fix: persist defaultProvider when user selects Claude Code CLI in onboarding (#4104)

The claude-cli onboarding path stored the auth sentinel for claude-code
but did not update defaultProvider in settings.json. Users who had an
existing Anthropic API key were left on the "anthropic" provider because
the startup migration in cli.ts correctly skips direct-key holders.

Write defaultProvider = "claude-code" to settings.json in the claude-cli
branch so the provider switch takes effect immediately.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/onboarding.ts

@@ -323,6 +323,15 @@ async function runLlmStep(p: ClackModule, pc: PicoModule, authStorage: AuthStora
     p.log.info('Your Claude subscription will be used for inference. No API key needed.')
     // Store sentinel so hasAuth('claude-code') returns true on future boots
     authStorage.set('claude-code', { type: 'api_key', key: 'cli' })
+    // Persist claude-code as the default provider so the startup migration in
+    // cli.ts does not need to fire and the user is not left on "anthropic".
+    const settingsPath = join(agentDir, 'settings.json')
+    try {
+      const raw = existsSync(settingsPath) ? JSON.parse(readFileSync(settingsPath, 'utf-8')) : {}
+      raw.defaultProvider = 'claude-code'
+      mkdirSync(dirname(settingsPath), { recursive: true })
+      writeFileSync(settingsPath, JSON.stringify(raw, null, 2), 'utf-8')
+    } catch { /* non-fatal — startup migration will catch it */ }
     return true
   }
 

src/tests/onboarding-claude-cli-provider.test.ts

@@ -0,0 +1,31 @@
+import test from "node:test"
+import assert from "node:assert/strict"
+import { readFileSync } from "node:fs"
+import { join } from "node:path"
+
+/**
+ * Source-level regression test: the claude-cli onboarding path must persist
+ * defaultProvider = 'claude-code' in settings.json so the user is not left
+ * on the 'anthropic' direct-API provider after selecting Claude Code CLI.
+ *
+ * Without this, the auto-migration in cli.ts does not fire when the user
+ * also has a stored Anthropic API key, leaving them on the wrong provider.
+ */
+test("onboarding claude-cli path persists defaultProvider to settings.json", () => {
+  const source = readFileSync(
+    join(import.meta.dirname, "..", "onboarding.ts"),
+    "utf-8",
+  )
+
+  // The claude-cli branch must write defaultProvider = 'claude-code' to settings.json
+  const cliBlock = source.slice(
+    source.indexOf("method === 'claude-cli'"),
+    source.indexOf("// ── Step 2"),
+  )
+  assert.ok(cliBlock.length > 0, "claude-cli block not found in onboarding.ts")
+  assert.match(
+    cliBlock,
+    /raw\.defaultProvider\s*=\s*['"]claude-code['"]/,
+    "claude-cli onboarding path must set defaultProvider = 'claude-code' in settings.json",
+  )
+})