Anthropic raised the maximum request size for its first-party Claude Messages and Token Counting APIs from 32 MB to 128 MB, according to its October 28, 2026 release note. Developers can now submit substantially larger requests to those two endpoints before hitting the API’s request-size ceiling. (Anthropic release notes)
The change matters most when a request carries large documents, many images or a growing computer-use history. Those payloads can run out of room in megabytes before exhausting the model’s context window. Raising the request limit removes that particular bottleneck for more workloads, but developers still need to check whether the model can process the contents.
The 128 MB limit is endpoint-specific. Message Batches, Files and the APIs for managed-agent Sessions, Agents and Environments retain different ceilings. Treating this as a platform-wide increase would leave some integrations with the wrong validation rules.
What Changed for Messages and Token Counting
The increase covers two first-party endpoints:
- Messages:
POST /v1/messages, which sends conversational requests to Claude. - Token Counting:
POST /v1/messages/count_tokens, which counts a message’s tokens before a developer submits it for inference.
Both move from 32 MB to 128 MB. Anthropic’s announcement explicitly limits the change to the first-party Claude API; developers using cloud-provider-managed endpoints should check that platform’s documentation instead of assuming the same ceiling applies. (Anthropic release notes, API overview)
Raising both limits together is a useful detail. If Messages accepted a larger payload while Token Counting retained the old ceiling, developers could lose their token-checking step precisely when handling bigger inputs. The matched limits allow more large requests to pass through that preflight workflow, although the counting request must still fit within its own 128 MB limit.
The release note describes a request-size increase, without specifying a required SDK upgrade, new API version or beta header for it. That makes the immediate integration task a review of application-side restrictions: a client, gateway or upload form still configured to reject requests above 32 MB could prevent developers from using the extra room.
Claude API Request Limits by Endpoint
Anthropic’s API overview lists the following first-party request-size ceilings. Only Messages and Token Counting are identified in the October 28 announcement as receiving the increase. (API overview)
| API | Maximum request size | Effect of the announced change |
|---|---|---|
| Messages | 128 MB | Increased from 32 MB |
| Token Counting | 128 MB | Increased from 32 MB |
| Message Batches | 256 MB | Separate limit, unchanged by this announcement |
| Files | 500 MB | Separate limit, unchanged by this announcement |
| Sessions | 32 MB | Separate limit, unchanged by this announcement |
| Agents | 32 MB | Separate limit, unchanged by this announcement |
| Environments | 32 MB | Separate limit, unchanged by this announcement |
These numbers describe different API operations. The Files API uploads and manages files for use across calls. Message Batches processes collections of Messages requests asynchronously. Sessions, Agents and Environments provide different pieces of Anthropic’s managed-agent infrastructure. Their limits should follow the endpoint receiving the request. (API overview)
For example, a hypothetical 40 MB request is below the new Messages ceiling but above the listed Sessions ceiling. An application cannot safely apply a single 128 MB check to both routes.
The 500 MB Files limit also needs careful interpretation. It describes the file-upload endpoint’s capacity; it does not promise that a model can consume every uploaded file in one turn. Similarly, the 32 MB Sessions request ceiling should not be read as a statement about the total amount of state a session can accumulate. The documentation labels these as request-size limits.
I’d keep these values in an endpoint-specific configuration table. The published differences are large enough that one shared “Claude upload limit” would either reject usable requests or allow requests that the destination will refuse.
Request Size and Context Windows Measure Different Things
Request size measures how much data is submitted to an endpoint. A model’s context window governs how much model input it can accommodate, measured in tokens. The October 28 announcement changes the former; it announces no expansion of model context windows. (Anthropic release notes)
The practical consequence is that a request has more than one test to pass:
- Does the request fit the endpoint’s size ceiling?
- Does the content fit the selected model’s context requirements?
Passing either check says nothing definitive about the other. A hypothetical 60 MB Messages request is below the new 128 MB ceiling, but its contents still need to fit the model’s context and satisfy the API’s other validation rules. Conversely, an image-heavy request could have context capacity available yet previously have exceeded the 32 MB request limit.
Token Counting helps with the second question. Anthropic describes that API as a way to count tokens before sending a message, supporting cost and rate-limit management. It now has the same larger request ceiling as Messages. (API overview)
I’d keep byte-size validation and token validation as distinct checks in an application. They diagnose different problems and suggest different remedies. Removing an oversized attachment might solve a request-size failure; shortening conversation history might address a context-capacity problem. An error message that simply says “input too large” hides that distinction from both users and developers.
Where the Extra Room Helps
Anthropic’s ClaudeDevs account identified large PDFs and long computer-use sessions as examples of workloads affected by the old ceiling. In a post reproduced by Dev Radar, the account said image-heavy requests had been reaching 32 MB while still having context capacity available. That is the vendor’s explanation of the update’s motivation, not an independent workload measurement. (Dev Radar’s reproduction of the ClaudeDevs post)
Frequently Asked Questions
4 questions
1Which Claude API endpoints now accept 128 MB requests?
The first-party Messages and Token Counting APIs. Anthropic announced the increase from 32 MB on October 28, 2026.
