diff --git a/apps/server/src/lib/worktree-metadata.ts b/apps/server/src/lib/worktree-metadata.ts
index 3f7ea60d..4742a5b0 100644
--- a/apps/server/src/lib/worktree-metadata.ts
+++ b/apps/server/src/lib/worktree-metadata.ts
@@ -5,18 +5,14 @@
 
 import * as secureFs from './secure-fs.js';
 import * as path from 'path';
+import type { PRState, WorktreePRInfo } from '@automaker/types';
+
+// Re-export types for backwards compatibility
+export type { PRState, WorktreePRInfo };
 
 /** Maximum length for sanitized branch names in filesystem paths */
 const MAX_SANITIZED_BRANCH_PATH_LENGTH = 200;
 
-export interface WorktreePRInfo {
-  number: number;
-  url: string;
-  title: string;
-  state: string;
-  createdAt: string;
-}
-
 export interface WorktreeMetadata {
   branch: string;
   createdAt: string;
diff --git a/apps/server/src/routes/worktree/routes/create-pr.ts b/apps/server/src/routes/worktree/routes/create-pr.ts
index 1bde9448..87777c69 100644
--- a/apps/server/src/routes/worktree/routes/create-pr.ts
+++ b/apps/server/src/routes/worktree/routes/create-pr.ts
@@ -13,6 +13,7 @@ import {
 } from '../common.js';
 import { updateWorktreePRInfo } from '../../../lib/worktree-metadata.js';
 import { createLogger } from '@automaker/utils';
+import { validatePRState } from '@automaker/types';
 
 const logger = createLogger('CreatePR');
 
@@ -268,11 +269,12 @@ export function createCreatePRHandler() {
             prAlreadyExisted = true;
 
             // Store the existing PR info in metadata
+            // GitHub CLI returns uppercase states: OPEN, MERGED, CLOSED
             await updateWorktreePRInfo(effectiveProjectPath, branchName, {
               number: existingPr.number,
               url: existingPr.url,
               title: existingPr.title || title,
-              state: existingPr.state || 'open',
+              state: validatePRState(existingPr.state),
               createdAt: new Date().toISOString(),
             });
             logger.debug(
@@ -319,11 +321,12 @@ export function createCreatePRHandler() {
 
               if (prNumber) {
                 try {
+                  // Note: GitHub doesn't have a 'DRAFT' state - drafts still show as 'OPEN'
                   await updateWorktreePRInfo(effectiveProjectPath, branchName, {
                     number: prNumber,
                     url: prUrl,
                     title,
-                    state: draft ? 'draft' : 'open',
+                    state: 'OPEN',
                     createdAt: new Date().toISOString(),
                   });
                   logger.debug(`Stored PR info for branch ${branchName}: PR #${prNumber}`);
@@ -352,11 +355,12 @@ export function createCreatePRHandler() {
                   prNumber = existingPr.number;
                   prAlreadyExisted = true;
 
+                  // GitHub CLI returns uppercase states: OPEN, MERGED, CLOSED
                   await updateWorktreePRInfo(effectiveProjectPath, branchName, {
                     number: existingPr.number,
                     url: existingPr.url,
                     title: existingPr.title || title,
-                    state: existingPr.state || 'open',
+                    state: validatePRState(existingPr.state),
                     createdAt: new Date().toISOString(),
                   });
                   logger.debug(`Fetched and stored existing PR: #${existingPr.number}`);
diff --git a/apps/server/src/routes/worktree/routes/list.ts b/apps/server/src/routes/worktree/routes/list.ts
index 96782d64..e82e5c14 100644
--- a/apps/server/src/routes/worktree/routes/list.ts
+++ b/apps/server/src/routes/worktree/routes/list.ts
@@ -14,8 +14,13 @@ import path from 'path';
 import * as secureFs from '../../../lib/secure-fs.js';
 import { isGitRepo } from '@automaker/git-utils';
 import { getErrorMessage, logError, normalizePath, execEnv, isGhCliAvailable } from '../common.js';
-import { readAllWorktreeMetadata, type WorktreePRInfo } from '../../../lib/worktree-metadata.js';
+import {
+  readAllWorktreeMetadata,
+  updateWorktreePRInfo,
+  type WorktreePRInfo,
+} from '../../../lib/worktree-metadata.js';
 import { createLogger } from '@automaker/utils';
+import { validatePRState } from '@automaker/types';
 import {
   checkGitHubRemote,
   type GitHubRemoteStatus,
@@ -168,8 +173,11 @@ async function getGitHubRemoteStatus(projectPath: string): Promise<GitHubRemoteS
 }
 
 /**
- * Fetch open PRs from GitHub and create a map of branch name to PR info.
- * This allows detecting PRs that were created outside the app.
+ * Fetch all PRs from GitHub and create a map of branch name to PR info.
+ * Uses --state all to include merged/closed PRs, allowing detection of
+ * state changes (e.g., when a PR is merged on GitHub).
+ *
+ * This also allows detecting PRs that were created outside the app.
  *
  * Uses cached GitHub remote status to avoid repeated warnings when the
  * project doesn't have a GitHub remote configured.
@@ -192,9 +200,9 @@ async function fetchGitHubPRs(projectPath: string): Promise<Map<string, Worktree
         ? `-R ${remoteStatus.owner}/${remoteStatus.repo}`
         : '';
 
-    // Fetch open PRs from GitHub
+    // Fetch all PRs from GitHub (including merged/closed to detect state changes)
     const { stdout } = await execAsync(
-      `gh pr list ${repoFlag} --state open --json number,title,url,state,headRefName,createdAt --limit 1000`,
+      `gh pr list ${repoFlag} --state all --json number,title,url,state,headRefName,createdAt --limit 1000`,
       { cwd: projectPath, env: execEnv, timeout: 15000 }
     );
 
@@ -212,7 +220,8 @@ async function fetchGitHubPRs(projectPath: string): Promise<Map<string, Worktree
         number: pr.number,
         url: pr.url,
         title: pr.title,
-        state: pr.state,
+        // GitHub CLI returns state as uppercase: OPEN, MERGED, CLOSED
+        state: validatePRState(pr.state),
         createdAt: pr.createdAt,
       });
     }
@@ -351,23 +360,36 @@ export function createListHandler() {
         }
       }
 
-      // Add PR info from metadata or GitHub for each worktree
-      // Only fetch GitHub PRs if includeDetails is requested (performance optimization)
+      // Assign PR info to each worktree, preferring fresh GitHub data over cached metadata.
+      // Only fetch GitHub PRs if includeDetails is requested (performance optimization).
+      // Uses --state all to detect merged/closed PRs, limited to 1000 recent PRs.
       const githubPRs = includeDetails
         ? await fetchGitHubPRs(projectPath)
         : new Map<string, WorktreePRInfo>();
 
       for (const worktree of worktrees) {
         const metadata = allMetadata.get(worktree.branch);
-        if (metadata?.pr) {
-          // Use stored metadata (more complete info)
-          worktree.pr = metadata.pr;
-        } else if (includeDetails) {
-          // Fall back to GitHub PR detection only when includeDetails is requested
-          const githubPR = githubPRs.get(worktree.branch);
-          if (githubPR) {
-            worktree.pr = githubPR;
+        const githubPR = githubPRs.get(worktree.branch);
+
+        if (githubPR) {
+          // Prefer fresh GitHub data (it has the current state)
+          worktree.pr = githubPR;
+
+          // Sync metadata with GitHub state when:
+          // 1. No metadata exists for this PR (PR created externally)
+          // 2. State has changed (e.g., merged/closed on GitHub)
+          const needsSync = !metadata?.pr || metadata.pr.state !== githubPR.state;
+          if (needsSync) {
+            // Fire and forget - don't block the response
+            updateWorktreePRInfo(projectPath, worktree.branch, githubPR).catch((err) => {
+              logger.warn(
+                `Failed to update PR info for ${worktree.branch}: ${getErrorMessage(err)}`
+              );
+            });
           }
+        } else if (metadata?.pr) {
+          // Fall back to stored metadata (for PRs not in recent GitHub response)
+          worktree.pr = metadata.pr;
         }
       }
 
diff --git a/apps/server/tests/unit/lib/worktree-metadata.test.ts b/apps/server/tests/unit/lib/worktree-metadata.test.ts
index ab7967f3..2f84af88 100644
--- a/apps/server/tests/unit/lib/worktree-metadata.test.ts
+++ b/apps/server/tests/unit/lib/worktree-metadata.test.ts
@@ -121,7 +121,7 @@ describe('worktree-metadata.ts', () => {
           number: 123,
           url: 'https://github.com/owner/repo/pull/123',
           title: 'Test PR',
-          state: 'open',
+          state: 'OPEN',
           createdAt: new Date().toISOString(),
         },
       };
@@ -158,7 +158,7 @@ describe('worktree-metadata.ts', () => {
           number: 456,
           url: 'https://github.com/owner/repo/pull/456',
           title: 'Updated PR',
-          state: 'closed',
+          state: 'CLOSED',
           createdAt: new Date().toISOString(),
         },
       };
@@ -177,7 +177,7 @@ describe('worktree-metadata.ts', () => {
         number: 789,
         url: 'https://github.com/owner/repo/pull/789',
         title: 'New PR',
-        state: 'open',
+        state: 'OPEN',
         createdAt: new Date().toISOString(),
       };
 
@@ -201,7 +201,7 @@ describe('worktree-metadata.ts', () => {
         number: 999,
         url: 'https://github.com/owner/repo/pull/999',
         title: 'Updated PR',
-        state: 'merged',
+        state: 'MERGED',
         createdAt: new Date().toISOString(),
       };
 
@@ -224,7 +224,7 @@ describe('worktree-metadata.ts', () => {
         number: 111,
         url: 'https://github.com/owner/repo/pull/111',
         title: 'PR',
-        state: 'open',
+        state: 'OPEN',
         createdAt: new Date().toISOString(),
       };
 
@@ -259,7 +259,7 @@ describe('worktree-metadata.ts', () => {
         number: 222,
         url: 'https://github.com/owner/repo/pull/222',
         title: 'Has PR',
-        state: 'open',
+        state: 'OPEN',
         createdAt: new Date().toISOString(),
       };
 
@@ -297,7 +297,7 @@ describe('worktree-metadata.ts', () => {
           number: 333,
           url: 'https://github.com/owner/repo/pull/333',
           title: 'PR 3',
-          state: 'open',
+          state: 'OPEN',
           createdAt: new Date().toISOString(),
         },
       };
diff --git a/apps/ui/src/components/views/board-view/worktree-panel/types.ts b/apps/ui/src/components/views/board-view/worktree-panel/types.ts
index d2040048..a9cdedca 100644
--- a/apps/ui/src/components/views/board-view/worktree-panel/types.ts
+++ b/apps/ui/src/components/views/board-view/worktree-panel/types.ts
@@ -1,10 +1,6 @@
-export interface WorktreePRInfo {
-  number: number;
-  url: string;
-  title: string;
-  state: string;
-  createdAt: string;
-}
+// Re-export shared types from @automaker/types
+export type { PRState, WorktreePRInfo } from '@automaker/types';
+import type { PRState, WorktreePRInfo } from '@automaker/types';
 
 export interface WorktreeInfo {
   path: string;
@@ -43,7 +39,8 @@ export interface PRInfo {
   number: number;
   title: string;
   url: string;
-  state: string;
+  /** PR state: OPEN, MERGED, or CLOSED */
+  state: PRState;
   author: string;
   body: string;
   comments: Array<{
diff --git a/libs/types/src/index.ts b/libs/types/src/index.ts
index a0145782..4a8c6af1 100644
--- a/libs/types/src/index.ts
+++ b/libs/types/src/index.ts
@@ -292,3 +292,7 @@ export type {
   EventReplayHookResult,
 } from './event-history.js';
 export { EVENT_HISTORY_VERSION, DEFAULT_EVENT_HISTORY_INDEX } from './event-history.js';
+
+// Worktree and PR types
+export type { PRState, WorktreePRInfo } from './worktree.js';
+export { PR_STATES, validatePRState } from './worktree.js';
diff --git a/libs/types/src/worktree.ts b/libs/types/src/worktree.ts
new file mode 100644
index 00000000..b81a075d
--- /dev/null
+++ b/libs/types/src/worktree.ts
@@ -0,0 +1,32 @@
+/**
+ * Worktree and PR-related types
+ * Shared across server and UI components
+ */
+
+/** GitHub PR states as returned by the GitHub API (uppercase) */
+export type PRState = 'OPEN' | 'MERGED' | 'CLOSED';
+
+/** Valid PR states for validation */
+export const PR_STATES: readonly PRState[] = ['OPEN', 'MERGED', 'CLOSED'] as const;
+
+/**
+ * Validates a PR state value from external APIs (e.g., GitHub CLI).
+ * Returns the validated state if it matches a known PRState, otherwise returns 'OPEN' as default.
+ * This is safer than type assertions as it handles unexpected values from external APIs.
+ *
+ * @param state - The state string to validate (can be any string)
+ * @returns A valid PRState value
+ */
+export function validatePRState(state: string | undefined | null): PRState {
+  return PR_STATES.find((s) => s === state) ?? 'OPEN';
+}
+
+/** PR information stored in worktree metadata */
+export interface WorktreePRInfo {
+  number: number;
+  url: string;
+  title: string;
+  /** PR state: OPEN, MERGED, or CLOSED */
+  state: PRState;
+  createdAt: string;
+}