Add workflow log listing & tail support (backend API + Tasks UI)

packages/frontend/src/hooks/useApi.ts

@@ -270,6 +270,21 @@ export type WorkflowDefinition = {
   steps: WorkflowStep[];
 };
 
+export type WorkflowLogSummary = {
+  name: string;
+  location: "var" | "tmp" | string;
+  path: string;
+  sizeBytes: number;
+  modifiedAt: string;
+};
+
+export type WorkflowLogTail = {
+  name: string;
+  location: "var" | "tmp" | string;
+  path: string;
+  tail: string;
+};
+
 export const api = {
   getDashboard: () =>
     request<{
@@ -478,6 +493,11 @@ export const api = {
     request<{ workflows: WorkflowDefinition[] }>("/workflows"),
   getWorkspaceWorkflows: () =>
     request<{ workflows: WorkspaceWorkflowSummary[] }>("/workspace/workflows"),
+  getWorkflowLogs: () => request<{ logs: WorkflowLogSummary[] }>("/workflow-logs"),
+  getWorkflowLogTail: (location: string, logName: string) =>
+    request<WorkflowLogTail>(
+      `/workflow-logs/${encodeURIComponent(location)}/${encodeURIComponent(logName)}`,
+    ),
   terminateWorkflow: (workflowId: string) =>
     request<{ success: boolean; message?: string }>(`/workflows/${encodeURIComponent(workflowId)}/terminate`, {
       method: "POST",

packages/frontend/src/pages/TasksPage.tsx

@@ -3,6 +3,7 @@ import { Link, useNavigate } from "react-router-dom";
 import {
   api,
   ArtefactSummary,
+  WorkflowLogSummary,
   WorkspaceWorkflowSummary,
 } from "../hooks/useApi";
 import { Panel } from "../components/Panel";
@@ -65,6 +66,19 @@ const formatWorkflowLastRun = (workflow: WorkspaceWorkflowSummary) => {
   return formatDateTime(workflow.lastRun);
 };
 
+const formatBytes = (value: number) => {
+  if (!Number.isFinite(value) || value < 0) {
+    return "-";
+  }
+  if (value < 1024) {
+    return `${value} B`;
+  }
+  if (value < 1024 * 1024) {
+    return `${(value / 1024).toFixed(1)} KB`;
+  }
+  return `${(value / (1024 * 1024)).toFixed(1)} MB`;
+};
+
 const renderWorkflowDiagnosticsSummary = (diagnostics: WorkflowDiagnostics) => {
   if (!diagnostics) {
     return <span className="meta-secondary">No diagnostics yet</span>;
@@ -107,6 +121,13 @@ export const TasksPage: React.FC = () => {
   const [workspaceWorkflows, setWorkspaceWorkflows] = useState<
     WorkspaceWorkflowSummary[]
   >([]);
+  const [workflowLogs, setWorkflowLogs] = useState<WorkflowLogSummary[]>([]);
+  const [logModal, setLogModal] = useState<{
+    open: boolean;
+    title: string;
+    content: string;
+  }>({ open: false, title: "", content: "" });
+  const [loadingLog, setLoadingLog] = useState<string | null>(null);
   const [createOpen, setCreateOpen] = useState(false);
   const [terminatingWorkflow, setTerminatingWorkflow] = useState<string | null>(null);
   const [terminateModal, setTerminateModal] = useState(false);
@@ -138,11 +159,13 @@ export const TasksPage: React.FC = () => {
 
   useEffect(() => {
     loadTasks();
-    api
-      .getWorkspaceWorkflows()
-      .then((res) => setWorkspaceWorkflows(res.workflows))
+    Promise.all([api.getWorkspaceWorkflows(), api.getWorkflowLogs()])
+      .then(([workflowRes, logRes]) => {
+        setWorkspaceWorkflows(workflowRes.workflows);
+        setWorkflowLogs(logRes.logs);
+      })
       .catch((error) =>
-        console.error("Failed to load workspace workflows", error),
+        console.error("Failed to load tasks page data", error),
       );
   }, []);
 
@@ -187,6 +210,27 @@ export const TasksPage: React.FC = () => {
     }
   };
 
+  const openLogTail = async (logFile: WorkflowLogSummary) => {
+    setLoadingLog(`${logFile.location}:${logFile.name}`);
+    try {
+      const result = await api.getWorkflowLogTail(logFile.location, logFile.name);
+      setLogModal({
+        open: true,
+        title: logFile.name,
+        content: result.tail || "-",
+      });
+    } catch (error) {
+      console.error("Failed to load workflow log tail", error);
+      setLogModal({
+        open: true,
+        title: logFile.name,
+        content: `Failed to read log file: ${error instanceof Error ? error.message : "Unknown error"}`,
+      });
+    } finally {
+      setLoadingLog(null);
+    }
+  };
+
   return (
     <div className="page">
       <h1>Tasks</h1>
@@ -264,6 +308,42 @@ export const TasksPage: React.FC = () => {
                       </tbody>
                     </table>
                   )}
+
+                  <h3>Available workflow logs</h3>
+                  {workflowLogs.length === 0 ? (
+                    <div className="empty">No workflow logs found.</div>
+                  ) : (
+                    <table className="git-table">
+                      <thead>
+                        <tr>
+                          <th>Filename</th>
+                          <th>Location</th>
+                          <th>Modified</th>
+                          <th>Size</th>
+                          <th>Actions</th>
+                        </tr>
+                      </thead>
+                      <tbody>
+                        {workflowLogs.map((logFile) => (
+                          <tr key={`${logFile.location}:${logFile.name}`}>
+                            <td>{logFile.name}</td>
+                            <td>{logFile.path}</td>
+                            <td>{formatDateTime(logFile.modifiedAt)}</td>
+                            <td>{formatBytes(logFile.sizeBytes)}</td>
+                            <td>
+                              <button
+                                className="secondary"
+                                onClick={() => void openLogTail(logFile)}
+                                disabled={loadingLog === `${logFile.location}:${logFile.name}`}
+                              >
+                                {loadingLog === `${logFile.location}:${logFile.name}` ? "Loading..." : "View tail"}
+                              </button>
+                            </td>
+                          </tr>
+                        ))}
+                      </tbody>
+                    </table>
+                  )}
                 </Panel>
 
                 <div className="button-bar">
@@ -383,6 +463,14 @@ export const TasksPage: React.FC = () => {
           </button>
         </div>
       </Modal>
+
+      <Modal
+        open={logModal.open}
+        title={logModal.title}
+        onClose={() => setLogModal({ open: false, title: "", content: "" })}
+      >
+        <pre className="workflow-log-tail">{logModal.content}</pre>
+      </Modal>
     </div>
   );
 };

packages/frontend/src/styles/page.css

@@ -497,3 +497,13 @@
   color: var(--text);
   font-size: 0.82rem;
 }
+
+.workflow-log-tail {
+  margin: 0;
+  max-height: 24rem;
+  overflow: auto;
+  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
+  font-size: 0.85rem;
+  line-height: 1.4;
+  white-space: pre-wrap;
+}

packages/frontend/src/templates/WORKFLOW_TO_HARNESS_PROMPT_TEMPLATE.md

@@ -106,8 +106,18 @@ Example format:
 
 Log destination preference:
 
-1.  `/var/log/<workflow>.log`
-2.  `/tmp/made-harness-logs/<workflow>.log`
+1.  `/var/log/made-<workflow-name>-<timestamp>-<PID>.log`
+2.  `/tmp/made-harness-logs/made-<workflow-name>-<timestamp>-<PID>.log`
+
+Required filename format:
+
+`made-[workflow-name]-[timestamp]-[PID].log`
+
+Where:
+
+• `workflow-name` is slug-safe (lowercase letters, digits, `-`)
+• `timestamp` uses UTC `YYYYMMDDTHHMMSSZ`
+• `PID` is shell `$$`
 
 If `/var/log` cannot be written, automatically fallback.
 

packages/pybackend/app.py

@@ -55,6 +55,8 @@
     force_terminate_job,
     get_cron_job_diagnostics,
     get_cron_job_last_runs,
+    list_workflow_logs,
+    read_workflow_log_tail,
     refresh_cron_clock,
     start_cron_clock,
     stop_cron_clock,
@@ -613,6 +615,32 @@ def workspace_workflows():
         )
 
 
+@app.get("/api/workflow-logs")
+def workflow_logs():
+    try:
+        logger.info("Listing workflow log files")
+        return {"logs": list_workflow_logs()}
+    except Exception as exc:
+        logger.exception("Failed to list workflow log files")
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail=str(exc)
+        )
+
+
+@app.get("/api/workflow-logs/{location}/{log_name}")
+def workflow_log_tail(location: str, log_name: str):
+    try:
+        logger.info("Reading workflow log tail for %s/%s", location, log_name)
+        return read_workflow_log_tail(location, log_name, max_lines=20)
+    except FileNotFoundError as exc:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(exc))
+    except Exception as exc:
+        logger.exception("Failed to read workflow log tail for %s/%s", location, log_name)
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail=str(exc)
+        )
+
+
 @app.post("/api/workflows/{workflow_id}/terminate")
 def terminate_workflow(workflow_id: str):
     """Terminate a running workflow job."""

packages/pybackend/cron_service.py

@@ -34,6 +34,11 @@
 
 DEFAULT_MAX_RUNTIME_MINUTES = 120  # 2 hours default
 _workflow_max_runtime: dict[str, int] = {}
+WORKFLOW_LOG_PREFIX = "made-"
+WORKFLOW_LOG_LOCATIONS: dict[str, Path] = {
+    "var": Path("/var/log"),
+    "tmp": Path("/tmp/made-harness-logs"),
+}
 
 
 def _terminate_running_job_unlocked(workflow_id: str) -> None:
@@ -81,6 +86,72 @@ def _tail_output(value: str, max_lines: int = 20) -> str:
     return "\n".join(lines[-max_lines:])
 
 
+def _is_workflow_log_file(file_path: Path) -> bool:
+    return (
+        file_path.is_file()
+        and file_path.name.startswith(WORKFLOW_LOG_PREFIX)
+        and file_path.suffix == ".log"
+    )
+
+
+def _validate_log_name(log_name: str) -> bool:
+    return (
+        bool(log_name)
+        and "/" not in log_name
+        and "\\" not in log_name
+        and log_name.startswith(WORKFLOW_LOG_PREFIX)
+        and log_name.endswith(".log")
+    )
+
+
+def list_workflow_logs() -> list[dict[str, object]]:
+    log_files: list[tuple[float, dict[str, object]]] = []
+    for location, log_dir in WORKFLOW_LOG_LOCATIONS.items():
+        if not log_dir.exists() or not log_dir.is_dir():
+            continue
+        for file_path in log_dir.iterdir():
+            if not _is_workflow_log_file(file_path):
+                continue
+            stat = file_path.stat()
+            modified_at = datetime.fromtimestamp(stat.st_mtime, timezone.utc)
+            log_files.append(
+                (
+                    stat.st_mtime,
+                    {
+                        "name": file_path.name,
+                        "location": location,
+                        "path": str(file_path),
+                        "sizeBytes": stat.st_size,
+                        "modifiedAt": modified_at.isoformat(),
+                    },
+                )
+            )
+
+    return [entry for _, entry in sorted(log_files, key=lambda item: item[0], reverse=True)]
+
+
+def read_workflow_log_tail(
+    location: str, log_name: str, max_lines: int = 20
+) -> dict[str, object]:
+    log_dir = WORKFLOW_LOG_LOCATIONS.get(location)
+    if log_dir is None:
+        raise FileNotFoundError("Unknown log location")
+    if not _validate_log_name(log_name):
+        raise FileNotFoundError("Invalid log filename")
+
+    file_path = log_dir / log_name
+    if not file_path.exists() or not file_path.is_file():
+        raise FileNotFoundError("Workflow log file not found")
+
+    content = file_path.read_text(encoding="utf-8", errors="replace")
+    return {
+        "name": log_name,
+        "location": location,
+        "path": str(file_path),
+        "tail": _tail_output(content, max_lines=max_lines),
+    }
+
+
 def _monitor_job_timeouts() -> None:
     """Periodically check for jobs exceeding runtime limits."""
     current_time = datetime.now(timezone.utc)

packages/pybackend/tests/unit/test_api.py

@@ -1114,6 +1114,43 @@ def test_workspace_workflows_success(self, mock_list, mock_last_runs, mock_diagn
             {"sample:wf_1": {"lastExitCode": 0, "running": False}},
         )
 
+    @patch("app.list_workflow_logs")
+    def test_workflow_logs_success(self, mock_list_logs):
+        mock_list_logs.return_value = [
+            {
+                "name": "made-nightly-20260325T120000Z-123.log",
+                "location": "tmp",
+                "path": "/tmp/made-harness-logs/made-nightly-20260325T120000Z-123.log",
+                "sizeBytes": 42,
+                "modifiedAt": "2026-03-25T12:00:00+00:00",
+            }
+        ]
+
+        response = client.get("/api/workflow-logs")
+
+        assert response.status_code == 200
+        assert response.json()["logs"][0]["name"].startswith("made-")
+        mock_list_logs.assert_called_once_with()
+
+    @patch("app.read_workflow_log_tail")
+    def test_workflow_log_tail_success(self, mock_read_log_tail):
+        mock_read_log_tail.return_value = {
+            "name": "made-nightly-20260325T120000Z-123.log",
+            "location": "tmp",
+            "path": "/tmp/made-harness-logs/made-nightly-20260325T120000Z-123.log",
+            "tail": "line-1\nline-2",
+        }
+
+        response = client.get(
+            "/api/workflow-logs/tmp/made-nightly-20260325T120000Z-123.log"
+        )
+
+        assert response.status_code == 200
+        assert response.json()["tail"] == "line-1\nline-2"
+        mock_read_log_tail.assert_called_once_with(
+            "tmp", "made-nightly-20260325T120000Z-123.log", max_lines=20
+        )
+
     @patch("app.read_workflows")
     @patch("app._repository_path")
     def test_repository_workflows_success(self, mock_repo_path, mock_read):