fusion/.changeset/fn-4389-token-usage-semantics.md

@runfusion/fusion

@runfusion/fusion
patch

Canonicalize task token usage semantics across heartbeat and executor paths by treating cachedTokens as cache-read only, storing cache writes in new cacheWriteTokens, and preserving raw inputTokens.

Dashboard token stats now render separate Cache read and Cache write values.

Historical rows created before this fix may still contain mixed cache-read+cache-write values inside cachedTokens; existing data is not backfilled.