diff --git a/agent/channels/github.ts b/agent/channels/github.ts
index f359590..2e5b929 100644
--- a/agent/channels/github.ts
+++ b/agent/channels/github.ts
@@ -32,6 +32,23 @@ async function actorPermission(ctx: GitHubInboundContext): Promise<string> {
   }
 }
 
+// The comment webhook payload eve surfaces does not carry the issue/PR state,
+// so a "skip closed threads" gate needs one REST lookup. Fails open: any error
+// allows dispatch, so a transient lookup failure never silently drops real work.
+async function conversationIsClosed(ctx: GitHubInboundContext): Promise<boolean> {
+  const number = ctx.conversation.pullRequestNumber ?? ctx.conversation.issueNumber;
+  if (number == null) return false;
+  try {
+    const response = await ctx.github.request<{ state?: string }>({
+      method: "GET",
+      path: `/repos/${encodeURIComponent(ctx.repository.owner)}/${encodeURIComponent(ctx.repository.name)}/issues/${number}`,
+    });
+    return response.body.state === "closed";
+  } catch {
+    return false;
+  }
+}
+
 // eve's issue.raw is the webhook payload's `issue` object only; the top-level
 // `label` key describing which label was applied is not passed through, so
 // dispatch is decided from the issue's current labels array instead.
@@ -49,8 +66,14 @@ export function issueHasLabel(raw: unknown, name: string): boolean {
   );
 }
 
-async function onComment(ctx: GitHubInboundContext, comment: GitHubComment) {
+// Exported for unit tests; not part of the channel's public behaviour.
+export async function onComment(ctx: GitHubInboundContext, comment: GitHubComment) {
   if (!matchesConfiguredRepository(ctx)) return null;
+  // Comments on a closed issue/PR are almost always housekeeping (e.g. a
+  // maintainer closing with a note). Dispatching there just spawns an idle
+  // session holding a sandbox. Skip them; open threads still dispatch, so the
+  // agent keeps its freedom to act on any live request.
+  if (await conversationIsClosed(ctx)) return null;
   const permission = await actorPermission(ctx);
   return {
     auth: defaultGitHubAuth(ctx),
diff --git a/tests/channels/github.test.ts b/tests/channels/github.test.ts
index 53a21f4..f5336ac 100644
--- a/tests/channels/github.test.ts
+++ b/tests/channels/github.test.ts
@@ -4,7 +4,12 @@ import type {
   GitHubApiResponse,
   GitHubInboundContext,
 } from "eve/channels/github";
-import { issueHasLabel, matchesConfiguredRepository, onIssue } from "../../agent/channels/github";
+import {
+  issueHasLabel,
+  matchesConfiguredRepository,
+  onComment,
+  onIssue,
+} from "../../agent/channels/github";
 
 const ORIGINAL_EVOLVE_REPOSITORY = process.env.EVOLVE_REPOSITORY;
 
@@ -26,6 +31,7 @@ function createContext(
     readonly repositoryFullName?: string;
     readonly senderLogin?: string;
     readonly permission?: string | null;
+    readonly state?: string;
     readonly requestError?: Error;
   } = {},
 ): { readonly ctx: GitHubInboundContext; readonly requestCalls: number[] } {
@@ -46,7 +52,10 @@ function createContext(
         requestCalls.push(1);
         if (overrides.requestError) throw overrides.requestError;
         return {
-          body: { permission: overrides.permission ?? "none" } as T,
+          body: {
+            permission: overrides.permission ?? "none",
+            state: overrides.state ?? "open",
+          } as T,
           ok: true,
           status: 200,
         };
@@ -201,3 +210,43 @@ for (const permission of ["admin", "maintain", "write"]) {
     assert.match(result!.context![0], /#23/);
   });
 }
+
+// onComment closed-thread gate
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+const STUB_COMMENT = { body: "hello", id: 1, raw: {} } as any;
+
+test("onComment dispatches on a comment in an open thread", async () => {
+  process.env.EVOLVE_REPOSITORY = "uk-agents/evolve";
+  const { ctx, requestCalls } = createContext({ permission: "admin", state: "open" });
+  const result = await onComment(ctx, STUB_COMMENT);
+  assert.notEqual(result, null);
+  assert.ok(result?.auth);
+  assert.equal(requestCalls.length, 2, "open thread should check state, then permission");
+});
+
+test("onComment suppresses a comment on a closed thread", async () => {
+  process.env.EVOLVE_REPOSITORY = "uk-agents/evolve";
+  const { ctx, requestCalls } = createContext({ permission: "admin", state: "closed" });
+  const result = await onComment(ctx, STUB_COMMENT);
+  assert.equal(result, null);
+  assert.equal(requestCalls.length, 1, "closed thread should short-circuit before the permission check");
+});
+
+test("onComment fails open (dispatches) when the state lookup errors", async () => {
+  process.env.EVOLVE_REPOSITORY = "uk-agents/evolve";
+  const { ctx } = createContext({ requestError: new Error("boom") });
+  const result = await onComment(ctx, STUB_COMMENT);
+  assert.notEqual(result, null, "a lookup failure must never silently drop a real comment");
+});
+
+test("onComment ignores a repository that does not match EVOLVE_REPOSITORY", async () => {
+  process.env.EVOLVE_REPOSITORY = "uk-agents/evolve";
+  const { ctx, requestCalls } = createContext({
+    permission: "admin",
+    repositoryFullName: "someone-else/other-repo",
+  });
+  const result = await onComment(ctx, STUB_COMMENT);
+  assert.equal(result, null);
+  assert.equal(requestCalls.length, 0, "no REST calls for an unconfigured repository");
+});