diff --git a/hooks/hook_runner.py b/hooks/hook_runner.py
index 4ee0fe17..02d00026 100644
--- a/hooks/hook_runner.py
+++ b/hooks/hook_runner.py
@@ -121,6 +121,50 @@ def _record_sync_signal(event: str, data: dict) -> None:
         pass
 
 
+# Dedup markers are only meaningful for the 500 ms double-fire window, but each
+# distinct (event, payload) writes its own file. Without pruning, the markers
+# directory leaks one file per unique tool call indefinitely. Sweep stale markers
+# on a coarse time-gate so the cost stays amortized-cheap.
+_DEDUP_TTL_SEC = 5  # markers older than this are stale (>> 500 ms dedup window)
+_DEDUP_SWEEP_INTERVAL_SEC = 60  # sweep at most once per minute
+_DEDUP_SWEEP_STAMP = MARKERS_DIR / "dedup-sweep.stamp"
+
+
+def _prune_stale_dedup_markers() -> None:
+    """Remove leaked ``hook-dedup-*`` markers older than the dedup window.
+
+    Time-gated to run at most once per ``_DEDUP_SWEEP_INTERVAL_SEC`` so a busy
+    session does not pay an O(N) directory scan on every hook invocation.
+
+    Fail-open: any I/O error is swallowed.
+    """
+    try:
+        now = time.time()
+        try:
+            if (
+                _DEDUP_SWEEP_STAMP.is_file()
+                and now - _DEDUP_SWEEP_STAMP.stat().st_mtime < _DEDUP_SWEEP_INTERVAL_SEC
+            ):
+                return
+        except Exception:
+            pass
+        # Claim the sweep slot before scanning so concurrent hooks do not all sweep.
+        try:
+            MARKERS_DIR.mkdir(parents=True, exist_ok=True)
+            _DEDUP_SWEEP_STAMP.write_text(str(int(now)), encoding="utf-8")
+        except Exception:
+            pass
+        cutoff = now - _DEDUP_TTL_SEC
+        for p in MARKERS_DIR.glob("hook-dedup-*"):
+            try:
+                if p.is_file() and p.stat().st_mtime < cutoff:
+                    p.unlink()
+            except Exception:
+                continue
+    except Exception:
+        pass
+
+
 def _check_and_set_dedup(event: str, payload_hash: str = "") -> bool:
     """Return True if this event+payload should be skipped as a double-fire duplicate.
 
@@ -131,6 +175,7 @@ def _check_and_set_dedup(event: str, payload_hash: str = "") -> bool:
     Fail-open: any I/O error → returns False (process normally).
     """
     try:
+        _prune_stale_dedup_markers()
         key = f"{event}-{payload_hash}" if payload_hash else event
         # Sanitise key to a safe filename: keep only alphanumeric + dash + dot
         safe_key = "".join(c if c.isalnum() or c in "-." else "_" for c in key)
diff --git a/hooks/rules/error_kb.py b/hooks/rules/error_kb.py
index cda20618..38c25c19 100644
--- a/hooks/rules/error_kb.py
+++ b/hooks/rules/error_kb.py
@@ -132,7 +132,18 @@ class ErrorFixNudgeRule(Rule):
 
     def evaluate(self, event, data):
         tool_name = data.get("toolName", "")
-        tool_args = data.get("toolArgs", {}) or {}
+        # toolArgs may arrive as a dict, a JSON string, or be absent depending on
+        # the runtime. Normalise to a dict so the later .get() calls never crash
+        # with "'str' object has no attribute 'get'".
+        tool_args = data.get("toolArgs", {})
+        if isinstance(tool_args, str):
+            try:
+                parsed = json.loads(tool_args)
+                tool_args = parsed if isinstance(parsed, dict) else {}
+            except Exception:
+                tool_args = {}
+        elif not isinstance(tool_args, dict):
+            tool_args = {}
 
         # Clear marker when learn.py is detected in bash command
         if tool_name == "bash":
diff --git a/hooks/rules/tentacle.py b/hooks/rules/tentacle.py
index e6f41ace..1b8902e2 100644
--- a/hooks/rules/tentacle.py
+++ b/hooks/rules/tentacle.py
@@ -109,9 +109,16 @@ def _read_edits(path):
                     return data
             except (json.JSONDecodeError, ValueError):
                 pass
-    # Legacy: flat set of file paths → migrate with current timestamp
-    now = time.time()
-    legacy_entries = [{"p": fp, "t": now} for fp in raw_set if fp]
+    # Legacy: flat set of file paths → migrate with the marker's last-modified
+    # time (NOT the current time). Stamping with now() on every read would
+    # perpetually refresh the entries so they never satisfy the 24 h TTL,
+    # permanently poisoning the "legacy" bucket. Using the file mtime lets
+    # migrated entries expire ~24 h after the marker was last written.
+    try:
+        base_ts = path.stat().st_mtime
+    except Exception:
+        base_ts = time.time()
+    legacy_entries = [{"p": fp, "t": base_ts} for fp in raw_set if fp]
     return {"legacy": legacy_entries}
 
 
diff --git a/tests/test_hook_rules_more.py b/tests/test_hook_rules_more.py
index 456d3d80..98f349bc 100644
--- a/tests/test_hook_rules_more.py
+++ b/tests/test_hook_rules_more.py
@@ -265,6 +265,30 @@ def _capture_run(args, **kwargs):
 test("ErrorKBRule name", rule.name == "error-kb")
 test("ErrorKBRule events", "errorOccurred" in rule.events)
 
+# 2j. ErrorFixNudgeRule must not crash when toolArgs is a string (regression).
+# Previously `data.get("toolArgs", {}) or {}` kept a non-empty string and the
+# subsequent `.get()` raised "'str' object has no attribute 'get'" (367 logged
+# errors in the wild).
+from rules.error_kb import ErrorFixNudgeRule
+
+_nudge_rule = ErrorFixNudgeRule()
+try:
+    _r2j = _nudge_rule.evaluate("postToolUse", {"toolName": "bash", "toolArgs": "not-a-dict"})
+    test("ErrorFixNudgeRule: string toolArgs does not crash", _r2j is None or isinstance(_r2j, dict))
+except Exception as _e2j:
+    test("ErrorFixNudgeRule: string toolArgs does not crash", False, f"raised: {_e2j}")
+
+# 2k. ErrorFixNudgeRule still parses a JSON-string toolArgs so the learn.py
+# marker-clear path keeps working when the runtime passes args as a string.
+try:
+    _r2k = _nudge_rule.evaluate(
+        "postToolUse",
+        {"toolName": "bash", "toolArgs": '{"command": "python3 learn.py --mistake x y"}'},
+    )
+    test("ErrorFixNudgeRule: JSON-string toolArgs parsed (learn.py clears nudge)", _r2k is None)
+except Exception as _e2k:
+    test("ErrorFixNudgeRule: JSON-string toolArgs parsed (learn.py clears nudge)", False, f"raised: {_e2k}")
+
 
 # ══════════════════════════════════════════════════════════════════════
 #  Section 3: SessionEndRule
diff --git a/tests/test_hook_runner_entrypoints.py b/tests/test_hook_runner_entrypoints.py
index 86057b10..a85af95b 100644
--- a/tests/test_hook_runner_entrypoints.py
+++ b/tests/test_hook_runner_entrypoints.py
@@ -1046,6 +1046,42 @@ def _run_dedup_event(event: str, payload: dict) -> subprocess.CompletedProcess:
 
 shutil.rmtree(str(_dd_home), ignore_errors=True)
 
+# 14b. Regression: stale hook-dedup-* markers are pruned so the directory does
+# not leak one file per unique tool call (previously grew to 130k+ files).
+_ddp_home = Path(tempfile.mkdtemp(prefix="test-ep-ddp-"))
+_ddp_markers = _ddp_home / ".copilot" / "markers"
+_ddp_markers.mkdir(parents=True, exist_ok=True)
+_ddp_env = {**os.environ, "HOME": str(_ddp_home), "USERPROFILE": str(_ddp_home), "HOOK_DRY_RUN": "1"}
+
+# Plant a stale dedup marker (mtime 10 s ago → older than the 5 s TTL).
+_stale_marker = _ddp_markers / "hook-dedup-preToolUse-deadbeef"
+_stale_marker.write_text("0", encoding="utf-8")
+_stale_ts = time.time() - 10
+os.utime(str(_stale_marker), (_stale_ts, _stale_ts))
+
+# No sweep stamp yet → the first hook invocation must run the sweep.
+_ddp_r = subprocess.run(
+    [sys.executable, str(RUNNER), "preToolUse"],
+    input=json.dumps({"toolName": "read", "toolArgs": {"path": "bar.py"}}),
+    capture_output=True,
+    text=True,
+    encoding="utf-8",
+    timeout=10,
+    env=_ddp_env,
+    cwd=str(REPO / "hooks"),
+)
+test(
+    "dedup-prune: stale hook-dedup marker removed by sweep",
+    not _stale_marker.exists(),
+    f"stale marker still present; markers={list(_ddp_markers.glob('hook-dedup-*'))}",
+)
+test(
+    "dedup-prune: fresh marker for current call survives sweep",
+    any(f.name.startswith("hook-dedup-preToolUse") for f in _ddp_markers.iterdir() if f.is_file()),
+    f"markers={list(_ddp_markers.glob('hook-dedup-*'))}",
+)
+shutil.rmtree(str(_ddp_home), ignore_errors=True)
+
 shutil.rmtree(_ISOLATED_HOME, ignore_errors=True)
 
 # ══════════════════════════════════════════════════════════════════════
diff --git a/tests/test_hooks.py b/tests/test_hooks.py
index b3278520..91579f2c 100644
--- a/tests/test_hooks.py
+++ b/tests/test_hooks.py
@@ -3809,6 +3809,32 @@ def _make_event21(command, *, edited_files=None):
     )
     test("17b2: all 3 legacy paths present", len(_loaded17b.get("legacy", [])) == 3, f"Got: {_loaded17b!r}")
 
+    # 17b3. Regression: legacy entries are stamped with the marker's mtime, NOT
+    # now(), so an old marker's entries expire via _prune_ttl instead of being
+    # perpetually refreshed (which previously caused permanent false-positive
+    # TENTACLE REQUIRED blocks).
+    _td17b3 = Path(tempfile.mkdtemp(prefix="test-17b3-"))
+    _marker17b3 = _td17b3 / "tentacle-edits"
+    _marker17b3.write_text("placeholder", encoding="utf-8")
+    _old_ts17b3 = _now17 - (86400 * 2)  # 2 days ago → outside the 24 h TTL
+    os.utime(str(_marker17b3), (_old_ts17b3, _old_ts17b3))
+    _orig_vlist17b3 = _rt17.verify_list_marker
+    _rt17.verify_list_marker = lambda p: {"src/old.py", "tests/old.py"}
+    _loaded17b3 = _read_edits(_marker17b3)
+    _rt17.verify_list_marker = _orig_vlist17b3
+    _legacy_ts17b3 = [e["t"] for e in _loaded17b3.get("legacy", [])]
+    test(
+        "17b3: legacy entries stamped with marker mtime (not now)",
+        bool(_legacy_ts17b3) and all(abs(t - _old_ts17b3) < 2 for t in _legacy_ts17b3),
+        f"Got timestamps: {_legacy_ts17b3!r} (expected ~{_old_ts17b3})",
+    )
+    test(
+        "17b3b: stale legacy entries expire via _prune_ttl",
+        _prune_ttl(_loaded17b3.get("legacy", []), _now17) == [],
+        f"Got: {_prune_ttl(_loaded17b3.get('legacy', []), _now17)!r}",
+    )
+    shutil.rmtree(str(_td17b3), ignore_errors=True)
+
     # 17c. Cross-repo isolation: repo-A entries invisible from repo-B
     _repo_a17c = "/fake/repo-a"
     _repo_b17c = "/fake/repo-b"