fix(executor): unset CLAUDECODE env to prevent nested session rejection

Claude Code v2.1.41+ sets CLAUDECODE=1 in all child Bash processes and
rejects startup when the variable is present. When codeagent-wrapper
spawns `claude -p` as a subprocess, it inherits this variable and gets
blocked with "cannot be launched inside another Claude Code session".

Add UnsetEnv method to commandRunner interface and strip CLAUDECODE
before spawning the claude backend.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

codeagent-wrapper/internal/app/executor_concurrent_test.go

@@ -169,6 +169,12 @@ func (f *execFakeRunner) Process() executor.ProcessHandle {
 	return &execFakeProcess{pid: 1}
 }
 
+func (f *execFakeRunner) UnsetEnv(keys ...string) {
+	for _, k := range keys {
+		delete(f.env, k)
+	}
+}
+
 func TestExecutorRunCodexTaskWithContext(t *testing.T) {
 	defer resetTestHooks()
 

codeagent-wrapper/internal/app/main_test.go

@@ -274,6 +274,10 @@ func (d *drainBlockingCmd) Process() executor.ProcessHandle {
 	return d.inner.Process()
 }
 
+func (d *drainBlockingCmd) UnsetEnv(keys ...string) {
+	d.inner.UnsetEnv(keys...)
+}
+
 type bufferWriteCloser struct {
 	buf    bytes.Buffer
 	mu     sync.Mutex
@@ -568,6 +572,14 @@ func (f *fakeCmd) Process() executor.ProcessHandle {
 	return f.process
 }
 
+func (f *fakeCmd) UnsetEnv(keys ...string) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	for _, k := range keys {
+		delete(f.env, k)
+	}
+}
+
 func (f *fakeCmd) runStdoutScript() {
 	if len(f.stdoutPlan) == 0 {
 		if !f.keepStdoutOpen {

codeagent-wrapper/internal/executor/env_stderr_test.go

@@ -41,6 +41,11 @@ func (f *fakeCmd) SetEnv(env map[string]string) {
 	}
 }
 func (f *fakeCmd) Process() processHandle { return nil }
+func (f *fakeCmd) UnsetEnv(keys ...string) {
+	for _, k := range keys {
+		delete(f.env, k)
+	}
+}
 
 func TestEnvInjection_LogsToStderrAndMasksKey(t *testing.T) {
 	// Arrange ~/.codeagent/models.json via HOME override.

codeagent-wrapper/internal/executor/executor.go

@@ -113,6 +113,7 @@ type commandRunner interface {
 	SetStderr(io.Writer)
 	SetDir(string)
 	SetEnv(env map[string]string)
+	UnsetEnv(keys ...string)
 	Process() processHandle
 }
 
@@ -221,6 +222,33 @@ func (r *realCmd) SetEnv(env map[string]string) {
 	r.cmd.Env = out
 }
 
+func (r *realCmd) UnsetEnv(keys ...string) {
+	if r == nil || r.cmd == nil || len(keys) == 0 {
+		return
+	}
+	// If cmd.Env is nil, Go inherits all parent env vars.
+	// Populate explicitly so we can selectively remove keys.
+	if r.cmd.Env == nil {
+		r.cmd.Env = os.Environ()
+	}
+	drop := make(map[string]struct{}, len(keys))
+	for _, k := range keys {
+		drop[k] = struct{}{}
+	}
+	filtered := make([]string, 0, len(r.cmd.Env))
+	for _, kv := range r.cmd.Env {
+		idx := strings.IndexByte(kv, '=')
+		name := kv
+		if idx >= 0 {
+			name = kv[:idx]
+		}
+		if _, ok := drop[name]; !ok {
+			filtered = append(filtered, kv)
+		}
+	}
+	r.cmd.Env = filtered
+}
+
 func (r *realCmd) Process() processHandle {
 	if r == nil || r.cmd == nil || r.cmd.Process == nil {
 		return nil
@@ -1126,6 +1154,13 @@ func RunCodexTaskWithContext(parentCtx context.Context, taskSpec TaskSpec, backe
 
 	injectTempEnv(cmd)
 
+	// Claude Code sets CLAUDECODE=1 in its child processes. If we don't
+	// remove it, the spawned `claude -p` detects the variable and refuses
+	// to start ("cannot be launched inside another Claude Code session").
+	if commandName == "claude" {
+		cmd.UnsetEnv("CLAUDECODE")
+	}
+
 	// For backends that don't support -C flag (claude, gemini), set working directory via cmd.Dir
 	// Codex passes workdir via -C flag, so we skip setting Dir for it to avoid conflicts
 	if cfg.Mode != "resume" && commandName != "codex" && cfg.WorkDir != "" {