diff --git a/src/cli/update.ts b/src/cli/update.ts
index a0cd35f5..11ef117c 100644
--- a/src/cli/update.ts
+++ b/src/cli/update.ts
@@ -1,4 +1,5 @@
 import chalk from 'chalk'
+import { getAPIProvider } from 'src/utils/model/providers.js'
 import { logEvent } from 'src/services/analytics/index.js'
 import {
   getLatestVersion,
@@ -28,6 +29,19 @@ import { gte } from 'src/utils/semver.js'
 import { getInitialSettings } from 'src/utils/settings/settings.js'
 
 export async function update() {
+  // Block updates for third-party providers. The update mechanism downloads
+  // from Anthropic's distribution bucket, which would silently replace the
+  // OpenClaude build (with the OpenAI shim) with the upstream Claude Code
+  // binary (without it).
+  if (getAPIProvider() !== 'firstParty') {
+    writeToStdout(
+      chalk.yellow('Auto-update is not available for third-party provider builds.\n') +
+      'To update, pull the latest source from the repository and rebuild:\n' +
+      '  git pull && bun install && bun run build\n',
+    )
+    return
+  }
+
   logEvent('tengu_update_check', {})
   writeToStdout(`Current version: ${MACRO.VERSION}\n`)
 
diff --git a/src/services/api/codexShim.ts b/src/services/api/codexShim.ts
index 26ae237e..e01facd5 100644
--- a/src/services/api/codexShim.ts
+++ b/src/services/api/codexShim.ts
@@ -264,7 +264,8 @@ export function convertAnthropicMessagesToResponsesInput(
 
     if (role === 'assistant') {
       const textBlocks = Array.isArray(content)
-        ? content.filter((block: { type?: string }) => block.type !== 'tool_use')
+        ? content.filter((block: { type?: string }) =>
+            block.type !== 'tool_use' && block.type !== 'thinking')
         : content
       const parts = convertContentBlocksToResponsesParts(textBlocks, 'assistant')
       if (parts.length > 0) {