Unclear It is not clear whether the line was dropped outright or moved elsewhere in the prompt, so whether the model still gets this instruction is unsettled.
The system prompt is the set of instructions Claude Code gives the model before your conversation starts. One part of it, about how the model should write its output, has several options.
One option, called "short", used to add a single line: "Write code that reads like the surrounding code: match its comment density, naming, and idiom." That option is now called "none" and adds nothing.
The same line shows up as a change in three prompts:
- the main system prompt
- the system prompt used by the Agent SDK
- the prompt used when compacting, which means shortening a long conversation by summarising it
This changes what the model is told about matching the style of the code around it. If edits start to follow the existing comments, naming or habits of a file less closely, this is a likely place to look.
It is not clear whether the line was dropped outright or moved elsewhere in the prompt, so whether the model still gets this instruction is…