#1163: MCP render_preview takes an artboard index

render_preview only rendered the first artboard, so an agent couldn't
look at pages 2 and on of a multi-artboard document without switching
to screenshot. It now takes an optional 0-based `artboard` (as
screenshot does) and refuses an index the document doesn't have.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

ROADMAP.md

@@ -127,7 +127,7 @@ Ranked; detail in [docs/roadmap.md](docs/roadmap.md) and [docs/gaps.md](docs/gap
 
 | Date | What landed |
 |---|---|
-| 2026-10-11 | Effect › Brush Strokes: Accented Edges, Angled Strokes, Crosshatch, Dark Strokes, Ink Outlines, Spatter, Sprayed Strokes, Sumi-e (G2). Command parameters from agents and files checked before anything changes (paint, place, cuts, dashes, crop, asset ids, anchors, paths, distort; #984–#999); command dialogs keep whole numbers whole, so Create Object Mosaic takes the tiles typed (#1000); stepper arrows take Shift (×10) and Ctrl/Cmd (÷10) like the arrow keys (#991). Exports and Rasterize supersample Art Optimized edges, so shapes meeting edge to edge leave no seam (#983). Character and paragraph styles take leading, kerning, mojikumi and the other attributes left out at their defaults (#1001). Drawing, typing and pasting with no layer shown and unlocked is refused instead of adding art to a hidden or locked layer (#1002). MCP `add_text` gives type on or in a path the colour asked for (#1003). MCP `screenshot` of a connected app renders the artboard asked for (#1004). `vectorcraft-cli run` ends quietly when its reader closes early (#1005). Select › All on Active Artboard selects on the artboard made active, not always the first (#1006). Reverse Gradient keeps off-centre midpoints, mirrored (#1007). A polar grid with no radial dividers draws none (#1008). Use Precise Cursors also covers the Pen's join pointer (#1009). SVGs with one absolute and one unitless root side import at their size, unstretched (#1010). DXF US survey inches, yards and miles open at their size and name (#1011). A file placed into a document with no other links follows its first change even while the app sits idle (#1031). PDF import keeps the style a font name says when the file doesn't embed the font (#1023). Shift selects ruler guides and art together, and Delete removes both (#1022). Open filled paths are hit by their fill on every side, the rotate cursor bows around the corner it is at, the flip icons match their flips, the Color Picker previews on the selection, and Properties › Transform reaches Scale Corners and Scale Strokes & Effects (#1036). Offset Path and the other booleans finish on outlines where the sweep used to loop until memory ran out (linesweeper 0.5, #1028). Floating panel groups stack into sets that move together, collapse to their tabs and dock as extra dock columns that scroll (#1020). Ruler guides live on layers: listed in the Layers panel, shown, hidden, locked, duplicated, merged and deleted with their layer, and moved between layers (#1021). A `.ai` whose editing data uses global process colours (`Xk`/`XK`) or pattern fills keeps its sublayers: the colours come in as global swatches at their tint, the patterns as pattern swatches (#1025). A `.ai` in PostScript form opens through its layers, read from the program itself, also when it names the prolog defining its operators without including it, as Rhino and other CAD apps write it (#1027). A fill or stroke chosen while the Type tool has characters selected colours just those characters (#1063). Scaled type shows its scaled font size, leading, baseline shift and horizontal scale in the Character panel, and a size typed there is the size you get (#1034). Character panel menu › Proportional Metrics sets Japanese and Chinese full-width glyphs on the font's proportional widths in horizontal type (#966). Align, Distribute, Move, Arrange, Lock, Hide, Ungroup and other Object commands that would change nothing no longer record an undo step or mark the document changed (#1060). Spot colours defined in Lab open with their Lab values from `.ai` and PDF files, instead of as wrong RGB colours or their CMYK equivalents (#1032). Build scripts leave a generated source they wouldn't change untouched, so the next build doesn't compile most of the workspace again where file times lose their sub-second part (#1051). A fill colour recolours the gradient mesh point last clicked with the Mesh tool or Direct Selection, and a Mesh tool click on a mesh's point selects that mesh (#1052). The All Tools drawer stays two tools wide instead of filling a wide window (#1054). Text Wrap's Make, Release and Options refuse a list of object ids with a malformed or unknown id instead of skipping it (#1055). A freeform gradient line with a malformed point index is refused instead of being shortened to the indices that are valid (#1056). The Corners dialog (`ui.corners`) refuses a malformed object id or a listed anchor that isn't a corner instead of editing the selection or the other corners (#1057). New View refuses a centre that isn't exactly [x, y] and a rotation that isn't a number, instead of trimming the one and saving the other as 0° (#1058). The command sweeps try junk scale, spacing and artboard values too, which they had skipped since before those bugs were fixed (#1059). EPS and PostScript `arc` and `arcn` with huge angles no longer hang the import, and an arc whose angles are whole turns apart is empty, as the PostScript reference defines it (#1062). Align and DisLine truncated
+| 2026-10-11 | Effect › Brush Strokes: Accented Edges, Angled Strokes, Crosshatch, Dark Strokes, Ink Outlines, Spatter, Sprayed Strokes, Sumi-e (G2). Command parameters from agents and files checked before anything changes (paint, place, cuts, dashes, crop, asset ids, anchors, paths, distort; #984–#999); command dialogs keep whole numbers whole, so Create Object Mosaic takes the tiles typed (#1000); stepper arrows take Shift (×10) and Ctrl/Cmd (÷10) like the arrow keys (#991). Exports and Rasterize supersample Art Optimized edges, so shapes meeting edge to edge leave no seam (#983). Character and paragraph styles take leading, kerning, mojikumi and the other attributes left out at their defaults (#1001). Drawing, typing and pasting with no layer shown and unlocked is refused instead of adding art to a hidden or locked layer (#1002). MCP `add_text` gives type on or in a path the colour asked for (#1003). MCP `screenshot` of a connected app renders the artboard asked for (#1004). `vectorcraft-cli run` ends quietly when its reader closes early (#1005). Select › All on Active Artboard selects on the artboard made active, not always the first (#1006). Reverse Gradient keeps off-centre midpoints, mirrored (#1007). A polar grid with no radial dividers draws none (#1008). Use Precise Cursors also covers the Pen's join pointer (#1009). SVGs with one absolute and one unitless root side import at their size, unstretched (#1010). DXF US survey inches, yards and miles open at their size and name (#1011). A file placed into a document with no other links follows its first change even while the app sits idle (#1031). PDF import keeps the style a font name says when the file doesn't embed the font (#1023). Shift selects ruler guides and art together, and Delete removes both (#1022). Open filled paths are hit by their fill on every side, the rotate cursor bows around the corner it is at, the flip icons match their flips, the Color Picker previews on the selection, and Properties › Transform reaches Scale Corners and Scale Strokes & Effects (#1036). Offset Path and the other booleans finish on outlines where the sweep used to loop until memory ran out (linesweeper 0.5, #1028). Floating panel groups stack into sets that move together, collapse to their tabs and dock as extra dock columns that scroll (#1020). Ruler guides live on layers: listed in the Layers panel, shown, hidden, locked, duplicated, merged and deleted with their layer, and moved between layers (#1021). A `.ai` whose editing data uses global process colours (`Xk`/`XK`) or pattern fills keeps its sublayers: the colours come in as global swatches at their tint, the patterns as pattern swatches (#1025). A `.ai` in PostScript form opens through its layers, read from the program itself, also when it names the prolog defining its operators without including it, as Rhino and other CAD apps write it (#1027). A fill or stroke chosen while the Type tool has characters selected colours just those characters (#1063). Scaled type shows its scaled font size, leading, baseline shift and horizontal scale in the Character panel, and a size typed there is the size you get (#1034). Character panel menu › Proportional Metrics sets Japanese and Chinese full-width glyphs on the font's proportional widths in horizontal type (#966). Align, Distribute, Move, Arrange, Lock, Hide, Ungroup and other Object commands that would change nothing no longer record an undo step or mark the document changed (#1060). Spot colours defined in Lab open with their Lab values from `.ai` and PDF files, instead of as wrong RGB colours or their CMYK equivalents (#1032). Build scripts leave a generated source they wouldn't change untouched, so the next build doesn't compile most of the workspace again where file times lose their sub-second part (#1051). A fill colour recolours the gradient mesh point last clicked with the Mesh tool or Direct Selection, and a Mesh tool click on a mesh's point selects that mesh (#1052). The All Tools drawer stays two tools wide instead of filling a wide window (#1054). Text Wrap's Make, Release and Options refuse a list of object ids with a malformed or unknown id instead of skipping it (#1055). A freeform gradient line with a malformed point index is refused instead of being shortened to the indices that are valid (#1056). The Corners dialog (`ui.corners`) refuses a malformed object id or a listed anchor that isn't a corner instead of editing the selection or the other corners (#1057). New View refuses a centre that isn't exactly [x, y] and a rotation that isn't a number, instead of trimming the one and saving the other as 0° (#1058). The command sweeps try junk scale, spacing and artboard values too, which they had skipped since before those bugs were fixed (#1059). EPS and PostScript `arc` and `arcn` with huge angles no longer hang the import, and an arc whose angles are whole turns apart is empty, as the PostScript reference defines it (#1062). Align and DisLine truncated
 | 2026-10-10 | Initial live Revolve (Effect › 3D and Materials, #846, #605), in its own `three-d` crate. Progress docs re-measured and restructured to the craftrules standard (this page, `docs/target-app-parity.md`, `gaps.md`, `ui-parity.md`, the format, hardware, localization, effects and type checklists). Same day: v0.8.0; Effect › Distort, Pixelate and Texture filters (13); German interface; Variables (data merge); Graph Type value axes and tick marks; restart when the first frame never reaches the screen (#964) |
 | 2026-10-09 | Radial Blur, Smart Blur, Unsharp Mask (gap 2 begins); 340 commits, the busiest day |
 | 2026-10-08 | v0.5.0–v0.7.0; community contributions: Pen and shape-tool modifiers, Layers, Artboards, Japanese composition, Hebrew/Arabic type, interface languages, saved selections |

crates/mcp/src/tests_conventions.rs

@@ -65,6 +65,17 @@ fn conventions_commands_batch_and_bounded_preview() {
     for max in [json!(0), json!(4097), json!("64")] {
         assert_eq!(call(&mut s, "render_preview", json!({"max_side":max}))["isError"], true);
     }
+    // Another artboard, three times wider than tall, previews by its index (#1163).
+    let r = call(&mut s, "run_command", json!({"command":"artboard.new","params":{"x":2000,"y":0,"width":300,"height":100}}));
+    assert_eq!(r["isError"], false, "{r}");
+    let r = call(&mut s, "render_preview", json!({"max_side":60,"artboard":1}));
+    assert_eq!(r["isError"], false, "{r}");
+    let png = vectorcraft_format::base64_decode(r["content"][0]["data"].as_str().unwrap()).unwrap();
+    let img = image::load_from_memory(&png).unwrap();
+    assert_eq!((img.width(), img.height()), (60, 20));
+    for board in [json!(2), json!(-1), json!("1")] {
+        assert_eq!(call(&mut s, "render_preview", json!({"artboard":board}))["isError"], true, "{board}");
+    }
     for name in ["ui_inspect", "ui_screenshot"] {
         assert_eq!(call(&mut s, name, json!({}))["isError"], true);
     }

crates/mcp/src/tools.rs

@@ -113,8 +113,11 @@ pub fn tool_definitions() -> Vec<Value> {
         tool(
             "render_preview",
             "Render a preview",
-            "Render the first artboard as inline PNG without changing the document. max_side defaults to 1024, limited to 1..4096.",
-            obj(json!({"max_side":{"type":"integer","minimum":1,"maximum":4096}}), &[]),
+            "Render an artboard (default the first) as inline PNG without changing the document. max_side defaults to 1024, limited to 1..4096.",
+            obj(
+                json!({"max_side":{"type":"integer","minimum":1,"maximum":4096},"artboard":{"type":"integer","minimum":0,"description":"0-based artboard (default 0)"}}),
+                &[],
+            ),
             true,
         ),
         tool("ui_inspect", "Inspect the interface", "Inspect the connected desktop interface; returns a tool error in headless mode.", empty(), true),
@@ -946,8 +949,13 @@ fn render_preview(b: &mut dyn Backend, a: &Args) -> Result<ToolResult, String> {
         None => 1024,
         Some(v) => v.as_u64().filter(|v| (1..=4096).contains(v)).ok_or("`max_side` must be an integer in 1..4096")?,
     };
+    let index = match a.get("artboard") {
+        None => 0,
+        Some(v) => v.as_u64().ok_or("`artboard` must be a 0-based artboard index")?,
+    };
     let doc = b.call("document.inspect", json!({"depth":0}))?;
-    let board = doc.get("artboards").and_then(Value::as_array).and_then(|v| v.first()).ok_or("no such artboard")?;
+    let board =
+        doc.get("artboards").and_then(Value::as_array).and_then(|v| v.get(usize::try_from(index).ok()?)).ok_or(format!("no artboard {index}"))?;
     let width = board.get("width").and_then(Value::as_f64).ok_or("artboard has no width")?;
     let height = board.get("height").and_then(Value::as_f64).ok_or("artboard has no height")?;
     if !width.is_finite() || !height.is_finite() || width <= 0.0 || height <= 0.0 {
@@ -959,7 +967,7 @@ fn render_preview(b: &mut dyn Backend, a: &Args) -> Result<ToolResult, String> {
     if width.max(height) * scale > 4096.0 {
         return Err("artboard is too large for a bounded preview".into());
     }
-    let r = b.call("ui.render", json!({"scale":scale}))?;
+    let r = b.call("ui.render", json!({"scale":scale, "artboard": index}))?;
     let encoded = r.get("pngBase64").and_then(Value::as_str).ok_or("renderer returned no image")?;
     let png = vectorcraft_format::base64_decode(encoded).ok_or("renderer returned bad base64")?;
     let img = image::load_from_memory_with_format(&png, image::ImageFormat::Png).map_err(|e| format!("read preview: {e}"))?;

docs/mcp.md

@@ -237,7 +237,7 @@ The older names below remain listed because existing workflows use them.
 | `command_run` | `id`, optional `params`; runs the command through the existing backend |
 | `command_batch` | `steps: [{id, params?}]`, optional `stop_on_error` (default true); returns `completed`, `failed`, `results: [{ok, result\|error}]`. Each edit has its own undo step; failures set `isError`. A param string `"$N.path"` or `"$last.path"` takes a value from an earlier step's result (see `run` below) |
 | `doc_inspect` | Optional `depth`, `childLimit`; same summary as `inspect_document` |
-| `render_preview` | Optional `max_side` (1–4096, default 1024); inline PNG of the first artboard without editing it. Artboards too large to render within the allocation bound return a tool error |
+| `render_preview` | Optional `max_side` (1–4096, default 1024) and `artboard` (0-based, default 0); inline PNG of that artboard without editing it. Artboards too large to render within the allocation bound return a tool error |
 | `ui_inspect`, `ui_screenshot` | Connected desktop state/window capture; tool errors in headless mode |
 
 Every tool declares read-only, destructive, idempotent and open-world hints. File-writing