phase 2 done

1 files changed, 50 insertions, 16 deletions

diff --git a/libpanto/src/config.zig b/libpanto/src/config.zig
index 74bdcc7..e395230 100644
--- a/libpanto/src/config.zig
+++ b/libpanto/src/config.zig
@@ -1,5 +1,14 @@
+//! Per-provider configuration.
+//!
+//! `Config` is a tagged union keyed by `APIStyle`. Each variant carries the
+//! settings specific to one wire dialect. New providers add a new tag and a
+//! new payload struct here; nothing else in libpanto needs a central enum
+//! refresh.
+
+/// The wire dialect a provider speaks.
 pub const APIStyle = enum {
     openai_chat,
+    anthropic_messages,
 };
 
 /// Reasoning intensity hint sent to providers that support it.
@@ -17,37 +26,62 @@ pub const ReasoningEffort = enum {
     high,
 };
 
-pub const Config = struct {
-    api_style: APIStyle,
+pub const OpenAIChatConfig = struct {
     api_key: []const u8,
     base_url: []const u8,
     model: []const u8,
     reasoning: ReasoningEffort = .default,
 };
 
+pub const AnthropicMessagesConfig = struct {
+    api_key: []const u8,
+    base_url: []const u8,
+    model: []const u8,
+    /// Value sent in the `anthropic-version` header.
+    api_version: []const u8 = "2023-06-01",
+    /// Required by Anthropic's Messages API.
+    max_tokens: u32 = 4096,
+};
+
+pub const Config = union(APIStyle) {
+    openai_chat: OpenAIChatConfig,
+    anthropic_messages: AnthropicMessagesConfig,
+
+    pub fn style(self: Config) APIStyle {
+        return @as(APIStyle, self);
+    }
+};
+
 const t = @import("std").testing;
 
-test "Config - construct with all fields" {
-    const cfg = Config{
-        .api_style = .openai_chat,
+test "Config - openai_chat variant" {
+    const cfg: Config = .{ .openai_chat = .{
         .api_key = "sk-test",
         .base_url = "https://api.openai.com/v1",
         .model = "gpt-4o",
         .reasoning = .high,
-    };
-    try t.expectEqual(APIStyle.openai_chat, cfg.api_style);
-    try t.expectEqualStrings("sk-test", cfg.api_key);
-    try t.expectEqualStrings("https://api.openai.com/v1", cfg.base_url);
-    try t.expectEqualStrings("gpt-4o", cfg.model);
-    try t.expectEqual(ReasoningEffort.high, cfg.reasoning);
+    } };
+    try t.expectEqual(APIStyle.openai_chat, cfg.style());
+    try t.expectEqualStrings("sk-test", cfg.openai_chat.api_key);
+    try t.expectEqual(ReasoningEffort.high, cfg.openai_chat.reasoning);
+}
+
+test "Config - anthropic_messages variant" {
+    const cfg: Config = .{ .anthropic_messages = .{
+        .api_key = "sk-ant-test",
+        .base_url = "https://api.anthropic.com",
+        .model = "claude-sonnet-4-20250514",
+    } };
+    try t.expectEqual(APIStyle.anthropic_messages, cfg.style());
+    try t.expectEqualStrings("2023-06-01", cfg.anthropic_messages.api_version);
+    try t.expectEqual(@as(u32, 4096), cfg.anthropic_messages.max_tokens);
 }
 
-test "Config - reasoning defaults to .default" {
-    const cfg = Config{
-        .api_style = .openai_chat,
+test "Config - openai_chat reasoning defaults to .default" {
+    const cfg: Config = .{ .openai_chat = .{
         .api_key = "k",
         .base_url = "u",
         .model = "m",
-    };
-    try t.expectEqual(ReasoningEffort.default, cfg.reasoning);
+    } };
+    try t.expectEqual(ReasoningEffort.default, cfg.openai_chat.reasoning);
 }