Claude Code’s to-do tool may burn usage on long sessions
Claude Code may use up a large part of a 5-hour usage window when TodoWrite keeps updating a task list inside a long conversation. TodoWrite adds a to-do reminder block near the start of the chat.
Each time Claude marks a task done, adds a task, or changes a task’s status, that whole block is written again. Because the block sits inside the , even a small list change can change the and invalidate the after the .
The next message may then write the whole conversation context back into cache, often around 800,000 to 900,000 tokens in a long session. The evidence claimed in the item points to 16.7 million tokens caused by repeated full-context rewrites during task updates.
Key points
- TodoWrite is blamed as a possible cause of sudden Claude Code usage spikes.
- Task-list changes can rewrite a reminder block near the start of the conversation.
- That rewrite may invalidate the and force the to be cached again.
- may rewrite around 800,000 to 900,000 tokens after one task update.
- The item claims 16.7 million tokens of evidence from repeated full-context rewrites.