diff --git a/packages/pi-coding-agent/src/core/sdk.ts b/packages/pi-coding-agent/src/core/sdk.ts
index 12da38d16..1558b10b2 100644
--- a/packages/pi-coding-agent/src/core/sdk.ts
+++ b/packages/pi-coding-agent/src/core/sdk.ts
@@ -219,6 +219,16 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 		time("resourceLoader.reload");
 	}
 
+	// Flush provider registrations queued during extension loading so that
+	// extension models (e.g. pi-claude-cli) are visible in the registry before
+	// findInitialModel() runs. bindCore() repeats this flush as a safety net
+	// for any late-arriving registrations.
+	const { runtime: extensionRuntime } = resourceLoader.getExtensions();
+	for (const { name, config } of extensionRuntime.pendingProviderRegistrations) {
+		modelRegistry.registerProvider(name, config);
+	}
+	extensionRuntime.pendingProviderRegistrations = [];
+
 	// Check if session has existing data to restore
 	const existingSession = sessionManager.buildSessionContext();
 	const hasExistingSession = existingSession.messages.length > 0;
diff --git a/src/cli.ts b/src/cli.ts
index b8a348e3e..29b7c804b 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -131,6 +131,48 @@ function parseCliArgs(argv: string[]): CliFlags {
   return flags
 }
 
+/**
+ * Validate the configured default model against the registry and reset it if
+ * it no longer exists.  Must run AFTER extensions have registered their
+ * providers so that extension models (e.g. pi-claude-cli) are visible.
+ */
+function validateConfiguredModel(
+  modelRegistry: ModelRegistry,
+  settingsManager: SettingsManager,
+): void {
+  const configuredProvider = settingsManager.getDefaultProvider()
+  const configuredModel = settingsManager.getDefaultModel()
+  const allModels = modelRegistry.getAll()
+  const availableModels = modelRegistry.getAvailable()
+  const configuredExists = configuredProvider && configuredModel &&
+    allModels.some((m) => m.provider === configuredProvider && m.id === configuredModel)
+  const configuredAvailable = configuredProvider && configuredModel &&
+    availableModels.some((m) => m.provider === configuredProvider && m.id === configuredModel)
+
+  if (!configuredModel || !configuredExists) {
+    // Model not configured at all, or removed from registry — pick a fallback.
+    // Only fires when the model is genuinely unknown (not just temporarily unavailable).
+    const piDefault = getPiDefaultModelAndProvider()
+    const preferred =
+      (piDefault
+        ? availableModels.find((m) => m.provider === piDefault.provider && m.id === piDefault.model)
+        : undefined) ||
+      availableModels.find((m) => m.provider === 'openai' && m.id === 'gpt-5.4') ||
+      availableModels.find((m) => m.provider === 'openai') ||
+      availableModels.find((m) => m.provider === 'anthropic' && m.id === 'claude-opus-4-6') ||
+      availableModels.find((m) => m.provider === 'anthropic' && m.id.includes('opus')) ||
+      availableModels.find((m) => m.provider === 'anthropic') ||
+      availableModels[0]
+    if (preferred) {
+      settingsManager.setDefaultModelAndProvider(preferred.provider, preferred.id)
+    }
+  }
+
+  if (settingsManager.getDefaultThinkingLevel() !== 'off' && !configuredExists) {
+    settingsManager.setDefaultThinkingLevel('off')
+  }
+}
+
 const cliFlags = parseCliArgs(process.argv)
 const isPrintMode = cliFlags.print || cliFlags.mode !== undefined
 
@@ -382,8 +424,23 @@ if (!isPrintMode && process.stdout.columns && process.stdout.columns < 40) {
   )
 }
 
-// --list-models: print available models and exit (no TTY needed)
+// --list-models: load extensions so that extension-registered providers (e.g.
+// pi-claude-cli) appear in the listing, then flush their pending registrations
+// into the model registry before printing.
 if (cliFlags.listModels !== undefined) {
+  exitIfManagedResourcesAreNewer(agentDir)
+  initResources(agentDir)
+  const listModelsLoader = new DefaultResourceLoader({
+    agentDir,
+    additionalExtensionPaths: cliFlags.extensions.length > 0 ? cliFlags.extensions : undefined,
+  })
+  await listModelsLoader.reload()
+  const listModelsExtensions = listModelsLoader.getExtensions()
+  for (const { name, config } of listModelsExtensions.runtime.pendingProviderRegistrations) {
+    modelRegistry.registerProvider(name, config)
+  }
+  listModelsExtensions.runtime.pendingProviderRegistrations = []
+
   const models = modelRegistry.getAvailable()
   if (models.length === 0) {
     console.log('No models available. Set API keys in environment variables.')
@@ -532,6 +589,11 @@ if (isPrintMode) {
     }
   }
 
+  // Validate configured model now that extension providers are registered.
+  // Must run after createAgentSession() which flushes pendingProviderRegistrations
+  // so extension models (e.g. pi-claude-cli) are visible in the registry.
+  validateConfiguredModel(modelRegistry, settingsManager)
+
   // Apply --model override if specified
   if (cliFlags.model) {
     const available = modelRegistry.getAvailable()
@@ -738,6 +800,11 @@ if (extensionsResult.errors.length > 0) {
   }
 }
 
+// Validate configured model now that extension providers are registered.
+// Must run after createAgentSession() which flushes pendingProviderRegistrations
+// so extension models (e.g. pi-claude-cli) are visible in the registry.
+validateConfiguredModel(modelRegistry, settingsManager)
+
 // Restore scoped models from settings on startup.
 // The upstream InteractiveMode reads enabledModels from settings when /scoped-models is opened,
 // but doesn't apply them to the session at startup — so Ctrl+P cycles all models instead of