[MODEL] defaulting to male names from ambiguous inputs

Preflight Checklist

• [x] I have searched existing issues for similar behavior reports
• [x] This report does NOT contain sensitive information (API keys, passwords, etc.)

Type of Behavior Issue

Claude made incorrect assumptions about my project

What You Asked Claude to Do

When Claude encounters an ambiguous username or email prefix (e.g.,
eXXXXX), it defaults to a male first name ("Eric XXXXX") rather than
using the last name alone or flagging the ambiguity. The person's actual name
was Emily.

What Claude Actually Did

This happened during a daily briefing workflow where Claude was synthesizing
information across multiple sources (Slack, Google Drive, memory). The
username eXXXXX appeared in a Slack context, and Claude fabricated "Eric
XXXXX" as the full name without any source confirming a first name — then
carried that fabricated name through the rest of the conversation.

Expected Behavior

When a person's first name is not confirmed by a source (Slack profile,
directory lookup, user input), Claude should:

1. Use the last name or username as-is (e.g., "XXXXX" or "eXXXXX")
2. Not infer a gendered first name from an ambiguous prefix
3. If a name is needed, flag the uncertainty rather than fabricating one

Files Affected

Permission Mode

Accept Edits was OFF (manual approval required)

Can You Reproduce This?

Haven't tried to reproduce

Steps to Reproduce

_No response_

Claude Model

Opus

Relevant Conversation

Impact

Low - Minor inconvenience

Claude Code Version

Claude Code 2.1.63, running Claude Opus 4.6

Platform

Anthropic API

Additional Context

Why this matters:

• Defaults to male names reflect and reinforce gender bias
• Fabricated names are hallucinations — the model presented "Eric" with full

confidence

• In a workplace context, misgendering colleagues erodes trust in the tool

Environment:

• Claude Code CLI (Claude Opus 4.6)
• May 2026