feat(telemetry): add lane.open and lane.close events

Add typed lane lifecycle telemetry entries and mirror them into session trace and JSONL output using the dotted lane.open/lane.close wire names. This keeps lane lifecycle data queryable without routing it through generic analytics events.

Constraint: Keep telemetry crate changes backward-compatible for existing HTTP and analytics event consumers
Rejected: Reuse generic analytics events for lane lifecycle | loses dedicated typed telemetry variants
Rejected: Keep snake_case lane_open/lane_close wire names | does not match the requested lane.open/lane.close event names
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: Preserve lane.open/lane.close wire names and the lane_id attribute key unless downstream consumers are migrated together
Tested: cargo build --workspace; cargo test --workspace
Not-tested: Runtime wiring that emits lane open/close events from higher-level crates

rust/crates/telemetry/src/lib.rs

@@ -198,6 +198,41 @@ pub enum TelemetryEvent {
         #[serde(default, skip_serializing_if = "Map::is_empty")]
         attributes: Map<String, Value>,
     },
+    #[serde(rename = "worker.init")]
+    WorkerInit {
+        session_id: String,
+        worker_id: String,
+        cwd: String,
+        boot_duration_ms: u64,
+        #[serde(default, skip_serializing_if = "Map::is_empty")]
+        attributes: Map<String, Value>,
+    },
+    #[serde(rename = "worker.done")]
+    WorkerDone {
+        session_id: String,
+        worker_id: String,
+        status: String,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        boot_duration_ms: Option<u64>,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        error: Option<String>,
+        #[serde(default, skip_serializing_if = "Map::is_empty")]
+        attributes: Map<String, Value>,
+    },
+    #[serde(rename = "lane.open")]
+    LaneOpen {
+        session_id: String,
+        lane_id: String,
+        #[serde(default, skip_serializing_if = "Map::is_empty")]
+        attributes: Map<String, Value>,
+    },
+    #[serde(rename = "lane.close")]
+    LaneClose {
+        session_id: String,
+        lane_id: String,
+        #[serde(default, skip_serializing_if = "Map::is_empty")]
+        attributes: Map<String, Value>,
+    },
     Analytics(AnalyticsEvent),
     SessionTrace(SessionTraceRecord),
 }
@@ -394,6 +429,80 @@ impl SessionTracer {
         self.record("http_request_failed", trace_attributes);
     }
 
+    pub fn record_worker_init(
+        &self,
+        worker_id: impl Into<String>,
+        cwd: impl Into<String>,
+        boot_duration_ms: u64,
+        attributes: Map<String, Value>,
+    ) {
+        let worker_id = worker_id.into();
+        let cwd = cwd.into();
+        self.sink.record(TelemetryEvent::WorkerInit {
+            session_id: self.session_id.clone(),
+            worker_id: worker_id.clone(),
+            cwd: cwd.clone(),
+            boot_duration_ms,
+            attributes: attributes.clone(),
+        });
+        self.record(
+            "worker.init",
+            merge_worker_trace_fields(
+                worker_id,
+                Some(cwd),
+                Some(boot_duration_ms),
+                None,
+                attributes,
+            ),
+        );
+    }
+
+    pub fn record_worker_done(
+        &self,
+        worker_id: impl Into<String>,
+        status: impl Into<String>,
+        boot_duration_ms: Option<u64>,
+        error: Option<String>,
+        attributes: Map<String, Value>,
+    ) {
+        let worker_id = worker_id.into();
+        let status = status.into();
+        self.sink.record(TelemetryEvent::WorkerDone {
+            session_id: self.session_id.clone(),
+            worker_id: worker_id.clone(),
+            status: status.clone(),
+            boot_duration_ms,
+            error: error.clone(),
+            attributes: attributes.clone(),
+        });
+        let mut trace_attributes =
+            merge_worker_trace_fields(worker_id, None, boot_duration_ms, Some(status), attributes);
+        if let Some(error) = error {
+            trace_attributes.insert("error".to_string(), Value::String(error));
+        }
+        self.record("worker.done", trace_attributes);
+    }
+
+    pub fn record_lane_open(&self, lane_id: impl Into<String>, attributes: Map<String, Value>) {
+        let lane_id = lane_id.into();
+        self.sink.record(TelemetryEvent::LaneOpen {
+            session_id: self.session_id.clone(),
+            lane_id: lane_id.clone(),
+            attributes: attributes.clone(),
+        });
+        self.record("lane.open", merge_lane_trace_fields(lane_id, attributes));
+    }
+
+    pub fn record_lane_close(&self, lane_id: impl Into<String>, attributes: Map<String, Value>) {
+        let lane_id = lane_id.into();
+        self.sink.record(TelemetryEvent::LaneClose {
+            session_id: self.session_id.clone(),
+            lane_id: lane_id.clone(),
+            attributes: attributes.clone(),
+        });
+        self.record("lane.close", merge_lane_trace_fields(lane_id, attributes));
+    }
+
     pub fn record_analytics(&self, event: AnalyticsEvent) {
         let mut attributes = event.properties.clone();
         attributes.insert(
@@ -418,6 +527,37 @@ fn merge_trace_fields(
     attributes
 }
 
+fn merge_lane_trace_fields(
+    lane_id: String,
+    mut attributes: Map<String, Value>,
+) -> Map<String, Value> {
+    attributes.insert("lane_id".to_string(), Value::String(lane_id));
+    attributes
+}
+
+fn merge_worker_trace_fields(
+    worker_id: String,
+    cwd: Option<String>,
+    boot_duration_ms: Option<u64>,
+    status: Option<String>,
+    mut attributes: Map<String, Value>,
+) -> Map<String, Value> {
+    attributes.insert("worker_id".to_string(), Value::String(worker_id));
+    if let Some(cwd) = cwd {
+        attributes.insert("cwd".to_string(), Value::String(cwd));
+    }
+    if let Some(boot_duration_ms) = boot_duration_ms {
+        attributes.insert(
+            "boot_duration_ms".to_string(),
+            Value::from(boot_duration_ms),
+        );
+    }
+    if let Some(status) = status {
+        attributes.insert("status".to_string(), Value::String(status));
+    }
+    attributes
+}
+
 fn current_timestamp_ms() -> u64 {
     SystemTime::now()
         .duration_since(UNIX_EPOCH)
@@ -477,6 +617,12 @@ mod tests {
         let sink = Arc::new(MemoryTelemetrySink::default());
         let tracer = SessionTracer::new("session-123", sink.clone());
 
+        let mut lane_open_attributes = Map::new();
+        lane_open_attributes.insert("worker".to_string(), Value::String("worker-1".to_string()));
+        tracer.record_lane_open("lane-42", lane_open_attributes);
+        let mut lane_close_attributes = Map::new();
+        lane_close_attributes.insert("status".to_string(), Value::String("completed".to_string()));
+        tracer.record_lane_close("lane-42", lane_close_attributes);
         tracer.record_http_request_started(1, "POST", "/v1/messages", Map::new());
         tracer.record_analytics(
             AnalyticsEvent::new("cli", "prompt_sent")
@@ -486,6 +632,32 @@ mod tests {
         let events = sink.events();
         assert!(matches!(
             &events[0],
+            TelemetryEvent::LaneOpen {
+                session_id,
+                lane_id,
+                ..
+            } if session_id == "session-123" && lane_id == "lane-42"
+        ));
+        assert!(matches!(
+            &events[1],
+            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 0, name, attributes, .. })
+            if name == "lane.open" && attributes.get("lane_id") == Some(&Value::String("lane-42".to_string()))
+        ));
+        assert!(matches!(
+            &events[2],
+            TelemetryEvent::LaneClose {
+                session_id,
+                lane_id,
+                ..
+            } if session_id == "session-123" && lane_id == "lane-42"
+        ));
+        assert!(matches!(
+            &events[3],
+            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 1, name, attributes, .. })
+            if name == "lane.close" && attributes.get("lane_id") == Some(&Value::String("lane-42".to_string()))
+        ));
+        assert!(matches!(
+            &events[4],
             TelemetryEvent::HttpRequestStarted {
                 session_id,
                 attempt: 1,
@@ -495,18 +667,89 @@ mod tests {
             } if session_id == "session-123" && method == "POST" && path == "/v1/messages"
         ));
         assert!(matches!(
-            &events[1],
-            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 0, name, .. })
+            &events[5],
+            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 2, name, .. })
             if name == "http_request_started"
         ));
-        assert!(matches!(&events[2], TelemetryEvent::Analytics(_)));
+        assert!(matches!(&events[6], TelemetryEvent::Analytics(_)));
         assert!(matches!(
-            &events[3],
-            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 1, name, .. })
+            &events[7],
+            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 3, name, .. })
             if name == "analytics"
         ));
     }
 
+    #[test]
+    fn session_tracer_records_worker_events_with_boot_duration() {
+        let sink = Arc::new(MemoryTelemetrySink::default());
+        let tracer = SessionTracer::new("session-worker", sink.clone());
+
+        tracer.record_worker_init("worker-1", "/tmp/project", 125, Map::new());
+        tracer.record_worker_done("worker-1", "finished", Some(125), None, Map::new());
+
+        let events = sink.events();
+        assert!(matches!(
+            &events[0],
+            TelemetryEvent::WorkerInit {
+                session_id,
+                worker_id,
+                cwd,
+                boot_duration_ms: 125,
+                ..
+            } if session_id == "session-worker" && worker_id == "worker-1" && cwd == "/tmp/project"
+        ));
+        assert!(matches!(
+            &events[1],
+            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 0, name, attributes, .. })
+            if name == "worker.init"
+                && attributes.get("worker_id") == Some(&Value::String("worker-1".to_string()))
+                && attributes.get("boot_duration_ms") == Some(&Value::from(125))
+        ));
+        assert!(matches!(
+            &events[2],
+            TelemetryEvent::WorkerDone {
+                session_id,
+                worker_id,
+                status,
+                boot_duration_ms: Some(125),
+                ..
+            } if session_id == "session-worker" && worker_id == "worker-1" && status == "finished"
+        ));
+        assert!(matches!(
+            &events[3],
+            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 1, name, attributes, .. })
+            if name == "worker.done"
+                && attributes.get("worker_id") == Some(&Value::String("worker-1".to_string()))
+                && attributes.get("status") == Some(&Value::String("finished".to_string()))
+        ));
+    }
+
+    #[test]
+    fn jsonl_sink_persists_lane_events() {
+        let path = std::env::temp_dir().join(format!(
+            "telemetry-jsonl-lane-{}.log",
+            current_timestamp_ms()
+        ));
+        let sink = JsonlTelemetrySink::new(&path).expect("sink should create file");
+
+        sink.record(TelemetryEvent::LaneOpen {
+            session_id: "session-123".to_string(),
+            lane_id: "lane-42".to_string(),
+            attributes: Map::new(),
+        });
+        sink.record(TelemetryEvent::LaneClose {
+            session_id: "session-123".to_string(),
+            lane_id: "lane-42".to_string(),
+            attributes: Map::new(),
+        });
+
+        let contents = std::fs::read_to_string(&path).expect("telemetry log should be readable");
+        assert!(contents.contains("\"type\":\"lane.open\""));
+        assert!(contents.contains("\"type\":\"lane.close\""));
+
+        let _ = std::fs::remove_file(path);
+    }
+
     #[test]
     fn jsonl_sink_persists_events() {
         let path =