diff --git a/packages/cli/src/commands/daemon/lifecycle.e2e.test.ts b/packages/cli/src/commands/daemon/lifecycle.e2e.test.ts
index dfffe1f61b..cb42c0b0a5 100644
--- a/packages/cli/src/commands/daemon/lifecycle.e2e.test.ts
+++ b/packages/cli/src/commands/daemon/lifecycle.e2e.test.ts
@@ -146,7 +146,7 @@ test("managed two-home restart retains its supervisor and never routes ordinary
     expect(await f.ok(["project", "ls", "--home", a])).toEqual([]);
     expect((await f.ok(["project", "ls", "--home", b], poisoned)).length).toBe(1);
     const stream = await f.run(["logs", "missing-agent", "--follow", "--home", b], poisoned);
-    expect(stream.stderr).toContain("Agent not found: missing-agent");
+    expect(stream.stderr).toContain("No agent found matching: missing-agent");
     const restart = await f.ok(["restart", "--home", b, "--timeout", "30"], poisoned);
     expect(restart.supervisorPid).toBe(launchB.pid);
     expect(restart.workerPid).not.toBe(beforeB.workerPid);
@@ -503,7 +503,7 @@ test("raw log following subscribes to a stored agent that exists only in B", asy
     const launchA = await f.ok(["start", "--home", a]);
     await f.ok(["start", "--home", b]);
     const absent = await f.run(["logs", agentId, "--home", a]);
-    expect(absent.stderr).toContain("Agent not found");
+    expect(absent.stderr).toContain(`No agent found matching: ${agentId}`);
     follower = spawn(
       process.execPath,
       [cli, "logs", agentId, "--follow", "--tail", "0", "--home", b],
@@ -522,7 +522,7 @@ test("raw log following subscribes to a stored agent that exists only in B", asy
       errors += data;
     });
     await expect.poll(() => output, { timeout: 15_000 }).toContain("Following logs (no history;");
-    expect(errors).not.toContain("Agent not found");
+    expect(errors).not.toContain("No agent found matching");
   } finally {
     if (follower && follower.exitCode === null) {
       const exited = new Promise((resolve) => follower!.once("exit", resolve));
diff --git a/packages/cli/tests/07-agent-stop.test.ts b/packages/cli/tests/07-agent-stop.test.ts
index 81b0cba66c..9416884a7b 100644
--- a/packages/cli/tests/07-agent-stop.test.ts
+++ b/packages/cli/tests/07-agent-stop.test.ts
@@ -19,6 +19,7 @@
 
 import assert from "node:assert";
 import { getAvailablePort } from "./helpers/network.ts";
+import { runPaseoCli, startTestDaemon } from "./helpers/test-daemon.ts";
 import { $ } from "zx";
 import { mkdtemp, rm } from "fs/promises";
 import { tmpdir } from "os";
@@ -129,6 +130,28 @@ try {
     assert(!output.includes("error: option"), "should not have option parsing error");
     console.log("✓ -q (quiet) flag is accepted with stop\n");
   }
+
+  {
+    console.log("Test 9: stop reports AGENT_NOT_FOUND for an unknown ID");
+    const daemon = await startTestDaemon();
+    try {
+      const result = await runPaseoCli(daemon, [
+        "agent",
+        "stop",
+        "does-not-exist",
+        "--host",
+        `127.0.0.1:${daemon.port}`,
+        "--json",
+      ]);
+      assert.notStrictEqual(result.exitCode, 0, "stop should fail for an unknown ID");
+      const { error } = JSON.parse(result.stderr);
+      assert.strictEqual(error.code, "AGENT_NOT_FOUND", result.stderr);
+      assert.match(error.details, /paseo ls/);
+    } finally {
+      await daemon.stop();
+    }
+    console.log("✓ stop reports AGENT_NOT_FOUND for an unknown ID\n");
+  }
 } finally {
   // Clean up temp directory
   await rm(paseoHome, { recursive: true, force: true });
diff --git a/packages/cli/tests/27-agent-delete.test.ts b/packages/cli/tests/27-agent-delete.test.ts
index bec523f9ca..349125109b 100644
--- a/packages/cli/tests/27-agent-delete.test.ts
+++ b/packages/cli/tests/27-agent-delete.test.ts
@@ -13,6 +13,7 @@
 import assert from "node:assert";
 import { runLocalPaseo } from "./helpers/local-cli.ts";
 import { getAvailablePort } from "./helpers/network.ts";
+import { runPaseoCli, startTestDaemon } from "./helpers/test-daemon.ts";
 import { mkdtemp, rm } from "fs/promises";
 import { tmpdir } from "os";
 import { join } from "path";
@@ -112,6 +113,28 @@ try {
     assert(!output.includes("error: option"), "should not have option parsing error");
     console.log("✓ -q (quiet) flag is accepted with delete\n");
   }
+
+  {
+    console.log("Test 9: delete reports AGENT_NOT_FOUND for an unknown ID");
+    const daemon = await startTestDaemon();
+    try {
+      const result = await runPaseoCli(daemon, [
+        "agent",
+        "delete",
+        "does-not-exist",
+        "--host",
+        `127.0.0.1:${daemon.port}`,
+        "--json",
+      ]);
+      assert.notStrictEqual(result.exitCode, 0, "delete should fail for an unknown ID");
+      const { error } = JSON.parse(result.stderr);
+      assert.strictEqual(error.code, "AGENT_NOT_FOUND", result.stderr);
+      assert.match(error.details, /paseo ls/);
+    } finally {
+      await daemon.stop();
+    }
+    console.log("✓ delete reports AGENT_NOT_FOUND for an unknown ID\n");
+  }
 } finally {
   await rm(paseoHome, { recursive: true, force: true });
 }
diff --git a/packages/server/src/server/session.ts b/packages/server/src/server/session.ts
index 3e6813e148..d57333da05 100644
--- a/packages/server/src/server/session.ts
+++ b/packages/server/src/server/session.ts
@@ -5216,10 +5216,10 @@ export class Session {
 
   private async resolveAgentIdentifier(
     identifier: string,
-  ): Promise<{ ok: true; agentId: string } | { ok: false; error: string }> {
+  ): Promise<{ ok: true; agentId: string } | { ok: false; notFound: boolean; error: string }> {
     const trimmed = identifier.trim();
     if (!trimmed) {
-      return { ok: false, error: "Agent identifier cannot be empty" };
+      return { ok: false, notFound: false, error: "Agent identifier cannot be empty" };
     }
 
     const stored = await this.agentStorage.list();
@@ -5243,6 +5243,7 @@ export class Session {
     if (prefixMatches.length > 1) {
       return {
         ok: false,
+        notFound: false,
         error: `Agent identifier "${trimmed}" is ambiguous (${prefixMatches
           .slice(0, 5)
           .map((id) => id.slice(0, 8))
@@ -5257,6 +5258,7 @@ export class Session {
     if (titleMatches.length > 1) {
       return {
         ok: false,
+        notFound: false,
         error: `Agent title "${trimmed}" is ambiguous (${titleMatches
           .slice(0, 5)
           .map((r) => r.id.slice(0, 8))
@@ -5264,7 +5266,7 @@ export class Session {
       };
     }
 
-    return { ok: false, error: `Agent not found: ${trimmed}` };
+    return { ok: false, notFound: true, error: `Agent not found: ${trimmed}` };
   }
 
   private async getAgentPayloadById(agentId: string): Promise<AgentSnapshotPayload | null> {
@@ -7574,11 +7576,17 @@ export class Session {
   }
 
   private async handleFetchAgent(agentIdOrIdentifier: string, requestId: string): Promise<void> {
+    // An unknown agent is a null agent, not an error. Errors are for empty or ambiguous identifiers.
     const resolved = await this.resolveAgentIdentifier(agentIdOrIdentifier);
     if (!resolved.ok) {
       this.emit({
         type: "fetch_agent_response",
-        payload: { requestId, agent: null, project: null, error: resolved.error },
+        payload: {
+          requestId,
+          agent: null,
+          project: null,
+          error: resolved.notFound ? null : resolved.error,
+        },
       });
       return;
     }
@@ -7587,12 +7595,7 @@ export class Session {
     if (!agent) {
       this.emit({
         type: "fetch_agent_response",
-        payload: {
-          requestId,
-          agent: null,
-          project: null,
-          error: `Agent not found: ${resolved.agentId}`,
-        },
+        payload: { requestId, agent: null, project: null, error: null },
       });
       return;
     }
diff --git a/packages/server/src/server/session.workspaces.test.ts b/packages/server/src/server/session.workspaces.test.ts
index 1be52bc997..001966ab39 100644
--- a/packages/server/src/server/session.workspaces.test.ts
+++ b/packages/server/src/server/session.workspaces.test.ts
@@ -3466,7 +3466,7 @@ test("fetch_agent_request still resolves archived historical agents", async () =
   session.resolveAgentIdentifier = async (identifier: string) =>
     identifier === "Archived History Agent"
       ? { ok: true, agentId: agent.id }
-      : { ok: false, error: `Agent not found: ${identifier}` };
+      : { ok: false, notFound: true, error: `Agent not found: ${identifier}` };
   session.getAgentPayloadById = async (agentId: string) => (agentId === agent.id ? agent : null);
   session.buildProjectPlacementForWorkspaceId = async () => ({
     projectKey: "proj-history-detail",