diff --git a/Packages/OsaurusCore/Managers/Model/ModelManager.swift b/Packages/OsaurusCore/Managers/Model/ModelManager.swift
index c87d515f6..dc6595695 100644
--- a/Packages/OsaurusCore/Managers/Model/ModelManager.swift
+++ b/Packages/OsaurusCore/Managers/Model/ModelManager.swift
@@ -188,7 +188,27 @@ final class ModelManager: NSObject, ObservableObject {
 
         // Pull the OsaurusAI HF org listing once on launch so newly published
         // models surface in the Recommended tab without requiring a code push.
-        Task { [weak self] in await self?.loadOsaurusAIOrgModels() }
+        //
+        // The unit-test runner constructs `ModelManager()` repeatedly to drive
+        // `applyOsaurusOrgFetch` directly. If the launch-time HF fetch races
+        // with those test calls, whichever finishes last wins and the merge
+        // result is non-deterministic — that's the regression class behind
+        // `ModelManagerSuggestedTests/applyOsaurusOrgFetch_*` flaking in CI.
+        // Skip the background fetch under XCTest; production launches still
+        // get it because `XCTestConfigurationFilePath` is only set inside
+        // a test host.
+        if !Self.isRunningInTestEnvironment {
+            Task { [weak self] in await self?.loadOsaurusAIOrgModels() }
+        }
+    }
+
+    /// True when the current process was launched by xctest. Used to gate
+    /// network-touching launch-time side effects so tests can drive the
+    /// affected code paths deterministically.
+    nonisolated private static var isRunningInTestEnvironment: Bool {
+        ProcessInfo.processInfo.environment["XCTestConfigurationFilePath"] != nil
+            || ProcessInfo.processInfo.environment["XCTestBundlePath"] != nil
+            || ProcessInfo.processInfo.environment["XCTestSessionIdentifier"] != nil
     }
 
     // MARK: - Public Methods
diff --git a/Packages/OsaurusCore/Networking/HTTPHandler.swift b/Packages/OsaurusCore/Networking/HTTPHandler.swift
index 0f8877549..008642f71 100644
--- a/Packages/OsaurusCore/Networking/HTTPHandler.swift
+++ b/Packages/OsaurusCore/Networking/HTTPHandler.swift
@@ -4089,7 +4089,25 @@ final class HTTPHandler: ChannelInboundHandler, Sendable {
                     finishReason: .toolCalls
                 )
             } catch {
-                let errorResp = AnthropicError(message: error.localizedDescription, errorType: "api_error")
+                // Mirror the /v1/chat/completions mapping from PR #863: an
+                // unknown model id is a 404 client error, a missing provider
+                // is 503, etc. Without this, every misconfigured request
+                // looks like a 500 server fault and the WorkView error
+                // classifier / API consumers can't give actionable feedback.
+                let status: HTTPResponseStatus
+                let anthropicErrorType: String
+                if let engineError = error as? ChatEngine.EngineError {
+                    status = HTTPResponseStatus(statusCode: engineError.httpStatus)
+                    anthropicErrorType = engineError.httpStatus >= 500 ? "api_error" : "invalid_request_error"
+                } else {
+                    status = .internalServerError
+                    anthropicErrorType = "api_error"
+                }
+                let errorMessage =
+                    (error as? ChatEngine.EngineError)?.errorDescription
+                    ?? error.localizedDescription
+                let errorResp = AnthropicError(
+                    message: errorMessage, errorType: anthropicErrorType)
                 let errorJson =
                     (try? JSONEncoder().encode(errorResp))
                     .map { String(decoding: $0, as: UTF8.self) }
@@ -4098,9 +4116,10 @@ final class HTTPHandler: ChannelInboundHandler, Sendable {
                 headers.append(contentsOf: cors)
                 let headersCopy = headers
                 let body = errorJson
+                let wireStatus = status
 
                 hop {
-                    var responseHead = HTTPResponseHead(version: head.version, status: .internalServerError)
+                    var responseHead = HTTPResponseHead(version: head.version, status: wireStatus)
                     var buffer = ctx.value.channel.allocator.buffer(capacity: body.utf8.count)
                     buffer.writeString(body)
                     var nioHeaders = HTTPHeaders()
@@ -4121,7 +4140,7 @@ final class HTTPHandler: ChannelInboundHandler, Sendable {
                     path: "/messages",
                     userAgent: logUserAgent,
                     requestBody: logRequestBody,
-                    responseStatus: 500,
+                    responseStatus: Int(status.code),
                     startTime: logStartTime,
                     model: logModel,
                     errorMessage: error.localizedDescription
@@ -4696,7 +4715,25 @@ final class HTTPHandler: ChannelInboundHandler, Sendable {
                     finishReason: .toolCalls
                 )
             } catch {
-                let errorResp = OpenResponsesErrorResponse(code: "api_error", message: error.localizedDescription)
+                // Mirror the /v1/chat/completions mapping from PR #863:
+                // unknown-model is 404, service-unavailable is 503, etc.,
+                // so API consumers and the WorkView error classifier see
+                // the same actionable status codes here as on the OpenAI
+                // chat-completions endpoint.
+                let status: HTTPResponseStatus
+                let errorCode: String
+                if let engineError = error as? ChatEngine.EngineError {
+                    status = HTTPResponseStatus(statusCode: engineError.httpStatus)
+                    errorCode = engineError.httpStatus >= 500 ? "api_error" : "invalid_request_error"
+                } else {
+                    status = .internalServerError
+                    errorCode = "api_error"
+                }
+                let errorMessage =
+                    (error as? ChatEngine.EngineError)?.errorDescription
+                    ?? error.localizedDescription
+                let errorResp = OpenResponsesErrorResponse(
+                    code: errorCode, message: errorMessage)
                 let errorJson =
                     (try? JSONEncoder().encode(errorResp))
                     .map { String(decoding: $0, as: UTF8.self) }
@@ -4705,9 +4742,10 @@ final class HTTPHandler: ChannelInboundHandler, Sendable {
                 headers.append(contentsOf: cors)
                 let headersCopy = headers
                 let body = errorJson
+                let wireStatus = status
 
                 hop {
-                    var responseHead = HTTPResponseHead(version: head.version, status: .internalServerError)
+                    var responseHead = HTTPResponseHead(version: head.version, status: wireStatus)
                     var buffer = ctx.value.channel.allocator.buffer(capacity: body.utf8.count)
                     buffer.writeString(body)
                     var nioHeaders = HTTPHeaders()
@@ -4728,7 +4766,7 @@ final class HTTPHandler: ChannelInboundHandler, Sendable {
                     path: "/responses",
                     userAgent: logUserAgent,
                     requestBody: logRequestBody,
-                    responseStatus: 500,
+                    responseStatus: Int(status.code),
                     startTime: logStartTime,
                     model: logModel,
                     errorMessage: error.localizedDescription