diff --git a/src/commands/completions.ts b/src/commands/completions.ts
new file mode 100644
index 0000000..be1c17a
--- /dev/null
+++ b/src/commands/completions.ts
@@ -0,0 +1,35 @@
+import type { Command } from 'commander';
+import { requireTrackedRepo } from '../utils/detect';
+import { configManager } from '../config/manager';
+
+async function runCompletions(type: string | undefined): Promise<void> {
+  try {
+    const projectId = await requireTrackedRepo();
+    const { branches } = await configManager.getBranches(projectId);
+
+    if (type === 'branches') {
+      for (const b of branches) {
+        if (b.status === 'active' || b.status === 'pr_open') {
+          console.log(b.branchName);
+        }
+      }
+    } else if (type === 'tickets') {
+      const seen = new Set<string>();
+      for (const b of branches) {
+        if (b.ticketId && !seen.has(b.ticketId)) {
+          seen.add(b.ticketId);
+          console.log(b.ticketId);
+        }
+      }
+    }
+  } catch {
+    // Silent — no output on error (repo not tracked, file missing, etc.)
+  }
+}
+
+export function registerCompletionsCommand(program: Command): void {
+  program
+    .command('_completions [type]')
+    .description('Output completion candidates (internal)')
+    .action((type: string | undefined) => runCompletions(type));
+}
diff --git a/src/commands/shell-init.ts b/src/commands/shell-init.ts
index b10518c..665de73 100644
--- a/src/commands/shell-init.ts
+++ b/src/commands/shell-init.ts
@@ -72,6 +72,11 @@ _morg_completion() {
     pr)
       COMPREPLY=( $(compgen -W "create review view" -- "\${cur}") )
       ;;
+    view)
+      if [[ "\${COMP_WORDS[1]}" == "pr" ]]; then
+        COMPREPLY=( $(compgen -W "$(command morg _completions branches 2>/dev/null)" -- "\${cur}") )
+      fi
+      ;;
     worktree)
       COMPREPLY=( $(compgen -W "list clean" -- "\${cur}") )
       ;;
@@ -84,6 +89,16 @@ _morg_completion() {
     completion)
       COMPREPLY=( $(compgen -W "bash zsh" -- "\${cur}") )
       ;;
+    switch|complete|delete|untrack)
+      COMPREPLY=( $(compgen -W "$(command morg _completions branches 2>/dev/null)" -- "\${cur}") )
+      ;;
+    track)
+      if [[ \${COMP_CWORD} == 2 ]]; then
+        COMPREPLY=( $(compgen -W "$(command morg _completions branches 2>/dev/null)" -- "\${cur}") )
+      elif [[ \${COMP_CWORD} == 3 ]]; then
+        COMPREPLY=( $(compgen -W "$(command morg _completions tickets 2>/dev/null)" -- "\${cur}") )
+      fi
+      ;;
     start)
       COMPREPLY=( $(compgen -W "--worktree --base" -- "\${cur}") )
       ;;
@@ -94,7 +109,7 @@ _morg_completion() {
       COMPREPLY=( $(compgen -W "--json --short" -- "\${cur}") )
       ;;
     tickets|ticket)
-      COMPREPLY=( $(compgen -W "--plain --json" -- "\${cur}") )
+      COMPREPLY=( $(compgen -W "--plain --json $(command morg _completions tickets 2>/dev/null)" -- "\${cur}") )
       ;;
     *)
       ;;
@@ -128,9 +143,15 @@ ${commandDefs}
     args)
       case \$words[2] in
         pr)
-          local -a subcmds
-          subcmds=('create' 'review' 'view')
-          _describe 'subcommand' subcmds
+          if [[ \$CURRENT -eq 4 && \$words[3] == "view" ]]; then
+            local -a branches
+            branches=(\${(f)"$(command morg _completions branches 2>/dev/null)"})
+            compadd -a branches
+          else
+            local -a subcmds
+            subcmds=('create' 'review' 'view')
+            _describe 'subcommand' subcmds
+          fi
           ;;
         worktree)
           local -a subcmds
@@ -162,6 +183,22 @@ ${commandDefs}
           shells=('bash' 'zsh')
           _describe 'shell' shells
           ;;
+        switch|complete|delete|untrack)
+          local -a branches
+          branches=(\${(f)"$(command morg _completions branches 2>/dev/null)"})
+          compadd -a branches
+          ;;
+        track)
+          if [[ \$CURRENT -eq 3 ]]; then
+            local -a branches
+            branches=(\${(f)"$(command morg _completions branches 2>/dev/null)"})
+            compadd -a branches
+          elif [[ \$CURRENT -eq 4 ]]; then
+            local -a tickets
+            tickets=(\${(f)"$(command morg _completions tickets 2>/dev/null)"})
+            compadd -a tickets
+          fi
+          ;;
         start)
           _arguments '--worktree[Create git worktree]' '--base[Base branch]'
           ;;
@@ -169,7 +206,10 @@ ${commandDefs}
           _arguments '--json[Output as JSON]' '--short[Short output]'
           ;;
         tickets|ticket)
+          local -a tickets
+          tickets=(\${(f)"$(command morg _completions tickets 2>/dev/null)"})
           _arguments '--plain[Plain output]' '--json[Output as JSON]'
+          compadd -a tickets
           ;;
       esac
       ;;
diff --git a/src/index.ts b/src/index.ts
index 1904694..6fad6ee 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -21,6 +21,7 @@ import { registerTicketsCommand } from './commands/tickets';
 import { registerInstallClaudeSkillCommand } from './commands/install-claude-skill';
 import { registerShellInitCommand } from './commands/shell-init';
 import { registerWorktreeCommand } from './commands/worktree';
+import { registerCompletionsCommand } from './commands/completions';
 import { getCurrentBranch } from './git/index';
 import { configManager } from './config/manager';
 import { findBranchCaseInsensitive } from './utils/ticket';
@@ -56,7 +57,12 @@ program.action(async () => {
   }
 });
 
-const NO_CONFIG_COMMANDS = new Set(['config', 'install-claude-skill', 'shell-init']);
+const NO_CONFIG_COMMANDS = new Set([
+  'config',
+  'install-claude-skill',
+  'shell-init',
+  '_completions',
+]);
 program.hook('preAction', async (_thisCommand, actionCommand) => {
   if (!NO_CONFIG_COMMANDS.has(actionCommand.name())) await requireConfig();
 });
@@ -81,5 +87,6 @@ registerTicketsCommand(program);
 registerInstallClaudeSkillCommand(program);
 registerShellInitCommand(program);
 registerWorktreeCommand(program);
+registerCompletionsCommand(program);
 
 program.parseAsync(process.argv).catch(handleError);
diff --git a/tests/completions.test.ts b/tests/completions.test.ts
new file mode 100644
index 0000000..eb9d153
--- /dev/null
+++ b/tests/completions.test.ts
@@ -0,0 +1,130 @@
+import { vi, describe, it, expect, beforeEach } from 'vitest';
+import type { Branch, BranchesFile } from '../src/config/schemas';
+
+vi.mock('../src/utils/detect', () => ({
+  requireTrackedRepo: vi.fn(),
+}));
+
+vi.mock('../src/config/manager', () => ({
+  configManager: {
+    getBranches: vi.fn(),
+  },
+}));
+
+import { requireTrackedRepo } from '../src/utils/detect';
+import { configManager } from '../src/config/manager';
+
+const mockRequireTrackedRepo = requireTrackedRepo as ReturnType<typeof vi.fn>;
+const mockGetBranches = configManager.getBranches as ReturnType<typeof vi.fn>;
+
+function makeBranch(overrides: Partial<Branch>): Branch {
+  return {
+    id: 'test-id',
+    branchName: 'feature/test',
+    ticketId: null,
+    ticketTitle: null,
+    ticketUrl: null,
+    status: 'active',
+    prNumber: null,
+    prUrl: null,
+    prStatus: null,
+    worktreePath: null,
+    createdAt: new Date().toISOString(),
+    updatedAt: new Date().toISOString(),
+    lastAccessedAt: new Date().toISOString(),
+    ...overrides,
+  };
+}
+
+// Dynamically import the module to get the action handler
+async function runCompletions(type?: string): Promise<string> {
+  const { registerCompletionsCommand } = await import('../src/commands/completions');
+  const { Command } = await import('commander');
+  const program = new Command();
+  registerCompletionsCommand(program);
+
+  const output: string[] = [];
+  const origLog = console.log;
+  console.log = (...args: unknown[]) => output.push(String(args[0]));
+
+  try {
+    await program.parseAsync(['node', 'test', '_completions', ...(type ? [type] : [])]);
+  } finally {
+    console.log = origLog;
+  }
+
+  return output.join('\n');
+}
+
+describe('_completions command', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockRequireTrackedRepo.mockResolvedValue('project-123');
+  });
+
+  describe('branches type', () => {
+    it('outputs active and pr_open branch names', async () => {
+      const branchesFile: BranchesFile = {
+        version: 1,
+        branches: [
+          makeBranch({ branchName: 'feature/one', status: 'active' }),
+          makeBranch({ branchName: 'feature/two', status: 'pr_open' }),
+          makeBranch({ branchName: 'feature/done', status: 'done' }),
+          makeBranch({ branchName: 'feature/abandoned', status: 'abandoned' }),
+        ],
+      };
+      mockGetBranches.mockResolvedValue(branchesFile);
+
+      const output = await runCompletions('branches');
+      expect(output).toBe('feature/one\nfeature/two');
+    });
+
+    it('outputs nothing when no branches exist', async () => {
+      mockGetBranches.mockResolvedValue({ version: 1, branches: [] });
+
+      const output = await runCompletions('branches');
+      expect(output).toBe('');
+    });
+  });
+
+  describe('tickets type', () => {
+    it('outputs deduplicated ticket IDs', async () => {
+      const branchesFile: BranchesFile = {
+        version: 1,
+        branches: [
+          makeBranch({ branchName: 'feature/one', ticketId: 'MORG-1' }),
+          makeBranch({ branchName: 'feature/two', ticketId: 'MORG-2' }),
+          makeBranch({ branchName: 'feature/three', ticketId: 'MORG-1' }),
+          makeBranch({ branchName: 'feature/no-ticket', ticketId: null }),
+        ],
+      };
+      mockGetBranches.mockResolvedValue(branchesFile);
+
+      const output = await runCompletions('tickets');
+      expect(output).toBe('MORG-1\nMORG-2');
+    });
+  });
+
+  describe('error handling', () => {
+    it('outputs nothing when repo is not tracked', async () => {
+      mockRequireTrackedRepo.mockRejectedValue(new Error('Not tracked'));
+
+      const output = await runCompletions('branches');
+      expect(output).toBe('');
+    });
+
+    it('outputs nothing when getBranches fails', async () => {
+      mockGetBranches.mockRejectedValue(new Error('File not found'));
+
+      const output = await runCompletions('branches');
+      expect(output).toBe('');
+    });
+
+    it('outputs nothing for unknown type', async () => {
+      mockGetBranches.mockResolvedValue({ version: 1, branches: [] });
+
+      const output = await runCompletions('unknown');
+      expect(output).toBe('');
+    });
+  });
+});