diff --git a/src/agents/skills/config.ts b/src/agents/skills/config.ts
index c053f2b39..a6287f7d8 100644
--- a/src/agents/skills/config.ts
+++ b/src/agents/skills/config.ts
@@ -77,13 +77,16 @@ export function isBundledSkillAllowed(entry: SkillEntry, allowlist?: string[]):
 export function hasBinary(bin: string): boolean {
   const pathEnv = process.env.PATH ?? "";
   const parts = pathEnv.split(path.delimiter).filter(Boolean);
+  const extensions = process.platform === "win32" ? [".exe", ".cmd", ".bat", ""] : [""];
   for (const part of parts) {
-    const candidate = path.join(part, bin);
-    try {
-      fs.accessSync(candidate, fs.constants.X_OK);
-      return true;
-    } catch {
-      // keep scanning
+    for (const ext of extensions) {
+      const candidate = path.join(part, bin + ext);
+      try {
+        fs.accessSync(candidate, fs.constants.X_OK);
+        return true;
+      } catch {
+        // keep scanning
+      }
     }
   }
   return false;
diff --git a/src/hooks/config.ts b/src/hooks/config.ts
index 8a1da761d..0cdb17481 100644
--- a/src/hooks/config.ts
+++ b/src/hooks/config.ts
@@ -54,13 +54,16 @@ export function resolveRuntimePlatform(): string {
 export function hasBinary(bin: string): boolean {
   const pathEnv = process.env.PATH ?? "";
   const parts = pathEnv.split(path.delimiter).filter(Boolean);
+  const extensions = process.platform === "win32" ? [".exe", ".cmd", ".bat", ""] : [""];
   for (const part of parts) {
-    const candidate = path.join(part, bin);
-    try {
-      fs.accessSync(candidate, fs.constants.X_OK);
-      return true;
-    } catch {
-      // keep scanning
+    for (const ext of extensions) {
+      const candidate = path.join(part, bin + ext);
+      try {
+        fs.accessSync(candidate, fs.constants.X_OK);
+        return true;
+      } catch {
+        // keep scanning
+      }
     }
   }
   return false;
diff --git a/src/process/exec.ts b/src/process/exec.ts
index 44f8b2ce0..371302e31 100644
--- a/src/process/exec.ts
+++ b/src/process/exec.ts
@@ -73,7 +73,12 @@ export async function runCommandWithTimeout(
     return false;
   })();
 
-  const resolvedEnv = env ? { ...process.env, ...env } : { ...process.env };
+  const mergedEnv = env ? { ...process.env, ...env } : { ...process.env };
+  const resolvedEnv = Object.fromEntries(
+    Object.entries(mergedEnv)
+      .filter(([, value]) => value !== undefined)
+      .map(([key, value]) => [key, String(value)]),
+  );
   if (shouldSuppressNpmFund) {
     if (resolvedEnv.NPM_CONFIG_FUND == null) resolvedEnv.NPM_CONFIG_FUND = "false";
     if (resolvedEnv.npm_config_fund == null) resolvedEnv.npm_config_fund = "false";
@@ -85,6 +90,7 @@ export async function runCommandWithTimeout(
     cwd,
     env: resolvedEnv,
     windowsVerbatimArguments,
+    shell: process.platform === "win32",
   });
   // Spawn with inherited stdin (TTY) so tools like `pi` stay interactive when needed.
   return await new Promise((resolve, reject) => {