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fix(dispatch): align A2A protocol with v0.3.0 message/send #48

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70 changes: 55 additions & 15 deletions src/dispatch.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -404,25 +404,31 @@ fn appendJsonString(buf: *std.ArrayListUnmanaged(u8), allocator: std.mem.Allocat

// ── A2A Protocol Support ──────────────────────────────────────────────

/// Build an A2A (Agent-to-Agent) JSON-RPC 2.0 request body using tasks/send.
/// Build an A2A (Agent-to-Agent) JSON-RPC 2.0 request body using message/send.
/// The context_id provides session persistence — same context_id means same conversation.
fn buildA2aRequestBody(
allocator: std.mem.Allocator,
prompt: []const u8,
context_id: []const u8,
) ![]const u8 {
// Build the parts array
// Generate a unique messageId from the context_id
const message_id = try std.fmt.allocPrint(allocator, "msg-{s}", .{context_id});
defer allocator.free(message_id);

// Build the parts array — A2A v0.3.0 uses "kind" discriminator
const parts = [_]struct {
type: []const u8,
kind: []const u8,
text: []const u8,
}{
.{ .type = "text", .text = prompt },
.{ .kind = "text", .text = prompt },
};

// Build the message
// Build the message — NullClaw requires kind + messageId per A2A v0.3.0
const message = .{
.role = "user",
.parts = parts[0..],
.kind = "message",
.messageId = message_id,
};

// Build the params
Expand All @@ -435,7 +441,7 @@ fn buildA2aRequestBody(
return std.json.Stringify.valueAlloc(allocator, .{
.jsonrpc = "2.0",
.id = context_id,
.method = "tasks/send",
.method = "message/send",
.params = params,
}, .{});
}
Expand Down Expand Up @@ -537,14 +543,33 @@ fn parseA2aResponse(allocator: std.mem.Allocator, response_body: []const u8) !Di
}
}

// Extract text from artifacts[0].parts[0].text
// message/send (A2A v0.3.0): the result IS the Message — extract text
// from parts[0].text directly.
if (result_obj.get("parts")) |parts_val| {
if (parts_val == .array and parts_val.array.items.len > 0) {
const first_part = parts_val.array.items[0];
if (first_part == .object) {
if (first_part.object.get("text")) |text_val| {
if (text_val == .string) {
return DispatchResult{
.output = try allocator.dupe(u8, text_val.string),
.success = true,
.error_text = null,
};
}
}
}
}
}

// Legacy tasks/send shape: extract text from artifacts[0].parts[0].text
if (result_obj.get("artifacts")) |artifacts_val| {
if (artifacts_val == .array and artifacts_val.array.items.len > 0) {
const first_artifact = artifacts_val.array.items[0];
if (first_artifact == .object) {
if (first_artifact.object.get("parts")) |parts_val| {
if (parts_val == .array and parts_val.array.items.len > 0) {
const first_part = parts_val.array.items[0];
if (first_artifact.object.get("parts")) |artifact_parts| {
if (artifact_parts == .array and artifact_parts.array.items.len > 0) {
const first_part = artifact_parts.array.items[0];
if (first_part == .object) {
// Check for "text" field (A2A uses "text" key for text parts)
if (first_part.object.get("text")) |text_val| {
Expand All @@ -566,7 +591,7 @@ fn parseA2aResponse(allocator: std.mem.Allocator, response_body: []const u8) !Di
return DispatchResult{
.output = "",
.success = false,
.error_text = "A2A: no text found in artifacts",
.error_text = "A2A: no text found in response parts or artifacts",
};
}

Expand Down Expand Up @@ -1054,17 +1079,21 @@ test "buildA2aRequestBody: produces valid JSON-RPC 2.0 request" {

try std.testing.expectEqualStrings("2.0", obj.get("jsonrpc").?.string);
try std.testing.expectEqualStrings("run_abc_step_fix", obj.get("id").?.string);
try std.testing.expectEqualStrings("tasks/send", obj.get("method").?.string);
try std.testing.expectEqualStrings("message/send", obj.get("method").?.string);

const params = obj.get("params").?.object;
try std.testing.expectEqualStrings("run_abc_step_fix", params.get("contextId").?.string);

const message = params.get("message").?.object;
try std.testing.expectEqualStrings("user", message.get("role").?.string);
// A2A v0.3.0: message carries kind + messageId
try std.testing.expectEqualStrings("message", message.get("kind").?.string);
try std.testing.expectEqualStrings("msg-run_abc_step_fix", message.get("messageId").?.string);

const parts = message.get("parts").?.array;
try std.testing.expectEqual(@as(usize, 1), parts.items.len);
try std.testing.expectEqualStrings("text", parts.items[0].object.get("type").?.string);
// A2A v0.3.0: parts use "kind" discriminator, not "type"
try std.testing.expectEqualStrings("text", parts.items[0].object.get("kind").?.string);
try std.testing.expectEqualStrings("Fix the bug in main.py", parts.items[0].object.get("text").?.string);
}

Expand All @@ -1078,7 +1107,7 @@ test "buildRequestBody: a2a protocol produces JSON-RPC body" {
const obj = parsed.value.object;

try std.testing.expectEqualStrings("2.0", obj.get("jsonrpc").?.string);
try std.testing.expectEqualStrings("tasks/send", obj.get("method").?.string);
try std.testing.expectEqualStrings("message/send", obj.get("method").?.string);
// context_id is "run_{run_id}_step_{step_id}"
try std.testing.expectEqualStrings("run_run-1_step_step-1", obj.get("id").?.string);
}
Expand All @@ -1094,6 +1123,17 @@ test "parseA2aResponse: extracts text from successful response" {
try std.testing.expectEqualStrings("The bug has been fixed.", result.output);
}

test "parseA2aResponse: extracts text from message/send result (A2A v0.3.0)" {
const allocator = std.testing.allocator;
const response =
\\{"jsonrpc":"2.0","id":"req-1","result":{"role":"agent","parts":[{"kind":"text","text":"Reply from the agent."}],"kind":"message","messageId":"msg-42","contextId":"ctx-1"}}
;
const result = try parseA2aResponse(allocator, response);
defer allocator.free(result.output);
try std.testing.expect(result.success);
try std.testing.expectEqualStrings("Reply from the agent.", result.output);
}

test "parseA2aResponse: handles JSON-RPC error" {
const allocator = std.testing.allocator;
const response =
Expand Down Expand Up @@ -1122,7 +1162,7 @@ test "parseA2aResponse: handles missing artifacts" {
;
const result = try parseA2aResponse(allocator, response);
try std.testing.expect(!result.success);
try std.testing.expectEqualStrings("A2A: no text found in artifacts", result.error_text.?);
try std.testing.expectEqualStrings("A2A: no text found in response parts or artifacts", result.error_text.?);
}

test "parseA2aResponse: handles invalid JSON" {
Expand Down