fix: add xAI/Grok API compatibility (#2809)

Co-authored-by: Amit Singh <amitksingh1490@gmail.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Author: 3 people

crates/forge_app/src/dto/openai/transformers/make_xai_compat.rs

@@ -0,0 +1,48 @@
+use forge_domain::Transformer;
+
+use crate::dto::openai::Request;
+
+/// Makes the Request compatible with xAI's API.
+/// xAI's /v1/chat/completions is OpenAI-compatible but rejects several
+/// parameters that OpenAI accepts.
+pub struct MakeXaiCompat;
+
+impl Transformer for MakeXaiCompat {
+    type Value = Request;
+
+    fn transform(&mut self, mut request: Self::Value) -> Self::Value {
+        // xAI rejects stream_options
+        request.stream_options = None;
+
+        // xAI uses max_tokens, not max_completion_tokens
+        // MakeOpenAiCompat already moved max_tokens → max_completion_tokens,
+        // so move it back
+        if request.max_completion_tokens.is_some() && request.max_tokens.is_none() {
+            request.max_tokens = request.max_completion_tokens.take();
+        }
+        request.max_completion_tokens = None;
+
+        // xAI does not support parallel_tool_calls
+        request.parallel_tool_calls = None;
+
+        // xAI does not support prediction
+        request.prediction = None;
+
+        // xAI does not support reasoning_effort (uses model variants instead)
+        request.reasoning_effort = None;
+
+        // xAI does not support thinking config
+        request.thinking = None;
+
+        // xAI does not support logit_bias
+        request.logit_bias = None;
+
+        // xAI does not support top_logprobs
+        request.top_logprobs = None;
+
+        // xAI does not support seed
+        request.seed = None;
+
+        request
+    }
+}

crates/forge_app/src/dto/openai/transformers/mod.rs

@@ -3,6 +3,7 @@ mod github_copilot_reasoning;
 mod kimi_k2_reasoning;
 mod make_cerebras_compat;
 mod make_openai_compat;
+mod make_xai_compat;
 mod minimax;
 mod normalize_tool_schema;
 mod pipeline;

crates/forge_app/src/dto/openai/transformers/pipeline.rs

@@ -6,6 +6,7 @@ use super::github_copilot_reasoning::GitHubCopilotReasoning;
 use super::kimi_k2_reasoning::KimiK2Reasoning;
 use super::make_cerebras_compat::MakeCerebrasCompat;
 use super::make_openai_compat::MakeOpenAiCompat;
+use super::make_xai_compat::MakeXaiCompat;
 use super::minimax::SetMinimaxParams;
 use super::normalize_tool_schema::{
     EnforceStrictResponseFormatSchema, EnforceStrictToolSchema, NormalizeToolSchema,
@@ -67,6 +68,8 @@ impl Transformer for ProviderPipeline<'_> {
 
         let cerebras_compat = MakeCerebrasCompat.when(move |_| provider.id == ProviderId::CEREBRAS);
 
+        let xai_compat = MakeXaiCompat.when(move |_| provider.id == ProviderId::XAI);
+
         let trim_tool_call_ids = TrimToolCallIds.when(move |_| provider.id == ProviderId::OPENAI);
 
         let strict_schema = EnforceStrictToolSchema
@@ -75,6 +78,7 @@ impl Transformer for ProviderPipeline<'_> {
                 provider.id == ProviderId::FIREWORKS_AI
                     || provider.id == ProviderId::OPENCODE_ZEN
                     || provider.id == ProviderId::OPENCODE_GO
+                    || provider.id == ProviderId::XAI
             });
 
         let mut combined = zai_thinking
@@ -85,6 +89,7 @@ impl Transformer for ProviderPipeline<'_> {
             .pipe(github_copilot_reasoning)
             .pipe(kimi_k2_reasoning)
             .pipe(cerebras_compat)
+            .pipe(xai_compat)
             .pipe(trim_tool_call_ids)
             .pipe(strict_schema)
             .pipe(NormalizeToolSchema);