diff --git a/scripts/hooks/session-end.js b/scripts/hooks/session-end.js
index 9709aa95a..5c31a8e0b 100644
--- a/scripts/hooks/session-end.js
+++ b/scripts/hooks/session-end.js
@@ -11,7 +11,7 @@
 
 const path = require('path');
 const fs = require('fs');
-const { getSessionsDir, getDateString, getTimeString, getSessionIdShort, sanitizeSessionId, getProjectName, ensureDir, readFile, writeFile, runCommand, stripAnsi, log } = require('../lib/utils');
+const { getSessionsDir, getDateString, getTimeString, getSessionIdShort, sanitizeSessionId, getProjectName, getRepoIdentity, ensureDir, readFile, writeFile, runCommand, stripAnsi, log } = require('../lib/utils');
 const { generateSessionSummary, getContextRemainingPct, getContextThreshold } = require('../lib/llm-summary');
 
 const SUMMARY_START_MARKER = '<!-- ECC:SUMMARY:START -->';
@@ -130,7 +130,8 @@ function getSessionMetadata() {
   return {
     project: getProjectName() || 'unknown',
     branch: branchResult.success ? branchResult.output : 'unknown',
-    worktree: process.cwd()
+    worktree: process.cwd(),
+    repo: getRepoIdentity()
   };
 }
 
@@ -145,16 +146,20 @@ function buildSessionHeader(today, currentTime, metadata, existingContent = '')
   const date = extractHeaderField(existingContent, 'Date') || today;
   const started = extractHeaderField(existingContent, 'Started') || currentTime;
 
-  return [
+  const lines = [
     heading,
     `**Date:** ${date}`,
     `**Started:** ${started}`,
     `**Last Updated:** ${currentTime}`,
     `**Project:** ${metadata.project}`,
     `**Branch:** ${metadata.branch}`,
-    `**Worktree:** ${metadata.worktree}`,
-    ''
-  ].join('\n');
+    `**Worktree:** ${metadata.worktree}`
+  ];
+  if (metadata.repo) {
+    lines.push(`**Repo:** ${metadata.repo}`);
+  }
+  lines.push('');
+  return lines.join('\n');
 }
 
 function mergeSessionHeader(content, today, currentTime, metadata) {
diff --git a/scripts/hooks/session-start.js b/scripts/hooks/session-start.js
index 63854aff1..7150f7ef5 100644
--- a/scripts/hooks/session-start.js
+++ b/scripts/hooks/session-start.js
@@ -14,6 +14,7 @@ const {
   getSessionSearchDirs,
   getLearnedSkillsDir,
   getProjectName,
+  getRepoIdentity,
   findFiles,
   ensureDir,
   readFile,
@@ -254,6 +255,7 @@ function pruneExpiredSessions(searchDirs, retentionDays) {
  * Session files written by session-end.js contain header fields like:
  *   **Project:** my-project
  *   **Worktree:** /path/to/project
+ *   **Repo:** /path/to/main-worktree/.git
  *
  * This function reads each session file once, caching its content, and
  * returns both the selected session object and its already-read content
@@ -261,11 +263,18 @@ function pruneExpiredSessions(searchDirs, retentionDays) {
  *
  * Priority (highest to lowest):
  *   1. Exact worktree (cwd) match — most recent
- *   2. Same project name match for legacy sessions without Worktree metadata
- *   3. No injection when sessions belong to a different worktree/project
+ *   2. Repository identity match: the session was recorded in another
+ *      worktree or subdirectory of the same repository. Identity is the
+ *      main worktree's common git dir (issue #3160), taken from the
+ *      recorded **Repo:** field or resolved from the recorded **Worktree:**
+ *      path for older session files. Unrelated repositories never match.
+ *   3. Same project name match for legacy sessions without Worktree/Repo
+ *      metadata
+ *   4. No injection when sessions belong to a different repository
  *
  * Sessions are already sorted newest-first, so the first match in each
- * category wins.
+ * category wins; the scan continues past repository and project matches so
+ * an exact worktree match always takes precedence.
  *
  * @param {Array<Object>} sessions - Deduplicated session list, sorted newest-first.
  * @param {string} cwd - Current working directory (process.cwd()).
@@ -279,7 +288,17 @@ function selectMatchingSession(sessions, cwd, currentProject) {
 
   // Normalize cwd once outside the loop to avoid repeated syscalls
   const normalizedCwd = normalizePath(cwd);
+  const currentRepoId = getRepoIdentity(cwd);
+  const repoIdByWorktree = new Map();
+  const repoIdOfRecordedWorktree = (recordedWorktree) => {
+    if (!repoIdByWorktree.has(recordedWorktree)) {
+      repoIdByWorktree.set(recordedWorktree, getRepoIdentity(recordedWorktree));
+    }
+    return repoIdByWorktree.get(recordedWorktree);
+  };
 
+  let repoMatch = null;
+  let repoMatchContent = null;
   let projectMatch = null;
   let projectMatchContent = null;
   let readableSessions = 0;
@@ -289,9 +308,11 @@ function selectMatchingSession(sessions, cwd, currentProject) {
     if (!content) continue;
     readableSessions++;
 
-    // Extract **Worktree:** field
+    // Extract **Worktree:** and **Repo:** fields
     const worktreeMatch = content.match(/\*\*Worktree:\*\*\s*(.+)$/m);
     const sessionWorktree = worktreeMatch ? worktreeMatch[1].trim() : '';
+    const repoFieldMatch = content.match(/\*\*Repo:\*\*\s*(.+)$/m);
+    const sessionRepo = repoFieldMatch ? repoFieldMatch[1].trim() : '';
 
     // Exact worktree match — best possible, return immediately
     // Normalize both paths to handle symlinks and case-insensitive filesystems
@@ -299,9 +320,24 @@ function selectMatchingSession(sessions, cwd, currentProject) {
       return { session, content, matchReason: 'worktree' };
     }
 
+    // Repository identity match (#3160): the summary lookup is scoped to the
+    // repository, not the cwd path, so a session recorded in worktree A is
+    // eligible in worktree B only when both resolve to the same common git
+    // dir. Unrelated repositories never share.
+    if (!repoMatch && currentRepoId && (sessionRepo || sessionWorktree)) {
+      const sessionRepoId = sessionRepo
+        ? normalizePath(sessionRepo)
+        : repoIdOfRecordedWorktree(sessionWorktree);
+      if (sessionRepoId && sessionRepoId === currentRepoId) {
+        repoMatch = session;
+        repoMatchContent = content;
+      }
+    }
+
     // Project name match is only safe for legacy session files written before
-    // Worktree metadata existed. A different explicit Worktree is not a match.
-    if (!projectMatch && currentProject && !sessionWorktree) {
+    // Worktree/Repo metadata existed. A different explicit Worktree or Repo
+    // is not a match.
+    if (!projectMatch && currentProject && !sessionWorktree && !sessionRepo) {
       const projectFieldMatch = content.match(/\*\*Project:\*\*\s*(.+)$/m);
       const sessionProject = projectFieldMatch ? projectFieldMatch[1].trim() : '';
       if (sessionProject && sessionProject === currentProject) {
@@ -311,6 +347,10 @@ function selectMatchingSession(sessions, cwd, currentProject) {
     }
   }
 
+  if (repoMatch) {
+    return { session: repoMatch, content: repoMatchContent, matchReason: 'repo' };
+  }
+
   if (projectMatch) {
     return { session: projectMatch, content: projectMatchContent, matchReason: 'project' };
   }
diff --git a/scripts/lib/utils.js b/scripts/lib/utils.js
index 5e29868eb..a32f1c200 100644
--- a/scripts/lib/utils.js
+++ b/scripts/lib/utils.js
@@ -135,6 +135,28 @@ function getGitRepoName() {
   return path.basename(result.output);
 }
 
+/**
+ * Get the repository identity for a directory: the canonical (real) path of
+ * the repository's common git dir, which is the main worktree's .git
+ * directory. Every linked worktree of one repository resolves to the same
+ * identity, while unrelated repositories never share one.
+ *
+ * @param {string} [dir] - Directory to resolve from (defaults to process.cwd()).
+ * @returns {string|null} The canonical common git dir, or null when dir is
+ *   not inside a git repository or does not exist.
+ */
+function getRepoIdentity(dir) {
+  const target = dir || process.cwd();
+  const result = runCommand('git rev-parse --git-common-dir', { cwd: target });
+  if (!result.success || !result.output) return null;
+  const commonDir = path.resolve(target, result.output);
+  try {
+    return fs.realpathSync(commonDir);
+  } catch {
+    return commonDir;
+  }
+}
+
 /**
  * Get project name from git repo or current directory
  */
@@ -642,6 +664,7 @@ module.exports = {
   sanitizeSessionId,
   getSessionIdShort,
   getGitRepoName,
+  getRepoIdentity,
   getProjectName,
 
   // File operations
diff --git a/tests/hooks/hooks.test.js b/tests/hooks/hooks.test.js
index 635566b27..374473d2b 100644
--- a/tests/hooks/hooks.test.js
+++ b/tests/hooks/hooks.test.js
@@ -103,6 +103,9 @@ const CLI_RESUME_SESSION_SENTINEL = 'CLI_RESUME_CONTEXT_SHOULD_NOT_BE_INJECTED';
 const CLI_CLEAR_SESSION_SENTINEL = 'CLI_CLEAR_CONTEXT_SHOULD_NOT_BE_INJECTED';
 const DESKTOP_CLEAR_SESSION_SENTINEL = 'DESKTOP_CLEAR_CONTEXT_SHOULD_NOT_BE_INJECTED';
 const PROJECT_ONLY_SESSION_SENTINEL = 'PROJECT_ONLY_CONTEXT_SHOULD_BE_INJECTED';
+const SAME_REPO_WORKTREE_SENTINEL = 'SAME_REPO_WORKTREE_CONTEXT_SHOULD_BE_INJECTED';
+const REPO_FIELD_SESSION_SENTINEL = 'REPO_FIELD_CONTEXT_SHOULD_BE_INJECTED';
+const UNRELATED_REPO_SESSION_SENTINEL = 'UNRELATED_REPO_CONTEXT_SHOULD_NOT_BE_INJECTED';
 
 function buildSessionStartFixture(content, options = {}) {
   const title = options.title ?? '# Session';
@@ -113,11 +116,41 @@ function buildSessionStartFixture(content, options = {}) {
   if (worktree) {
     lines.push(`**Worktree:** ${worktree}`);
   }
+  if (options.repo) {
+    lines.push(`**Repo:** ${options.repo}`);
+  }
   lines.push('', content, '');
 
   return lines.join('\n');
 }
 
+function initGitRepoWithWorktrees(baseDir, worktreeNames) {
+  const mainrepo = path.join(baseDir, 'mainrepo');
+  execFileSync('git', ['init', '-q', mainrepo]);
+  execFileSync('git', ['config', 'user.email', 't@t.local'], { cwd: mainrepo });
+  execFileSync('git', ['config', 'user.name', 't'], { cwd: mainrepo });
+  fs.writeFileSync(path.join(mainrepo, 'README.md'), 'seed\n');
+  execFileSync('git', ['add', '-A'], { cwd: mainrepo });
+  execFileSync('git', ['commit', '-q', '-m', 'seed'], { cwd: mainrepo });
+  const worktrees = {};
+  for (const name of worktreeNames) {
+    const target = path.join(baseDir, name);
+    execFileSync('git', ['worktree', 'add', '-q', '-b', name, target, 'HEAD'], { cwd: mainrepo });
+    worktrees[name] = target;
+  }
+  return { mainrepo, worktrees };
+}
+
+function gitCommonDirRealpath(dir) {
+  const out = execFileSync('git', ['rev-parse', '--git-common-dir'], { cwd: dir, encoding: 'utf8' }).trim();
+  const resolved = path.resolve(dir, out);
+  try {
+    return fs.realpathSync(resolved);
+  } catch {
+    return resolved;
+  }
+}
+
 // Test helper
 function test(name, fn) {
   try {
@@ -145,9 +178,10 @@ async function asyncTest(name, fn) {
 }
 
 // Run a script and capture output
-function runScript(scriptPath, input = '', env = {}) {
+function runScript(scriptPath, input = '', env = {}, cwd = process.cwd()) {
   return new Promise((resolve, reject) => {
     const proc = spawn('node', [scriptPath], {
+      cwd,
       env: { ...process.env, ...env },
       stdio: ['pipe', 'pipe', 'pipe']
     });
@@ -952,6 +986,119 @@ async function runTests() {
     passed++;
   else failed++;
 
+  if (
+    await asyncTest('injects a same-repository session recorded in a different worktree (#3160)', async () => {
+      const isoHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-3160-samerepo-home-'));
+      const sessionsDir = getCanonicalSessionsDir(isoHome);
+      fs.mkdirSync(sessionsDir, { recursive: true });
+      fs.mkdirSync(path.join(isoHome, '.claude', 'skills', 'learned'), { recursive: true });
+      const repoBase = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-3160-samerepo-'));
+      const { worktrees } = initGitRepoWithWorktrees(repoBase, ['wt-a', 'wt-b']);
+
+      const sessionFile = path.join(sessionsDir, '2026-02-11-samerepo-session.tmp');
+      fs.writeFileSync(
+        sessionFile,
+        buildSessionStartFixture(SAME_REPO_WORKTREE_SENTINEL, {
+          project: 'wt-a',
+          worktree: worktrees['wt-a']
+        })
+      );
+
+      try {
+        const result = await runScript(path.join(scriptsDir, 'session-start.js'), '', {
+          HOME: isoHome,
+          USERPROFILE: isoHome
+        }, worktrees['wt-b']);
+        assert.strictEqual(result.code, 0);
+        const additionalContext = getSessionStartAdditionalContext(result.stdout);
+        assert.ok(additionalContext.includes(SAME_REPO_WORKTREE_SENTINEL), 'Should inject a session recorded in another worktree of the same repository');
+        assert.ok(result.stderr.includes('(match: repo)'), `Should report repository identity match, stderr: ${result.stderr}`);
+      } finally {
+        fs.rmSync(isoHome, { recursive: true, force: true });
+        fs.rmSync(repoBase, { recursive: true, force: true });
+      }
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    await asyncTest('scopes sessions by recorded repository identity when the worktree path is gone (#3160)', async () => {
+      const isoHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-3160-repofield-home-'));
+      const sessionsDir = getCanonicalSessionsDir(isoHome);
+      fs.mkdirSync(sessionsDir, { recursive: true });
+      fs.mkdirSync(path.join(isoHome, '.claude', 'skills', 'learned'), { recursive: true });
+      const repoBase = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-3160-repofield-'));
+      const { mainrepo, worktrees } = initGitRepoWithWorktrees(repoBase, ['wt-b']);
+
+      const sessionFile = path.join(sessionsDir, '2026-02-11-repofield-session.tmp');
+      fs.writeFileSync(
+        sessionFile,
+        buildSessionStartFixture(REPO_FIELD_SESSION_SENTINEL, {
+          project: 'wt-removed',
+          worktree: path.join(repoBase, 'wt-removed'),
+          repo: gitCommonDirRealpath(mainrepo)
+        })
+      );
+
+      try {
+        const result = await runScript(path.join(scriptsDir, 'session-start.js'), '', {
+          HOME: isoHome,
+          USERPROFILE: isoHome
+        }, worktrees['wt-b']);
+        assert.strictEqual(result.code, 0);
+        const additionalContext = getSessionStartAdditionalContext(result.stdout);
+        assert.ok(additionalContext.includes(REPO_FIELD_SESSION_SENTINEL), 'Should match on the recorded common git dir when the recorded worktree path no longer resolves');
+        assert.ok(result.stderr.includes('(match: repo)'), `Should report repository identity match, stderr: ${result.stderr}`);
+      } finally {
+        fs.rmSync(isoHome, { recursive: true, force: true });
+        fs.rmSync(repoBase, { recursive: true, force: true });
+      }
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    await asyncTest('never injects a session from an unrelated repository (#3160)', async () => {
+      const isoHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-3160-unrelated-home-'));
+      const sessionsDir = getCanonicalSessionsDir(isoHome);
+      fs.mkdirSync(sessionsDir, { recursive: true });
+      fs.mkdirSync(path.join(isoHome, '.claude', 'skills', 'learned'), { recursive: true });
+      const repoBaseX = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-3160-repox-'));
+      const repoX = initGitRepoWithWorktrees(repoBaseX, ['wt-x']);
+      const repoBaseY = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-3160-repoy-'));
+      const repoY = initGitRepoWithWorktrees(repoBaseY, ['wt-y']);
+
+      const sessionFile = path.join(sessionsDir, '2026-02-11-unrelated-session.tmp');
+      fs.writeFileSync(
+        sessionFile,
+        buildSessionStartFixture(UNRELATED_REPO_SESSION_SENTINEL, {
+          project: 'wt-x',
+          worktree: repoX.worktrees['wt-x'],
+          repo: gitCommonDirRealpath(repoX.mainrepo)
+        })
+      );
+
+      try {
+        const result = await runScript(path.join(scriptsDir, 'session-start.js'), '', {
+          HOME: isoHome,
+          USERPROFILE: isoHome
+        }, repoY.worktrees['wt-y']);
+        assert.strictEqual(result.code, 0);
+        const additionalContext = getSessionStartAdditionalContext(result.stdout);
+        assert.ok(!additionalContext.includes(UNRELATED_REPO_SESSION_SENTINEL), 'Should never inject a session from an unrelated repository');
+        assert.ok(result.stderr.includes('No worktree/project session match found'), `Should log no-match reason, stderr: ${result.stderr}`);
+      } finally {
+        fs.rmSync(isoHome, { recursive: true, force: true });
+        fs.rmSync(repoBaseX, { recursive: true, force: true });
+        fs.rmSync(repoBaseY, { recursive: true, force: true });
+      }
+    })
+  )
+    passed++;
+  else failed++;
+
   if (
     await asyncTest('reports learned skills count', async () => {
       const isoHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-skills-start-'));
@@ -1259,6 +1406,7 @@ async function runTests() {
         assert.ok(content.includes(`**Project:** ${project}`), 'Should persist project metadata');
         assert.ok(content.includes(`**Branch:** ${branch}`), 'Should persist branch metadata');
         assert.ok(content.includes(`**Worktree:** ${process.cwd()}`), 'Should persist worktree metadata');
+        assert.ok(content.includes(`**Repo:** ${gitCommonDirRealpath(process.cwd())}`), 'Should persist repository identity metadata');
       } finally {
         fs.rmSync(isoHome, { recursive: true, force: true });
       }