feat: freeze typed metrics registry and bounded exemplars

crates/crank-metrics/tests/contract.rs

@@ -8,7 +8,7 @@ use crank_metrics::{
     metric_schema, record_cache_outcome, record_confirmation_outcome, record_export_failure,
     record_http_request, record_idempotency_outcome, record_invocation_history_lost,
     record_limit_rejection, record_mcp_request, record_tool_invocation, record_upstream_request,
-    set_catalog, set_db_pool_connections, set_mcp_active_sessions,
+    set_catalog, set_db_pool_connections, set_mcp_active_sessions, set_mcp_session_metrics_fresh,
 };
 use metrics_util::debugging::DebuggingRecorder;
 
@@ -80,6 +80,26 @@ fn application_outcomes_are_distinct_from_transport_success() {
     assert_eq!(ConfirmationOutcome::Required.as_str(), "required");
 }
 
+#[test]
+fn impossible_tool_outcome_pairs_are_normalized() {
+    let recorder = DebuggingRecorder::new();
+    let snapshotter = recorder.snapshotter();
+    metrics::with_local_recorder(&recorder, || {
+        record_tool_invocation(
+            InvocationSource::AgentToolCall,
+            ToolOutcome::Success,
+            ToolErrorKind::Mapping,
+            Duration::ZERO,
+        );
+    });
+    let snapshot = snapshotter.snapshot().into_vec();
+    assert!(snapshot.iter().any(|(key, _, _, _)| {
+        key.key().name() == "crank_tool_invocations_total"
+            && has_label(key.key(), "outcome", "success")
+            && has_label(key.key(), "error_kind", "none")
+    }));
+}
+
 #[test]
 fn dropped_product_guards_record_aborted_outcomes() {
     let recorder = DebuggingRecorder::new();
@@ -128,6 +148,7 @@ fn diverse_calls_cannot_create_unbounded_series() {
                 McpMethod::ToolsCall,
                 McpResponseMode::Json,
                 McpOutcome::ToolError,
+                Duration::from_millis(1),
             );
             record_tool_invocation(
                 InvocationSource::AgentToolCall,
@@ -147,7 +168,7 @@ fn diverse_calls_cannot_create_unbounded_series() {
         .map(|(key, _, _, _)| format!("{:?}", key.key()))
         .collect::<BTreeSet<_>>();
 
-    assert_eq!(series.len(), 8);
+    assert_eq!(series.len(), 9);
     assert!(
         series
             .iter()
@@ -172,8 +193,10 @@ fn every_recording_api_matches_the_declared_schema() {
             McpMethod::ToolsCall,
             McpResponseMode::Json,
             McpOutcome::Success,
+            Duration::from_millis(1),
         );
         set_mcp_active_sessions(1);
+        set_mcp_session_metrics_fresh(true);
         let _stream = InFlightGuard::mcp_stream();
         let _runtime = InFlightGuard::runtime();
         record_tool_invocation(