diff --git a/src/session.ts b/src/session.ts
index 413211c4..dfbb8860 100644
--- a/src/session.ts
+++ b/src/session.ts
@@ -2075,7 +2075,12 @@ export class Session extends EventEmitter {
     }
 
     // Set claudeSessionId — when resuming, the Claude conversation ID is the resumed one.
-    this._claudeSessionId = this._resumeSessionId || this.id;
+    // Mirrors the mux branch above and must not clobber it: this line runs
+    // unconditionally after both the mux and direct-PTY paths, so it also needs
+    // the ompConfig fallback or it stomps the mux branch's correctly-resolved
+    // OMP alias back to this.id on every mux/plain-reattach boot recovery
+    // (the "third reset point" — see DECISIONS.md).
+    this._claudeSessionId = this._resumeSessionId || this._ompConfig?.resumeSessionId || this.id;
 
     this._pid = this.ptyProcess.pid;
     console.log('[Session] Interactive PTY spawned with PID:', this._pid);
diff --git a/src/utils/omp-session-resolver.ts b/src/utils/omp-session-resolver.ts
index 37b67a44..d17897e6 100644
--- a/src/utils/omp-session-resolver.ts
+++ b/src/utils/omp-session-resolver.ts
@@ -17,17 +17,30 @@
 
 import { readdirSync, statSync } from 'node:fs';
 import { homedir } from 'node:os';
-import { join } from 'node:path';
+import { join, sep } from 'node:path';
 
 /** A real OMP session file is `<ISO-ish-timestamp>_<uuid>.jsonl`; only the uuid matters here. */
 const OMP_SESSION_FILE_PATTERN = /^.+_([a-zA-Z0-9-]+)\.jsonl$/;
 
 /**
- * Mirrors `omp`'s own directory mangling: every path separator becomes a
- * dash. Pure so it's unit-testable without touching the filesystem.
+ * Mirrors `omp`'s own directory mangling. Confirmed empirically against real
+ * `~/.omp/agent/sessions/` directory names (2026-08-27): unlike Claude Code's
+ * `~/.claude/projects/*`, which keeps the home prefix (`-home-user-dev-foo`),
+ * omp collapses a home-relative workingDir to its home-relative remainder
+ * FIRST (`/home/user/dev/foo` -> `/dev/foo`) and only then dash-replaces
+ * (`-dev-foo`) — a path outside $HOME (e.g. `/tmp/...`) is dash-replaced as-is.
+ * Getting this wrong doesn't error, it just silently returns an empty
+ * directory listing: findLatestOmpSessionId() below then always falls through
+ * to null, so continuation pinning quietly degrades to omp's own ambiguous
+ * `--continue` for every case under $HOME (i.e. virtually all real Codeman
+ * cases) while appearing to work in `/tmp`-based manual testing.
+ * Pure so it's unit-testable without touching the filesystem.
  */
 export function mangleOmpWorkingDir(workingDir: string): string {
-  return workingDir.replace(/\//g, '-');
+  const home = homedir();
+  const relative =
+    workingDir === home || workingDir.startsWith(home + sep) ? workingDir.slice(home.length) : workingDir;
+  return relative.replace(/\//g, '-');
 }
 
 /** `~/.omp` — no known env override exists (unlike DSH_HOME); revisit if omp adds one. */
diff --git a/test/omp-session-resolver.test.ts b/test/omp-session-resolver.test.ts
new file mode 100644
index 00000000..f500c8a2
--- /dev/null
+++ b/test/omp-session-resolver.test.ts
@@ -0,0 +1,69 @@
+/**
+ * @fileoverview Tests for OMP session-id resolution from disk.
+ *
+ * Pins the home-relative directory mangling bug found 2026-08-27: omp
+ * collapses a home-relative workingDir to its home-relative remainder BEFORE
+ * dash-replacing (`/home/user/dev/foo` -> `-dev-foo`), unlike Claude Code's
+ * `~/.claude/projects/*` convention (`-home-user-dev-foo`) this module was
+ * originally written to mirror. Getting this wrong doesn't throw — it just
+ * makes findLatestOmpSessionId() silently return null for every case under
+ * $HOME (virtually all real Codeman cases), so continuation pinning quietly
+ * degraded to omp's own ambiguous `--continue` while appearing to work in
+ * manual testing done entirely under /tmp (which sits outside $HOME and was
+ * mangled correctly by coincidence).
+ *
+ * test/setup.ts gives this file its own temp $HOME, so homedir() below is
+ * already sandboxed — writing real files under it is safe and exercises the
+ * exact home-relative path the bug hid behind.
+ */
+import { mkdirSync, rmSync, utimesSync, writeFileSync } from 'node:fs';
+import { homedir } from 'node:os';
+import { join } from 'node:path';
+import { afterEach, describe, expect, it } from 'vitest';
+import { findLatestOmpSessionId, mangleOmpWorkingDir } from '../src/utils/omp-session-resolver.js';
+
+describe('mangleOmpWorkingDir', () => {
+  it('strips the home prefix before dash-replacing a home-relative path', () => {
+    const home = homedir();
+    expect(mangleOmpWorkingDir(join(home, 'codeman-cases', 'testcase'))).toBe('-codeman-cases-testcase');
+  });
+
+  it('dash-replaces a path outside $HOME as-is', () => {
+    expect(mangleOmpWorkingDir('/tmp/omp-verify-case')).toBe('-tmp-omp-verify-case');
+  });
+
+  it('treats workingDir === home as the empty remainder', () => {
+    expect(mangleOmpWorkingDir(homedir())).toBe('');
+  });
+
+  it('does not false-positive on a sibling directory sharing a prefix with $HOME', () => {
+    const sibling = `${homedir()}-other/dev/foo`;
+    expect(mangleOmpWorkingDir(sibling)).toBe(sibling.replace(/\//g, '-'));
+  });
+});
+
+describe('findLatestOmpSessionId', () => {
+  const sessionDir = join(homedir(), '.omp', 'agent', 'sessions', '-codeman-cases-testcase');
+
+  afterEach(() => {
+    rmSync(join(homedir(), '.omp'), { recursive: true, force: true });
+  });
+
+  it('finds the newest session file under a home-relative workingDir', () => {
+    const workingDir = join(homedir(), 'codeman-cases', 'testcase');
+    mkdirSync(sessionDir, { recursive: true });
+    writeFileSync(join(sessionDir, '2026-08-27T17-15-57-989Z_older-id.jsonl'), '{}');
+    const newer = join(sessionDir, '2026-08-27T17-31-08-001Z_newer-id.jsonl');
+    writeFileSync(newer, '{}');
+    // Force a deterministic mtime order regardless of filesystem timestamp resolution.
+    const now = Date.now() / 1000;
+    utimesSync(join(sessionDir, '2026-08-27T17-15-57-989Z_older-id.jsonl'), now, now);
+    utimesSync(newer, now + 1, now + 1);
+
+    expect(findLatestOmpSessionId(workingDir)).toBe('newer-id');
+  });
+
+  it('returns null when the mangled directory does not exist', () => {
+    expect(findLatestOmpSessionId(join(homedir(), 'never-launched'))).toBeNull();
+  });
+});