feat(web): add optional PR/MR summary comment to review agent

Adds REVIEW_AGENT_SUMMARY_ENABLED (default false) and REVIEW_AGENT_SUMMARY_MAX_LENGTH (default 250) env vars. When enabled, the review agent generates a concise markdown summary of the PR/MR changes and posts it as a top-level comment before pushing inline review comments.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Gavin Williams

.devcontainer/docker-compose.yml

@@ -27,6 +27,7 @@ services:
       REVIEW_AGENT_LOGGING_ENABLED: "true"
       REVIEW_AGENT_AUTO_REVIEW_ENABLED: "false"
       REVIEW_AGENT_REVIEW_COMMAND: review
+      REVIEW_AGENT_SUMMARY_ENABLED: "false"
     depends_on:
       - postgres
       - redis

.env.development

@@ -49,6 +49,7 @@ REDIS_URL="redis://localhost:6379"
 REVIEW_AGENT_LOGGING_ENABLED=true
 REVIEW_AGENT_AUTO_REVIEW_ENABLED=false
 REVIEW_AGENT_REVIEW_COMMAND=review
+REVIEW_AGENT_SUMMARY_ENABLED=false
 
 # Misc
 

docs/docs/configuration/environment-variables.mdx

@@ -74,6 +74,8 @@ The following environment variables allow you to configure your Sourcebot deploy
 | `REVIEW_AGENT_AUTO_REVIEW_ENABLED` | `false` | <p>Enables/disables automatic code reviews by the review agent.</p> |
 | `REVIEW_AGENT_LOGGING_ENABLED` | `true` | <p>Enables/disables logging for the review agent. Logs are saved in `DATA_CACHE_DIR/review-agent`</p> |
 | `REVIEW_AGENT_REVIEW_COMMAND` | `review` | <p>The command used to trigger a code review by the review agent.</p> |
+| `REVIEW_AGENT_SUMMARY_ENABLED` | `false` | <p>Enables/disables posting a concise summary comment on the PR/MR after each review.</p> |
+| `REVIEW_AGENT_SUMMARY_MAX_LENGTH` | `250` | <p>Maximum character length of the summary comment posted by the review agent.</p> |
 
 ### Overriding environment variables from the config
 

docs/docs/features/agents/review-agent.mdx

@@ -145,3 +145,5 @@ You can also trigger a review manually by commenting `/review` on any PR or MR.
 | `REVIEW_AGENT_REVIEW_COMMAND` | `review` | Comment command that triggers a manual review (without the `/`) |
 | `REVIEW_AGENT_MODEL` | first configured model | `displayName` of the language model to use for reviews |
 | `REVIEW_AGENT_LOGGING_ENABLED` | unset | Write prompt and response logs to disk for debugging |
+| `REVIEW_AGENT_SUMMARY_ENABLED` | `false` | Post a concise summary comment on the PR/MR after each review |
+| `REVIEW_AGENT_SUMMARY_MAX_LENGTH` | `250` | Maximum character length of the summary comment |

packages/shared/src/env.server.ts

@@ -240,6 +240,8 @@ const options = {
         REVIEW_AGENT_LOGGING_ENABLED: booleanSchema.default('true'),
         REVIEW_AGENT_AUTO_REVIEW_ENABLED: booleanSchema.default('false'),
         REVIEW_AGENT_REVIEW_COMMAND: z.string().default('review'),
+        REVIEW_AGENT_SUMMARY_ENABLED: booleanSchema.default('false'),
+        REVIEW_AGENT_SUMMARY_MAX_LENGTH: numberSchema.default(250),
 
         ANTHROPIC_API_KEY: z.string().optional(),
         ANTHROPIC_AUTH_TOKEN: z.string().optional(),

packages/web/src/features/agents/review-agent/app.ts

@@ -1,6 +1,7 @@
 import { Octokit } from "octokit";
 import { Gitlab } from "@gitbeaker/rest";
 import { generatePrReviews } from "@/features/agents/review-agent/nodes/generatePrReview";
+import { generatePrSummary } from "@/features/agents/review-agent/nodes/generatePrSummary";
 import { githubPushPrReviews } from "@/features/agents/review-agent/nodes/githubPushPrReviews";
 import { githubPrParser } from "@/features/agents/review-agent/nodes/githubPrParser";
 import { getReviewAgentLogDir } from "@/features/agents/review-agent/nodes/invokeDiffReviewLlm";
@@ -55,7 +56,17 @@ export async function processGitHubPullRequest(octokit: Octokit, pullRequest: Gi
 
     const prPayload = await githubPrParser(octokit, pullRequest);
     const fileDiffReviews = await generatePrReviews(reviewAgentLogPath, prPayload, rules);
-    await githubPushPrReviews(octokit, prPayload, fileDiffReviews);
+
+    let summary: string | undefined;
+    if (env.REVIEW_AGENT_SUMMARY_ENABLED) {
+        try {
+            summary = await generatePrSummary(prPayload);
+        } catch (error) {
+            logger.error(`Error generating PR summary: ${error}`);
+        }
+    }
+
+    await githubPushPrReviews(octokit, prPayload, fileDiffReviews, summary);
 }
 
 export async function processGitLabMergeRequest(
@@ -70,5 +81,15 @@ export async function processGitLabMergeRequest(
 
     const prPayload = await gitlabMrParser(gitlabClient, mrPayload, hostDomain);
     const fileDiffReviews = await generatePrReviews(reviewAgentLogPath, prPayload, rules);
-    await gitlabPushMrReviews(gitlabClient, projectId, prPayload, fileDiffReviews);
+
+    let summary: string | undefined;
+    if (env.REVIEW_AGENT_SUMMARY_ENABLED) {
+        try {
+            summary = await generatePrSummary(prPayload);
+        } catch (error) {
+            logger.error(`Error generating MR summary: ${error}`);
+        }
+    }
+
+    await gitlabPushMrReviews(gitlabClient, projectId, prPayload, fileDiffReviews, summary);
 }

packages/web/src/features/agents/review-agent/nodes/generatePrSummary.ts

@@ -0,0 +1,51 @@
+import { sourcebot_pr_payload } from "@/features/agents/review-agent/types";
+import { getAISDKLanguageModelAndOptions, getConfiguredLanguageModels } from "@/features/chat/utils.server";
+import { env } from "@sourcebot/shared";
+import { generateText } from "ai";
+import { createLogger } from "@sourcebot/shared";
+
+const logger = createLogger('generate-pr-summary');
+
+export const generatePrSummary = async (prPayload: sourcebot_pr_payload): Promise<string> => {
+    const maxSummaryLength = env.REVIEW_AGENT_SUMMARY_MAX_LENGTH;
+    logger.debug("Executing generate_pr_summary");
+
+    const models = await getConfiguredLanguageModels();
+    if (models.length === 0) {
+        throw new Error("No language models are configured");
+    }
+
+    let selectedModel = models[0];
+    if (env.REVIEW_AGENT_MODEL) {
+        const match = models.find((m) => m.displayName === env.REVIEW_AGENT_MODEL);
+        if (match) {
+            selectedModel = match;
+        } else {
+            logger.warn(`REVIEW_AGENT_MODEL="${env.REVIEW_AGENT_MODEL}" did not match any configured model displayName. Falling back to the first configured model.`);
+        }
+    }
+
+    const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(selectedModel);
+
+    const filesChanged = prPayload.file_diffs.map(f => f.to).join(", ");
+
+    const prompt = `Summarize the following pull request changes in ${maxSummaryLength} characters or fewer. Be concise and focus on what changed and why. You may use inline markdown (e.g. \`code\`, **bold**) but avoid headers, bullet lists, and block-level formatting.
+
+PR Title: ${prPayload.title}
+PR Description: ${prPayload.description}
+Files changed: ${filesChanged}
+`;
+
+    const result = await generateText({
+        model,
+        system: `You are a code review assistant. Generate a concise markdown-compatible summary of pull request changes. The summary must be ${maxSummaryLength} characters or fewer. Avoid headers, bullet lists, and block-level formatting.`,
+        prompt,
+        providerOptions,
+        temperature,
+    });
+
+    const summary = result.text.trim().slice(0, maxSummaryLength);
+
+    logger.debug("Completed generate_pr_summary");
+    return summary;
+};

packages/web/src/features/agents/review-agent/nodes/githubPushPrReviews.ts

@@ -4,9 +4,22 @@ import { createLogger } from "@sourcebot/shared";
 
 const logger = createLogger('github-push-pr-reviews');
 
-export const githubPushPrReviews = async (octokit: Octokit, pr_payload: sourcebot_pr_payload, file_diff_reviews: sourcebot_file_diff_review[]) => {
+export const githubPushPrReviews = async (octokit: Octokit, pr_payload: sourcebot_pr_payload, file_diff_reviews: sourcebot_file_diff_review[], summary?: string) => {
     logger.info("Executing github_push_pr_reviews");
 
+    if (summary) {
+        try {
+            await octokit.rest.issues.createComment({
+                owner: pr_payload.owner,
+                repo: pr_payload.repo,
+                issue_number: pr_payload.number,
+                body: summary,
+            });
+        } catch (error) {
+            logger.error(`Error posting PR summary comment: ${error}`);
+        }
+    }
+
     try {
         for (const file_diff_review of file_diff_reviews) {
             for (const review of file_diff_review.reviews) {

packages/web/src/features/agents/review-agent/nodes/gitlabPushMrReviews.ts

@@ -9,9 +9,22 @@ export const gitlabPushMrReviews = async (
     projectId: number,
     prPayload: sourcebot_pr_payload,
     fileDiffReviews: sourcebot_file_diff_review[],
+    summary?: string,
 ): Promise<void> => {
     logger.info("Executing gitlab_push_mr_reviews");
 
+    if (summary) {
+        try {
+            await gitlabClient.MergeRequestNotes.create(
+                projectId,
+                prPayload.number,
+                summary,
+            );
+        } catch (error) {
+            logger.error(`Error posting MR summary note: ${error}`);
+        }
+    }
+
     if (!prPayload.diff_refs) {
         logger.error("diff_refs is missing from pr_payload, cannot post inline GitLab MR reviews");
         return;