diff --git a/cron/evolution/hydra.yaml b/cron/evolution/hydra.yaml
index 9547cac1ca..401a953622 100644
--- a/cron/evolution/hydra.yaml
+++ b/cron/evolution/hydra.yaml
@@ -26,6 +26,12 @@ prompt: |
   2. DECIDE which stages have fresh upstream output newer than their consumer.
   3. DISPATCH up to 3 subagents per tick, upstream stages first.
   4. APPEND a brief record to KNOWLEDGE/hydra-dispatch-{date}.jsonl.
+     NAMING CONVENTION (#120): tick1 IS the base file hydra-dispatch-{date}.jsonl —
+     there is no separate hydra-dispatch-{date}-tick1.json(l). Per-tick snapshots
+     are named hydra-dispatch-{date}-tickN.jsonl for N >= 2 ONLY. Before reading a
+     dispatch artifact, list KNOWLEDGE/hydra-dispatch-* and read the newest existing
+     file; never guess a tickN path (that File-not-found breaks the pre-run gate).
+     Canonical templates live in ONE place: scripts/evolution_dispatch_paths.py.
 
   ## Stage definitions (delegate_task goal only)
   research – scan for new AI agent frameworks/papers/trends.
diff --git a/scripts/evolution_dispatch_paths.py b/scripts/evolution_dispatch_paths.py
new file mode 100644
index 0000000000..e743d1a163
--- /dev/null
+++ b/scripts/evolution_dispatch_paths.py
@@ -0,0 +1,62 @@
+#!/usr/bin/env python3
+"""Canonical Hydra dispatch artifact path templates (issue #120).
+
+Single source of truth for the dispatch-file naming convention so the
+reader and writer can never drift:
+
+  * tick1 == the base file:  hydra-dispatch-{date}.jsonl
+  * per-tick snapshots:      hydra-dispatch-{date}-tickN.jsonl  (N >= 2)
+
+Usage:
+  python scripts/evolution_dispatch_paths.py base 2026-08-26
+  python scripts/evolution_dispatch_paths.py tick 2026-08-26 7
+  python scripts/evolution_dispatch_paths.py latest [KNOWLEDGE_DIR]
+"""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+DISPATCH_BASE_TEMPLATE = "hydra-dispatch-{date}.jsonl"
+
+
+def base_path(date: str) -> str:
+    """tick1 — the base dispatch file for ``date``."""
+    return DISPATCH_BASE_TEMPLATE.format(date=date)
+
+
+def tick_path(date: str, tick: int) -> str:
+    """Per-tick snapshot path. tick 1 is the base file, NOT a tick1 file."""
+    if tick <= 1:
+        return base_path(date)
+    return f"hydra-dispatch-{date}-tick{tick}.jsonl"
+
+
+def latest(known: Path) -> Path | None:
+    """Newest existing hydra-dispatch-*.jsonl under ``known`` (or None)."""
+    matches = sorted(known.glob("hydra-dispatch-*.jsonl"), key=lambda p: p.name)
+    return matches[-1] if matches else None
+
+
+def main(argv: list[str]) -> int:
+    if len(argv) < 2:
+        print(__doc__)
+        return 2
+    cmd = argv[1]
+    if cmd == "base" and len(argv) >= 3:
+        print(base_path(argv[2]))
+        return 0
+    if cmd == "tick" and len(argv) >= 4:
+        print(tick_path(argv[2], int(argv[3])))
+        return 0
+    if cmd == "latest":
+        known = Path(argv[2]) if len(argv) >= 3 else Path.home() / ".hermes" / "knowledge"
+        hit = latest(known)
+        print(hit if hit else "<none>")
+        return 0 if hit else 1
+    print(__doc__)
+    return 2
+
+
+if __name__ == "__main__":
+    raise SystemExit(main(sys.argv))