diff --git a/.changeset/agile-newts-roar.md b/.changeset/agile-newts-roar.md
new file mode 100644
index 000000000..a767ec9c2
--- /dev/null
+++ b/.changeset/agile-newts-roar.md
@@ -0,0 +1,7 @@
+---
+type: Changed
+pr: 1813
+---
+**Internal: the installer's `program` (display-name) + `command` (slash-invocation) chains are now single-source lookups** — the 14-line `program` chain (an exact duplicate of `runtimeLabel`) → `getRuntimeLabel`, and the 14-line `command` chain (the per-runtime `/gsd-new-project` syntax: gemini `/gsd:`, codex `$`, cursor skill-mention, kimi `/skill:`, default `/gsd-new-project`) → new `getRuntimeNewProjectCommand(runtime)` helper (ADR-1239 Phase B / #1679 AC2 slice 4). `runtime ===` count in `bin/install.js`: 53 → 25 (cumulative this session: 129 → 25). Stdout strings preserved byte-for-byte; no install-output change (golden-parity 16/16). No user-facing change.
+
+<!-- docs-exempt: internal refactor; no user-facing doc surface -->
diff --git a/bin/install.js b/bin/install.js
index 0e361f834..6ab82cf7b 100755
--- a/bin/install.js
+++ b/bin/install.js
@@ -37,7 +37,7 @@ const {
 // installer to the runtime-name-policy leaf (ADR-1508 / #1510 Phase 1) so the
 // conversion module's rewrite engine can consume it without importing
 // bin/install.js. Re-exported below for back-compat consumers/tests.
-const { getDirName, getRuntimeLabel, getGlobalConfigHomeFragment, runtimeFlags } = require('../gsd-core/bin/lib/runtime-name-policy.cjs');
+const { getDirName, getRuntimeLabel, getGlobalConfigHomeFragment, runtimeFlags, getRuntimeNewProjectCommand } = require('../gsd-core/bin/lib/runtime-name-policy.cjs');
 const {
   applyWorktreeBaseRef,
   readBaseRefFromSettings,
@@ -10519,37 +10519,11 @@ function finishInstall(settingsPath, settings, statuslineCommand, shouldInstallS
     }
   }
 
-  let program = 'Claude Code';
-  if (runtime === 'opencode') program = 'OpenCode';
-  if (runtime === 'gemini') program = 'Gemini';
-  if (runtime === 'kilo') program = 'Kilo';
-  if (runtime === 'codex') program = 'Codex';
-  if (runtime === 'copilot') program = 'Copilot';
-  if (runtime === 'antigravity') program = 'Antigravity';
-  if (runtime === 'cursor') program = 'Cursor';
-  if (runtime === 'windsurf') program = 'Windsurf';
-  if (runtime === 'augment') program = 'Augment';
-  if (runtime === 'trae') program = 'Trae';
-  if (runtime === 'cline') program = 'Cline';
-  if (runtime === 'qwen') program = 'Qwen Code';
-  if (runtime === 'hermes') program = 'Hermes Agent';
-  if (runtime === 'kimi') program = 'Kimi CLI';
-
-  let command = '/gsd-new-project';
-  if (runtime === 'opencode') command = '/gsd-new-project';
-  if (runtime === 'kilo') command = '/gsd-new-project';
-  if (runtime === 'gemini') command = '/gsd:new-project';
-  if (runtime === 'codex') command = '$gsd-new-project';
-  if (runtime === 'copilot') command = '/gsd-new-project';
-  if (runtime === 'antigravity') command = '/gsd-new-project';
-  if (runtime === 'cursor') command = 'gsd-new-project (mention the skill name)';
-  if (runtime === 'windsurf') command = '/gsd-new-project';
-  if (runtime === 'augment') command = '/gsd-new-project';
-  if (runtime === 'trae') command = '/gsd-new-project';
-  if (runtime === 'cline') command = '/gsd-new-project';
-  if (runtime === 'qwen') command = '/gsd-new-project';
-  if (runtime === 'hermes') command = '/gsd-new-project';
-  if (runtime === 'kimi') command = '/skill:gsd-new-project';
+  // program + command are now single-source lookups (ADR-1239 Phase B / #1679):
+  // program is the runtime display label; command is the per-host /gsd-new-project
+  // invocation syntax.
+  const program = getRuntimeLabel(runtime);
+  const command = getRuntimeNewProjectCommand(runtime);
 
   // Claude Code global installs use the skills/ format (CC 2.1.88+).
   // Restart is required for CC to pick up newly-installed skills, and the
diff --git a/src/runtime-name-policy.cts b/src/runtime-name-policy.cts
index 94ddab70d..6df48adba 100644
--- a/src/runtime-name-policy.cts
+++ b/src/runtime-name-policy.cts
@@ -284,3 +284,24 @@ export function runtimeFlags(runtime: string): Readonly<Record<string, boolean>>
   }
   return Object.freeze(flags);
 }
+
+/**
+ * The `/gsd-new-project` invocation syntax per runtime — the post-install
+ * "next step" command string. Most runtimes use the default `/gsd-new-project`;
+ * a few hosts need a different surface syntax. Collapses the 14-line
+ * `if (runtime === 'x') command = ...` chain in bin/install.js's next-step
+ * message (ADR-1239 Phase B / #1679 AC2). Pure: no I/O.
+ */
+const DEFAULT_NEW_PROJECT_COMMAND = '/gsd-new-project';
+const RUNTIME_NEW_PROJECT_COMMANDS: Readonly<Record<string, string>> = {
+  gemini: '/gsd:new-project',
+  codex: '$gsd-new-project',
+  cursor: 'gsd-new-project (mention the skill name)',
+  kimi: '/skill:gsd-new-project',
+};
+
+export function getRuntimeNewProjectCommand(runtime: string): string {
+  if (!runtime) return DEFAULT_NEW_PROJECT_COMMAND;
+  const c = RUNTIME_NEW_PROJECT_COMMANDS[runtime];
+  return typeof c === 'string' && c.length > 0 ? c : DEFAULT_NEW_PROJECT_COMMAND;
+}
diff --git a/tests/runtime-label-policy.test.cjs b/tests/runtime-label-policy.test.cjs
index 119e02e45..953885eb3 100644
--- a/tests/runtime-label-policy.test.cjs
+++ b/tests/runtime-label-policy.test.cjs
@@ -33,7 +33,7 @@ const assert = require('node:assert/strict');
 const runtimeNamePolicy = require('../gsd-core/bin/lib/runtime-name-policy.cjs');
 const registry = require('../gsd-core/bin/lib/capability-registry.cjs');
 
-const { getRuntimeLabel } = runtimeNamePolicy;
+const { getRuntimeLabel, getRuntimeNewProjectCommand } = runtimeNamePolicy;
 
 // Golden oracle: hardcoded expected map of all 16 runtime ids to their short
 // install/uninstall display label. A pinned expected value in a TEST is correct
@@ -101,3 +101,30 @@ test('getRuntimeLabel fallback: alias is NOT auto-expanded (raw id match only)',
   assert.strictEqual(getRuntimeLabel('claude-code'), 'Claude Code',
     'getRuntimeLabel("claude-code") must return the default "Claude Code" (raw-id match only; aliases are not expanded)');
 });
+
+// ---------------------------------------------------------------------------
+// getRuntimeNewProjectCommand (ADR-1239 Phase B / #1679 AC2) — the per-runtime
+// /gsd-new-project invocation syntax for the post-install next-step message.
+// ---------------------------------------------------------------------------
+
+const GOLDEN_COMMAND_MAP = {
+  // 4 real overrides (the rest use the default):
+  gemini: '/gsd:new-project',
+  codex: '$gsd-new-project',
+  cursor: 'gsd-new-project (mention the skill name)',
+  kimi: '/skill:gsd-new-project',
+};
+const DEFAULT_CMD = '/gsd-new-project';
+
+test('getRuntimeNewProjectCommand: the 4 overrides + the default for the other 12 runtimes', () => {
+  for (const [id, expected] of Object.entries(GOLDEN_COMMAND_MAP)) {
+    assert.strictEqual(getRuntimeLabel ? getRuntimeNewProjectCommand(id) : null, expected, `override ${id}`);
+  }
+  // sanity: getRuntimeNewProjectCommand is imported alongside getRuntimeLabel above
+});
+
+test('getRuntimeNewProjectCommand: claude/unknown/empty + the 12 non-override runtimes → default', () => {
+  for (const id of ['claude', 'opencode', 'kilo', 'copilot', 'antigravity', 'windsurf', 'augment', 'trae', 'cline', 'qwen', 'hermes', 'codebuddy', 'unknown', '']) {
+    assert.strictEqual(getRuntimeNewProjectCommand(id), DEFAULT_CMD, `runtime '${id}' must return the default command`);
+  }
+});