feat(coding-agent,tui): add stacked autocomplete providers closes #2983

packages/ai/test/openai-completions-cache-control-format.test.ts

@@ -126,9 +126,27 @@ describe("openai-completions cacheControlFormat", () => {
 		mockState.lastParams = undefined;
 	});
 
-	it("applies Anthropic-style cache markers for built-in opencode-go Qwen models", async () => {
-		const model = getModel("opencode-go", "qwen3.5-plus");
-		expect(model.compat?.cacheControlFormat).toBe("anthropic");
+	it("applies Anthropic-style cache markers when model compat enables them", async () => {
+		const model: Model<"openai-completions"> = {
+			id: "custom-qwen",
+			name: "Custom Qwen",
+			api: "openai-completions",
+			provider: "openrouter",
+			baseUrl: "https://example.com/v1",
+			reasoning: true,
+			input: ["text"],
+			cost: {
+				input: 0,
+				output: 0,
+				cacheRead: 0,
+				cacheWrite: 0,
+			},
+			contextWindow: 128000,
+			maxTokens: 32000,
+			compat: {
+				cacheControlFormat: "anthropic",
+			},
+		};
 
 		const params = await capturePayload(model);
 		expectAnthropicCacheMarkers(params);
@@ -141,7 +159,26 @@ describe("openai-completions cacheControlFormat", () => {
 	});
 
 	it("omits Anthropic-style cache markers when cacheRetention is none", async () => {
-		const model = getModel("opencode-go", "qwen3.5-plus");
+		const model: Model<"openai-completions"> = {
+			id: "custom-qwen",
+			name: "Custom Qwen",
+			api: "openai-completions",
+			provider: "openrouter",
+			baseUrl: "https://example.com/v1",
+			reasoning: true,
+			input: ["text"],
+			cost: {
+				input: 0,
+				output: 0,
+				cacheRead: 0,
+				cacheWrite: 0,
+			},
+			contextWindow: 128000,
+			maxTokens: 32000,
+			compat: {
+				cacheControlFormat: "anthropic",
+			},
+		};
 		const params = await capturePayload(model, { cacheRetention: "none" });
 		const instructionMessage = getInstructionMessage(params);
 

packages/coding-agent/CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - Added `structured-output.ts` extension example plus extension docs for terminating tool results, showing how a custom tool can return `terminate: true` so the agent ends on the tool call without an extra follow-up LLM turn ([#3525](https://github.com/badlogic/pi-mono/issues/3525))
 - Added OSC 9;4 terminal progress indicators during agent streaming and compaction, so terminals like iTerm2, WezTerm, Windows Terminal, and Kitty show activity in their tab bar
+- Added `ctx.ui.addAutocompleteProvider(...)` for stacking extension autocomplete providers on top of the built-in slash/path provider, plus a `github-issue-autocomplete.ts` example and extension docs ([#2983](https://github.com/badlogic/pi-mono/issues/2983))
 
 ### Breaking Changes
 

packages/coding-agent/docs/extensions.md

@@ -2063,6 +2063,7 @@ Extensions can interact with users via `ctx.ui` methods and customize how messag
 - Status indicators (setStatus)
 - Working message and indicator during streaming (`setWorkingMessage`, `setWorkingIndicator`)
 - Widgets above/below editor (setWidget)
+- Autocomplete providers layered on top of built-in slash/path completion (addAutocompleteProvider)
 - Custom footers (setFooter)
 
 ### Dialogs
@@ -2184,6 +2185,28 @@ const current = ctx.ui.getEditorText();
 // Paste into editor (triggers paste handling, including collapse for large content)
 ctx.ui.pasteToEditor("pasted content");
 
+// Stack custom autocomplete behavior on top of the built-in provider
+ctx.ui.addAutocompleteProvider((current) => ({
+  async getSuggestions(lines, line, col, options) {
+    const beforeCursor = (lines[line] ?? "").slice(0, col);
+    const match = beforeCursor.match(/(?:^|[ \t])#([^\s#]*)$/);
+    if (!match) {
+      return current.getSuggestions(lines, line, col, options);
+    }
+
+    return {
+      prefix: `#${match[1] ?? ""}`,
+      items: [{ value: "#2983", label: "#2983", description: "Extension API for autocomplete" }],
+    };
+  },
+  applyCompletion(lines, line, col, item, prefix) {
+    return current.applyCompletion(lines, line, col, item, prefix);
+  },
+  shouldTriggerFileCompletion(lines, line, col) {
+    return current.shouldTriggerFileCompletion?.(lines, line, col) ?? true;
+  },
+}));
+
 // Tool output expansion
 const wasExpanded = ctx.ui.getToolsExpanded();
 ctx.ui.setToolsExpanded(true);
@@ -2206,6 +2229,50 @@ ctx.ui.theme.fg("accent", "styled text");  // Access current theme
 
 Custom working-indicator frames are rendered verbatim. If you want colors, add them to the frame strings yourself, for example with `ctx.ui.theme.fg(...)`.
 
+### Autocomplete Providers
+
+Use `ctx.ui.addAutocompleteProvider()` to stack custom autocomplete logic on top of the built-in slash-command and path provider.
+
+Typical pattern:
+
+- inspect the text before the cursor
+- return your own suggestions when your extension-specific syntax matches
+- otherwise delegate to `current.getSuggestions(...)`
+- delegate `applyCompletion(...)` unless you need custom insertion behavior
+
+```typescript
+pi.on("session_start", (_event, ctx) => {
+  ctx.ui.addAutocompleteProvider((current) => ({
+    async getSuggestions(lines, cursorLine, cursorCol, options) {
+      const line = lines[cursorLine] ?? "";
+      const beforeCursor = line.slice(0, cursorCol);
+      const match = beforeCursor.match(/(?:^|[ \t])#([^\s#]*)$/);
+      if (!match) {
+        return current.getSuggestions(lines, cursorLine, cursorCol, options);
+      }
+
+      return {
+        prefix: `#${match[1] ?? ""}`,
+        items: [
+          { value: "#2983", label: "#2983", description: "Extension API for registering custom @ autocomplete providers" },
+          { value: "#2753", label: "#2753", description: "Reload stale resource settings" },
+        ],
+      };
+    },
+
+    applyCompletion(lines, cursorLine, cursorCol, item, prefix) {
+      return current.applyCompletion(lines, cursorLine, cursorCol, item, prefix);
+    },
+
+    shouldTriggerFileCompletion(lines, cursorLine, cursorCol) {
+      return current.shouldTriggerFileCompletion?.(lines, cursorLine, cursorCol) ?? true;
+    },
+  }));
+});
+```
+
+See [github-issue-autocomplete.ts](../examples/extensions/github-issue-autocomplete.ts) for a complete example that preloads the latest open GitHub issues with `gh issue list` and filters them locally for fast `#...` completion. It requires GitHub CLI (`gh`) and a GitHub repository checkout.
+
 ### Custom Components
 
 For complex UI, use `ctx.ui.custom()`. This temporarily replaces the editor with your component until `done()` is called:
@@ -2429,6 +2496,7 @@ All examples in [examples/extensions/](../examples/extensions/).
 | **UI Components** |||
 | `status-line.ts` | Footer status indicator | `setStatus`, session events |
 | `working-indicator.ts` | Customize the streaming working indicator | `setWorkingIndicator`, `registerCommand` |
+| `github-issue-autocomplete.ts` | Add `#1234` issue completions on top of built-in autocomplete by preloading recent open issues from `gh issue list` | `addAutocompleteProvider`, `on("session_start")`, `exec` |
 | `custom-footer.ts` | Replace footer entirely | `registerCommand`, `setFooter` |
 | `custom-header.ts` | Replace startup header | `on("session_start")`, `setHeader` |
 | `modal-editor.ts` | Vim-style modal editor | `setEditorComponent`, `CustomEditor` |

packages/coding-agent/examples/extensions/README.md

@@ -52,6 +52,7 @@ cp permission-gate.ts ~/.pi/agent/extensions/
 | `handoff.ts` | Transfer context to a new focused session via `/handoff <goal>` |
 | `qna.ts` | Extracts questions from last response into editor via `ctx.ui.setEditorText()` |
 | `status-line.ts` | Shows turn progress in footer via `ctx.ui.setStatus()` with themed colors |
+| `github-issue-autocomplete.ts` | Adds `#1234` issue completions by stacking a custom autocomplete provider that preloads open issues from `gh issue list` |
 | `widget-placement.ts` | Shows widgets above and below the editor via `ctx.ui.setWidget()` placement |
 | `hidden-thinking-label.ts` | Customizes the collapsed thinking label via `ctx.ui.setHiddenThinkingLabel()` |
 | `working-indicator.ts` | Customizes the streaming working indicator via `ctx.ui.setWorkingIndicator()` |

packages/coding-agent/examples/extensions/github-issue-autocomplete.ts

@@ -0,0 +1,185 @@
+// Requires GitHub CLI (`gh`) and a GitHub repository checkout.
+// Preloads the latest open issues once per session, then filters them locally for fast `#...` completion.
+
+import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";
+import {
+	type AutocompleteItem,
+	type AutocompleteProvider,
+	type AutocompleteSuggestions,
+	fuzzyFilter,
+} from "@mariozechner/pi-tui";
+
+type GitHubIssue = {
+	number: number;
+	title: string;
+	state: string;
+};
+
+type RepoResolution = { ok: true; repo: string } | { ok: false; error: string };
+
+const MAX_ISSUES = 100;
+const MAX_SUGGESTIONS = 20;
+
+function extractIssueToken(textBeforeCursor: string): string | undefined {
+	const match = textBeforeCursor.match(/(?:^|[ \t])#([^\s#]*)$/);
+	return match?.[1];
+}
+
+function parseGitHubRepo(remoteUrl: string): string | undefined {
+	const sshMatch = remoteUrl.match(/^git@github\.com:([^/]+\/[^/]+?)(?:\.git)?$/);
+	if (sshMatch) {
+		return sshMatch[1];
+	}
+
+	const httpsMatch = remoteUrl.match(/^https?:\/\/github\.com\/([^/]+\/[^/]+?)(?:\.git)?$/);
+	if (httpsMatch) {
+		return httpsMatch[1];
+	}
+
+	return undefined;
+}
+
+async function resolveGitHubRepo(pi: ExtensionAPI, cwd: string): Promise<RepoResolution> {
+	const result = await pi.exec("git", ["remote", "-v"], { cwd, timeout: 5_000 });
+	if (result.code !== 0) {
+		return { ok: false, error: "github-issue-autocomplete: cwd is not a git repository" };
+	}
+
+	for (const line of result.stdout.split("\n")) {
+		const columns = line.trim().split(/\s+/);
+		const remoteUrl = columns[1];
+		if (!remoteUrl) {
+			continue;
+		}
+		const repo = parseGitHubRepo(remoteUrl);
+		if (repo) {
+			return { ok: true, repo };
+		}
+	}
+
+	return { ok: false, error: "github-issue-autocomplete: cwd is not a GitHub repository" };
+}
+
+function formatIssueItem(issue: GitHubIssue): AutocompleteItem {
+	return {
+		value: `#${issue.number}`,
+		label: `#${issue.number}`,
+		description: `[${issue.state.toLowerCase()}] ${issue.title}`,
+	};
+}
+
+function filterIssues(issues: GitHubIssue[], query: string): AutocompleteItem[] {
+	if (!query.trim()) {
+		return issues.slice(0, MAX_SUGGESTIONS).map(formatIssueItem);
+	}
+
+	if (/^\d+$/.test(query)) {
+		const numericMatches = issues
+			.filter((issue) => String(issue.number).startsWith(query))
+			.slice(0, MAX_SUGGESTIONS)
+			.map(formatIssueItem);
+		if (numericMatches.length > 0) {
+			return numericMatches;
+		}
+	}
+
+	return fuzzyFilter(issues, query, (issue) => `${issue.number} ${issue.title}`)
+		.slice(0, MAX_SUGGESTIONS)
+		.map(formatIssueItem);
+}
+
+function createIssueAutocompleteProvider(
+	current: AutocompleteProvider,
+	getIssues: () => Promise<GitHubIssue[] | undefined>,
+): AutocompleteProvider {
+	return {
+		async getSuggestions(lines, cursorLine, cursorCol, options): Promise<AutocompleteSuggestions | null> {
+			const currentLine = lines[cursorLine] ?? "";
+			const textBeforeCursor = currentLine.slice(0, cursorCol);
+			const token = extractIssueToken(textBeforeCursor);
+			if (token === undefined) {
+				return current.getSuggestions(lines, cursorLine, cursorCol, options);
+			}
+
+			const issues = await getIssues();
+			if (options.signal.aborted || !issues || issues.length === 0) {
+				return current.getSuggestions(lines, cursorLine, cursorCol, options);
+			}
+
+			const suggestions = filterIssues(issues, token);
+			if (suggestions.length === 0) {
+				return current.getSuggestions(lines, cursorLine, cursorCol, options);
+			}
+
+			return {
+				items: suggestions,
+				prefix: `#${token}`,
+			};
+		},
+
+		applyCompletion(lines, cursorLine, cursorCol, item, prefix) {
+			return current.applyCompletion(lines, cursorLine, cursorCol, item, prefix);
+		},
+
+		shouldTriggerFileCompletion(lines, cursorLine, cursorCol) {
+			return current.shouldTriggerFileCompletion?.(lines, cursorLine, cursorCol) ?? true;
+		},
+	};
+}
+
+export default function (pi: ExtensionAPI): void {
+	pi.on("session_start", async (_event, ctx) => {
+		const resolvedRepo = await resolveGitHubRepo(pi, ctx.cwd);
+		if (!resolvedRepo.ok) {
+			ctx.ui.notify(resolvedRepo.error, "error");
+			return;
+		}
+
+		const repo = resolvedRepo.repo;
+		let issuesPromise: Promise<GitHubIssue[] | undefined> | undefined;
+		let loadErrorShown = false;
+
+		const getIssues = async (): Promise<GitHubIssue[] | undefined> => {
+			issuesPromise ||= (async () => {
+				const result = await pi.exec(
+					"gh",
+					[
+						"issue",
+						"list",
+						"--repo",
+						repo,
+						"--state",
+						"open",
+						"--limit",
+						String(MAX_ISSUES),
+						"--json",
+						"number,title,state",
+					],
+					{ cwd: ctx.cwd, timeout: 5_000 },
+				);
+				if (result.code !== 0) {
+					if (!loadErrorShown) {
+						loadErrorShown = true;
+						const details = result.stderr.trim() || `exit code ${result.code}`;
+						ctx.ui.notify(`github-issue-autocomplete: failed to load issues: ${details}`, "error");
+					}
+					return undefined;
+				}
+
+				try {
+					return JSON.parse(result.stdout) as GitHubIssue[];
+				} catch {
+					if (!loadErrorShown) {
+						loadErrorShown = true;
+						ctx.ui.notify("github-issue-autocomplete: failed to parse gh issue list output", "error");
+					}
+					return undefined;
+				}
+			})();
+			return issuesPromise;
+		};
+
+		void getIssues();
+		ctx.ui.addAutocompleteProvider((current) => createIssueAutocompleteProvider(current, getIssues));
+	});
+}

packages/coding-agent/src/core/extensions/index.ts

@@ -29,6 +29,7 @@ export type {
 	AppendEntryHandler,
 	// App keybindings (for custom editors)
 	AppKeybinding,
+	AutocompleteProviderFactory,
 	// Events - Tool (ToolCallEvent types)
 	BashToolCallEvent,
 	BashToolResultEvent,

packages/coding-agent/src/core/extensions/runner.ts

@@ -204,6 +204,7 @@ const noOpUIContext: ExtensionUIContext = {
 	setEditorText: () => {},
 	getEditorText: () => "",
 	editor: async () => undefined,
+	addAutocompleteProvider: () => {},
 	setEditorComponent: () => {},
 	get theme() {
 		return theme;

packages/coding-agent/src/core/extensions/types.ts

@@ -30,6 +30,7 @@ import type {
 } from "@mariozechner/pi-ai";
 import type {
 	AutocompleteItem,
+	AutocompleteProvider,
 	Component,
 	EditorComponent,
 	EditorTheme,
@@ -112,6 +113,9 @@ export interface WorkingIndicatorOptions {
 	intervalMs?: number;
 }
 
+/** Wrap the current autocomplete provider with additional behavior. */
+export type AutocompleteProviderFactory = (current: AutocompleteProvider) => AutocompleteProvider;
+
 /**
  * UI context for extensions to request interactive UI.
  * Each mode (interactive, RPC, print) provides its own implementation.
@@ -206,6 +210,9 @@ export interface ExtensionUIContext {
 	/** Show a multi-line editor for text editing. */
 	editor(title: string, prefill?: string): Promise<string | undefined>;
 
+	/** Stack additional autocomplete behavior on top of the built-in provider. */
+	addAutocompleteProvider(factory: AutocompleteProviderFactory): void;
+
 	/**
 	 * Set a custom editor component via factory function.
 	 * Pass undefined to restore the default editor.

packages/coding-agent/src/index.ts

@@ -54,6 +54,7 @@ export type {
 	AgentToolResult,
 	AgentToolUpdateCallback,
 	AppKeybinding,
+	AutocompleteProviderFactory,
 	BashToolCallEvent,
 	BeforeAgentStartEvent,
 	BeforeAgentStartEventResult,

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -11,6 +11,7 @@ import type { AgentMessage } from "@mariozechner/pi-agent-core";
 import type { AssistantMessage, ImageContent, Message, Model, OAuthProviderId } from "@mariozechner/pi-ai";
 import type {
 	AutocompleteItem,
+	AutocompleteProvider,
 	EditorComponent,
 	EditorTheme,
 	Keybinding,
@@ -50,6 +51,7 @@ import {
 import { type AgentSession, type AgentSessionEvent, parseSkillBlock } from "../../core/agent-session.js";
 import { type AgentSessionRuntime, SessionImportFileNotFoundError } from "../../core/agent-session-runtime.js";
 import type {
+	AutocompleteProviderFactory,
 	ExtensionCommandContext,
 	ExtensionContext,
 	ExtensionRunner,
@@ -191,7 +193,8 @@ export class InteractiveMode {
 	private statusContainer: Container;
 	private defaultEditor: CustomEditor;
 	private editor: EditorComponent;
-	private autocompleteProvider: CombinedAutocompleteProvider | undefined;
+	private autocompleteProvider: AutocompleteProvider | undefined;
+	private autocompleteProviderWrappers: AutocompleteProviderFactory[] = [];
 	private fdPath: string | undefined;
 	private editorContainer: Container;
 	private footer: FooterComponent;
@@ -391,7 +394,7 @@ export class InteractiveMode {
 			}));
 	}
 
-	private setupAutocomplete(fdPath: string | undefined): void {
+	private createBaseAutocompleteProvider(): AutocompleteProvider {
 		// Define commands for autocomplete
 		const slashCommands: SlashCommand[] = BUILTIN_SLASH_COMMANDS.map((command) => ({
 			name: command.name,
@@ -461,15 +464,23 @@ export class InteractiveMode {
 			}
 		}
 
-		// Setup autocomplete
-		this.autocompleteProvider = new CombinedAutocompleteProvider(
+		return new CombinedAutocompleteProvider(
 			[...slashCommands, ...templateCommands, ...extensionCommands, ...skillCommandList],
 			this.sessionManager.getCwd(),
-			fdPath,
+			this.fdPath,
 		);
-		this.defaultEditor.setAutocompleteProvider(this.autocompleteProvider);
+	}
+
+	private setupAutocompleteProvider(): void {
+		let provider = this.createBaseAutocompleteProvider();
+		for (const wrapProvider of this.autocompleteProviderWrappers) {
+			provider = wrapProvider(provider);
+		}
+
+		this.autocompleteProvider = provider;
+		this.defaultEditor.setAutocompleteProvider(provider);
 		if (this.editor !== this.defaultEditor) {
-			this.editor.setAutocompleteProvider?.(this.autocompleteProvider);
+			this.editor.setAutocompleteProvider?.(provider);
 		}
 	}
 
@@ -1492,7 +1503,7 @@ export class InteractiveMode {
 		});
 
 		setRegisteredThemes(this.session.resourceLoader.getThemes().themes);
-		this.setupAutocomplete(this.fdPath);
+		this.setupAutocompleteProvider();
 
 		const extensionRunner = this.session.extensionRunner;
 		this.setupExtensionShortcuts(extensionRunner);
@@ -1708,7 +1719,9 @@ export class InteractiveMode {
 		this.clearExtensionWidgets();
 		this.footerDataProvider.clearExtensionStatuses();
 		this.footer.invalidate();
+		this.autocompleteProviderWrappers = [];
 		this.setCustomEditorComponent(undefined);
+		this.setupAutocompleteProvider();
 		this.defaultEditor.onExtensionShortcut = undefined;
 		this.updateTerminalTitle();
 		this.pendingWorkingMessage = undefined;
@@ -1886,6 +1899,10 @@ export class InteractiveMode {
 			setEditorText: (text) => this.editor.setText(text),
 			getEditorText: () => this.editor.getExpandedText?.() ?? this.editor.getText(),
 			editor: (title, prefill) => this.showExtensionEditor(title, prefill),
+			addAutocompleteProvider: (factory) => {
+				this.autocompleteProviderWrappers.push(factory);
+				this.setupAutocompleteProvider();
+			},
 			setEditorComponent: (factory) => this.setCustomEditorComponent(factory),
 			get theme() {
 				return theme;
@@ -3705,7 +3722,7 @@ export class InteractiveMode {
 					},
 					onEnableSkillCommandsChange: (enabled) => {
 						this.settingsManager.setEnableSkillCommands(enabled);
-						this.setupAutocomplete(this.fdPath);
+						this.setupAutocompleteProvider();
 					},
 					onSteeringModeChange: (mode) => {
 						this.session.setSteeringMode(mode);
@@ -4493,7 +4510,7 @@ export class InteractiveMode {
 			}
 			this.ui.setShowHardwareCursor(this.settingsManager.getShowHardwareCursor());
 			this.ui.setClearOnShrink(this.settingsManager.getClearOnShrink());
-			this.setupAutocomplete(this.fdPath);
+			this.setupAutocompleteProvider();
 			const runner = this.session.extensionRunner;
 			this.setupExtensionShortcuts(runner);
 			this.rebuildChatFromMessages();

packages/coding-agent/src/modes/rpc/rpc-mode.ts

@@ -259,6 +259,10 @@ export async function runRpcMode(runtimeHost: AgentSessionRuntime): Promise<neve
 			});
 		},
 
+		addAutocompleteProvider(): void {
+			// Autocomplete provider composition is not supported in RPC mode
+		},
+
 		setEditorComponent(): void {
 			// Custom editor components not supported in RPC mode
 		},

packages/coding-agent/test/interactive-mode-status.test.ts

@@ -1,7 +1,8 @@
 import { homedir } from "node:os";
 import * as path from "node:path";
-import { Container } from "@mariozechner/pi-tui";
+import { type AutocompleteProvider, CombinedAutocompleteProvider, Container } from "@mariozechner/pi-tui";
 import { beforeAll, describe, expect, test, vi } from "vitest";
+import type { AutocompleteProviderFactory } from "../src/core/extensions/types.js";
 import type { SourceInfo } from "../src/core/source-info.js";
 import { InteractiveMode } from "../src/modes/interactive/interactive-mode.js";
 import { initTheme } from "../src/modes/interactive/theme/theme.js";
@@ -147,6 +148,75 @@ describe("InteractiveMode.createExtensionUIContext setTheme", () => {
 	});
 });
 
+describe("InteractiveMode.createExtensionUIContext addAutocompleteProvider", () => {
+	test("stores wrapper factories and rebuilds autocomplete immediately", () => {
+		const wrapper: AutocompleteProviderFactory = (current) => current;
+		const fakeThis = {
+			autocompleteProviderWrappers: [] as AutocompleteProviderFactory[],
+			setupAutocompleteProvider: vi.fn(),
+		};
+
+		const uiContext = (InteractiveMode as any).prototype.createExtensionUIContext.call(fakeThis);
+		uiContext.addAutocompleteProvider(wrapper);
+
+		expect(fakeThis.autocompleteProviderWrappers).toEqual([wrapper]);
+		expect(fakeThis.setupAutocompleteProvider).toHaveBeenCalledTimes(1);
+	});
+});
+
+describe("InteractiveMode.setupAutocompleteProvider", () => {
+	test("stacks wrapper factories over a fresh base provider", () => {
+		const defaultEditor = { setAutocompleteProvider: vi.fn() };
+		const customEditor = { setAutocompleteProvider: vi.fn() };
+		const calls: string[] = [];
+
+		const wrap1: AutocompleteProviderFactory = (current): AutocompleteProvider => ({
+			async getSuggestions(lines, cursorLine, cursorCol, options) {
+				calls.push("getSuggestions:wrap1");
+				return current.getSuggestions(lines, cursorLine, cursorCol, options);
+			},
+			applyCompletion(lines, cursorLine, cursorCol, item, prefix) {
+				calls.push("applyCompletion:wrap1");
+				return current.applyCompletion(lines, cursorLine, cursorCol, item, prefix);
+			},
+			shouldTriggerFileCompletion(lines, cursorLine, cursorCol) {
+				calls.push("shouldTrigger:wrap1");
+				return current.shouldTriggerFileCompletion?.(lines, cursorLine, cursorCol) ?? true;
+			},
+		});
+		const wrap2: AutocompleteProviderFactory = (current): AutocompleteProvider => ({
+			async getSuggestions(lines, cursorLine, cursorCol, options) {
+				calls.push("getSuggestions:wrap2");
+				return current.getSuggestions(lines, cursorLine, cursorCol, options);
+			},
+			applyCompletion(lines, cursorLine, cursorCol, item, prefix) {
+				calls.push("applyCompletion:wrap2");
+				return current.applyCompletion(lines, cursorLine, cursorCol, item, prefix);
+			},
+			shouldTriggerFileCompletion(lines, cursorLine, cursorCol) {
+				calls.push("shouldTrigger:wrap2");
+				return current.shouldTriggerFileCompletion?.(lines, cursorLine, cursorCol) ?? true;
+			},
+		});
+
+		const fakeThis = {
+			createBaseAutocompleteProvider: () => new CombinedAutocompleteProvider([], "/tmp/project", undefined),
+			defaultEditor,
+			editor: customEditor,
+			autocompleteProviderWrappers: [wrap1, wrap2],
+		};
+
+		(InteractiveMode as any).prototype.setupAutocompleteProvider.call(fakeThis);
+
+		expect(defaultEditor.setAutocompleteProvider).toHaveBeenCalledTimes(1);
+		expect(customEditor.setAutocompleteProvider).toHaveBeenCalledTimes(1);
+		const provider = defaultEditor.setAutocompleteProvider.mock.calls[0]?.[0] as AutocompleteProvider;
+		expect(provider).toBe(customEditor.setAutocompleteProvider.mock.calls[0]?.[0]);
+		expect(provider.shouldTriggerFileCompletion?.(["foo"], 0, 3)).toBe(true);
+		expect(calls).toEqual(["shouldTrigger:wrap2", "shouldTrigger:wrap1"]);
+	});
+});
+
 describe("InteractiveMode.showLoadedResources", () => {
 	beforeAll(() => {
 		initTheme("dark");

packages/tui/CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Added
 
 - Added `setProgress(active: boolean)` to the `Terminal` interface for OSC 9;4 progress indicator support
+- Added generic stacked autocomplete support for extension wrappers via `AutocompleteProvider.shouldTriggerFileCompletion?()` and `#` as a natural autocomplete trigger alongside `@` ([#2983](https://github.com/badlogic/pi-mono/issues/2983))
 
 ## [0.68.1] - 2026-04-22
 

packages/tui/src/autocomplete.ts

@@ -261,6 +261,9 @@ export interface AutocompleteProvider {
 		cursorLine: number;
 		cursorCol: number;
 	};
+
+	// Check if file completion should trigger for explicit Tab completion
+	shouldTriggerFileCompletion?(lines: string[], cursorLine: number, cursorCol: number): boolean;
 }
 
 // Combined provider that handles both slash commands and file paths

packages/tui/src/components/editor.ts

@@ -1,4 +1,4 @@
-import type { AutocompleteProvider, AutocompleteSuggestions, CombinedAutocompleteProvider } from "../autocomplete.js";
+import type { AutocompleteProvider, AutocompleteSuggestions } from "../autocomplete.js";
 import { getKeybindings } from "../keybindings.js";
 import { decodePrintableKey, matchesKey } from "../keys.js";
 import { KillRing } from "../kill-ring.js";
@@ -1054,17 +1054,16 @@ export class Editor implements Component, Focusable {
 			if (char === "/" && this.isAtStartOfMessage()) {
 				this.tryTriggerAutocomplete();
 			}
-			// Auto-trigger for "@" file reference (fuzzy search)
-			else if (char === "@") {
+			// Auto-trigger for symbol-based completion like @ or # at token boundaries
+			else if (char === "@" || char === "#") {
 				const currentLine = this.state.lines[this.state.cursorLine] || "";
 				const textBeforeCursor = currentLine.slice(0, this.state.cursorCol);
-				// Only trigger if @ is after whitespace or at start of line
-				const charBeforeAt = textBeforeCursor[textBeforeCursor.length - 2];
-				if (textBeforeCursor.length === 1 || charBeforeAt === " " || charBeforeAt === "\t") {
+				const charBeforeSymbol = textBeforeCursor[textBeforeCursor.length - 2];
+				if (textBeforeCursor.length === 1 || charBeforeSymbol === " " || charBeforeSymbol === "\t") {
 					this.tryTriggerAutocomplete();
 				}
 			}
-			// Also auto-trigger when typing letters in a slash command context
+			// Also auto-trigger when typing letters in a slash command or symbol completion context
 			else if (/[a-zA-Z0-9.\-_]/.test(char)) {
 				const currentLine = this.state.lines[this.state.cursorLine] || "";
 				const textBeforeCursor = currentLine.slice(0, this.state.cursorCol);
@@ -1072,8 +1071,8 @@ export class Editor implements Component, Focusable {
 				if (this.isInSlashCommandContext(textBeforeCursor)) {
 					this.tryTriggerAutocomplete();
 				}
-				// Check if we're in an @ file reference context
-				else if (textBeforeCursor.match(/(?:^|[\s])@[^\s]*$/)) {
+				// Check if we're in a symbol-based completion context like @ or #
+				else if (textBeforeCursor.match(/(?:^|[\s])[@#][^\s]*$/)) {
 					this.tryTriggerAutocomplete();
 				}
 			}
@@ -1240,8 +1239,8 @@ export class Editor implements Component, Focusable {
 			if (this.isInSlashCommandContext(textBeforeCursor)) {
 				this.tryTriggerAutocomplete();
 			}
-			// @ file reference context
-			else if (textBeforeCursor.match(/(?:^|[\s])@[^\s]*$/)) {
+			// Symbol-based completion context like @ or #
+			else if (textBeforeCursor.match(/(?:^|[\s])[@#][^\s]*$/)) {
 				this.tryTriggerAutocomplete();
 			}
 		}
@@ -1604,8 +1603,8 @@ export class Editor implements Component, Focusable {
 			if (this.isInSlashCommandContext(textBeforeCursor)) {
 				this.tryTriggerAutocomplete();
 			}
-			// @ file reference context
-			else if (textBeforeCursor.match(/(?:^|[\s])@[^\s]*$/)) {
+			// Symbol-based completion context like @ or #
+			else if (textBeforeCursor.match(/(?:^|[\s])[@#][^\s]*$/)) {
 				this.tryTriggerAutocomplete();
 			}
 		}
@@ -2108,10 +2107,13 @@ export class Editor implements Component, Focusable {
 		if (!this.autocompleteProvider) return;
 
 		if (options.force) {
-			const provider = this.autocompleteProvider as CombinedAutocompleteProvider;
 			const shouldTrigger =
-				!provider.shouldTriggerFileCompletion ||
-				provider.shouldTriggerFileCompletion(this.state.lines, this.state.cursorLine, this.state.cursorCol);
+				!this.autocompleteProvider.shouldTriggerFileCompletion ||
+				this.autocompleteProvider.shouldTriggerFileCompletion(
+					this.state.lines,
+					this.state.cursorLine,
+					this.state.cursorCol,
+				);
 			if (!shouldTrigger) {
 				return;
 			}
@@ -2162,8 +2164,8 @@ export class Editor implements Component, Focusable {
 
 		const currentLine = this.state.lines[this.state.cursorLine] || "";
 		const textBeforeCursor = currentLine.slice(0, this.state.cursorCol);
-		const isAttachmentContext = /(?:^|[ \t])@(?:"[^"]*|[^\s]*)$/.test(textBeforeCursor);
-		return isAttachmentContext ? ATTACHMENT_AUTOCOMPLETE_DEBOUNCE_MS : 0;
+		const isSymbolAutocompleteContext = /(?:^|[ \t])(?:@(?:"[^"]*|[^\s]*)|#[^\s]*)$/.test(textBeforeCursor);
+		return isSymbolAutocompleteContext ? ATTACHMENT_AUTOCOMPLETE_DEBOUNCE_MS : 0;
 	}
 
 	private async runAutocompleteRequest(

packages/tui/test/editor.test.ts

@@ -2132,6 +2132,39 @@ describe("Editor component", () => {
 			assert.strictEqual(editor.isShowingAutocomplete(), true);
 		});
 
+		it("debounces # autocomplete while typing", async () => {
+			const editor = new Editor(createTestTUI(), defaultEditorTheme);
+			let suggestionCalls = 0;
+
+			const mockProvider: AutocompleteProvider = {
+				getSuggestions: async (lines, _cursorLine, cursorCol) => {
+					suggestionCalls += 1;
+					const text = (lines[0] || "").slice(0, cursorCol);
+					return {
+						items: [{ value: "#2983", label: "#2983" }],
+						prefix: text,
+					};
+				},
+				applyCompletion,
+			};
+
+			editor.setAutocompleteProvider(mockProvider);
+
+			editor.handleInput("#");
+			editor.handleInput("2");
+			editor.handleInput("9");
+			editor.handleInput("8");
+
+			assert.strictEqual(suggestionCalls, 0);
+			assert.strictEqual(editor.isShowingAutocomplete(), false);
+
+			await new Promise((resolve) => setTimeout(resolve, 50));
+			await flushAutocomplete();
+
+			assert.strictEqual(suggestionCalls, 1);
+			assert.strictEqual(editor.isShowingAutocomplete(), true);
+		});
+
 		it("aborts active @ autocomplete when typing continues", async () => {
 			const editor = new Editor(createTestTUI(), defaultEditorTheme);
 			let aborts = 0;