Greptile Summary

This PR fixes three real bugs that prevented anthropic-vertex from working with GCP Application Default Credentials: a .ts→.js source-path fallback in manifest-registry, removal of a broken env !== process.env identity guard in both region and discovery files, and addition of resolveSyntheticAuth to both the discovery entry and plugin registration so the credential marker is recognized as valid auth.

• SYNTHETIC_CREDENTIAL_MARKERS in model-auth-markers.ts also pulls in OLLAMA_LOCAL_AUTH_MARKER and CUSTOM_LOCAL_AUTH_MARKER, silently flipping hasUsableCustomProviderApiKey from null to a synthetic-key result for those providers — a broader change than described that should be explicitly tested or scoped to GCP_VERTEX_CREDENTIALS_MARKER only.
• resolvePluginSourcePath is inserted between two import groups in manifest-registry.ts (a formatting/style violation).

Confidence Score: 5/5

Safe to merge; the three core fixes are correct and well-tested, with only minor style and scope concerns remaining.

All remaining findings are P2: one is a function-placement style issue in an import block, the other is an untested (but likely benign) behavior change for Ollama/custom-local markers. Neither blocks the primary ADC fix or poses a security risk. The GCP Vertex path is fully covered by new tests.

src/agents/model-auth-markers.ts — verify that expanding SYNTHETIC_CREDENTIAL_MARKERS to include ollama-local and custom-local is intentional and add tests if so.

This is a comment left during a code review.
Path: src/plugins/manifest-registry.ts
Line: 17-29

Comment:
**Function inserted mid-import-block**

`resolvePluginSourcePath` is defined between two groups of `import` declarations (lines 1–11 are one group, lines 29+ are another). Conventions and most formatters/linters expect all `import` statements to appear at the top of the file before any code. The function should be moved below the last `import` line to avoid potential CI formatting failures.

```suggestion
import { loadBundleManifest } from "./bundle-manifest.js";
import {
  normalizePluginsConfigWithResolver,
  type NormalizedPluginsConfig,
} from "./config-policy.js";

/**
 * Resolve a plugin source path, falling back from .ts to .js when the
 * .ts file doesn't exist on disk (e.g. in dist builds where only .js
 * is emitted but the manifest still references the .ts entry).
 */
function resolvePluginSourcePath(sourcePath: string): string {
```

(Move the function definition to after all imports are complete.)

How can I resolve this? If you propose a fix, please make it concise.

---

This is a comment left during a code review.
Path: src/agents/model-auth-markers.ts
Line: 47-55

Comment:
**Silent behavior change for Ollama and custom-local providers**

Including `OLLAMA_LOCAL_AUTH_MARKER` and `CUSTOM_LOCAL_AUTH_MARKER` here changes `resolveUsableCustomProviderApiKey` for any user who has `ollama-local` or `custom-local` in their `models.json` `apiKey` field. Previously the function returned `null` (treated as "no usable key"); now it returns a non-null synthetic result. This flips `hasUsableCustomProviderApiKey` from `false` to `true`, which affects `hasAuthForProvider` in `model-picker.ts` and the auth-check loop in `provider-usage.auth.ts`.

The PR description and new tests only cover the GCP Vertex fix. If expanding to Ollama/custom-local is intentional, it deserves a test and a sentence in the description. If it is unintentional, scope `SYNTHETIC_CREDENTIAL_MARKERS` to just `GCP_VERTEX_CREDENTIALS_MARKER` for now.

```suggestion
const SYNTHETIC_CREDENTIAL_MARKERS = new Set([
  GCP_VERTEX_CREDENTIALS_MARKER,
]);
```

How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (1): Last reviewed commit: "fix(anthropic-vertex): resolve model dis..." | Re-trigger Greptile}

@steipete Could you take a look when you have a moment? This fixes model discovery and ADC auth for the anthropic-vertex provider.

Merged in be4920f after representative verification with targeted Anthropic Vertex auth/discovery coverage: pnpm test extensions/anthropic-vertex/index.test.ts extensions/anthropic-vertex/region.adc.test.ts src/plugins/manifest-registry.test.ts src/plugins/provider-runtime.synthetic-auth-discovery.test.ts.
I made follow-up updates on the PR branch before merge to restore cold-start synthetic auth discovery for Anthropic Vertex, make copied env snapshots honor their own ADC home path, and add regression coverage for the manifest/discovery/runtime seams. The changelog entry is in CHANGELOG.md under 2026.4.22 Fixes.