Profile resolution

Markers are discovered by walking up from $PWD through the project tree — the nearest match wins. On each ancestor directory, .claude/claude-shim.json (per-project) is checked first and takes priority over .claude-shim.json (workspace-wide) at the same level. The walk stops before $HOME, so a marker placed directly in $HOME is not picked up as a global default.

When no project marker is found, the shim resolves the profile in this order:

1. <config dir>/claude-shim/default-profile — a text file containing one profile name. Recommended way to set a global default. The config dir is platform-specific: ~/Library/Application Support/claude-shim/ on macOS, ${XDG_CONFIG_HOME:-~/.config}/claude-shim/ on Linux.
2. ~/.claude/ itself — used as the profile if it exists, for installs that pre-date claude-shim.
3. Otherwise the shim refuses to run rather than silently fall back to an arbitrary profile.

Migrating an existing ~/.claude setup to a named profile is covered in Migration.