[FEATURE] Auto-assign sessions to groups based on working directory

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Problem
I work on multiple projects in parallel and use Claude Code's session groups to keep them organized in the sidebar. Today, the only automatic grouping is by fork lineage (/branch / --fork-session). Every fresh session I start in a project folder lands ungrouped, and I have to drag it into the right group manually.

With 3+ active projects, this becomes constant overhead — and easy to forget, which defeats the point of groups.

Why this matters
Session groups only deliver value if they reflect how I think about my work (per-project), and that mapping is stable and obvious — it's the folder I'm cd'd into. Manual assignment is the worst of both worlds: the data the system needs is already present, but it asks me to re-enter it every session.

Environment
Claude Code CLI on macOS (Darwin 25.3.0)
Model: Opus 4.7

Proposed Solution

Proposed solution
Let users map a working directory (cwd) to a group name in settings.json. When a session starts in (or under) that directory, it's automatically assigned to that group.

{
"sessionGroups": {
"/Users/berk/Desktop/paff": "paff",
"/Users/berk/code/acme-web": "acme",
"~/work/side-projects": "side"
}
}
Match should be longest-prefix wins, and ~ should expand.

Alternative (or complement)
Expose group assignment to the SessionStart hook so users can script arbitrary logic (e.g. derive group from git remote, branch name, or a .claude/group file):

{
"hooks": {
"SessionStart": [{
"hooks": [{ "type": "command", "command": "echo paff" }],
"output": "sessionGroup"
}]
}
}
The hook's stdout becomes the group name.

Alternative Solutions

_No response_

Priority

Critical - Blocking my work

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

_No response_