diff --git a/server/src/__tests__/adapter-registry.test.ts b/server/src/__tests__/adapter-registry.test.ts
index cb0e007e..983011fe 100644
--- a/server/src/__tests__/adapter-registry.test.ts
+++ b/server/src/__tests__/adapter-registry.test.ts
@@ -61,12 +61,14 @@ describe("server adapter registry", () => {
     unregisterServerAdapter("external_test");
     unregisterServerAdapter("claude_local");
     setOverridePaused("claude_local", false);
+    setOverridePaused("hermes_local", true);
   });
 
   afterEach(() => {
     unregisterServerAdapter("external_test");
     unregisterServerAdapter("claude_local");
     setOverridePaused("claude_local", false);
+    setOverridePaused("hermes_local", false);
     hermesExecuteMock.mockClear();
   });
 
@@ -385,6 +387,105 @@ describe("server adapter registry", () => {
     expect(patchedCtx.agent.adapterConfig.env.PAPERCLIP_API_KEY).toBe("agent-run-jwt");
   });
 
+  it("passes Hermes custom providers through extraArgs while injecting auth", async () => {
+    const adapter = requireServerAdapter("hermes_local");
+
+    await adapter.execute({
+      runId: "run-123",
+      agent: {
+        id: "agent-123",
+        companyId: "company-123",
+        name: "Hermes Agent",
+        role: "engineer",
+        adapterType: "hermes_local",
+        adapterConfig: {
+          provider: "custom:paperclip-openai",
+          extraArgs: ["--source", "tool"],
+        },
+      },
+      runtime: {},
+      config: {},
+      context: {},
+      onLog: async () => {},
+      onMeta: async () => {},
+      onSpawn: async () => {},
+      authToken: "agent-run-jwt",
+    });
+
+    const [patchedCtx] = hermesExecuteMock.mock.calls[0];
+    expect(patchedCtx.agent.adapterConfig.provider).toBe("custom:paperclip-openai");
+    expect(patchedCtx.agent.adapterConfig.extraArgs).toEqual([
+      "--source",
+      "tool",
+      "--provider",
+      "custom:paperclip-openai",
+    ]);
+    expect(patchedCtx.agent.adapterConfig.env.PAPERCLIP_API_KEY).toBe("agent-run-jwt");
+  });
+
+  it("does not duplicate an explicit Hermes provider extraArg", async () => {
+    const adapter = requireServerAdapter("hermes_local");
+
+    await adapter.execute({
+      runId: "run-123",
+      agent: {
+        id: "agent-123",
+        companyId: "company-123",
+        name: "Hermes Agent",
+        role: "engineer",
+        adapterType: "hermes_local",
+        adapterConfig: {
+          provider: "custom:paperclip-openai",
+          extraArgs: ["--provider=custom:paperclip-openai"],
+        },
+      },
+      runtime: {},
+      config: {},
+      context: {},
+      onLog: async () => {},
+      onMeta: async () => {},
+      onSpawn: async () => {},
+      authToken: "agent-run-jwt",
+    });
+
+    const [patchedCtx] = hermesExecuteMock.mock.calls[0];
+    expect(patchedCtx.agent.adapterConfig.extraArgs).toEqual([
+      "--provider=custom:paperclip-openai",
+    ]);
+  });
+
+  it("does not duplicate spaced Hermes provider extraArgs", async () => {
+    const adapter = requireServerAdapter("hermes_local");
+
+    await adapter.execute({
+      runId: "run-123",
+      agent: {
+        id: "agent-123",
+        companyId: "company-123",
+        name: "Hermes Agent",
+        role: "engineer",
+        adapterType: "hermes_local",
+        adapterConfig: {
+          provider: "custom:paperclip-openai",
+          extraArgs: ["--provider", "custom:paperclip-openai"],
+        },
+      },
+      runtime: {},
+      config: {},
+      context: {},
+      onLog: async () => {},
+      onMeta: async () => {},
+      onSpawn: async () => {},
+      authToken: "agent-run-jwt",
+    });
+
+    const [patchedCtx] = hermesExecuteMock.mock.calls[0];
+    expect(patchedCtx.agent.adapterConfig.extraArgs).toEqual([
+      "--provider",
+      "custom:paperclip-openai",
+    ]);
+  });
+
   it("passes the original Hermes context through when authToken is absent", async () => {
     const adapter = requireServerAdapter("hermes_local");
     const ctx = {
diff --git a/server/src/adapters/registry.ts b/server/src/adapters/registry.ts
index 55bce77b..09f6b2a2 100644
--- a/server/src/adapters/registry.ts
+++ b/server/src/adapters/registry.ts
@@ -214,6 +214,24 @@ function normalizeHermesConfig<T extends { config?: unknown; agent?: unknown }>(
   return ctx;
 }
 
+function passHermesCustomProviderThroughExtraArgs(config: Record<string, unknown>): Record<string, unknown> {
+  const provider = typeof config.provider === "string" ? config.provider.trim() : "";
+  if (!provider.startsWith("custom:")) return config;
+
+  const existingExtraArgs = Array.isArray(config.extraArgs)
+    ? config.extraArgs.filter((arg): arg is string => typeof arg === "string")
+    : [];
+  const alreadyHasProviderArg = existingExtraArgs.some((arg) =>
+    arg === "--provider" || arg.startsWith("--provider=")
+  );
+  if (alreadyHasProviderArg) return config;
+
+  return {
+    ...config,
+    extraArgs: [...existingExtraArgs, "--provider", provider],
+  };
+}
+
 function dedupeAdapterModels(models: AdapterModel[]): AdapterModel[] {
   const seen = new Set<string>();
   const result: AdapterModel[] = [];
@@ -470,19 +488,20 @@ const hermesLocalAdapter: ServerAdapterModule = {
         PAPERCLIP_RUN_ID: normalizedCtx.runId,
       },
     };
+    const effectivePatchedConfig = passHermesCustomProviderThroughExtraArgs(patchedConfig);
 
     // Only inject the auth guard into promptTemplate when a custom template already exists.
     // When no custom template is set, Hermes uses its built-in default heartbeat/task prompt —
     // overwriting it with only the auth guard text would strip the assigned issue/workflow instructions.
     if (promptTemplate) {
-      patchedConfig.promptTemplate = `${authGuardPrompt}\n\n${promptTemplate}`;
+      effectivePatchedConfig.promptTemplate = `${authGuardPrompt}\n\n${promptTemplate}`;
     }
 
     const patchedCtx = {
       ...normalizedCtx,
       agent: {
         ...normalizedCtx.agent,
-        adapterConfig: patchedConfig,
+        adapterConfig: effectivePatchedConfig,
       },
     };