fix(cli): add save command parity

crates/op-cli/src/main.rs

@@ -191,6 +191,10 @@ fn command_from_positionals(positionals: &[String], flags: &Flags) -> Result<Com
                 .unwrap_or_default();
             tool_call("open_document", args)
         }
+        "save" => {
+            let file_path = required_pos(positionals, 1, "Usage: op save <file.op>")?;
+            tool_call("save_document", vec![pair("filePath", file_path)])
+        }
         "get" => map_get(flags),
         "selection" => tool_call("get_selection", vec![]),
         "insert" => map_insert(positionals),
@@ -222,7 +226,7 @@ fn command_from_positionals(positionals: &[String], flags: &Flags) -> Result<Com
         "codegen:plan" | "codegen:submit" | "codegen:assemble" | "codegen:clean" => {
             codegen_cli::map_codegen(positionals, flags)
         }
-        "start" | "stop" | "save" | "install" | "uninstall" => Err(format!(
+        "start" | "stop" | "install" | "uninstall" => Err(format!(
             "TS command {:?} is not implemented by the Rust HTTP MCP CLI yet",
             positionals[0]
         )),

crates/op-cli/src/tests.rs

@@ -155,6 +155,18 @@ fn parse_args_maps_ts_open_to_open_document() {
     );
 }
 
+#[test]
+fn parse_args_maps_ts_save_to_save_document_tool() {
+    let p = parse_args(&["save".to_string(), "/tmp/copy.op".to_string()]).expect("parse save");
+    assert_eq!(
+        p.command,
+        Command::ToolCall {
+            tool: "save_document".to_string(),
+            args: vec![("filePath".to_string(), "/tmp/copy.op".to_string())],
+        }
+    );
+}
+
 #[test]
 fn parse_args_maps_ts_page_list_alias_to_rust_tool() {
     let args = vec!["page".to_string(), "list".to_string()];

crates/op-host-desktop/src/mcp_serve.rs

@@ -1,10 +1,8 @@
 //! Stdio MCP server mode for the desktop binary.
 //!
-//! When `openpencil-desktop --mcp <path>` is invoked, we skip the
-//! winit event loop and run a JSON-RPC stdio server against the
-//! `.op` file at `<path>`. External CLIs (Claude Code / Codex /
-//! Gemini / Copilot) can spawn the binary in this mode to drive
-//! the Rust editor exactly the way they drive TS pen-mcp today.
+//! `openpencil-desktop --mcp <path>` runs JSON-RPC stdio against a
+//! `.op` file. External CLIs can spawn this mode to drive the Rust
+//! editor the way they drive TS pen-mcp today.
 //! The server backs the `.op` file with an `op_editor_core::
 //! EditorState` (the canonical `jian_ops_schema::PenDocument`), not
 //! the old shell-core `Document`. Loading a `.op` into a `PenDocument`
@@ -41,18 +39,19 @@ use op_mcp::{
     redo_snapshot, remove_node_effect_snapshot, remove_page_snapshot, rename_component_snapshot,
     rename_page_snapshot, rename_variable_snapshot, reorder_page_snapshot,
     reorder_selected_snapshot, replace_all_matching_properties_snapshot, replace_node_snapshot,
-    run_stdio_with_applier, save_theme_preset_snapshot, search_all_unique_properties_snapshot,
-    selection_snapshot, set_active_axis_value_snapshot, set_active_page_snapshot,
-    set_active_tool_snapshot, set_design_md_snapshot, set_ellipse_arc_snapshot,
-    set_node_collapsed_snapshot, set_node_corner_radius_snapshot, set_node_fill_hex_snapshot,
-    set_node_flip_snapshot, set_node_font_size_snapshot, set_node_font_weight_snapshot,
-    set_node_hidden_snapshot, set_node_locked_snapshot, set_node_name_snapshot,
-    set_node_rotation_snapshot, set_node_stroke_hex_snapshot, set_node_stroke_width_snapshot,
-    set_node_text_snapshot, set_selection_set_snapshot, set_selection_snapshot,
-    set_themes_snapshot, set_variable_boolean_snapshot, set_variable_color_snapshot,
-    set_variable_number_snapshot, set_variable_string_snapshot, set_variables_snapshot,
-    set_viewport_snapshot, snapshot_layout_snapshot, toggle_node_selection_snapshot, undo_snapshot,
-    ungroup_selected_snapshot, update_node_snapshot, ToolRegistry,
+    run_stdio_with_applier, save_document_snapshot, save_theme_preset_snapshot,
+    search_all_unique_properties_snapshot, selection_snapshot, set_active_axis_value_snapshot,
+    set_active_page_snapshot, set_active_tool_snapshot, set_design_md_snapshot,
+    set_ellipse_arc_snapshot, set_node_collapsed_snapshot, set_node_corner_radius_snapshot,
+    set_node_fill_hex_snapshot, set_node_flip_snapshot, set_node_font_size_snapshot,
+    set_node_font_weight_snapshot, set_node_hidden_snapshot, set_node_locked_snapshot,
+    set_node_name_snapshot, set_node_rotation_snapshot, set_node_stroke_hex_snapshot,
+    set_node_stroke_width_snapshot, set_node_text_snapshot, set_selection_set_snapshot,
+    set_selection_snapshot, set_themes_snapshot, set_variable_boolean_snapshot,
+    set_variable_color_snapshot, set_variable_number_snapshot, set_variable_string_snapshot,
+    set_variables_snapshot, set_viewport_snapshot, snapshot_layout_snapshot,
+    toggle_node_selection_snapshot, undo_snapshot, ungroup_selected_snapshot, update_node_snapshot,
+    ToolRegistry,
 };
 
 /// Load a `.op` file into an `EditorState`. The `.op` format is plain
@@ -373,6 +372,7 @@ fn rebuild_registry(doc: &EditorState) -> ToolRegistry {
         r.register(Box::new(tool));
     }
     r.register(Box::new(open_document_snapshot(doc)));
+    r.register(Box::new(save_document_snapshot(doc)));
     r.register(Box::new(document_info_snapshot(doc)));
     r.register(Box::new(selection_snapshot(doc)));
     r.register(Box::new(get_node_snapshot(doc)));
@@ -679,6 +679,7 @@ fn tools_list_response(id_raw: &str, state: &EditorState) -> String {
 const TOOL_SCHEMAS: &[&str] = &[
     // --- read tools ---
     r#"{"name":"open_document","description":"Connect to the current Rust MCP document and return metadata, context summary, and design prompt. filePath is accepted for TS CLI compatibility; the Rust server remains bound to the document it was started with.","inputSchema":{"type":"object","properties":{"filePath":{"type":"string","description":"Accepted for TS compatibility; use live://canvas/current server document"}}}}"#,
+    r#"{"name":"save_document","description":"Save the current Rust MCP document snapshot to a .op file. Used by the Rust HTTP CLI to match TS `op save`.","inputSchema":{"type":"object","properties":{"filePath":{"type":"string","description":"Target .op file path"}},"required":["filePath"]}}"#,
     r#"{"name":"get_document_info","description":"Summarize the open document (page count, active page, etc).","inputSchema":{"type":"object","properties":{},"additionalProperties":false}}"#,
     r#"{"name":"get_selection","description":"Return the current selection state (ids, count).","inputSchema":{"type":"object","properties":{},"additionalProperties":false}}"#,
     r#"{"name":"get_node","description":"Read a node by id with depth-limited descendants.","inputSchema":{"type":"object","properties":{"node_id":{"type":"string","description":"u64 node id"}},"required":["node_id"]}}"#,

crates/op-host-desktop/src/mcp_serve/tests.rs

@@ -57,7 +57,7 @@ fn tools_list_response_includes_all_registered_tools() {
     // TOOL_SCHEMAS without being added to the list below.
     assert_eq!(
         TOOL_SCHEMAS.len(),
-        105,
+        106,
         "tools/list catalog count must match the registered tools — add the new tool to this test"
     );
     // Production catalog excludes debug tools (we removed the
@@ -90,6 +90,7 @@ fn tools_list_response_includes_all_registered_tools() {
     for name in [
         "get_document_info",
         "open_document",
+        "save_document",
         "get_selection",
         "get_node",
         "list_pages",

crates/op-mcp/src/document_save.rs

@@ -0,0 +1,55 @@
+//! Document save tool used by the Rust HTTP CLI transport.
+
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+
+use op_editor_core::EditorState;
+
+use super::{McpTool, ToolErrorCode, ToolOutcome};
+
+pub struct SaveDocument {
+    document_json: String,
+}
+
+impl McpTool for SaveDocument {
+    fn name(&self) -> &str {
+        "save_document"
+    }
+
+    fn call(&self, args: &BTreeMap<String, String>) -> ToolOutcome {
+        let Some(path) = args.get("filePath").filter(|path| !path.trim().is_empty()) else {
+            return ToolOutcome::Err(
+                ToolErrorCode::MissingArgument,
+                "filePath is required".into(),
+            );
+        };
+        let path = resolve_path(path);
+        if let Err(e) = std::fs::write(&path, &self.document_json) {
+            return ToolOutcome::Err(
+                ToolErrorCode::ToolFailed,
+                format!("save document failed: {e}"),
+            );
+        }
+        let mut out = BTreeMap::new();
+        out.insert("ok".into(), "true".into());
+        out.insert("filePath".into(), path.display().to_string());
+        ToolOutcome::Ok(out)
+    }
+}
+
+pub fn save_document_snapshot(state: &EditorState) -> SaveDocument {
+    SaveDocument {
+        document_json: serde_json::to_string(&state.doc).unwrap_or_else(|_| "{}".into()),
+    }
+}
+
+fn resolve_path(raw: &str) -> PathBuf {
+    let path = PathBuf::from(raw);
+    if path.is_absolute() {
+        path
+    } else {
+        std::env::current_dir()
+            .unwrap_or_else(|_| PathBuf::from("."))
+            .join(path)
+    }
+}

crates/op-mcp/src/document_save_tests.rs

@@ -0,0 +1,57 @@
+//! Document save tool tests.
+
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+
+use super::test_fixtures::sample;
+use super::{save_document_snapshot, McpTool, ToolErrorCode, ToolOutcome};
+
+#[test]
+fn save_document_writes_current_pen_document_to_target_path() {
+    let state = sample();
+    let dir = temp_dir("save-document");
+    std::fs::create_dir_all(&dir).expect("temp dir");
+    let out_path = dir.join("copy.op");
+
+    let tool = save_document_snapshot(&state);
+    let mut args = BTreeMap::new();
+    args.insert("filePath".into(), out_path.display().to_string());
+
+    match tool.call(&args) {
+        ToolOutcome::Ok(out) => {
+            assert_eq!(out.get("ok"), Some(&"true".to_string()));
+            assert_eq!(out.get("filePath"), Some(&out_path.display().to_string()));
+            let saved: serde_json::Value =
+                serde_json::from_str(&std::fs::read_to_string(&out_path).expect("saved document"))
+                    .expect("saved document json");
+            assert_eq!(saved["version"], state.doc.version);
+            assert!(saved["children"].is_array() || saved["pages"].is_array());
+        }
+        other => panic!("expected save ok, got {other:?}"),
+    }
+
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn save_document_requires_file_path() {
+    let tool = save_document_snapshot(&sample());
+    match tool.call(&BTreeMap::new()) {
+        ToolOutcome::Err(code, message) => {
+            assert_eq!(code, ToolErrorCode::MissingArgument);
+            assert!(message.contains("filePath"));
+        }
+        other => panic!("expected missing argument, got {other:?}"),
+    }
+}
+
+fn temp_dir(label: &str) -> PathBuf {
+    let nanos = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .expect("clock")
+        .as_nanos();
+    std::env::temp_dir().join(format!(
+        "openpencil-document-save-{label}-{}-{nanos}",
+        std::process::id()
+    ))
+}

crates/op-mcp/src/lib.rs

@@ -41,6 +41,9 @@ mod design_md_tools_tests;
 pub mod design_prompt;
 #[cfg(test)]
 mod design_prompt_tests;
+pub mod document_save;
+#[cfg(test)]
+mod document_save_tests;
 pub mod element_tools;
 pub mod extra_read_tools;
 #[cfg(test)]
@@ -126,6 +129,7 @@ pub use design_md_tools::{
     GetDesignMd, SetDesignMd,
 };
 pub use design_prompt::{get_design_prompt_snapshot, GetDesignPrompt};
+pub use document_save::{save_document_snapshot, SaveDocument};
 pub use extra_read_tools::{get_node_children_snapshot, ChildRecord, GetNodeChildren};
 pub use json_serializer::response_to_json;
 pub use node_attr_tools::{