeral {
+            return Err(miette::miette!(
+                "the backlinks feature is not supported with HYDRANT_EPHEMERAL / ephemeral"
+            ));
+        }
+
         #[cfg(feature = "relay")]
         if self.only_index_links {
             return Err(miette::miette!(
@@ -464,6 +474,33 @@ mod tests {
         assert!(config.validate().is_ok());
     }
 
+    #[test]
+    #[cfg(feature = "backlinks")]
+    fn ephemeral_rejected_when_backlinks_feature_enabled() {
+        let mut config = Config::default();
+        config.ephemeral = true;
+        config.enable_backlinks = false;
+        let res = config.validate();
+        assert!(res.is_err());
+        let err = res.unwrap_err().to_string();
+        assert!(err.contains("HYDRANT_EPHEMERAL") || err.contains("ephemeral"));
+        assert!(err.contains("backlinks feature"));
+
+        config.enable_backlinks = true;
+        assert!(config.validate().is_err());
+
+        config.ephemeral = false;
+        assert!(config.validate().is_ok());
+    }
+
+    #[test]
+    #[cfg(all(feature = "indexer_stream", not(feature = "backlinks")))]
+    fn ephemeral_allowed_when_backlinks_feature_disabled() {
+        let mut config = Config::default();
+        config.ephemeral = true;
+        assert!(config.validate().is_ok());
+    }
+
     #[test]
     #[cfg(all(feature = "indexer", not(feature = "indexer_stream")))]
     fn ephemeral_requires_stream_storage() {
-- 
2.51.2