[Bug] CPU regression from WebGPU renderer update on M4 Mac (90%+ usage)

Bug Description
CPU regression from silent renderer update April 13 — M4 Mac Mini
Since a silent internal update pushed April 13 (~5:50–6:30 PM), every Claude response drives my M4 Mac Mini to 90%+ CPU. Claude Helper Renderer hits 60–70%, WindowServer gets dragged to 40%+. This machine runs 3 local LLMs without the CPU moving — this is clearly a regression.
The specific artifacts that rebuilt on April 13: DawnWebGPUCache, Code Cache, and Cache directory inside ~/Library/Application Support/Claude/. The DawnWebGPU change is the likely culprit — something in the new WebGPU rendering path is CPU-bound on M4 instead of using the GPU.
App version: 1.1348.0. Please escalate to the desktop/renderer team.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.92
• Feedback ID: c0a64b5a-2d69-42b1-ae79-48d87356fc19

Errors

[{"error":"Error: Plugin MCP server error - mcp-config-invalid: MCP server github invalid: Missing environment variables: GITHUB_PERSONAL_ACCESS_TOKEN\n    at lAH (/$bunfs/root/src/entrypoints/cli.js:1526:34345)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T16:54:33.524Z"},{"error":"Error: Plugin MCP server error - mcp-config-invalid: MCP server github invalid: Missing environment variables: GITHUB_PERSONAL_ACCESS_TOKEN\n    at lAH (/$bunfs/root/src/entrypoints/cli.js:1526:34345)\n    at async W (/$bunfs/root/src/entrypoints/cli.js:5820:10283)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T16:54:38.096Z"},{"error":"Error: Plugin MCP server error - mcp-config-invalid: MCP server github invalid: Missing environment variables: GITHUB_PERSONAL_ACCESS_TOKEN\n    at lAH (/$bunfs/root/src/entrypoints/cli.js:1526:34345)\n    at async Z (/$bunfs/root/src/entrypoints/cli.js:5820:11053)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T16:54:38.096Z"},{"error":"Error: Failed to clone repository for git-subdir source: Cloning into '/Users/guildcoucil13/.claude/plugins/cache/temp_subdir_1776185678162_s6tv3d.clone'...\ngit@github.com: Permission denied (publickey).\r\nfatal: Could not read from remote repository.\n\nPlease make sure you have the correct access rights\nand the repository exists.\n    at gt1 (/$bunfs/root/src/entrypoints/cli.js:4500:20766)\n    at async s8_ (/$bunfs/root/src/entrypoints/cli.js:4500:22945)\n    at async Qt1 (/$bunfs/root/src/entrypoints/cli.js:4504:9615)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T16:54:38.921Z"},{"error":"Error: Failed to clone repository for git-subdir source: Cloning into '/Users/guildcoucil13/.claude/plugins/cache/temp_subdir_1776185678158_in1jxx.clone'...\ngit@github.com: Permission denied (publickey).\r\nfatal: Could not read from remote repository.\n\nPlease make sure you have the correct access rights\nand the repository exists.\n    at gt1 (/$bunfs/root/src/entrypoints/cli.js:4500:20766)\n    at async s8_ (/$bunfs/root/src/entrypoints/cli.js:4500:22945)\n    at async Qt1 (/$bunfs/root/src/entrypoints/cli.js:4504:9615)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T16:54:38.921Z"},{"error":"Error: Failed to clone repository for git-subdir source: Cloning into '/Users/guildcoucil13/.claude/plugins/cache/temp_subdir_1776185797824_nrcp07.clone'...\ngit@github.com: Permission denied (publickey).\r\nfatal: Could not read from remote repository.\n\nPlease make sure you have the correct access rights\nand the repository exists.\n    at gt1 (/$bunfs/root/src/entrypoints/cli.js:4500:20766)\n    at async s8_ (/$bunfs/root/src/entrypoints/cli.js:4500:22945)\n    at async Qt1 (/$bunfs/root/src/entrypoints/cli.js:4504:9615)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T16:56:38.278Z"},{"error":"Error: Failed to clone repository for git-subdir source: Cloning into '/Users/guildcoucil13/.claude/plugins/cache/temp_subdir_1776185797827_yhbeob.clone'...\ngit@github.com: Permission denied (publickey).\r\nfatal: Could not read from remote repository.\n\nPlease make sure you have the correct access rights\nand the repository exists.\n    at gt1 (/$bunfs/root/src/entrypoints/cli.js:4500:20766)\n    at async s8_ (/$bunfs/root/src/entrypoints/cli.js:4500:22945)\n    at async Qt1 (/$bunfs/root/src/entrypoints/cli.js:4504:9615)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T16:56:38.278Z"},{"error":"Error: Failed to clone repository for git-subdir source: Cloning into '/Users/guildcoucil13/.claude/plugins/cache/temp_subdir_1776186200496_2487wp.clone'...\ngit@github.com: Permission denied (publickey).\r\nfatal: Could not read from remote repository.\n\nPlease make sure you have the correct access rights\nand the repository exists.\n    at gt1 (/$bunfs/root/src/entrypoints/cli.js:4500:20766)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T17:03:20.922Z"},{"error":"Error: Failed to clone repository for git-subdir source: Cloning into '/Users/guildcoucil13…

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