diff --git a/packages/ai/src/stream.ts b/packages/ai/src/stream.ts
index 3f8520ad3..1aa0b3992 100644
--- a/packages/ai/src/stream.ts
+++ b/packages/ai/src/stream.ts
@@ -13,7 +13,7 @@ import {
 	resolveWireModelId,
 } from "@oh-my-pi/pi-catalog/model-thinking";
 import { CATALOG_PROVIDERS, type ProviderCatalogEntry } from "@oh-my-pi/pi-catalog/provider-models";
-import { $env, $pickenv, getConfigRootDir, isEnoent, logger } from "@oh-my-pi/pi-utils";
+import { $env, $pickenv, getConfigRootDir, isEnoent, logger, withExtraCaFetch } from "@oh-my-pi/pi-utils";
 import { getCustomApi } from "./api-registry";
 import { AUTH_RETRY_STEPS, isApiKeyResolver, resolveRetryKey } from "./auth-retry";
 import * as AIError from "./error";
@@ -75,7 +75,6 @@ import { wrapLeakedThinkingStream } from "./utils/leaked-thinking-stream";
 import { wrapFetchForProxy } from "./utils/proxy";
 import { withRequestDebugFetch } from "./utils/request-debug";
 import { withGeminiThinkingLoopGuard } from "./utils/thinking-loop";
-import { withExtraCaFetch } from "./utils/tls-fetch";
 
 function isGoogleVertexAuthenticatedModel(model: Model<Api>): boolean {
 	return (
diff --git a/packages/utils/CHANGELOG.md b/packages/utils/CHANGELOG.md
index 951f03fe5..f08a98a15 100644
--- a/packages/utils/CHANGELOG.md
+++ b/packages/utils/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- Added `wrapFetchForExtraCa` / `withExtraCaFetch` (moved from `@oh-my-pi/pi-ai` internals): a fetch wrapper that applies `NODE_EXTRA_CA_CERTS` to Bun's `RequestInit.tls.ca`, shared by provider streaming and catalog model discovery.
+
 ## [16.2.9] - 2026-06-30
 
 ### Added
diff --git a/packages/utils/src/index.ts b/packages/utils/src/index.ts
index 3fcfe829e..2816db33f 100644
--- a/packages/utils/src/index.ts
+++ b/packages/utils/src/index.ts
@@ -29,6 +29,7 @@ export * from "./snowflake";
 export * from "./stream";
 export * from "./tab-spacing";
 export * from "./temp";
+export * from "./tls-fetch";
 export * from "./type-guards";
 export * from "./which";
 
diff --git a/packages/ai/src/utils/tls-fetch.ts b/packages/utils/src/tls-fetch.ts
similarity index 75%
rename from packages/ai/src/utils/tls-fetch.ts
rename to packages/utils/src/tls-fetch.ts
index 10fa26766..2e3a21c64 100644
--- a/packages/ai/src/utils/tls-fetch.ts
+++ b/packages/utils/src/tls-fetch.ts
@@ -1,15 +1,13 @@
 /**
- * `NODE_EXTRA_CA_CERTS` shim for the Bun fetch path used by every provider
- * stream.
+ * `NODE_EXTRA_CA_CERTS` shim for Bun's `fetch`.
  *
  * Node's TLS layer honours `NODE_EXTRA_CA_CERTS` natively, but Bun's
- * `fetch` does not, and the OpenAI-compatible providers (`openai-responses`,
- * `openai-completions`, `openai-codex-responses`, `ollama-chat`, ...) route
- * every request through Bun's runtime. Without this wrapper, corporate
- * relays and private gateways behind a custom CA bundle fail with
+ * `fetch` does not, and both the provider streams (`openai-responses`,
+ * `openai-completions`, `openai-codex-responses`, `ollama-chat`, ...) and
+ * catalog model discovery (`/models` probes) route every request through
+ * Bun's runtime. Without this wrapper, corporate relays and private
+ * gateways behind a custom CA bundle fail with
  * `unknown certificate verification error` even when the env var is set.
- * (Foundry mTLS in {@link resolveFoundryTlsOptions} consumed the env var for
- * the Anthropic path only — issue #3731.)
  *
  * The wrapper merges the resolved CA bundle into Bun's `RequestInit.tls.ca`.
  * Bun's `tls.ca` REPLACES the default trust store when set, so the wrapper
@@ -18,9 +16,29 @@
  */
 import * as fs from "node:fs";
 import * as tls from "node:tls";
-import { $env, isEnoent } from "@oh-my-pi/pi-utils";
-import * as AIError from "../error";
-import type { FetchImpl } from "../types";
+import { $env } from "./env";
+import { isEnoent } from "./fs-error";
+
+/**
+ * `fetch`-compatible function. Accepts any callable matching the standard
+ * fetch signature; `preconnect` is optional because non-Bun runtimes
+ * (browsers, test mocks) won't expose it.
+ */
+export type FetchImpl = ((input: string | URL | Request, init?: RequestInit) => Promise<Response>) & {
+	preconnect?: typeof globalThis.fetch.preconnect;
+};
+
+/**
+ * `NODE_EXTRA_CA_CERTS` was set but unusable (path does not exist). This is
+ * a config/contract error, not a transient transport fault — it is never
+ * retried.
+ */
+export class ExtraCaError extends Error {
+	constructor(message: string, options?: { cause?: unknown }) {
+		super(message, options?.cause === undefined ? undefined : { cause: options.cause });
+		this.name = "ExtraCaError";
+	}
+}
 
 /** Bun extension to `RequestInit` for the TLS options we touch. */
 type BunTlsOptions = {
@@ -41,7 +59,7 @@ type ExtraCaFetch = FetchImpl & { [EXTRA_CA_FETCH_MARKER]?: true };
  * Cached resolution of `NODE_EXTRA_CA_CERTS`. Keyed on the env value plus
  * the file mtime for path values so on-disk cert rotation (short-lived
  * corporate bundles) invalidates the cache instead of pinning the first
- * read forever. Mirrors {@link foundryTlsOptionsCacheKey}.
+ * read forever.
  */
 let cacheKey: string | undefined;
 let cacheValue: string | undefined;
@@ -56,7 +74,7 @@ let cacheValue: string | undefined;
  *   shell exports.
  * - File path. Anything that does not contain a PEM header is treated as a
  *   path, matching Node's "extensionless filename is still a path" contract.
- *   `ENOENT` becomes {@link AIError.ValidationError}; other I/O errors bubble.
+ *   `ENOENT` becomes {@link ExtraCaError}; other I/O errors bubble.
  */
 function resolveExtraCa(): string | undefined {
 	const raw = $env.NODE_EXTRA_CA_CERTS?.trim();
@@ -81,7 +99,7 @@ function resolveExtraCa(): string | undefined {
 			cacheValue = fs.readFileSync(raw, "utf8");
 		} catch (error) {
 			if (isEnoent(error)) {
-				throw new AIError.ValidationError(`NODE_EXTRA_CA_CERTS path does not exist: ${raw}`);
+				throw new ExtraCaError(`NODE_EXTRA_CA_CERTS path does not exist: ${raw}`);
 			}
 			throw error;
 		}
@@ -101,7 +119,7 @@ export function __resetExtraCaCache(): void {
  * list, the system root store is included alongside the extra bundle —
  * Bun's `tls.ca` replaces the default trust store, so omitting roots would
  * break every public host. When the caller already curated a list (e.g.
- * Anthropic Foundry's {@link resolveFoundryTlsOptions}, which already seeds
+ * Anthropic Foundry's mTLS options, which already seed
  * `tls.rootCertificates`), only the extra CA is appended.
  */
 function withExtraCaInit(init: RequestInit | undefined, extraCa: string): RequestInit {
@@ -146,9 +164,10 @@ export function wrapFetchForExtraCa(fetchImpl: FetchImpl): FetchImpl {
 }
 
 /**
- * Convenience for the stream-entry composition in `stream.ts`. Mirrors
- * {@link withRequestDebugFetch} so the proxy/debug/extra-CA wrappers compose
- * uniformly. No-op when the env var is unset.
+ * Convenience for options-bag composition (e.g. the stream-entry path in
+ * `@oh-my-pi/pi-ai`'s `stream.ts`, which mirrors `withRequestDebugFetch` so
+ * the proxy/debug/extra-CA wrappers compose uniformly). No-op when the env
+ * var is unset.
  */
 export function withExtraCaFetch<T extends { fetch?: FetchImpl } | undefined>(options: T): T {
 	if (!$env.NODE_EXTRA_CA_CERTS?.trim()) return options;
diff --git a/packages/ai/src/utils/__tests__/tls-fetch.test.ts b/packages/utils/test/tls-fetch.test.ts
similarity index 95%
rename from packages/ai/src/utils/__tests__/tls-fetch.test.ts
rename to packages/utils/test/tls-fetch.test.ts
index e8b4f60b6..1053a6ad7 100644
--- a/packages/ai/src/utils/__tests__/tls-fetch.test.ts
+++ b/packages/utils/test/tls-fetch.test.ts
@@ -3,9 +3,13 @@ import * as fs from "node:fs/promises";
 import * as os from "node:os";
 import * as path from "node:path";
 import * as tls from "node:tls";
-import * as AIError from "../../error";
-import type { FetchImpl } from "../../types";
-import { __resetExtraCaCache, withExtraCaFetch, wrapFetchForExtraCa } from "../tls-fetch";
+import {
+	__resetExtraCaCache,
+	ExtraCaError,
+	type FetchImpl,
+	withExtraCaFetch,
+	wrapFetchForExtraCa,
+} from "@oh-my-pi/pi-utils/tls-fetch";
 
 const SAMPLE_PEM =
 	"-----BEGIN CERTIFICATE-----\nMIIBkTCCATegAwIBAgIUF/sample/extra/ca/for/tests/1234567=\n-----END CERTIFICATE-----\n";
@@ -128,12 +132,12 @@ describe("wrapFetchForExtraCa", () => {
 		expect(ca).not.toContain(SAMPLE_PEM);
 	});
 
-	it("throws ValidationError when the configured path does not exist", async () => {
+	it("throws ExtraCaError when the configured path does not exist", async () => {
 		Bun.env.NODE_EXTRA_CA_CERTS = path.join(tmpDir, "missing.pem");
 
 		const { fetchImpl } = makeRecordingFetch();
 		const wrapped = wrapFetchForExtraCa(fetchImpl);
-		await expect(wrapped("https://corp.example/v1")).rejects.toBeInstanceOf(AIError.ValidationError);
+		await expect(wrapped("https://corp.example/v1")).rejects.toBeInstanceOf(ExtraCaError);
 	});
 
 	it("is idempotent — wrapping a wrapped fetch returns the same reference", async () => {