[Bug] Claude repeatedly performs computations outside Rust libraries despite explicit instructions

Bug Description
"Have worked on this app on and off for 6 months, architecture: 2 native mobile apps using RUst libs, so we KNOW critical computations are always identical, have told claude a MILLION times NEVER do computations outside the Rust code, just does it ENDLESSLY.."

Environment Info

• Platform: darwin
• Terminal: Apple_Terminal
• Version: 2.1.123
• Feedback ID: 4ea448a0-38a2-448d-af76-0d734a859232

Errors

[{"error":"Error: Was there a typo in the url or port?\n    at from (/$bunfs/root/src/entrypoints/cli.js:112:7862)\n    at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:120:12898)\n    at emitError (node:events:43:23)\n    at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:119:1149)\n    at emitError (node:events:43:23)\n    at <anonymous> (node:_http_client:253:22)\n    at processTicksAndRejections (native:7:39)\n    at request (/$bunfs/root/src/entrypoints/cli.js:122:2467)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T14:10:11.776Z"},{"error":"Error: Request was aborted.\n    at makeRequest (/$bunfs/root/src/entrypoints/cli.js:50:3448)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T15:18:40.771Z"},{"error":"Error: LSP server 'plugin:rust-analyzer-lsp:rust-analyzer' exceeded max crash recovery attempts (3)\n    at Y (/$bunfs/root/src/entrypoints/cli.js:3201:24719)\n    at z (/$bunfs/root/src/entrypoints/cli.js:3201:30119)\n    at j (/$bunfs/root/src/entrypoints/cli.js:3201:30504)\n    at J (/$bunfs/root/src/entrypoints/cli.js:3201:31063)\n    at call (/$bunfs/root/src/entrypoints/cli.js:4919:1412)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T16:36:34.832Z"},{"error":"Error: Failed to start LSP server for file /Users/robwilliams/workspaces/dminder/rust/dose-ledger/src/lib.rs: LSP server 'plugin:rust-analyzer-lsp:rust-analyzer' exceeded max crash recovery attempts (3)\n    at z (/$bunfs/root/src/entrypoints/cli.js:3201:30145)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T16:36:34.832Z"},{"error":"Error: LSP server 'plugin:rust-analyzer-lsp:rust-analyzer' exceeded max crash recovery attempts (3)\n    at Y (/$bunfs/root/src/entrypoints/cli.js:3201:24719)\n    at z (/$bunfs/root/src/entrypoints/cli.js:3201:30119)\n    at j (/$bunfs/root/src/entrypoints/cli.js:3201:30504)\n    at J (/$bunfs/root/src/entrypoints/cli.js:3201:31063)\n    at call (/$bunfs/root/src/entrypoints/cli.js:4919:1412)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T16:36:34.833Z"},{"error":"Error: LSP server 'plugin:rust-analyzer-lsp:rust-analyzer' exceeded max crash recovery attempts (3)\n    at Y (/$bunfs/root/src/entrypoints/cli.js:3201:24719)\n    at z (/$bunfs/root/src/entrypoints/cli.js:3201:30119)\n    at j (/$bunfs/root/src/entrypoints/cli.js:3201:30504)\n    at J (/$bunfs/root/src/entrypoints/cli.js:3201:31063)\n    at call (/$bunfs/root/src/entrypoints/cli.js:4919:1412)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T16:36:38.988Z"},{"error":"Error: Failed to start LSP server for file /Users/robwilliams/workspaces/dminder/rust/dose-ledger/src/lib.rs: LSP server 'plugin:rust-analyzer-lsp:rust-analyzer' exceeded max crash recovery attempts (3)\n    at z (/$bunfs/root/src/entrypoints/cli.js:3201:30145)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T16:36:38.988Z"},{"error":"Error: LSP server 'plugin:rust-analyzer-lsp:rust-analyzer' exceeded max crash recovery attempts (3)\n    at Y (/$bunfs/root/src/entrypoints/cli.js:3201:24719)\n    at z (/$bunfs/root/src/entrypoints/cli.js:3201:30119)\n    at j (/$bunfs/root/src/entrypoints/cli.js:3201:30504)\n    at J (/$bunfs/root/src/entrypoints/cli.js:3201:31063)\n    at call (/$bunfs/root/src/entrypoints/cli.js:4919:1412)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T16:36:38.988Z"},{"error":"Error: LSP server 'plugin:rust-analyzer-lsp:rust-analyzer' exceeded max crash recovery attempts (3)\n    at Y (/$bunfs/root/src/entrypoints/cli.js:3201:24719)\n    at z (/$bunfs/root/src/entrypoints/cli.js:3201:30119)\n    at j (/$bunfs/root/src/entrypoints/cli.js:3201:30504)\n    at J (/$bunfs/root/src/entrypoints/cli.js:3201:31063)\n    at call (/$bunfs/root/src/entrypoints/cli.js:4919:1412)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T16:36:42.562Z"},{"error":"Error: Failed to start LSP server for file /Users/robwilliams/workspaces/dminder/rust/dose-ledger/src/lib.rs: LSP server 'plugin:rust-analyzer-lsp:rust-analyzer' exceeded max crash recovery attempts (3)\n    at z (/$bunfs/root/src/entrypoints/cli.js:3201:30145)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-07T16:36:42.563Z"},{"error":"Error: LSP server 'plugin:rust-analyzer-lsp:rust-anal…

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