diff --git a/docs/design.md b/docs/design.md
index 72e2f52..f4ea295 100644
--- a/docs/design.md
+++ b/docs/design.md
@@ -1059,6 +1059,33 @@ Acceptance Criteria:
 
 ---
 
+## Phase 21: Read-Only Web Dashboard
+
+* [ ] Add a Flask-based `nightshift web` command
+* [ ] Read run state from `.nightshift/runs/`
+* [ ] Show latest run summary
+* [ ] Show task status and retry count
+* [ ] Show stage results and artifact links
+* [ ] Render markdown/plain-text artifacts safely
+* [ ] Add simple auto-refresh
+* [ ] Keep the dashboard read-only
+* [ ] Add tests for route rendering and missing artifact handling
+
+Acceptance Criteria:
+
+* User can monitor a run from a browser without controlling execution
+* Dashboard works from existing artifact files
+* Missing or partial run artifacts do not crash the server
+* No config, task, command, or pipeline mutation is exposed from the UI
+
+Notes:
+
+* This phase should avoid websockets and process control at first.
+* The dashboard should be artifact-driven so it remains decoupled from pipeline internals.
+* Start/stop controls, authentication, live log streaming, and approval gates are separate future work.
+
+---
+
 # Appendix A: Design Decisions and Rationale
 
 ## A.1 Local-first architecture
diff --git a/docs/devlog/phase12.md b/docs/devlog/phase12.md
new file mode 100644
index 0000000..292c614
--- /dev/null
+++ b/docs/devlog/phase12.md
@@ -0,0 +1,18 @@
+# Phase 12 Devlog: Status Command
+
+## Implemented
+
+- Added `nightshift/status.py`.
+- Implemented project status inspection for config path, project root, task counts, next runnable task, latest run directory, and warnings.
+- Wired `nightshift status --config ...` into the CLI.
+- Added status tests.
+
+## Decisions Made
+
+- Status is read-only and uses existing config/task/artifact files.
+- The next task is dependency-aware, so blocked tasks are not reported as runnable.
+- Latest run detection is filesystem-based and uses the newest run directory by modification time.
+
+## Notes
+
+- Status warnings currently focus on dependency problems. Broader validation warnings can be added without changing the CLI shape.
diff --git a/docs/devlog/phase13.md b/docs/devlog/phase13.md
new file mode 100644
index 0000000..c7f95e5
--- /dev/null
+++ b/docs/devlog/phase13.md
@@ -0,0 +1,20 @@
+# Phase 13 Devlog: Git Safety and Diff Artifacts
+
+## Implemented
+
+- Added `nightshift/git.py`.
+- Implemented clean-worktree enforcement when `require_clean_worktree` is true.
+- Captured pre-run and post-run git status artifacts.
+- Wrote per-task `diff.patch` artifacts.
+- Handled non-git repositories and git failures gracefully when clean worktree is not required.
+- Added git tests with temporary repositories.
+
+## Decisions Made
+
+- Clean-worktree enforcement runs before artifact creation so NightShift does not dirty a repo before checking it.
+- If clean worktree is required and git status cannot be read, execution fails safely.
+- Diff artifacts are written even when git is unavailable, with a readable explanation instead of crashing.
+
+## Notes
+
+- Existing final reports already include modified files when git status is available.
diff --git a/docs/devlog/phase14.md b/docs/devlog/phase14.md
new file mode 100644
index 0000000..4aa2a41
--- /dev/null
+++ b/docs/devlog/phase14.md
@@ -0,0 +1,19 @@
+# Phase 14 Devlog: Task Completion Updates
+
+## Implemented
+
+- Added task-file mutation helper to mark successful tasks complete.
+- Successful runs update the target task from `[ ]` to `[x]`.
+- Failed runs leave tasks incomplete.
+- Added `task-completion.md` artifacts recording the completion decision.
+- Added tests for task completion mutation and pipeline completion artifacts.
+
+## Decisions Made
+
+- Task completion uses a minimal line edit instead of rewriting the parsed task file.
+- Already-completed tasks are treated as no-op updates.
+- Completion happens before final report generation so reports can include task-file changes when git status is available.
+
+## Notes
+
+- More advanced task-file formatting preservation can be revisited if broader markdown support is added.
diff --git a/docs/devlog/phase15.md b/docs/devlog/phase15.md
new file mode 100644
index 0000000..aff024b
--- /dev/null
+++ b/docs/devlog/phase15.md
@@ -0,0 +1,22 @@
+# Phase 15 Devlog: Multi-Task Run Mode
+
+## Implemented
+
+- Added `nightshift run --all`.
+- Added `PipelineRunner.run_tasks()`.
+- Processes incomplete tasks in file order.
+- Reuses one artifact store/run directory for the batch.
+- Stops on first failure by default.
+- Added `pipeline.continue_on_task_failure` config support, defaulting to false.
+- Writes aggregate run summaries with completed and failed counts.
+- Added multi-task tests.
+
+## Decisions Made
+
+- `--all` and `--task` are mutually exclusive.
+- Failed and blocked tasks count as failed in aggregate summaries.
+- The default remains conservative: stop on first failure unless explicitly configured otherwise.
+
+## Notes
+
+- Multi-task mode is still sequential. Parallel execution remains out of scope.
diff --git a/docs/devlog/phase16.md b/docs/devlog/phase16.md
new file mode 100644
index 0000000..511de62
--- /dev/null
+++ b/docs/devlog/phase16.md
@@ -0,0 +1,21 @@
+# Phase 16 Devlog: Dependency Handling
+
+## Implemented
+
+- Parsed existing `Dependencies:` bullets into dependency lists.
+- Added dependency validation for missing references and simple cycles.
+- Added dependency-aware next-task selection.
+- Blocked specific task runs when dependencies are incomplete.
+- Blocked multi-task entries when dependencies are not satisfied by completed or earlier successful tasks.
+- Reported dependency warnings through status.
+- Added dependency tests.
+
+## Decisions Made
+
+- Dependencies are simple task IDs listed as bullets under `Dependencies:`.
+- Dependency enforcement is deterministic and follows task file order.
+- Missing references and cycles are validation errors; incomplete dependencies are runtime blockers.
+
+## Notes
+
+- No dependency solver or reordering is implemented. File order remains the source of execution order.
diff --git a/nightshift/cli.py b/nightshift/cli.py
index 1506dbf..8bc0601 100644
--- a/nightshift/cli.py
+++ b/nightshift/cli.py
@@ -10,7 +10,14 @@ from .config import validate_config
 from .errors import NightShiftError
 from .init import init_project
 from .pipeline import PipelineRunner
-from .tasks import parse_task_file, select_next_incomplete_task, select_task_by_id
+from .status import build_status, format_status
+from .tasks import (
+    ensure_dependencies_satisfied,
+    parse_task_file,
+    select_next_runnable_task,
+    select_task_by_id,
+    validate_task_dependencies,
+)
 
 
 def build_parser() -> argparse.ArgumentParser:
@@ -29,8 +36,10 @@ def build_parser() -> argparse.ArgumentParser:
     run_parser = subparsers.add_parser("run", help="Run the configured pipeline for one task.")
     run_parser.add_argument("--config", default="nightshift.yaml", help="Config file to use.")
     run_parser.add_argument("--task", help="Specific task id to run.")
+    run_parser.add_argument("--all", action="store_true", help="Run all runnable incomplete tasks.")
 
-    subparsers.add_parser("status", help="Status reporting is planned for a later phase.")
+    status_parser = subparsers.add_parser("status", help="Inspect NightShift project status.")
+    status_parser.add_argument("--config", default="nightshift.yaml", help="Config file to inspect.")
 
     return parser
 
@@ -50,6 +59,7 @@ def main(argv: list[str] | None = None) -> int:
         if args.command == "validate":
             config = validate_config(args.config)
             tasks = parse_task_file(config.project.root, config.project.task_file)
+            validate_task_dependencies(tasks)
             incomplete = sum(1 for task in tasks if not task.completed)
             print(f"Config valid: {config.path}")
             print(f"Project: {config.project.name}")
@@ -61,8 +71,23 @@ def main(argv: list[str] | None = None) -> int:
         if args.command == "run":
             config = validate_config(args.config)
             tasks = parse_task_file(config.project.root, config.project.task_file)
-            task = select_task_by_id(tasks, args.task) if args.task else select_next_incomplete_task(tasks)
-            result = PipelineRunner(config).run_task(task)
+            validate_task_dependencies(tasks)
+            if args.all and args.task:
+                parser.error("run accepts either --all or --task, not both.")
+            runner = PipelineRunner(config)
+            if args.all:
+                selected = [task for task in tasks if not task.completed]
+                result = runner.run_tasks(selected)
+                print(f"Status: {result.status}")
+                print(f"Tasks run: {len(result.task_results)}")
+                print(f"Completed: {result.completed_count}")
+                print(f"Failed: {result.failed_count}")
+                print(f"Reason: {result.reason}")
+                return 0 if result.status == "complete" else 1
+
+            task = select_task_by_id(tasks, args.task) if args.task else select_next_runnable_task(tasks)
+            ensure_dependencies_satisfied(tasks, task)
+            result = runner.run_task(task)
             print(f"Task: {result.task_id}")
             print(f"Status: {result.status}")
             print(f"Retries: {result.retry_count}")
@@ -70,8 +95,11 @@ def main(argv: list[str] | None = None) -> int:
             print(f"Reason: {result.reason}")
             return 0 if result.status == "complete" else 1
 
-        if args.command in {"status"}:
-            parser.error(f"'{args.command}' is not implemented yet.")
+        if args.command == "status":
+            config = validate_config(args.config)
+            tasks = parse_task_file(config.project.root, config.project.task_file)
+            print(format_status(build_status(config, tasks)))
+            return 0
 
     except NightShiftError as exc:
         print(str(exc), file=sys.stderr)
diff --git a/nightshift/config.py b/nightshift/config.py
index 541343a..73db4a9 100644
--- a/nightshift/config.py
+++ b/nightshift/config.py
@@ -58,6 +58,7 @@ class StageConfig:
 class PipelineConfig:
     max_task_retries: int
     stages: tuple[StageConfig, ...]
+    continue_on_task_failure: bool = False
 
 
 @dataclass(frozen=True)
@@ -188,6 +189,10 @@ def parse_config(raw: dict[str, Any], config_path: Path) -> NightShiftConfig:
     )
     if max_task_retries < 0:
         raise ConfigError("Config error: pipeline.max_task_retries must be zero or greater.")
+    continue_on_task_failure = _optional_bool(
+        pipeline_raw.get("continue_on_task_failure", False),
+        "pipeline.continue_on_task_failure",
+    )
 
     stages_raw = pipeline_raw.get("stages")
     if not isinstance(stages_raw, list) or not stages_raw:
@@ -254,7 +259,11 @@ def parse_config(raw: dict[str, Any], config_path: Path) -> NightShiftConfig:
         project=project,
         safety=safety,
         agents=agents,
-        pipeline=PipelineConfig(max_task_retries=max_task_retries, stages=tuple(stages)),
+        pipeline=PipelineConfig(
+            max_task_retries=max_task_retries,
+            stages=tuple(stages),
+            continue_on_task_failure=continue_on_task_failure,
+        ),
     )
 
 
diff --git a/nightshift/git.py b/nightshift/git.py
new file mode 100644
index 0000000..368bb1d
--- /dev/null
+++ b/nightshift/git.py
@@ -0,0 +1,89 @@
+"""Git safety and diff artifact helpers."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from pathlib import Path
+import subprocess
+
+from .artifacts import ArtifactStore
+from .errors import SafetyError
+
+
+@dataclass(frozen=True)
+class GitCommandResult:
+    available: bool
+    exit_code: int
+    stdout: str
+    stderr: str
+
+
+def run_git(project_root: Path, args: list[str], timeout_seconds: int = 15) -> GitCommandResult:
+    try:
+        completed = subprocess.run(
+            ["git", *args],
+            cwd=project_root,
+            capture_output=True,
+            text=True,
+            timeout=timeout_seconds,
+        )
+    except (OSError, subprocess.TimeoutExpired) as exc:
+        return GitCommandResult(False, -1, "", str(exc))
+    return GitCommandResult(completed.returncode == 0, completed.returncode, completed.stdout, completed.stderr)
+
+
+def get_git_status(project_root: Path) -> GitCommandResult:
+    return run_git(project_root, ["status", "--short"])
+
+
+def ensure_clean_worktree(project_root: Path, require_clean: bool) -> None:
+    if not require_clean:
+        return
+    status = get_git_status(project_root)
+    if not status.available:
+        raise SafetyError(
+            "Safety error: clean worktree is required, but git status could not be read: "
+            f"{status.stderr.strip() or 'unknown git error'}"
+        )
+    if status.stdout.strip():
+        raise SafetyError("Safety error: clean worktree is required, but repository is dirty.")
+
+
+def write_git_artifacts(artifacts: ArtifactStore, task_id: str, when: str) -> Path:
+    status = get_git_status(artifacts.project_root)
+    content = format_git_status(status, when)
+    return artifacts.write_stage_output(task_id, f"git-status-{when}.txt", content)
+
+
+def write_diff_artifact(artifacts: ArtifactStore, task_id: str) -> Path:
+    diff = run_git(artifacts.project_root, ["diff", "--binary"], timeout_seconds=30)
+    if not diff.available:
+        content = "Git diff unavailable.\n\n" + (diff.stderr or "")
+    elif diff.stdout:
+        content = diff.stdout
+    else:
+        content = "No tracked-file diff detected.\n"
+    return artifacts.write_stage_output(task_id, "diff.patch", content)
+
+
+def format_git_status(status: GitCommandResult, when: str) -> str:
+    lines = [
+        f"# Git Status {when}",
+        "",
+        f"Available: {str(status.available).lower()}",
+        f"Exit code: {status.exit_code}",
+        "",
+        "## stdout",
+        "",
+        "```text",
+        status.stdout.rstrip(),
+        "```",
+        "",
+        "## stderr",
+        "",
+        "```text",
+        status.stderr.rstrip(),
+        "```",
+        "",
+    ]
+    return "\n".join(lines)
diff --git a/nightshift/pipeline.py b/nightshift/pipeline.py
index 995697e..9512b9e 100644
--- a/nightshift/pipeline.py
+++ b/nightshift/pipeline.py
@@ -12,9 +12,10 @@ from .config import COMMAND_STAGE_TYPES, NightShiftConfig, StageConfig
 from .context import ContextManager
 from .errors import PipelineError
 from .errors import NightShiftError
+from .git import ensure_clean_worktree, write_diff_artifact, write_git_artifacts
 from .reports import ReportGenerator
 from .stages import StageResult
-from .tasks import Task
+from .tasks import Task, mark_task_completed
 
 
 @dataclass(frozen=True)
@@ -27,6 +28,15 @@ class PipelineResult:
     reason: str
 
 
+@dataclass(frozen=True)
+class MultiTaskResult:
+    status: str
+    task_results: tuple[PipelineResult, ...]
+    completed_count: int
+    failed_count: int
+    reason: str
+
+
 class PipelineRunner:
     """Execute configured stages for one task."""
 
@@ -55,9 +65,11 @@ class PipelineRunner:
         )
 
     def run_task(self, task: Task) -> PipelineResult:
+        ensure_clean_worktree(self.config.project.root, self.config.safety.require_clean_worktree)
         self.artifacts.initialize_run()
         self.artifacts.write_config_snapshot(self.config.path)
         self.artifacts.write_task_snapshot(task)
+        write_git_artifacts(self.artifacts, task.id, "before")
         self.context.ensure_project_context()
         self.context.create_task_context(task)
 
@@ -133,6 +145,20 @@ class PipelineRunner:
                 if result.context_update
             ],
         )
+        completion_changed = False
+        if final_status == "complete":
+            completion_changed = mark_task_completed(
+                self.config.project.root,
+                self.config.project.task_file,
+                task.id,
+            )
+        self.artifacts.write_stage_output(
+            task.id,
+            "task-completion.md",
+            format_task_completion(task, final_status, completion_changed),
+        )
+        write_git_artifacts(self.artifacts, task.id, "after")
+        write_diff_artifact(self.artifacts, task.id)
         self.reports.write_reports(
             task,
             final_status,
@@ -151,6 +177,59 @@ class PipelineRunner:
             reason=final_reason,
         )
 
+    def run_tasks(self, tasks: list[Task] | tuple[Task, ...]) -> MultiTaskResult:
+        self.artifacts.initialize_run()
+        results: list[PipelineResult] = []
+        known_ids = {task.id for task in tasks}
+        completed_ids = {task.id for task in tasks if task.completed}
+        for task in tasks:
+            if task.completed:
+                continue
+            missing_refs = [dependency for dependency in task.dependencies if dependency not in known_ids]
+            incomplete_deps = [
+                dependency for dependency in task.dependencies if dependency in known_ids and dependency not in completed_ids
+            ]
+            if missing_refs or incomplete_deps:
+                reason_parts = []
+                if missing_refs:
+                    reason_parts.append(f"missing dependencies: {', '.join(missing_refs)}")
+                if incomplete_deps:
+                    reason_parts.append(f"incomplete dependencies: {', '.join(incomplete_deps)}")
+                blocked = PipelineResult(
+                    task_id=task.id,
+                    status="blocked",
+                    retry_count=0,
+                    stage_results=(),
+                    artifact_dir="",
+                    reason="Task blocked by " + "; ".join(reason_parts),
+                )
+                results.append(blocked)
+                if not self.config.pipeline.continue_on_task_failure:
+                    break
+                continue
+            result = self.run_task(task)
+            results.append(result)
+            if result.status == "complete":
+                completed_ids.add(task.id)
+            if result.status != "complete" and not self.config.pipeline.continue_on_task_failure:
+                break
+
+        completed_count = sum(1 for result in results if result.status == "complete")
+        failed_count = sum(1 for result in results if result.status != "complete")
+        status = "complete" if failed_count == 0 else "failed"
+        reason = "All selected tasks completed." if status == "complete" else "One or more tasks failed."
+        self.artifacts.run_summary_path.write_text(
+            format_aggregate_run_summary(results, status, reason),
+            encoding="utf-8",
+        )
+        return MultiTaskResult(
+            status=status,
+            task_results=tuple(results),
+            completed_count=completed_count,
+            failed_count=failed_count,
+            reason=reason,
+        )
+
     def _run_stage(
         self,
         stage: StageConfig,
@@ -217,3 +296,40 @@ def format_summary_stage(
             "",
         ]
     )
+
+
+def format_task_completion(task: Task, status: str, changed: bool) -> str:
+    return "\n".join(
+        [
+            "# Task Completion",
+            "",
+            f"Task: `{task.id}`",
+            f"Pipeline status: {status}",
+            f"Marked complete: {str(changed).lower()}",
+            "",
+        ]
+    )
+
+
+def format_aggregate_run_summary(results: list[PipelineResult], status: str, reason: str) -> str:
+    lines = [
+        "# Run Summary",
+        "",
+        f"Status: {status}",
+        f"Reason: {reason}",
+        f"Tasks run: {len(results)}",
+        f"Completed tasks: {sum(1 for result in results if result.status == 'complete')}",
+        f"Failed tasks: {sum(1 for result in results if result.status != 'complete')}",
+        "",
+        "## Tasks",
+        "",
+    ]
+    if not results:
+        lines.append("- None")
+    for result in results:
+        lines.append(
+            f"- `{result.task_id}`: {result.status} "
+            f"(retries: {result.retry_count}) - {result.reason}"
+        )
+    lines.append("")
+    return "\n".join(lines)
diff --git a/nightshift/status.py b/nightshift/status.py
new file mode 100644
index 0000000..d2e3215
--- /dev/null
+++ b/nightshift/status.py
@@ -0,0 +1,67 @@
+"""Project status inspection."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from pathlib import Path
+
+from .config import NightShiftConfig
+from .tasks import Task, dependency_problems, select_next_runnable_task
+
+
+@dataclass(frozen=True)
+class ProjectStatus:
+    config_path: Path
+    project_root: Path
+    task_count: int
+    completed_count: int
+    incomplete_count: int
+    next_task_id: str | None
+    latest_run_dir: Path | None
+    warnings: tuple[str, ...]
+
+
+def build_status(config: NightShiftConfig, tasks: list[Task]) -> ProjectStatus:
+    latest = latest_run_dir(config.project.root / config.project.artifact_dir / "runs")
+    warnings = dependency_problems(tasks)
+    try:
+        next_task = select_next_runnable_task(tasks)
+        next_task_id = next_task.id
+    except Exception:
+        next_task_id = None
+    completed = sum(1 for task in tasks if task.completed)
+    return ProjectStatus(
+        config_path=config.path,
+        project_root=config.project.root,
+        task_count=len(tasks),
+        completed_count=completed,
+        incomplete_count=len(tasks) - completed,
+        next_task_id=next_task_id,
+        latest_run_dir=latest,
+        warnings=tuple(warnings),
+    )
+
+
+def latest_run_dir(runs_dir: Path) -> Path | None:
+    if not runs_dir.exists() or not runs_dir.is_dir():
+        return None
+    candidates = [path for path in runs_dir.iterdir() if path.is_dir()]
+    if not candidates:
+        return None
+    return max(candidates, key=lambda path: path.stat().st_mtime)
+
+
+def format_status(status: ProjectStatus) -> str:
+    lines = [
+        f"Config: {status.config_path}",
+        f"Project root: {status.project_root}",
+        f"Tasks: {status.task_count}",
+        f"Completed tasks: {status.completed_count}",
+        f"Incomplete tasks: {status.incomplete_count}",
+        f"Next task: {status.next_task_id or '<none>'}",
+        f"Latest run: {status.latest_run_dir or '<none>'}",
+    ]
+    if status.warnings:
+        lines.append("Warnings:")
+        lines.extend(f"- {warning}" for warning in status.warnings)
+    return "\n".join(lines)
diff --git a/nightshift/tasks.py b/nightshift/tasks.py
index 6cf3cc8..b8bed76 100644
--- a/nightshift/tasks.py
+++ b/nightshift/tasks.py
@@ -41,6 +41,13 @@ def parse_task_file(project_root: str | Path, task_file: str | Path) -> list[Tas
     return parse_tasks(path.read_text(encoding="utf-8"))
 
 
+def task_file_path(project_root: str | Path, task_file: str | Path) -> Path:
+    try:
+        return resolve_inside_root(project_root, task_file, "task file")
+    except SafetyError as exc:
+        raise TaskError(str(exc)) from exc
+
+
 def parse_tasks(markdown: str) -> list[Task]:
     """Parse NightShift's documented markdown checklist task format."""
 
@@ -114,6 +121,24 @@ def select_next_incomplete_task(tasks: list[Task] | tuple[Task, ...]) -> Task:
     raise TaskError("Task error: no incomplete tasks found.")
 
 
+def select_next_runnable_task(tasks: list[Task] | tuple[Task, ...]) -> Task:
+    """Return the first incomplete task whose dependencies are complete."""
+
+    completed = {task.id for task in tasks if task.completed}
+    blocked: list[str] = []
+    for task in tasks:
+        if task.completed:
+            continue
+        missing = [dependency for dependency in task.dependencies if dependency not in completed]
+        if missing:
+            blocked.append(f"{task.id} blocked by {', '.join(missing)}")
+            continue
+        return task
+    if blocked:
+        raise TaskError("Task error: no runnable incomplete tasks. " + "; ".join(blocked))
+    raise TaskError("Task error: no incomplete tasks found.")
+
+
 def select_task_by_id(tasks: list[Task] | tuple[Task, ...], task_id: str) -> Task:
     """Return a task by id."""
 
@@ -124,6 +149,58 @@ def select_task_by_id(tasks: list[Task] | tuple[Task, ...], task_id: str) -> Tas
     raise TaskError(f"Task error: unknown task id '{task_id}'. Available tasks: {available}.")
 
 
+def ensure_dependencies_satisfied(tasks: list[Task] | tuple[Task, ...], task: Task) -> None:
+    task_ids = {candidate.id for candidate in tasks}
+    completed = {candidate.id for candidate in tasks if candidate.completed}
+    missing_refs = [dependency for dependency in task.dependencies if dependency not in task_ids]
+    if missing_refs:
+        raise TaskError(
+            f"Task error: task '{task.id}' references missing dependencies: "
+            f"{', '.join(missing_refs)}."
+        )
+    incomplete = [dependency for dependency in task.dependencies if dependency not in completed]
+    if incomplete:
+        raise TaskError(
+            f"Task error: task '{task.id}' is blocked by incomplete dependencies: "
+            f"{', '.join(incomplete)}."
+        )
+
+
+def dependency_problems(tasks: list[Task] | tuple[Task, ...]) -> list[str]:
+    task_ids = {task.id for task in tasks}
+    problems: list[str] = []
+    for task in tasks:
+        for dependency in task.dependencies:
+            if dependency not in task_ids:
+                problems.append(f"Task '{task.id}' references missing dependency '{dependency}'.")
+    problems.extend(_cycle_problems(tasks))
+    return problems
+
+
+def validate_task_dependencies(tasks: list[Task] | tuple[Task, ...]) -> None:
+    problems = dependency_problems(tasks)
+    if problems:
+        raise TaskError("Task dependency error: " + " ".join(problems))
+
+
+def mark_task_completed(project_root: str | Path, task_file: str | Path, task_id: str) -> bool:
+    """Mark a task complete in the markdown task file with a minimal line edit."""
+
+    path = task_file_path(project_root, task_file)
+    if not path.exists():
+        raise TaskError(f"Task error: task file does not exist: {path}")
+    lines = path.read_text(encoding="utf-8").splitlines(keepends=True)
+    for index, line in enumerate(lines):
+        match = TASK_HEADER_RE.match(line.rstrip("\r\n"))
+        if match and match.group("id") == task_id:
+            if match.group("mark").lower() == "x":
+                return False
+            lines[index] = re.sub(r"\[[ ]\]", "[x]", line, count=1)
+            path.write_text("".join(lines), encoding="utf-8")
+            return True
+    raise TaskError(f"Task error: cannot mark unknown task complete: {task_id}.")
+
+
 def _extract_section(block: list[str], section_name: str) -> str:
     start = _find_section_index(block, section_name)
     if start is None:
@@ -161,3 +238,28 @@ def _find_section_index(block: list[str], section_name: str) -> int | None:
         if line.strip().lower() == expected:
             return index
     return None
+
+
+def _cycle_problems(tasks: list[Task] | tuple[Task, ...]) -> list[str]:
+    graph = {task.id: tuple(dep for dep in task.dependencies if dep in {item.id for item in tasks}) for task in tasks}
+    visiting: set[str] = set()
+    visited: set[str] = set()
+    problems: list[str] = []
+
+    def visit(task_id: str, path: list[str]) -> None:
+        if task_id in visited:
+            return
+        if task_id in visiting:
+            cycle_start = path.index(task_id) if task_id in path else 0
+            cycle = " -> ".join(path[cycle_start:] + [task_id])
+            problems.append(f"Dependency cycle detected: {cycle}.")
+            return
+        visiting.add(task_id)
+        for dependency in graph.get(task_id, ()):
+            visit(dependency, path + [dependency])
+        visiting.remove(task_id)
+        visited.add(task_id)
+
+    for task_id in graph:
+        visit(task_id, [task_id])
+    return problems
diff --git a/tests/test_git.py b/tests/test_git.py
new file mode 100644
index 0000000..15d2686
--- /dev/null
+++ b/tests/test_git.py
@@ -0,0 +1,43 @@
+from pathlib import Path
+import shutil
+import subprocess
+import tempfile
+import unittest
+
+from nightshift.artifacts import ArtifactStore
+from nightshift.errors import SafetyError
+from nightshift.git import ensure_clean_worktree, write_diff_artifact, write_git_artifacts
+
+
+def git_available() -> bool:
+    return shutil.which("git") is not None
+
+
+@unittest.skipUnless(git_available(), "git is not available")
+class GitSafetyTests(unittest.TestCase):
+    def test_clean_worktree_requirement_blocks_dirty_repo(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            subprocess.run(["git", "init"], cwd=root, check=True, capture_output=True, text=True)
+            (root / "file.txt").write_text("dirty", encoding="utf-8")
+
+            with self.assertRaisesRegex(SafetyError, "repository is dirty"):
+                ensure_clean_worktree(root, True)
+
+    def test_git_artifacts_are_written_for_repo(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            subprocess.run(["git", "init"], cwd=root, check=True, capture_output=True, text=True)
+            (root / "file.txt").write_text("dirty", encoding="utf-8")
+            artifacts = ArtifactStore(root, ".nightshift", run_id="test-run")
+
+            status_path = write_git_artifacts(artifacts, "TASK-001", "before")
+            diff_path = write_diff_artifact(artifacts, "TASK-001")
+
+            self.assertTrue(status_path.exists())
+            self.assertTrue(diff_path.exists())
+            self.assertIn("Git Status before", status_path.read_text(encoding="utf-8"))
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/test_pipeline.py b/tests/test_pipeline.py
index d5cfa22..c9b0853 100644
--- a/tests/test_pipeline.py
+++ b/tests/test_pipeline.py
@@ -145,6 +145,89 @@ class PipelineRunnerTests(unittest.TestCase):
                 (root / ".nightshift" / "runs" / "test-run" / "tasks" / task.id / "final-notes.md").exists()
             )
 
+    def test_successful_task_is_marked_complete_and_git_artifacts_exist(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            _write_common_files(root)
+            stages = (
+                StageConfig(id="plan", type="agent", agent="planner", output="plan.md"),
+            )
+            config = make_config(root, stages)
+            runner = PipelineRunner(config, ArtifactStore(root, ".nightshift", run_id="test-run"))
+            task = parse_tasks(TASK_MD)[0]
+
+            result = runner.run_task(task)
+
+            self.assertEqual(result.status, "complete")
+            self.assertIn("- [x] TASK-001", (root / "tasks.md").read_text(encoding="utf-8"))
+            task_dir = root / ".nightshift" / "runs" / "test-run" / "tasks" / task.id
+            self.assertTrue((task_dir / "task-completion.md").exists())
+            self.assertTrue((task_dir / "git-status-before.txt").exists())
+            self.assertTrue((task_dir / "git-status-after.txt").exists())
+            self.assertTrue((task_dir / "diff.patch").exists())
+
+    def test_multi_task_run_writes_aggregate_summary_and_stops_on_failure(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            _write_common_files(root)
+            tasks_md = TASK_MD + """
+
+- [ ] TASK-002: Second task
+
+Description:
+Should not run after failure.
+
+Acceptance Criteria:
+- skipped
+"""
+            (root / "tasks.md").write_text(tasks_md, encoding="utf-8")
+            stages = (
+                StageConfig(
+                    id="test",
+                    type="command",
+                    commands=('python -c "print(\'missing\')"',),
+                    output="../bad.txt",
+                ),
+            )
+            config = make_config(root, stages, max_retries=0)
+            runner = PipelineRunner(config, ArtifactStore(root, ".nightshift", run_id="test-run"))
+            tasks = parse_tasks(tasks_md)
+
+            result = runner.run_tasks(tasks)
+
+            self.assertEqual(result.status, "failed")
+            self.assertEqual(len(result.task_results), 1)
+            summary = (root / ".nightshift" / "runs" / "test-run" / "run-summary.md").read_text(encoding="utf-8")
+            self.assertIn("Tasks run: 1", summary)
+
+    def test_multi_task_run_blocks_incomplete_dependency(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            _write_common_files(root)
+            tasks_md = """# Tasks
+
+- [ ] TASK-001: Blocked
+
+Dependencies:
+- TASK-002
+
+Acceptance Criteria:
+- blocked
+
+- [ ] TASK-002: Later
+
+Acceptance Criteria:
+- later
+"""
+            (root / "tasks.md").write_text(tasks_md, encoding="utf-8")
+            config = make_config(root, (), max_retries=0)
+            runner = PipelineRunner(config, ArtifactStore(root, ".nightshift", run_id="test-run"))
+
+            result = runner.run_tasks(parse_tasks(tasks_md))
+
+            self.assertEqual(result.status, "failed")
+            self.assertEqual(result.task_results[0].status, "blocked")
+
 
 def _write_common_files(root: Path) -> None:
     (root / "nightshift.yaml").write_text("project:\n  name: test\n", encoding="utf-8")
diff --git a/tests/test_status.py b/tests/test_status.py
new file mode 100644
index 0000000..dd2fd87
--- /dev/null
+++ b/tests/test_status.py
@@ -0,0 +1,33 @@
+from pathlib import Path
+import tempfile
+import unittest
+
+from nightshift.artifacts import ArtifactStore
+from nightshift.config import load_config
+from nightshift.init import init_project
+from nightshift.status import build_status, format_status
+from nightshift.tasks import parse_task_file
+
+
+class StatusTests(unittest.TestCase):
+    def test_status_reports_counts_and_latest_run(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            init_project(root)
+            ArtifactStore(root, ".nightshift", run_id="run-a").initialize_run()
+            config = load_config(root / "nightshift.yaml")
+            tasks = parse_task_file(config.project.root, config.project.task_file)
+
+            status = build_status(config, tasks)
+            output = format_status(status)
+
+            self.assertEqual(status.task_count, 1)
+            self.assertEqual(status.incomplete_count, 1)
+            self.assertEqual(status.next_task_id, "TASK-001")
+            self.assertIsNotNone(status.latest_run_dir)
+            self.assertIn("Project root:", output)
+            self.assertIn("Latest run:", output)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/test_tasks.py b/tests/test_tasks.py
index fedf73d..710f004 100644
--- a/tests/test_tasks.py
+++ b/tests/test_tasks.py
@@ -4,10 +4,15 @@ import unittest
 
 from nightshift.errors import TaskError
 from nightshift.tasks import (
+    dependency_problems,
+    ensure_dependencies_satisfied,
+    mark_task_completed,
     parse_task_file,
     parse_tasks,
     select_next_incomplete_task,
+    select_next_runnable_task,
     select_task_by_id,
+    validate_task_dependencies,
 )
 
 
@@ -107,6 +112,61 @@ No acceptance criteria.
         with self.assertRaisesRegex(TaskError, "no tasks found"):
             parse_tasks("# Tasks\n\nNothing here.\n")
 
+    def test_dependency_blocks_specific_task_selection(self) -> None:
+        tasks = parse_tasks(TASKS_MD.replace("[x] TASK-001", "[ ] TASK-001"))
+
+        with self.assertRaisesRegex(TaskError, "blocked by incomplete dependencies"):
+            ensure_dependencies_satisfied(tasks, tasks[1])
+
+    def test_select_next_runnable_skips_blocked_tasks(self) -> None:
+        markdown = TASKS_MD.replace("[x] TASK-001", "[ ] TASK-001")
+        tasks = parse_tasks(markdown)
+
+        selected = select_next_runnable_task(tasks)
+
+        self.assertEqual(selected.id, "TASK-001")
+
+    def test_dependency_validation_reports_missing_and_cycles(self) -> None:
+        markdown = """# Tasks
+
+- [ ] TASK-001: First
+
+Dependencies:
+- TASK-002
+
+Acceptance Criteria:
+- ok
+
+- [ ] TASK-002: Second
+
+Dependencies:
+- TASK-001
+- TASK-999
+
+Acceptance Criteria:
+- ok
+"""
+        tasks = parse_tasks(markdown)
+
+        problems = dependency_problems(tasks)
+
+        self.assertTrue(any("TASK-999" in problem for problem in problems))
+        self.assertTrue(any("cycle" in problem.lower() for problem in problems))
+        with self.assertRaisesRegex(TaskError, "Task dependency error"):
+            validate_task_dependencies(tasks)
+
+    def test_mark_task_completed_updates_only_target_line(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            task_path = root / "tasks.md"
+            task_path.write_text(TASKS_MD, encoding="utf-8")
+
+            changed = mark_task_completed(root, "tasks.md", "TASK-002")
+
+            self.assertTrue(changed)
+            content = task_path.read_text(encoding="utf-8")
+            self.assertIn("- [x] TASK-002: Add artifact directory creation", content)
+
 
 if __name__ == "__main__":
     unittest.main()