Faults and error pipeline

This host installs a service behavior for observability but constructs no typed fault anywhere in its own source. Every failure that is not intercepted by that behavior reaches the caller as WCF's default fault for the thrown exception, carrying full exception detail.

Error handler

Aspect	Finding
IErrorHandler installed	Not readable from this host's source.** The in-repository sibling implementation, ErrorLogErrorHandler : IErrorHandler (src/WCF/SAIF.Services.WCF.Host/Extensions/ErrorLogErrorHandler.cs:11), logs the exception and does not shape the fault. The packaged SAIF.Services.WCF.Common.Extensions behavior applied here is expected to follow the same shape,* but this could not be verified from this repository.
ProvideFault behavior	Unknown — the type is external and its implementation is not in this repository**

Service behaviors

Aspect	Finding
IServiceBehavior applied	[LogErrorBehavior] on UC4Service (src/WCF/SAIF.Services.WCF.UC4.Host/UC4Service.cs:20)
Where the attribute type lives	Namespace SAIF.Services.WCF.Common.Extensions, not in this repository — it arrives from a referenced SAIF.* package whose identity could not be resolved from packages.config**
The in-repository look-alike	src/WCF/SAIF.Services.WCF.Host/Extensions/LogErrorBehaviorAttribute.cs declares LogErrorBehaviorAttribute : Attribute, IServiceBehavior in namespace SAIF.Services.WCF.Extensions — a different namespace — and this host has no project reference to it, so it is not the type applied here
Behavior configuration scope	The <serviceBehaviors><behavior> element in Web.config is unnamed, so it applies to every service in the host by default
Services decorated	UC4Service — the only service class this host registers

Caller-visible consequence: reading the [LogErrorBehavior] registration as a custom fault envelope would be a defect. By the shape of its in-repository sibling, the applied behavior's ProvideFault does not set a fault* — its contribution is observability, not the fault contract.

Include exception detail in faults

Setting	Value	Source
serviceDebug includeExceptionDetailInFaults	true	src/WCF/SAIF.Services.WCF.UC4.Host/Web.config
system.web/customErrors mode	Off	Web.config
system.webServer/httpErrors errorMode	Detailed	Web.config

Server exception detail, including stack traces, is returned to every caller of every operation. This host ships no Web.Release.config / Web.Debug.config transform, so the deployed configuration is the checked-in one unless a release-time transform outside this repository intervenes.**

Declared fault contracts

Element	Finding
[FaultContract] declarations	Unknown** — declared, if at all, on the external IUC4Service interface, which is not in scope
throw new FaultException / FaultException<T> in host code	None. A search of src/WCF/SAIF.Services.WCF.UC4.Host/*.cs for FaultException returns no match. No operation constructs a typed or untyped fault.

Failure modes by operation

Operation	What the caller receives on failure
ExecuteJob, ExecuteJobWithValues, ExecuteJobWithParameters, ExecuteJobWithJson (enum forms)	Whatever UC4EnvironmentFactory.GetUC4ClientId(environment) throws for an unmapped enum value**, then the failure modes of the corresponding AndClientId form; all surfaced as WCF default faults with exception detail
ExecuteJobWithClientId	Failure modes of ExecuteJobWithValuesAndClientId (it delegates with an empty value array)
ExecuteJobWithValuesAndClientId, ExecuteJobWithParametersAndClientId	ArgumentNullException-family exception from Enforce.ArgumentNotNull(jobName, "jobName") when jobName is null; NullReferenceException if the uc4.rules document is missing or does not deserialize (rules.UC4Rules.Environments is dereferenced unguarded)*; any exception thrown constructing UC4Client or calling the downstream service — all as WCF default faults
ExecuteJobWithJsonAndClientId	As above, plus Newtonsoft.Json deserialization exceptions from JsonConvert.DeserializeObject(jsonKeyValuePairs) on malformed caller input
All eight	A blocked job is not a fault. When IsJobAllowed returns false, the operation returns a default-constructed UC4Result and the explanatory message is discarded — see BR-UC4-005

Swallowed failures

No catch block in this host discards an exception without surfacing or logging it. A search of src/WCF/SAIF.Services.WCF.UC4.Host/*.cs for catch returns no matches at all — this host contains no try/catch block anywhere in its own source; every exception propagates unhandled to the WCF dispatcher.

Related documentation

• Index
• Overview
• Architecture
• Activation and hosting
• Operations
• Authentication and authorization
• Dependencies
• Configuration
• Operations and processes
• Business rules
• Operational runbook
• Tech debt

Note: Statements marked with * were inferred from code structure, naming conventions, or contextual evidence where direct confirmation was not available in source artifacts. Statements marked with ** could not be confirmed; treat as unknown until verified.

Sources

• src/WCF/SAIF.Services.WCF.UC4.Host/UC4Service.cs
• src/WCF/SAIF.Services.WCF.UC4.Host/Uc4Client.cs
• src/WCF/SAIF.Services.WCF.UC4.Host/Web.config
• src/WCF/SAIF.Services.WCF.Host/Extensions/LogErrorBehaviorAttribute.cs (comparison only — different namespace, not referenced by this host)
• src/WCF/SAIF.Services.WCF.Host/Extensions/ErrorLogErrorHandler.cs (comparison only)