diff --git a/CHANGELOG.md b/CHANGELOG.md
index e986e0b0..94e0f6d0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,15 @@
 
 ### Added
 
+- **Interactive Research Mode**: Human-in-the-loop research using graph-based decision nodes
+  - `haiku-rag research --interactive` starts conversational CLI chat
+  - Natural language interpretation for user commands (search, modify questions, synthesize)
+  - Chat with assistant before starting research, and during decision points
+  - Review collected answers and pending questions at each decision point
+  - Add, remove, or modify sub-questions through natural conversation
+  - New `human_decide` graph node emits AG-UI tool calls (`TOOL_CALL_START/ARGS/END`) for frontend integration
+  - New `emit_tool_call_start()`, `emit_tool_call_args()`, `emit_tool_call_end()` AG-UI event helpers
+  - New `AGUIEmitter.emit()` method for direct event emission
 - **HotpotQA Evaluation**: Added HotpotQA dataset adapter for multi-hop QA benchmarks
   - Extracts unique documents from validation set context paragraphs
   - Uses MAP for retrieval evaluation (multiple supporting documents per question)
diff --git a/docs/agents.md b/docs/agents.md
index 59c48482..103afa9c 100644
--- a/docs/agents.md
+++ b/docs/agents.md
@@ -196,3 +196,27 @@ report = await graph.run(state=state, deps=deps)
 ```
 
 The filter applies to all search operations in the graph. See [Filtering Search Results](python.md#filtering-search-results) for available filter columns and syntax.
+
+### Interactive Research Mode
+
+Interactive mode provides human-in-the-loop control over the research process through a conversational interface.
+
+**CLI usage:**
+
+```bash
+# Start interactive research mode
+haiku-rag research --interactive
+
+# With document filter
+haiku-rag research --interactive --filter "uri LIKE '%report%'"
+```
+
+In interactive mode, you can:
+
+- Chat with the assistant before starting research
+- Review the generated sub-questions after planning
+- Add, remove, or modify questions through natural conversation
+- Execute searches and review collected answers
+- Continue researching or synthesize when ready
+
+For a web-based interactive experience, see the [AG-UI Research Example](https://github.com/ggozad/haiku.rag/tree/main/examples/ag-ui-research).
diff --git a/examples/ag-ui-research/backend/agent.py b/examples/ag-ui-research/backend/agent.py
index e697145f..9537a4c3 100644
--- a/examples/ag-ui-research/backend/agent.py
+++ b/examples/ag-ui-research/backend/agent.py
@@ -9,10 +9,10 @@ from pydantic_ai import Agent, RunContext
 from haiku.rag.client import HaikuRAG
 from haiku.rag.config import load_yaml_config
 from haiku.rag.config.models import AppConfig
-from haiku.rag.graph.common import get_model
 from haiku.rag.graph.research.dependencies import ResearchContext
 from haiku.rag.graph.research.graph import build_research_graph
 from haiku.rag.graph.research.state import ResearchDeps, ResearchState
+from haiku.rag.utils import get_model
 
 if TYPE_CHECKING:
     from haiku.rag.graph.agui.emitter import AGUIEmitter
diff --git a/haiku_rag_slim/haiku/rag/cli.py b/haiku_rag_slim/haiku/rag/cli.py
index 42f8fbd9..cc8be9f6 100644
--- a/haiku_rag_slim/haiku/rag/cli.py
+++ b/haiku_rag_slim/haiku/rag/cli.py
@@ -321,7 +321,8 @@ def ask(
 @cli.command("research", help="Run multi-agent research and output a concise report")
 def research(
     question: str = typer.Argument(
-        help="The research question to investigate",
+        None,
+        help="The research question to investigate (required unless --interactive)",
     ),
     db: Path | None = typer.Option(
         None,
@@ -339,9 +340,33 @@ def research(
         "-f",
         help="SQL WHERE clause to filter documents (e.g., \"uri LIKE '%arxiv%'\")",
     ),
+    interactive: bool = typer.Option(
+        False,
+        "--interactive",
+        "-i",
+        help="Start interactive research mode with human-in-the-loop",
+    ),
 ):
     app = create_app(db)
-    asyncio.run(app.research(question=question, verbose=verbose, filter=filter))
+
+    if interactive:
+        from haiku.rag.cli_chat import interactive_research
+        from haiku.rag.client import HaikuRAG
+
+        client = HaikuRAG(db_path=app.db_path, config=app.config)
+        try:
+            interactive_research(
+                client=client,
+                config=app.config,
+                search_filter=filter,
+            )
+        finally:
+            client.close()
+    else:
+        if question is None:
+            typer.echo("Error: Question is required unless using --interactive mode")
+            raise typer.Exit(1)
+        asyncio.run(app.research(question=question, verbose=verbose, filter=filter))
 
 
 @cli.command("settings", help="Display current configuration settings")
diff --git a/haiku_rag_slim/haiku/rag/cli_chat.py b/haiku_rag_slim/haiku/rag/cli_chat.py
new file mode 100644
index 00000000..bf67f300
--- /dev/null
+++ b/haiku_rag_slim/haiku/rag/cli_chat.py
@@ -0,0 +1,465 @@
+"""Interactive CLI chat loop for research graph with human-in-the-loop."""
+
+import asyncio
+
+from pydantic_ai import Agent
+from rich.console import Console
+from rich.markdown import Markdown
+from rich.panel import Panel
+from rich.prompt import Prompt
+
+from haiku.rag.client import HaikuRAG
+from haiku.rag.config import get_config
+from haiku.rag.config.models import AppConfig
+from haiku.rag.graph.agui.emitter import AGUIEmitter
+from haiku.rag.graph.research.dependencies import ResearchContext
+from haiku.rag.graph.research.graph import build_research_graph
+from haiku.rag.graph.research.models import ResearchReport
+from haiku.rag.graph.research.state import HumanDecision, ResearchDeps, ResearchState
+from haiku.rag.utils import get_model
+
+INITIAL_CHAT_PROMPT = """You are a research assistant. The user hasn't started a research task yet.
+
+You can:
+1. Chat with the user - greet them, answer questions about what you can do
+2. Detect when they want to research something
+
+## Actions:
+- "chat": User is chatting, greeting, or asking questions (set message with your response)
+- "research": User wants to research a topic (extract the research question into research_question)
+
+## Guidelines:
+- If the user provides a clear research question or topic, set action="research" and extract the question
+- If the user is just chatting or asking what you can do, set action="chat" and respond helpfully
+- Be friendly and explain you can help them research topics by searching a knowledge base
+
+Examples:
+- "hi" → action="chat", message="Hello! I'm a research assistant. I can help you research topics by searching through documents and synthesizing findings. What would you like to explore?"
+- "what can you do?" → action="chat", message="I help you conduct research! Give me a question or topic, and I'll break it into sub-questions, search for answers, and synthesize a report. What are you curious about?"
+- "tell me about Python's memory management" → action="research", research_question="How does Python's memory management work?"
+- "I want to understand how RAG systems work" → action="research", research_question="How do RAG (Retrieval-Augmented Generation) systems work?"
+"""
+
+RESEARCH_ASSISTANT_PROMPT = """You are a research assistant helping the user conduct research on a topic.
+
+You are at a decision point in the research workflow. You can:
+1. Chat with the user - answer questions, discuss the research, make suggestions
+2. Take workflow actions when the user requests them
+
+## Workflow Actions (set in the action field):
+- "search": Search the pending questions (user says: "go", "search", "yes", "continue", "looks good")
+- "synthesize": Generate final report (user says: "done", "finish", "synthesize", "generate report")
+- "add_questions": Add NEW research questions to the existing list
+- "modify_questions": REPLACE all pending questions with a new list (use when user wants to remove, keep only certain questions, or change the questions)
+- "chat": Have a conversation without modifying questions
+
+## IMPORTANT - Modifying Questions:
+- "use only the first question" → action="modify_questions", questions=[first question from the list]
+- "drop questions 2 and 3" → action="modify_questions", questions=[remaining questions]
+- "keep only questions about X" → action="modify_questions", questions=[filtered list]
+- "remove the duplicate" → action="modify_questions", questions=[deduplicated list]
+- When user wants to reduce/filter/keep-only, use "modify_questions" NOT "chat"
+
+## Guidelines:
+- If the user wants to modify the question list in ANY way (remove, keep only, filter), use "modify_questions"
+- For "modify_questions", include ALL questions that should remain in the questions field
+- You can combine "chat" with a message to explain what you're doing
+- If just chatting without changes, set action="chat" and provide helpful response in message
+"""
+
+
+async def initial_chat(
+    user_message: str,
+    config: AppConfig,
+) -> HumanDecision:
+    """Handle initial conversation before research starts.
+
+    Args:
+        user_message: The user's message
+        config: Application configuration
+
+    Returns:
+        HumanDecision with chat response or research question
+    """
+    agent: Agent[None, HumanDecision] = Agent(
+        model=get_model(config.research.model, config),
+        output_type=HumanDecision,
+        instructions=INITIAL_CHAT_PROMPT,
+        retries=2,
+    )
+
+    result = await agent.run(user_message)
+    return result.output
+
+
+async def interpret_user_decision(
+    user_message: str,
+    sub_questions: list[str],
+    qa_responses: list[dict],
+    config: AppConfig,
+) -> HumanDecision:
+    """Interpret a natural language user message into a HumanDecision.
+
+    Args:
+        user_message: The user's natural language input
+        sub_questions: Current sub-questions pending search
+        qa_responses: Answers already collected
+        config: Application configuration
+
+    Returns:
+        HumanDecision with the interpreted action, questions, and/or message
+    """
+    agent: Agent[None, HumanDecision] = Agent(
+        model=get_model(config.research.model, config),
+        output_type=HumanDecision,
+        instructions=RESEARCH_ASSISTANT_PROMPT,
+        retries=2,
+    )
+
+    # Build context with full research state
+    answers_summary = ""
+    if qa_responses:
+        answers_parts = []
+        for qa in qa_responses:
+            conf = f"{qa['confidence']:.0%}" if qa.get("confidence") else "N/A"
+            answers_parts.append(
+                f"Q: {qa['query']}\nA: {qa['answer'][:300]}... (confidence: {conf})"
+            )
+        answers_summary = "\n\n".join(answers_parts)
+
+    context = f"""Current research state:
+- Answers collected: {len(qa_responses)}
+- Pending questions to search: {len(sub_questions)}
+
+Pending questions:
+{chr(10).join(f"- {q}" for q in sub_questions) if sub_questions else "(none)"}
+
+{f"Collected answers:{chr(10)}{answers_summary}" if answers_summary else ""}
+
+User message: {user_message}"""
+
+    result = await agent.run(context)
+    return result.output
+
+
+async def run_interactive_research(
+    question: str,
+    client: HaikuRAG,
+    config: AppConfig | None = None,
+    search_filter: str | None = None,
+) -> ResearchReport:
+    """Run interactive research with human-in-the-loop decision points.
+
+    Args:
+        question: The research question
+        client: HaikuRAG client for document operations
+        config: Application configuration (uses global config if None)
+        search_filter: Optional SQL WHERE clause to filter documents
+
+    Returns:
+        ResearchReport with the final synthesis
+    """
+    config = config or get_config()
+    console = Console()
+
+    # Build interactive graph
+    graph = build_research_graph(config=config, include_plan=True, interactive=True)
+
+    # Create async queue for human input
+    human_input_queue: asyncio.Queue[HumanDecision] = asyncio.Queue()
+
+    # Create emitter
+    emitter: AGUIEmitter[ResearchState, ResearchReport] = AGUIEmitter()
+
+    # Create deps with queue
+    deps = ResearchDeps(
+        client=client,
+        agui_emitter=emitter,
+        human_input_queue=human_input_queue,
+        interactive=True,
+    )
+
+    # Create initial state
+    context = ResearchContext(original_question=question)
+    state = ResearchState.from_config(context=context, config=config)
+    state.search_filter = search_filter
+
+    # Start the run
+    emitter.start_run(state)
+
+    # Run graph in background task
+    async def run_graph() -> ResearchReport:
+        try:
+            result = await graph.run(state=state, deps=deps)
+            emitter.finish_run(result)
+            return result
+        except Exception as e:
+            emitter.error(e)
+            raise
+
+    graph_task = asyncio.create_task(run_graph())
+
+    # Process events and handle human decision points
+    try:
+        async for event in emitter:
+            event_type = event.get("type")
+
+            if event_type == "STEP_STARTED":
+                step_name = event.get("stepName", "")
+                if step_name == "plan":
+                    console.print("[dim]Planning research...[/dim]")
+                elif step_name.startswith("search:"):
+                    query = step_name.replace("search: ", "")
+                    console.print(f"[dim]Searching: {query}[/dim]")
+                elif step_name == "synthesize":
+                    console.print("[dim]Synthesizing report...[/dim]")
+
+            elif event_type == "STATE_SNAPSHOT" or event_type == "STATE_DELTA":
+                # State updated, could show progress
+                pass
+
+            elif event_type == "TOOL_CALL_START":
+                tool_name = event.get("toolCallName")
+                if tool_name == "human_decision":
+                    # Will get args in next event
+                    pass
+
+            elif event_type == "TOOL_CALL_ARGS":
+                args = event.get("delta", {})
+                original_question = args.get("original_question", "")
+                sub_questions = list(args.get("sub_questions", []))
+                qa_responses = args.get("qa_responses", [])
+                iterations = args.get("iterations", 0)
+
+                # Loop for modifications until user wants to proceed
+                while True:
+                    # Show research state
+                    console.print()
+                    console.print(
+                        Panel(
+                            f"[bold]{original_question}[/bold]",
+                            title="Research Question",
+                            border_style="blue",
+                        )
+                    )
+
+                    # Show collected answers
+                    if qa_responses:
+                        answers_text = []
+                        for i, qa in enumerate(qa_responses, 1):
+                            conf = (
+                                f"{qa['confidence']:.0%}"
+                                if qa.get("confidence")
+                                else "N/A"
+                            )
+                            answer_preview = (
+                                qa["answer"][:200] + "..."
+                                if len(qa["answer"]) > 200
+                                else qa["answer"]
+                            )
+                            answers_text.append(
+                                f"[cyan]{i}. {qa['query']}[/cyan]\n"
+                                f"   [dim]Confidence: {conf} | Citations: {qa.get('citations_count', 0)}[/dim]\n"
+                                f"   {answer_preview}"
+                            )
+                        console.print(
+                            Panel(
+                                "\n\n".join(answers_text),
+                                title=f"Answers Collected ({len(qa_responses)})",
+                                border_style="green",
+                            )
+                        )
+
+                    # Show pending questions
+                    if sub_questions:
+                        console.print(
+                            Panel(
+                                "\n".join(
+                                    f"{i + 1}. {q}" for i, q in enumerate(sub_questions)
+                                ),
+                                title="Pending Questions to Search",
+                                border_style="cyan",
+                            )
+                        )
+                    else:
+                        console.print("[dim]No pending questions.[/dim]")
+
+                    if iterations > 0:
+                        console.print(f"[dim]Iteration: {iterations}[/dim]")
+
+                    # Prompt user for natural language input
+                    console.print()
+                    user_input = Prompt.ask("[bold]What would you like to do?[/bold]")
+
+                    # Chat with research assistant
+                    console.print("[dim]Thinking...[/dim]")
+                    decision = await interpret_user_decision(
+                        user_message=user_input,
+                        sub_questions=sub_questions,
+                        qa_responses=qa_responses,
+                        config=config,
+                    )
+
+                    # Handle modifications and chat locally, continue loop
+                    if decision.action == "chat":
+                        if decision.message:
+                            console.print(
+                                f"\n[bold cyan]Assistant:[/bold cyan] {decision.message}"
+                            )
+                        continue
+                    elif decision.action == "add_questions" and decision.questions:
+                        sub_questions.extend(decision.questions)
+                        console.print(
+                            f"[green]Added {len(decision.questions)} question(s)[/green]"
+                        )
+                        continue
+                    elif decision.action == "modify_questions" and decision.questions:
+                        sub_questions = list(decision.questions)
+                        console.print(
+                            f"[green]Replaced with {len(decision.questions)} question(s)[/green]"
+                        )
+                        continue
+
+                    # User wants to proceed - send final decision
+                    action_display = {
+                        "search": "Searching questions",
+                        "synthesize": "Generating report",
+                    }
+                    console.print(
+                        f"[dim]→ {action_display.get(decision.action, decision.action)}[/dim]"
+                    )
+
+                    # Include any accumulated question changes
+                    if decision.action == "search":
+                        decision = HumanDecision(
+                            action="modify_questions", questions=sub_questions
+                        )
+
+                    await human_input_queue.put(decision)
+                    break
+
+            elif event_type == "TEXT_MESSAGE_CHUNK":
+                # Log message from graph
+                message = event.get("delta", "")
+                if message:
+                    console.print(f"[dim]{message}[/dim]")
+
+            elif event_type == "RUN_FINISHED":
+                break
+
+            elif event_type == "RUN_ERROR":
+                error_msg = event.get("message", "Unknown error")
+                console.print(f"[red]Error: {error_msg}[/red]")
+                break
+
+        # Wait for graph to complete
+        report = await graph_task
+        return report
+
+    except Exception as e:
+        graph_task.cancel()
+        raise e
+    finally:
+        await emitter.close()
+
+
+async def run_chat_loop(
+    client: HaikuRAG,
+    config: AppConfig | None = None,
+    search_filter: str | None = None,
+) -> None:
+    """Run an interactive chat loop for research.
+
+    Args:
+        client: HaikuRAG client for document operations
+        config: Application configuration (uses global config if None)
+        search_filter: Optional SQL WHERE clause to filter documents
+    """
+    config = config or get_config()
+    console = Console()
+
+    console.print(
+        Panel(
+            "[bold cyan]Interactive Research Mode[/bold cyan]\n\n"
+            "Chat with me or tell me what you'd like to research.\n"
+            "Type [green]exit[/green] or [green]quit[/green] to end the session.",
+            title="haiku.rag Research Assistant",
+            border_style="cyan",
+        )
+    )
+
+    while True:
+        try:
+            # Initial conversation loop - chat until user wants to research
+            research_question = None
+            while research_question is None:
+                user_input = Prompt.ask("\n[bold blue]You[/bold blue]")
+
+                if not user_input.strip():
+                    continue
+
+                if user_input.lower().strip() in ("exit", "quit", "q"):
+                    console.print("[dim]Goodbye![/dim]")
+                    return
+
+                console.print("[dim]Thinking...[/dim]")
+                decision = await initial_chat(user_input, config)
+
+                if decision.action == "research" and decision.research_question:
+                    research_question = decision.research_question
+                    console.print(f"[dim]Starting research: {research_question}[/dim]")
+                elif decision.action == "chat" and decision.message:
+                    console.print(
+                        f"\n[bold cyan]Assistant:[/bold cyan] {decision.message}"
+                    )
+                else:
+                    # Fallback - treat as research question
+                    research_question = user_input
+
+            console.print()
+            report = await run_interactive_research(
+                question=research_question,
+                client=client,
+                config=config,
+                search_filter=search_filter,
+            )
+
+            # Display final report
+            console.print()
+            console.print(
+                Panel(
+                    Markdown(f"## {report.title}\n\n{report.executive_summary}"),
+                    title="Research Report",
+                    border_style="green",
+                )
+            )
+
+            if report.main_findings:
+                findings = "\n".join(f"- {f}" for f in report.main_findings[:5])
+                console.print(Markdown(f"**Key Findings:**\n{findings}"))
+
+            if report.conclusions:
+                conclusions = "\n".join(f"- {c}" for c in report.conclusions[:3])
+                console.print(Markdown(f"**Conclusions:**\n{conclusions}"))
+
+            console.print(Markdown(f"**Sources:** {report.sources_summary}"))
+
+        except KeyboardInterrupt:
+            console.print("\n[dim]Interrupted. Type 'exit' to quit.[/dim]")
+        except Exception as e:
+            console.print(f"[red]Error: {e}[/red]")
+
+
+def interactive_research(
+    client: HaikuRAG,
+    config: AppConfig | None = None,
+    search_filter: str | None = None,
+) -> None:
+    """Entry point for interactive research mode.
+
+    Args:
+        client: HaikuRAG client for document operations
+        config: Application configuration (uses global config if None)
+        search_filter: Optional SQL WHERE clause to filter documents
+    """
+    asyncio.run(run_chat_loop(client, config, search_filter))
diff --git a/haiku_rag_slim/haiku/rag/graph/agui/emitter.py b/haiku_rag_slim/haiku/rag/graph/agui/emitter.py
index b2cf5e3e..7df847f5 100644
--- a/haiku_rag_slim/haiku/rag/graph/agui/emitter.py
+++ b/haiku_rag_slim/haiku/rag/graph/agui/emitter.py
@@ -80,8 +80,8 @@ class AGUIEmitter[StateT: BaseModel, ResultT]:
             self._thread_id = self._generate_thread_id(state_json)
 
         # RunStarted (state snapshot follows immediately with full state)
-        self._emit(emit_run_started(self._thread_id, self._run_id))
-        self._emit(emit_state_snapshot(initial_state))
+        self.emit(emit_run_started(self._thread_id, self._run_id))
+        self.emit(emit_state_snapshot(initial_state))
         # Store a deep copy to detect future changes
         self._last_state = initial_state.model_copy(deep=True)
 
@@ -92,12 +92,12 @@ class AGUIEmitter[StateT: BaseModel, ResultT]:
             step_name: Name of the step being started
         """
         self._current_step = step_name
-        self._emit(emit_step_started(step_name))
+        self.emit(emit_step_started(step_name))
 
     def finish_step(self) -> None:
         """Emit StepFinished event for the current step."""
         if self._current_step:
-            self._emit(emit_step_finished(self._current_step))
+            self.emit(emit_step_finished(self._current_step))
             self._current_step = None
 
     def log(self, message: str, role: str = "assistant") -> None:
@@ -107,7 +107,7 @@ class AGUIEmitter[StateT: BaseModel, ResultT]:
             message: The message content
             role: The role of the sender (default: assistant)
         """
-        self._emit(emit_text_message(message, role))
+        self.emit(emit_text_message(message, role))
 
     def update_state(self, new_state: StateT) -> None:
         """Emit StateDelta or StateSnapshot for state change.
@@ -117,10 +117,10 @@ class AGUIEmitter[StateT: BaseModel, ResultT]:
         """
         if self._use_deltas and self._last_state is not None:
             # Emit delta for incremental updates
-            self._emit(emit_state_delta(self._last_state, new_state))
+            self.emit(emit_state_delta(self._last_state, new_state))
         else:
             # Emit full snapshot for initial state or when deltas disabled
-            self._emit(emit_state_snapshot(new_state))
+            self.emit(emit_state_snapshot(new_state))
         # Store a deep copy to detect future changes
         self._last_state = new_state.model_copy(deep=True)
 
@@ -139,7 +139,7 @@ class AGUIEmitter[StateT: BaseModel, ResultT]:
         """
         if message_id is None:
             message_id = str(uuid4())
-        self._emit(emit_activity(message_id, activity_type, content))
+        self.emit(emit_activity(message_id, activity_type, content))
 
     def finish_run(self, result: ResultT) -> None:
         """Emit RunFinished event.
@@ -147,7 +147,7 @@ class AGUIEmitter[StateT: BaseModel, ResultT]:
         Args:
             result: The final result from the graph
         """
-        self._emit(emit_run_finished(self._thread_id, self._run_id, result))
+        self.emit(emit_run_finished(self._thread_id, self._run_id, result))
 
     def error(self, error: Exception, code: str | None = None) -> None:
         """Emit RunError event.
@@ -156,9 +156,9 @@ class AGUIEmitter[StateT: BaseModel, ResultT]:
             error: The exception that occurred
             code: Optional error code
         """
-        self._emit(emit_run_error(str(error), code))
+        self.emit(emit_run_error(str(error), code))
 
-    def _emit(self, event: AGUIEvent) -> None:
+    def emit(self, event: AGUIEvent) -> None:
         """Put event in queue.
 
         Args:
diff --git a/haiku_rag_slim/haiku/rag/graph/agui/events.py b/haiku_rag_slim/haiku/rag/graph/agui/events.py
index eec980f2..49710126 100644
--- a/haiku_rag_slim/haiku/rag/graph/agui/events.py
+++ b/haiku_rag_slim/haiku/rag/graph/agui/events.py
@@ -252,3 +252,60 @@ def emit_activity_delta(
         "activityType": activity_type,
         "patch": patch,
     }
+
+
+def emit_tool_call_start(
+    tool_call_id: str,
+    tool_name: str,
+    parent_message_id: str | None = None,
+) -> dict[str, Any]:
+    """Create a ToolCallStart event.
+
+    Args:
+        tool_call_id: Unique identifier for this tool call
+        tool_name: Name of the tool being called
+        parent_message_id: Optional parent message ID
+
+    Returns:
+        ToolCallStart event dict
+    """
+    event: dict[str, Any] = {
+        "type": "TOOL_CALL_START",
+        "toolCallId": tool_call_id,
+        "toolCallName": tool_name,
+    }
+    if parent_message_id:
+        event["parentMessageId"] = parent_message_id
+    return event
+
+
+def emit_tool_call_args(tool_call_id: str, args: dict[str, Any]) -> dict[str, Any]:
+    """Create a ToolCallArgs event.
+
+    Args:
+        tool_call_id: Identifier for the tool call
+        args: Tool arguments
+
+    Returns:
+        ToolCallArgs event dict
+    """
+    return {
+        "type": "TOOL_CALL_ARGS",
+        "toolCallId": tool_call_id,
+        "delta": args,
+    }
+
+
+def emit_tool_call_end(tool_call_id: str) -> dict[str, Any]:
+    """Create a ToolCallEnd event.
+
+    Args:
+        tool_call_id: Identifier for the tool call being completed
+
+    Returns:
+        ToolCallEnd event dict
+    """
+    return {
+        "type": "TOOL_CALL_END",
+        "toolCallId": tool_call_id,
+    }
diff --git a/haiku_rag_slim/haiku/rag/graph/agui/server.py b/haiku_rag_slim/haiku/rag/graph/agui/server.py
index 1ccba823..26b463e6 100644
--- a/haiku_rag_slim/haiku/rag/graph/agui/server.py
+++ b/haiku_rag_slim/haiku/rag/graph/agui/server.py
@@ -166,7 +166,10 @@ def create_agui_server(  # pragma: no cover
     from haiku.rag.client import HaikuRAG
     from haiku.rag.graph.research.dependencies import ResearchContext
     from haiku.rag.graph.research.graph import build_research_graph
-    from haiku.rag.graph.research.state import ResearchDeps, ResearchState
+    from haiku.rag.graph.research.state import (
+        ResearchDeps,
+        ResearchState,
+    )
 
     # Store client reference for proper lifecycle management
     _client_cache: dict[str, HaikuRAG] = {}
diff --git a/haiku_rag_slim/haiku/rag/graph/research/graph.py b/haiku_rag_slim/haiku/rag/graph/research/graph.py
index 4e190665..8d996607 100644
--- a/haiku_rag_slim/haiku/rag/graph/research/graph.py
+++ b/haiku_rag_slim/haiku/rag/graph/research/graph.py
@@ -1,4 +1,6 @@
 import asyncio
+from typing import Literal
+from uuid import uuid4
 
 from pydantic_ai import Agent, RunContext, format_as_xml
 from pydantic_ai.output import ToolOutput
@@ -7,6 +9,11 @@ from pydantic_graph.beta.join import reduce_list_append
 
 from haiku.rag.config import Config
 from haiku.rag.config.models import AppConfig
+from haiku.rag.graph.agui.events import (
+    emit_tool_call_args,
+    emit_tool_call_end,
+    emit_tool_call_start,
+)
 from haiku.rag.graph.research.dependencies import ResearchContext, ResearchDependencies
 from haiku.rag.graph.research.models import (
     EvaluationResult,
@@ -54,12 +61,14 @@ def format_context_for_prompt(context: ResearchContext) -> str:
 def build_research_graph(
     config: AppConfig = Config,
     include_plan: bool = True,
+    interactive: bool = False,
 ) -> Graph[ResearchState, ResearchDeps, None, ResearchReport]:
     """Build the Research graph.
 
     Args:
         config: AppConfig object (uses config.research for provider, model, and graph parameters)
         include_plan: Whether to include the planning step (False for execute-only mode)
+        interactive: Whether to include human decision nodes for HIL
 
     Returns:
         Configured Research graph
@@ -240,7 +249,7 @@ def build_research_graph(
 
     @g.step
     async def get_batch(
-        ctx: StepContext[ResearchState, ResearchDeps, None | bool],
+        ctx: StepContext[ResearchState, ResearchDeps, None | bool | str],
     ) -> list[str] | None:
         """Get all remaining questions for this iteration."""
         state = ctx.state
@@ -302,9 +311,16 @@ def build_research_graph(
             state.last_eval = output
             state.iterations += 1
 
+            # Get already-answered questions to avoid duplicates
+            answered_queries = {qa.query.lower() for qa in state.context.qa_responses}
+
             for new_q in output.new_questions:
-                if new_q not in state.context.sub_questions:
-                    state.context.sub_questions.append(new_q)
+                # Skip if already in pending or already answered
+                if new_q in state.context.sub_questions:
+                    continue
+                if new_q.lower() in answered_queries:
+                    continue
+                state.context.sub_questions.append(new_q)
 
             if deps.agui_emitter:
                 deps.agui_emitter.update_state(state)
@@ -329,9 +345,75 @@ def build_research_graph(
             if deps.agui_emitter:
                 deps.agui_emitter.finish_step()
 
+    @g.step
+    async def human_decide(
+        ctx: StepContext[ResearchState, ResearchDeps, list[SearchAnswer] | None | bool],
+    ) -> Literal["search", "synthesize"]:
+        """Wait for human decision on whether to continue searching or synthesize."""
+        state = ctx.state
+        deps = ctx.deps
+
+        if deps.agui_emitter:
+            deps.agui_emitter.start_step("human_decide")
+            deps.agui_emitter.update_state(state)
+
+        try:
+            # Emit tool call for human input
+            tool_call_id = str(uuid4())
+
+            if deps.agui_emitter:
+                deps.agui_emitter.emit(
+                    emit_tool_call_start(tool_call_id, "human_decision")
+                )
+                # Include full state for display
+                qa_responses = [
+                    {
+                        "query": qa.query,
+                        "answer": qa.answer,
+                        "confidence": qa.confidence,
+                        "citations_count": len(qa.citations),
+                    }
+                    for qa in state.context.qa_responses
+                ]
+                deps.agui_emitter.emit(
+                    emit_tool_call_args(
+                        tool_call_id,
+                        {
+                            "original_question": state.context.original_question,
+                            "sub_questions": list(state.context.sub_questions),
+                            "qa_responses": qa_responses,
+                            "iterations": state.iterations,
+                        },
+                    )
+                )
+                deps.agui_emitter.emit(emit_tool_call_end(tool_call_id))
+
+            # Wait for human input
+            if deps.human_input_queue is None:
+                raise RuntimeError("human_input_queue is required for interactive mode")
+
+            decision = await deps.human_input_queue.get()
+
+            # Process decision
+            if decision.action == "modify_questions" and decision.questions:
+                state.context.sub_questions = list(decision.questions)
+            elif decision.action == "add_questions" and decision.questions:
+                state.context.sub_questions.extend(decision.questions)
+
+            if deps.agui_emitter:
+                deps.agui_emitter.update_state(state)
+
+            if decision.action in ("search", "modify_questions", "add_questions"):
+                return "search"
+            else:
+                return "synthesize"
+        finally:
+            if deps.agui_emitter:
+                deps.agui_emitter.finish_step()
+
     @g.step
     async def synthesize(
-        ctx: StepContext[ResearchState, ResearchDeps, None | bool],
+        ctx: StepContext[ResearchState, ResearchDeps, None | bool | str],
     ) -> ResearchReport:
         """Generate final research report."""
         state = ctx.state
@@ -375,39 +457,76 @@ def build_research_graph(
         initial_factory=list[SearchAnswer],
     )
 
-    if include_plan:
+    if interactive:
+        # Interactive mode: human decides after plan and after evaluation
+        if include_plan:
+            g.add(
+                g.edge_from(g.start_node).to(plan),
+                g.edge_from(plan).to(human_decide),
+            )
+        else:
+            g.add(g.edge_from(g.start_node).to(human_decide))
+
         g.add(
-            g.edge_from(g.start_node).to(plan),
-            g.edge_from(plan).to(get_batch),
+            g.edge_from(human_decide).to(
+                g.decision()
+                .branch(
+                    g.match(str, matches=lambda x: x == "search")
+                    .label("Search")
+                    .to(get_batch)
+                )
+                .branch(
+                    g.match(str, matches=lambda x: x == "synthesize")
+                    .label("Synthesize")
+                    .to(synthesize)
+                )
+            ),
+            g.edge_from(get_batch).to(
+                g.decision()
+                .branch(g.match(list).label("Has questions").map().to(search_one))
+                .branch(g.match(type(None)).label("No questions").to(human_decide))
+            ),
+            g.edge_from(search_one).to(collect_answers),
+            # After search, evaluate to suggest new questions, then human decides
+            g.edge_from(collect_answers).to(decide),
+            g.edge_from(decide).to(human_decide),
+            g.edge_from(synthesize).to(g.end_node),
         )
     else:
-        g.add(g.edge_from(g.start_node).to(get_batch))
-
-    g.add(
-        g.edge_from(get_batch).to(
-            g.decision()
-            .branch(g.match(list).label("Has questions").map().to(search_one))
-            .branch(g.match(type(None)).label("No questions").to(synthesize))
-        ),
-        g.edge_from(search_one).to(collect_answers),
-        g.edge_from(collect_answers).to(decide),
-    )
-
-    g.add(
-        g.edge_from(decide).to(
-            g.decision()
-            .branch(
-                g.match(bool, matches=lambda x: x)
-                .label("Continue research")
-                .to(get_batch)
+        # Non-interactive mode: automatic decision based on confidence/iterations
+        if include_plan:
+            g.add(
+                g.edge_from(g.start_node).to(plan),
+                g.edge_from(plan).to(get_batch),
             )
-            .branch(
-                g.match(bool, matches=lambda x: not x)
-                .label("Done researching")
-                .to(synthesize)
-            )
-        ),
-        g.edge_from(synthesize).to(g.end_node),
-    )
+        else:
+            g.add(g.edge_from(g.start_node).to(get_batch))
+
+        g.add(
+            g.edge_from(get_batch).to(
+                g.decision()
+                .branch(g.match(list).label("Has questions").map().to(search_one))
+                .branch(g.match(type(None)).label("No questions").to(synthesize))
+            ),
+            g.edge_from(search_one).to(collect_answers),
+            g.edge_from(collect_answers).to(decide),
+        )
+
+        g.add(
+            g.edge_from(decide).to(
+                g.decision()
+                .branch(
+                    g.match(bool, matches=lambda x: x)
+                    .label("Continue research")
+                    .to(get_batch)
+                )
+                .branch(
+                    g.match(bool, matches=lambda x: not x)
+                    .label("Done researching")
+                    .to(synthesize)
+                )
+            ),
+            g.edge_from(synthesize).to(g.end_node),
+        )
 
     return g.build()
diff --git a/haiku_rag_slim/haiku/rag/graph/research/state.py b/haiku_rag_slim/haiku/rag/graph/research/state.py
index fbf4fc39..93448a4c 100644
--- a/haiku_rag_slim/haiku/rag/graph/research/state.py
+++ b/haiku_rag_slim/haiku/rag/graph/research/state.py
@@ -1,6 +1,6 @@
 import asyncio
 from dataclasses import dataclass
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Literal
 
 from pydantic import BaseModel, Field
 
@@ -13,6 +13,17 @@ if TYPE_CHECKING:
     from haiku.rag.graph.agui.emitter import AGUIEmitter
 
 
+class HumanDecision(BaseModel):
+    """Human decision input for interactive research."""
+
+    action: Literal[
+        "search", "synthesize", "modify_questions", "add_questions", "chat", "research"
+    ]
+    questions: list[str] | None = None
+    message: str | None = None
+    research_question: str | None = None
+
+
 @dataclass
 class ResearchDeps:
     """Dependencies for research graph execution."""
@@ -20,6 +31,8 @@ class ResearchDeps:
     client: HaikuRAG
     agui_emitter: "AGUIEmitter[ResearchState, ResearchReport] | None" = None
     semaphore: asyncio.Semaphore | None = None
+    human_input_queue: asyncio.Queue[HumanDecision] | None = None
+    interactive: bool = False
 
     def emit_log(self, message: str, state: "ResearchState | None" = None) -> None:
         """Emit a log message through AG-UI events."""
diff --git a/tests/graph/agui/test_events.py b/tests/graph/agui/test_events.py
index 6b807e32..297229e6 100644
--- a/tests/graph/agui/test_events.py
+++ b/tests/graph/agui/test_events.py
@@ -11,6 +11,9 @@ from haiku.rag.graph.agui.events import (
     emit_step_finished,
     emit_step_started,
     emit_text_message,
+    emit_tool_call_args,
+    emit_tool_call_end,
+    emit_tool_call_start,
 )
 
 
@@ -135,6 +138,44 @@ def test_emit_activity():
     assert event["content"] == {"message": "Working on task"}
 
 
+def test_emit_tool_call_start():
+    """Test TOOL_CALL_START event creation."""
+    event = emit_tool_call_start("call-1", "search_documents")
+
+    assert event["type"] == "TOOL_CALL_START"
+    assert event["toolCallId"] == "call-1"
+    assert event["toolCallName"] == "search_documents"
+    assert "parentMessageId" not in event
+
+
+def test_emit_tool_call_start_with_parent():
+    """Test TOOL_CALL_START event with parent message ID."""
+    event = emit_tool_call_start("call-1", "search", parent_message_id="msg-1")
+
+    assert event["type"] == "TOOL_CALL_START"
+    assert event["toolCallId"] == "call-1"
+    assert event["toolCallName"] == "search"
+    assert event["parentMessageId"] == "msg-1"
+
+
+def test_emit_tool_call_args():
+    """Test TOOL_CALL_ARGS event creation."""
+    args = {"query": "test query", "limit": 10}
+    event = emit_tool_call_args("call-1", args)
+
+    assert event["type"] == "TOOL_CALL_ARGS"
+    assert event["toolCallId"] == "call-1"
+    assert event["delta"] == args
+
+
+def test_emit_tool_call_end():
+    """Test TOOL_CALL_END event creation."""
+    event = emit_tool_call_end("call-1")
+
+    assert event["type"] == "TOOL_CALL_END"
+    assert event["toolCallId"] == "call-1"
+
+
 def test_event_structure_consistency():
     """Test that all events have consistent structure."""
     events = [
@@ -146,6 +187,9 @@ def test_event_structure_consistency():
         emit_text_message("text"),
         emit_state_snapshot(TestState(value=1)),
         emit_activity("m1", "type", {"content": "value"}),
+        emit_tool_call_start("c1", "tool"),
+        emit_tool_call_args("c1", {"arg": "value"}),
+        emit_tool_call_end("c1"),
     ]
 
     for event in events: