diff --git a/apps/cli/src/commands.test.ts b/apps/cli/src/commands.test.ts
index 20d6e9b..deced6c 100644
--- a/apps/cli/src/commands.test.ts
+++ b/apps/cli/src/commands.test.ts
@@ -419,4 +419,19 @@ describe('inspector + export commands', () => {
     const out = await reg.match('/export')!.cmd.run([], makeContext({ history: [] }));
     expect(out.join('\n')).toMatch(/Nothing to export/);
   });
+
+  it('/compact needs a provider', async () => {
+    const ctx = makeContext({
+      history: [{ role: 'user', content: [{ type: 'text', text: 'x' }] }],
+    });
+    const out = await reg.match('/compact')!.cmd.run([], ctx);
+    expect(out.join('\n')).toMatch(/needs a provider/);
+  });
+
+  it('/compact reports nothing with empty history', async () => {
+    const out = await reg
+      .match('/compact')!
+      .cmd.run([], makeContext({ provider: { name: 'm', runTurn: async () => ({}) } as never }));
+    expect(out.join('\n')).toMatch(/Nothing to compact/);
+  });
 });
diff --git a/apps/cli/src/commands.ts b/apps/cli/src/commands.ts
index b2d6d91..b6eb0fb 100644
--- a/apps/cli/src/commands.ts
+++ b/apps/cli/src/commands.ts
@@ -678,6 +678,27 @@ export const ExportCommand: SlashCommand = {
   },
 };
 
+export const CompactCommand: SlashCommand = {
+  name: '/compact',
+  description: 'Summarize the conversation so far to free up context.',
+  async run(_args, ctx) {
+    if (!ctx.provider) return ['(/compact needs a provider — none configured.)'];
+    const history = ctx.history ?? [];
+    if (history.length === 0) return ['Nothing to compact yet.'];
+    try {
+      const { compact } = await import('@deepcode/core');
+      const result = await compact(history, { provider: ctx.provider });
+      if (result.messagesRemoved === 0) {
+        return ['Conversation is already short enough — nothing to compact.'];
+      }
+      ctx.newHistory = result.history;
+      return [`✓ Compacted ${result.messagesRemoved} messages → ${result.history.length} kept.`];
+    } catch (err) {
+      return [`(Compaction failed: ${(err as Error).message})`];
+    }
+  },
+};
+
 /** Render a conversation as readable markdown (text + tool calls). */
 function historyToMarkdown(history: StoredMessage[]): string {
   const out: string[] = ['# DeepCode conversation export', ''];
@@ -732,6 +753,7 @@ export const BUILTIN_COMMANDS: SlashCommand[] = [
   AgentsCommand,
   SkillsCommand,
   ExportCommand,
+  CompactCommand,
 ];
 
 // ──────────────────────────────────────────────────────────────────────────
diff --git a/docs/BEHAVIOR_PARITY.md b/docs/BEHAVIOR_PARITY.md
index e7b9220..c31b0d7 100644
--- a/docs/BEHAVIOR_PARITY.md
+++ b/docs/BEHAVIOR_PARITY.md
@@ -26,7 +26,7 @@ Legend: `✅` matches · `🟡` matches with caveats · `🔄` deferred · `⚠
 | `/add-dir`            | ✓           | ✓ (records intent) | 🟡 — M3 will enforce                                                                       |
 | `/todos`              | ✓           | ✓                  | ✅ — reads `<sessionDir>/todos.json` written by TodoWrite tool                             |
 | `/plugins`            | ✓           | ✓                  | ✅ — lists wired plugins + contributed hook events + warnings (M5.2)                       |
-| `/compact`            | ✓           | ✓ auto-trigger     | 🟡 — manual `/compact` slash command not exposed yet (auto works via agent loop)           |
+| `/compact`            | ✓           | ✓                  | ✅ — manual `/compact` + automatic threshold trigger in the agent loop                     |
 | `/btw`                | ✓           | ✗                  | 🔄                                                                                         |
 | `/recap`              | ✓           | ✗                  | 🔄                                                                                         |
 | `/rewind`             | ✓           | ✓                  | ✅ — 5 ops (code/conversation/both/summarize-from/up-to); `Esc Esc` bound                  |