diff --git a/plugins/fusion-plugin-omp-runtime/src/__tests__/tool-bridge.test.ts b/plugins/fusion-plugin-omp-runtime/src/__tests__/tool-bridge.test.ts
index 88de7f42e5..9551e1cfd9 100644
--- a/plugins/fusion-plugin-omp-runtime/src/__tests__/tool-bridge.test.ts
+++ b/plugins/fusion-plugin-omp-runtime/src/__tests__/tool-bridge.test.ts
@@ -2,6 +2,7 @@ import { existsSync } from "node:fs";
 import { describe, expect, it } from "vitest";
 import {
   FUSION_OMP_TOOL_BRIDGE_URL,
+  fusionToolsMcpServerPath,
   startFusionToolBridge,
   toolsToMcpToolDefs,
 } from "../tool-bridge.js";
@@ -97,6 +98,12 @@ describe("tool-bridge", () => {
     expect(await startFusionToolBridge(undefined)).toBeNull();
   });
 
+  it("resolves mcp-schema-server.cjs next to the plugin package", () => {
+    const path = fusionToolsMcpServerPath();
+    expect(path).toBeTruthy();
+    expect(existsSync(path!)).toBe(true);
+  });
+
   it("describes fusion tools in system rules", () => {
     const rules = buildOmpFusionToolRules({ fusionToolCount: 12, operatorMcpCount: 1 });
     expect(rules).toContain("fusion-custom-tools");
diff --git a/plugins/fusion-plugin-omp-runtime/src/acp-settings.ts b/plugins/fusion-plugin-omp-runtime/src/acp-settings.ts
index ed0ecfb038..abd7418c89 100644
--- a/plugins/fusion-plugin-omp-runtime/src/acp-settings.ts
+++ b/plugins/fusion-plugin-omp-runtime/src/acp-settings.ts
@@ -34,6 +34,14 @@ export const OMP_ACP_ENV_ALLOWLIST = [
   "GEMINI_API_KEY",
   "XAI_API_KEY",
   "GROK_API_KEY",
+  // FNXC:OmpAcp 2026-07-18-23:50: default omp models often use zai/minimax/kimi keys in env.
+  "ZAI_API_KEY",
+  "Z_AI_API_KEY",
+  "GLM_API_KEY",
+  "MINIMAX_API_KEY",
+  "MINIMAX_GROUP_ID",
+  "KIMI_API_KEY",
+  "MOONSHOT_API_KEY",
 ] as const;
 
 /**
diff --git a/plugins/fusion-plugin-omp-runtime/src/runtime-adapter.ts b/plugins/fusion-plugin-omp-runtime/src/runtime-adapter.ts
index 11fa363a75..43bc16e355 100644
--- a/plugins/fusion-plugin-omp-runtime/src/runtime-adapter.ts
+++ b/plugins/fusion-plugin-omp-runtime/src/runtime-adapter.ts
@@ -1,3 +1,4 @@
+import { existsSync } from "node:fs";
 import { AcpRuntimeAdapter } from "./acp/index.js";
 import {
   buildOmpAcpRuntimeSettings,
@@ -82,16 +83,66 @@ function compactDiagnostic(value: string): string {
   return value.replace(/\s+/g, " ").trim();
 }
 
+/*
+FNXC:OmpAcp 2026-07-18-23:50:
+omp returns JSON-RPC errors as `{ message: "Internal error", data: { details: "..." } }`.
+The ACP SDK often only puts `message` on Error.message, which hid the real cause
+(e.g. fusion-custom-tools ENOENT or "No API key found for alibaba-coding-plan").
+Prefer data.details / nested cause when present so operators can fix auth or packaging.
+*/
+function extractErrorReason(error: unknown): string {
+  if (error == null) return "unknown error";
+  if (typeof error === "string") return error;
+  if (error instanceof Error) {
+    const anyErr = error as Error & {
+      data?: { details?: unknown; message?: unknown } | string;
+      cause?: unknown;
+    };
+    const data = anyErr.data;
+    if (typeof data === "string" && data.trim()) {
+      return `${anyErr.message}: ${data.trim()}`;
+    }
+    if (data && typeof data === "object") {
+      const details = data.details;
+      if (typeof details === "string" && details.trim()) {
+        return `${anyErr.message}: ${details.trim()}`;
+      }
+      if (typeof data.message === "string" && data.message.trim() && data.message !== anyErr.message) {
+        return `${anyErr.message}: ${data.message.trim()}`;
+      }
+    }
+    if (anyErr.cause) {
+      const causeReason = extractErrorReason(anyErr.cause);
+      if (causeReason && causeReason !== anyErr.message) {
+        return `${anyErr.message}: ${causeReason}`;
+      }
+    }
+    return anyErr.message || String(error);
+  }
+  if (typeof error === "object") {
+    const rec = error as { message?: unknown; data?: { details?: unknown } };
+    const message = typeof rec.message === "string" ? rec.message : String(error);
+    const details = rec.data && typeof rec.data === "object" ? rec.data.details : undefined;
+    if (typeof details === "string" && details.trim()) {
+      return `${message}: ${details.trim()}`;
+    }
+    return message;
+  }
+  return String(error);
+}
+
 function describeCreateFailure(error: unknown): string {
-  const reason = error instanceof Error ? error.message : String(error ?? "unknown error");
+  const reason = extractErrorReason(error);
   return compactDiagnostic(
     `OMP ACP failed to start: ${reason}. Ensure the \`omp\` binary is installed and authenticated (` +
-      `\`omp acp\`, credentials under ~/.omp), or set provider API keys in the environment.`,
+      `\`omp acp\`, credentials under ~/.omp), or set provider API keys in the environment. ` +
+      `If the details mention fusion-custom-tools / mcp-schema-server ENOENT, rebuild the CLI package so mcp-schema-server.cjs ships next to the omp plugin. ` +
+      `If they mention "No API key" for a provider, pick a qualified model (e.g. minimax-code/MiniMax-M2.5 or zai/glm-5.2) or re-auth that provider in omp.`,
   );
 }
 
 function describePromptFailure(error: unknown): string {
-  const reason = error instanceof Error ? error.message : String(error ?? "unknown error");
+  const reason = extractErrorReason(error);
   return compactDiagnostic(`OMP ACP turn failed: ${reason}`);
 }
 
@@ -275,10 +326,25 @@ export class OmpRuntimeAdapter implements AgentRuntime {
       toolBridge = null;
     }
 
+    /*
+    FNXC:OmpAcp 2026-07-18-23:50:
+    Drop stdio MCP entries whose command binary is missing before session/new.
+    omp turns a single ENOENT into JSON-RPC Internal error and aborts the whole
+    ACP session (observed as "OMP ACP failed to start: Internal error").
+    */
     const mcpServers: AcpMcpServer[] = [
       ...operatorMcp,
       ...(toolBridge ? [toolBridge.mcpServer] : []),
-    ];
+    ].filter((server) => {
+      if (!("command" in server) || typeof server.command !== "string") return true;
+      const command = server.command.trim();
+      if (!command) return false;
+      // Absolute paths must exist; PATH names are left to omp's spawn resolution.
+      if (command.includes("/") || command.includes("\\")) {
+        return existsSync(command);
+      }
+      return true;
+    });
 
     const toolRules = buildOmpFusionToolRules({
       fusionToolCount: toolBridge?.toolCount,
diff --git a/plugins/fusion-plugin-omp-runtime/src/tool-bridge.ts b/plugins/fusion-plugin-omp-runtime/src/tool-bridge.ts
index bf68b42e40..31f692108f 100644
--- a/plugins/fusion-plugin-omp-runtime/src/tool-bridge.ts
+++ b/plugins/fusion-plugin-omp-runtime/src/tool-bridge.ts
@@ -8,7 +8,7 @@ after the session ends. Ported from fusion-plugin-grok-runtime for full fn_* par
 */
 
 import { createServer, type Server } from "node:http";
-import { unlinkSync, writeFileSync } from "node:fs";
+import { existsSync, unlinkSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { dirname, join } from "node:path";
 import { fileURLToPath } from "node:url";
@@ -62,9 +62,29 @@ export function toolsToMcpToolDefs(tools: ReadonlyArray<ToolLike> | undefined):
     }));
 }
 
-function fusionToolsMcpServerPath(): string {
-  // Packaged CLI copies this as mcp-schema-server.cjs next to the bundled plugin.
-  return join(dirname(fileURLToPath(import.meta.url)), "mcp-schema-server.cjs");
+/**
+ * FNXC:OmpAcp 2026-07-18-23:50:
+ * Resolve `mcp-schema-server.cjs` for the fusion-custom-tools stdio MCP child.
+ * `import.meta.url` can land on source (`src/`), packaged `bundled.js`, or a
+ * hot-reload sibling (`.bundled.reload-*.js`). If the file is missing, omp's
+ * session/new fails with JSON-RPC Internal error / ENOENT and the entire OMP
+ * ACP session dies before any turn runs — surface a clear miss instead.
+ */
+export function fusionToolsMcpServerPath(): string | null {
+  const here = dirname(fileURLToPath(import.meta.url));
+  const candidates = [
+    // Packaged CLI / same-dir as bundled.js or tool-bridge source.
+    join(here, "mcp-schema-server.cjs"),
+    // Source layout when running from dist/ that still has ../src assets.
+    join(here, "src", "mcp-schema-server.cjs"),
+    join(here, "..", "src", "mcp-schema-server.cjs"),
+    // Monorepo plugin root relative to src/ or dist/plugins/.../bundled.js.
+    join(here, "..", "mcp-schema-server.cjs"),
+  ];
+  for (const candidate of candidates) {
+    if (existsSync(candidate)) return candidate;
+  }
+  return null;
 }
 
 function resultToText(result: unknown): string {
@@ -182,6 +202,22 @@ export async function startFusionToolBridge(
 
   const bridgeUrl = `http://127.0.0.1:${address.port}`;
   const serverPath = fusionToolsMcpServerPath();
+  /*
+  FNXC:OmpAcp 2026-07-18-23:50:
+  Prefer a session without Fusion fn_* tools over a hard session/new Internal
+  error when the MCP schema server asset is missing (ENOENT on posix_spawn).
+  */
+  if (!serverPath) {
+    await new Promise<void>((resolve) => {
+      server.close(() => resolve());
+    });
+    try {
+      unlinkSync(schemaPath);
+    } catch {
+      // best-effort
+    }
+    return null;
+  }
 
   return {
     toolCount: defs.length,