diff --git a/.env.example b/.env.example
index 420f3f1..094c788 100644
--- a/.env.example
+++ b/.env.example
@@ -25,14 +25,18 @@ VITE_API_URL=http://localhost:2000   # local | prod: https://agos.armco.dev
 # IAM is deployed at https://iam.armco.dev
 # Issuer claim in JWTs: stuffle-iam  |  Audience for AGOS API: stuffle-api
 #
-# SPA clients registered (frontend only — no secret, PKCE):
-#   local IAM (localhost:5000): client_53ab7b22d1d845d5a435b21e9e0b15e1  → http://localhost:2001/callback
-#   remote dev IAM:             client_5bb63e4ae1644c9d97ffc84a5d228c7c  → http://localhost:2001/callback
-#   prod:                       client_2dbeb454ddf14203b092eb4636a8e3d7  → https://agos.stuffle.ai/callback
+# Client ID selection uses TWO axes (resolved automatically in iam.ts):
+#   1. VITE_IAM_PROVIDER_ENV — which IAM server ("local" | "prod", default "prod")
+#   2. import.meta.env.MODE  — "development" (vite dev) or "production" (vite build)
 #
-# Set VITE_IAM_PROVIDER_ENV to select which IAM to use:
-#   "local" → http://localhost:5000  + local client
-#   "prod"  → https://iam.armco.dev  + prod/dev client  (default when unset)
+# Registered SPA clients (frontend only — no secret, PKCE):
+#   IAM local  + agOS local  → client_53ab7b22d1d845d5a435b21e9e0b15e1  (localhost:2001/callback)
+#   IAM prod   + agOS local  → client_5bb63e4ae1644c9d97ffc84a5d228c7c  (localhost:2001/callback)
+#   IAM prod   + agOS prod   → client_2dbeb454ddf14203b092eb4636a8e3d7  (agos.stuffle.ai/callback)
+#
+# Set VITE_IAM_PROVIDER_ENV to select which IAM server to talk to:
+#   "local" → http://localhost:5000   (for local IAM dev)
+#   "prod"  → https://iam.armco.dev  (default when unset)
 VITE_IAM_PROVIDER_ENV=prod
 VITE_IAM_AUDIENCE=stuffle-api
 # Optional when IAM expects OAuth resource indicators in addition to audience.
diff --git a/src/auth/iam.ts b/src/auth/iam.ts
index d2e73e5..cae95e8 100644
--- a/src/auth/iam.ts
+++ b/src/auth/iam.ts
@@ -20,24 +20,48 @@ import { createStuffleIAMClient } from '@armco/iam-client'
 import { DEV_BYPASS_ACTIVE as _devBypassActive } from './dev-bypass'
 import { recordAuthTelemetry } from './authTelemetry'
 
-const _IAM_CONFIGS = {
-  local: {
-    issuer: 'http://localhost:5000',
-    clientId: 'client_53ab7b22d1d845d5a435b21e9e0b15e1',
-  },
-  prod: {
-    issuer: 'https://iam.armco.dev',
-    clientId: 'client_2dbeb454ddf14203b092eb4636a8e3d7',
-  },
+// ── IAM issuer lookup (which IAM server) ────────────────────────────────────
+const _IAM_ISSUERS = {
+  local: 'http://localhost:5000',
+  prod: 'https://iam.armco.dev',
 } as const
 
+// ── Client ID matrix: [iamEnv][agosEnv] ─────────────────────────────────────
+// Each IAM server has separate registered clients for "agOS running locally"
+// vs "agOS running in production" (different redirect URIs).
+//
+//  iamEnv  × agosEnv   → registered client
+//  local   × local     → "agOS local" in local IAM  (redirect: localhost:2001)
+//  prod    × local     → "agOS local" in prod IAM   (redirect: localhost:2001)
+//  prod    × prod      → "agOS"       in prod IAM   (redirect: agos.stuffle.ai)
+//  local   × prod      → not a real scenario (prod deploy never talks to local IAM)
+const _IAM_CLIENT_IDS: Record<string, Record<string, string>> = {
+  local: {
+    local: 'client_53ab7b22d1d845d5a435b21e9e0b15e1',
+  },
+  prod: {
+    local: 'client_5bb63e4ae1644c9d97ffc84a5d228c7c',
+    prod:  'client_2dbeb454ddf14203b092eb4636a8e3d7',
+  },
+}
+
+// VITE_IAM_PROVIDER_ENV selects which IAM server to talk to
 const _iamProviderEnv = (import.meta.env.VITE_IAM_PROVIDER_ENV as string | undefined) ?? 'prod'
 if (_iamProviderEnv !== 'local' && _iamProviderEnv !== 'prod') {
   console.warn(`[iam] Unrecognized VITE_IAM_PROVIDER_ENV="${_iamProviderEnv}". Falling back to "prod".`)
 }
-const _iamConfig = _iamProviderEnv === 'local' ? _IAM_CONFIGS.local : _IAM_CONFIGS.prod
-const _issuer = _iamConfig.issuer
-const _clientId = _iamConfig.clientId
+// import.meta.env.MODE is "development" during `vite dev`, "production" during `vite build`
+const _agosEnv = import.meta.env.MODE === 'development' ? 'local' : 'prod'
+const _resolvedIamEnv = _iamProviderEnv === 'local' ? 'local' : 'prod'
+const _issuer = _IAM_ISSUERS[_resolvedIamEnv]
+const _clientId = _IAM_CLIENT_IDS[_resolvedIamEnv]?.[_agosEnv] ?? ''
+
+if (_clientId === '') {
+  console.warn(
+    `[iam] No client ID for iamEnv="${_resolvedIamEnv}" + agosEnv="${_agosEnv}". ` +
+    'This combination may not be registered. Check _IAM_CLIENT_IDS in iam.ts.',
+  )
+}
 
 /** Resolved IAM issuer URL for the active provider env. Use this instead of reading env vars directly. */
 export const iamIssuer = _issuer
@@ -77,7 +101,8 @@ const _createClient = () => {
   const redirectUri = _getEffectiveRedirectUri()
   const clientId = _getEffectiveClientId()
   console.info('[agos:auth] creating IAM client', {
-    providerEnv: _iamProviderEnv,
+    iamProviderEnv: _resolvedIamEnv,
+    agosEnv: _agosEnv,
     issuer: _issuer ?? '',
     clientId,
     redirectUri,