diff --git a/java/hiddenapi_modular.go b/java/hiddenapi_modular.go
index 335f5b8..8174524 100644
--- a/java/hiddenapi_modular.go
+++ b/java/hiddenapi_modular.go
@@ -166,7 +166,7 @@
 //
 // The rule is initialized but not built so that the caller can modify it and select an appropriate
 // name.
-func ruleToGenerateHiddenAPIStubFlagsFile(ctx android.BuilderContext, outputPath android.OutputPath, bootDexJars android.Paths, sdkKindToPathList map[android.SdkKind]android.Paths) *android.RuleBuilder {
+func ruleToGenerateHiddenAPIStubFlagsFile(ctx android.BuilderContext, outputPath android.WritablePath, bootDexJars android.Paths, sdkKindToPathList map[android.SdkKind]android.Paths) *android.RuleBuilder {
 	// Singleton rule which applies hiddenapi on all boot class path dex files.
 	rule := android.NewRuleBuilder(pctx, ctx)
 
@@ -338,23 +338,49 @@
 	},
 }
 
-// hiddenAPIFlagFileInfo contains paths resolved from HiddenAPIFlagFileProperties
+// hiddenAPIFlagFileInfo contains paths resolved from HiddenAPIFlagFileProperties and also generated
+// by hidden API processing.
+//
+// This is used both for an individual bootclasspath_fragment to provide it to other modules and
+// for a module to collate the files from the fragments it depends upon. That is why the fields are
+// all Paths even though they are initialized with a single path.
 type hiddenAPIFlagFileInfo struct {
 	// categoryToPaths maps from the flag file category to the paths containing information for that
 	// category.
 	categoryToPaths map[*hiddenAPIFlagFileCategory]android.Paths
+
+	// The paths to the generated stub-flags.csv files.
+	StubFlagsPaths android.Paths
+
+	// The paths to the generated annotation-flags.csv files.
+	AnnotationFlagsPaths android.Paths
+
+	// The paths to the generated metadata.csv files.
+	MetadataPaths android.Paths
+
+	// The paths to the generated index.csv files.
+	IndexPaths android.Paths
+
+	// The paths to the generated all-flags.csv files.
+	AllFlagsPaths android.Paths
 }
 
 func (i *hiddenAPIFlagFileInfo) append(other hiddenAPIFlagFileInfo) {
 	for _, category := range hiddenAPIFlagFileCategories {
 		i.categoryToPaths[category] = append(i.categoryToPaths[category], other.categoryToPaths[category]...)
 	}
+	i.StubFlagsPaths = append(i.StubFlagsPaths, other.StubFlagsPaths...)
+	i.AnnotationFlagsPaths = append(i.AnnotationFlagsPaths, other.AnnotationFlagsPaths...)
+	i.MetadataPaths = append(i.MetadataPaths, other.MetadataPaths...)
+	i.IndexPaths = append(i.IndexPaths, other.IndexPaths...)
+	i.AllFlagsPaths = append(i.AllFlagsPaths, other.AllFlagsPaths...)
 }
 
 var hiddenAPIFlagFileInfoProvider = blueprint.NewProvider(hiddenAPIFlagFileInfo{})
 
-// ruleToGenerateHiddenApiFlags creates a rule to create the monolithic hidden API flags from the
-// flags from all the modules, the stub flags, augmented with some additional configuration files.
+// buildRuleToGenerateHiddenApiFlags creates a rule to create the monolithic hidden API flags from
+// the flags from all the modules, the stub flags, augmented with some additional configuration
+// files.
 //
 // baseFlagsPath is the path to the flags file containing all the information from the stubs plus
 // an entry for every single member in the dex implementation jars of the individual modules. Every
@@ -365,19 +391,7 @@
 //
 // augmentationInfo is a struct containing paths to files that augment the information provided by
 // the moduleSpecificFlagsPaths.
-// ruleToGenerateHiddenApiFlags creates a rule to create the monolithic hidden API flags from the
-// flags from all the modules, the stub flags, augmented with some additional configuration files.
-//
-// baseFlagsPath is the path to the flags file containing all the information from the stubs plus
-// an entry for every single member in the dex implementation jars of the individual modules. Every
-// signature in any of the other files MUST be included in this file.
-//
-// moduleSpecificFlagsPaths are the paths to the flags files generated by each module using
-// information from the baseFlagsPath as well as from annotations within the source.
-//
-// augmentationInfo is a struct containing paths to files that augment the information provided by
-// the moduleSpecificFlagsPaths.
-func ruleToGenerateHiddenApiFlags(ctx android.BuilderContext, outputPath android.WritablePath, baseFlagsPath android.Path, moduleSpecificFlagsPaths android.Paths, augmentationInfo hiddenAPIFlagFileInfo) {
+func buildRuleToGenerateHiddenApiFlags(ctx android.BuilderContext, name, desc string, outputPath android.WritablePath, baseFlagsPath android.Path, moduleSpecificFlagsPaths android.Paths, flagFileInfo *hiddenAPIFlagFileInfo) {
 	tempPath := tempPathForRestat(ctx, outputPath)
 	rule := android.NewRuleBuilder(pctx, ctx)
 	command := rule.Command().
@@ -388,7 +402,7 @@
 
 	// Add the options for the different categories of flag files.
 	for _, category := range hiddenAPIFlagFileCategories {
-		paths := augmentationInfo.categoryToPaths[category]
+		paths := flagFileInfo.categoryToPaths[category]
 		for _, path := range paths {
 			category.commandMutator(command, path)
 		}
@@ -396,5 +410,103 @@
 
 	commitChangeForRestat(rule, tempPath, outputPath)
 
-	rule.Build("hiddenAPIFlagsFile", "hiddenapi flags")
+	rule.Build(name, desc)
+}
+
+// hiddenAPIGenerateAllFlagsForBootclasspathFragment will generate all the flags for a fragment
+// of the bootclasspath.
+//
+// It takes:
+// * Map from android.SdkKind to stub dex jar paths defining the API for that sdk kind.
+// * The list of modules that are the contents of the fragment.
+// * The additional manually curated flag files to use.
+//
+// It generates:
+// * stub-flags.csv
+// * annotation-flags.csv
+// * metadata.csv
+// * index.csv
+// * all-flags.csv
+func hiddenAPIGenerateAllFlagsForBootclasspathFragment(ctx android.ModuleContext, contents []android.Module, stubJarsByKind map[android.SdkKind]android.Paths, flagFileInfo *hiddenAPIFlagFileInfo) {
+
+	hiddenApiSubDir := "modular-hiddenapi"
+
+	bootDexJars := android.Paths{}
+	classesJars := android.Paths{}
+	for _, module := range contents {
+		if hiddenAPI, ok := module.(hiddenAPIIntf); ok {
+			classesJars = append(classesJars, hiddenAPI.classesJars()...)
+			bootDexJar := hiddenAPI.bootDexJar()
+			if bootDexJar == nil {
+				ctx.ModuleErrorf("module %s does not provide a dex jar", module)
+			} else {
+				bootDexJars = append(bootDexJars, bootDexJar)
+			}
+		} else {
+			ctx.ModuleErrorf("module %s does not implement hiddenAPIIntf", module)
+		}
+	}
+
+	// Generate the stub-flags.csv.
+	stubFlagsCSV := android.PathForModuleOut(ctx, hiddenApiSubDir, "stub-flags.csv")
+	rule := ruleToGenerateHiddenAPIStubFlagsFile(ctx, stubFlagsCSV, bootDexJars, stubJarsByKind)
+	rule.Build("modularHiddenAPIStubFlagsFile", "modular hiddenapi stub flags")
+
+	// Generate the set of flags from the annotations in the source code.
+	annotationFlagsCSV := android.PathForModuleOut(ctx, hiddenApiSubDir, "annotation-flags.csv")
+	ctx.Build(pctx, android.BuildParams{
+		Rule:        hiddenAPIGenerateCSVRule,
+		Description: "modular hiddenapi annotation flags",
+		Inputs:      classesJars,
+		Output:      annotationFlagsCSV,
+		Implicit:    stubFlagsCSV,
+		Args: map[string]string{
+			"outFlag":      "--write-flags-csv",
+			"stubAPIFlags": stubFlagsCSV.String(),
+		},
+	})
+
+	// Generate the metadata from the annotations in the source code.
+	metadataCSV := android.PathForModuleOut(ctx, hiddenApiSubDir, "metadata.csv")
+	ctx.Build(pctx, android.BuildParams{
+		Rule:        hiddenAPIGenerateCSVRule,
+		Description: "modular hiddenapi metadata",
+		Inputs:      classesJars,
+		Output:      metadataCSV,
+		Implicit:    stubFlagsCSV,
+		Args: map[string]string{
+			"outFlag":      "--write-metadata-csv",
+			"stubAPIFlags": stubFlagsCSV.String(),
+		},
+	})
+
+	// Generate the index file from the annotations in the source code.
+	indexCSV := android.PathForModuleOut(ctx, hiddenApiSubDir, "index.csv")
+	rule = android.NewRuleBuilder(pctx, ctx)
+	rule.Command().
+		BuiltTool("merge_csv").
+		Flag("--zip_input").
+		Flag("--key_field signature").
+		FlagWithOutput("--output=", indexCSV).
+		Inputs(classesJars)
+	rule.Build("modular-hiddenapi-index", "modular hiddenapi index")
+
+	// Removed APIs need to be marked and in order to do that the flagFileInfo needs to specify files
+	// containing dex signatures of all the removed APIs. In the monolithic files that is done by
+	// manually combining all the removed.txt files for each API and then converting them to dex
+	// signatures, see the combined-removed-dex module. That will all be done automatically in future.
+	// For now removed APIs are ignored.
+	// TODO(b/179354495): handle removed apis automatically.
+
+	// Generate the all-flags.csv which are the flags that will, in future, be encoded into the dex
+	// files.
+	outputPath := android.PathForModuleOut(ctx, hiddenApiSubDir, "all-flags.csv")
+	buildRuleToGenerateHiddenApiFlags(ctx, "modularHiddenApiAllFlags", "modular hiddenapi all flags", outputPath, stubFlagsCSV, android.Paths{annotationFlagsCSV}, flagFileInfo)
+
+	// Store the paths in the info for use by other modules and sdk snapshot generation.
+	flagFileInfo.StubFlagsPaths = android.Paths{stubFlagsCSV}
+	flagFileInfo.AnnotationFlagsPaths = android.Paths{annotationFlagsCSV}
+	flagFileInfo.MetadataPaths = android.Paths{metadataCSV}
+	flagFileInfo.IndexPaths = android.Paths{indexCSV}
+	flagFileInfo.AllFlagsPaths = android.Paths{outputPath}
 }