What
SessionStart hooks now receive the messages carried over from a resumed session, not just the bare start event, so a hook can inspect prior conversation content.
Details
- The messages are passed in as
resumedMessagesand transformed before hooks run. - No flag controls this; the field is present whenever the resume supplies messages.
Evidence
resumedMessages: v
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Names in the bundleSessionStart
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Added since
A small documentation edit on Hooks reference touched a line naming SessionStart after this was published.
The same wait applies at launch, including a resumed session: a prompt you send while SessionStart hooks are still running doesn't reach Claude until they finish.hooks see the edit
Confirmed since
Anthropic's documentation has since written up SessionStart, on Claude Code changelog.
* Improved `--continue` / `--resume`: the conversation appears immediately instead of waiting for SessionStart hooks, and the first message no longer re-reads the whole transcriptchangelog see the edit
Two sources agreeTwo things we can check say the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up SessionStart, on Claude Code changelog.
Anthropic's release notes agree
Added PreModelSwitch and PostModelSwitch hook events (block, confirm, or annotate a model switch); SessionStart resume hooks now receive…