feat(files): double-click opens text files as a preview in a new block

docs/docs/config.mdx

@@ -94,7 +94,7 @@ wsh editconfig
 | preview:showhiddenfiles              | bool     | set to false to disable showing hidden files in the directory preview (defaults to true)                                                                                                                                                                      |
 | preview:defaultsort <VersionBadge version="v0.14.2" />                 | string   | sets the default sort column for directory preview. `"name"` (default) sorts alphabetically by name ascending; `"modtime"` sorts by last modified time descending (newest first)                                                                               |
 | preview:dirsfirst                    | bool     | list folders before files in the file browser, whatever the sort column or direction (defaults to true) |
-| preview:doubleclickopen              | string   | what double-clicking a file in the file browser does: `"external"` (default) opens it in the OS default application (Windows shows the "Open with" picker if nothing is associated), `"preview"` opens it inside Wave. Remote (SSH/WSL) files are downloaded to a temp folder, opened locally, and uploaded back to the host every time you save them; if the remote file changed since you opened it you are asked before it is overwritten |
+| preview:doubleclickopen              | string   | what double-clicking a file in the file browser does: `"auto"` (default) opens text files (by extension or mimetype) as a preview in a new block and everything else in the OS default application, `"external"` always opens it in the OS default application (Windows shows the "Open with" picker if nothing is associated), `"preview"` opens it inside Wave. Remote (SSH/WSL) files are downloaded to a temp folder, opened locally, and uploaded back to the host every time you save them; if the remote file changed since you opened it you are asked before it is overwritten |
 | preview:externaleditor               | string   | path to the editor used by the "Open in …" file menu item (e.g. `C:\\Program Files\\Notepad++\\notepad++.exe`). When empty, Notepad++ is detected in its standard Windows install location |
 | markdown:fontsize                    | float64  | font size for the normal text when rendering markdown in preview. headers are scaled up from this size, (default 14px)                                                                                                                                        |
 | markdown:fixedfontsize               | float64  | font size for the code blocks when rendering markdown in preview (default is 12px)                                                                                                                                                                            |

frontend/app/view/preview/preview-directory.tsx

@@ -9,7 +9,8 @@ import { TabRpcClient } from "@/app/store/wshrpcutil";
 import { useWaveEnv } from "@/app/waveenv/waveenv";
 import { checkKeyPressed, isCharacterKeyEvent } from "@/util/keyutil";
 import { PLATFORM, PlatformMacOS } from "@/util/platformutil";
-import { addOpenMenuItems, openFileExternally } from "@/util/previewutil";
+import { addOpenMenuItems, openFileExternally, openPreviewInNewBlock } from "@/util/previewutil";
+import { isTextCapableFile } from "@/util/textfiles";
 import { fireAndForget } from "@/util/util";
 import { formatRemoteUri } from "@/util/waveutil";
 import { offset, useDismiss, useFloating, useInteractions } from "@floating-ui/react";
@@ -600,7 +601,7 @@ function TableRow({
     const env = useWaveEnv<PreviewEnv>();
     const dirPath = useAtomValue(model.statFilePath);
     const connection = useAtomValue(model.connection);
-    const doubleClickOpen = useAtomValue(env.getSettingsKeyAtom("preview:doubleclickopen")) ?? "external";
+    const doubleClickOpen = useAtomValue(env.getSettingsKeyAtom("preview:doubleclickopen")) ?? "auto";
 
     const dragItem: DraggedFile = {
         relName: row.getValue("name") as string,
@@ -630,6 +631,14 @@ function TableRow({
             data-rowindex={idx}
             onDoubleClick={() => {
                 const newFileName = row.getValue("path") as string;
+                if (!row.original.isdir && doubleClickOpen === "auto") {
+                    if (isTextCapableFile(row.original.name, row.original.mimetype)) {
+                        openPreviewInNewBlock(newFileName, connection);
+                        return;
+                    }
+                    openFileExternally(newFileName, connection, "default");
+                    return;
+                }
                 if (!row.original.isdir && doubleClickOpen === "external") {
                     openFileExternally(newFileName, connection, "default");
                     return;

frontend/util/previewutil.ts

@@ -15,6 +15,17 @@ export function openFileExternally(path: string, conn: string, mode: OpenExterna
     );
 }
 
+export function openPreviewInNewBlock(path: string, conn: string) {
+    const blockDef: BlockDef = {
+        meta: {
+            view: "preview",
+            file: path,
+            connection: conn,
+        },
+    };
+    fireAndForget(() => createBlock(blockDef));
+}
+
 function addExternalOpenItems(menu: ContextMenuItem[], conn: string, finfo: FileInfo) {
     const remoteSuffix = conn ? " (edit locally)" : "";
     menu.push({
@@ -73,17 +84,7 @@ export function addOpenMenuItems(menu: ContextMenuItem[], conn: string, finfo: F
     if (!finfo.isdir) {
         menu.push({
             label: "Open Preview in New Block",
-            click: () =>
-                fireAndForget(async () => {
-                    const blockDef: BlockDef = {
-                        meta: {
-                            view: "preview",
-                            file: finfo.path,
-                            connection: conn,
-                        },
-                    };
-                    await createBlock(blockDef);
-                }),
+            click: () => openPreviewInNewBlock(finfo.path, conn),
         });
     }
     menu.push({

frontend/util/textfiles.test.ts

@@ -0,0 +1,31 @@
+// Copyright 2026, Command Line Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+import { describe, expect, it } from "vitest";
+import { isTextCapableFile } from "./textfiles";
+
+describe("isTextCapableFile", () => {
+    it("matches by extension even when the mimetype is wrong", () => {
+        expect(isTextCapableFile("main.ts", "video/mp2t")).toBe(true);
+        expect(isTextCapableFile("main.go", "application/octet-stream")).toBe(true);
+        expect(isTextCapableFile("README.MD", "")).toBe(true);
+    });
+
+    it("matches dotfiles and well-known extensionless names", () => {
+        expect(isTextCapableFile(".gitignore", "application/octet-stream")).toBe(true);
+        expect(isTextCapableFile(".env", null)).toBe(true);
+        expect(isTextCapableFile("Makefile", null)).toBe(true);
+    });
+
+    it("falls back to the mimetype", () => {
+        expect(isTextCapableFile("notes.weird", "text/plain; charset=utf-8")).toBe(true);
+        expect(isTextCapableFile("data.bin", "application/json")).toBe(true);
+    });
+
+    it("rejects binaries", () => {
+        expect(isTextCapableFile("photo.png", "image/png")).toBe(false);
+        expect(isTextCapableFile("app.exe", "application/octet-stream")).toBe(false);
+        expect(isTextCapableFile("archive.zip", "application/zip")).toBe(false);
+        expect(isTextCapableFile("noext", null)).toBe(false);
+    });
+});

frontend/util/textfiles.ts

@@ -0,0 +1,190 @@
+// Copyright 2026, Command Line Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+// Mimetype sniffing misses many source files (".ts" is sniffed as video/mp2t, ".go" and dotfiles as
+// octet-stream), so the extension list is checked first.
+const TextExtensions = new Set([
+    // plain text and docs
+    "txt",
+    "text",
+    "md",
+    "markdown",
+    "mdx",
+    "rst",
+    "adoc",
+    "org",
+    "tex",
+    "log",
+    "nfo",
+    "rtf",
+    // data and config
+    "json",
+    "jsonc",
+    "json5",
+    "jsonl",
+    "ndjson",
+    "yaml",
+    "yml",
+    "toml",
+    "ini",
+    "cfg",
+    "conf",
+    "config",
+    "properties",
+    "env",
+    "xml",
+    "csv",
+    "tsv",
+    "plist",
+    "lock",
+    "editorconfig",
+    "gitignore",
+    "gitattributes",
+    "dockerignore",
+    "npmrc",
+    "prettierrc",
+    "eslintrc",
+    "babelrc",
+    // web
+    "html",
+    "htm",
+    "xhtml",
+    "css",
+    "scss",
+    "sass",
+    "less",
+    "svg",
+    "vue",
+    "svelte",
+    "astro",
+    // scripting and shell
+    "sh",
+    "bash",
+    "zsh",
+    "fish",
+    "ps1",
+    "psm1",
+    "bat",
+    "cmd",
+    "awk",
+    "sed",
+    // languages
+    "js",
+    "mjs",
+    "cjs",
+    "jsx",
+    "ts",
+    "mts",
+    "cts",
+    "tsx",
+    "py",
+    "pyi",
+    "rb",
+    "php",
+    "pl",
+    "pm",
+    "lua",
+    "r",
+    "go",
+    "rs",
+    "c",
+    "h",
+    "cc",
+    "cpp",
+    "cxx",
+    "hpp",
+    "hh",
+    "hxx",
+    "cs",
+    "java",
+    "kt",
+    "kts",
+    "scala",
+    "swift",
+    "m",
+    "mm",
+    "dart",
+    "ex",
+    "exs",
+    "erl",
+    "hs",
+    "clj",
+    "cljs",
+    "fs",
+    "fsx",
+    "vb",
+    "groovy",
+    "gradle",
+    "zig",
+    "nim",
+    "jl",
+    "sql",
+    "graphql",
+    "gql",
+    "proto",
+    "tf",
+    "tfvars",
+    "hcl",
+    "nix",
+    "cmake",
+    "make",
+    "mk",
+    "dockerfile",
+    "vim",
+    "diff",
+    "patch",
+    "service",
+    "timer",
+    "desktop",
+]);
+
+// extensionless names that are always text
+const TextFileNames = new Set([
+    "makefile",
+    "dockerfile",
+    "readme",
+    "license",
+    "licence",
+    "changelog",
+    "authors",
+    "contributing",
+    "codeowners",
+    "procfile",
+    "gemfile",
+    "rakefile",
+    "vagrantfile",
+    "jenkinsfile",
+    "taskfile",
+]);
+
+function hasTextMimetype(mimeType: string): boolean {
+    if (mimeType == null) {
+        return false;
+    }
+    return (
+        mimeType.startsWith("text/") ||
+        mimeType.includes("json") ||
+        mimeType.includes("yaml") ||
+        mimeType.includes("toml") ||
+        mimeType.includes("xml") ||
+        mimeType.includes("javascript") ||
+        mimeType.includes("typescript") ||
+        mimeType === "application/x-sh" ||
+        mimeType === "application/sql" ||
+        mimeType === "application/x-python" ||
+        mimeType === "application/x-ruby"
+    );
+}
+
+export function isTextCapableFile(name: string, mimeType: string): boolean {
+    const base = (name ?? "").split(/[\\/]/).pop().toLowerCase();
+    if (TextFileNames.has(base)) {
+        return true;
+    }
+    const dot = base.lastIndexOf(".");
+    const ext = dot >= 0 ? base.slice(dot + 1) : "";
+    if (ext !== "" && TextExtensions.has(ext)) {
+        return true;
+    }
+    return hasTextMimetype(mimeType);
+}

pkg/wconfig/defaultconfig/settings.json

@@ -49,5 +49,5 @@
     "waveai:defaultmode": "waveai@balanced",
     "preview:defaultsort": "name",
     "preview:dirsfirst": true,
-    "preview:doubleclickopen": "external"
+    "preview:doubleclickopen": "auto"
 }

pkg/wconfig/settingsconfig.go

@@ -142,7 +142,7 @@ type SettingsType struct {
 	PreviewShowHiddenFiles *bool  `json:"preview:showhiddenfiles,omitempty"`
 	PreviewDefaultSort     string `json:"preview:defaultsort,omitempty" jsonschema:"enum=name,enum=modtime"`
 	PreviewDirsFirst       *bool  `json:"preview:dirsfirst,omitempty"`
-	PreviewDoubleClickOpen string `json:"preview:doubleclickopen,omitempty" jsonschema:"enum=external,enum=preview"`
+	PreviewDoubleClickOpen string `json:"preview:doubleclickopen,omitempty" jsonschema:"enum=auto,enum=external,enum=preview"`
 	PreviewExternalEditor  string `json:"preview:externaleditor,omitempty"`
 
 	TabPreset       string `json:"tab:preset,omitempty"`

schema/settings.json

@@ -260,6 +260,7 @@
         "preview:doubleclickopen": {
           "type": "string",
           "enum": [
+            "auto",
             "external",
             "preview"
           ]