[Bug] API Error:500 + strange Planning Behavior

Bug Description
I had to edit this in GitHub because feedback was failing after 3 letters... I was creating a complicated plan to patch a Knowledge pipeline flow with many agent prompts and process docs needing to be edited. We were doing this in planning mode to make sure the whole problem was scoped before starting and every time I would give a very detailed reply to the plan and ask for changes the same original plan would be spit back out to me. I explained this but Claude was unaware of an existing bug that the web version of Claude pointed out to me later where the old plan gets stuck and returned repeatedly. After a number of long thinking sessions with the same result I realized it was updating a plan track and was able to work with Claude to fix all the bad fixes from me telling it the plan was wrong and it thinking it misunderstood me vs showed me the wrong file. We were able to get it started. This took a lot of Resources though and I have now use 4% of my Max plan which just reset late last night... Anyway if that can be looked at to give me a bit of a credit back I would appreciate it. I am still getting the API Error 500 on trying to make the changes and sub agents do not seem to be working at all. But from what I can tell this is a bigger issue you are dealing with based on all the Issues logged around mine. Please let me know if I can give you more feedback. I'm not sure this issue track captures the whole problem as I did restart Claude a few times and didn't resume them all in my troubleshooting efforts...
Environment Info

• Platform: darwin
• Terminal: Apple_Terminal
• Version: 2.1.31
• Feedback ID: a7561ca3-d2af-4a54-a9f7-e3e8b80ec6a0

Errors

[{"error":"Error: 500 {\"type\":\"error\",\"error\":{\"type\":\"api_error\",\"message\":\"Internal server error\"},\"request_id\":\"req_011CXoMpsWzVq6jo9wipfUdx\"}\n    at g4.generate (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:405:8907)\n    at _C.makeStatusError (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:422:2195)\n    at _C.makeRequest (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:422:5420)\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)","timestamp":"2026-02-04T16:40:11.382Z"},{"error":"SyntaxError: Unexpected token 'A', \"API Error:\"... is not valid JSON\n    at JSON.parse (<anonymous>)\n    at file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:67:810\n    at K (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:8:6811)\n    at qT7 (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:822:93043)\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)","timestamp":"2026-02-04T16:40:11.383Z"},{"error":"Error: 500 {\"type\":\"error\",\"error\":{\"type\":\"api_error\",\"message\":\"Internal server error\"},\"request_id\":\"req_011CXoMtxVkChQsEM1bV6v73\"}\n    at g4.generate (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:405:8907)\n    at _C.makeStatusError (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:422:2195)\n    at _C.makeRequest (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:422:5420)\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)","timestamp":"2026-02-04T16:41:08.528Z"},{"error":"Error: 500 {\"type\":\"error\",\"error\":{\"type\":\"api_error\",\"message\":\"Internal server error\"},\"request_id\":\"req_011CXoNAPfkB3SSjokbzFgvf\"}\n    at g4.generate (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:405:8907)\n    at _C.makeStatusError (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:422:2195)\n    at _C.makeRequest (file:///Users/greglang/.nvm/versions/node/v24.13.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:422:5420)\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)","timestamp":"2026-02-04T16:44:35.222Z"}]