Summing Claude Code JSONL per line double-counts token usage
10/19/2026 — 10/19, 19:19·1 sources (all)·1 reports (all)
Key takeaways
- Claude Code stores each session as JSONL, and a single API response can span multiple lines that each carry a full usage object, so summing…
Background & analysis
On October 19, 2026, a DEV Community post reported that summing Claude Code usage line by line roughly doubles the token count. According to the article, Claude Code stores each session as JSONL, and a single API response may be written across multiple lines, with every line carrying the full usage object for that response. Adding up the lines therefore counts the same tokens more than once. The author cites a session from August 2026 in issue #87303: summing cache_creation_input_tokens line by line gives 1,075,420, while deduplicating by message.id gives 560,751, an overcount of about 1.92x. The post notes that Anthropic closed the issue as "documented behavior." That is where the matter currently stands, and the source material contains no further developments.
AI-generated from 1 reports · updated 4 hours ago
Latest turnClaude Code stores each session as JSONL, and one API response can span several lines that each carry the full usage object, so summing lines counts the same tokens again. In an August 2026 session cited from issue #87303, cache_creation_input_tokens summed to 1,075,420 versus 560,751 after deduplicating by message.id. Anthropic closed the issue as documented behaviour.
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Claude Code stores each session as JSONL, and one API response can span several lines that each carry the full usage object, so summing lines counts the same tokens again. In an August 2026 session cited from issue #87303, cache_creation_input_tokens summed to 1,075,420 versus 560,751 after deduplicating by message.id. Anthropic closed the issue as documented behaviour.
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