Bug: OpenRouter @provider pin silently lost — routes to wrong backend (e.g. Alibaba instead of Novita)

Bug: OpenRouter @provider pin silently lost — routes to wrong backend (e.g. Alibaba instead of Novita)

Summary

When using /model z-ai/glm-5.2@Novita, jcode silently routes to a different OpenRouter backend provider (e.g. Alibaba) instead of the user's pinned choice. The @provider pin is lost in multiple code paths, and the default allow_fallbacks=true lets OpenRouter fall back to whatever provider it ranks first.

Reproduction

1. Have OPENROUTER_API_KEY configured
2. Start jcode
3. Run /model z-ai/glm-5.2@Novita
4. Send a message
5. Check the session header — it shows via Alibaba instead of via Novita

Root Cause (confirmed via runtime logs)

Four bugs combine:

1. OpenRouterProvider::fork() resets provider_pin to None instead of copying from the parent. Forked providers lose the pin entirely.

2. provider.model() returns the bare model id (z-ai/glm-5.2) without the @Novita pin. Session save/restore paths all used provider.model(), so sessions restored without the pin. OpenRouter then used endpoint ranking, Alibaba served first, and the observed session pin locked onto Alibaba with allow_fallbacks=false.

3. handle_auth_changed replaces the OpenRouter runtime with a fresh one (losing the pin) when reconcile_auth_if_provider_missing triggers on_auth_changed().

4. Explicit @provider pins allowed fallbacks by default — @Novita (without !) set allow_fallbacks=true, so OpenRouter could fall back to a different provider. Once Alibaba served a request, it got observed-pinned and locked the session.

Log evidence

# First request: no pin, endpoint ranking (Alibaba first)
OpenRouter routing: model=z-ai/glm-5.2, order=Some(["CoreWeave", "Cloudflare", ..., "Alibaba", ..., "Novita", ...]), allow_fallbacks=true

# Subsequent requests: locked to Alibaba via observed pin
OpenRouter routing: model=z-ai/glm-5.2, order=Some(["Alibaba"]), allow_fallbacks=false

Fix

A fix is available on my fork: https://github.com/ewheels44/ecode/pull/1

Branch: fix/openrouter-provider-pin (3 commits, cherry-picked clean from upstream/master)

Changes:

• OpenRouterProvider::fork() now copies provider_pin from parent
• Added explicit_provider_pin_for_current_model() on MultiProvider to reconstruct full model@pin spec
• All session save/restore paths use provider_model() which includes the pin
• handle_auth_changed re-applies model+pin when replacing the OpenRouter runtime
• Explicit @provider pins now always set allow_fallbacks=false

After fix:

OpenRouter routing: model=z-ai/glm-5.2, order=Some(["Novita"]), allow_fallbacks=false

Environment

• jcode v0.61.14-dev
• macOS aarch64
• OpenRouter API key configured
• Affects all OpenRouter models with @provider syntax

Start with OpenRouterProvider::fork(), MultiProvider::explicit_provider_pin_for_current_model(), the session save/restore paths, and handle_auth_changed. Compare the behavior with the fix described on the linked fork, then verify that an explicit @provider request remains pinned through forking, persistence, and authentication changes, with fallbacks disabled.