diff --git a/README.md b/README.md
index 4fd259f..bfe1760 100644
--- a/README.md
+++ b/README.md
@@ -83,6 +83,7 @@ agentrace list                  # every subagent run: description, duration, siz
 agentrace check                 # flag suspicious results
 agentrace check --severity high # only the ones that definitely matter
 agentrace check --strict        # exit 1 on any high finding (CI-friendly)
+agentrace check --slow-seconds 300 # tune the slow-run threshold (default: 900)
 agentrace show 6e7fAJ8T         # read one run in full: prompt, result, findings
 agentrace stats --json          # aggregate, machine-readable
 ```
diff --git a/agentrace/checks.py b/agentrace/checks.py
index 4204050..41e7020 100644
--- a/agentrace/checks.py
+++ b/agentrace/checks.py
@@ -336,10 +336,13 @@ def check_runaway(run: AgentRun, slow_s: float = 900.0) -> list[Finding]:
 ]
 
 
-def analyse(run: AgentRun) -> list[Finding]:
+def analyse(run: AgentRun, slow_s: float = 900.0) -> list[Finding]:
     findings: list[Finding] = []
     for check in CHECKS:
-        findings.extend(check(run))
+        if check is check_runaway:
+            findings.extend(check_runaway(run, slow_s=slow_s))
+        else:
+            findings.extend(check(run))
     order = {"high": 0, "medium": 1, "low": 2}
     findings.sort(key=lambda f: order.get(f.severity, 9))
     return findings
diff --git a/agentrace/cli.py b/agentrace/cli.py
index c511699..c7cda50 100644
--- a/agentrace/cli.py
+++ b/agentrace/cli.py
@@ -85,7 +85,8 @@ def cmd_check(args) -> int:
     total_findings = 0
     has_high = False
     for r in runs:
-        findings = analyse(r)
+        slow_seconds = getattr(args, "slow_seconds", 900.0)
+        findings = analyse(r) if slow_seconds == 900.0 else analyse(r, slow_s=slow_seconds)
         if args.severity:
             findings = [f for f in findings if f.severity == args.severity]
         has_high = has_high or any(f.severity == "high" for f in findings)
@@ -204,6 +205,12 @@ def main(argv: list[str] | None = None) -> int:
 
     c = sub.add_parser("check", help="flag suspicious results")
     c.add_argument("--severity", choices=["high", "medium", "low"], help="only this severity")
+    c.add_argument(
+        "--slow-seconds",
+        type=float,
+        default=900.0,
+        help="flag runs longer than this many seconds (default: 900)",
+    )
     c.add_argument("--strict", action="store_true", help="exit 1 if any displayed high severity finding")
     c.set_defaults(func=cmd_check)
 
diff --git a/tests/test_agentrace.py b/tests/test_agentrace.py
index ec90a7d..22ce91a 100644
--- a/tests/test_agentrace.py
+++ b/tests/test_agentrace.py
@@ -11,7 +11,7 @@
 from __future__ import annotations
 
 import json
-from datetime import UTC, datetime
+from datetime import UTC, datetime, timedelta
 
 from agentrace.checks import analyse
 from agentrace.parse import AgentRun, parse_session
@@ -296,6 +296,15 @@ def test_slow_run_is_flagged():
     assert "slow_run" in _codes(r)
 
 
+def test_slow_run_threshold_is_configurable():
+    start = datetime(2026, 7, 16, 12, 0, tzinfo=UTC)
+    thirty_minutes = _run(started_at=start, ended_at=start + timedelta(minutes=30))
+    two_minutes = _run(started_at=start, ended_at=start + timedelta(minutes=2))
+
+    assert "slow_run" not in {f.check for f in analyse(thirty_minutes, slow_s=1801)}
+    assert "slow_run" in {f.check for f in analyse(two_minutes, slow_s=60)}
+
+
 def test_clean_run_produces_nothing():
     """The most important test here. A checker that flags everything gets ignored."""
     r = _run(