tasks/patches/TASK_CR_013_tests.patch

diff --git a/cache/cache_test.go b/cache/cache_test.go
index 2be551e7..60213366 100644
--- a/cache/cache_test.go
+++ b/cache/cache_test.go
@@ -87,7 +87,7 @@ func testCacheOperation(
 		prepareFakeCreateAdapter(t, operationName, tc)
 
 		config := prepareFakeConfig(tc)
-		adaptor := GetAdapter(config, 3600*time.Second, "shorttoken", "10", tc.key)
+		adaptor := GetAdapter(config, 3600*time.Second, "shorttoken", "10", tc.key, false)
 		generatedURL := operation(ctx, adaptor)
 		assert.Equal(t, tc.expectedURL, generatedURL.URL)
 
@@ -179,9 +179,10 @@ func defaultCacheConfig() *cacheconfig.Config {
 }
 
 type generateObjectNameTestCase struct {
-	key    string
-	path   string
-	shared bool
+	key     string
+	path    string
+	shared  bool
+	sharded bool
 
 	expectedObjectName string
 	expectedError      string
@@ -235,6 +236,23 @@ func TestGenerateObjectName(t *testing.T) {
 			key:           "../10-outside",
 			expectedError: "computed cache path outside of project bucket",
 		},
+		"sharded key uses first two chars as prefix": {
+			key:                "d03a852ba491ba611e907b1ef60ad5c4516a05b8f3aae6abb77f42bc60325aed",
+			sharded:            true,
+			expectedObjectName: "runner/longtoken/project/10/d0/d03a852ba491ba611e907b1ef60ad5c4516a05b8f3aae6abb77f42bc60325aed",
+		},
+		"sharded key with path prefix": {
+			key:                "d03a852ba491ba611e907b1ef60ad5c4516a05b8f3aae6abb77f42bc60325aed",
+			path:               "builds",
+			sharded:            true,
+			expectedObjectName: "builds/runner/longtoken/project/10/d0/d03a852ba491ba611e907b1ef60ad5c4516a05b8f3aae6abb77f42bc60325aed",
+		},
+		"sharded key with shared runner": {
+			key:                "d03a852ba491ba611e907b1ef60ad5c4516a05b8f3aae6abb77f42bc60325aed",
+			shared:             true,
+			sharded:            true,
+			expectedObjectName: "project/10/d0/d03a852ba491ba611e907b1ef60ad5c4516a05b8f3aae6abb77f42bc60325aed",
+		},
 	}
 
 	for name, tc := range tests {
@@ -255,7 +273,7 @@ func TestGenerateObjectName(t *testing.T) {
 				createAdapter = oldCreateAdapter
 			})
 
-			adapter := GetAdapter(cache, 3600*time.Second, "longtoken", "10", tc.key)
+			adapter := GetAdapter(cache, 3600*time.Second, "longtoken", "10", tc.key, tc.sharded)
 
 			if tc.expectedError != "" {
 				// The error/warning cases return a nopAdaptor and log instead of returning an error
diff --git a/shells/abstract_test.go b/shells/abstract_test.go
index de6342fb..153d2be4 100644
--- a/shells/abstract_test.go
+++ b/shells/abstract_test.go
@@ -1642,6 +1642,22 @@ func getCacheKeyHasher(hash bool) func(string) string {
 	}
 }
 
+// getShardedObjectKey returns a function that, given a (hashed) cache key,
+// returns the object path component used by GetAdapter. When sharded is true
+// (i.e. FF_HASH_CACHE_KEYS is on), the first two hex characters are inserted
+// as a prefix: "<shard>/<key>". Otherwise the key is returned unchanged.
+func getShardedObjectKey(sharded bool) func(string) string {
+	if !sharded {
+		return func(key string) string { return key }
+	}
+	return func(key string) string {
+		if len(key) < 2 {
+			return key
+		}
+		return key[:2] + "/" + key
+	}
+}
+
 func TestAbstractShell_extractCacheWithDefaultFallbackKey(t *testing.T) {
 	const cacheEnvFile = "/some/path/to/runner-cache-env"
 
@@ -1865,6 +1881,7 @@ func TestAbstractShell_extractCacheWithDefaultFallbackKey(t *testing.T) {
 
 	for _, hashCacheKeys := range []bool{false, true} {
 		hashed := getCacheKeyHasher(hashCacheKeys)
+		shardedObjectPath := getShardedObjectKey(hashCacheKeys)
 
 		t.Run(fmt.Sprintf("%s:%t", featureflags.HashCacheKeys, hashCacheKeys), func(t *testing.T) {
 			for tn, tc := range tests {
@@ -1943,7 +1960,7 @@ func TestAbstractShell_extractCacheWithDefaultFallbackKey(t *testing.T) {
 								"--timeout",
 								"10",
 								"--url",
-								fmt.Sprintf("test://download/project/1000/%s", expectedHashedCacheKey),
+								fmt.Sprintf("test://download/project/1000/%s", shardedObjectPath(expectedHashedCacheKey)),
 							).Once()
 						} else {
 							mockWriter.On("DotEnvVariables", "gitlab_runner_cache_env", mock.Anything).Return(cacheEnvFile).Once()
@@ -1955,7 +1972,7 @@ func TestAbstractShell_extractCacheWithDefaultFallbackKey(t *testing.T) {
 								"--timeout",
 								"10",
 								"--gocloud-url",
-								fmt.Sprintf("gocloud://test/project/1000/%s", expectedHashedCacheKey),
+								fmt.Sprintf("gocloud://test/project/1000/%s", shardedObjectPath(expectedHashedCacheKey)),
 								"--env-file", cacheEnvFile,
 							).Once()
 						}
@@ -2081,6 +2098,7 @@ func TestAbstractShell_extractCacheWithMultipleFallbackKeys(t *testing.T) {
 
 	for _, hashedCacheKey := range []bool{false, true} {
 		hashed := getCacheKeyHasher(hashedCacheKey)
+		shardedObjectPath := getShardedObjectKey(hashedCacheKey)
 
 		t.Run(fmt.Sprintf("%s:%t", featureflags.HashCacheKeys, hashedCacheKey), func(t *testing.T) {
 			for tn, tc := range tests {
@@ -2149,7 +2167,7 @@ func TestAbstractShell_extractCacheWithMultipleFallbackKeys(t *testing.T) {
 							"--timeout",
 							"10",
 							"--url",
-							fmt.Sprintf("test://download/project/1000/%s", hashedCacheKey),
+							fmt.Sprintf("test://download/project/1000/%s", shardedObjectPath(hashedCacheKey)),
 						).Once()
 						mockWriter.On("Noticef", "Successfully extracted cache").Once()
 						mockWriter.On("Else").Once()
@@ -2265,6 +2283,7 @@ func TestAbstractShell_extractCacheWithMultipleFallbackKeysWithCleanup(t *testin
 
 	for _, hashedCacheKey := range []bool{false, true} {
 		hashed := getCacheKeyHasher(hashedCacheKey)
+		shardedObjectPath := getShardedObjectKey(hashedCacheKey)
 
 		t.Run(fmt.Sprintf("%s:%t", featureflags.HashCacheKeys, hashedCacheKey), func(t *testing.T) {
 			for tn, tc := range tests {
@@ -2337,7 +2356,7 @@ func TestAbstractShell_extractCacheWithMultipleFallbackKeysWithCleanup(t *testin
 							"--timeout",
 							"10",
 							"--url",
-							fmt.Sprintf("test://download/project/1000/%s", hashedCacheKey),
+							fmt.Sprintf("test://download/project/1000/%s", shardedObjectPath(hashedCacheKey)),
 						).Once()
 						mockWriter.On("Noticef", "Successfully extracted cache").Once()
 						mockWriter.On("Else").Once()