diff --git a/docs/32-md文件关联.md b/docs/32-md文件关联.md
new file mode 100644
index 0000000..49fa7e5
--- /dev/null
+++ b/docs/32-md文件关联.md
@@ -0,0 +1,48 @@
+# docs/32 .md 文件关联（默认打开方式）
+
+2026-11-15 用户要求：「支持设置 md 格式的打开方式」。目标：在资源
+管理器双击 .md 能用本程序打开，且程序内能发起设置。三条链路：
+
+## 1. 安装器注册（tauri.conf.json）
+
+`bundle.fileAssociations` 增加 md/markdown（name=NewMarkdown，
+role=Editor）。NSIS/MSI 安装时写入关联注册信息，本程序出现在
+「打开方式」候选里，用户在打开方式对话框勾「始终」或在系统设置
+里选一次即设为默认。注意：需用新版安装包**重装一次**才生效。
+
+## 2. 程序内发起设置（文件菜单）
+
+「文件 → 设为 .md 默认打开方式…」（仅桌面模式）：Rust 命令
+`register_file_association` 用 reg.exe 写当前用户注册表（免管理员）：
+ProgID `NewMarkdown.md`（类型名、打开命令 `"<exe>" "%1"`、图标）、
+.md/.markdown 的 OpenWithProgids、Applications 的 SupportedTypes 与
+打开命令——便携版/未走安装器的场景也能注册，且指向当前 exe 路径。
+写完后打开 `ms-settings:defaultapps` 并弹窗说明：**Windows 不允许
+程序直接抢占默认**（UserChoice 带哈希校验），最后一步必须由用户
+在设置里把 .md 选为 new-markdown，只需一次。
+
+## 3. 双击真正打开文件
+
+- 单实例插件（tauri-plugin-single-instance，须最先注册）：程序已
+  运行时双击第二个文件不再起新进程，第二实例的参数经回调转入
+  待打开队列并发 `pending-open-files` 事件，同时聚焦主窗口。
+- 冷启动：setup 里读 `std::env::args`，与第二实例共用纯函数
+  `md_files_from_args` 过滤（跳过开关项、只收存在的 .md/.markdown），
+  存入 `PendingOpen` 队列。
+- 前端：新命令 `take_pending_open_files` 取走队列并逐个 openPath。
+  主窗口在启动流程末尾拉一次（冷启动），并监听事件随时拉（热转
+  发）。**只由 label=main 的窗口消费**：子窗口（?file= 打开的）跑
+  同一套 App，不拦会把文件抢到子窗口里。
+
+命令总数 31 → 33。
+
+## 验证
+
+- 参数过滤纯函数抽入独立 crate 实测：开关项/.txt/不存在的文件被
+  排除，.md 与 .markdown 存在文件入选。
+- rustfmt 语法解析通过；命令数对账 33=33；tsc 0；vitest 全过
+  （InfoModal 新增 1 例）；生产构建通过。
+- 沙箱验不了（待真机）：Windows 完整构建（含单实例插件与
+  cfg(windows) 的 reg.exe 分支）、安装包关联注册实效、双击冷启动
+  打开、已运行双击第二个文件转发到主窗口、菜单项注册后在系统
+  设置里选默认全流程。
diff --git a/src-tauri/Cargo.lock b/src-tauri/Cargo.lock
index b55d7c4..7fcce34 100644
--- a/src-tauri/Cargo.lock
+++ b/src-tauri/Cargo.lock
@@ -59,6 +59,137 @@ version = "1.0.104"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "330a5ed07fa54e4702c9d6c4174f74427fc0ef6e214bbd677ae50a5099946470"
 
+[[package]]
+name = "async-broadcast"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "435a87a52755b8f27fcf321ac4f04b2802e337c8c4872923137471ec39c37532"
+dependencies = [
+ "event-listener",
+ "event-listener-strategy",
+ "futures-core",
+ "pin-project-lite",
+]
+
+[[package]]
+name = "async-channel"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "924ed96dd52d1b75e9c1a3e6275715fd320f5f9439fb5a4a11fa51f4221158d2"
+dependencies = [
+ "concurrent-queue",
+ "event-listener-strategy",
+ "futures-core",
+ "pin-project-lite",
+]
+
+[[package]]
+name = "async-executor"
+version = "1.14.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f426a31126c735126297bc5ea7a521263c9faff4f63ca415267ee625651c4f37"
+dependencies = [
+ "async-task",
+ "concurrent-queue",
+ "fastrand",
+ "futures-lite",
+ "pin-project-lite",
+ "slab",
+]
+
+[[package]]
+name = "async-io"
+version = "2.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "456b8a8feb6f42d237746d4b3e9a178494627745c3c56c6ea55d92ba50d026fc"
+dependencies = [
+ "autocfg",
+ "cfg-if",
+ "concurrent-queue",
+ "futures-io",
+ "futures-lite",
+ "parking",
+ "polling",
+ "rustix",
+ "slab",
+ "windows-sys 0.61.2",
+]
+
+[[package]]
+name = "async-lock"
+version = "3.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0876700b0d007ad25d5508865a4259c3af9af6d296bf663a0d586d0bc3369f6f"
+dependencies = [
+ "event-listener",
+ "event-listener-strategy",
+ "pin-project-lite",
+]
+
+[[package]]
+name = "async-process"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fc50921ec0055cdd8a16de48773bfeec5c972598674347252c0399676be7da75"
+dependencies = [
+ "async-channel",
+ "async-io",
+ "async-lock",
+ "async-signal",
+ "async-task",
+ "blocking",
+ "cfg-if",
+ "event-listener",
+ "futures-lite",
+ "rustix",
+]
+
+[[package]]
+name = "async-recursion"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4f8abc12baad266b1c8cec146854c195b5864b4221d4b2ca7296a7ae82d9e451"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 3.0.10",
+]
+
+[[package]]
+name = "async-signal"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "52b5aaafa020cf5053a01f2a60e8ff5dccf550f0f77ec54a4e47285ac2bab485"
+dependencies = [
+ "async-io",
+ "async-lock",
+ "atomic-waker",
+ "cfg-if",
+ "futures-core",
+ "futures-io",
+ "rustix",
+ "signal-hook-registry",
+ "slab",
+ "windows-sys 0.61.2",
+]
+
+[[package]]
+name = "async-task"
+version = "4.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b75356056920673b02621b35afd0f7dda9306d03c79a30f5c56c44cf256e3de"
+
+[[package]]
+name = "async-trait"
+version = "0.1.92"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "82f6aeea286b8eb4dd3431a1be1b59d290ace00f5bfd8e2a159bc2a05e2c1667"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 3.0.10",
+]
+
 [[package]]
 name = "atk"
 version = "0.18.2"
@@ -175,6 +306,19 @@ dependencies = [
  "objc2",
 ]
 
+[[package]]
+name = "blocking"
+version = "1.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a70e4329df6cb94385eed412ec92375c3cdd8a6e502493d1229b6414e4036dfa"
+dependencies = [
+ "async-channel",
+ "async-task",
+ "futures-io",
+ "futures-lite",
+ "piper",
+]
+
 [[package]]
 name = "brotli"
 version = "9.1.1"
@@ -382,6 +526,15 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "concurrent-queue"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ca0197aee26d1ae37445ee532fefce43251d24cc7c166799f4d46817f1d3973"
+dependencies = [
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "cookie"
 version = "0.18.2"
@@ -785,6 +938,33 @@ dependencies = [
  "simdutf8",
 ]
 
+[[package]]
+name = "endi"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "66b7e2430c6dff6a955451e2cfc438f09cea1965a9d6f87f7e3b90decc014099"
+
+[[package]]
+name = "enumflags2"
+version = "0.7.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1027f7680c853e056ebcec683615fb6fbbc07dbaa13b4d5d9442b146ded4ecef"
+dependencies = [
+ "enumflags2_derive",
+ "serde",
+]
+
+[[package]]
+name = "enumflags2_derive"
+version = "0.7.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "67c78a4d8fdf9953a5c9d458f9efe940fd97a0cab0941c075a813ac594733827"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
 [[package]]
 name = "equivalent"
 version = "1.0.3"
@@ -802,6 +982,36 @@ dependencies = [
  "typeid",
 ]
 
+[[package]]
+name = "errno"
+version = "0.3.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e35d6e78f4cebb90e51d543db8fe41528851d6deeef6ef21ebd4bfdc1e784776"
+dependencies = [
+ "libc",
+ "windows-sys 0.61.2",
+]
+
+[[package]]
+name = "event-listener"
+version = "5.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a23add41df1562121a9393cb065eab5146a1242410f23a644851e90cfd669d2"
+dependencies = [
+ "parking",
+ "pin-project-lite",
+]
+
+[[package]]
+name = "event-listener-strategy"
+version = "0.5.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8be9f3dfaaffdae2972880079a491a1a8bb7cbed0b8dd7a347f668b4150a3b93"
+dependencies = [
+ "event-listener",
+ "pin-project-lite",
+]
+
 [[package]]
 name = "fallible-iterator"
 version = "0.3.0"
@@ -937,6 +1147,19 @@ version = "0.3.34"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "53c0fa8157de1303bfffdaa1cc2a673bfffb60102f76b0ef4441659124373fed"
 
+[[package]]
+name = "futures-lite"
+version = "2.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f78e10609fe0e0b3f4157ffab1876319b5b0db102a2c60dc4626306dc46b44ad"
+dependencies = [
+ "fastrand",
+ "futures-core",
+ "futures-io",
+ "parking",
+ "pin-project-lite",
+]
+
 [[package]]
 name = "futures-macro"
 version = "0.3.34"
@@ -1314,6 +1537,12 @@ version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
 
+[[package]]
+name = "hermit-abi"
+version = "0.5.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e17592d60ebacc7d5e169f4663c5f84f9161cc90328abcfe8456f41e4dfcb284"
+
 [[package]]
 name = "hex"
 version = "0.4.3"
@@ -1867,6 +2096,12 @@ dependencies = [
  "vcpkg",
 ]
 
+[[package]]
+name = "linux-raw-sys"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32a66949e030da00e8c7d4434b251670a91556f4144941d37452769c25d58a53"
+
 [[package]]
 name = "litemap"
 version = "0.8.3"
@@ -2040,6 +2275,7 @@ dependencies = [
  "tauri",
  "tauri-build",
  "tauri-plugin-dialog",
+ "tauri-plugin-single-instance",
  "trash",
 ]
 
@@ -2295,6 +2531,16 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "04744f49eae99ab78e0d5c0b603ab218f515ea8cfe5a456d7629ad883a3b6e7d"
 
+[[package]]
+name = "ordered-stream"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9aa2b01e1d916879f73a53d01d1d6cee68adbb31d6d9177a8cfce093cced1d50"
+dependencies = [
+ "futures-core",
+ "pin-project-lite",
+]
+
 [[package]]
 name = "pango"
 version = "0.18.3"
@@ -2320,6 +2566,12 @@ dependencies = [
  "system-deps",
 ]
 
+[[package]]
+name = "parking"
+version = "2.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f38d5652c16fde515bb1ecef450ab0f6a219d619a7274976324d5e377f7dceba"
+
 [[package]]
 name = "parking_lot"
 version = "0.12.5"
@@ -2461,6 +2713,17 @@ version = "0.2.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a89322df9ebe1c1578d689c92318e070967d1042b512afbe49518723f4e6d5cd"
 
+[[package]]
+name = "piper"
+version = "0.2.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c835479a4443ded371d6c535cbfd8d31ad92c5d23ae9770a61bc155e4992a3c1"
+dependencies = [
+ "atomic-waker",
+ "fastrand",
+ "futures-io",
+]
+
 [[package]]
 name = "pkg-config"
 version = "0.3.34"
@@ -2493,6 +2756,20 @@ dependencies = [
  "miniz_oxide 0.8.9",
 ]
 
+[[package]]
+name = "polling"
+version = "3.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5d0e4f59085d47d8241c88ead0f274e8a0cb551f3625263c05eb8dd897c34218"
+dependencies = [
+ "cfg-if",
+ "concurrent-queue",
+ "hermit-abi",
+ "pin-project-lite",
+ "rustix",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "portable-atomic"
 version = "1.15.0"
@@ -2920,6 +3197,19 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "rustix"
+version = "1.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e5e76742e5294153d4dde1207dbec5bdd81eef6fabdc0d2118babadabfd858aa"
+dependencies = [
+ "bitflags 2.13.2",
+ "errno",
+ "libc",
+ "linux-raw-sys",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "rustls"
 version = "0.23.46"
@@ -3276,6 +3566,16 @@ version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8fadd59c855ef2080decdef8ff161eb6661b86933c9d82e5ba29dc602a55aba"
 
+[[package]]
+name = "signal-hook-registry"
+version = "1.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4db69cba1110affc0e9f7bcd48bbf87b3f4fc7c61fc9155afd4c469eb3d6c1b"
+dependencies = [
+ "errno",
+ "libc",
+]
+
 [[package]]
 name = "simd-adler32"
 version = "0.3.10"
@@ -3742,6 +4042,22 @@ dependencies = [
  "url",
 ]
 
+[[package]]
+name = "tauri-plugin-single-instance"
+version = "2.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "726b6da0dd5bd1344f84f4108a622c07d01923baacb5c803a605189672c5352f"
+dependencies = [
+ "serde",
+ "serde_json",
+ "tauri",
+ "thiserror 2.0.21",
+ "tokio",
+ "tracing",
+ "windows-sys 0.61.2",
+ "zbus",
+]
+
 [[package]]
 name = "tauri-runtime"
 version = "2.12.2"
@@ -3841,6 +4157,19 @@ dependencies = [
  "toml 1.2.1+spec-1.1.0",
 ]
 
+[[package]]
+name = "tempfile"
+version = "3.27.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd"
+dependencies = [
+ "fastrand",
+ "getrandom 0.4.3",
+ "once_cell",
+ "rustix",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "tendril"
 version = "0.5.1"
@@ -4121,9 +4450,21 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "63e71662fa4b2a2c3a26f570f037eb95bb1f85397f3cd8076caed2f026a6d100"
 dependencies = [
  "pin-project-lite",
+ "tracing-attributes",
  "tracing-core",
 ]
 
+[[package]]
+name = "tracing-attributes"
+version = "0.1.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7490cfa5ec963746568740651ac6781f701c9c5ea257c58e057f3ba8cf69e8da"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
 [[package]]
 name = "tracing-core"
 version = "0.1.36"
@@ -4192,6 +4533,17 @@ version = "1.20.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b6f5e870be6c3b371b77fe0ee0bafb859fa4964b4404c27de1d380043c4dda20"
 
+[[package]]
+name = "uds_windows"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f2f6fb2847f6742cd76af783a2a2c49e9375d0a111c7bef6f71cd9e738c72d6e"
+dependencies = [
+ "memoffset",
+ "tempfile",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.27"
@@ -4980,6 +5332,76 @@ dependencies = [
  "synstructure",
 ]
 
+[[package]]
+name = "zbus"
+version = "5.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5db4be7c075cb421e4b7ee645541604239bd243ba7c357511f4ff3a74b555907"
+dependencies = [
+ "async-broadcast",
+ "async-executor",
+ "async-io",
+ "async-lock",
+ "async-process",
+ "async-recursion",
+ "async-task",
+ "async-trait",
+ "blocking",
+ "enumflags2",
+ "event-listener",
+ "futures-core",
+ "futures-lite",
+ "hex",
+ "libc",
+ "ordered-stream",
+ "rustix",
+ "serde",
+ "serde_repr",
+ "tracing",
+ "uds_windows",
+ "uuid",
+ "windows-sys 0.61.2",
+ "winnow 1.0.5",
+ "zbus_macros",
+ "zbus_names",
+ "zvariant",
+]
+
+[[package]]
+name = "zbus_macros"
+version = "5.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2990635d09ade6df1868f72f8cac69a876a90981e8bd3c40b1be413f8dc88f40"
+dependencies = [
+ "proc-macro-crate 3.5.0",
+ "proc-macro2",
+ "quote",
+ "syn 3.0.10",
+ "zbus_names",
+ "zvariant",
+ "zvariant_utils",
+]
+
+[[package]]
+name = "zbus_names"
+version = "4.3.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "812a12be4ead7a59e18ea8f047d08add0066b73bc62fc1467066a2472ae088dd"
+dependencies = [
+ "serde",
+ "winnow 1.0.5",
+ "zvariant",
+]
+
+[[package]]
+name = "zcheapstr"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "939f186d9ecebe044315a5cb6d6f78568bbc21152adc954d5a0c2f58bdbc9920"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "zerocopy"
 version = "0.8.63"
@@ -5071,3 +5493,44 @@ name = "zmij"
 version = "1.0.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "29666d0abbfad1e3dc4dcf6144730dd3a3ab225bbbdac83319345b1b44ccfc1b"
+
+[[package]]
+name = "zvariant"
+version = "5.15.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "80bf6d6cd6a4b601acb64cfb8284cdc643fcfa75ef26ae3c46ec8aa4e8a1fbb7"
+dependencies = [
+ "endi",
+ "enumflags2",
+ "serde",
+ "winnow 1.0.5",
+ "zcheapstr",
+ "zvariant_derive",
+ "zvariant_utils",
+]
+
+[[package]]
+name = "zvariant_derive"
+version = "5.15.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef2672456ba1cb54b5eaec136e63135b3c7495fb938e53b28a62e633496d486d"
+dependencies = [
+ "proc-macro-crate 3.5.0",
+ "proc-macro2",
+ "quote",
+ "syn 3.0.10",
+ "zvariant_utils",
+]
+
+[[package]]
+name = "zvariant_utils"
+version = "4.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bad0294361a320b694a328460dc73add56c306150f5cb6bfafc44446120008a3"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "serde",
+ "syn 3.0.10",
+ "winnow 1.0.5",
+]
diff --git a/src-tauri/Cargo.toml b/src-tauri/Cargo.toml
index b0bee22..f345ee7 100644
--- a/src-tauri/Cargo.toml
+++ b/src-tauri/Cargo.toml
@@ -14,6 +14,7 @@ tauri-build = { version = "2", features = [] }
 [dependencies]
 tauri = { version = "2", features = [] }
 tauri-plugin-dialog = "2"
+tauri-plugin-single-instance = "2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 encoding_rs = "0.8"
diff --git a/src-tauri/src/commands.rs b/src-tauri/src/commands.rs
index f05c7d6..bf1cb36 100644
--- a/src-tauri/src/commands.rs
+++ b/src-tauri/src/commands.rs
@@ -941,6 +941,76 @@ pub async fn s3_upload_image(
         .map_err(|e| format!("上传任务失败：{e}"))?
 }
 
+/// 取走待打开文件队列（docs/32）：启动参数/第二实例双击转来的 .md 文件。
+#[tauri::command]
+pub fn take_pending_open_files(state: tauri::State<'_, crate::PendingOpen>) -> Vec<String> {
+    match state.0.lock() {
+        Ok(mut queue) => std::mem::take(&mut *queue),
+        Err(_) => Vec::new(),
+    }
+}
+
+/// 把本程序注册为 .md/.markdown 的候选打开方式（docs/32），并打开 Windows
+/// 「默认应用」设置页让用户确认。Windows 不允许程序直接抢占默认（UserChoice
+/// 带校验），应用能做的是注册候选 + 引导用户点一次。
+#[tauri::command]
+pub async fn register_file_association() -> Result<String, String> {
+    tauri::async_runtime::spawn_blocking(register_file_association_impl)
+        .await
+        .map_err(|e| format!("注册任务失败：{e}"))?
+}
+
+#[cfg(not(windows))]
+fn register_file_association_impl() -> Result<String, String> {
+    Err("文件关联设置仅支持 Windows。".into())
+}
+
+#[cfg(windows)]
+fn register_file_association_impl() -> Result<String, String> {
+    use std::os::windows::process::CommandExt;
+    use std::process::Command;
+    const CREATE_NO_WINDOW: u32 = 0x0800_0000;
+    let exe = std::env::current_exe().map_err(|e| format!("无法定位程序位置：{e}"))?;
+    let exe_s = exe.to_string_lossy().to_string();
+    let exe_name = exe
+        .file_name()
+        .map(|n| n.to_string_lossy().to_string())
+        .unwrap_or_else(|| "new-markdown.exe".into());
+    let prog_id = "NewMarkdown.md";
+    let open_cmd = format!("\"{exe_s}\" \"%1\"");
+    let mut failures: Vec<String> = Vec::new();
+    let mut reg = |args: &[&str]| {
+        match Command::new("reg.exe")
+            .args(args)
+            .creation_flags(CREATE_NO_WINDOW)
+            .status()
+        {
+            Ok(st) if st.success() => {}
+            Ok(st) => failures.push(format!("reg {:?} 退出码 {}", args.get(1), st.code().unwrap_or(-1))),
+            Err(e) => failures.push(format!("reg 执行失败：{e}")),
+        }
+    };
+    // ProgID：类型名、打开命令、图标
+    reg(&["add", &format!(r"HKCU\Software\Classes\{prog_id}"), "/ve", "/d", "Markdown 文档", "/f"]);
+    reg(&["add", &format!(r"HKCU\Software\Classes\{prog_id}\shell\open\command"), "/ve", "/d", &open_cmd, "/f"]);
+    reg(&["add", &format!(r"HKCU\Software\Classes\{prog_id}\DefaultIcon"), "/ve", "/d", &format!("\"{exe_s}\",0"), "/f"]);
+    for ext in [".md", ".markdown"] {
+        // 扩展名的候选列表 + 应用的 SupportedTypes（出现在「打开方式」里）
+        reg(&["add", &format!(r"HKCU\Software\Classes\{ext}\OpenWithProgids"), "/v", prog_id, "/t", "REG_SZ", "/d", "", "/f"]);
+        reg(&["add", &format!(r"HKCU\Software\Classes\Applications\{exe_name}\SupportedTypes"), "/v", ext, "/t", "REG_SZ", "/d", "", "/f"]);
+    }
+    reg(&["add", &format!(r"HKCU\Software\Classes\Applications\{exe_name}\shell\open\command"), "/ve", "/d", &open_cmd, "/f"]);
+    if !failures.is_empty() {
+        return Err(format!("注册表写入失败：{}", failures.join("；")));
+    }
+    // 打开系统「默认应用」设置，用户在那里把 .md 选成本程序（只需一次）
+    let _ = Command::new("explorer.exe")
+        .arg("ms-settings:defaultapps")
+        .creation_flags(CREATE_NO_WINDOW)
+        .spawn();
+    Ok("已把 new-markdown 注册为 .md / .markdown 的候选打开方式，并打开了 Windows「默认应用」设置。请在设置里找到 .md，把默认应用选为 new-markdown（Windows 要求手动确认一次）。".into())
+}
+
 #[tauri::command]
 pub async fn s3_upload_base64(
     config: crate::s3::S3Config,
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 58a06d5..a2b09a1 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -4,11 +4,28 @@ mod search;
 mod storage;
 
 use std::sync::Mutex;
-use tauri::Manager;
+use tauri::{Emitter, Manager};
 
 /// 应用数据库句柄（阶段 4）：连接在启动时打开并建表，命令层经 State 访问。
 pub struct AppDb(pub Mutex<rusqlite::Connection>);
 
+/// 待打开文件队列（docs/32）：启动参数与第二实例转发的 .md 文件先存这里，
+/// 前端就绪后经 take_pending_open_files 命令取走打开。
+pub struct PendingOpen(pub Mutex<Vec<String>>);
+
+/// 从命令行参数里挑出要打开的 Markdown 文件：跳过开关项，只收扩展名
+/// .md/.markdown 且确实存在的文件。
+pub fn md_files_from_args<I: IntoIterator<Item = String>>(args: I) -> Vec<String> {
+    args.into_iter()
+        .filter(|a| !a.starts_with('-'))
+        .filter(|a| {
+            let lower = a.to_lowercase();
+            (lower.ends_with(".md") || lower.ends_with(".markdown"))
+                && std::path::Path::new(a).is_file()
+        })
+        .collect()
+}
+
 /// 打开数据库并建表：WAL 降低并发写冲突，busy_timeout 让多开实例的写操作排队而非直接报错。
 fn open_and_init(path: &std::path::Path) -> Result<rusqlite::Connection, String> {
     let conn = rusqlite::Connection::open(path).map_err(|e| e.to_string())?;
@@ -22,6 +39,23 @@ fn open_and_init(path: &std::path::Path) -> Result<rusqlite::Connection, String>
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     tauri::Builder::default()
+        // 单实例必须最先注册：双击第二个 .md 时不再起新进程，把文件转给
+        // 已运行的窗口打开（docs/32）。
+        .plugin(tauri_plugin_single_instance::init(|app, argv, _cwd| {
+            let files = md_files_from_args(argv);
+            if !files.is_empty() {
+                if let Some(state) = app.try_state::<PendingOpen>() {
+                    if let Ok(mut queue) = state.0.lock() {
+                        queue.extend(files);
+                    }
+                }
+                let _ = app.emit("pending-open-files", ());
+            }
+            if let Some(w) = app.get_webview_window("main") {
+                let _ = w.unminimize();
+                let _ = w.set_focus();
+            }
+        }))
         .plugin(tauri_plugin_dialog::init())
         .setup(|app| {
             let data_dir = app.path().app_data_dir().expect("app data dir");
@@ -50,6 +84,9 @@ pub fn run() {
                 }
             };
             app.manage(AppDb(Mutex::new(conn)));
+            // 冷启动参数（双击 .md 打开本程序时，文件路径在这里）
+            let initial = md_files_from_args(std::env::args().skip(1));
+            app.manage(PendingOpen(Mutex::new(initial)));
             Ok(())
         })
         .invoke_handler(tauri::generate_handler![
@@ -70,6 +107,8 @@ pub fn run() {
             commands::s3_upload_image,
             commands::s3_upload_base64,
             commands::s3_test_connection,
+            commands::take_pending_open_files,
+            commands::register_file_association,
             commands::delete_to_trash,
             commands::db_recent_list,
             commands::db_recent_add,
diff --git a/src-tauri/tauri.conf.json b/src-tauri/tauri.conf.json
index 057e181..c353a05 100644
--- a/src-tauri/tauri.conf.json
+++ b/src-tauri/tauri.conf.json
@@ -1 +1 @@
-{"$schema":"https://schema.tauri.app/config/2","app":{"security":{"csp":null},"windows":[{"center":true,"decorations":false,"height":820,"label":"main","minHeight":600,"minWidth":920,"resizable":true,"title":"new-markdown","width":1280,"dragDropEnabled":false}]},"build":{"beforeBuildCommand":"npm run build","beforeDevCommand":"npm run dev","devUrl":"http://localhost:1420","frontendDist":"../dist"},"bundle":{"active":true,"category":"Productivity","windows":{"nsis":{"languages":["SimpChinese"],"displayLanguageSelector":false},"wix":{"language":"zh-CN"}},"icon":["icons/32x32.png","icons/128x128.png","icons/128x128@2x.png","icons/icon.ico","icons/icon.png"],"shortDescription":"Windows Markdown 所见即所得编辑器","targets":["nsis","msi"]},"identifier":"app.newmarkdown.desktop","productName":"new-markdown","version":"0.1.0"}
\ No newline at end of file
+{"$schema":"https://schema.tauri.app/config/2","app":{"security":{"csp":null},"windows":[{"center":true,"decorations":false,"height":820,"label":"main","minHeight":600,"minWidth":920,"resizable":true,"title":"new-markdown","width":1280,"dragDropEnabled":false}]},"build":{"beforeBuildCommand":"npm run build","beforeDevCommand":"npm run dev","devUrl":"http://localhost:1420","frontendDist":"../dist"},"bundle":{"active":true,"category":"Productivity","windows":{"nsis":{"languages":["SimpChinese"],"displayLanguageSelector":false},"wix":{"language":"zh-CN"}},"icon":["icons/32x32.png","icons/128x128.png","icons/128x128@2x.png","icons/icon.ico","icons/icon.png"],"shortDescription":"Windows Markdown 所见即所得编辑器","targets":["nsis","msi"],"fileAssociations":[{"ext":["md","markdown"],"name":"NewMarkdown","description":"Markdown 文档","role":"Editor"}]},"identifier":"app.newmarkdown.desktop","productName":"new-markdown","version":"0.1.0"}
\ No newline at end of file
diff --git a/src/App.tsx b/src/App.tsx
index 6f70efd..add71ac 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -18,7 +18,7 @@ const SourceEditor = lazy(() => import('./components/SourceEditor'))
 import { offsetInMarkdown, type CursorAnchor } from './editor/cursorSync'
 import { insertPlainText, insertLinkText } from './editor/paste'
 import { isImeComposing } from './utils/ime'
-import { ConfirmSaveModal, AboutModal, ShortcutsModal, LinkModal, ErrorModal , EncodingConvertModal, ImageSizeModal, ImageLinkModal } from './components/Modals'
+import { ConfirmSaveModal, AboutModal, ShortcutsModal, LinkModal, ErrorModal , EncodingConvertModal, ImageSizeModal, ImageLinkModal, InfoModal } from './components/Modals'
 import { tabsReducer, createTab, activeTab, isDirty, type DocTab, type TabsState } from './stores/tabs'
 import { countWords, countChars, extractOutline, baseName, isPathInside, type OutlineItem } from './utils/text'
 import { callUndo, callRedo, focusEditor, type CursorInfo } from './editor/editor'
@@ -29,7 +29,7 @@ import {
   pickImageFile, pickAnyFile, pickAndReadWebImage, copyToAssets, saveBytesToAssets, fileToBase64,
   statFile, createTextFile, createDirPath, renamePath, deleteToTrash, revealInExplorer, type DirEntry, type RecoveryEntry,
   pickSaveHtmlFile, pickImportFile, readFileBase64, readBinaryFile, pickAndReadWebImport,
-  gitStatus, gitInitRepo, gitSetRemote, gitSyncNow, s3UploadImage, s3UploadBase64, type GitStatusInfo,
+  gitStatus, gitInitRepo, gitSetRemote, gitSyncNow, s3UploadImage, s3UploadBase64, takePendingOpenFiles, registerFileAssociation, type GitStatusInfo,
 } from './services/platform'
 import * as store from './services/store'
 import { recoveryKey, planRecovery } from './utils/recovery'
@@ -708,11 +708,47 @@ export default function App() {
       // 审计修复：这段原先写在恢复记录的提前 return 之后，无恢复记录时永远执行不到。
       const startupFile = new URLSearchParams(window.location.search).get('file')
       if (!cancelled && startupFile) void openPath(startupFile)
+      // 双击 .md 冷启动：文件路径经启动参数进 Rust 的待打开队列（docs/32）。
+      // 只由主窗口消费——子窗口（?file= 打开的）也在跑同一套启动流程，
+      // 不拦会把队列里的文件抢去自己窗口打开。
+      if (!cancelled && tauriMode) {
+        try {
+          const { getCurrentWindow } = await import('@tauri-apps/api/window')
+          if (getCurrentWindow().label === 'main') {
+            const pending = await takePendingOpenFiles()
+            for (const p of pending) { if (!cancelled) await openPath(p) }
+          }
+        } catch { /* 队列不可用时不影响正常启动 */ }
+      }
     })()
     return () => { cancelled = true }
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [])
 
+  // 第二个文件双击转来时（单实例转发）：Rust 发事件，这里取队列打开（docs/32）
+  useEffect(() => {
+    if (!tauriMode) return
+    let unlisten: (() => void) | undefined
+    let cancelled = false
+    void (async () => {
+      try {
+        const { getCurrentWindow } = await import('@tauri-apps/api/window')
+        if (getCurrentWindow().label !== 'main') return // 只由主窗口消费（理由同冷启动）
+        const { listen } = await import('@tauri-apps/api/event')
+        const un = await listen('pending-open-files', async () => {
+          try {
+            const pending = await takePendingOpenFiles()
+            for (const p of pending) await openPath(p)
+          } catch { /* 同上 */ }
+        })
+        if (cancelled) un()
+        else unlisten = un
+      } catch { /* 事件不可用时退化为仅冷启动打开 */ }
+    })()
+    return () => { cancelled = true; unlisten?.() }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [tauriMode])
+
   useEffect(() => {
     if (workspaceRoot) {
       store.addWorkspace(workspaceRoot)
@@ -1090,6 +1126,8 @@ export default function App() {
   /** 右键图片的「超链接」目标（图片模式链接弹窗）与「调整大小」目标（docs/31） */
   const [imageLinkTarget, setImageLinkTarget] = useState<{ tabId: string; el: HTMLElement; src: string; href: string } | null>(null)
   const [imageSizeTarget, setImageSizeTarget] = useState<{ tabId: string; el: HTMLElement; width: string | null } | null>(null)
+  /** 文件关联注册后的引导文案（docs/32） */
+  const [assocMsg, setAssocMsg] = useState<string | null>(null)
   const openEditorMenu = (e: React.MouseEvent) => {
     const target = e.target as HTMLElement
     const inEditor = sourceMode
@@ -1586,6 +1624,8 @@ export default function App() {
         { divider: true },
         { label: '上传文档图片到 S3…', disabled: !tab || sourceMode, onClick: () => void runBatchImageUpload() },
         { label: 'S3 上传设置…', onClick: () => setS3SettingsOpen(true) },
+        { divider: true },
+        { label: '设为 .md 默认打开方式…', disabled: !tauriMode, onClick: () => { void (async () => { try { setAssocMsg(await registerFileAssociation()) } catch (e) { setError(e instanceof Error ? e.message : String(e)) } })() } },
       ],
     },
     {
@@ -2091,6 +2131,7 @@ export default function App() {
           }}
         />
       )}
+      {assocMsg && <InfoModal title="文件关联" message={assocMsg} onClose={() => setAssocMsg(null)} />}
       {imageSizeTarget && (
         <ImageSizeModal
           current={imageSizeTarget.width}
diff --git a/src/components/Modals.tsx b/src/components/Modals.tsx
index aa591f6..135a8dc 100644
--- a/src/components/Modals.tsx
+++ b/src/components/Modals.tsx
@@ -260,6 +260,16 @@ export function ImageLinkModal({ src, linkHref, onSubmit, onCancel }: {
   )
 }
 
+export function InfoModal({ title, message, onClose }: { title: string; message: string; onClose: () => void }) {
+  return (
+    <Shell onCancel={onClose}>
+      <h3>{title}</h3>
+      <p>{message}</p>
+      <div className="modal-actions"><button className="primary" onClick={onClose}>知道了</button></div>
+    </Shell>
+  )
+}
+
 export function ErrorModal({ message, onClose }: { message: string; onClose: () => void }) {
   return (
     <Shell onCancel={onClose}>
diff --git a/src/services/platform.ts b/src/services/platform.ts
index 5d9dcc1..675c8de 100644
--- a/src/services/platform.ts
+++ b/src/services/platform.ts
@@ -366,6 +366,16 @@ export async function s3UploadImage(config: S3ConfigPayload, filePath: string, f
   return invoke<string>('s3_upload_image', { config, filePath, fileName })
 }
 
+/** 取走待打开文件队列：启动参数/双击第二个文件转来的 .md 路径（docs/32）。 */
+export async function takePendingOpenFiles(): Promise<string[]> {
+  return invoke<string[]>('take_pending_open_files')
+}
+
+/** 注册 .md/.markdown 文件关联并打开系统默认应用设置，返回引导文案（docs/32）。 */
+export async function registerFileAssociation(): Promise<string> {
+  return invoke<string>('register_file_association')
+}
+
 /** 上传文档内嵌的 base64 图片（已剥 data: 前缀的纯 base64），返回回填地址。 */
 export async function s3UploadBase64(config: S3ConfigPayload, base64: string, fileName: string): Promise<string> {
   return invoke<string>('s3_upload_base64', { config, base64, fileName })
diff --git a/tests/info-modal.test.tsx b/tests/info-modal.test.tsx
new file mode 100644
index 0000000..af46b1e
--- /dev/null
+++ b/tests/info-modal.test.tsx
@@ -0,0 +1,24 @@
+// 通用信息弹窗（docs/32 文件关联引导用）：标题/正文渲染，点「知道了」关闭。
+import { describe, it, expect, vi } from 'vitest'
+import { createRoot } from 'react-dom/client'
+import { act } from 'react-dom/test-utils'
+import { InfoModal } from '../src/components/Modals'
+
+describe('InfoModal', () => {
+  it('渲染标题与正文，点知道了回调关闭', async () => {
+    const container = document.createElement('div')
+    document.body.appendChild(container)
+    const root = createRoot(container)
+    const onClose = vi.fn()
+    await act(async () => {
+      root.render(<InfoModal title="文件关联" message="已注册为候选打开方式。" onClose={onClose} />)
+    })
+    expect(container.textContent).toContain('文件关联')
+    expect(container.textContent).toContain('已注册为候选打开方式。')
+    const btn = [...container.querySelectorAll('button')].find((b) => b.textContent === '知道了')!
+    await act(async () => { btn.dispatchEvent(new MouseEvent('click', { bubbles: true })) })
+    expect(onClose).toHaveBeenCalledTimes(1)
+    await act(async () => { root.unmount() })
+    container.remove()
+  })
+})