Add claude-sonnet-4-5 model support (OpenHands#11179)

Co-authored-by: openhands <[email protected]>

Author: xingyaoww

README.md

@@ -100,7 +100,7 @@ docker run -it --rm --pull=always \
 ### Getting Started
 
 When you open the application, you'll be asked to choose an LLM provider and add an API key.
-[Anthropic's Claude Sonnet 4](https://www.anthropic.com/api) (`anthropic/claude-sonnet-4-20250514`)
+[Anthropic's Claude Sonnet 4.5](https://www.anthropic.com/api) (`anthropic/claude-sonnet-4-5-20250929`)
 works best, but you have [many options](https://docs.all-hands.dev/usage/llms).
 
 See the [Running OpenHands](https://docs.all-hands.dev/usage/installation) guide for

docs/usage/how-to/cli-mode.mdx

@@ -105,7 +105,7 @@ The conversation history will be saved in `~/.openhands/sessions`.
 
 1. Set the following environment variables in your terminal:
    - `SANDBOX_VOLUMES` to specify the directory you want OpenHands to access ([See using SANDBOX_VOLUMES for more info](../runtimes/docker#using-sandbox_volumes))
-   - `LLM_MODEL` - the LLM model to use (e.g. `export LLM_MODEL="anthropic/claude-sonnet-4-20250514"`)
+   - `LLM_MODEL` - the LLM model to use (e.g. `export LLM_MODEL="anthropic/claude-sonnet-4-20250514"` or `export LLM_MODEL="anthropic/claude-sonnet-4-5-20250929"`)
    - `LLM_API_KEY` - your API key (e.g. `export LLM_API_KEY="sk_test_12345"`)
 
 2. Run the following command:

docs/usage/how-to/headless-mode.mdx

@@ -53,7 +53,7 @@ Set environment variables and run the Docker command:
 ```bash
 # Set required environment variables
 export SANDBOX_VOLUMES="/path/to/workspace:/workspace:rw"  # Format: host_path:container_path:mode
-export LLM_MODEL="anthropic/claude-sonnet-4-20250514"
+export LLM_MODEL="anthropic/claude-sonnet-4-20250514"  # or "anthropic/claude-sonnet-4-5-20250929"
 export LLM_API_KEY="your-api-key"
 export SANDBOX_SELECTED_REPO="owner/repo-name"  # Optional: requires GITHUB_TOKEN
 export GITHUB_TOKEN="your-token"  # Required for repository operations

docs/usage/llms/llms.mdx

@@ -18,6 +18,7 @@ Based on these findings and community feedback, these are the latest models that
 ### Cloud / API-Based Models
 
 - [anthropic/claude-sonnet-4-20250514](https://www.anthropic.com/api) (recommended)
+- [anthropic/claude-sonnet-4-5-20250929](https://www.anthropic.com/api) (recommended)
 - [openai/gpt-5-2025-08-07](https://openai.com/api/) (recommended)
 - [gemini/gemini-2.5-pro](https://blog.google/technology/google-deepmind/gemini-model-thinking-updates-march-2025/)
 - [deepseek/deepseek-chat](https://api-docs.deepseek.com/)

docs/usage/llms/openhands-llms.mdx

@@ -15,7 +15,7 @@ description: OpenHands LLM provider with access to state-of-the-art (SOTA) agent
 
 When running OpenHands, you'll need to set the following in the OpenHands UI through the Settings under the `LLM` tab:
 - `LLM Provider` to `OpenHands`
-- `LLM Model` to the model you will be using (e.g. claude-sonnet-4-20250514)
+- `LLM Model` to the model you will be using (e.g. claude-sonnet-4-20250514 or claude-sonnet-4-5-20250929)
 - `API Key` to your OpenHands LLM API key copied from above
 
 ## Using OpenHands LLM Provider in the CLI
@@ -36,6 +36,7 @@ Pricing follows official API provider rates. Below are the current pricing detai
 |-------|----------------------------|-----------------------------------|------------------------------|------------------|-------------------|
 | claude-opus-4-20250514 | $15.00 | $1.50 | $75.00 | 200,000 | 32,000 |
 | claude-sonnet-4-20250514 | $3.00 | $0.30 | $15.00 | 200,000 | 64,000 |
+| claude-sonnet-4-5-20250929 | $3.00 | $0.30 | $15.00 | 200,000 | 64,000 |
 | devstral-medium-2507 | $0.40 | N/A | $2.00 | 128,000 | 128,000 |
 | devstral-small-2505 | $0.10 | N/A | $0.30 | 128,000 | 128,000 |
 | devstral-small-2507 | $0.10 | N/A | $0.30 | 128,000 | 128,000 |

frontend/src/mocks/handlers.ts

@@ -115,7 +115,9 @@ const openHandsHandlers = [
       "gpt-4o-mini",
       "anthropic/claude-3.5",
       "anthropic/claude-sonnet-4-20250514",
+      "anthropic/claude-sonnet-4-5-20250929",
       "openhands/claude-sonnet-4-20250514",
+      "openhands/claude-sonnet-4-5-20250929",
       "sambanova/Meta-Llama-3.1-8B-Instruct",
     ]),
   ),

frontend/src/utils/verified-models.ts

@@ -13,6 +13,7 @@ export const VERIFIED_MODELS = [
   "claude-3-5-sonnet-20241022",
   "claude-3-7-sonnet-20250219",
   "claude-sonnet-4-20250514",
+  "claude-sonnet-4-5-20250929",
   "claude-opus-4-20250514",
   "claude-opus-4-1-20250805",
   "gemini-2.5-pro",
@@ -51,6 +52,7 @@ export const VERIFIED_ANTHROPIC_MODELS = [
   "claude-3-5-haiku-20241022",
   "claude-3-7-sonnet-20250219",
   "claude-sonnet-4-20250514",
+  "claude-sonnet-4-5-20250929",
   "claude-opus-4-20250514",
   "claude-opus-4-1-20250805",
 ];
@@ -67,6 +69,7 @@ export const VERIFIED_MISTRAL_MODELS = [
 // (e.g., they return `claude-sonnet-4-20250514` instead of `openhands/claude-sonnet-4-20250514`)
 export const VERIFIED_OPENHANDS_MODELS = [
   "claude-sonnet-4-20250514",
+  "claude-sonnet-4-5-20250929",
   "gpt-5-2025-08-07",
   "gpt-5-mini-2025-08-07",
   "claude-opus-4-20250514",

openhands/cli/utils.py

@@ -165,6 +165,7 @@ def organize_models_and_providers(
 
 VERIFIED_ANTHROPIC_MODELS = [
     'claude-sonnet-4-20250514',
+    'claude-sonnet-4-5-20250929',
     'claude-opus-4-20250514',
     'claude-opus-4-1-20250805',
     'claude-3-7-sonnet-20250219',
@@ -186,6 +187,7 @@ def organize_models_and_providers(
 
 VERIFIED_OPENHANDS_MODELS = [
     'claude-sonnet-4-20250514',
+    'claude-sonnet-4-5-20250929',
     'gpt-5-2025-08-07',
     'gpt-5-mini-2025-08-07',
     'claude-opus-4-20250514',

openhands/llm/llm.py

@@ -148,7 +148,10 @@ def __init__(
                 logger.debug(
                     f'Gemini model {self.config.model} with reasoning_effort {self.config.reasoning_effort} mapped to thinking {kwargs.get("thinking")}'
                 )
-
+            elif 'claude-sonnet-4-5' in self.config.model:
+                kwargs.pop(
+                    'reasoning_effort', None
+                )  # don't send reasoning_effort to Claude Sonnet 4.5
             else:
                 kwargs['reasoning_effort'] = self.config.reasoning_effort
             kwargs.pop(
@@ -507,6 +510,7 @@ def init_model_info(self) -> None:
                 'claude-3-7-sonnet',
                 'claude-3.7-sonnet',
                 'claude-sonnet-4',
+                'claude-sonnet-4-5-20250929',
             ]
             if any(model in self.config.model for model in sonnet_models):
                 self.config.max_output_tokens = 64000  # litellm set max to 128k, but that requires a header to be set
@@ -817,6 +821,8 @@ def format_messages_for_llm(self, messages: Message | list[Message]) -> list[dic
                 message.force_string_serializer = True
             if 'openrouter/anthropic/claude-sonnet-4' in self.config.model:
                 message.force_string_serializer = True
+            if 'openrouter/anthropic/claude-sonnet-4-5-20250929' in self.config.model:
+                message.force_string_serializer = True
 
         # let pydantic handle the serialization
         return [message.model_dump() for message in messages]

openhands/llm/model_features.py

@@ -103,6 +103,7 @@ class ModelFeatures:
     'gpt-5*',
     # DeepSeek reasoning family
     'deepseek-r1-0528*',
+    'claude-sonnet-4-5*',
 ]
 
 PROMPT_CACHE_PATTERNS: list[str] = [