diff --git a/packages/web/src/lib/__tests__/project-utils.test.ts b/packages/web/src/lib/__tests__/project-utils.test.ts
new file mode 100644
index 0000000000..9675eb2c0a
--- /dev/null
+++ b/packages/web/src/lib/__tests__/project-utils.test.ts
@@ -0,0 +1,22 @@
+import { describe, expect, it } from "vitest";
+import { filterProjectSessions } from "../project-utils";
+
+describe("filterProjectSessions", () => {
+  const projects = {
+    app: { sessionPrefix: "app" },
+    appx: { sessionPrefix: "appx" },
+  };
+
+  it("does not match another project's longer prefix as the selected project", () => {
+    // Regression: prefix containment leaked appx sessions into app views.
+    // Found by /qa on 2026-05-01.
+    const sessions = [
+      { id: "app-1", projectId: "unknown" },
+      { id: "appx-1", projectId: "unknown" },
+    ];
+
+    expect(filterProjectSessions(sessions, "app", projects)).toEqual([
+      { id: "app-1", projectId: "unknown" },
+    ]);
+  });
+});
diff --git a/packages/web/src/lib/__tests__/serialize.test.ts b/packages/web/src/lib/__tests__/serialize.test.ts
index 34eaa89169..140dc09bac 100644
--- a/packages/web/src/lib/__tests__/serialize.test.ts
+++ b/packages/web/src/lib/__tests__/serialize.test.ts
@@ -17,6 +17,7 @@ import {
   sessionToDashboard,
   resolveProject,
   enrichSessionPR,
+  enrichSessionIssue,
   readPREnrichmentFromMetadata,
   enrichSessionAgentSummary,
   enrichSessionIssueTitle,
@@ -349,6 +350,17 @@ describe("resolveProject", () => {
     expect(resolveProject(session, projects)).toBe(projects.lib);
   });
 
+  it("should not match another project's longer prefix", () => {
+    const projects = {
+      app: makeProject({ name: "app", sessionPrefix: "app" }),
+      appx: makeProject({ name: "appx", sessionPrefix: "appx" }),
+    };
+    // Regression: prefix containment could resolve appx sessions as app.
+    // Found by /qa on 2026-05-01.
+    const session = createCoreSession({ id: "appx-1", projectId: "unknown" });
+    expect(resolveProject(session, projects)).toBe(projects.appx);
+  });
+
   it("should fall back to first project when nothing matches", () => {
     const projects = {
       app: makeProject({ name: "app", sessionPrefix: "app" }),
diff --git a/packages/web/src/lib/project-utils.ts b/packages/web/src/lib/project-utils.ts
index e37935e845..6157155c44 100644
--- a/packages/web/src/lib/project-utils.ts
+++ b/packages/web/src/lib/project-utils.ts
@@ -1,4 +1,5 @@
 import { isOrchestratorSession } from "@aoagents/ao-core/types";
+import { matchesSessionPrefix } from "./session-utils";
 
 type ProjectWithPrefix = { sessionPrefix?: string };
 type SessionLike = { id: string; projectId: string; metadata?: Record<string, string> };
@@ -18,7 +19,9 @@ function matchesProject(
 ): boolean {
   if (session.projectId === projectId) return true;
   const project = projects[projectId];
-  if (project?.sessionPrefix && session.id.startsWith(project.sessionPrefix)) return true;
+  if (project?.sessionPrefix && matchesSessionPrefix(session.id, project.sessionPrefix)) {
+    return true;
+  }
   return projects[session.projectId]?.sessionPrefix === projectId;
 }
 
diff --git a/packages/web/src/lib/serialize.ts b/packages/web/src/lib/serialize.ts
index fd207f3dfd..b2231a7a18 100644
--- a/packages/web/src/lib/serialize.ts
+++ b/packages/web/src/lib/serialize.ts
@@ -26,6 +26,7 @@ import {
   getAttentionLevel,
 } from "./types";
 import { TTLCache, type PREnrichmentData } from "./cache";
+import { matchesSessionPrefix } from "./session-utils";
 
 /** Cache for issue titles (5 min TTL — issue titles rarely change) */
 const issueTitleCache = new TTLCache<string>(300_000);
@@ -51,7 +52,9 @@ export function resolveProject(
   if (direct) return direct;
 
   // Match by session prefix
-  const entry = Object.entries(projects).find(([, p]) => core.id.startsWith(p.sessionPrefix));
+  const entry = Object.entries(projects).find(([, p]) =>
+    matchesSessionPrefix(core.id, p.sessionPrefix),
+  );
   if (entry) return entry[1];
 
   // Fall back to first project
diff --git a/packages/web/src/lib/session-utils.ts b/packages/web/src/lib/session-utils.ts
new file mode 100644
index 0000000000..6b81c1de3b
--- /dev/null
+++ b/packages/web/src/lib/session-utils.ts
@@ -0,0 +1,3 @@
+export function matchesSessionPrefix(sessionId: string, prefix: string): boolean {
+  return sessionId === prefix || sessionId.startsWith(`${prefix}-`);
+}