session.start
A Claude Code settings key, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.
Two hook events arrive: session.start fires on terminal session start, and prompt.context is registered but has no emitter here.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.259.
In the changelogs
9Releases whose published page names session.start.
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v2.1.318
Some mod calls are refused in a
classic.SessionStarthook on pre-started sessionsIf a host started the session early, some mod calls made from a
classic.SessionStarthook are now refused instead of hangingfound in this entry's text, named in this entry
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v2.1.292
Plugin hooks are kept from setting themselves off again
The hooks module now skips a hook that would run again inside its own plugin, and limits hooks that asked to catch errors to answering
found in this entry's text
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v2.1.281
Hooks-module session.start and session.end lifecycle tweaks
Hook session.start now skips if it is no longer wanted after modules load, and session.end waits for its fallback under the timeout
found in this entry's text
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v2.1.271
Turn-scoped tracking for plugin-originated prompt submissions
Prompts submitted by plugins are now tracked against the current conversation turn
found in this entry's text
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v2.1.265
Hook registry gains command.describe as a core hook event
Claude Code adds a new internal hook event called command.describe
found in this entry's text
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v2.1.260
Late-loaded plugins now get session.start events replayed
Plugins loaded late now correctly receive the session-start event they previously missed.
found in this entry's text, named in this entry
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v2.1.260
New plugin-authoring skill for function-hooks plugins
A new bundled skill teaches how to write function-hook plugins.
found in this entry's text
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v2.1.259
New plugin/hook events 'prompt.context' and 'session.start'
Two hook events arrive: session.start fires on terminal session start, and prompt.context is registered but has no emitter here.
found in this entry's text, named in this entry
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v2.1.259
prompt.context dispatch hook point
Computed prompt context blocks are forwarded through a registered prompt.context handler when one exists, alongside a session-bound extension point.
found in this entry's text, named in this entry
First cited
7The earliest release whose published evidence quoted session.start was v2.1.259, 2 Sep 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
1 further span in the ledger name it. The list above is the earliest first and stops at 6.
Presence across releases
0The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the settings key does. All settings keys.