[BUG] Buddy Species (Companion) inconsistent between sessions with same userId

Preflight Checklist

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

What's Wrong?

Summary

Buddy (Companion) species changes between different sessions despite having the same userId, contradicting the documented "deterministic generation" behavior.

### Environment

• Claude Code version: 2.1.91
• Platform: macOS (Darwin 24.6.0)
• UserId: 316e1a34235bed116f602ce642f1544453ed96a59f5180752c1721f162e82090

### Problem
According to source code analysis, the Buddy system uses Mulberry32 PRNG with userId hash as seed for deterministic pet generation. However, the same userId
produces different species across sessions:

| Timestamp (UTC) | Species | Session ID |
|------------------------|----------|----------------------------------------|
| 2026-04-03T03:34:17 | mushroom | 19165375-f14e-4346-a4d9-cbbe60e81a24 |
| 2026-04-03T06:20:05 | mushroom | be9dc702-f7d3-4801-afa6-027f9040b816 |
| 2026-04-03T07:15:41 | ghost | 8e8e9b97-d935-4196-a4b4-dd0e0ee44204 ← Changed!
| 2026-04-03T07:36:48 | ghost | c57504ff-4eaf-457f-b7b9-350a222f752d |
| 2026-04-03T08:13:22 | ghost | b5b17b2a-5588-418b-b4e2-e9520b84b676 |

### Local Config (.claude.json)
```json
{
"companion": {
"name": "Moth",
"personality": "A common mushroom of few words.",
"hatchedAt": 1775185329846
}
}
The config only stores name, personality, hatchedAt - does NOT store species or attribute values.

Attempted Solutions

1. Modified personality field → No effect
2. Reset hatchedAt timestamp → No effect
3. Restarted Claude Code → No effect

Expected Behavior

• Same userId should always generate the same species
• OR species should be persisted in local config

Actual Behavior

• Species varies between sessions
• Local config cannot control species

Possible Causes

1. Incomplete Beta feature: Source comments mention "planned May 2026 launch", current behavior might be an unfinished evolution mechanism
2. Seed includes sessionId: If hash seed includes sessionId, each session would generate different species
3. Bug: Deterministic generation logic has a flaw

Suggested Fix

1. If species should be fixed: persist species to .claude.json companion object
2. If species should evolve: display evolution logic and data in UI

---

另外，我已确认配置已正确恢复：
```json
"companion": {
"name": "Moth",
"personality": "A common mushroom of few words.",
"hatchedAt": 1775185329846
}

What Should Happen?

Summary

Buddy (Companion) species changes between different sessions despite having the same userId, contradicting the documented "deterministic generation" behavior.

### Environment

• Claude Code version: 2.1.91
• Platform: macOS (Darwin 24.6.0)
• UserId: 316e1a34235bed116f602ce642f1544453ed96a59f5180752c1721f162e82090

### Problem
According to source code analysis, the Buddy system uses Mulberry32 PRNG with userId hash as seed for deterministic pet generation. However, the same userId
produces different species across sessions:

| Timestamp (UTC) | Species | Session ID |
|------------------------|----------|----------------------------------------|
| 2026-04-03T03:34:17 | mushroom | 19165375-f14e-4346-a4d9-cbbe60e81a24 |
| 2026-04-03T06:20:05 | mushroom | be9dc702-f7d3-4801-afa6-027f9040b816 |
| 2026-04-03T07:15:41 | ghost | 8e8e9b97-d935-4196-a4b4-dd0e0ee44204 ← Changed!
| 2026-04-03T07:36:48 | ghost | c57504ff-4eaf-457f-b7b9-350a222f752d |
| 2026-04-03T08:13:22 | ghost | b5b17b2a-5588-418b-b4e2-e9520b84b676 |

### Local Config (.claude.json)
```json
{
"companion": {
"name": "Moth",
"personality": "A common mushroom of few words.",
"hatchedAt": 1775185329846
}
}
The config only stores name, personality, hatchedAt - does NOT store species or attribute values.

Attempted Solutions

1. Modified personality field → No effect
2. Reset hatchedAt timestamp → No effect
3. Restarted Claude Code → No effect

Expected Behavior

• Same userId should always generate the same species
• OR species should be persisted in local config

Actual Behavior

• Species varies between sessions
• Local config cannot control species

Possible Causes

1. Incomplete Beta feature: Source comments mention "planned May 2026 launch", current behavior might be an unfinished evolution mechanism
2. Seed includes sessionId: If hash seed includes sessionId, each session would generate different species
3. Bug: Deterministic generation logic has a flaw

Suggested Fix

1. If species should be fixed: persist species to .claude.json companion object
2. If species should evolve: display evolution logic and data in UI

---

另外，我已确认配置已正确恢复：
```json
"companion": {
"name": "Moth",
"personality": "A common mushroom of few words.",
"hatchedAt": 1775185329846
}

Error Messages/Logs

Steps to Reproduce

Bug: Buddy species changes between sessions (mushroom ↔ ghost) despite same userId.

Fix needed: Persist species in .claude.json companion config, or fix deterministic generation.

Version: Claude Code 2.1.91 (macOS)

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

v2.1.91

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

_No response_