pi: providers can come from ~/.config/pi/models.d, like settings already do

models.json was a plain symlink to the tracked file, which left a machine whose
models are served from somewhere other than a vendor's own API with nowhere to
say so. pi reads providers from exactly one path -- join(getAgentDir(),
"models.json") -- and a `providers` block in a settings fragment is inert,
because the settings schema has no such key. So on such a machine pi cannot be
used at all, and the endpoint is not something this repo may name.

link/pi.sh now generates models.json the way it already generates settings.json:
the repo's file, then every ~/.config/pi/models.d/*.json. No three-way merge
here -- pi never writes this file, keeping runtime state in the sibling
models-store.json -- so a hand-edit of ~/.pi/agent/models.json no longer
survives a relink. Put it in a fragment.

It reports which provider came from which fragment, added or replaced, so a
local file shadowing a provider the repo ships cannot do it quietly.

Proposed as a change request from the machine that needs it; verified here
against pi 0.84.2 before applying.

3 files changed, 92 insertions, 3 deletions

diff --git a/CLAUDE.md b/CLAUDE.md
index 6d0c4a7..4cb78b6 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -50,6 +50,7 @@ what it needs through these, each of them optional and absent by default:
 | `~/.config/claude/mcp-servers.d/*.json` | MCP servers, registered by `link/claude.sh` |
 | `~/.claude/rules/*.md` | extra Claude Code user memory, loaded next to `config/claude/CLAUDE.md` |
 | `~/.config/pi/settings.d/*.json` | pi settings merged into the generated `~/.pi/agent/settings.json` by `link/pi.sh` |
+| `~/.config/pi/models.d/*.json` | pi providers merged into the generated `~/.pi/agent/models.json` by `link/pi.sh` |
 | `~/.config/agent-skills.d/*` | agent skills, linked into every installed agent by `link/skills.sh` |
 | `~/.local/share/szecret/{store,id.pub}` | the szecret store; the tool is here, its secrets are not |
 | `~/.config/shell/dir-hashes.zsh` | more zsh named directories, sourced by `config/zshrc` |
@@ -135,6 +136,7 @@ tracked config says so, and in no repo:
 | `~/.local/share/alacritty/local.toml` | Alacritty | imported by `config/alacritty/alacritty.toml` |
 | `~/.config/dot/skip` | which `link/` parts this machine does not want, one name per line | `link/lib.sh`, as each part starts |
 | `~/.config/dot/inbox-key` | the key this machine signs change requests with | `bin/dot-request` |
+| `~/.config/pi/models.d/*.json` | pi providers only this machine has -- a model served somewhere other than a vendor's own API | `link/pi.sh`, merged over `config/pi/models.json` |
 
 Not covered today: nvim, tmux, bat, lsd, and `~/.claude/settings.json` -- which
 a machine can only leave alone entirely, by naming `claude` in the skip file.
diff --git a/link.sh b/link.sh
index 53bbf85..4f5bbff 100755
--- a/link.sh
+++ b/link.sh
@@ -36,9 +36,8 @@ link_all "$config_dir/bat" "$xdg_config_dir/bat"
 
 link "$config_dir/aider.conf.yml" "$HOME/.aider.conf.yml"
 link "$config_dir/pi/extensions" "$HOME/.pi/agent/extensions"
-link "$config_dir/pi/models.json" "$HOME/.pi/agent/models.json"
-# settings.json is generated by link/pi.sh; AGENTS.md and mcp.json, if any,
-# come from another layer.
+# settings.json and models.json are both generated by link/pi.sh; AGENTS.md and
+# mcp.json, if any, come from another layer.
 
 # Utils
 bin="$HOME/.bin"
diff --git a/link/pi.sh b/link/pi.sh
index 2f0a05c..22ecd96 100755
--- a/link/pi.sh
+++ b/link/pi.sh
@@ -229,3 +229,91 @@ case "${pi_status%%:*}" in
   locked)      yellow "pi settings: pi holds its settings lock; left as is, the next link catches up" ;;
   error)       red "pi settings: ${pi_status#*:}" ;;
 esac
+
+# pi's models.json, generated too. It used to be a plain symlink to the tracked
+# file, which left a machine whose models come from somewhere other than a
+# vendor's own API with nowhere to say so: pi reads providers from exactly one
+# path (join(getAgentDir(), "models.json")), and a `providers` block in a
+# settings fragment is inert, since the settings schema has no such key.
+#
+# So the same shape as the settings above: the repo's file, then every
+# ~/.config/pi/models.d/*.json another layer or this machine puts there. Unlike
+# the settings this is a plain generated file with no three-way merge -- pi
+# never writes it, keeping its runtime state in the sibling models-store.json --
+# so what lands is whatever the repo and the fragments say. A hand-edit of
+# ~/.pi/agent/models.json does not survive a relink; put it in a fragment.
+pi_models_out="$(DRY_RUN="$is_dry_run" python3 - \
+  "$config_dir/pi/models.json" \
+  "$xdg_config_dir/pi/models.d" \
+  "$pi_dir/models.json" <<'PY'
+import glob, json, os, sys
+
+base_path, frag_dir, target = sys.argv[1:4]
+
+
+def load(path):
+    with open(path) as f:
+        return json.load(f)
+
+
+# The repo's providers, then each fragment's. A fragment may add a provider or
+# replace one of the same name; any other top-level key takes the last file's
+# value. Which provider came from where is reported: a fragment quietly
+# shadowing a provider the repo ships would otherwise be invisible.
+desired = {}
+notes = []
+for path in [base_path] + sorted(glob.glob(os.path.join(frag_dir, "*.json"))):
+    try:
+        layer = load(path)
+    except (OSError, ValueError) as e:
+        print("error:cannot read %s: %s" % (path, e))
+        sys.exit(0)
+    for key, value in layer.items():
+        if key == "providers":
+            providers = desired.setdefault("providers", {})
+            if path != base_path:
+                for name in value:
+                    notes.append("%s %s by %s" % (
+                        name,
+                        "replaced" if name in providers else "added",
+                        os.path.basename(path),
+                    ))
+            providers.update(value)
+        else:
+            desired[key] = value
+
+# A symlink is the pre-generation state: replace it, even with no fragments, so
+# the live file is never the tracked one.
+was_link = os.path.islink(target)
+try:
+    current = None if was_link else load(target)
+except (OSError, ValueError):
+    current = None
+
+for note in notes:
+    print("note:" + note)
+
+if current == desired:
+    print("unchanged:")
+elif os.environ.get("DRY_RUN"):
+    print("would-write:" + ("replacing the link" if was_link else "merged changes"))
+else:
+    tmp = target + ".dotfiles-tmp"
+    with open(tmp, "w") as f:
+        json.dump(desired, f, indent=2)
+        f.write("\n")
+    os.replace(tmp, target)
+    print("wrote:" + ("replaced the link" if was_link else "merged changes"))
+PY
+)"
+
+while IFS= read -r line
+do
+  case "${line%%:*}" in
+    note)        yellow "pi models: ${line#*:}" ;;
+    wrote)       green "pi models: ${line#*:}" ;;
+    unchanged)   green "pi models: unchanged" ;;
+    would-write) yellow "pi models will be generated: ${line#*:}" ;;
+    error)       red "pi models: ${line#*:}" ;;
+  esac
+done <<< "$pi_models_out"