diff --git a/packages/server/src/server/agent/agent-mcp.e2e.test.ts b/packages/server/src/server/agent/agent-mcp.e2e.test.ts
index d36412b6b..a1b639a8c 100644
--- a/packages/server/src/server/agent/agent-mcp.e2e.test.ts
+++ b/packages/server/src/server/agent/agent-mcp.e2e.test.ts
@@ -285,6 +285,65 @@ describe("agent MCP end-to-end (offline)", () => {
     }
   }, 30_000);
 
+  test("create_agent injects a loopback MCP URL when the daemon listens on all interfaces", async () => {
+    const paseoHome = await mkdtemp(path.join(os.tmpdir(), "paseo-home-"));
+    const staticDir = await mkdtemp(path.join(os.tmpdir(), "paseo-static-"));
+    const agentCwd = await mkdtemp(path.join(os.tmpdir(), "paseo-agent-cwd-"));
+    const port = await getAvailablePort();
+
+    const daemonConfig: PaseoDaemonConfig = {
+      listen: `0.0.0.0:${port}`,
+      paseoHome,
+      corsAllowedOrigins: [],
+      hostnames: true,
+      mcpEnabled: true,
+      staticDir,
+      mcpDebug: false,
+      agentClients: createTestAgentClients(),
+      agentStoragePath: path.join(paseoHome, "agents"),
+    };
+
+    const daemon = await createPaseoDaemon(daemonConfig, pino({ level: "silent" }));
+    await daemon.start();
+
+    const client = await createMcpClient(`http://127.0.0.1:${port}/mcp/agents`);
+
+    let agentId: string | null = null;
+    try {
+      const result = await client.callTool({
+        name: "create_agent",
+        args: {
+          cwd: agentCwd,
+          title: "Wildcard MCP",
+          provider: "claude/claude-test-model",
+          mode: "bypassPermissions",
+          initialPrompt: "reply with done and stop",
+          background: true,
+        },
+      });
+      const payload = getStructuredContent(result);
+      agentId = typeof payload?.agentId === "string" ? payload.agentId : null;
+      expect(agentId).toBeTruthy();
+
+      const injectedAgent = daemon.agentManager.getAgent(agentId!);
+      expect(injectedAgent?.config.mcpServers).toMatchObject({
+        paseo: {
+          type: "http",
+          url: `http://127.0.0.1:${port}/mcp/agents?callerAgentId=${agentId!}`,
+        },
+      });
+    } finally {
+      if (agentId) {
+        await client.callTool({ name: "kill_agent", args: { agentId } });
+      }
+      await client.close();
+      await daemon.stop();
+      await rm(paseoHome, { recursive: true, force: true });
+      await rm(staticDir, { recursive: true, force: true });
+      await rm(agentCwd, { recursive: true, force: true });
+    }
+  }, 30_000);
+
   test("create_agent with background initialPrompt reflects running state once the first turn starts", async () => {
     const paseoHome = await mkdtemp(path.join(os.tmpdir(), "paseo-home-"));
     const staticDir = await mkdtemp(path.join(os.tmpdir(), "paseo-static-"));
diff --git a/packages/server/src/server/agent/providers/opencode-agent.test.ts b/packages/server/src/server/agent/providers/opencode-agent.test.ts
index a5a7cc875..32813ef0a 100644
--- a/packages/server/src/server/agent/providers/opencode-agent.test.ts
+++ b/packages/server/src/server/agent/providers/opencode-agent.test.ts
@@ -753,6 +753,43 @@ describe("OpenCode adapter startTurn error handling", () => {
     }
   });
 
+  test("fails the turn when OpenCode reports MCP add failure in data payload", async () => {
+    const runtime = new TestOpenCodeRuntime();
+    const openCodeClient = new TestOpenCodeClient();
+    openCodeClient.mcpAddResponse = {
+      data: {
+        paseo: {
+          status: "failed",
+          error: "SSE error: Non-200 status code (400)",
+        },
+      },
+    };
+    runtime.enqueueClient(openCodeClient);
+    const cwd = tmpCwd();
+    const client = new OpenCodeAgentClient(createTestLogger(), undefined, { runtime });
+
+    try {
+      const session = await client.createSession({
+        provider: "opencode",
+        cwd,
+        mcpServers: {
+          paseo: {
+            type: "http",
+            url: "http://127.0.0.1:6767/mcp/agents?callerAgentId=test-agent",
+          },
+        },
+      });
+
+      await expect(collectTurnEvents(streamSession(session, "hello"))).rejects.toThrow(
+        /Failed to add OpenCode MCP server 'paseo': SSE error/,
+      );
+
+      await session.close();
+    } finally {
+      rmSync(cwd, { recursive: true, force: true });
+    }
+  });
+
   test("emits turn_started before live OpenCode timeline items", async () => {
     const eventsGate = createTestDeferred<void>();
     const globalEvents = [
diff --git a/packages/server/src/server/agent/providers/opencode-agent.ts b/packages/server/src/server/agent/providers/opencode-agent.ts
index 51005a803..9192d943a 100644
--- a/packages/server/src/server/agent/providers/opencode-agent.ts
+++ b/packages/server/src/server/agent/providers/opencode-agent.ts
@@ -425,6 +425,15 @@ function isAlreadyPresentMcpError(error: unknown): boolean {
   return MCP_ALREADY_PRESENT_ERROR_TOKENS.some((token) => normalized.includes(token));
 }
 
+function readOpenCodeMcpOperationError(data: unknown, name: string): unknown {
+  const root = readOpenCodeRecord(data);
+  const entry = readOpenCodeRecord(root?.[name]);
+  if (!entry || entry.status !== "failed") {
+    return undefined;
+  }
+  return entry.error ?? `OpenCode reported MCP server '${name}' failed`;
+}
+
 function resolvePartDedupeKey(
   part: { id: string; messageID: string },
   partType: "text" | "reasoning",
@@ -3507,10 +3516,10 @@ class OpenCodeAgentSession implements AgentSession {
   private async runMcpOperation(
     operation: "add",
     name: string,
-    run: () => Promise<{ error?: unknown }>,
+    run: () => Promise<{ data?: unknown; error?: unknown }>,
   ): Promise<void> {
     const response = await run();
-    const error = response.error;
+    const error = response.error ?? readOpenCodeMcpOperationError(response.data, name);
     if (!error) {
       return;
     }
diff --git a/packages/server/src/server/bootstrap.ts b/packages/server/src/server/bootstrap.ts
index 95e0d4d00..76fa76e07 100644
--- a/packages/server/src/server/bootstrap.ts
+++ b/packages/server/src/server/bootstrap.ts
@@ -152,13 +152,24 @@ function formatHostForHttpUrl(host: string): string {
   return host.includes(":") && !host.startsWith("[") ? `[${host}]` : host;
 }
 
+function resolveAgentMcpClientHost(host: string): string {
+  if (host === "0.0.0.0") {
+    return "127.0.0.1";
+  }
+  if (host === "::" || host === "[::]") {
+    return "::1";
+  }
+  return host;
+}
+
 function createAgentMcpBaseUrl(listenTarget: ListenTarget | null): string | null {
   if (!listenTarget || listenTarget.type !== "tcp") {
     return null;
   }
+  const host = resolveAgentMcpClientHost(listenTarget.host);
   return new URL(
     "/mcp/agents",
-    `http://${formatHostForHttpUrl(listenTarget.host)}:${listenTarget.port}`,
+    `http://${formatHostForHttpUrl(host)}:${listenTarget.port}`,
   ).toString();
 }