diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 34e214b90..15ad4eaa6 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Breaking Changes
 
 - Renamed the bundled agent explore to scout, including its configuration keys, prompt files, and task definitions. Any configurations, allowlists, or invocations referencing explore must now use scout.
+- Changed the public `selectLaunchAdapter()` result from `DapResolvedAdapter | null` to `LaunchAdapterSelection`; callers must handle `adapter`, `unavailable`, and `none` outcomes.
 
 ### Added
 
@@ -12,6 +13,7 @@
 
 ### Fixed
 
+- Fixed Go debug launches falling back to native debuggers when Delve is unavailable; nested modules and `go.work` workspaces now resolve local Delve adapters before PATH, newly installed adapters are detected without restart, and missing adapter errors include install or configuration guidance. ([#5037](https://github.com/can1357/oh-my-pi/issues/5037))
 - Fixed a memory leak (large retained JavaScriptCore heaps) in the TUI during session transcript rebuilds and refreshes by properly handling snapcompact archive image frames.
 - Fixed a crash in interactive TUI sessions (Cannot set cwd while another same-realm JS runtime is running) when the JS evaluation worker falls back to the in-process inline path.
 - Fixed compaction aborting when Amazon Bedrock credential resolution fails, ensuring it now falls back to trying an authenticated model.
diff --git a/packages/coding-agent/src/dap/config.ts b/packages/coding-agent/src/dap/config.ts
index bb5748fd7..0aaa27eea 100644
--- a/packages/coding-agent/src/dap/config.ts
+++ b/packages/coding-agent/src/dap/config.ts
@@ -1,7 +1,7 @@
 import * as fs from "node:fs";
 import * as os from "node:os";
 import * as path from "node:path";
-import { isRecord, logger } from "@oh-my-pi/pi-utils";
+import { isRecord, logger, WhichCachePolicy } from "@oh-my-pi/pi-utils";
 import { YAML } from "bun";
 import { getConfigDirPaths } from "../config";
 import { getPreloadedPluginRoots } from "../discovery/helpers";
@@ -9,7 +9,7 @@ import { hasRootMarkers, resolveCommand } from "../lsp/config";
 import DEFAULTS from "./defaults.json" with { type: "json" };
 import type { DapAdapterConfig, DapResolvedAdapter } from "./types";
 
-const EXTENSIONLESS_DEBUGGER_ORDER = ["gdb", "lldb-dap"] as const;
+const EXTENSIONLESS_DEBUGGER_ORDER: readonly string[] = ["gdb", "lldb-dap"];
 
 interface NormalizedConfig {
 	adapters: Record<string, unknown>;
@@ -188,10 +188,18 @@ function resolveAdapterFromConfig(
 	adapterName: string,
 	configs: Record<string, DapAdapterConfig>,
 	cwd: string,
+	localRoots?: readonly string[],
 ): DapResolvedAdapter | null {
 	const config = configs[adapterName];
 	if (!config) return null;
-	const resolvedCommand = resolveCommand(normalizeCommandForCwd(config.command, cwd), cwd);
+	const normalizedCommand = normalizeCommandForCwd(config.command, cwd);
+	const commandIsBare =
+		!path.isAbsolute(config.command) && !config.command.includes("/") && !config.command.includes("\\");
+	const resolvedCommand = resolveCommand(normalizedCommand, cwd, {
+		cache: WhichCachePolicy.Fresh,
+		PATH: process.env.PATH,
+		localRoots: commandIsBare ? localRoots : undefined,
+	});
 	if (!resolvedCommand) return null;
 	return {
 		name: adapterName,
@@ -219,33 +227,125 @@ export function getAvailableAdapters(cwd: string): DapResolvedAdapter[] {
 		.filter((adapter): adapter is DapResolvedAdapter => adapter !== null);
 }
 
-function getMatchingAdapters(program: string, cwd: string): DapResolvedAdapter[] {
-	const extension = path.extname(program).toLowerCase();
-	const available = getAvailableAdapters(cwd);
-	if (!extension) {
-		// For extensionless binaries, only consider native debuggers (gdb, lldb-dap)
-		// or adapters that match by root markers. Don't silently fall back to
-		// unrelated adapters like debugpy for a C binary.
-		const nativeDebuggers: ReadonlySet<string> = new Set(EXTENSIONLESS_DEBUGGER_ORDER);
-		return available.filter(
-			adapter =>
-				nativeDebuggers.has(adapter.name) ||
-				(adapter.rootMarkers.length > 0 && hasRootMarkers(cwd, adapter.rootMarkers)),
-		);
-	}
-	const exactMatches = available.filter(adapter => adapter.fileTypes.includes(extension));
-	if (exactMatches.length > 0) {
-		return exactMatches;
-	}
-	return available;
+/** Launch adapter selection, including a configured adapter whose command is unavailable. */
+export type LaunchAdapterSelection =
+	| { kind: "adapter"; adapter: DapResolvedAdapter }
+	| { kind: "unavailable"; adapterName: string; command: string }
+	| { kind: "none" };
+
+interface LaunchAdapterCandidate {
+	name: string;
+	rootDir: string | null;
 }
 
-function sortAdaptersForLaunch(program: string, cwd: string, adapters: DapResolvedAdapter[]): DapResolvedAdapter[] {
+function findRootMarkerInLaunchAncestry(
+	program: string,
+	cwd: string,
+	markers: string[],
+	programKind: LaunchProgramKind,
+): string | null {
+	if (markers.length === 0) return null;
+	let dir = programKind === "directory" ? path.resolve(cwd, program) : path.dirname(path.resolve(cwd, program));
+	while (true) {
+		if (hasRootMarkers(dir, markers)) return dir;
+		const parent = path.dirname(dir);
+		if (parent === dir) return null;
+		dir = parent;
+	}
+}
+
+function resolveAdapterForLaunch(
+	adapterName: string,
+	configs: Record<string, DapAdapterConfig>,
+	cwd: string,
+	rootDir: string | null,
+): DapResolvedAdapter | null {
+	const localRoots = rootDir && rootDir !== cwd ? [rootDir, cwd] : undefined;
+	return resolveAdapterFromConfig(adapterName, configs, cwd, localRoots);
+}
+
+function unavailableAdapter(
+	candidate: LaunchAdapterCandidate,
+	configs: Record<string, DapAdapterConfig>,
+): LaunchAdapterSelection {
+	const config = configs[candidate.name];
+	if (!config) return { kind: "none" };
+	return { kind: "unavailable", adapterName: candidate.name, command: config.command };
+}
+
+function selectAutomaticLaunchAdapter(
+	program: string,
+	cwd: string,
+	programKind: LaunchProgramKind,
+	configs: Record<string, DapAdapterConfig>,
+): LaunchAdapterSelection {
+	const extension = path.extname(program).toLowerCase();
+	if (extension) {
+		const configured: LaunchAdapterCandidate[] = [];
+		const available: DapResolvedAdapter[] = [];
+		for (const name in configs) {
+			const config = configs[name];
+			if (!config || !(config.fileTypes ?? []).includes(extension)) continue;
+			const rootDir = findRootMarkerInLaunchAncestry(program, cwd, config.rootMarkers ?? [], programKind);
+			configured.push({ name, rootDir });
+			const adapter = resolveAdapterForLaunch(name, configs, cwd, rootDir);
+			if (adapter) available.push(adapter);
+		}
+		const selected = sortAdaptersForLaunch(program, cwd, programKind, available)[0];
+		if (selected) return { kind: "adapter", adapter: selected };
+		const rootMatch = configured.find(candidate => candidate.rootDir !== null);
+		const unavailable = rootMatch ?? configured[0];
+		if (unavailable) return unavailableAdapter(unavailable, configs);
+	}
+
+	const available: DapResolvedAdapter[] = [];
+	const rootMatches: LaunchAdapterCandidate[] = [];
+	const directoryMatches: LaunchAdapterCandidate[] = [];
+	for (const name in configs) {
+		const config = configs[name];
+		if (!config) continue;
+		const rootDir = findRootMarkerInLaunchAncestry(program, cwd, config.rootMarkers ?? [], programKind);
+		const candidate = { name, rootDir };
+		if (rootDir) {
+			rootMatches.push(candidate);
+			if (config.acceptsDirectoryProgram === true) directoryMatches.push(candidate);
+		}
+		if (!EXTENSIONLESS_DEBUGGER_ORDER.includes(name) && !rootDir) continue;
+		const adapter = resolveAdapterForLaunch(name, configs, cwd, rootDir);
+		if (adapter) available.push(adapter);
+	}
+
+	if (programKind === "directory" && directoryMatches.length > 0) {
+		const matchingNames = new Set(directoryMatches.map(candidate => candidate.name));
+		const directoryAdapters = available.filter(
+			adapter => adapter.acceptsDirectoryProgram && matchingNames.has(adapter.name),
+		);
+		const selected = sortAdaptersForLaunch(program, cwd, programKind, directoryAdapters)[0];
+		if (selected) return { kind: "adapter", adapter: selected };
+		const unavailable = directoryMatches[0];
+		return unavailable ? unavailableAdapter(unavailable, configs) : { kind: "none" };
+	}
+
+	const directoryAdapters =
+		programKind === "directory" ? available.filter(adapter => adapter.acceptsDirectoryProgram) : available;
+	const candidates = directoryAdapters.length > 0 ? directoryAdapters : available;
+	const selected = sortAdaptersForLaunch(program, cwd, programKind, candidates)[0];
+	if (selected) return { kind: "adapter", adapter: selected };
+	const unavailable = rootMatches[0];
+	return unavailable ? unavailableAdapter(unavailable, configs) : { kind: "none" };
+}
+
+function sortAdaptersForLaunch(
+	program: string,
+	cwd: string,
+	programKind: LaunchProgramKind,
+	adapters: DapResolvedAdapter[],
+): DapResolvedAdapter[] {
 	const extension = path.extname(program).toLowerCase();
 	const rootAware = adapters.map(adapter => ({
 		adapter,
 		hasExtensionMatch: extension.length > 0 && adapter.fileTypes.includes(extension),
-		hasRootMatch: adapter.rootMarkers.length > 0 && hasRootMarkers(cwd, adapter.rootMarkers),
+		hasRootMatch: findRootMarkerInLaunchAncestry(program, cwd, adapter.rootMarkers, programKind) !== null,
 	}));
 	rootAware.sort((left, right) => {
 		if (left.hasExtensionMatch !== right.hasExtensionMatch) {
@@ -254,36 +354,33 @@ function sortAdaptersForLaunch(program: string, cwd: string, adapters: DapResolv
 		if (left.hasRootMatch !== right.hasRootMatch) {
 			return left.hasRootMatch ? -1 : 1;
 		}
-		const leftDebuggerRank = EXTENSIONLESS_DEBUGGER_ORDER.indexOf(
-			left.adapter.name as (typeof EXTENSIONLESS_DEBUGGER_ORDER)[number],
-		);
-		const rightDebuggerRank = EXTENSIONLESS_DEBUGGER_ORDER.indexOf(
-			right.adapter.name as (typeof EXTENSIONLESS_DEBUGGER_ORDER)[number],
-		);
-		const normalizedLeftRank = leftDebuggerRank === -1 ? Number.MAX_SAFE_INTEGER : leftDebuggerRank;
-		const normalizedRightRank = rightDebuggerRank === -1 ? Number.MAX_SAFE_INTEGER : rightDebuggerRank;
-		if (normalizedLeftRank !== normalizedRightRank) {
-			return normalizedLeftRank - normalizedRightRank;
-		}
+		const leftRank = EXTENSIONLESS_DEBUGGER_ORDER.indexOf(left.adapter.name);
+		const rightRank = EXTENSIONLESS_DEBUGGER_ORDER.indexOf(right.adapter.name);
+		const normalizedLeftRank = leftRank === -1 ? Number.MAX_SAFE_INTEGER : leftRank;
+		const normalizedRightRank = rightRank === -1 ? Number.MAX_SAFE_INTEGER : rightRank;
+		const rankDelta = normalizedLeftRank - normalizedRightRank;
+		if (rankDelta !== 0) return rankDelta;
 		return left.adapter.name.localeCompare(right.adapter.name);
 	});
 	return rootAware.map(entry => entry.adapter);
 }
 
+/** Selects a launch adapter or reports why matching configuration cannot run. */
 export function selectLaunchAdapter(
 	program: string,
 	cwd: string,
 	adapterName?: string,
 	programKind: LaunchProgramKind = "file",
-): DapResolvedAdapter | null {
+): LaunchAdapterSelection {
+	const configs = getAdapterConfigs(cwd);
 	if (adapterName) {
-		return resolveAdapter(adapterName, cwd);
+		const config = configs[adapterName];
+		if (!config) return { kind: "none" };
+		const rootDir = findRootMarkerInLaunchAncestry(program, cwd, config.rootMarkers ?? [], programKind);
+		const adapter = resolveAdapterForLaunch(adapterName, configs, cwd, rootDir);
+		return adapter ? { kind: "adapter", adapter } : { kind: "unavailable", adapterName, command: config.command };
 	}
-	const matches = getMatchingAdapters(program, cwd);
-	const candidates =
-		programKind === "directory" ? matches.filter(adapter => adapter.acceptsDirectoryProgram) : matches;
-	const sorted = sortAdaptersForLaunch(program, cwd, candidates.length > 0 ? candidates : matches);
-	return sorted[0] ?? null;
+	return selectAutomaticLaunchAdapter(program, cwd, programKind, configs);
 }
 
 export function selectAttachAdapter(cwd: string, adapterName?: string, port?: number): DapResolvedAdapter | null {
diff --git a/packages/coding-agent/src/dap/defaults.json b/packages/coding-agent/src/dap/defaults.json
index 5ea74ef25..c33eb20ba 100644
--- a/packages/coding-agent/src/dap/defaults.json
+++ b/packages/coding-agent/src/dap/defaults.json
@@ -64,7 +64,7 @@
 		"connectMode": "socket",
 		"languages": ["go"],
 		"fileTypes": [".go"],
-		"rootMarkers": ["go.mod", "go.sum"],
+		"rootMarkers": ["go.mod", "go.sum", "go.work"],
 		"acceptsDirectoryProgram": true,
 		"launchDefaults": {
 			"request": "launch",
diff --git a/packages/coding-agent/src/lsp/config.ts b/packages/coding-agent/src/lsp/config.ts
index e9b650bd6..336c113ba 100644
--- a/packages/coding-agent/src/lsp/config.ts
+++ b/packages/coding-agent/src/lsp/config.ts
@@ -1,7 +1,7 @@
 import * as fs from "node:fs";
 import * as os from "node:os";
 import * as path from "node:path";
-import { $which, isRecord, logger, pathIsWithin } from "@oh-my-pi/pi-utils";
+import { $which, isRecord, logger, pathIsWithin, type WhichOptions } from "@oh-my-pi/pi-utils";
 import { YAML } from "bun";
 import { getConfigDirPaths } from "../config";
 import { type ClaudePluginRoot, getPreloadedPluginRoots } from "../discovery/helpers";
@@ -249,7 +249,7 @@ const LOCAL_BIN_PATHS: Array<{ markers: string[]; binDir: string }> = [
 	{ markers: ["Gemfile", "Gemfile.lock"], binDir: "vendor/bundle/bin" },
 	{ markers: ["Gemfile", "Gemfile.lock"], binDir: "bin" },
 	// Go - check project-local bin
-	{ markers: ["go.mod", "go.sum"], binDir: "bin" },
+	{ markers: ["go.mod", "go.sum", "go.work"], binDir: "bin" },
 ];
 
 const WINDOWS_LOCAL_EXECUTABLE_EXTENSIONS = [".exe", ".cmd", ".bat"] as const;
@@ -267,6 +267,21 @@ function resolveLocalCommand(basePath: string): string | null {
 	return null;
 }
 
+function resolveCommandFromLocalRoot(command: string, cwd: string): string | null {
+	for (const { markers, binDir } of LOCAL_BIN_PATHS) {
+		if (!hasRootMarkers(cwd, markers)) continue;
+		const resolved = resolveLocalCommand(path.join(cwd, binDir, command));
+		if (resolved) return resolved;
+	}
+	return null;
+}
+
+/** Controls project-local and PATH executable lookup. */
+export interface ResolveCommandOptions extends Pick<WhichOptions, "cache" | "PATH"> {
+	/** Ordered project roots checked before PATH; defaults to the command cwd. */
+	localRoots?: readonly string[];
+}
+
 /**
  * Resolve a command to an executable path.
  * Checks project-local bin directories first, then falls back to $PATH.
@@ -275,20 +290,19 @@ function resolveLocalCommand(basePath: string): string | null {
  * @param cwd - Working directory to search from
  * @returns Absolute path to the executable, or null if not found
  */
-export function resolveCommand(command: string, cwd: string): string | null {
-	// Check local bin directories based on project markers
-	for (const { markers, binDir } of LOCAL_BIN_PATHS) {
-		if (hasRootMarkers(cwd, markers)) {
-			const localPath = path.join(cwd, binDir, command);
-			const resolvedLocalPath = resolveLocalCommand(localPath);
-			if (resolvedLocalPath) {
-				return resolvedLocalPath;
-			}
+export function resolveCommand(command: string, cwd: string, options?: ResolveCommandOptions): string | null {
+	if (options?.localRoots) {
+		for (const root of options.localRoots) {
+			const resolved = resolveCommandFromLocalRoot(command, root);
+			if (resolved) return resolved;
 		}
+	} else {
+		const resolved = resolveCommandFromLocalRoot(command, cwd);
+		if (resolved) return resolved;
 	}
 
-	// Fall back to $PATH
-	return $which(command);
+	if (!options) return $which(command);
+	return $which(command, { cache: options.cache, PATH: options.PATH });
 }
 
 interface ConfigSource {
diff --git a/packages/coding-agent/src/prompts/tools/debug.md b/packages/coding-agent/src/prompts/tools/debug.md
index eddbabaa8..3412066ae 100644
--- a/packages/coding-agent/src/prompts/tools/debug.md
+++ b/packages/coding-agent/src/prompts/tools/debug.md
@@ -2,7 +2,7 @@ Debugger access.
 
 <instruction>
 - You SHOULD prefer this over bash for program state, breakpoints, stepping, thread inspection, or interrupting a running process.
-- `action: "launch"` starts a session; `program` required, `adapter` optional. Python: `adapter: "debugpy"`, `program` = target `.py`, interpreter/script flags in `args`.
+- `action: "launch"` starts a session; `program` required, `adapter` optional. Python: `program` = target `.py`, interpreter/script flags in `args`. Go: `program` = package directory, `.go` file, or compiled binary.
 - `action: "attach"` connects to a running process: `pid` (local), `port` (remote), `adapter` forces a specific debugger.
 - **Breakpoints**: `set_breakpoint`/`remove_breakpoint` with source (`file`+`line`) or function (`function`); optional `condition`.
 - **Flow control**: `continue` (resume), `step_over`/`step_in`/`step_out` (single-step), `pause` (interrupt a running program).
@@ -11,7 +11,7 @@ Debugger access.
 
 <caution>
 - Only one active debug session at a time.
-- Valid `adapter` values: `gdb`, `lldb-dap`, `python -m debugpy.adapter`, `dlv dap` (must be installed locally).
-- `program` must be an executable file or debug target, not a directory or bare interpreter name.
-- Python debugging requires `debugpy`; `pip install debugpy` if unavailable.
+- `adapter` is a configured id: `gdb`, `lldb-dap`, `debugpy`, `dlv`, `rdbg`, or any `dap.json` entry; its command must be installed.
+- `program` is a target path, not a shell command. Directories require a directory-capable adapter such as `dlv`.
+- Python requires `debugpy` (`pip install debugpy`); Go requires Delve (`go install github.com/go-delve/delve/cmd/dlv@latest`); Ruby requires `rdbg` (`gem install debug`).
 </caution>
diff --git a/packages/coding-agent/src/tools/debug.ts b/packages/coding-agent/src/tools/debug.ts
index 3d0680d37..690243120 100644
--- a/packages/coding-agent/src/tools/debug.ts
+++ b/packages/coding-agent/src/tools/debug.ts
@@ -31,6 +31,7 @@ import {
 	type DapThread,
 	type DapVariable,
 	dapSessionManager,
+	getAdapterConfigs,
 	getAvailableAdapters,
 	type LaunchProgramKind,
 	resolveLaunchOverrides,
@@ -50,6 +51,7 @@ import {
 	formatStatusIcon,
 	PREVIEW_LIMITS,
 	replaceTabs,
+	shortenPath,
 	TRUNCATE_LENGTHS,
 	truncateToWidth,
 } from "./render-utils";
@@ -106,9 +108,9 @@ const debugActionSchema = type.enumerated(
 );
 const debugSchema = type({
 	action: debugActionSchema,
-	"program?": type("string").describe("program path"),
+	"program?": type("string").describe("debug target path; Delve accepts Go package directories"),
 	"args?": type("string[]").describe("program arguments"),
-	"adapter?": type("string").describe("debugger adapter (gdb, lldb-dap, debugpy, dlv)"),
+	"adapter?": type("string").describe("configured adapter id (gdb, lldb-dap, debugpy, dlv, rdbg, or dap.json entry)"),
 	cwd: "string?",
 	"file?": type("string").describe("source file"),
 	"line?": type("number").describe("source line"),
@@ -494,7 +496,33 @@ function buildOutcomeText(outcome: DapContinueOutcome, timeoutSec: number, verb:
 
 function getConfiguredAdapters(cwd: string): string {
 	const adapters = getAvailableAdapters(cwd).map(adapter => adapter.name);
-	return adapters.length > 0 ? adapters.join(", ") : "none";
+	const names = adapters.length > 0 ? adapters.join(", ") : "none";
+	return truncateToWidth(replaceTabs(names), TRUNCATE_LENGTHS.LONG);
+}
+
+const ADAPTER_UNAVAILABLE_MESSAGES: Readonly<Record<string, string>> = {
+	debugpy: "adapter 'debugpy' is not available: python not found in PATH",
+	dlv: "adapter 'dlv' is not available: install with 'go install github.com/go-delve/delve/cmd/dlv@latest'",
+	rdbg: "adapter 'rdbg' is not available: install with 'gem install debug'",
+};
+
+const ADAPTER_CANONICAL_COMMANDS: Readonly<Record<string, string>> = {
+	debugpy: "python",
+	dlv: "dlv",
+	rdbg: "rdbg",
+};
+
+function formatAdapterUnavailable(adapterName: string, command: string, cwd: string): string {
+	const displayName = truncateToWidth(replaceTabs(adapterName), TRUNCATE_LENGTHS.SHORT);
+	const canonicalCommand = ADAPTER_CANONICAL_COMMANDS[adapterName] ?? adapterName;
+	if (command !== canonicalCommand) {
+		const displayCommand = truncateToWidth(replaceTabs(shortenPath(command)), TRUNCATE_LENGTHS.CONTENT);
+		return `adapter '${displayName}' is not available: configured command '${displayCommand}' did not resolve. Check the DAP adapter config for this workspace.`;
+	}
+	return (
+		ADAPTER_UNAVAILABLE_MESSAGES[adapterName] ??
+		`adapter '${displayName}' is not available. Installed adapters: ${getConfiguredAdapters(cwd)}`
+	);
 }
 
 async function classifyLaunchProgram(program: string): Promise<LaunchProgramKind> {
@@ -515,7 +543,7 @@ function validateLaunchProgram(
 	if (programKind !== "directory" || adapter.acceptsDirectoryProgram) return;
 	const displayPath = formatPathRelativeToCwd(program, cwd, { trailingSlash: true });
 	throw new ToolError(
-		`launch program resolves to a directory: ${displayPath}. Pass an executable file path, or for Python use adapter "debugpy" with program set to the .py file.`,
+		`launch program resolves to a directory: ${displayPath}. Pass an executable file path or choose an adapter that supports package directories.`,
 	);
 }
 
@@ -711,15 +739,16 @@ export class DebugTool implements AgentTool<typeof debugSchema, DebugToolDetails
 				const commandCwd = params.cwd ? resolveToCwd(params.cwd, this.session.cwd) : this.session.cwd;
 				const program = resolveToCwd(params.program, commandCwd);
 				const programKind = await classifyLaunchProgram(program);
-				const adapter = selectLaunchAdapter(program, commandCwd, params.adapter, programKind);
-				if (!adapter) {
-					if (params.adapter === "debugpy") {
-						throw new ToolError("adapter 'debugpy' is not available: python not found in PATH");
-					}
+				const selection = selectLaunchAdapter(program, commandCwd, params.adapter, programKind);
+				if (selection.kind === "unavailable") {
+					throw new ToolError(formatAdapterUnavailable(selection.adapterName, selection.command, commandCwd));
+				}
+				if (selection.kind === "none") {
 					throw new ToolError(
 						`No debugger adapter available. Installed adapters: ${getConfiguredAdapters(commandCwd)}`,
 					);
 				}
+				const { adapter } = selection;
 				validateLaunchProgram(program, commandCwd, programKind, adapter);
 				const extraLaunchArguments = resolveLaunchOverrides(adapter, program, programKind);
 				const snapshot = await dapSessionManager.launch(
@@ -738,8 +767,9 @@ export class DebugTool implements AgentTool<typeof debugSchema, DebugToolDetails
 				const commandCwd = params.cwd ? resolveToCwd(params.cwd, this.session.cwd) : this.session.cwd;
 				const adapter = selectAttachAdapter(commandCwd, params.adapter, params.port);
 				if (!adapter) {
-					if (params.adapter === "debugpy") {
-						throw new ToolError("adapter 'debugpy' is not available: python not found in PATH");
+					if (params.adapter) {
+						const command = getAdapterConfigs(commandCwd)[params.adapter]?.command ?? params.adapter;
+						throw new ToolError(formatAdapterUnavailable(params.adapter, command, commandCwd));
 					}
 					throw new ToolError(
 						`No debugger adapter available. Installed adapters: ${getConfiguredAdapters(commandCwd)}`,
diff --git a/packages/coding-agent/test/debug/dap-config.test.ts b/packages/coding-agent/test/debug/dap-config.test.ts
index a4940403e..665278ab9 100644
--- a/packages/coding-agent/test/debug/dap-config.test.ts
+++ b/packages/coding-agent/test/debug/dap-config.test.ts
@@ -2,7 +2,14 @@ import { afterEach, describe, expect, it, vi } from "bun:test";
 import * as fs from "node:fs/promises";
 import * as os from "node:os";
 import * as path from "node:path";
-import { getAdapterConfigs, resolveAdapter, selectLaunchAdapter } from "../../src/dap/config";
+import * as piUtils from "@oh-my-pi/pi-utils";
+import {
+	getAdapterConfigs,
+	type LaunchAdapterSelection,
+	resolveAdapter,
+	selectLaunchAdapter,
+} from "../../src/dap/config";
+import type { DapResolvedAdapter } from "../../src/dap/types";
 import { injectPluginDirRoots } from "../../src/discovery/helpers";
 
 const tempDirs: string[] = [];
@@ -15,6 +22,45 @@ async function makeTempDir(prefix: string): Promise<string> {
 	return cwd;
 }
 
+interface NestedGoProgram {
+	moduleRoot: string;
+	program: string;
+}
+
+async function writeExecutable(filePath: string): Promise<void> {
+	await fs.mkdir(path.dirname(filePath), { recursive: true });
+	await fs.writeFile(filePath, process.platform === "win32" ? "@echo off\r\n" : "#!/bin/sh\n");
+	await fs.chmod(filePath, 0o755);
+}
+
+async function writeDlvOverride(cwd: string, command: string): Promise<void> {
+	await fs.writeFile(path.join(cwd, "dap.json"), JSON.stringify({ adapters: { dlv: { command } } }));
+}
+
+async function setupMissingDlvProject(cwd: string): Promise<string> {
+	const missingCommand = path.join(cwd, "tools", "missing-dlv");
+	await fs.writeFile(path.join(cwd, "go.mod"), "module example.com/app\n\ngo 1.22\n");
+	await writeExecutable(path.join(cwd, "bin", "gdb"));
+	await writeDlvOverride(cwd, missingCommand);
+	return missingCommand;
+}
+
+async function setupNestedGoProgram(cwd: string): Promise<NestedGoProgram> {
+	const moduleRoot = path.join(cwd, "services", "api");
+	const program = path.join(moduleRoot, "main.go");
+	await fs.mkdir(moduleRoot, { recursive: true });
+	await fs.writeFile(path.join(moduleRoot, "go.mod"), "module example.com/api\n\ngo 1.22\n");
+	await fs.writeFile(program, "package main\n\nfunc main() {}\n");
+	return { moduleRoot, program };
+}
+
+function requireSelectedAdapter(selection: LaunchAdapterSelection): DapResolvedAdapter {
+	if (selection.kind !== "adapter") {
+		throw new Error(`Expected an available adapter, received '${selection.kind}'`);
+	}
+	return selection.adapter;
+}
+
 afterEach(async () => {
 	vi.restoreAllMocks();
 	if (ORIGINAL_OMP_PLUGIN_DIR === undefined) {
@@ -63,8 +109,8 @@ describe("DAP adapter configuration", () => {
 		expect(adapter?.launchDefaults).toEqual({ request: "launch", mainClass: "" });
 		expect(adapter?.attachDefaults).toEqual({ request: "attach", host: "127.0.0.1" });
 
-		const selected = selectLaunchAdapter(path.join("src", "Main.java"), cwd);
-		expect(selected?.name).toBe("custom-jvm");
+		const selected = requireSelectedAdapter(selectLaunchAdapter(path.join("src", "Main.java"), cwd));
+		expect(selected.name).toBe("custom-jvm");
 	});
 
 	it("merges partial user overrides over built-in adapters", async () => {
@@ -116,9 +162,9 @@ describe("DAP adapter configuration", () => {
 			].join("\n"),
 		);
 
-		const selected = selectLaunchAdapter("Main.kt", cwd);
-		expect(selected?.name).toBe("yaml-kotlin");
-		expect(selected?.launchDefaults).toEqual({ request: "launch", projectRoot: "." });
+		const selected = requireSelectedAdapter(selectLaunchAdapter("Main.kt", cwd));
+		expect(selected.name).toBe("yaml-kotlin");
+		expect(selected.launchDefaults).toEqual({ request: "launch", projectRoot: "." });
 	});
 
 	it("resolves relative adapter commands from the debug cwd", async () => {
@@ -195,4 +241,100 @@ describe("DAP adapter configuration", () => {
 		expect(config["missing-command"]).toBeUndefined();
 		expect(config.valid?.command).toBe("bun");
 	});
+
+	it("reports missing dlv for Go source instead of falling back to a native debugger", async () => {
+		const cwd = await makeTempDir("omp-dap-go-source-missing-");
+		const missingCommand = await setupMissingDlvProject(cwd);
+		const program = path.join(cwd, "main.go");
+		await fs.writeFile(program, "package main\n\nfunc main() {}\n");
+
+		const selection = selectLaunchAdapter(program, cwd);
+
+		expect(selection).toEqual({ kind: "unavailable", adapterName: "dlv", command: missingCommand });
+	});
+
+	it("reports missing dlv for Go package directories instead of selecting a native debugger", async () => {
+		const cwd = await makeTempDir("omp-dap-go-directory-missing-");
+		const missingCommand = await setupMissingDlvProject(cwd);
+		const program = path.join(cwd, "cmd", "server");
+		await fs.mkdir(program, { recursive: true });
+
+		const selection = selectLaunchAdapter(program, cwd, undefined, "directory");
+
+		expect(selection).toEqual({ kind: "unavailable", adapterName: "dlv", command: missingCommand });
+	});
+
+	it("prefers a nested module adapter over cwd and PATH for inferred launches", async () => {
+		const cwd = await makeTempDir("omp-dap-go-nested-local-");
+		const { moduleRoot, program } = await setupNestedGoProgram(cwd);
+		const nestedDlv = path.join(moduleRoot, "bin", "dlv");
+		await writeExecutable(nestedDlv);
+		await fs.writeFile(path.join(cwd, "go.mod"), "module example.com/repo\n\ngo 1.22\n");
+		await writeExecutable(path.join(cwd, "bin", "dlv"));
+		const whichSpy = vi.spyOn(piUtils, "$which").mockReturnValue(path.join(cwd, "global", "dlv"));
+
+		const selected = requireSelectedAdapter(selectLaunchAdapter(program, cwd));
+
+		expect(selected.resolvedCommand).toBe(nestedDlv);
+		expect(whichSpy).not.toHaveBeenCalled();
+	});
+
+	it("uses a nested module adapter when dlv is requested explicitly", async () => {
+		const cwd = await makeTempDir("omp-dap-go-nested-explicit-");
+		const { moduleRoot, program } = await setupNestedGoProgram(cwd);
+		const nestedDlv = path.join(moduleRoot, "bin", "dlv");
+		await writeExecutable(nestedDlv);
+		const whichSpy = vi.spyOn(piUtils, "$which").mockReturnValue(path.join(cwd, "global", "dlv"));
+
+		const selected = requireSelectedAdapter(selectLaunchAdapter(program, cwd, "dlv"));
+
+		expect(selected.resolvedCommand).toBe(nestedDlv);
+		expect(whichSpy).not.toHaveBeenCalled();
+	});
+
+	it("prefers the session cwd adapter over PATH after a nested-root miss", async () => {
+		const cwd = await makeTempDir("omp-dap-go-nested-cwd-");
+		const { program } = await setupNestedGoProgram(cwd);
+		const cwdDlv = path.join(cwd, "bin", "dlv");
+		await fs.writeFile(path.join(cwd, "go.mod"), "module example.com/repo\n\ngo 1.22\n");
+		await writeExecutable(cwdDlv);
+		const whichSpy = vi.spyOn(piUtils, "$which").mockReturnValue(path.join(cwd, "global", "dlv"));
+
+		const selected = requireSelectedAdapter(selectLaunchAdapter(program, cwd));
+
+		expect(selected.resolvedCommand).toBe(cwdDlv);
+		expect(whichSpy).not.toHaveBeenCalled();
+	});
+
+	it("resolves a local dlv for Go workspaces rooted by go.work", async () => {
+		const cwd = await makeTempDir("omp-dap-go-work-");
+		const program = path.join(cwd, "cmd", "worker");
+		const localDlv = path.join(cwd, "bin", "dlv");
+		await fs.writeFile(path.join(cwd, "go.work"), "go 1.22\n\nuse ./cmd/worker\n");
+		await fs.mkdir(program, { recursive: true });
+		await writeExecutable(localDlv);
+
+		const selected = requireSelectedAdapter(selectLaunchAdapter(program, cwd, undefined, "directory"));
+
+		expect(selected.resolvedCommand).toBe(localDlv);
+	});
+
+	it("re-resolves an adapter installed after an earlier miss", async () => {
+		const cwd = await makeTempDir("omp-dap-go-fresh-");
+		const program = path.join(cwd, "main.go");
+		const command = path.join(cwd, "tools", process.platform === "win32" ? "dlv.cmd" : "dlv");
+		await fs.writeFile(path.join(cwd, "go.mod"), "module example.com/cache\n\ngo 1.22\n");
+		await fs.writeFile(program, "package main\n\nfunc main() {}\n");
+		await writeDlvOverride(cwd, command);
+
+		expect(selectLaunchAdapter(program, cwd)).toEqual({
+			kind: "unavailable",
+			adapterName: "dlv",
+			command,
+		});
+
+		await writeExecutable(command);
+		const selected = requireSelectedAdapter(selectLaunchAdapter(program, cwd));
+		expect(selected.resolvedCommand).toBe(command);
+	});
 });
diff --git a/packages/coding-agent/test/debug/dap-launch-failures.test.ts b/packages/coding-agent/test/debug/dap-launch-failures.test.ts
index 6d02e49b7..6e1f63622 100644
--- a/packages/coding-agent/test/debug/dap-launch-failures.test.ts
+++ b/packages/coding-agent/test/debug/dap-launch-failures.test.ts
@@ -489,7 +489,10 @@ describe("DAP launch failure handling", () => {
 
 describe("DebugTool launch validation", () => {
 	it("rejects directory programs when the selected adapter cannot debug a directory", async () => {
-		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue(TEST_ADAPTER);
+		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue({
+			kind: "adapter",
+			adapter: TEST_ADAPTER,
+		});
 		try {
 			const cwd = await fs.mkdtemp(path.join(os.tmpdir(), "omp-debug-program-"));
 			try {
@@ -523,7 +526,10 @@ describe("DebugTool launch validation", () => {
 			launchDefaults: { request: "launch", mode: "debug", stopOnEntry: true },
 			acceptsDirectoryProgram: true,
 		};
-		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue(dlvAdapter);
+		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue({
+			kind: "adapter",
+			adapter: dlvAdapter,
+		});
 		const sessionLaunchSpy = spyOn(dapModule.dapSessionManager, "launch").mockImplementation(async opts => {
 			throw Object.assign(new Error("captured launch"), { capturedOptions: opts });
 		});
@@ -603,7 +609,10 @@ describe("DebugTool launch validation", () => {
 			launchDefaults: { request: "launch", mode: "debug", stopOnEntry: true },
 			acceptsDirectoryProgram: true,
 		};
-		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue(dlvAdapter);
+		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue({
+			kind: "adapter",
+			adapter: dlvAdapter,
+		});
 		const sessionLaunchSpy = spyOn(dapModule.dapSessionManager, "launch").mockImplementation(async opts => {
 			throw Object.assign(new Error("captured launch"), { capturedOptions: opts });
 		});
@@ -635,7 +644,11 @@ describe("DebugTool launch validation", () => {
 	});
 
 	it("throws targeted 'python not found in PATH' when adapter:'debugpy' is unresolvable for launch", async () => {
-		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue(null);
+		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue({
+			kind: "unavailable",
+			adapterName: "debugpy",
+			command: "python",
+		});
 		try {
 			const cwd = await fs.mkdtemp(path.join(os.tmpdir(), "omp-debug-debugpy-"));
 			try {
@@ -685,8 +698,93 @@ describe("DebugTool launch validation", () => {
 		}
 	});
 
+	it("shows the Delve install command when the canonical dlv adapter is unavailable", async () => {
+		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue({
+			kind: "unavailable",
+			adapterName: "dlv",
+			command: "dlv",
+		});
+		try {
+			const cwd = await fs.mkdtemp(path.join(os.tmpdir(), "omp-debug-dlv-hint-"));
+			try {
+				await fs.writeFile(path.join(cwd, "main.go"), "package main\n\nfunc main() {}\n");
+				const session: ToolSession = {
+					cwd,
+					hasUI: false,
+					getSessionFile: () => null,
+					getSessionSpawns: () => "*",
+					settings: Settings.isolated({ "debug.enabled": true }),
+				};
+				const tool = new DebugTool(session);
+
+				await expect(tool.execute("call", { action: "launch", program: "main.go" })).rejects.toThrow(
+					/go install github\.com\/go-delve\/delve\/cmd\/dlv@latest/,
+				);
+			} finally {
+				await removeWithRetries(cwd);
+			}
+		} finally {
+			launchSpy.mockRestore();
+		}
+	});
+
+	it("points to DAP configuration when a custom adapter command is unavailable", async () => {
+		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue({
+			kind: "unavailable",
+			adapterName: "dlv",
+			command: "./bin/missing-dlv",
+		});
+		try {
+			const cwd = await fs.mkdtemp(path.join(os.tmpdir(), "omp-debug-dlv-config-"));
+			try {
+				await fs.writeFile(path.join(cwd, "main.go"), "package main\n\nfunc main() {}\n");
+				const session: ToolSession = {
+					cwd,
+					hasUI: false,
+					getSessionFile: () => null,
+					getSessionSpawns: () => "*",
+					settings: Settings.isolated({ "debug.enabled": true }),
+				};
+				const tool = new DebugTool(session);
+
+				await expect(tool.execute("call", { action: "launch", program: "main.go" })).rejects.toThrow(
+					/configured command '\.\/bin\/missing-dlv' did not resolve.*DAP adapter config/,
+				);
+			} finally {
+				await removeWithRetries(cwd);
+			}
+		} finally {
+			launchSpy.mockRestore();
+		}
+	});
+
+	it("shows the rdbg install command for explicit Ruby attach", async () => {
+		const attachSpy = spyOn(dapModule, "selectAttachAdapter").mockReturnValue(null);
+		try {
+			const cwd = await fs.mkdtemp(path.join(os.tmpdir(), "omp-debug-rdbg-attach-"));
+			try {
+				const session: ToolSession = {
+					cwd,
+					hasUI: false,
+					getSessionFile: () => null,
+					getSessionSpawns: () => "*",
+					settings: Settings.isolated({ "debug.enabled": true }),
+				};
+				const tool = new DebugTool(session);
+
+				await expect(tool.execute("call", { action: "attach", pid: 1234, adapter: "rdbg" })).rejects.toThrow(
+					/gem install debug/,
+				);
+			} finally {
+				await removeWithRetries(cwd);
+			}
+		} finally {
+			attachSpy.mockRestore();
+		}
+	});
+
 	it("falls back to the generic 'No debugger adapter' error when adapter is unspecified", async () => {
-		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue(null);
+		const launchSpy = spyOn(dapModule, "selectLaunchAdapter").mockReturnValue({ kind: "none" });
 		try {
 			const cwd = await fs.mkdtemp(path.join(os.tmpdir(), "omp-debug-noadapter-"));
 			try {