diff --git a/packages/opencode/src/permission/next.ts b/packages/opencode/src/permission/next.ts
index f95aaf34525..7d9dd62fb99 100644
--- a/packages/opencode/src/permission/next.ts
+++ b/packages/opencode/src/permission/next.ts
@@ -44,7 +44,13 @@ export namespace PermissionNext {
         })
         continue
       }
-      ruleset.push(...Object.entries(value).map(([pattern, action]) => ({ permission: key, pattern, action })))
+      ruleset.push(
+        ...Object.entries(value).map(([pattern, action]) => ({
+          permission: key,
+          pattern: pattern.replace(/\\/g, "/"), // Normalize to forward slashes for cross-platform compatibility
+          action,
+        })),
+      )
     }
     return ruleset
   }
diff --git a/packages/opencode/src/util/wildcard.ts b/packages/opencode/src/util/wildcard.ts
index 9b595a0a9ec..373f4964b51 100644
--- a/packages/opencode/src/util/wildcard.ts
+++ b/packages/opencode/src/util/wildcard.ts
@@ -2,16 +2,21 @@ import { sortBy, pipe } from "remeda"
 
 export namespace Wildcard {
   export function match(str: string, pattern: string) {
+    // Normalize path separators to forward slashes for cross-platform compatibility
+    // This allows configs to use either / or \ and work on all platforms
+    const normalizedStr = str.replace(/\\/g, "/")
+    const normalizedPattern = pattern.replace(/\\/g, "/")
+
     const regex = new RegExp(
       "^" +
-        pattern
+        normalizedPattern
           .replace(/[.+^${}()|[\]\\]/g, "\\$&") // escape special regex chars
           .replace(/\*/g, ".*") // * becomes .*
           .replace(/\?/g, ".") + // ? becomes .
         "$",
       "s", // s flag enables multiline matching
     )
-    return regex.test(str)
+    return regex.test(normalizedStr)
   }
 
   export function all(input: string, patterns: Record<string, any>) {
diff --git a/packages/opencode/test/permission/next.test.ts b/packages/opencode/test/permission/next.test.ts
index 68dc653de6d..ef88c3bc95d 100644
--- a/packages/opencode/test/permission/next.test.ts
+++ b/packages/opencode/test/permission/next.test.ts
@@ -650,3 +650,132 @@ test("ask - allows all patterns when all match allow rules", async () => {
     },
   })
 })
+
+// Cross-platform path separator tests for permission system
+test("fromConfig - normalizes backslashes to forward slashes", () => {
+  const result = PermissionNext.fromConfig({
+    edit: {
+      "*": "deny",
+      "openspec\\*": "allow",
+      "src\\main.ts": "deny",
+    },
+  })
+  expect(result).toEqual([
+    { permission: "edit", pattern: "*", action: "deny" },
+    { permission: "edit", pattern: "openspec/*", action: "allow" },
+    { permission: "edit", pattern: "src/main.ts", action: "deny" },
+  ])
+})
+
+test("fromConfig - handles mixed separators", () => {
+  const result = PermissionNext.fromConfig({
+    read: {
+      "openspec/*": "allow",
+      "src\\*": "deny",
+      "C:/Users/*": "allow",
+    },
+  })
+  expect(result).toEqual([
+    { permission: "read", pattern: "openspec/*", action: "allow" },
+    { permission: "read", pattern: "src/*", action: "deny" },
+    { permission: "read", pattern: "C:/Users/*", action: "allow" },
+  ])
+})
+
+test("evaluate - Windows paths with Unix config patterns", () => {
+  const ruleset = PermissionNext.fromConfig({
+    edit: {
+      "*": "deny",
+      "openspec/*": "allow",
+    },
+  })
+
+  // Windows path should match Unix pattern
+  expect(PermissionNext.evaluate("edit", "openspec\\api.yaml", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "openspec\\sub\\file.ts", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "src\\main.ts", ruleset).action).toBe("deny")
+})
+
+test("evaluate - Unix paths with Windows config patterns", () => {
+  const ruleset = PermissionNext.fromConfig({
+    edit: {
+      "*": "deny",
+      "openspec\\*": "allow",
+    },
+  })
+
+  // Unix path should match Windows pattern
+  expect(PermissionNext.evaluate("edit", "openspec/api.yaml", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "openspec/sub/file.ts", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "src/main.ts", ruleset).action).toBe("deny")
+})
+
+test("evaluate - Mixed separators in paths and patterns", () => {
+  const ruleset = PermissionNext.fromConfig({
+    edit: {
+      "openspec\\*": "allow",
+    },
+  })
+
+  // Mixed separators should work
+  expect(PermissionNext.evaluate("edit", "openspec/sub\\file.txt", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "openspec\\sub/file.txt", ruleset).action).toBe("allow")
+})
+
+test("evaluate - UNC paths", () => {
+  const ruleset = PermissionNext.fromConfig({
+    read: {
+      "//server/share/*": "allow",
+    },
+  })
+
+  // Windows UNC path should match
+  expect(PermissionNext.evaluate("read", "\\\\server\\share\\file.txt", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("read", "\\\\server\\share\\sub\\file.txt", ruleset).action).toBe("allow")
+})
+
+test("evaluate - Drive letters", () => {
+  const ruleset = PermissionNext.fromConfig({
+    edit: {
+      "C:/project/*": "allow",
+      "D:\\*": "deny",
+    },
+  })
+
+  expect(PermissionNext.evaluate("edit", "C:\\project\\src\\main.ts", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "C:/project/src/main.ts", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "D:\\file.txt", ruleset).action).toBe("deny")
+  expect(PermissionNext.evaluate("edit", "D:/file.txt", ruleset).action).toBe("deny")
+})
+
+test("evaluate - Complex Windows path patterns", () => {
+  const ruleset = PermissionNext.fromConfig({
+    edit: {
+      "*": "ask",
+      "src\\components\\*.tsx": "allow",
+      "openspec/**/*.yaml": "allow",
+    },
+  })
+
+  expect(PermissionNext.evaluate("edit", "src\\components\\Button.tsx", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "src\\components\\Button.js", ruleset).action).toBe("ask")
+  expect(PermissionNext.evaluate("edit", "openspec\\api\\v1\\schema.yaml", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "openspec\\api\\v1\\schema.json", ruleset).action).toBe("ask")
+})
+
+test("evaluate - Permission precedence with Windows paths", () => {
+  const ruleset = PermissionNext.fromConfig({
+    edit: {
+      "*": "deny",
+      "openspec/*": "allow",
+      "openspec/secret/*": "deny",
+      "openspec/secret/ok.ts": "allow",
+    },
+  })
+
+  // Last matching rule wins
+  expect(PermissionNext.evaluate("edit", "openspec\\api.yaml", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "openspec\\secret\\password.txt", ruleset).action).toBe("deny")
+  expect(PermissionNext.evaluate("edit", "openspec\\secret\\ok.ts", ruleset).action).toBe("allow")
+  expect(PermissionNext.evaluate("edit", "src\\main.ts", ruleset).action).toBe("deny")
+})
diff --git a/packages/opencode/test/util/wildcard.test.ts b/packages/opencode/test/util/wildcard.test.ts
index f7f1e15457b..6de06be411c 100644
--- a/packages/opencode/test/util/wildcard.test.ts
+++ b/packages/opencode/test/util/wildcard.test.ts
@@ -53,3 +53,84 @@ test("allStructured handles sed flags", () => {
   expect(Wildcard.allStructured({ head: "sed", tail: ["-n", "1p", "file"] }, rules)).toBe("allow")
   expect(Wildcard.allStructured({ head: "sed", tail: ["-i", "-n", "/./p", "myfile.txt"] }, rules)).toBe("ask")
 })
+
+// Cross-platform path separator tests
+test("match handles Windows paths with forward slash patterns", () => {
+  // Unix config pattern matching Windows path
+  expect(Wildcard.match("openspec\\api.yaml", "openspec/*")).toBe(true)
+  expect(Wildcard.match("src\\main.ts", "src/*")).toBe(true)
+  expect(Wildcard.match("C:\\Users\\name\\file.txt", "C:/*")).toBe(true)
+  expect(Wildcard.match("openspec\\sub\\file.txt", "openspec/*")).toBe(true)
+})
+
+test("match handles Windows paths with backslash patterns", () => {
+  // Windows config pattern matching Windows path
+  expect(Wildcard.match("openspec\\api.yaml", "openspec\\*")).toBe(true)
+  expect(Wildcard.match("src\\main.ts", "src\\*")).toBe(true)
+  expect(Wildcard.match("C:\\Users\\name\\file.txt", "C:\\*")).toBe(true)
+})
+
+test("match handles Unix paths with backslash patterns", () => {
+  // Windows config pattern matching Unix path
+  expect(Wildcard.match("openspec/api.yaml", "openspec\\*")).toBe(true)
+  expect(Wildcard.match("src/main.ts", "src\\*")).toBe(true)
+})
+
+test("match handles mixed separators", () => {
+  expect(Wildcard.match("openspec\\sub/file.txt", "openspec/*")).toBe(true)
+  expect(Wildcard.match("src/sub\\file.txt", "src\\*")).toBe(true)
+})
+
+test("match handles UNC paths", () => {
+  expect(Wildcard.match("\\\\server\\share\\file.txt", "//server/share/*")).toBe(true)
+  expect(Wildcard.match("//server/share/file.txt", "\\\\server\\share\\*")).toBe(true)
+  expect(Wildcard.match("\\\\server\\share\\sub\\file.txt", "//server/share/*")).toBe(true)
+})
+
+test("match handles drive letters", () => {
+  expect(Wildcard.match("C:\\Users\\name\\file.txt", "C:/*")).toBe(true)
+  expect(Wildcard.match("D:\\project\\src\\main.ts", "D:/project/*")).toBe(true)
+  expect(Wildcard.match("C:/Users/name/file.txt", "C:\\*")).toBe(true)
+})
+
+test("match handles relative vs absolute paths", () => {
+  // Relative paths
+  expect(Wildcard.match("src\\main.ts", "src/*")).toBe(true)
+  expect(Wildcard.match("src/main.ts", "src\\*")).toBe(true)
+
+  // Absolute paths
+  expect(Wildcard.match("/home/user/project/src/main.ts", "/home/user/project/src/*")).toBe(true)
+  expect(Wildcard.match("\\home\\user\\project\\src\\main.ts", "/home/user/project/src/*")).toBe(true)
+})
+
+test("match handles complex patterns with Windows paths", () => {
+  expect(Wildcard.match("openspec\\api.yaml", "openspec/*.yaml")).toBe(true)
+  expect(Wildcard.match("openspec\\sub\\test.ts", "openspec/*/test.ts")).toBe(true)
+  expect(Wildcard.match("src\\components\\Button.tsx", "src/components/*.tsx")).toBe(true)
+  expect(Wildcard.match("C:\\project\\src\\test.ts", "C:/project/src/test.ts")).toBe(true)
+})
+
+test("match handles wildcards with Windows paths", () => {
+  expect(Wildcard.match("openspec\\file1.txt", "openspec/*")).toBe(true)
+  expect(Wildcard.match("openspec\\sub\\file2.txt", "openspec/**")).toBe(true)
+  expect(Wildcard.match("src\\test\\file.ts", "src/*/file.ts")).toBe(true)
+})
+
+test("match handles question mark with Windows paths", () => {
+  expect(Wildcard.match("file\\1.txt", "file\\?.txt")).toBe(true)
+  expect(Wildcard.match("file\\12.txt", "file\\?.txt")).toBe(false)
+  expect(Wildcard.match("file/1.txt", "file\\?.txt")).toBe(true)
+})
+
+test("match handles special regex chars in Windows paths", () => {
+  // These should be escaped properly
+  expect(Wildcard.match("src\\file+more.txt", "src/file+more.txt")).toBe(true)
+  expect(Wildcard.match("src\\file[1-3].txt", "src/file[1-3].txt")).toBe(true)
+  expect(Wildcard.match("src\\file.txt", "src/file.txt")).toBe(true)
+})
+
+test("match handles empty strings and patterns", () => {
+  expect(Wildcard.match("", "")).toBe(true)
+  expect(Wildcard.match("\\", "/")).toBe(true)
+  expect(Wildcard.match("/", "\\")).toBe(true)
+})