fix(acp): apply configured models the agent does not advertise (#6273)

* fix(acp): apply configured models the agent does not advertise

A model added through a provider's models or additionalModels was listed
in the picker, but an ACP session only accepted ids the agent advertised
in session/new, so the agent silently ran on its default model. The
registry now passes configured model ids to the session, which applies
them through session/set_model. Unconfigured, unadvertised ids are still
skipped with a warning.

* fix(acp): send configured models when the agent advertises none

Also covers the resume path in the regression test.

* test(acp): keep configured-model tests in the ACP agent suite

---------

Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>

packages/server/src/server/agent/agent-sdk-types.ts

@@ -628,6 +628,11 @@ export interface AgentCreateSessionOptions {
    * Defaults to true. Providers that cannot honor false should no-op.
    */
   persistSession?: boolean;
+  /**
+   * Model ids added by provider configuration (`models` / `additionalModels`).
+   * Providers that validate against runtime-advertised models must accept these.
+   */
+  configuredModelIds?: readonly string[];
 }
 
 /** What a resumed session is for: driving the agent, or reading what it already did. */
@@ -637,6 +642,8 @@ export type AgentResumePurpose = "interactive" | "history";
 export interface AgentResumeSessionOptions {
   /** Defaults to interactive. History loading may be read-only for archived native sessions. */
   purpose?: AgentResumePurpose;
+  /** See AgentCreateSessionOptions.configuredModelIds. */
+  configuredModelIds?: readonly string[];
 }
 
 /**

packages/server/src/server/agent/provider-registry.ts

@@ -492,6 +492,7 @@ function wrapClientProvider(
   const listFeatures = inner.listFeatures?.bind(inner);
   const archiveNativeSession = inner.archiveNativeSession?.bind(inner);
   const unarchiveNativeSession = inner.unarchiveNativeSession?.bind(inner);
+  const configuredModelIds = [...profileModels, ...additionalModels].map((model) => model.id);
 
   return {
     provider,
@@ -509,7 +510,7 @@ function wrapClientProvider(
             providerOptions: mergeProviderOptions(providerOptions, config.providerOptions),
           },
           launchContext,
-          options,
+          { ...options, configuredModelIds },
         ),
       ),
     resumeSession: async (handle, overrides, launchContext, options) =>
@@ -526,7 +527,7 @@ function wrapClientProvider(
             providerOptions: mergeProviderOptions(providerOptions, overrides?.providerOptions),
           },
           launchContext,
-          options,
+          { ...options, configuredModelIds },
         ),
       ),
     fetchCatalog: async (options, context) => {

packages/server/src/server/agent/providers/acp-agent.test.ts

@@ -5,7 +5,7 @@ import { createRequire } from "node:module";
 import { tmpdir } from "node:os";
 import path from "node:path";
 import { pathToFileURL } from "node:url";
-import { afterEach, describe, expect, test, vi } from "vitest";
+import { afterEach, beforeEach, describe, expect, test, vi } from "vitest";
 import {
   AgentSideConnection,
   ClientSideConnection,
@@ -54,8 +54,10 @@ import type { AgentStreamEvent } from "../agent-sdk-types.js";
 import type {
   AgentCapabilityFlags,
   AgentPersistenceHandle,
+  AgentSession,
   ProviderRefreshContext,
 } from "../agent-sdk-types.js";
+import { buildProviderRegistry } from "../provider-registry.js";
 import { createTestLogger } from "../../../test-utils/test-logger.js";
 import { buildStringCommandShellInvocation } from "../../../utils/string-command-shell.js";
 import { asInternals } from "../../test-utils/class-mocks.js";
@@ -4370,3 +4372,151 @@ describe("ACPAgentSession close() with an unresponsive provider", () => {
     expect(isProcessAlive(pid)).toBe(false);
   }, 15_000);
 });
+
+// An ACP agent that advertises two models (or none, with ACP_ADVERTISE_MODELS=none) but,
+// like Cline, runs any model id it is given.
+const PERMISSIVE_MODEL_ACP_AGENT = `
+import { Readable, Writable } from "node:stream";
+const { AgentSideConnection, PROTOCOL_VERSION, ndJsonStream } = await import(process.env.ACP_SDK_URL);
+let currentModelId = "advertised-default";
+const modelState = () =>
+  process.env.ACP_ADVERTISE_MODELS === "none"
+    ? undefined
+    : {
+        currentModelId,
+        availableModels: [
+          { modelId: "advertised-default", name: "Advertised default" },
+          { modelId: "advertised-other", name: "Advertised other" },
+        ],
+      };
+new AgentSideConnection(
+  () => ({
+    async initialize() {
+      return { protocolVersion: PROTOCOL_VERSION, agentCapabilities: { loadSession: true } };
+    },
+    async newSession() {
+      return { sessionId: "permissive-session", models: modelState() };
+    },
+    async loadSession() {
+      return { models: modelState() };
+    },
+    async unstable_setSessionModel({ modelId }) {
+      currentModelId = modelId;
+      return {};
+    },
+    async authenticate() {},
+    async cancel() {},
+    async prompt() {
+      return { stopReason: "end_turn" };
+    },
+  }),
+  ndJsonStream(Writable.toWeb(process.stdout), Readable.toWeb(process.stdin)),
+);
+`;
+
+describe("custom ACP provider with configured models", () => {
+  let dir: string;
+  let agentScript: string;
+  let session: AgentSession | null = null;
+
+  beforeEach(async () => {
+    dir = await mkdtemp(path.join(tmpdir(), "paseo-acp-configured-models-"));
+    agentScript = path.join(dir, "agent.mjs");
+    await writeFile(agentScript, PERMISSIVE_MODEL_ACP_AGENT);
+  });
+
+  afterEach(async () => {
+    await session?.close();
+    session = null;
+    await rm(dir, { recursive: true, force: true });
+  });
+
+  function buildRegistry(
+    override: {
+      models?: Array<{ id: string; label: string }>;
+      additionalModels?: Array<{ id: string; label: string }>;
+    },
+    agentEnv: Record<string, string> = {},
+  ) {
+    return buildProviderRegistry(createTestLogger(), {
+      providerOverrides: {
+        permissive: {
+          extends: "acp",
+          label: "Permissive",
+          command: [process.execPath, agentScript],
+          env: {
+            ACP_SDK_URL: pathToFileURL(
+              createRequire(import.meta.url).resolve("@agentclientprotocol/sdk"),
+            ).href,
+            ...agentEnv,
+          },
+          ...override,
+        },
+      },
+    });
+  }
+
+  async function createSessionOnModel(
+    registry: ReturnType<typeof buildRegistry>,
+    model: string,
+  ): Promise<AgentSession> {
+    const client = registry.permissive.createClient(createTestLogger());
+    session = await client.createSession({ provider: "permissive", cwd: dir, model });
+    return session;
+  }
+
+  test("runs on a model added through additionalModels that the agent does not advertise", async () => {
+    const registry = buildRegistry({
+      additionalModels: [{ id: "stealth/pixel-canary", label: "Pixel Canary" }],
+    });
+
+    const created = await createSessionOnModel(registry, "stealth/pixel-canary");
+
+    expect((await created.getRuntimeInfo()).model).toBe("stealth/pixel-canary");
+  });
+
+  test("runs on a model from a replacement models list that the agent does not advertise", async () => {
+    const registry = buildRegistry({
+      models: [{ id: "stealth/pixel-canary", label: "Pixel Canary" }],
+    });
+
+    const created = await createSessionOnModel(registry, "stealth/pixel-canary");
+
+    expect((await created.getRuntimeInfo()).model).toBe("stealth/pixel-canary");
+  });
+
+  test("runs on a model from additionalModels when the agent advertises no models", async () => {
+    const registry = buildRegistry(
+      { additionalModels: [{ id: "stealth/pixel-canary", label: "Pixel Canary" }] },
+      { ACP_ADVERTISE_MODELS: "none" },
+    );
+
+    const created = await createSessionOnModel(registry, "stealth/pixel-canary");
+
+    expect((await created.getRuntimeInfo()).model).toBe("stealth/pixel-canary");
+  });
+
+  test("resumes on a model added through additionalModels that the agent does not advertise", async () => {
+    const registry = buildRegistry({
+      additionalModels: [{ id: "stealth/pixel-canary", label: "Pixel Canary" }],
+    });
+    const client = registry.permissive.createClient(createTestLogger());
+
+    session = await client.resumeSession(
+      { provider: "permissive", sessionId: "permissive-session", metadata: { cwd: dir } },
+      { model: "stealth/pixel-canary" },
+    );
+
+    expect((await session.getRuntimeInfo()).model).toBe("stealth/pixel-canary");
+  });
+
+  test("keeps the agent's model when the requested model is neither advertised nor configured", async () => {
+    const registry = buildRegistry({
+      additionalModels: [{ id: "stealth/pixel-canary", label: "Pixel Canary" }],
+    });
+
+    const created = await createSessionOnModel(registry, "stale/removed-model");
+
+    expect((await created.getRuntimeInfo()).model).toBe("advertised-default");
+  });
+});

packages/server/src/server/agent/providers/acp-agent.ts

@@ -77,6 +77,7 @@ import {
   type AgentPromptContentBlock,
   type AgentPromptInput,
   type AgentResumePurpose,
+  type AgentCreateSessionOptions,
   type AgentResumeSessionOptions,
   type AgentRunOptions,
   type AgentRunResult,
@@ -512,6 +513,7 @@ interface ACPAgentSessionOptions {
   extensionCommandsParser?: ACPExtensionCommandsParser;
   handle?: AgentPersistenceHandle;
   resumePurpose?: AgentResumePurpose;
+  configuredModelIds?: readonly string[];
   agentId?: string;
   launchEnv?: Record<string, string>;
   waitForInitialCommands?: boolean;
@@ -979,6 +981,7 @@ export class ACPAgentClient implements AgentClient {
   async createSession(
     config: AgentSessionConfig,
     launchContext?: AgentLaunchContext,
+    options?: AgentCreateSessionOptions,
   ): Promise<AgentSession> {
     this.assertProvider(config);
     const providerOptions = ACPProviderOptionsSchema.parse(config.providerOptions ?? {});
@@ -1006,6 +1009,7 @@ export class ACPAgentClient implements AgentClient {
           supportsMcpServers:
             providerOptions.supportsMcpServers ?? this.capabilities.supportsMcpServers,
         },
+        configuredModelIds: options?.configuredModelIds,
         agentId: launchContext?.agentId,
         launchEnv: launchContext?.env,
         extensionCommandsParser: this.extensionCommandsParser,
@@ -1064,6 +1068,7 @@ export class ACPAgentClient implements AgentClient {
       },
       handle,
       resumePurpose: options?.purpose,
+      configuredModelIds: options?.configuredModelIds,
       agentId: launchContext?.agentId,
       launchEnv: launchContext?.env,
       extensionCommandsParser: this.extensionCommandsParser,
@@ -1692,6 +1697,7 @@ export class ACPAgentSession implements AgentSession, ACPClient {
     configOptions: SessionConfigOption[],
   ) => SessionConfigOption[];
   private readonly configFeatureOptions: ACPConfigFeatureOption[];
+  private readonly configuredModelIds: ReadonlySet<string>;
   private readonly clientCapabilities?: ACPClientCapabilities;
   private readonly clientCapabilityMeta?: ACPClientCapabilityMeta;
   private readonly modeIdTransformer?: (modeId: string) => string | null;
@@ -1760,6 +1766,7 @@ export class ACPAgentSession implements AgentSession, ACPClient {
     this.sessionResponseTransformer = options.sessionResponseTransformer;
     this.configOptionsTransformer = options.configOptionsTransformer;
     this.configFeatureOptions = options.configFeatureOptions ?? [];
+    this.configuredModelIds = new Set(options.configuredModelIds);
     this.clientCapabilities = options.clientCapabilities;
     this.clientCapabilityMeta = options.clientCapabilityMeta;
     this.modeIdTransformer = options.modeIdTransformer;
@@ -2194,12 +2201,20 @@ export class ACPAgentSession implements AgentSession, ACPClient {
       return;
     }
 
+    await this.setModelWithSelection({ modelId, selection: this.resolveModelSelection(modelId) });
+  }
+
+  private resolveModelSelection(modelId: string): ACPModelSelection {
     const selection = resolveACPModelSelection({
       modelId,
       availableModels: this.availableModels,
       configOptions: this.configOptions,
     });
-    await this.setModelWithSelection({ modelId, selection });
+    if (selection.availableModel || !this.configuredModelIds.has(modelId)) {
+      return selection;
+    }
+    // A model the user added in provider config is applied even when the agent does not advertise it.
+    return { ...selection, availableModel: { modelId, name: modelId } };
   }
 
   private async setModelWithSelection({
@@ -2213,21 +2228,20 @@ export class ACPAgentSession implements AgentSession, ACPClient {
       throw new Error("ACP session not initialized");
     }
 
-    if (selection.hasAvailableModels) {
-      if (!selection.availableModel) {
-        this.warnInvalidSelection(
-          modelId,
-          `is not a valid ${this.provider} model. Available options: ${this.availableModels
-            ?.map((model) => model.modelId)
-            .join(", ")}`,
-        );
-        return;
-      }
-
-      if (typeof this.connection.unstable_setSessionModel !== "function") {
-        throw new Error(this.modelSelectionUnavailableMessage());
-      }
+    if (selection.hasAvailableModels && !selection.availableModel) {
+      this.warnInvalidSelection(
+        modelId,
+        `is not a valid ${this.provider} model. Available options: ${this.availableModels
+          ?.map((model) => model.modelId)
+          .join(", ")}`,
+      );
+      return;
+    }
 
+    if (
+      selection.availableModel &&
+      typeof this.connection.unstable_setSessionModel === "function"
+    ) {
       try {
         await this.connection.unstable_setSessionModel({
           sessionId: this.sessionId,
@@ -2922,13 +2936,11 @@ export class ACPAgentSession implements AgentSession, ACPClient {
     const configuredModelId = this.config.model;
     let switchedModel = false;
     if (configuredModelId && configuredModelId !== this.currentModel) {
-      const selection = resolveACPModelSelection({
-        modelId: configuredModelId,
-        availableModels: this.availableModels,
-        configOptions: this.configOptions,
-      });
       try {
-        await this.setModelWithSelection({ modelId: configuredModelId, selection });
+        await this.setModelWithSelection({
+          modelId: configuredModelId,
+          selection: this.resolveModelSelection(configuredModelId),
+        });
         switchedModel = true;
       } catch (error) {
         if (!this.isModelSelectionUnavailableError(error)) {