diff --git a/service/index.html b/service/index.html
index 372698d..3d3de0e 100644
--- a/service/index.html
+++ b/service/index.html
@@ -451,6 +451,12 @@
         border: 1px solid rgba(21, 32, 27, 0.08);
       }
 
+      button.danger {
+        background: linear-gradient(135deg, #c73528 0%, #8f1f18 100%);
+        color: #fff;
+        border: 1px solid rgba(143, 31, 24, 0.22);
+      }
+
       .pill {
         display: inline-flex;
         align-items: center;
@@ -2093,8 +2099,11 @@ A+B</textarea>
           strand_sequence_design_placeholder: "a b ~c 或 N10A5",
           run_btn: "开始分析",
           run_design_btn: "开始设计",
-          run_waiting_btn: "等待结果返回...",
-          submission_locked: "已有任务在等待结果返回，请等待完成；如需强制重新提交请刷新页面。",
+          run_waiting_btn: "终止任务",
+          status_canceling: "正在终止任务...",
+          status_canceled: "任务已终止",
+          cancel_job_failed: "终止任务失败",
+          submission_locked: "已有任务在等待结果返回，请终止或等待。",
           example_btn: "载入示例",
           history_title: "最近任务",
           clear_history: "清空历史",
@@ -2401,8 +2410,11 @@ A+B</textarea>
           strand_sequence_design_placeholder: "a b ~c or N10A5",
           run_btn: "Run Analysis",
           run_design_btn: "Run Design",
-          run_waiting_btn: "Waiting for result...",
-          submission_locked: "A job is already waiting for results. Wait for it to finish, or refresh the page to submit again.",
+          run_waiting_btn: "Terminate Job",
+          status_canceling: "Terminating job...",
+          status_canceled: "Job canceled",
+          cancel_job_failed: "Cancel job failed",
+          submission_locked: "A job is already waiting for results. Cancel or wait.",
           example_btn: "Load Example",
           history_title: "Recent Jobs",
           clear_history: "Clear History",
@@ -2660,6 +2672,7 @@ A+B</textarea>
       let lastResult = null;
       let currentJobId = null;
       let activeSubmission = false;
+      let cancellationRequested = false;
       let probabilitySvgCache = new Map();
       let styledSvgCache = new Map();
       let viewerScale = 1;
@@ -2686,8 +2699,11 @@ A+B</textarea>
       }
 
       function updateRunButtonState() {
-        runBtn.disabled = activeSubmission;
+        runBtn.disabled = activeSubmission && (!currentJobId || cancellationRequested);
         runBtn.setAttribute("aria-busy", activeSubmission ? "true" : "false");
+        runBtn.classList.toggle("primary", !activeSubmission);
+        runBtn.classList.toggle("secondary", false);
+        runBtn.classList.toggle("danger", activeSubmission);
         runBtn.textContent = activeSubmission ? t("run_waiting_btn") : runButtonBaseLabel();
       }
 
@@ -2696,6 +2712,27 @@ A+B</textarea>
         updateRunButtonState();
       }
 
+      async function cancelCurrentJob() {
+        if (!currentJobId || cancellationRequested) return;
+        cancellationRequested = true;
+        setStatus(formatStatus(t("status_canceling")));
+        updateRunButtonState();
+        try {
+          const { response, data } = await fetchJsonOrThrow(`/api/jobs/${encodeURIComponent(currentJobId)}/cancel`, {
+            method: "POST",
+          });
+          if (!response.ok || data.status !== "success") {
+            throw new Error(data?.error || `Cancel failed with HTTP ${response.status}`);
+          }
+          refreshHealth();
+        } catch (error) {
+          cancellationRequested = false;
+          setStatus(`${t("cancel_job_failed")}: ${error.message}`, true);
+        } finally {
+          updateRunButtonState();
+        }
+      }
+
       function setQueueMetric(node, value) {
         node.textContent = value === undefined || value === null ? "-" : String(value);
       }
@@ -5370,7 +5407,6 @@ A+B</textarea>
       }
 
       async function waitForJob(jobId) {
-        const startedAt = Date.now();
         for (;;) {
           const { response, data: job } = await fetchJsonOrThrow(`/api/jobs/${jobId}`);
           if (!response.ok) {
@@ -5380,6 +5416,11 @@ A+B</textarea>
             setStatus(formatStatus(t("status_queued")));
           } else if (job.status === "running") {
             setStatus(formatStatus(t("status_polling")));
+          } else if (job.status === "cancel_requested") {
+            setStatus(formatStatus(t("status_canceling")));
+          } else if (job.status === "canceled") {
+            refreshHealth();
+            throw new Error(t("status_canceled"));
           } else if (job.status === "success") {
             refreshHealth();
             if (job.result && typeof job.elapsed_seconds === "number") {
@@ -5390,9 +5431,6 @@ A+B</textarea>
             refreshHealth();
             throw new Error(job.error?.message || "Job failed");
           }
-          if (Date.now() - startedAt > 10 * 60 * 1000) {
-            throw new Error(t("request_timeout"));
-          }
           await new Promise((resolve) => setTimeout(resolve, 1200));
         }
       }
@@ -5412,8 +5450,9 @@ A+B</textarea>
           return;
         }
 
-        setSubmissionLocked(true);
         currentJobId = null;
+        cancellationRequested = false;
+        setSubmissionLocked(true);
         setStatus(formatStatus(t("status_running")));
         results.innerHTML = "";
 
@@ -5428,6 +5467,7 @@ A+B</textarea>
             throw new Error(data?.error || `Analysis failed with HTTP ${response.status}`);
           }
           currentJobId = data.job_id;
+          updateRunButtonState();
           setStatus(formatStatus(t("status_waiting_job")));
           const result = await waitForJob(data.job_id);
           result.job_id = data.job_id;
@@ -5438,11 +5478,19 @@ A+B</textarea>
           renderHistory();
           setStatus(formatStatus(t("status_done")));
         } catch (error) {
-          results.innerHTML = `<div class="result-card"><h3>${t("request_failed")}</h3><pre>${String(error)}</pre></div>`;
-          setStatus(t("status_error"), true);
+          if (cancellationRequested) {
+            results.innerHTML = `<div class="result-card"><h3>${t("status_canceled")}</h3><pre>${String(error)}</pre></div>`;
+            setStatus(formatStatus(t("status_canceled")));
+          } else {
+            results.innerHTML = `<div class="result-card"><h3>${t("request_failed")}</h3><pre>${String(error)}</pre></div>`;
+            setStatus(t("status_error"), true);
+          }
           refreshHealth();
         } finally {
           setSubmissionLocked(false);
+          currentJobId = null;
+          cancellationRequested = false;
+          updateRunButtonState();
         }
       }
 
@@ -5459,8 +5507,9 @@ A+B</textarea>
           return;
         }
 
-        setSubmissionLocked(true);
         currentJobId = null;
+        cancellationRequested = false;
+        setSubmissionLocked(true);
         setStatus(formatStatus(t("status_running")));
         results.innerHTML = "";
 
@@ -5475,6 +5524,7 @@ A+B</textarea>
             throw new Error(data?.error || `Analysis failed with HTTP ${response.status}`);
           }
           currentJobId = data.job_id;
+          updateRunButtonState();
           setStatus(formatStatus(t("status_waiting_job")));
           const result = await waitForJob(data.job_id);
           result.job_id = data.job_id;
@@ -5485,11 +5535,19 @@ A+B</textarea>
           renderHistory();
           setStatus(formatStatus(t("status_done")));
         } catch (error) {
-          results.innerHTML = `<div class="result-card"><h3>${t("request_failed")}</h3><pre>${String(error)}</pre></div>`;
-          setStatus(t("status_error"), true);
+          if (cancellationRequested) {
+            results.innerHTML = `<div class="result-card"><h3>${t("status_canceled")}</h3><pre>${String(error)}</pre></div>`;
+            setStatus(formatStatus(t("status_canceled")));
+          } else {
+            results.innerHTML = `<div class="result-card"><h3>${t("request_failed")}</h3><pre>${String(error)}</pre></div>`;
+            setStatus(t("status_error"), true);
+          }
           refreshHealth();
         } finally {
           setSubmissionLocked(false);
+          currentJobId = null;
+          cancellationRequested = false;
+          updateRunButtonState();
         }
       }
 
@@ -5727,7 +5785,13 @@ A+B</textarea>
           historyImportInput.value = "";
         }
       });
-      runBtn.addEventListener("click", runAnalysis);
+      runBtn.addEventListener("click", () => {
+        if (activeSubmission) {
+          cancelCurrentJob();
+          return;
+        }
+        runAnalysis();
+      });
       document.getElementById("exampleBtn").addEventListener("click", loadExample);
       workflowSelect.addEventListener("change", () => {
         syncWorkflow();
diff --git a/service/server.py b/service/server.py
index 8f0d065..771724e 100644
--- a/service/server.py
+++ b/service/server.py
@@ -1,6 +1,8 @@
 import json
 import mimetypes
+import multiprocessing
 import os
+import queue
 import re
 import threading
 import time
@@ -80,6 +82,9 @@ IUPAC_CODES = "ACGTUWSMKRYBDHVN"
 IUPAC_CONSTRAINT_TOKEN = re.compile(rf"[{IUPAC_CODES}](?:\d+)?")
 
 VALID_COMPUTE = {"pfunc", "pairs", "mfe", "sample", "subopt", "ensemble_size"}
+CANCEL_REQUESTED_STATUS = "cancel_requested"
+CANCELED_STATUS = "canceled"
+TERMINAL_JOB_STATUSES = {"success", "error", CANCELED_STATUS}
 JOB_STORE = {}
 JOB_LOCK = threading.Lock()
 JOB_TTL_SECONDS = int(os.environ.get("NP_JOB_TTL_SECONDS", "3600"))
@@ -1321,12 +1326,14 @@ def run_job_payload(payload):
 
     if workflow == "design":
         design_options = parse_design_options(payload)
-        design_job_options = DesignOptions(
-            f_stop=design_options["stop_condition"],
-            seed=design_options["seed"],
-            wobble_mutations=design_options["wobble_mutations"],
-            max_time=design_options["max_time_seconds"],
-        )
+        design_job_option_kwargs = {
+            "f_stop": design_options["stop_condition"],
+            "seed": design_options["seed"],
+            "wobble_mutations": design_options["wobble_mutations"],
+        }
+        if design_options["max_time_seconds"] > 0:
+            design_job_option_kwargs["max_time"] = design_options["max_time_seconds"]
+        design_job_options = DesignOptions(**design_job_option_kwargs)
         design_domain_map, design_domains = build_design_domains(payload.get("design_domains") or [])
         target_strand_map, design_strands = build_design_strands(
             payload.get("strands") or [],
@@ -1562,21 +1569,64 @@ def set_job_data(job):
         JOB_STORE[job["job_id"]] = dict(job)
 
 
+def get_job_data(job_id, include_payload=False):
+    if redis_enabled():
+        raw = redis_client().get(job_key(job_id))
+        if raw is None:
+            return None
+        job = json.loads(raw)
+        if not include_payload:
+            job.pop("payload", None)
+        return job
+    with JOB_LOCK:
+        prune_jobs()
+        job = JOB_STORE.get(job_id)
+        if job is None:
+            return None
+        output = dict(job)
+        if not include_payload:
+            output.pop("payload", None)
+        return output
+
+
+def should_keep_cancel_state(current, updates):
+    current_status = current.get("status") if current else None
+    next_status = updates.get("status")
+    if current_status in {CANCEL_REQUESTED_STATUS, CANCELED_STATUS}:
+        return next_status not in {CANCEL_REQUESTED_STATUS, CANCELED_STATUS}
+    return False
+
+
 def update_job_data(job_id, **updates):
     if redis_enabled():
         client = redis_client()
-        current = get_job(job_id)
-        if current is None:
-            current = {"job_id": job_id, "created_at": time.time()}
-        current.update(updates)
-        current["updated_at"] = time.time()
-        client.setex(job_key(job_id), JOB_TTL_SECONDS, json.dumps(current, ensure_ascii=False))
-        return current
+        key = job_key(job_id)
+        while True:
+            pipe = client.pipeline()
+            try:
+                pipe.watch(key)
+                raw = pipe.get(key)
+                current = json.loads(raw) if raw is not None else {"job_id": job_id, "created_at": time.time()}
+                if should_keep_cancel_state(current, updates):
+                    pipe.unwatch()
+                    return current
+                current.update(updates)
+                current["updated_at"] = time.time()
+                pipe.multi()
+                pipe.setex(key, JOB_TTL_SECONDS, json.dumps(current, ensure_ascii=False))
+                pipe.execute()
+                return current
+            except redis.WatchError:
+                continue
+            finally:
+                pipe.reset()
 
     with JOB_LOCK:
         current = JOB_STORE.get(job_id)
         if current is None:
             current = {"job_id": job_id, "created_at": time.time()}
+        if should_keep_cancel_state(current, updates):
+            return dict(current)
         current.update(updates)
         current["updated_at"] = time.time()
         prune_jobs(current["updated_at"])
@@ -1607,52 +1657,161 @@ def create_job(payload):
     return job_id
 
 
+def _job_process_entry(payload, result_queue):
+    apply_thread_limits()
+    try:
+        result_queue.put({"status": "success", "result": run_job_payload(payload)})
+    except BaseException as exc:
+        result_queue.put(
+            {
+                "status": "error",
+                "error": {
+                    "message": str(exc),
+                    "traceback": traceback.format_exc(),
+                },
+            }
+        )
+
+
+def terminate_process(process):
+    if not process.is_alive():
+        return
+    if hasattr(process, "kill"):
+        process.kill()
+    else:
+        process.terminate()
+    process.join(timeout=2)
+    if process.is_alive():
+        process.terminate()
+        process.join(timeout=2)
+
+
 def _run_job(job_id, payload):
     started_at = time.time()
+    current = get_job_data(job_id)
+    if current and current.get("status") in {CANCEL_REQUESTED_STATUS, CANCELED_STATUS}:
+        elapsed = round(time.time() - started_at, 3)
+        update_job_data(job_id, status=CANCELED_STATUS, payload=None, elapsed_seconds=elapsed)
+        return
+
     log_event(f"running job_id={job_id}")
     update_job_data(job_id, status="running")
     if redis_enabled():
         redis_client().sadd(JOB_RUNNING_KEY, job_id)
+
+    ctx = multiprocessing.get_context("spawn")
+    result_queue = ctx.Queue(maxsize=1)
+    process = ctx.Process(target=_job_process_entry, args=(payload, result_queue), daemon=True)
+    message = None
+
     try:
-        result = run_job_payload(payload)
+        process.start()
+        while process.is_alive():
+            current = get_job_data(job_id)
+            if current and current.get("status") in {CANCEL_REQUESTED_STATUS, CANCELED_STATUS}:
+                terminate_process(process)
+                elapsed = round(time.time() - started_at, 3)
+                update_job_data(
+                    job_id,
+                    status=CANCELED_STATUS,
+                    error={"message": "Job canceled by user."},
+                    result=None,
+                    payload=None,
+                    elapsed_seconds=elapsed,
+                )
+                log_event(f"canceled job_id={job_id} elapsed={elapsed}s")
+                return
+            try:
+                message = result_queue.get_nowait()
+                break
+            except queue.Empty:
+                time.sleep(0.25)
+
+        process.join(timeout=2)
+        if message is None:
+            try:
+                message = result_queue.get_nowait()
+            except queue.Empty:
+                message = None
+
+        current = get_job_data(job_id)
+        if current and current.get("status") in {CANCEL_REQUESTED_STATUS, CANCELED_STATUS}:
+            elapsed = round(time.time() - started_at, 3)
+            update_job_data(
+                job_id,
+                status=CANCELED_STATUS,
+                error={"message": "Job canceled by user."},
+                result=None,
+                payload=None,
+                elapsed_seconds=elapsed,
+            )
+            log_event(f"canceled job_id={job_id} elapsed={elapsed}s")
+            return
+
         elapsed = round(time.time() - started_at, 3)
-        update_job_data(job_id, status="success", result=result, payload=None, elapsed_seconds=elapsed)
-        log_event(f"success job_id={job_id} elapsed={elapsed}s")
-    except Exception as exc:
-        elapsed = round(time.time() - started_at, 3)
-        update_job_data(
-            job_id,
-            status="error",
-            error={
-                "message": str(exc),
-                "traceback": traceback.format_exc(),
-            },
-            payload=None,
-            elapsed_seconds=elapsed,
-        )
-        log_event(f"error job_id={job_id} elapsed={elapsed}s message={exc}")
+        if message and message.get("status") == "success":
+            update_job_data(job_id, status="success", result=message["result"], payload=None, elapsed_seconds=elapsed)
+            log_event(f"success job_id={job_id} elapsed={elapsed}s")
+        elif message and message.get("status") == "error":
+            update_job_data(
+                job_id,
+                status="error",
+                error=message.get("error") or {"message": "Job failed."},
+                payload=None,
+                elapsed_seconds=elapsed,
+            )
+            log_event(f"error job_id={job_id} elapsed={elapsed}s message={message.get('error', {}).get('message')}")
+        else:
+            update_job_data(
+                job_id,
+                status="error",
+                error={"message": f"Job process exited with code {process.exitcode}."},
+                payload=None,
+                elapsed_seconds=elapsed,
+            )
+            log_event(f"error job_id={job_id} elapsed={elapsed}s exitcode={process.exitcode}")
     finally:
+        terminate_process(process)
+        result_queue.close()
+        result_queue.join_thread()
         if redis_enabled():
             redis_client().srem(JOB_RUNNING_KEY, job_id)
 
 
-def get_job(job_id):
-    if redis_enabled():
-        raw = redis_client().get(job_key(job_id))
-        if raw is None:
-            return None
-        job = json.loads(raw)
-        job.pop("payload", None)
-        return job
-    with JOB_LOCK:
-        prune_jobs()
-        job = JOB_STORE.get(job_id)
-        if job is None:
-            return None
-        output = dict(job)
+def cancel_job(job_id):
+    current = get_job_data(job_id, include_payload=True)
+    if current is None:
+        return None
+    status = current.get("status")
+    if status in TERMINAL_JOB_STATUSES:
+        output = dict(current)
         output.pop("payload", None)
         return output
 
+    if redis_enabled() and status == "queued":
+        redis_client().lrem(JOB_QUEUE_KEY, 0, job_id)
+
+    if status == "queued":
+        updated = update_job_data(
+            job_id,
+            status=CANCELED_STATUS,
+            error={"message": "Job canceled by user."},
+            result=None,
+            payload=None,
+        )
+    else:
+        updated = update_job_data(
+            job_id,
+            status=CANCEL_REQUESTED_STATUS,
+            error={"message": "Cancellation requested."},
+        )
+    updated.pop("payload", None)
+    return updated
+
+
+def get_job(job_id):
+    return get_job_data(job_id, include_payload=False)
+
 
 def prune_shares(now=None):
     if SHARE_MAX_COUNT < 1:
@@ -1759,6 +1918,8 @@ def run_worker_loop():
             if raw is None:
                 continue
             job = json.loads(raw)
+            if job.get("status") in {CANCEL_REQUESTED_STATUS, CANCELED_STATUS}:
+                continue
             payload = job.get("payload")
             if payload is None:
                 continue
@@ -1975,6 +2136,14 @@ class AppHandler(BaseHTTPRequestHandler):
         parsed = urlparse(self.path)
 
         if parsed.path != "/api/analyze":
+            if parsed.path.startswith("/api/jobs/") and parsed.path.endswith("/cancel"):
+                job_id = parsed.path.split("/")[-2]
+                job = cancel_job(job_id)
+                if job is None:
+                    self._respond(*json_bytes({"error": "Job not found"}, status=HTTPStatus.NOT_FOUND))
+                    return
+                self._respond(*json_bytes({"status": "success", "job": job}))
+                return
             if parsed.path == "/api/jobs":
                 try:
                     length = int(self.headers.get("Content-Length", "0"))