diff --git a/README.md b/README.md
index 8c21793..0477307 100644
--- a/README.md
+++ b/README.md
@@ -219,6 +219,12 @@ if (boundaryLocation is not null)
 
 ## Custom Merge Strategy
 
+### Merge identity
+
+If your merge strategy inlines/expands directives (e.g., `@import`, `#include`), use the authoritative dependency
+identity returned by your `IResourceResolver<TContent>`. TinyPreprocessor provides this mapping to merge via
+`MergeContext<TContent, TDirective>.ResolvedReferences`.
+
 Implement `IMergeStrategy<TContent, TDirective, TContext>` for custom output formatting:
 
 ```csharp
@@ -237,6 +243,11 @@ public sealed class JsonMergeStrategy : IMergeStrategy<ReadOnlyMemory<char>, Inc
         //   mergeContext.SourceMapBuilder.AddOffsetSegment(resourceId, generatedStartOffset, originalStartOffset, length)
         // Use mergeContext.Diagnostics to report issues
 
+        // If you need to inline/expand directives:
+        // - Use mergeContext.ResolvedReferences to map (requestingResourceId, directiveIndex) -> resolved dependency ResourceId
+        // - Then fetch the already-processed dependency content from mergeContext.ResolvedCache
+        // Do NOT re-derive ResourceIds from raw reference strings (resolvers may implement custom mapping).
+
         return ReadOnlyMemory<char>.Empty;
     }
 }
diff --git a/docs/02-diagnostics-system.md b/docs/02-diagnostics-system.md
index 276a84a..22c4d59 100644
--- a/docs/02-diagnostics-system.md
+++ b/docs/02-diagnostics-system.md
@@ -161,29 +161,26 @@ diagnostics = new DiagnosticCollection()
 result = await resolver.ResolveAsync(reference, currentResource, ct)
 if not result.IsSuccess:
     diagnostics.Add(result.Error)
-    
-// During merge
-// Merge strategies should only add diagnostics for merge-time concerns (e.g., directive placement rules,
-// unsupported constructs, or missing data needed to build output), not for reference resolution.
-    // Continue processing other directives
+// During cycle detection
+for each cycle in graph.DetectCycles():
+    diagnostics.Add(new CircularDependencyDiagnostic(cycle))
+```
 
 ### Resolution vs. Merge Responsibility
 
 TinyPreprocessor separates responsibilities between phases:
 
 - **Resolution diagnostics** (e.g., `TPP0100` `ResolutionFailedDiagnostic`) are emitted when
-    `IResourceResolver.ResolveAsync(reference, relativeTo)` cannot produce an `IResource`.
+  `IResourceResolver.ResolveAsync(reference, relativeTo)` cannot produce an `IResource`.
 - **Merge diagnostics** (e.g., `TPP0300` `NonWholeLineDirectiveDiagnostic`) are emitted when merge logic detects
-    issues while producing output.
+  issues while producing output.
 
-Merge strategies that inline/expand directives must use the authoritative resolved dependency identity provided via
-`MergeContext.ResolvedReferences`. They must not re-derive a `ResourceId` from the raw reference string using
-path heuristics, because resolvers may implement custom mapping.
+Merge strategies should only add diagnostics for merge-time concerns (e.g., directive placement rules, unsupported
+constructs, or missing data needed to build output), not for reference resolution.
 
-// During cycle detection
-for each cycle in graph.DetectCycles():
-    diagnostics.Add(new CircularDependencyDiagnostic(cycle))
-```
+Merge strategies that inline/expand directives must use the authoritative resolved dependency identity provided via
+`MergeContext.ResolvedReferences`. They must not re-derive a `ResourceId` from the raw reference string using path
+heuristics, because resolvers may implement custom mapping.
 
 ### Checking Results
 
diff --git a/docs/05-merge-system.md b/docs/05-merge-system.md
index ee4e496..761965d 100644
--- a/docs/05-merge-system.md
+++ b/docs/05-merge-system.md
@@ -37,7 +37,7 @@ class MergeContext<TContent, TDirective>
         SourceMapBuilder : SourceMapBuilder   // for recording mappings
         Diagnostics      : DiagnosticCollection // for reporting issues
         ResolvedCache    : IReadOnlyDictionary<ResourceId, IResource<TContent>>  // for cross-referencing
-    ResolvedReferences : IReadOnlyDictionary<ResolvedReferenceKey, ResourceId> // directive occurrence -> resolved dependency id
+        ResolvedReferences : IReadOnlyDictionary<ResolvedReferenceKey, ResourceId> // directive occurrence -> resolved dependency id
         DirectiveModel   : IDirectiveModel<TDirective>  // for interpreting directive locations
         ContentModel     : IContentModel<TContent>  // for interpreting offsets + slicing content
 ```
@@ -62,6 +62,8 @@ dependency content. For these strategies, the **only** correct way to identify a
   - `directiveIndex` is the zero-based index of the directive in that resource's parsed directive list
 - **Value**: the resolved target `ResourceId` returned by the resolver
 
+In code, the key type is `MergeContext<TContent, TDirective>.ResolvedReferenceKey`.
+
 If a directive failed to resolve, it has **no entry** in this map.
 
 ---
diff --git a/docs/06-preprocessor-orchestrator.md b/docs/06-preprocessor-orchestrator.md
index 22bd6c4..5d8448f 100644
--- a/docs/06-preprocessor-orchestrator.md
+++ b/docs/06-preprocessor-orchestrator.md
@@ -81,7 +81,7 @@ class Preprocessor<TContent, TDirective, TContext>
         graph ← new ResourceDependencyGraph()
         cache ← new Dictionary<ResourceId, ResolvedResource>()
         sourceMapBuilder ← new SourceMapBuilder()
-        resolvedReferences ← new Dictionary<(ResourceId, directiveIndex), ResourceId>()
+        resolvedReferences ← new Dictionary<MergeContext.ResolvedReferenceKey, ResourceId>()
 
         // Phase 1: Recursive resolution
         await ResolveRecursiveAsync(root, depth: 0, ...)