feat(github): add review thread replies

github/README.md

@@ -48,6 +48,8 @@ When commenting on specific lines, opencode receives:
 
 This allows for more targeted requests without needing to specify file paths or line numbers manually.
 
+By default, opencode replies with a top-level PR comment. Set `reply_to_review_thread: true` to reply directly in the triggering review comment thread instead.
+
 ## Installation
 
 Run the following command in the terminal from your GitHub repo:
@@ -80,6 +82,8 @@ This will walk you through installing the GitHub app, creating the workflow, and
        runs-on: ubuntu-latest
        permissions:
          id-token: write
+         pull-requests: write
+         issues: write
        steps:
           - name: Checkout repository
             uses: actions/checkout@v6
@@ -95,6 +99,7 @@ This will walk you through installing the GitHub app, creating the workflow, and
            with:
              model: anthropic/claude-sonnet-4-20250514
              use_github_token: true
+             reply_to_review_thread: true
    ```
 
 3. Store the API keys in secrets. In your organization or project **settings**, expand **Secrets and variables** on the left and select **Actions**. Add the required API keys.

github/action.yml

@@ -38,6 +38,11 @@ inputs:
     description: "Base URL for OIDC token exchange API. Only required when running a custom GitHub App install. Defaults to https://api.opencode.ai"
     required: false
 
+  reply_to_review_thread:
+    description: "Reply in the triggering pull request review thread when handling pull_request_review_comment events"
+    required: false
+    default: "false"
+
 runs:
   using: "composite"
   steps:
@@ -77,3 +82,4 @@ runs:
         MENTIONS: ${{ inputs.mentions }}
         VARIANT: ${{ inputs.variant }}
         OIDC_BASE_URL: ${{ inputs.oidc_base_url }}
+        REPLY_TO_REVIEW_THREAD: ${{ inputs.reply_to_review_thread }}

github/index.ts

@@ -118,6 +118,7 @@ let accessToken: string
 let octoRest: Octokit
 let octoGraph: typeof graphql
 let commentId: number
+let commentType: "issue" | "review" = "issue"
 let gitConfig: string
 let session: { id: string; title: string; version: string }
 let shareId: string | undefined
@@ -331,6 +332,14 @@ function useEnvShare() {
   throw new Error(`Invalid share value: ${value}. Share must be a boolean.`)
 }
 
+function useEnvReplyToReviewThread() {
+  const value = process.env["REPLY_TO_REVIEW_THREAD"]
+  if (!value) return false
+  if (value === "true") return true
+  if (value === "false") return false
+  throw new Error(`Invalid reply_to_review_thread value: ${value}. reply_to_review_thread must be a boolean.`)
+}
+
 function useEnvMock() {
   return {
     mockEvent: process.env["MOCK_EVENT"],
@@ -349,6 +358,8 @@ function isMock() {
 
 function isPullRequest() {
   const context = useContext()
+  if (context.eventName === "pull_request_review_comment") return true
+
   const payload = context.payload as IssueCommentEvent
   return Boolean(payload.issue.pull_request)
 }
@@ -358,7 +369,13 @@ function useContext() {
 }
 
 function useIssueId() {
-  const payload = useContext().payload as IssueCommentEvent
+  const context = useContext()
+  if (context.eventName === "pull_request_review_comment") {
+    const payload = context.payload as PullRequestReviewCommentEvent
+    return payload.pull_request.number
+  }
+
+  const payload = context.payload as IssueCommentEvent
   return payload.issue.number
 }
 
@@ -402,7 +419,24 @@ async function getAccessToken() {
 
 async function createComment() {
   const { repo } = useContext()
+  const reviewContext = getReviewCommentContext()
+
+  if (reviewContext && useEnvReplyToReviewThread()) {
+    const payload = useContext().payload as PullRequestReviewCommentEvent
+    const reviewCommentId = payload.comment.in_reply_to_id ?? payload.comment.id
+    console.log("Creating review thread reply...")
+    commentType = "review"
+    return await octoRest.rest.pulls.createReplyForReviewComment({
+      owner: repo.owner,
+      repo: repo.repo,
+      pull_number: useIssueId(),
+      comment_id: reviewCommentId,
+      body: `[Working...](${useEnvRunUrl()})`,
+    })
+  }
+
   console.log("Creating comment...")
+  commentType = "issue"
   return await octoRest.rest.issues.createComment({
     owner: repo.owner,
     repo: repo.repo,
@@ -798,6 +832,15 @@ async function updateComment(body: string) {
   console.log("Updating comment...")
 
   const { repo } = useContext()
+  if (commentType === "review") {
+    return await octoRest.rest.pulls.updateReviewComment({
+      owner: repo.owner,
+      repo: repo.repo,
+      comment_id: commentId,
+      body,
+    })
+  }
+
   return await octoRest.rest.issues.updateComment({
     owner: repo.owner,
     repo: repo.repo,