diff --git a/pkg/agent/core.go b/pkg/agent/core.go
index 94cbcfd..6a29106 100644
--- a/pkg/agent/core.go
+++ b/pkg/agent/core.go
@@ -34,6 +34,7 @@ type AgentEnv struct {
 	tools        []backend.Tool
 	exec         toolExecutor
 	classifyTool toolClassifier
+	classifyTier func(name string) ResultTier
 	Hooks        Hooks
 	preamble     string
 	genParams    backend.GenerationParams
@@ -138,6 +139,22 @@ func BuildAgentEnv(cfg *config.Config, d tools.Dispatcher, cwd string) AgentEnv
 		}
 	}
 
+	var tierFn func(string) ResultTier
+	if srv, ok := d.GetServer("execute"); ok {
+		if tc, ok := srv.(tools.TierClassifier); ok {
+			tierFn = func(name string) ResultTier {
+				switch tc.ResultTier(name) {
+				case "cold":
+					return TierCold
+				case "warm":
+					return TierWarm
+				default:
+					return TierHot
+				}
+			}
+		}
+	}
+
 	var backendName, modelName string
 	if cfg != nil {
 		backendName = cfg.Backend
@@ -149,6 +166,7 @@ func BuildAgentEnv(cfg *config.Config, d tools.Dispatcher, cwd string) AgentEnv
 		tools:        allTools,
 		exec:         exec,
 		classifyTool: classify,
+		classifyTier: tierFn,
 		Hooks:        hooks,
 		preamble:     preamble,
 		genParams:    genParams,
@@ -352,6 +370,7 @@ func NewAgentCore(cfg AgentCoreConfig) Core {
 		Tools:              cfg.Env.tools,
 		Exec:               cfg.Env.exec,
 		ClassifyTool:       cfg.Env.classifyTool,
+		ClassifyTier:       cfg.Env.classifyTier,
 		ToolResultMaxBytes: defaultToolResultMaxBytes,
 		GenerationParams:   cfg.Env.genParams,
 		MaxSteps:           cfg.Env.maxSteps,
diff --git a/pkg/agent/loop.go b/pkg/agent/loop.go
index cee06e6..bdd1a62 100644
--- a/pkg/agent/loop.go
+++ b/pkg/agent/loop.go
@@ -38,8 +38,9 @@ type agentConfig struct {
 	Backend              backend.Backend
 	Tools                []backend.Tool
 	Exec                 toolExecutor
-	ClassifyTool         func(name string) bool // nil=treat all as serial; true=parallel-read-safe
-	ToolResultMaxBytes   int                    // 0=unlimited; truncate tool results beyond this size
+	ClassifyTool         func(name string) bool       // nil=treat all as serial; true=parallel-read-safe
+	ClassifyTier         func(name string) ResultTier // nil=TierHot for all; tools self-classify retention
+	ToolResultMaxBytes   int                          // 0=unlimited; truncate tool results beyond this size
 	Output               EventHandler
 	preamble             string // compiled system+agent prompt sent as the system role
 	GenerationParams     backend.GenerationParams
@@ -332,7 +333,11 @@ func run(ctx context.Context, cfg agentConfig, state state) error {
 				resultCache.Store(tc.Name+"\x00"+string(tc.Arguments), result)
 			}
 			emit(cfg, Event{Role: "tool", Name: tc.Name, Content: result})
-			return toolResult{ToolCallID: tc.ID, Name: tc.Name, Content: result, IsError: isErr}, false
+			tier := TierHot
+			if !isErr && cfg.ClassifyTier != nil {
+				tier = cfg.ClassifyTier(tc.Name)
+			}
+			return toolResult{ToolCallID: tc.ID, Name: tc.Name, Content: result, IsError: isErr, Tier: tier}, false
 		}
 
 		isParallelSafe := func(name string) bool {
diff --git a/pkg/agent/session.go b/pkg/agent/session.go
index be6f0b8..b86495f 100644
--- a/pkg/agent/session.go
+++ b/pkg/agent/session.go
@@ -216,14 +216,28 @@ func (s *Session) recordTurnCost(model string) {
 func (s *Session) update(assistant backend.Message, results []toolResult) {
 	s.messages = append(s.messages, assistant)
 	for _, r := range results {
+		content := r.Content
+		if r.Tier == TierCold && !r.IsError {
+			// Immediately collapse cold results to a one-line summary.
+			content = summarizeToolResult(r.Name, content)
+		}
 		s.messages = append(s.messages, backend.Message{
 			Role:       "tool",
-			Content:    r.Content,
+			Content:    content,
 			ToolCallID: r.ToolCallID,
 		})
 	}
 }
 
+// summarizeToolResult produces a compact one-line summary of a tool result
+// for cold-tier results that don't need to stay verbatim.
+func summarizeToolResult(name, content string) string {
+	if len(content) <= 200 {
+		return content
+	}
+	return fmt.Sprintf("[%s: %d bytes, first 200: %s…]", name, len(content), content[:200])
+}
+
 // removeCancelledToolResults filters out tool results that were cancelled due
 // to interrupt, keeping completed work. Also removes the corresponding tool
 // calls from assistant messages to maintain a valid message sequence.
diff --git a/pkg/agent/state.go b/pkg/agent/state.go
index b87c67d..33148d5 100644
--- a/pkg/agent/state.go
+++ b/pkg/agent/state.go
@@ -2,12 +2,22 @@ package agent
 
 import "ollie/pkg/backend"
 
+// ResultTier classifies how long a tool result stays in the hot message list.
+type ResultTier int
+
+const (
+	TierHot  ResultTier = iota // stays verbatim in messages (default)
+	TierWarm                   // summarized on next compaction pass
+	TierCold                   // immediately summarized at update time
+)
+
 // toolResult holds the output of a single tool call.
 type toolResult struct {
 	ToolCallID string // may be empty (Ollama does not always set this)
 	Name       string
 	Content    string
 	IsError    bool
+	Tier       ResultTier // default TierHot; tools may self-classify
 }
 
 // state is the interface both ephemeral and bead-backed state must satisfy.
diff --git a/pkg/tools/execute/tier.go b/pkg/tools/execute/tier.go
new file mode 100644
index 0000000..f85e308
--- /dev/null
+++ b/pkg/tools/execute/tier.go
@@ -0,0 +1,40 @@
+package execute
+
+import "strings"
+
+// ResultTier implements tools.TierClassifier. It reads the tool script's
+// "ollie:tier" annotation to determine result retention. Returns "hot" if
+// no annotation is found.
+func (e *Server) ResultTier(name string) string {
+	code, err := ReadTool(name)
+	if err != nil {
+		return "hot"
+	}
+	return detectTier(code)
+}
+
+// detectTier scans the first 10 lines of a tool script for an
+// "ollie:tier" annotation. Matches "ollie:tier hot", "ollie:tier warm",
+// or "ollie:tier cold" anywhere in the line.
+func detectTier(code string) string {
+	lines := strings.SplitN(code, "\n", 11)
+	if len(lines) > 10 {
+		lines = lines[:10]
+	}
+	for _, line := range lines {
+		idx := strings.Index(line, "ollie:tier")
+		if idx < 0 {
+			continue
+		}
+		rest := strings.TrimSpace(line[idx+len("ollie:tier"):])
+		switch {
+		case rest == "cold" || strings.HasPrefix(rest, "cold "):
+			return "cold"
+		case rest == "warm" || strings.HasPrefix(rest, "warm "):
+			return "warm"
+		case rest == "hot" || strings.HasPrefix(rest, "hot "):
+			return "hot"
+		}
+	}
+	return "hot"
+}
diff --git a/pkg/tools/tools.go b/pkg/tools/tools.go
index 8df4fcf..aaf308d 100644
--- a/pkg/tools/tools.go
+++ b/pkg/tools/tools.go
@@ -126,3 +126,10 @@ type ToolRestrictionSetter interface {
 type ParallelClassifier interface {
 	IsParallelRead(name string) bool
 }
+
+// TierClassifier is implemented by tool servers that can report the retention
+// tier of a tool's results: "hot" (verbatim), "warm" (summarized on compaction),
+// or "cold" (immediately summarized). Returns "hot" for unknown tools.
+type TierClassifier interface {
+	ResultTier(name string) string
+}