feat(codec): add OCI Generative AI provider support

crates/adaptive/src/acg/request_surfaces/mod.rs

@@ -48,6 +48,8 @@ impl RequestSurface {
             ProviderSurface::OpenAIChat => Some(Self::OpenAIChat),
             ProviderSurface::OpenAIResponses => Some(Self::OpenAIResponses),
             ProviderSurface::AnthropicMessages => Some(Self::AnthropicMessages),
+            // No semantic ACG applier exists for OCI GenAI request shapes yet.
+            ProviderSurface::OCIGenAI => None,
             // Gemini generateContent ACG request editing is intentionally unsupported.
             ProviderSurface::GeminiGenerateContent => None,
         }

crates/adaptive/src/response_cache/key.rs

@@ -338,6 +338,12 @@ fn lossy_request_shape(surface: ProviderSurface, content: &Json) -> bool {
                     .is_some_and(|blocks| blocks.iter().any(lossy_system_block))
         }
         ProviderSurface::OpenAIResponses => false,
+        // OCI GenAI requests carry an envelope (`compartmentId`, `servingMode`)
+        // whose unmodeled fields the decode does not preserve in `extra`, and
+        // the generic scalar checks above target OpenAI-shaped keys rather
+        // than OCI camelCase. Keep OCI raw-keyed — a fallback only ever costs
+        // a miss.
+        ProviderSurface::OCIGenAI => true,
         ProviderSurface::GeminiGenerateContent => {
             object
                 .get("generationConfig")

crates/adaptive/src/response_cache/replay.rs

@@ -80,6 +80,11 @@ fn synthesize_replay_chunks(aggregate: &Json) -> Option<Vec<Json>> {
         ProviderSurface::AnthropicMessages => synthesize_anthropic_chunks(aggregate),
         ProviderSurface::OpenAIChat => synthesize_chat_chunks(aggregate),
         ProviderSurface::OpenAIResponses => synthesize_responses_chunks(aggregate),
+        // OCI GenAI streaming events are ChatResult-shaped deltas; the OCI
+        // stream collector accepts a full `chatResponse` aggregate as a single
+        // native chunk. `replay_is_lossy` still re-aggregates it and rejects
+        // shapes the streaming collector cannot preserve exactly.
+        ProviderSurface::OCIGenAI => vec![aggregate.clone()],
         // Gemini streaming events are GenerateContentResponse objects; a stored
         // aggregate is a valid single native chunk. `replay_is_lossy` still
         // re-aggregates it and rejects shapes the streaming collector cannot

crates/core/src/api/runtime/callbacks.rs

@@ -160,6 +160,8 @@ pub enum BuiltinLlmCodec {
     OpenAiResponses,
     /// Anthropic Messages request and response payloads.
     AnthropicMessages,
+    /// OCI Generative AI chat request and response payloads.
+    OCIGenAI,
     /// Gemini generateContent request and response payloads.
     GeminiGenerateContent,
 }
@@ -172,6 +174,7 @@ impl BuiltinLlmCodec {
             Self::OpenAiChat => "openai_chat",
             Self::OpenAiResponses => "openai_responses",
             Self::AnthropicMessages => "anthropic_messages",
+            Self::OCIGenAI => "oci_genai",
             Self::GeminiGenerateContent => "gemini_generate_content",
         }
     }

crates/core/src/codec/mod.rs

@@ -17,6 +17,7 @@
 pub mod anthropic;
 pub mod gemini_generate_content;
 pub mod model_pricing;
+pub mod oci_genai;
 pub mod openai_chat;
 pub mod openai_responses;
 pub mod optimization;