fix: retry on timeout errors instead of failing

AbortSignal.timeout() throws DOMException with name 'TimeoutError',
which was not handled in fromError(). This caused timeout errors to
become Unknown errors (not retryable), stopping the session instead
of retrying.

Now timeout errors are converted to APIError with isRetryable: true,
enabling automatic retry with exponential backoff.

Fixes #13138

Signed-off-by: Mörgæsis <morgaesis+git@morgaes.is>

Author: morgaesis

packages/opencode/src/session/message-v2.ts

@@ -971,6 +971,14 @@ export function fromError(
           cause: e,
         },
       ).toObject()
+    case e instanceof DOMException && e.name === "TimeoutError":
+      return new APIError(
+        {
+          message: e.message || "Operation timed out",
+          isRetryable: true,
+        },
+        { cause: e },
+      ).toObject()
     case OutputLengthError.isInstance(e):
       return e
     case LoadAPIKeyError.isInstance(e):

packages/opencode/test/session/message-v2.test.ts

@@ -950,6 +950,14 @@ describe("session.message-v2.toModelMessage", () => {
 })
 
 describe("session.message-v2.fromError", () => {
+  test("classifies timeout DOMException as retryable APIError", () => {
+    const result = MessageV2.fromError(new DOMException("operation timed out", "TimeoutError"), { providerID })
+
+    expect(MessageV2.APIError.isInstance(result)).toBe(true)
+    expect((result as MessageV2.APIError).data.message).toBe("operation timed out")
+    expect((result as MessageV2.APIError).data.isRetryable).toBe(true)
+  })
+
   test("serializes context_length_exceeded as ContextOverflowError", () => {
     const input = {
       type: "error",