Microsoft 365 Copilot + SharePoint

Short answer:

• Yes—Microsoft is working to expand what Copilot can handle
• Combining outputs across files is possible today

There isn’t a single, official MB limit published across all Copilot surfaces. In practice, chat uploads do throw size errors (like the 150 MB message you saw). Microsoft’s public stance is to watch content length (e.g., up to ~300 pages / ~1.5 M words for full‑document summarization) and they’ll raise limits over time—just no date yet.

Practical ways to get what you need today
1) One combined summary for a handful of files (fast)

In OneDrive on the web, select up to 5 files → Copilot ▸ Summarize for a single, consolidated summary panel you can iterate on (“compare positions,” “list contradictions with citations,” etc.).

2) Cross‑document synthesis at site/library scale

Use SharePoint agents (built into SharePoint). Create an agent scoped to your matter site, library, or a set of folders/files. Then ask for a single issues list, timeline, or executive brief across everything you’re allowed to see. This is the best option for large matters.
FYI on limits: when agents read from SharePoint, enhanced search supports files up to ~200 MB per item; when you upload files to an agent as knowledge sources, the per‑file cap is 512 MB. That helps some big files—but not multi‑GB PDFs.

3) Copilot Notebooks for a single, combined deliverable

Copilot Notebooks let you collect references (SharePoint/OneDrive files, chats, pages) and ask Copilot for one consolidated output (e.g., “Create an executive summary with sections: Background, Claims, Key Facts, Procedural History, Open Issues.
Notebooks are great for ongoing matters (you can keep adding references) and keep Copilot’s answers scoped to your notebook. They do not bypass file‑ingestion caps; they just help you combine and structure results.

4) Work a single large document without chat‑upload limits

Open (transform) the file in Word and use Copilot side‑by‑side; Copilot can reason over the open document (often avoids the chat upload gate). Still follow the length guidance for best results.

For very large legal files (500 MB–2 GB)

Pre‑process before AI: OCR scanned PDFs, remove unnecessary images, or split by logical sections (exhibits, transcript days, motion/response/reply). Then use SharePoint agents or Notebooks for the combined brief and Word + Copilot to polish. (This aligns with Microsoft’s guidance that results are more accurate when the model can access the full relevant context.)