Quick start: your first JSONL session

This is the shortest path from an installed SumDoc to a proven “command → model change → DOCX write → re-read” cycle.

What you’ll have after 10–15 minutes

The Rust process will respond to ping and report the fastdoc.session-serve.v1 protocol; a DOCX will be opened, its first paragraph changed through the API and saved as a separate file; the result will open in SumDoc.

What you need before you start

The commands below run in the prepared ~/Desktop/SumDoc-API-first-run folder. It comes, together with the a4-api-demo.mjs and start-web-demo.sh scripts, from the Evaluation Kit — a separate delivery artifact (see What is delivered). It is not part of the SumDoc installer and cannot be downloaded from dl.layers.md: request it from the vendor.

If you don’t have the Evaluation Kit yet, an installed SumDoc is enough to follow the same path manually: fastdoc-cli lives inside the application (see Installation and verification), the request format is described in Request and response objects, and the full list of commands is in the reference. SumSheet has an example of a fully written-out script: verified script.

Your first real call: a JSONL session

JSONL is the simplest contract for a first integration: one JSON request per stdin line, one JSON response per stdout line. Rust holds the open document’s state between commands.

Setup

1. Open a terminal.
2. Check Node.js with node --version — you need version 22 LTS or newer.
3. Go to the prepared folder on your desktop.
4. Run the demo client, passing explicit input and output file paths.

macOS

cd ~/Desktop/SumDoc-API-first-run
node --version

node a4-api-demo.mjs \
  "/Applications/SumDoc.app/Contents/Resources/app/fixtures/docx/simple_text.docx" \
  "$PWD/api-demo-result.docx"

Windows

cd $HOME\Desktop\SumDoc-API-first-run
node --version

node a4-api-demo.mjs `
  "C:\Program Files\SumDoc\resources\app\fixtures\docx\simple_text.docx" `
  "$PWD\api-demo-result.docx"

Linux

cd ~/Desktop/SumDoc-API-first-run
node --version

node a4-api-demo.mjs \
  "/opt/SumDoc/resources/app/fixtures/docx/simple_text.docx" \
  "$PWD/api-demo-result.docx"

What the script does

1. Starts fastdoc-cli serve from the application package.
2. Reads the protocol greeting and the list of session commands (there are 41).
3. Sends ping, then open and model.
4. Uses the mutate command to insert the text “API DEMO:” at the start of the first paragraph.
5. Reads status and saves a copy with the save command.
6. Ends the process with the shutdown command.

Actual output from a verified run

Connected: fastdoc.session-serve.v1
Commands available: 28
Ping: true
Session: rust-session-20320-1
Before: This is a sample word document. It has two pages, but no headers or footers.
After:  API DEMO: This is a sample word document. It has two pages, but no headers or footers.
Revision: 1; dirty: true
Saved: /Users/tester/Desktop/SumDoc-API-first-run/api-demo-result.docx

Success criteria

Ping: true, revision=1, dirty=true, and a new api-demo-result.docx on disk.

Open the result and see the change

macOS

open -a SumDoc ~/Desktop/SumDoc-API-first-run/api-demo-result.docx

Windows

& "C:\Program Files\SumDoc\SumDoc.exe" "$HOME\Desktop\SumDoc-API-first-run\api-demo-result.docx"

Linux

/opt/SumDoc/a4 ~/Desktop/SumDoc-API-first-run/api-demo-result.docx

The prefix API DEMO: should appear at the start of the first paragraph. This confirms the full cycle: the command reached Rust, changed the document model, was written to DOCX, and was read back by the graphical editor.

This path was proven exactly this way: on August 26, 2026, on an installed SumDoc, with that same prefix in the first paragraph.

Verify the saved file without a GUI

macOS

CLI="/Applications/SumDoc.app/Contents/Resources/runtime/native/fastdoc-cli"
"$CLI" model-docx \
  "$HOME/Desktop/SumDoc-API-first-run/api-demo-result.docx" \
  --format json

Windows

$CLI = "C:\Program Files\SumDoc\resources\runtime\native\fastdoc-cli.exe"
& $CLI model-docx `
  "$HOME\Desktop\SumDoc-API-first-run\api-demo-result.docx" `
  --format json

Linux

CLI="/opt/SumDoc/resources/runtime/native/fastdoc-cli"
"$CLI" model-docx \
  "$HOME/Desktop/SumDoc-API-first-run/api-demo-result.docx" \
  --format json

What to look for in the JSON

In body.blocks, find the first object with kind=paragraph. Its text should start with API DEMO:. This is direct access to the document’s structure, not reading an image or a PDF.

What’s next

• Work through the request and response format — Request and response objects.
• The same commands, but over WebSocket — The same contract over WebSocket.
• Show the document to the user — Starting Web Surface, then Embedding Surface.
• The full list of session commands — the reference.
• Something won’t start — Diagnostics and checklist.