From df2edee86eec2a8deb0ad57b5d20552199c12b65 Mon Sep 17 00:00:00 2001
From: T <t@tjp.lol>
Date: Mon, 25 May 2026 13:24:02 -0700
Subject: phase 1 done

---
 libpanto/src/provider.zig | 47 ++++++++++++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 15 deletions(-)

(limited to 'libpanto/src/provider.zig')

diff --git a/libpanto/src/provider.zig b/libpanto/src/provider.zig
index 8d6eea5..16c3dd6 100644
--- a/libpanto/src/provider.zig
+++ b/libpanto/src/provider.zig
@@ -14,36 +14,53 @@ pub const BlockMeta = struct {
     tool_name: ?[]const u8 = null,
 };
 
+/// Vtable for receiving streaming events from a Provider.
+///
+/// The lifecycle callbacks (`onMessageStart` ... `onMessageComplete`) return
+/// `anyerror!void`. Returning an error aborts the in-flight turn: the Provider
+/// stops streaming, calls `onError(err)`, and propagates `err` out of
+/// `streamStep`. No partial assistant message is appended to the conversation.
+///
+/// `onError` is the receiver's cleanup hook. It fires exactly once per failed
+/// turn, whether the error originated in the receiver itself (a write failure)
+/// or in the Provider (HTTP/parse/stream failure). It is the last callback the
+/// receiver will see for that turn. `onError` itself cannot fail; receivers
+/// must swallow secondary failures during cleanup.
 pub const ReceiverVTable = struct {
-    onMessageStart: *const fn (*anyopaque, conversation.MessageRole) void,
-    onBlockStart: *const fn (*anyopaque, ContentBlockType, usize, ?BlockMeta) void,
-    onContentDelta: *const fn (*anyopaque, usize, []const u8) void,
-    onBlockComplete: *const fn (*anyopaque, usize, conversation.ContentBlock) void,
-    onMessageComplete: *const fn (*anyopaque, conversation.Message) void,
+    onMessageStart: *const fn (*anyopaque, conversation.MessageRole) anyerror!void,
+    onBlockStart: *const fn (*anyopaque, ContentBlockType, usize, ?BlockMeta) anyerror!void,
+    onContentDelta: *const fn (*anyopaque, usize, []const u8) anyerror!void,
+    onBlockComplete: *const fn (*anyopaque, usize, conversation.ContentBlock) anyerror!void,
+    onMessageComplete: *const fn (*anyopaque, conversation.Message) anyerror!void,
+    onError: *const fn (*anyopaque, anyerror) void,
 };
 
 pub const Receiver = struct {
     ptr: *anyopaque,
     vtable: *const ReceiverVTable,
 
-    pub fn onMessageStart(self: Receiver, role: conversation.MessageRole) void {
-        self.vtable.onMessageStart(self.ptr, role);
+    pub fn onMessageStart(self: Receiver, role: conversation.MessageRole) !void {
+        try self.vtable.onMessageStart(self.ptr, role);
     }
 
-    pub fn onBlockStart(self: Receiver, block_type: ContentBlockType, index: usize, meta: ?BlockMeta) void {
-        self.vtable.onBlockStart(self.ptr, block_type, index, meta);
+    pub fn onBlockStart(self: Receiver, block_type: ContentBlockType, index: usize, meta: ?BlockMeta) !void {
+        try self.vtable.onBlockStart(self.ptr, block_type, index, meta);
     }
 
-    pub fn onContentDelta(self: Receiver, block_index: usize, delta: []const u8) void {
-        self.vtable.onContentDelta(self.ptr, block_index, delta);
+    pub fn onContentDelta(self: Receiver, block_index: usize, delta: []const u8) !void {
+        try self.vtable.onContentDelta(self.ptr, block_index, delta);
     }
 
-    pub fn onBlockComplete(self: Receiver, block_index: usize, block: conversation.ContentBlock) void {
-        self.vtable.onBlockComplete(self.ptr, block_index, block);
+    pub fn onBlockComplete(self: Receiver, block_index: usize, block: conversation.ContentBlock) !void {
+        try self.vtable.onBlockComplete(self.ptr, block_index, block);
     }
 
-    pub fn onMessageComplete(self: Receiver, message: conversation.Message) void {
-        self.vtable.onMessageComplete(self.ptr, message);
+    pub fn onMessageComplete(self: Receiver, message: conversation.Message) !void {
+        try self.vtable.onMessageComplete(self.ptr, message);
+    }
+
+    pub fn onError(self: Receiver, err: anyerror) void {
+        self.vtable.onError(self.ptr, err);
     }
 };
 
-- 
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