From 07a687880fa908c6f6ff48ee5f49c24f662f4005 Mon Sep 17 00:00:00 2001
From: Charles Packer <packercharles@gmail.com>
Date: Sat, 4 Oct 2025 20:21:04 -0700
Subject: [PATCH] feat(core): add sonnet 1m support [LET-4620] (#5152)

feat(core): add sonnet 1m support
---
 letta/llm_api/anthropic_client.py    | 46 ++++++++++++++++++++++++++--
 letta/schemas/providers/anthropic.py | 11 +++++++
 letta/settings.py                    |  9 ++++++
 3 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/letta/llm_api/anthropic_client.py b/letta/llm_api/anthropic_client.py
index 7c8ebbb0..9a500fe2 100644
--- a/letta/llm_api/anthropic_client.py
+++ b/letta/llm_api/anthropic_client.py
@@ -55,15 +55,46 @@ class AnthropicClient(LLMClientBase):
     @deprecated("Synchronous version of this is no longer valid. Will result in model_dump of coroutine")
     def request(self, request_data: dict, llm_config: LLMConfig) -> dict:
         client = self._get_anthropic_client(llm_config, async_client=False)
-        response = client.beta.messages.create(**request_data)
+        betas: list[str] = []
+        # 1M context beta for Sonnet 4/4.5 when enabled
+        try:
+            from letta.settings import model_settings
+
+            if model_settings.anthropic_sonnet_1m and (
+                llm_config.model.startswith("claude-sonnet-4") or llm_config.model.startswith("claude-sonnet-4-5")
+            ):
+                betas.append("context-1m-2025-08-07")
+        except Exception:
+            pass
+
+        if betas:
+            response = client.beta.messages.create(**request_data, betas=betas)
+        else:
+            response = client.beta.messages.create(**request_data)
         return response.model_dump()
 
     @trace_method
     async def request_async(self, request_data: dict, llm_config: LLMConfig) -> dict:
         client = await self._get_anthropic_client_async(llm_config, async_client=True)
 
+        betas: list[str] = []
+        # interleaved thinking for reasoner
         if llm_config.enable_reasoner:
-            response = await client.beta.messages.create(**request_data, betas=["interleaved-thinking-2025-05-14"])
+            betas.append("interleaved-thinking-2025-05-14")
+
+        # 1M context beta for Sonnet 4/4.5 when enabled
+        try:
+            from letta.settings import model_settings
+
+            if model_settings.anthropic_sonnet_1m and (
+                llm_config.model.startswith("claude-sonnet-4") or llm_config.model.startswith("claude-sonnet-4-5")
+            ):
+                betas.append("context-1m-2025-08-07")
+        except Exception:
+            pass
+
+        if betas:
+            response = await client.beta.messages.create(**request_data, betas=betas)
         else:
             response = await client.beta.messages.create(**request_data)
 
@@ -84,6 +115,17 @@ class AnthropicClient(LLMClientBase):
         if llm_config.enable_reasoner:
             betas.append("interleaved-thinking-2025-05-14")
 
+        # 1M context beta for Sonnet 4/4.5 when enabled
+        try:
+            from letta.settings import model_settings
+
+            if model_settings.anthropic_sonnet_1m and (
+                llm_config.model.startswith("claude-sonnet-4") or llm_config.model.startswith("claude-sonnet-4-5")
+            ):
+                betas.append("context-1m-2025-08-07")
+        except Exception:
+            pass
+
         return await client.beta.messages.create(**request_data, betas=betas)
 
     @trace_method
diff --git a/letta/schemas/providers/anthropic.py b/letta/schemas/providers/anthropic.py
index 4b08324d..c72f315e 100644
--- a/letta/schemas/providers/anthropic.py
+++ b/letta/schemas/providers/anthropic.py
@@ -148,6 +148,17 @@ class AnthropicProvider(Provider):
                     warnings.warn(f"Couldn't find context window size for model {model['id']}, defaulting to 200,000")
                     model["context_window"] = 200000
 
+            # Optional override: enable 1M context for Sonnet 4/4.5 when flag is set
+            try:
+                from letta.settings import model_settings
+
+                if model_settings.anthropic_sonnet_1m and (
+                    model["id"].startswith("claude-sonnet-4") or model["id"].startswith("claude-sonnet-4-5")
+                ):
+                    model["context_window"] = 1_000_000
+            except Exception:
+                pass
+
             max_tokens = 8192
             if "claude-3-opus" in model["id"]:
                 max_tokens = 4096
diff --git a/letta/settings.py b/letta/settings.py
index 28882ac1..4aad0195 100644
--- a/letta/settings.py
+++ b/letta/settings.py
@@ -137,6 +137,15 @@ class ModelSettings(BaseSettings):
     # anthropic
     anthropic_api_key: Optional[str] = None
     anthropic_max_retries: int = 3
+    anthropic_sonnet_1m: bool = Field(
+        default=False,
+        description=(
+            "Enable 1M-token context window for Claude Sonnet 4/4.5. When true, adds the"
+            " 'context-1m-2025-08-07' beta to Anthropic requests and sets model context_window"
+            " to 1,000,000 instead of 200,000. Note: This feature is in beta and not available"
+            " to all orgs; once GA, this flag can be removed and behavior can default to on."
+        ),
+    )
 
     # ollama
     ollama_base_url: Optional[str] = None