fix(cli): require input source for --quiet and drop empty final-only JSON on failure

- `--quiet` with neither `--prompt` nor `--input-format` now fails validation
  ("Quiet mode requires --prompt or --input-format.") instead of entering print
  mode and crashing on an undefined prompt.
- `PromptFinalJsonWriter.finish()` skips emitting when there is no final text,
  matching the text writer — a failed `--final-message-only` turn no longer
  prints a spurious `{"role":"assistant","content":""}` before its error line.

Adds a changeset for the print-mode stream-json work.

.changeset/print-mode-stream-json.md

@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/kimi-code": patch
+---
+
+Expand `kimi -p` print mode to cover (and slightly exceed) kimi-cli's non-interactive `stream-json` capabilities: emit model thinking as its own JSONL line; add `--input-format text|stream-json` (multi-turn prompts over stdin), `--final-message-only` and the `--quiet` shorthand; surface background-task/cron events as `notification` lines; report turn failures as `{"type":"error",...}` JSON with retryable provider errors mapped to exit code 75; wait for background tasks before exit (gated by `background.keepAliveOnExit`); and emit the TUI activity layer (tool progress, subagent lifecycle, warnings, skill/MCP/compaction/goal/agent-status/tool-list updates) on stdout so the stream-json output stays both complete and entirely JSON.

apps/kimi-code/src/cli/options.ts

@@ -53,6 +53,11 @@ export function validateOptions(opts: CLIOptions): ValidatedOptions {
   if (opts.quiet === true && opts.outputFormat !== undefined && opts.outputFormat !== 'text') {
     throw new OptionConflictError('Quiet mode implies --output-format text.');
   }
+  // Prompt mode needs an input source. `--prompt` and `--input-format` provide
+  // one; `--quiet` on its own does not, so it must be paired with either.
+  if (promptMode && !hasPrompt && opts.inputFormat === undefined) {
+    throw new OptionConflictError('Quiet mode requires --prompt or --input-format.');
+  }
   if (hasPrompt && opts.inputFormat !== undefined) {
     throw new OptionConflictError(
       'Cannot combine --prompt with --input-format; the prompt is read from stdin.',

apps/kimi-code/src/cli/run-prompt.ts

@@ -950,7 +950,12 @@ class PromptFinalJsonWriter implements PromptTurnWriter {
   }
 
   finish(): void {
-    this.stdout.write(`${JSON.stringify({ role: 'assistant', content: this.assistantText })}\n`);
+    // Only emit when there is a final message: a failed turn settles through
+    // finish() before its error line, so an empty emit would read as a spurious
+    // successful empty answer. Mirrors PromptFinalTextWriter.
+    if (this.assistantText.length > 0) {
+      this.stdout.write(`${JSON.stringify({ role: 'assistant', content: this.assistantText })}\n`);
+    }
   }
 }
 

apps/kimi-code/test/cli/options.test.ts

@@ -362,19 +362,31 @@ describe('CLI options parsing', () => {
       expect(parse([]).quiet).toBe(false);
     });
 
-    it('enters print mode on its own', () => {
-      const opts = parse(['--quiet']);
+    it('enters print mode when paired with --prompt', () => {
+      const opts = parse(['--quiet', '-p', 'hi']);
       expect(opts.quiet).toBe(true);
       expect(validateOptions(opts).uiMode).toBe('print');
     });
 
+    it('enters print mode when paired with --input-format', () => {
+      const opts = parse(['--quiet', '--input-format', 'text']);
+      expect(opts.quiet).toBe(true);
+      expect(validateOptions(opts).uiMode).toBe('print');
+    });
+
+    it('rejects --quiet on its own (no input source)', () => {
+      const opts = parse(['--quiet']);
+      expect(() => validateOptions(opts)).toThrow(OptionConflictError);
+      expect(() => validateOptions(opts)).toThrow('Quiet mode requires --prompt or --input-format.');
+    });
+
     it('is allowed alongside an explicit --output-format text', () => {
-      const opts = parse(['--quiet', '--output-format', 'text']);
+      const opts = parse(['--quiet', '-p', 'hi', '--output-format', 'text']);
       expect(() => validateOptions(opts)).not.toThrow();
     });
 
     it('rejects --quiet with --output-format stream-json', () => {
-      const opts = parse(['--quiet', '--output-format', 'stream-json']);
+      const opts = parse(['--quiet', '-p', 'hi', '--output-format', 'stream-json']);
       expect(() => validateOptions(opts)).toThrow(OptionConflictError);
       expect(() => validateOptions(opts)).toThrow('Quiet mode implies --output-format text.');
     });

apps/kimi-code/test/cli/run-prompt.test.ts

@@ -811,6 +811,34 @@ describe('runPrompt', () => {
     expect(stderr.text()).toBe('');
   });
 
+  it('does not emit an empty final assistant message when a final-only turn fails', async () => {
+    mocks.session.prompt.mockImplementationOnce(async () => {
+      for (const handler of mocks.eventHandlers) {
+        handler(mocks.mainEvent({ type: 'turn.started', turnId: 41, origin: { kind: 'user' } }));
+        handler(
+          mocks.mainEvent({
+            type: 'turn.ended',
+            turnId: 41,
+            reason: 'failed',
+            error: { code: 'provider.api_error', message: 'boom', retryable: false },
+          }),
+        );
+      }
+    });
+    const stdout = writer();
+
+    await runPrompt(opts({ outputFormat: 'stream-json', finalMessageOnly: true }), '1.2.3-test', {
+      stdout,
+      stderr: writer(),
+    });
+
+    // Only the error line — no spurious `{"role":"assistant","content":""}` first.
+    expect(stdout.text()).toBe(
+      '{"type":"error","code":"provider.api_error","message":"boom","retryable":false}\n',
+    );
+    expect(process.exitCode).toBe(1);
+  });
+
   it('emits only the final text in text final-message-only mode and skips the resume hint (output B)', async () => {
     const stdout = writer();
     const stderr = writer();