Fix Sonnet 4.5 effort parameter error by converting to thinking API

claude-sonnet-4-5 doesn't support output_config.effort — it needs the
older thinking API with budget_tokens. Add an `effort` feature flag to
ModelFeatures and have the Anthropic adapter auto-convert reasoning_effort
to a thinking config for models that lack effort support.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/crates/fabro-llm/src/providers/anthropic.rs

@@ -523,6 +523,18 @@ fn extract_thinking_config(
         .cloned()
 }
 
+/// Map a reasoning effort level to a thinking `budget_tokens` value for models
+/// that don't support the `output_config.effort` parameter (e.g. claude-sonnet-4-5).
+fn effort_to_budget_tokens(effort: &str, max_tokens: i64) -> i64 {
+    let budget = match effort {
+        "low" => max_tokens / 4,
+        "high" => max_tokens * 3 / 4,
+        _ => max_tokens / 2, // "medium" or unknown
+    };
+    // Anthropic requires budget_tokens >= 1024
+    budget.max(1024)
+}
+
 fn is_auto_cache_enabled(provider_options: Option<&serde_json::Value>) -> bool {
     provider_options
         .and_then(|opts| opts.get("anthropic"))
@@ -1072,22 +1084,48 @@ fn build_api_request(
         apply_cache_control_to_conversation_prefix(&mut api_messages);
     }
 
-    let thinking = extract_thinking_config(request.provider_options.as_ref());
+    let explicit_thinking = extract_thinking_config(request.provider_options.as_ref());
 
-    let output_config = request
-        .reasoning_effort
-        .as_ref()
-        .map(|effort| serde_json::json!({"effort": effort}));
+    // Check whether this model supports the `output_config.effort` parameter.
+    // Older reasoning models (e.g. claude-sonnet-4-5) need `thinking` with
+    // `budget_tokens` instead.
+    let model_info = fabro_model::get_model_info(&request.model);
+    let supports_effort = model_info.as_ref().is_none_or(|m| m.features.effort);
+
+    let mut resolved_max_tokens = request
+        .max_tokens
+        .or_else(|| model_info.as_ref().and_then(|m| m.limits.max_output))
+        .unwrap_or(65536);
+
+    let (thinking, output_config) = if let Some(effort) = &request.reasoning_effort {
+        if supports_effort {
+            (
+                explicit_thinking,
+                Some(serde_json::json!({"effort": effort})),
+            )
+        } else if explicit_thinking.is_none() {
+            // Convert effort level to a thinking budget for models that don't
+            // support the effort parameter (e.g. claude-sonnet-4-5).
+            let budget = effort_to_budget_tokens(effort, resolved_max_tokens);
+            if resolved_max_tokens <= budget {
+                resolved_max_tokens = budget + 1024;
+            }
+            (
+                Some(serde_json::json!({"type": "enabled", "budget_tokens": budget})),
+                None,
+            )
+        } else {
+            // thinking already configured via provider_options; skip output_config
+            (explicit_thinking, None)
+        }
+    } else {
+        (explicit_thinking, None)
+    };
 
     let api_request = ApiRequest {
         model: request.model.clone(),
         messages: api_messages,
-        max_tokens: request
-            .max_tokens
-            .or_else(|| {
-                fabro_model::get_model_info(&request.model).and_then(|m| m.limits.max_output)
-            })
-            .unwrap_or(65536),
+        max_tokens: resolved_max_tokens,
         system: system_value,
         temperature: request.temperature,
         top_p: request.top_p,

lib/crates/fabro-model/src/catalog.json

@@ -6,7 +6,7 @@
     "display_name": "Claude Opus 4.6",
     "limits": { "context_window": 1000000, "max_output": 128000 },
     "training": "2025-08-01",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 15.0,
       "output_cost_per_mtok": 75.0,
@@ -38,7 +38,7 @@
     "display_name": "Claude Sonnet 4.6",
     "limits": { "context_window": 200000, "max_output": 64000 },
     "training": "2025-08-01",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 3.0,
       "output_cost_per_mtok": 15.0,
@@ -71,7 +71,7 @@
     "display_name": "GPT-5.2",
     "limits": { "context_window": 1047576, "max_output": 128000 },
     "training": "2025-08-31",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 1.75,
       "output_cost_per_mtok": 14.0,
@@ -87,7 +87,7 @@
     "display_name": "GPT-5 Mini",
     "limits": { "context_window": 1047576, "max_output": 128000 },
     "training": "2025-08-31",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 0.25,
       "output_cost_per_mtok": 2.0,
@@ -103,7 +103,7 @@
     "display_name": "GPT-5.2 Codex",
     "limits": { "context_window": 1047576, "max_output": 128000 },
     "training": "2025-08-31",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 1.75,
       "output_cost_per_mtok": 14.0,
@@ -119,7 +119,7 @@
     "display_name": "GPT-5.3 Codex",
     "limits": { "context_window": 1047576, "max_output": 128000 },
     "training": "2025-08-31",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 1.75,
       "output_cost_per_mtok": 14.0,
@@ -135,7 +135,7 @@
     "display_name": "GPT-5.3 Codex Spark",
     "limits": { "context_window": 131072, "max_output": 128000 },
     "training": "2025-08-31",
-    "features": { "tools": true, "vision": false, "reasoning": true },
+    "features": { "tools": true, "vision": false, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": null,
       "output_cost_per_mtok": null,
@@ -151,7 +151,7 @@
     "display_name": "GPT-5.4",
     "limits": { "context_window": 1047576, "max_output": 128000 },
     "training": "2025-08-31",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 2.5,
       "output_cost_per_mtok": 15.0,
@@ -168,7 +168,7 @@
     "display_name": "GPT-5.4 Pro",
     "limits": { "context_window": 1047576, "max_output": 128000 },
     "training": "2025-08-31",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 30.0,
       "output_cost_per_mtok": 180.0,
@@ -184,7 +184,7 @@
     "display_name": "GPT-5.4 Mini",
     "limits": { "context_window": 400000, "max_output": 128000 },
     "training": "2025-08-31",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 0.75,
       "output_cost_per_mtok": 4.50,
@@ -200,7 +200,7 @@
     "display_name": "Gemini 3.1 Pro (Preview)",
     "limits": { "context_window": 1048576, "max_output": 65536 },
     "training": "2025-01-01",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 2.0,
       "output_cost_per_mtok": 12.0,
@@ -217,7 +217,7 @@
     "display_name": "Gemini 3.1 Pro Custom Tools (Preview)",
     "limits": { "context_window": 1048576, "max_output": 65536 },
     "training": "2025-01-01",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 2.0,
       "output_cost_per_mtok": 12.0,
@@ -233,7 +233,7 @@
     "display_name": "Gemini 3 Flash (Preview)",
     "limits": { "context_window": 1048576, "max_output": 65536 },
     "training": "2025-01-01",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 0.5,
       "output_cost_per_mtok": 3.0,
@@ -249,7 +249,7 @@
     "display_name": "Gemini 3.1 Flash Lite (Preview)",
     "limits": { "context_window": 1048576, "max_output": 65536 },
     "training": "2025-01-01",
-    "features": { "tools": true, "vision": true, "reasoning": true },
+    "features": { "tools": true, "vision": true, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 0.25,
       "output_cost_per_mtok": 1.5,
@@ -316,7 +316,7 @@
     "display_name": "Mercury 2",
     "limits": { "context_window": 131072, "max_output": 50000 },
     "training": null,
-    "features": { "tools": true, "vision": false, "reasoning": true },
+    "features": { "tools": true, "vision": false, "reasoning": true, "effort": true },
     "costs": {
       "input_cost_per_mtok": 0.25,
       "output_cost_per_mtok": 0.75,

lib/crates/fabro-model/src/types.rs

@@ -13,6 +13,12 @@ pub struct ModelFeatures {
     pub tools: bool,
     pub vision: bool,
     pub reasoning: bool,
+    /// Whether the model supports the `reasoning_effort` / `effort` parameter
+    /// directly (e.g. Anthropic `output_config.effort`, OpenAI `reasoning.effort`).
+    /// Models with `reasoning=true` but `effort=false` (e.g. claude-sonnet-4-5)
+    /// need the older `thinking` API with `budget_tokens` instead.
+    #[serde(default)]
+    pub effort: bool,
 }
 
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]