diff --git a/package.json b/package.json
index 513a989..6860eaf 100644
--- a/package.json
+++ b/package.json
@@ -23,7 +23,7 @@
     "prebuild:renderer": "npm run gen:catalog",
     "catalog:check": "node scripts/check-catalog-stale.mjs",
     "test": "npm run build:main && npm run test:unit",
-    "test:unit": "node scripts/test-extract-base-url.mjs && node scripts/test-doctor.mjs && node scripts/test-versions.mjs && node scripts/test-secrets.mjs && node scripts/test-homebrew.mjs && node scripts/test-install-methods.mjs && node scripts/test-codex-auth.mjs && node scripts/test-probes-cloud.mjs",
+    "test:unit": "node scripts/test-extract-base-url.mjs && node scripts/test-doctor.mjs && node scripts/test-versions.mjs && node scripts/test-secrets.mjs && node scripts/test-homebrew.mjs && node scripts/test-install-methods.mjs && node scripts/test-codex-auth.mjs && node scripts/test-probes-cloud.mjs && node scripts/test-probe-context.mjs",
     "test:extractor": "node scripts/test-extract-base-url.mjs",
     "package": "npm run build && electron-builder"
   },
diff --git a/scripts/test-probe-context.mjs b/scripts/test-probe-context.mjs
new file mode 100644
index 0000000..e4db1d6
--- /dev/null
+++ b/scripts/test-probe-context.mjs
@@ -0,0 +1,66 @@
+#!/usr/bin/env node
+/**
+ * Unit tests for probe context resolution (src/main/probes/context.ts).
+ * Pure logic, no Electron and no live provider keys.
+ */
+import { createRequire } from 'node:module'
+import { existsSync } from 'node:fs'
+import { join, dirname } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const root = join(dirname(fileURLToPath(import.meta.url)), '..')
+const contextJs = join(root, 'dist/main/probes/context.js')
+if (!existsSync(contextJs)) {
+  console.error('dist/main/probes/context.js missing - run npm run build:main first')
+  process.exit(1)
+}
+
+const require = createRequire(import.meta.url)
+const { buildProbeContext, probeRequiresApiKey } = require(contextJs)
+
+let failed = 0
+function assert(cond, msg) {
+  if (cond) console.log(`  ✓ ${msg}`)
+  else {
+    failed++
+    console.error(`  ✗ ${msg}`)
+  }
+}
+
+{
+  const ctx = buildProbeContext({ providerId: 'vertex', apiKey: 'tok', storedProject: 'stored-proj', storedRegion: 'europe-west1' })
+  assert(ctx.project === 'stored-proj', 'stored project is used when explicit is missing')
+  assert(ctx.region === 'europe-west1', 'stored region is used when explicit is missing')
+  assert(ctx.apiKey === 'tok' && ctx.providerId === 'vertex', 'api key and provider pass through')
+}
+{
+  const ctx = buildProbeContext({ providerId: 'vertex', apiKey: 'tok', project: 'explicit-proj', region: 'us-central1', storedProject: 'stored-proj', storedRegion: 'europe-west1' })
+  assert(ctx.project === 'explicit-proj', 'explicit project wins over stored')
+  assert(ctx.region === 'us-central1', 'explicit region wins over stored')
+}
+{
+  const ctx = buildProbeContext({ providerId: 'vertex', apiKey: 'tok', project: '  ', region: '', storedProject: ' stored-proj ', storedRegion: ' europe-west1 ' })
+  assert(ctx.project === 'stored-proj', 'blank explicit project falls back to trimmed stored')
+  assert(ctx.region === 'europe-west1', 'blank explicit region falls back to trimmed stored')
+}
+{
+  const ctx = buildProbeContext({ providerId: 'vertex', apiKey: 'tok', storedProject: '  ', storedRegion: '' })
+  assert(ctx.project === undefined, 'blank stored project becomes undefined')
+  assert(ctx.region === undefined, 'blank stored region becomes undefined')
+}
+{
+  const ctx = buildProbeContext({ providerId: 'anthropic' })
+  assert(ctx.apiKey === '', 'missing api key becomes empty string')
+  assert(ctx.project === undefined && ctx.region === undefined, 'non-cloud provider has no project or region')
+}
+assert(probeRequiresApiKey('aws') === false, 'aws probe does not require a vault api key')
+assert(probeRequiresApiKey('gcp') === true, 'gcp probe requires a token')
+assert(probeRequiresApiKey('azure') === true, 'azure probe requires a key')
+assert(probeRequiresApiKey('anthropicModels') === true, 'anthropic probe requires a key')
+assert(probeRequiresApiKey(undefined) === true, 'unknown probe kind requires a key by default')
+
+if (failed > 0) {
+  console.error(`\n${failed} probe context case(s) failed`)
+  process.exit(1)
+}
+console.log('\nall probe context cases passed')
diff --git a/scripts/test-secrets.mjs b/scripts/test-secrets.mjs
index e8c9800..fa42dce 100644
--- a/scripts/test-secrets.mjs
+++ b/scripts/test-secrets.mjs
@@ -16,7 +16,7 @@ if (!existsSync(secretsJs)) {
 }
 
 const require = createRequire(import.meta.url)
-const { secretIdForProvider, providerIdFromSecretId } = require(secretsJs)
+const { secretIdForProvider, providerIdFromSecretId, secretIdForProviderConfig, providerConfigFromSecretId, isProviderConfigSecretId } = require(secretsJs)
 
 let failed = 0
 function assert(cond, msg) {
@@ -33,6 +33,16 @@ assert(providerIdFromSecretId('provider:anthropic:api_key') === 'anthropic', 'pa
 assert(providerIdFromSecretId('provider:openai:api_key') === 'openai', 'parse openai')
 assert(providerIdFromSecretId('random') === null, 'reject non-canonical')
 assert(providerIdFromSecretId(secretIdForProvider('groq')) === 'groq', 'round-trip')
+assert(secretIdForProviderConfig('vertex', 'project') === 'provider:vertex:project', 'vertex project secret id')
+assert(secretIdForProviderConfig('vertex', 'region') === 'provider:vertex:region', 'vertex region secret id')
+assert(JSON.stringify(providerConfigFromSecretId('provider:vertex:project')) === JSON.stringify({ providerId: 'vertex', field: 'project' }), 'parse vertex project config id')
+assert(JSON.stringify(providerConfigFromSecretId('provider:vertex:region')) === JSON.stringify({ providerId: 'vertex', field: 'region' }), 'parse vertex region config id')
+assert(providerConfigFromSecretId('provider:vertex:api_key') === null, 'api_key is not a config id')
+assert(providerConfigFromSecretId('provider:vertex:other') === null, 'unknown field is not a config id')
+assert(providerConfigFromSecretId('random') === null, 'reject non-canonical config id')
+assert(isProviderConfigSecretId('provider:vertex:project') === true, 'isProviderConfigSecretId accepts project')
+assert(isProviderConfigSecretId('provider:vertex:api_key') === false, 'isProviderConfigSecretId rejects api_key')
+assert(providerIdFromSecretId('provider:vertex:project') === null, 'config id does not parse as api_key')
 
 if (failed > 0) {
   console.error(`\n${failed} secrets assertion(s) failed`)
diff --git a/src/main/ipc.ts b/src/main/ipc.ts
index 36456e3..d6b1dff 100644
--- a/src/main/ipc.ts
+++ b/src/main/ipc.ts
@@ -4,6 +4,8 @@ import { createSafeStorageBackend } from './secrets/safestorage'
 import { maskSecret } from './secrets/backend'
 import type { SecretBackend } from './secrets/backend'
 import { runProbe } from './probes'
+import { buildProbeContext, probeRequiresApiKey } from './probes/context'
+import { secretIdForProviderConfig } from '../shared/secrets'
 import { runHarnessUsage, runProviderUsage } from './usage'
 import { libraryDiscover } from './library'
 import { discoverAll, installHarness, uninstallHarness } from './installer'
@@ -43,6 +45,8 @@ interface ProbeRequest {
   secretId?: string
   apiKey?: string
   baseUrl?: string
+  project?: string
+  region?: string
 }
 
 type UsageRequest =
@@ -312,14 +316,28 @@ export function registerIpcHandlers(): void {
 
   ipcMain.handle(CHANNELS.probeRun, async (_evt, req: ProbeRequest) => {
     try {
+      const provider = findProvider(req.providerId)
       let apiKey = req.apiKey
       if (!apiKey && req.secretId) {
         apiKey = (await getBackend().get(req.secretId)) ?? undefined
       }
-      if (!apiKey) {
+      if (!apiKey && probeRequiresApiKey(provider?.probeKind)) {
         return { ok: false as const, error: 'No API key available for probe.' }
       }
-      const result = await runProbe({ providerId: req.providerId, apiKey, baseUrl: req.baseUrl })
+      const backend = getBackend()
+      const storedProject = req.project ? undefined : await backend.get(secretIdForProviderConfig(req.providerId, 'project')).catch(() => null)
+      const storedRegion = req.region ? undefined : await backend.get(secretIdForProviderConfig(req.providerId, 'region')).catch(() => null)
+      const result = await runProbe(
+        buildProbeContext({
+          providerId: req.providerId,
+          apiKey,
+          baseUrl: req.baseUrl,
+          project: req.project,
+          region: req.region,
+          storedProject,
+          storedRegion,
+        }),
+      )
       return { ok: true as const, result }
     } catch (err) {
       return { ok: false as const, error: errMsg(err) }
diff --git a/src/main/probes/context.ts b/src/main/probes/context.ts
new file mode 100644
index 0000000..07cd4a8
--- /dev/null
+++ b/src/main/probes/context.ts
@@ -0,0 +1,37 @@
+import type { ProbeContext } from './index'
+import type { ProbeKind } from './types'
+
+export interface ProbeContextInput {
+  providerId: string
+  apiKey?: string
+  baseUrl?: string
+  /** Explicit project from the probe request. Wins over the stored value. */
+  project?: string
+  /** Explicit region from the probe request. Wins over the stored value. */
+  region?: string
+  /** Project read from the vault beside the API key. */
+  storedProject?: string | null
+  /** Region read from the vault beside the API key. */
+  storedRegion?: string | null
+}
+
+function trimmed(value: string | null | undefined): string | undefined {
+  const next = value?.trim()
+  return next ? next : undefined
+}
+
+/** Build a probe context, preferring explicit fields over stored vault config. */
+export function buildProbeContext(input: ProbeContextInput): ProbeContext {
+  return {
+    providerId: input.providerId,
+    apiKey: input.apiKey ?? '',
+    baseUrl: input.baseUrl,
+    project: trimmed(input.project) ?? trimmed(input.storedProject),
+    region: trimmed(input.region) ?? trimmed(input.storedRegion),
+  }
+}
+
+/** The aws probe reads the AWS env chain, so it needs no vault API key. */
+export function probeRequiresApiKey(probeKind: ProbeKind | string | undefined): boolean {
+  return probeKind !== 'aws'
+}
diff --git a/src/preload/api.ts b/src/preload/api.ts
index ca76613..0be8b8c 100644
--- a/src/preload/api.ts
+++ b/src/preload/api.ts
@@ -186,6 +186,8 @@ export interface ProviderSummary {
   featured?: boolean
   envKeys: string[]
   baseUrlEnv?: string
+  authType?: string
+  probeKind?: string
   defaultBaseUrl?: string
   notes?: string
 }
@@ -243,6 +245,10 @@ export interface ProbeRequest {
   secretId?: string
   apiKey?: string
   baseUrl?: string
+  /** GCP project id for the Vertex probe. Falls back to the vault value in main. */
+  project?: string
+  /** Cloud region for the Vertex and Bedrock probes. Falls back to the vault value in main. */
+  region?: string
 }
 
 export interface ProbeResponse {
diff --git a/src/renderer/App.tsx b/src/renderer/App.tsx
index 6fbe35e..d1ef69c 100644
--- a/src/renderer/App.tsx
+++ b/src/renderer/App.tsx
@@ -39,7 +39,7 @@ import {
   type DoctorAction,
   type DoctorFinding,
 } from '../shared/doctor'
-import { providerIdFromSecretId, secretIdForProvider } from '../shared/secrets'
+import { isProviderConfigSecretId, providerIdFromSecretId, secretIdForProvider, secretIdForProviderConfig } from '../shared/secrets'
 
 declare global {
   interface Window {
@@ -394,7 +394,7 @@ export function App() {
         return
       }
       const byId = new Map(providerList.map((p) => [p.id, p]))
-      const rows: KeyRow[] = vaultRes.entries.map((e: VaultEntry) => {
+      const rows: KeyRow[] = vaultRes.entries.filter((e: VaultEntry) => !isProviderConfigSecretId(e.id)).map((e: VaultEntry) => {
         const pid = providerIdFromSecretId(e.id) ?? e.id
         const prov = byId.get(pid)
         return {
@@ -504,7 +504,15 @@ export function App() {
     try {
       const res = await window.hoist.vault.delete(secretId)
       if (!res.ok) showToast(res.error ?? 'Delete failed')
-      else showToast('Key deleted')
+      else {
+        const pid = providerIdFromSecretId(secretId)
+        if (pid) {
+          for (const field of ['project', 'region'] as const) {
+            await window.hoist.vault.delete(secretIdForProviderConfig(pid, field)).catch(() => undefined)
+          }
+        }
+        showToast('Key deleted')
+      }
       await refreshKeys()
     } catch (err) {
       showToast(err instanceof Error ? err.message : String(err))
@@ -523,10 +531,16 @@ export function App() {
     }
   }, [showToast])
 
-  const saveKey = useCallback(async (providerId: string, value: string, label: string) => {
+  const saveKey = useCallback(async (providerId: string, value: string, label: string, config?: { project: string; region: string }) => {
     const id = secretIdForProvider(providerId)
     const res = await window.hoist.vault.set({ id, value, label })
     if (!res.ok) throw new Error(res.error ?? 'Failed to save key')
+    if (config) {
+      const projectRes = await window.hoist.vault.set({ id: secretIdForProviderConfig(providerId, 'project'), value: config.project, label: `${label} project` })
+      if (!projectRes.ok) throw new Error(projectRes.error ?? 'Failed to save project')
+      const regionRes = await window.hoist.vault.set({ id: secretIdForProviderConfig(providerId, 'region'), value: config.region, label: `${label} region` })
+      if (!regionRes.ok) throw new Error(regionRes.error ?? 'Failed to save region')
+    }
     await refreshKeys()
     setSelectedKeyId(id)
     // Best-effort probe after save
@@ -775,8 +789,8 @@ export function App() {
           providers={providers}
           existingIds={new Set(keys.map((k) => k.providerId))}
           onClose={() => setAddKeyOpen(false)}
-          onSave={async (providerId, value, label) => {
-            await saveKey(providerId, value, label)
+          onSave={async (providerId, value, label, config) => {
+            await saveKey(providerId, value, label, config)
             setAddKeyOpen(false)
           }}
         />
@@ -2087,17 +2101,20 @@ function AddKeyModal({
   providers: ProviderSummary[]
   existingIds: Set<string>
   onClose: () => void
-  onSave: (providerId: string, value: string, label: string) => Promise<void>
+  onSave: (providerId: string, value: string, label: string, config?: { project: string; region: string }) => Promise<void>
 }) {
   const [step, setStep] = useState<'pick' | 'enter'>('pick')
   const [picked, setPicked] = useState<ProviderSummary | null>(null)
   const [query, setQuery] = useState('')
   const [value, setValue] = useState('')
+  const [project, setProject] = useState('')
+  const [region, setRegion] = useState('')
   const [error, setError] = useState<string | null>(null)
   const [saving, setSaving] = useState(false)
+  const isVertex = picked?.id === 'vertex'
 
   const list = providers
-    .filter((p) => p.envKeys && p.envKeys.length > 0)
+    .filter((p) => (p.envKeys && p.envKeys.length > 0) || p.id === 'vertex')
     .filter((p) => {
       if (!query) return true
       const q = query.toLowerCase()
@@ -2107,10 +2124,11 @@ function AddKeyModal({
 
   const submit = async () => {
     if (!picked || !value.trim()) return
+    if (isVertex && (!project.trim() || !region.trim())) return
     setSaving(true)
     setError(null)
     try {
-      await onSave(picked.id, value.trim(), picked.label)
+      await onSave(picked.id, value.trim(), picked.label, isVertex ? { project: project.trim(), region: region.trim() } : undefined)
     } catch (err) {
       setError(err instanceof Error ? err.message : String(err))
       setSaving(false)
@@ -2151,7 +2169,7 @@ function AddKeyModal({
                         {p.label}
                         {existingIds.has(p.id) && <span className="badge" style={{ marginLeft: 6 }}>stored</span>}
                       </div>
-                      <div className="hoist-catalogue-tile-sub muted mono">{p.envKeys[0]}</div>
+                      <div className="hoist-catalogue-tile-sub muted mono">{p.envKeys[0] ?? 'PROJECT + REGION'}</div>
                     </div>
                   </button>
                 ))}
@@ -2161,14 +2179,35 @@ function AddKeyModal({
             <div className="hoist-addkey-form">
               <p className="muted" style={{ marginTop: 0 }}>
                 Stored as <span className="mono">{secretIdForProvider(picked!.id)}</span>.
-                Env: <span className="mono">{picked!.envKeys[0]}</span>
+                {isVertex ? ' Project and region are stored beside the token.' : <> Env: <span className="mono">{picked!.envKeys[0]}</span></>}
               </p>
-              <label className="hoist-field-label" htmlFor="key-value">API key</label>
+              {isVertex && (
+                <>
+                  <label className="hoist-field-label" htmlFor="vertex-project">GCP project id</label>
+                  <input
+                    id="vertex-project"
+                    className="input input-lg"
+                    autoFocus
+                    placeholder="my-gcp-project"
+                    value={project}
+                    onChange={(e) => setProject(e.target.value)}
+                  />
+                  <label className="hoist-field-label" htmlFor="vertex-region">Region</label>
+                  <input
+                    id="vertex-region"
+                    className="input input-lg"
+                    placeholder="us-central1"
+                    value={region}
+                    onChange={(e) => setRegion(e.target.value)}
+                  />
+                </>
+              )}
+              <label className="hoist-field-label" htmlFor="key-value">{isVertex ? 'Access token' : 'API key'}</label>
               <input
                 id="key-value"
                 className="input input-lg"
                 type="password"
-                autoFocus
+                autoFocus={!isVertex}
                 placeholder="Paste secret…"
                 value={value}
                 onChange={(e) => setValue(e.target.value)}
@@ -2184,7 +2223,7 @@ function AddKeyModal({
                 <button
                   type="button"
                   className="btn btn-primary btn-sm btn-pill"
-                  disabled={saving || !value.trim()}
+                  disabled={saving || !value.trim() || (isVertex && (!project.trim() || !region.trim()))}
                   onClick={() => void submit()}
                 >
                   {saving ? 'Saving…' : 'Save key'}
diff --git a/src/shared/secrets.ts b/src/shared/secrets.ts
index 9055be5..c365e89 100644
--- a/src/shared/secrets.ts
+++ b/src/shared/secrets.ts
@@ -8,3 +8,24 @@ export function providerIdFromSecretId(secretId: string): string | null {
   const m = /^provider:([^:]+):api_key$/.exec(secretId)
   return m ? m[1] : null
 }
+
+/** Non-credential config a provider probe needs, stored beside the API key. */
+export type ProviderConfigField = 'project' | 'region'
+
+/** Canonical vault secret id for a provider config field, for example `provider:vertex:project`. */
+export function secretIdForProviderConfig(providerId: string, field: ProviderConfigField): string {
+  return `provider:${providerId}:${field}`
+}
+
+/** Extract provider id and field from a provider config secret id, if it matches. */
+export function providerConfigFromSecretId(
+  secretId: string,
+): { providerId: string; field: ProviderConfigField } | null {
+  const m = /^provider:([^:]+):(project|region)$/.exec(secretId)
+  return m ? { providerId: m[1], field: m[2] as ProviderConfigField } : null
+}
+
+/** True when the secret id holds provider config, not a credential. */
+export function isProviderConfigSecretId(secretId: string): boolean {
+  return providerConfigFromSecretId(secretId) !== null
+}