Two follow-ups from PR #2543's multi-model code review (audit #253).
1. **Log silent yaml.Unmarshal errors (#256).** When a malformed
config.yaml made `yaml.Unmarshal(data, &raw)` fail, the affected
template silently disappeared from /templates with no trace —
operator could not distinguish "excluded due to parse error" from
"never existed." That widened a real foot-gun once PR #2543 added
structured top-level `providers:` (a string-shaped top-level
`providers:` decoded into `[]providerRegistryEntry` would fail and
drop the whole entry). Now logs `templates list: skip <id>:
yaml.Unmarshal: <err>` and continues with the rest.
2. **Coexistence test (#257 part 1).** PR #2543 covered the structured
registry and slug list in isolation. claude-code-default in
production ships BOTH: top-level `providers:` (structured registry,
2 entries) AND `runtime_config.providers:` (slug list, 3 entries).
New `TestTemplatesList_BothProviderShapesCoexist` mirrors that
layout, asserts both shapes surface independently with no
cross-talk (e.g. a slug-only entry like `anthropic-api` does NOT
synthesize a stub in the structured registry), and pins the JSON
wire-shape for both fields side-by-side.
3. **`base_url: null` decoding assertion (#257 part 3).** Adds an
explicit `got[0].BaseURL == ""` check in the existing
`TestTemplatesList_SurfacesProviderRegistry` test, locking in the
`string` (not `*string`) type. A future change to `*string` would
surface as JSON `null` and break canvas's "no base_url = use
provider defaults" branch — caught loudly by this assertion.
Tests: 11 TestTemplatesList_* now green, including the new
MalformedYAMLLogsAndSkips and BothProviderShapesCoexist.
The remaining piece of #257 — renaming `Providers []string` JSON tag
to `provider_slugs` — requires coordinated canvas updates across 4
files and is intentionally deferred to a separate PR (no canvas
churn while user is mid-test).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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