[Bug] Anthropic API: Degraded token efficiency and model quality regression in Opus 4.7/4.6

Bug Description
I'm on a Max plan using Claude Code daily for a multi-repo project (6 repos, Swift + Next.js + Supabase). A few observations over the past couple weeks: - Token burn rate feels ~10x higher than it was. Tasks that used to fit comfortably in a session now exhaust my allowance partway through. I've gone from shipping 3-5 features/session to 1-2 per week. - Model quality has regressed on Opus 4.7. Even with extended thinking enabled, the model goes in circles on diagnostic tasks — reading the same files repeatedly, speculating instead of checking evidence first (e.g., not looking at a screenshot that was right there). I find myself pushing back constantly on conclusions I can't trust. - Opus 4.6 also feels degraded. Switching to 4.6 to conserve tokens doesn't help — it's noticeably less capable than it was a few months ago. - Session-level rate limits hit too early. Even when I have daily allowance remaining, I get throttled mid-task, which breaks flow on multi-step work. What changed? I'm not sure if I landed in a test group, if the token accounting changed, or if the models were updated, but the practical result is that Claude Code has gone from my primary development tool to something I can barely use for substantive work. The agent/subagent architecture is excellent — the economics just don't work anymore. Environment: macOS, Claude Code CLI, Max plan, primarily Opus 4.7 with fallback to 4.6

Environment Info

• Platform: darwin
• Terminal: Apple_Terminal
• Version: 2.1.126
• Feedback ID: 6caa4155-999c-4d0a-bb2c-589778c9e74e

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/sterlinglcannon/.local/share/claude/versions/2.1.126 (expected in multi-process scenarios)\n    at r86 (/$bunfs/root/src/entrypoints/cli.js:2768:2177)\n    at HD8 (/$bunfs/root/src/entrypoints/cli.js:2768:1257)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-03T23:55:22.625Z"},{"error":"Error: File does not exist. Note: your current working directory is /Users/sterlinglcannon/Desktop/Mahjic.\n    at call (/$bunfs/root/src/entrypoints/cli.js:4866:11399)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-03T23:59:30.636Z"},{"error":"Error: File does not exist. Note: your current working directory is /Users/sterlinglcannon/Desktop/Mahjic.\n    at call (/$bunfs/root/src/entrypoints/cli.js:4866:11399)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-03T23:59:35.850Z"},{"error":"Error: File does not exist. Note: your current working directory is /Users/sterlinglcannon/Desktop/Mahjic.\n    at call (/$bunfs/root/src/entrypoints/cli.js:4866:11399)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-03T23:59:37.785Z"}]