Studio: allow --secure with --api-only (headless secure API server) and add --api-only to `unsloth studio run` by danielhanchen · Pull Request #6591 · unslothai/unsloth

danielhanchen · 2026-06-23T02:36:37Z

Summary

--secure is meant to expose Studio ONLY through the authenticated Cloudflare HTTPS link (it forces a loopback bind and fails closed if the tunnel can't start). But the tunnel start gate excluded api-only mode, so --secure --api-only started no tunnel and then fell on its own fail-closed check:

A secure Cloudflare link is not allowed, use --no-secure which provides a 0.0.0.0 link

That blocked the natural headless use case: serve just the API (no web UI) over the secure tunnel for remote API calling.

Root cause

def _cloudflare_tunnel_should_start(*, cloudflare, host, secure, api_only, is_colab):
    return cloudflare and (host == "0.0.0.0" or secure) and not api_only and not is_colab

The not api_only term was there to keep the Tauri desktop app (which loads the API on loopback) from tunnelling. But it also suppressed the tunnel under --secure, where the tunnel is the only way in, so secure + api-only could never start.

Changes

studio/backend/run.py: _cloudflare_tunnel_should_start now starts the tunnel whenever --secure is set, even api-only. The non-secure path is unchanged: tunnel only a 0.0.0.0 bind, never api-only (Tauri) or Colab.
unsloth_cli/commands/studio.py: add --api-only to unsloth studio run and forward it through both the re-exec args and the in-venv run_server(api_only=...) call. unsloth studio run --secure --api-only --model ... is now a one-liner headless secure API server.

Behaviour

invocation	before	after
`run.py --secure` (UI)	tunnel up	tunnel up (unchanged)
`run.py --secure --api-only`	fail closed	tunnel up, API only
`run.py --api-only` (Tauri)	no tunnel	no tunnel (unchanged)
`run.py -H 0.0.0.0`	tunnel up	tunnel up (unchanged)
`--secure` on Colab	no tunnel	no tunnel (unchanged)

Testing

python -m pytest studio/backend/tests/test_secure_tunnel_gate.py \
                 unsloth_cli/tests/test_studio_run_parallel_flag.py -q
56 passed

Updated the tunnel-gate truth table: secure + api-only now tunnels; secure + Colab still does not.
Added --api-only registration plus re-exec and in-venv run_server forwarding coverage to the run CLI tests.

Verified end to end on a host where the quick tunnel can establish: run.py --secure --api-only brings up the tunnel and serves /api/health over it (200), with / returning 404 (no UI).

…and add --api-only to `unsloth studio run` --secure exposes ONLY the Cloudflare link (it forces a loopback bind), but _cloudflare_tunnel_should_start gated the tunnel on `not api_only`, so `run.py --secure --api-only` started no tunnel and then fail-closed with "A secure Cloudflare link is not allowed". That blocked the natural headless use: serve just the API (no web UI) over the authenticated tunnel. Make --secure start the tunnel regardless of api_only (the non-secure path is unchanged: tunnel only a 0.0.0.0 bind, never api-only Tauri or Colab). Then expose --api-only on `unsloth studio run` and forward it through both the re-exec args and the in-venv run_server call, so `unsloth studio run --secure --api-only --model ...` is a one-liner secure API server. Verified end to end: `run.py --secure --api-only` now brings up the tunnel and serves /api/health over it (200), with / returning 404 (no UI). Tests: update the tunnel-gate truth table (secure+api-only now tunnels; secure+colab still does not) and add --api-only registration + re-exec/in-venv forwarding coverage to the run CLI tests.

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danielhanchen · 2026-06-23T06:07:09Z

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chatgpt-codex-connector · 2026-06-23T06:15:21Z

+    api_only: bool = typer.Option(
+        False,
+        "--api-only",
+        help = "Serve only the API (no web UI), for a headless model server. "
+        "Pairs with --secure to expose the API over the Cloudflare link alone.",


Reject parent-level --api-only before run

When the user places the new flag before the subcommand, e.g. unsloth studio --api-only run --secure --model ..., Typer consumes --api-only in the parent studio_default callback, whose subcommand guard currently rejects --parallel, --secure, etc. but not --api-only; the run command therefore receives api_only=False and serves the web UI, potentially over the secure tunnel, despite the user requesting a headless API server. Please add the same parent-level rejection/redirect guidance for --api-only that the surrounding callback uses for the other run-specific flags.

Useful? React with 👍 / 👎.

Fixed in 25f6bc9. The parent studio_default callback now rejects --api-only when a subcommand is invoked, matching the existing guidance for --parallel/--secure/--verbose: it exits 2 and tells the user to put the flag after the subcommand (unsloth studio run --api-only ...). Added test_studio_default_rejects_api_only_when_subcommand_invoked.

chatgpt-codex-connector · 2026-06-23T06:15:21Z

+    if is_colab or not cloudflare:
+        return False
+    if secure:
+        return True


Keep secure API-only CORS usable remotely

With --secure --api-only, this branch now publishes an API-only server through Cloudflare, but run_server(api_only=True) sets UNSLOTH_API_ONLY=1 before importing main, and studio/backend/main.py:858-867 switches CORS from * to a Tauri/localhost-only allowlist. Browser-based remote API clients calling the new Cloudflare URL from any other origin will fail preflight even with a valid API key, whereas --secure without --api-only works. If this mode is meant to support remote API callers, keep the UI disabled without enabling the Tauri-only CORS profile or allow the tunnel origin.

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Fixed in 25f6bc9. Secure api-only is a remote server behind Cloudflare, so it now keeps the any-origin CORS profile; the Tauri-only lockdown still applies to plain local api-only. The decision is factored into cors_origins_for_mode(api_only, secure) (returns the Tauri allowlist only when api_only and not secure, else [""]), and run_server exports UNSLOTH_SECURE before importing main so main.py can tell the two apart. With allow_credentials=True and [""], Starlette reflects the request Origin, so remote browser preflight succeeds. Added test_cors_origins_for_mode and test_run_server_exports_secure_env_for_cors.

…unnel

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danielhanchen · 2026-06-23T10:47:04Z

@codex review

- Reject --api-only on the parent `unsloth studio` group when a subcommand is invoked, with the same redirect guidance used for --parallel/--secure; otherwise the flag was silently dropped and the UI served anyway. - Keep CORS any-origin for secure api-only serving: that mode publishes the API over Cloudflare for remote browser clients, so the Tauri-only lockdown (still applied to plain local api-only) would break preflight. Factored the decision into cors_origins_for_mode() and gate it on api_only and not secure; run_server exports UNSLOTH_SECURE before importing main.

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chatgpt-codex-connector · 2026-06-23T10:52:33Z

+    if secure:
+        return True


Allow remote CORS origins for secure API-only tunnels

When --secure --api-only now reaches this branch, run_server sets UNSLOTH_API_ONLY=1 before importing main.py; main.py then restricts CORS to Tauri/localhost origins only. Browser-based clients using the advertised Cloudflare URL (for example an Origin on https://*.trycloudflare.com or another web app) will fail the authenticated API preflight even though this mode is intended to expose the headless API remotely. Please use the non-Tauri CORS policy for secure headless serving or add appropriate remote/tunnel origins.

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This review ran against 3c38e30, which is the commit just before the fix. It is already addressed in 25f6bc9 (now 25f6bc9..a652338 after a pre-commit.ci reformat): secure api-only uses the non-Tauri policy. cors_origins_for_mode(api_only, secure) returns the Tauri allowlist only when api_only and not secure, otherwise ["*"], and run_server exports UNSLOTH_SECURE before importing main so --secure --api-only resolves to the any-origin profile (same one --secure without --api-only already uses). Covered by test_cors_origins_for_mode and test_run_server_exports_secure_env_for_cors.

danielhanchen · 2026-06-23T12:15:04Z

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chatgpt-codex-connector · 2026-06-23T12:25:54Z

+
+
+@pytest.mark.parametrize("extra,present", [(["--api-only"], True), ([], False)])
+def test_reexec_forwards_api_only(monkeypatch, extra, present):


Use a unique name for the api-only re-exec test

When pytest imports this module, this second test_reexec_forwards_api_only definition replaces the earlier one added above, so the explicit --secure --api-only re-exec case is never collected. Rename or merge one of these tests so the headline secure headless path is actually exercised.

Useful? React with 👍 / 👎.

Fixed in ce11c5d. That duplicate definition was shadowing the parametrized test_reexec_forwards_api_only below it, so the secure case was never collected. I removed the duplicate (and the redundant omit-by-default test, already covered by the parametrized ([], False) case) and folded the secure headless path in as a param: (['--secure', '--api-only'], True). One canonical test now, and the secure case is collected.

chatgpt-codex-connector · 2026-06-23T12:25:54Z

        host = host,
        port = port,
        silent = True,
+        api_only = api_only,


Do not leak TAURI_PORT from headless run output

When unsloth studio run --api-only reaches this in-venv path, it passes api_only=True into run_server, whose api-only branch unconditionally prints the Tauri-only TAURI_PORT=... line even though this caller uses silent=True and then prints the run subcommand's URL:/API Key: banner. This makes the new headless run --api-only mode emit an extra unrelated line before the documented output, including under --silent, which can break scripts that parse the one-liner server output; gate that port print to the desktop/Tauri launch path instead.

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Fixed in ce11c5d. run_server now takes emit_tauri_port (default True, so the Tauri/desktop and studio_default paths are unchanged), and the TAURI_PORT= line is gated on api_only and emit_tauri_port. The headless run --api-only path passes emit_tauri_port=False, so it no longer prepends that machine line before the URL:/API Key: banner, including under --silent. Covered by test_run_server_emit_tauri_port_defaults_on, test_tauri_port_print_is_gated_in_source, and an emit_tauri_port=False assertion in test_in_venv_path_passes_api_only_to_run_server.

- run_server gains emit_tauri_port (default True, unchanged for the Tauri/ desktop path). The new headless `run --api-only` path passes False so the Tauri-only TAURI_PORT= line no longer prepends the documented URL/API key banner (it ran even under --silent and could break one-liner parsers). - Remove a duplicate test_reexec_forwards_api_only that shadowed the parametrized one; fold the --secure --api-only case into it so the secure headless path is actually collected.

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danielhanchen · 2026-06-23T12:37:26Z

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chatgpt-codex-connector · 2026-06-23T12:43:39Z

Codex Review: Didn't find any major issues. Bravo.

Reviewed commit: ce11c5df12

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chatgpt-codex-connector Bot reviewed Jun 23, 2026

View reviewed changes

Merge remote-tracking branch 'origin/main' into fix-secure-api-only-t…

ab093cf

…unnel

Trim comments to be succinct (no behavior change)

3c38e30

[pre-commit.ci] auto fixes from pre-commit.com hooks

a652338

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chatgpt-codex-connector Bot reviewed Jun 23, 2026

View reviewed changes

danielhanchen merged commit 76cbddb into main Jun 23, 2026
50 checks passed

danielhanchen deleted the fix-secure-api-only-tunnel branch June 23, 2026 12:44



		@pytest.mark.parametrize("extra,present", [(["--api-only"], True), ([], False)])
		def test_reexec_forwards_api_only(monkeypatch, extra, present):

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