diff --git a/desktop/src/features/agents/observerRelayStore.ts b/desktop/src/features/agents/observerRelayStore.ts
index 6aa397edbc..1ac54e7efd 100644
--- a/desktop/src/features/agents/observerRelayStore.ts
+++ b/desktop/src/features/agents/observerRelayStore.ts
@@ -84,17 +84,26 @@ function registerKnownAgents(
   subscriptionId: string,
   pubkeys: readonly string[],
 ) {
-  knownAgentsBySubscription.set(
-    subscriptionId,
-    new Set(pubkeys.map((pubkey) => normalizePubkey(pubkey))),
-  );
+  const normalizedPubkeys = pubkeys.map((pubkey) => normalizePubkey(pubkey));
+  knownAgentsBySubscription.set(subscriptionId, new Set(normalizedPubkeys));
   recomputeKnownAgentPubkeys();
+  pillDiagLog("registerKnownAgents", {
+    subscriptionId,
+    subscriptionPubkeys: pillDiagPubkeys(normalizedPubkeys),
+  });
 }
 
 function unregisterKnownAgents(subscriptionId: string) {
-  if (knownAgentsBySubscription.delete(subscriptionId)) {
+  const removedPubkeys = knownAgentsBySubscription.get(subscriptionId);
+  const removed = knownAgentsBySubscription.delete(subscriptionId);
+  if (removed) {
     recomputeKnownAgentPubkeys();
   }
+  pillDiagLog("unregisterKnownAgents", {
+    subscriptionId,
+    removed,
+    removedPubkeys: removedPubkeys ? pillDiagPubkeys(removedPubkeys) : [],
+  });
 }
 
 let connectionState: ConnectionState = "idle";
@@ -104,6 +113,44 @@ let startPromise: Promise<void> | null = null;
 let eventProcessingQueue: Promise<void> = Promise.resolve();
 let generation = 0;
 
+function pillDiagPubkeys(pubkeys: Iterable<string>) {
+  return [...pubkeys].map((pubkey) => normalizePubkey(pubkey)).sort();
+}
+
+function pillDiagState(extra: Record<string, unknown> = {}) {
+  return {
+    generation,
+    connectionState,
+    hasRelaySubscription: Boolean(unsubscribeRelay),
+    hasStartPromise: Boolean(startPromise),
+    knownAgentCount: knownAgentPubkeys.size,
+    knownAgents: pillDiagPubkeys(knownAgentPubkeys),
+    subscriptionCount: knownAgentsBySubscription.size,
+    subscriptionSizes: Object.fromEntries(
+      [...knownAgentsBySubscription.entries()].map(
+        ([subscriptionId, pubkeys]) => [subscriptionId, pubkeys.size],
+      ),
+    ),
+    at: new Date().toISOString(),
+    ...extra,
+  };
+}
+
+function pillDiagLog(label: string, extra: Record<string, unknown> = {}) {
+  console.log(`[pill-diag] observer ${label}`, pillDiagState(extra));
+}
+
+function pillDiagEvent(event: RelayEvent) {
+  const agentPubkey = observerTag(event, "agent");
+  return {
+    eventId: event.id,
+    eventPubkey: normalizePubkey(event.pubkey),
+    agentPubkey: agentPubkey ? normalizePubkey(agentPubkey) : null,
+    frame: observerTag(event, "frame"),
+    createdAt: event.created_at,
+  };
+}
+
 function notifyListeners() {
   for (const listener of listeners) {
     listener();
@@ -191,26 +238,52 @@ async function handleRelayObserverEvent(
   const agentPubkey = observerTag(event, "agent");
   const frame = observerTag(event, "frame");
   if (!agentPubkey || frame !== "telemetry") {
+    pillDiagLog("drop nonTelemetryFrame", {
+      activeGeneration,
+      event: pillDiagEvent(event),
+    });
     return;
   }
 
   // Verify agent is known/trusted before decrypting.
   // Silently drop events from agents we are not managing.
   if (!knownAgentPubkeys.has(normalizePubkey(agentPubkey))) {
+    pillDiagLog("drop unknownAgent", {
+      activeGeneration,
+      event: pillDiagEvent(event),
+    });
     return;
   }
 
   // Defense-in-depth: verify the event sender matches the claimed agent pubkey.
   // The relay gates on is_agent_owner, but a compromised relay could misroute.
   if (normalizePubkey(event.pubkey) !== normalizePubkey(agentPubkey)) {
+    pillDiagLog("drop senderMismatch", {
+      activeGeneration,
+      event: pillDiagEvent(event),
+    });
     return;
   }
 
   try {
     const parsed = (await decryptObserverEvent(event)) as ObserverEvent;
     if (activeGeneration !== generation) {
+      pillDiagLog("drop staleGenerationAfterDecrypt", {
+        activeGeneration,
+        event: pillDiagEvent(event),
+        parsedKind: parsed.kind,
+        parsedSeq: parsed.seq,
+        parsedTimestamp: parsed.timestamp,
+      });
       return;
     }
+    pillDiagLog("appendFrame", {
+      activeGeneration,
+      event: pillDiagEvent(event),
+      parsedKind: parsed.kind,
+      parsedSeq: parsed.seq,
+      parsedTimestamp: parsed.timestamp,
+    });
     appendAgentEvent(agentPubkey, parsed);
     if (parsed.kind === "session_config_captured") {
       void putAgentSessionConfig(agentPubkey, parsed.payload);
@@ -220,8 +293,18 @@ async function handleRelayObserverEvent(
     }
   } catch (error) {
     if (activeGeneration !== generation) {
+      pillDiagLog("drop staleGenerationAfterError", {
+        activeGeneration,
+        event: pillDiagEvent(event),
+        error: error instanceof Error ? error.message : String(error),
+      });
       return;
     }
+    pillDiagLog("decryptError", {
+      activeGeneration,
+      event: pillDiagEvent(event),
+      error: error instanceof Error ? error.message : String(error),
+    });
     setConnectionState(
       "error",
       error instanceof Error
@@ -233,25 +316,44 @@ async function handleRelayObserverEvent(
 
 export function ensureRelayObserverSubscription() {
   if (unsubscribeRelay) {
+    pillDiagLog("ensure reuseOpenSubscription");
     return Promise.resolve();
   }
   if (startPromise) {
+    pillDiagLog("ensure reuseStartPromise");
     return startPromise;
   }
 
   const activeGeneration = generation;
+  pillDiagLog("ensure start", { activeGeneration });
   setConnectionState("connecting", null);
   startPromise = (async () => {
     const identity = await getIdentity();
+    pillDiagLog("subscribeToAgentObserverFrames start", {
+      activeGeneration,
+      identityPubkey: normalizePubkey(identity.pubkey),
+    });
     const unsubscribe = await subscribeToAgentObserverFrames(
       identity.pubkey,
       (event) => {
+        pillDiagLog("frame received", {
+          activeGeneration,
+          event: pillDiagEvent(event),
+        });
         eventProcessingQueue = eventProcessingQueue
           .then(() => handleRelayObserverEvent(event, activeGeneration))
           .catch((error) => {
             if (activeGeneration !== generation) {
+              pillDiagLog("drop staleGenerationInQueueCatch", {
+                activeGeneration,
+                error: error instanceof Error ? error.message : String(error),
+              });
               return;
             }
+            pillDiagLog("eventHandlingError", {
+              activeGeneration,
+              error: error instanceof Error ? error.message : String(error),
+            });
             setConnectionState(
               "error",
               error instanceof Error
@@ -262,13 +364,19 @@ export function ensureRelayObserverSubscription() {
       },
     );
     if (activeGeneration !== generation) {
+      pillDiagLog("subscribe resolved staleGeneration", { activeGeneration });
       await unsubscribe();
       return;
     }
     unsubscribeRelay = unsubscribe;
+    pillDiagLog("subscribe open", { activeGeneration });
     setConnectionState("open", null);
   })()
     .catch((error) => {
+      pillDiagLog("subscribe error", {
+        activeGeneration,
+        error: error instanceof Error ? error.message : String(error),
+      });
       if (activeGeneration === generation) {
         setConnectionState(
           "error",
@@ -279,6 +387,7 @@ export function ensureRelayObserverSubscription() {
       }
     })
     .finally(() => {
+      pillDiagLog("ensure finally", { activeGeneration });
       if (activeGeneration === generation) {
         startPromise = null;
       }
@@ -406,6 +515,7 @@ export function useManagedAgentObserverBridge(
   }, [subscriptionId, agentPubkeys]);
 
   React.useEffect(() => {
+    pillDiagLog("bridge activeEffect", { hasActiveAgent });
     if (!hasActiveAgent) {
       return;
     }
@@ -425,6 +535,7 @@ export function useManagedAgentObserverBridge(
 }
 
 export function resetAgentObserverStore() {
+  pillDiagLog("reset start", { nextGeneration: generation + 1 });
   generation += 1;
   const unsubscribe = unsubscribeRelay;
   unsubscribeRelay = null;
@@ -439,5 +550,6 @@ export function resetAgentObserverStore() {
   connectionState = "idle";
   errorMessage = null;
   notifyListeners();
+  pillDiagLog("reset afterClear", { hadUnsubscribe: Boolean(unsubscribe) });
   void unsubscribe?.();
 }