[Bug] ACP: every IPython tool call is titled "IPython cell" and shows no cell source

[AndriyPytel]

Affected area

Coding agent and CLI (ACP mode)

What happened?

Every IPython tool call reaches an ACP client titled IPython cell, with the cell source only in rawInput. IPython is Prime Agent's model-facing tool, so that is the title of nearly every row in the session: the transcript becomes a column of identical rows. A client that renders content blocks rather than rawInput shows those rows empty, so there is nothing to tell one cell from another.

Steps to reproduce

1. Run prime-agent --mode acp and connect an ACP client.
2. Prompt anything that runs a few IPython cells.
3. Every tool_call arrives with title: "IPython cell".
4. In a client that renders content blocks, each row is also empty.

Expected behavior

The call is titled by what the cell actually does — its first meaningful line — and the source travels as content, not only as rawInput, so a content-rendering client shows the cell.

Two details matter: a leading cell magic should be paired with the line after it (%%bash alone names the interpreter, not the work), and the source has to be repeated on tool_call_update, because a client replaces a tool call's content on update rather than appending — otherwise the cell disappears the moment the call completes.

Prime Agent version

0.7.1 (also reproduced on main at 7787f07)

Environment

macOS, prime-agent --mode acp driven over stdio by an ACP client

Additional context

Tracked as #1307. A focused patch is up as #1309, with tests in test/acp-events.test.ts covering a plain cell, a %%bash cell, a blank cell, a 200-character line, and completion carrying both the cell and the result; npm run check passes.

Opening this Discussion because the new contribution process routes intake here.

[AndriyPytel]

@sethkarten same note here, since ACP mode is yours.

This is the other one I hit daily driving Prime Agent over ACP: because IPython is the model-facing tool, nearly every row in the transcript is titled IPython cell, so the session view carries no information at all. In a client that renders content blocks rather than rawInput, those rows are also empty.

Patch is up as #1309 with unit tests over the event mapper. The one non-obvious part is that the cell has to be re-sent on tool_call_update, because clients replace a tool call's content rather than appending to it — without that the cell vanishes exactly when the call completes. Happy to adjust the title format if you have a preference.