diff --git a/src/agent/async-agent.ts b/src/agent/async-agent.ts
index c1eb9a5e..c1b30ea4 100644
--- a/src/agent/async-agent.ts
+++ b/src/agent/async-agent.ts
@@ -51,11 +51,14 @@ export class AsyncAgent {
         // Normal text is delivered via message_end event; only handle errors here
         if (result.error) {
           this.channel.send({ id: uuidv7(), content: `[error] ${result.error}` });
+          this.agent.emitError(result.error);
         }
       })
       .catch((err) => {
         const message = err instanceof Error ? err.message : String(err);
         this.channel.send({ id: uuidv7(), content: `[error] ${message}` });
+        // Also emit through subscriber mechanism so IPC listeners receive the error
+        this.agent.emitError(message);
       })
       .finally(() => {
         this.pendingWrites = Math.max(0, this.pendingWrites - 1);
diff --git a/src/agent/events.ts b/src/agent/events.ts
index 8eb8b422..3ae35b64 100644
--- a/src/agent/events.ts
+++ b/src/agent/events.ts
@@ -21,10 +21,16 @@ export type CompactionEndEvent = {
   type: "compaction_end";
   removed: number;
   kept: number;
-  tokensRemoved?: number;
-  tokensKept?: number;
+  tokensRemoved?: number | undefined;
+  tokensKept?: number | undefined;
   reason: "count" | "tokens" | "summary" | "pruning";
 };
 
+/** Emitted when an agent encounters an error during execution */
+export type AgentErrorEvent = {
+  type: "agent_error";
+  message: string;
+};
+
 /** Union of all Multica-specific events */
-export type MulticaEvent = CompactionStartEvent | CompactionEndEvent;
+export type MulticaEvent = CompactionStartEvent | CompactionEndEvent | AgentErrorEvent;
diff --git a/src/agent/runner.ts b/src/agent/runner.ts
index d364f0fa..c6fa4566 100644
--- a/src/agent/runner.ts
+++ b/src/agent/runner.ts
@@ -1,7 +1,7 @@
 import { Agent as PiAgentCore, type AgentEvent, type AgentMessage } from "@mariozechner/pi-agent-core";
 import { v7 as uuidv7 } from "uuid";
 import type { AgentOptions, AgentRunResult, ReasoningMode } from "./types.js";
-import type { MulticaEvent } from "./events.js";
+import type { MulticaEvent, CompactionEndEvent } from "./events.js";
 import { createAgentOutput } from "./cli/output.js";
 import { resolveModel, resolveTools, type ResolveToolsOptions } from "./tools.js";
 import {
@@ -159,11 +159,14 @@ export class Agent {
         : 0;
     }
 
-    this.agent = new PiAgentCore(
-      this.currentApiKey
-        ? { getApiKey: (_provider: string) => this.currentApiKey! }
-        : {},
-    );
+    this.agent = new PiAgentCore({
+      getApiKey: (_provider: string) => {
+        if (!this.currentApiKey) {
+          throw new Error(`No API key configured for provider: ${this.resolvedProvider}`);
+        }
+        return this.currentApiKey;
+      },
+    });
 
     // Load Agent Profile (if profileId is specified)
     // Every Agent should have a Profile for memory, tools config, and other settings
@@ -352,6 +355,11 @@ export class Agent {
     }
   }
 
+  /** Emit an error event through the subscriber mechanism */
+  emitError(message: string): void {
+    this.emitMulticaEvent({ type: "agent_error", message });
+  }
+
   async run(prompt: string): Promise<AgentRunResult> {
     await this.ensureInitialized();
     this.output.state.lastAssistantText = "";
@@ -461,14 +469,15 @@ export class Agent {
       if (result?.kept) {
         this.agent.replaceMessages(result.kept);
       }
-      this.emitMulticaEvent({
+      const endEvent: CompactionEndEvent = {
         type: "compaction_end",
         removed: result?.removedCount ?? 0,
         kept: result?.kept.length ?? messages.length,
         tokensRemoved: result?.tokensRemoved,
         tokensKept: result?.tokensKept,
         reason: result?.reason ?? "tokens",
-      });
+      };
+      this.emitMulticaEvent(endEvent);
     } catch (err) {
       throw err;
     }