diff --git a/Makefile b/Makefile
index 388b217..41155ae 100644
--- a/Makefile
+++ b/Makefile
@@ -66,8 +66,10 @@ test-suite-live: cli
 	./test/suite/run.sh --live
 
 ## Local gateway integration (unit tests run separately via 'make test')
+## Builds sandbox image locally — no registry push needed for Podman.
 test-local: cli
-	./test/test-flow.sh local-container
+	$(CONTAINER_CLI) build -t $(IMAGE) profiles/images/sandbox-default/
+	HARNESS_OS_IMAGE=$(IMAGE) ./test/test-flow.sh local-container
 
 ## Kind: self-contained cluster lifecycle
 ## Builds sandbox image locally and pre-loads into kind (no registry push needed).
@@ -77,8 +79,8 @@ test-kind: cli
 	@echo ""
 	HARNESS_OS_IMAGE=$(IMAGE) CONTAINER_CLI=$(CONTAINER_CLI) ./test/kind-lifecycle.sh $(if $(KEEP),--keep)
 
-## Remote (OCP): requires KUBECONFIG set
-test-remote: cli dev-sandbox
+## Remote (OCP): requires KUBECONFIG set. Pushes image since the cluster pulls from registry.
+test-remote: cli dev-push
 	@test -n "$${KUBECONFIG}" || { echo "ERROR: Set KUBECONFIG for OCP (e.g. export KUBECONFIG=infracluster/kubeconfig)"; exit 1; }
 	@echo ""
 	HARNESS_OS_IMAGE=$(IMAGE) ./test/test-flow.sh openshift
diff --git a/README.md b/README.md
index 432ac59..cd0b5f1 100644
--- a/README.md
+++ b/README.md
@@ -23,17 +23,21 @@ harness apply -f harness.yaml --task @skills/cpp-pro/SKILL.md
 
 ### Clone a repo into the sandbox
 
-The `repo` field clones a repository outside the sandbox and uploads it. Git credentials never enter the sandbox.
+The `repo` field clones a repository outside the sandbox and uploads it. Git credentials never enter the sandbox unless needed.
+
+Use `base_agent` to inherit providers, env, and payloads from an existing config — you only specify what's different:
 
 ```yaml
 name: reviewer
+base_agent: default
 repo: https://github.com/stackrox/collector
-entrypoint: claude
 task: "identify the highest-priority C++ remediation"
 ```
 
+This inherits everything from `agent-default.yaml` (providers, inference routing, payloads) and adds the repo and task. Without `base_agent`, you'd need to specify the inference provider and env vars yourself.
+
 ```bash
-harness apply -f reviewer.yaml --task "focus on RAII and move semantics"
+harness apply -f reviewer.yaml
 ```
 
 ### Getting results out
@@ -226,14 +230,9 @@ make test-remote      # full e2e on OCP (needs KUBECONFIG)
 
 `test-kind` creates its own kind cluster, builds and loads the sandbox image, runs the full flow, and deletes the cluster on exit. Use `KEEP=1` to keep the cluster for debugging.
 
-`test-remote` requires `KUBECONFIG` pointing at an OCP cluster. Use `--reuse-gateway` to skip deploy/teardown when iterating.
+`test-remote` requires `KUBECONFIG` pointing at an OCP cluster and pushes the image automatically. Use `--reuse-gateway` to skip deploy/teardown when iterating.
 
-Dev images must be pushed before integration tests will pass:
-
-```bash
-make dev-push         # build + push multi-arch sandbox image
-make test-local       # now sandbox create can pull the image
-```
+Each integration target builds (and pushes, for remote) the sandbox image automatically.
 
 ## Documentation
 
diff --git a/SPEC.md b/SPEC.md
index 7f46025..ae8dce9 100644
--- a/SPEC.md
+++ b/SPEC.md
@@ -37,10 +37,12 @@ env:
 
 Fields:
 - `name` (required) -- sandbox name, used for `openshell sandbox connect`
+- `base_agent` -- name of a base agent config to inherit from (e.g., `default` resolves `agent-default.yaml`). Providers, env, and payloads are merged additively; scalar fields (entrypoint, gateway, repo, task, image, policy) from the overlay win when non-empty.
 - `image` -- container image for the sandbox (default: version-matched from ghcr.io, override with `HARNESS_OS_IMAGE` env)
 - `entrypoint` -- command to run (default: `claude`). Supports `claude`, `opencode`, `bash`, or any binary on PATH.
 - `tty` -- enable TTY (default: true)
-- `repo` -- git URL to clone outside the sandbox and upload to `/sandbox/<repo-name>`. Shallow clone (`--depth 1`). Git credentials never enter the sandbox.
+- `repo` -- git URL to clone outside the sandbox and upload to `/sandbox/<repo-name>`. Shallow clone (`--depth 1`) with submodules. Git credentials never enter the sandbox unless needed.
+- `repo_ref` -- branch, tag, or ref to clone (default: HEAD). Passed as `--branch` to git clone.
 - `task` -- path to a task.md file, passed to entrypoint via `-p "$(cat task.md)"`
 - `providers` -- list of provider profile references
 - `providers[].profile` -- OpenShell provider profile name
diff --git a/cmd/executor.go b/cmd/executor.go
index bd3b3bc..6f099b8 100644
--- a/cmd/executor.go
+++ b/cmd/executor.go
@@ -75,10 +75,14 @@ func upLocal(opts upLocalOpts) error {
 
 	registered := ensureProviders(opts.harnessDir, gw, agentCfg, opts.providerRefresh, opts.harness)
 
+	if needsInference(agentCfg.EffectiveEntrypoint()) && !hasInferenceProvider(agentCfg.Providers) {
+		status.Warn("No inference provider configured — the agent will not be able to authenticate. Add google-vertex-ai to providers.")
+	}
+
 	// Clone repo outside the sandbox so git credentials never enter it.
 	var repoUpload *gateway.Upload
 	if agentCfg.Repo != "" {
-		upload, cleanup, err := cloneRepo(agentCfg.Repo)
+		upload, cleanup, err := cloneRepo(agentCfg.Repo, agentCfg.RepoRef)
 		if err != nil {
 			return fmt.Errorf("cloning repo: %w", err)
 		}
@@ -166,7 +170,7 @@ func upLocal(opts upLocalOpts) error {
 // that places it at /sandbox/<repo-name>. The clone happens outside the sandbox
 // so git credentials never enter it. Returns a cleanup function that removes
 // the temp directory.
-func cloneRepo(repo string) (gateway.Upload, func(), error) {
+func cloneRepo(repo, ref string) (gateway.Upload, func(), error) {
 	repoName := strings.TrimSuffix(path.Base(repo), ".git")
 	tmpDir, err := os.MkdirTemp("", "harness-repo-")
 	if err != nil {
@@ -175,9 +179,19 @@ func cloneRepo(repo string) (gateway.Upload, func(), error) {
 	cleanup := func() { os.RemoveAll(tmpDir) }
 
 	cloneDir := filepath.Join(tmpDir, repoName)
-	status.Infof("Repo:  %s", repo)
+	if ref != "" {
+		status.Infof("Repo:  %s (ref: %s)", repo, ref)
+	} else {
+		status.Infof("Repo:  %s", repo)
+	}
 
-	cmd := exec.Command("git", "clone", "--depth", "1", repo, cloneDir)
+	args := []string{"clone", "--depth", "1", "--recurse-submodules", "--shallow-submodules"}
+	if ref != "" {
+		args = append(args, "--branch", ref)
+	}
+	args = append(args, repo, cloneDir)
+
+	cmd := exec.Command("git", args...)
 	cmd.Stdout = os.Stderr
 	cmd.Stderr = os.Stderr
 	if err := cmd.Run(); err != nil {
@@ -188,3 +202,24 @@ func cloneRepo(repo string) (gateway.Upload, func(), error) {
 	status.OKf("Cloned %s", repoName)
 	return gateway.Upload{Src: cloneDir, Dst: "/sandbox"}, cleanup, nil
 }
+
+var inferenceProviders = map[string]bool{
+	"google-vertex-ai": true,
+}
+
+func needsInference(entrypoint string) bool {
+	switch entrypoint {
+	case "claude", "opencode":
+		return true
+	}
+	return false
+}
+
+func hasInferenceProvider(providers []agent.ProviderRef) bool {
+	for _, p := range providers {
+		if inferenceProviders[p.Profile] {
+			return true
+		}
+	}
+	return false
+}
diff --git a/cmd/resolve.go b/cmd/resolve.go
index dc09c42..eb3122f 100644
--- a/cmd/resolve.go
+++ b/cmd/resolve.go
@@ -48,6 +48,12 @@ func resolveHarness(harnessDir, agentName, agentFile string) (*agent.Harness, er
 	path := resolveAgentPath(harnessDir, agentName, agentFile)
 	h, err := agent.ParseHarnessFile(path)
 	if err == nil {
+		if h.Agent.BaseAgent != "" {
+			h, err = resolveBaseAgent(harnessDir, h)
+			if err != nil {
+				return nil, err
+			}
+		}
 		return h, nil
 	}
 	if agentFile != "" || agentName != "default" || len(DefaultAgentConfig) == 0 {
@@ -59,6 +65,36 @@ func resolveHarness(harnessDir, agentName, agentFile string) (*agent.Harness, er
 	return agent.ParseHarness(DefaultAgentConfig)
 }
 
+func resolveBaseAgent(harnessDir string, overlay *agent.Harness) (*agent.Harness, error) {
+	baseName := overlay.Agent.BaseAgent
+	basePath := resolveAgentPath(harnessDir, baseName, "")
+	baseH, err := agent.ParseHarnessFile(basePath)
+	if err != nil {
+		if len(DefaultAgentConfig) > 0 && baseName == "default" {
+			baseH, err = agent.ParseHarness(DefaultAgentConfig)
+		}
+		if err != nil {
+			return nil, fmt.Errorf("resolving base_agent %q: %w", baseName, err)
+		}
+	}
+	overlay.Agent = baseH.Agent.MergeOver(overlay.Agent)
+	// Merge base harness-level payloads, providers, gateways, policy
+	for name, data := range baseH.Providers {
+		if _, exists := overlay.Providers[name]; !exists {
+			overlay.Providers[name] = data
+		}
+	}
+	for name, data := range baseH.Gateways {
+		if _, exists := overlay.Gateways[name]; !exists {
+			overlay.Gateways[name] = data
+		}
+	}
+	if overlay.Policy == nil {
+		overlay.Policy = baseH.Policy
+	}
+	return overlay, nil
+}
+
 func resolveGatewayConfigWithHarness(harnessDir, name string, h *agent.Harness) (*gateway.GatewayConfig, error) {
 	if h != nil {
 		if data, ok := h.Gateways[name]; ok {
diff --git a/internal/agent/agent.go b/internal/agent/agent.go
index 94115c6..579985b 100644
--- a/internal/agent/agent.go
+++ b/internal/agent/agent.go
@@ -24,8 +24,10 @@ type PayloadEntry struct {
 
 type AgentConfig struct {
 	Name       string            `yaml:"name"`
+	BaseAgent  string            `yaml:"base_agent,omitempty"`
 	Gateway    string            `yaml:"gateway,omitempty"`
 	Repo       string            `yaml:"repo,omitempty"`
+	RepoRef    string            `yaml:"repo_ref,omitempty"`
 	Providers  []ProviderRef     `yaml:"providers"`
 	Env        map[string]string `yaml:"env,omitempty"`
 	Task       string            `yaml:"task,omitempty"`
@@ -37,6 +39,77 @@ type AgentConfig struct {
 	Payloads   []PayloadEntry    `yaml:"payloads,omitempty"`
 }
 
+// MergeOver applies overlay fields on top of a base config. Non-empty
+// overlay fields win. Providers and env are additive (overlay appends
+// to base). The overlay's name always wins.
+func (base *AgentConfig) MergeOver(overlay *AgentConfig) *AgentConfig {
+	merged := *base
+	merged.Name = overlay.Name
+	if overlay.Gateway != "" {
+		merged.Gateway = overlay.Gateway
+	}
+	if overlay.Repo != "" {
+		merged.Repo = overlay.Repo
+	}
+	if overlay.RepoRef != "" {
+		merged.RepoRef = overlay.RepoRef
+	}
+	if overlay.Entrypoint != "" {
+		merged.Entrypoint = overlay.Entrypoint
+	}
+	if overlay.Task != "" {
+		merged.Task = overlay.Task
+	}
+	if overlay.TTY != nil {
+		merged.TTY = overlay.TTY
+	}
+	if overlay.Policy != "" {
+		merged.Policy = overlay.Policy
+	}
+	if overlay.Image != "" {
+		merged.Image = overlay.Image
+	}
+
+	// Providers: base + overlay (deduplicated by profile name)
+	if len(overlay.Providers) > 0 {
+		seen := make(map[string]bool)
+		var providers []ProviderRef
+		for _, p := range overlay.Providers {
+			seen[p.Profile] = true
+			providers = append(providers, p)
+		}
+		for _, p := range base.Providers {
+			if !seen[p.Profile] {
+				providers = append(providers, p)
+			}
+		}
+		merged.Providers = providers
+	}
+
+	// Env: base + overlay (overlay wins on conflicts)
+	if len(overlay.Env) > 0 {
+		env := make(map[string]string)
+		for k, v := range base.Env {
+			env[k] = v
+		}
+		for k, v := range overlay.Env {
+			env[k] = v
+		}
+		merged.Env = env
+	}
+
+	// Payloads and includes: append
+	if len(overlay.Payloads) > 0 {
+		merged.Payloads = append(merged.Payloads, overlay.Payloads...)
+	}
+	if len(overlay.Include) > 0 {
+		merged.Include = append(merged.Include, overlay.Include...)
+	}
+
+	merged.BaseAgent = ""
+	return &merged
+}
+
 func (c *AgentConfig) NoTTY() bool {
 	if c.TTY == nil {
 		return false
diff --git a/internal/agent/agent_test.go b/internal/agent/agent_test.go
index ec2aa10..7ca58d5 100644
--- a/internal/agent/agent_test.go
+++ b/internal/agent/agent_test.go
@@ -752,3 +752,84 @@ func TestRenderPayload_IncludePathTraversal(t *testing.T) {
 		t.Errorf("error = %q, want 'escapes base directory'", err)
 	}
 }
+
+func TestMergeOver(t *testing.T) {
+	base := &AgentConfig{
+		Name:       "base",
+		Entrypoint: "claude",
+		Gateway:    "local-container",
+		Providers: []ProviderRef{
+			{Profile: "github"},
+			{Profile: "google-vertex-ai"},
+		},
+		Env: map[string]string{
+			"ANTHROPIC_BASE_URL": "https://inference.local",
+			"ANTHROPIC_API_KEY":  "sk-ant-openshell-proxy-managed",
+		},
+		Payloads: []PayloadEntry{
+			{SandboxPath: "/sandbox/.claude/CLAUDE.md", Content: "base instructions"},
+		},
+	}
+
+	overlay := &AgentConfig{
+		Name: "reviewer",
+		Repo: "https://github.com/stackrox/collector",
+		Task: "identify the highest-priority C++ remediation",
+		Providers: []ProviderRef{
+			{Profile: "atlassian", Env: map[string]string{"JIRA_URL": "https://issues.redhat.com"}},
+		},
+		Env: map[string]string{
+			"CUSTOM_VAR": "value",
+		},
+	}
+
+	merged := base.MergeOver(overlay)
+
+	if merged.Name != "reviewer" {
+		t.Errorf("Name = %q, want reviewer", merged.Name)
+	}
+	if merged.Entrypoint != "claude" {
+		t.Errorf("Entrypoint = %q, want claude (from base)", merged.Entrypoint)
+	}
+	if merged.Gateway != "local-container" {
+		t.Errorf("Gateway = %q, want local-container (from base)", merged.Gateway)
+	}
+	if merged.Repo != "https://github.com/stackrox/collector" {
+		t.Errorf("Repo = %q, want stackrox/collector", merged.Repo)
+	}
+	if merged.Task != "identify the highest-priority C++ remediation" {
+		t.Errorf("Task = %q, want overlay task", merged.Task)
+	}
+
+	// Providers: overlay (atlassian) + base (github, vertex) — deduplicated
+	if len(merged.Providers) != 3 {
+		t.Fatalf("Providers count = %d, want 3", len(merged.Providers))
+	}
+	providerNames := make(map[string]bool)
+	for _, p := range merged.Providers {
+		providerNames[p.Profile] = true
+	}
+	for _, want := range []string{"atlassian", "github", "google-vertex-ai"} {
+		if !providerNames[want] {
+			t.Errorf("missing provider %q", want)
+		}
+	}
+
+	// Env: base + overlay merged
+	if merged.Env["ANTHROPIC_BASE_URL"] != "https://inference.local" {
+		t.Error("missing base env ANTHROPIC_BASE_URL")
+	}
+	if merged.Env["CUSTOM_VAR"] != "value" {
+		t.Error("missing overlay env CUSTOM_VAR")
+	}
+
+	// Payloads: base preserved
+	if len(merged.Payloads) != 1 {
+		t.Errorf("Payloads count = %d, want 1 (from base)", len(merged.Payloads))
+	}
+
+	// BaseAgent field cleared
+	if merged.BaseAgent != "" {
+		t.Errorf("BaseAgent = %q, want empty (cleared after merge)", merged.BaseAgent)
+	}
+}
diff --git a/profiles/README.md b/profiles/README.md
index 9a56053..f768877 100644
--- a/profiles/README.md
+++ b/profiles/README.md
@@ -8,9 +8,11 @@ Define what runs in the sandbox. One agent config = one sandbox.
 
 ```yaml
 name: agent                     # sandbox name
+base_agent: default             # inherit from agent-default.yaml (providers, env, payloads)
 entrypoint: claude              # claude, opencode, bash, or any binary on PATH
 tty: true                       # enable TTY (default: true)
 repo: https://github.com/org/repo  # cloned outside sandbox, uploaded to /sandbox/<repo>
+repo_ref: main                  # branch, tag, or ref to clone (default: HEAD)
 gateway: openshift              # target gateway (default: local-container)
 task: @tasks/review.md          # task file passed to entrypoint via -p
 image: ghcr.io/...              # override sandbox image