feat(coding-agent): added toggleable prompt cache miss markers

- Added `display.cacheMissMarker` setting to enable visual indicators for prompt cache invalidation in assistant messages.
- Included updated theme symbols to represent cache misses across supported icon sets.
- Configured the selector controller to rebuild the chat display when the marker visibility setting is toggled.

packages/coding-agent/CHANGELOG.md

@@ -3,7 +3,7 @@
 ## [Unreleased]
 ### Added
 
-- Added visual markers to assistant messages when prompt caching is invalidated
+- Added a prompt-cache miss marker: a slim `⊘ cache miss · <n> tokens` divider above an assistant turn whose request lost the provider prompt cache. Detected from per-turn usage — the previous turn cached a meaningful prefix but this request read none of it back and reprocessed the prompt (e.g. after a thinking-level / service-tier / model change, tool or system-prompt change, or a history rewrite). Reports the reprocessed token count. Toggle with the `display.cacheMissMarker` setting (Appearance → Display, on by default).
 
 ### Changed
 

packages/coding-agent/src/config/settings-schema.ts

@@ -849,6 +849,17 @@ export const SETTINGS_SCHEMA = {
 		},
 	},
 
+	"display.cacheMissMarker": {
+		type: "boolean",
+		default: true,
+		ui: {
+			tab: "appearance",
+			group: "Display",
+			label: "Cache Miss Marker",
+			description: "Show a divider above an assistant turn whose request lost (missed) the prompt cache",
+		},
+	},
+
 	showHardwareCursor: {
 		type: "boolean",
 		default: true, // will be computed based on platform if undefined

packages/coding-agent/src/modes/components/chat-transcript-builder.ts

@@ -252,8 +252,10 @@ export class ChatTranscriptBuilder {
 		);
 		this.container.addChild(assistantComponent);
 
-		const invalidation = detectCacheInvalidation(this.#lastAssistantUsage, message.usage);
-		if (invalidation) assistantComponent.setCacheInvalidation(invalidation);
+		if (settings.get("display.cacheMissMarker")) {
+			const invalidation = detectCacheInvalidation(this.#lastAssistantUsage, message.usage);
+			if (invalidation) assistantComponent.setCacheInvalidation(invalidation);
+		}
 		if (message.usage.cacheRead + message.usage.cacheWrite + message.usage.input > 0) {
 			this.#lastAssistantUsage = message.usage;
 		}

packages/coding-agent/src/modes/controllers/event-controller.ts

@@ -664,8 +664,10 @@ export class EventController {
 			// meaningful prefix and this request read none of it back, flag the turn.
 			const usage = event.message.usage;
 			if (usage.cacheRead + usage.cacheWrite + usage.input > 0) {
-				const invalidation = detectCacheInvalidation(this.ctx.lastAssistantUsage, usage);
-				if (invalidation) this.ctx.streamingComponent.setCacheInvalidation(invalidation);
+				if (settings.get("display.cacheMissMarker")) {
+					const invalidation = detectCacheInvalidation(this.ctx.lastAssistantUsage, usage);
+					if (invalidation) this.ctx.streamingComponent.setCacheInvalidation(invalidation);
+				}
 				this.ctx.lastAssistantUsage = usage;
 			}
 			this.#lastAssistantComponent = this.ctx.streamingComponent;

packages/coding-agent/src/modes/controllers/selector-controller.ts

@@ -327,6 +327,13 @@ export class SelectorController {
 				// InputController.toggleThinkingBlockVisibility).
 				this.ctx.ui.resetDisplay();
 				break;
+			case "display.cacheMissMarker":
+				// Rebuild re-runs the usage-based detection under the new setting so
+				// markers appear/disappear; full reset retires any already committed
+				// to native scrollback (mirrors hideThinking).
+				this.ctx.rebuildChatFromMessages();
+				this.ctx.ui.resetDisplay();
+				break;
 			case "tui.tight":
 				setTuiTight(value as boolean);
 				this.ctx.ui.invalidate();

packages/coding-agent/src/modes/theme/theme.ts

@@ -111,6 +111,7 @@ export type SymbolKey =
 	| "icon.agents"
 	| "icon.job"
 	| "icon.cache"
+	| "icon.cacheMiss"
 	| "icon.input"
 	| "icon.output"
 	| "icon.host"
@@ -310,6 +311,7 @@ const UNICODE_SYMBOLS: SymbolMap = {
 	"icon.agents": "👥",
 	"icon.job": "⚙",
 	"icon.cache": "💾",
+	"icon.cacheMiss": "⊘",
 	"icon.input": "⤵",
 	"icon.output": "⤴",
 	"icon.host": "🖥",
@@ -579,6 +581,8 @@ const NERD_SYMBOLS: SymbolMap = {
 	"icon.job": "\uf013",
 	// pick:  | alt:  
 	"icon.cache": "\uf1c0",
+	// pick:  (fa-ban) | alt: ⊘
+	"icon.cacheMiss": "\uf05e",
 	// pick:  | alt:  →
 	"icon.input": "\uf090",
 	// pick:  | alt:  →
@@ -810,6 +814,7 @@ const ASCII_SYMBOLS: SymbolMap = {
 	"icon.agents": "AG",
 	"icon.job": "bg",
 	"icon.cache": "cache",
+	"icon.cacheMiss": "!",
 	"icon.input": "in:",
 	"icon.output": "out:",
 	"icon.host": "host",
@@ -1770,6 +1775,7 @@ export class Theme {
 			agents: this.#symbols["icon.agents"],
 			job: this.#symbols["icon.job"],
 			cache: this.#symbols["icon.cache"],
+			cacheMiss: this.#symbols["icon.cacheMiss"],
 			input: this.#symbols["icon.input"],
 			output: this.#symbols["icon.output"],
 			host: this.#symbols["icon.host"],

packages/coding-agent/src/modes/utils/ui-helpers.ts

@@ -412,8 +412,10 @@ export class UiHelpers {
 				const assistantComponent = lastChild instanceof AssistantMessageComponent ? lastChild : undefined;
 				if (assistantComponent) {
 					const usage = message.usage;
-					const invalidation = detectCacheInvalidation(this.ctx.lastAssistantUsage, usage);
-					if (invalidation) assistantComponent.setCacheInvalidation(invalidation);
+					if (this.ctx.settings.get("display.cacheMissMarker")) {
+						const invalidation = detectCacheInvalidation(this.ctx.lastAssistantUsage, usage);
+						if (invalidation) assistantComponent.setCacheInvalidation(invalidation);
+					}
 					if (usage.cacheRead + usage.cacheWrite + usage.input > 0) {
 						this.ctx.lastAssistantUsage = usage;
 					}