diff --git a/packages/cli/src/ui/hooks/useCommandCompletion.test.tsx b/packages/cli/src/ui/hooks/useCommandCompletion.test.tsx
index 8f91013070..2d20100d0e 100644
--- a/packages/cli/src/ui/hooks/useCommandCompletion.test.tsx
+++ b/packages/cli/src/ui/hooks/useCommandCompletion.test.tsx
@@ -20,7 +20,7 @@ import {
   useCommandCompletion,
   CompletionMode,
 } from './useCommandCompletion.js';
-import type { CommandContext } from '../commands/types.js';
+import type { CommandContext, SlashCommand } from '../commands/types.js';
 import type { Config } from '@google/gemini-cli-core';
 import { useTextBuffer } from '../components/shared/text-buffer.js';
 import type { Suggestion } from '../components/SuggestionsDisplay.js';
@@ -56,7 +56,11 @@ const setupMocks = ({
   shellSuggestions = [],
   isLoading = false,
   isPerfectMatch = false,
-  slashCompletionRange = { completionStart: 0, completionEnd: 0 },
+  slashCompletionRange = {
+    completionStart: 0,
+    completionEnd: 0,
+    getCommandFromSuggestion: () => undefined,
+  },
   shellCompletionRange = { completionStart: 0, completionEnd: 0, query: '' },
 }: {
   atSuggestions?: Suggestion[];
@@ -64,7 +68,13 @@ const setupMocks = ({
   shellSuggestions?: Suggestion[];
   isLoading?: boolean;
   isPerfectMatch?: boolean;
-  slashCompletionRange?: { completionStart: number; completionEnd: number };
+  slashCompletionRange?: {
+    completionStart: number;
+    completionEnd: number;
+    getCommandFromSuggestion: (
+      suggestion: Suggestion,
+    ) => SlashCommand | undefined;
+  };
   shellCompletionRange?: {
     completionStart: number;
     completionEnd: number;
@@ -427,10 +437,15 @@ describe('useCommandCompletion', () => {
   });
 
   describe('handleAutocomplete', () => {
-    it('should complete a partial command', async () => {
+    it('should complete a partial command and NOT add a space if it has an action', async () => {
       setupMocks({
         slashSuggestions: [{ label: 'memory', value: 'memory' }],
-        slashCompletionRange: { completionStart: 1, completionEnd: 4 },
+        slashCompletionRange: {
+          completionStart: 1,
+          completionEnd: 4,
+          getCommandFromSuggestion: () =>
+            ({ action: vi.fn() }) as unknown as SlashCommand,
+        },
       });
 
       const { result } = renderCommandCompletionHook('/mem');
@@ -443,12 +458,40 @@ describe('useCommandCompletion', () => {
         result.current.handleAutocomplete(0);
       });
 
-      expect(result.current.textBuffer.text).toBe('/memory ');
+      expect(result.current.textBuffer.text).toBe('/memory');
+    });
+
+    it('should complete a partial command and ADD a space if it has NO action (e.g. just a parent)', async () => {
+      setupMocks({
+        slashSuggestions: [{ label: 'chat', value: 'chat' }],
+        slashCompletionRange: {
+          completionStart: 1,
+          completionEnd: 5,
+          getCommandFromSuggestion: () => ({}) as unknown as SlashCommand, // No action
+        },
+      });
+
+      const { result } = renderCommandCompletionHook('/chat');
+
+      await waitFor(() => {
+        expect(result.current.suggestions.length).toBe(1);
+      });
+
+      act(() => {
+        result.current.handleAutocomplete(0);
+      });
+
+      expect(result.current.textBuffer.text).toBe('/chat ');
     });
 
     it('should complete a file path', async () => {
       setupMocks({
         atSuggestions: [{ label: 'src/file1.txt', value: 'src/file1.txt' }],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = renderCommandCompletionHook('@src/fi');
@@ -470,6 +513,11 @@ describe('useCommandCompletion', () => {
 
       setupMocks({
         atSuggestions: [{ label: 'src/file1.txt', value: 'src/file1.txt' }],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = renderCommandCompletionHook(text, cursorOffset);
@@ -490,6 +538,11 @@ describe('useCommandCompletion', () => {
     it('should complete a directory path ending with / without a trailing space', async () => {
       setupMocks({
         atSuggestions: [{ label: 'src/components/', value: 'src/components/' }],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = renderCommandCompletionHook('@src/comp');
@@ -510,6 +563,11 @@ describe('useCommandCompletion', () => {
         atSuggestions: [
           { label: 'src\\components\\', value: 'src\\components\\' },
         ],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = renderCommandCompletionHook('@src\\comp');
@@ -713,6 +771,11 @@ describe('useCommandCompletion', () => {
     it('should complete file path and add trailing space', async () => {
       setupMocks({
         atSuggestions: [{ label: 'src/file.txt', value: 'src/file.txt' }],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = renderCommandCompletionHook('/cmd @src/fi');
diff --git a/packages/cli/src/ui/hooks/useCommandCompletion.tsx b/packages/cli/src/ui/hooks/useCommandCompletion.tsx
index f9b772bc93..4674e2a188 100644
--- a/packages/cli/src/ui/hooks/useCommandCompletion.tsx
+++ b/packages/cli/src/ui/hooks/useCommandCompletion.tsx
@@ -361,10 +361,19 @@ export function useCommandCompletion({
 
       const lineCodePoints = toCodePoints(buffer.lines[cursorRow] || '');
       const charAfterCompletion = lineCodePoints[end];
+
+      const command = slashCompletionRange.getCommandFromSuggestion(suggestion);
+      // Don't add a space if the command has an action (can be executed)
+      // and doesn't have a completion function (doesn't REQUIRE more arguments)
+      const isExecutableCommand = !!(command && command.action);
+      const requiresArguments = !!(command && command.completion);
+      const shouldAddSpace = !isExecutableCommand || requiresArguments;
+
       if (
         charAfterCompletion !== ' ' &&
         !suggestionText.endsWith('/') &&
-        !suggestionText.endsWith('\\')
+        !suggestionText.endsWith('\\') &&
+        shouldAddSpace
       ) {
         suggestionText += ' ';
       }
diff --git a/packages/cli/src/ui/hooks/useSlashCompletion.test.ts b/packages/cli/src/ui/hooks/useSlashCompletion.test.ts
index ea320b80a1..d210d8782d 100644
--- a/packages/cli/src/ui/hooks/useSlashCompletion.test.ts
+++ b/packages/cli/src/ui/hooks/useSlashCompletion.test.ts
@@ -492,13 +492,45 @@ describe('useSlashCompletion', () => {
       );
 
       await waitFor(() => {
-        // Should show subcommands of 'chat'
-        expect(result.current.suggestions).toHaveLength(2);
-        expect(result.current.suggestions.map((s) => s.label)).toEqual(
-          expect.arrayContaining(['list', 'save']),
-        );
-        // completionStart should be at the end of '/chat' to append subcommands
-        expect(result.current.completionStart).toBe(5);
+        // Should show 'chat' as the suggestion, NOT its subcommands
+        expect(result.current.suggestions).toHaveLength(1);
+        expect(result.current.suggestions[0].label).toBe('chat');
+        // completionStart should be at 1 (to replace 'chat')
+        expect(result.current.completionStart).toBe(1);
+      });
+      unmount();
+    });
+
+    it('should NOT suggest subcommands when a parent command is fully typed without a trailing space (fix for over-eager completion)', async () => {
+      const slashCommands = [
+        createTestCommand({
+          name: 'stats',
+          description: 'Check session stats',
+          action: vi.fn(), // Has action
+          subCommands: [
+            createTestCommand({
+              name: 'session',
+              description: 'Show session-specific usage statistics',
+            }),
+          ],
+        }),
+      ];
+
+      const { result, unmount } = renderHook(() =>
+        useTestHarnessForSlashCompletion(
+          true,
+          '/stats',
+          slashCommands,
+          mockCommandContext,
+        ),
+      );
+
+      await waitFor(() => {
+        // Should show 'stats' as the suggestion, NOT 'session'
+        expect(result.current.suggestions).toHaveLength(1);
+        expect(result.current.suggestions[0].label).toBe('stats');
+        // isPerfectMatch should be true because it has an action
+        expect(result.current.isPerfectMatch).toBe(true);
       });
       unmount();
     });
diff --git a/packages/cli/src/ui/hooks/useSlashCompletion.ts b/packages/cli/src/ui/hooks/useSlashCompletion.ts
index a53a469571..3cd047945d 100644
--- a/packages/cli/src/ui/hooks/useSlashCompletion.ts
+++ b/packages/cli/src/ui/hooks/useSlashCompletion.ts
@@ -54,7 +54,6 @@ interface CommandParserResult {
   partial: string;
   currentLevel: readonly SlashCommand[] | undefined;
   leafCommand: SlashCommand | null;
-  exactMatchAsParent: SlashCommand | undefined;
   isArgumentCompletion: boolean;
 }
 
@@ -70,7 +69,6 @@ function useCommandParser(
         partial: '',
         currentLevel: slashCommands,
         leafCommand: null,
-        exactMatchAsParent: undefined,
         isArgumentCompletion: false,
       };
     }
@@ -112,34 +110,6 @@ function useCommandParser(
       }
     }
 
-    let exactMatchAsParent: SlashCommand | undefined;
-    if (!hasTrailingSpace && currentLevel) {
-      exactMatchAsParent = currentLevel.find(
-        (cmd) => matchesCommand(cmd, partial) && cmd.subCommands,
-      );
-
-      if (exactMatchAsParent) {
-        // Only descend if there are NO other matches for the partial at this level.
-        // This ensures that typing "/memory" still shows "/memory-leak" if it exists.
-        const otherMatches = currentLevel.filter(
-          (cmd) =>
-            cmd !== exactMatchAsParent &&
-            (cmd.name.toLowerCase().startsWith(partial.toLowerCase()) ||
-              cmd.altNames?.some((alt) =>
-                alt.toLowerCase().startsWith(partial.toLowerCase()),
-              )),
-        );
-
-        if (otherMatches.length === 0) {
-          leafCommand = exactMatchAsParent;
-          currentLevel = exactMatchAsParent.subCommands as
-            | readonly SlashCommand[]
-            | undefined;
-          partial = '';
-        }
-      }
-    }
-
     const depth = commandPathParts.length;
     const isArgumentCompletion = !!(
       leafCommand?.completion &&
@@ -153,7 +123,6 @@ function useCommandParser(
       partial,
       currentLevel,
       leafCommand,
-      exactMatchAsParent,
       isArgumentCompletion,
     };
   }, [query, slashCommands]);
@@ -356,10 +325,10 @@ function useCompletionPositions(
       return { start: -1, end: -1 };
     }
 
-    const { hasTrailingSpace, partial, exactMatchAsParent } = parserResult;
+    const { hasTrailingSpace, partial } = parserResult;
 
     // Set completion start/end positions
-    if (hasTrailingSpace || exactMatchAsParent) {
+    if (hasTrailingSpace) {
       return { start: query.length, end: query.length };
     } else if (partial) {
       if (parserResult.isArgumentCompletion) {