Router: reload doesn't reconcile alias_to_name → get_meta mis-resolves removed/moved aliases (stale cache)

[marksverdhei]

Summary

After a router reload (POST /models/reload, or a preset/source change that triggers load_models()) that changes a model's aliases, get_meta() resolves the affected alias incorrectly:

• Removed alias → still resolves to the old model (should be not-found).
• Moved alias (from model foo to model baz) → resolves to foo (the old owner), mis-routing the request to the wrong model.

has_model() is correct in both cases, so the two disagree after a reload — a code path that gates on has_model and one that resolves via get_meta will diverge.

Root cause

load_models() reload rebuilds each model's inst.meta.aliases but never reconciles the global alias_to_name map:

• The cleanup at tools/server/server-models.cpp:595 only erases alias_to_name entries whose target model is gone (mapping.find(it->second) == end). It does not touch entries whose target still exists but no longer owns the alias.
• The re-parse loop at :604-635 does inst.meta.aliases.clear() + re-inserts from the new preset, but writes nothing to alias_to_name.

So an alias removed-from or moved-between still-existing models leaves a stale alias_to_name[oldalias] -> oldname.

Why it mis-resolves (resolution ordering)

get_meta() (:760) resolves in this order:

1. direct name in mapping
2. alias_to_name.find(name) (:766) → returns that target's meta
3. fallback scan of every model's meta.aliases (:774)

Step 2 short-circuits on the stale entry before the authoritative step-3 scan runs. By contrast has_model() skips alias_to_name entirely and uses only the meta.aliases scan — which is why it stays correct and the two diverge.

Why not just drop alias_to_name

Per #135 (ecf2de428, fixing #122) the map exists specifically to resolve aliases when a loaded instance's meta.aliases are shadowed/lost — i.e. the meta.aliases scan is not always sufficient. So the fix is to keep alias_to_name in sync on reload, not remove it.

Repro

1. Preset INI: [foo] with alias = bar; start router.
2. Edit preset: remove bar from [foo] (or move alias = bar to a new [baz]).
3. POST /models/reload.
4. Resolve the model by bar (e.g. GET /models lookup / a request targeting bar): it still resolves to foo via the stale alias_to_name, instead of not-found (removed) or baz (moved). has_model("bar") disagrees.

Suggested fix

After the re-parse loop finishes rebuilding all meta.aliases, rebuild alias_to_name from scratch (clear + repopulate from each model's final aliases), or update it inside the re-parse loop (drop the model's old alias entries, add the new ones). Keep the existing dead-target cleanup. A regression test can extend test_router_reload_models to move an alias between two preset sections and assert resolution follows.

Severity

Medium — requires an alias-changing reload (a real ops action: editing the preset INI + reload), but then silently routes requests to the wrong model or produces get_meta/has_model inconsistency. Same alias-map-consistency class as #135 / #122.

Found via idle bug-hunt; verified against origin/ht (90ae01b7a). Happy to PR the reconcile fix — holding it until #148 lands to avoid conflicts on server-models.cpp.