fix: validate resolved context engine contracts

src/context-engine/context-engine.test.ts

@@ -709,6 +709,71 @@ describe("Invalid engine fallback", () => {
       expect(message).toContain("legacy");
     }
   });
+
+  it("rejects resolved engines that omit info metadata", async () => {
+    const engineId = `invalid-info-${Date.now().toString(36)}`;
+    registerContextEngine(
+      engineId,
+      () =>
+        ({
+          async ingest() {
+            return { ingested: false };
+          },
+          async assemble({ messages }: { messages: AgentMessage[] }) {
+            return { messages, estimatedTokens: 0 };
+          },
+          async compact() {
+            return { ok: true, compacted: false };
+          },
+        }) as unknown as ContextEngine,
+    );
+
+    await expect(resolveContextEngine(configWithSlot(engineId))).rejects.toThrow(
+      `Context engine "${engineId}" factory returned an invalid ContextEngine: missing info.`,
+    );
+  });
+
+  it("rejects resolved engines that omit required info fields", async () => {
+    const engineId = `invalid-info-fields-${Date.now().toString(36)}`;
+    registerContextEngine(
+      engineId,
+      () =>
+        ({
+          info: { id: engineId },
+          async ingest() {
+            return { ingested: false };
+          },
+          async assemble({ messages }: { messages: AgentMessage[] }) {
+            return { messages, estimatedTokens: 0 };
+          },
+          async compact() {
+            return { ok: true, compacted: false };
+          },
+        }) as unknown as ContextEngine,
+    );
+
+    await expect(resolveContextEngine(configWithSlot(engineId))).rejects.toThrow(
+      `Context engine "${engineId}" factory returned an invalid ContextEngine: missing info.name.`,
+    );
+  });
+
+  it("rejects resolved engines that omit required lifecycle methods", async () => {
+    const engineId = `invalid-methods-${Date.now().toString(36)}`;
+    registerContextEngine(
+      engineId,
+      () =>
+        ({
+          info: { id: engineId, name: "Broken Engine" },
+          async ingest() {
+            return { ingested: false };
+          },
+        }) as unknown as ContextEngine,
+    );
+
+    await expect(resolveContextEngine(configWithSlot(engineId))).rejects.toThrow(
+      `Context engine "${engineId}" factory returned an invalid ContextEngine: missing assemble(), missing compact().`,
+    );
+  });
 });
 
 // ═══════════════════════════════════════════════════════════════════════════

src/context-engine/registry.ts

@@ -395,6 +395,46 @@ export function listContextEngineIds(): string[] {
   return [...getContextEngineRegistryState().engines.keys()];
 }
 
+function describeResolvedContextEngineContractError(
+  engineId: string,
+  engine: unknown,
+): string | null {
+  if (!engine || typeof engine !== "object") {
+    return `Context engine "${engineId}" factory returned ${JSON.stringify(engine)} instead of a ContextEngine object.`;
+  }
+
+  const candidate = engine as Record<string, unknown>;
+  const issues: string[] = [];
+  const info = candidate.info;
+  if (!info || typeof info !== "object") {
+    issues.push("missing info");
+  } else {
+    const infoRecord = info as Record<string, unknown>;
+    if (typeof infoRecord.id !== "string" || !infoRecord.id.trim()) {
+      issues.push("missing info.id");
+    }
+    if (typeof infoRecord.name !== "string" || !infoRecord.name.trim()) {
+      issues.push("missing info.name");
+    }
+  }
+
+  if (typeof candidate.ingest !== "function") {
+    issues.push("missing ingest()");
+  }
+  if (typeof candidate.assemble !== "function") {
+    issues.push("missing assemble()");
+  }
+  if (typeof candidate.compact !== "function") {
+    issues.push("missing compact()");
+  }
+
+  if (issues.length === 0) {
+    return null;
+  }
+
+  return `Context engine "${engineId}" factory returned an invalid ContextEngine: ${issues.join(", ")}.`;
+}
+
 // ---------------------------------------------------------------------------
 // Resolution
 // ---------------------------------------------------------------------------
@@ -423,5 +463,11 @@ export async function resolveContextEngine(config?: OpenClawConfig): Promise<Con
     );
   }
 
-  return wrapContextEngineWithSessionKeyCompat(await entry.factory());
+  const engine = await entry.factory();
+  const contractError = describeResolvedContextEngineContractError(engineId, engine);
+  if (contractError) {
+    throw new Error(contractError);
+  }
+
+  return wrapContextEngineWithSessionKeyCompat(engine);
 }