1 files changed, 214 insertions, 0 deletions
diff --git a/crates/phone-opus/src/mcp/fault.rs b/crates/phone-opus/src/mcp/fault.rs
new file mode 100644
index 0000000..5b23f79
--- /dev/null
+++ b/crates/phone-opus/src/mcp/fault.rs
@@ -0,0 +1,214 @@
+use libmcp::{Fault, FaultClass, FaultCode, Generation, RecoveryDirective, ToolErrorDetail};
+use serde::{Deserialize, Serialize};
+use serde_json::{Value, json};
+
+#[derive(Clone, Copy, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub(crate) enum FaultStage {
+    Host,
+    Worker,
+    Claude,
+    Transport,
+    Protocol,
+    Rollout,
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub(crate) struct FaultRecord {
+    pub(crate) fault: Fault,
+    pub(crate) stage: FaultStage,
+    pub(crate) operation: String,
+    pub(crate) jsonrpc_code: i64,
+    pub(crate) retryable: bool,
+    pub(crate) retried: bool,
+}
+
+impl FaultRecord {
+    pub(crate) fn invalid_input(
+        generation: Generation,
+        stage: FaultStage,
+        operation: impl Into<String>,
+        detail: impl Into<String>,
+    ) -> Self {
+        Self::new(
+            generation,
+            FaultClass::Protocol,
+            "invalid_input",
+            RecoveryDirective::AbortRequest,
+            stage,
+            operation,
+            detail,
+            -32602,
+        )
+    }
+
+    pub(crate) fn not_initialized(
+        generation: Generation,
+        stage: FaultStage,
+        operation: impl Into<String>,
+        detail: impl Into<String>,
+    ) -> Self {
+        Self::new(
+            generation,
+            FaultClass::Protocol,
+            "not_initialized",
+            RecoveryDirective::AbortRequest,
+            stage,
+            operation,
+            detail,
+            -32002,
+        )
+    }
+
+    pub(crate) fn transport(
+        generation: Generation,
+        stage: FaultStage,
+        operation: impl Into<String>,
+        detail: impl Into<String>,
+    ) -> Self {
+        Self::new(
+            generation,
+            FaultClass::Transport,
+            "transport_failure",
+            RecoveryDirective::RestartAndReplay,
+            stage,
+            operation,
+            detail,
+            -32603,
+        )
+    }
+
+    pub(crate) fn process(
+        generation: Generation,
+        stage: FaultStage,
+        operation: impl Into<String>,
+        detail: impl Into<String>,
+    ) -> Self {
+        Self::new(
+            generation,
+            FaultClass::Process,
+            "process_failure",
+            RecoveryDirective::RestartAndReplay,
+            stage,
+            operation,
+            detail,
+            -32603,
+        )
+    }
+
+    pub(crate) fn downstream(
+        generation: Generation,
+        stage: FaultStage,
+        operation: impl Into<String>,
+        detail: impl Into<String>,
+    ) -> Self {
+        Self::new(
+            generation,
+            FaultClass::Downstream,
+            "downstream_failure",
+            RecoveryDirective::AbortRequest,
+            stage,
+            operation,
+            detail,
+            -32603,
+        )
+    }
+
+    pub(crate) fn internal(
+        generation: Generation,
+        stage: FaultStage,
+        operation: impl Into<String>,
+        detail: impl Into<String>,
+    ) -> Self {
+        Self::new(
+            generation,
+            FaultClass::Invariant,
+            "internal_failure",
+            RecoveryDirective::AbortRequest,
+            stage,
+            operation,
+            detail,
+            -32603,
+        )
+    }
+
+    pub(crate) fn rollout(
+        generation: Generation,
+        operation: impl Into<String>,
+        detail: impl Into<String>,
+    ) -> Self {
+        Self::new(
+            generation,
+            FaultClass::Rollout,
+            "rollout_failure",
+            RecoveryDirective::RestartAndReplay,
+            FaultStage::Rollout,
+            operation,
+            detail,
+            -32603,
+        )
+    }
+
+    pub(crate) fn mark_retried(mut self) -> Self {
+        self.retried = true;
+        self
+    }
+
+    pub(crate) fn message(&self) -> &str {
+        self.fault.detail.as_str()
+    }
+
+    pub(crate) fn error_detail(&self) -> ToolErrorDetail {
+        ToolErrorDetail {
+            code: Some(self.jsonrpc_code),
+            kind: Some(self.fault.code.as_str().to_owned()),
+            message: Some(self.message().to_owned()),
+        }
+    }
+
+    pub(crate) fn into_jsonrpc_error(self) -> Value {
+        json!({
+            "code": self.jsonrpc_code,
+            "message": self.message(),
+            "data": self,
+        })
+    }
+
+    pub(crate) fn into_tool_result(self) -> Value {
+        json!({
+            "content": [{
+                "type": "text",
+                "text": self.message(),
+            }],
+            "structuredContent": self,
+            "isError": true,
+        })
+    }
+
+    fn new(
+        generation: Generation,
+        class: FaultClass,
+        code: &'static str,
+        directive: RecoveryDirective,
+        stage: FaultStage,
+        operation: impl Into<String>,
+        detail: impl Into<String>,
+        jsonrpc_code: i64,
+    ) -> Self {
+        let fault = Fault::new(generation, class, fault_code(code), directive, detail);
+        Self {
+            retryable: directive != RecoveryDirective::AbortRequest,
+            fault,
+            stage,
+            operation: operation.into(),
+            jsonrpc_code,
+            retried: false,
+        }
+    }
+}
+
+fn fault_code(code: &'static str) -> FaultCode {
+    match FaultCode::try_new(code.to_owned()) {
+        Ok(value) => value,
+        Err(_) => std::process::abort(),
+    }
+}