improve errors: retries, surfacing provider errors to the user

1 files changed, 31 insertions, 0 deletions

diff --git a/libpanto/src/provider_openai_chat.zig b/libpanto/src/provider_openai_chat.zig
index 5152d3e..5713b5d 100644
--- a/libpanto/src/provider_openai_chat.zig
+++ b/libpanto/src/provider_openai_chat.zig
@@ -214,8 +214,14 @@ pub const ResumableResponse = struct {
     const vtable: provider_mod.ProviderStream.VTable = .{
         .produce = produceVT,
         .deinit = deinitVT,
+        .last_error = lastErrorVT,
     };
 
+    fn lastErrorVT(ptr: *anyopaque) ?[]const u8 {
+        const self: *ResumableResponse = @ptrCast(@alignCast(ptr));
+        return self.state.stream_error_message;
+    }
+
     fn produceVT(ptr: *anyopaque, out: *EventQueue) anyerror!ProduceStatus {
         const self: *ResumableResponse = @ptrCast(@alignCast(ptr));
         return self.produce(out);
@@ -339,6 +345,11 @@ const StreamState = struct {
     /// `stream_options.include_usage: true` AND the server honored it).
     usage: ?provider_mod.Usage = null,
 
+    /// Owned, human-readable description of a mid-stream error embedded in an
+    /// HTTP-200 SSE body, surfaced to the agent via `ProviderStream.lastError`
+    /// so the retry notice can explain *why*.
+    stream_error_message: ?[]u8 = null,
+
     const ToolUseInProgress = struct {
         /// Block index emitted to the receiver for this tool call's
         /// onBlockStart / onContentDelta / onBlockComplete callbacks.
@@ -385,6 +396,23 @@ const StreamState = struct {
         self.blocks.deinit(self.allocator);
         if (self.active_tool) |*tu| tu.deinit(self.allocator);
         self.closed_tool_indices.deinit();
+        if (self.stream_error_message) |s| self.allocator.free(s);
+    }
+
+    /// Record a readable description of an embedded stream error, combining
+    /// the error `type` and `message` into one owned string (either may be
+    /// absent). Replaces any previous value.
+    fn setStreamErrorMessage(self: *StreamState, kind: ?[]const u8, message: ?[]const u8) !void {
+        if (self.stream_error_message) |old| self.allocator.free(old);
+        self.stream_error_message = null;
+        self.stream_error_message = if (kind != null and message != null)
+            try std.fmt.allocPrint(self.allocator, "{s}: {s}", .{ kind.?, message.? })
+        else if (kind) |k|
+            try self.allocator.dupe(u8, k)
+        else if (message) |m|
+            try self.allocator.dupe(u8, m)
+        else
+            null;
     }
 
     /// Close the active text/thinking block (if any) and emit
@@ -683,6 +711,9 @@ fn handleEvent(
                 d.error_type, d.error_message,
             });
         }
+        // Stash a readable description so the agent's retry notice can
+        // explain *why* the stream failed. Owned by `state`.
+        state.setStreamErrorMessage(d.error_type, d.error_message) catch {};
         return error.ProviderStreamMalformed;
     }