diff --git a/src/resources/extensions/gsd/guided-flow.ts b/src/resources/extensions/gsd/guided-flow.ts
index 016f5335b..c576d820d 100644
--- a/src/resources/extensions/gsd/guided-flow.ts
+++ b/src/resources/extensions/gsd/guided-flow.ts
@@ -295,8 +295,10 @@ async function dispatchWorkflow(
   // "Grammar is too complex" when the combined tool schema is too large.
   // Discuss flows only need a small subset of GSD tools — strip the heavy
   // planning/execution/completion tools to keep the grammar within limits.
+  let savedTools: string[] | null = null;
   if (unitType?.startsWith("discuss-")) {
     const currentTools = pi.getActiveTools();
+    savedTools = currentTools;
     // Keep all non-GSD tools (builtins, other extensions) and only the
     // GSD tools on the discuss allowlist.
     const scopedTools = currentTools.filter(
@@ -322,6 +324,13 @@ async function dispatchWorkflow(
     },
     { triggerTurn: true },
   );
+
+  // Restore full tool set after the message is queued. The LLM turn has
+  // already captured the scoped set — restoring prevents the narrowed
+  // tools from leaking into subsequent dispatches (#3628).
+  if (savedTools) {
+    pi.setActiveTools(savedTools);
+  }
 }
 
 /**
diff --git a/src/resources/extensions/gsd/tests/restore-tools-after-discuss.test.ts b/src/resources/extensions/gsd/tests/restore-tools-after-discuss.test.ts
new file mode 100644
index 000000000..a820125e9
--- /dev/null
+++ b/src/resources/extensions/gsd/tests/restore-tools-after-discuss.test.ts
@@ -0,0 +1,63 @@
+/**
+ * Regression test for #3628 — restore tool set after discuss flow scoping
+ *
+ * The discuss flow narrows the active tool set to avoid "grammar too complex"
+ * errors. Without restoring after sendMessage, the narrowed tools leaked into
+ * subsequent dispatches, breaking plan/execute flows.
+ *
+ * The fix saves the full tool set before scoping and restores it after
+ * sendMessage returns.
+ */
+
+import { describe, it } from 'node:test'
+import assert from 'node:assert/strict'
+import { readFileSync } from 'node:fs'
+import { resolve } from 'node:path'
+
+const src = readFileSync(
+  resolve(process.cwd(), 'src', 'resources', 'extensions', 'gsd', 'guided-flow.ts'),
+  'utf-8',
+)
+
+describe('restore tools after discuss flow scoping (#3628)', () => {
+  it('savedTools is declared before the discuss scoping block', () => {
+    // savedTools must be declared before the discuss-* check
+    const savedToolsDecl = src.indexOf('let savedTools')
+    const discussCheck = src.indexOf('if (unitType?.startsWith("discuss-"))')
+    assert.ok(savedToolsDecl !== -1, 'savedTools variable must be declared')
+    assert.ok(discussCheck !== -1, 'discuss-* type check must exist')
+    assert.ok(
+      savedToolsDecl < discussCheck,
+      'savedTools must be declared before the discuss scoping block',
+    )
+  })
+
+  it('savedTools captures current tools inside the discuss block', () => {
+    const discussCheck = src.indexOf('if (unitType?.startsWith("discuss-"))')
+    assert.ok(discussCheck !== -1)
+
+    // Look for savedTools assignment within the discuss block
+    const blockAfter = src.slice(discussCheck, discussCheck + 500)
+    assert.ok(
+      blockAfter.includes('savedTools = currentTools'),
+      'savedTools must be assigned from currentTools inside the discuss block',
+    )
+  })
+
+  it('savedTools is restored after sendMessage', () => {
+    // Find the sendMessage call
+    const sendMsg = src.indexOf('triggerTurn: true')
+    assert.ok(sendMsg !== -1, 'sendMessage with triggerTurn must exist')
+
+    // After sendMessage, savedTools should be restored via setActiveTools
+    const afterSend = src.slice(sendMsg, sendMsg + 500)
+    assert.ok(
+      afterSend.includes('if (savedTools)'),
+      'savedTools restoration guard must exist after sendMessage',
+    )
+    assert.ok(
+      afterSend.includes('setActiveTools(savedTools)'),
+      'setActiveTools(savedTools) must be called to restore the full tool set',
+    )
+  })
+})