diff --git a/src/cli-agent.ts b/src/cli-agent.ts
index fc3fec03..efacd654 100644
--- a/src/cli-agent.ts
+++ b/src/cli-agent.ts
@@ -343,6 +343,18 @@ export const httpRequest: ApiRequest = (ctx, options) => {
   });
 };
 
+/**
+ * One line describing a thrown request error. Node 22 rejects a refused connection to a host
+ * that resolves to both ::1 and 127.0.0.1 with an AggregateError whose `message` is empty, so
+ * fall back to its `code` (ECONNREFUSED) before a generic line rather than printing nothing.
+ */
+export function describeRequestError(error: unknown): string {
+  const message = getErrorMessage(error);
+  if (message) return message;
+  const code = (error as { code?: unknown } | null | undefined)?.code;
+  return code ? String(code) : 'request failed without a message';
+}
+
 /** One line describing a failed response, for humans. Plain-text guards (401/403/429) have no envelope. */
 export function describeFailure(res: ApiResponse): string {
   if (res.json && !res.json.success) {
@@ -573,7 +585,7 @@ export async function agentSpawn(deps: AgentDeps, options: SpawnOptions): Promis
         ready = !dead && Boolean(result?.matched);
       }
     } catch (error) {
-      readinessError = getErrorMessage(error) || 'Readiness request failed';
+      readinessError = describeRequestError(error);
     }
   }
 
@@ -1042,7 +1054,7 @@ async function run(json: boolean, verb: (deps: AgentDeps) => Promise<number>): P
   try {
     process.exitCode = await verb(deps);
   } catch (err) {
-    console.error(palette.err(`${GLYPH.fail} ${getErrorMessage(err)}`));
+    console.error(palette.err(`${GLYPH.fail} ${describeRequestError(err)}`));
     process.exitCode = EXIT.error;
   }
 }
diff --git a/src/mcp-server.ts b/src/mcp-server.ts
index c79b2b4a..7d9a1b81 100644
--- a/src/mcp-server.ts
+++ b/src/mcp-server.ts
@@ -38,6 +38,7 @@ import {
   buildSendBody,
   composerReadyMark,
   describeFailure,
+  describeRequestError,
   httpRequest,
   inputRefusal,
   isSelfSession,
@@ -497,7 +498,7 @@ export function createToolRunner(deps: ToolRunnerDeps) {
     } catch (err) {
       if (signal?.aborted) throw err;
       throw new ToolError(
-        `Cannot reach Codeman at ${ctx.apiUrl}: ${getErrorMessage(err)}. Check that it is running. If every call ` +
+        `Cannot reach Codeman at ${ctx.apiUrl}: ${describeRequestError(err)}. Check that it is running. If every call ` +
           'fails at once, a sandbox around this MCP server may be blocking network access to this machine.'
       );
     }
diff --git a/test/cli-agent.test.ts b/test/cli-agent.test.ts
index ff41f7ce..7f579696 100644
--- a/test/cli-agent.test.ts
+++ b/test/cli-agent.test.ts
@@ -30,6 +30,7 @@ import {
   buildSendBody,
   deleteRefusal,
   describeFailure,
+  describeRequestError,
   httpRequest,
   inboxCell,
   inputRefusal,
@@ -589,9 +590,34 @@ describe('agent spawn', () => {
 
     expect(await agentSpawn(deps, { caseName: 'c', mode: 'claude', ready: true, timeoutMs: 1000 })).toBe(EXIT.error);
     expect(deps.out).toHaveLength(1);
-    expect(JSON.parse(deps.out[0])).toEqual({ sessionId: OTHER, readinessError: 'Readiness request failed' });
+    expect(JSON.parse(deps.out[0])).toEqual({ sessionId: OTHER, readinessError: 'request failed without a message' });
     expect(deps.calls).toHaveLength(2);
   });
+
+  it('keeps the error code when a refused connection rejects with an empty AggregateError', async () => {
+    // Node 22 on a host resolving to ::1 and 127.0.0.1: message '', code ECONNREFUSED.
+    const refused = Object.assign(new AggregateError([new Error('connect ECONNREFUSED ::1:3000')], ''), {
+      code: 'ECONNREFUSED',
+    });
+    const deps = fakeDeps((options) => {
+      if (options.path === '/api/v1/quick-start') return ok({ sessionId: OTHER });
+      throw refused;
+    }, true);
+
+    expect(await agentSpawn(deps, { caseName: 'c', mode: 'claude', ready: true, timeoutMs: 1000 })).toBe(EXIT.error);
+    expect(JSON.parse(deps.out[0])).toEqual({ sessionId: OTHER, readinessError: 'ECONNREFUSED' });
+  });
+});
+
+describe('describeRequestError', () => {
+  it('prefers the message, then the code, then a generic line', () => {
+    expect(describeRequestError(new Error('socket hang up'))).toBe('socket hang up');
+    expect(describeRequestError(Object.assign(new AggregateError([], ''), { code: 'ECONNREFUSED' }))).toBe(
+      'ECONNREFUSED'
+    );
+    expect(describeRequestError(new Error(''))).toBe('request failed without a message');
+    expect(describeRequestError('')).toBe('request failed without a message');
+  });
 });
 
 describe('session id prefixes', () => {
diff --git a/test/mcp-server.test.ts b/test/mcp-server.test.ts
index fc552cf2..a6f47e88 100644
--- a/test/mcp-server.test.ts
+++ b/test/mcp-server.test.ts
@@ -248,6 +248,17 @@ describe('protocol: both eras', () => {
     expect(result.isError).toBe(true);
     expect(result.content[0].text).toContain('CODEMAN_API_URL');
   });
+
+  it('a refused connection with an empty AggregateError still names the error code', async () => {
+    const refused: ApiRequest = async () => {
+      throw Object.assign(new AggregateError([new Error('connect ECONNREFUSED ::1:9')], ''), { code: 'ECONNREFUSED' });
+    };
+    const { out, send } = server(config(), { request: refused, calls: [] });
+    await send({ jsonrpc: '2.0', id: 1, method: 'tools/call', params: { name: 'list_sessions', arguments: {} } });
+    const result = (out[0] as { result: { isError: boolean; content: Array<{ text: string }> } }).result;
+    expect(result.isError).toBe(true);
+    expect(result.content[0].text).toContain('Cannot reach Codeman at http://127.0.0.1:9: ECONNREFUSED.');
+  });
 });
 
 describe('tool definitions', () => {