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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Bug Report: Claude Models Fail in Copilot for Xcode (HTTP 400 – Invalid Request Body)","articleBody":"\u003c!-- Please search existing issues to avoid creating duplicates --\u003e\n\n**Describe the bug**\nClaude models consistently fail in GitHub Copilot for Xcode with an HTTP 400 Bad Request error. The error indicates an invalid_request_body caused by a malformed or empty thinking block in the request payload.\nAs a result, Claude models are effectively unusable in Agent mode and auto-edit workflows in Xcode.\n\nThis does not occur with non-Claude models.\n**Versions**\nCopilot for Xcode: Latest available version (at time of report)\nXcode: 26.2 (reproducible across recent versions)\nmacOS: 15.7.4+ (Sequoia)\n\nCopilot Pro subscription is active and confirmed via github education plan.\n**Steps to reproduce**\n1. Open Xcode\n2. Enable GitHub Copilot for Xcode\n3. Select a Claude model (Sonnet 4.5 or Opus 4.5)\n4. Enable Agent mode (or attempt auto-edit / multi-step tasks)\n5. Ask Copilot to perform a file edit or multi-step task\n6. Observe failure during or immediately after generation\n\n**Screenshots**\n\u003cimg width=\"375\" height=\"140\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/ffc3977a-8ae1-41f4-b52e-f5fc42ebc593\" /\u003e\n\u003cimg width=\"357\" height=\"391\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/648cf1fd-1d9b-42ca-85b6-606000f0ed35\" /\u003e\n\u003cimg width=\"367\" height=\"528\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/d66700b6-6895-46aa-8869-ff4bc40a431f\" /\u003e\n\u003cimg width=\"364\" height=\"293\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/5f6647a8-6c66-4ab3-95a0-6d709b008d4e\" /\u003e\n\n\n\n\n**Logs**\n\n\n[github-copilot-for-xcode.log](https://github.com/user-attachments/files/24693473/github-copilot-for-xcode.log)\n\n\n\n**Additional context**\nIssue only occurs with Claude models\n\nOther Copilot-supported models work correctly in Agent mode\n\nReproduced after:\n\nFull uninstall \u0026 reinstall of Copilot for Xcode\n\nClearing Copilot, Claude, and Xcode extension caches\n\nRebooting macOS\n\nRe-authenticating GitHub\n\nStrongly suggests a Copilot ↔ Claude integration issue, where Copilot sends malformed or empty thinking blocks that Claude strictly rejects\n\nThis appears to be a backend schema compatibility issue, not a local configuration problem\n\nImpact: Claude models cannot be used for Agent workflows in Xcode, forcing manual copy-paste usage and degrading developer productivity.\n","author":{"url":"https://github.com/abbinavv","@type":"Person","name":"abbinavv"},"datePublished":"2026-01-18T04:06:35.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/714/CopilotForXcode/issues/714"}