Native project-prefix session titles for cross-project date view

Problem

When working across multiple projects, the desktop sidebar's date-sorted view loses project context. A title like Review monthly costs is ambiguous — which project is it about? Currently the only way to disambiguate is to switch the sidebar into project-grouped mode (which loses chronological context) or manually /rename every session with a prefix.

Use case

Solo operators, consultants, and anyone juggling 5–10 active projects need to scan recent activity across projects in date order. A sidebar entry like [ProjectA] Review monthly costs immediately tells you which project it belongs to without losing the date sort.

Proposed UX

A setting (settings.json or UI) along these lines:

{
  \"sessionTitlePrefix\": {
    \"enabled\": true,
    \"format\": \"[{alias}] {title}\",
    \"aliasMap\": {
      \"/path/to/project-a\": \"ProjectA\",
      \"/path/to/project-b\": \"ProjectB\",
      \"/path/to/personal-blog\": \"Blog\"
    },
    \"fallback\": \"basename\"
  }
}

Behaviour:

• When auto-generating a session title, prefix it with [alias] derived from the cwd.
• Lookup is path-prefix-match against aliasMap; if no match, fall back to basename(cwd) (or skip the prefix if fallback: null).
• Works in both auto-titles and manual /rename-d titles (or only auto, configurable).
• Match nested paths too: /path/to/project-a/.claude/worktrees/foo → [ProjectA].

Why this should be a native feature, not just a hook

Even with the UserPromptSubmit sessionTitle hook (see related issue), users still need to:

1. Write a shell script.
2. Maintain the alias map themselves.
3. Re-implement title generation (LLM call or heuristic).

That's a lot of plumbing for what's fundamentally one product setting. Native support would let everyone with a multi-project workflow benefit without scripting.

Optional v2

A {project} template variable that resolves to the project name from ~/.claude/projects/ rather than cwd basename, and a per-project override in the project's CLAUDE.md.

Related

Companion issue tracking the underlying hook bug that surfaces this need.