From 2bbacacca3c523eb1d5705ab881b6a0ceaa1b4f8 Mon Sep 17 00:00:00 2001
From: marcusquinn <6428977+marcusquinn@users.noreply.github.com>
Date: Sat, 14 Mar 2026 16:28:51 +0000
Subject: [PATCH] fix: is_model_available returns failure for unknown providers

PR #2366 review feedback (issue #3210): the unknown-provider branch
previously returned 0 (success), allowing resolve_chain to emit a model
string with no credential or health verification. This produces silent
runtime failures when the routing table is extended beyond the known
providers (anthropic/openai/google).

Change: return 1 with a warning for unknown providers, consistent with
the existing behaviour for known providers with missing API keys. The
model-availability-helper.sh delegation path is unaffected.
---
 .agents/scripts/fallback-chain-helper.sh | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/.agents/scripts/fallback-chain-helper.sh b/.agents/scripts/fallback-chain-helper.sh
index e386a4e96..3e5255a4f 100755
--- a/.agents/scripts/fallback-chain-helper.sh
+++ b/.agents/scripts/fallback-chain-helper.sh
@@ -109,8 +109,10 @@ is_model_available() {
 		return 1
 	fi
 
-	# Unknown provider — assume available (AI will handle errors)
-	return 0
+	# Unknown provider — fail explicitly so resolve_chain skips to the next model
+	# rather than emitting a model string with no credential/health verification.
+	[[ "$quiet" != "true" ]] && print_warning "Unknown provider: $provider (no availability check available)" >&2
+	return 1
 }
 
 # Walk the tier's model list and return the first available model.