diff --git a/server/src/__tests__/authorization-service.test.ts b/server/src/__tests__/authorization-service.test.ts
index b5dc54111b..1d156105c6 100644
--- a/server/src/__tests__/authorization-service.test.ts
+++ b/server/src/__tests__/authorization-service.test.ts
@@ -598,16 +598,62 @@ describeEmbeddedPostgres("authorization service", () => {
       membershipRole: "member",
     });
 
-    const decision = await authorizationService(db).decide({
+    const authorization = authorizationService(db);
+
+    await expect(authorization.decide({
       actor: { type: "board", userId, source: "session" },
       action: "agent:wake",
       resource: { type: "agent", companyId: company.id, agentId: targetAgent.id },
-    });
-
-    expect(decision).toMatchObject({
+    })).resolves.toMatchObject({
       allowed: false,
       reason: "deny_unsupported_action",
     });
+    const issue = await createIssue(db, company.id, { title: "Wake denied issue" });
+    await expect(authorization.decide({
+      actor: { type: "board", userId, source: "session" },
+      action: "issue:mutate",
+      resource: { type: "issue", companyId: company.id, issueId: issue.id },
+    })).resolves.toMatchObject({
+      allowed: false,
+      reason: "deny_unsupported_action",
+    });
+  });
+
+  it("limits viewer members to read-only visibility actions", async () => {
+    const company = await createCompany(db, "BoardViewerVisibility");
+    const userId = `user-${randomUUID()}`;
+    const targetAgent = await createAgent(db, company.id, { role: "engineer" });
+    await db.insert(companyMemberships).values({
+      companyId: company.id,
+      principalType: "user",
+      principalId: userId,
+      status: "active",
+      membershipRole: "viewer",
+    });
+
+    const authorization = authorizationService(db);
+    const actor = { type: "board", userId, source: "session" } as const;
+
+    await expect(authorization.decide({
+      actor,
+      action: "agent:read",
+      resource: { type: "agent", companyId: company.id, agentId: targetAgent.id },
+    })).resolves.toMatchObject({ allowed: true, reason: "allow_simple_company_member" });
+    await expect(authorization.decide({
+      actor,
+      action: "company_scope:read",
+      resource: { type: "company", companyId: company.id },
+    })).resolves.toMatchObject({ allowed: true, reason: "allow_simple_company_member" });
+    await expect(authorization.decide({
+      actor,
+      action: "runtime:manage",
+      resource: { type: "company", companyId: company.id },
+    })).resolves.toMatchObject({ allowed: false, reason: "deny_missing_grant" });
+    await expect(authorization.decide({
+      actor,
+      action: "secrets:read",
+      resource: { type: "company", companyId: company.id },
+    })).resolves.toMatchObject({ allowed: false, reason: "deny_missing_grant" });
   });
 
   it("denies legacy board assignment context for viewers", async () => {
diff --git a/server/src/services/authorization.ts b/server/src/services/authorization.ts
index 4461ced2e8..df7af2a595 100644
--- a/server/src/services/authorization.ts
+++ b/server/src/services/authorization.ts
@@ -967,13 +967,24 @@ export function authorizationService(db: Db) {
           input.action === "secrets:read"
         ) {
           const membership = await getActiveMembership(companyId, "user", input.actor.userId);
-          if (membership) {
+          // Mirroring the tasks:assign carve-out above, viewers keep the
+          // read-only visibility actions but not the privileged ones.
+          const requiresNonViewer =
+            input.action === "runtime:manage" || input.action === "secrets:read";
+          if (membership && (!requiresNonViewer || membership.membershipRole !== "viewer")) {
             return allow({
               action: input.action,
               reason: "allow_simple_company_member",
               explanation: "Allowed by standard same-company board membership visibility.",
             });
           }
+          if (membership) {
+            return deny({
+              action: input.action,
+              reason: "deny_missing_grant",
+              explanation: `Viewer membership does not grant ${input.action}.`,
+            });
+          }
           return deny({
             action: input.action,
             reason: "deny_missing_membership",