Blaxel Sandboxes provide tools for managing files and their contents, specialized for code generation (“codegen”) use cases. These tools are accessible exclusively through the sandboxes’ MCP server.

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Fast apply of file edits

With this tool, you can apply code changes suggested by an LLM to your existing code files fast (2000+ tokens/second).

Traditional code generation requires generating the entire files every time, which can be slow for large files. This approach is more efficient: your LLM only generates the specific changes needed, and this tool quickly applies them to the original file.

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Get started

Fast apply of file edits is powered by MorphLLM. In order for this tool to work, make sure to pass your Morph API key and Morph model (default = morph-v2) set as environment variables when creating the sandbox.

import { SandboxInstance } from "@blaxel/core"

export async function createOrGetSandbox({sandboxName, wait = true}: {sandboxName: string, wait?: boolean}) {
  const envs = []
  if (process.env.MORPH_API_KEY) {
    envs.push({
      name: "MORPH_API_KEY",
      value: process.env.MORPH_API_KEY
    })
  }
  if (process.env.MORPH_MODEL) {
    envs.push({
      name: "MORPH_MODEL",
      value: process.env.MORPH_MODEL
    })
  }
  const sandboxModel = {
    metadata: {
      name: sandboxName
    },
    spec: {
      runtime: {
        image: "blaxel/prod-nextjs:latest",
        memory: 4096,
        ports: [
          {
            name: "sandbox-api",
            target: 8080,
            protocol: "HTTP",
          },
          {
            name: "preview",
            target: 3000,
            protocol: "HTTP",
          }
        ]
      },
      envs
    }
  }
  const sandbox = await SandboxInstance.createIfNotExists(sandboxModel)
  if (wait) {
    await sandbox.wait({ maxWait: 120000, interval: 1000 })
  }
  return sandbox
}
If you do not pass the MORPH_API_KEY, this specific tool will not be available.

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Use the tool

Call the codegenEditFile tool on the MCP server of a sandbox to fast-apply a targeted edit to a specified file, with instructions and partial contents.

Use Blaxel SDK to retrieve the tool in any compatible agent framework (here in AI SDK format):

import { blTools } from '@blaxel/vercel'; // or any compatible agent framework

// Get all tools in the sandbox MCP
const allTools = await blTools([`sandboxes/YOUR-SANDBOX-ID`], maxDuration * 1000)

// Filter on just codegenEditFile
const tools = Object.fromEntries(Object.entries(allTools).filter(([key]) => key.startsWith('codegenEditFile')))

// You can then pass 'tools' in your agent, so it can autonomously use it
...

Check out the following file on GitHub to see a full example of using the fast apply tool in an agent.

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Other tools built for codegen

Use the following codegen-optimized functions by making tool calls through the MCP server of a sandbox. See example above on how to retrieve and execute the tools.

  1. codegenCodebaseSearch - Find semantic code snippets from the codebase based on a natural language query.
  2. codegenFileSearch - Fast fuzzy filename search in the project.
  3. codegenGrepSearch - Run fast, exact regex/text searches on files for locating patterns or strings.
  4. codegenListDir - List contents of a directory in the project.
  5. codegenParallelApply - Plan and apply similar changes to multiple locations/files simultaneously.
  6. codegenReadFileRange - Read a specific range of lines in a file (max 250 lines at once).
  7. codegenReapply - Retry the application of the last edit, in case it previously failed.