Attachments

You can attach files to your chat messages so the AI can read, analyze, or reference them in its response. Pentos supports images, PDFs, documents, spreadsheets, text files, and code files.

Supported File Types

Not every model supports every file type. For the full list of file types Pentos accepts, see Uploading Files. If the selected model cannot read one of your attachments, Pentos tells you before sending, so you can remove it or pick another model. The model selector’s Supports row shows whether a model takes text files and images.

Every model except DeepSeek V4 Pro and DeepSeek V4 Flash can read PDFs:

Read directly: Claude, Gemini and Mistral models, and GPT models other than GPT OSS, read the PDF itself, including scanned pages, charts and layout, on later messages too.
Read as text: Other models read the text Pentos extracts from the PDF, so they don’t see its images, and they tell you when a PDF is scanned or made of images and has no text to read.

How to Attach Files

There are three ways to attach files to a message:

Files: Select a file from Pentos Files, or upload a new one.
Drag and Drop: Drag files from your computer into the chat to upload and attach them.
Paste: Paste an image, or a block of text over 5,000 characters, and Pentos turns it into a file attachment.

Every upload is scanned for security before it can be sent. The send button stays unavailable until all of your attachments finish uploading and pass the scan.

Limits

Limits depend on the model you choose:

File size: most models accept files up to 20 MB each. Claude models accept PDFs up to 30 MB.
Files per message: this varies widely. Mistral models take up to 8 files per message, Claude models up to 100, and some OpenAI and Google models accept far more images.
Context window: everything you attach counts toward how much the model can read at once. If an attachment is too large for the selected model, Pentos tells you and suggests a smaller file, Max Mode, or a model with a larger window.

If you go over a limit, Pentos tells you which one before your message is sent.

Large Text and Data Files

When a text-based file, such as a large CSV, log, or document, is too big to fit comfortably in the conversation, Pentos gives it to the AI through a secure sandbox instead. The AI reads a preview of the file and uses code to search, filter, and calculate over the whole thing, so you can still ask questions about data that would never fit in a single message.

The Files Sidebar lists every file attached to the current chat, so you don’t have to scroll through the conversation to find them.

To open it, click the + chat menu in the top-left corner of the chat and select Files.

Each file is listed with:

File name: The name of the attached file.
File size: The size of the file.
Upload date: When the file was added, shown as “Today”, “Yesterday”, or a date.

Previewing Files

Click any file to preview it. Pentos has built-in viewers for images, video, audio, code, text, and spreadsheets (including CSV and TSV). PDFs open in a new browser tab. If a file type has no viewer, Pentos tells you.

Where Attachments Are Stored

All of your files are stored securely in Pentos Files. When you upload a file directly to a chat, Pentos moves it into a folder for that chat under Chats in your File Manager, where you can manage it alongside your other files. Files you attach from elsewhere in your library stay where they are. Files the AI creates in the chat, such as images and charts, are saved in the chat’s folder too. See Using Files With AI.

If you rename the chat, its folder is renamed to match.

In a shared chat, the people in the chat can open the files attached to it, with some limits. See Sharing & Permissions.