feat(js): added reasoning part type and implemented for googleai and vertexai

genkit-tools/common/src/types/document.ts

@@ -27,6 +27,7 @@ const EmptyPartSchema = z.object({
   data: z.unknown().optional(),
   metadata: z.record(z.unknown()).optional(),
   custom: z.record(z.unknown()).optional(),
+  reasoning: z.never().optional(),
 });
 
 /**
@@ -37,6 +38,14 @@ export const TextPartSchema = EmptyPartSchema.extend({
   text: z.string(),
 });
 
+/**
+ * Zod schema for a reasoning part.
+ */
+export const ReasoningPartSchema = EmptyPartSchema.extend({
+  /** The reasoning text of the message. */
+  reasoning: z.string(),
+});
+
 /**
  * Text part.
  */

genkit-tools/common/src/types/model.ts

@@ -22,6 +22,7 @@ import {
   DocumentDataSchema,
   MediaPart,
   MediaPartSchema,
+  ReasoningPartSchema,
   TextPart,
   TextPartSchema,
   ToolRequestPart,
@@ -58,6 +59,7 @@ export const PartSchema = z.union([
   ToolResponsePartSchema,
   DataPartSchema,
   CustomPartSchema,
+  ReasoningPartSchema,
 ]);
 
 /**

genkit-tools/genkit-schema.json

@@ -24,6 +24,9 @@
         "custom": {
           "type": "object",
           "additionalProperties": {}
+        },
+        "reasoning": {
+          "not": {}
         }
       },
       "required": [
@@ -53,6 +56,9 @@
         "custom": {
           "type": "object",
           "additionalProperties": {}
+        },
+        "reasoning": {
+          "$ref": "#/$defs/CustomPart/properties/reasoning"
         }
       },
       "additionalProperties": false
@@ -109,6 +115,9 @@
         },
         "custom": {
           "$ref": "#/$defs/DataPart/properties/custom"
+        },
+        "reasoning": {
+          "$ref": "#/$defs/CustomPart/properties/reasoning"
         }
       },
       "required": [
@@ -131,6 +140,39 @@
       ],
       "additionalProperties": false
     },
+    "ReasoningPart": {
+      "type": "object",
+      "properties": {
+        "text": {
+          "$ref": "#/$defs/CustomPart/properties/text"
+        },
+        "media": {
+          "$ref": "#/$defs/CustomPart/properties/media"
+        },
+        "toolRequest": {
+          "$ref": "#/$defs/CustomPart/properties/toolRequest"
+        },
+        "toolResponse": {
+          "$ref": "#/$defs/CustomPart/properties/toolResponse"
+        },
+        "data": {
+          "$ref": "#/$defs/CustomPart/properties/data"
+        },
+        "metadata": {
+          "$ref": "#/$defs/CustomPart/properties/metadata"
+        },
+        "custom": {
+          "$ref": "#/$defs/DataPart/properties/custom"
+        },
+        "reasoning": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "reasoning"
+      ],
+      "additionalProperties": false
+    },
     "TextPart": {
       "type": "object",
       "properties": {
@@ -154,6 +196,9 @@
         },
         "custom": {
           "$ref": "#/$defs/DataPart/properties/custom"
+        },
+        "reasoning": {
+          "$ref": "#/$defs/CustomPart/properties/reasoning"
         }
       },
       "required": [
@@ -184,6 +229,9 @@
         },
         "custom": {
           "$ref": "#/$defs/DataPart/properties/custom"
+        },
+        "reasoning": {
+          "$ref": "#/$defs/CustomPart/properties/reasoning"
         }
       },
       "required": [
@@ -230,6 +278,9 @@
         },
         "custom": {
           "$ref": "#/$defs/DataPart/properties/custom"
+        },
+        "reasoning": {
+          "$ref": "#/$defs/CustomPart/properties/reasoning"
         }
       },
       "required": [
@@ -1043,6 +1094,9 @@
         },
         {
           "$ref": "#/$defs/CustomPart"
+        },
+        {
+          "$ref": "#/$defs/ReasoningPart"
         }
       ]
     },

js/ai/src/document.ts

@@ -25,6 +25,7 @@ const EmptyPartSchema = z.object({
   data: z.unknown().optional(),
   metadata: z.record(z.unknown()).optional(),
   custom: z.record(z.unknown()).optional(),
+  reasoning: z.never().optional(),
 });
 
 /**
@@ -35,6 +36,14 @@ export const TextPartSchema = EmptyPartSchema.extend({
   text: z.string(),
 });
 
+/**
+ * Zod schema for a reasoning part.
+ */
+export const ReasoningPartSchema = EmptyPartSchema.extend({
+  /** The reasoning text of the message. */
+  reasoning: z.string(),
+});
+
 /**
  * Text part.
  */

js/ai/src/generate/chunk.ts

@@ -70,6 +70,14 @@ export class GenerateResponseChunk<T = unknown>
     return this.content.map((part) => part.text || '').join('');
   }
 
+  /**
+   * Concatenates all `reasoning` parts present in the chunk with no delimiter.
+   * @returns A string of all concatenated reasoning parts.
+   */
+  get reasoning(): string {
+    return this.content.map((part) => part.reasoning || '').join('');
+  }
+
   /**
    * Concatenates all `text` parts of all chunks from the response thus far.
    * @returns A string of all concatenated chunk text content.

js/ai/src/generate/response.ts

@@ -44,6 +44,8 @@ export class GenerateResponse<O = unknown> implements ModelResponseData {
   usage: GenerationUsage;
   /** Provider-specific response data. */
   custom: unknown;
+  /** Provider-specific response data. */
+  raw: unknown;
   /** The request that generated this response. */
   request?: GenerateRequest;
   /** The parser for output parsing of this response. */
@@ -70,6 +72,7 @@ export class GenerateResponse<O = unknown> implements ModelResponseData {
       response.finishMessage || response.candidates?.[0]?.finishMessage;
     this.usage = response.usage || {};
     this.custom = response.custom || {};
+    this.raw = response.raw || this.custom;
     this.request = options?.request;
   }
 
@@ -133,6 +136,14 @@ export class GenerateResponse<O = unknown> implements ModelResponseData {
     return this.message?.text || '';
   }
 
+  /**
+   * Concatenates all `reasoning` parts present in the generated message with no delimiter.
+   * @returns A string of all concatenated reasoning parts.
+   */
+  get reasoning(): string {
+    return this.message?.reasoning || '';
+  }
+
   /**
    * Returns the first detected media part in the generated message. Useful for
    * extracting (for example) an image from a generation expected to create one.
@@ -184,10 +195,6 @@ export class GenerateResponse<O = unknown> implements ModelResponseData {
     return [...this.request?.messages, this.message.toJSON()];
   }
 
-  get raw(): unknown {
-    return this.raw ?? this.custom;
-  }
-
   toJSON(): ModelResponseData {
     const out = {
       message: this.message?.toJSON(),

js/ai/src/message.ts

@@ -95,6 +95,14 @@ export class Message<T = unknown> implements MessageData {
     return this.content.map((part) => part.text || '').join('');
   }
 
+  /**
+   * Concatenates all `reasoning` parts present in the message with no delimiter.
+   * @returns A string of all concatenated reasoning parts.
+   */
+  get reasoning(): string {
+    return this.content.map((part) => part.reasoning || '').join('');
+  }
+
   /**
    * Returns the first media part detected in the message. Useful for extracting
    * (for example) an image from a generation expected to create one.

js/ai/src/model.ts

@@ -36,6 +36,7 @@ import {
   DocumentDataSchema,
   MediaPart,
   MediaPartSchema,
+  ReasoningPartSchema,
   TextPart,
   TextPartSchema,
   ToolRequestPart,
@@ -81,6 +82,7 @@ export const PartSchema = z.union([
   ToolResponsePartSchema,
   DataPartSchema,
   CustomPartSchema,
+  ReasoningPartSchema,
 ]);
 
 /**

js/plugins/googleai/src/gemini.ts

@@ -690,7 +690,12 @@ function fromGeminiPart(
   jsonMode: boolean,
   ref: string
 ): Part {
-  if (part.text !== undefined) return { text: part.text };
+  if (part.text !== undefined) {
+    if ((part as any).thought === true) {
+      return { reasoning: part.text };
+    }
+    return { text: part.text };
+  }
   if (part.inlineData) return fromInlineData(part);
   if (part.functionCall) return fromFunctionCall(part, ref);
   if (part.functionResponse) return fromFunctionResponse(part);

js/plugins/vertexai/src/gemini.ts

@@ -819,7 +819,12 @@ function fromGeminiPart(
   jsonMode: boolean,
   ref?: string
 ): Part {
-  if (part.text !== undefined) return { text: part.text };
+  if (part.text !== undefined) {
+    if ((part as any).thought === true) {
+      return { reasoning: part.text };
+    }
+    return { text: part.text };
+  }
   if (part.inlineData) return fromGeminiInlineDataPart(part);
   if (part.fileData) return fromGeminiFileDataPart(part);
   if (part.functionCall) return fromGeminiFunctionCallPart(part, ref);

js/testapps/flow-simple-ai/src/index.ts

@@ -945,3 +945,19 @@ ai.defineFlow('embedders-tester', async () => {
     })
   );
 });
+
+ai.defineFlow('reasoning', async (_, { sendChunk }) => {
+  const { message } = await ai.generate({
+    prompt: 'whats heavier, one kilo of steel or or one kilo of feathers',
+    model: googleAI.model('gemini-2.5-flash-preview-04-17'),
+    config: {
+      thinkingConfig: {
+        thinkingBudget: 1024,
+        includeThoughts: true,
+      },
+    },
+    onChunk: sendChunk,
+  });
+
+  return message;
+});

py/packages/genkit/src/genkit/core/typing.py

@@ -55,6 +55,7 @@ class CustomPart(BaseModel):
     data: Any | None = None
     metadata: dict[str, Any] | None = None
     custom: dict[str, Any]
+    reasoning: Any | None = None
 
 
 class Media(BaseModel):
@@ -479,6 +480,12 @@ class Metadata(RootModel[dict[str, Any] | None]):
     root: dict[str, Any] | None = None
 
 
+class Reasoning(RootModel[Any]):
+    """Root model for reasoning."""
+
+    root: Any
+
+
 class Text(RootModel[Any]):
     """Root model for text."""
 
@@ -574,6 +581,7 @@ class DataPart(BaseModel):
     data: Any | None = None
     metadata: Metadata | None = None
     custom: dict[str, Any] | None = None
+    reasoning: Reasoning | None = None
 
 
 class MediaPart(BaseModel):
@@ -587,6 +595,21 @@ class MediaPart(BaseModel):
     data: Data | None = None
     metadata: Metadata | None = None
     custom: Custom | None = None
+    reasoning: Reasoning | None = None
+
+
+class ReasoningPart(BaseModel):
+    """Model for reasoningpart data."""
+
+    model_config = ConfigDict(extra='forbid', populate_by_name=True)
+    text: Text | None = None
+    media: MediaModel | None = None
+    tool_request: ToolRequestModel | None = Field(None, alias='toolRequest')
+    tool_response: ToolResponseModel | None = Field(None, alias='toolResponse')
+    data: Data | None = None
+    metadata: Metadata | None = None
+    custom: Custom | None = None
+    reasoning: str
 
 
 class TextPart(BaseModel):
@@ -600,6 +623,7 @@ class TextPart(BaseModel):
     data: Data | None = None
     metadata: Metadata | None = None
     custom: Custom | None = None
+    reasoning: Reasoning | None = None
 
 
 class ToolRequestPart(BaseModel):
@@ -613,6 +637,7 @@ class ToolRequestPart(BaseModel):
     data: Data | None = None
     metadata: Metadata | None = None
     custom: Custom | None = None
+    reasoning: Reasoning | None = None
 
 
 class ToolResponsePart(BaseModel):
@@ -626,6 +651,7 @@ class ToolResponsePart(BaseModel):
     data: Data | None = None
     metadata: Metadata | None = None
     custom: Custom | None = None
+    reasoning: Reasoning | None = None
 
 
 class EmbedResponse(BaseModel):
@@ -673,10 +699,12 @@ class Resume(BaseModel):
     metadata: dict[str, Any] | None = None
 
 
-class Part(RootModel[TextPart | MediaPart | ToolRequestPart | ToolResponsePart | DataPart | CustomPart]):
+class Part(
+    RootModel[TextPart | MediaPart | ToolRequestPart | ToolResponsePart | DataPart | CustomPart | ReasoningPart]
+):
     """Root model for part."""
 
-    root: TextPart | MediaPart | ToolRequestPart | ToolResponsePart | DataPart | CustomPart
+    root: TextPart | MediaPart | ToolRequestPart | ToolResponsePart | DataPart | CustomPart | ReasoningPart
 
 
 class Link(BaseModel):