diff --git a/packages/core/src/event-bus.ts b/packages/core/src/event-bus.ts
index b5143375b..8d6560bce 100644
--- a/packages/core/src/event-bus.ts
+++ b/packages/core/src/event-bus.ts
@@ -117,9 +117,13 @@ export function createEventBus(logPath: string | null): EventBus {
 
   return {
     emit(event: OrchestratorEvent): void {
-      // Persist to JSONL
+      // Persist to JSONL (non-fatal on disk errors)
       if (logPath) {
-        appendFileSync(logPath, serializeEvent(event) + "\n", "utf-8");
+        try {
+          appendFileSync(logPath, serializeEvent(event) + "\n", "utf-8");
+        } catch {
+          // Disk error — event still propagated in-memory
+        }
       }
 
       // Store in memory
diff --git a/packages/core/src/lifecycle-manager.ts b/packages/core/src/lifecycle-manager.ts
index b78625340..5ab6bd2a7 100644
--- a/packages/core/src/lifecycle-manager.ts
+++ b/packages/core/src/lifecycle-manager.ts
@@ -79,7 +79,7 @@ function eventToReactionKey(eventType: EventType): string | null {
     case "merge.ready": return "approved-and-green";
     case "session.stuck": return "agent-stuck";
     case "session.needs_input": return "agent-needs-input";
-    case "session.exited": return "agent-exited";
+    case "session.killed": return "agent-exited";
     case "summary.all_complete": return "all-complete";
     default: return null;
   }
@@ -92,9 +92,9 @@ export interface LifecycleManagerDeps {
   eventBus: EventBus;
 }
 
-/** Track retry counts for reactions per session. */
+/** Track attempt counts for reactions per session. */
 interface ReactionTracker {
-  retries: number;
+  attempts: number;
   firstTriggered: Date;
 }
 
@@ -210,16 +210,19 @@ export function createLifecycleManager(
     let tracker = reactionTrackers.get(trackerKey);
 
     if (!tracker) {
-      tracker = { retries: 0, firstTriggered: new Date() };
+      tracker = { attempts: 0, firstTriggered: new Date() };
       reactionTrackers.set(trackerKey, tracker);
     }
 
+    // Increment attempts before checking escalation
+    tracker.attempts++;
+
     // Check if we should escalate
     const maxRetries = reactionConfig.retries ?? Infinity;
     const escalateAfter = reactionConfig.escalateAfter;
     let shouldEscalate = false;
 
-    if (tracker.retries >= maxRetries) {
+    if (tracker.attempts > maxRetries) {
       shouldEscalate = true;
     }
 
@@ -230,7 +233,7 @@ export function createLifecycleManager(
       }
     }
 
-    if (typeof escalateAfter === "number" && tracker.retries >= escalateAfter) {
+    if (typeof escalateAfter === "number" && tracker.attempts > escalateAfter) {
       shouldEscalate = true;
     }
 
@@ -253,14 +256,13 @@ export function createLifecycleManager(
         if (reactionConfig.message) {
           try {
             await sessionManager.send(event.sessionId, reactionConfig.message);
-            tracker.retries++;
 
             eventBus.emit(
               createEvent("reaction.triggered", {
                 sessionId: event.sessionId,
                 projectId: event.projectId,
                 message: `Reaction '${reactionKey}' sent message to agent`,
-                data: { reactionKey, retries: tracker.retries },
+                data: { reactionKey, attempts: tracker.attempts },
               })
             );
 
diff --git a/packages/core/src/metadata.ts b/packages/core/src/metadata.ts
index dd98211ec..351023b6b 100644
--- a/packages/core/src/metadata.ts
+++ b/packages/core/src/metadata.ts
@@ -43,8 +43,18 @@ function serializeMetadata(data: Record<string, string>): string {
     .join("\n") + "\n";
 }
 
+/** Validate sessionId to prevent path traversal. */
+const VALID_SESSION_ID = /^[a-zA-Z0-9_-]+$/;
+
+function validateSessionId(sessionId: SessionId): void {
+  if (!VALID_SESSION_ID.test(sessionId)) {
+    throw new Error(`Invalid session ID: ${sessionId}`);
+  }
+}
+
 /** Get the metadata file path for a session. */
 function metadataPath(dataDir: string, sessionId: SessionId): string {
+  validateSessionId(sessionId);
   return join(dataDir, "sessions", sessionId);
 }
 
diff --git a/packages/core/src/session-manager.ts b/packages/core/src/session-manager.ts
index e88a913f7..d5d847518 100644
--- a/packages/core/src/session-manager.ts
+++ b/packages/core/src/session-manager.ts
@@ -68,6 +68,19 @@ function safeJsonParse<T>(str: string): T | null {
   }
 }
 
+/** Valid session statuses for validation. */
+const VALID_STATUSES: ReadonlySet<string> = new Set([
+  "spawning", "working", "pr_open", "ci_failed", "review_pending",
+  "changes_requested", "approved", "mergeable", "merged",
+  "needs_input", "stuck", "errored", "killed",
+]);
+
+/** Validate and normalize a status string. */
+function validateStatus(raw: string | undefined): SessionStatus {
+  if (raw && VALID_STATUSES.has(raw)) return raw as SessionStatus;
+  return "spawning";
+}
+
 /** Reconstruct a Session object from raw metadata key=value pairs. */
 function metadataToSession(
   sessionId: SessionId,
@@ -76,7 +89,7 @@ function metadataToSession(
   return {
     id: sessionId,
     projectId: meta["project"] ?? "",
-    status: (meta["status"] ?? "unknown") as SessionStatus,
+    status: validateStatus(meta["status"]),
     activity: "idle",
     branch: meta["branch"] || null,
     issueId: meta["issue"] || null,
@@ -201,16 +214,25 @@ export function createSessionManager(deps: SessionManagerDeps): SessionManager {
     const launchCommand = plugins.agent.getLaunchCommand(agentLaunchConfig);
     const environment = plugins.agent.getEnvironment(agentLaunchConfig);
 
-    // Create runtime session
-    const handle = await plugins.runtime.create({
-      sessionId,
-      workspacePath,
-      launchCommand,
-      environment: {
-        ...environment,
-        AO_SESSION: sessionId,
-      },
-    });
+    // Create runtime session — clean up workspace on failure
+    let handle: RuntimeHandle;
+    try {
+      handle = await plugins.runtime.create({
+        sessionId,
+        workspacePath,
+        launchCommand,
+        environment: {
+          ...environment,
+          AO_SESSION: sessionId,
+        },
+      });
+    } catch (err) {
+      // Clean up workspace if runtime creation failed
+      if (plugins.workspace && workspacePath !== project.path) {
+        try { await plugins.workspace.destroy(workspacePath); } catch { /* best effort */ }
+      }
+      throw err;
+    }
 
     // Write metadata
     writeMetadata(config.dataDir, sessionId, {