refactor(agent): derive recall guidance from the tool set, drop the flag

The prompt's "Recall rules" block and the recall tools (recent_entries/
get_entry) were two switches that had to be flipped together: the renderer
carried RecallEnabled while the tools were wired off the agent's RecentEntries
buffer. They could drift — a prompt advertising a recall ability the tool set
doesn't back.

Make the tool set the single source of truth: PromptRenderer.Render now derives
the recall guidance from whether input.Tools advertises recent_entries (which
the harness already populates each turn from the runner's tool registry). The
RecallEnabled field and buildBookEngine's recall parameter are gone; wiring the
recall tools is what turns the guidance on.

No behavior change: TUI wires the recall tools (guidance on), book-run/bench
don't (off).

Author: flarexium

agent/prompt.go

@@ -25,9 +25,6 @@ type PromptRenderer struct {
 	Branches         []accounting.Branch
 	OperatorBranchID string
 	Clock            bookkeeping.Clock
-	// RecallEnabled adds the recall guidance to the prompt; set it when the
-	// bookkeeper carries a RecentEntries buffer and the recent_entries/get_entry tools.
-	RecallEnabled bool
 }
 
 // NewPromptRenderer snapshots the company, chart, periods, and branches from repo.
@@ -64,7 +61,7 @@ func NewPromptRenderer(ctx context.Context, repo accounting.LedgerRepository) (P
 
 func (r PromptRenderer) Render(input llm.ReasoningInput) ([]llm.Message, error) {
 	messages := []llm.Message{
-		{Role: llm.MessageRoleSystem, Content: r.systemPrompt()},
+		{Role: llm.MessageRoleSystem, Content: r.systemPrompt(hasTool(input.Tools, toolRecentEntries))},
 		{Role: llm.MessageRoleUser, Content: taskMessage(input)},
 	}
 
@@ -256,19 +253,32 @@ func (r PromptRenderer) branchesText() string {
 	return b.String()
 }
 
+// hasTool reports whether specs advertise a tool with the given name. The
+// recall guidance is keyed off the recent_entries tool's presence so the prompt
+// can never advertise a recall ability the tool set does not back.
+func hasTool(specs []llm.ToolSpec, name string) bool {
+	for _, s := range specs {
+		if s.Name == name {
+			return true
+		}
+	}
+	return false
+}
+
 // systemPrompt assembles everything that is stable for this renderer's
 // lifetime: agent role, intent catalog from the registry, payload format
-// rules, behavior rules, and the tenant snapshot. The user message only
-// carries the per-call task and any optional Instructions.
-func (r PromptRenderer) systemPrompt() string {
+// rules, behavior rules, and the tenant snapshot. recall adds the recall
+// guidance; it is derived from the available tools, not stored. The user
+// message only carries the per-call task and any optional Instructions.
+func (r PromptRenderer) systemPrompt(recall bool) string {
 	var b strings.Builder
 	b.WriteString(systemPromptHeader)
 	b.WriteString("\n\nAvailable intents:\n")
 	b.WriteString(intentsText())
 	b.WriteString(systemPromptFormatRules)
 	b.WriteString(systemPromptBehaviorRules)
 	b.WriteString(systemPromptMultiActionRules)
-	if r.RecallEnabled {
+	if recall {
 		b.WriteString(systemPromptRecallRules)
 	}
 	b.WriteString("\n\n")

agent/prompt_test.go

@@ -118,7 +118,7 @@ func TestPromptRenderer_TeachesFinalAction(t *testing.T) {
 	}
 }
 
-func TestPromptRenderer_RecallRulesGatedByFlag(t *testing.T) {
+func TestPromptRenderer_RecallRulesDerivedFromTools(t *testing.T) {
 	_, repo := awsBillScenario(t)
 	renderer, err := agent.NewPromptRenderer(context.Background(), repo)
 	if err != nil {
@@ -127,14 +127,16 @@ func TestPromptRenderer_RecallRulesGatedByFlag(t *testing.T) {
 
 	off, _ := renderer.Render(llm.ReasoningInput{Task: "x"})
 	if strings.Contains(off[0].Content, "Recall rules") {
-		t.Errorf("recall rules should be absent when RecallEnabled is false")
+		t.Errorf("recall rules should be absent when the recent_entries tool is not advertised")
 	}
 
-	renderer.RecallEnabled = true
-	on, _ := renderer.Render(llm.ReasoningInput{Task: "x"})
+	on, _ := renderer.Render(llm.ReasoningInput{
+		Task:  "x",
+		Tools: []llm.ToolSpec{{Name: "recent_entries"}},
+	})
 	for _, want := range []string{"Recall rules", "recent_entries", "self-contained"} {
 		if !strings.Contains(on[0].Content, want) {
-			t.Errorf("recall-enabled prompt missing %q", want)
+			t.Errorf("recall prompt missing %q when recent_entries tool is present", want)
 		}
 	}
 }

cmd/ledger/bench.go

@@ -148,7 +148,7 @@ func benchEngineFactory() benchmark.EngineFactory {
 			APIKey:                       m.APIKey,
 			BaseURL:                      m.BaseURL,
 			DisableStrictSchemaWithTools: m.DisableStrictSchemaWithTools,
-		}, "", false)
+		}, "")
 	}
 }
 

cmd/ledger/book_run.go

@@ -103,7 +103,7 @@ func runBook(ctx context.Context, c *cli.Command, stdout io.Writer) error {
 	}
 	defer bus.Close()
 
-	engine, err := buildBookEngine(ctx, repo, llmCfg, "", false)
+	engine, err := buildBookEngine(ctx, repo, llmCfg, "")
 	if err != nil {
 		return err
 	}

cmd/ledger/compose.go

@@ -119,15 +119,16 @@ func firstOpenPeriod(ctx context.Context, repo accounting.LedgerRepository) (acc
 }
 
 // buildBookEngine wires the OpenAI bookkeeper reasoning engine. operatorBranchID
-// is injected into the prompt; pass "" to omit the operator-branch hint. recall
-// adds the cross-turn recall guidance (pair it with a RecentEntries buffer on the agent).
-func buildBookEngine(ctx context.Context, repo accounting.LedgerRepository, llmCfg config.LLM, operatorBranchID string, recall bool) (llm.ReasoningEngine[bookkeeping.Intent], error) {
+// is injected into the prompt; pass "" to omit the operator-branch hint. The
+// recall guidance is derived from the tool set at render time, so it needs no
+// flag here -- wiring the recent_entries tool (via the agent's RecentEntries
+// buffer) is what turns it on.
+func buildBookEngine(ctx context.Context, repo accounting.LedgerRepository, llmCfg config.LLM, operatorBranchID string) (llm.ReasoningEngine[bookkeeping.Intent], error) {
 	renderer, err := agent.NewPromptRenderer(ctx, repo)
 	if err != nil {
 		return nil, fmt.Errorf("book-run: openai engine: %w", err)
 	}
 	renderer.OperatorBranchID = operatorBranchID
-	renderer.RecallEnabled = recall
 	adapter, err := openai.NewAdapter(openai.Config[bookkeeping.Intent]{
 		APIKey:                       llmCfg.APIKey,
 		BaseURL:                      llmCfg.BaseURL,

cmd/ledger/tui_run.go

@@ -111,7 +111,7 @@ func (comp tuiComposer) bookOption(repo accounting.LedgerRepository, bus bookkee
 		Label: branch.Name,
 		Hint:  branch.ID,
 		Start: func(ctx context.Context) (tui.Session, error) {
-			engine, err := buildBookEngine(ctx, repo, comp.llmCfg, branch.ID, true)
+			engine, err := buildBookEngine(ctx, repo, comp.llmCfg, branch.ID)
 			if err != nil {
 				return nil, err
 			}