feat(ai-moderation): use per-server nickname (displayName) in analysis payload

- resolveDisplayName(): member.displayName from captured metadata,
  falls back to global username
- Applied to context lines, target message blocks, and media message
  blocks — LLM sees the name the channel actually sees (nickname can
  carry moderation signal itself)

services/discord-gateway/src/modules/ai-moderation/conversationContext.ts

@@ -6,6 +6,7 @@ import {
 } from "../message-capture/messageMetadata.js";
 import type { MessageRecord } from "../message-capture/types.js";
 import { sanitizeDiscordTokens } from "./discordTokens.js";
+import { resolveDisplayName } from "./moderationBuilders.js";
 
 const logger = createChildLogger("conversationContext");
 
@@ -130,7 +131,7 @@ export function formatMessageForPrompt(
   const mediaEvidence = formatMediaEvidenceForPrompt(msg.metadata);
   const mediaSuffix = mediaEvidence ? ` ${mediaEvidence}` : "";
   const refInfo = formatReferenceInfo(msg);
-  return `[${label}] id=${msg.id} time=${timestamp} user=${msg.username}: ${content}${mediaSuffix}${refInfo}`;
+  return `[${label}] id=${msg.id} time=${timestamp} user=${resolveDisplayName(msg)}: ${content}${mediaSuffix}${refInfo}`;
 }
 
 /**

services/discord-gateway/src/modules/ai-moderation/moderationBuilders.ts

@@ -36,6 +36,27 @@ export function getAnalysisContent(message: MessageRecord): string {
   ).trim();
 }
 
+/**
+ * Server nickname (member.displayName) when captured, else the author
+ * username. Discord shows the server nickname to other members, so the LLM
+ * should see the same name the channel sees — and a nickname can carry
+ * moderation signal itself (offensive nick + clean message → low warn).
+ */
+export function resolveDisplayName(msg: MessageRecord): string {
+  if (msg.metadata) {
+    try {
+      const meta = JSON.parse(msg.metadata) as {
+        member?: { displayName?: string | null } | null;
+      };
+      const dn = meta?.member?.displayName;
+      if (dn && dn.trim().length > 0) return dn;
+    } catch {
+      // malformed metadata — fall back to username
+    }
+  }
+  return msg.username;
+}
+
 /**
  * Builds a <reference> XML element for reply/forward/crosspost context.
  */

services/discord-gateway/src/modules/ai-moderation/textBatchProcessor.ts

@@ -21,6 +21,7 @@ import {
   buildReferenceXml,
   escapeXml,
   getAnalysisContent,
+  resolveDisplayName,
 } from "./moderationBuilders.js";
 import {
   buildSystemPrompt as buildSystemPromptModular,
@@ -308,7 +309,7 @@ export async function runTextOnlyBatch(
             const userCtx = userContexts.get(msg.user_id) ?? "";
             const userProfileCtx = userProfiles.get(msg.user_id) ?? "";
             const refXml = await buildReferenceXml(msg);
-            return `<message id="${msg.id}" user="${msg.username}">\n  ${userCtx}${userProfileCtx ? `\n  ${userProfileCtx}` : ""}${refXml ? `\n  ${refXml}` : ""}\n  <content>${escapeXml(content)}</content>${webContext}${mediaEvidenceCtx}\n</message>`;
+            return `<message id="${msg.id}" user="${resolveDisplayName(msg)}">\n  ${userCtx}${userProfileCtx ? `\n  ${userProfileCtx}` : ""}${refXml ? `\n  ${refXml}` : ""}\n  <content>${escapeXml(content)}</content>${webContext}${mediaEvidenceCtx}\n</message>`;
           }),
         )
       ).join("\n");

services/discord-gateway/src/modules/ai-moderation/visionAnalyzer.ts

@@ -39,6 +39,7 @@ import {
   buildReferenceXml,
   escapeXml,
   getAnalysisContent,
+  resolveDisplayName,
 } from "./moderationBuilders.js";
 import {
   buildCustomEmojiVisionPrompt,
@@ -367,6 +368,6 @@ export async function prepareMediaMessage(
   const profile = await getUserProfile(target.user_id);
   const refXml = await buildReferenceXml(target);
 
-  const messageBlock = `<message id="${escapeXml(target.id)}" user="${escapeXml(target.username)}">\n  <user_reputation trust_score="${rep.trust_score}" />${profile ? `\n  <user_profile>${sanitizeAiContent(profile.profile_summary)}</user_profile>` : ""}${refXml ? `\n  ${refXml}` : ""}\n  <content>${escapeXml(content)}</content>${mediaContext ? ` ${escapeXml(mediaContext)}` : ""}${webContext}${mediaAnalysisContext}${searxngXml}\n</message>`;
+  const messageBlock = `<message id="${escapeXml(target.id)}" user="${escapeXml(resolveDisplayName(target))}">\n  <user_reputation trust_score="${rep.trust_score}" />${profile ? `\n  <user_profile>${sanitizeAiContent(profile.profile_summary)}</user_profile>` : ""}${refXml ? `\n  ${refXml}` : ""}\n  <content>${escapeXml(content)}</content>${mediaContext ? ` ${escapeXml(mediaContext)}` : ""}${webContext}${mediaAnalysisContext}${searxngXml}\n</message>`;
   return { targetId, messageBlock };
 }

services/discord-gateway/tests/conversationContext.test.ts

@@ -5,6 +5,7 @@ import { describe, expect, it } from "vitest";
 import {
   buildConversationContext,
   buildLocationContext,
+  formatMessageForPrompt,
 } from "../src/modules/ai-moderation/conversationContext.js";
 import { extractOgMeta } from "../src/modules/ai-moderation/urlFetcher.js";
 import type { MessageRecord } from "../src/modules/message-capture/types.js";
@@ -139,6 +140,30 @@ describe("buildConversationContext — recency gating", () => {
   });
 });
 
+describe("formatMessageForPrompt — server nickname (displayName)", () => {
+  it("renders member.displayName when captured (per-server nickname)", () => {
+    const m = msg("n1", NOW - MIN);
+    m.metadata = JSON.stringify({
+      member: {
+        displayName: "Si Goblok Server",
+        roles: [],
+        joinedTimestamp: null,
+      },
+    });
+    const line = formatMessageForPrompt(m, "context");
+    expect(line).toContain("user=Si Goblok Server");
+    expect(line).not.toContain("user_user_n1");
+  });
+
+  it("falls back to global username when displayName missing", () => {
+    const line = formatMessageForPrompt(
+      msg("n2", NOW - MIN, "halo"),
+      "context",
+    );
+    expect(line).toContain("user=user_n2");
+  });
+});
+
 describe("buildLocationContext — channel/thread/nsfw enrichment", () => {
   it("renders channel name + thread name from captured metadata", () => {
     const t = target();