fix(agent): ground time-relative statements in the live clock (#3602) (#3752)

Co-authored-by: Claude <noreply@anthropic.com>

tests/agent_round26_raw_coverage_e2e.rs

@@ -466,11 +466,15 @@ async fn builder_dedupes_visible_native_tools_and_seed_resume_bounds_history() -
         .messages
         .iter()
         .any(|msg| msg.role == "user" && msg.content == "falls back to user"));
+    // The live turn's user message is stamped with the per-turn
+    // `Current Date & Time:` line (#3602), so match by suffix rather than
+    // exact equality — the dedup contract (exactly one "current message"
+    // user turn after resume) still holds.
     assert_eq!(
         requests[0]
             .messages
             .iter()
-            .filter(|msg| msg.role == "user" && msg.content == "current message")
+            .filter(|msg| msg.role == "user" && msg.content.ends_with("current message"))
             .count(),
         1
     );

tests/calendar_grounding_e2e.rs

@@ -121,12 +121,32 @@ async fn test_orchestrator_has_current_date_context() -> Result<()> {
     let _ = agent.turn("what is on my calendar this week?").await?;
 
     let messages = captured_messages.lock();
-    let system_prompt = messages
+    // The system prompt carries the static grounding *rule* (#3602) — the
+    // concrete clock no longer lives here, it rides the per-turn user message
+    // so a long-lived session can't go stale.
+    messages
         .iter()
         .find(|m| m.role == "system" && m.content.contains("## Current Date & Time"))
-        .expect("System prompt should contain Current Date & Time");
+        .expect("System prompt should carry the Current Date & Time grounding rule");
 
-    assert!(system_prompt.content.contains("202"));
+    // The live date/time is injected on the user message every turn. Assert it
+    // carries the stamp and a concrete year token.
+    let user_msg = messages
+        .iter()
+        .find(|m| m.role == "user" && m.content.contains("Current Date & Time:"))
+        .expect("User message should carry the per-turn Current Date & Time stamp");
+    // Assert a concrete `YYYY-MM-DD HH:MM:SS` shape rather than a decade token
+    // (which would rot as years advance).
+    let after = user_msg
+        .content
+        .split("Current Date & Time: ")
+        .nth(1)
+        .expect("stamp must follow the canonical prefix");
+    let dt = after
+        .get(0..19)
+        .expect("stamp must include YYYY-MM-DD HH:MM:SS");
+    chrono::NaiveDateTime::parse_from_str(dt, "%Y-%m-%d %H:%M:%S")
+        .expect("user message stamp must include a parseable YYYY-MM-DD HH:MM:SS");
 
     Ok(())
 }