feat(core): add the output-style layer to the system prompt

packages/cli/src/ui/commands/contextCommand.test.ts

@@ -8,6 +8,11 @@ import { describe, it, expect, vi, beforeEach } from 'vitest';
 import * as os from 'node:os';
 import * as path from 'node:path';
 import type { Config } from '@qwen-code/qwen-code-core';
+import {
+  getBuiltInOutputStyle,
+  getCoreSystemPrompt,
+  resolveInteractionMode,
+} from '@qwen-code/qwen-code-core';
 import { t } from '../../i18n/index.js';
 import {
   collectContextData,
@@ -50,6 +55,8 @@ function makeMockConfig(contextWindowSize = 32_000): Config {
     }),
     getVisibleTools: vi.fn().mockReturnValue(new Set()),
     getUserMemory: vi.fn().mockReturnValue(''),
+    getSystemPrompt: vi.fn().mockReturnValue(undefined),
+    getOutputStyle: vi.fn().mockReturnValue(undefined),
     getAutoMemoryPrompt: vi.fn().mockReturnValue(''),
     getSkillManager: vi.fn().mockReturnValue({
       listSkills: vi.fn().mockResolvedValue([]),
@@ -83,6 +90,8 @@ describe('collectContextData (contextCommand)', () => {
       }),
       getVisibleTools: vi.fn().mockReturnValue(new Set()),
       getUserMemory: vi.fn().mockReturnValue(''),
+      getSystemPrompt: vi.fn().mockReturnValue(undefined),
+      getOutputStyle: vi.fn().mockReturnValue(undefined),
       getAutoMemoryPrompt: vi.fn().mockReturnValue(''),
       getSkillManager: vi.fn().mockReturnValue({
         listSkills: vi.fn().mockResolvedValue([]),
@@ -207,6 +216,8 @@ describe('collectContextData (contextCommand)', () => {
       }),
       getVisibleTools: vi.fn().mockReturnValue(new Set()),
       getUserMemory: vi.fn().mockReturnValue(''),
+      getSystemPrompt: vi.fn().mockReturnValue(undefined),
+      getOutputStyle: vi.fn().mockReturnValue(undefined),
       getAutoMemoryPrompt: vi.fn().mockReturnValue(''),
       getSkillManager: vi.fn().mockReturnValue({
         listSkills: vi.fn().mockResolvedValue([]),
@@ -254,6 +265,8 @@ describe('collectContextData (contextCommand)', () => {
       }),
       getVisibleTools: vi.fn().mockReturnValue(new Set(['web_fetch'])),
       getUserMemory: vi.fn().mockReturnValue(''),
+      getSystemPrompt: vi.fn().mockReturnValue(undefined),
+      getOutputStyle: vi.fn().mockReturnValue(undefined),
       getAutoMemoryPrompt: vi.fn().mockReturnValue(''),
       getSkillManager: vi.fn().mockReturnValue({
         listSkills: vi.fn().mockResolvedValue([]),
@@ -280,6 +293,7 @@ describe('collectContextData (contextCommand)', () => {
     const config = {
       ...makeMockConfig(),
       getUserMemory: vi.fn().mockReturnValue(''),
+      getOutputStyle: vi.fn().mockReturnValue(undefined),
       getAutoMemoryPrompt: vi
         .fn()
         .mockReturnValue('# auto memory\nMEMORY_INDEX_MARKER'),
@@ -306,6 +320,7 @@ describe('collectContextData (contextCommand)', () => {
     const config = {
       ...makeMockConfig(),
       getUserMemory: vi.fn().mockReturnValue(memory),
+      getOutputStyle: vi.fn().mockReturnValue(undefined),
       getAutoMemoryPrompt: vi.fn().mockReturnValue(''),
       getWorkingDir: vi.fn().mockReturnValue(workingDir),
     } as unknown as Config;
@@ -331,6 +346,7 @@ describe('collectContextData (contextCommand)', () => {
     const config = {
       ...makeMockConfig(),
       getUserMemory: vi.fn().mockReturnValue(memory),
+      getOutputStyle: vi.fn().mockReturnValue(undefined),
       getAutoMemoryPrompt: vi.fn().mockReturnValue(''),
       getWorkingDir: vi.fn().mockReturnValue(workingDir),
     } as unknown as Config;
@@ -446,6 +462,47 @@ describe('/context shows three-tier thresholds', () => {
     expect(text).not.toMatch(/Compaction thresholds/);
   });
 
+  it('bills the active output style into the system-prompt estimate', async () => {
+    const concise = getBuiltInOutputStyle('Concise')!;
+    const plainConfig = makeMockConfig(200_000);
+    const styledConfig = {
+      ...makeMockConfig(200_000),
+      getOutputStyle: vi.fn().mockReturnValue(concise),
+    } as unknown as Config;
+
+    // No API token count, so breakdown.systemPrompt is the raw estimate
+    // rather than a scaled share — the style section shows up undiluted.
+    const plain = await collectContextData(plainConfig, false);
+    const styled = await collectContextData(styledConfig, false);
+
+    const tokenDelta =
+      styled.breakdown.systemPrompt - plain.breakdown.systemPrompt;
+    expect(tokenDelta).toBeGreaterThan(0);
+
+    // ...and the delta has to be the style layer itself, not incidental
+    // drift: estimateTokens bills ASCII at ~4 chars/token.
+    const mode = resolveInteractionMode(styledConfig);
+    const charDelta =
+      getCoreSystemPrompt(undefined, 'test-model', undefined, mode, concise)
+        .length -
+      getCoreSystemPrompt(undefined, 'test-model', undefined, mode, undefined)
+        .length;
+    expect(tokenDelta).toBeGreaterThan(charDelta / 4 - 5);
+    expect(tokenDelta).toBeLessThan(charDelta / 4 + 5);
+  });
+
+  it('estimates the custom system prompt used by the live client', async () => {
+    const config = {
+      ...makeMockConfig(200_000),
+      getSystemPrompt: vi.fn().mockReturnValue('CUSTOM'),
+      getOutputStyle: vi.fn().mockReturnValue(getBuiltInOutputStyle('Concise')),
+    } as unknown as Config;
+
+    const data = await collectContextData(config, false);
+
+    expect(data.breakdown.systemPrompt).toBe(2);
+  });
+
   it('propagates custom autoCompactThreshold through to /context thresholds', async () => {
     // config.getAutoCompactThreshold() returns 0.5 → computeThresholds(32000, 0.5)
     // = { warn: 0, auto: 16,000, hard: 19,000, effectiveWindow: 12,000 }

packages/cli/src/ui/commands/contextCommand.ts

@@ -21,8 +21,7 @@ import {
 import {
   DiscoveredMCPTool,
   uiTelemetryService,
-  getCoreSystemPrompt,
-  resolveInteractionMode,
+  getMainSessionBaseSystemPrompt,
   DEFAULT_TOKEN_LIMIT,
   ToolNames,
   buildSkillLlmContent,
@@ -139,12 +138,7 @@ export async function collectContextData(
   // refines the messages-vs-cache split, not the headline total or tier.
   const apiCachedTokens = uiTelemetryService.getLastCachedContentTokenCount();
 
-  const systemPromptText = getCoreSystemPrompt(
-    undefined,
-    modelName,
-    undefined,
-    resolveInteractionMode(config),
-  );
+  const systemPromptText = getMainSessionBaseSystemPrompt(config);
   const systemPromptTokens = estimateTokens(systemPromptText);
 
   const toolRegistry = config.getToolRegistry();

packages/core/src/agents/arena/ArenaManager.test.ts

@@ -13,6 +13,7 @@ import { ArenaEventType } from './arena-events.js';
 import { ArenaSessionStatus, ARENA_MAX_AGENTS } from './types.js';
 import { AgentStatus } from '../runtime/agent-types.js';
 import { ApprovalMode } from '../../config/config.js';
+import { getBuiltInOutputStyle } from '../../core/output-styles.js';
 
 const hoistedMockSetupWorktrees = vi.hoisted(() => vi.fn());
 const hoistedMockCleanupSession = vi.hoisted(() => vi.fn());
@@ -72,6 +73,7 @@ const createMockConfig = (
   getModel: () => 'test-model',
   getSessionId: () => 'test-session',
   getUserMemory: () => '',
+  getOutputStyle: (): ReturnType<typeof getBuiltInOutputStyle> => undefined,
   getAutoMemoryPrompt: () => '',
   getToolRegistry: () => ({
     getFunctionDeclarations: () => [],
@@ -405,14 +407,18 @@ describe('ArenaManager', () => {
       }
     });
 
-    it('builds the in-process worker system prompt in headless interaction mode', async () => {
+    it('builds the in-process worker prompt with headless mode and the active style', async () => {
       // Arena workers run non-interactively, so ArenaManager passes 'headless'
       // as the interaction mode (4th arg) to getCoreSystemPrompt. A regression
       // that drops that argument would fall back to the interactive prompt,
       // telling arena workers to ask the user questions no one can answer.
       // Assert on the produced prompt: the headless variant carries a
       // single-turn marker that is absent from every other interaction mode.
       mockBackend.type = 'in-process';
+      mockConfig = {
+        ...createMockConfig(tempDir, { worktreeBaseDir: tempDir }),
+        getOutputStyle: () => getBuiltInOutputStyle('Concise'),
+      };
       const manager = new ArenaManager(mockConfig as never);
 
       await manager.start(createValidStartOptions());
@@ -429,6 +435,7 @@ describe('ArenaManager', () => {
         expect(systemPrompt).toContain(
           'This is a non-interactive, single-turn run',
         );
+        expect(systemPrompt).toContain('# Output Style: Concise');
       }
     });
 

packages/core/src/agents/arena/ArenaManager.ts

@@ -1089,6 +1089,7 @@ export class ArenaManager {
                 model.modelId,
                 undefined,
                 'headless',
+                this.config.getOutputStyle(),
               ),
               contextFiles: this.config.getUserMemory(),
             }),

packages/core/src/config/config.ts

@@ -37,6 +37,7 @@ import type { TeamContext } from '../agents/team/types.js';
 import { BaseLlmClient } from '../core/baseLlmClient.js';
 import { GeminiClient } from '../core/client.js';
 import { resolveInteractionMode } from '../core/prompts.js';
+import type { OutputStyleDefinition } from '../core/output-styles.js';
 import {
   AuthType,
   createContentGenerator,
@@ -975,6 +976,7 @@ export interface ConfigParameters {
   question?: string;
   systemPrompt?: string;
   appendSystemPrompt?: string;
+  outputStyle?: OutputStyleDefinition;
   coreTools?: string[];
   allowedTools?: string[];
   excludeTools?: string[];
@@ -1858,6 +1860,7 @@ export class Config {
   private readonly systemPrompt: string | undefined;
   private readonly appendSystemPrompt: string | undefined;
   private liveAppendSystemPrompt: string | undefined;
+  private outputStyle: OutputStyleDefinition | undefined;
   private readonly coreTools: string[] | undefined;
   private readonly allowedTools: string[] | undefined;
   private readonly excludeTools: string[] | undefined;
@@ -2197,6 +2200,7 @@ export class Config {
     this.question = params.question;
     this.systemPrompt = params.systemPrompt;
     this.appendSystemPrompt = params.appendSystemPrompt;
+    this.outputStyle = params.outputStyle;
     this.coreTools = params.coreTools;
     this.allowedTools = params.allowedTools;
     this.excludeTools = params.excludeTools;
@@ -5483,6 +5487,19 @@ export class Config {
     this.liveAppendSystemPrompt = prompt;
   }
 
+  getOutputStyle(): OutputStyleDefinition | undefined {
+    return this.outputStyle;
+  }
+
+  /**
+   * Swaps the active output style. Callers that change it mid-session must
+   * follow up with `GeminiClient.refreshSystemInstruction()`, since the style
+   * lives in the stable layer of an already-bound system instruction.
+   */
+  setOutputStyle(style: OutputStyleDefinition | undefined): void {
+    this.outputStyle = style;
+  }
+
   /** @deprecated Use getPermissionsAllow() instead. */
   getCoreTools(): string[] | undefined {
     if (this.getBareMode()) {

packages/core/src/core/client.test.ts

@@ -79,6 +79,7 @@ import {
   getCustomSystemPrompt,
   getPlanModeSystemReminder,
 } from './prompts.js';
+import { getBuiltInOutputStyle } from './output-styles.js';
 import { DEFAULT_QWEN_FLASH_MODEL } from '../config/models.js';
 import { FileDiscoveryService } from '../services/fileDiscoveryService.js';
 import { promptIdContext } from '../utils/promptIdContext.js';
@@ -602,6 +603,7 @@ describe('Gemini Client (client.ts)', () => {
       getAutoMemoryPrompt: vi.fn().mockReturnValue(''),
       getSystemPrompt: vi.fn().mockReturnValue(undefined),
       getAppendSystemPrompt: vi.fn().mockReturnValue(undefined),
+      getOutputStyle: vi.fn().mockReturnValue(undefined),
       getStaticSystemPrefix: vi.fn().mockReturnValue(undefined),
       setStaticSystemPrefix: vi.fn(),
       getFullContext: vi.fn().mockReturnValue(false),
@@ -13260,6 +13262,7 @@ Other open files:
         'test-model',
         undefined,
         'headless',
+        undefined,
       );
       expect(mockContentGenerator.generateContent).toHaveBeenCalledWith(
         expect.objectContaining({
@@ -13271,6 +13274,30 @@ Other open files:
       );
     });
 
+    it('passes the active output style to the core system prompt', async () => {
+      const contents = [{ role: 'user', parts: [{ text: 'hello' }] }];
+      const abortSignal = new AbortController().signal;
+      const concise = getBuiltInOutputStyle('Concise');
+
+      vi.mocked(getCoreSystemPrompt).mockClear();
+      vi.spyOn(client['config'], 'getOutputStyle').mockReturnValue(concise);
+
+      await client.generateContent(
+        contents,
+        {},
+        abortSignal,
+        DEFAULT_QWEN_FLASH_MODEL,
+      );
+
+      expect(getCoreSystemPrompt).toHaveBeenCalledWith(
+        undefined,
+        'test-model',
+        undefined,
+        'headless',
+        concise,
+      );
+    });
+
     it.each([
       ['interactive', true, false],
       ['acp', false, true],
@@ -13299,6 +13326,7 @@ Other open files:
           'test-model',
           undefined,
           mode,
+          undefined,
         );
       },
     );

packages/core/src/core/client.ts

@@ -346,6 +346,31 @@ const SKILL_WRITE_TOOL_NAMES: ReadonlySet<string> = new Set([
   ToolNames.EDIT,
 ]);
 
+type MainSessionPromptConfig = Pick<
+  Config,
+  | 'getSystemPrompt'
+  | 'getModel'
+  | 'getOutputStyle'
+  | 'getExperimentalZedIntegration'
+  | 'getInputFormat'
+  | 'isInteractive'
+>;
+
+export function getMainSessionBaseSystemPrompt(
+  config: MainSessionPromptConfig,
+): string {
+  const overrideSystemPrompt = config.getSystemPrompt();
+  return overrideSystemPrompt
+    ? getCustomSystemPrompt(overrideSystemPrompt)
+    : getCoreSystemPrompt(
+        undefined,
+        config.getModel(),
+        undefined,
+        resolveInteractionMode(config),
+        config.getOutputStyle(),
+      );
+}
+
 export class GeminiClient {
   private chat?: GeminiChat;
   private initializedSessionId: string | undefined;
@@ -1161,15 +1186,7 @@ export class GeminiClient {
   }
 
   private getMainSessionSystemInstruction(): string {
-    const overrideSystemPrompt = this.config.getSystemPrompt();
-    const base = overrideSystemPrompt
-      ? getCustomSystemPrompt(overrideSystemPrompt)
-      : getCoreSystemPrompt(
-          undefined,
-          this.config.getModel(),
-          undefined,
-          resolveInteractionMode(this.config),
-        );
+    const base = getMainSessionBaseSystemPrompt(this.config);
     const stableLayers = {
       base,
       contextFiles: this.config.getUserMemory(),