fix(desktop): connection base URL gate is looser than the Runtime Host contract, so a rejected endpoint reports a misleading error

[shaokeyibb]

What happened

The Desktop connection forms accept baseUrl values that the Runtime Host will refuse, so a custom relay endpoint containing a query string, a fragment, or embedded credentials is accepted by the form, sent over IPC, and then rejected by the Host. The rejection is not classified, so the user is shown the generic fallback copy:

模型连接服务暂时不可用，请稍后重试。
The model connection service is temporarily unavailable. Try again later.

That message is wrong twice over: the service is available, and retrying can never succeed. Nothing points at the endpoint field, which is the actual problem, and the field is not marked — the error lands on field: 'form'.

Two validators disagree about what a connection base URL is:

Input	Desktop IPC gate (validateConnectionBaseUrl)	Runtime Host (normalizeCatalogConnectionBaseUrl)
https://gw.example.com/v1?api-version=2024-06	accepted verbatim	rejected — "must not contain a query or fragment"
https://user:pw@gw.example.com/v1	accepted verbatim	rejected — "must not contain credentials"
https://gw.example.com	kept as typed	canonicalized to https://gw.example.com/
https://Relay.Example.com/V1	kept as typed	canonicalized to https://relay.example.com/V1

validateConnectionBaseUrl (packages/core/src/llm-connections.ts:602) checks only length, URL parseability, and an http/https scheme allowlist, and normalizeConnectionBaseUrl (:668) documents "Trim is the only canonicalization". The Host codec (packages/core/src/runtime-policy/connection-catalog-codec.ts:633) additionally rejects credentials and query/fragment, canonicalizes through URL.toString(), and enforces a 2048-byte cap rather than a 2048-character one.

Both write paths use the lenient gate — connections:create and connections:update each route through normalizeConnectionBaseUrlForIpc (apps/desktop/src/main/connections-ipc-validation.ts:111, and normalizeUpdateInput at apps/desktop/src/main/runtime-host-connections-ipc-main.ts:471) — so both adding a relay and editing an existing endpoint fail the same way.

The client-side form gate does not narrow this either: validateAddProviderDraft (apps/desktop/src/renderer/settings/provider-add-submission.ts:89) only checks that a required base URL is non-empty.

How to reproduce

1. Open Desktop → Settings → Models → Add provider.
2. Pick 自定义中转站（OpenAI Chat） / Custom relay (OpenAI Chat-compatible) (openai-compatible).
3. Enter any API key and set the endpoint to https://gw.example.com/v1?api-version=2024-06.
4. Save.

Expected: the endpoint field reports, before anything is sent, that a query string is not allowed.
Actual: the form submits, the Host rejects the write, and the form shows "模型连接服务暂时不可用，请稍后重试。" with no field marked.

The same happens on an existing connection via Settings → Models → (connection) → 端点 → 编辑.

The three layers can be exercised directly against a built tree, which is how the table above was produced:

import { normalizeCreateConnectionInputForIpc } from './apps/desktop/dist/main/connections-ipc-validation.js';
import { normalizeCatalogConnectionBaseUrl } from './packages/core/dist/runtime-policy/connection-catalog-codec.js';
import { validateAddProviderDraft } from './apps/desktop/dist/renderer/settings/provider-add-submission.js';

const url = 'https://gw.example.com/v1?api-version=2024-06';

validateAddProviderDraft({
  providerType: 'openai-compatible', slug: 'my-relay', existingSlugs: [],
  apiKey: 'sk-test', cloudflareAccountId: '', baseUrl: url,
});
// -> null  (add-form field gate: accepted)

normalizeCreateConnectionInputForIpc({
  slug: 'my-relay', name: 'My relay', providerType: 'openai-compatible',
  baseUrl: url, defaultModel: 'gpt-4o',
}).baseUrl;
// -> 'https://gw.example.com/v1?api-version=2024-06'  (main-process IPC gate: accepted)

normalizeCatalogConnectionBaseUrl(url, 'openai-compatible');
// -> throws: connection base URL must not contain a query or fragment

Environment

• Maka commit: 3bb645e99
• OS and version: macOS 15 (Darwin 25.5.0), Apple Silicon
• Surface: Desktop (Settings → Models add/edit forms) against a local Runtime Host
• Node.js version: 22.19.0

Logs, screenshots, or additional context

The message the user ends up seeing is the unclassified fallback, not the Host's sentence. providerPanelActionErrorMessage (apps/desktop/src/renderer/settings/provider-panel-shared.ts:56) strips the Electron wrapper via cleanErrorMessage, finds no match in shared.lastTest, sees no CJK, and gets '' back from generalizedErrorMessageChinese/generalizedErrorMessage, so it returns shared.actionFallback (apps/desktop/src/renderer/locales/settings-provider-copy.ts:154, :299).

Suggested boundary, and the one I would like to implement:

1. Make the client-side gate agree with the Host contract. validateConnectionBaseUrl should reject credentials and query/fragment and enforce the byte cap, so normalizeConnectionBaseUrl and the add-form gate inherit the same rules and the failure is raised before the IPC call. The Host stays the authority; the client stops promising something the Host will not honor.
2. Report it on the endpoint field with localized copy rather than as a form-level generic error, so the message names the rule that was broken.
3. Canonicalize on the client the same way the Host does, so a saved endpoint reads back as the value that was persisted instead of silently differing by a trailing slash or host case.

This deliberately does not relax the Host. Allowing query strings (e.g. Azure-style ?api-version=) would be a product and security decision for dev@maka.apache.org, not an implementation detail; this issue is only about the client agreeing with the contract that already exists.

Related but distinct: #3405 / #3467 cover the TUI wizard being unable to create relay connections at all. This issue is about the Desktop surface that can already create them.

[shaokeyibb]

Claiming this — implementing the proposed boundary as written: align validateConnectionBaseUrl with the Host's normalizeCatalogConnectionBaseUrl rules (reject credentials and query/fragment, enforce the byte cap, canonicalize identically), surface the failure on the endpoint field with localized copy instead of the form-level fallback, and leave the Host contract untouched.