fix(dotprompt): properly group prompt variants

ai/src/main/java/com/google/genkit/ai/Prompt.java

@@ -43,6 +43,7 @@
 public class Prompt<I> implements Action<I, ModelRequest, Void> {
 
   private final String name;
+  private final String variant;
   private final String model;
   private final String template;
   private final Map<String, Object> inputSchema;
@@ -55,6 +56,7 @@ public class Prompt<I> implements Action<I, ModelRequest, Void> {
    * Creates a new Prompt.
    *
    * @param name the prompt name
+   * @param variant the prompt variant
    * @param model the default model name
    * @param template the prompt template
    * @param inputSchema the input JSON schema
@@ -64,13 +66,15 @@ public class Prompt<I> implements Action<I, ModelRequest, Void> {
    */
   public Prompt(
       String name,
+      String variant,
       String model,
       String template,
       Map<String, Object> inputSchema,
       GenerationConfig config,
       Class<I> inputClass,
       BiFunction<ActionContext, I, ModelRequest> renderer) {
     this.name = name;
+    this.variant = variant;
     this.model = model;
     this.template = template;
     this.inputSchema = inputSchema;
@@ -86,7 +90,17 @@ public Prompt(
 
     // Build the prompt sub-object with detailed metadata
     Map<String, Object> promptMetadata = new HashMap<>();
-    promptMetadata.put("name", name);
+
+    // The 'name' in metadata should be the base name (without variant)
+    String baseName = name;
+    if (variant != null && name.endsWith("." + variant)) {
+      baseName = name.substring(0, name.length() - variant.length() - 1);
+    }
+
+    promptMetadata.put("name", baseName);
+    if (variant != null) {
+      promptMetadata.put("variant", variant);
+    }
     promptMetadata.put("model", model);
     promptMetadata.put("template", template);
     if (inputSchema != null) {
@@ -113,6 +127,15 @@ public String getName() {
     return name;
   }
 
+  /**
+   * Gets the prompt variant.
+   *
+   * @return the variant name, or null if none
+   */
+  public String getVariant() {
+    return variant;
+  }
+
   @Override
   public ActionType getType() {
     return ActionType.EXECUTABLE_PROMPT;
@@ -213,6 +236,7 @@ public GenerationConfig getConfig() {
    */
   public static class Builder<I> {
     private String name;
+    private String variant;
     private String model;
     private String template;
     private Map<String, Object> inputSchema;
@@ -225,6 +249,11 @@ public Builder<I> name(String name) {
       return this;
     }
 
+    public Builder<I> variant(String variant) {
+      this.variant = variant;
+      return this;
+    }
+
     public Builder<I> model(String model) {
       this.model = model;
       return this;
@@ -262,7 +291,8 @@ public Prompt<I> build() {
       if (renderer == null) {
         throw new IllegalStateException("Prompt renderer is required");
       }
-      return new Prompt<>(name, model, template, inputSchema, config, inputClass, renderer);
+      return new Prompt<>(
+          name, variant, model, template, inputSchema, config, inputClass, renderer);
     }
   }
 }

ai/src/test/java/com/google/genkit/ai/PromptTest.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.google.genkit.ai;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import com.google.genkit.core.ActionType;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+/** Unit tests for Prompt. */
+class PromptTest {
+
+  @Test
+  void testPromptVariantAndMetadata() {
+    Prompt<String> prompt =
+        Prompt.<String>builder()
+            .name("recipe.robot")
+            .variant("robot")
+            .model("openai/gpt-4o")
+            .template("Tell me a recipe for {{input}}")
+            .renderer((ctx, input) -> ModelRequest.builder().addUserMessage(input).build())
+            .build();
+
+    assertEquals("recipe.robot", prompt.getName());
+    assertEquals("robot", prompt.getVariant());
+    assertEquals(ActionType.EXECUTABLE_PROMPT, prompt.getType());
+
+    Map<String, Object> metadata = prompt.getMetadata();
+    assertEquals(ActionType.EXECUTABLE_PROMPT.getValue(), metadata.get("type"));
+
+    @SuppressWarnings("unchecked")
+    Map<String, Object> promptMetadata = (Map<String, Object>) metadata.get("prompt");
+    assertNotNull(promptMetadata);
+    assertEquals("recipe", promptMetadata.get("name"));
+    assertEquals("robot", promptMetadata.get("variant"));
+    assertEquals("openai/gpt-4o", promptMetadata.get("model"));
+    assertEquals("Tell me a recipe for {{input}}", promptMetadata.get("template"));
+  }
+
+  @Test
+  void testPromptWithoutVariant() {
+    Prompt<String> prompt =
+        Prompt.<String>builder()
+            .name("recipe")
+            .model("openai/gpt-4o")
+            .template("Tell me a recipe for {{input}}")
+            .renderer((ctx, input) -> ModelRequest.builder().addUserMessage(input).build())
+            .build();
+
+    assertEquals("recipe", prompt.getName());
+    assertNull(prompt.getVariant());
+
+    Map<String, Object> metadata = prompt.getMetadata();
+    @SuppressWarnings("unchecked")
+    Map<String, Object> promptMetadata = (Map<String, Object>) metadata.get("prompt");
+    assertEquals("recipe", promptMetadata.get("name"));
+    assertNull(promptMetadata.get("variant"));
+  }
+
+  @Test
+  void testPromptVariantMismatch() {
+    // If name doesn't end with variant, baseName should be the full name
+    Prompt<String> prompt =
+        Prompt.<String>builder()
+            .name("recipe")
+            .variant("robot")
+            .model("openai/gpt-4o")
+            .template("Tell me a recipe for {{input}}")
+            .renderer((ctx, input) -> ModelRequest.builder().addUserMessage(input).build())
+            .build();
+
+    assertEquals("recipe", prompt.getName());
+    assertEquals("robot", prompt.getVariant());
+
+    Map<String, Object> metadata = prompt.getMetadata();
+    @SuppressWarnings("unchecked")
+    Map<String, Object> promptMetadata = (Map<String, Object>) metadata.get("prompt");
+    assertEquals("recipe", promptMetadata.get("name"));
+    assertEquals("robot", promptMetadata.get("variant"));
+  }
+}

genkit/src/main/java/com/google/genkit/prompt/DotPrompt.java

@@ -105,6 +105,7 @@ public Charset getCharset() {
   private static final Handlebars sharedHandlebars = new Handlebars(partialLoader);
 
   private final String name;
+  private final String variant;
   private final String model;
   private final String template;
   private final Map<String, Object> inputSchema;
@@ -115,18 +116,21 @@ public Charset getCharset() {
    * Creates a new DotPrompt.
    *
    * @param name the prompt name
+   * @param variant the prompt variant
    * @param model the default model name
    * @param template the Handlebars template
    * @param inputSchema the input JSON schema
    * @param config the default generation config
    */
   public DotPrompt(
       String name,
+      String variant,
       String model,
       String template,
       Map<String, Object> inputSchema,
       GenerationConfig config) {
     this.name = name;
+    this.variant = variant;
     this.model = model;
     this.template = template;
     this.inputSchema = inputSchema;
@@ -298,7 +302,15 @@ public static <I> DotPrompt<I> parse(String name, String content) throws GenkitE
       name = name.substring(name.lastIndexOf('/') + 1);
     }
 
-    return new DotPrompt<>(name, model, template, inputSchema, config);
+    // Extract variant from name (e.g., "recipe.robot" -> variant="robot")
+    // Note: name remains the full name (e.g., "recipe.robot") for registry key uniqueness
+    String variant = null;
+    int dotIndex = name.lastIndexOf('.');
+    if (dotIndex != -1) {
+      variant = name.substring(dotIndex + 1);
+    }
+
+    return new DotPrompt<>(name, variant, model, template, inputSchema, config);
   }
 
   /**
@@ -364,6 +376,7 @@ public ModelRequest toModelRequest(I input) throws GenkitException {
   public Prompt<I> toPrompt(Class<I> inputClass) {
     return Prompt.<I>builder()
         .name(name)
+        .variant(variant)
         .model(model)
         .template(template)
         .inputSchema(inputSchema)
@@ -512,6 +525,10 @@ public String getName() {
     return name;
   }
 
+  public String getVariant() {
+    return variant;
+  }
+
   public String getModel() {
     return model;
   }

genkit/src/test/java/com/google/genkit/prompt/DotPromptTest.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.google.genkit.prompt;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import com.google.genkit.ai.Prompt;
+import com.google.genkit.core.GenkitException;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+/** Unit tests for DotPrompt. */
+class DotPromptTest {
+
+  @Test
+  void testParseVariant() throws GenkitException {
+    String content = "---\nmodel: openai/gpt-4o\n---\nHello {{input}}";
+    DotPrompt<Map<String, Object>> dotPrompt = DotPrompt.parse("recipe.robot", content);
+
+    assertEquals("recipe.robot", dotPrompt.getName());
+    assertEquals("robot", dotPrompt.getVariant());
+    assertEquals("openai/gpt-4o", dotPrompt.getModel());
+    assertEquals("Hello {{input}}", dotPrompt.getTemplate());
+  }
+
+  @Test
+  void testParseWithoutVariant() throws GenkitException {
+    String content = "---\nmodel: openai/gpt-4o\n---\nHello {{input}}";
+    DotPrompt<Map<String, Object>> dotPrompt = DotPrompt.parse("recipe", content);
+
+    assertEquals("recipe", dotPrompt.getName());
+    assertNull(dotPrompt.getVariant());
+  }
+
+  @Test
+  void testParseWithMultipleDots() throws GenkitException {
+    String content = "---\nmodel: openai/gpt-4o\n---\nHello {{input}}";
+    // Should use last dot for variant
+    DotPrompt<Map<String, Object>> dotPrompt = DotPrompt.parse("my.awesome.recipe.robot", content);
+
+    assertEquals("my.awesome.recipe.robot", dotPrompt.getName());
+    assertEquals("robot", dotPrompt.getVariant());
+  }
+
+  @Test
+  void testToPrompt() throws GenkitException {
+    String content = "---\nmodel: openai/gpt-4o\n---\nHello {{input}}";
+    DotPrompt<Map<String, Object>> dotPrompt = DotPrompt.parse("recipe.robot", content);
+
+    @SuppressWarnings("unchecked")
+    Prompt<Map<String, Object>> prompt =
+        (Prompt<Map<String, Object>>) dotPrompt.toPrompt((Class) Map.class);
+
+    assertEquals("recipe.robot", prompt.getName());
+    assertEquals("robot", prompt.getVariant());
+
+    @SuppressWarnings("unchecked")
+    Map<String, Object> promptMetadata = (Map<String, Object>) prompt.getMetadata().get("prompt");
+    assertEquals("recipe", promptMetadata.get("name"));
+    assertEquals("robot", promptMetadata.get("variant"));
+  }
+}

samples/dotprompt/src/main/java/com/google/genkit/samples/DotPromptSample.java

@@ -143,18 +143,18 @@ public static void main(String[] args) throws Exception {
 
         // Load and auto-register prompts using genkit.prompt()
         // This automatically loads from /prompts directory and registers as actions
-        ExecutablePrompt<StoryInput> storyPrompt = genkit.prompt("story", StoryInput.class);
-        ExecutablePrompt<TravelInput> travelPrompt = genkit.prompt("travel-planner", TravelInput.class);
         ExecutablePrompt<CodeReviewInput> codeReviewPrompt = genkit.prompt("code-review", CodeReviewInput.class);
-
-        // Load prompt with variant (e.g., recipe.robot.prompt)
+        ExecutablePrompt<RecipeInput> recipePrompt = genkit.prompt("recipe", RecipeInput.class);
+        ExecutablePrompt<TravelInput> travelPrompt = genkit.prompt("travel-planner", TravelInput.class);
+
+        // Load prompt with variant (e.g., recipe.prompt, recipe.robot.prompt)
         ExecutablePrompt<RecipeInput> robotRecipePrompt = genkit.prompt("recipe", RecipeInput.class, "robot");
-        
+
         // ============================================================
         // Method 2: Load prompts manually using DotPrompt.loadFromResource()
         // Useful when you need more control over the loading process
         // ============================================================
-        DotPrompt<RecipeInput> recipePrompt = DotPrompt.loadFromResource("/prompts/recipe.prompt");
+        DotPrompt<StoryInput> manualStoryPrompt = DotPrompt.loadFromResource("/prompts/story.prompt");
 
         // ============================================================
         // Flow Examples: Different ways to use prompts
@@ -220,7 +220,7 @@ public static void main(String[] args) throws Exception {
                 String.class,
                 (ctx, input) -> {
                     // Generate with custom temperature override
-                    ModelResponse response = storyPrompt.generate(input, 
+                    ModelResponse response = manualStoryPrompt.generate(genkit.getRegistry(), input, 
                             GenerateOptions.builder()
                                     .config(GenerationConfig.builder()
                                             .temperature(0.9)