diff --git a/.github/workflows/opencode-review.yml b/.github/workflows/opencode-review.yml
index 2253da17e..e88cd0bfa 100644
--- a/.github/workflows/opencode-review.yml
+++ b/.github/workflows/opencode-review.yml
@@ -2995,6 +2995,23 @@ jobs:
                   "apiKey": "{env:OPENAI_API_KEY}"
                 },
                 "models": {
+                  "gpt-5.6-luna": {
+                    "name": "OpenAI GPT-5.6 Luna (direct)",
+                    "tool_call": true,
+                    "reasoning": true,
+                    "options": {
+                      "reasoningEffort": "high"
+                    },
+                    "variants": {
+                      "high": {
+                        "reasoningEffort": "high"
+                      }
+                    },
+                    "limit": {
+                      "context": 1000000,
+                      "output": 128000
+                    }
+                  },
                   "gpt-5": {
                     "name": "OpenAI GPT-5 (direct)",
                     "tool_call": true,
@@ -3253,7 +3270,11 @@ jobs:
           # High-sensitivity review candidates only. DeepSeek V3 has been the
           # most reliable first-pass reviewer in the org queue, then the pool
           # falls through to full-size GPT/o3 and reasoning-capable fallbacks.
-          OPENCODE_MODEL_CANDIDATES: "github-models/deepseek/deepseek-v3-0324 openai/gpt-5 github-models/openai/gpt-5 github-models/openai/gpt-5-chat github-models/openai/o3 github-models/deepseek/deepseek-r1-0528 github-models/deepseek/deepseek-r1"
+          # The direct-OpenAI slot runs GPT-5.6 Luna: the newest family's
+          # cost-efficient tier, cheaper than the legacy gpt-5 it replaced
+          # ($1/$6 vs $1.25/$10 per 1M tokens) so the org OpenAI budget
+          # stretches further between top-ups.
+          OPENCODE_MODEL_CANDIDATES: "github-models/deepseek/deepseek-v3-0324 openai/gpt-5.6-luna github-models/openai/gpt-5 github-models/openai/gpt-5-chat github-models/openai/o3 github-models/deepseek/deepseek-r1-0528 github-models/deepseek/deepseek-r1"
           # One attempt per model, then fall through to the next model. Retrying
           # the SAME model 5x let a rate-limited/hung leader consume the whole
           # step, so the pool never reached a healthy fallback model.
diff --git a/tests/test_opencode_agent_contract.py b/tests/test_opencode_agent_contract.py
index d7b425eba..d543bb728 100644
--- a/tests/test_opencode_agent_contract.py
+++ b/tests/test_opencode_agent_contract.py
@@ -86,14 +86,14 @@ def test_opencode_model_pool_sets_high_effort_for_capable_candidates():
     assert candidate_pairs
     assert candidate_pairs == [
         ["github-models", "deepseek/deepseek-v3-0324"],
-        ["openai", "gpt-5"],
+        ["openai", "gpt-5.6-luna"],
         ["github-models", "openai/gpt-5"],
         ["github-models", "openai/gpt-5-chat"],
         ["github-models", "openai/o3"],
         ["github-models", "deepseek/deepseek-r1-0528"],
         ["github-models", "deepseek/deepseek-r1"],
     ]
-    assert direct_openai_models == ["gpt-5"]
+    assert direct_openai_models == ["gpt-5.6-luna"]
     assert set(github_candidate_models).issubset(set(github_models))
     assert github_candidate_models == [
         "deepseek/deepseek-v3-0324",
@@ -681,7 +681,7 @@ def test_workflow_provisions_sandbox_tool_and_reviewer_agent():
     assert "Skipping publish-step failed-check OpenCode diagnosis for central review-process self-repair" in workflow
     assert (
         'OPENCODE_MODEL_CANDIDATES: "github-models/deepseek/deepseek-v3-0324 '
-        "openai/gpt-5 "
+        "openai/gpt-5.6-luna "
         "github-models/openai/gpt-5 "
         "github-models/openai/gpt-5-chat "
         "github-models/openai/o3 "
@@ -767,7 +767,7 @@ def test_workflow_provisions_sandbox_tool_and_reviewer_agent():
     assert 'OPENCODE_MODEL_CANDIDATES: "github-models/openai/gpt-5-nano"' not in workflow
     assert (
         'OPENCODE_MODEL_CANDIDATES: "github-models/deepseek/deepseek-v3-0324 '
-        "openai/gpt-5 "
+        "openai/gpt-5.6-luna "
         "github-models/openai/gpt-5 "
         "github-models/openai/gpt-5-chat "
         "github-models/openai/o3 "