System prompt and status bar report wrong model name when using claude-opus-4-6

Summary

When claude-opus-4-6 (Opus 4.6) is set as the model — either via settings.json or the /model custom model option — two things report the wrong model name:

1. System prompt tells Claude: "You are powered by the model named Opus 4" — should say Opus 4.6
2. Status bar displays: "Currently using Opus 4. Opus 4.5 is our best model for coding · /model to upgrade" — doesn't recognize claude-opus-4-6 as a current model

Impact

This caused Claude to confidently confabulate the wrong model name to the user. When asked "what model are you?", Claude read the system prompt, saw "Opus 4", and told the user they were on "Opus 4, revision 6" — not Opus 4.6. Claude even constructed a fabricated naming-convention breakdown table and stated "There is no Opus 4.6 model."

The user had to manually direct Claude to check the official docs before the error was corrected.

In a follow-up session with updated guardrail instructions (including a concrete negative example of this exact failure), Claude repeated the same mistake — because the system prompt still injects "Opus 4" as authoritative ground truth, overriding any user-level instructions.

Reproduction

1. Set "model": "claude-opus-4-6" in ~/.claude/settings.json
2. Start a new Claude Code session
3. Observe the status bar in the bottom right — it says "Currently using Opus 4" and suggests upgrading to Opus 4.5
4. Ask Claude: "What model are you running on?"
5. Claude will say "Opus 4" (from the system prompt), not "Opus 4.6"

Expected Behavior

• System prompt should say "You are powered by the model named Opus 4.6" when the model ID is claude-opus-4-6
• Status bar should recognize claude-opus-4-6 as Opus 4.6 and not suggest a downgrade to Opus 4.5
• Alternatively, the status bar could show "Currently using Opus 4.6" with no upgrade nudge (since the user is already on the default opus model)

Environment

• Claude Code on WSL2 (Ubuntu), latest version
• Model set via settings.json: "model": "claude-opus-4-6"
• Official docs confirm opus alias resolves to Opus 4.6: https://code.claude.com/docs/en/model-config