fix(session): title user /skill invocations from name and args

Session titles ignored /skill:<name> <args> because the invocation is a
custom skill-prompt, not a user turn. Feed the chip or reconstructed
/skill line into first-title generation and replan context, never the
expanded SKILL.md body.

packages/coding-agent/src/session/agent-session.ts

@@ -308,6 +308,7 @@ import {
 	sanitizeAssistantForReparentedHistory,
 	USER_INTERRUPT_LABEL,
 } from "./messages";
+import { skillPromptTitleInput } from "./skill-title-input";
 import { ModelControls, type ModelControlsHost } from "./model-controls";
 import { isPrewalkPlanNudge, PrewalkCoordinator, type PrewalkCoordinatorHost } from "./prewalk";
 import {
@@ -5466,11 +5467,20 @@ export class AgentSession {
 		let keywordNotices: CustomMessage[] = [];
 		if (message.customType === SKILL_PROMPT_MESSAGE_TYPE && message.attribution === "user") {
 			const details = message.details;
+			let skillName: string | undefined;
 			let skillArgs = "";
-			if (details && typeof details === "object" && "args" in details && typeof details.args === "string") {
-				skillArgs = details.args;
+			if (details && typeof details === "object") {
+				if ("name" in details && typeof details.name === "string") skillName = details.name;
+				if ("args" in details && typeof details.args === "string") skillArgs = details.args;
 			}
 			keywordNotices = this.#createMagicKeywordNotices(skillArgs);
+			this.maybeStartTitleGeneration(
+				skillPromptTitleInput({
+					name: skillName,
+					args: skillArgs,
+					queueChipText: options?.queueChipText,
+				}),
+			);
 		}
 
 		if (options?.queueOnly) {

packages/coding-agent/src/session/messages.ts

@@ -38,6 +38,7 @@ export {
 
 import type { OutputMeta } from "../tools/output-meta";
 import { formatOutputNotice } from "../tools/output-meta";
+import { titleTextFromSkillPrompt } from "./skill-title-input";
 
 export const SKILL_PROMPT_MESSAGE_TYPE = "skill-prompt";
 export const LSP_LATE_DIAGNOSTIC_MESSAGE_TYPE = "lsp-late-diagnostic";
@@ -163,6 +164,11 @@ function thinkingFromContent(content: unknown): string {
 }
 
 function titleConversationTurnFromMessage(message: AgentMessage): TitleConversationTurn | undefined {
+	if (message.role === "custom") {
+		const text = titleTextFromSkillPrompt(message);
+		if (!text) return undefined;
+		return { role: "user", text };
+	}
 	if (message.role !== "user" && message.role !== "assistant") return undefined;
 	const text = textFromContent(message.content);
 	const thinking = message.role === "assistant" ? thinkingFromContent(message.content) : undefined;

packages/coding-agent/src/session/skill-title-input.ts

@@ -0,0 +1,36 @@
+/** Compact title-model input for a user-invoked `/skill:<name>` prompt. */
+export function skillPromptTitleInput(input: {
+	name?: string;
+	args?: string;
+	queueChipText?: string;
+}): string {
+	const chip = input.queueChipText?.trim();
+	if (chip) return chip;
+	const name = input.name?.trim();
+	const args = input.args?.trim();
+	if (name && args) return `/skill:${name} ${args}`;
+	if (name) return `/skill:${name}`;
+	return args ?? "";
+}
+
+/** Title text for a persisted skill-prompt custom message. Never the expanded SKILL.md body. */
+export function titleTextFromSkillPrompt(message: {
+	role: string;
+	customType?: string;
+	attribution?: string;
+	details?: unknown;
+}): string | undefined {
+	if (message.role !== "custom" || message.customType !== "skill-prompt" || message.attribution !== "user") {
+		return undefined;
+	}
+	let name: string | undefined;
+	let args: string | undefined;
+	let queueChipText: string | undefined;
+	if (message.details && typeof message.details === "object") {
+		const details = message.details as Record<string, unknown>;
+		if (typeof details.name === "string") name = details.name;
+		if (typeof details.args === "string") args = details.args;
+		if (typeof details.__queueChipText === "string") queueChipText = details.__queueChipText;
+	}
+	return skillPromptTitleInput({ name, args, queueChipText }) || undefined;
+}