graph: support multiturn chat for graph (#423)

Author: WineChord

agent/graphagent/graph_agent.go

@@ -17,6 +17,8 @@ import (
 	"trpc.group/trpc-go/trpc-agent-go/agent"
 	"trpc.group/trpc-go/trpc-agent-go/event"
 	"trpc.group/trpc-go/trpc-agent-go/graph"
+	"trpc.group/trpc-go/trpc-agent-go/internal/flow/processor"
+	"trpc.group/trpc-go/trpc-agent-go/model"
 	"trpc.group/trpc-go/trpc-agent-go/tool"
 )
 
@@ -137,7 +139,7 @@ func (ga *GraphAgent) Run(ctx context.Context, invocation *agent.Invocation) (<-
 	ga.setupInvocation(invocation)
 
 	// Prepare initial state.
-	initialState := ga.createInitialState(invocation)
+	initialState := ga.createInitialState(ctx, invocation)
 
 	// Execute the graph.
 	if ga.agentCallbacks != nil {
@@ -165,7 +167,7 @@ func (ga *GraphAgent) Run(ctx context.Context, invocation *agent.Invocation) (<-
 	return eventChan, nil
 }
 
-func (ga *GraphAgent) createInitialState(invocation *agent.Invocation) graph.State {
+func (ga *GraphAgent) createInitialState(ctx context.Context, invocation *agent.Invocation) graph.State {
 	var initialState graph.State
 
 	if ga.initialState != nil {
@@ -182,6 +184,23 @@ func (ga *GraphAgent) createInitialState(invocation *agent.Invocation) graph.Sta
 		}
 	}
 
+	// Seed messages from session events so multi‑turn runs share history.
+	// This mirrors ContentRequestProcessor behavior used by non-graph flows.
+	if invocation.Session != nil {
+		// Build a temporary request to reuse the processor logic.
+		req := &model.Request{}
+		// Default processor: IncludeContentsFiltered + AddContextPrefix.
+		p := processor.NewContentRequestProcessor(
+			processor.WithIncludeContents(processor.IncludeContentsAll),
+			processor.WithPreserveSameBranch(true),
+		)
+		// We only need messages side effect; no output channel needed.
+		p.ProcessRequest(ctx, invocation, req, nil)
+		if len(req.Messages) > 0 {
+			initialState[graph.StateKeyMessages] = req.Messages
+		}
+	}
+
 	// Add invocation message to state.
 	// When resuming from checkpoint, only add user input if it's meaningful content
 	// (not just a resume signal), following LangGraph's pattern.

examples/graph/multiturn/README.md

@@ -0,0 +1,64 @@
+# Graph Multi‑Turn Chat (GraphAgent + Runner)
+
+This example demonstrates an interactive, multi‑turn chat built on the graph package using GraphAgent and Runner. It highlights:
+
+- Persisted conversation history via the session service across turns
+- Tool‑augmented LLM chat with a calculator tool and automatic tool routing
+- Streaming outputs and interactive REPL experience
+- Message‑oriented state with `graph.MessagesStateSchema`
+
+## What It Shows
+
+- Graph‑first design: a single LLM node (`chat`) and a tools node (`tools`), connected with `AddToolsConditionalEdges` so the LLM can call tools when needed, then continue the conversation.
+- Natural multi‑turn: every user input is appended to the session; the next run reads full history from the same session so the LLM responds contextually.
+- Streaming UX: tokens stream as they arrive, just like other examples.
+
+## Graph Overview
+
+```
+Entry: chat (LLM) ──→ tools (when tool calls are present) ──→ back to chat
+Finish: chat
+```
+
+- Schema: `graph.MessagesStateSchema()`
+ - Tool:
+   - `calculator(expression)` → evaluates arithmetic expressions (+, -, *, /, ^, parentheses)
+
+## Usage
+
+### Run
+
+```bash
+cd examples/graph/multiturn
+go run . -model deepseek-chat
+```
+
+Then chat interactively:
+
+```
+You: hello
+Assistant: …streaming…
+
+You: what is (12.5+3)*2?
+Assistant: …calls calculator tool and answers…
+```
+
+Type `exit` or `quit` to leave.
+
+Notes:
+- The example generates a session ID once per process start and reuses it for all turns in the session, so the assistant has memory across turns.
+- To persist the same session across process restarts, you can pin `sessionID` to a fixed value in `main.go`.
+
+## Requirements
+
+- Go 1.21+
+- Network access and a compatible LLM model (default: `deepseek-chat`). Set any required API keys (e.g., `OPENAI_API_KEY`).
+
+## Key Files
+
+- `main.go` — builds the graph, wraps it with `GraphAgent`, and runs via `Runner` in an interactive loop.
+
+## Related Examples
+
+- `examples/graph/basic` — richer workflow with conditional routing and formatting
+- `examples/runwithmessages` — demonstrates Runner + session seeding from a non‑graph flow