diff --git a/src/resources/extensions/gsd/bootstrap/register-extension.ts b/src/resources/extensions/gsd/bootstrap/register-extension.ts
index 20c801c0a..1ed3031cd 100644
--- a/src/resources/extensions/gsd/bootstrap/register-extension.ts
+++ b/src/resources/extensions/gsd/bootstrap/register-extension.ts
@@ -2,7 +2,6 @@
 
 import type { ExtensionAPI, ExtensionCommandContext } from "@gsd/pi-coding-agent";
 
-import { registerGSDCommand } from "../commands.js";
 import { registerExitCommand } from "../exit-command.js";
 import { registerWorktreeCommand } from "../worktree-command.js";
 import { registerDbTools } from "./db-tools.js";
@@ -58,7 +57,8 @@ function installEpipeGuard(): void {
 }
 
 export function registerGsdExtension(pi: ExtensionAPI): void {
-  registerGSDCommand(pi);
+  // Note: registerGSDCommand is called by index.ts before this function,
+  // so we intentionally skip it here to avoid double-registration.
   registerWorktreeCommand(pi);
   registerExitCommand(pi);
 
@@ -71,10 +71,24 @@ export function registerGsdExtension(pi: ExtensionAPI): void {
     },
   });
 
-  registerDynamicTools(pi);
-  registerDbTools(pi);
-  registerJournalTools(pi);
-  registerQueryTools(pi);
-  registerShortcuts(pi);
-  registerHooks(pi);
+  // Wrap non-critical registrations individually so one failure
+  // doesn't prevent the others from loading.
+  const nonCriticalRegistrations: Array<[string, () => void]> = [
+    ["dynamic-tools", () => registerDynamicTools(pi)],
+    ["db-tools", () => registerDbTools(pi)],
+    ["journal-tools", () => registerJournalTools(pi)],
+    ["query-tools", () => registerQueryTools(pi)],
+    ["shortcuts", () => registerShortcuts(pi)],
+    ["hooks", () => registerHooks(pi)],
+  ];
+
+  for (const [name, register] of nonCriticalRegistrations) {
+    try {
+      register();
+    } catch (err) {
+      process.stderr.write(
+        `[gsd] Failed to register ${name}: ${err instanceof Error ? err.message : String(err)}\n`,
+      );
+    }
+  }
 }
diff --git a/src/resources/extensions/gsd/index.ts b/src/resources/extensions/gsd/index.ts
index d61786f6f..a50fd6c24 100644
--- a/src/resources/extensions/gsd/index.ts
+++ b/src/resources/extensions/gsd/index.ts
@@ -16,6 +16,20 @@ export {
 } from "./bootstrap/write-gate.js";
 
 export default async function registerExtension(pi: ExtensionAPI) {
-  const { registerGsdExtension } = await import("./bootstrap/register-extension.js");
-  registerGsdExtension(pi);
+  // Always register the core /gsd command first, in isolation.
+  // This ensures /gsd is available even if the full bootstrap (shortcuts,
+  // tools, hooks) fails — e.g. due to a Windows-specific import error.
+  const { registerGSDCommand } = await import("./commands/index.js");
+  registerGSDCommand(pi);
+
+  // Full setup (shortcuts, tools, hooks) in a separate try/catch so that
+  // any platform-specific load failure doesn't take out the core command.
+  try {
+    const { registerGsdExtension } = await import("./bootstrap/register-extension.js");
+    registerGsdExtension(pi);
+  } catch (err) {
+    process.stderr.write(
+      `[gsd] Extension setup partially failed — /gsd commands are available but shortcuts/tools may be missing: ${err instanceof Error ? err.message : String(err)}\n`,
+    );
+  }
 }
diff --git a/src/resources/extensions/gsd/tests/extension-bootstrap-isolation.test.ts b/src/resources/extensions/gsd/tests/extension-bootstrap-isolation.test.ts
new file mode 100644
index 000000000..24c2193e0
--- /dev/null
+++ b/src/resources/extensions/gsd/tests/extension-bootstrap-isolation.test.ts
@@ -0,0 +1,150 @@
+// Structural contracts for GSD extension bootstrap isolation.
+//
+// The /gsd command must survive failures in the full extension bootstrap
+// (register-extension.ts). This guards against the regression where a
+// Windows-specific import failure in register-shortcuts.ts silently
+// prevented /gsd from being registered at all (#4168, #4172).
+
+import { describe, test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const indexSrc = readFileSync(join(__dirname, "../index.ts"), "utf-8");
+const registerExtSrc = readFileSync(
+  join(__dirname, "../bootstrap/register-extension.ts"),
+  "utf-8",
+);
+
+// ─── index.ts: core /gsd command must be registered before full bootstrap ─────
+
+describe("index.ts bootstrap isolation", () => {
+  test("imports registerGSDCommand from commands/index.js separately", () => {
+    assert.ok(
+      indexSrc.includes('./commands/index.js"') || indexSrc.includes("./commands/index.js'"),
+      "index.ts must import registerGSDCommand from ./commands/index.js",
+    );
+  });
+
+  test("calls registerGSDCommand before importing register-extension.js", () => {
+    const gsdCommandCallPos = indexSrc.indexOf("registerGSDCommand(pi)");
+    const bootstrapImportPos = indexSrc.indexOf(
+      './bootstrap/register-extension.js"',
+    );
+
+    assert.ok(gsdCommandCallPos >= 0, "must call registerGSDCommand(pi)");
+    assert.ok(bootstrapImportPos >= 0, "must import register-extension.js");
+    assert.ok(
+      gsdCommandCallPos < bootstrapImportPos,
+      "registerGSDCommand(pi) must be called BEFORE importing register-extension.js",
+    );
+  });
+
+  test("wraps register-extension.js import in try-catch", () => {
+    // The dynamic import of register-extension.js must be inside a try block
+    const tryPos = indexSrc.indexOf("try {");
+    const bootstrapImportPos = indexSrc.indexOf(
+      './bootstrap/register-extension.js"',
+    );
+    const catchPos = indexSrc.indexOf("catch (err)");
+
+    assert.ok(tryPos >= 0, "must have try block");
+    assert.ok(catchPos >= 0, "must have catch block");
+    assert.ok(
+      tryPos < bootstrapImportPos && bootstrapImportPos < catchPos,
+      "register-extension.js import must be wrapped in try-catch",
+    );
+  });
+
+  test("writes to stderr on bootstrap failure", () => {
+    assert.ok(
+      indexSrc.includes("process.stderr.write"),
+      "must write to stderr when bootstrap fails",
+    );
+    assert.ok(
+      indexSrc.includes("[gsd] Extension setup partially failed"),
+      "stderr message must indicate partial failure with /gsd still available",
+    );
+  });
+});
+
+// ─── register-extension.ts: no double-registration + defensive wrapping ───────
+
+describe("register-extension.ts defensive registration", () => {
+  test("does NOT import or call registerGSDCommand (avoids double-registration)", () => {
+    // registerGSDCommand is now called by index.ts, not register-extension.ts
+    assert.ok(
+      !registerExtSrc.includes("import { registerGSDCommand }"),
+      "register-extension.ts must NOT import registerGSDCommand",
+    );
+
+    // Check the function body of registerGsdExtension doesn't call it
+    const funcBodyStart = registerExtSrc.indexOf(
+      "export function registerGsdExtension",
+    );
+    const funcBody = registerExtSrc.slice(funcBodyStart);
+    assert.ok(
+      !funcBody.includes("registerGSDCommand(pi)"),
+      "registerGsdExtension must NOT call registerGSDCommand(pi)",
+    );
+  });
+
+  test("still registers worktree, exit, and kill commands", () => {
+    const funcBodyStart = registerExtSrc.indexOf(
+      "export function registerGsdExtension",
+    );
+    const funcBody = registerExtSrc.slice(funcBodyStart);
+
+    assert.ok(
+      funcBody.includes("registerWorktreeCommand(pi)"),
+      "must register worktree command",
+    );
+    assert.ok(
+      funcBody.includes("registerExitCommand(pi)"),
+      "must register exit command",
+    );
+    assert.ok(
+      funcBody.includes('"kill"'),
+      "must register kill command",
+    );
+  });
+
+  test("wraps non-critical registrations in individual try-catch blocks", () => {
+    const funcBodyStart = registerExtSrc.indexOf(
+      "export function registerGsdExtension",
+    );
+    const funcBody = registerExtSrc.slice(funcBodyStart);
+
+    // Each non-critical registration should be wrapped with error handling
+    const registrationNames = [
+      "dynamic-tools",
+      "db-tools",
+      "journal-tools",
+      "query-tools",
+      "shortcuts",
+      "hooks",
+    ];
+
+    for (const name of registrationNames) {
+      assert.ok(
+        funcBody.includes(`"${name}"`),
+        `non-critical registration "${name}" must be present`,
+      );
+    }
+
+    // Must have try-catch inside the registration loop
+    assert.ok(
+      funcBody.includes("try {") && funcBody.includes("catch (err)"),
+      "must have try-catch for non-critical registrations",
+    );
+  });
+
+  test("writes to stderr when a non-critical registration fails", () => {
+    assert.ok(
+      registerExtSrc.includes("[gsd] Failed to register"),
+      "must write descriptive error to stderr for individual registration failures",
+    );
+  });
+});