WebSearch and WebFetch tools fail with invalid model reference (claude-sonnet-4-20250514)

Description

WebSearch and WebFetch tools consistently fail with the following error:

There's an issue with the selected model (anthropic/claude-sonnet-4-20250514). It may not exist or you may not have access to it. Run /model to pick a different model.

Environment

• Claude Code version: 2.1.92 (latest)
• Model: Opus 4.6 (1M context) — set via /model
• Platform: macOS (Darwin 25.3.0)

Steps to Reproduce

1. Start a Claude Code session
2. Set model to Opus 4.6 via /model
3. Use WebSearch or WebFetch tool (e.g., search for anything)
4. Both tools return the same error referencing anthropic/claude-sonnet-4-20250514

Expected Behavior

WebSearch and WebFetch should work regardless of the primary model selected. The internal model used for processing web content should reference a valid, available model.

Actual Behavior

Both tools fail every time. The error suggests they internally try to use anthropic/claude-sonnet-4-20250514, which does not exist or is not accessible.

Workaround

Using curl via Bash tool works as a workaround for fetching web content.

Notes

• Changing the model via /model does not help — the error always references the same Sonnet model ID
• This affects all web search/fetch operations in the session
• No plugin or settings configuration references this model — it appears to be hardcoded internally