diff --git a/pkg/workflow/testdata/TestWasmGolden_CompileFixtures/basic-copilot.golden b/pkg/workflow/testdata/TestWasmGolden_CompileFixtures/basic-copilot.golden
index 97e86e73c31..4216c17bfcc 100644
--- a/pkg/workflow/testdata/TestWasmGolden_CompileFixtures/basic-copilot.golden
+++ b/pkg/workflow/testdata/TestWasmGolden_CompileFixtures/basic-copilot.golden
@@ -409,8 +409,9 @@ jobs:
             -- /bin/bash -c 'GH_AW_NODE_EXEC="${GH_AW_NODE_BIN:-}"; if [ -z "$GH_AW_NODE_EXEC" ] || [ ! -x "$GH_AW_NODE_EXEC" ]; then GH_AW_NODE_EXEC="$(command -v node 2>/dev/null || echo node)"; fi; "$GH_AW_NODE_EXEC" ${RUNNER_TEMP}/gh-aw/actions/copilot_driver.cjs /usr/local/bin/copilot --add-dir /tmp/gh-aw/ --log-level all --log-dir /tmp/gh-aw/sandbox/agent/logs/ --disable-builtin-mcps --no-ask-user --allow-all-tools --allow-all-paths --add-dir "${GITHUB_WORKSPACE}" --prompt-file /tmp/gh-aw/aw-prompts/prompt.txt' 2>&1 | tee -a /tmp/gh-aw/agent-stdio.log
         env:
           COPILOT_AGENT_RUNNER_TYPE: STANDALONE
+          COPILOT_API_KEY: dummy-byok-key-for-offline-mode
           COPILOT_GITHUB_TOKEN: ${{ secrets.COPILOT_GITHUB_TOKEN }}
-          COPILOT_MODEL: ${{ vars.GH_AW_MODEL_DETECTION_COPILOT || '' }}
+          COPILOT_MODEL: ${{ vars.GH_AW_MODEL_DETECTION_COPILOT || 'claude-sonnet-4.6' }}
           GH_AW_MCP_CONFIG: /home/runner/.copilot/mcp-config.json
           GH_AW_PHASE: agent
           GH_AW_PROMPT: /tmp/gh-aw/aw-prompts/prompt.txt
diff --git a/pkg/workflow/testdata/TestWasmGolden_CompileFixtures/with-imports.golden b/pkg/workflow/testdata/TestWasmGolden_CompileFixtures/with-imports.golden
index 905637124d5..9b105c18c6c 100644
--- a/pkg/workflow/testdata/TestWasmGolden_CompileFixtures/with-imports.golden
+++ b/pkg/workflow/testdata/TestWasmGolden_CompileFixtures/with-imports.golden
@@ -410,8 +410,9 @@ jobs:
             -- /bin/bash -c 'GH_AW_NODE_EXEC="${GH_AW_NODE_BIN:-}"; if [ -z "$GH_AW_NODE_EXEC" ] || [ ! -x "$GH_AW_NODE_EXEC" ]; then GH_AW_NODE_EXEC="$(command -v node 2>/dev/null || echo node)"; fi; "$GH_AW_NODE_EXEC" ${RUNNER_TEMP}/gh-aw/actions/copilot_driver.cjs /usr/local/bin/copilot --add-dir /tmp/gh-aw/ --log-level all --log-dir /tmp/gh-aw/sandbox/agent/logs/ --disable-builtin-mcps --no-ask-user --allow-all-tools --allow-all-paths --add-dir "${GITHUB_WORKSPACE}" --prompt-file /tmp/gh-aw/aw-prompts/prompt.txt' 2>&1 | tee -a /tmp/gh-aw/agent-stdio.log
         env:
           COPILOT_AGENT_RUNNER_TYPE: STANDALONE
+          COPILOT_API_KEY: dummy-byok-key-for-offline-mode
           COPILOT_GITHUB_TOKEN: ${{ secrets.COPILOT_GITHUB_TOKEN }}
-          COPILOT_MODEL: ${{ vars.GH_AW_MODEL_DETECTION_COPILOT || '' }}
+          COPILOT_MODEL: ${{ vars.GH_AW_MODEL_DETECTION_COPILOT || 'claude-sonnet-4.6' }}
           GH_AW_MCP_CONFIG: /home/runner/.copilot/mcp-config.json
           GH_AW_PHASE: agent
           GH_AW_PROMPT: /tmp/gh-aw/aw-prompts/prompt.txt
diff --git a/pkg/workflow/threat_detection_test.go b/pkg/workflow/threat_detection_test.go
index cc4fe1e079d..5a1e4ae7683 100644
--- a/pkg/workflow/threat_detection_test.go
+++ b/pkg/workflow/threat_detection_test.go
@@ -1087,7 +1087,7 @@ func TestCopilotDetectionDefaultModel(t *testing.T) {
 			shouldContainModel: true,
 			// Detection uses env var fallback (same pattern as main agent), allowing
 			// the Copilot CLI to pick its native default (currently claude-sonnet-4.6)
-			expectedModel: "${{ vars." + constants.EnvVarModelDetectionCopilot + " || '' }}",
+			expectedModel: "${{ vars." + constants.EnvVarModelDetectionCopilot + " || '" + constants.CopilotBYOKDefaultModel + "' }}",
 		},
 		{
 			name: "copilot engine with custom model uses specified model",
@@ -1133,7 +1133,7 @@ func TestCopilotDetectionDefaultModel(t *testing.T) {
 				},
 			},
 			shouldContainModel: true,
-			expectedModel:      "${{ vars." + constants.EnvVarModelDetectionCopilot + " || '' }}",
+			expectedModel:      "${{ vars." + constants.EnvVarModelDetectionCopilot + " || '" + constants.CopilotBYOKDefaultModel + "' }}",
 		},
 		{
 			name: "claude engine does not add model parameter",