Fix chat model picker hiding models when metadata.id collides across vendors

[fishcharlie]

Fixes #312908

Problem

In buildModelPickerItems, the placed set was keyed on both a model's full identifier (e.g. customoai/<group>/<id>) and its bare metadata.id (e.g. claude-opus-4.7). Once any one model was placed in the Auto / Promoted (selected / recently-used / featured) section, every other model from a different vendor that happened to share the same metadata.id was filtered out of the "Other Models" section — and was therefore unreachable from the chat model picker entirely (search included), even though it appeared correctly in the Language Models settings view.

Fix

Track promoted models strictly by identifier in the placed set. The lookup paths that match by bare metadata.id (resolving featured / recent IDs from the control manifest to a concrete model via modelsByMetadataId) still resolve via that map, but only record the resulting identifier in placed.

Control-manifest entries that have no concrete matching model (!entry.exists placeholders) keep using their entry id — those IDs live in a separate id-namespace and don't collide with vendors' metadata.ids.

The "Other Models" filter is now models.filter(m => !placed.has(m.identifier)).

Tests

Two new tests in chatModelPicker.test.ts:

• models from different vendors sharing a metadata.id all appear (issue #312908) — covers the selected-model promotion path.
• promoted model does not hide other models with same metadata.id from Other Models — covers the recently-used and featured promotion paths.

Both fail before the fix and pass after.

All 42 buildModelPickerItems tests pass; ran the broader chat picker / language models suite with no regressions.

[Copilot]

Pull request overview

Fixes an issue in the chat model picker where models could become unreachable when different vendors share the same metadata.id, by ensuring “placed/promoted” tracking and “Other Models” filtering are based on unique model identifiers.

Changes:

• Stop tracking promoted models by bare metadata.id; track only by concrete identifier (and manifest-only placeholder IDs).
• Update “Other Models” filtering to exclude only models whose identifier is already placed.
• Add tests covering vendor metadata.id collisions to prevent regressions.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/vs/workbench/contrib/chat/browser/widget/input/chatModelPicker.ts	Updates promotion/placement bookkeeping and the “Other Models” filter to avoid dropping models due to cross-vendor metadata.id collisions.
src/vs/workbench/contrib/chat/test/browser/widget/input/chatModelPicker.test.ts	Adds regression tests for metadata.id collisions across vendors in the model picker.

[Copilot]

This test can pass even if the original bug (filtering Other Models by metadata.id) regresses, because the featured path here can resolve to (and promote) the BYOK model via modelsByMetadataId (it keeps only one model per metadata.id). In that case the BYOK model would still be visible (as featured) even though it might be incorrectly filtered out of Other Models. Consider restructuring/asserting sections so the test guarantees one model is promoted and the other remains under the other section (e.g. assert that at least one of the two actions has section === 'other', or split into separate tests for recently-used vs featured promotion).

Suggested change

	const labels = getActionLabels(items);
	assert.ok(labels.includes('gemma:7b'), 'Featured/recent Ollama model should appear');
	assert.ok(labels.includes('gemma:7b (my-endpoint)'), 'BYOK model with colliding metadata.id should still appear in Other Models');
	const actions = getActionItems(items);
	const promotedOllama = actions.find(a => a.label === 'gemma:7b' && a.section !== 'other');
	const otherByok = actions.find(a => a.label === 'gemma:7b (my-endpoint)' && a.section === 'other');
	assert.ok(promotedOllama, 'Featured/recent Ollama model should appear in a promoted section');
	assert.ok(otherByok, 'BYOK model with colliding metadata.id should still appear in Other Models');