fix(switchboard): disable the pi-harness flag on the headless (cloud) path

The experimental pi harness should not run on the headless-DONOTUSE-EXPERIMENTAL
cloud path. Thread a `headless` signal from the session (set only for that flag,
not --ci) into the switchboard, and decline the wizard-use-pi-harness flag when
it is set — the run stays on the anthropic binding default.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: gewenyu99

src/lib/agent/runner/__tests__/switchboard.test.ts

@@ -163,6 +163,27 @@ describe('switchboard resolveHarness — pi flag is gated to posthog-integration
     expect(pick).toEqual({ harness: Harness.pi, model: GPT5_4_MODEL });
   });
 
+  it('disables the pi flag on the headless (cloud) path, even for posthog-integration', () => {
+    const pick = resolveHarness({
+      program: 'posthog-integration',
+      flags: { [WIZARD_USE_PI_HARNESS_FLAG_KEY]: 'true' },
+      headless: true,
+    });
+    expect(pick).toEqual({
+      harness: Harness.anthropic,
+      model: DEFAULT_AGENT_MODEL,
+    });
+  });
+
+  it('keeps the pi flag for a non-headless (local/--ci) posthog-integration run', () => {
+    const pick = resolveHarness({
+      program: 'posthog-integration',
+      flags: { [WIZARD_USE_PI_HARNESS_FLAG_KEY]: 'true' },
+      headless: false,
+    });
+    expect(pick.harness).toBe(Harness.pi);
+  });
+
   it('ignores the pi flag for self-driving — stays on the anthropic default', () => {
     const pick = resolveHarness({
       program: 'self-driving',

src/lib/agent/runner/index.ts

@@ -130,6 +130,7 @@ function resolveProgramRunner(
     cliHarness: session.harness,
     cliSequence: session.sequence,
     cliModel: session.model,
+    headless: session.headless,
   };
   const binding = resolveBinding(ctx);
   tagBinding(boot, binding);

src/lib/agent/runner/sequence/linear.ts

@@ -130,6 +130,7 @@ export async function runLinearProgram(
     flags: wizardFlags,
     cliHarness: session.harness,
     cliModel: session.model,
+    headless: session.headless,
   });
   const agentResult = await getHarness(pick.harness).run({
     session,

src/lib/agent/runner/switchboard/harness.ts

@@ -60,6 +60,8 @@ const PI_FLAG_PROGRAMS = new Set<ProgramId>(['posthog-integration']);
 const flagRunnerOverride: Middleware<HarnessPick> = (ctx, next) => {
   const pick = next();
   if (ctx.flags[WIZARD_USE_PI_HARNESS_FLAG_KEY] !== 'true') return pick;
+  // The pi experiment is disabled on the headless-DONOTUSE-EXPERIMENTAL (cloud) path.
+  if (ctx.headless) return pick;
   if (!PI_FLAG_PROGRAMS.has(ctx.program)) return pick;
   if (ctx.trace) Object.assign(ctx.trace, { harness: 'flag', model: 'flag' });
   const variant = ctx.flags[WIZARD_PI_MODEL_FLAG_KEY] ?? '';

src/lib/agent/runner/switchboard/index.ts

@@ -31,6 +31,8 @@ export interface SwitchboardCtx {
   cliSequence?: Sequence;
   /** CLI override (`--model`, gateway id). Wins over the binding's model. */
   cliModel?: string;
+  /** The headless-DONOTUSE-EXPERIMENTAL (cloud) run path; disables the pi-harness flag. */
+  headless?: boolean;
   /** Filled during resolution; read by the caller for telemetry. */
   trace?: SwitchboardTrace;
 }

src/lib/runners/run-non-interactive.ts

@@ -107,6 +107,7 @@ export function runNonInteractive(
       debug: options.debug as boolean | undefined,
       installDir,
       ci: true,
+      headless: mode === 'headless',
       signup: options.signup as boolean | undefined,
       localMcp: options.localMcp as boolean | undefined,
       apiKey,

src/lib/wizard-session.ts

@@ -171,6 +171,8 @@ export interface WizardSession {
   debug: boolean;
   installDir: string;
   ci: boolean;
+  /** The experimental headless-DONOTUSE-EXPERIMENTAL (cloud) run path; false for --ci. */
+  headless: boolean;
   signup: boolean;
   localMcp: boolean;
   mcpFeatures?: string[];
@@ -342,6 +344,7 @@ export function buildSession(args: {
   debug?: boolean;
   installDir?: string;
   ci?: boolean;
+  headless?: boolean;
   signup?: boolean;
   localMcp?: boolean;
   mcpFeatures?: string[];
@@ -363,6 +366,7 @@ export function buildSession(args: {
     debug: args.debug ?? false,
     installDir: args.installDir ?? process.cwd(),
     ci: args.ci ?? false,
+    headless: args.headless ?? false,
     signup: args.signup ?? false,
     localMcp: args.localMcp ?? false,
     mcpFeatures: args.mcpFeatures,