diff --git a/docs/contributing/api-patterns.md b/docs/contributing/api-patterns.md
index 82f86e5dc..106b6a53e 100644
--- a/docs/contributing/api-patterns.md
+++ b/docs/contributing/api-patterns.md
@@ -21,6 +21,13 @@ rg -n "class OrganizationAIConversations|ai-conversations" ~/src/sentry/src ~/sr
 Use the verified source contract to define Zod schemas, query parameters,
 pagination behavior, feature-gate handling, and test fixtures.
 
+### Issue Activity Attribution
+
+`source` identifies the channel or client, such as `mcp:claude`; `user` and
+`sentry_app` identify the actor. `commentId` is the reference accepted by the
+notes endpoints and can differ from the activity `id`. For comment creation
+responses, use `commentId ?? id`. Both `source` and `commentId` may be absent or null.
+
 ### Client Creation
 
 ```typescript
diff --git a/packages/mcp-core/src/api-client/schema.test.ts b/packages/mcp-core/src/api-client/schema.test.ts
index af8279144..cab4ccf98 100644
--- a/packages/mcp-core/src/api-client/schema.test.ts
+++ b/packages/mcp-core/src/api-client/schema.test.ts
@@ -14,6 +14,7 @@ import {
   EventSchema,
   FlamegraphSchema,
   IssueSchema,
+  IssueActivitySchema,
   IssueTagValuesSchema,
   ProfileChunkResponseSchema,
   ProfileChunkSampleSchema,
@@ -28,6 +29,28 @@ import {
   TransactionProfileSchema,
 } from "./schema";
 
+describe("IssueActivitySchema", () => {
+  it("types source metadata and the separate comment reference", () => {
+    const activity = {
+      id: "activity-1",
+      commentId: "comment-1",
+      source: "mcp:claude",
+    };
+    expect(IssueActivitySchema.parse(activity)).toEqual(activity);
+    expect(
+      IssueActivitySchema.safeParse({ ...activity, source: 123 }).success,
+    ).toBe(false);
+  });
+
+  it("accepts missing or null metadata from older and system activity", () => {
+    expect(IssueActivitySchema.parse({ id: "activity-1" })).toEqual({
+      id: "activity-1",
+    });
+    const activity = { id: "activity-1", commentId: null, source: null };
+    expect(IssueActivitySchema.parse(activity)).toEqual(activity);
+  });
+});
+
 describe("IssueSchema", () => {
   it("should parse a standard error issue", () => {
     const errorIssue = {
diff --git a/packages/mcp-core/src/api-client/schema.ts b/packages/mcp-core/src/api-client/schema.ts
index 3ffea37c8..191e3df1f 100644
--- a/packages/mcp-core/src/api-client/schema.ts
+++ b/packages/mcp-core/src/api-client/schema.ts
@@ -830,6 +830,8 @@ export const CommittersResponseSchema = z.object({
 export const IssueActivitySchema = z
   .object({
     id: ApiResourceIdSchema,
+    commentId: ApiResourceIdSchema.nullable().optional(),
+    source: z.string().nullable().optional(),
     type: z.string().nullable().optional(),
     dateCreated: z.string().datetime().nullable().optional(),
     user: ApiActorSchema.nullable().optional(),
diff --git a/packages/mcp-core/src/server.test.ts b/packages/mcp-core/src/server.test.ts
index 1256b4f09..3b685213a 100644
--- a/packages/mcp-core/src/server.test.ts
+++ b/packages/mcp-core/src/server.test.ts
@@ -1513,6 +1513,50 @@ describe("buildServer", () => {
       );
     });
 
+    it.each([
+      ["get_issue_activity", {}],
+      ["add_issue_note", { text: "Investigating after the latest deploy." }],
+    ] as const)(
+      "execute_sentry_tool preserves attribution for %s",
+      async (name, args) => {
+        mswServer.use(
+          http.post(
+            "*/api/0/organizations/:org/issues/:issueId/notes/",
+            ({ params }) => {
+              expect(params.org).toBe("sentry-mcp-evals");
+              return HttpResponse.json({
+                id: "activity-1",
+                commentId: "comment-1",
+                type: "note",
+                source: "mcp:claude",
+                user: { name: "Jane Developer" },
+                data: { text: "Investigating after the latest deploy." },
+              });
+            },
+          ),
+        );
+        const server = buildServer({
+          context: {
+            ...baseContext,
+            constraints: {
+              organizationSlug: "sentry-mcp-evals",
+              projectSlug: null,
+            },
+          },
+        });
+
+        const result = await callRegisteredTool(server, "execute_sentry_tool", {
+          name,
+          arguments: { issueId: "CLOUDFLARE-MCP-41", ...args },
+        });
+
+        expect(result.isError).not.toBe(true);
+        expect(getTextContent(result)).toContain(
+          "Jane Developer (Claude via MCP)",
+        );
+      },
+    );
+
     it("execute_sentry_tool dispatches to catalog-only event stacktrace", async () => {
       const server = buildServer({
         context: baseContext,
diff --git a/packages/mcp-core/src/tools/catalog/add-issue-note.test.ts b/packages/mcp-core/src/tools/catalog/add-issue-note.test.ts
index f9862f3e5..b4124c22e 100644
--- a/packages/mcp-core/src/tools/catalog/add-issue-note.test.ts
+++ b/packages/mcp-core/src/tools/catalog/add-issue-note.test.ts
@@ -1,4 +1,6 @@
-import { describe, expect, it } from "vitest";
+import { afterEach, describe, expect, it } from "vitest";
+import { mswServer } from "@sentry/mcp-server-mocks";
+import { http, HttpResponse } from "msw";
 import addIssueNote from "./add-issue-note.js";
 
 const context = {
@@ -9,7 +11,52 @@ const context = {
   userId: "1",
 };
 
+afterEach(() => {
+  mswServer.resetHandlers();
+});
+
 describe("add_issue_note", () => {
+  it("includes MCP attribution and the comment reference returned by Sentry", async () => {
+    mswServer.use(
+      http.post("*/api/0/organizations/:org/issues/:issueId/notes/", () =>
+        HttpResponse.json({
+          id: "activity-1",
+          commentId: "comment-1",
+          type: "note",
+          source: "mcp:claude",
+          user: { name: "Jane Developer" },
+          dateCreated: "2025-04-14T12:34:56.000Z",
+          data: { text: "Investigating after the latest deploy." },
+        }),
+      ),
+    );
+
+    const result = await addIssueNote.handler(
+      {
+        organizationSlug: "sentry-mcp-evals",
+        regionUrl: null,
+        issueId: "CLOUDFLARE-MCP-41",
+        text: "Investigating after the latest deploy.",
+      },
+      context,
+    );
+
+    expect(result).toMatchInlineSnapshot(`
+      "# Added Note to Issue CLOUDFLARE-MCP-41 in **sentry-mcp-evals**
+
+      **Comment ID**: comment-1
+      **Type**: note
+      **Author**: Jane Developer (Claude via MCP)
+      **Created**: 2025-04-14T12:34:56.000Z
+      **Text**: Investigating after the latest deploy.
+
+      ## Response Notes
+
+      - The note is visible in the issue activity feed."
+    `);
+    expect(result).not.toContain("activity-1");
+  });
+
   it("serializes the created note", async () => {
     const result = await addIssueNote.handler(
       {
diff --git a/packages/mcp-core/src/tools/catalog/add-issue-note.ts b/packages/mcp-core/src/tools/catalog/add-issue-note.ts
index 1a0403c69..fd99eef4c 100644
--- a/packages/mcp-core/src/tools/catalog/add-issue-note.ts
+++ b/packages/mcp-core/src/tools/catalog/add-issue-note.ts
@@ -14,19 +14,15 @@ import {
 } from "../../schema";
 import { setTargetTagsAndAttributes } from "../../telem/scope";
 import type { ServerContext } from "../../types";
-import {
-  formatActor,
-  formatDate,
-  formatId,
-  readString,
-} from "./support/api-formatting";
+import { formatDate, formatId, readString } from "./support/api-formatting";
+import { formatActivityAuthor } from "./support/activity-formatting";
 
 function formatComment(comment: IssueComment): string {
-  const actor = comment.user ? formatActor(comment.user) : "current user";
+  const actor = formatActivityAuthor(comment, "current user");
   const text = comment.data ? readString(comment.data, "text") : null;
 
   return [
-    `**Comment ID**: ${formatId(comment.id)}`,
+    `**Comment ID**: ${formatId(comment.commentId ?? comment.id)}`,
     `**Type**: ${comment.type ?? "note"}`,
     `**Author**: ${actor}`,
     formatDate(comment.dateCreated)
diff --git a/packages/mcp-core/src/tools/catalog/get-issue-activity.test.ts b/packages/mcp-core/src/tools/catalog/get-issue-activity.test.ts
index 35cebdeec..ec8e36232 100644
--- a/packages/mcp-core/src/tools/catalog/get-issue-activity.test.ts
+++ b/packages/mcp-core/src/tools/catalog/get-issue-activity.test.ts
@@ -1,5 +1,7 @@
 import { mswServer } from "@sentry/mcp-server-mocks";
 import { afterEach, describe, expect, it } from "vitest";
+import { http, HttpResponse } from "msw";
+import type { IssueActivity } from "../../api-client/types";
 import getIssueActivity from "./get-issue-activity.js";
 
 const context = {
@@ -10,22 +12,32 @@ const context = {
   userId: "1",
 };
 
+const params = {
+  organizationSlug: "sentry-mcp-evals",
+  regionUrl: null,
+  issueId: "CLOUDFLARE-MCP-41",
+  includeComments: true,
+  limit: 25,
+};
+
+function mockActivity(activity: IssueActivity) {
+  mswServer.use(
+    http.get("*/api/0/organizations/:org/issues/:issueId/activities/", () =>
+      HttpResponse.json({ activity: [activity] }),
+    ),
+    http.get("*/api/0/organizations/:org/issues/:issueId/notes/", () =>
+      HttpResponse.json([activity]),
+    ),
+  );
+}
+
 afterEach(() => {
   mswServer.resetHandlers();
 });
 
 describe("get_issue_activity", () => {
   it("serializes issue activity and comments", async () => {
-    const result = await getIssueActivity.handler(
-      {
-        organizationSlug: "sentry-mcp-evals",
-        regionUrl: null,
-        issueId: "CLOUDFLARE-MCP-41",
-        includeComments: true,
-        limit: 25,
-      },
-      context,
-    );
+    const result = await getIssueActivity.handler(params, context);
 
     expect(result).toMatchInlineSnapshot(`
       "# Activity for Issue CLOUDFLARE-MCP-41 in **sentry-mcp-evals**
@@ -34,12 +46,77 @@ describe("get_issue_activity", () => {
 
       - 2025-04-10T22:55:22.411Z: auto_set_ongoing by system (4633815464)
         - Data: {"after_days":7}
-      - 2025-04-14T12:00:00.000Z: note by Jane Developer (4633816000)
+      - 2025-04-14T12:00:00.000Z: note by Jane Developer (Claude via MCP) (4633816000)
+        - Investigating after the latest deploy.
+
+      ## Comments
+
+      - 2025-04-14T12:00:00.000Z: note by Jane Developer (Claude via MCP) (4633816000)
+        - Investigating after the latest deploy.
+
+      ## Response Notes
+
+      - Use the Sentry tool \`add_issue_note\` to add a new human-visible issue comment.
+      "
+    `);
+  });
+
+  it.each([
+    ["mcp:claude-code", "Claude via MCP"],
+    ["mcp:cursor", "Cursor via MCP"],
+    ["mcp", "via MCP"],
+    ["mcp:new-client", "via MCP"],
+    ["api", "via API"],
+    ["sentry-cli", "via Sentry CLI"],
+    ["web", null],
+    [null, null],
+    [undefined, null],
+  ])(
+    "formats source %s in both activity and comments",
+    async (source, label) => {
+      mockActivity({
+        id: "activity-1",
+        type: "note",
+        source,
+        user: { name: "Jane Developer" },
+      });
+      const result = await getIssueActivity.handler(params, context);
+      const attribution = label
+        ? `Jane Developer (${label})`
+        : "Jane Developer";
+      const [activity, comments] = result.split("## Comments");
+      expect(activity).toContain(`by ${attribution} (activity-1)`);
+      expect(comments).toContain(`by ${attribution} (activity-1)`);
+      expect(result).not.toContain("Comment ID:");
+    },
+  );
+
+  it("attributes Sentry Apps by name and separates comment IDs from activity IDs", async () => {
+    mockActivity({
+      id: "activity-1",
+      commentId: "comment-1",
+      type: "note",
+      dateCreated: "2025-04-14T12:00:00.000Z",
+      source: "api",
+      user: null,
+      sentry_app: { name: "Example App", slug: "example-app" },
+      data: { text: "Investigating after the latest deploy." },
+    });
+
+    const result = await getIssueActivity.handler(params, context);
+    expect(result).toMatchInlineSnapshot(`
+      "# Activity for Issue CLOUDFLARE-MCP-41 in **sentry-mcp-evals**
+
+      ## Activity
+
+      - 2025-04-14T12:00:00.000Z: note by Example App (activity-1)
+        - Comment ID: comment-1
         - Investigating after the latest deploy.
 
       ## Comments
 
-      - 2025-04-14T12:00:00.000Z: note by Jane Developer (4633816000)
+      - 2025-04-14T12:00:00.000Z: note by Example App (activity-1)
+        - Comment ID: comment-1
         - Investigating after the latest deploy.
 
       ## Response Notes
@@ -47,26 +124,19 @@ describe("get_issue_activity", () => {
       - Use the Sentry tool \`add_issue_note\` to add a new human-visible issue comment.
       "
     `);
+    expect(result).not.toContain("by system");
+    expect(result).not.toContain("via API");
   });
 
   it("omits add_issue_note guidance when the tool is unavailable", async () => {
-    const result = await getIssueActivity.handler(
-      {
-        organizationSlug: "sentry-mcp-evals",
-        regionUrl: null,
-        issueId: "CLOUDFLARE-MCP-41",
-        includeComments: true,
-        limit: 25,
-      },
-      {
-        ...context,
-        availableToolNames: new Set([
-          "get_issue_activity",
-          "execute_sentry_tool",
-        ]),
-        directToolNames: new Set(["execute_sentry_tool"]),
-      },
-    );
+    const result = await getIssueActivity.handler(params, {
+      ...context,
+      availableToolNames: new Set([
+        "get_issue_activity",
+        "execute_sentry_tool",
+      ]),
+      directToolNames: new Set(["execute_sentry_tool"]),
+    });
 
     expect(result).not.toContain("Response Notes");
     expect(result).not.toContain("add_issue_note");
diff --git a/packages/mcp-core/src/tools/catalog/get-issue-activity.ts b/packages/mcp-core/src/tools/catalog/get-issue-activity.ts
index 5bf5fa503..3cffc5d8c 100644
--- a/packages/mcp-core/src/tools/catalog/get-issue-activity.ts
+++ b/packages/mcp-core/src/tools/catalog/get-issue-activity.ts
@@ -17,12 +17,12 @@ import {
 import { setTargetTagsAndAttributes } from "../../telem/scope";
 import type { ServerContext } from "../../types";
 import {
-  formatActor,
   formatDate,
   formatId,
   formatUnknown,
   readString,
 } from "./support/api-formatting";
+import { formatActivityAuthor } from "./support/activity-formatting";
 
 function getActivityText(
   activity: IssueActivity | IssueComment,
@@ -41,7 +41,7 @@ function getActivityText(
 }
 
 function formatActivity(activity: IssueActivity | IssueComment): string {
-  const actor = activity.user ? formatActor(activity.user) : "system";
+  const actor = formatActivityAuthor(activity);
   const date = formatDate(activity.dateCreated) ?? "unknown time";
   const text = getActivityText(activity);
   const details =
@@ -50,7 +50,12 @@ function formatActivity(activity: IssueActivity | IssueComment): string {
     Object.keys(activity.data).length > 0
       ? `\n  - Data: ${formatUnknown(activity.data)}`
       : "";
-  return `- ${date}: ${activity.type ?? "activity"} by ${actor} (${formatId(activity.id)})${text ? `\n  - ${text}` : ""}${details}`;
+  const commentId = activity.commentId;
+  const commentDetails =
+    commentId != null && String(commentId) !== String(activity.id)
+      ? `\n  - Comment ID: ${formatId(commentId)}`
+      : "";
+  return `- ${date}: ${activity.type ?? "activity"} by ${actor} (${formatId(activity.id)})${commentDetails}${text ? `\n  - ${text}` : ""}${details}`;
 }
 
 export default defineTool({
diff --git a/packages/mcp-core/src/tools/catalog/support/activity-formatting.ts b/packages/mcp-core/src/tools/catalog/support/activity-formatting.ts
new file mode 100644
index 000000000..a59fa0177
--- /dev/null
+++ b/packages/mcp-core/src/tools/catalog/support/activity-formatting.ts
@@ -0,0 +1,44 @@
+import type { IssueActivity } from "../../../api-client/types";
+import { formatActor, readString } from "./api-formatting";
+
+const MCP_CLIENT_NAMES = new Map([
+  ["claude", "Claude"],
+  ["claude-code", "Claude"],
+  ["codex", "Codex"],
+  ["copilot", "GitHub Copilot"],
+  ["cursor", "Cursor"],
+  ["opencode", "OpenCode"],
+]);
+
+function formatActivitySource(
+  source: string | null | undefined,
+): string | null {
+  const [channel, client] = source?.split(":") ?? [];
+  switch (channel) {
+    case "api":
+      return "via API";
+    case "sentry-cli":
+      return "via Sentry CLI";
+    case "mcp": {
+      const name = client ? MCP_CLIENT_NAMES.get(client) : undefined;
+      return name ? `${name} via MCP` : "via MCP";
+    }
+    default:
+      return null;
+  }
+}
+
+export function formatActivityAuthor(
+  activity: IssueActivity,
+  fallback = "system",
+): string {
+  const actor =
+    readString(activity.sentry_app, "name") ??
+    readString(activity.sentry_app, "slug") ??
+    (activity.user ? formatActor(activity.user) : fallback);
+  // Sentry Apps are attributed by name rather than their API channel.
+  const source = activity.sentry_app
+    ? null
+    : formatActivitySource(activity.source);
+  return source ? `${actor} (${source})` : actor;
+}
diff --git a/packages/mcp-server-mocks/src/fixtures/issue-activity.json b/packages/mcp-server-mocks/src/fixtures/issue-activity.json
index ec52d1c48..229a5e159 100644
--- a/packages/mcp-server-mocks/src/fixtures/issue-activity.json
+++ b/packages/mcp-server-mocks/src/fixtures/issue-activity.json
@@ -2,6 +2,8 @@
   "activity": [
     {
       "id": "4633815464",
+      "commentId": null,
+      "source": null,
       "user": null,
       "sentry_app": null,
       "type": "auto_set_ongoing",
@@ -12,6 +14,8 @@
     },
     {
       "id": "4633816000",
+      "commentId": "4633816000",
+      "source": "mcp:claude",
       "user": {
         "id": "12345",
         "name": "Jane Developer",
diff --git a/packages/mcp-server-mocks/src/fixtures/issue-comments.json b/packages/mcp-server-mocks/src/fixtures/issue-comments.json
index 56c36bc2d..9bacd0c78 100644
--- a/packages/mcp-server-mocks/src/fixtures/issue-comments.json
+++ b/packages/mcp-server-mocks/src/fixtures/issue-comments.json
@@ -1,6 +1,8 @@
 [
   {
     "id": "4633816000",
+    "commentId": "4633816000",
+    "source": "mcp:claude",
     "user": {
       "id": "12345",
       "name": "Jane Developer",