diff --git a/crates/agent-gui/src-tauri/src/runtime/shell_runner.rs b/crates/agent-gui/src-tauri/src/runtime/shell_runner.rs
index f0127897..37f65d7d 100644
--- a/crates/agent-gui/src-tauri/src/runtime/shell_runner.rs
+++ b/crates/agent-gui/src-tauri/src/runtime/shell_runner.rs
@@ -316,6 +316,65 @@ fn windows_cmd_command(cmd: &str) -> String {
     format!("chcp 65001>nul & {cmd}")
 }
 
+#[cfg(windows)]
+fn is_windows_system32_dir(dir: &Path) -> bool {
+    let Some(root) = std::env::var_os("SystemRoot") else {
+        return false;
+    };
+    let normalize = |p: &Path| {
+        p.to_string_lossy()
+            .trim_end_matches(['\\', '/'])
+            .to_ascii_lowercase()
+    };
+    normalize(dir) == normalize(&Path::new(&root).join("System32"))
+}
+
+/// Git Bash 解析（对标 Claude Code）：env 覆盖 → PATH → Git for Windows 默认安装路径。
+#[cfg(windows)]
+fn find_git_bash() -> Option<PathBuf> {
+    for var in ["LIVEAGENT_GIT_BASH_PATH", "CLAUDE_CODE_GIT_BASH_PATH"] {
+        if let Ok(raw) = std::env::var(var) {
+            let trimmed = raw.trim().trim_matches('"');
+            if !trimmed.is_empty() {
+                let path = expand_tilde_path(trimmed);
+                if path.is_file() {
+                    return Some(path);
+                }
+            }
+        }
+    }
+
+    let path_var = std::env::var_os("PATH").unwrap_or_default();
+    for dir in std::env::split_paths(&path_var) {
+        // System32 下的 bash.exe 是 WSL 启动器，不是 Git Bash。
+        if is_windows_system32_dir(&dir) {
+            continue;
+        }
+        let candidate = dir.join("bash.exe");
+        if candidate.is_file() {
+            return Some(candidate);
+        }
+    }
+
+    let roots = ["ProgramFiles", "ProgramW6432", "ProgramFiles(x86)"]
+        .iter()
+        .filter_map(|var| std::env::var_os(var).map(PathBuf::from))
+        .chain([
+            PathBuf::from(r"C:\Program Files"),
+            PathBuf::from(r"C:\Program Files (x86)"),
+        ]);
+    for root in roots {
+        // bin\bash.exe 是带 MSYS 环境注入的启动器，优先于 usr\bin 的裸 bash。
+        for rel in [r"Git\bin\bash.exe", r"Git\usr\bin\bash.exe"] {
+            let candidate = root.join(rel);
+            if candidate.is_file() {
+                return Some(candidate);
+            }
+        }
+    }
+    None
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub(crate) struct ShellExecutionProfile {
     pub platform: &'static str,
@@ -339,61 +398,75 @@ pub(crate) struct SpawnedPlatformShell {
 fn platform_shell_candidates(cmd: &str) -> Vec<ShellCandidate> {
     #[cfg(windows)]
     {
-        let powershell_command = windows_powershell_command(cmd);
-        return vec![
-            ShellCandidate {
+        let mut candidates = Vec::new();
+        if let Some(bash) = find_git_bash() {
+            candidates.push(ShellCandidate {
                 profile: ShellExecutionProfile {
                     platform: "windows",
-                    profile: "windows-pwsh",
-                    shell_family: "powershell",
-                    display_shell: "pwsh",
+                    profile: "windows-git-bash",
+                    shell_family: "posix",
+                    display_shell: "bash",
                 },
-                program: PathBuf::from("pwsh"),
-                args: vec![
-                    "-NoLogo".to_string(),
-                    "-NoProfile".to_string(),
-                    "-NonInteractive".to_string(),
-                    "-Command".to_string(),
-                    powershell_command.clone(),
-                ],
+                program: bash,
+                // 非登录 -c：-lc 会执行 /etc/profile 并 cd $HOME，破坏 cwd 语义。
+                args: vec!["-c".to_string(), cmd.to_string()],
                 augment_macos_path: false,
+            });
+        }
+        let powershell_command = windows_powershell_command(cmd);
+        candidates.push(ShellCandidate {
+            profile: ShellExecutionProfile {
+                platform: "windows",
+                profile: "windows-pwsh",
+                shell_family: "powershell",
+                display_shell: "pwsh",
             },
-            ShellCandidate {
-                profile: ShellExecutionProfile {
-                    platform: "windows",
-                    profile: "windows-powershell",
-                    shell_family: "powershell",
-                    display_shell: "powershell",
-                },
-                program: PathBuf::from("powershell.exe"),
-                args: vec![
-                    "-NoLogo".to_string(),
-                    "-NoProfile".to_string(),
-                    "-NonInteractive".to_string(),
-                    "-ExecutionPolicy".to_string(),
-                    "Bypass".to_string(),
-                    "-Command".to_string(),
-                    powershell_command,
-                ],
-                augment_macos_path: false,
+            program: PathBuf::from("pwsh"),
+            args: vec![
+                "-NoLogo".to_string(),
+                "-NoProfile".to_string(),
+                "-NonInteractive".to_string(),
+                "-Command".to_string(),
+                powershell_command.clone(),
+            ],
+            augment_macos_path: false,
+        });
+        candidates.push(ShellCandidate {
+            profile: ShellExecutionProfile {
+                platform: "windows",
+                profile: "windows-powershell",
+                shell_family: "powershell",
+                display_shell: "powershell",
             },
-            ShellCandidate {
-                profile: ShellExecutionProfile {
-                    platform: "windows",
-                    profile: "windows-cmd",
-                    shell_family: "cmd",
-                    display_shell: "cmd",
-                },
-                program: PathBuf::from("cmd.exe"),
-                args: vec![
-                    "/D".to_string(),
-                    "/S".to_string(),
-                    "/C".to_string(),
-                    windows_cmd_command(cmd),
-                ],
-                augment_macos_path: false,
+            program: PathBuf::from("powershell.exe"),
+            args: vec![
+                "-NoLogo".to_string(),
+                "-NoProfile".to_string(),
+                "-NonInteractive".to_string(),
+                "-ExecutionPolicy".to_string(),
+                "Bypass".to_string(),
+                "-Command".to_string(),
+                powershell_command,
+            ],
+            augment_macos_path: false,
+        });
+        candidates.push(ShellCandidate {
+            profile: ShellExecutionProfile {
+                platform: "windows",
+                profile: "windows-cmd",
+                shell_family: "cmd",
+                display_shell: "cmd",
             },
-        ];
+            program: PathBuf::from("cmd.exe"),
+            args: vec![
+                "/D".to_string(),
+                "/S".to_string(),
+                "/C".to_string(),
+                windows_cmd_command(cmd),
+            ],
+            augment_macos_path: false,
+        });
+        return candidates;
     }
 
     #[cfg(target_os = "macos")]
@@ -760,8 +833,12 @@ mod tests {
         let profile = default_platform_shell_profile();
         if cfg!(windows) {
             assert_eq!(profile.platform, "windows");
-            assert_eq!(profile.profile, "windows-pwsh");
-            assert_eq!(profile.shell_family, "powershell");
+            // 首候选取决于测试机是否装了 Git Bash。
+            match profile.profile {
+                "windows-git-bash" => assert_eq!(profile.shell_family, "posix"),
+                "windows-pwsh" => assert_eq!(profile.shell_family, "powershell"),
+                other => panic!("unexpected windows profile: {other}"),
+            }
         } else if cfg!(target_os = "macos") {
             assert_eq!(profile.platform, "macos");
             assert_eq!(profile.profile, "posix-zsh");
@@ -773,6 +850,49 @@ mod tests {
         }
     }
 
+    #[cfg(windows)]
+    #[test]
+    fn windows_shell_chain_orders_git_bash_before_powershell_fallbacks() {
+        let profiles: Vec<&'static str> = super::platform_shell_candidates("echo hi")
+            .iter()
+            .map(|candidate| candidate.profile.profile)
+            .collect();
+        let tail = ["windows-pwsh", "windows-powershell", "windows-cmd"];
+        match profiles.len() {
+            4 => {
+                assert_eq!(profiles[0], "windows-git-bash");
+                assert_eq!(profiles[1..], tail);
+            }
+            3 => assert_eq!(profiles[..], tail),
+            other => panic!("unexpected windows candidate count: {other}"),
+        }
+    }
+
+    #[cfg(windows)]
+    #[test]
+    fn find_git_bash_env_override_prefers_liveagent_var() {
+        // 单个测试函数串行覆盖所有 env 场景，避免并行 env 竞态。
+        let dir = tempfile::tempdir().expect("tempdir");
+        let liveagent_bash = dir.path().join("liveagent-bash.exe");
+        let claude_bash = dir.path().join("claude-bash.exe");
+        fs::write(&liveagent_bash, b"").unwrap();
+        fs::write(&claude_bash, b"").unwrap();
+
+        std::env::set_var("LIVEAGENT_GIT_BASH_PATH", &liveagent_bash);
+        std::env::set_var("CLAUDE_CODE_GIT_BASH_PATH", &claude_bash);
+        assert_eq!(super::find_git_bash(), Some(liveagent_bash.clone()));
+
+        // LIVEAGENT 指向不存在的文件时回退 CLAUDE_CODE。
+        std::env::set_var(
+            "LIVEAGENT_GIT_BASH_PATH",
+            dir.path().join("missing-bash.exe"),
+        );
+        assert_eq!(super::find_git_bash(), Some(claude_bash.clone()));
+
+        std::env::remove_var("LIVEAGENT_GIT_BASH_PATH");
+        std::env::remove_var("CLAUDE_CODE_GIT_BASH_PATH");
+    }
+
     #[test]
     fn shell_registry_cancel_marks_registered_run() {
         let registry = ShellRunRegistry::default();
diff --git a/crates/agent-gui/src/lib/chat/runner/agentRunner.ts b/crates/agent-gui/src/lib/chat/runner/agentRunner.ts
index 82d656a5..c85ab7ca 100644
--- a/crates/agent-gui/src/lib/chat/runner/agentRunner.ts
+++ b/crates/agent-gui/src/lib/chat/runner/agentRunner.ts
@@ -295,10 +295,10 @@ export function buildToolsSuffix(
     const bashPlatformLines =
       runtimePlatform === "windows"
         ? [
-            `- Current platform: ${platformLabel}. Bash runs through Windows-native shells: pwsh, then Windows PowerShell, then cmd.`,
-            '- Use PowerShell syntax by default: `Write-Output`, `$env:NAME = "value"`, semicolon separators, and PowerShell quoting.',
-            "- Do not assume Git Bash or POSIX syntax on Windows: avoid `export`, `nohup`, `/dev/null`, and POSIX background detachment.",
-            "- For long-running Windows commands, dev servers, watchers, or detached processes, use ManagedProcess instead of background shell syntax.",
+            `- Current platform: ${platformLabel}. Bash runs through Git Bash with POSIX semantics; pwsh, Windows PowerShell, and cmd are fallbacks used only when Git Bash is not installed.`,
+            "- Write POSIX/bash-compatible commands by default: `export`, `&&`, `/dev/null`, forward-slash paths.",
+            "- Background commands using `&` must redirect stdout and stderr before detaching, for example `nohup command > /tmp/liveagent-task.log 2>&1 < /dev/null &`.",
+            "- If a Bash result header reports `shell_family: powershell` or `shell_family: cmd`, Git Bash is missing: switch to PowerShell syntax and suggest installing Git for Windows or setting `LIVEAGENT_GIT_BASH_PATH`.",
           ]
         : [
             `- Current platform: ${platformLabel}. Bash runs through POSIX shells.`,
@@ -349,9 +349,7 @@ export function buildToolsSuffix(
 
   if (has("ManagedProcess")) {
     const managedProcessPreference =
-      runtimePlatform === "windows"
-        ? "- Prefer ManagedProcess over Bash for `pnpm dev`, `deno run main.ts`, `vite`, file watchers, local web servers, or commands that otherwise require detached Windows process syntax."
-        : "- Prefer ManagedProcess over Bash for `pnpm dev`, `deno run main.ts`, `vite`, file watchers, local web servers, or commands that otherwise require `nohup` and log redirection.";
+      "- Prefer ManagedProcess over Bash for `pnpm dev`, `deno run main.ts`, `vite`, file watchers, local web servers, or commands that otherwise require `nohup` and log redirection.";
     sections.push(
       [
         "## ManagedProcess",
diff --git a/crates/agent-gui/src/lib/tools/shellTools.ts b/crates/agent-gui/src/lib/tools/shellTools.ts
index 81c441e4..aa4022d4 100644
--- a/crates/agent-gui/src/lib/tools/shellTools.ts
+++ b/crates/agent-gui/src/lib/tools/shellTools.ts
@@ -322,12 +322,8 @@ function buildCancelledResult(params: {
     exit_code: -1,
     shell: params.shell || "unknown",
     platform: params.runtimePlatform,
-    profile: params.runtimePlatform === "windows" ? "windows-pwsh" : undefined,
-    shell_family: params.runtimePlatform
-      ? params.runtimePlatform === "windows"
-        ? "powershell"
-        : "posix"
-      : undefined,
+    profile: params.runtimePlatform === "windows" ? "windows-git-bash" : undefined,
+    shell_family: params.runtimePlatform ? "posix" : undefined,
     stdout: "",
     stderr: "Cancelled",
     stdout_truncated: false,
@@ -379,14 +375,12 @@ export function createShellTools(params: {
   const platformLabel = runtimePlatformLabel(runtimePlatform);
   const shellPolicy =
     runtimePlatform === "windows"
-      ? 'Windows runs Bash commands with the native Windows shell chain: pwsh first, then Windows PowerShell, then cmd. Use PowerShell syntax by default: `Write-Output`, `$env:NAME = "value"`, semicolon separators, and `Start-Process` when a process must be detached. Do not assume Git Bash, `export`, `nohup`, `/dev/null`, or POSIX background syntax.'
+      ? "Windows runs Bash commands with Git Bash (POSIX semantics) when available, falling back to pwsh, then Windows PowerShell, then cmd only if Git Bash is not installed. Write POSIX/bash syntax by default: `export NAME=value`, `&&`, `/dev/null`, forward-slash paths. If the result header reports `shell_family: powershell` or `shell_family: cmd`, Git Bash is missing on this machine — switch to PowerShell syntax and suggest installing Git for Windows or setting LIVEAGENT_GIT_BASH_PATH."
       : runtimePlatform === "macos"
         ? "macOS runs Bash commands with POSIX shell syntax: zsh first, then Bash, then sh."
         : "Linux runs Bash commands with POSIX shell syntax: Bash first, then zsh, then sh.";
   const backgroundPolicy =
-    runtimePlatform === "windows"
-      ? "For dev servers, watchers, or long-running commands on Windows, use ManagedProcess instead of detached shell syntax."
-      : "Background commands using `&` must detach stdout and stderr first, for example `nohup command > /tmp/liveagent-task.log 2>&1 < /dev/null &`; otherwise the tool rejects them because inherited pipes can keep Bash running forever.";
+    "Background commands using `&` must detach stdout and stderr first, for example `nohup command > /tmp/liveagent-task.log 2>&1 < /dev/null &`; otherwise the tool rejects them because inherited pipes can keep Bash running forever. Prefer ManagedProcess for dev servers, watchers, or anything long-running.";
   const workdir = params.workdir;
   const allowSkillsRoot = params.skillsRootEnabled === true;
   const allowManagedProcess = params.managedProcessEnabled !== false;
@@ -572,18 +566,19 @@ export function createShellTools(params: {
     command: string;
     stdout: string;
     stderr: string;
+    shellFamily?: string;
   }) {
     const combined = [params.command, params.stdout, params.stderr].join("\n");
     const hints: string[] = [];
 
     if (
       runtimePlatform === "windows" &&
-      /(^|[\s;&|])(?:export|nohup)\b|\/dev\/null|not recognized as|不是内部或外部命令|无法将.*识别为/i.test(
-        combined,
-      )
+      (params.shellFamily === "powershell" || params.shellFamily === "cmd")
     ) {
       hints.push(
-        'Hint: This Bash tool is running with Windows-native shells. Use PowerShell syntax such as `Write-Output`, `$env:NAME = "value"`, and `;`, or use ManagedProcess for long-running commands.',
+        `Hint: Git Bash was not found, so this command ran under ${
+          params.shellFamily === "cmd" ? "cmd" : "PowerShell"
+        } where POSIX syntax like \`export\`, \`nohup\`, and \`/dev/null\` fails. Rewrite the command in PowerShell syntax for now, and suggest installing Git for Windows or setting LIVEAGENT_GIT_BASH_PATH to restore Bash semantics.`,
       );
     }
 
@@ -772,7 +767,7 @@ export function createShellTools(params: {
         const command =
           typeof toolCall.arguments?.command === "string" ? toolCall.arguments.command.trim() : "";
         if (!command) throw new Error('ManagedProcess.command is required for action="start"');
-        if (runtimePlatform !== "windows" && scanShellSyntax(command).background) {
+        if (scanShellSyntax(command).background) {
           throw new Error(
             "ManagedProcess.command must be a foreground command. Remove `&`; ManagedProcess starts it in the background and captures logs automatically.",
           );
@@ -995,20 +990,18 @@ export function createShellTools(params: {
       };
     }
 
-    if (runtimePlatform !== "windows") {
-      try {
-        validateBashBackgroundStdio(command);
-      } catch (err) {
-        return {
-          role: "toolResult",
-          toolCallId: toolCall.id,
-          toolName: toolCall.name,
-          content: [{ type: "text", text: asErrorMessage(err) }],
-          details: {},
-          isError: true,
-          timestamp: now,
-        };
-      }
+    try {
+      validateBashBackgroundStdio(command);
+    } catch (err) {
+      return {
+        role: "toolResult",
+        toolCallId: toolCall.id,
+        toolName: toolCall.name,
+        content: [{ type: "text", text: asErrorMessage(err) }],
+        details: {},
+        isError: true,
+        timestamp: now,
+      };
     }
 
     const timeoutRaw = toolCall.arguments?.timeout_ms;
@@ -1073,6 +1066,7 @@ export function createShellTools(params: {
               command,
               stdout: res.stdout || "",
               stderr: res.stderr || "",
+              shellFamily: res.shell_family,
             })
           : "";
 
diff --git a/crates/agent-gui/test/chat/markdown-image-policy.test.mjs b/crates/agent-gui/test/chat/markdown-image-policy.test.mjs
index 9dfb02ac..b453f73f 100644
--- a/crates/agent-gui/test/chat/markdown-image-policy.test.mjs
+++ b/crates/agent-gui/test/chat/markdown-image-policy.test.mjs
@@ -271,16 +271,17 @@ test("agent tool rules route installed Skill scripts through skill cwd", () => {
   assert.match(suffix, /Do not cd into ~\/\.liveagent\/skills or workspace skills\/ guesses/);
 });
 
-test("agent Bash rules are Windows-native when runtime platform is Windows", () => {
+test("agent Bash rules are Git Bash-first when runtime platform is Windows", () => {
   const suffix = agentRunnerModule.buildToolsSuffix(
     "/workspace",
     ["Bash", "ManagedProcess"],
     "windows",
   );
   assert.match(suffix, /Current platform: Windows/);
-  assert.match(suffix, /Use PowerShell syntax by default/);
-  assert.match(suffix, /avoid `export`, `nohup`, `\/dev\/null`/);
-  assert.match(suffix, /detached Windows process syntax/);
+  assert.match(suffix, /Git Bash with POSIX semantics/);
+  assert.match(suffix, /Write POSIX\/bash-compatible commands by default/);
+  assert.match(suffix, /shell_family: powershell/);
+  assert.match(suffix, /require `nohup` and log redirection/);
 });
 
 test("fs tool descriptions keep Image as the only display path for images", () => {
diff --git a/crates/agent-gui/test/tools/shell-tools.test.mjs b/crates/agent-gui/test/tools/shell-tools.test.mjs
index 8cbaa624..18f1fa90 100644
--- a/crates/agent-gui/test/tools/shell-tools.test.mjs
+++ b/crates/agent-gui/test/tools/shell-tools.test.mjs
@@ -14,7 +14,7 @@ function createBashCall(command = "echo ready") {
   };
 }
 
-test("Bash tool keeps one Bash entry and uses Windows-native policy for Claude Code", async () => {
+test("Bash tool keeps one Bash entry and uses Git Bash-first policy for Claude Code", async () => {
   const calls = [];
   const loader = createTsModuleLoader({
     mocks: {
@@ -24,10 +24,10 @@ test("Bash tool keeps one Bash entry and uses Windows-native policy for Claude C
           assert.equal(command, "shell_run");
           return {
             exit_code: 0,
-            shell: "pwsh",
+            shell: "bash",
             platform: "windows",
-            profile: "windows-pwsh",
-            shell_family: "powershell",
+            profile: "windows-git-bash",
+            shell_family: "posix",
             stdout: "ready\n",
             stderr: "",
             stdout_truncated: false,
@@ -50,8 +50,9 @@ test("Bash tool keeps one Bash entry and uses Windows-native policy for Claude C
   });
 
   assert.match(bundle.tools[0].description, /Windows runs Bash commands/);
-  assert.match(bundle.tools[0].description, /pwsh first/);
-  assert.doesNotMatch(bundle.tools[0].description, /Git Bash first/);
+  assert.match(bundle.tools[0].description, /Git Bash \(POSIX semantics\)/);
+  assert.match(bundle.tools[0].description, /Write POSIX\/bash syntax by default/);
+  assert.doesNotMatch(bundle.tools[0].description, /native Windows shell chain/);
 
   const result = await bundle.executeToolCall(createBashCall());
 
@@ -60,10 +61,10 @@ test("Bash tool keeps one Bash entry and uses Windows-native policy for Claude C
   assert.equal(calls[0].args.provider_id, "claude_code");
   assert.equal(calls[0].args.max_timeout_ms, 600_000);
   assert.match(result.content[0].text, /platform: windows/);
-  assert.match(result.content[0].text, /profile: windows-pwsh/);
+  assert.match(result.content[0].text, /profile: windows-git-bash/);
 });
 
-test("Bash tool uses the same Windows-native policy for Codex", async () => {
+test("Bash tool uses the same Git Bash-first policy for Codex", async () => {
   const calls = [];
   const loader = createTsModuleLoader({
     mocks: {
@@ -73,10 +74,10 @@ test("Bash tool uses the same Windows-native policy for Codex", async () => {
           assert.equal(command, "shell_run");
           return {
             exit_code: 0,
-            shell: "pwsh",
+            shell: "bash",
             platform: "windows",
-            profile: "windows-pwsh",
-            shell_family: "powershell",
+            profile: "windows-git-bash",
+            shell_family: "posix",
             stdout: "ready\n",
             stderr: "",
             stdout_truncated: false,
@@ -99,7 +100,7 @@ test("Bash tool uses the same Windows-native policy for Codex", async () => {
   });
 
   assert.match(bundle.tools[0].description, /Windows runs Bash commands/);
-  assert.match(bundle.tools[0].description, /PowerShell syntax/);
+  assert.match(bundle.tools[0].description, /Git Bash \(POSIX semantics\)/);
   assert.doesNotMatch(bundle.tools[0].description, /Codex-style auto shell selection/);
 
   const result = await bundle.executeToolCall(createBashCall());
@@ -278,7 +279,36 @@ test("Bash tool rejects background commands with only stderr append redirected",
   assert.deepEqual(calls, []);
 });
 
-test("Bash tool does not apply POSIX ampersand background validation on Windows", async () => {
+test("Bash tool applies POSIX ampersand background validation on Windows", async () => {
+  const calls = [];
+  const loader = createTsModuleLoader({
+    mocks: {
+      "@tauri-apps/api/core": {
+        async invoke(command, args) {
+          calls.push({ command, args });
+          throw new Error("shell_run should not be invoked for rejected commands");
+        },
+      },
+    },
+  });
+
+  const { createShellTools } = loader.loadModule("src/lib/tools/shellTools.ts");
+  const bundle = createShellTools({
+    workdir: "/repo",
+    providerId: "codex",
+    runtimePlatform: "windows",
+  });
+
+  const result = await bundle.executeToolCall(
+    createBashCall("deno run --allow-net main.ts 2>> /tmp/server.err &"),
+  );
+
+  assert.equal(result.isError, true);
+  assert.match(result.content[0].text, /Background Bash commands must detach stdout and stderr/);
+  assert.equal(calls.length, 0);
+});
+
+test("Bash tool allows detached background commands on Windows", async () => {
   const calls = [];
   const loader = createTsModuleLoader({
     mocks: {
@@ -288,10 +318,10 @@ test("Bash tool does not apply POSIX ampersand background validation on Windows"
           assert.equal(command, "shell_run");
           return {
             exit_code: 0,
-            shell: "pwsh",
+            shell: "bash",
             platform: "windows",
-            profile: "windows-pwsh",
-            shell_family: "powershell",
+            profile: "windows-git-bash",
+            shell_family: "posix",
             stdout: "ok\n",
             stderr: "",
             stdout_truncated: false,
@@ -313,12 +343,72 @@ test("Bash tool does not apply POSIX ampersand background validation on Windows"
     runtimePlatform: "windows",
   });
 
-  const result = await bundle.executeToolCall(createBashCall('& "C:/Program Files/App/app.exe"'));
+  const result = await bundle.executeToolCall(
+    createBashCall("nohup deno run main.ts > /tmp/liveagent-test.log 2>&1 < /dev/null &"),
+  );
 
   assert.equal(result.isError, false);
   assert.equal(calls.length, 1);
 });
 
+function createWindowsFailureLoader(shellFamily, shell) {
+  return createTsModuleLoader({
+    mocks: {
+      "@tauri-apps/api/core": {
+        async invoke(command, args) {
+          assert.equal(command, "shell_run");
+          return {
+            exit_code: 1,
+            shell,
+            platform: "windows",
+            profile: shellFamily === "posix" ? "windows-git-bash" : "windows-pwsh",
+            shell_family: shellFamily,
+            stdout: "",
+            stderr: "export : The term 'export' is not recognized",
+            stdout_truncated: false,
+            stderr_truncated: false,
+            timed_out: false,
+            cancelled: false,
+            effective_timeout_ms: args.timeout_ms,
+            duration_ms: 12,
+          };
+        },
+      },
+    },
+  });
+}
+
+test("Bash tool hints about missing Git Bash when Windows falls back to PowerShell", async () => {
+  const loader = createWindowsFailureLoader("powershell", "pwsh");
+  const { createShellTools } = loader.loadModule("src/lib/tools/shellTools.ts");
+  const bundle = createShellTools({
+    workdir: "/repo",
+    providerId: "claude_code",
+    runtimePlatform: "windows",
+  });
+
+  const result = await bundle.executeToolCall(createBashCall("export NAME=value"));
+
+  assert.equal(result.isError, true);
+  assert.match(result.content[0].text, /Git Bash was not found/);
+  assert.match(result.content[0].text, /LIVEAGENT_GIT_BASH_PATH/);
+});
+
+test("Bash tool does not hint about Git Bash when a Windows failure ran under Git Bash", async () => {
+  const loader = createWindowsFailureLoader("posix", "bash");
+  const { createShellTools } = loader.loadModule("src/lib/tools/shellTools.ts");
+  const bundle = createShellTools({
+    workdir: "/repo",
+    providerId: "claude_code",
+    runtimePlatform: "windows",
+  });
+
+  const result = await bundle.executeToolCall(createBashCall("exit 1"));
+
+  assert.equal(result.isError, true);
+  assert.doesNotMatch(result.content[0].text, /Git Bash was not found/);
+});
+
 test("Bash tool allows background commands with detached stdio", async () => {
   const calls = [];
   const loader = createTsModuleLoader({
@@ -475,29 +565,14 @@ test("ManagedProcess rejects nested shell background operators", async () => {
   assert.deepEqual(calls, []);
 });
 
-test("ManagedProcess does not apply POSIX ampersand background validation on Windows", async () => {
+test("ManagedProcess rejects background ampersand commands on Windows", async () => {
   const calls = [];
   const loader = createTsModuleLoader({
     mocks: {
       "@tauri-apps/api/core": {
         async invoke(command, args) {
           calls.push({ command, args });
-          assert.equal(command, "managed_process_start");
-          return {
-            process: {
-              id: "proc-win",
-              label: null,
-              command: args.command,
-              cwd: "C:\\repo",
-              shell: "pwsh",
-              pid: 456,
-              log_path: "C:\\Users\\me\\.liveagent\\process-logs\\proc-win.log",
-              started_at: 10,
-              finished_at: null,
-              exit_code: null,
-              running: true,
-            },
-          };
+          throw new Error("managed_process_start should not be invoked for rejected commands");
         },
       },
     },
@@ -516,12 +591,13 @@ test("ManagedProcess does not apply POSIX ampersand background validation on Win
     name: "ManagedProcess",
     arguments: {
       action: "start",
-      command: '& "C:/Program Files/App/app.exe"',
+      command: "vite --port 5173 &",
     },
   });
 
-  assert.equal(result.isError, false);
-  assert.equal(calls.length, 1);
+  assert.equal(result.isError, true);
+  assert.match(result.content[0].text, /must be a foreground command/);
+  assert.equal(calls.length, 0);
 });
 
 test("Bash tool marks stdio-open shell responses as errors", async () => {