Problem

normalize_model_name() in agent/anthropic_adapter.py unconditionally converts dots to hyphens in all model names (line 1117). This causes non-Anthropic models to be mangled when routed through the Anthropic adapter path:

• gpt-5.4 → gpt-5-4 → HTTP 404 from Codex backend
• gemini-2.5-pro → gemini-2-5-pro → would fail similarly

This affects the webui session route when resolve_model_provider() doesn't infer the provider from the model name, and the Anthropic adapter is auto-selected as default.

Fix

Added a guard in normalize_model_name() to only apply dot→hyphen conversion for models that look like Anthropic models (claude-* or anthropic/*). Non-Anthropic models pass through unchanged.

Before:

model = model.replace(".", "-")  # ALL models

After:

_lower = model.lower()
if _lower.startswith("claude-") or _lower.startswith("anthropic/"):
    model = model.replace(".", "-")  # Only Anthropic models

Before vs After

Tests

All existing tests pass — they all use Claude model names which still get dot→hyphen conversion.

Fixes #17171
Related: #7421, #13061, #16417