diff --git a/src/llm.ts b/src/llm.ts
index 37c9691..e72d21d 100644
--- a/src/llm.ts
+++ b/src/llm.ts
@@ -1,7 +1,15 @@
+import { jsonrepair } from 'jsonrepair'
+import Mustache from 'mustache'
+import { dedent } from 'ts-dedent'
 import { ZodRawShape, ZodTypeAny, z } from 'zod'
+import { printNode, zodToTs } from 'zod-to-ts'
 
 import * as types from './types'
 import { BaseTaskCallBuilder } from './task'
+import {
+  extractJSONArrayFromString,
+  extractJSONObjectFromString
+} from './utils'
 
 export abstract class BaseLLMCallBuilder<
   TInput extends ZodRawShape | ZodTypeAny = ZodTypeAny,
@@ -59,10 +67,11 @@ export abstract class BaseLLMCallBuilder<
   // }): Promise<TOutput>
 }
 
-export abstract class ChatModelBuilder<
+export abstract class BaseChatModelBuilder<
   TInput extends ZodRawShape | ZodTypeAny = ZodTypeAny,
   TOutput extends ZodRawShape | ZodTypeAny = z.ZodType<string>,
-  TModelParams extends Record<string, any> = Record<string, any>
+  TModelParams extends Record<string, any> = Record<string, any>,
+  TChatCompletionResponse extends Record<string, any> = Record<string, any>
 > extends BaseLLMCallBuilder<TInput, TOutput, TModelParams> {
   _messages: types.ChatMessage[]
 
@@ -71,4 +80,153 @@ export abstract class ChatModelBuilder<
 
     this._messages = options.messages
   }
+
+  protected abstract _createChatCompletion(
+    messages: types.ChatMessage[]
+  ): Promise<types.BaseChatCompletionResponse<TChatCompletionResponse>>
+
+  override async call(
+    input?: types.ParsedData<TInput>
+  ): Promise<types.ParsedData<TOutput>> {
+    if (this._inputSchema) {
+      const inputSchema =
+        this._inputSchema instanceof z.ZodType
+          ? this._inputSchema
+          : z.object(this._inputSchema)
+
+      // TODO: handle errors gracefully
+      input = inputSchema.parse(input)
+    }
+
+    // TODO: validate input message variables against input schema
+
+    const messages = this._messages
+      .map((message) => {
+        return {
+          ...message,
+          content: message.content
+            ? Mustache.render(dedent(message.content), input).trim()
+            : ''
+        }
+      })
+      .filter((message) => message.content)
+
+    if (this._examples?.length) {
+      // TODO: smarter example selection
+      for (const example of this._examples) {
+        messages.push({
+          role: 'system',
+          content: `Example input: ${example.input}\n\nExample output: ${example.output}`
+        })
+      }
+    }
+
+    if (this._outputSchema) {
+      const outputSchema =
+        this._outputSchema instanceof z.ZodType
+          ? this._outputSchema
+          : z.object(this._outputSchema)
+
+      const { node } = zodToTs(outputSchema)
+
+      if (node.kind === 152) {
+        // handle raw strings differently
+        messages.push({
+          role: 'system',
+          content: dedent`Output a raw string only, without any additional text.`
+        })
+      } else {
+        const tsTypeString = printNode(node, {
+          removeComments: false,
+          // TODO: this doesn't seem to actually work, so we're doing it manually below
+          omitTrailingSemicolon: true,
+          noEmitHelpers: true
+        })
+          .replace(/^    /gm, '  ')
+          .replace(/;$/gm, '')
+
+        messages.push({
+          role: 'system',
+          content: dedent`Output JSON only in the following TypeScript format:
+          \`\`\`ts
+          ${tsTypeString}
+          \`\`\``
+        })
+      }
+    }
+
+    // TODO: filter/compress messages based on token counts
+
+    console.log('>>>')
+    console.log(messages)
+
+    const completion = await this._createChatCompletion(messages)
+    let output: any = completion.message.content
+
+    console.log('===')
+    console.log(output)
+    console.log('<<<')
+
+    if (this._outputSchema) {
+      const outputSchema =
+        this._outputSchema instanceof z.ZodType
+          ? this._outputSchema
+          : z.object(this._outputSchema)
+
+      if (outputSchema instanceof z.ZodArray) {
+        try {
+          const trimmedOutput = extractJSONArrayFromString(output)
+          output = JSON.parse(jsonrepair(trimmedOutput ?? output))
+        } catch (err) {
+          // TODO
+          throw err
+        }
+      } else if (outputSchema instanceof z.ZodObject) {
+        try {
+          const trimmedOutput = extractJSONObjectFromString(output)
+          output = JSON.parse(jsonrepair(trimmedOutput ?? output))
+        } catch (err) {
+          // TODO
+          throw err
+        }
+      } else if (outputSchema instanceof z.ZodBoolean) {
+        output = output.toLowerCase().trim()
+        const booleanOutputs = {
+          true: true,
+          false: false,
+          yes: true,
+          no: false,
+          1: true,
+          0: false
+        }
+
+        const booleanOutput = booleanOutputs[output]
+        if (booleanOutput !== undefined) {
+          output = booleanOutput
+        } else {
+          // TODO
+          throw new Error(`invalid boolean output: ${output}`)
+        }
+      } else if (outputSchema instanceof z.ZodNumber) {
+        output = output.trim()
+
+        const numberOutput = outputSchema.isInt
+          ? parseInt(output)
+          : parseFloat(output)
+
+        if (isNaN(numberOutput)) {
+          // TODO
+          throw new Error(`invalid number output: ${output}`)
+        } else {
+          output = numberOutput
+        }
+      }
+
+      // TODO: handle errors, retry logic, and self-healing
+
+      return outputSchema.parse(output)
+    } else {
+      return output
+    }
+  }
 }
diff --git a/src/openai.ts b/src/openai.ts
index 9e30b5a..6fe0e86 100644
--- a/src/openai.ts
+++ b/src/openai.ts
@@ -1,25 +1,18 @@
-import { jsonrepair } from 'jsonrepair'
-import Mustache from 'mustache'
-import { dedent } from 'ts-dedent'
 import type { SetRequired } from 'type-fest'
 import { ZodRawShape, ZodTypeAny, z } from 'zod'
-import { printNode, zodToTs } from 'zod-to-ts'
 
 import * as types from './types'
 import { defaultOpenAIModel } from './constants'
-import { ChatModelBuilder } from './llm'
-import {
-  extractJSONArrayFromString,
-  extractJSONObjectFromString
-} from './utils'
+import { BaseChatModelBuilder } from './llm'
 
 export class OpenAIChatModelBuilder<
   TInput extends ZodRawShape | ZodTypeAny = ZodTypeAny,
   TOutput extends ZodRawShape | ZodTypeAny = z.ZodType<string>
-> extends ChatModelBuilder<
+> extends BaseChatModelBuilder<
   TInput,
   TOutput,
-  SetRequired<Omit<types.openai.ChatCompletionParams, 'messages'>, 'model'>
+  SetRequired<Omit<types.openai.ChatCompletionParams, 'messages'>, 'model'>,
+  types.openai.ChatCompletionResponse
 > {
   _client: types.openai.OpenAIClient
 
@@ -40,151 +33,20 @@ export class OpenAIChatModelBuilder<
     this._client = client
   }
 
-  override async call(
-    input?: types.ParsedData<TInput>
-  ): Promise<types.ParsedData<TOutput>> {
-    if (this._inputSchema) {
-      const inputSchema =
-        this._inputSchema instanceof z.ZodType
-          ? this._inputSchema
-          : z.object(this._inputSchema)
-
-      // TODO: handle errors gracefully
-      input = inputSchema.parse(input)
-    }
-
-    // TODO: validate input message variables against input schema
-
-    const messages = this._messages
-      .map((message) => {
-        return {
-          ...message,
-          content: message.content
-            ? Mustache.render(dedent(message.content), input).trim()
-            : ''
-        }
-      })
-      .filter((message) => message.content)
-
-    if (this._examples?.length) {
-      // TODO: smarter example selection
-      for (const example of this._examples) {
-        messages.push({
-          role: 'system',
-          content: `Example input: ${example.input}\n\nExample output: ${example.output}`
-        })
-      }
-    }
-
-    if (this._outputSchema) {
-      const outputSchema =
-        this._outputSchema instanceof z.ZodType
-          ? this._outputSchema
-          : z.object(this._outputSchema)
-
-      const { node } = zodToTs(outputSchema)
-
-      if (node.kind === 152) {
-        // handle raw strings differently
-        messages.push({
-          role: 'system',
-          content: dedent`Output a raw string only, without any additional text.`
-        })
-      } else {
-        const tsTypeString = printNode(node, {
-          removeComments: false,
-          // TODO: this doesn't seem to actually work, so we're doing it manually below
-          omitTrailingSemicolon: true,
-          noEmitHelpers: true
-        })
-          .replace(/^    /gm, '  ')
-          .replace(/;$/gm, '')
-
-        messages.push({
-          role: 'system',
-          content: dedent`Output JSON only in the following TypeScript format:
-          \`\`\`ts
-          ${tsTypeString}
-          \`\`\``
-        })
-      }
-    }
-
-    // TODO: filter/compress messages based on token counts
-
-    console.log('>>>')
-    console.log(messages)
-    const completion = await this._client.createChatCompletion({
-      model: defaultOpenAIModel, // TODO: this shouldn't be necessary but TS is complaining
-      ...this._outputSchema,
+  protected override async _createChatCompletion(
+    messages: types.ChatMessage[]
+  ): Promise<
+    types.BaseChatCompletionResponse<types.openai.ChatCompletionResponse>
+  > {
+    const response = await this._client.createChatCompletion({
+      model: this._model,
+      ...this._modelParams,
       messages
     })
 
-    if (this._outputSchema) {
-      const outputSchema =
-        this._outputSchema instanceof z.ZodType
-          ? this._outputSchema
-          : z.object(this._outputSchema)
-
-      let output: any = completion.message.content
-      console.log('===')
-      console.log(output)
-      console.log('<<<')
-
-      if (outputSchema instanceof z.ZodArray) {
-        try {
-          const trimmedOutput = extractJSONArrayFromString(output)
-          output = JSON.parse(jsonrepair(trimmedOutput ?? output))
-        } catch (err) {
-          // TODO
-          throw err
-        }
-      } else if (outputSchema instanceof z.ZodObject) {
-        try {
-          const trimmedOutput = extractJSONObjectFromString(output)
-          output = JSON.parse(jsonrepair(trimmedOutput ?? output))
-        } catch (err) {
-          // TODO
-          throw err
-        }
-      } else if (outputSchema instanceof z.ZodBoolean) {
-        output = output.toLowerCase().trim()
-        const booleanOutputs = {
-          true: true,
-          false: false,
-          yes: true,
-          no: false,
-          1: true,
-          0: false
-        }
-
-        const booleanOutput = booleanOutputs[output]
-        if (booleanOutput !== undefined) {
-          output = booleanOutput
-        } else {
-          // TODO
-          throw new Error(`invalid boolean output: ${output}`)
-        }
-      } else if (outputSchema instanceof z.ZodNumber) {
-        output = output.trim()
-
-        const numberOutput = outputSchema.isInt
-          ? parseInt(output)
-          : parseFloat(output)
-
-        if (isNaN(numberOutput)) {
-          // TODO
-          throw new Error(`invalid number output: ${output}`)
-        } else {
-          output = numberOutput
-        }
-      }
-
-      // TODO: handle errors, retry logic, and self-healing
-
-      return outputSchema.parse(output)
-    } else {
-      return completion.message.content as any
+    return {
+      message: response.message,
+      response: response.response
     }
   }
 }
diff --git a/src/types.ts b/src/types.ts
index 54614f3..5b8c217 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -61,7 +61,13 @@ export interface LLMOptions<
   promptSuffix?: string
 }
 
-export type ChatMessageRole = 'user' | 'system' | 'assistant'
+// export type ChatMessageRole = 'user' | 'system' | 'assistant'
+export const ChatMessageRoleSchema = z.union([
+  z.literal('user'),
+  z.literal('system'),
+  z.literal('assistant')
+])
+export type ChatMessageRole = z.infer<typeof ChatMessageRoleSchema>
 
 export interface ChatMessage {
   role: ChatMessageRole
@@ -76,6 +82,16 @@ export interface ChatModelOptions<
   messages: ChatMessage[]
 }
 
+export interface BaseChatCompletionResponse<
+  TChatCompletionResponse extends Record<string, any> = Record<string, any>
+> {
+  /** The completion message. */
+  message: ChatMessage
+
+  /** The raw response from the LLM provider. */
+  response: TChatCompletionResponse
+}
+
 export interface LLMExample {
   input: string
   output: string