diff --git a/server/internal/daemon/daemon.go b/server/internal/daemon/daemon.go
index af87269c0..2e04ae104 100644
--- a/server/internal/daemon/daemon.go
+++ b/server/internal/daemon/daemon.go
@@ -2579,6 +2579,30 @@ func providerNeedsInlineSystemPrompt(provider string) bool {
 	}
 }
 
+// gateResumeToReusedWorkdir clears the task's prior session unless the task
+// runs in the exact workdir the session was recorded against, and reports
+// whether that workdir was reused. CLI backends key their session stores to
+// the cwd (Claude Code looks sessions up under ~/.claude/projects/<encoded-cwd>/),
+// so a session id from a different workdir can never resolve: the CLI exits
+// within a second and the run fails before doing any work — permanently,
+// because the failed run records no session and the next claim serves the
+// same stale pointer again. This fires whenever the prior workdir no longer
+// exists (GC'd after the issue went done, daemon reinstall, manual cleanup)
+// and execenv.Reuse fell back to a fresh Prepare (GitHub #3854).
+func gateResumeToReusedWorkdir(task *Task, taskCtx *execenv.TaskContextForEnv, envWorkDir string, taskLog *slog.Logger) bool {
+	reused := task.PriorWorkDir != "" && envWorkDir == task.PriorWorkDir
+	if !reused && task.PriorSessionID != "" {
+		taskLog.Info("dropping prior session: workdir not reused, per-cwd session cannot resolve",
+			"session_id", task.PriorSessionID,
+			"prior_workdir", task.PriorWorkDir,
+			"workdir", envWorkDir,
+		)
+		task.PriorSessionID = ""
+		taskCtx.PriorSessionResumed = false
+	}
+	return reused
+}
+
 func (d *Daemon) runTask(ctx context.Context, task Task, provider string, slot int, taskLog *slog.Logger) (TaskResult, error) {
 	// Refuse to spawn an agent without a workspace. An empty workspace_id
 	// here would make MULTICA_WORKSPACE_ID empty in the agent env, and the
@@ -2721,6 +2745,8 @@ func (d *Daemon) runTask(ctx context.Context, task Task, provider string, slot i
 		defer d.unmarkActiveEnvRoot(env.RootDir)
 	}
 
+	reused := gateResumeToReusedWorkdir(&task, &taskCtx, env.WorkDir, taskLog)
+
 	// Inject runtime-specific config (meta skill) so the agent discovers .agent_context/.
 	runtimeBrief, err := execenv.InjectRuntimeConfig(env.WorkDir, provider, taskCtx)
 	if err != nil {
@@ -2853,7 +2879,6 @@ func (d *Daemon) runTask(ctx context.Context, task Task, provider string, slot i
 		return TaskResult{}, fmt.Errorf("create agent backend: %w", err)
 	}
 
-	reused := task.PriorWorkDir != "" && env.WorkDir == task.PriorWorkDir
 	taskLog.Info("starting agent",
 		"provider", provider,
 		"workdir", env.WorkDir,
diff --git a/server/internal/daemon/daemon_test.go b/server/internal/daemon/daemon_test.go
index de1d462de..fa748e5f9 100644
--- a/server/internal/daemon/daemon_test.go
+++ b/server/internal/daemon/daemon_test.go
@@ -18,6 +18,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/multica-ai/multica/server/internal/daemon/execenv"
 	"github.com/multica-ai/multica/server/internal/daemon/repocache"
 	"github.com/multica-ai/multica/server/pkg/agent"
 )
@@ -896,6 +897,71 @@ func newRepoReadyTestDaemon(t *testing.T, handler http.HandlerFunc) *Daemon {
 	return d
 }
 
+func TestGateResumeToReusedWorkdir(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name        string
+		sessionID   string
+		priorDir    string
+		envDir      string
+		wantSession string
+		wantReused  bool
+	}{
+		{
+			name:        "same workdir keeps session",
+			sessionID:   "sess-1",
+			priorDir:    "/ws/task-a/workdir",
+			envDir:      "/ws/task-a/workdir",
+			wantSession: "sess-1",
+			wantReused:  true,
+		},
+		{
+			name:        "fresh workdir drops session",
+			sessionID:   "sess-1",
+			priorDir:    "/ws/task-a/workdir",
+			envDir:      "/ws/task-b/workdir",
+			wantSession: "",
+			wantReused:  false,
+		},
+		{
+			name:        "session without recorded workdir drops session",
+			sessionID:   "sess-1",
+			priorDir:    "",
+			envDir:      "/ws/task-b/workdir",
+			wantSession: "",
+			wantReused:  false,
+		},
+		{
+			name:        "no prior session is a no-op",
+			sessionID:   "",
+			priorDir:    "/ws/task-a/workdir",
+			envDir:      "/ws/task-b/workdir",
+			wantSession: "",
+			wantReused:  false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			task := Task{PriorSessionID: tt.sessionID, PriorWorkDir: tt.priorDir}
+			taskCtx := execenv.TaskContextForEnv{PriorSessionResumed: tt.sessionID != ""}
+
+			reused := gateResumeToReusedWorkdir(&task, &taskCtx, tt.envDir, slog.Default())
+
+			if reused != tt.wantReused {
+				t.Fatalf("reused = %v, want %v", reused, tt.wantReused)
+			}
+			if task.PriorSessionID != tt.wantSession {
+				t.Fatalf("PriorSessionID = %q, want %q", task.PriorSessionID, tt.wantSession)
+			}
+			if taskCtx.PriorSessionResumed != (tt.wantSession != "") {
+				t.Fatalf("PriorSessionResumed = %v, want %v", taskCtx.PriorSessionResumed, tt.wantSession != "")
+			}
+		})
+	}
+}
+
 func TestExecuteAndDrain_ResumeFailureFallback(t *testing.T) {
 	t.Parallel()