[FEATURE] /effort should be per-session, not global — breaks parallel workflows

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

Running /effort high in one Claude Code session persists the setting to
~/.claude/settings.json, which immediately affects all other running
sessions. In parallel workflows (multiple claude instances), changing effort
in one session silently changes it in all others.

Expected behavior

/effort should change the effort level for the current session only, without
writing to the shared settings file. Other parallel sessions should be
unaffected.

Current workarounds

• --effort flag at launch (session-scoped, but can't change mid-session)
• CLAUDE_CODE_EFFORT_LEVEL env var (per-shell, but can't change mid-session)

Neither allows adjusting effort multiple times during a running session
without affecting other sessions.

Proposed Solution

Suggested solution

Make /effort session-scoped by default. Add /effort --persist (or similar)
for users who explicitly want to update the global default.

Alternative Solutions

_No response_

Priority

Critical - Blocking my work

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

_No response_