From 3f77cb6dfb6f6ae6d2ab132fa32d09414efd1279 Mon Sep 17 00:00:00 2001
From: Parth Sareen <parth.sareen@ollama.com>
Date: Fri, 4 Sep 2026 13:07:33 -0700
Subject: [PATCH] openai: add Codex compaction support (#18224)

---
 openai/responses.go              |  17 +
 openai/responses_compact.go      | 699 +++++++++++++++++++++++++++++++
 openai/responses_compact_test.go | 313 ++++++++++++++
 server/responses_compact.go      | 219 ++++++++++
 server/responses_compact_test.go | 282 +++++++++++++
 server/routes.go                 |   3 +-
 6 files changed, 1532 insertions(+), 1 deletion(-)
 create mode 100644 openai/responses_compact.go
 create mode 100644 openai/responses_compact_test.go
 create mode 100644 server/responses_compact.go
 create mode 100644 server/responses_compact_test.go

diff --git a/openai/responses.go b/openai/responses.go
index b5a739d2b..c08dd3cb2 100644
--- a/openai/responses.go
+++ b/openai/responses.go
@@ -2,6 +2,7 @@ package openai
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"math/rand"
 	"strings"
@@ -323,6 +324,18 @@ func unmarshalResponsesInputItem(data []byte) (ResponsesInputItem, error) {
 			return nil, err
 		}
 		return call, nil
+	case "compaction":
+		var compaction ResponsesCompactionItem
+		if err := json.Unmarshal(data, &compaction); err != nil {
+			return nil, err
+		}
+		return compaction, nil
+	case "compaction_trigger":
+		var trigger ResponsesCompactionTrigger
+		if err := json.Unmarshal(data, &trigger); err != nil {
+			return nil, err
+		}
+		return trigger, nil
 	default:
 		if itemType == "" {
 			return nil, fmt.Errorf("input item missing required 'type' field")
@@ -594,6 +607,10 @@ func FromResponsesRequest(r ResponsesRequest) (*api.ChatRequest, error) {
 		case ResponsesWebSearchCall:
 			// Built-in tool calls are history metadata. The assistant message
 			// that follows carries the model-visible result of the prior search.
+		case ResponsesCompactionItem:
+			return nil, errors.New("compaction items must be expanded before Responses conversion")
+		case ResponsesCompactionTrigger:
+			return nil, errors.New("compaction_trigger must be handled before Responses conversion")
 		}
 	}
 
diff --git a/openai/responses_compact.go b/openai/responses_compact.go
new file mode 100644
index 000000000..f8c7e9de7
--- /dev/null
+++ b/openai/responses_compact.go
@@ -0,0 +1,699 @@
+package openai
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+	"time"
+
+	"github.com/ollama/ollama/api"
+)
+
+const (
+	OllamaCompactionPayloadType    = "ollama_compaction"
+	OllamaCompactionPayloadVersion = 1
+	CreateSummaryToolName          = "create_summary"
+	compactionSummaryToolName      = "ollama_compaction_summary"
+)
+
+// ResponsesCompactionTrigger is the terminal input item sent by current Codex
+// clients when they request remote compaction through POST /v1/responses.
+type ResponsesCompactionTrigger struct {
+	Type string `json:"type"`
+}
+
+func (ResponsesCompactionTrigger) responsesInputItem() {}
+
+// ResponsesCompactionItem is the opaque continuation item understood by Codex.
+// Ollama stores a versioned JSON payload in EncryptedContent; the payload is not
+// encrypted and must be consumed by Ollama before another model request.
+type ResponsesCompactionItem struct {
+	Type             string `json:"type"`
+	EncryptedContent string `json:"encrypted_content"`
+}
+
+func (ResponsesCompactionItem) responsesInputItem() {}
+
+// OllamaCompactionPayload is Ollama's stateless continuation format.
+type OllamaCompactionPayload struct {
+	Type     string        `json:"type"`
+	Version  int           `json:"version"`
+	Summary  string        `json:"summary"`
+	Retained []api.Message `json:"retained"`
+}
+
+// CompactionTranscriptItem is one ordered input item shown to the compaction
+// model. Ref is request-local and is the only value the model may select.
+type CompactionTranscriptItem struct {
+	Ref     string      `json:"ref"`
+	Type    string      `json:"type"`
+	Message api.Message `json:"message"`
+}
+
+type compactionToolMetadata struct {
+	Name        string `json:"name"`
+	Description string `json:"description,omitempty"`
+}
+
+type compactionTranscript struct {
+	Items []CompactionTranscriptItem `json:"items"`
+	Tools []compactionToolMetadata   `json:"tools,omitempty"`
+}
+
+type compactionToolGroup struct {
+	CallRef   string
+	ResultRef string
+}
+
+// ResponsesCompactionPlan contains the validated, ordered state required to
+// make and verify a compaction-model request.
+type ResponsesCompactionPlan struct {
+	Model  string
+	Stream bool
+
+	items      []CompactionTranscriptItem
+	tools      []compactionToolMetadata
+	groups     []compactionToolGroup
+	forcedRefs map[string]struct{}
+}
+
+// ResponsesCompactionResult is the validated result of a compaction-model call.
+type ResponsesCompactionResult struct {
+	Item  ResponsesCompactionItem
+	Usage *ResponsesUsage
+}
+
+type summarySelection struct {
+	Summary       string   `json:"summary"`
+	RetainItemIDs []string `json:"retain_item_ids"`
+}
+
+type rawResponsesRequest struct {
+	Model  string                     `json:"model"`
+	Input  json.RawMessage            `json:"input"`
+	Stream *bool                      `json:"stream,omitempty"`
+	Tools  []ResponsesTool            `json:"tools,omitempty"`
+	Fields map[string]json.RawMessage `json:"-"`
+}
+
+// PrepareTriggeredCompaction recognizes the Codex v2 terminal trigger. It
+// returns requested=false without changing ordinary Responses requests.
+func PrepareTriggeredCompaction(body []byte) (*ResponsesCompactionPlan, bool, error) {
+	req, items, err := decodeRawResponsesRequest(body)
+	if err != nil {
+		return nil, false, err
+	}
+	if len(items) == 0 || rawInputItemType(items[len(items)-1]) != "compaction_trigger" {
+		return nil, false, nil
+	}
+	if req.Stream == nil || !*req.Stream {
+		return nil, true, errors.New("compaction_trigger requires stream=true")
+	}
+	for _, item := range items[:len(items)-1] {
+		if rawInputItemType(item) == "compaction_trigger" {
+			return nil, true, errors.New("compaction_trigger must be the final and only compaction trigger")
+		}
+	}
+
+	items, _, err = expandOllamaCompactionItems(items[:len(items)-1])
+	if err != nil {
+		return nil, true, err
+	}
+	plan, err := newResponsesCompactionPlan(req, items)
+	return plan, true, err
+}
+
+// PrepareStandaloneCompaction validates a POST /v1/responses/compact body.
+func PrepareStandaloneCompaction(body []byte) (*ResponsesCompactionPlan, error) {
+	req, items, err := decodeRawResponsesRequest(body)
+	if err != nil {
+		return nil, err
+	}
+	for _, item := range items {
+		if rawInputItemType(item) == "compaction_trigger" {
+			return nil, errors.New("compaction_trigger is only valid on POST /v1/responses")
+		}
+	}
+	items, _, err = expandOllamaCompactionItems(items)
+	if err != nil {
+		return nil, err
+	}
+	return newResponsesCompactionPlan(req, items)
+}
+
+// ExpandResponsesCompactionInput replaces the newest Ollama compaction item
+// with its summary and retained messages. Items on either side of the
+// compaction item remain in their original order.
+func ExpandResponsesCompactionInput(body []byte) ([]byte, bool, error) {
+	req, items, err := decodeRawResponsesRequest(body)
+	if err != nil {
+		return nil, false, err
+	}
+	items, changed, err := expandOllamaCompactionItems(items)
+	if err != nil || !changed {
+		return body, changed, err
+	}
+
+	input, err := json.Marshal(items)
+	if err != nil {
+		return nil, false, err
+	}
+	req.Fields["input"] = input
+	rewritten, err := json.Marshal(req.Fields)
+	return rewritten, true, err
+}
+
+func decodeRawResponsesRequest(body []byte) (rawResponsesRequest, []json.RawMessage, error) {
+	var fields map[string]json.RawMessage
+	if err := json.Unmarshal(body, &fields); err != nil {
+		return rawResponsesRequest{}, nil, fmt.Errorf("invalid Responses request: %w", err)
+	}
+
+	var req rawResponsesRequest
+	if raw, ok := fields["model"]; !ok || json.Unmarshal(raw, &req.Model) != nil || strings.TrimSpace(req.Model) == "" {
+		return rawResponsesRequest{}, nil, errors.New("model is required")
+	}
+	req.Model = strings.TrimSpace(req.Model)
+	req.Fields = fields
+	req.Input = fields["input"]
+	if raw := fields["stream"]; len(raw) > 0 {
+		if err := json.Unmarshal(raw, &req.Stream); err != nil {
+			return rawResponsesRequest{}, nil, fmt.Errorf("invalid stream value: %w", err)
+		}
+	}
+	if raw := fields["tools"]; len(raw) > 0 {
+		if err := json.Unmarshal(raw, &req.Tools); err != nil {
+			return rawResponsesRequest{}, nil, fmt.Errorf("invalid tools: %w", err)
+		}
+	}
+
+	items, err := decodeRawResponsesInput(req.Input)
+	if err != nil {
+		return rawResponsesRequest{}, nil, err
+	}
+	return req, items, nil
+}
+
+func decodeRawResponsesInput(input json.RawMessage) ([]json.RawMessage, error) {
+	if len(input) == 0 || bytes.Equal(bytes.TrimSpace(input), []byte("null")) {
+		return nil, errors.New("input is required")
+	}
+
+	var text string
+	if err := json.Unmarshal(input, &text); err == nil {
+		item, err := json.Marshal(map[string]any{
+			"type": "message", "role": "user", "content": text,
+		})
+		if err != nil {
+			return nil, err
+		}
+		return []json.RawMessage{item}, nil
+	}
+
+	var items []json.RawMessage
+	if err := json.Unmarshal(input, &items); err != nil {
+		return nil, fmt.Errorf("input must be a string or array: %w", err)
+	}
+	if items == nil {
+		return nil, errors.New("input must be a string or array")
+	}
+	return items, nil
+}
+
+func rawInputItemType(item json.RawMessage) string {
+	var header struct {
+		Type string `json:"type"`
+		Role string `json:"role"`
+	}
+	if json.Unmarshal(item, &header) != nil {
+		return ""
+	}
+	if header.Type == "" && header.Role != "" {
+		return "message"
+	}
+	return header.Type
+}
+
+func expandOllamaCompactionItems(items []json.RawMessage) ([]json.RawMessage, bool, error) {
+	boundary := -1
+	for i := range items {
+		if rawInputItemType(items[i]) == "compaction" {
+			boundary = i
+		}
+	}
+	if boundary < 0 {
+		return items, false, nil
+	}
+
+	payload, err := decodeOllamaCompactionItem(items[boundary])
+	if err != nil {
+		return nil, false, err
+	}
+	expanded, err := payloadToResponsesItems(payload)
+	if err != nil {
+		return nil, false, err
+	}
+	rewritten := make([]json.RawMessage, 0, len(items)-1+len(expanded))
+	rewritten = append(rewritten, items[:boundary]...)
+	rewritten = append(rewritten, expanded...)
+	rewritten = append(rewritten, items[boundary+1:]...)
+	return rewritten, true, nil
+}
+
+func decodeOllamaCompactionItem(item json.RawMessage) (OllamaCompactionPayload, error) {
+	var wire ResponsesCompactionItem
+	if err := json.Unmarshal(item, &wire); err != nil {
+		return OllamaCompactionPayload{}, fmt.Errorf("invalid compaction item: %w", err)
+	}
+	if wire.Type != "compaction" || wire.EncryptedContent == "" {
+		return OllamaCompactionPayload{}, errors.New("invalid compaction item")
+	}
+
+	var payload OllamaCompactionPayload
+	decoder := json.NewDecoder(strings.NewReader(wire.EncryptedContent))
+	decoder.DisallowUnknownFields()
+	if err := decoder.Decode(&payload); err != nil {
+		return OllamaCompactionPayload{}, errors.New("unsupported compaction item: encrypted_content is not an Ollama payload")
+	}
+	if payload.Type != OllamaCompactionPayloadType || payload.Version != OllamaCompactionPayloadVersion {
+		return OllamaCompactionPayload{}, fmt.Errorf("unsupported Ollama compaction payload type or version")
+	}
+	if strings.TrimSpace(payload.Summary) == "" {
+		return OllamaCompactionPayload{}, errors.New("Ollama compaction payload has an empty summary")
+	}
+	if err := decoder.Decode(&struct{}{}); !errors.Is(err, io.EOF) {
+		return OllamaCompactionPayload{}, errors.New("unsupported compaction item: encrypted_content contains more than one JSON value")
+	}
+	return payload, nil
+}
+
+func payloadToResponsesItems(payload OllamaCompactionPayload) ([]json.RawMessage, error) {
+	b, err := json.Marshal(payload)
+	if err != nil {
+		return nil, err
+	}
+	hash := sha256.Sum256(b)
+	callID := "call_ollama_compaction_" + hex.EncodeToString(hash[:6])
+	args, _ := json.Marshal(map[string]any{"version": payload.Version})
+
+	items := make([]json.RawMessage, 0, 2+len(payload.Retained))
+	call, err := json.Marshal(map[string]any{
+		"type": "function_call", "call_id": callID, "name": compactionSummaryToolName, "arguments": string(args),
+	})
+	if err != nil {
+		return nil, err
+	}
+	result, err := json.Marshal(map[string]any{
+		"type": "function_call_output", "call_id": callID, "output": payload.Summary,
+	})
+	if err != nil {
+		return nil, err
+	}
+	items = append(items, call, result)
+	for _, message := range payload.Retained {
+		converted, err := messageToResponsesItems(message)
+		if err != nil {
+			return nil, fmt.Errorf("invalid retained message: %w", err)
+		}
+		items = append(items, converted...)
+	}
+	return items, nil
+}
+
+func messageToResponsesItems(message api.Message) ([]json.RawMessage, error) {
+	if len(message.Images) > 0 {
+		return nil, errors.New("retained images are not supported")
+	}
+
+	var values []any
+	if message.Thinking != "" {
+		values = append(values, map[string]any{
+			"type":    "reasoning",
+			"summary": []map[string]string{{"type": "summary_text", "text": message.Thinking}},
+		})
+	}
+	if message.Role == "tool" {
+		if message.ToolCallID == "" {
+			return nil, errors.New("retained tool message is missing tool_call_id")
+		}
+		values = append(values, map[string]any{
+			"type": "function_call_output", "call_id": message.ToolCallID, "output": message.Content,
+		})
+	} else if message.Content != "" || len(message.ToolCalls) == 0 {
+		values = append(values, map[string]any{
+			"type": "message", "role": message.Role, "content": message.Content,
+		})
+	}
+	for _, call := range message.ToolCalls {
+		if call.ID == "" || call.Function.Name == "" {
+			return nil, errors.New("retained function call is missing call_id or name")
+		}
+		arguments, err := json.Marshal(call.Function.Arguments)
+		if err != nil {
+			return nil, err
+		}
+		values = append(values, map[string]any{
+			"type": "function_call", "call_id": call.ID, "name": call.Function.Name, "arguments": string(arguments),
+		})
+	}
+
+	items := make([]json.RawMessage, 0, len(values))
+	for _, value := range values {
+		item, err := json.Marshal(value)
+		if err != nil {
+			return nil, err
+		}
+		items = append(items, item)
+	}
+	return items, nil
+}
+
+func newResponsesCompactionPlan(req rawResponsesRequest, rawItems []json.RawMessage) (*ResponsesCompactionPlan, error) {
+	if len(rawItems) == 0 {
+		return nil, errors.New("compaction input is empty")
+	}
+
+	items := make([]CompactionTranscriptItem, 0, len(rawItems))
+	for i, raw := range rawItems {
+		item, err := unmarshalResponsesInputItem(raw)
+		if err != nil {
+			return nil, fmt.Errorf("input[%d]: %w", i, err)
+		}
+		message, kind, err := compactionMessage(item)
+		if err != nil {
+			return nil, fmt.Errorf("input[%d]: %w", i, err)
+		}
+		if len(message.Images) > 0 {
+			return nil, fmt.Errorf("input[%d]: image inputs are not supported by compaction", i)
+		}
+		items = append(items, CompactionTranscriptItem{
+			Ref: fmt.Sprintf("item_%06d", i+1), Type: kind, Message: message,
+		})
+	}
+
+	groups, forced, err := analyzeCompactionToolState(items)
+	if err != nil {
+		return nil, err
+	}
+	stream := req.Stream != nil && *req.Stream
+	return &ResponsesCompactionPlan{
+		Model: req.Model, Stream: stream, items: items, tools: collectCompactionToolMetadata(req.Tools), groups: groups, forcedRefs: forced,
+	}, nil
+}
+
+func compactionMessage(item ResponsesInputItem) (api.Message, string, error) {
+	switch value := item.(type) {
+	case ResponsesInputMessage:
+		message, err := convertInputMessage(value)
+		return message, "message", err
+	case ResponsesFunctionCall:
+		var arguments api.ToolCallFunctionArguments
+		if value.Arguments != "" {
+			if err := json.Unmarshal([]byte(value.Arguments), &arguments); err != nil {
+				return api.Message{}, "", fmt.Errorf("invalid function arguments: %w", err)
+			}
+		}
+		return api.Message{Role: "assistant", ToolCalls: []api.ToolCall{{
+			ID: value.CallID, Function: api.ToolCallFunction{Name: value.Name, Arguments: arguments},
+		}}}, "function_call", nil
+	case ResponsesFunctionCallOutput:
+		content := value.Output
+		var images []api.ImageData
+		if len(value.OutputItems) > 0 {
+			var err error
+			content, images, err = convertResponsesContent(value.OutputItems)
+			if err != nil {
+				return api.Message{}, "", err
+			}
+		}
+		return api.Message{Role: "tool", Content: content, Images: images, ToolCallID: value.CallID}, "function_call_output", nil
+	case ResponsesReasoningInput:
+		var summary strings.Builder
+		for _, part := range value.Summary {
+			summary.WriteString(part.Text)
+		}
+		thinking := summary.String()
+		if thinking == "" && value.EncryptedContent != "" {
+			thinking = "[opaque reasoning state omitted during Ollama compaction]"
+		}
+		return api.Message{Role: "assistant", Thinking: thinking}, "reasoning", nil
+	case ResponsesCompactionItem, ResponsesCompactionTrigger:
+		return api.Message{}, "", errors.New("unexpected compaction control item")
+	default:
+		return api.Message{}, "", fmt.Errorf("unsupported compaction input type %T", item)
+	}
+}
+
+func analyzeCompactionToolState(items []CompactionTranscriptItem) ([]compactionToolGroup, map[string]struct{}, error) {
+	type pendingGroup struct {
+		callIndex   int
+		resultIndex int
+		group       compactionToolGroup
+	}
+	byCallID := make(map[string]*pendingGroup)
+	ignoredCallIDs := make(map[string]struct{})
+	var ordered []*pendingGroup
+
+	for i, item := range items {
+		switch item.Type {
+		case "function_call":
+			call := item.Message.ToolCalls[0]
+			if call.ID == "" {
+				return nil, nil, fmt.Errorf("%s: function call is missing call_id", item.Ref)
+			}
+			if call.Function.Name == compactionSummaryToolName && strings.HasPrefix(call.ID, "call_ollama_compaction_") {
+				ignoredCallIDs[call.ID] = struct{}{}
+				continue
+			}
+			if _, exists := byCallID[call.ID]; exists {
+				return nil, nil, fmt.Errorf("%s: duplicate function call_id %q", item.Ref, call.ID)
+			}
+			group := &pendingGroup{callIndex: i, resultIndex: -1, group: compactionToolGroup{CallRef: item.Ref}}
+			byCallID[call.ID] = group
+			ordered = append(ordered, group)
+		case "function_call_output":
+			callID := item.Message.ToolCallID
+			if _, ignored := ignoredCallIDs[callID]; ignored {
+				continue
+			}
+			group := byCallID[callID]
+			if group == nil {
+				return nil, nil, fmt.Errorf("%s: function output has no matching call %q", item.Ref, callID)
+			}
+			if group.resultIndex >= 0 {
+				return nil, nil, fmt.Errorf("%s: duplicate function output for call %q", item.Ref, callID)
+			}
+			group.resultIndex = i
+			group.group.ResultRef = item.Ref
+		}
+	}
+
+	forced := make(map[string]struct{})
+	groups := make([]compactionToolGroup, 0, len(ordered))
+	for _, candidate := range ordered {
+		groups = append(groups, candidate.group)
+		active := candidate.resultIndex < 0
+		if !active {
+			active = true
+			for _, item := range items[candidate.resultIndex+1:] {
+				if item.Type == "reasoning" || item.Type == "function_call" || (item.Type == "message" && item.Message.Role == "assistant") {
+					active = false
+					break
+				}
+			}
+		}
+		if active {
+			forced[candidate.group.CallRef] = struct{}{}
+			if candidate.group.ResultRef != "" {
+				forced[candidate.group.ResultRef] = struct{}{}
+			}
+		}
+	}
+	return groups, forced, nil
+}
+
+func collectCompactionToolMetadata(tools []ResponsesTool) []compactionToolMetadata {
+	var metadata []compactionToolMetadata
+	var add func(prefix string, tools []ResponsesTool)
+	add = func(prefix string, tools []ResponsesTool) {
+		for _, tool := range tools {
+			name := tool.Name
+			if prefix != "" && !strings.HasPrefix(name, prefix+".") {
+				name = prefix + "." + name
+			}
+			if tool.Type == "namespace" {
+				add(name, tool.Tools)
+				continue
+			}
+			description := ""
+			if tool.Description != nil {
+				description = *tool.Description
+			}
+			metadata = append(metadata, compactionToolMetadata{Name: name, Description: description})
+		}
+	}
+	add("", tools)
+	return metadata
+}
+
+// SummaryRequest returns an ordinary non-streaming Responses request. A repair
+// request includes the validation error from the first model response.
+func (p *ResponsesCompactionPlan) SummaryRequest(repairError string) ([]byte, error) {
+	// TODO(compaction): enforce the 40% retained-context target after the
+	// selected model's prompt renderer and token budget are available here.
+	transcript, err := json.Marshal(compactionTranscript{Items: p.items, Tools: p.tools})
+	if err != nil {
+		return nil, err
+	}
+	prompt := `Summarize the conversation for another coding agent. Preserve the goal, decisions, constraints, repository state, changed files, test results, failures, active work, and next actions. Use retain_item_ids only for exact source items that cannot safely be paraphrased. Tool calls and results are execution state; do not invent or edit them. Call create_summary exactly once.`
+	if repairError != "" {
+		prompt += " Your previous create_summary call was invalid: " + repairError + ". Return one corrected create_summary call."
+	}
+
+	description := "Return the compact summary and the exact input item references that must remain verbatim."
+	strict := true
+	request := map[string]any{
+		"model": p.Model,
+		"input": []any{
+			map[string]any{"type": "message", "role": "system", "content": prompt},
+			map[string]any{"type": "message", "role": "user", "content": string(transcript)},
+		},
+		"tools": []ResponsesTool{{
+			Type: "function", Name: CreateSummaryToolName, Description: &description, Strict: &strict,
+			Parameters: map[string]any{
+				"type": "object",
+				"properties": map[string]any{
+					"summary":         map[string]any{"type": "string"},
+					"retain_item_ids": map[string]any{"type": "array", "items": map[string]any{"type": "string"}},
+				},
+				"required":             []string{"summary", "retain_item_ids"},
+				"additionalProperties": false,
+			},
+		}},
+		"tool_choice":         map[string]any{"type": "function", "name": CreateSummaryToolName},
+		"parallel_tool_calls": false,
+		"store":               false,
+		"stream":              false,
+	}
+	return json.Marshal(request)
+}
+
+// Complete validates create_summary and builds the stateless continuation.
+func (p *ResponsesCompactionPlan) Complete(body []byte) (ResponsesCompactionResult, error) {
+	var response ResponsesResponse
+	if err := json.Unmarshal(body, &response); err != nil {
+		return ResponsesCompactionResult{}, fmt.Errorf("invalid summary response: %w", err)
+	}
+
+	var calls []ResponsesOutputItem
+	for _, item := range response.Output {
+		if item.Type == "function_call" && item.Name == CreateSummaryToolName {
+			calls = append(calls, item)
+		}
+	}
+	if len(calls) != 1 {
+		return ResponsesCompactionResult{}, fmt.Errorf("expected one %s call, got %d", CreateSummaryToolName, len(calls))
+	}
+
+	var selection summarySelection
+	if err := json.Unmarshal([]byte(calls[0].Arguments), &selection); err != nil {
+		return ResponsesCompactionResult{}, fmt.Errorf("invalid %s arguments: %w", CreateSummaryToolName, err)
+	}
+	selection.Summary = strings.TrimSpace(selection.Summary)
+	if selection.Summary == "" {
+		return ResponsesCompactionResult{}, errors.New("create_summary returned an empty summary")
+	}
+
+	known := make(map[string]struct{}, len(p.items))
+	for _, item := range p.items {
+		known[item.Ref] = struct{}{}
+	}
+	selected := make(map[string]struct{}, len(selection.RetainItemIDs)+len(p.forcedRefs))
+	for _, ref := range selection.RetainItemIDs {
+		if _, ok := known[ref]; !ok {
+			return ResponsesCompactionResult{}, fmt.Errorf("create_summary selected unknown item %q", ref)
+		}
+		if _, duplicate := selected[ref]; duplicate {
+			return ResponsesCompactionResult{}, fmt.Errorf("create_summary selected duplicate item %q", ref)
+		}
+		selected[ref] = struct{}{}
+	}
+	for ref := range p.forcedRefs {
+		selected[ref] = struct{}{}
+	}
+	for _, group := range p.groups {
+		_, callSelected := selected[group.CallRef]
+		_, resultSelected := selected[group.ResultRef]
+		if callSelected || resultSelected {
+			selected[group.CallRef] = struct{}{}
+			if group.ResultRef != "" {
+				selected[group.ResultRef] = struct{}{}
+			}
+		}
+	}
+
+	retained := make([]api.Message, 0, len(selected))
+	for _, item := range p.items {
+		if _, ok := selected[item.Ref]; ok {
+			retained = append(retained, item.Message)
+		}
+	}
+	payload := OllamaCompactionPayload{
+		Type: OllamaCompactionPayloadType, Version: OllamaCompactionPayloadVersion, Summary: selection.Summary, Retained: retained,
+	}
+	payloadJSON, err := json.Marshal(payload)
+	if err != nil {
+		return ResponsesCompactionResult{}, err
+	}
+	return ResponsesCompactionResult{
+		Item: ResponsesCompactionItem{Type: "compaction", EncryptedContent: string(payloadJSON)}, Usage: response.Usage,
+	}, nil
+}
+
+// ResponsesCompactedResponse is returned by POST /v1/responses/compact.
+type ResponsesCompactedResponse struct {
+	ID        string                    `json:"id"`
+	Object    string                    `json:"object"`
+	CreatedAt int64                     `json:"created_at"`
+	Output    []ResponsesCompactionItem `json:"output"`
+	Usage     *ResponsesUsage           `json:"usage"`
+}
+
+// NewResponsesCompactedResponse builds the standalone compact response.
+func NewResponsesCompactedResponse(id string, result ResponsesCompactionResult) ResponsesCompactedResponse {
+	return ResponsesCompactedResponse{
+		ID: id, Object: "response.compaction", CreatedAt: time.Now().Unix(), Output: []ResponsesCompactionItem{result.Item}, Usage: result.Usage,
+	}
+}
+
+// NewResponsesCompactionStreamEvents builds the Codex v2 stream. Codex uses
+// output_item.done and requires exactly one compaction item before completed.
+func NewResponsesCompactionStreamEvents(id, model string, result ResponsesCompactionResult) []ResponsesStreamEvent {
+	converter := NewResponsesStreamConverter(id, "", model, ResponsesRequest{Model: model})
+	created := converter.buildResponseObject("in_progress", []any{}, nil)
+	completedUsage := map[string]any(nil)
+	if result.Usage != nil {
+		completedUsage = map[string]any{
+			"input_tokens":          result.Usage.InputTokens,
+			"output_tokens":         result.Usage.OutputTokens,
+			"total_tokens":          result.Usage.TotalTokens,
+			"input_tokens_details":  result.Usage.InputTokensDetails,
+			"output_tokens_details": result.Usage.OutputTokensDetails,
+		}
+	}
+	completed := converter.buildResponseObject("completed", []any{result.Item}, completedUsage)
+	completed["completed_at"] = time.Now().Unix()
+
+	return []ResponsesStreamEvent{
+		converter.newEvent("response.created", map[string]any{"response": created}),
+		converter.newEvent("response.in_progress", map[string]any{"response": created}),
+		converter.newEvent("response.output_item.added", map[string]any{"output_index": 0, "item": result.Item}),
+		converter.newEvent("response.output_item.done", map[string]any{"output_index": 0, "item": result.Item}),
+		converter.newEvent("response.completed", map[string]any{"response": completed}),
+	}
+}
diff --git a/openai/responses_compact_test.go b/openai/responses_compact_test.go
new file mode 100644
index 000000000..eb08c35e5
--- /dev/null
+++ b/openai/responses_compact_test.go
@@ -0,0 +1,313 @@
+package openai
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+
+	"github.com/ollama/ollama/api"
+)
+
+func compactionResponseBody(t *testing.T, selection map[string]any) []byte {
+	t.Helper()
+	arguments, err := json.Marshal(selection)
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, err := json.Marshal(map[string]any{
+		"id":     "resp_summary",
+		"object": "response",
+		"status": "completed",
+		"output": []any{map[string]any{
+			"id": "fc_summary", "type": "function_call", "status": "completed",
+			"call_id": "call_summary", "name": CreateSummaryToolName, "arguments": string(arguments),
+		}},
+		"usage": map[string]any{"input_tokens": 100, "output_tokens": 20, "total_tokens": 120},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return body
+}
+
+func decodeResultPayload(t *testing.T, result ResponsesCompactionResult) OllamaCompactionPayload {
+	t.Helper()
+	item, err := json.Marshal(result.Item)
+	if err != nil {
+		t.Fatal(err)
+	}
+	payload, err := decodeOllamaCompactionItem(item)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return payload
+}
+
+func TestPrepareTriggeredCompactionBuildsSummaryRequest(t *testing.T) {
+	description := "Read a file"
+	body := []byte(`{
+		"model":"qwen3:4b",
+		"stream":true,
+		"instructions":"do not send this to the compactor",
+		"tools":[{"type":"function","name":"read_file","description":"Read a file","strict":false,"parameters":{"type":"object"}}],
+		"input":[
+			{"type":"message","role":"user","content":"inspect main.go"},
+			{"type":"function_call","call_id":"call_1","name":"read_file","arguments":"{\"path\":\"main.go\"}"},
+			{"type":"function_call_output","call_id":"call_1","output":"package main"},
+			{"type":"compaction_trigger"}
+		]
+	}`)
+
+	plan, requested, err := PrepareTriggeredCompaction(body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !requested {
+		t.Fatal("expected compaction request")
+	}
+	if plan.Model != "qwen3:4b" || !plan.Stream {
+		t.Fatalf("unexpected plan: model=%q stream=%v", plan.Model, plan.Stream)
+	}
+
+	requestBody, err := plan.SummaryRequest("")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var request struct {
+		Input []struct {
+			Role    string `json:"role"`
+			Content string `json:"content"`
+		} `json:"input"`
+		Tools        []ResponsesTool `json:"tools"`
+		Instructions string          `json:"instructions"`
+		Stream       bool            `json:"stream"`
+	}
+	if err := json.Unmarshal(requestBody, &request); err != nil {
+		t.Fatal(err)
+	}
+	if request.Stream {
+		t.Fatal("summary inference must be non-streaming")
+	}
+	if request.Instructions != "" {
+		t.Fatalf("original instructions leaked into summary request: %q", request.Instructions)
+	}
+	if len(request.Tools) != 1 || request.Tools[0].Name != CreateSummaryToolName {
+		t.Fatalf("unexpected callable tools: %+v", request.Tools)
+	}
+	if len(request.Input) != 2 || !strings.Contains(request.Input[1].Content, description) || !strings.Contains(request.Input[1].Content, "read_file") {
+		t.Fatalf("summary transcript is missing tool metadata: %+v", request.Input)
+	}
+	if strings.Contains(request.Input[1].Content, `"instructions"`) {
+		t.Fatalf("original instructions leaked into transcript: %s", request.Input[1].Content)
+	}
+
+	result, err := plan.Complete(compactionResponseBody(t, map[string]any{
+		"summary": "Continue inspecting main.go.", "retain_item_ids": []string{},
+	}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	payload := decodeResultPayload(t, result)
+	if payload.Summary != "Continue inspecting main.go." {
+		t.Fatalf("unexpected summary: %q", payload.Summary)
+	}
+	if len(payload.Retained) != 2 {
+		t.Fatalf("expected active call and result to be forced, got %+v", payload.Retained)
+	}
+	if payload.Retained[0].ToolCalls[0].ID != "call_1" || payload.Retained[1].ToolCallID != "call_1" {
+		t.Fatalf("tool state was not retained in order: %+v", payload.Retained)
+	}
+}
+
+func TestPrepareTriggeredCompactionRequiresStreaming(t *testing.T) {
+	body := []byte(`{"model":"test","input":[{"type":"message","role":"user","content":"hi"},{"type":"compaction_trigger"}]}`)
+	_, requested, err := PrepareTriggeredCompaction(body)
+	if !requested || err == nil || !strings.Contains(err.Error(), "stream=true") {
+		t.Fatalf("requested=%v err=%v", requested, err)
+	}
+}
+
+func TestCompactionSelectionKeepsCompleteToolGroupInOriginalOrder(t *testing.T) {
+	body := []byte(`{
+		"model":"test",
+		"stream":true,
+		"input":[
+			{"type":"message","role":"user","content":"run it"},
+			{"type":"function_call","call_id":"call_1","name":"shell","arguments":"{}"},
+			{"type":"function_call_output","call_id":"call_1","output":"ok"},
+			{"type":"message","role":"assistant","content":"done"},
+			{"type":"compaction_trigger"}
+		]
+	}`)
+	plan, requested, err := PrepareTriggeredCompaction(body)
+	if err != nil || !requested {
+		t.Fatalf("prepare: requested=%v err=%v", requested, err)
+	}
+
+	result, err := plan.Complete(compactionResponseBody(t, map[string]any{
+		"summary": "The command completed.", "retain_item_ids": []string{"item_000003"},
+	}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	payload := decodeResultPayload(t, result)
+	if len(payload.Retained) != 2 {
+		t.Fatalf("expected complete tool group, got %+v", payload.Retained)
+	}
+	if len(payload.Retained[0].ToolCalls) != 1 || payload.Retained[1].Role != "tool" {
+		t.Fatalf("tool group order changed: %+v", payload.Retained)
+	}
+}
+
+func TestCompactionRejectsInvalidToolStateAndSelections(t *testing.T) {
+	t.Run("orphan result", func(t *testing.T) {
+		body := []byte(`{"model":"test","stream":true,"input":[{"type":"function_call_output","call_id":"missing","output":"x"},{"type":"compaction_trigger"}]}`)
+		_, requested, err := PrepareTriggeredCompaction(body)
+		if !requested || err == nil || !strings.Contains(err.Error(), "no matching call") {
+			t.Fatalf("requested=%v err=%v", requested, err)
+		}
+	})
+
+	t.Run("unknown ref", func(t *testing.T) {
+		body := []byte(`{"model":"test","stream":true,"input":[{"type":"message","role":"user","content":"hi"},{"type":"compaction_trigger"}]}`)
+		plan, _, err := PrepareTriggeredCompaction(body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		_, err = plan.Complete(compactionResponseBody(t, map[string]any{
+			"summary": "hi", "retain_item_ids": []string{"missing"},
+		}))
+		if err == nil || !strings.Contains(err.Error(), "unknown item") {
+			t.Fatalf("expected unknown item error, got %v", err)
+		}
+	})
+}
+
+func TestExpandResponsesCompactionInputPreservesCodexRetainedPrefix(t *testing.T) {
+	payload := OllamaCompactionPayload{
+		Type: OllamaCompactionPayloadType, Version: OllamaCompactionPayloadVersion,
+		Summary: "The user chose option A.",
+		Retained: []api.Message{{Role: "assistant", ToolCalls: []api.ToolCall{{
+			ID: "call_live", Function: api.ToolCallFunction{Name: "shell", Arguments: api.NewToolCallFunctionArguments()},
+		}}}},
+	}
+	payloadJSON, err := json.Marshal(payload)
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, err := json.Marshal(map[string]any{
+		"model": "test",
+		"input": []any{
+			map[string]any{"type": "message", "role": "user", "content": "first user turn retained by Codex"},
+			map[string]any{"type": "message", "role": "user", "content": "second user turn retained by Codex"},
+			ResponsesCompactionItem{Type: "compaction", EncryptedContent: string(payloadJSON)},
+			map[string]any{"type": "message", "role": "user", "content": "new turn"},
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rewritten, changed, err := ExpandResponsesCompactionInput(body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !changed {
+		t.Fatal("expected rewritten input")
+	}
+	var request struct {
+		Input []json.RawMessage `json:"input"`
+	}
+	if err := json.Unmarshal(rewritten, &request); err != nil {
+		t.Fatal(err)
+	}
+	if len(request.Input) != 6 {
+		t.Fatalf("expected retained prefix, summary pair, retained call, and new turn; got %s", rewritten)
+	}
+	var types []string
+	for _, item := range request.Input {
+		types = append(types, rawInputItemType(item))
+	}
+	want := []string{"message", "message", "function_call", "function_call_output", "function_call", "message"}
+	for i := range want {
+		if types[i] != want[i] {
+			t.Fatalf("types=%v want=%v", types, want)
+		}
+	}
+	for _, marker := range []string{"first user turn retained by Codex", "second user turn retained by Codex"} {
+		if strings.Count(string(rewritten), marker) != 1 {
+			t.Fatalf("retained user message %q was lost or duplicated: %s", marker, rewritten)
+		}
+	}
+	if !strings.Contains(string(rewritten), "new turn") {
+		t.Fatalf("post-boundary input was lost: %s", rewritten)
+	}
+}
+
+func TestExpandResponsesCompactionInputRejectsForeignPayload(t *testing.T) {
+	body := []byte(`{"model":"test","input":[{"type":"compaction","encrypted_content":"opaque-provider-state"}]}`)
+	_, changed, err := ExpandResponsesCompactionInput(body)
+	if changed || err == nil || !strings.Contains(err.Error(), "not an Ollama payload") {
+		t.Fatalf("changed=%v err=%v", changed, err)
+	}
+}
+
+func TestRepeatedCompactionReplacesRatherThanNestsPayload(t *testing.T) {
+	oldPayload, err := json.Marshal(OllamaCompactionPayload{
+		Type: OllamaCompactionPayloadType, Version: OllamaCompactionPayloadVersion, Summary: "old summary",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, err := json.Marshal(map[string]any{
+		"model": "test", "stream": true,
+		"input": []any{
+			map[string]any{"type": "message", "role": "user", "content": "retained prefix"},
+			ResponsesCompactionItem{Type: "compaction", EncryptedContent: string(oldPayload)},
+			map[string]any{"type": "message", "role": "user", "content": "new work"},
+			ResponsesCompactionTrigger{Type: "compaction_trigger"},
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	plan, requested, err := PrepareTriggeredCompaction(body)
+	if err != nil || !requested {
+		t.Fatalf("prepare: requested=%v err=%v", requested, err)
+	}
+	result, err := plan.Complete(compactionResponseBody(t, map[string]any{
+		"summary": "replacement summary", "retain_item_ids": []string{},
+	}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	payload := decodeResultPayload(t, result)
+	if len(payload.Retained) != 0 {
+		t.Fatalf("old synthetic summary pair was retained: %+v", payload.Retained)
+	}
+	if strings.Contains(result.Item.EncryptedContent, "old summary") || strings.Contains(result.Item.EncryptedContent, "retained prefix") {
+		t.Fatalf("old compaction was nested: %s", result.Item.EncryptedContent)
+	}
+}
+
+func TestCompactionStreamContainsExactlyOneCompletedItem(t *testing.T) {
+	result := ResponsesCompactionResult{Item: ResponsesCompactionItem{Type: "compaction", EncryptedContent: `{"type":"ollama_compaction","version":1}`}}
+	events := NewResponsesCompactionStreamEvents("resp_1", "test", result)
+	var done, completed int
+	for _, event := range events {
+		switch event.Event {
+		case "response.output_item.done":
+			done++
+			data := event.Data.(map[string]any)
+			item := data["item"].(ResponsesCompactionItem)
+			if item.Type != "compaction" {
+				t.Fatalf("unexpected item: %+v", item)
+			}
+		case "response.completed":
+			completed++
+		}
+	}
+	if done != 1 || completed != 1 {
+		t.Fatalf("done=%d completed=%d events=%+v", done, completed, events)
+	}
+}
diff --git a/server/responses_compact.go b/server/responses_compact.go
new file mode 100644
index 000000000..8aae4d334
--- /dev/null
+++ b/server/responses_compact.go
@@ -0,0 +1,219 @@
+package server
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/klauspost/compress/zstd"
+
+	"github.com/ollama/ollama/middleware"
+	"github.com/ollama/ollama/openai"
+)
+
+// responsesCompactionMiddleware intercepts only Codex compaction control items.
+// Ordinary Responses requests continue through the existing route unchanged.
+func (s *Server) responsesCompactionMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		body, err := readResponsesCompactionBody(c)
+		if err != nil {
+			writeResponsesCompactionError(c, http.StatusBadRequest, "invalid_request_error", err.Error())
+			return
+		}
+
+		plan, requested, err := openai.PrepareTriggeredCompaction(body)
+		if err != nil {
+			writeResponsesCompactionError(c, http.StatusBadRequest, "invalid_request_error", err.Error())
+			return
+		}
+		if requested {
+			c.Abort()
+			s.handleResponsesCompaction(c, plan, true)
+			return
+		}
+
+		rewritten, changed, err := openai.ExpandResponsesCompactionInput(body)
+		if err != nil {
+			writeResponsesCompactionError(c, http.StatusBadRequest, "invalid_request_error", err.Error())
+			return
+		}
+		if changed {
+			resetResponsesRequestBody(c.Request, rewritten)
+		}
+		c.Next()
+	}
+}
+
+// ResponsesCompactHandler implements POST /v1/responses/compact with an
+// Ollama-owned ordinary inference request rather than upstream passthrough.
+func (s *Server) ResponsesCompactHandler(c *gin.Context) {
+	body, err := readResponsesCompactionBody(c)
+	if err != nil {
+		writeResponsesCompactionError(c, http.StatusBadRequest, "invalid_request_error", err.Error())
+		return
+	}
+	plan, err := openai.PrepareStandaloneCompaction(body)
+	if err != nil {
+		writeResponsesCompactionError(c, http.StatusBadRequest, "invalid_request_error", err.Error())
+		return
+	}
+	s.handleResponsesCompaction(c, plan, false)
+}
+
+func readResponsesCompactionBody(c *gin.Context) ([]byte, error) {
+	if c.GetHeader("Content-Encoding") == "zstd" {
+		reader, err := zstd.NewReader(c.Request.Body, zstd.WithDecoderMaxMemory(8<<20))
+		if err != nil {
+			return nil, fmt.Errorf("failed to decompress zstd body")
+		}
+		decompressed, err := io.ReadAll(http.MaxBytesReader(c.Writer, io.NopCloser(reader), maxDecompressedBodySize))
+		reader.Close()
+		if err != nil {
+			return nil, err
+		}
+		c.Request.Header.Del("Content-Encoding")
+		resetResponsesRequestBody(c.Request, decompressed)
+	}
+
+	body, err := readRequestBody(c.Request)
+	if err != nil {
+		return nil, err
+	}
+	if len(bytes.TrimSpace(body)) == 0 {
+		return nil, fmt.Errorf("missing request body")
+	}
+	return body, nil
+}
+
+func resetResponsesRequestBody(r *http.Request, body []byte) {
+	r.Body = io.NopCloser(bytes.NewReader(body))
+	r.ContentLength = int64(len(body))
+	r.Header.Set("Content-Length", strconv.Itoa(len(body)))
+}
+
+func (s *Server) handleResponsesCompaction(c *gin.Context, plan *openai.ResponsesCompactionPlan, stream bool) {
+	var validationErr error
+	for range 2 {
+		repair := ""
+		if validationErr != nil {
+			repair = validationErr.Error()
+		}
+		request, err := plan.SummaryRequest(repair)
+		if err != nil {
+			writeResponsesCompactionError(c, http.StatusInternalServerError, "compaction_failed", "compaction failed; the original conversation is unchanged")
+			return
+		}
+
+		response := s.runResponsesCompactionInference(c, request)
+		if response.status < http.StatusOK || response.status >= http.StatusMultipleChoices {
+			copyResponsesCompactionResponse(c, response)
+			return
+		}
+
+		result, err := plan.Complete(response.body.Bytes())
+		if err != nil {
+			validationErr = err
+			continue
+		}
+
+		id := fmt.Sprintf("resp_compact_%d", time.Now().UnixNano())
+		if stream {
+			writeResponsesCompactionStream(c, openai.NewResponsesCompactionStreamEvents(id, plan.Model, result))
+			return
+		}
+		c.JSON(http.StatusOK, openai.NewResponsesCompactedResponse(id, result))
+		return
+	}
+
+	writeResponsesCompactionError(c, http.StatusInternalServerError, "compaction_failed", "compaction failed; the selected model did not return a valid summary and the original conversation is unchanged")
+}
+
+// runResponsesCompactionInference uses the normal Responses stack without the
+// compaction dispatcher. This keeps local and cloud model selection identical
+// to an ordinary request and permits one isolated repair retry.
+func (s *Server) runResponsesCompactionInference(c *gin.Context, body []byte) *responsesInferenceRecorder {
+	router := gin.New()
+	router.POST("/v1/responses",
+		cloudPassthroughMiddleware(cloudErrRemoteInferenceUnavailable),
+		middleware.ResponsesMiddleware(),
+		s.ChatHandler,
+	)
+
+	req, err := http.NewRequestWithContext(c.Request.Context(), http.MethodPost, "/v1/responses", bytes.NewReader(body))
+	if err != nil {
+		return &responsesInferenceRecorder{header: make(http.Header), status: http.StatusInternalServerError, body: *bytes.NewBufferString(err.Error())}
+	}
+	req.Header = c.Request.Header.Clone()
+	req.Header.Del("Content-Encoding")
+	req.Header.Set("Content-Type", "application/json")
+	req.ContentLength = int64(len(body))
+
+	recorder := &responsesInferenceRecorder{header: make(http.Header)}
+	router.ServeHTTP(recorder, req)
+	return recorder
+}
+
+type responsesInferenceRecorder struct {
+	header http.Header
+	body   bytes.Buffer
+	status int
+}
+
+func (r *responsesInferenceRecorder) Header() http.Header {
+	return r.header
+}
+
+func (r *responsesInferenceRecorder) WriteHeader(status int) {
+	if r.status == 0 {
+		r.status = status
+	}
+}
+
+func (r *responsesInferenceRecorder) Write(data []byte) (int, error) {
+	if r.status == 0 {
+		r.status = http.StatusOK
+	}
+	return r.body.Write(data)
+}
+
+func (r *responsesInferenceRecorder) Flush() {}
+
+func copyResponsesCompactionResponse(c *gin.Context, response *responsesInferenceRecorder) {
+	for key, values := range response.header {
+		if key == "Content-Length" {
+			continue
+		}
+		for _, value := range values {
+			c.Header(key, value)
+		}
+	}
+	c.Data(response.status, response.header.Get("Content-Type"), response.body.Bytes())
+}
+
+func writeResponsesCompactionStream(c *gin.Context, events []openai.ResponsesStreamEvent) {
+	c.Header("Content-Type", "text/event-stream")
+	c.Header("Cache-Control", "no-cache")
+	c.Header("Connection", "keep-alive")
+	c.Status(http.StatusOK)
+	for _, event := range events {
+		data, err := json.Marshal(event.Data)
+		if err != nil {
+			return
+		}
+		_, _ = fmt.Fprintf(c.Writer, "event: %s\ndata: %s\n\n", event.Event, data)
+	}
+	if flusher, ok := c.Writer.(http.Flusher); ok {
+		flusher.Flush()
+	}
+}
+
+func writeResponsesCompactionError(c *gin.Context, status int, code, message string) {
+	response := openai.NewError(status, message)
+	response.Error.Code = &code
+	c.AbortWithStatusJSON(status, response)
+}
diff --git a/server/responses_compact_test.go b/server/responses_compact_test.go
new file mode 100644
index 000000000..02d654419
--- /dev/null
+++ b/server/responses_compact_test.go
@@ -0,0 +1,282 @@
+package server
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/ollama/ollama/openai"
+)
+
+func summaryResponse(t *testing.T, summary string, retained []string) []byte {
+	t.Helper()
+	arguments, err := json.Marshal(map[string]any{"summary": summary, "retain_item_ids": retained})
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, err := json.Marshal(map[string]any{
+		"id": "resp_summary", "object": "response", "status": "completed", "model": "fixture",
+		"output": []any{map[string]any{
+			"id": "fc_summary", "type": "function_call", "status": "completed", "call_id": "call_summary",
+			"name": openai.CreateSummaryToolName, "arguments": string(arguments),
+		}},
+		"usage": map[string]any{
+			"input_tokens": 100, "output_tokens": 20, "total_tokens": 120,
+			"input_tokens_details":  map[string]any{"cached_tokens": 0},
+			"output_tokens_details": map[string]any{"reasoning_tokens": 0},
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return body
+}
+
+type compactionUpstreamCapture struct {
+	mu     sync.Mutex
+	paths  []string
+	bodies [][]byte
+}
+
+func (c *compactionUpstreamCapture) add(path string, body []byte) int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.paths = append(c.paths, path)
+	c.bodies = append(c.bodies, append([]byte(nil), body...))
+	return len(c.bodies)
+}
+
+func (c *compactionUpstreamCapture) snapshot() ([]string, [][]byte) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	paths := append([]string(nil), c.paths...)
+	bodies := make([][]byte, len(c.bodies))
+	for i := range c.bodies {
+		bodies[i] = append([]byte(nil), c.bodies[i]...)
+	}
+	return paths, bodies
+}
+
+func newCompactionTestServer(t *testing.T, handler func(int, http.ResponseWriter, *http.Request, []byte)) (*httptest.Server, *compactionUpstreamCapture) {
+	t.Helper()
+	gin.SetMode(gin.TestMode)
+	setTestHome(t, t.TempDir())
+
+	capture := &compactionUpstreamCapture{}
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, _ := io.ReadAll(r.Body)
+		attempt := capture.add(r.URL.Path, body)
+		handler(attempt, w, r, body)
+	}))
+	t.Cleanup(upstream.Close)
+
+	original := cloudProxyBaseURL
+	cloudProxyBaseURL = upstream.URL
+	t.Cleanup(func() { cloudProxyBaseURL = original })
+
+	s := &Server{}
+	router, err := s.GenerateRoutes()
+	if err != nil {
+		t.Fatal(err)
+	}
+	local := httptest.NewServer(router)
+	t.Cleanup(local.Close)
+	return local, capture
+}
+
+func postCompactionRequest(t *testing.T, server *httptest.Server, path, body string) (int, http.Header, []byte) {
+	t.Helper()
+	req, err := http.NewRequestWithContext(t.Context(), http.MethodPost, server.URL+path, strings.NewReader(body))
+	if err != nil {
+		t.Fatal(err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	response, err := server.Client().Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer response.Body.Close()
+	responseBody, err := io.ReadAll(response.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return response.StatusCode, response.Header.Clone(), responseBody
+}
+
+func TestResponsesCompactUsesOrdinarySelectedCloudModel(t *testing.T) {
+	local, capture := newCompactionTestServer(t, func(_ int, w http.ResponseWriter, _ *http.Request, _ []byte) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write(summaryResponse(t, "Continue the task.", nil))
+	})
+
+	status, _, body := postCompactionRequest(t, local, "/v1/responses/compact", `{
+		"model":"fixture:cloud",
+		"instructions":"original agent instructions",
+		"input":[{"type":"message","role":"user","content":"hello"}],
+		"tools":[{"type":"function","name":"shell","description":"Run a command","strict":false,"parameters":{"type":"object"}}]
+	}`)
+	if status != http.StatusOK {
+		t.Fatalf("status=%d body=%s", status, body)
+	}
+	var compacted openai.ResponsesCompactedResponse
+	if err := json.Unmarshal(body, &compacted); err != nil {
+		t.Fatal(err)
+	}
+	if compacted.Object != "response.compaction" || len(compacted.Output) != 1 || compacted.Output[0].Type != "compaction" {
+		t.Fatalf("unexpected compact response: %+v", compacted)
+	}
+
+	paths, bodies := capture.snapshot()
+	if len(paths) != 1 || paths[0] != "/v1/responses" {
+		t.Fatalf("compaction must use one ordinary Responses inference call, paths=%v", paths)
+	}
+	if bytes.Contains(bodies[0], []byte("original agent instructions")) {
+		t.Fatalf("top-level instructions leaked to compactor: %s", bodies[0])
+	}
+	var summaryRequest struct {
+		Model  string                 `json:"model"`
+		Stream bool                   `json:"stream"`
+		Tools  []openai.ResponsesTool `json:"tools"`
+	}
+	if err := json.Unmarshal(bodies[0], &summaryRequest); err != nil {
+		t.Fatal(err)
+	}
+	if summaryRequest.Model != "fixture" || summaryRequest.Stream {
+		t.Fatalf("unexpected upstream summary request: %+v", summaryRequest)
+	}
+	if len(summaryRequest.Tools) != 1 || summaryRequest.Tools[0].Name != openai.CreateSummaryToolName {
+		t.Fatalf("unexpected callable tools: %+v", summaryRequest.Tools)
+	}
+	if !bytes.Contains(bodies[0], []byte("shell")) {
+		t.Fatalf("original tool metadata missing from transcript: %s", bodies[0])
+	}
+}
+
+func TestResponsesCompactionTriggerReturnsCodexStream(t *testing.T) {
+	local, capture := newCompactionTestServer(t, func(_ int, w http.ResponseWriter, _ *http.Request, _ []byte) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write(summaryResponse(t, "Compact summary.", nil))
+	})
+
+	status, header, body := postCompactionRequest(t, local, "/v1/responses", `{
+		"model":"fixture:cloud","stream":true,
+		"input":[{"type":"message","role":"user","content":"hello"},{"type":"compaction_trigger"}]
+	}`)
+	if status != http.StatusOK {
+		t.Fatalf("status=%d body=%s", status, body)
+	}
+	if got := header.Get("Content-Type"); !strings.HasPrefix(got, "text/event-stream") {
+		t.Fatalf("content-type=%q", got)
+	}
+	text := string(body)
+	if strings.Count(text, "event: response.output_item.done") != 1 || strings.Count(text, `"type":"compaction"`) == 0 {
+		t.Fatalf("missing single compaction output item: %s", text)
+	}
+	if strings.Count(text, "event: response.completed") != 1 {
+		t.Fatalf("missing response.completed: %s", text)
+	}
+	paths, requests := capture.snapshot()
+	if len(paths) != 1 || paths[0] != "/v1/responses" {
+		t.Fatalf("paths=%v requests=%s", paths, requests)
+	}
+}
+
+func TestResponsesCompactionRepairsMalformedSummaryOnce(t *testing.T) {
+	local, capture := newCompactionTestServer(t, func(attempt int, w http.ResponseWriter, _ *http.Request, _ []byte) {
+		w.Header().Set("Content-Type", "application/json")
+		if attempt == 1 {
+			_, _ = w.Write([]byte(`{"id":"bad","object":"response","output":[{"type":"message","role":"assistant","content":[]}]}`))
+			return
+		}
+		_, _ = w.Write(summaryResponse(t, "Repaired summary.", nil))
+	})
+
+	status, _, body := postCompactionRequest(t, local, "/v1/responses/compact", `{"model":"fixture:cloud","input":"hello"}`)
+	if status != http.StatusOK {
+		t.Fatalf("status=%d body=%s", status, body)
+	}
+	_, bodies := capture.snapshot()
+	if len(bodies) != 2 {
+		t.Fatalf("expected one repair retry, got %d requests", len(bodies))
+	}
+	if !bytes.Contains(bodies[1], []byte("previous create_summary call was invalid")) {
+		t.Fatalf("repair request does not explain the validation error: %s", bodies[1])
+	}
+}
+
+func TestResponsesCompactionFailsAfterOneRepair(t *testing.T) {
+	local, capture := newCompactionTestServer(t, func(_ int, w http.ResponseWriter, _ *http.Request, _ []byte) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"id":"bad","object":"response","output":[]}`))
+	})
+
+	status, _, body := postCompactionRequest(t, local, "/v1/responses/compact", `{"model":"fixture:cloud","input":"hello"}`)
+	if status != http.StatusInternalServerError {
+		t.Fatalf("status=%d body=%s", status, body)
+	}
+	var errorResponse openai.ErrorResponse
+	if err := json.Unmarshal(body, &errorResponse); err != nil {
+		t.Fatal(err)
+	}
+	if errorResponse.Error.Code == nil || *errorResponse.Error.Code != "compaction_failed" {
+		t.Fatalf("unexpected error: %+v", errorResponse)
+	}
+	paths, _ := capture.snapshot()
+	if len(paths) != 2 {
+		t.Fatalf("expected exactly two attempts, got %d", len(paths))
+	}
+}
+
+func TestResponsesCompactionPayloadIsExpandedBeforeCloudPassthrough(t *testing.T) {
+	local, capture := newCompactionTestServer(t, func(_ int, w http.ResponseWriter, _ *http.Request, _ []byte) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"id":"resp_next","object":"response","status":"completed","model":"fixture","output":[],"usage":null}`))
+	})
+	payload, err := json.Marshal(openai.OllamaCompactionPayload{
+		Type: openai.OllamaCompactionPayloadType, Version: openai.OllamaCompactionPayloadVersion,
+		Summary: "The build is ready.",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	request, err := json.Marshal(map[string]any{
+		"model": "fixture:cloud", "stream": false,
+		"input": []any{
+			map[string]any{"type": "message", "role": "user", "content": "first retained user turn"},
+			map[string]any{"type": "message", "role": "user", "content": "second retained user turn"},
+			openai.ResponsesCompactionItem{Type: "compaction", EncryptedContent: string(payload)},
+			map[string]any{"type": "message", "role": "user", "content": "new turn"},
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	status, _, body := postCompactionRequest(t, local, "/v1/responses", string(request))
+	if status != http.StatusOK {
+		t.Fatalf("status=%d body=%s", status, body)
+	}
+	paths, bodies := capture.snapshot()
+	if len(paths) != 1 || paths[0] != "/v1/responses" {
+		t.Fatalf("paths=%v", paths)
+	}
+	forwarded := string(bodies[0])
+	if strings.Contains(forwarded, `"type":"compaction"`) {
+		t.Fatalf("compaction boundary was forwarded: %s", forwarded)
+	}
+	for _, marker := range []string{"first retained user turn", "second retained user turn"} {
+		if strings.Count(forwarded, marker) != 1 {
+			t.Fatalf("retained user message %q was lost or duplicated: %s", marker, forwarded)
+		}
+	}
+	if !strings.Contains(forwarded, "The build is ready.") || !strings.Contains(forwarded, "new turn") || !strings.Contains(forwarded, "ollama_compaction_summary") {
+		t.Fatalf("expanded state is incomplete: %s", forwarded)
+	}
+}
diff --git a/server/routes.go b/server/routes.go
index 263c7e27a..63a889761 100644
--- a/server/routes.go
+++ b/server/routes.go
@@ -1922,7 +1922,8 @@ func (s *Server) GenerateRoutes() (http.Handler, error) {
 	r.POST("/v1/embeddings", cloudPassthroughMiddleware(cloudErrRemoteInferenceUnavailable), middleware.EmbeddingsMiddleware(), s.EmbedHandler)
 	r.GET("/v1/models", middleware.ListMiddleware(), s.ListHandler)
 	r.GET("/v1/models/:model", cloudModelPathPassthroughMiddleware(cloudErrRemoteModelDetailsUnavailable), middleware.RetrieveMiddleware(), s.ShowHandler)
-	r.POST("/v1/responses", s.withInferenceRequestLogging("/v1/responses", cloudPassthroughMiddleware(cloudErrRemoteInferenceUnavailable), middleware.ResponsesMiddleware(), s.ChatHandler)...)
+	r.POST("/v1/responses", s.withInferenceRequestLogging("/v1/responses", s.responsesCompactionMiddleware(), cloudPassthroughMiddleware(cloudErrRemoteInferenceUnavailable), middleware.ResponsesMiddleware(), s.ChatHandler)...)
+	r.POST("/v1/responses/compact", s.ResponsesCompactHandler)
 	// OpenAI-compatible audio endpoint
 	r.POST("/v1/audio/transcriptions", middleware.TranscriptionMiddleware(), s.ChatHandler)