diff --git a/packages/cli/src/commands/agent/open.ts b/packages/cli/src/commands/agent/open.ts
index 2119bd130b..2c1eab36d2 100644
--- a/packages/cli/src/commands/agent/open.ts
+++ b/packages/cli/src/commands/agent/open.ts
@@ -1,5 +1,6 @@
 import type { Command } from "commander";
 import { connectToDaemon } from "../../utils/client.js";
+import type { AgentDeepLinkTarget } from "@getpaseo/protocol/agent-deep-link";
 import { openDesktopWithAgent } from "../open.js";
 import type {
   CommandError,
@@ -30,10 +31,21 @@ export function addOpenOptions(command: Command): Command {
     .option("--server <server-id>", "Server ID (defaults to the local daemon)");
 }
 
-async function resolveServerId(options: CommandOptions): Promise<string> {
+function toOpenError(err: unknown): CommandError {
+  if (err && typeof err === "object" && "code" in err) {
+    return err as CommandError;
+  }
+  const message = err instanceof Error ? err.message : String(err);
+  return { code: "OPEN_FAILED", message: `Failed to open agent: ${message}` };
+}
+
+async function resolveAgentTarget(
+  agentId: string,
+  options: CommandOptions,
+): Promise<AgentDeepLinkTarget> {
   const explicitServerId = typeof options.server === "string" ? options.server.trim() : "";
   if (explicitServerId) {
-    return explicitServerId;
+    return { serverId: explicitServerId, agentId };
   }
 
   const client = await connectToDaemon({ target: options.daemonTarget });
@@ -46,7 +58,19 @@ async function resolveServerId(options: CommandOptions): Promise<string> {
       };
       throw error;
     }
-    return serverId;
+
+    const fetchResult = await client.fetchAgent({ agentId });
+    if (!fetchResult) {
+      const error: CommandError = {
+        code: "AGENT_NOT_FOUND",
+        message: `Agent not found: ${agentId}`,
+        details: 'Use "paseo ls" to list available agents',
+      };
+      throw error;
+    }
+    return { serverId, agentId: fetchResult.agent.id };
+  } catch (err) {
+    throw toOpenError(err);
   } finally {
     await client.close().catch(() => {});
   }
@@ -66,12 +90,12 @@ export async function runOpenCommand(
     throw error;
   }
 
-  const serverId = await resolveServerId(options);
-  await openDesktopWithAgent({ serverId, agentId });
+  const target = await resolveAgentTarget(agentId, options);
+  await openDesktopWithAgent(target);
 
   return {
     type: "single",
-    data: { agentId, serverId, status: "opened" },
+    data: { ...target, status: "opened" },
     schema: openAgentSchema,
   };
 }
diff --git a/packages/cli/tests/42-agent-open.test.ts b/packages/cli/tests/42-agent-open.test.ts
new file mode 100644
index 0000000000..d468dfe16d
--- /dev/null
+++ b/packages/cli/tests/42-agent-open.test.ts
@@ -0,0 +1,52 @@
+#!/usr/bin/env npx tsx
+
+import assert from "node:assert";
+import { chmod, mkdir, readFile, writeFile } from "node:fs/promises";
+import { existsSync } from "node:fs";
+import { join } from "node:path";
+import { runPaseoCli, startTestDaemon } from "./helpers/test-daemon.ts";
+
+console.log("=== Agent Open Command Tests ===\n");
+
+if (process.platform !== "linux") {
+  console.log("Skipped: the fake Desktop app is a Linux AppImage path.");
+  process.exit(0);
+}
+
+const daemon = await startTestDaemon();
+
+// runPaseoCli sets HOME to the daemon's home, where the CLI looks for
+// ~/Applications/Paseo.AppImage on Linux. The fake app records its launch.
+const launchRecord = join(daemon.paseoHome, "desktop-launches.txt");
+const fakeDesktop = join(daemon.paseoHome, "Applications", "Paseo.AppImage");
+await mkdir(join(daemon.paseoHome, "Applications"), { recursive: true });
+await writeFile(fakeDesktop, `#!/bin/sh\necho "$@" >> "${launchRecord}"\n`);
+await chmod(fakeDesktop, 0o755);
+
+try {
+  {
+    console.log("Test 1: an unknown agent ID fails without opening Desktop");
+    const result = await runPaseoCli(daemon, [
+      "agent",
+      "open",
+      "does-not-exist",
+      "--host",
+      `127.0.0.1:${daemon.port}`,
+      "--json",
+    ]);
+
+    assert.notStrictEqual(result.exitCode, 0, "open should fail for an unknown agent");
+    assert.match(JSON.parse(result.stderr).error.message, /Agent not found: does-not-exist/);
+    // Give a wrongly spawned detached app time to write its record.
+    await new Promise((resolve) => setTimeout(resolve, 500));
+    assert.ok(
+      !existsSync(launchRecord),
+      `Desktop should not open, but was launched with: ${existsSync(launchRecord) ? await readFile(launchRecord, "utf8") : ""}`,
+    );
+    console.log("✓ unknown agent ID fails without opening Desktop\n");
+  }
+} finally {
+  await daemon.stop();
+}
+
+console.log("=== All agent open tests passed ===");