Claude Code 2.1.258

• [changed] Subagent instructions now state that agents run in the background by default, and reserve run_in_background: false for when the very next step truly depends on the result and nothing else can usefully proceed — otherwise background so you can interject. Still never fabricates or predicts a pending agent’s results; if you ask early, it reports that the agent is still running.
• [changed] Permission-denied tool-use messaging is tightened so a rejected action (for example a file edit whose new_string was not written) is spelled out clearly, with paths for trying another approach or incorporating the user’s denial feedback.

Models & prompts

• Built-in subagent guidance emphasizes background-by-default and when not to block the turn on a synchronous result, including existing limits (run_in_background / name unavailable for sync-only contexts; teammates cannot spawn teammates; isolation: "remote" is always background in a remote CCR sandbox).

Under the hood

• Instrumentation for orphaned permissions that were never applied by turn end, to improve how unapplied permission state is handled at turn boundaries.
• SDK compatibility matrix no longer lists wrapper 0.3.216 among tested versions (still covers newer 0.3.x wrappers).