fix(worker): harden CLI injection, stuck-Running, chain wedge, and Fail guard

1. ArgumentList (fix injection): ClaudeArgsBuilder.Build() now returns
   IReadOnlyList<string>; ClaudeProcess populates ProcessStartInfo.ArgumentList
   instead of Arguments, so values like system prompts are never shell-split.
   DailyPrepPrompt, RefinePrompt, and WeekReportService migrated similarly.
   All IClaudeProcess fakes updated.

2. ContinueAsync exception guard: wrap RunOnceAsync in try/catch matching
   the RunAsync pattern so an unexpected exception never leaves the task
   stuck in Running status.

3. Planning chain cascade: OnChildFinishedAsync now calls CancelAsync on
   the immediate blocked successor when a child fails or is cancelled,
   triggering a recursive cascade that clears the entire remaining chain
   instead of leaving it wedged.

4. FailAsync guard: restrict valid source states to Running and Queued;
   WaitingForReview -> Failed is now rejected, preventing an invalid
   transition that could corrupt the review workflow.

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

tests/ClaudeDo.Worker.Tests/Planning/PlanningChainCoordinatorTests.cs

@@ -125,7 +125,7 @@ public sealed class PlanningChainCoordinatorTests : IDisposable
     }
 
     [Fact]
-    public async Task OnChildFailed_DoesNotAdvanceChain()
+    public async Task OnChildFailed_CancelsPendingSuccessors_ChainIsNotWedged()
     {
         await SeedPlanningFamilyAsync("P", 3);
         await _sut.SetupChainAsync("P", default);
@@ -139,12 +139,43 @@ public sealed class PlanningChainCoordinatorTests : IDisposable
 
         var advanced = await _sut.OnChildFinishedAsync("P-c0", TaskStatus.Failed, default);
 
+        // No "advancement" — the chain does not continue on failure.
         Assert.Null(advanced);
         var kids = await GetChildrenAsync("P");
         Assert.Equal(TaskStatus.Failed, kids[0].Status);
-        // Successors remain blocked on the failed predecessor.
-        Assert.Equal(kids[0].Id, kids[1].BlockedByTaskId);
-        Assert.Equal(kids[1].Id, kids[2].BlockedByTaskId);
+        // Successors must be Cancelled, not left stuck as Queued.
+        Assert.Equal(TaskStatus.Cancelled, kids[1].Status);
+        Assert.Equal(TaskStatus.Cancelled, kids[2].Status);
+    }
+
+    [Fact]
+    public async Task OnChildFailed_MidChain_CancelsAllDownstreamSuccessors()
+    {
+        // Chain: c0 → c1 → c2 → c3. c1 fails mid-chain; c2 and c3 must be cancelled.
+        await SeedPlanningFamilyAsync("P", 4);
+        await _sut.SetupChainAsync("P", default);
+
+        // Mark c0 Done so c1 was unblocked; c1 ran and failed.
+        await using (var ctx = _factory.CreateDbContext())
+        {
+            var c0 = await ctx.Tasks.FirstAsync(t => t.Id == "P-c0");
+            c0.Status = TaskStatus.Done;
+            c0.BlockedByTaskId = null;
+            var c1 = await ctx.Tasks.FirstAsync(t => t.Id == "P-c1");
+            c1.Status = TaskStatus.Failed;
+            c1.BlockedByTaskId = null;
+            await ctx.SaveChangesAsync();
+        }
+
+        // Announce that c1 finished as Failed — the coordinator must cascade to c2/c3.
+        var advanced = await _sut.OnChildFinishedAsync("P-c1", TaskStatus.Failed, default);
+
+        Assert.Null(advanced);
+        var kids = await GetChildrenAsync("P");
+        Assert.Equal(TaskStatus.Done, kids[0].Status);
+        Assert.Equal(TaskStatus.Failed, kids[1].Status);
+        Assert.Equal(TaskStatus.Cancelled, kids[2].Status);
+        Assert.Equal(TaskStatus.Cancelled, kids[3].Status);
     }
 
     [Fact]

tests/ClaudeDo.Worker.Tests/Prime/DailyPrepPromptTests.cs

@@ -19,8 +19,10 @@ public class DailyPrepPromptTests
     public void Build_args_allows_only_the_two_tools()
     {
         var args = DailyPrepPrompt.BuildArgs(maxTurns: 30);
-        Assert.Contains("--output-format stream-json", args);
-        Assert.Contains("--max-turns 30", args);
+        Assert.Contains("--output-format", args);
+        Assert.Contains("stream-json", args);
+        Assert.Contains("--max-turns", args);
+        Assert.Contains("30", args);
         Assert.Contains("--allowedTools", args);
         Assert.Contains("mcp__claudedo__get_daily_prep_candidates", args);
         Assert.Contains("mcp__claudedo__set_my_day", args);

tests/ClaudeDo.Worker.Tests/Prime/PrimeRunnerTests.cs

@@ -31,7 +31,7 @@ public class PrimeRunnerTests : IDisposable
         }
 
         public async Task<RunResult> RunAsync(
-            string arguments,
+            IReadOnlyList<string> arguments,
             string prompt,
             string workingDirectory,
             Func<string, Task> onStdoutLine,

tests/ClaudeDo.Worker.Tests/Refine/RefinePromptTests.cs

@@ -11,9 +11,12 @@ public sealed class RefinePromptTests
     {
         var args = RefinePrompt.BuildArgs(20, canReadRepo: true);
 
-        Assert.Contains("--permission-mode acceptEdits", args);
+        Assert.Contains("--permission-mode", args);
+        Assert.Contains("acceptEdits", args);
         Assert.Contains("mcp__claudedo__add_subtask", args);
-        Assert.Contains(" Read Grep Glob", args);
+        Assert.Contains("Read", args);
+        Assert.Contains("Grep", args);
+        Assert.Contains("Glob", args);
     }
 
     [Fact]

tests/ClaudeDo.Worker.Tests/Refine/RefineRunnerTests.cs

@@ -105,7 +105,7 @@ internal sealed class RecordingClaudeProcess : IClaudeProcess
 
     public RecordingClaudeProcess(bool success) => _success = success;
 
-    public Task<RunResult> RunAsync(string arguments, string prompt, string workingDirectory,
+    public Task<RunResult> RunAsync(IReadOnlyList<string> arguments, string prompt, string workingDirectory,
         Func<string, Task> onStdoutLine, CancellationToken ct)
     {
         Interlocked.Increment(ref _callCount);

tests/ClaudeDo.Worker.Tests/Report/WeekReportServiceTests.cs

@@ -27,7 +27,7 @@ public class WeekReportServiceTests : IDisposable
     {
         public int Calls;
         public RunResult Next = new() { ExitCode = 0, ResultMarkdown = "## Bericht" };
-        public Task<RunResult> RunAsync(string args, string prompt, string wd, Func<string, Task> onLine, CancellationToken ct)
+        public Task<RunResult> RunAsync(IReadOnlyList<string> args, string prompt, string wd, Func<string, Task> onLine, CancellationToken ct)
         { Calls++; return Task.FromResult(Next); }
     }
 

tests/ClaudeDo.Worker.Tests/Runner/ClaudeArgsBuilderTests.cs

@@ -11,9 +11,11 @@ public sealed class ClaudeArgsBuilderTests
     {
         var args = _builder.Build(new ClaudeRunConfig(null, null, null, null));
         Assert.Contains("-p", args);
-        Assert.Contains("--output-format stream-json", args);
+        Assert.Contains("--output-format", args);
+        Assert.Contains("stream-json", args);
         Assert.Contains("--verbose", args);
-        Assert.Contains("--permission-mode auto", args);
+        Assert.Contains("--permission-mode", args);
+        Assert.Contains("auto", args);
         Assert.DoesNotContain("--dangerously-skip-permissions", args);
         Assert.Contains("--json-schema", args);
         Assert.DoesNotContain("--model", args);
@@ -26,7 +28,8 @@ public sealed class ClaudeArgsBuilderTests
     public void Model_Adds_Model_Flag()
     {
         var args = _builder.Build(new ClaudeRunConfig("sonnet-4-6", null, null, null));
-        Assert.Contains("--model sonnet-4-6", args);
+        Assert.Contains("--model", args);
+        Assert.Contains("sonnet-4-6", args);
     }
 
     [Fact]
@@ -42,63 +45,74 @@ public sealed class ClaudeArgsBuilderTests
     {
         var args = _builder.Build(new ClaudeRunConfig(null, null, "/path/to/agent.md", null));
         Assert.Contains("--agents", args);
-        Assert.Contains("/path/to/agent.md", args);
+        Assert.Contains(args, a => a.Contains("/path/to/agent.md"));
     }
 
     [Fact]
     public void ResumeSessionId_Adds_Resume_Flag()
     {
         var args = _builder.Build(new ClaudeRunConfig(null, null, null, "sess-abc-123"));
-        Assert.Contains("--resume sess-abc-123", args);
+        Assert.Contains("--resume", args);
+        Assert.Contains("sess-abc-123", args);
     }
 
     [Fact]
     public void All_Options_Set_Includes_All_Flags()
     {
         var args = _builder.Build(new ClaudeRunConfig("opus-4-6", "Be thorough.", "/agents/dev.md", "sess-xyz"));
-        Assert.Contains("--model opus-4-6", args);
+        Assert.Contains("--model", args);
+        Assert.Contains("opus-4-6", args);
         Assert.Contains("--append-system-prompt", args);
         Assert.Contains("--agents", args);
-        Assert.Contains("--resume sess-xyz", args);
+        Assert.Contains("--resume", args);
+        Assert.Contains("sess-xyz", args);
         Assert.Contains("--json-schema", args);
     }
 
     [Fact]
-    public void SystemPrompt_With_Quotes_Is_Escaped()
+    public void SystemPrompt_With_Quotes_Is_Passed_Verbatim()
     {
-        var args = _builder.Build(new ClaudeRunConfig(null, """Don't say "hello".""", null, null));
+        var prompt = """Don't say "hello".""";
+        var args = _builder.Build(new ClaudeRunConfig(null, prompt, null, null));
         Assert.Contains("--append-system-prompt", args);
+        Assert.Contains(prompt, args);
     }
 
     [Fact]
-    public void Build_quotes_system_prompt_with_newline()
+    public void SystemPrompt_With_Newline_Is_Passed_As_Single_Element()
     {
+        var prompt = "line1\nline2";
         var args = _builder.Build(new ClaudeRunConfig(
             Model: null,
-            SystemPrompt: "line1\nline2",
+            SystemPrompt: prompt,
             AgentPath: null,
             ResumeSessionId: null));
 
-        Assert.Contains("--append-system-prompt \"line1\\nline2\"", args);
+        var list = args.ToList();
+        var idx = list.IndexOf("--append-system-prompt");
+        Assert.True(idx >= 0);
+        Assert.Equal(prompt, list[idx + 1]);
     }
 
     [Fact]
-    public void Build_quotes_system_prompt_with_tab()
+    public void SystemPrompt_With_Tab_Is_Passed_As_Single_Element()
     {
+        var prompt = "col1\tcol2";
         var args = _builder.Build(new ClaudeRunConfig(
             Model: null,
-            SystemPrompt: "col1\tcol2",
+            SystemPrompt: prompt,
             AgentPath: null,
             ResumeSessionId: null));
 
-        Assert.Contains("\"col1", args);
+        Assert.Contains(prompt, args);
     }
 
     [Fact]
     public void MaxTurns_Adds_Flag_When_Positive()
     {
         var args = _builder.Build(new ClaudeRunConfig(null, null, null, null, MaxTurns: 25));
-        Assert.Contains("--max-turns 25", args);
+        Assert.Contains("--max-turns", args);
+        Assert.Contains("25", args);
     }
 
     [Fact]
@@ -114,7 +128,8 @@ public sealed class ClaudeArgsBuilderTests
     public void PermissionMode_bypass_Maps_To_Auto()
     {
         var args = _builder.Build(new ClaudeRunConfig(null, null, null, null, PermissionMode: "bypassPermissions"));
-        Assert.Contains("--permission-mode auto", args);
+        Assert.Contains("--permission-mode", args);
+        Assert.Contains("auto", args);
         Assert.DoesNotContain("--dangerously-skip-permissions", args);
     }
 
@@ -122,7 +137,8 @@ public sealed class ClaudeArgsBuilderTests
     public void PermissionMode_acceptEdits_Emits_PermissionMode_Flag()
     {
         var args = _builder.Build(new ClaudeRunConfig(null, null, null, null, PermissionMode: "acceptEdits"));
-        Assert.Contains("--permission-mode acceptEdits", args);
+        Assert.Contains("--permission-mode", args);
+        Assert.Contains("acceptEdits", args);
         Assert.DoesNotContain("--dangerously-skip-permissions", args);
     }
 
@@ -130,7 +146,8 @@ public sealed class ClaudeArgsBuilderTests
     public void PermissionMode_Null_Defaults_To_Auto()
     {
         var args = _builder.Build(new ClaudeRunConfig(null, null, null, null));
-        Assert.Contains("--permission-mode auto", args);
+        Assert.Contains("--permission-mode", args);
+        Assert.Contains("auto", args);
         Assert.DoesNotContain("--dangerously-skip-permissions", args);
     }
 
@@ -142,8 +159,26 @@ public sealed class ClaudeArgsBuilderTests
             McpConfigPath: "C:\\tmp\\t_mcp.json",
             AllowedTools: "mcp__claudedo_run__SuggestImprovement"));
         Assert.Contains("--mcp-config", args);
-        Assert.Contains("t_mcp.json", args);
-        Assert.Contains("--allowedTools mcp__claudedo_run__SuggestImprovement", args);
+        Assert.Contains(args, a => a.Contains("t_mcp.json"));
+        Assert.Contains("--allowedTools", args);
+        Assert.Contains("mcp__claudedo_run__SuggestImprovement", args);
+    }
+
+    [Fact]
+    public void SystemPrompt_ContainingDangerousFlag_IsPassedAsLiteral_NotAsFlag()
+    {
+        // If the system prompt contains "--dangerously-skip-permissions", it must arrive
+        // as the VALUE of --append-system-prompt, not as a standalone CLI flag.
+        const string dangerousPrompt = "--dangerously-skip-permissions";
+        var args = _builder.Build(new ClaudeRunConfig(null, dangerousPrompt, null, null));
+
+        var list = args.ToList();
+        var flagIdx = list.IndexOf("--append-system-prompt");
+        Assert.True(flagIdx >= 0, "--append-system-prompt flag must be present");
+        // The dangerous string sits immediately after the flag as its value.
+        Assert.Equal(dangerousPrompt, list[flagIdx + 1]);
+        // It does NOT appear as a separate element (i.e., not treated as its own flag).
+        Assert.Equal(1, list.Count(a => a == dangerousPrompt));
     }
 }
 

tests/ClaudeDo.Worker.Tests/Runner/ContinueAsyncExceptionTests.cs

@@ -0,0 +1,106 @@
+using ClaudeDo.Data;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Data.Repositories;
+using ClaudeDo.Worker.Config;
+using ClaudeDo.Worker.Hub;
+using ClaudeDo.Worker.Runner;
+using ClaudeDo.Worker.Tests.Infrastructure;
+using ClaudeDo.Worker.Tests.Services;
+using Microsoft.Extensions.Logging.Abstractions;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Tests.Runner;
+
+/// <summary>
+/// Verifies that ContinueAsync wraps RunOnceAsync exceptions so the task
+/// is never left stuck in Running status on an unexpected error.
+/// </summary>
+public sealed class ContinueAsyncExceptionTests : IDisposable
+{
+    private readonly DbFixture _db = new();
+    private readonly string _tempDir;
+    private readonly WorkerConfig _cfg;
+
+    public ContinueAsyncExceptionTests()
+    {
+        _tempDir = Path.Combine(Path.GetTempPath(), $"cd_continue_{Guid.NewGuid():N}");
+        Directory.CreateDirectory(_tempDir);
+        _cfg = new WorkerConfig { SandboxRoot = _tempDir, LogRoot = _tempDir };
+    }
+
+    public void Dispose() { _db.Dispose(); try { Directory.Delete(_tempDir, true); } catch { } }
+
+    private TaskRunner BuildRunner(IClaudeProcess claude, ClaudeDoDbContext ctx)
+    {
+        var dbFactory = _db.CreateFactory();
+        var broadcaster = new HubBroadcaster(new FakeHubContext());
+        var state = TaskStateServiceBuilder.Build(dbFactory).State;
+        var wt = new WorktreeManager(new ClaudeDo.Data.Git.GitService(), dbFactory, _cfg, NullLogger<WorktreeManager>.Instance);
+        return new TaskRunner(claude, dbFactory, broadcaster, wt, new ClaudeArgsBuilder(), _cfg,
+            NullLogger<TaskRunner>.Instance, state, new TaskRunTokenRegistry());
+    }
+
+    [Fact]
+    public async Task ContinueAsync_UnhandledException_MarksTaskFailed_NotStuckRunning()
+    {
+        var dbFactory = _db.CreateFactory();
+        string listId, taskId;
+
+        using (var ctx = _db.CreateContext())
+        {
+            listId = Guid.NewGuid().ToString();
+            ctx.Lists.Add(new ListEntity { Id = listId, Name = "L", WorkingDir = null, CreatedAt = DateTime.UtcNow });
+
+            taskId = Guid.NewGuid().ToString();
+            ctx.Tasks.Add(new TaskEntity
+            {
+                Id = taskId,
+                ListId = listId,
+                Title = "Continue me",
+                Status = TaskStatus.WaitingForReview,
+                CreatedAt = DateTime.UtcNow,
+            });
+            await ctx.SaveChangesAsync();
+
+            // A prior run with a session ID is required for ContinueAsync to proceed.
+            await new TaskRunRepository(ctx).AddAsync(new TaskRunEntity
+            {
+                Id = Guid.NewGuid().ToString(),
+                TaskId = taskId,
+                RunNumber = 1,
+                IsRetry = false,
+                Prompt = "original prompt",
+                SessionId = "sess-continue-test",
+                StartedAt = DateTime.UtcNow.AddMinutes(-5),
+                FinishedAt = DateTime.UtcNow.AddMinutes(-1),
+                ExitCode = 0,
+                ResultMarkdown = "first result",
+            });
+        }
+
+        // This process throws a non-cancellation exception to simulate an unexpected failure.
+        var throwingProcess = new ThrowingClaudeProcess(new InvalidOperationException("disk full"));
+
+        using var ctx2 = _db.CreateContext();
+        var runner = BuildRunner(throwingProcess, ctx2);
+
+        // ContinueAsync must not propagate the exception and must leave the task in Failed.
+        await runner.ContinueAsync(taskId, "please continue", "slot-1", CancellationToken.None);
+
+        using var verify = _db.CreateContext();
+        var task = await new TaskRepository(verify).GetByIdAsync(taskId);
+        Assert.NotNull(task);
+        Assert.Equal(TaskStatus.Failed, task.Status);
+    }
+
+    private sealed class ThrowingClaudeProcess : IClaudeProcess
+    {
+        private readonly Exception _ex;
+        public ThrowingClaudeProcess(Exception ex) => _ex = ex;
+
+        public Task<RunResult> RunAsync(
+            IReadOnlyList<string> arguments, string prompt, string workingDirectory,
+            Func<string, Task> onStdoutLine, CancellationToken ct)
+            => throw _ex;
+    }
+}

tests/ClaudeDo.Worker.Tests/Services/QueueServiceSlotGuardTests.cs

@@ -46,7 +46,7 @@ public sealed class QueueServiceSlotGuardTests : IDisposable
     private QueueWaker _waker = null!;
 
     private (QueueService service, FakeClaudeProcess fakeProcess) CreateService(
-        Func<string, string, string, Func<string, Task>, CancellationToken, Task<RunResult>>? handler = null)
+        Func<string, string, IReadOnlyList<string>, Func<string, Task>, CancellationToken, Task<RunResult>>? handler = null)
     {
         var fake = new FakeClaudeProcess(handler);
         var broadcaster = new HubBroadcaster(new FakeHubContext());

tests/ClaudeDo.Worker.Tests/Services/QueueServiceTests.cs

@@ -47,7 +47,7 @@ public sealed class QueueServiceTests : IDisposable
     private QueueWaker _waker = null!;
 
     private (QueueService service, FakeClaudeProcess fakeProcess) CreateService(
-        Func<string, string, string, Func<string, Task>, CancellationToken, Task<RunResult>>? handler = null)
+        Func<string, string, IReadOnlyList<string>, Func<string, Task>, CancellationToken, Task<RunResult>>? handler = null)
     {
         var fake = new FakeClaudeProcess(handler);
         var broadcaster = new HubBroadcaster(new FakeHubContext());
@@ -118,7 +118,7 @@ public sealed class QueueServiceTests : IDisposable
     {
         var (listId, _) = await SeedListWithAgentTag();
 
-        string? capturedArgs = null;
+        IReadOnlyList<string>? capturedArgs = null;
         string? capturedPrompt = null;
         var done = new TaskCompletionSource();
 
@@ -157,7 +157,9 @@ public sealed class QueueServiceTests : IDisposable
         _waker.Wake();
         await done.Task.WaitAsync(TimeSpan.FromSeconds(5));
 
-        Assert.Contains("--resume sess-1", capturedArgs);
+        Assert.NotNull(capturedArgs);
+        Assert.Contains("--resume", capturedArgs);
+        Assert.Contains("sess-1", capturedArgs);
         Assert.Equal("fix the bug", capturedPrompt);
 
         // Feedback is cleared after the run reaches a successful terminal state (post-run),
@@ -346,19 +348,19 @@ public sealed class QueueServiceTests : IDisposable
 
 internal sealed class FakeClaudeProcess : IClaudeProcess
 {
-    private readonly Func<string, string, string, Func<string, Task>, CancellationToken, Task<RunResult>> _handler;
+    private readonly Func<string, string, IReadOnlyList<string>, Func<string, Task>, CancellationToken, Task<RunResult>> _handler;
     private int _callCount;
 
     public int CallCount => _callCount;
 
     public FakeClaudeProcess(
-        Func<string, string, string, Func<string, Task>, CancellationToken, Task<RunResult>>? handler = null)
+        Func<string, string, IReadOnlyList<string>, Func<string, Task>, CancellationToken, Task<RunResult>>? handler = null)
     {
         _handler = handler ?? ((_, _, _, _, _) =>
             Task.FromResult(new RunResult { ExitCode = 0, ResultMarkdown = "ok" }));
     }
 
-    public async Task<RunResult> RunAsync(string arguments, string prompt, string workingDirectory,
+    public async Task<RunResult> RunAsync(IReadOnlyList<string> arguments, string prompt, string workingDirectory,
         Func<string, Task> onStdoutLine, CancellationToken ct)
     {
         Interlocked.Increment(ref _callCount);

tests/ClaudeDo.Worker.Tests/State/TaskStateServiceTests.cs

@@ -243,6 +243,17 @@ public sealed class TaskStateServiceTests : IDisposable
         Assert.Equal(TaskStatus.Done, await GetStatusAsync(id));
     }
 
+    [Fact]
+    public async Task FailAsync_FromWaitingForReview_IsNoOp()
+    {
+        var id = await SeedTaskAsync(TaskStatus.WaitingForReview);
+
+        var result = await _sut.FailAsync(id, DateTime.UtcNow, "oops", default);
+
+        Assert.False(result.Ok);
+        Assert.Equal(TaskStatus.WaitingForReview, await GetStatusAsync(id));
+    }
+
     // ─── CancelAsync ──────────────────────────────────────────────────────
 
     [Fact]