diff --git a/src/server/routers/claude.ts b/src/server/routers/claude.ts
index 74605d56..389947bf 100644
--- a/src/server/routers/claude.ts
+++ b/src/server/routers/claude.ts
@@ -10,6 +10,7 @@ import {
   answerUserInput,
   hasPendingInput,
   getPendingInput,
+  getSessionCommands,
 } from '../services/claude-runner';
 import { loadMergedSessionSettings } from '../services/settings-merger';
 import { getSessionWorkingDir } from '../services/worktree-manager';
@@ -257,9 +258,7 @@ export const claudeRouter = router({
 
   getCommands: protectedProcedure
     .input(z.object({ sessionId: z.string().uuid() }))
-    .query(async () => {
-      // Commands are now emitted via SSE during query initialization.
-      // This endpoint returns empty for now - the frontend gets commands via SSE.
-      return { commands: [] as Array<{ name: string; description: string; argumentHint: string }> };
+    .query(async ({ input }) => {
+      return { commands: getSessionCommands(input.sessionId) };
     }),
 });
diff --git a/src/server/services/claude-runner.test.ts b/src/server/services/claude-runner.test.ts
index db52b81f..af1b52da 100644
--- a/src/server/services/claude-runner.test.ts
+++ b/src/server/services/claude-runner.test.ts
@@ -43,6 +43,8 @@ vi.mock('@anthropic-ai/claude-agent-sdk', () => ({
 
 import {
   buildSystemPrompt,
+  mergeSlashCommands,
+  getSessionCommands,
   answerUserInput,
   hasPendingInput,
   isClaudeRunning,
@@ -119,6 +121,74 @@ describe('claude-runner', () => {
     });
   });
 
+  describe('mergeSlashCommands', () => {
+    it('should return existing commands when no new names provided', () => {
+      const existing = [{ name: 'commit', description: 'Commit changes', argumentHint: '' }];
+      const result = mergeSlashCommands(existing, []);
+      expect(result).toEqual(existing);
+    });
+
+    it('should add new commands not in existing list', () => {
+      const existing = [{ name: 'commit', description: 'Commit changes', argumentHint: '' }];
+      const result = mergeSlashCommands(existing, ['compact', 'cost']);
+      expect(result).toHaveLength(3);
+      expect(result[0]).toEqual({
+        name: 'commit',
+        description: 'Commit changes',
+        argumentHint: '',
+      });
+      expect(result[1]).toEqual({ name: 'compact', description: '', argumentHint: '' });
+      expect(result[2]).toEqual({ name: 'cost', description: '', argumentHint: '' });
+    });
+
+    it('should not duplicate commands already in existing list', () => {
+      const existing = [
+        { name: 'commit', description: 'Commit changes', argumentHint: '' },
+        { name: 'review', description: 'Review code', argumentHint: '<pr>' },
+      ];
+      const result = mergeSlashCommands(existing, ['commit', 'review', 'compact']);
+      expect(result).toHaveLength(3);
+      // Original rich metadata preserved
+      expect(result[0]).toEqual({
+        name: 'commit',
+        description: 'Commit changes',
+        argumentHint: '',
+      });
+      expect(result[1]).toEqual({
+        name: 'review',
+        description: 'Review code',
+        argumentHint: '<pr>',
+      });
+      // New command added with empty metadata
+      expect(result[2]).toEqual({ name: 'compact', description: '', argumentHint: '' });
+    });
+
+    it('should handle empty existing commands', () => {
+      const result = mergeSlashCommands([], ['compact', 'cost']);
+      expect(result).toHaveLength(2);
+      expect(result[0]).toEqual({ name: 'compact', description: '', argumentHint: '' });
+      expect(result[1]).toEqual({ name: 'cost', description: '', argumentHint: '' });
+    });
+
+    it('should handle both empty', () => {
+      const result = mergeSlashCommands([], []);
+      expect(result).toEqual([]);
+    });
+
+    it('should deduplicate names within slashCommandNames', () => {
+      const result = mergeSlashCommands([], ['compact', 'compact', 'cost', 'cost']);
+      expect(result).toHaveLength(2);
+      expect(result[0]).toEqual({ name: 'compact', description: '', argumentHint: '' });
+      expect(result[1]).toEqual({ name: 'cost', description: '', argumentHint: '' });
+    });
+  });
+
+  describe('getSessionCommands', () => {
+    it('should return empty array for nonexistent sessions', () => {
+      expect(getSessionCommands('nonexistent-session')).toEqual([]);
+    });
+  });
+
   describe('answerUserInput', () => {
     it('should return false when no pending input exists', () => {
       const result = answerUserInput('nonexistent-session', { q: 'answer' });
diff --git a/src/server/services/claude-runner.ts b/src/server/services/claude-runner.ts
index 0a4b4431..b76e8382 100644
--- a/src/server/services/claude-runner.ts
+++ b/src/server/services/claude-runner.ts
@@ -10,9 +10,9 @@
  * parking a promise that resolves when the user answers via tRPC.
  */
 
-import { query, type McpServerConfig } from '@anthropic-ai/claude-agent-sdk';
+import { query, type McpServerConfig, type SlashCommand } from '@anthropic-ai/claude-agent-sdk';
 import { prisma } from '@/lib/prisma';
-import { getMessageType } from '@/lib/claude-messages';
+import { getMessageType, SystemInitContentSchema } from '@/lib/claude-messages';
 import { extractRepoFullName } from '@/lib/utils';
 import { v4 as uuid, v5 as uuidv5 } from 'uuid';
 import { sseEvents } from './events';
@@ -23,6 +23,35 @@ import { StreamAccumulator } from './stream-accumulator';
 
 const log = createLogger('claude-runner');
 
+/**
+ * Merges slash command names from the system init message with rich SlashCommand
+ * objects from `supportedCommands()`.
+ *
+ * The SDK's `supportedCommands()` only returns "skills" — a subset with rich
+ * metadata (name, description, argumentHint). The system init message's
+ * `slash_commands` array contains ALL available commands as bare strings.
+ *
+ * This function merges both: keeping the rich metadata for known skills and
+ * synthesizing minimal SlashCommand objects for commands that only appear in
+ * the slash_commands list.
+ */
+export function mergeSlashCommands(
+  existingCommands: SlashCommand[],
+  slashCommandNames: string[]
+): SlashCommand[] {
+  const existingNames = new Set(existingCommands.map((cmd) => cmd.name));
+  const merged = [...existingCommands];
+
+  for (const name of slashCommandNames) {
+    if (!existingNames.has(name)) {
+      merged.push({ name, description: '', argumentHint: '' });
+      existingNames.add(name);
+    }
+  }
+
+  return merged;
+}
+
 // Namespace UUID for generating deterministic IDs from error content
 const ERROR_LINE_NAMESPACE = '6ba7b810-9dad-11d1-80b4-00c04fd430c8';
 
@@ -49,6 +78,8 @@ interface SessionState {
   pendingInput: PendingUserInput | null;
   /** Working directory for this session */
   workingDir: string;
+  /** Discovered slash commands (cached for getCommands endpoint) */
+  commands: SlashCommand[];
 }
 
 /** Active sessions tracked in memory */
@@ -152,6 +183,7 @@ function getSessionState(sessionId: string, workingDir: string): SessionState {
       currentQuery: null,
       pendingInput: null,
       workingDir,
+      commands: [],
     };
     sessions.set(sessionId, state);
   }
@@ -351,7 +383,45 @@ export async function runClaudeCommand(options: RunClaudeCommandOptions): Promis
     const q = query({ prompt, options: sdkOptions });
     state.currentQuery = q;
 
+    // Fetch rich command metadata from the SDK asynchronously.
+    // The init message may arrive before this resolves, so we merge
+    // with any names already discovered to avoid losing commands.
+    void q
+      .supportedCommands()
+      .then((commands) => {
+        const alreadyDiscovered = state.commands.map((c) => c.name);
+        state.commands = mergeSlashCommands(commands, alreadyDiscovered);
+        sseEvents.emitCommands(sessionId, state.commands);
+        log.info('Emitted supported commands from SDK', {
+          sessionId,
+          count: state.commands.length,
+        });
+      })
+      .catch((err) => {
+        log.debug('Failed to fetch supportedCommands', { sessionId, error: toError(err).message });
+      });
+
     for await (const message of q) {
+      // Extract slash_commands from system init messages and merge with
+      // rich commands from supportedCommands(). The SDK's supportedCommands()
+      // only returns "skills", but the system init message contains all
+      // slash commands (e.g. /compact, /cost, /review, etc.)
+      const initParsed = SystemInitContentSchema.safeParse(message);
+      if (initParsed.success && initParsed.data.slash_commands) {
+        const merged = mergeSlashCommands(state.commands, initParsed.data.slash_commands);
+        const newNames = new Set(merged.map((c) => c.name));
+        const oldNames = new Set(state.commands.map((c) => c.name));
+        const hasNewCommands = [...newNames].some((n) => !oldNames.has(n));
+        if (hasNewCommands) {
+          state.commands = merged;
+          sseEvents.emitCommands(sessionId, merged);
+          log.info('Merged slash_commands from system init', {
+            sessionId,
+            total: merged.length,
+          });
+        }
+      }
+
       // Handle stream_events for partial messages
       if (message.type === 'stream_event') {
         const partial = accumulator.accumulate(
@@ -504,6 +574,14 @@ export function answerUserInput(sessionId: string, answers: Record<string, strin
   return true;
 }
 
+/**
+ * Get cached slash commands for a session.
+ * Returns commands discovered during the last query, or empty if none.
+ */
+export function getSessionCommands(sessionId: string): SlashCommand[] {
+  return sessions.get(sessionId)?.commands ?? [];
+}
+
 /**
  * Check if a session has a pending user input request.
  */