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layout default
title Chapter 3: Model and Provider Routing
nav_order 3
parent OpenCode Tutorial

Chapter 3: Model and Provider Routing

Welcome to Chapter 3: Model and Provider Routing. In this part of OpenCode Tutorial: Open-Source Terminal Coding Agent at Scale, you will build an intuitive mental model first, then move into concrete implementation details and practical production tradeoffs.

OpenCode is provider-agnostic by design. A strong routing strategy controls quality, cost, and latency.

Routing Strategy

Workload Recommended Model Class
repo analysis high-context reasoning model
code edits fast coding-focused model
long refactors stable high-accuracy model
follow-up fixes low-latency model

Practical Controls

  • use explicit model defaults for repetitive workflows
  • define fallback providers for outage resilience
  • separate experimentation profiles from production defaults

Common Failure Modes

  • oscillating output quality due to unpinned model selection
  • silent cost spikes from oversized model defaults
  • context-window mismatches for large monorepos

Source References

Summary

You now know how to build a provider strategy instead of relying on a single default model.

Next: Chapter 4: Tools, Permissions, and Execution

Depth Expansion Playbook

Source Code Walkthrough

github/index.ts

The useShareUrl function in github/index.ts handles a key part of this chapter's functionality:

  console.log("opencode session", session.id)
  if (shareId) {
    console.log("Share link:", `${useShareUrl()}/s/${shareId}`)
  }

  // Handle 3 cases
  // 1. Issue
  // 2. Local PR
  // 3. Fork PR
  if (isPullRequest()) {
    const prData = await fetchPR()
    // Local PR
    if (prData.headRepository.nameWithOwner === prData.baseRepository.nameWithOwner) {
      await checkoutLocalBranch(prData)
      const dataPrompt = buildPromptDataForPR(prData)
      const response = await chat(`${userPrompt}\n\n${dataPrompt}`, promptFiles)
      if (await branchIsDirty()) {
        const summary = await summarize(response)
        await pushToLocalBranch(summary)
      }
      const hasShared = prData.comments.nodes.some((c) => c.body.includes(`${useShareUrl()}/s/${shareId}`))
      await updateComment(`${response}${footer({ image: !hasShared })}`)
    }
    // Fork PR
    else {
      await checkoutForkBranch(prData)
      const dataPrompt = buildPromptDataForPR(prData)
      const response = await chat(`${userPrompt}\n\n${dataPrompt}`, promptFiles)
      if (await branchIsDirty()) {
        const summary = await summarize(response)
        await pushToForkBranch(summary, prData)
      }

This function is important because it defines how OpenCode Tutorial: Open-Source Terminal Coding Agent at Scale implements the patterns covered in this chapter.

github/index.ts

The getAccessToken function in github/index.ts handles a key part of this chapter's functionality:

  await assertOpencodeConnected()

  accessToken = await getAccessToken()
  octoRest = new Octokit({ auth: accessToken })
  octoGraph = graphql.defaults({
    headers: { authorization: `token ${accessToken}` },
  })

  const { userPrompt, promptFiles } = await getUserPrompt()
  await configureGit(accessToken)
  await assertPermissions()

  const comment = await createComment()
  commentId = comment.data.id

  // Setup opencode session
  const repoData = await fetchRepo()
  session = await client.session.create<true>().then((r) => r.data)
  await subscribeSessionEvents()
  shareId = await (async () => {
    if (useEnvShare() === false) return
    if (!useEnvShare() && repoData.data.private) return
    await client.session.share<true>({ path: session })
    return session.id.slice(-8)
  })()
  console.log("opencode session", session.id)
  if (shareId) {
    console.log("Share link:", `${useShareUrl()}/s/${shareId}`)
  }

  // Handle 3 cases
  // 1. Issue

This function is important because it defines how OpenCode Tutorial: Open-Source Terminal Coding Agent at Scale implements the patterns covered in this chapter.

github/index.ts

The createComment function in github/index.ts handles a key part of this chapter's functionality:

  await assertPermissions()

  const comment = await createComment()
  commentId = comment.data.id

  // Setup opencode session
  const repoData = await fetchRepo()
  session = await client.session.create<true>().then((r) => r.data)
  await subscribeSessionEvents()
  shareId = await (async () => {
    if (useEnvShare() === false) return
    if (!useEnvShare() && repoData.data.private) return
    await client.session.share<true>({ path: session })
    return session.id.slice(-8)
  })()
  console.log("opencode session", session.id)
  if (shareId) {
    console.log("Share link:", `${useShareUrl()}/s/${shareId}`)
  }

  // Handle 3 cases
  // 1. Issue
  // 2. Local PR
  // 3. Fork PR
  if (isPullRequest()) {
    const prData = await fetchPR()
    // Local PR
    if (prData.headRepository.nameWithOwner === prData.baseRepository.nameWithOwner) {
      await checkoutLocalBranch(prData)
      const dataPrompt = buildPromptDataForPR(prData)
      const response = await chat(`${userPrompt}\n\n${dataPrompt}`, promptFiles)
      if (await branchIsDirty()) {

This function is important because it defines how OpenCode Tutorial: Open-Source Terminal Coding Agent at Scale implements the patterns covered in this chapter.

github/index.ts

The getUserPrompt function in github/index.ts handles a key part of this chapter's functionality:

let shareId: string | undefined
let exitCode = 0
type PromptFiles = Awaited<ReturnType<typeof getUserPrompt>>["promptFiles"]

try {
  assertContextEvent("issue_comment", "pull_request_review_comment")
  assertPayloadKeyword()
  await assertOpencodeConnected()

  accessToken = await getAccessToken()
  octoRest = new Octokit({ auth: accessToken })
  octoGraph = graphql.defaults({
    headers: { authorization: `token ${accessToken}` },
  })

  const { userPrompt, promptFiles } = await getUserPrompt()
  await configureGit(accessToken)
  await assertPermissions()

  const comment = await createComment()
  commentId = comment.data.id

  // Setup opencode session
  const repoData = await fetchRepo()
  session = await client.session.create<true>().then((r) => r.data)
  await subscribeSessionEvents()
  shareId = await (async () => {
    if (useEnvShare() === false) return
    if (!useEnvShare() && repoData.data.private) return
    await client.session.share<true>({ path: session })
    return session.id.slice(-8)
  })()

This function is important because it defines how OpenCode Tutorial: Open-Source Terminal Coding Agent at Scale implements the patterns covered in this chapter.

How These Components Connect

flowchart TD
    A[useShareUrl]
    B[getAccessToken]
    C[createComment]
    D[getUserPrompt]
    E[subscribeSessionEvents]
    A --> B
    B --> C
    C --> D
    D --> E
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