quantfive · lightninglu10 · Dec 19, 2025 · Dec 17, 2025
diff --git a/src/agent/agent-system-prompt.ts b/src/agent/agent-system-prompt.ts
@@ -204,6 +204,49 @@ export function getInteractiveSystemPrompt(
     If you cannot verify a claim, do not make it.
   </verification>
 
+  <!-- EXISTING REVIEW COMMENTS POLICY -->
+  <existingCommentsPolicy>
+    When other reviewers have already commented on the PR (shown in <existingReviewComments>):
+
+    1. **DO NOT DUPLICATE**: Never repeat feedback that another reviewer has already given.
+       If someone already pointed out an issue, do not post the same comment.
+
+    2. **USE EMOJI REACTIONS**: When you agree with an existing comment but have nothing
+       substantial to add, use an emoji reaction instead of posting a new comment.
+       This is a lightweight way to show your agreement without adding noise.
+
+       The comment ID is provided in each <comment> element's \`<commentId>\` field.
+       Use it to add a reaction:
+       \`gh api repos/OWNER/REPO/pulls/comments/COMMENT_ID/reactions -f content="+1"\`
+
+       Available reactions:
+       • \`+1\` (👍) - Agree with the comment
+       • \`-1\` (👎) - Disagree (prefer posting a counter-opinion with explanation)
+       • \`heart\` (❤️) - Great catch/suggestion
+       • \`rocket\` (🚀) - Excellent improvement
+       • \`eyes\` (👀) - Interesting point, needs attention
+       • \`confused\` (😕) - Unclear or questionable suggestion
+
+    3. **REINFORCE when valuable**: If you strongly agree with an existing comment and have
+       additional context or a stronger argument, you MAY add a supporting comment.
+       Example: "I agree with @reviewer's point about X. Additionally, this could cause Y..."
+
+    4. **RESPECTFULLY DISAGREE**: If you believe an existing comment is incorrect or
+       the suggested change would be harmful, you may respectfully provide a counter-opinion.
+       Be constructive and explain your reasoning with evidence.
+       Example: "I have a different perspective on @reviewer's suggestion about X.
+       The current approach is actually preferred because..."
+
+    5. **FACTOR INTO ASSESSMENT**: Consider existing comments when deciding your overall
+       review verdict. If issues have already been raised that warrant changes, acknowledge
+       them in your review summary even if you don't add new comments about them.
+
+    6. **STILL DO A FULL REVIEW**: You should review ALL the code in the diff and form your
+       own judgement about everything. Existing comments don't mean you skip those areas.
+       Just avoid posting duplicate feedback for issues already raised - use emoji reactions
+       or add to the discussion with new insights instead.
+  </existingCommentsPolicy>
+
   <!-- PROACTIVE ANALYSIS - USE YOUR TOOLS -->
   <proactiveAnalysis>
     Don't just read the diff - actively investigate using your tools:

diff --git a/src/agent/index.ts b/src/agent/index.ts
@@ -2,7 +2,7 @@ import { Agent, Runner } from "@openai/agents";
 import { aisdk } from "@openai/agents-extensions";
 import { debugError, debugLog } from "../debug";
 import { createModel } from "../model-factory";
-import { ModelConfig } from "../types";
+import { ExistingReviewComment, ModelConfig } from "../types";
 import { getInteractiveSystemPrompt } from "./agent-system-prompt";
 import { allTools, resetTodoList } from "./tools";
 
@@ -38,6 +38,41 @@ export interface PRContext {
   commitSha: string;
 }
 
+/**
+ * Formats existing review comments into a readable string for the agent.
+ */
+function formatExistingComments(comments: ExistingReviewComment[]): string {
+  if (comments.length === 0) {
+    return "";
+  }
+
+  const formattedComments = comments.map((comment, index) => {
+    const lineInfo = comment.line ? `Line ${comment.line}` : "File-level";
+    return `<comment index="${index + 1}" id="${comment.id}">
+  <author>${comment.author}</author>
+  <file>${comment.path}</file>
+  <location>${lineInfo}</location>
+  <commentId>${comment.id}</commentId>
+  <body>${comment.body}</body>
+  <codeContext>
+${comment.diffHunk}
+  </codeContext>
+</comment>`;
+  });
+
+  return `
+<existingReviewComments count="${comments.length}">
+  These are review comments made by other reviewers on this PR.
+  Consider them in your review:
+  - DO NOT duplicate feedback that has already been given
+  - If you agree with a comment, you may reinforce it or add additional context
+  - If you disagree with a comment, you may respectfully provide a counter-opinion
+  - Factor these comments into your overall assessment of the PR
+
+${formattedComments.join("\n\n")}
+</existingReviewComments>`;
+}
+
 /**
  * Reviews an entire PR diff using a single interactive agent.
  * The agent has full autonomy to:
@@ -53,6 +88,7 @@ export async function reviewFullDiff(
   prContext: PRContext,
   maxTurns: number = 75,
   blockingOnly: boolean = false,
+  existingComments: ExistingReviewComment[] = [],
 ): Promise<void> {
   // Reset todo list for fresh review
   resetTodoList();
@@ -76,6 +112,12 @@ export async function reviewFullDiff(
     );
   }
 
+  // Format existing comments for inclusion
+  const existingCommentsSection = formatExistingComments(existingComments);
+  if (existingComments.length > 0) {
+    debugLog(`📝 Including ${existingComments.length} existing review comments in context`);
+  }
+
   const initialMessage = `
 You are reviewing PR #${prContext.prNumber} in repository ${prContext.repo}.
 Commit SHA: ${prContext.commitSha}
@@ -87,6 +129,7 @@ ${fileList}
 <fullDiff>
 ${fullDiff}
 </fullDiff>
+${existingCommentsSection}
 
 <instruction>
 Please review this pull request. You have the complete diff above.
@@ -98,7 +141,7 @@ Please review this pull request. You have the complete diff above.
    - Run \`gh pr view ${prContext.prNumber} --json body -q '.body'\` to check if description is blank
    - **If body is empty/blank, you MUST update it immediately:**
      \`gh pr edit ${prContext.prNumber} --body "## Summary\\n\\n<describe what this PR does based on the diff>\\n\\n## Changes\\n\\n- <list key changes>"\`
-   - Run \`gh api repos/${prContext.repo}/pulls/${prContext.prNumber}/comments\` to check existing comments (avoid duplicates)
+   - Review the <existingReviewComments> section above (if present) to understand what other reviewers have already commented on
 
 2. **Deep review each changed file:**
    For each file in the diff:

diff --git a/src/index.ts b/src/index.ts
@@ -2,6 +2,7 @@ import * as core from "@actions/core";
 import * as github from "@actions/github";
 import { writeFileSync } from "node:fs";
 import { resolve } from "node:path";
+import { ExistingReviewComment } from "./types";
 
 interface TriggerConfig {
   runOnPrOpened: boolean;
@@ -327,6 +328,48 @@ async function run(): Promise<void> {
       core.info(
         `Generated diff file: ${diffFile} (${diffOutput.length} bytes)`,
       );
+
+      // Fetch existing review comments from other reviewers
+      const existingCommentsFile = resolve("pr-comments.json");
+      try {
+        const { data: reviewComments } =
+          await octokit.rest.pulls.listReviewComments({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            pull_number: prNumber,
+          });
+
+        // Filter out bot comments and map to our interface
+        const existingComments: ExistingReviewComment[] = reviewComments
+          .filter(
+            (comment) =>
+              comment.user &&
+              !comment.user.login.includes("[bot]") &&
+              comment.user.login !== "github-actions",
+          )
+          .map((comment) => ({
+            id: comment.id,
+            author: comment.user?.login || "unknown",
+            body: comment.body,
+            path: comment.path,
+            line: comment.line ?? comment.original_line ?? null,
+            diffHunk: comment.diff_hunk,
+            createdAt: comment.created_at,
+          }));
+
+        writeFileSync(
+          existingCommentsFile,
+          JSON.stringify(existingComments, null, 2),
+        );
+        core.info(
+          `Found ${existingComments.length} existing review comments from other reviewers`,
+        );
+      } catch (commentError) {
+        core.warning(
+          `Failed to fetch existing comments (continuing without them): ${commentError}`,
+        );
+        writeFileSync(existingCommentsFile, "[]");
+      }
     } catch (error) {
       core.setFailed(`Failed to fetch diff from GitHub API: ${error}`);
       return;

diff --git a/src/review-service.ts b/src/review-service.ts
@@ -5,7 +5,7 @@ import { resolve } from "path";
 import { PRContext, reviewFullDiff } from "./agent";
 import { getModelConfig } from "./config";
 import { debugLog } from "./debug";
-import type { ReviewConfig } from "./types";
+import type { ExistingReviewComment, ReviewConfig } from "./types";
 
 /**
  * Service class that orchestrates the review process.
@@ -81,6 +81,20 @@ export class ReviewService {
       console.error("COMMIT_SHA not set - agent will not be able to post inline comments");
     }
 
+    // Load existing review comments from other reviewers
+    const commentsFile = resolve("pr-comments.json");
+    let existingComments: ExistingReviewComment[] = [];
+    if (existsSync(commentsFile)) {
+      try {
+        existingComments = JSON.parse(readFileSync(commentsFile, "utf8"));
+        if (existingComments.length > 0) {
+          debugLog(`📝 Found ${existingComments.length} existing review comments from other reviewers`);
+        }
+      } catch (error) {
+        debugLog("⚠️ Failed to parse existing comments file, continuing without them");
+      }
+    }
+
     // Run the autonomous agent review
     debugLog("🚀 Starting autonomous PR review...");
     const modelConfig = getModelConfig();
@@ -93,6 +107,7 @@ export class ReviewService {
         prContext,
         this.config.maxTurns,
         this.config.blockingOnly,
+        existingComments,
       );
       debugLog("✅ Review completed!");
     } catch (error: unknown) {

diff --git a/src/types.ts b/src/types.ts
@@ -29,3 +29,24 @@ export interface ParsedArgs {
   diff: string;
   pr: number;
 }
+
+/**
+ * Represents an existing review comment on the PR.
+ * These are comments made by other reviewers that the bot should be aware of.
+ */
+export interface ExistingReviewComment {
+  /** GitHub comment ID (for adding reactions) */
+  id: number;
+  /** GitHub username of the commenter */
+  author: string;
+  /** The comment body/text */
+  body: string;
+  /** File path the comment is on */
+  path: string;
+  /** Line number in the new version of the file (may be null for file-level comments) */
+  line: number | null;
+  /** The diff hunk context around the comment */
+  diffHunk: string;
+  /** ISO timestamp when the comment was created */
+  createdAt: string;
+}
diff --git a/test/review-service.test.ts b/test/review-service.test.ts
@@ -89,6 +89,7 @@ diff --git a/src/test.ts b/src/test.ts
         }), // prContext
         20, // maxTurns
         false, // blockingOnly
+        [], // existingComments (empty when no pr-comments.json)
       );
     });
 
@@ -107,6 +108,7 @@ diff --git a/src/test.ts b/src/test.ts
         expect.any(Object),
         20,
         true, // blockingOnly should be true
+        [], // existingComments
       );
     });