diff --git a/packages/app/e2e/utils.ts b/packages/app/e2e/utils.ts
index 0dbc5f8b5..f07a8d3f1 100644
--- a/packages/app/e2e/utils.ts
+++ b/packages/app/e2e/utils.ts
@@ -57,7 +57,7 @@ export function sessionPath(directory: string, sessionID?: string) {
 }
 
 export function workspacePersistKey(directory: string, key: string) {
-  const head = directory.slice(0, 12) || "workspace"
+  const head = (directory.slice(0, 12) || "workspace").replace(/[^a-zA-Z0-9._-]/g, "-")
   const sum = checksum(directory) ?? "0"
   return `opencode.workspace.${head}.${sum}.dat:workspace:${key}`
 }
diff --git a/packages/app/src/utils/persist.test.ts b/packages/app/src/utils/persist.test.ts
index 2a2c349b7..673acd224 100644
--- a/packages/app/src/utils/persist.test.ts
+++ b/packages/app/src/utils/persist.test.ts
@@ -104,4 +104,12 @@ describe("persist localStorage resilience", () => {
     const result = persistTesting.normalize({ value: "ok" }, '{"value":"\\x"}')
     expect(result).toBeUndefined()
   })
+
+  test("workspace storage sanitizes Windows filename characters", () => {
+    const result = persistTesting.workspaceStorage("C:\\Users\\foo")
+
+    expect(result).toStartWith("opencode.workspace.")
+    expect(result.endsWith(".dat")).toBeTrue()
+    expect(/[:\\/]/.test(result)).toBeFalse()
+  })
 })
diff --git a/packages/app/src/utils/persist.ts b/packages/app/src/utils/persist.ts
index 91c504742..bee2f3e7d 100644
--- a/packages/app/src/utils/persist.ts
+++ b/packages/app/src/utils/persist.ts
@@ -204,7 +204,7 @@ function normalize(defaults: unknown, raw: string, migrate?: (value: unknown) =>
 }
 
 function workspaceStorage(dir: string) {
-  const head = dir.slice(0, 12) || "workspace"
+  const head = (dir.slice(0, 12) || "workspace").replace(/[^a-zA-Z0-9._-]/g, "-")
   const sum = checksum(dir) ?? "0"
   return `opencode.workspace.${head}.${sum}.dat`
 }
@@ -300,6 +300,7 @@ export const PersistTesting = {
   localStorageDirect,
   localStorageWithPrefix,
   normalize,
+  workspaceStorage,
 }
 
 export const Persist = {