spring-projects/spring-ai · error · IllegalArgumentException

Unsupported media type: . Supported types are: images (image

Error message

Unsupported media type: . Supported types are: images (image/*) and PDF documents (application/pdf)

What it means

AnthropicChatModel.createMediaBlockParam only supports image/* media and PDF documents (application/pdf) when converting a Media entry in a UserMessage into Anthropic content blocks. Any other MIME type (video, audio, text, application/json, or an unknown/blank type) hits the final throw. The library throws IllegalArgumentException because the Anthropic Messages API simply has no content-block representation for that media.

Source

Thrown at models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/AnthropicChatModel.java:1369

	/**
	 * Converts a Spring AI {@link Media} object to an Anthropic SDK
	 * {@link ContentBlockParam}. Supports images (PNG, JPEG, GIF, WebP) and PDF
	 * documents. Data can be provided as byte[] (base64 encoded) or HTTPS URL string.
	 * @param media the media object containing MIME type and data
	 * @return the appropriate ContentBlockParam (ImageBlockParam or DocumentBlockParam)
	 * @throws IllegalArgumentException if the media type is unsupported
	 */
	private ContentBlockParam getContentBlockParamByMedia(Media media) {
		MimeType mimeType = media.getMimeType();
		String data = fromMediaData(media.getData());

		if (isImageMedia(mimeType)) {
			return createImageBlockParam(mimeType, data);
		}
		else if (isPdfMedia(mimeType)) {
			return createDocumentBlockParam(data);
		}
		throw new IllegalArgumentException("Unsupported media type: " + mimeType
				+ ". Supported types are: images (image/*) and PDF documents (application/pdf)");
	}

	/**
	 * Checks if the given MIME type represents an image.
	 * @param mimeType the MIME type to check
	 * @return true if the type is image/*
	 */
	private boolean isImageMedia(MimeType mimeType) {
		return "image".equals(mimeType.getType());
	}

	/**
	 * Checks if the given MIME type represents a PDF document.
	 * @param mimeType the MIME type to check
	 * @return true if the type is application/pdf
	 */
	private boolean isPdfMedia(MimeType mimeType) {

View on GitHub (pinned to 98a7beda4f)

Solutions

Change the Media MIME type to an image type (image/png, image/jpeg, image/gif, image/webp) or application/pdf.
If the file is another format, convert it (e.g. render a document page to PNG, or embed text directly in the prompt text instead of as Media).
Verify the MIME type is not empty/generic: pass an explicit MimeType rather than relying on detection of application/octet-stream.
If you need non-image/PDF media, switch to a model module that supports it (e.g. a different Spring AI model integration).

Example fix

// before
var media = new Media(MimeTypeUtils.APPLICATION_OCTET_STREAM, pdfBytes);
// after
var media = new Media(MimeType.valueOf("application/pdf"), pdfBytes);

Defensive patterns

Strategy: validation

Validate before calling

MimeType type = media.getMimeType();
boolean supported = (type.getType().equals("image")) || type.toString().equals("application/pdf");
if (!supported) throw new IllegalArgumentException("Anthropic supports only image/* or application/pdf, got: " + type);

Try / catch

try {
    client.call(new Prompt(new UserMessage(text, List.of(media))));
} catch (IllegalArgumentException e) {
    if (e.getMessage().startsWith("Unsupported media type")) {
        log.error("Media {} not supported by Anthropic: {}", media.getMimeType(), e.getMessage());
    } else throw e;
}

Prevention

Whitelist image/* and application/pdf at the point where Media objects are constructed.
Never rely on detected MIME types like application/octet-stream; set explicit types.
Convert text/other documents to prompt text or PDF before sending to Anthropic.

When it happens

Trigger: Passing a Media with a MIME type that is neither image/* nor application/pdf into a UserMessage, e.g. new Media(MimeTypeUtils.APPLICATION_OCTET_STREAM, bytes), MimeType.valueOf("audio/mpeg"), or a Media whose MIME type was not detected (empty string) and therefore does not match isImageMedia/isPdfMedia.

Common situations: Developers attaching audio, video, zip or plain-text files to prompts assuming multimodal support; building Media from a downloaded Resource with generic application/octet-stream content type; upgrading Spring AI and forgetting that only images and PDFs are accepted by the Anthropic model.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of spring-projects/spring-ai@98a7beda4f (2026-09-11). Data as JSON: /api/errors/7bede6f90ac29c02. Report an issue: GitHub.