fix(pi): point the provider at the daemon root and pin the transport per family

The generated models.json set the provider base URL to `<daemon>/v1`, which is
only safe for transports that append their endpoint without a version segment.
A model carrying `api: "anthropic-messages"` makes the Anthropic SDK append
`/v1/messages` itself, so the effective path became `/v1/v1/messages` — a 404
from every provider in the pool.

Use the daemon root, the one base URL that resolves for every transport:

  gpt-*   -> {root}/responses        -> `responses`
  claude* -> {root}/v1/messages      -> `messages`
  other   -> {root}/chat/completions -> `chat/completions`

and pin `api` by family the way gpt-* already was, extending the pin to
claude* models. The pins override a curated value — a stale per-model `api`
picks an endpoint that does not match the provider's intent and is invisible
in models.json — while models outside the pinned families keep whatever the
user curated. getDaemonBaseUrl() strips a trailing slash, so the root cannot
double the separator either (routstr-core rejects empty path segments).

src/integrations/pi.ts

@@ -92,6 +92,13 @@ export function deriveThinkingFields(
 
 const isDeepSeekModel = (id: string): boolean => id.startsWith("deepseek");
 const isGptModel = (id: string): boolean => id.startsWith("gpt-");
+/**
+ * Anthropic-served models (claude-opus-5.5, claude-sonnet-5, claude-fable-5.1,
+ * ...). routstr nodes proxy the Anthropic-native `messages` route, so pi's
+ * Anthropic transport can talk to the node's own endpoint instead of the
+ * OpenAI-shaped translation.
+ */
+const isClaudeModel = (id: string): boolean => id.startsWith("claude");
 
 /** Project one daemon model onto a pi config entry. */
 export function buildPiModelEntry(
@@ -115,11 +122,22 @@ export function buildPiModelEntry(
   if (mods.includes("image")) input.push("image");
   entry.input = input;
 
-  // gpt-* models are served through OpenAI's Responses API; the provider-level
+  // Per-model transport pins. `api` is per-model while the provider `baseUrl`
-  // `api: "openai-completions"` stays the default for everything else. For
+  // is shared, and the transports disagree about what a base URL means: the
-  // non-gpt models keep whatever per-model api the user curated.
+  // OpenAI SDKs append only their endpoint (`/chat/completions`, `/responses`)
+  // while Anthropic SDKs append `/v1/messages` themselves. The provider base
+  // URL is therefore the daemon ROOT (see installPiIntegration), which is the
+  // one spelling that resolves correctly for every transport:
+  //   gpt-*   -> {root}/responses        -> `responses`
+  //   claude* -> {root}/v1/messages      -> `messages`
+  //   other   -> {root}/chat/completions -> `chat/completions`
+  // Pins override a curated value: a stale `anthropic-messages` left on a
+  // non-claude model picks an endpoint the daemon is not expecting, and the
+  // user cannot see from models.json which family needs which transport.
   if (isGptModel(model.id)) {
     entry.api = "openai-responses";
+  } else if (isClaudeModel(model.id)) {
+    entry.api = "anthropic-messages";
   } else if (previous?.api !== undefined) {
     entry.api = previous.api;
   }
@@ -185,7 +203,16 @@ export async function installPiIntegration(
   console.log("\nInstalling routstr models in pi models.json...");
   console.log(`Using API key for ${name}`);
 
-  const baseUrl = `${getDaemonBaseUrlFn(config)}/v1`;
+  // The daemon ROOT, deliberately without `/v1`. Every transport appends its
+  // own endpoint path, and only the Anthropic ones add a version prefix
+  // (`/v1/messages`); a base URL that already carries `/v1` therefore yields
+  // the doubled `/v1/v1/messages`, which routstr-core rejects with a 404 from
+  // every provider in the pool (it canonicalizes exactly one optional `v1/`).
+  // At the root, openai-completions -> `/chat/completions`, openai-responses
+  // -> `/responses` and anthropic-messages -> `/v1/messages` all land on an
+  // allowed route. getDaemonBaseUrl() strips any trailing slash, so no path
+  // can be double-slashed either.
+  const baseUrl = getDaemonBaseUrlFn(config);
 
   let piConfig: PiConfig = {};
 
@@ -219,7 +246,9 @@ export async function installPiIntegration(
     // models.json is always a faithful projection of the daemon's state.
     // Thinking fields are derived from the model's published reasoning allowlist;
     // when the daemon has none, the user's hand-curated values are preserved.
-    // `compat` stays user-curated, except for the deepseek* pin applied below.
+    // `compat` stays user-curated, except for the deepseek* pin applied below;
+    // `api` is pinned per family (see buildPiModelEntry), since the family
+    // decides which transport — and so which endpoint — the model is served by.
     const existingModels = new Map<string, PiModelEntry>(
       (piConfig.providers["routstr"]?.models ?? []).map((m) => [m.id, m]),
     );

tests/integrations/pi.test.ts

@@ -35,6 +35,12 @@ const MOCK_DEPS: Partial<PiIntegrationDeps> = {
           context_length: 262144,
           architecture: { input_modalities: ["text", "image"] },
         },
+        {
+          id: "claude-opus-5.5",
+          name: "Claude Opus 5.5",
+          context_length: 1000000,
+          architecture: { input_modalities: ["text", "image"] },
+        },
       ],
     },
   }),
@@ -56,6 +62,56 @@ async function readProvider(configPath: string) {
 }
 
 describe("installPiIntegration", () => {
+  it("points the provider at the daemon root, with no /v1", async () => {
+    const dir = mkdtempSync(join(tmpdir(), "pi-models-"));
+    const configPath = join(dir, "models.json");
+    await installPiIntegration(CONFIG, "key", makeIntegration(configPath), MOCK_DEPS);
+
+    const parsed = JSON.parse(readFileSync(configPath, "utf-8")) as {
+      providers: Record<string, { baseUrl?: string; api?: string }>;
+    };
+    // Every transport appends its own endpoint (/chat/completions,
+    // /responses, /v1/messages). A base URL carrying /v1 would double the
+    // prefix for Anthropic models and 404 on every provider.
+    expect(parsed.providers["routstr"].baseUrl).toBe("http://127.0.0.1:8008");
+    expect(parsed.providers["routstr"].api).toBe("openai-completions");
+  });
+
+  it("pins anthropic-messages for claude* models", async () => {
+    const dir = mkdtempSync(join(tmpdir(), "pi-models-"));
+    const configPath = join(dir, "models.json");
+    await installPiIntegration(CONFIG, "key", makeIntegration(configPath), MOCK_DEPS);
+
+    const provider = await readProvider(configPath);
+    const claude = provider.models.find((m) => m.id === "claude-opus-5.5");
+    expect(claude?.api).toBe("anthropic-messages");
+    // Non-claude, non-gpt models fall through to the provider default.
+    const glm = provider.models.find((m) => m.id === "glm-5.3");
+    expect("api" in glm!).toBe(false);
+  });
+
+  it("replaces a stale hand-written api override on claude* models", async () => {
+    const dir = mkdtempSync(join(tmpdir(), "pi-models-"));
+    const configPath = join(dir, "models.json");
+    await installPiIntegration(CONFIG, "key", makeIntegration(configPath), MOCK_DEPS);
+
+    const parsed = JSON.parse(readFileSync(configPath, "utf-8")) as {
+      providers: Record<string, { models: Array<Record<string, unknown>> }>;
+    };
+    const claude = parsed.providers["routstr"].models.find(
+      (m) => m.id === "claude-opus-5.5",
+    );
+    claude!.api = "openai-completions";
+    const { writeFileSync } = await import("fs");
+    writeFileSync(configPath, JSON.stringify(parsed));
+
+    await installPiIntegration(CONFIG, "key", makeIntegration(configPath), MOCK_DEPS);
+    const provider = await readProvider(configPath);
+    expect(provider.models.find((m) => m.id === "claude-opus-5.5")?.api).toBe(
+      "anthropic-messages",
+    );
+  });
+
   it("pins supportsDeveloperRole=false for deepseek* models", async () => {
     const dir = mkdtempSync(join(tmpdir(), "pi-models-"));
     const configPath = join(dir, "models.json");
@@ -327,7 +383,22 @@ describe("buildPiModelEntry", () => {
     expect(entry.api).toBe("openai-responses");
   });
 
-  it("preserves a user-curated api on non-gpt models and omits it otherwise", () => {
+  it("pins api=anthropic-messages for claude* models, overriding any curated value", () => {
+    for (const id of [
+      "claude-opus-5.5",
+      "claude-sonnet-5.5",
+      "claude-fable-5.1",
+      "claude-haiku-4.5",
+    ]) {
+      const entry = buildPiModelEntry(model({ id }), {
+        id,
+        api: "openai-completions",
+      });
+      expect(entry.api).toBe("anthropic-messages");
+    }
+  });
+
+  it("preserves a user-curated api on models outside the pinned families", () => {
     const curated = buildPiModelEntry(
       model({ id: "glm-5.3" }),
       { id: "glm-5.3", api: "openai-responses" },