Source Intelligence

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

All of v2.1.66 Home All releases olderv2.1.64 v2.1.67newer
Claude Code v2.1.66

Enhanced Microcompaction with Boundary Messages

The automatic context microcompaction system now produces visible boundary messages when it operates. When tool results are cleared to save context space, a "Context microcompacted" system message is inserted with metadata including token counts saved, number of tool results compacted, and images cleared. Old tool results are replaced with "[Old tool result content cleared]" markers that point to saved files on disk.

Evidence

Microcompaction boundaries (search for "Context microcompacted" and "[Old tool result content cleared]")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.66 →