What
A tool call is a single action Claude takes, such as reading a file or running a command. When a turn, one round of Claude responding, ends on an error, pending tool calls are cancelled with one of two new messages:
- "The turn ended on an error, so this tool call was cancelled..." followed by the error.
- "An image in this turn could not be sent to the API, so this tool call was cancelled. If it had already started, some of its effects may have happened."
Why
A cancelled action now says why it was cancelled and warns that it may already have partly run, so it is worth checking whether it changed anything.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
The finding does not say whether these messages are shown to the user or only passed to the model.