Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
SessionsArea: what it touches
Internal ChangesKind: in v2.1.265,
Internal ChangesSection of the release
Unclear What the reserved ID prefix specifically identifies is not shown by the evidence.
What
When Claude Code resumes a session and figures out which prior tool calls can be reconstructed, a tool call whose ID starts with a specific reserved prefix is now immediately classified as "underivable_excluded", before the normal checks for whether it was superseded or mismatched even run.
Why
This ensures tool calls carrying that reserved ID prefix are never mistakenly reconstructed during resume, treating them as excluded from the start rather than relying on the standard classification logic to catch them.
Read from
Names in the bundleunderivable_excluded
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtWhat the reserved ID prefix specifically identifies is not shown by the evidence.
