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perf(coding-agent): concurrent skill loading + startup indicator through TUI import #1282

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51cd6da
perf(coding-agent): load skill files concurrently
Sep 2, 2026
2d732d3
fix(interactive): keep the startup indicator through the TUI graph im…
Sep 2, 2026
7eb6b8e
fix(coding-agent): address cubic review findings
Sep 2, 2026
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8 changes: 8 additions & 0 deletions packages/coding-agent/changes.md
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Original file line number Diff line number Diff line change
@@ -1,5 +1,13 @@
# Local fork changes

## 2026-09-02 - Load skill files concurrently at startup

- `loadSkills` / `loadSkillsFromDir` are now async and read skill files concurrently while preserving skill and diagnostic order exactly. `resource-loader`'s `extendResources` / `updateSkillsFromPaths` and the app-server skills loader await them; startup with many skills no longer serializes disk reads.

## 2026-09-02 - Keep the startup indicator through the interactive-mode import

- The startup loading indicator now stays visible through the dynamic import of the interactive-mode module graph (the largest cold-start cost after resource loading) instead of stopping before it, which left a blank terminal that looked frozen.

## 2026-09-01 - Acknowledge RPC abort before quiesce

- The RPC `abort` command now acknowledges immediately after dispatching the abort signal, while observing quiesce failures through the existing `rpc_error` event path.
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2 changes: 1 addition & 1 deletion packages/coding-agent/src/core/agent-session.ts
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Expand Up @@ -6637,7 +6637,7 @@ export class AgentSession {
hookPaths: this.buildExtensionResourcePaths(hookPaths),
};

this._resourceLoader.extendResources(extensionPaths);
await this._resourceLoader.extendResources(extensionPaths);
if (skillPaths.length > 0 || promptPaths.length > 0 || themePaths.length > 0) {
this._baseSystemPrompt = this._rebuildSystemPrompt(this.getActiveToolNames());
this.agent.state.systemPrompt = this._baseSystemPrompt;
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12 changes: 6 additions & 6 deletions packages/coding-agent/src/core/resource-loader.ts
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Expand Up @@ -77,7 +77,7 @@ export interface ResourceLoader {
getAppendSystemPrompt(): string[];
getLoadedHookSources?(): LoadedHookSources;
getAppendSystemPromptSources(): Array<{ path: string }>;
extendResources(paths: ResourceExtensionPaths): void;
extendResources(paths: ResourceExtensionPaths): Promise<void>;
reload(options?: ResourceLoaderReloadOptions): Promise<void>;
}

Expand Down Expand Up @@ -520,7 +520,7 @@ export class DefaultResourceLoader implements ResourceLoader {
return this.appendSystemPromptSourcePaths.map((path) => ({ path }));
}

extendResources(paths: ResourceExtensionPaths): void {
async extendResources(paths: ResourceExtensionPaths): Promise<void> {

@cubic-dev-ai cubic-dev-ai Bot Sep 2, 2026

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P2: When callers invoke extendResources() without awaiting it, newly discovered skills are not available on the next statement. Update every caller and the existing resource-loader tests to await the new Promise-returning API before reading resources.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At packages/coding-agent/src/core/resource-loader.ts, line 523:

<comment>When callers invoke `extendResources()` without awaiting it, newly discovered skills are not available on the next statement. Update every caller and the existing resource-loader tests to await the new Promise-returning API before reading resources.</comment>

<file context>
@@ -520,7 +520,7 @@ export class DefaultResourceLoader implements ResourceLoader {
 	}
 
-	extendResources(paths: ResourceExtensionPaths): void {
+	async extendResources(paths: ResourceExtensionPaths): Promise<void> {
 		const skillPaths = this.normalizeExtensionPaths(paths.skillPaths ?? []);
 		const promptPaths = this.normalizeExtensionPaths(paths.promptPaths ?? []);
</file context>

const skillPaths = this.normalizeExtensionPaths(paths.skillPaths ?? []);
const promptPaths = this.normalizeExtensionPaths(paths.promptPaths ?? []);
const themePaths = this.normalizeExtensionPaths(paths.themePaths ?? []);
Expand All @@ -541,7 +541,7 @@ export class DefaultResourceLoader implements ResourceLoader {
this.lastSkillPaths,
skillPaths.map((entry) => entry.path),
);
this.updateSkillsFromPaths(this.lastSkillPaths, this.resourceMetadataByPath);
await this.updateSkillsFromPaths(this.lastSkillPaths, this.resourceMetadataByPath);
}

if (promptPaths.length > 0) {
Expand Down Expand Up @@ -687,7 +687,7 @@ export class DefaultResourceLoader implements ResourceLoader {
: this.mergePaths([...cliEnabledSkills, ...enabledSkills], this.additionalSkillPaths);

this.lastSkillPaths = skillPaths;
this.updateSkillsFromPaths(skillPaths, metadataByPath);
await this.updateSkillsFromPaths(skillPaths, metadataByPath);
time("skills", "extensions");
for (const p of this.additionalSkillPaths) {
if (isLocalPath(p)) {
Expand Down Expand Up @@ -953,12 +953,12 @@ export class DefaultResourceLoader implements ResourceLoader {
};
}

private updateSkillsFromPaths(skillPaths: string[], metadataByPath?: Map<string, PathMetadata>): void {
private async updateSkillsFromPaths(skillPaths: string[], metadataByPath?: Map<string, PathMetadata>): Promise<void> {
Comment thread
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let skillsResult: { skills: Skill[]; diagnostics: ResourceDiagnostic[] };
if (this.noSkills && skillPaths.length === 0) {
skillsResult = { skills: [], diagnostics: [] };
} else {
skillsResult = loadSkills({
skillsResult = await loadSkills({
cwd: this.cwd,
agentDir: this.agentDir,
skillPaths,
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65 changes: 37 additions & 28 deletions packages/coding-agent/src/core/skills.ts
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@@ -1,4 +1,5 @@
import { existsSync, readdirSync, readFileSync, statSync } from "fs";
import { existsSync, readdirSync, statSync } from "fs";
import { readFile } from "fs/promises";
import ignore from "ignore";
import { basename, dirname, join, relative, resolve, sep } from "path";
import { CONFIG_DIR_NAME, getAgentDir } from "../config.ts";
Expand Down Expand Up @@ -165,7 +166,7 @@ function createSkillSourceInfo(filePath: string, baseDir: string, source: string
* - otherwise, load direct .md children in the root
* - recurse into subdirectories to find SKILL.md
*/
export function loadSkillsFromDir(options: LoadSkillsFromDirOptions): LoadSkillsResult {
export async function loadSkillsFromDir(options: LoadSkillsFromDirOptions): Promise<LoadSkillsResult> {
const { dir, source } = options;
return loadSkillsFromDirInternal(dir, source, true);
}
Expand All @@ -176,12 +177,12 @@ function loadSkillsFromDirInternal(
includeRootFiles: boolean,
ignoreMatcher?: IgnoreMatcher,
rootDir?: string,
): LoadSkillsResult {
): Promise<LoadSkillsResult> {
const skills: Skill[] = [];
const diagnostics: ResourceDiagnostic[] = [];

if (!existsSync(dir)) {
return { skills, diagnostics };
return Promise.resolve({ skills, diagnostics });
}

const root = rootDir ?? dir;
Expand Down Expand Up @@ -212,14 +213,17 @@ function loadSkillsFromDirInternal(
continue;
}

const result = loadSkillFromFile(fullPath, source);
if (result.skill) {
skills.push(result.skill);
}
diagnostics.push(...result.diagnostics);
return { skills, diagnostics };
// A root SKILL.md is the whole skill root: do not recurse.
return loadSkillFromFile(fullPath, source).then((result) => ({
skills: result.skill ? [result.skill] : [],
diagnostics: result.diagnostics,
}));
}

// Collect the work in traversal order, then run the (IO-bound) file reads
// concurrently so a large skill tree does not serialize disk access. Order
// and diagnostics stay identical to the sequential walk.
const pending: Array<Promise<LoadSkillsResult>> = [];
for (const entry of entries) {
if (entry.name.startsWith(".")) {
continue;
Expand Down Expand Up @@ -253,37 +257,42 @@ function loadSkillsFromDirInternal(
}

if (isDirectory) {
const subResult = loadSkillsFromDirInternal(fullPath, source, false, ig, root);
skills.push(...subResult.skills);
diagnostics.push(...subResult.diagnostics);
pending.push(loadSkillsFromDirInternal(fullPath, source, false, ig, root));
continue;
}

if (!isFile || !includeRootFiles || !entry.name.endsWith(".md")) {
continue;
}

const result = loadSkillFromFile(fullPath, source);
if (result.skill) {
skills.push(result.skill);
}
diagnostics.push(...result.diagnostics);
pending.push(loadSkillFromFile(fullPath, source).then((result) => ({
skills: result.skill ? [result.skill] : [],
diagnostics: result.diagnostics,
})));
}
} catch {}

return { skills, diagnostics };
return Promise.all(pending).then((results) => {
for (const result of results) {
skills.push(...result.skills);
diagnostics.push(...result.diagnostics);
}
return { skills, diagnostics };
});
} catch {
return Promise.resolve({ skills, diagnostics });
}
}

function loadSkillFromFile(
async function loadSkillFromFile(
filePath: string,
source: string,
): { skill: Skill | null; diagnostics: ResourceDiagnostic[] } {
): Promise<{ skill: Skill | null; diagnostics: ResourceDiagnostic[] }> {
const diagnostics: ResourceDiagnostic[] = [];
const isDeclaredSkill = basename(filePath) === "SKILL.md";

let rawContent: string;
try {
rawContent = readFileSync(filePath, "utf-8");
rawContent = await readFile(filePath, "utf-8");
} catch (error) {
const message = error instanceof Error ? error.message : "failed to read skill file";
diagnostics.push({ type: "warning", message, path: filePath });
Expand Down Expand Up @@ -404,7 +413,7 @@ export interface LoadSkillsOptions {
* Load skills from all configured locations.
* Returns skills and any validation diagnostics.
*/
export function loadSkills(options: LoadSkillsOptions): LoadSkillsResult {
export async function loadSkills(options: LoadSkillsOptions): Promise<LoadSkillsResult> {
const { agentDir, skillPaths, includeDefaults } = options;

// Resolve agentDir - if not provided, use default from config
Expand Down Expand Up @@ -448,8 +457,8 @@ export function loadSkills(options: LoadSkillsOptions): LoadSkillsResult {
}

if (includeDefaults) {
addSkills(loadSkillsFromDirInternal(join(resolvedAgentDir, "skills"), "user", true));
addSkills(loadSkillsFromDirInternal(resolve(resolvedCwd, CONFIG_DIR_NAME, "skills"), "project", true));
addSkills(await loadSkillsFromDirInternal(join(resolvedAgentDir, "skills"), "user", true));
addSkills(await loadSkillsFromDirInternal(resolve(resolvedCwd, CONFIG_DIR_NAME, "skills"), "project", true));
}

const userSkillsDir = join(resolvedAgentDir, "skills");
Expand Down Expand Up @@ -483,9 +492,9 @@ export function loadSkills(options: LoadSkillsOptions): LoadSkillsResult {
const stats = statSync(resolvedPath);
const source = getSource(resolvedPath);
if (stats.isDirectory()) {
addSkills(loadSkillsFromDirInternal(resolvedPath, source, true));
addSkills(await loadSkillsFromDirInternal(resolvedPath, source, true));
} else if (stats.isFile() && resolvedPath.endsWith(".md")) {
const result = loadSkillFromFile(resolvedPath, source);
const result = await loadSkillFromFile(resolvedPath, source);
if (result.skill) {
addSkills({ skills: [result.skill], diagnostics: result.diagnostics });
} else {
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8 changes: 5 additions & 3 deletions packages/coding-agent/src/main.ts
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Expand Up @@ -1117,8 +1117,6 @@ export async function main(args: string[], options?: MainOptions) {
cwd: sessionManager.getCwd(),
agentDir,
sessionManager,
}).finally(() => {
startupLoadingIndicator.stop();
});
time("createAgentSessionRuntime");
let selectedRuntime = runtime;
Expand Down Expand Up @@ -1222,7 +1220,11 @@ export async function main(args: string[], options?: MainOptions) {
} else if (appMode === "interactive") {
// Keep the TUI graph out of headless RPC children. This is intentionally at the
// mode seam: interactive startup still loads the same module before first use.
const { InteractiveMode } = await import("./modes/interactive/interactive-mode.ts");
const { InteractiveMode } = await import("./modes/interactive/interactive-mode.ts").finally(() => {
// The startup indicator must stop on success AND failure: an import rejection
// must not leave the spinner running with the cursor hidden.
startupLoadingIndicator.stop();
});
const interactiveMode = new InteractiveMode(selectedRuntime, {
migratedProviders,
modelFallbackMessage,
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4 changes: 2 additions & 2 deletions packages/coding-agent/src/modes/app-server/server/skills.ts
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Expand Up @@ -131,11 +131,11 @@ function findLoadedLoader(

async function createLoader(cwd: string, options: SkillsListEntryOptions): Promise<SkillResourceLoader> {
if (options.resourceLoaderFactory) return options.resourceLoaderFactory(cwd);
let loaded = loadSkills({ cwd, agentDir: options.agentDir, skillPaths: [], includeDefaults: true });
let loaded = await loadSkills({ cwd, agentDir: options.agentDir, skillPaths: [], includeDefaults: true });
return {
getSkills: () => loaded,
reload: async () => {
loaded = loadSkills({ cwd, agentDir: options.agentDir, skillPaths: [], includeDefaults: true });
loaded = await loadSkills({ cwd, agentDir: options.agentDir, skillPaths: [], includeDefaults: true });
},
};
}
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2 changes: 1 addition & 1 deletion packages/coding-agent/test/imagegen-skill-gating.test.ts
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Expand Up @@ -74,7 +74,7 @@ describe("imagegen skill contribution", () => {

const resources = await runner.emitResourcesDiscover(cwd, "startup");
const skillPaths = resources.skillPaths.map((entry) => entry.path);
const loaded = loadSkills({ cwd, agentDir: join(cwd, "agent"), skillPaths, includeDefaults: false });
const loaded = await loadSkills({ cwd, agentDir: join(cwd, "agent"), skillPaths, includeDefaults: false });
const prompt = await runner.emitBeforeAgentStart("draw an image", undefined, "base", { cwd });

expect(skillPaths).toHaveLength(1);
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6 changes: 3 additions & 3 deletions packages/coding-agent/test/resource-loader.test.ts
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Expand Up @@ -716,7 +716,7 @@ Extra prompt content`,
const loader = new DefaultResourceLoader({ cwd, agentDir });
await loader.reload();

loader.extendResources({
await loader.extendResources({
skillPaths: [
{
path: extraSkillDir,
Expand Down Expand Up @@ -770,7 +770,7 @@ Extra content`,
const loader = new DefaultResourceLoader({ cwd, agentDir });
await loader.reload();

loader.extendResources({
await loader.extendResources({
skillPaths: [
{
path: pathToFileURL(extraSkillDir).href,
Expand Down Expand Up @@ -865,7 +865,7 @@ Extension prompt content`,
scope: "temporary",
origin: "top-level",
} as const;
loader.extendResources({
await loader.extendResources({
skillPaths: [{ path: extensionSkillDir, metadata: extensionMetadata }],
promptPaths: [{ path: extensionPromptsDir, metadata: extensionMetadata }],
themePaths: [{ path: extensionThemesDir, metadata: extensionMetadata }],
Expand Down
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