diff --git a/plugins/os-backlog/hooks/hooks.json b/plugins/os-backlog/hooks/hooks.json
new file mode 100644
index 0000000..cdb73ee
--- /dev/null
+++ b/plugins/os-backlog/hooks/hooks.json
@@ -0,0 +1,16 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "matcher": "startup|resume|compact",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 ${CLAUDE_PLUGIN_ROOT}/hooks/session_start.py",
+            "timeout": 5
+          }
+        ]
+      }
+    ]
+  }
+}
diff --git a/plugins/os-backlog/hooks/session_start.py b/plugins/os-backlog/hooks/session_start.py
new file mode 100644
index 0000000..013ca73
--- /dev/null
+++ b/plugins/os-backlog/hooks/session_start.py
@@ -0,0 +1,69 @@
+#!/usr/bin/env python3
+"""session_start.py — deterministic SessionStart injection note for os-backlog.
+
+Modeled on os-adr's session_start.py (the wording-source-of-record pattern).
+Injects the backlog process rules — WHEN->THEN mechanical triggers only.
+Deliberately contains ZERO board state and no briefs (notification policy v2:
+pull beats push — board state is fetched on demand via /os-backlog:list, never
+pushed into a session).
+
+  git project      -> additionalContext note (rules only, near-zero tokens)
+  not a git repo   -> silent (process rules only apply inside real projects)
+
+Autonomy-label semantics in NOTE are the ADR-029 contract (which supersedes
+the wording in issue #16's body): hitl never picked up autonomously; semi
+stops at Review for human sign-off; afk-ready goes straight to Done after
+verification, skipping Review.
+
+Pure function of the project's filesystem state; no model, no network, no
+Ruby, no Planka call. Always exits 0 — the hook must never block a session.
+"""
+
+from __future__ import annotations
+
+import json
+import sys
+from pathlib import Path
+from typing import Optional
+
+NOTE = """\
+[os-backlog] Backlog process rules (rules only — this note never carries board state; board state is pull-only via /os-backlog:list when the user asks).
+- CAPTURE: WHEN a concrete follow-up task, bug, or piece of deferred work surfaces mid-session that will NOT be done this session -> capture it as a Backlog card via /os-backlog:capture. Never a TODO comment in code, never only a mention in chat.
+- ROUTING: WHEN process/backlog/spec-tracking work surfaces -> read the tracker key from .cc-os/config (`tracker=planka:<board>` | `forgejo:<owner>/<repo>` | `github:<owner>/<repo>` | `repo:<path>`) and send work where it says. WHEN this is a git project and no tracker key is configured -> suggest /os-backlog:route once; do not nag.
+- PROMOTION: WHEN a Planka-tracked effort accretes significant code or design decisions in card comments -> flag promotion to the user (never silently): carve out a repo, move the durable spec into git issues via /to-issues, and keep the Planka card as a pointer (title + link). Never duplicate spec text into a card description.
+- COLUMN OWNERSHIP (CLI-enforced per ADR-029; a violating card-move fails with the rule named): create cards at Backlog only. Never move a card into or out of Next — Next is human-curated in both directions. Never move a card labeled hitl; never move a card out of Done. Working a card MEANS moving it via card-move: Doing when work starts, Waiting + a blocker comment when blocked, and on shipping: Review (semi) or Done (afk-ready, only after verification).
+- AUTONOMY LABELS (ADR-029): hitl -> human-owned; never picked up autonomously. semi -> run the mechanical parts, stop at named decision gates; shipped work goes to Review for human sign-off. afk-ready -> shipped + verified goes straight to Done, skipping Review.
+"""
+
+
+def find_project_root(cwd: Path) -> Optional[Path]:
+    """Nearest ancestor (including cwd) containing .git, else None."""
+    for candidate in [cwd, *cwd.parents]:
+        if (candidate / ".git").exists():
+            return candidate
+    return None
+
+
+def run(root: Optional[Path], out) -> str:
+    """Pure decision: ('context'|'silent'). Emits hook JSON when in a project."""
+    if root is None:
+        return "silent"
+    out.write(json.dumps({
+        "hookSpecificOutput": {
+            "hookEventName": "SessionStart",
+            "additionalContext": NOTE,
+        }
+    }))
+    return "context"
+
+
+def main() -> int:
+    try:
+        run(find_project_root(Path.cwd()), sys.stdout)
+    except Exception:
+        pass  # never block a session
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/plugins/os-backlog/lib/backlog/tracker.rb b/plugins/os-backlog/lib/backlog/tracker.rb
index fee4c7d..8480022 100644
--- a/plugins/os-backlog/lib/backlog/tracker.rb
+++ b/plugins/os-backlog/lib/backlog/tracker.rb
@@ -25,6 +25,22 @@ module Backlog
       nil
     end
 
+    # Where /to-issues output (spec slices) should be published, given the
+    # repo's tracker key. The ADR'd boundary: git issues = specs, Planka =
+    # state. So forgejo:/github: keys route spec slices to that git issue
+    # tracker. `planka:` / `repo:` / nil deliberately map to
+    # :planka_default — what that MEANS for spec-shaped output is a named
+    # decision gate at wording review (issue #16), not settled here.
+    #
+    # @return [Symbol] :git_issues | :planka_default | :unrouted (invalid key)
+    def self.issues_destination(value)
+      case kind(value)
+      when :forgejo, :github then :git_issues
+      when :planka, :repo then :planka_default
+      else value.nil? ? :planka_default : :unrouted
+      end
+    end
+
     # Parse the first remote line of `git remote -v` output and classify it
     # as a Forgejo or GitHub remote (or :unknown for anything else).
     #
diff --git a/plugins/os-backlog/tests/issues_routing_test.rb b/plugins/os-backlog/tests/issues_routing_test.rb
new file mode 100644
index 0000000..251474f
--- /dev/null
+++ b/plugins/os-backlog/tests/issues_routing_test.rb
@@ -0,0 +1,29 @@
+# /to-issues routing wiring (issue #16): spec-slice output honors the
+# tracker key per the ADR'd boundary (git issues = specs, Planka = state).
+require_relative "test_helper"
+
+class IssuesRoutingTest < Minitest::Test
+  def test_forgejo_tracker_routes_spec_slices_to_git_issues
+    assert_equal :git_issues, Backlog::Tracker.issues_destination("forgejo:jared/cc-os")
+  end
+
+  def test_github_tracker_routes_spec_slices_to_git_issues
+    assert_equal :git_issues, Backlog::Tracker.issues_destination("github:jared/some-repo")
+  end
+
+  def test_planka_tracker_is_the_gated_default
+    assert_equal :planka_default, Backlog::Tracker.issues_destination("planka:cc-os")
+  end
+
+  def test_repo_tracker_is_the_gated_default
+    assert_equal :planka_default, Backlog::Tracker.issues_destination("repo:docs/issues")
+  end
+
+  def test_absent_tracker_is_the_gated_default
+    assert_equal :planka_default, Backlog::Tracker.issues_destination(nil)
+  end
+
+  def test_invalid_tracker_is_unrouted
+    assert_equal :unrouted, Backlog::Tracker.issues_destination("jira:whatever")
+  end
+end