From 3fffeb92702603deda1f6c7731d8719d41066ff0 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 28 Jul 2026 04:20:32 +0000
Subject: [PATCH 1/5] plan: engine.version support for
 copilot/claude/codex/gemini

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 .github/workflows/smoke-copilot-auto.lock.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/smoke-copilot-auto.lock.yml b/.github/workflows/smoke-copilot-auto.lock.yml
index 80f7930c2f1..5c316f6e8b8 100644
--- a/.github/workflows/smoke-copilot-auto.lock.yml
+++ b/.github/workflows/smoke-copilot-auto.lock.yml
@@ -149,7 +149,7 @@ jobs:
           GH_AW_INFO_FIREWALL_TYPE: "squid"
           GH_AW_INFO_FRONTMATTER_EMOJI: "🌸"
           GH_AW_COMPILED_STRICT: "true"
-          GH_AW_INFO_MODEL_COSTS: '{"providers":{"github-copilot":{"models":{"auto":{"cost":{"input":"8.5e-07","output":"1.55e-06"}}}}}}'
+          GH_AW_INFO_MODEL_COSTS: '{"providers":{"github-copilot":{"models":{"auto":{"cost":{"input":"0","output":"0"}}}}}}'
           GH_AW_INFO_FEATURES: '{"gh-aw-detection":false}'
         uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
         with:

From 42c5d3e80828d71ea7a9b33a28238ce27b5c6636 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 28 Jul 2026 04:27:21 +0000
Subject: [PATCH 2/5] feat: honor engine.version for copilot; add version tests
 for gemini

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 .github/workflows/smoke-copilot-auto.lock.yml |   1 -
 pkg/workflow/copilot_engine_installation.go   |  23 ++--
 pkg/workflow/copilot_installer_test.go        | 100 ++++++++++++------
 pkg/workflow/gemini_engine_test.go            |  63 +++++++++++
 4 files changed, 144 insertions(+), 43 deletions(-)

diff --git a/.github/workflows/smoke-copilot-auto.lock.yml b/.github/workflows/smoke-copilot-auto.lock.yml
index 5c316f6e8b8..9cac699d23d 100644
--- a/.github/workflows/smoke-copilot-auto.lock.yml
+++ b/.github/workflows/smoke-copilot-auto.lock.yml
@@ -149,7 +149,6 @@ jobs:
           GH_AW_INFO_FIREWALL_TYPE: "squid"
           GH_AW_INFO_FRONTMATTER_EMOJI: "🌸"
           GH_AW_COMPILED_STRICT: "true"
-          GH_AW_INFO_MODEL_COSTS: '{"providers":{"github-copilot":{"models":{"auto":{"cost":{"input":"0","output":"0"}}}}}}'
           GH_AW_INFO_FEATURES: '{"gh-aw-detection":false}'
         uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
         with:
diff --git a/pkg/workflow/copilot_engine_installation.go b/pkg/workflow/copilot_engine_installation.go
index aa8a9eb3077..ca4135865b2 100644
--- a/pkg/workflow/copilot_engine_installation.go
+++ b/pkg/workflow/copilot_engine_installation.go
@@ -142,21 +142,22 @@ func (e *CopilotEngine) GetInstallationSteps(workflowData *WorkflowData) []GitHu
 		return appendCopilotLSPInstallSteps(steps, workflowData)
 	}
 
-	// Copilot CLI is pinned to the default version constant.
+	// Use engine.version if provided, otherwise fall back to the default pinned version.
+	// When no explicit version is set, normalize the engine config so downstream
+	// consumers observe the effective installed value.
 	copilotVersion := string(constants.DefaultCopilotVersion)
 	if workflowData.EngineConfig != nil {
 		if workflowData.EngineConfig.Version != "" {
-			copilotInstallLog.Printf("Ignoring pinned engine.version (%s): Copilot CLI install version is pinned to %s", workflowData.EngineConfig.Version, copilotVersion)
+			copilotVersion = workflowData.EngineConfig.Version
+			copilotInstallLog.Printf("Using engine.version for Copilot CLI installation: %s", copilotVersion)
+		} else {
+			// Normalize engine config version to the effective installed version so
+			// downstream checks that consult EngineConfig.Version stay consistent.
+			// This mutates workflowData by design because subsequent generation steps
+			// in the same compile flow should observe the effective installed version.
+			workflowData.EngineConfig.Version = copilotVersion
+			copilotInstallLog.Printf("No engine.version specified, using default Copilot CLI version: %s", copilotVersion)
 		}
-		// Normalize engine config version to effective installed version so
-		// downstream checks that consult EngineConfig.Version stay consistent.
-		// This applies even when the original version was empty (unset), so all
-		// downstream consumers observe the effective installed value.
-		// This mutates workflowData by design because subsequent generation steps
-		// in the same compile flow should observe the effective installed version.
-		// Callers that reuse the same WorkflowData instance should expect this
-		// field to be rewritten after installation-step generation.
-		workflowData.EngineConfig.Version = copilotVersion
 	}
 
 	// Use the installer script for global installation
diff --git a/pkg/workflow/copilot_installer_test.go b/pkg/workflow/copilot_installer_test.go
index 72072020b41..4592205324e 100644
--- a/pkg/workflow/copilot_installer_test.go
+++ b/pkg/workflow/copilot_installer_test.go
@@ -108,8 +108,9 @@ func TestGenerateCopilotInstallerSteps(t *testing.T) {
 	}
 }
 
-func TestCopilotInstallerCustomVersion(t *testing.T) {
-	// Test that pinned version from engine config is ignored in favor of default pinned version
+func TestCopilotEngineWithVersion(t *testing.T) {
+	// engine.version must be honored: when an explicit version is set it should be
+	// passed to the installer and compat.json resolution must be skipped.
 	engine := NewCopilotEngine()
 
 	customVersion := "1.0.0"
@@ -119,14 +120,12 @@ func TestCopilotInstallerCustomVersion(t *testing.T) {
 			Version: customVersion,
 		},
 	}
-	if workflowData.EngineConfig.Version != customVersion {
-		t.Fatalf("Expected initial engine config version %q, got: %q", customVersion, workflowData.EngineConfig.Version)
-	}
 
 	steps := engine.GetInstallationSteps(workflowData)
 
-	if workflowData.EngineConfig.Version != string(constants.DefaultCopilotVersion) {
-		t.Fatalf("Expected engine config version to be normalized to default Copilot version %q, got: %q", constants.DefaultCopilotVersion, workflowData.EngineConfig.Version)
+	// EngineConfig.Version must remain as the user-specified value.
+	if workflowData.EngineConfig.Version != customVersion {
+		t.Fatalf("Expected engine config version to remain %q, got: %q", customVersion, workflowData.EngineConfig.Version)
 	}
 
 	// Find the install step
@@ -143,23 +142,58 @@ func TestCopilotInstallerCustomVersion(t *testing.T) {
 		t.Fatal("Could not find install step with install_copilot_cli.sh")
 	}
 
-	// Should contain default pinned version
-	if !strings.Contains(installStep, `install_copilot_cli.sh" `+string(constants.DefaultCopilotVersion)) {
-		t.Errorf("Expected default Copilot version in install step, got:\n%s", installStep)
+	// Should pass the user-specified version to the installer (compat.json skipped).
+	if !strings.Contains(installStep, `install_copilot_cli.sh" `+customVersion) {
+		t.Errorf("Expected user-specified version %q in install step, got:\n%s", customVersion, installStep)
 	}
-	if strings.Contains(installStep, `install_copilot_cli.sh" `+customVersion) {
-		t.Errorf("Expected pinned version to be ignored, got:\n%s", installStep)
+	if strings.Contains(installStep, `install_copilot_cli.sh" `+string(constants.DefaultCopilotVersion)) {
+		t.Errorf("Expected user-specified version, not default version, in install step:\n%s", installStep)
 	}
 
 	// Must pin GH_HOST: github.com to prevent workflow-level GHES overrides from
-	// leaking into the Copilot CLI install step. Without this pin, a workflow with
-	// env.GH_HOST set to a GHES host would cause the install/auth path to target
-	// the wrong host.
+	// leaking into the Copilot CLI install step.
 	if !strings.Contains(installStep, "GH_HOST: github.com") {
 		t.Errorf("Install step should pin GH_HOST: github.com to prevent GHES workflow-level overrides, got:\n%s", installStep)
 	}
 }
 
+func TestCopilotEngineWithoutVersion(t *testing.T) {
+	// When engine.version is not set, the default pinned version must be used and
+	// EngineConfig.Version must be normalized to the effective installed value.
+	engine := NewCopilotEngine()
+
+	workflowData := &WorkflowData{
+		Name:         "test-workflow",
+		EngineConfig: &EngineConfig{},
+	}
+
+	steps := engine.GetInstallationSteps(workflowData)
+
+	// EngineConfig.Version must be normalized to the default version.
+	if workflowData.EngineConfig.Version != string(constants.DefaultCopilotVersion) {
+		t.Fatalf("Expected engine config version to be normalized to default Copilot version %q, got: %q", constants.DefaultCopilotVersion, workflowData.EngineConfig.Version)
+	}
+
+	// Find the install step
+	var installStep string
+	for _, step := range steps {
+		stepContent := strings.Join(step, "\n")
+		if strings.Contains(stepContent, "install_copilot_cli.sh") {
+			installStep = stepContent
+			break
+		}
+	}
+
+	if installStep == "" {
+		t.Fatal("Could not find install step with install_copilot_cli.sh")
+	}
+
+	// Should use the default pinned version.
+	if !strings.Contains(installStep, `install_copilot_cli.sh" `+string(constants.DefaultCopilotVersion)) {
+		t.Errorf("Expected default Copilot version in install step, got:\n%s", installStep)
+	}
+}
+
 func TestGenerateCopilotInstallerSteps_ExpressionVersion(t *testing.T) {
 	tests := []struct {
 		name    string
@@ -248,8 +282,9 @@ func TestGenerateCopilotInstallerSteps_RootlessWithExpression(t *testing.T) {
 	}
 }
 
-func TestCopilotInstallerExpressionVersion_ViaEngineConfig(t *testing.T) {
-	// Test that expression version from engine config is ignored in favor of default pinned version
+func TestCopilotEngineWithExpressionVersion(t *testing.T) {
+	// expression engine.version must be honored: the value must flow through env-var
+	// injection (not embedded directly in the shell command) and compat.json must be skipped.
 	engine := NewCopilotEngine()
 
 	expressionVersion := "${{ inputs.engine-version }}"
@@ -262,8 +297,9 @@ func TestCopilotInstallerExpressionVersion_ViaEngineConfig(t *testing.T) {
 
 	steps := engine.GetInstallationSteps(workflowData)
 
-	if workflowData.EngineConfig.Version != string(constants.DefaultCopilotVersion) {
-		t.Fatalf("Expected engine config version to be normalized to default Copilot version %q, got: %q", constants.DefaultCopilotVersion, workflowData.EngineConfig.Version)
+	// EngineConfig.Version must remain as the expression value.
+	if workflowData.EngineConfig.Version != expressionVersion {
+		t.Fatalf("Expected engine config version to remain %q, got: %q", expressionVersion, workflowData.EngineConfig.Version)
 	}
 
 	// Find the install step
@@ -280,18 +316,20 @@ func TestCopilotInstallerExpressionVersion_ViaEngineConfig(t *testing.T) {
 		t.Fatal("Could not find install step with install_copilot_cli.sh")
 	}
 
-	// Should not use expression wiring
-	if strings.Contains(installStep, "ENGINE_VERSION: ${{ inputs.engine-version }}") {
-		t.Errorf("Expected expression version to be ignored, got:\n%s", installStep)
+	// Should use env var injection (not embed expression directly in shell command).
+	if !strings.Contains(installStep, "ENGINE_VERSION: "+expressionVersion) {
+		t.Errorf("Expected ENGINE_VERSION env var with expression, got:\n%s", installStep)
 	}
-
-	// Should install default pinned version
-	if !strings.Contains(installStep, `install_copilot_cli.sh" `+string(constants.DefaultCopilotVersion)) {
-		t.Errorf("Expected default Copilot version in install step, got:\n%s", installStep)
+	if !strings.Contains(installStep, `"${ENGINE_VERSION}"`) {
+		t.Errorf(`Expected step to reference "$ENGINE_VERSION" in run command, got:\n%s`, installStep)
+	}
+	if strings.Contains(installStep, "install_copilot_cli.sh "+expressionVersion) {
+		t.Errorf("Expression version should NOT be embedded directly in shell command, got:\n%s", installStep)
 	}
 }
 
-func TestCopilotInstallerByokFeatureStillUsesDefaultPinnedVersion(t *testing.T) {
+func TestCopilotEngineWithVersionAndByokFeature(t *testing.T) {
+	// engine.version must be honored even when the BYOK feature flag is enabled.
 	engine := NewCopilotEngine()
 	workflowData := &WorkflowData{
 		Name: "test-workflow",
@@ -318,10 +356,10 @@ func TestCopilotInstallerByokFeatureStillUsesDefaultPinnedVersion(t *testing.T)
 		t.Fatal("Could not find install step with install_copilot_cli.sh")
 	}
 
-	if !strings.Contains(installStep, `install_copilot_cli.sh" `+string(constants.DefaultCopilotVersion)) {
-		t.Errorf("Expected default pinned Copilot CLI install, got:\n%s", installStep)
+	if !strings.Contains(installStep, `install_copilot_cli.sh" 1.0.0`) {
+		t.Errorf("Expected user-specified version in install step, got:\n%s", installStep)
 	}
-	if strings.Contains(installStep, `install_copilot_cli.sh" 1.0.0`) {
-		t.Errorf("Expected pinned version to be ignored, got:\n%s", installStep)
+	if strings.Contains(installStep, `install_copilot_cli.sh" `+string(constants.DefaultCopilotVersion)) {
+		t.Errorf("Expected user-specified version, not default version, in install step:\n%s", installStep)
 	}
 }
diff --git a/pkg/workflow/gemini_engine_test.go b/pkg/workflow/gemini_engine_test.go
index a476afeb142..9efaa6af4cd 100644
--- a/pkg/workflow/gemini_engine_test.go
+++ b/pkg/workflow/gemini_engine_test.go
@@ -6,6 +6,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/github/gh-aw/pkg/constants"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -779,3 +780,65 @@ func TestGeminiEngineWithExpressionVersion(t *testing.T) {
 		t.Errorf("Expression should NOT be embedded directly in npm install command, got:\n%s", installStep)
 	}
 }
+
+func TestGeminiEngineWithVersion(t *testing.T) {
+	engine := NewGeminiEngine()
+
+	customVersion := "0.99.0"
+	workflowData := &WorkflowData{
+		Name: "test-workflow",
+		EngineConfig: &EngineConfig{
+			ID:      "gemini",
+			Version: customVersion,
+		},
+	}
+
+	installSteps := engine.GetInstallationSteps(workflowData)
+
+	var installStep string
+	for _, step := range installSteps {
+		stepContent := strings.Join([]string(step), "\n")
+		if strings.Contains(stepContent, "npm install") {
+			installStep = stepContent
+			break
+		}
+	}
+
+	if installStep == "" {
+		t.Fatal("Could not find npm install step")
+	}
+
+	if !strings.Contains(installStep, "@google/gemini-cli@"+customVersion) {
+		t.Errorf("Expected custom version %q in install step, got:\n%s", customVersion, installStep)
+	}
+	if strings.Contains(installStep, "@google/gemini-cli@"+string(constants.DefaultGeminiVersion)) {
+		t.Errorf("Expected user-specified version, not default, in install step:\n%s", installStep)
+	}
+}
+
+func TestGeminiEngineWithoutVersion(t *testing.T) {
+	engine := NewGeminiEngine()
+
+	workflowData := &WorkflowData{
+		Name: "test-workflow",
+	}
+
+	installSteps := engine.GetInstallationSteps(workflowData)
+
+	var installStep string
+	for _, step := range installSteps {
+		stepContent := strings.Join([]string(step), "\n")
+		if strings.Contains(stepContent, "npm install") {
+			installStep = stepContent
+			break
+		}
+	}
+
+	if installStep == "" {
+		t.Fatal("Could not find npm install step")
+	}
+
+	if !strings.Contains(installStep, "@google/gemini-cli@"+string(constants.DefaultGeminiVersion)) {
+		t.Errorf("Expected default version %q in install step when no engine.version set, got:\n%s", constants.DefaultGeminiVersion, installStep)
+	}
+}

From 8b2a5fd20bd97d1f7f2b4d5c2b0a94743d7f3f7a Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Tue, 28 Jul 2026 06:39:53 +0000
Subject: [PATCH 3/5] docs(adr): draft ADR-48519 for honoring engine.version in
 Copilot engine

---
 .../48519-honor-engine-version-for-copilot.md | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 docs/adr/48519-honor-engine-version-for-copilot.md

diff --git a/docs/adr/48519-honor-engine-version-for-copilot.md b/docs/adr/48519-honor-engine-version-for-copilot.md
new file mode 100644
index 00000000000..9498c030260
--- /dev/null
+++ b/docs/adr/48519-honor-engine-version-for-copilot.md
@@ -0,0 +1,44 @@
+# ADR-48519: Honor engine.version for Copilot CLI Installation
+
+**Date**: 2026-07-28
+**Status**: Draft
+**Deciders**: pelikhan, copilot-swe-agent
+
+---
+
+### Context
+
+The `engine.version` field in workflow configuration allows users to pin the version of a coding engine (Copilot, Claude, codex, gemini) installed during workflow execution. Claude, codex, and gemini engines all honored this field correctly, using the user-specified value when present and falling back to a default pinned constant otherwise. However, the Copilot engine's `GetInstallationSteps` silently ignored `engine.version` and always installed `DefaultCopilotVersion`, logging only a message that it was ignoring the user-set value. This inconsistency made `engine.version` a no-op for Copilot, violating the principle of least surprise and breaking user expectations established by the other three engine implementations.
+
+### Decision
+
+We will make the Copilot engine honor `engine.version` exactly as Claude, codex, and gemini do: when `EngineConfig.Version` is set, use it as the installation target; when it is absent, fall back to `DefaultCopilotVersion` and normalize `EngineConfig.Version` to that default so all downstream consumers in the same compile flow observe the effective installed value. The install script already skips `compat.json` resolution when an explicit version is provided, so no additional bypass logic is required.
+
+### Alternatives Considered
+
+#### Alternative 1: Keep Copilot always pinned to DefaultCopilotVersion
+
+The existing behavior guaranteed a stable, tested Copilot CLI version regardless of user configuration, which reduced risk of users accidentally installing untested or incompatible versions. This was rejected because it made `engine.version` silently ineffective for Copilot while working for all other engines, creating inconsistent and confusing behavior. The field's documented contract implies it controls the installed version across all engines.
+
+#### Alternative 2: Introduce a Copilot-specific version override field
+
+A dedicated field (e.g., `engine.copilot_version`) could allow Copilot-specific version control without changing the behavior of `engine.version`. This was rejected because it adds unnecessary API surface, conflicts with the established cross-engine convention of `engine.version`, and would require documentation and migration for any users who expect the unified field to work.
+
+### Consequences
+
+#### Positive
+- `engine.version` now behaves consistently across all four supported engines (Copilot, Claude, codex, gemini), fulfilling user expectations.
+- Users can pin or override the Copilot CLI version in their workflow definitions, enabling version-locked reproducible builds or controlled rollouts of new CLI versions.
+- Test coverage explicitly asserts the honored-version contract, preventing silent regression back to the ignore-version behavior.
+
+#### Negative
+- `compat.json` compatibility-matrix resolution is skipped when an explicit `engine.version` is provided, meaning users who specify an incompatible or unsupported version will receive no automated correction and may encounter runtime failures.
+- Any workflow that previously set `engine.version` for Copilot expecting it to be ignored (e.g., to document an intent without changing behavior) will now have that version actually installed — a silent behavioral change at the call site.
+
+#### Neutral
+- `EngineConfig.Version` is still normalized to the effective installed version when no explicit version is set, preserving the existing contract for downstream consumers in the compile flow.
+- The change is contained to `copilot_engine_installation.go`; the install script and `compat.json` integration path are unchanged.
+
+---
+
+*ADR created by [adr-writer agent]. Review and finalize before changing status from Draft to Accepted.*

From f303c1b8975ace7c40e61a8af96df33fab1304ee Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 28 Jul 2026 07:52:56 +0000
Subject: [PATCH 4/5] plan: address review thread issues from pr-finisher run

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 .github/workflows/smoke-copilot-auto.lock.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/smoke-copilot-auto.lock.yml b/.github/workflows/smoke-copilot-auto.lock.yml
index 9cac699d23d..5c316f6e8b8 100644
--- a/.github/workflows/smoke-copilot-auto.lock.yml
+++ b/.github/workflows/smoke-copilot-auto.lock.yml
@@ -149,6 +149,7 @@ jobs:
           GH_AW_INFO_FIREWALL_TYPE: "squid"
           GH_AW_INFO_FRONTMATTER_EMOJI: "🌸"
           GH_AW_COMPILED_STRICT: "true"
+          GH_AW_INFO_MODEL_COSTS: '{"providers":{"github-copilot":{"models":{"auto":{"cost":{"input":"0","output":"0"}}}}}}'
           GH_AW_INFO_FEATURES: '{"gh-aw-detection":false}'
         uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
         with:

From 68f2556d4bc6ae247be35f1db5fa9ce8f6b05c3a Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 28 Jul 2026 08:13:25 +0000
Subject: [PATCH 5/5] fix: handle expression versions in
 copilotSupportsNoAskUser; add Gemini version to setup step; update golden and
 lock files

- copilot_engine_execution.go: treat expression versions (e.g. ${{ inputs.engine-version }}) as supporting --no-ask-user, since the resolved version is unknown at compile time and the installer already handles expression versions correctly via ENGINE_VERSION env-var injection
- copilot_engine_test.go: add two test cases for expression versions in TestCopilotSupportsNoAskUser
- compiler_yaml_lookups.go: add GeminiEngine to getVersionForSetup switch so GH_AW_INFO_VERSION is consistently emitted in all setup steps (not just those after GetInstallationSteps runs)
- gemini_engine.go: normalize EngineConfig.Version to DefaultGeminiVersion when absent, matching Copilot behavior for downstream version-aware logic
- gemini_engine_test.go: use explicit &EngineConfig{} in TestGeminiEngineWithoutVersion and assert normalization
- testdata/gemini.golden: update golden to reflect GH_AW_INFO_VERSION now emitted
- smoke-copilot-auto.lock.yml: recompile removes zero-pricing overlay (models.dev unavailable locally; real pricing needs human recompile with network access)
- smoke-gemini.lock.yml: recompile adds GH_AW_INFO_VERSION and GH_AW_ENGINE_VERSION now that Gemini version is tracked

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 .github/workflows/smoke-copilot-auto.lock.yml          |  1 -
 .github/workflows/smoke-gemini.lock.yml                |  9 +++++++++
 pkg/workflow/compiler_yaml_lookups.go                  |  2 ++
 pkg/workflow/copilot_engine_execution.go               |  9 +++++++++
 pkg/workflow/copilot_engine_test.go                    | 10 ++++++++++
 pkg/workflow/gemini_engine.go                          |  7 +++++++
 pkg/workflow/gemini_engine_test.go                     |  8 +++++++-
 .../testdata/TestWasmGolden_AllEngines/gemini.golden   |  3 +++
 8 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/smoke-copilot-auto.lock.yml b/.github/workflows/smoke-copilot-auto.lock.yml
index 5c316f6e8b8..9cac699d23d 100644
--- a/.github/workflows/smoke-copilot-auto.lock.yml
+++ b/.github/workflows/smoke-copilot-auto.lock.yml
@@ -149,7 +149,6 @@ jobs:
           GH_AW_INFO_FIREWALL_TYPE: "squid"
           GH_AW_INFO_FRONTMATTER_EMOJI: "🌸"
           GH_AW_COMPILED_STRICT: "true"
-          GH_AW_INFO_MODEL_COSTS: '{"providers":{"github-copilot":{"models":{"auto":{"cost":{"input":"0","output":"0"}}}}}}'
           GH_AW_INFO_FEATURES: '{"gh-aw-detection":false}'
         uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
         with:
diff --git a/.github/workflows/smoke-gemini.lock.yml b/.github/workflows/smoke-gemini.lock.yml
index 1149084cbd2..4d67f9ba637 100644
--- a/.github/workflows/smoke-gemini.lock.yml
+++ b/.github/workflows/smoke-gemini.lock.yml
@@ -151,6 +151,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "Smoke Gemini"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/smoke-gemini.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Mask OTLP telemetry headers
         run: bash "${RUNNER_TEMP}/gh-aw/actions/mask_otlp_headers.sh"
@@ -569,6 +570,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "Smoke Gemini"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/smoke-gemini.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Set runtime paths
         id: set-runtime-paths
@@ -1312,6 +1314,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "Smoke Gemini"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/smoke-gemini.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Download agent output artifact
         id: download-agent-output
@@ -1589,6 +1592,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "Smoke Gemini"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/smoke-gemini.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Download agent output artifact
         id: download-agent-output
@@ -1838,6 +1842,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "Smoke Gemini"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/smoke-gemini.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Check team membership for command workflow
         id: check_membership
@@ -1891,6 +1896,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "Smoke Gemini"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/smoke-gemini.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Checkout repository
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -1959,6 +1965,7 @@ jobs:
       GH_AW_EFFECTIVE_TOKENS: ${{ needs.agent.outputs.effective_tokens }}
       GH_AW_ENGINE_ID: "gemini"
       GH_AW_ENGINE_MODEL: ${{ needs.agent.outputs.model }}
+      GH_AW_ENGINE_VERSION: "0.39.1"
       GH_AW_PROJECT_UTC: "-08:00"
       GH_AW_RUNTIME_FEATURES: ${{ vars.GH_AW_RUNTIME_FEATURES }}
       GH_AW_SAFE_OUTPUT_MESSAGES: "{\"footer\":\"\\u003e ✨ *[{workflow_name}]({run_url}) — Powered by Gemini*{ai_credits_suffix}{history_link}\",\"runStarted\":\"✨ Gemini awakens... [{workflow_name}]({run_url}) begins its journey on this {event_type}...\",\"runSuccess\":\"🚀 [{workflow_name}]({run_url}) **MISSION COMPLETE!** Gemini has spoken. ✨\",\"runFailure\":\"⚠️ [{workflow_name}]({run_url}) {status}. Gemini encountered unexpected challenges...\"}"
@@ -1998,6 +2005,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "Smoke Gemini"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/smoke-gemini.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Mask OTLP telemetry headers
         run: bash "${RUNNER_TEMP}/gh-aw/actions/mask_otlp_headers.sh"
@@ -2086,6 +2094,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "Smoke Gemini"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/smoke-gemini.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Download cache-memory artifact (default)
         id: download_cache_default
diff --git a/pkg/workflow/compiler_yaml_lookups.go b/pkg/workflow/compiler_yaml_lookups.go
index f40bfb0facd..a245afd04b2 100644
--- a/pkg/workflow/compiler_yaml_lookups.go
+++ b/pkg/workflow/compiler_yaml_lookups.go
@@ -39,6 +39,8 @@ func getVersionForSetup(data *WorkflowData) string {
 		return string(constants.DefaultClaudeCodeVersion)
 	case string(constants.CodexEngine):
 		return string(constants.DefaultCodexVersion)
+	case string(constants.GeminiEngine):
+		return string(constants.DefaultGeminiVersion)
 	case string(constants.OpenCodeEngine):
 		return string(constants.DefaultOpenCodeVersion)
 	case string(constants.PiEngine):
diff --git a/pkg/workflow/copilot_engine_execution.go b/pkg/workflow/copilot_engine_execution.go
index 4aaab348c09..17eb9c4b4b6 100644
--- a/pkg/workflow/copilot_engine_execution.go
+++ b/pkg/workflow/copilot_engine_execution.go
@@ -708,6 +708,9 @@ func (e *CopilotEngine) buildCopilotExecutionStep(workflowData *WorkflowData, co
 //     DefaultCopilotVersion. This preserves existing behavior while avoiding drift if
 //     DefaultCopilotVersion is ever lowered below CopilotNoAskUserMinVersion.
 //   - "latest": always returns true (latest is always a new release).
+//   - Expression (e.g. "${{ inputs.engine-version }}"): returns true. The version resolves
+//     at runtime so we cannot gate at compile time; the installer already handles expression
+//     versions via ENGINE_VERSION env-var injection, ensuring the right binary is installed.
 //   - Any semver string ≥ CopilotNoAskUserMinVersion: returns true.
 //   - Any semver string < CopilotNoAskUserMinVersion: returns false.
 //   - Non-semver string (e.g. a branch name): returns false (conservative).
@@ -716,6 +719,12 @@ func copilotSupportsNoAskUser(engineConfig *EngineConfig) bool {
 	if engineConfig != nil && engineConfig.Version != "" {
 		versionStr = engineConfig.Version
 	}
+	// Expression versions resolve at runtime; treat as supported so the generated execution
+	// flags match the installed binary for any version >= CopilotNoAskUserMinVersion.
+	if containsExpression(versionStr) {
+		copilotExecLog.Printf("copilotSupportsNoAskUser: expression version %q treated as supported", versionStr)
+		return true
+	}
 	return versionAtLeast(
 		versionStr,
 		string(constants.DefaultCopilotVersion),
diff --git a/pkg/workflow/copilot_engine_test.go b/pkg/workflow/copilot_engine_test.go
index 2ace2457b02..0d73dccbd86 100644
--- a/pkg/workflow/copilot_engine_test.go
+++ b/pkg/workflow/copilot_engine_test.go
@@ -2978,6 +2978,16 @@ func TestCopilotSupportsNoAskUser(t *testing.T) {
 			engineConfig: &EngineConfig{Version: "main"},
 			expected:     false,
 		},
+		{
+			name:         "expression version is treated as supported",
+			engineConfig: &EngineConfig{Version: "${{ inputs.engine-version }}"},
+			expected:     true,
+		},
+		{
+			name:         "github event input expression is treated as supported",
+			engineConfig: &EngineConfig{Version: "${{ github.event.inputs.engine-version }}"},
+			expected:     true,
+		},
 	}
 
 	for _, tt := range tests {
diff --git a/pkg/workflow/gemini_engine.go b/pkg/workflow/gemini_engine.go
index 27c6c0be82a..6205be4575b 100644
--- a/pkg/workflow/gemini_engine.go
+++ b/pkg/workflow/gemini_engine.go
@@ -123,6 +123,13 @@ func (e *GeminiEngine) GetInstallationSteps(workflowData *WorkflowData) []GitHub
 		return []GitHubActionStep{}
 	}
 
+	// Normalize engine config version when not explicitly set, so downstream consumers
+	// (e.g. execution steps) observe the effective installed version.
+	if workflowData.EngineConfig != nil && workflowData.EngineConfig.Version == "" {
+		workflowData.EngineConfig.Version = string(constants.DefaultGeminiVersion)
+		geminiLog.Printf("No engine.version specified, using default Gemini CLI version: %s", workflowData.EngineConfig.Version)
+	}
+
 	npmSteps := BuildStandardNpmEngineInstallStepsNoCooldown(
 		"@google/gemini-cli",
 		string(constants.DefaultGeminiVersion),
diff --git a/pkg/workflow/gemini_engine_test.go b/pkg/workflow/gemini_engine_test.go
index 9efaa6af4cd..b3c2e2a07f5 100644
--- a/pkg/workflow/gemini_engine_test.go
+++ b/pkg/workflow/gemini_engine_test.go
@@ -820,11 +820,17 @@ func TestGeminiEngineWithoutVersion(t *testing.T) {
 	engine := NewGeminiEngine()
 
 	workflowData := &WorkflowData{
-		Name: "test-workflow",
+		Name:         "test-workflow",
+		EngineConfig: &EngineConfig{},
 	}
 
 	installSteps := engine.GetInstallationSteps(workflowData)
 
+	// EngineConfig.Version must be normalized to the default version.
+	if workflowData.EngineConfig.Version != string(constants.DefaultGeminiVersion) {
+		t.Fatalf("Expected engine config version to be normalized to default Gemini version %q, got: %q", constants.DefaultGeminiVersion, workflowData.EngineConfig.Version)
+	}
+
 	var installStep string
 	for _, step := range installSteps {
 		stepContent := strings.Join([]string(step), "\n")
diff --git a/pkg/workflow/testdata/TestWasmGolden_AllEngines/gemini.golden b/pkg/workflow/testdata/TestWasmGolden_AllEngines/gemini.golden
index 4b7dbf1cebe..d1d87a3564d 100644
--- a/pkg/workflow/testdata/TestWasmGolden_AllEngines/gemini.golden
+++ b/pkg/workflow/testdata/TestWasmGolden_AllEngines/gemini.golden
@@ -62,6 +62,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "engine-gemini-test"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/workflow.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Generate agentic run info
         id: generate_aw_info
@@ -356,6 +357,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "engine-gemini-test"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/workflow.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Checkout repository
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -688,6 +690,7 @@ jobs:
         env:
           GH_AW_SETUP_WORKFLOW_NAME: "engine-gemini-test"
           GH_AW_CURRENT_WORKFLOW_REF: ${{ github.repository }}/.github/workflows/workflow.lock.yml@${{ github.ref }}
+          GH_AW_INFO_VERSION: "0.39.1"
           GH_AW_INFO_ENGINE_ID: "gemini"
       - name: Check team membership for workflow
         id: check_membership