diff --git a/static/messages.js b/static/messages.js
index 53d0659d..431ca13d 100644
--- a/static/messages.js
+++ b/static/messages.js
@@ -2741,6 +2741,15 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
     if(lastAsst&&lastAsst._turnDuration!==undefined&&lastAsst._turnDuration!==null) return lastAsst._turnDuration;
     if(base&&base.turn_duration!==undefined&&base.turn_duration!==null) return base.turn_duration;
     const session=(typeof S!=='undefined'&&S&&S.session)?S.session:null;
+    // The `pending_started_at` fallback below is the START of an IN-FLIGHT turn.
+    // For a SETTLED turn that recorded no live duration, computing
+    // `now - pending_started_at` is wrong: pending_started_at is either stale
+    // (left over from an earlier turn / a session that sat idle) or belongs to a
+    // different, still-pending turn — which rendered a bogus "Processed 15h 32m"
+    // on fresh conversations (#4930). Only use it while a turn is actually in
+    // flight; otherwise show no duration rather than a fabricated one.
+    const turnInFlight=!!(session&&(session.active_stream_id||session.pending_user_message));
+    if(!turnInFlight) return undefined;
     const candidates=[
       session&&session.pending_started_at,
       session&&session.active_started_at,
diff --git a/tests/test_issue4930_stale_turn_duration.py b/tests/test_issue4930_stale_turn_duration.py
new file mode 100644
index 00000000..dac416c2
--- /dev/null
+++ b/tests/test_issue4930_stale_turn_duration.py
@@ -0,0 +1,104 @@
+"""Regression coverage for #4930 — a settled turn must not render a fabricated
+"Processed 15h 32m" from a stale `pending_started_at`.
+
+`_anchorSceneTurnDurationForSettlement` prefers a recorded live duration
+(`lastAsst._turnDuration` / `base.turn_duration`). Its last-resort fallback used
+to compute `(Date.now()/1000) - session.pending_started_at` unconditionally — but
+`pending_started_at` is the start of an IN-FLIGHT turn, so for a settled turn it
+is either stale (a session that sat idle) or about a different pending turn,
+producing a wildly wrong duration. The fallback is now gated on a turn actually
+being in flight (active_stream_id / pending_user_message); otherwise it returns
+no duration rather than a fabricated one.
+"""
+from __future__ import annotations
+
+import json
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+REPO_ROOT = Path(__file__).parent.parent.resolve()
+MESSAGES_JS = REPO_ROOT / "static" / "messages.js"
+NODE = shutil.which("node")
+
+pytestmark = pytest.mark.skipif(NODE is None, reason="node not on PATH")
+
+# Grab the nested function body and eval it with a controllable global S.
+_DRIVER = r"""
+const fs = require('fs');
+const src = fs.readFileSync(process.argv[2], 'utf8');
+const m = src.match(/function _anchorSceneTurnDurationForSettlement\([^]*?\n  }/);
+if (!m) throw new Error('_anchorSceneTurnDurationForSettlement not found');
+const payload = JSON.parse(process.argv[3] || '{}');
+global.S = payload.S || null;
+// Pin Date.now well past any pending_started_at so a stale stamp would yield a
+// large bogus elapsed if the gate were absent.
+const FIXED_NOW = (payload.nowSeconds || 0) * 1000;
+Date.now = () => FIXED_NOW;
+eval('global._fn = (' + m[0] + ');');
+const out = global._fn(payload.lastAsst || null, payload.base || null);
+process.stdout.write(JSON.stringify({ duration: out === undefined ? null : out }));
+"""
+
+
+def _run(payload: dict) -> dict:
+    assert NODE is not None
+    p = REPO_ROOT / ".tmp_4930_driver.js"
+    p.write_text(_DRIVER, encoding="utf-8")
+    try:
+        result = subprocess.run(
+            [NODE, str(p), str(MESSAGES_JS), json.dumps(payload)],
+            capture_output=True, text=True, timeout=30,
+        )
+    finally:
+        p.unlink(missing_ok=True)
+    if result.returncode != 0:
+        raise RuntimeError(result.stderr)
+    return json.loads(result.stdout)
+
+
+def test_stale_pending_started_at_not_used_when_no_turn_in_flight():
+    """Settled turn, no live duration, stale pending_started_at, NOT in flight →
+    no fabricated duration (the #4930 bug)."""
+    out = _run({
+        "S": {"session": {"pending_started_at": 1000.0}},  # ~15.5h before now
+        "nowSeconds": 1000.0 + 55920,  # 15h 32m later
+        "lastAsst": {},
+        "base": {},
+    })
+    assert out["duration"] is None, f"stale pending_started_at must not produce a duration: {out}"
+
+
+def test_pending_started_at_used_when_turn_in_flight():
+    """When a turn IS in flight, the elapsed-from-pending_started_at fallback is
+    still used (live progress timer behavior preserved)."""
+    out = _run({
+        "S": {"session": {"pending_started_at": 1000.0, "active_stream_id": "s1"}},
+        "nowSeconds": 1000.0 + 5,  # 5s in flight
+        "lastAsst": {},
+        "base": {},
+    })
+    assert out["duration"] is not None and abs(out["duration"] - 5) < 0.5, out
+
+
+def test_recorded_live_duration_always_wins():
+    """A recorded _turnDuration is returned regardless of the in-flight gate."""
+    out = _run({
+        "S": {"session": {"pending_started_at": 1000.0}},
+        "nowSeconds": 1000.0 + 55920,
+        "lastAsst": {"_turnDuration": 4.2},
+        "base": {},
+    })
+    assert abs(out["duration"] - 4.2) < 0.001, out
+
+
+def test_base_turn_duration_wins_over_fallback():
+    out = _run({
+        "S": {"session": {"pending_started_at": 1000.0}},
+        "nowSeconds": 1000.0 + 55920,
+        "lastAsst": {},
+        "base": {"turn_duration": 7.5},
+    })
+    assert abs(out["duration"] - 7.5) < 0.001, out