diff --git a/.changeset/2097-eos-augment-imperative-adapter.md b/.changeset/2097-eos-augment-imperative-adapter.md
new file mode 100644
index 000000000..fe67b40f2
--- /dev/null
+++ b/.changeset/2097-eos-augment-imperative-adapter.md
@@ -0,0 +1,6 @@
+---
+type: Changed
+pr: 2166
+---
+
+**Augment Code now installs through its capability descriptor, with a native MCP companion** — installing GSD into Augment registers the GSD companion server in Augment's `settings.json` `mcpServers` and drives command/skill/agent conversion from Augment's negotiated descriptor instead of hardcoded runtime special-cases. (#2097)
diff --git a/bin/install.js b/bin/install.js
index c5bfdb513..027c6c8c6 100755
--- a/bin/install.js
+++ b/bin/install.js
@@ -2606,14 +2606,6 @@ function convertClaudeAgentToWindsurfAgent(content) {
 // Augment uses a tool set similar to Cursor/Windsurf.
 // Config lives in .augment/ (local) and ~/.augment/ (global).
 
-const claudeToAugmentTools = {
-  Bash: 'launch-process',
-  Edit: 'str-replace-editor',
-  AskUserQuestion: null,
-  SlashCommand: null,
-  TodoWrite: 'add_tasks',
-};
-
 // #1675 (ADR-1508): the augment converter family below was a byte-identical
 // duplicate of runtime-artifact-conversion.cjs:
 //   convertSlashCommandsToAugmentSkillMentions, convertClaudeToAugmentMarkdown,
@@ -7546,6 +7538,21 @@ function uninstall(isGlobal, runtime = DEFAULT_RUNTIME) {
       }
     }
 
+    // #2097 UPGRADE 3 — Remove the MCP companion entry from settings.json for
+    // runtimes that host MCP there (Augment), symmetric to the mcp_config.json
+    // removal for Antigravity below. Only the GSD-owned mcpServers.gsd key is
+    // removed — any other user-configured MCP servers are preserved.
+    if (_hostBehaviors(runtime).mcpCompanion === 'settings-json' &&
+      settings.mcpServers && typeof settings.mcpServers === 'object' &&
+      settings.mcpServers.gsd !== undefined) {
+      delete settings.mcpServers.gsd;
+      if (Object.keys(settings.mcpServers).length === 0) {
+        delete settings.mcpServers;
+      }
+      settingsModified = true;
+      console.log(`  ${green}✓${reset} Removed GSD MCP companion server from settings.json`);
+    }
+
     if (settingsModified) {
       writeSettings(settingsPath, settings);
       removedCount++;
@@ -8078,6 +8085,27 @@ function configureAntigravityMcpConfig(isGlobal = true, configDir = null) {
   console.log(`  ${green}✓${reset} Configured Antigravity MCP companion server (gsd)`);
 }
 
+/**
+ * #2097 (ADR-1239 transport:mcp): register the GSD companion MCP server inside a
+ * runtime's settings.json (Augment hosts MCP in settings.json.mcpServers, unlike
+ * Antigravity's standalone mcp_config.json). Mutates the in-memory settings object
+ * that finishInstall already writes — non-destructive + idempotent: only sets
+ * mcpServers.gsd, preserving any user-defined servers (a user's own `gsd` override
+ * is respected — Hyrum's Law).
+ * @param {object} settings - the in-memory settings object finishInstall will write
+ */
+function mergeGsdMcpServerIntoSettings(settings) {
+  if (!settings.mcpServers || typeof settings.mcpServers !== 'object' || Array.isArray(settings.mcpServers)) {
+    settings.mcpServers = {};
+  }
+  if (settings.mcpServers.gsd === undefined) {
+    settings.mcpServers.gsd = {
+      command: 'npx',
+      args: ['-y', '-p', PACKAGE_NAME, 'gsd-mcp-server'],
+    };
+  }
+}
+
 /**
  * Verify a directory exists and contains files
  */
@@ -9643,10 +9671,6 @@ function install(isGlobal, runtime = DEFAULT_RUNTIME, options = {}) {
           content = convertClaudeAgentToCopilotAgent(content, isGlobal);
         } else if (isWindsurf) {
           content = convertClaudeAgentToWindsurfAgent(content);
-        } else if (isAugment) {
-          content = convertClaudeAgentToAugmentAgent(content);
-        } else if (isTrae) {
-          content = convertClaudeAgentToTraeAgent(content);
         } else if (isCodebuddy) {
           content = convertClaudeAgentToCodebuddyAgent(content);
         } else if (_hostBehaviors(runtime).frontmatterDialect === 'cline') {
@@ -10918,6 +10942,12 @@ function finishInstall(settingsPath, settings, statuslineCommand, shouldInstallS
     mergeClaudePermissions(settings);
   }
 
+  // #2097 UPGRADE 3 (transport:mcp): companion MCP server for runtimes that host
+  // MCP in settings.json (Augment). settings.json is golden-excluded, so no golden change.
+  if (_hostBehaviors(runtime).mcpCompanion === 'settings-json' && settings && plan.writesSharedSettings) {
+    mergeGsdMcpServerIntoSettings(settings);
+  }
+
   // Write settings when runtime supports settings.json.
   // #3002 CR: defense-in-depth — re-run validateHookFields right before
   // serialization. The push-site guards above already skip null-command
@@ -11930,6 +11960,8 @@ module.exports = {
     buildAntigravityAllowRules,
     configureAntigravityPermissions,
     configureAntigravityMcpConfig,
+    // #2097 UPGRADE 3 — Augment MCP companion (settings.json-hosted)
+    mergeGsdMcpServerIntoSettings,
     claudeToCopilotTools,
     convertCopilotToolName,
     convertClaudeToCopilotContent,
diff --git a/capabilities/augment/capability.json b/capabilities/augment/capability.json
index a7e7c5683..a712d16f2 100644
--- a/capabilities/augment/capability.json
+++ b/capabilities/augment/capability.json
@@ -82,6 +82,10 @@
     "writesSharedSettings": true,
     "permissionWriter": null,
     "extendedHookEvents": [],
+    "hostBehaviors": {
+      "commandBodyConverter": "convertClaudeToAugmentMarkdown",
+      "mcpCompanion": "settings-json"
+    },
     "hostIntegration": {
       "embeddingMode": "declarative",
       "commandSurface": "slash-file",
diff --git a/docs/how-to/connect-gsd-mcp-server.md b/docs/how-to/connect-gsd-mcp-server.md
index 37cbbed89..468289f8a 100644
--- a/docs/how-to/connect-gsd-mcp-server.md
+++ b/docs/how-to/connect-gsd-mcp-server.md
@@ -1,7 +1,8 @@
 # How to connect a host to the GSD companion MCP server
 
 This guide shows you how to make a MCP-capable host (Claude Code, Codex,
-OpenCode, VS Code, Antigravity CLI, Cursor, Cline, Hermes) drive GSD — run GSD
+OpenCode, VS Code, Antigravity CLI, Cursor, Cline, Hermes, Augment Code) drive
+GSD — run GSD
 commands and read/write `.planning/` state — through the companion MCP server,
 with no bespoke plugin.
 
@@ -28,6 +29,11 @@ host.
 
 - **Claude Code / Codex / Cursor / Cline / Hermes** — under the host's
   `mcpServers` object (project or user config).
+- **Augment Code** — under the `mcpServers` block of its own
+  `settings.json` (not a standalone MCP config file, unlike Antigravity)
+  — global at `~/.augment/settings.json`, project-local at
+  `.augment/settings.json`. GSD's installer configures this entry
+  automatically (`--augment` installs).
 - **VS Code** — in the workspace MCP servers list.
 - **Antigravity** — under the `mcpServers` block of its standalone
   `mcp_config.json` profile (not embedded in `settings.json`) — global at
diff --git a/docs/how-to/install-on-your-runtime.md b/docs/how-to/install-on-your-runtime.md
index 6835d0e00..70fc779f6 100644
--- a/docs/how-to/install-on-your-runtime.md
+++ b/docs/how-to/install-on-your-runtime.md
@@ -397,7 +397,7 @@ Qwen Code supports 15 hook events. GSD registers the following events automatica
 npx @opengsd/gsd-core@latest --augment --global
 ```
 
-Skills land in `~/.augment/skills/` and slash command definitions land in `~/.augment/commands/`. GSD installs skills, agents, and commands (`/gsd-phase`, `/gsd-ship`, etc.). No hook or statusline ownership.
+Skills land in `~/.augment/skills/` and slash command definitions land in `~/.augment/commands/`. GSD installs skills, agents, and commands (`/gsd-phase`, `/gsd-ship`, etc.). GSD's managed lifecycle hooks are registered into Augment's own `settings.json` `hooks` block (Claude hook event dialect, covering session-start, tool-use, and phase-boundary events) — no statusline ownership. #2097 also registers the GSD companion MCP server under `settings.json`'s `mcpServers.gsd` (see [Connect a host to the GSD MCP server](connect-gsd-mcp-server.md)).
 
 ---
 
diff --git a/docs/reference/host-integration-capability-matrix.md b/docs/reference/host-integration-capability-matrix.md
index c8046ec56..1898c9215 100644
--- a/docs/reference/host-integration-capability-matrix.md
+++ b/docs/reference/host-integration-capability-matrix.md
@@ -334,6 +334,35 @@ Documentation gaps:
 - dispatch.nested
 - dispatch.maxDepth
 
+**EoS migration status (#2097):** Folded onto descriptor-driven dispatch.
+Augment already installed through the declarative adapter (nested-skill
+artifact layout, `settings-json` hook surface, Claude hook event dialect), but
+carried two remaining runtime-literal branches in
+`src/runtime-artifact-conversion.cts`: the 4 `~/.augment`/`$HOME/.augment`
+dot-dir rewrites in `_applyRuntimeRewrites`'s `case 'augment':` block are now
+built from `getDirName('augment')` (dirName-derived, byte-identical) instead
+of a hardcoded `.augment` literal, and the
+`applyRuntimeContentRewritesForCommandsInPlace` command-body conversion
+dispatch now reads `runtime.hostBehaviors.commandBodyConverter`
+(`"convertClaudeToAugmentMarkdown"`) instead of a hardcoded
+`runtime === 'augment'` branch. Two dead-code sites were also removed from
+`bin/install.js`: the orphaned `claudeToAugmentTools` map (superseded by the
+single-sourced converters per ADR-1508 / #1675) and the unreachable
+`else if (isAugment) { content = convertClaudeAgentToAugmentAgent(content); }`
+inline agent-conversion branch (augment has been on the descriptor-agents path
+since `_DESCRIPTOR_AGENTS_RUNTIMES` was introduced, making that `if`/`else if`
+arm dead). **UPGRADE 3 — MCP companion config**
+(`mergeGsdMcpServerIntoSettings`) registers the `gsd` MCP server directly
+inside the same `settings.json` `mcpServers` block GSD's own hook
+registration already writes (Augment hosts MCP in `settings.json`, unlike
+Antigravity's standalone `mcp_config.json`) — non-destructively preserving
+any other user-configured `mcpServers` entries; uninstall removes only the
+GSD-owned `gsd` entry. `settings.json` is golden-excluded
+(`HOOK_CONFIG_FILES`), so this upgrade produces no golden fixture change.
+Source-grep guard + fail-closed negotiation coverage is in
+`tests/declarative-reference-augment.test.cjs`; the dispatch/hook-bus/MCP
+upgrade coverage is in `tests/augment-upgrades.test.cjs`.
+
 ---
 
 ## qwen
diff --git a/gsd-core/bin/lib/capability-registry.cjs b/gsd-core/bin/lib/capability-registry.cjs
index f1899a7ab..e5c62b7a7 100644
--- a/gsd-core/bin/lib/capability-registry.cjs
+++ b/gsd-core/bin/lib/capability-registry.cjs
@@ -360,6 +360,10 @@ const capabilities = {
       "writesSharedSettings": true,
       "permissionWriter": null,
       "extendedHookEvents": [],
+      "hostBehaviors": {
+        "commandBodyConverter": "convertClaudeToAugmentMarkdown",
+        "mcpCompanion": "settings-json"
+      },
       "hostIntegration": {
         "embeddingMode": "declarative",
         "commandSurface": "slash-file",
@@ -3953,6 +3957,10 @@ const runtimes = {
       "writesSharedSettings": true,
       "permissionWriter": null,
       "extendedHookEvents": [],
+      "hostBehaviors": {
+        "commandBodyConverter": "convertClaudeToAugmentMarkdown",
+        "mcpCompanion": "settings-json"
+      },
       "hostIntegration": {
         "embeddingMode": "declarative",
         "commandSurface": "slash-file",
diff --git a/src/runtime-artifact-conversion.cts b/src/runtime-artifact-conversion.cts
index c1e2f6576..0a235a09b 100644
--- a/src/runtime-artifact-conversion.cts
+++ b/src/runtime-artifact-conversion.cts
@@ -1107,6 +1107,11 @@ function convertClaudeToAugmentMarkdown(content) {
   return converted;
 }
 
+// #2097 (ADR-1239): command-body converters selected by descriptor
+// (runtime.hostBehaviors.commandBodyConverter) instead of a runtime-name
+// branch. Degrade-closed: unknown/absent name → no conversion.
+const COMMAND_BODY_CONVERTERS = { convertClaudeToAugmentMarkdown };
+
 function getAugmentSkillAdapterHeader(skillName) {
   return `<augment_skill_adapter>
 ## A. Skill Invocation
@@ -2442,19 +2447,24 @@ function _applyRuntimeRewrites(content, runtime, pathPrefix, isGlobal = false, a
       break;
     }
 
-    case 'augment':
+    case 'augment': {
       content = content.replace(/~\/\.claude\//g, pathPrefix);
       content = content.replace(/\$HOME\/\.claude\//g, pathPrefix);
       content = content.replace(/\.\/\.claude\//g, `./${dirName}/`);
       content = content.replace(/~\/\.claude(?![\w-])/g, normalizedPathPrefix);
       content = content.replace(/\$HOME\/\.claude(?![\w-])/g, normalizedPathPrefix);
       content = content.replace(/\.\/\.claude(?![\w-])/g, `./${dirName}`);
-      content = content.replace(/~\/\.augment\//g, pathPrefix);
-      content = content.replace(/\$HOME\/\.augment\//g, pathPrefix);
-      content = content.replace(/~\/\.augment(?![\w-])/g, normalizedPathPrefix);
-      content = content.replace(/\$HOME\/\.augment(?![\w-])/g, normalizedPathPrefix);
+      // #2097: dot-dir self-references (~/.augment/…) → resolved prefix,
+      // dirName-derived (no runtime literal). getDirName('augment') resolves
+      // to '.augment', so this is byte-identical to the prior hardcoded regexes.
+      const _dd = escapeRegExp(dirName);
+      content = content.replace(new RegExp('~/' + _dd + '/', 'g'), pathPrefix);
+      content = content.replace(new RegExp('\\$HOME/' + _dd + '/', 'g'), pathPrefix);
+      content = content.replace(new RegExp('~/' + _dd + '(?![\\w-])', 'g'), normalizedPathPrefix);
+      content = content.replace(new RegExp('\\$HOME/' + _dd + '(?![\\w-])', 'g'), normalizedPathPrefix);
       content = processAttribution(content, attribution);
       break;
+    }
 
     case 'trae':
       content = content.replace(/~\/\.claude\//g, pathPrefix);
@@ -2631,8 +2641,11 @@ function applyRuntimeContentRewritesForCommandsInPlace(stagedDir, runtime, pathP
       if (!entry.isFile() || !entry.name.endsWith('.md')) continue;
       let content = fs.readFileSync(path.join(stagedDir, entry.name), 'utf8');
       content = _applyRuntimeRewrites(content, runtime, pathPrefix, isGlobal, attribution);
-      if (runtime === 'augment') {
-        content = convertClaudeToAugmentMarkdown(content);
+      // #2097 (ADR-1239): descriptor-driven — commandBodyConverter name comes
+      // from runtime.hostBehaviors instead of a hardcoded runtime-name branch.
+      const _cmdConv = _hostBehaviors(runtime).commandBodyConverter;
+      if (_cmdConv && COMMAND_BODY_CONVERTERS[_cmdConv]) {
+        content = COMMAND_BODY_CONVERTERS[_cmdConv](content);
       }
       fs.writeFileSync(path.join(tempDir, entry.name), content);
     }
diff --git a/tests/augment-upgrades.test.cjs b/tests/augment-upgrades.test.cjs
new file mode 100644
index 000000000..323d902ae
--- /dev/null
+++ b/tests/augment-upgrades.test.cjs
@@ -0,0 +1,243 @@
+'use strict';
+
+/**
+ * Augment Code capability UPGRADES — ADR-1239 / #2097 (EoS/augment migration).
+ *
+ * Mirrors tests/antigravity-upgrades.test.cjs's structure. Augment already
+ * shipped as a declarative-CLI host prior to #2097 (nested-skill artifact
+ * layout, settings-json hook surface, Claude hook event dialect, dispatch
+ * namedDispatch/background/subagentToolkit:'full'), so UPGRADE 1 (dispatch)
+ * and UPGRADE 2 (hook-bus) below are REGRESSION locks on that pre-existing
+ * wiring, not new capabilities. UPGRADE 3 (MCP companion) IS new: #2097 adds
+ * `mergeGsdMcpServerIntoSettings`, registering the GSD companion MCP server
+ * inside Augment's own settings.json `mcpServers` block (Augment hosts MCP
+ * there, unlike Antigravity's standalone mcp_config.json) — non-destructively
+ * appending GSD's own entry while preserving any other user-configured
+ * `mcpServers` entries. Uninstall removes only the GSD-owned `gsd` entry.
+ */
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const os = require('node:os');
+const { spawnSync } = require('node:child_process');
+
+const { runMinimalInstall, installerEnv, INSTALL_SCRIPT } = require('./helpers/install-shared.cjs');
+const { cleanup } = require('./helpers.cjs');
+const {
+  mergeGsdMcpServerIntoSettings,
+} = require('../bin/install.js');
+const { negotiateHostCapabilities } = require('../gsd-core/bin/lib/host-integration.cjs');
+const { PACKAGE_NAME } = require('../gsd-core/bin/lib/package-identity.cjs');
+
+const AUGMENT_CAP = JSON.parse(
+  fs.readFileSync(path.join(__dirname, '..', 'capabilities', 'augment', 'capability.json'), 'utf8'),
+);
+
+// ---------------------------------------------------------------------------
+// UPGRADE 1: dispatch — descriptor + negotiation regression lock
+// ---------------------------------------------------------------------------
+
+test('capabilities/augment/capability.json declares dispatch.namedDispatch/background/subagentToolkit for full subagent support (UPGRADE 1)', () => {
+  const dispatch = AUGMENT_CAP.runtime.hostIntegration.dispatch;
+  assert.equal(dispatch.namedDispatch, true);
+  assert.equal(dispatch.background, true);
+  assert.equal(dispatch.subagentToolkit, 'full');
+});
+
+test('negotiateHostCapabilities does NOT flatten dispatch for augment — namedDispatch/background/subagentToolkit survive negotiation (UPGRADE 1)', () => {
+  const { effective } = negotiateHostCapabilities(AUGMENT_CAP.runtime.hostIntegration);
+  assert.equal(effective.dispatch.namedDispatch, true,
+    'documented namedDispatch:true must survive negotiation unflattened');
+  assert.equal(effective.dispatch.background, true,
+    'documented background:true must survive negotiation unflattened (not capped to false)');
+  assert.equal(effective.dispatch.subagentToolkit, 'full',
+    'documented subagentToolkit:full must survive negotiation unflattened');
+});
+
+// ---------------------------------------------------------------------------
+// UPGRADE 2: hook-bus — live install proves the settings.json hook surface
+// (SessionStart/PostToolUse/PreToolUse) is actually wired for augment.
+// ---------------------------------------------------------------------------
+
+for (const scope of ['global', 'local']) {
+  test(`augment --${scope}: settings.json contains GSD's managed hook entries (UPGRADE 2)`, (t) => {
+    const { configDir, root } = runMinimalInstall({ runtime: 'augment', scope });
+    t.after(() => cleanup(root));
+
+    const settingsPath = path.join(configDir, 'settings.json');
+    assert.ok(fs.existsSync(settingsPath), `${settingsPath} must exist`);
+
+    const settings = JSON.parse(fs.readFileSync(settingsPath, 'utf8'));
+    assert.ok(settings.hooks && typeof settings.hooks === 'object', 'settings.hooks must be an object');
+
+    // Augment's hookEvents dialect is 'claude' (capabilities/augment/capability.json),
+    // so it gets the Claude-dialect event names (PostToolUse/PreToolUse), not
+    // antigravity's gemini-dialect (AfterTool/BeforeTool).
+    assert.ok(Array.isArray(settings.hooks.SessionStart) && settings.hooks.SessionStart.length > 0,
+      'settings.hooks.SessionStart must be registered');
+    assert.ok(Array.isArray(settings.hooks.PostToolUse) && settings.hooks.PostToolUse.length > 0,
+      'settings.hooks.PostToolUse must be registered');
+    assert.ok(Array.isArray(settings.hooks.PreToolUse) && settings.hooks.PreToolUse.length > 0,
+      'settings.hooks.PreToolUse must be registered');
+
+    const hasGsdCommand = (entries) => entries.some(
+      (entry) => entry && Array.isArray(entry.hooks) &&
+        entry.hooks.some((h) => h && typeof h.command === 'string' && h.command.includes('gsd-')),
+    );
+    assert.ok(hasGsdCommand(settings.hooks.SessionStart), 'SessionStart must reference a gsd- managed hook');
+    assert.ok(hasGsdCommand(settings.hooks.PostToolUse), 'PostToolUse must reference a gsd- managed hook');
+    assert.ok(hasGsdCommand(settings.hooks.PreToolUse), 'PreToolUse must reference a gsd- managed hook');
+  });
+}
+
+// ---------------------------------------------------------------------------
+// UPGRADE 3: MCP companion config — direct-unit idempotency + preservation
+// (mirrors antigravity's configureAntigravityMcpConfig unit tests exactly,
+// scoped to the in-memory settings object mergeGsdMcpServerIntoSettings mutates).
+// ---------------------------------------------------------------------------
+
+test('mergeGsdMcpServerIntoSettings adds mcpServers.gsd with command "npx" and args including gsd-mcp-server + PACKAGE_NAME', () => {
+  const settings = {};
+  mergeGsdMcpServerIntoSettings(settings);
+  assert.ok(settings.mcpServers && settings.mcpServers.gsd, 'mcpServers.gsd must be present');
+  assert.equal(settings.mcpServers.gsd.command, 'npx');
+  assert.deepEqual(settings.mcpServers.gsd.args, ['-y', '-p', PACKAGE_NAME, 'gsd-mcp-server']);
+});
+
+test('mergeGsdMcpServerIntoSettings is idempotent — a second call does not clobber an existing gsd entry', () => {
+  const settings = {};
+  mergeGsdMcpServerIntoSettings(settings);
+  // Simulate a user hand-edit of the gsd entry after install.
+  settings.mcpServers.gsd.args.push('--custom-flag');
+
+  mergeGsdMcpServerIntoSettings(settings);
+
+  assert.ok(settings.mcpServers.gsd.args.includes('--custom-flag'),
+    "a user-owned gsd override is never clobbered (Hyrum's Law)");
+  assert.equal(Object.keys(settings.mcpServers).length, 1, 'exactly one mcpServers entry (gsd)');
+});
+
+test('mergeGsdMcpServerIntoSettings preserves a pre-existing unrelated mcpServers entry', () => {
+  const settings = {
+    mcpServers: {
+      'my-own-server': { command: 'my-tool', args: ['--flag'] },
+    },
+  };
+  mergeGsdMcpServerIntoSettings(settings);
+
+  assert.deepEqual(settings.mcpServers['my-own-server'], { command: 'my-tool', args: ['--flag'] });
+  assert.ok(settings.mcpServers.gsd);
+  assert.equal(Object.keys(settings.mcpServers).length, 2, 'both entries present');
+});
+
+test('mergeGsdMcpServerIntoSettings recovers a corrupted (non-object) mcpServers field', () => {
+  const settingsArrayCase = { mcpServers: ['not', 'an', 'object'] };
+  mergeGsdMcpServerIntoSettings(settingsArrayCase);
+  assert.ok(settingsArrayCase.mcpServers.gsd, 'array mcpServers must be recovered to an object with gsd set');
+
+  const settingsStringCase = { mcpServers: 'corrupted-string' };
+  mergeGsdMcpServerIntoSettings(settingsStringCase);
+  assert.ok(settingsStringCase.mcpServers.gsd, 'non-object mcpServers must be recovered to an object with gsd set');
+});
+
+// ---------------------------------------------------------------------------
+// UPGRADE 3: MCP companion config — live install (both scopes) proves the
+// end-to-end wiring through finishInstall, not just the unit function.
+// ---------------------------------------------------------------------------
+
+for (const scope of ['global', 'local']) {
+  test(`augment --${scope}: settings.json registers the gsd MCP companion (UPGRADE 3)`, (t) => {
+    const { configDir, root } = runMinimalInstall({ runtime: 'augment', scope });
+    t.after(() => cleanup(root));
+
+    const settingsPath = path.join(configDir, 'settings.json');
+    assert.ok(fs.existsSync(settingsPath), `${settingsPath} must exist`);
+
+    const settings = JSON.parse(fs.readFileSync(settingsPath, 'utf8'));
+    assert.ok(settings.mcpServers && settings.mcpServers.gsd, 'mcpServers.gsd must be present');
+    assert.equal(settings.mcpServers.gsd.command, 'npx');
+    assert.deepEqual(settings.mcpServers.gsd.args, ['-y', '-p', PACKAGE_NAME, 'gsd-mcp-server']);
+  });
+}
+
+test('augment --global: reinstalling does not duplicate or clobber the gsd MCP companion entry (live-install idempotency)', (t) => {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-augment-mcp-idem-'));
+  t.after(() => cleanup(root));
+
+  const args = [INSTALL_SCRIPT, '--augment', '--global', '--config-dir', root];
+  const env = installerEnv({ HOME: root, USERPROFILE: root });
+
+  const first = spawnSync(process.execPath, args, { encoding: 'utf8', env });
+  assert.strictEqual(first.status, 0, `first install failed: ${first.stderr}`);
+
+  const settingsPath = path.join(root, 'settings.json');
+  const afterFirst = JSON.parse(fs.readFileSync(settingsPath, 'utf8'));
+  assert.ok(afterFirst.mcpServers.gsd);
+  // Simulate a user hand-edit of the gsd entry between installs.
+  afterFirst.mcpServers.gsd.args.push('--custom-flag');
+  fs.writeFileSync(settingsPath, JSON.stringify(afterFirst, null, 2) + '\n');
+
+  const second = spawnSync(process.execPath, args, { encoding: 'utf8', env });
+  assert.strictEqual(second.status, 0, `second install failed: ${second.stderr}`);
+
+  const afterSecond = JSON.parse(fs.readFileSync(settingsPath, 'utf8'));
+  assert.equal(Object.keys(afterSecond.mcpServers).length, 1, 'reinstall must not duplicate the gsd entry');
+  assert.ok(afterSecond.mcpServers.gsd.args.includes('--custom-flag'),
+    "a user-owned gsd override is never clobbered across reinstall (Hyrum's Law)");
+});
+
+test('augment --global: installing preserves a pre-existing unrelated mcpServers entry (live-install preservation)', (t) => {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-augment-mcp-preserve-'));
+  fs.mkdirSync(root, { recursive: true });
+  t.after(() => cleanup(root));
+
+  // Pre-seed settings.json with a user's own MCP server BEFORE install runs.
+  fs.writeFileSync(path.join(root, 'settings.json'), JSON.stringify({
+    mcpServers: {
+      other: { command: 'my-tool', args: ['--flag'] },
+    },
+  }, null, 2));
+
+  const args = [INSTALL_SCRIPT, '--augment', '--global', '--config-dir', root];
+  const result = spawnSync(process.execPath, args, {
+    encoding: 'utf8',
+    env: installerEnv({ HOME: root, USERPROFILE: root }),
+  });
+  assert.strictEqual(result.status, 0, `install failed: ${result.stderr}`);
+
+  const settings = JSON.parse(fs.readFileSync(path.join(root, 'settings.json'), 'utf8'));
+  assert.deepEqual(settings.mcpServers.other, { command: 'my-tool', args: ['--flag'] },
+    "the user's pre-existing mcpServers entry must be preserved");
+  assert.ok(settings.mcpServers.gsd, 'the gsd companion entry must also be present');
+});
+
+// ---------------------------------------------------------------------------
+// Uninstall — symmetric cleanup for the MCP companion entry.
+// ---------------------------------------------------------------------------
+
+test('augment --global uninstall removes only the GSD-owned mcpServers.gsd entry, preserving user data', (t) => {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-augment-uninstall-'));
+  t.after(() => cleanup(root));
+
+  const env = installerEnv({ HOME: root, USERPROFILE: root });
+  const installArgs = [INSTALL_SCRIPT, '--augment', '--global', '--config-dir', root];
+  const installResult = spawnSync(process.execPath, installArgs, { encoding: 'utf8', env });
+  assert.strictEqual(installResult.status, 0, `install failed: ${installResult.stderr}`);
+
+  // Seed user-owned data alongside GSD's contributions, post-install.
+  const settingsPath = path.join(root, 'settings.json');
+  const settings = JSON.parse(fs.readFileSync(settingsPath, 'utf8'));
+  settings.mcpServers['my-own-server'] = { command: 'my-tool', args: [] };
+  fs.writeFileSync(settingsPath, JSON.stringify(settings, null, 2) + '\n');
+
+  const uninstallArgs = [INSTALL_SCRIPT, '--augment', '--global', '--config-dir', root, '--uninstall'];
+  const uninstallResult = spawnSync(process.execPath, uninstallArgs, { encoding: 'utf8', env });
+  assert.strictEqual(uninstallResult.status, 0, `uninstall failed: ${uninstallResult.stderr}`);
+
+  const settingsAfter = JSON.parse(fs.readFileSync(settingsPath, 'utf8'));
+  assert.equal(settingsAfter.mcpServers && settingsAfter.mcpServers.gsd, undefined, 'gsd MCP entry removed');
+  assert.deepEqual(settingsAfter.mcpServers['my-own-server'], { command: 'my-tool', args: [] },
+    'user MCP server preserved');
+});
diff --git a/tests/declarative-reference-augment.test.cjs b/tests/declarative-reference-augment.test.cjs
new file mode 100644
index 000000000..68bfe52e9
--- /dev/null
+++ b/tests/declarative-reference-augment.test.cjs
@@ -0,0 +1,202 @@
+// allow-test-rule: structural-regression-guard — the descriptor-migration contract (no `runtime === 'augment'` / `isAugment`-as-conversion-branch dispatch logic left in the folded modules) is a property of the source text itself, so a source-grep is the only faithful check (#2097, mirrors tests/declarative-reference-antigravity.test.cjs #2096 AC2 guard).
+'use strict';
+
+/**
+ * Declarative reference host coverage — Augment Code (ADR-1239 / #2097
+ * EoS/augment migration).
+ *
+ * Augment is already a declarative-CLI host (nested-skill artifact layout,
+ * settings-json hook surface, Claude hook event dialect). #2097 folds its two
+ * remaining runtime-literal branches in src/runtime-artifact-conversion.cts
+ * onto descriptor-driven dispatch (runtime.hostBehaviors.commandBodyConverter)
+ * and deletes 2 dead-code sites in bin/install.js — mirroring the Antigravity
+ * migration (#2096) structure without duplicating its Antigravity-specific
+ * (GEMINI.md / reviewerCli / noPathRewrite) assertions.
+ *
+ * UPGRADE 3 (MCP companion, settings.json-hosted) live-install coverage is in
+ * tests/augment-upgrades.test.cjs — not duplicated here.
+ */
+
+const { test, before } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const { execFileSync } = require('node:child_process');
+
+const {
+  profileOf,
+  negotiateHostCapabilities,
+  UNDOCUMENTED,
+} = require('../gsd-core/bin/lib/host-integration.cjs');
+const { createDeclarativeAdapter } = require('../gsd-core/bin/lib/adapter-declarative.cjs');
+const { cleanup } = require('./helpers.cjs');
+const { walk, runMinimalInstall, BUILD_SCRIPT } = require('./helpers/install-shared.cjs');
+
+const DESC = path.join(__dirname, '..', 'capabilities', 'augment', 'capability.json');
+const AUGMENT_CAP = JSON.parse(fs.readFileSync(DESC, 'utf8'));
+const AUGMENT_AXES = AUGMENT_CAP.runtime.hostIntegration;
+
+// hooks/dist is gitignored and built (mirrors golden-install-parity harness).
+before(() => {
+  execFileSync(process.execPath, [BUILD_SCRIPT], { encoding: 'utf-8', stdio: 'pipe' });
+});
+
+test('Augment classifies as the declarative-cli profile (profileOf)', () => {
+  const desc = JSON.parse(fs.readFileSync(DESC, 'utf8'));
+  const axes = desc.runtime.hostIntegration;
+  assert.ok(axes && axes.embeddingMode, 'augment descriptor declares hostIntegration axes');
+  assert.equal(profileOf(axes), 'declarative-cli', 'Augment is a declarative-CLI host');
+});
+
+test('the public declarative adapter classifies Augment as a declarative host', () => {
+  const adapter = createDeclarativeAdapter({ runtime: 'augment' });
+  assert.equal(adapter.kind, 'declarative');
+  assert.equal(adapter.runtime, 'augment');
+  assert.equal(typeof adapter.install, 'function');
+  assert.equal(typeof adapter.uninstall, 'function');
+});
+
+test('a real Augment install emits a gsd command/skill surface (invocable)', () => {
+  const { configDir, root } = runMinimalInstall({ runtime: 'augment', scope: 'global' });
+  try {
+    const files = walk(configDir);
+    assert.ok(files.length > 0, 'install must emit artifacts');
+    const gsdSurface = files.filter((f) => /gsd/i.test(path.relative(configDir, f)));
+    assert.ok(gsdSurface.length > 0,
+      'install must emit a gsd command/skill surface (declarative reference)');
+  } finally {
+    cleanup(root);
+  }
+});
+
+// ---------------------------------------------------------------------------
+// #2097 EoS/augment — fail-closed negotiation + folded dispatch sub-axes
+// (mirrors the antigravity/kimi reference tests).
+// ---------------------------------------------------------------------------
+
+test('negotiateHostCapabilities never throws for augment, even fully corrupted', () => {
+  assert.doesNotThrow(() => negotiateHostCapabilities({}));
+  assert.doesNotThrow(() => negotiateHostCapabilities({ ...AUGMENT_AXES, embeddingMode: UNDOCUMENTED }));
+  assert.doesNotThrow(() => negotiateHostCapabilities({ ...AUGMENT_AXES, embeddingMode: 'future-unknown' }));
+  assert.doesNotThrow(() => negotiateHostCapabilities({ ...AUGMENT_AXES, dispatch: 'corrupted-not-an-object' }));
+  assert.doesNotThrow(() => negotiateHostCapabilities({ ...AUGMENT_AXES, dispatch: { ...AUGMENT_AXES.dispatch, maxDepth: 'not-a-number' } }));
+});
+
+// AC-style proof: the 3 still-`undocumented` dispatch sub-axes (nested/
+// maxDepth/backgroundDispatch) must degrade to the most-restrictive KNOWN
+// value, never their optimistic value — mirrors antigravity's equivalent
+// test, but Augment documents namedDispatch/background (unlike antigravity),
+// so only 3 sub-axes are undocumented here, not 4. Real values confirmed via:
+//   node -e "const {negotiateHostCapabilities}=require('./gsd-core/bin/lib/host-integration.cjs');
+//            const cap=require('./capabilities/augment/capability.json');
+//            console.log(negotiateHostCapabilities(cap.runtime.hostIntegration).effective.dispatch)"
+// -> { namedDispatch:true, nested:false, maxDepth:0, background:true, subagentToolkit:'full', backgroundDispatch:false }
+test("augment's 3 still-undocumented dispatch sub-axes (nested/maxDepth/backgroundDispatch) degrade to the most-restrictive known value, not their optimistic value", () => {
+  // Sanity: the descriptor itself still declares these 3 as the undocumented
+  // sentinel, while namedDispatch/background/subagentToolkit are documented.
+  assert.equal(AUGMENT_AXES.dispatch.nested, 'undocumented');
+  assert.equal(AUGMENT_AXES.dispatch.maxDepth, 'undocumented');
+  assert.equal(AUGMENT_AXES.dispatch.backgroundDispatch, 'undocumented');
+  assert.equal(AUGMENT_AXES.dispatch.namedDispatch, true, 'sanity: namedDispatch is documented, not part of the undocumented set');
+  assert.equal(AUGMENT_AXES.dispatch.background, true, 'sanity: background is documented, not part of the undocumented set');
+  assert.equal(AUGMENT_AXES.dispatch.subagentToolkit, 'full', 'sanity: subagentToolkit is documented, not part of the undocumented set');
+
+  const { effective, warnings } = negotiateHostCapabilities(AUGMENT_AXES);
+
+  assert.equal(effective.dispatch.nested, false, 'undocumented nested must degrade to false, never true');
+  assert.equal(effective.dispatch.maxDepth, 0, 'undocumented maxDepth must degrade to 0, never -1/unbounded');
+  assert.equal(effective.dispatch.backgroundDispatch, false, 'undocumented backgroundDispatch must degrade to false, never true');
+
+  // namedDispatch/background/subagentToolkit are documented — they are
+  // trusted and survive negotiation unchanged, in contrast to the 3
+  // undocumented sub-axes above. Augment's negotiation must NOT flatten
+  // dispatch the way a fully-undocumented descriptor (e.g. antigravity's
+  // namedDispatch) would.
+  assert.equal(effective.dispatch.namedDispatch, true, "documented 'true' namedDispatch is trusted, unlike the undocumented sub-axes");
+  assert.equal(effective.dispatch.background, true, "documented 'true' background is trusted — not capped to false, since namedDispatch did not degrade closed");
+  assert.equal(effective.dispatch.subagentToolkit, 'full', "documented 'full' subagentToolkit is trusted, unlike the undocumented sub-axes");
+
+  for (const axis of ['nested', 'backgroundDispatch']) {
+    assert.ok(
+      warnings.some((w) => w.includes(`dispatch.${axis}`) && w.includes('undocumented')),
+      `a warning must be raised for the undocumented dispatch.${axis} axis`,
+    );
+  }
+  assert.ok(
+    warnings.some((w) => w.includes('dispatch.maxDepth')),
+    'a warning must be raised for the undocumented dispatch.maxDepth axis (reported as missing/non-number)',
+  );
+});
+
+// ---------------------------------------------------------------------------
+// #2097 AC2-equivalent — the hardcoded conversion-dispatch branches folded by
+// this migration are retired from the folded modules.
+//
+// Unlike antigravity (#2096), where `isAntigravity` was eliminated from
+// bin/install.js entirely, Augment's `isAugment` flag legitimately remains
+// (destructured from runtimeFlags() and used for non-conversion verification
+// logic — e.g. counting installed commands/ files). So this guard does NOT
+// assert zero `isAugment` occurrences (that would be a false failure); it
+// asserts no `isAugment` occurrence gates a call to an Augment *converter*
+// function (the exact shape of the dead branch this migration deleted:
+// `else if (isAugment) { content = convertClaudeAgentToAugmentAgent(content); }`).
+// The switch `case 'augment':` label in _applyRuntimeRewrites is intentionally
+// NOT flagged — it does plain dirName-derived path-prefix rewriting (same as
+// the still-`case`-labeled trae/codebuddy/cursor/windsurf branches), not
+// conversion-function dispatch, and antigravity's own guard tolerates its
+// `case 'antigravity':` label for the identical reason (its regex only
+// matches `runtime === 'x'`, never a `case` label).
+// ---------------------------------------------------------------------------
+
+test('no `runtime === "augment"` string-equality branch remains in the descriptor-migrated modules', () => {
+  const strip = (src) => src
+    .replace(/\/\*[\s\S]*?\*\//g, '')
+    .replace(/\/\/[^\r\n]*/g, '')
+    .replace(/`[^`]*`/g, '');
+  const repoRoot = path.join(__dirname, '..');
+  const files = [
+    path.join(repoRoot, 'bin', 'install.js'),
+    path.join(repoRoot, 'src', 'runtime-artifact-conversion.cts'),
+  ];
+  for (const file of files) {
+    const src = fs.readFileSync(file, 'utf8');
+    const stripped = strip(src);
+    const eqOffenders = stripped.match(/runtime\s*[!=]==\s*'augment'/g) || [];
+    assert.deepEqual(eqOffenders, [],
+      `no hardcoded runtime==='augment' branch may remain in ${path.relative(repoRoot, file)}; found: ${eqOffenders.join(', ')}`);
+  }
+});
+
+test('no `isAugment` occurrence gates a call to an Augment converter function (the deleted dead-code shape)', () => {
+  const converterNames = [
+    'convertClaudeAgentToAugmentAgent',
+    'convertClaudeToAugmentMarkdown',
+    'convertClaudeCommandToAugmentSkill',
+    'convertSlashCommandsToAugmentSkillMentions',
+  ];
+  const converterCallPattern = new RegExp(`(${converterNames.join('|')})\\s*\\(`);
+
+  const file = path.join(__dirname, '..', 'bin', 'install.js');
+  const lines = fs.readFileSync(file, 'utf8').split(/\r?\n/);
+  const offenders = [];
+  for (let i = 0; i < lines.length; i++) {
+    const line = lines[i];
+    // Only condition-position occurrences count (`if (isAugment)` / `else if
+    // (isAugment)`), not the runtimeFlags() destructure or unrelated reads.
+    if (!/(?:if|else if)\s*\(\s*isAugment\s*\)/.test(line)) continue;
+    const window = lines.slice(i, i + 4).join('\n');
+    if (converterCallPattern.test(window)) {
+      offenders.push(`line ${i + 1}: ${line.trim()}`);
+    }
+  }
+  assert.deepEqual(offenders, [],
+    `no isAugment-gated call to an Augment converter may remain in bin/install.js; found: ${offenders.join(' | ')}`);
+});
+
+test('legitimate isAugment destructure/enumeration sites survive (not eliminated, unlike isAntigravity)', () => {
+  const file = path.join(__dirname, '..', 'bin', 'install.js');
+  const src = fs.readFileSync(file, 'utf8');
+  assert.ok(/isAugment/.test(src), 'isAugment must still be destructured from runtimeFlags() for non-conversion uses');
+  assert.ok(/_DESCRIPTOR_AGENTS_RUNTIMES\s*=\s*new Set\(\[[^\]]*'augment'/.test(src),
+    'augment must remain in _DESCRIPTOR_AGENTS_RUNTIMES (descriptor-driven agent layout)');
+});