claude-opus-4-5-migration

# Opus 4.5 Migration Guide

One-shot migration from Sonnet 4.0, Sonnet 4.5, or Opus 4.1 to Opus 4.5.

## Migration Workflow

1. Search codebase for model strings and API calls
2. Update model strings to Opus 4.5 (see platform-specific strings below)
3. Remove unsupported beta headers
4. Add effort parameter set to `"high"` (see `references/effort.md`)
5. Summarize all changes made
6. Tell the user: "If you encounter any issues with Opus 4.5, let me know and I can help adjust your prompts."

## Model String Updates

Identify which platform the codebase uses, then replace model strings accordingly.

### Unsupported Beta Headers

Remove the `context-1m-2025-08-07` beta header if present—it is not yet supported with Opus 4.5. Leave a comment noting this:

```python
# Note: 1M context beta (context-1m-2025-08-07) not yet supported with Opus 4.5
```

### Target Model Strings (Opus 4.5)

| Platform | Opus 4.5 Model String |
|----------|----------------------|
| Anthropic API (1P) | `claude-opus-4-5-20251101` |
| AWS Bedrock | `anthropic.claude-opus-4-5-20251101-v1:0` |
| Google Vertex AI | `claude-opus-4-5@20251101` |
| Azure AI Foundry | `claude-opus-4-5-20251101` |

### Source Model Strings to Replace

| Source Model | Anthropic API (1P) | AWS Bedrock | Google Vertex AI |
|--------------|-------------------|-------------|------------------|
| Sonnet 4.0 | `claude-sonnet-4-20250514` | `anthropic.claude-sonnet-4-20250514-v1:0` | `claude-sonnet-4@20250514` |
| Sonnet 4.5 | `claude-sonnet-4-5-20250929` | `anthropic.claude-sonnet-4-5-20250929-v1:0` | `claude-sonnet-4-5@20250929` |
| Opus 4.1 | `claude-opus-4-1-20250422` | `anthropic.claude-opus-4-1-20250422-v1:0` | `claude-opus-4-1@20250422` |

**Do NOT migrate**: Any Haiku models (e.g., `claude-haiku-4-5-20251001`).

## Prompt Adjustments

Opus 4.5 has known behavioral differences from previous models. **Only apply these fixes if the user explicitly requests them or reports a specific issue.** By default, just update model s