[BUG] Project slug encoding replaces all non-alphanumeric characters with "-", causing guaranteed path collisions

Preflight Checklist

• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code
• [x] I have searched existing issues and this hasn't been reported yet

What's Wrong?

Claude Code replaces all non-alphanumeric characters (including _ - .
and all non-ASCII characters) with a single - when generating the project
slug, causing different directory names to resolve to the same slug.

The function OVK / oU8 applies this regex:

``js
path.replace(/[^a-zA-Z0-9]/g, "-")
``

If a character is in a-z A-Z 0-9 → keep it. Otherwise → replace with -.

### Collision case 1: ASCII separators

``
E:\MatLab_HomeWork → E--MatLab-HomeWork
E:\MatLab-HomeWork → E--MatLab-HomeWork ← same slug
E:\MatLab.HomeWork → E--MatLab-HomeWork ← same slug
``

_ - . are all outside [a-zA-Z0-9], so they all become - and are
indistinguishable from each other.

### Collision case 2: non-ASCII characters

``
D:\桌面\资料\matlab综合 → D--------matlab--
D:\其他\目录\matlab内容 → D--------matlab-- ← same slug
``

Each Chinese character becomes exactly one -, retaining no identity.
Two paths with the same number of non-ASCII characters in the same
positions will always collide.

## Steps to reproduce

1. Create two directories, e.g. E:\test_v1 and E:\test-v1
2. Open Claude Code in each directory
3. Observe they share the same project slug, causing session history and

memory to leak across directories

## Expected behavior

_, -, and . should produce distinct slugs. Non-ASCII characters
should be encoded in a way that preserves distinguishable information.

## Environment

• OS: Windows 11
• Claude Code version: 2.1.153

## Additional context

Same root cause as issue #40946.

What Should Happen?

Different directory paths should produce different project slugs. Specifically:

• _, -, and . in path names should remain distinct in the slug rather

than all collapsing to the same character

• Non-ASCII characters should be encoded in a lossless way (e.g., URL-style

percent encoding or base36 encoding of codepoints), so that two paths
containing different non-ASCII characters do not accidentally collide

Error Messages/Logs

Steps to Reproduce

1.Open a terminal and create two directories with names differing only
by _ vs -:

mkdir E:\tsa_demo
mkdir E:\tsa-demo

1. Navigate to the first directory and start Claude Code:

cd E:\tsa_demo
claude

1. Type a message (e.g. "hello"), then exit Claude Code.

1. Navigate to the second directory and start Claude Code with --continue:

cd E:\tsa-demo
claude -c

1. Observe that claude -c resumes the conversation from step 3 — it

treats both directories as the same project.

1. Optionally, verify the slug collision by checking the project storage:

ls ~/.claude/projects/
# Both directories map to the single slug: E--tsa-demo

Claude Model

Other

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Code version: 2.1.153

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_