sonnet-5 flag

src/lib/__tests__/agent-interface.test.ts

@@ -5,9 +5,15 @@ import {
   runAgent,
   createStopHook,
   isWarlockDisabled,
+  resolveAgentModel,
   buildAuthErrorContext,
 } from '@lib/agent/agent-interface';
-import { WIZARD_WARLOCK_DISABLED_FLAG_KEY } from '@lib/constants';
+import {
+  DEFAULT_AGENT_MODEL,
+  SONNET_5_MODEL,
+  WIZARD_SONNET_5_FLAG_KEY,
+  WIZARD_WARLOCK_DISABLED_FLAG_KEY,
+} from '@lib/constants';
 import { AgentOutputSignals } from '@lib/agent/output-signals';
 import type { WizardRunOptions } from '@utils/types';
 import type { SpinnerHandle } from '@ui';
@@ -539,6 +545,34 @@ describe('isWarlockDisabled (kill switch)', () => {
   });
 });
 
+describe('resolveAgentModel (sonnet-5 opt-in)', () => {
+  // Fail-safe: an unset or fetch-failed flag map must NOT shift everyone
+  // onto Sonnet 5. The default has to be the explicit DEFAULT_AGENT_MODEL.
+  it('stays on the default with no flags or an empty flag map', () => {
+    expect(resolveAgentModel()).toBe(DEFAULT_AGENT_MODEL);
+    expect(resolveAgentModel({})).toBe(DEFAULT_AGENT_MODEL);
+  });
+
+  it('stays on the default when the flag is anything other than "true"', () => {
+    expect(resolveAgentModel({ [WIZARD_SONNET_5_FLAG_KEY]: 'false' })).toBe(
+      DEFAULT_AGENT_MODEL,
+    );
+    // Case-sensitive match: only the literal 'true' opts in.
+    expect(resolveAgentModel({ [WIZARD_SONNET_5_FLAG_KEY]: 'True' })).toBe(
+      DEFAULT_AGENT_MODEL,
+    );
+    expect(resolveAgentModel({ 'some-other-flag': 'true' })).toBe(
+      DEFAULT_AGENT_MODEL,
+    );
+  });
+
+  it('opts into Sonnet 5 when the flag resolves to "true"', () => {
+    expect(resolveAgentModel({ [WIZARD_SONNET_5_FLAG_KEY]: 'true' })).toBe(
+      SONNET_5_MODEL,
+    );
+  });
+});
+
 describe('buildAuthErrorContext', () => {
   const GATEWAY = 'https://gateway.us.posthog.com/wizard';
   let home: string;

src/lib/agent/agent-interface.ts

@@ -15,9 +15,11 @@ import {
   WIZARD_REMARK_EVENT_NAME,
   POSTHOG_PROPERTY_HEADER_PREFIX,
   WIZARD_ORCHESTRATOR_FLAG_KEY,
+  WIZARD_SONNET_5_FLAG_KEY,
   WIZARD_USER_AGENT,
   WIZARD_WARLOCK_DISABLED_FLAG_KEY,
   DEFAULT_AGENT_MODEL,
+  SONNET_5_MODEL,
 } from '@lib/constants';
 import {
   type AdditionalFeature,
@@ -349,6 +351,21 @@ export function isOrchestratorEnabled(
   return flags[WIZARD_ORCHESTRATOR_FLAG_KEY] === 'true';
 }
 
+/**
+ * Pick the model the main agent runner should use this run. Defaults to
+ * `DEFAULT_AGENT_MODEL` (Sonnet 4.6); flips to `SONNET_5_MODEL` only when
+ * the `wizard-sonnet-5` flag resolves to the literal string 'true'. A
+ * missing flag, an empty flag map (the safe default returned when the flag
+ * fetch fails), or any other value stays on the default — Sonnet 5 must
+ * be an explicit opt-in so a flag-fetch failure can't shift everyone onto
+ * a different model.
+ */
+export function resolveAgentModel(flags: Record<string, string> = {}): string {
+  return flags[WIZARD_SONNET_5_FLAG_KEY] === 'true'
+    ? SONNET_5_MODEL
+    : DEFAULT_AGENT_MODEL;
+}
+
 /**
  * Build env for the SDK subprocess: process.env plus ANTHROPIC_CUSTOM_HEADERS, which always
  * includes `x-posthog-use-bedrock-fallback: true` so the LLM gateway falls back to Bedrock on
@@ -711,7 +728,7 @@ export async function initializeAgent(
 
     // Bare model IDs (no `anthropic/` prefix) so the LLM gateway's Bedrock
     // fallback can match map_to_bedrock_model()'s strict lookup.
-    const model = config.modelOverride ?? DEFAULT_AGENT_MODEL;
+    const model = config.modelOverride ?? resolveAgentModel(config.wizardFlags);
 
     const agentRunConfig: AgentRunConfig = {
       workingDirectory: config.workingDirectory,

src/lib/constants.ts

@@ -12,6 +12,13 @@ import { VERSION } from './version';
  */
 export const DEFAULT_AGENT_MODEL = 'claude-sonnet-4-6';
 
+/**
+ * Newer Sonnet, opt-in via the `wizard-sonnet-5` feature flag (see
+ * `resolveAgentModel` in `agent-interface.ts`). Kept separate from
+ * `DEFAULT_AGENT_MODEL` so the off-by-default behavior is obvious.
+ */
+export const SONNET_5_MODEL = 'claude-sonnet-5';
+
 /**
  * Cheaper, faster model for mechanical agent work (e.g. repo classification
  * during source-map detection). Passed via AgentConfig.modelOverride.
@@ -187,6 +194,14 @@ export const WIZARD_INTERACTION_EVENT_NAME = 'wizard interaction';
 export const WIZARD_REMARK_EVENT_NAME = 'wizard remark';
 /** Boolean feature flag that routes a run to the experimental orchestrator runner. */
 export const WIZARD_ORCHESTRATOR_FLAG_KEY = 'wizard-orchestrator';
+/**
+ * Boolean feature flag that opts the main agent runner into Sonnet 5
+ * (`SONNET_5_MODEL`). When false or missing, the main runner uses
+ * `DEFAULT_AGENT_MODEL` (Sonnet 4.6). Only the main runner reads this — the
+ * MCP suggested-prompts screen and the orchestrator task default stay on
+ * `DEFAULT_AGENT_MODEL` regardless.
+ */
+export const WIZARD_SONNET_5_FLAG_KEY = 'wizard-sonnet-5';
 /** Feature flag key that gates the intro-screen "Tools" menu. */
 export const WIZARD_TOOLS_MENU_FLAG_KEY = 'wizard-tools-menu';
 /**