diff --git a/.github/workflows/sync.yml b/.github/workflows/sync.yml
index 88284d4..beb6331 100644
--- a/.github/workflows/sync.yml
+++ b/.github/workflows/sync.yml
@@ -3,7 +3,7 @@ name: sync
 # per branch: main goes out to every copy, fast-forward only (a copy with commits of its own is reported, never
 # overwritten); the branches a copy is told to send back (claude/* from cloud sessions on GitHub) come in as PRs here,
 # and Time's council reviews and lands them like any other. Each copy's token is a secret named in sync.json and passed
-# below; a copy without one is skipped. On a GitHub copy, turn GitHub Actions off: these workflows must run here only.
+# below (a token for https, a deploy key for ssh); a copy without one is skipped. On a GitHub copy, turn GitHub Actions off: these workflows must run here only.
 on:
   push:
     branches: [main]
@@ -27,9 +27,12 @@ jobs:
         with:
           sparse-checkout: .github/time
           persist-credentials: false
+      # a copy over SSH (a deploy key) needs the ssh client; the job image may not have it
+      - run: command -v ssh || (apt-get update -qq && apt-get install -y -qq --no-install-recommends openssh-client >/dev/null)
       - run: python3 .github/time/sync.py
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           TIME_TOKEN: ${{ secrets.TIME_TOKEN }}   # branches and PRs on the home go in as the `time` user
           SYNC_FORCE: ${{ inputs.force && '1' || '' }}
-          GITHUB_MIRROR_TOKEN: ${{ secrets.GITHUB_MIRROR_TOKEN }}   # github.com/teahubxyz/time: Contents read/write
+          GITHUB_MIRROR_KEY: ${{ secrets.GITHUB_MIRROR_KEY }}       # github.com/teahubxyz/time: a deploy key with write access
+          GITHUB_MIRROR_TOKEN: ${{ secrets.GITHUB_MIRROR_TOKEN }}   # or a token, for a copy over https
diff --git a/time/sync.json b/time/sync.json
index a042f4c..31cea5f 100644
--- a/time/sync.json
+++ b/time/sync.json
@@ -1,7 +1,21 @@
 {
- "_about": "Copies of repos on other forges, kept in step by .github/time/sync.py (the sync workflow). Each repo has one home (this forge) and every branch one writer: the `out` branches go from the home to each copy, fast-forward only; a copy's branches matching its `import` patterns come back to the home as PRs. `token` names the secret holding the copy's token, never the token itself; a copy whose secret isn't set is skipped. A GitHub copy needs GitHub Actions turned off, since these workflows must only run here.",
+ "_about": "Copies of repos on other forges, kept in step by .github/time/sync.py (the sync workflow). Each repo has one home (this forge) and every branch one writer: the `out` branches go from the home to each copy, fast-forward only; a copy's branches matching its `import` patterns come back to the home as PRs. `token` (https) or `ssh_key` (a deploy key, for ssh/git@ URLs; host keys pinned) names the secret that holds the credential, never the credential itself; a copy whose secret isn't set is skipped. A GitHub copy needs GitHub Actions turned off, since these workflows must only run here.",
  "repos": [
-  {"repo": "teahubxyz/time", "out": ["main"],
-   "copies": [{"name": "github", "url": "https://github.com/teahubxyz/time.git", "token": "GITHUB_MIRROR_TOKEN", "import": ["claude/*"]}]}
+  {
+   "repo": "teahubxyz/time",
+   "out": [
+    "main"
+   ],
+   "copies": [
+    {
+     "name": "github",
+     "url": "git@github.com:teahubxyz/time.git",
+     "ssh_key": "GITHUB_MIRROR_KEY",
+     "import": [
+      "claude/*"
+     ]
+    }
+   ]
+  }
  ]
 }