feat: add wave-based parallel task execution to Task Loop

src/lib/components/TaskLoopPanel.svelte

@@ -4,7 +4,9 @@
   import { invoke } from "@tauri-apps/api/core";
   import {
     taskLoopStore,
-    findNextPendingIndex,
+    getReadyTasks,
+    computeWaves,
+    isTaskBlocked,
     buildTaskPrompt,
     normalizeToUnixPath,
     type TaskLoopTask,
@@ -23,53 +25,60 @@
 
   const tasks = $derived(taskLoopStore.tasks);
   const loopStatus = $derived(taskLoopStore.loopStatus);
-  const currentTaskIndex = $derived(taskLoopStore.currentTaskIndex);
   const sourceFile = $derived(taskLoopStore.sourceFile);
   const conversations = $derived(claudeStore.conversations);
+  const concurrencyLimit = $derived(taskLoopStore.concurrencyLimit);
 
-  // Orchestration phase (panel-local, not persisted)
+  // Per-task orchestration phases (panel-local, not persisted)
   type LoopPhase = "waiting_for_connection" | "waiting_for_completion";
-  let loopPhase = $state<LoopPhase | null>(null);
+  let activePhases = $state<Record<number, LoopPhase>>({});
-  let taskEverStarted = $state(false);
+  let taskEverStartedMap = $state<Record<number, boolean>>({});
   let isLoading = $state(false);
   let errorMessage = $state<string | null>(null);
 
   const completedCount = $derived($tasks.filter((t) => t.status === "completed").length);
   const failedCount = $derived($tasks.filter((t) => t.status === "failed").length);
+  const blockedCount = $derived($tasks.filter((t) => t.status === "blocked").length);
+  const runningCount = $derived($tasks.filter((t) => t.status === "running").length);
   const totalCount = $derived($tasks.length);
+  const waves = $derived(computeWaves($tasks));
+  const multiWave = $derived(waves.length > 1);
 
   const workingStates: CharacterState[] = ["thinking", "typing", "coding", "searching", "mcp"];
 
-  // Watch the current task's conversation for state transitions
+  // Watch all active tasks' conversations for state transitions
   $effect(() => {
-    const phase = loopPhase;
+    for (const [idxStr, phase] of Object.entries(activePhases)) {
-    if (!phase) return;
+      const taskIdx = Number(idxStr);
+      const taskList = $tasks;
+      if (taskIdx < 0 || taskIdx >= taskList.length) continue;
 
-    const taskIdx = $currentTaskIndex;
+      const currentTask = taskList[taskIdx];
-    const taskList = $tasks;
+      if (!currentTask.conversationId) continue;
-    if (taskIdx < 0 || taskIdx >= taskList.length) return;
 
-    const currentTask = taskList[taskIdx];
+      const conv = $conversations.get(currentTask.conversationId);
-    if (!currentTask.conversationId) return;
+      if (!conv) continue;
 
-    const conv = $conversations.get(currentTask.conversationId);
+      if (phase === "waiting_for_connection" && conv.connectionStatus === "connected") {
-    if (!conv) return;
+        activePhases = { ...activePhases, [taskIdx]: "waiting_for_completion" };
-
+        taskEverStartedMap = { ...taskEverStartedMap, [taskIdx]: false };
-    if (phase === "waiting_for_connection" && conv.connectionStatus === "connected") {
+        void sendTaskPrompt(currentTask, taskIdx, taskList.length);
-      loopPhase = "waiting_for_completion";
+        continue;
-      taskEverStarted = false;
-      void sendTaskPrompt(currentTask, taskIdx, taskList.length);
-      return;
-    }
-
-    if (phase === "waiting_for_completion") {
-      if (workingStates.includes(conv.characterState)) {
-        taskEverStarted = true;
       }
-      if (taskEverStarted && conv.characterState === "idle") {
+
-        taskEverStarted = false;
+      if (phase === "waiting_for_completion") {
-        loopPhase = null;
+        if (workingStates.includes(conv.characterState)) {
-        void onTaskCompleted(taskIdx, "completed");
+          taskEverStartedMap = { ...taskEverStartedMap, [taskIdx]: true };
+        }
+        if (taskEverStartedMap[taskIdx] && conv.characterState === "idle") {
+          activePhases = Object.fromEntries(
+            Object.entries(activePhases).filter(([k]) => Number(k) !== taskIdx)
+          );
+          taskEverStartedMap = Object.fromEntries(
+            Object.entries(taskEverStartedMap).filter(([k]) => Number(k) !== taskIdx)
+          );
+          void onTaskCompleted(taskIdx, "completed");
+        }
       }
     }
   });
@@ -83,7 +92,9 @@
       });
     } catch (error) {
       console.error("Failed to send task prompt:", error);
-      loopPhase = null;
+      activePhases = Object.fromEntries(
+        Object.entries(activePhases).filter(([k]) => Number(k) !== taskIdx)
+      );
       void onTaskCompleted(taskIdx, "failed");
     }
   }
@@ -94,16 +105,34 @@
     const currentLoopStatus = get(taskLoopStore.loopStatus);
     if (currentLoopStatus !== "running") return;
 
-    const taskList = get(taskLoopStore.tasks);
+    // If any tasks are still active, wait for them
-    const nextIdx = findNextPendingIndex(taskList);
+    if (Object.keys(activePhases).length > 0) return;
 
-    if (nextIdx === -1) {
+    await advanceToNextWave();
+  }
+
+  async function advanceToNextWave(): Promise<void> {
+    const currentLoopStatus = get(taskLoopStore.loopStatus);
+    if (currentLoopStatus !== "running") return;
+
+    // Mark any newly-blocked tasks
+    const taskList = get(taskLoopStore.tasks);
+    taskList.forEach((task, i) => {
+      if (task.status === "pending" && isTaskBlocked(task, taskList)) {
+        taskLoopStore.setTaskStatus(i, "blocked");
+      }
+    });
+
+    const updatedTaskList = get(taskLoopStore.tasks);
+    const limit = get(taskLoopStore.concurrencyLimit);
+    const readyIndices = getReadyTasks(updatedTaskList, limit);
+
+    if (readyIndices.length === 0) {
       taskLoopStore.setLoopStatus("stopped");
-      taskLoopStore.setCurrentTaskIndex(-1);
       return;
     }
 
-    await startTask(nextIdx, taskList);
+    await Promise.all(readyIndices.map((i) => startTask(i, updatedTaskList)));
   }
 
   async function startTask(taskIdx: number, taskList: TaskLoopTask[]): Promise<void> {
@@ -113,19 +142,17 @@
       ...new Set([...get(claudeStore.grantedTools), ...(config.auto_granted_tools ?? [])]),
     ];
 
-    // sourceFile is already normalised to a Unix path at import time.
     const filePath = get(taskLoopStore.sourceFile);
     const workingDir = filePath.split("/").slice(0, -1).join("/");
 
-    // Create a new conversation for this task
     const conversationId = claudeStore.createConversation(task.title);
     void claudeStore.switchConversation(conversationId);
 
     taskLoopStore.setTaskConversationId(taskIdx, conversationId);
     taskLoopStore.setTaskStatus(taskIdx, "running");
-    taskLoopStore.setCurrentTaskIndex(taskIdx);
+
-    loopPhase = "waiting_for_connection";
+    activePhases = { ...activePhases, [taskIdx]: "waiting_for_connection" };
-    taskEverStarted = false;
+    taskEverStartedMap = { ...taskEverStartedMap, [taskIdx]: false };
 
     try {
       await invoke("start_claude", {
@@ -144,7 +171,9 @@
       });
     } catch (error) {
       console.error("Failed to start Claude for task:", error);
-      loopPhase = null;
+      activePhases = Object.fromEntries(
+        Object.entries(activePhases).filter(([k]) => Number(k) !== taskIdx)
+      );
       void onTaskCompleted(taskIdx, "failed");
     }
   }
@@ -170,58 +199,54 @@
 
   async function handleStart(): Promise<void> {
     const taskList = get(taskLoopStore.tasks);
-    const nextIdx = findNextPendingIndex(taskList);
+    const limit = get(taskLoopStore.concurrencyLimit);
-    if (nextIdx === -1) return;
+    const readyIndices = getReadyTasks(taskList, limit);
+    if (readyIndices.length === 0) return;
 
     taskLoopStore.setLoopStatus("running");
-    await startTask(nextIdx, taskList);
+    await Promise.all(readyIndices.map((i) => startTask(i, taskList)));
   }
 
   function handlePause(): void {
     taskLoopStore.setLoopStatus("paused");
   }
 
-  function handleResume(): void {
+  async function handleResume(): Promise<void> {
     taskLoopStore.setLoopStatus("running");
-    // If we're between tasks (no active phase), advance immediately
+    if (Object.keys(activePhases).length === 0) {
-    if (!loopPhase) {
+      await advanceToNextWave();
-      const taskList = get(taskLoopStore.tasks);
-      const nextIdx = findNextPendingIndex(taskList);
-      if (nextIdx !== -1) {
-        void startTask(nextIdx, taskList);
-      } else {
-        taskLoopStore.setLoopStatus("stopped");
-      }
     }
   }
 
   async function handleStop(): Promise<void> {
-    const taskIdx = get(taskLoopStore.currentTaskIndex);
-    const taskList = get(taskLoopStore.tasks);
-    const currentTask = taskIdx >= 0 ? taskList[taskIdx] : null;
-
     taskLoopStore.setLoopStatus("stopped");
-    loopPhase = null;
 
-    // Stop Claude process for the current task if running
+    // Stop all active Claude processes
-    if (currentTask?.conversationId) {
+    const taskList = get(taskLoopStore.tasks);
-      try {
+    const stopPromises = Object.keys(activePhases).map(async (idxStr) => {
-        await invoke("stop_claude", { conversationId: currentTask.conversationId });
+      const taskIdx = Number(idxStr);
-      } catch (error) {
+      const task = taskList[taskIdx];
-        console.error("Failed to stop Claude for current task:", error);
+      if (task?.conversationId) {
+        try {
+          await invoke("stop_claude", { conversationId: task.conversationId });
+        } catch (error) {
+          console.error("Failed to stop Claude for task:", error);
+        }
+        if (task.status === "running") {
+          taskLoopStore.setTaskStatus(taskIdx, "failed");
+        }
       }
-      if (currentTask.status === "running") {
+    });
-        taskLoopStore.setTaskStatus(taskIdx, "failed");
+    await Promise.all(stopPromises);
-      }
-    }
 
-    taskLoopStore.setCurrentTaskIndex(-1);
+    activePhases = {};
+    taskEverStartedMap = {};
   }
 
   function handleReset(): void {
     taskLoopStore.reset();
-    loopPhase = null;
+    activePhases = {};
-    taskEverStarted = false;
+    taskEverStartedMap = {};
     errorMessage = null;
   }
 
@@ -235,6 +260,8 @@
         return "text-green-400";
       case "failed":
         return "text-red-400";
+      case "blocked":
+        return "text-[var(--text-tertiary)] opacity-50";
     }
   }
 
@@ -248,6 +275,8 @@
         return "✓";
       case "failed":
         return "✗";
+      case "blocked":
+        return "⊘";
     }
   }
 
@@ -261,6 +290,8 @@
         return "bg-green-500/20 text-green-400 border-green-500/30";
     }
   }
+
+  const hasPendingTasks = $derived($tasks.some((t) => t.status === "pending"));
 </script>
 
 <div
@@ -288,9 +319,7 @@
           <span
             class="text-xs px-2 py-0.5 rounded-full bg-blue-500/20 text-blue-400 border border-blue-500/30 animate-pulse"
           >
-            Running {completedCount +
+            {runningCount} running · {completedCount}/{totalCount} done
-              failedCount +
-              ($loopStatus === "running" ? 1 : 0)}/{totalCount}
           </span>
         {:else if $loopStatus === "paused"}
           <span
@@ -304,7 +333,7 @@
           >
             {completedCount}/{totalCount} completed{failedCount > 0
               ? `, ${failedCount} failed`
-              : ""}
+              : ""}{blockedCount > 0 ? `, ${blockedCount} blocked` : ""}
           </span>
         {/if}
       </div>
@@ -373,48 +402,81 @@
           {$sourceFile}
         </div>
 
-        <!-- Task list -->
+        <!-- Wave-grouped task list -->
-        <div class="flex flex-col gap-2">
+        <div class="flex flex-col gap-4">
-          {#each $tasks as task, index (task.id)}
+          {#each waves as waveIndices, waveIdx (waveIdx)}
-            <div
+            <div>
-              class="bg-[var(--bg-secondary)] border border-[var(--border-color)] rounded-lg p-3 flex items-start gap-3 {$currentTaskIndex ===
+              {#if multiWave}
-                index && $loopStatus === 'running'
+                <div class="flex items-center gap-2 mb-2">
-                ? 'border-blue-500/40 bg-blue-500/5'
-                : ''}"
-            >
-              <!-- Status icon -->
-              <span
-                class="text-sm font-mono mt-0.5 w-4 text-center shrink-0 {statusColour(
-                  task.status
-                )}"
-              >
-                {statusIcon(task.status)}
-              </span>
-              <!-- Task info -->
-              <div class="flex-1 min-w-0">
-                <div class="flex items-center gap-2 flex-wrap">
-                  <span class="text-sm font-medium text-[var(--text-primary)] truncate">
-                    {task.title}
-                  </span>
                   <span
-                    class="text-xs px-1.5 py-0.5 rounded-full border shrink-0 {priorityColour(
+                    class="text-xs font-semibold text-[var(--text-tertiary)] uppercase tracking-wide"
-                      task.priority
-                    )}"
                   >
-                    {task.priority}
+                    Wave {waveIdx + 1}
                   </span>
-                  {#if $currentTaskIndex === index && $loopStatus === "running"}
+                  {#if waveIndices.length > 1}
-                    <span class="text-xs text-blue-400 animate-pulse shrink-0">● running</span>
+                    <span class="text-xs text-[var(--text-tertiary)]">
+                      ({waveIndices.length} parallel)
+                    </span>
                   {/if}
+                  <div class="flex-1 border-t border-[var(--border-color)]"></div>
                 </div>
-                <p class="text-xs text-[var(--text-tertiary)] mt-0.5 line-clamp-2 font-mono">
+              {/if}
-                  {task.prompt}
+              <div class="flex flex-col gap-2">
-                </p>
+                {#each waveIndices as taskIdx (taskIdx)}
+                  {@const task = $tasks[taskIdx]}
+                  {#if task}
+                    <div
+                      class="bg-[var(--bg-secondary)] border border-[var(--border-color)] rounded-lg p-3 flex items-start gap-3 {task.status ===
+                      'running'
+                        ? 'border-blue-500/40 bg-blue-500/5'
+                        : task.status === 'blocked'
+                          ? 'opacity-50'
+                          : ''}"
+                    >
+                      <!-- Status icon -->
+                      <span
+                        class="text-sm font-mono mt-0.5 w-4 text-center shrink-0 {statusColour(
+                          task.status
+                        )} {task.status === 'running' ? 'animate-spin' : ''}"
+                      >
+                        {statusIcon(task.status)}
+                      </span>
+                      <!-- Task info -->
+                      <div class="flex-1 min-w-0">
+                        <div class="flex items-center gap-2 flex-wrap">
+                          <span class="text-sm font-medium text-[var(--text-primary)] truncate">
+                            {task.title}
+                          </span>
+                          <span
+                            class="text-xs px-1.5 py-0.5 rounded-full border shrink-0 {priorityColour(
+                              task.priority
+                            )}"
+                          >
+                            {task.priority}
+                          </span>
+                          {#if task.status === "running"}
+                            <span class="text-xs text-blue-400 animate-pulse shrink-0"
+                              >● running</span
+                            >
+                          {:else if task.status === "blocked"}
+                            <span class="text-xs text-[var(--text-tertiary)] shrink-0">blocked</span
+                            >
+                          {/if}
+                        </div>
+                        <p
+                          class="text-xs text-[var(--text-tertiary)] mt-0.5 line-clamp-2 font-mono"
+                        >
+                          {task.prompt}
+                        </p>
+                      </div>
+                      <!-- Task number -->
+                      <span class="text-xs text-[var(--text-tertiary)] font-mono shrink-0"
+                        >#{taskIdx + 1}</span
+                      >
+                    </div>
+                  {/if}
+                {/each}
               </div>
-              <!-- Task number -->
-              <span class="text-xs text-[var(--text-tertiary)] font-mono shrink-0"
-                >#{index + 1}</span
-              >
             </div>
           {/each}
         </div>
@@ -447,13 +509,37 @@
             Reset
           </button>
         {/if}
+
+        <!-- Concurrency limit control -->
+        {#if totalCount > 0}
+          <div class="flex items-center gap-1 ml-2">
+            <span class="text-xs text-[var(--text-tertiary)]">Parallel:</span>
+            <button
+              onclick={() => taskLoopStore.setConcurrencyLimit($concurrencyLimit - 1)}
+              class="w-5 h-5 flex items-center justify-center text-xs text-[var(--text-secondary)] hover:text-[var(--text-primary)] bg-[var(--bg-secondary)] hover:bg-[var(--bg-tertiary)] border border-[var(--border-color)] rounded transition-colors"
+              aria-label="Decrease concurrency limit"
+            >
+              −
+            </button>
+            <span class="text-xs font-mono text-[var(--text-primary)] w-4 text-center"
+              >{$concurrencyLimit}</span
+            >
+            <button
+              onclick={() => taskLoopStore.setConcurrencyLimit($concurrencyLimit + 1)}
+              class="w-5 h-5 flex items-center justify-center text-xs text-[var(--text-secondary)] hover:text-[var(--text-primary)] bg-[var(--bg-secondary)] hover:bg-[var(--bg-tertiary)] border border-[var(--border-color)] rounded transition-colors"
+              aria-label="Increase concurrency limit"
+            >
+              +
+            </button>
+          </div>
+        {/if}
       </div>
 
       <div class="flex items-center gap-2">
         {#if totalCount === 0}
           <!-- no actions until tasks are loaded -->
         {:else if $loopStatus === "idle" || $loopStatus === "stopped"}
-          {#if findNextPendingIndex($tasks) !== -1}
+          {#if hasPendingTasks}
             <button
               onclick={handleStart}
               class="px-4 py-1.5 text-sm btn-trans-gradient rounded-lg transition-colors"

src/lib/stores/prd.ts

@@ -6,6 +6,7 @@ export interface PrdTask {
   title: string;
   prompt: string;
   priority: "high" | "medium" | "low";
+  dependsOn?: string[];
 }
 
 export interface PrdFile {
@@ -31,7 +32,8 @@ Write the file to \`${workingDirectory}/hikari-tasks.json\` containing valid JSO
       "id": "task-1",
       "title": "<short descriptive title>",
       "prompt": "<detailed prompt that Claude Code can execute to complete this task>",
-      "priority": "<high|medium|low>"
+      "priority": "<high|medium|low>",
+      "dependsOn": []
     }
   ]
 }
@@ -43,6 +45,7 @@ Guidelines:
 - Prompts should be specific and actionable, not vague
 - Order tasks logically (dependencies first)
 - Assign priority: high for critical path, medium for features, low for polish/cleanup
+- Fill in \`dependsOn\` with IDs of tasks that must complete before this one (use \`[]\` if none)
 - Write only the JSON file — no explanations needed`;
 }
 

src/lib/stores/taskLoop.test.ts

@@ -4,15 +4,23 @@ import {
   countByStatus,
   buildTaskPrompt,
   normalizeToUnixPath,
+  isTaskBlocked,
+  getReadyTasks,
+  computeWaves,
   type TaskLoopTask,
 } from "./taskLoop";
 
-const makeTask = (id: string, status: TaskLoopTask["status"] = "pending"): TaskLoopTask => ({
+const makeTask = (
+  id: string,
+  status: TaskLoopTask["status"] = "pending",
+  dependsOn?: string[]
+): TaskLoopTask => ({
   id,
   title: `Task ${id}`,
   prompt: `Do the thing for ${id}`,
   priority: "medium",
   status,
+  dependsOn,
 });
 
 describe("findNextPendingIndex", () => {
@@ -125,3 +133,140 @@ describe("normalizeToUnixPath", () => {
     expect(normalizeToUnixPath("")).toBe("");
   });
 });
+
+describe("isTaskBlocked", () => {
+  it("returns false when dependsOn is empty", () => {
+    const task = makeTask("a", "pending", []);
+    expect(isTaskBlocked(task, [task])).toBe(false);
+  });
+
+  it("returns false when dependsOn is undefined", () => {
+    const task = makeTask("a", "pending");
+    expect(isTaskBlocked(task, [task])).toBe(false);
+  });
+
+  it("returns false when all dependencies are completed", () => {
+    const dep = makeTask("dep", "completed");
+    const task = makeTask("a", "pending", ["dep"]);
+    expect(isTaskBlocked(task, [dep, task])).toBe(false);
+  });
+
+  it("returns true when a dependency has failed", () => {
+    const dep = makeTask("dep", "failed");
+    const task = makeTask("a", "pending", ["dep"]);
+    expect(isTaskBlocked(task, [dep, task])).toBe(true);
+  });
+
+  it("returns true when a dependency is blocked", () => {
+    const dep = makeTask("dep", "blocked");
+    const task = makeTask("a", "pending", ["dep"]);
+    expect(isTaskBlocked(task, [dep, task])).toBe(true);
+  });
+
+  it("returns false when a dependency is still pending (not yet failed)", () => {
+    const dep = makeTask("dep", "pending");
+    const task = makeTask("a", "pending", ["dep"]);
+    expect(isTaskBlocked(task, [dep, task])).toBe(false);
+  });
+
+  it("returns false when dependency ID does not exist in task list", () => {
+    const task = makeTask("a", "pending", ["nonexistent"]);
+    expect(isTaskBlocked(task, [task])).toBe(false);
+  });
+});
+
+describe("getReadyTasks", () => {
+  it("returns empty array when task list is empty", () => {
+    expect(getReadyTasks([], 3)).toEqual([]);
+  });
+
+  it("returns all pending tasks with no deps when under limit", () => {
+    const tasks = [makeTask("a", "pending"), makeTask("b", "pending"), makeTask("c", "pending")];
+    expect(getReadyTasks(tasks, 5)).toEqual([0, 1, 2]);
+  });
+
+  it("respects the concurrency limit", () => {
+    const tasks = [makeTask("a", "pending"), makeTask("b", "pending"), makeTask("c", "pending")];
+    expect(getReadyTasks(tasks, 2)).toEqual([0, 1]);
+  });
+
+  it("skips tasks whose dependencies are not completed", () => {
+    const tasks = [makeTask("a", "pending"), makeTask("b", "pending", ["a"])];
+    // b depends on a which is pending, not completed — so only a is ready
+    expect(getReadyTasks(tasks, 5)).toEqual([0]);
+  });
+
+  it("includes task when all its dependencies are completed", () => {
+    const tasks = [makeTask("a", "completed"), makeTask("b", "pending", ["a"])];
+    expect(getReadyTasks(tasks, 5)).toEqual([1]);
+  });
+
+  it("skips running, completed, failed, and blocked tasks", () => {
+    const tasks = [
+      makeTask("a", "running"),
+      makeTask("b", "completed"),
+      makeTask("c", "failed"),
+      makeTask("d", "blocked"),
+      makeTask("e", "pending"),
+    ];
+    expect(getReadyTasks(tasks, 5)).toEqual([4]);
+  });
+
+  it("returns empty when limit is 0", () => {
+    const tasks = [makeTask("a", "pending")];
+    expect(getReadyTasks(tasks, 0)).toEqual([]);
+  });
+});
+
+describe("computeWaves", () => {
+  it("returns empty array for empty task list", () => {
+    expect(computeWaves([])).toEqual([]);
+  });
+
+  it("puts all independent tasks in a single wave", () => {
+    const tasks = [makeTask("a", "pending"), makeTask("b", "pending"), makeTask("c", "pending")];
+    expect(computeWaves(tasks)).toEqual([[0, 1, 2]]);
+  });
+
+  it("creates one wave per task for a linear chain", () => {
+    const tasks = [
+      makeTask("a", "pending"),
+      makeTask("b", "pending", ["a"]),
+      makeTask("c", "pending", ["b"]),
+    ];
+    expect(computeWaves(tasks)).toEqual([[0], [1], [2]]);
+  });
+
+  it("handles diamond dependency: A → B,C → D", () => {
+    // A has no deps, B and C depend on A, D depends on B and C
+    const tasks = [
+      makeTask("a", "pending"),
+      makeTask("b", "pending", ["a"]),
+      makeTask("c", "pending", ["a"]),
+      makeTask("d", "pending", ["b", "c"]),
+    ];
+    const waves = computeWaves(tasks);
+    expect(waves).toHaveLength(3);
+    expect(waves[0]).toEqual([0]);
+    expect(waves[1]).toEqual([1, 2]);
+    expect(waves[2]).toEqual([3]);
+  });
+
+  it("groups circular dependencies into a final overflow wave", () => {
+    // a→b, b→a — circular; c has no deps so goes in wave 0
+    const tasks = [
+      makeTask("a", "pending", ["b"]),
+      makeTask("b", "pending", ["a"]),
+      makeTask("c", "pending"),
+    ];
+    const waves = computeWaves(tasks);
+    // c goes in wave 0, then a+b get dumped in overflow
+    expect(waves[0]).toEqual([2]);
+    expect(waves[1]).toEqual([0, 1]);
+  });
+
+  it("ignores unknown dependency IDs (treats them as satisfied)", () => {
+    const tasks = [makeTask("a", "pending", ["nonexistent"])];
+    expect(computeWaves(tasks)).toEqual([[0]]);
+  });
+});

src/lib/stores/taskLoop.ts

@@ -2,7 +2,7 @@ import { writable } from "svelte/store";
 import { invoke } from "@tauri-apps/api/core";
 import type { PrdTask, PrdFile } from "./prd";
 
-export type TaskStatus = "pending" | "running" | "completed" | "failed";
+export type TaskStatus = "pending" | "running" | "completed" | "failed" | "blocked";
 export type LoopStatus = "idle" | "running" | "paused" | "stopped";
 
 export interface TaskLoopTask extends PrdTask {
@@ -20,6 +20,87 @@ export function countByStatus(tasks: TaskLoopTask[], status: TaskStatus): number
   return tasks.filter((t) => t.status === status).length;
 }
 
+/**
+ * Returns true if a task is blocked — i.e. any of its `dependsOn` IDs refer to a
+ * task that has failed or is already blocked.
+ */
+export function isTaskBlocked(task: TaskLoopTask, allTasks: TaskLoopTask[]): boolean {
+  if (!task.dependsOn || task.dependsOn.length === 0) return false;
+  return task.dependsOn.some((depId) => {
+    const dep = allTasks.find((t) => t.id === depId);
+    return dep !== undefined && (dep.status === "failed" || dep.status === "blocked");
+  });
+}
+
+/**
+ * Returns indices of tasks that are ready to start: status is `pending` and all
+ * `dependsOn` tasks are `completed`. Respects `limit` (concurrency cap).
+ */
+export function getReadyTasks(tasks: TaskLoopTask[], limit: number): number[] {
+  const ready: number[] = [];
+  for (let i = 0; i < tasks.length; i++) {
+    if (ready.length >= limit) break;
+    const task = tasks[i];
+    if (task.status !== "pending") continue;
+    const depsAllDone =
+      !task.dependsOn ||
+      task.dependsOn.length === 0 ||
+      task.dependsOn.every((depId) => {
+        const dep = tasks.find((t) => t.id === depId);
+        return dep === undefined || dep.status === "completed";
+      });
+    if (depsAllDone) {
+      ready.push(i);
+    }
+  }
+  return ready;
+}
+
+/**
+ * Groups task indices into waves for UI display. Tasks with no pending dependencies
+ * form wave 0; tasks whose deps are all in earlier waves form the next wave, etc.
+ * Circular dependencies are collected into a final "overflow" wave.
+ */
+export function computeWaves(tasks: TaskLoopTask[]): number[][] {
+  const waves: number[][] = [];
+  const assigned = new Set<number>();
+
+  // Build an id→index map
+  const idToIndex = new Map<string, number>();
+  tasks.forEach((t, i) => idToIndex.set(t.id, i));
+
+  let remaining = tasks.map((_, i) => i).filter((i) => !assigned.has(i));
+
+  while (remaining.length > 0) {
+    const wave: number[] = [];
+    for (const i of remaining) {
+      const task = tasks[i];
+      const depsAllAssigned =
+        !task.dependsOn ||
+        task.dependsOn.length === 0 ||
+        task.dependsOn.every((depId) => {
+          const depIdx = idToIndex.get(depId);
+          return depIdx === undefined || assigned.has(depIdx);
+        });
+      if (depsAllAssigned) {
+        wave.push(i);
+      }
+    }
+
+    if (wave.length === 0) {
+      // Circular dependency — dump all remaining into a single wave
+      waves.push(remaining);
+      break;
+    }
+
+    wave.forEach((i) => assigned.add(i));
+    waves.push(wave);
+    remaining = remaining.filter((i) => !assigned.has(i));
+  }
+
+  return waves;
+}
+
 /**
  * Normalises a file-picker path to a Unix path.
  *
@@ -51,6 +132,7 @@ function createTaskLoopStore() {
   const loopStatus = writable<LoopStatus>("idle");
   const currentTaskIndex = writable<number>(-1);
   const sourceFile = writable<string>("");
+  const concurrencyLimit = writable<number>(3);
 
   async function loadFile(path: string): Promise<void> {
     const content = await invoke<string>("read_file_content", { path });
@@ -90,6 +172,10 @@ function createTaskLoopStore() {
     currentTaskIndex.set(index);
   }
 
+  function setConcurrencyLimit(limit: number): void {
+    concurrencyLimit.set(Math.max(1, limit));
+  }
+
   function reset(): void {
     tasks.set([]);
     loopStatus.set("idle");
@@ -102,11 +188,13 @@ function createTaskLoopStore() {
     loopStatus: { subscribe: loopStatus.subscribe },
     currentTaskIndex: { subscribe: currentTaskIndex.subscribe },
     sourceFile: { subscribe: sourceFile.subscribe },
+    concurrencyLimit: { subscribe: concurrencyLimit.subscribe },
     loadFile,
     setTaskStatus,
     setTaskConversationId,
     setLoopStatus,
     setCurrentTaskIndex,
+    setConcurrencyLimit,
     reset,
   };
 }