diff --git a/bin/install.js b/bin/install.js
index e5a6a4d5..737e7cd6 100755
--- a/bin/install.js
+++ b/bin/install.js
@@ -1113,11 +1113,31 @@ function convertClaudeCommandToCopilotSkill(content, skillName, isGlobal = false
   return `${fm}\n${body}`;
 }
 
+/**
+ * Map a skill directory name (gsd-<cmd>) to the frontmatter `name:` used
+ * by Claude Code as the skill identity. Workflows emit `Skill(skill="gsd:<cmd>")`
+ * (colon form) and Claude Code resolves skills by frontmatter `name:`, not
+ * directory name — so emit colon form here. Directory stays hyphenated for
+ * Windows path safety. See #2643.
+ *
+ * Codex must NOT use this helper: its adapter invokes skills as `$gsd-<cmd>`
+ * (shell-var syntax) and a colon would terminate the variable name. Codex
+ * keeps the hyphen form via `yamlQuote(skillName)` directly.
+ */
+function skillFrontmatterName(skillDirName) {
+  if (typeof skillDirName !== 'string') return skillDirName;
+  // Idempotent on already-colon form.
+  if (skillDirName.includes(':')) return skillDirName;
+  // Only rewrite the first hyphen after the `gsd` prefix.
+  return skillDirName.replace(/^gsd-/, 'gsd:');
+}
+
 /**
  * Convert a Claude command (.md) to a Claude skill (SKILL.md).
  * Claude Code is the native format, so minimal conversion needed —
- * preserve allowed-tools as YAML multiline list, preserve argument-hint,
- * convert name from gsd:xxx to gsd-xxx format.
+ * preserve allowed-tools as YAML multiline list, preserve argument-hint.
+ * Emits `name: gsd:<cmd>` (colon) so Skill(skill="gsd:<cmd>") calls in
+ * workflows resolve on flat-skills installs — see #2643.
  */
 function convertClaudeCommandToClaudeSkill(content, skillName) {
   const { frontmatter, body } = extractFrontmatterAndBody(content);
@@ -1137,7 +1157,8 @@ function convertClaudeCommandToClaudeSkill(content, skillName) {
   }
 
   // Reconstruct frontmatter in Claude skill format
-  let fm = `---\nname: ${skillName}\ndescription: ${yamlQuote(description)}\n`;
+  const frontmatterName = skillFrontmatterName(skillName);
+  let fm = `---\nname: ${frontmatterName}\ndescription: ${yamlQuote(description)}\n`;
   if (argumentHint) fm += `argument-hint: ${yamlQuote(argumentHint)}\n`;
   if (agent) fm += `agent: ${agent}\n`;
   if (toolsBlock) fm += toolsBlock;
@@ -7265,6 +7286,7 @@ if (process.env.GSD_TEST_MODE) {
     convertClaudeAgentToAntigravityAgent,
     copyCommandsAsAntigravitySkills,
     convertClaudeCommandToClaudeSkill,
+    skillFrontmatterName,
     copyCommandsAsClaudeSkills,
     convertClaudeToWindsurfMarkdown,
     convertClaudeCommandToWindsurfSkill,
diff --git a/tests/bug-2643-skill-frontmatter-name.test.cjs b/tests/bug-2643-skill-frontmatter-name.test.cjs
new file mode 100644
index 00000000..a5983fb8
--- /dev/null
+++ b/tests/bug-2643-skill-frontmatter-name.test.cjs
@@ -0,0 +1,90 @@
+'use strict';
+
+process.env.GSD_TEST_MODE = '1';
+
+/**
+ * Bug #2643: workflows emit Skill(skill="gsd:<cmd>") but flat-skills install
+ * registers `gsd-<cmd>` as the frontmatter `name:`. Claude Code uses the
+ * frontmatter name (not dir name) as the skill identity — so the emitted
+ * `name:` must match the colon form used by workflow Skill() calls.
+ *
+ * The directory name stays hyphenated for Windows path safety.
+ */
+
+const { test, describe } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const ROOT = path.join(__dirname, '..');
+const {
+  convertClaudeCommandToClaudeSkill,
+  skillFrontmatterName,
+} = require(path.join(ROOT, 'bin', 'install.js'));
+
+const WORKFLOWS_DIR = path.join(ROOT, 'get-shit-done', 'workflows');
+const COMMANDS_DIR = path.join(ROOT, 'commands', 'gsd');
+
+function collectFiles(dir, results) {
+  if (!results) results = [];
+  let entries;
+  try { entries = fs.readdirSync(dir, { withFileTypes: true }); } catch { return results; }
+  for (const e of entries) {
+    const full = path.join(dir, e.name);
+    if (e.isDirectory()) collectFiles(full, results);
+    else if (e.name.endsWith('.md')) results.push(full);
+  }
+  return results;
+}
+
+function extractSkillNames(content) {
+  const names = new Set();
+  const rx = /Skill\(skill=['"]gsd:([a-z0-9-]+)['"]/gi;
+  let m;
+  while ((m = rx.exec(content)) !== null) names.add('gsd:' + m[1]);
+  return names;
+}
+
+describe('skill frontmatter name parity (#2643)', () => {
+  test('skillFrontmatterName helper emits colon form', () => {
+    assert.strictEqual(typeof skillFrontmatterName, 'function');
+    assert.strictEqual(skillFrontmatterName('gsd-execute-phase'), 'gsd:execute-phase');
+    assert.strictEqual(skillFrontmatterName('gsd-plan-phase'), 'gsd:plan-phase');
+    assert.strictEqual(skillFrontmatterName('gsd:next'), 'gsd:next');
+  });
+
+  test('convertClaudeCommandToClaudeSkill emits name: gsd:<cmd>', () => {
+    const input = '---\nname: old\ndescription: test\n---\n\nBody.';
+    const result = convertClaudeCommandToClaudeSkill(input, 'gsd-execute-phase');
+    assert.match(result, /^---\nname: gsd:execute-phase\n/);
+  });
+
+  test('every workflow Skill(skill="gsd:<cmd>") resolves to an emitted skill name', () => {
+    const workflowFiles = collectFiles(WORKFLOWS_DIR);
+    const referenced = new Set();
+    for (const f of workflowFiles) {
+      const src = fs.readFileSync(f, 'utf-8');
+      for (const n of extractSkillNames(src)) referenced.add(n);
+    }
+    assert.ok(referenced.size > 0, 'expected at least one Skill(skill="gsd:<cmd>") reference');
+
+    const emitted = new Set();
+    const cmdFiles = fs.readdirSync(COMMANDS_DIR).filter(f => f.endsWith('.md'));
+    for (const cmd of cmdFiles) {
+      const base = cmd.replace(/\.md$/, '');
+      const skillDirName = 'gsd-' + base;
+      const src = fs.readFileSync(path.join(COMMANDS_DIR, cmd), 'utf-8');
+      const out = convertClaudeCommandToClaudeSkill(src, skillDirName);
+      const m = out.match(/^---\nname:\s*(.+)$/m);
+      if (m) emitted.add(m[1].trim());
+    }
+
+    const missing = [];
+    for (const r of referenced) if (!emitted.has(r)) missing.push(r);
+    assert.deepStrictEqual(
+      missing,
+      [],
+      'workflow refs not emitted as skill names: ' + missing.join(', '),
+    );
+  });
+});
diff --git a/tests/claude-skills-migration.test.cjs b/tests/claude-skills-migration.test.cjs
index ceec0392..64c36023 100644
--- a/tests/claude-skills-migration.test.cjs
+++ b/tests/claude-skills-migration.test.cjs
@@ -69,7 +69,7 @@ describe('convertClaudeCommandToClaudeSkill', () => {
     );
   });
 
-  test('converts name format from gsd:xxx to skill naming', () => {
+  test('emits colon-form name (gsd:<cmd>) from hyphen-form dir (#2643)', () => {
     const input = [
       '---',
       'name: gsd:next',
@@ -79,9 +79,10 @@ describe('convertClaudeCommandToClaudeSkill', () => {
       'Body.',
     ].join('\n');
 
+    // Directory name is gsd-next (hyphen, Windows-safe), frontmatter name is
+    // gsd:next (colon) so Claude Code resolves `/gsd:next` against the skill.
     const result = convertClaudeCommandToClaudeSkill(input, 'gsd-next');
-    assert.ok(result.includes('name: gsd-next'), 'name uses skill naming convention');
-    assert.ok(!result.includes('name: gsd:next'), 'old name format removed');
+    assert.ok(result.includes('name: gsd:next'), 'frontmatter name uses colon form');
   });
 
   test('preserves body content unchanged', () => {
diff --git a/tests/qwen-skills-migration.test.cjs b/tests/qwen-skills-migration.test.cjs
index 10cce4b1..f226898b 100644
--- a/tests/qwen-skills-migration.test.cjs
+++ b/tests/qwen-skills-migration.test.cjs
@@ -66,7 +66,7 @@ describe('Qwen Code: convertClaudeCommandToClaudeSkill', () => {
     );
   });
 
-  test('converts name format from gsd:xxx to skill naming', () => {
+  test('emits colon-form name (gsd:<cmd>) from hyphen-form dir (#2643)', () => {
     const input = [
       '---',
       'name: gsd:next',
@@ -76,9 +76,10 @@ describe('Qwen Code: convertClaudeCommandToClaudeSkill', () => {
       'Body.',
     ].join('\n');
 
+    // Directory name is gsd-next (hyphen, Windows-safe), frontmatter name is
+    // gsd:next (colon) so Claude Code resolves `/gsd:next` against the skill.
     const result = convertClaudeCommandToClaudeSkill(input, 'gsd-next');
-    assert.ok(result.includes('name: gsd-next'), 'name uses skill naming convention');
-    assert.ok(!result.includes('name: gsd:next'), 'old name format removed');
+    assert.ok(result.includes('name: gsd:next'), 'frontmatter name uses colon form');
   });
 
   test('preserves body content unchanged', () => {
@@ -153,7 +154,7 @@ describe('Qwen Code: copyCommandsAsClaudeSkills', () => {
 
     // Verify content
     const content = fs.readFileSync(skillPath, 'utf8');
-    assert.ok(content.includes('name: gsd-quick'), 'skill name converted');
+    assert.ok(content.includes('name: gsd:quick'), 'frontmatter name uses colon form (#2643)');
     assert.ok(content.includes('description:'), 'description present');
     assert.ok(content.includes('allowed-tools:'), 'allowed-tools preserved');
     assert.ok(content.includes('<objective>'), 'body content preserved');
@@ -273,7 +274,7 @@ describe('Qwen Code: SKILL.md format validation', () => {
     assert.ok(fmMatch, 'has frontmatter block');
 
     const fmLines = fmMatch[1].split('\n');
-    const hasName = fmLines.some(l => l.startsWith('name: gsd-review'));
+    const hasName = fmLines.some(l => l.startsWith('name: gsd:review'));
     const hasDesc = fmLines.some(l => l.startsWith('description:'));
     const hasAgent = fmLines.some(l => l.startsWith('agent:'));
     const hasTools = fmLines.some(l => l.startsWith('allowed-tools:'));