refactor: remove dead descriptor-driven mechanisms (no remaining consumer)

Drop code whose only consumer was a retired runtime: hostBehaviors readers for
agentFileExtension, localTargetIsProjectRoot, sharedHooksDirName,
skillsManifestPrefix and skipCodexSkillsManifest; the empty
NON_REGISTRY_CONFIG_HOME_DESCRIPTORS array and live-config-guard plumbing; the
empty RUNTIME_NOTE_AUDIENCE_BY_HEADING filter; the unused resolveVersionFrom
export; and the WINDSURF_SESSION_ID workstream session key. Delete tests that
only exercised those mechanisms.

src/active-workstream-store.cts

@@ -33,7 +33,6 @@ const WORKSTREAM_SESSION_ENV_KEYS: ReadonlyArray<string> = [
   'OPENCODE_SESSION_ID',
   'GEMINI_SESSION_ID',
   'CURSOR_SESSION_ID',
-  'WINDSURF_SESSION_ID',
   'TERM_SESSION_ID',
   'WT_SESSION',
   'TMUX_PANE',

src/agent-install-check.cts

@@ -159,17 +159,10 @@ function getAgentsDir(runtime?: string, projectRoot?: string): string {
     return installRelative;
   }
   if (projectRoot) {
-    // eslint-disable-next-line @typescript-eslint/no-require-imports
-    const { runtimes } = require('./capability-registry.cjs') as {
-      runtimes: Record<string, { runtime?: { hostBehaviors?: { localTargetIsProjectRoot?: boolean } } }>;
-    };
-    const runtimeConfig = runtimes[resolved]?.runtime;
     const localConfigDirName = getDirName(resolved);
     const localConfigDir = localConfigDirName === NO_LOCAL_CONFIG_DIR_SENTINEL
       ? undefined
-      : runtimeConfig?.hostBehaviors?.localTargetIsProjectRoot
-        ? projectRoot
-        : path.join(projectRoot, localConfigDirName);
+      : path.join(projectRoot, localConfigDirName);
     if (!localConfigDir) {
       return path.join(getGlobalConfigDir(resolved), 'agents');
     }

src/install-engine.cts

@@ -789,13 +789,7 @@ function _copyStaged(stagedDir: string, destDir: string, kind: any, configDir: s
     let destName: string;
     if (kind.kind === 'agents') {
       // Agent files already carry the msd- prefix in the source dir.
-      // #2099: descriptor-driven via hostBehaviors.agentFileExtension. No
-      // current runtime declares one, so destName falls back to entry.name
-      // unchanged (byte-parity, #1575 origin comment).
-      const _agentExt = runtime ? _hostBehaviors(runtime).agentFileExtension : undefined;
-      destName = _agentExt
-        ? entry.name.replace(/\.md$/, _agentExt)
-        : entry.name;
+      destName = entry.name;
     } else {
       // Commands: filename composition (namespacedByDir ? `${stem}.md` :
       // `${prefix}${stem}.md`) is single-sourced with resolveTriggerSurface's
@@ -1919,7 +1913,7 @@ function installOpencodeFamilyArtifacts(
     homeDir: posixNormalize(os.homedir()),
     // #4377: the runtime's own localConfigDir, so an opted-in local install
     // emits `<dir>/...` instead of this checkout's absolute path.
-    localDirName: runtimeArtifactConversion._localIncludeDirName(runtime),
+    localDirName: getDirName(runtime),
   });
 
   // #2329: destDir is derived from the SAME hostBehaviors.flatCommandDir

src/runtime-artifact-conversion.cts

@@ -18,7 +18,6 @@
 
 import path from 'node:path';
 import os from 'node:os';
-import fs from 'node:fs';
 // #2874 (ADR-58 cleanup phase): route this module's content-rewrite-pass fs
 // calls through the installRuntimeArtifacts call tree's injectable seam —
 // see install-fs-adapter.cts's module doc. Resolves to real `node:fs` unless
@@ -49,40 +48,6 @@ import { isGlobalScope } from './install-scope.cjs';
 import installEffortResolver = require('./install-effort-resolver.cjs');
 const { readMsdEffectiveEffortConfig, resolveInstallTimeEffort, _getMsdEffortCatalog } = installEffortResolver;
 
-// #1383: resolve MSD's version WITHOUT a top-level
-// `require('../../../package.json')`. That require ran at module load on every
-// msd-tools invocation (this module sits in the msd-tools loader chain) and
-// threw `Cannot find module '../../../package.json'` on runtimes whose root has
-// no package.json — originally just Codex, where the installer never wrote the
-// synthetic root package.json; since #2544 that is true of EVERY runtime, as
-// MSD's markers moved into `hooks/` and the native plugin dir and the config
-// root is no longer written at all — taking the entire CLI down before it did
-// anything. And even where it used to resolve (the synthetic
-// `{"type":"commonjs"}`), there is no `version` field, so the single consumer
-// below already emitted `version: undefined`. Resolve lazily and defensively
-// instead:
-//   1. Installed trees carry <root>/msd-core/VERSION (written by the installer);
-//      this module lives at <root>/msd-core/bin/lib, so VERSION is two dirs up.
-//   2. The source / npm-package tree has no msd-core/VERSION but carries a real
-//      package.json three dirs up — read it lazily, never at module-load time.
-// A failed/invalid lookup degrades to '' (the caller omits the field) rather
-// than crashing or emitting `version: undefined`. Both sources are validated
-// against the same semver shape the repo's other VERSION reader enforces
-// (src/update-context.cts) so a garbled VERSION file is never emitted verbatim.
-// Exported for the #1383 regression (no in-module consumer remains).
-const SEMVER_PREFIX = /^\d+\.\d+\.\d+/; // mirrors src/update-context.cts SEMVER_PREFIX
-function resolveVersionFrom(libDir: string): string {
-  try {
-    const v = fs.readFileSync(path.join(libDir, '..', '..', 'VERSION'), 'utf8').trim();
-    if (SEMVER_PREFIX.test(v)) return v;
-  } catch { /* not an installed tree (no msd-core/VERSION) */ }
-  try {
-    const pkg = require(path.join(libDir, '..', '..', '..', 'package.json'));
-    if (pkg && typeof pkg.version === 'string' && SEMVER_PREFIX.test(pkg.version)) return pkg.version;
-  } catch { /* runtime root has no package.json (e.g. Codex) */ }
-  return '';
-}
-
 /**
  * Host-specific install behaviors declared on the runtime descriptor
  * (capabilities/<runtime>/capability.json -> runtime.hostBehaviors). Mirrors
@@ -104,19 +69,6 @@ function _hostBehaviors(runtime: string): Record<string, unknown> {
   );
 }
 
-/**
- * Public accessor for the `hostBehaviors.agentFileExtension` descriptor field
- * (ADR-1239 / #2099 / #2103). Returns the runtime's declared agent-file
- * destination-suffix rename target, or `undefined` when the runtime declares
- * none (the generic no-rename default). Exported so callers outside this
- * module (surface.cts's `_syncMsdDir`) can derive the SAME rename decision as
- * install-engine.cts's staged-copy loop from ONE descriptor read (#2103 fold).
- */
-function agentFileExtensionFor(runtime: string): string | undefined {
-  const ext = _hostBehaviors(runtime).agentFileExtension;
-  return typeof ext === 'string' ? ext : undefined;
-}
-
 
 const colorNameToHex = {
   cyan: '#00FFFF',
@@ -874,24 +826,11 @@ function frontmatterScalar(key: string, value: string): string {
     : `${key} ${value}`;
 }
 
-// Bold `**<Runtime>:**` section headings inside a `<runtime_note>` that are
-// scoped to one runtime. Empty today — every runtime that declared one has
-// been retired — but the filter below still honours the map so a future
-// runtime-scoped heading can be added without touching the parser.
-const RUNTIME_NOTE_AUDIENCE_BY_HEADING = new Map<string, string>([]);
-
 function filterRuntimeNotesForTarget(content: string, targetRuntime: string): string {
   return content.replace(/<runtime_note(?:\s+runtime=["']([^"']+)["'])?>([\s\S]*?)<\/runtime_note>/g,
     (whole, declaredAudience: string | undefined, inner: string) => {
     if (declaredAudience && declaredAudience.toLowerCase() !== targetRuntime) return '';
-    const remaining = inner.replace(
-      /(?:^|\n)[ \t]*\*\*([^*\n]+):\*\*[^\n]*(?:\n(?![ \t]*\n)[^\n]*)*/g,
-      (section, heading: string) => {
-        const audience = RUNTIME_NOTE_AUDIENCE_BY_HEADING.get(heading.trim().toLowerCase());
-        return audience && audience !== targetRuntime ? '' : section;
-      },
-    );
-    const body = remaining.trim();
+    const body = inner.trim();
     return body ? `<runtime_note>\n${body}\n</runtime_note>` : '';
   });
 }
@@ -1456,14 +1395,6 @@ function projectRelativePrefixFromProjectRoot(projectRoot: unknown, resolvedTarg
   return projectRelativePrefix(relative);
 }
 
-/**
- * A runtime installed directly at the project root cannot use its descriptor
- * directory in a project-relative include: that directory was never created.
- */
-function localIncludeDirName(runtime: string): string | undefined {
-  return _hostBehaviors(runtime).localTargetIsProjectRoot === true ? undefined : getDirName(runtime);
-}
-
 /**
  * #4377: the project-relative prefix for a local install, or `''` when the
  * runtime cannot express one and the caller must fall back to absolute.
@@ -1982,7 +1913,7 @@ function rewriteStagedSkillBodies(stagedDir, opts) {
   const isWindowsHost = platform === 'win32';
   // #4377: localDirName lets a local install emit a project-relative prefix
   // when opted in; ignored for a global install and when the opt-in is off.
-  const pathPrefix = computePathPrefix({ isGlobal, isOpencode, isWindowsHost, resolvedTarget, homeDir, localDirName: localIncludeDirName(runtime) });
+  const pathPrefix = computePathPrefix({ isGlobal, isOpencode, isWindowsHost, resolvedTarget, homeDir, localDirName: getDirName(runtime) });
   const attribution = resolveAttribution ? resolveAttribution(runtime) : undefined;
 
   applyRuntimeContentRewritesInPlace(stagedDir, runtime, pathPrefix, isGlobal, attribution);
@@ -2036,7 +1967,7 @@ function rewriteStagedCommandBodies(stagedDir, opts) {
   const isWindowsHost = platform === 'win32';
   // #4377: localDirName lets a local install emit a project-relative prefix
   // when opted in; ignored for a global install and when the opt-in is off.
-  const pathPrefix = computePathPrefix({ isGlobal, isOpencode, isWindowsHost, resolvedTarget, homeDir, localDirName: localIncludeDirName(runtime) });
+  const pathPrefix = computePathPrefix({ isGlobal, isOpencode, isWindowsHost, resolvedTarget, homeDir, localDirName: getDirName(runtime) });
   const attribution = resolveAttribution ? resolveAttribution(runtime) : undefined;
 
   return applyRuntimeContentRewritesForCommandsInPlace(stagedDir, runtime, pathPrefix, isGlobal, attribution);
@@ -2305,10 +2236,6 @@ function processAttribution(
 export = {
   processAttribution,
   appendAgentTools,
-  // #2103: public accessor for hostBehaviors.agentFileExtension, exported so
-  // surface.cts's _syncMsdDir can derive any agent-file rename from the SAME
-  // descriptor read as install-engine.cts.
-  agentFileExtensionFor,
   yamlIdentifier,
   yamlQuote,
   toSingleLine,
@@ -2345,9 +2272,6 @@ export = {
   _splitToolScalars: splitToolScalars,
   readMsdCommandNames,
   transformContentToHyphen,
-  // #1383: version resolver (exported for regression test of the Codex
-  // missing-package.json crash + the VERSION-file source of truth).
-  resolveVersionFrom,
   // #1182: agent converters + tool-name table dependency closure
   claudeToAntigravityTools,
   convertAntigravityToolName,
@@ -2384,7 +2308,6 @@ export = {
   _relativeIncludesEnabled: relativeIncludesEnabled,
   _projectRelativePrefix: projectRelativePrefix,
   _projectRelativePrefixFromProjectRoot: projectRelativePrefixFromProjectRoot,
-  _localIncludeDirName: localIncludeDirName,
   _restoreClaudeGlobalAtRefTilde: restoreClaudeGlobalAtRefTilde,
   _applyRuntimeRewrites,
   _stampNonClaudeRuntimeDefaults,

src/runtime-artifact-install-plan.cts

@@ -12,6 +12,7 @@
 const _require: NodeRequire = require;
 const path = _require('node:path') as typeof import('node:path');
 const { tryWithinRootLexical } = _require('./security.cjs') as typeof import('./security.cjs');
+const { getDirName } = _require('./runtime-name-policy.cjs') as typeof import('./runtime-name-policy.cjs');
 
 // #2870: InstallScope is owned by install-scope.cts, not re-declared here.
 // `isGlobalScope` centralizes the `scope === 'global'` boolean projection
@@ -93,7 +94,6 @@ interface RuntimeArtifactConversionExports {
   rewriteStagedSkillBodies: (stagedDir: string, opts: RewriteOpts) => string | void;
   rewriteStagedCommandBodies: (stagedDir: string, opts: RewriteOpts) => string | void;
   _computePathPrefix: (opts: ComputePathPrefixOpts) => string;
-  _localIncludeDirName: (runtime: string) => string | undefined;
 }
 
 interface PlanItem {
@@ -222,7 +222,7 @@ function createRuntimeArtifactInstallPlan(args: CreateRuntimeArtifactInstallPlan
   const isWindowsHost = (platform ?? process.platform) === 'win32';
   // #4377: descriptor-derived local dir name, so an opted-in local install
   // emits a project-relative prefix instead of this checkout's absolute path.
-  const pathPrefix = conversionExports._computePathPrefix({ isGlobal, isOpencode, isWindowsHost, resolvedTarget, homeDir, localDirName: conversionExports._localIncludeDirName(layout.runtime) });
+  const pathPrefix = conversionExports._computePathPrefix({ isGlobal, isOpencode, isWindowsHost, resolvedTarget, homeDir, localDirName: getDirName(layout.runtime) });
   const attribution = resolveAttribution ? resolveAttribution(layout.runtime) : undefined;
   // #2875 Part 2 (row I1): layout.configDir IS the install root the inline
   // agent loop called `targetDir` — same value, same resolution.

src/runtime-homes.cts

@@ -410,16 +410,6 @@ export function detectAntigravityDirAmbiguity(
   };
 }
 
-/**
- * Config-home descriptors resolved OUTSIDE the capability registry.
- *
- * Anything added here is picked up by every derived consumer in the same commit —
- * which is the property that makes the derivation structurally incapable of being
- * narrower than the surface it guards. Adding a hardcoded resolver WITHOUT adding
- * its descriptor here is the defect this array exists to make hard.
- */
-export const NON_REGISTRY_CONFIG_HOME_DESCRIPTORS: ConfigHomeDescriptor[] = [];
-
 /**
  * MSD's OWN location vars — a second family, not runtime configHomes.
  *

src/surface.cts

@@ -63,6 +63,7 @@ import type { ClusterMap } from './clusters.cjs';
 import { isGlobalScope } from './install-scope.cjs';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import runtimeArtifactLayout = require('./runtime-artifact-layout.cjs');
+import { getDirName } from './runtime-name-policy.cjs';
 const { findInstallSourceRoot } = runtimeArtifactLayout;
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import runtimeArtifactConversion = require('./runtime-artifact-conversion.cjs');
@@ -425,7 +426,7 @@ function applySurface(runtimeConfigDir: string, layout: Layout, manifest: Map<st
   // A later msd-tools surface apply runs in another process, so it must reuse
   // the persisted, root-relative prefix the installer actually emitted.
   const _relativeIncludePrefix = readRelativeIncludePrefix(runtimeConfigDir);
-  const _pathPrefix = runtimeArtifactConversion._computePathPrefix({ isGlobal: _isGlobal, isOpencode: _isOpencode, isWindowsHost: _isWindowsHost, resolvedTarget: _resolvedTarget, homeDir: _homeDir, projectRelative: !_isGlobal && typeof _relativeIncludePrefix === 'string', projectRelativePath: _relativeIncludePrefix, localDirName: runtimeArtifactConversion._localIncludeDirName(layout.runtime) });
+  const _pathPrefix = runtimeArtifactConversion._computePathPrefix({ isGlobal: _isGlobal, isOpencode: _isOpencode, isWindowsHost: _isWindowsHost, resolvedTarget: _resolvedTarget, homeDir: _homeDir, projectRelative: !_isGlobal && typeof _relativeIncludePrefix === 'string', projectRelativePath: _relativeIncludePrefix, localDirName: getDirName(layout.runtime) });
   const _attribution = opts?.resolveAttribution ? opts.resolveAttribution(layout.runtime) : undefined;
   // #2875 Part 2 (row I1): layout.configDir is this call's install root.
   const agentCtx: AgentCtx = { runtime: layout.runtime, pathPrefix: _pathPrefix, attribution: _attribution, targetDir: layout.configDir };
@@ -495,7 +496,7 @@ function applySurface(runtimeConfigDir: string, layout: Layout, manifest: Map<st
     // and the persisted surface state untouched.
     retiredArtifactCleanup.pruneRetiredRuntimeArtifacts(layout.runtime, layout.configDir);
     for (const item of stagedKinds) {
-      _syncMsdDir(item.staged, item.dest, item.kind, skillManifest, layout.runtime);
+      _syncMsdDir(item.staged, item.dest, item.kind, skillManifest);
     }
 
     if (hasCandidateState) {
@@ -642,7 +643,7 @@ function pruneSkillDirs(skillsDir: string, retainedNames: Set<string>, prefix: s
  * user-owned dirs. MSD-owned = stem in manifest; removal targets = in manifest AND
  * not in staged set. User-owned (not in manifest) are always preserved.
  */
-function _syncMsdDir(stagedDir: string, destDir: string, kind: ArtifactKind | string, manifest?: Map<string, string[]>, runtime?: string): void {
+function _syncMsdDir(stagedDir: string, destDir: string, kind: ArtifactKind | string, manifest?: Map<string, string[]>): void {
   if (!fs.existsSync(stagedDir)) return;
   fs.mkdirSync(destDir, { recursive: true });
 
@@ -650,15 +651,6 @@ function _syncMsdDir(stagedDir: string, destDir: string, kind: ArtifactKind | st
   const kindName = (typeof kind === 'string') ? kind : kind.kind;
   const kindPrefix = (typeof kind === 'object' && kind !== null) ? kind.prefix : 'msd-';
 
-  // #1575 / #2103: agent files are renamed .md -> <agentFileExtension> at copy
-  // time when the runtime's descriptor declares hostBehaviors.agentFileExtension
-  // mirroring install-engine.cts's staged-copy loop (`_copyStaged`) — ONE
-  // descriptor read shared by both surfaces. Runtimes with no
-  // agentFileExtension declared (all of them today) keep the staged filename
-  // verbatim.
-  const _agentExt = runtime ? runtimeArtifactConversion.agentFileExtensionFor(runtime) : undefined;
-  const isRenamedAgents = !!_agentExt && kindName === 'agents';
-
   if (kindName === 'skills') {
     // Skills kind: work with directories, not files.
     // Each staged entry is a directory named ${prefix}${stem}.
@@ -695,11 +687,9 @@ function _syncMsdDir(stagedDir: string, destDir: string, kind: ArtifactKind | st
     const stagedFiles = fs.readdirSync(stagedDir).filter(f => f.endsWith('.md'));
     const stagedDestNames = new Set<string>();
     for (const file of stagedFiles) {
-      const destName = isRenamedAgents
-        ? file.replace(/\.md$/, _agentExt)
-        : (kindName === 'agents' || namespacedByDir)
-          ? file
-          : `${kindPrefix}${file.slice(0, -3)}.md`;
+      const destName = (kindName === 'agents' || namespacedByDir)
+        ? file
+        : `${kindPrefix}${file.slice(0, -3)}.md`;
       fs.copyFileSync(path.join(stagedDir, file), path.join(destDir, destName));
       stagedDestNames.add(destName);
     }