fix anthropic thinking effort json placement

1 files changed, 9 insertions, 3 deletions

diff --git a/libpanto/src/config.zig b/libpanto/src/config.zig
index 587f00a..4aae81f 100644
--- a/libpanto/src/config.zig
+++ b/libpanto/src/config.zig
@@ -46,7 +46,8 @@ pub const Thinking = enum {
     /// Do not request extended thinking.
     disabled,
     /// Manual extended thinking with an explicit token budget (`thinking_budget_tokens`).
-    /// Supported on all current models including Haiku 4.5. Default.
+    /// Supported on Haiku 4.5 and older models, but NOT on Opus 4.8+ (which
+    /// only accepts adaptive). Not safe as a cross-model default.
     enabled,
     /// Adaptive thinking: Claude decides when and how much to think.
     /// Requires Opus 4.6 / Sonnet 4.6 or newer; automatic on Opus 4.7+.
@@ -82,7 +83,12 @@ pub const AnthropicMessagesConfig = struct {
     /// Extended-thinking mode. `.enabled` sends a manual thinking block with
     /// `thinking_budget_tokens`; `.adaptive` lets Claude decide and uses
     /// `effort` instead. `.disabled` omits thinking entirely.
-    thinking: Thinking = .enabled,
+    ///
+    /// Defaults to `.disabled`: it is the only mode accepted by every current
+    /// model. `.enabled` fails on Opus 4.8+ (adaptive-only) and `.adaptive`
+    /// fails on Haiku 4.5 (no adaptive support), so neither is a safe default
+    /// without parsing model strings.
+    thinking: Thinking = .disabled,
     /// Effort level for adaptive thinking. Only emitted on the wire when
     /// `thinking == .adaptive`; ignored otherwise.
     effort: Effort = .medium,
@@ -274,7 +280,7 @@ test "ProviderConfig - anthropic_messages variant" {
     try t.expectEqual(APIStyle.anthropic_messages, cfg.style());
     try t.expectEqualStrings("2023-06-01", cfg.anthropic_messages.api_version);
     try t.expectEqual(@as(u32, 64_000), cfg.anthropic_messages.max_tokens);
-    try t.expectEqual(Thinking.enabled, cfg.anthropic_messages.thinking);
+    try t.expectEqual(Thinking.disabled, cfg.anthropic_messages.thinking);
     try t.expectEqual(Effort.medium, cfg.anthropic_messages.effort);
     try t.expectEqual(@as(?u32, 32_000), cfg.anthropic_messages.thinking_budget_tokens);
     try t.expectEqual(false, cfg.anthropic_messages.thinking_interleaved);