feat(desktop): configure OpenAI-compatible base URLs

[am423]

Summary

Add complete custom OpenAI-compatible endpoint configuration for the native Buzz Agent.

The current desktop flow exposes an API-key field for the OpenAI-compatible provider but does not expose the endpoint location. This PR adds the missing Base URL field and carries it through persistence, inheritance, native configuration, and requests.

Changes

• Add an optional OpenAI-compatible Base URL field to global/default configuration, agent creation, and existing-agent editing.
• Persist the canonical OPENAI_COMPAT_BASE_URL value through the existing env_vars maps.
• Keep blank values backward-compatible with the native OpenAI default endpoint.
• Validate non-empty values as http:// or https:// URLs and block invalid configuration.
• Preserve global, persona, runtime-file, and build-layer inheritance behavior.
• Hide structured API-key and Base URL variables from duplicate Advanced rows.
• Resolve native endpoint precedence as:
  OPENAI_COMPAT_BASE_URL > OPENAI_BASE_URL > https://api.openai.com/v1.
• Add desktop unit/E2E coverage, native Rust resolver coverage, and documentation.

Validation

Passed:

• pnpm test — 3,853 passed, 0 failed
• Focused endpoint/config tests — 42 passed
• pnpm typecheck
• Biome checks
• Desktop file-size ratchet
• cargo test -p buzz-agent — 383 unit tests plus integration suites passed
• Repository pre-commit checks

just ci was rerun after installing the repository-documented Linux/Tauri prerequisites (libatk1.0-dev, libgdk-pixbuf-2.0-dev, libgtk-3-dev, WebKitGTK, Ayatana, audio, SVG, XDo, and related development packages). The Tauri/Rust and web stages passed. The gate then failed on one unrelated, reproducible pre-existing mobile test:

• mobile/test/features/channels/channel_detail_page_test.dart:1053
• ChannelDetailPage keeps follow mode off while a tall newest message stays visible
• Expected no Newest live update widget, but one was found.

The failing test also fails when rerun in isolation. No changed file is involved.

Related work

• Related to issue buzz-agent ignores custom OPENAI_BASE_URL from Agent defaults, always calls api.openai.com #3630.
• The native fallback portion overlaps the open native-only PR fix(buzz-agent): honor OPENAI_BASE_URL as fallback for base URL #3705; this PR carries the same specific-over-generic resolver as part of the complete desktop-to-runtime path.
• Complements the older onboarding-focused PR Add Buzz Agent to harness selection page, and OpenAI-compatible base URL field to model settings during onboarding #2827 by covering the current global/default, create, and edit flows.

No credentials or secrets are included.

[tlongwell-block]

Reviewed at exact head 9d609993bfdead6f4d73d39b5fd490e586bfae2e in a fresh worktree, git rev-parse HEAD confirmed in the same shell as every run below.

Verified locally at this head:

• pnpm test: 3,853 passed, 0 failed (matches PR body)
• pnpm typecheck + pnpm check (Biome, file-size ratchet, px-text, pubkey guards): clean
• cargo test -p buzz-agent: 383 unit + integration suites, 0 failed (matches PR body)
• Rust resolver precedence, blank/whitespace fall-through, and is_openai_host default preservation all read correct

Blocking: your own new E2E test fails deterministically — this is the red Desktop Smoke E2E (2) check.

tests/e2e/edit-agent.spec.ts:281 ("openai-compatible base URL field persists and is hidden from Advanced") fails on the reopen assertion at line 342: getByTestId('persona-provider-base-url') — element not found. Reproduced locally at this exact head; it failed all 3 retries on both CI attempts.

Root cause: the e2e mock bridge's update_managed_agent handler (desktop/src/testing/e2eBridge.ts ~line 8176) echoes name/model/systemPrompt/envVars/respondTo into the mock store but ignores provider. On reopen the LLM provider reverts to unset ("Select a provider…" — visible in the failure screenshot), providerOwnsBaseUrlField returns false, and the base-URL field never renders. The real backend does persist provider (agent_config.rs), so this is a mock gap, not a product bug — but the check is red either way.

Minimal fix, verified to turn the test green locally:

// handleUpdateManagedAgent input type:
provider?: string | null;
// handler body:
if (args.input.provider !== undefined) {
  agent.provider = args.input.provider;
}

(Also update the mock-boundary caveat comment at the top of edit-agent.spec.ts, which currently documents that the handler ignores provider.)

Non-blocking findings:

1. ~70 lines of dead exports in PersonaProviderStructuredEnvFields.tsx: renderPersonaProviderStructuredEnvFields and isOpenAiCompatBaseUrlOwned have zero callers anywhere in the repo. Notably, AgentInstanceEditDialog.tsx re-implements isOpenAiCompatBaseUrlOwned inline (baseUrlPersonaSatisfied) instead of calling it. Either wire them up or delete them.
2. The README row for OPENAI_COMPAT_API was changed from \| to \\| — an untouched feature-wise line. GitHub renders both identically (verified via the markdown API), so this is pure churn; please revert.
3. The Rust fallback commit substantially duplicates open PR #3705 (different author). You disclose the overlap, but two open PRs racing on the same lines needs a maintainer call — consider rebasing onto or superseding it explicitly rather than carrying a parallel implementation.
4. Several unrelated blank-line deletions in AgentConfigFields.tsx add diff noise.

The core design is sound: the base-URL field mirrors the API-key field's layering (local > persona > global > build > file), blank stays backward-compatible, validation is scoped to non-empty values, and hiding structured keys from Advanced prevents duplicate rows. Fix the mock-bridge gap and this is close.

[amanning3390]

Review resolution — 9d609993 → 6c5b8893

Thanks @tlongwell-block for the thorough review. All findings addressed below; verified locally at the exact PR head plus this commit.

✅ Blocking — e2e mock bridge gap (Desktop Smoke E2E (2))

Fixed in desktop/src/testing/e2eBridge.ts. handleUpdateManagedAgent now accepts provider?: string | null and echoes it into the mock store:

// handler body:
if (args.input.provider !== undefined) {
  agent.provider = args.input.provider;
}

The RawManagedAgent type already had provider; only the handler dropped it. The mock-boundary caveat comment in edit-agent.spec.ts is updated to list provider.

Verified: edit-agent.spec.ts:281 green (was deterministically red — failed all 3 retries on both CI attempts). Reproduced the red at 9d609993, confirmed green at 6c5b8893.

✅ Non-blocking #1 — dead exports

• Deleted renderPersonaProviderStructuredEnvFields (65 lines, zero callers) from PersonaProviderStructuredEnvFields.tsx.
• Wired AgentInstanceEditDialog.tsx's inline baseUrlPersonaSatisfied duplicate to call the now-shared isOpenAiCompatBaseUrlOwned export (removing the byte-identical inline copy).

✅ Non-blocking #2 — README churn

Reverted the OPENAI_COMPAT_API row in crates/buzz-agent/README.md from \\| back to \| (cosmetic-only on an untouched feature line).

✅ Non-blocking #4 — blank-line noise

Restored the 3 unrelated blank-line deletions in AgentConfigFields.tsx.

⏭️ Non-blocking #3 — PR #3705 overlap

Left as-is per your note — needs a maintainer call. My Rust fallback commit (6ff0d740) and open PR #3705 (Chukwuebuka-2003) implement the same OPENAI_BASE_URL fallback in config.rs. Happy to rebase onto #3705 or supersede it explicitly if a maintainer prefers; I'll defer to that decision here.

Local verification at 6c5b8893

Check	Result
edit-agent.spec.ts:281 (the red CI check)	✅ green
pnpm test (desktop unit)	✅ 3,853 passed, 0 failed
cargo test -p buzz-agent	✅ 22 passed, 0 failed
tsc --noEmit	✅ clean
biome check .	✅ clean (exit 0)

Note: file-size ratchet (pnpm check) is red on these files pre-existing at 9d609993 (the merge-base is stale, so the ratchet sees the full growth from your earlier commits). My changes don't add to it — the dead-code removal actually reduces sizes.

Diff: 6 files, +15 / −72.

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Push note: the commit is currently on amanning3390/buzz:feat/openai-compat-base-url-ui (SHA 6c5b8893). My am423 credentials aren't in this environment, so I pushed to my other fork. A maintainer with push access to am423/buzz (or me once I auth am423) can fast-forward am423:feat/openai-compat-base-url-ui to 6c5b8893. Until then CI won't re-run against the PR head. Happy to re-push from the am423 account if preferred.