From 48335d7797efecdd51945486c867f10407436fc0 Mon Sep 17 00:00:00 2001
From: viettranx <viettranx@gmail.com>
Date: Wed, 15 Apr 2026 11:24:49 +0700
Subject: [PATCH] feat(pruning)!: faithful port of TS context pruning +
 backfill migration

Port goclaw context pruning to match upstream TS design in
openclaw/src/agents/pi-hooks/context-pruning/:

- Opt-in default: prune only when mode="cache-ttl" (was opt-out)
- Remove Pass 0 per-result 30% guard (duplicated Pass 1 with different
  suffix, caused wobble)
- Dedupe double prune call per iteration: PruneStage owns the single
  entry point; loop_history only runs limitHistoryTurns + sanitizeHistory
- Add cache-TTL gate for Anthropic prompt cache: skip prune while cache
  is live, scoped per-session via sync.Map
- Add context.pruned event emission for observability
- Configurable TTL as Go duration string ("5m", "30s")

BREAKING CHANGE: context pruning now opt-in. Add
contextPruning.mode: "cache-ttl" to config.agents.defaults to restore.

Migration 51 / SQLite v19 backfills mode="cache-ttl" for agents with
existing custom context_pruning config missing the mode field, so
previously-configured agents keep pruning after the opt-in flip.
NULL configs stay NULL (new opt-in default applies).

Web UI adds Cache TTL input + toggle wiring mode to cache-ttl/off.
---
 CHANGELOG.md                                  |  29 +++
 docs/01-agent-loop.md                         |  47 +++--
 docs/17-changelog.md                          |  34 ++++
 internal/agent/loop_history.go                |   6 +-
 internal/agent/loop_history_test.go           |   9 +-
 internal/agent/loop_pipeline_adapter.go       |  15 ++
 internal/agent/loop_pipeline_callbacks.go     |  27 ++-
 internal/agent/loop_types.go                  |   8 +
 internal/agent/pruning.go                     |  60 ++----
 internal/agent/pruning_integration_test.go    |  62 ++++++
 internal/agent/pruning_test.go                | 154 +++++++++++++--
 internal/config/config.go                     |  11 +-
 internal/eventbus/event_types.go              |  16 ++
 internal/pipeline/deps.go                     |  18 +-
 internal/pipeline/prune_stage.go              | 110 ++++++++++-
 internal/pipeline/stages_test.go              | 180 ++++++++++++++++--
 internal/store/sqlitestore/schema.go          |  14 +-
 internal/upgrade/version.go                   |   2 +-
 ...051_backfill_context_pruning_mode.down.sql |   4 +
 ...00051_backfill_context_pruning_mode.up.sql |  12 ++
 ui/web/src/i18n/locales/en/agents.json        |   3 +-
 ui/web/src/i18n/locales/vi/agents.json        |   3 +-
 ui/web/src/i18n/locales/zh/agents.json        |   3 +-
 .../agent-advanced-state-utils.ts             |   4 +-
 .../context-pruning-section.tsx               |  13 ++
 ui/web/src/types/agent.ts                     |   1 +
 26 files changed, 730 insertions(+), 115 deletions(-)
 create mode 100644 internal/agent/pruning_integration_test.go
 create mode 100644 migrations/000051_backfill_context_pruning_mode.down.sql
 create mode 100644 migrations/000051_backfill_context_pruning_mode.up.sql

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4b03c2a0..f640b6a7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,35 @@
 
 All notable changes to GoClaw are documented here. For full documentation, see [docs.goclaw.sh](https://docs.goclaw.sh).
 
+## Unreleased
+
+### Breaking Changes
+
+- **Context pruning now opt-in.** Previously tool-result trimming ran by default
+  for all providers; now requires explicit `contextPruning.mode: "cache-ttl"` in
+  `config.agents.defaults` to enable. Matches upstream TS design and prevents
+  silent prompt-cache invalidation on Anthropic.
+
+  Migration — add to `config.json5`:
+  ```json5
+  agents: {
+    defaults: {
+      contextPruning: { mode: "cache-ttl" }
+    }
+  }
+  ```
+
+### Improvements
+
+- **Context pruning cleanup.** Removed redundant Pass 0 (per-result 30% guard),
+  deduplicated double prune call per iteration, added SanitizeHistory to
+  PruneStage for broken tool_use/tool_result pair cleanup.
+- **Context pruning config backfill (migration).** Agents with existing custom
+  `context_pruning` config (e.g., `softTrimRatio`, `keepLastAssistants`) but
+  missing a `mode` field get auto-backfilled with `mode: "cache-ttl"` to
+  preserve their intent after the opt-in flip. Rows with NULL config stay
+  NULL (new opt-in default applies). PG migration 51; SQLite schema v19.
+
 ## Project Status
 
 ### Implemented & Tested in Production
diff --git a/docs/01-agent-loop.md b/docs/01-agent-loop.md
index fea3a1e5..f7e24a4d 100644
--- a/docs/01-agent-loop.md
+++ b/docs/01-agent-loop.md
@@ -59,15 +59,16 @@ Finalize (runs once, uses background context if cancelled)
 - Resolve workspace + context files dynamically
 - Build system prompt (15+ sections)
 - Inject conversation summary if exists
-- Run history pipeline (limitHistoryTurns → pruneContextMessages → sanitizeHistory)
+- Run history pipeline (limitHistoryTurns → sanitizeHistory)
 - Filter tools through PolicyEngine (RBAC)
 - Call LLM, record span with token counts
 - Emit `chunk` events (streaming) or single response
 
-**PruneStage**
+**PruneStage** (opt-in via `contextPruning.mode: "cache-ttl"`)
 - Estimate token ratio vs context window
-- If >= 30%, run soft trim pass (keep first/last 1500 chars, replace middle with "...")
+- If >= 25%, run soft trim pass (keep first/last 3000 chars, replace middle with "...")
 - If >= 50%, run hard clear pass (replace with placeholder)
+- Run sanitizeHistory to fix broken tool_use/tool_result pairs after prune
 - Trigger memory flush (synchronous) if compaction threshold exceeded
 
 **ToolStage**
@@ -183,7 +184,7 @@ flowchart TD
 
     subgraph PH3["Phase 3: Build Messages"]
         P3A[Build system prompt - 15+ sections] --> P3B[Inject conversation summary if present]
-        P3B --> P3C["History pipeline: limitHistoryTurns --> pruneContextMessages --> sanitizeHistory"]
+        P3B --> P3C["History pipeline: limitHistoryTurns --> sanitizeHistory"]
         P3C --> P3D[Append current user message]
         P3D --> P3E[Buffer user message locally - deferred write]
     end
@@ -398,25 +399,20 @@ All security events use the `slog.Warn("security.injection_detected")` conventio
 
 ## 5. History Pipeline
 
-The history pipeline prepares conversation history before sending it to the LLM. It runs in three sequential stages.
+The history pipeline prepares conversation history before sending it to the LLM. It runs in two sequential stages. Context pruning is handled separately by PruneStage (opt-in via `contextPruning.mode: "cache-ttl"`).
 
 ```mermaid
 flowchart TD
     RAW[Raw Session History] --> S1
     S1["Stage 1: limitHistoryTurns<br/>Keep the last N user turns<br/>plus their associated assistant/tool messages"] --> S2
-    S2["Stage 2: pruneContextMessages<br/>2-pass tool result trimming<br/>(see Section 6)"] --> S3
-    S3["Stage 3: sanitizeHistory<br/>Repair broken tool_use / tool_result pairing<br/>after truncation"] --> OUT[Cleaned History]
+    S2["Stage 2: sanitizeHistory<br/>Repair broken tool_use / tool_result pairing<br/>after truncation"] --> OUT[Cleaned History]
 ```
 
 ### Stage 1: limitHistoryTurns
 
 Takes the raw session history and a `historyLimit` parameter. Keeps only the last N user turns along with all associated assistant and tool messages that belong to those turns. Earlier messages are discarded.
 
-### Stage 2: pruneContextMessages
-
-Applies the 2-pass context pruning algorithm described in Section 6.
-
-### Stage 3: sanitizeHistory
+### Stage 2: sanitizeHistory
 
 Repairs tool message pairing that may have been broken by truncation or compaction:
 
@@ -429,15 +425,17 @@ Repairs tool message pairing that may have been broken by truncation or compacti
 
 ## 6. Context Pruning
 
-Context pruning reduces oversized tool results using a 2-pass algorithm. It only activates when the estimated token-to-context-window ratio crosses a threshold.
+Context pruning reduces oversized tool results using a 2-pass algorithm. **It is opt-in** — configure `contextPruning.mode: "cache-ttl"` to enable. When disabled (default), zero overhead. Owned by PruneStage in the agent pipeline.
 
 ```mermaid
 flowchart TD
-    START[Estimate token ratio vs context window] --> CHECK{Ratio >= softTrimRatio 0.3?}
+    START[Check mode == cache-ttl?] --> GATE{Mode enabled?}
+    GATE -->|No| SKIP[No pruning - zero overhead]
+    GATE -->|Yes| CHECK{Ratio >= softTrimRatio 0.25?}
     CHECK -->|No| DONE[No pruning needed]
     CHECK -->|Yes| PASS1
 
-    PASS1["Pass 1: Soft Trim<br/>For each eligible tool result > 4000 chars:<br/>Keep first 1500 chars + last 1500 chars<br/>Replace middle with '...'"]
+    PASS1["Pass 1: Soft Trim<br/>For each eligible tool result > 6000 chars:<br/>Keep first 3000 chars + last 3000 chars<br/>Replace middle with '...'"]
     PASS1 --> CHECK2{"Ratio >= hardClearRatio 0.5?"}
     CHECK2 -->|No| DONE
     CHECK2 -->|Yes| PASS2
@@ -446,12 +444,25 @@ flowchart TD
     PASS2 --> DONE
 ```
 
+### Configuration
+
+Enable pruning by setting `contextPruning.mode` in agent defaults:
+
+```json5
+agents: {
+  defaults: {
+    contextPruning: { mode: "cache-ttl" }
+  }
+}
+```
+
 ### Defaults
 
 | Parameter | Default | Description |
 |-----------|---------|-------------|
+| `mode` | `""` (disabled) | `""` or `"off"` = disabled; `"cache-ttl"` = enabled |
 | `keepLastAssistants` | 3 | Number of recent assistant messages protected from pruning |
-| `softTrimRatio` | 0.3 | Token ratio threshold to trigger Pass 1 |
+| `softTrimRatio` | 0.25 | Token ratio threshold to trigger Pass 1 |
 | `hardClearRatio` | 0.5 | Token ratio threshold to trigger Pass 2 |
 | `minPrunableToolChars` | 50,000 | Minimum tool result length eligible for hard clear |
 
@@ -719,8 +730,8 @@ Enabled via the `GOCLAW_TRACE_VERBOSE=1` environment variable.
 | `internal/agent/loop_run.go` | Run() entry point: dual-mode gate (v2 vs v3), trace creation, span management |
 | `internal/agent/loop_pipeline_adapter.go` | Bridge v2 Loop to v3 Pipeline: state conversion, dependency injection, callback wiring |
 | `internal/agent/loop.go` | runLoop() core loop: LLM iteration, tool execution, message buffering (v2 path) |
-| `internal/agent/loop_history.go` | History pipeline: limitHistoryTurns, pruneContextMessages, sanitizeHistory, summary injection |
-| `internal/agent/pruning.go` | Context pruning: 2-pass soft trim and hard clear algorithm |
+| `internal/agent/loop_history.go` | History pipeline: limitHistoryTurns, sanitizeHistory, summary injection |
+| `internal/agent/pruning.go` | Context pruning: 2-pass soft trim and hard clear algorithm (opt-in via PruneStage) |
 | `internal/agent/loop_compact.go` | Mid-loop compaction: in-memory message summarization during iterations |
 | `internal/agent/systemprompt.go` | System prompt assembly (19+ sections), PromptFull and PromptMinimal modes |
 | `internal/agent/systemprompt_sections.go` | Individual section builders (tooling, workspace, sandbox, skills, MCP, etc.) |
diff --git a/docs/17-changelog.md b/docs/17-changelog.md
index c1e29591..b5bbaccd 100644
--- a/docs/17-changelog.md
+++ b/docs/17-changelog.md
@@ -6,6 +6,40 @@ All notable changes to GoClaw Gateway are documented here. Format follows [Keep
 
 ## [Unreleased] — 2026-04-15
 
+#### ElevenLabs Audio Manager Refactor — Phase 6 (2026-04-15)
+
+Desktop UI parity: voice picker + STT admin form ported from web to Wails desktop frontend. Completes 6-phase plan; all audio surfaces (TTS/STT/Music/SFX) now manageable from both web and desktop Lite editions.
+
+### Added
+- **Desktop voice picker**: `ui/desktop/frontend/src/components/agents/voice-picker.tsx` — uses desktop's native Combobox primitive; embedded in `AgentDetailPanel` with `other_config.tts_voice_id` persistence via spread-merge pattern
+- **Desktop voice preview button**: `ui/desktop/frontend/src/components/agents/voice-preview-button.tsx` — singleton `<audio>` (module-level `currentAudio` ref); hidden when `preview_url` absent (resolves P6-L)
+- **Desktop STT admin form**: `ui/desktop/frontend/src/components/builtin-tools/stt-provider-form.tsx` — mirrors web fields + `whatsapp_enabled` toggle + privacy banner; routed via `ToolSettingsDialog` when `tool.name === 'stt'`
+- **Desktop voices service + hook**: `services/voices.ts` (`listVoices`, `refreshVoices`) + `hooks/use-voices.ts` (plain useState/useEffect — no React Query on desktop; mirrors web hook shape)
+- **Desktop Vitest infrastructure**: `vitest.config.ts` + `test/setup.ts` (jsdom + jest-dom + HTMLMediaElement mock) — resolves P6-H3 (desktop tests previously impossible)
+- **Desktop i18n `tts` namespace**: `i18n/locales/{en,vi,zh}/tts.json` (15 → 16 total namespaces registered in `i18n/index.ts`) + `tools.json` extended with `builtin.sttForm.*` keys
+- **Desktop component tests**: voice picker (4 tests) + STT form (3 tests) — parity subset covering render, save, preview, privacy banner
+
+### Changed
+- **Desktop `AgentDetailPanel`**: Added `ttsVoiceId` local state + `onSaveWithVoice` wrapper that preserves existing `other_config` fields via spread-merge before overwriting `tts_voice_id`
+- **Desktop `ToolSettingsDialog`**: Added `tool.name === 'stt'` routing branch before JsonSettingsForm fallback; existing `web_fetch` + MEDIA_TOOLS routing unchanged
+- **Desktop `package.json`**: Added devDeps (`vitest`, `@testing-library/react`, `@testing-library/jest-dom`, `jsdom`, `@vitejs/plugin-react`) + `test` / `test:watch` npm scripts
+
+### Resolved
+- **Audit finding P6-B1**: Gate G5 verified — Phase 5 merged green before Phase 6 work began
+- **Audit finding P6-B2**: Desktop path rewrite confirmed — no `pages/` dir used; component composition via `AgentDetailPanel` + `ToolSettingsDialog`
+- **Audit finding P6-B3**: `tts.json` namespace created + registered in desktop `i18n/index.ts` (web-desktop i18n parity)
+- **Audit finding P6-H1**: `tools.json` extended with STT labels; `tts.json` created per Decision 4
+- **Audit finding P6-H2**: SttProviderForm integration point identified (`ToolSettingsDialog.tsx` name-routing) + wired
+- **Audit finding P6-H3**: Vitest installed + configured in desktop frontend (was previously absent)
+- **Audit finding P6-L**: Voice preview button hidden (not disabled) when `preview_url` null/empty
+- **Audit finding P6-M** (codec): MP3 + Opus codec smoke test remains on manual verification checklist (user to confirm on macOS WKWebView + Windows WebView2)
+- **Cross-phase XP-5**: Desktop paths confirmed — `components/agents/`, `components/builtin-tools/`, `services/`, `hooks/` (no `pages/`)
+
+### Deferred
+- **Manual smoke test**: `wails dev -tags sqliteonly` voice picker save + STT form submit + codec playback requires user verification (cannot run headless in automation)
+
+---
+
 #### ElevenLabs Audio Manager Refactor — Phase 5 (2026-04-15)
 
 Channel STT migration (Telegram/Feishu/Discord) + WhatsApp voice transcription with tenant opt-in (default disabled due to E2E encryption trade-off, resolves privacy red-team finding).
diff --git a/internal/agent/loop_history.go b/internal/agent/loop_history.go
index 6853988b..855d6200 100644
--- a/internal/agent/loop_history.go
+++ b/internal/agent/loop_history.go
@@ -256,10 +256,10 @@ func (l *Loop) buildMessages(ctx context.Context, history []providers.Message, s
 		})
 	}
 
-	// History pipeline matching TS: limitHistoryTurns → pruneContext → sanitizeHistory.
+	// History pipeline: limitHistoryTurns → sanitizeHistory.
+	// Pruning is owned by PruneStage in the pipeline (single entry point).
 	trimmed := limitHistoryTurns(history, historyLimit)
-	pruned := pruneContextMessages(trimmed, l.contextWindow, l.contextPruningCfg, l.tokenCounter, l.model)
-	sanitized, droppedCount := sanitizeHistory(pruned)
+	sanitized, droppedCount := sanitizeHistory(trimmed)
 	messages = append(messages, sanitized...)
 
 	// If orphaned messages were found and dropped, persist the cleaned history
diff --git a/internal/agent/loop_history_test.go b/internal/agent/loop_history_test.go
index e73ab5b6..33ee6683 100644
--- a/internal/agent/loop_history_test.go
+++ b/internal/agent/loop_history_test.go
@@ -602,7 +602,7 @@ func TestEstimateOverhead(t *testing.T) {
 }
 
 func TestPruneContextMessagesDefaultEnabled(t *testing.T) {
-	// With nil config, pruning should run (not return early).
+	// Phase 04: nil config → no pruning (opt-in). To enable, use Mode: "cache-ttl".
 	// Create messages with a large tool result that exceeds soft trim threshold.
 	largeContent := make([]byte, 10000)
 	for i := range largeContent {
@@ -619,9 +619,10 @@ func TestPruneContextMessagesDefaultEnabled(t *testing.T) {
 		{Role: "assistant", Content: "Sure, here you go."},
 	}
 
-	// With nil config and small context window (to trigger soft trim ratio > 0.3),
+	// With cache-ttl mode and small context window (to trigger soft trim ratio > 0.3),
 	// pruning should trim the large tool result.
-	result := pruneContextMessages(msgs, 5000, nil, nil, "")
+	cfg := &config.ContextPruningConfig{Mode: "cache-ttl"}
+	result := pruneContextMessages(msgs, 5000, cfg, nil, "", nil)
 
 	// The large tool result should have been trimmed.
 	toolMsg := result[2]
@@ -635,7 +636,7 @@ func TestPruneContextMessagesExplicitOff(t *testing.T) {
 		{Role: "user", Content: "Hello"},
 	}
 	cfg := &config.ContextPruningConfig{Mode: "off"}
-	result := pruneContextMessages(msgs, 200000, cfg, nil, "")
+	result := pruneContextMessages(msgs, 200000, cfg, nil, "", nil)
 	// Should return original messages unchanged.
 	if len(result) != len(msgs) {
 		t.Errorf("expected %d messages, got %d", len(msgs), len(result))
diff --git a/internal/agent/loop_pipeline_adapter.go b/internal/agent/loop_pipeline_adapter.go
index 4e4ac20d..024a8fa1 100644
--- a/internal/agent/loop_pipeline_adapter.go
+++ b/internal/agent/loop_pipeline_adapter.go
@@ -3,6 +3,7 @@ package agent
 import (
 	"context"
 
+	"github.com/nextlevelbuilder/goclaw/internal/config"
 	"github.com/nextlevelbuilder/goclaw/internal/eventbus"
 	"github.com/nextlevelbuilder/goclaw/internal/memory"
 	"github.com/nextlevelbuilder/goclaw/internal/pipeline"
@@ -111,8 +112,22 @@ func (l *Loop) buildPipelineDeps(req *RunRequest, bridgeRS *runState) pipeline.P
 
 		// Prune callbacks
 		PruneMessages:   cb.pruneMessages,
+		SanitizeHistory: cb.sanitizeHistory,
 		CompactMessages: cb.compactMessages,
 
+		// Cache-TTL gate callbacks (Phase 06)
+		GetProviderCaps: func() providers.ProviderCapabilities {
+			if ca, ok := l.provider.(providers.CapabilitiesAware); ok {
+				return ca.Capabilities()
+			}
+			return providers.ProviderCapabilities{}
+		},
+		GetPruningConfig: func() *config.ContextPruningConfig {
+			return l.contextPruningCfg
+		},
+		GetCacheTouch:    l.cacheTouchAt,
+		MarkCacheTouched: l.markCacheTouched,
+
 		// Memory flush
 		RunMemoryFlush: cb.runMemoryFlush,
 
diff --git a/internal/agent/loop_pipeline_callbacks.go b/internal/agent/loop_pipeline_callbacks.go
index 06a08130..e2789528 100644
--- a/internal/agent/loop_pipeline_callbacks.go
+++ b/internal/agent/loop_pipeline_callbacks.go
@@ -47,6 +47,7 @@ func (l *Loop) pipelineCallbacks(req *RunRequest, bridgeRS *runState) pipelineCa
 		buildFilteredTools: l.makeBuildFilteredTools(req),
 		callLLM:            l.makeCallLLM(req, emitRun),
 		pruneMessages:      l.makePruneMessages(),
+		sanitizeHistory:    sanitizeHistory,
 		compactMessages:    l.makeCompactMessages(req),
 		runMemoryFlush:     l.makeRunMemoryFlush(),
 		executeToolCall:    l.makeExecuteToolCall(req, bridgeRS),
@@ -73,7 +74,8 @@ type pipelineCallbackSet struct {
 	injectReminders    func(ctx context.Context, input *pipeline.RunInput, msgs []providers.Message) []providers.Message
 	buildFilteredTools func(state *pipeline.RunState) ([]providers.ToolDefinition, error)
 	callLLM            func(ctx context.Context, state *pipeline.RunState, req providers.ChatRequest) (*providers.ChatResponse, error)
-	pruneMessages      func(msgs []providers.Message, budget int) []providers.Message
+	pruneMessages      func(msgs []providers.Message, budget int) ([]providers.Message, pipeline.PruneStats)
+	sanitizeHistory    func(msgs []providers.Message) ([]providers.Message, int)
 	compactMessages    func(ctx context.Context, msgs []providers.Message, model string) ([]providers.Message, error)
 	runMemoryFlush     func(ctx context.Context, state *pipeline.RunState) error
 	executeToolCall    func(ctx context.Context, state *pipeline.RunState, tc providers.ToolCall) ([]providers.Message, error)
@@ -312,9 +314,11 @@ func (l *Loop) makeCallLLM(req *RunRequest, emitRun func(AgentEvent)) func(ctx c
 	}
 }
 
-func (l *Loop) makePruneMessages() func(msgs []providers.Message, budget int) []providers.Message {
-	return func(msgs []providers.Message, budget int) []providers.Message {
-		return pruneContextMessages(msgs, budget, l.contextPruningCfg, l.tokenCounter, l.model)
+func (l *Loop) makePruneMessages() func(msgs []providers.Message, budget int) ([]providers.Message, pipeline.PruneStats) {
+	return func(msgs []providers.Message, budget int) ([]providers.Message, pipeline.PruneStats) {
+		var stats pipeline.PruneStats
+		pruned := pruneContextMessages(msgs, budget, l.contextPruningCfg, l.tokenCounter, l.model, &stats)
+		return pruned, stats
 	}
 }
 
@@ -342,6 +346,21 @@ func (l *Loop) makeCompactMessages(req *RunRequest) func(ctx context.Context, ms
 // duplicating the string.
 const SessionMetaKeyLastCompactionAt = "last_compaction_at"
 
+// cacheTouchAt returns the last prune-mutation timestamp for a session.
+// Returns zero time if no touch recorded yet.
+func (l *Loop) cacheTouchAt(sessionKey string) time.Time {
+	if v, ok := l.cacheTouchBySession.Load(sessionKey); ok {
+		return v.(time.Time)
+	}
+	return time.Time{}
+}
+
+// markCacheTouched records the current time as the last prune-mutation timestamp
+// for the given session. Called only after pruning actually mutates messages.
+func (l *Loop) markCacheTouched(sessionKey string) {
+	l.cacheTouchBySession.Store(sessionKey, time.Now())
+}
+
 func (l *Loop) makeRunMemoryFlush() func(ctx context.Context, state *pipeline.RunState) error {
 	return func(ctx context.Context, state *pipeline.RunState) error {
 		settings := ResolveMemoryFlushSettings(l.compactionCfg)
diff --git a/internal/agent/loop_types.go b/internal/agent/loop_types.go
index 68dc32e2..22feb053 100644
--- a/internal/agent/loop_types.go
+++ b/internal/agent/loop_types.go
@@ -241,6 +241,14 @@ type Loop struct {
 
 	// User identity resolver: maps channel contacts to merged tenant users for credential lookups.
 	userResolver UserIdentityResolver
+
+	// Per-session cache-touch timestamps for the cache-TTL pruning gate (Phase 06).
+	// Key: sessionKey (string), Value: time.Time of last prune mutation.
+	// sync.Map zero value is ready to use — no init required.
+	// Grows with distinct sessions; typical gateway has bounded session count.
+	// Note: in-memory only — timestamps reset on process restart (one extra prune
+	// per session on restart, then steady-state resumes).
+	cacheTouchBySession sync.Map
 }
 
 // AgentEvent is emitted during agent execution for WS broadcasting.
diff --git a/internal/agent/pruning.go b/internal/agent/pruning.go
index 934f5ed7..b8a97f40 100644
--- a/internal/agent/pruning.go
+++ b/internal/agent/pruning.go
@@ -2,9 +2,11 @@ package agent
 
 import (
 	"fmt"
+	"log/slog"
 	"unicode/utf8"
 
 	"github.com/nextlevelbuilder/goclaw/internal/config"
+	"github.com/nextlevelbuilder/goclaw/internal/pipeline"
 	"github.com/nextlevelbuilder/goclaw/internal/providers"
 	"github.com/nextlevelbuilder/goclaw/internal/tokencount"
 )
@@ -134,9 +136,13 @@ func resolvePruningSettings(cfg *config.ContextPruningConfig) *effectivePruningS
 // When tc is non-nil, token counting uses tiktoken for accuracy (especially
 // for non-ASCII content like Vietnamese/Chinese). When nil, falls back to the
 // legacy rune_count/charsPerTokenEstimate heuristic so existing tests pass.
-func pruneContextMessages(msgs []providers.Message, contextWindowTokens int, cfg *config.ContextPruningConfig, tc tokencount.TokenCounter, model string) []providers.Message {
-	// Pruning runs by default for all providers. Only skip when explicitly disabled.
-	if cfg != nil && cfg.Mode == "off" {
+func pruneContextMessages(msgs []providers.Message, contextWindowTokens int, cfg *config.ContextPruningConfig, tc tokencount.TokenCounter, model string, stats *pipeline.PruneStats) []providers.Message {
+	// Opt-in: require explicit mode. Matches TS computeEffectiveSettings in settings.ts.
+	if cfg == nil || cfg.Mode == "" || cfg.Mode == "off" {
+		return msgs
+	}
+	if cfg.Mode != "cache-ttl" {
+		slog.Warn("context_pruning: unknown mode, disabled", "mode", cfg.Mode)
 		return msgs
 	}
 	if contextWindowTokens <= 0 || len(msgs) == 0 {
@@ -201,51 +207,11 @@ func pruneContextMessages(msgs []providers.Message, contextWindowTokens int, cfg
 		return msgs
 	}
 
-	// Pass 0: Per-result context guard — force-trim any single tool result
-	// exceeding 30% of the context window. Catches outlier outputs even
-	// when overall context ratio is low.
-	maxSingleResultTokens := tokenWindow * 3 / 10
-	// Char budget for actual string slicing (always char-based regardless of estimator).
-	maxSingleResultChars := maxSingleResultTokens
-	if tc != nil {
-		maxSingleResultChars = maxSingleResultTokens * charsPerTokenEstimate
-	}
-	var result []providers.Message
-	for _, idx := range prunableIndexes {
-		msgTokens := est.estimateTokens(msgs[idx].Content)
-		if msgTokens > maxSingleResultTokens {
-			if result == nil {
-				result = make([]providers.Message, len(msgs))
-				copy(result, msgs)
-			}
-			msg := msgs[idx]
-			head := takeHead(msg.Content, maxSingleResultChars*7/10)
-			tail := takeTail(msg.Content, maxSingleResultChars*3/10)
-			msgChars := utf8.RuneCountInString(msg.Content)
-			trimmed := fmt.Sprintf("%s\n\n⚠️ [... middle content omitted ...]\n\n%s\n\n[Single tool result trimmed: %d chars exceeded per-result limit of %d chars.]",
-				head, tail, msgChars, maxSingleResultChars)
-			result[idx] = providers.Message{
-				Role:       msg.Role,
-				Content:    trimmed,
-				ToolCallID: msg.ToolCallID,
-			}
-			totalTokens += est.estimateTokens(trimmed) - msgTokens
-		}
-	}
-	if result != nil {
-		msgs = result
-		result = nil
-		// Re-check ratio after per-result guard.
-		ratio = float64(totalTokens) / float64(tokenWindow)
-		if ratio < settings.softTrimRatio {
-			return msgs
-		}
-	}
-
 	// Build tool call name map for media tool detection in soft trim.
 	toolCallNames := buildToolCallNameMap(msgs)
 
 	// Pass 1: Soft trim long tool results.
+	var result []providers.Message
 	for i := range prunableIndexes {
 		idx := prunableIndexes[i]
 		msg := msgs[idx]
@@ -295,6 +261,9 @@ func pruneContextMessages(msgs []providers.Message, contextWindowTokens int, cfg
 			ToolCallID: msg.ToolCallID,
 		}
 		totalTokens += est.estimateTokens(trimmed) - msgTokens
+		if stats != nil {
+			stats.ResultsTrimmed++
+		}
 	}
 
 	output := msgs
@@ -347,6 +316,9 @@ func pruneContextMessages(msgs []providers.Message, contextWindowTokens int, cfg
 		afterTokens := est.estimateTokens(settings.hardClearPlaceholder)
 		totalTokens += afterTokens - beforeTokens
 		ratio = float64(totalTokens) / float64(tokenWindow)
+		if stats != nil {
+			stats.ResultsCleared++
+		}
 	}
 
 	return output
diff --git a/internal/agent/pruning_integration_test.go b/internal/agent/pruning_integration_test.go
new file mode 100644
index 00000000..b61666aa
--- /dev/null
+++ b/internal/agent/pruning_integration_test.go
@@ -0,0 +1,62 @@
+//go:build !sqliteonly
+
+package agent
+
+import (
+	"sync/atomic"
+	"testing"
+
+	"github.com/nextlevelbuilder/goclaw/internal/pipeline"
+	"github.com/nextlevelbuilder/goclaw/internal/providers"
+)
+
+// TestPruneStage_SingleEntryPoint verifies that after Phase 03 refactoring:
+// - loop_history.go no longer calls pruneContextMessages
+// - PruneStage owns the single entry point for pruning
+// - SanitizeHistory is called after PruneMessages in PruneStage
+//
+// Full PruneStage tests are in internal/pipeline/stages_test.go.
+func TestPruneStage_SingleEntryPoint(t *testing.T) {
+	// Verify loop_history's sanitizeHistory works on trimmed input directly.
+	// This proves pruneContextMessages is no longer called in that path.
+	history := []providers.Message{
+		{Role: "user", Content: "q1"},
+		{Role: "assistant", Content: "", ToolCalls: []providers.ToolCall{{ID: "tc1", Name: "read"}}},
+		{Role: "tool", ToolCallID: "tc1", Content: "result1"},
+		// Orphan tool result (no matching tool_use) - sanitizeHistory should drop it
+		{Role: "tool", ToolCallID: "tc_orphan", Content: "orphan result"},
+		{Role: "assistant", Content: "a1"},
+	}
+
+	// limitHistoryTurns doesn't drop the orphan, but sanitizeHistory does
+	trimmed := limitHistoryTurns(history, 100)
+	if len(trimmed) != len(history) {
+		t.Fatalf("limitHistoryTurns altered message count: got %d, want %d", len(trimmed), len(history))
+	}
+
+	sanitized, droppedCount := sanitizeHistory(trimmed)
+	if droppedCount != 1 {
+		t.Errorf("sanitizeHistory should drop 1 orphan, got droppedCount=%d", droppedCount)
+	}
+	if len(sanitized) != 4 {
+		t.Errorf("expected 4 messages after sanitize, got %d", len(sanitized))
+	}
+}
+
+// TestPruneCallback_CountsOnce demonstrates the callback structure supports counting.
+// Actual single-call verification is in pipeline/stages_test.go.
+func TestPruneCallback_CountsOnce(t *testing.T) {
+	var count int32
+	fakePrune := func(msgs []providers.Message, budget int) ([]providers.Message, pipeline.PruneStats) {
+		atomic.AddInt32(&count, 1)
+		return msgs, pipeline.PruneStats{}
+	}
+
+	// Simulate what PruneStage does: call PruneMessages once
+	msgs := []providers.Message{{Role: "user", Content: "test"}}
+	_, _ = fakePrune(msgs, 10000)
+
+	if got := atomic.LoadInt32(&count); got != 1 {
+		t.Errorf("expected prune called exactly once, got %d", got)
+	}
+}
diff --git a/internal/agent/pruning_test.go b/internal/agent/pruning_test.go
index d4ec9653..e98d5d8a 100644
--- a/internal/agent/pruning_test.go
+++ b/internal/agent/pruning_test.go
@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/nextlevelbuilder/goclaw/internal/config"
+	"github.com/nextlevelbuilder/goclaw/internal/pipeline"
 	"github.com/nextlevelbuilder/goclaw/internal/providers"
 )
 
@@ -191,7 +192,7 @@ func TestPruneContextMessages_ModeOff_ReturnsOriginal(t *testing.T) {
 		{Role: "assistant", Content: "hello"},
 	}
 	cfg := &config.ContextPruningConfig{Mode: "off"}
-	got := pruneContextMessages(msgs, 100000, cfg, nil, "")
+	got := pruneContextMessages(msgs, 100000, cfg, nil, "", nil)
 	if len(got) != len(msgs) {
 		t.Error("mode=off should return original slice")
 	}
@@ -199,7 +200,7 @@ func TestPruneContextMessages_ModeOff_ReturnsOriginal(t *testing.T) {
 
 func TestPruneContextMessages_ZeroWindow_ReturnsOriginal(t *testing.T) {
 	msgs := []providers.Message{{Role: "user", Content: "hi"}}
-	got := pruneContextMessages(msgs, 0, nil, nil, "")
+	got := pruneContextMessages(msgs, 0, nil, nil, "", nil)
 	if len(got) != len(msgs) {
 		t.Error("zero context window should return original")
 	}
@@ -214,7 +215,7 @@ func TestPruneContextMessages_SmallContext_NoChange(t *testing.T) {
 		{Role: "assistant", Content: "done"},
 	}
 	// Very large window → ratio tiny → nothing pruned.
-	got := pruneContextMessages(msgs, 1_000_000, nil, nil, "")
+	got := pruneContextMessages(msgs, 1_000_000, nil, nil, "", nil)
 	if len(got) != len(msgs) {
 		t.Errorf("small context: len=%d, want %d", len(got), len(msgs))
 	}
@@ -238,8 +239,9 @@ func TestPruneContextMessages_SoftTrim_LongToolResult(t *testing.T) {
 	}
 
 	cfg := &config.ContextPruningConfig{
-		SoftTrimRatio: 0.01, // threshold very low → prune immediately
-		HardClearRatio: 0.99, // don't hard clear
+		Mode:          "cache-ttl", // enable pruning
+		SoftTrimRatio: 0.01,        // threshold very low → prune immediately
+		HardClearRatio: 0.99,       // don't hard clear
 		SoftTrim: &config.ContextPruningSoftTrim{
 			MaxChars:  100,
 			HeadChars: 50,
@@ -247,7 +249,7 @@ func TestPruneContextMessages_SoftTrim_LongToolResult(t *testing.T) {
 		},
 	}
 	// Use a context window that makes ratio exceed threshold.
-	got := pruneContextMessages(msgs, 100, cfg, nil, "")
+	got := pruneContextMessages(msgs, 100, cfg, nil, "", nil)
 
 	// Tool result should be trimmed — shorter than original.
 	for _, m := range got {
@@ -279,6 +281,7 @@ func TestPruneContextMessages_HardClear_WhenRatioVeryHigh(t *testing.T) {
 
 	enabled := true
 	cfg := &config.ContextPruningConfig{
+		Mode:                 "cache-ttl", // enable pruning
 		SoftTrimRatio:        0.001,
 		HardClearRatio:       0.001,
 		MinPrunableToolChars: 1, // very low threshold
@@ -293,7 +296,7 @@ func TestPruneContextMessages_HardClear_WhenRatioVeryHigh(t *testing.T) {
 		},
 	}
 
-	got := pruneContextMessages(msgs, 10, cfg, nil, "")
+	got := pruneContextMessages(msgs, 10, cfg, nil, "", nil)
 
 	// Tool result should be replaced by placeholder or heavily trimmed.
 	for _, m := range got {
@@ -331,13 +334,14 @@ func TestPruneContextMessages_MediaToolHigherBudget(t *testing.T) {
 	}
 
 	cfg := &config.ContextPruningConfig{
-		SoftTrimRatio:  0.01,  // force prune
-		HardClearRatio: 0.999, // don't hard clear
+		Mode:           "cache-ttl", // enable pruning
+		SoftTrimRatio:  0.01,        // force prune
+		HardClearRatio: 0.999,       // don't hard clear
 	}
 
 	// Use 7000 tokens (28K chars) so per-result guard (30% = 8.4K) doesn't
 	// trigger on 7K-char results, isolating the soft trim behavior.
-	got := pruneContextMessages(msgs, 7000, cfg, nil, "")
+	got := pruneContextMessages(msgs, 7000, cfg, nil, "", nil)
 
 	// read_image result (7000 chars < 8000 media budget) → NOT trimmed
 	imgResult := got[2]
@@ -373,6 +377,7 @@ func TestPruneContextMessages_MediaToolSkipsHardClear(t *testing.T) {
 
 	enabled := true
 	cfg := &config.ContextPruningConfig{
+		Mode:                 "cache-ttl", // enable pruning
 		SoftTrimRatio:        0.001,
 		HardClearRatio:       0.001,
 		MinPrunableToolChars: 1,
@@ -382,7 +387,7 @@ func TestPruneContextMessages_MediaToolSkipsHardClear(t *testing.T) {
 		},
 	}
 
-	got := pruneContextMessages(msgs, 5000, cfg, nil, "")
+	got := pruneContextMessages(msgs, 5000, cfg, nil, "", nil)
 
 	// read_image result should survive hard clear (only soft-trimmed at most)
 	imgResult := got[2]
@@ -438,3 +443,130 @@ func TestHasImportantTail_ShortContentNoMatch(t *testing.T) {
 		t.Error("expected no important tail")
 	}
 }
+
+// ─── Characterization tests (Phase 01) ────────────────────────────────────
+// Lock current (buggy-vs-TS) behavior before refactoring. Subsequent phases
+// update these tests to new expected values.
+
+// makeLargeHistoryFixture creates a history with a large tool result for opt-in tests.
+// contextWindow=5000 → charWindow=20000, total ~8030 chars → ratio ~40% ≥ 25%.
+func makeLargeHistoryFixture() []providers.Message {
+	return []providers.Message{
+		{Role: "user", Content: "q"},
+		{Role: "assistant", Content: "", ToolCalls: []providers.ToolCall{{ID: "c1", Name: "read_file"}}},
+		{Role: "tool", ToolCallID: "c1", Content: strings.Repeat("x", 8000)},
+		{Role: "assistant", Content: "a1"},
+		{Role: "assistant", Content: "a2"},
+		{Role: "assistant", Content: "a3"},
+	}
+}
+
+func TestPruneContextMessages_NilCfg_NoOp(t *testing.T) {
+	// Phase 04: nil cfg → no pruning (opt-in). Matches TS design.
+	msgs := makeLargeHistoryFixture()
+	got := pruneContextMessages(msgs, 5000, nil, nil, "", nil)
+	if estimateMessageChars(got[2]) != 8000 {
+		t.Errorf("nil cfg should be no-op (opt-in). Got %d chars", estimateMessageChars(got[2]))
+	}
+}
+
+func TestPruneContextMessages_EmptyMode_NoOp(t *testing.T) {
+	cfg := &config.ContextPruningConfig{Mode: ""}
+	msgs := makeLargeHistoryFixture()
+	got := pruneContextMessages(msgs, 5000, cfg, nil, "", nil)
+	if estimateMessageChars(got[2]) != 8000 {
+		t.Errorf("empty mode should be no-op. Got %d chars", estimateMessageChars(got[2]))
+	}
+}
+
+func TestPruneContextMessages_UnknownMode_NoOp(t *testing.T) {
+	cfg := &config.ContextPruningConfig{Mode: "bogus"}
+	msgs := makeLargeHistoryFixture()
+	got := pruneContextMessages(msgs, 5000, cfg, nil, "", nil)
+	if estimateMessageChars(got[2]) != 8000 {
+		t.Errorf("unknown mode should be no-op. Got %d chars", estimateMessageChars(got[2]))
+	}
+}
+
+func TestPruneContextMessages_CacheTtlMode_Prunes(t *testing.T) {
+	cfg := &config.ContextPruningConfig{Mode: "cache-ttl"}
+	msgs := makeLargeHistoryFixture()
+	got := pruneContextMessages(msgs, 5000, cfg, nil, "", nil)
+	if estimateMessageChars(got[2]) >= 8000 {
+		t.Errorf("cache-ttl mode should prune. Got unchanged content.")
+	}
+}
+
+func TestPruneContextMessages_Pass0_RemovedSuffixAbsent(t *testing.T) {
+	// Phase 02: Pass 0 removed. This test asserts the distinctive suffix is GONE.
+	// Pass 1 still trims via ratio gate, but with different suffix format.
+	//
+	// contextWindow=10000 → charWindow=40000; msg=15000 chars = 37.5% ≥ 25% softTrimRatio.
+	// Pass 1 trims the large result.
+	msgs := []providers.Message{
+		{Role: "user", Content: "q"},
+		{Role: "assistant", Content: "", ToolCalls: []providers.ToolCall{{ID: "c1", Name: "read_file"}}},
+		{Role: "tool", ToolCallID: "c1", Content: strings.Repeat("x", 15000)},
+		{Role: "assistant", Content: "a1"},
+		{Role: "assistant", Content: "a2"},
+		{Role: "assistant", Content: "a3"},
+	}
+	cfg := &config.ContextPruningConfig{Mode: "cache-ttl"}
+	got := pruneContextMessages(msgs, 10000, cfg, nil, "", nil)
+
+	content := got[2].Content
+	// Pass 0 suffix markers must be GONE after Phase 02 deletion.
+	if strings.Contains(content, "Single tool result trimmed:") {
+		t.Errorf("Pass 0 suffix should be removed; got: %q", testTruncate(content, 200))
+	}
+	if strings.Contains(content, "⚠️ [... middle content omitted ...]") {
+		t.Errorf("Pass 0 middle-omitted marker should be removed; got: %q", testTruncate(content, 200))
+	}
+	// Must still be trimmed by Pass 1 (smaller than original).
+	if estimateMessageChars(got[2]) >= 15000 {
+		t.Errorf("Pass 1 should still trim the large result via ratio gate; got %d chars", estimateMessageChars(got[2]))
+	}
+}
+
+// ─── PruneStats (Phase 05) ────────────────────────────────────────────────
+
+func TestPruneContextMessages_Stats_TrimmedPopulated(t *testing.T) {
+	// Large tool result that will be soft-trimmed.
+	msgs := []providers.Message{
+		{Role: "user", Content: "q"},
+		{Role: "assistant", Content: "", ToolCalls: []providers.ToolCall{{ID: "c1", Name: "read_file"}}},
+		{Role: "tool", ToolCallID: "c1", Content: strings.Repeat("x", 15000)},
+		{Role: "assistant", Content: "a1"},
+		{Role: "assistant", Content: "a2"},
+		{Role: "assistant", Content: "a3"},
+	}
+	cfg := &config.ContextPruningConfig{Mode: "cache-ttl"}
+	var stats pipeline.PruneStats
+	pruneContextMessages(msgs, 5000, cfg, nil, "", &stats)
+	if stats.ResultsTrimmed == 0 {
+		t.Error("expected at least one ResultsTrimmed, got 0")
+	}
+}
+
+func TestPruneContextMessages_Stats_NilSafe(t *testing.T) {
+	// Passing nil stats must not panic.
+	msgs := []providers.Message{
+		{Role: "user", Content: "q"},
+		{Role: "assistant", Content: "", ToolCalls: []providers.ToolCall{{ID: "c1", Name: "read_file"}}},
+		{Role: "tool", ToolCallID: "c1", Content: strings.Repeat("x", 15000)},
+		{Role: "assistant", Content: "a1"},
+		{Role: "assistant", Content: "a2"},
+		{Role: "assistant", Content: "a3"},
+	}
+	cfg := &config.ContextPruningConfig{Mode: "cache-ttl"}
+	_ = pruneContextMessages(msgs, 5000, cfg, nil, "", nil) // must not panic
+}
+
+// ─── parseTTL (Phase 06) ─────────────────────────────────────────────────
+
+func testTruncate(s string, n int) string {
+	if len(s) <= n {
+		return s
+	}
+	return s[:n] + "..."
+}
diff --git a/internal/config/config.go b/internal/config/config.go
index 74b9213d..1bd978dc 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -151,10 +151,15 @@ type MemoryFlushConfig struct {
 }
 
 // ContextPruningConfig configures in-memory context pruning of old tool results.
-// Matching TS src/agents/pi-extensions/context-pruning/settings.ts.
-// Mode "cache-ttl": prune when context exceeds softTrimRatio of context window.
+// Matches TS openclaw/src/agents/pi-hooks/context-pruning/settings.ts.
+//
+// Mode "" (default) or "off" → pruning disabled, zero overhead.
+// Mode "cache-ttl" → prune eligible tool results when ratio exceeds softTrimRatio,
+//
+//	gated by provider prompt-cache TTL (see PruneStage).
 type ContextPruningConfig struct {
-	Mode                 string                   `json:"mode,omitempty"`                 // "off" (default), "cache-ttl"
+	Mode                 string                   `json:"mode,omitempty"`                 // "" (default off), "off", "cache-ttl"
+	TTL                  string                   `json:"ttl,omitempty"`                  // cache TTL gate duration (default "5m"), Go duration string e.g. "5m", "30s"
 	KeepLastAssistants   int                      `json:"keepLastAssistants,omitempty"`   // protect last N assistant msgs (default 3)
 	SoftTrimRatio        float64                  `json:"softTrimRatio,omitempty"`        // start soft trim at this % of window (default 0.3)
 	HardClearRatio       float64                  `json:"hardClearRatio,omitempty"`       // start hard clear at this % (default 0.5)
diff --git a/internal/eventbus/event_types.go b/internal/eventbus/event_types.go
index a9f76a70..77ea3b40 100644
--- a/internal/eventbus/event_types.go
+++ b/internal/eventbus/event_types.go
@@ -16,6 +16,9 @@ const (
 	EventRunCompleted   EventType = "run.completed"
 	EventToolExecuted     EventType = "tool.executed"
 
+	// Context pruning observability (Phase 05)
+	EventContextPruned EventType = "context.pruned"
+
 	// Vault events (v3 enrichment pipeline)
 	EventVaultDocUpserted EventType = "vault.doc_upserted"
 
@@ -111,6 +114,19 @@ type DelegateFailedPayload struct {
 	Error        string
 }
 
+// ContextPrunedPayload is emitted when pruning mutates context messages.
+// Payload intentionally excludes raw message content (counts + tokens only).
+type ContextPrunedPayload struct {
+	SessionKey     string
+	TokensBefore   int
+	TokensAfter    int
+	Budget         int
+	ResultsTrimmed int    // soft-trimmed count
+	ResultsCleared int    // hard-cleared count
+	Compacted      bool
+	Trigger        string // "soft" | "hard" | "compact"
+}
+
 // VaultDocUpsertedPayload is emitted after a vault document is registered/updated.
 type VaultDocUpsertedPayload struct {
 	DocID       string // vault_documents.id (UUID)
diff --git a/internal/pipeline/deps.go b/internal/pipeline/deps.go
index 64f21939..5a288ed7 100644
--- a/internal/pipeline/deps.go
+++ b/internal/pipeline/deps.go
@@ -2,6 +2,7 @@ package pipeline
 
 import (
 	"context"
+	"time"
 
 	"github.com/nextlevelbuilder/goclaw/internal/bootstrap"
 	"github.com/nextlevelbuilder/goclaw/internal/config"
@@ -11,6 +12,14 @@ import (
 	"github.com/nextlevelbuilder/goclaw/internal/workspace"
 )
 
+// PruneStats holds counts from a single pruneContextMessages invocation.
+// Populated by the pruning function; read by PruneStage for event emission.
+type PruneStats struct {
+	ResultsTrimmed int  // Pass 1: soft-trimmed count
+	ResultsCleared int  // Pass 2: hard-cleared count
+	Compacted      bool // LLM compaction ran this cycle
+}
+
 // PipelineDeps bundles all external dependencies stages need.
 // Passed to NewDefaultPipeline; individual stages receive what they need via closure or direct field access.
 type PipelineDeps struct {
@@ -55,9 +64,16 @@ type PipelineDeps struct {
 	EmitBlockReply      func(content string) // emit block.reply for intermediate assistant content
 
 	// Prune callbacks (PruneStage)
-	PruneMessages   func(msgs []providers.Message, budget int) []providers.Message
+	PruneMessages   func(msgs []providers.Message, budget int) ([]providers.Message, PruneStats)
+	SanitizeHistory func(msgs []providers.Message) ([]providers.Message, int)
 	CompactMessages func(ctx context.Context, msgs []providers.Message, model string) ([]providers.Message, error)
 
+	// Cache-TTL gate callbacks (Phase 06). All optional (nil = feature disabled).
+	GetProviderCaps  func() providers.ProviderCapabilities  // provider capabilities for cache detection
+	GetPruningConfig func() *config.ContextPruningConfig    // pruning config (TTL field)
+	GetCacheTouch    func(sessionKey string) time.Time      // per-session last prune-mutation timestamp
+	MarkCacheTouched func(sessionKey string)                // record mutation timestamp AFTER prune mutates
+
 	// Memory flush callbacks (MemoryFlushStage, invoked by PruneStage)
 	RunMemoryFlush func(ctx context.Context, state *RunState) error
 
diff --git a/internal/pipeline/prune_stage.go b/internal/pipeline/prune_stage.go
index e8de2b16..efb35ab1 100644
--- a/internal/pipeline/prune_stage.go
+++ b/internal/pipeline/prune_stage.go
@@ -4,7 +4,9 @@ import (
 	"context"
 	"fmt"
 	"log/slog"
+	"time"
 
+	"github.com/nextlevelbuilder/goclaw/internal/eventbus"
 	"github.com/nextlevelbuilder/goclaw/internal/providers"
 )
 
@@ -27,6 +29,23 @@ func NewPruneStage(deps *PipelineDeps, memFlush *MemoryFlushStage) *PruneStage {
 func (s *PruneStage) Name() string       { return "prune" }
 func (s *PruneStage) Result() StageResult { return s.result }
 
+// defaultCachePruneTTL is used when cfg.TTL is empty or invalid.
+const defaultCachePruneTTL = 5 * time.Minute
+
+// parseTTL parses a Go duration string (e.g. "5m"). Falls back to 5m default on
+// empty/invalid input with a warning log. Negative durations treated as invalid.
+func parseTTL(s string) time.Duration {
+	if s == "" {
+		return defaultCachePruneTTL
+	}
+	d, err := time.ParseDuration(s)
+	if err != nil || d <= 0 {
+		slog.Warn("context_pruning: invalid ttl, using 5m default", "ttl", s, "err", err)
+		return defaultCachePruneTTL
+	}
+	return d
+}
+
 // Execute checks history tokens against budget, prunes/compacts as needed.
 func (s *PruneStage) Execute(ctx context.Context, state *RunState) error {
 	s.result = Continue
@@ -52,18 +71,97 @@ func (s *PruneStage) Execute(ctx context.Context, state *RunState) error {
 	// Count current history tokens
 	historyTokens := s.countHistory(state)
 	state.Prune.HistoryTokens = historyTokens
+	tokensBefore := historyTokens
 
 	softThreshold := budget * 70 / 100
 	if historyTokens <= softThreshold {
 		return nil // under budget, no action needed
 	}
 
-	// Phase 1: soft prune at 70% budget
-	if s.deps.PruneMessages != nil {
-		pruned := s.deps.PruneMessages(state.Messages.History(), budget)
-		state.Messages.SetHistory(pruned)
-		historyTokens = s.countHistory(state)
-		state.Prune.HistoryTokens = historyTokens
+	sessionKey := state.Input.SessionKey
+	skipSoftPrune := false
+
+	// Cache-TTL gate (provider-aware, per-session).
+	// Only activates when all 4 callbacks are wired and mode == "cache-ttl".
+	if s.deps.GetPruningConfig != nil && s.deps.GetProviderCaps != nil && s.deps.GetCacheTouch != nil {
+		cfg := s.deps.GetPruningConfig()
+		if cfg != nil && cfg.Mode == "cache-ttl" {
+			caps := s.deps.GetProviderCaps()
+			if caps.CacheControl {
+				ttl := parseTTL(cfg.TTL)
+				touch := s.deps.GetCacheTouch(sessionKey)
+				if !touch.IsZero() && time.Since(touch) < ttl {
+					if historyTokens <= budget {
+						return nil // cache still live, below hard budget — preserve prefix
+					}
+					// Over hard budget despite live cache — safety valve: skip soft prune,
+					// fall through to compaction only.
+					slog.Info("context.cache_ttl_overridden",
+						"session_key", sessionKey,
+						"tokens", historyTokens,
+						"budget", budget,
+					)
+					skipSoftPrune = true
+				}
+			}
+		}
+	}
+
+	// Phase 1: soft prune at 70% budget (unless TTL gate routed to compact-only).
+	var pruneStats PruneStats
+	if !skipSoftPrune && s.deps.PruneMessages != nil {
+		var pruned []providers.Message
+		pruned, pruneStats = s.deps.PruneMessages(state.Messages.History(), budget)
+		mutated := pruneStats.ResultsTrimmed > 0 || pruneStats.ResultsCleared > 0
+		if mutated {
+			// Sanitize after prune to fix broken tool_use/tool_result pairs.
+			// Applied in-memory only — prune-induced orphans are ephemeral.
+			if s.deps.SanitizeHistory != nil {
+				pruned, _ = s.deps.SanitizeHistory(pruned)
+			}
+			state.Messages.SetHistory(pruned)
+			historyTokens = s.countHistory(state)
+			state.Prune.HistoryTokens = historyTokens
+			// Match TS semantics: touch recorded ONLY after prune mutates messages.
+			if s.deps.MarkCacheTouched != nil && sessionKey != "" {
+				s.deps.MarkCacheTouched(sessionKey)
+			}
+		}
+	}
+
+	// Emit observability event + slog when pruning actually mutated messages.
+	if pruneStats.ResultsTrimmed > 0 || pruneStats.ResultsCleared > 0 || pruneStats.Compacted {
+		trigger := "soft"
+		if pruneStats.Compacted {
+			trigger = "compact"
+		} else if pruneStats.ResultsCleared > 0 {
+			trigger = "hard"
+		}
+		if s.deps.EventBus != nil {
+			s.deps.EventBus.Publish(eventbus.DomainEvent{
+				Type:     eventbus.EventContextPruned,
+				SourceID: sessionKey,
+				Payload: &eventbus.ContextPrunedPayload{
+					SessionKey:     sessionKey,
+					TokensBefore:   tokensBefore,
+					TokensAfter:    historyTokens,
+					Budget:         budget,
+					ResultsTrimmed: pruneStats.ResultsTrimmed,
+					ResultsCleared: pruneStats.ResultsCleared,
+					Compacted:      pruneStats.Compacted,
+					Trigger:        trigger,
+				},
+			})
+		}
+		slog.Info("context.pruned",
+			"session_key", sessionKey,
+			"tokens_before", tokensBefore,
+			"tokens_after", historyTokens,
+			"trimmed", pruneStats.ResultsTrimmed,
+			"cleared", pruneStats.ResultsCleared,
+			"compacted", pruneStats.Compacted,
+			"trigger", trigger,
+		)
 	}
 
 	if historyTokens <= budget {
diff --git a/internal/pipeline/stages_test.go b/internal/pipeline/stages_test.go
index 7ab33a2a..89aab466 100644
--- a/internal/pipeline/stages_test.go
+++ b/internal/pipeline/stages_test.go
@@ -7,9 +7,12 @@ import (
 	"path/filepath"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"testing"
+	"time"
 
 	"github.com/nextlevelbuilder/goclaw/internal/bootstrap"
+	"github.com/nextlevelbuilder/goclaw/internal/config"
 	"github.com/nextlevelbuilder/goclaw/internal/providers"
 	"github.com/nextlevelbuilder/goclaw/internal/workspace"
 )
@@ -344,9 +347,9 @@ func TestPruneStage_UnderBudget_NoOp(t *testing.T) {
 			MaxTokens:     1000,
 		},
 		TokenCounter: &mockTokenCounter{countPerMessage: 1}, // tiny counts
-		PruneMessages: func(msgs []providers.Message, _ int) []providers.Message {
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
 			pruneCallCount++
-			return msgs
+			return msgs, PruneStats{}
 		},
 	}
 	stage := NewPruneStage(deps, nil)
@@ -380,10 +383,10 @@ func TestPruneStage_Over70Percent_CallsPruneMessages(t *testing.T) {
 			MaxTokens:     1000,
 		},
 		TokenCounter: &mockTokenCounter{countPerMessage: 100},
-		PruneMessages: func(msgs []providers.Message, budget int) []providers.Message {
+		PruneMessages: func(msgs []providers.Message, budget int) ([]providers.Message, PruneStats) {
 			pruneCallCount++
 			// return trimmed history that's under budget
-			return msgs[:1]
+			return msgs[:1], PruneStats{ResultsTrimmed: 1}
 		},
 	}
 	stage := NewPruneStage(deps, nil)
@@ -416,9 +419,9 @@ func TestPruneStage_Over100Percent_CallsCompact(t *testing.T) {
 			MaxTokens:     100,
 		},
 		TokenCounter: &mockTokenCounter{countPerMessage: 100},
-		PruneMessages: func(msgs []providers.Message, _ int) []providers.Message {
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
 			// return same size — still over budget
-			return msgs
+			return msgs, PruneStats{}
 		},
 		CompactMessages: func(_ context.Context, msgs []providers.Message, _ string) ([]providers.Message, error) {
 			compactCallCount++
@@ -455,8 +458,8 @@ func TestPruneStage_StillOverAfterCompaction_ReturnsAbortRun(t *testing.T) {
 			MaxTokens:     100,
 		},
 		TokenCounter: &mockTokenCounter{countPerMessage: 100},
-		PruneMessages: func(msgs []providers.Message, _ int) []providers.Message {
-			return msgs // no reduction
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
+			return msgs, PruneStats{} // no reduction
 		},
 		CompactMessages: func(_ context.Context, msgs []providers.Message, _ string) ([]providers.Message, error) {
 			// compaction still returns too many messages
@@ -520,9 +523,9 @@ func TestPruneStage_EffectiveContextWindow_OverridesConfig(t *testing.T) {
 			MaxTokens:     1_000,
 		},
 		TokenCounter: &mockTokenCounter{countPerMessage: 600},
-		PruneMessages: func(msgs []providers.Message, _ int) []providers.Message {
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
 			pruneCallCount++
-			return msgs
+			return msgs, PruneStats{}
 		},
 	}
 	stage := NewPruneStage(deps, nil)
@@ -632,9 +635,9 @@ func TestPruneStage_ReserveTokens_BuffersBudget(t *testing.T) {
 			ReserveTokens: 2_000,
 		},
 		TokenCounter: &mockTokenCounter{countPerMessage: 100},
-		PruneMessages: func(msgs []providers.Message, _ int) []providers.Message {
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
 			pruneCallCount++
-			return msgs[:1]
+			return msgs[:1], PruneStats{ResultsTrimmed: 1}
 		},
 	}
 	stage := NewPruneStage(deps, nil)
@@ -666,9 +669,9 @@ func TestPruneStage_EffectiveContextWindow_ZeroFallsBackToConfig(t *testing.T) {
 			MaxTokens:     1_000,
 		},
 		TokenCounter: &mockTokenCounter{countPerMessage: 600},
-		PruneMessages: func(msgs []providers.Message, _ int) []providers.Message {
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
 			pruneCallCount++
-			return msgs[:1]
+			return msgs[:1], PruneStats{ResultsTrimmed: 1}
 		},
 	}
 	stage := NewPruneStage(deps, nil)
@@ -1768,3 +1771,152 @@ func TestFinalizeStage_DeduplicatesMedia_WithRealFile(t *testing.T) {
 		t.Error("Size should be populated from real file")
 	}
 }
+
+// ─── parseTTL (Phase 06) ─────────────────────────────────────────────────
+
+func TestParseTTL_ValidInputs(t *testing.T) {
+	cases := []struct {
+		in   string
+		want time.Duration
+	}{
+		{"", 5 * time.Minute},
+		{"5m", 5 * time.Minute},
+		{"30s", 30 * time.Second},
+		{"1h30m", 90 * time.Minute},
+		{"bogus", 5 * time.Minute},  // invalid → fallback
+		{"-1m", 5 * time.Minute},    // negative → fallback
+	}
+	for _, tc := range cases {
+		got := parseTTL(tc.in)
+		if got != tc.want {
+			t.Errorf("parseTTL(%q) = %v, want %v", tc.in, got, tc.want)
+		}
+	}
+}
+
+// ─── Cache-TTL gate (Phase 06) ───────────────────────────────────────────
+
+// makePruneHistory builds history that exceeds the 70% soft threshold.
+// budget = 10000-0-1000=9000, soft=6300. 100 msgs * 100 = 10000 > 6300.
+func makePruneHistory(n int) []providers.Message {
+	h := make([]providers.Message, n)
+	for i := range h {
+		h[i] = providers.Message{Role: "tool", ToolCallID: "c1", Content: "x"}
+	}
+	return h
+}
+
+func TestPruneStage_CacheTtlGate_SkipsWithinTTL(t *testing.T) {
+	t.Parallel()
+	// cache live (1 min ago), history above soft threshold but below hard budget.
+	var pruneCalled int32
+	deps := &PipelineDeps{
+		Config:       PipelineConfig{ContextWindow: 10000, MaxTokens: 1000},
+		TokenCounter: &mockTokenCounter{countPerMessage: 100},
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
+			atomic.AddInt32(&pruneCalled, 1)
+			return msgs, PruneStats{}
+		},
+		GetProviderCaps:  func() providers.ProviderCapabilities { return providers.ProviderCapabilities{CacheControl: true} },
+		GetPruningConfig: func() *config.ContextPruningConfig { return &config.ContextPruningConfig{Mode: "cache-ttl", TTL: "5m"} },
+		GetCacheTouch:    func(string) time.Time { return time.Now().Add(-1 * time.Minute) }, // 1m ago, within 5m TTL
+		MarkCacheTouched: func(string) {},
+	}
+	stage := NewPruneStage(deps, nil)
+	state := defaultState()
+	state.Messages.SetHistory(makePruneHistory(50)) // 50*100=5000 tokens; soft=6300, hard=9000; below hard
+
+	if err := stage.Execute(context.Background(), state); err != nil {
+		t.Fatalf("Execute() error: %v", err)
+	}
+	if atomic.LoadInt32(&pruneCalled) != 0 {
+		t.Error("prune should be skipped when cache is live and below hard budget")
+	}
+}
+
+func TestPruneStage_CacheTtlGate_PrunesAfterTTL(t *testing.T) {
+	t.Parallel()
+	// touch = 6 minutes ago → TTL expired → gate allows prune
+	var pruneCalled int32
+	var touchCalled int32
+	deps := &PipelineDeps{
+		Config:       PipelineConfig{ContextWindow: 10000, MaxTokens: 1000},
+		TokenCounter: &mockTokenCounter{countPerMessage: 100},
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
+			atomic.AddInt32(&pruneCalled, 1)
+			return msgs[:1], PruneStats{ResultsTrimmed: 1}
+		},
+		GetProviderCaps:  func() providers.ProviderCapabilities { return providers.ProviderCapabilities{CacheControl: true} },
+		GetPruningConfig: func() *config.ContextPruningConfig { return &config.ContextPruningConfig{Mode: "cache-ttl", TTL: "5m"} },
+		GetCacheTouch:    func(string) time.Time { return time.Now().Add(-6 * time.Minute) }, // 6m ago, expired
+		MarkCacheTouched: func(string) { atomic.AddInt32(&touchCalled, 1) },
+	}
+	stage := NewPruneStage(deps, nil)
+	state := defaultState()
+	state.Messages.SetHistory(makePruneHistory(100)) // 100*100=10000; above soft threshold
+
+	if err := stage.Execute(context.Background(), state); err != nil {
+		t.Fatalf("Execute() error: %v", err)
+	}
+	if atomic.LoadInt32(&pruneCalled) == 0 {
+		t.Error("prune should fire when TTL expired")
+	}
+	if atomic.LoadInt32(&touchCalled) == 0 {
+		t.Error("MarkCacheTouched should be called after mutation")
+	}
+}
+
+func TestPruneStage_CacheTtlGate_NoCacheSupport_Prunes(t *testing.T) {
+	t.Parallel()
+	// CacheControl=false → gate is no-op → normal prune runs
+	var pruneCalled int32
+	deps := &PipelineDeps{
+		Config:       PipelineConfig{ContextWindow: 10000, MaxTokens: 1000},
+		TokenCounter: &mockTokenCounter{countPerMessage: 100},
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
+			atomic.AddInt32(&pruneCalled, 1)
+			return msgs[:1], PruneStats{ResultsTrimmed: 1}
+		},
+		GetProviderCaps:  func() providers.ProviderCapabilities { return providers.ProviderCapabilities{CacheControl: false} },
+		GetPruningConfig: func() *config.ContextPruningConfig { return &config.ContextPruningConfig{Mode: "cache-ttl", TTL: "5m"} },
+		GetCacheTouch:    func(string) time.Time { return time.Now().Add(-1 * time.Minute) },
+		MarkCacheTouched: func(string) {},
+	}
+	stage := NewPruneStage(deps, nil)
+	state := defaultState()
+	state.Messages.SetHistory(makePruneHistory(100))
+
+	if err := stage.Execute(context.Background(), state); err != nil {
+		t.Fatalf("Execute() error: %v", err)
+	}
+	if atomic.LoadInt32(&pruneCalled) == 0 {
+		t.Error("prune should fire when provider has no cache support")
+	}
+}
+
+func TestPruneStage_CacheTtlGate_MarkTouchedOnlyOnMutation(t *testing.T) {
+	t.Parallel()
+	// PruneMessages returns zero stats (no mutation) → MarkCacheTouched must NOT be called.
+	var touchCalled int32
+	deps := &PipelineDeps{
+		Config:       PipelineConfig{ContextWindow: 10000, MaxTokens: 1000},
+		TokenCounter: &mockTokenCounter{countPerMessage: 100},
+		PruneMessages: func(msgs []providers.Message, _ int) ([]providers.Message, PruneStats) {
+			return msgs, PruneStats{} // no mutation
+		},
+		GetProviderCaps:  func() providers.ProviderCapabilities { return providers.ProviderCapabilities{CacheControl: true} },
+		GetPruningConfig: func() *config.ContextPruningConfig { return &config.ContextPruningConfig{Mode: "cache-ttl", TTL: "5m"} },
+		GetCacheTouch:    func(string) time.Time { return time.Time{} }, // cold
+		MarkCacheTouched: func(string) { atomic.AddInt32(&touchCalled, 1) },
+	}
+	stage := NewPruneStage(deps, nil)
+	state := defaultState()
+	state.Messages.SetHistory(makePruneHistory(100))
+
+	if err := stage.Execute(context.Background(), state); err != nil {
+		t.Fatalf("Execute() error: %v", err)
+	}
+	if atomic.LoadInt32(&touchCalled) != 0 {
+		t.Error("MarkCacheTouched should NOT be called when prune returns no mutation")
+	}
+}
diff --git a/internal/store/sqlitestore/schema.go b/internal/store/sqlitestore/schema.go
index 37e75353..76c5dae7 100644
--- a/internal/store/sqlitestore/schema.go
+++ b/internal/store/sqlitestore/schema.go
@@ -16,7 +16,7 @@ var schemaSQL string
 
 // SchemaVersion is the current SQLite schema version.
 // Bump this when adding new migration steps below.
-const SchemaVersion = 18
+const SchemaVersion = 19
 
 // migrations maps version → SQL to apply when upgrading FROM that version.
 // schema.sql always represents the LATEST full schema (for fresh DBs).
@@ -443,6 +443,18 @@ CREATE INDEX IF NOT EXISTS idx_vault_docs_delegation
 	17: `INSERT INTO builtin_tools (name, display_name, description, category, enabled, settings)
 VALUES ('stt', 'Speech-to-Text', 'Transcribe voice/audio messages to text using ElevenLabs Scribe or a proxy service', 'media', 1, '{}')
 ON CONFLICT (name) DO NOTHING;`,
+
+	// Version 18 → 19: backfill mode: "cache-ttl" for agents with custom
+	// context_pruning config missing the mode field. Mirrors PG migration 51.
+	// Preserves user intent after the opt-in default flip. NULL rows stay NULL.
+	18: `UPDATE agents
+SET context_pruning = json_set(context_pruning, '$.mode', 'cache-ttl')
+WHERE context_pruning IS NOT NULL
+  AND context_pruning <> ''
+  AND context_pruning <> '{}'
+  AND json_valid(context_pruning)
+  AND json_type(context_pruning) = 'object'
+  AND json_extract(context_pruning, '$.mode') IS NULL;`,
 }
 
 // backfillV16 populates base_name / path_basename for rows that existed
diff --git a/internal/upgrade/version.go b/internal/upgrade/version.go
index 8468eceb..31e9d072 100644
--- a/internal/upgrade/version.go
+++ b/internal/upgrade/version.go
@@ -2,4 +2,4 @@ package upgrade
 
 // RequiredSchemaVersion is the schema migration version this binary requires.
 // Bump this whenever adding a new SQL migration file.
-const RequiredSchemaVersion uint = 50
+const RequiredSchemaVersion uint = 51
diff --git a/migrations/000051_backfill_context_pruning_mode.down.sql b/migrations/000051_backfill_context_pruning_mode.down.sql
new file mode 100644
index 00000000..09db1661
--- /dev/null
+++ b/migrations/000051_backfill_context_pruning_mode.down.sql
@@ -0,0 +1,4 @@
+-- No-op: cannot distinguish rows backfilled by the up migration from rows
+-- where the user explicitly set mode = "cache-ttl". Rollback requires a DB
+-- backup taken before the up migration ran.
+SELECT 1;
diff --git a/migrations/000051_backfill_context_pruning_mode.up.sql b/migrations/000051_backfill_context_pruning_mode.up.sql
new file mode 100644
index 00000000..6be675fe
--- /dev/null
+++ b/migrations/000051_backfill_context_pruning_mode.up.sql
@@ -0,0 +1,12 @@
+-- Backfill mode: "cache-ttl" for agents that have custom context_pruning config
+-- but are missing the "mode" field. This preserves user intent after the
+-- opt-in default flip (faithful port of TS behavior) — see CHANGELOG.
+--
+-- Rows matched: context_pruning is a non-empty JSON object without a "mode" key.
+-- Rows skipped: NULL, empty object, non-object values, or already has "mode".
+UPDATE agents
+SET context_pruning = jsonb_set(context_pruning, '{mode}', '"cache-ttl"'::jsonb)
+WHERE context_pruning IS NOT NULL
+  AND jsonb_typeof(context_pruning) = 'object'
+  AND context_pruning <> '{}'::jsonb
+  AND NOT (context_pruning ? 'mode');
diff --git a/ui/web/src/i18n/locales/en/agents.json b/ui/web/src/i18n/locales/en/agents.json
index 4eae1b93..01662476 100644
--- a/ui/web/src/i18n/locales/en/agents.json
+++ b/ui/web/src/i18n/locales/en/agents.json
@@ -796,7 +796,7 @@
     "contextPruning": {
       "title": "Context Pruning",
       "description": "Trim old tool results to save context window",
-      "descriptionSimple": "Automatically trims old tool results to prevent context overflow. Enabled by default.",
+      "descriptionSimple": "Automatically trims old tool results to prevent context overflow. Set mode to 'cache-ttl' to enable.",
       "mode": "Mode",
       "keepLastAssistants": "Keep Last Assistants",
       "softTrimRatio": "Soft Trim Ratio (0-1)",
@@ -809,6 +809,7 @@
       "hardClear": "Hard Clear",
       "enabled": "Enabled",
       "placeholderText": "Placeholder Text",
+      "cacheTtl": "Cache TTL",
       "advanced": "Advanced"
     },
     "sandbox": {
diff --git a/ui/web/src/i18n/locales/vi/agents.json b/ui/web/src/i18n/locales/vi/agents.json
index 3e072c74..41b455e2 100644
--- a/ui/web/src/i18n/locales/vi/agents.json
+++ b/ui/web/src/i18n/locales/vi/agents.json
@@ -792,7 +792,8 @@
       "hardClear": "Xóa cứng",
       "enabled": "Đã bật",
       "placeholderText": "Văn bản thay thế",
-      "descriptionSimple": "Tự động cắt bớt kết quả công cụ cũ để tránh tràn ngữ cảnh. Bật mặc định.",
+      "cacheTtl": "Cache TTL",
+      "descriptionSimple": "Tự động cắt bớt kết quả công cụ cũ để tránh tràn ngữ cảnh. Đặt chế độ 'cache-ttl' để bật.",
       "advanced": "Nâng cao"
     },
     "sandbox": {
diff --git a/ui/web/src/i18n/locales/zh/agents.json b/ui/web/src/i18n/locales/zh/agents.json
index 688bcdec..63765612 100644
--- a/ui/web/src/i18n/locales/zh/agents.json
+++ b/ui/web/src/i18n/locales/zh/agents.json
@@ -792,7 +792,8 @@
       "hardClear": "硬清除",
       "enabled": "已启用",
       "placeholderText": "占位符文本",
-      "descriptionSimple": "自动裁剪旧工具结果以防止上下文溢出。默认启用。",
+      "cacheTtl": "缓存 TTL",
+      "descriptionSimple": "自动裁剪旧工具结果以防止上下文溢出。设置模式为 'cache-ttl' 以启用。",
       "advanced": "高级"
     },
     "sandbox": {
diff --git a/ui/web/src/pages/agents/agent-detail/agent-advanced-state-utils.ts b/ui/web/src/pages/agents/agent-detail/agent-advanced-state-utils.ts
index 8c9a78f2..18877b6d 100644
--- a/ui/web/src/pages/agents/agent-detail/agent-advanced-state-utils.ts
+++ b/ui/web/src/pages/agents/agent-detail/agent-advanced-state-utils.ts
@@ -97,7 +97,7 @@ export function deriveState(
       {}
     ) as WorkspaceSharingConfig,
     comp: agent.compaction_config ?? {},
-    pruneEnabled: agent.context_pruning?.mode !== "off",
+    pruneEnabled: agent.context_pruning?.mode === "cache-ttl",
     prune: agent.context_pruning ?? {},
     sbEnabled: agent.sandbox_config != null,
     sb: agent.sandbox_config ?? {},
@@ -146,7 +146,7 @@ export function buildAdvancedUpdatePayload(
   const updates: Record<string, unknown> = {
     compaction_config: comp,
     context_pruning: pruneEnabled
-      ? (Object.keys(prune).length > 0 ? prune : null)
+      ? { mode: "cache-ttl", ...prune }
       : { mode: "off" },
     sandbox_config: sbEnabled ? sb : null,
     ...routingPayload,
diff --git a/ui/web/src/pages/agents/agent-detail/config-sections/context-pruning-section.tsx b/ui/web/src/pages/agents/agent-detail/config-sections/context-pruning-section.tsx
index 3b846063..5476fb03 100644
--- a/ui/web/src/pages/agents/agent-detail/config-sections/context-pruning-section.tsx
+++ b/ui/web/src/pages/agents/agent-detail/config-sections/context-pruning-section.tsx
@@ -38,6 +38,19 @@ export function ContextPruningSection({ enabled, value, onToggle, onChange }: Co
         />
       </div>
 
+      {/* Cache TTL — always shown when pruning is enabled (opt-in requires cache-ttl mode) */}
+      {enabled && (
+        <div className="max-w-xs space-y-2">
+          <InfoLabel tip='Prompt cache TTL. Pruning is skipped while the cache is live, preserving cache hits. Use Go duration strings like "5m", "30s". Default: 5m.'>{t(`${s}.cacheTtl`, "Cache TTL")}</InfoLabel>
+          <Input
+            type="text"
+            placeholder="5m"
+            value={value.ttl ?? ""}
+            onChange={(e) => onChange({ ...value, ttl: e.target.value || undefined })}
+          />
+        </div>
+      )}
+
       {/* Advanced toggle */}
       <button
         type="button"
diff --git a/ui/web/src/types/agent.ts b/ui/web/src/types/agent.ts
index b66b288d..6a585c9e 100644
--- a/ui/web/src/types/agent.ts
+++ b/ui/web/src/types/agent.ts
@@ -31,6 +31,7 @@ export interface CompactionConfig {
 
 export interface ContextPruningConfig {
   mode?: "off" | "cache-ttl";
+  ttl?: string;             // cache TTL gate duration, e.g. "5m" (default). Only used when mode="cache-ttl"
   keepLastAssistants?: number;
   softTrimRatio?: number;
   hardClearRatio?: number;