pi-model-sync

An extension for omp (oh my pi) and upstream pi: rewrites the model used by subsequent subagents based on the spawning session's current model. Two delegation paths are supported:

• omp native subagents (task / eval agent() / workpool workers).
• The subagent tool of pi-subagent (@mjakl/pi-subagent), under both omp and upstream pi (pi-subagent itself requires Pi ≥ 0.87.1 or a compatible host).

After the main model changes, newly spawned/delegated subagents switch to the model mapped by the matching profile; running subagents never switch mid-flight. Nested spawns (a subagent spawning further subagents) are intercepted too: the lookup key is the spawning session's current model.

Installation

No build, no dependencies — both hosts run the TypeScript sources directly.

omp

# from git (pin a tag for a fixed version)
omp plugin install git:github.com/SenCha930511/pi-model-sync@v0.2.0
# or from npm (the same package feeds the Pi gallery)
omp plugin install npm:@sencha930511/pi-model-sync

upstream pi

# from npm (listed in the Pi package gallery at pi.dev/packages)
pi install npm:@sencha930511/pi-model-sync
# or straight from git
pi install git:github.com/SenCha930511/pi-model-sync@v0.2.0

One-off trial without installing: omp --extension /path/to/pi-model-sync / pi --extension /path/to/pi-model-sync (-e is repeatable; pi -e npm:@sencha930511/pi-model-sync works too).

Local / offline

1. Copy the whole directory to ~/.omp/agent/extensions/pi-model-sync/ (omp) or ~/.pi/agent/extensions/pi-model-sync/ (upstream pi); each package.json load key points at ./index.ts.

2. omp alternative: add to ~/.omp/agent/config.yml:

   extensions:
     - /path/to/pi-model-sync
   

Config files

Two layers, same JSON format:

• Global: ~/.omp/agent/pi-model-sync.json
  • PI_MODEL_SYNC_CONFIG overrides the path (relative paths resolve against cwd).
  • When PI_CODING_AGENT_DIR is set: <its value>/pi-model-sync.json (lower precedence than PI_MODEL_SYNC_CONFIG).
  • Dual-host landing: when none of the above applies, if the ~/.omp file does not exist and ~/.pi/agent/pi-model-sync.json does, the .pi path is used; when neither exists, the write target stays the ~/.omp path.
• Project: <repo>/.omp/pi-model-sync.json (current directory only, no upward search)
  • Isomorphic fallback: when the .omp file does not exist and <repo>/.pi/pi-model-sync.json does, the .pi path is used.

An existing project file wholly replaces the global file (no per-key merge; a broken-JSON project file counts as "exists with no profiles").

{
  "profiles": [
    {
      "main": "openai/gpt-6.1-sol",
      "subagents": {
        "*": "openai/gpt-6-luna",
        "scout": "openai/gpt-6-mini"
      }
    },
    {
      "main": "anthropic/claude-opus-*",
      "subagents": "anthropic/claude-sonnet-5"
    }
  ]
}

• main: the main model to match (rules below).
• subagents:
  • a string → every agent under this profile uses that model;
  • an object → keys are agent names (e.g. task, scout); "*" is the profile default.
• Selectors pass through verbatim to host resolution: provider/id, bare id, role aliases (e.g. @smol), and :level suffixes (e.g. openai/gpt-6-luna:high) are handed to the host resolver as-is. Under upstream pi, see "pi-subagent routing rules" for validation semantics.

Matching rules

• main without * → exact equality against provider/id or bare id (case-insensitive).
• main with * → explicit glob wildcard (* crosses /), tested against both the provider/id and bare id forms.
• No implicit substring matching; the first match in file order wins.

pi-subagent routing rules

The extension intercepts pi-subagent's subagent tool input {calls: [{agent, prompt, model?, ...}]} at tool_call time: when a call has no model, the spawning session's current model is matched against profile main, the call's agent name picks a selector (exact key first, then "*"; key matching is case-sensitive — align pi-subagent agent names with profile keys manually), and call.model is injected. All other fields (prompt, thinking, cwd, session, ...) are preserved.

• An explicit per-call model always wins and is never overwritten. pi-subagent's own precedence is call model → agent frontmatter model → parent model; injection sits at the call-model layer, so an agent frontmatter model is overridden by profile routing — by design: the profile is the single source of "which model to use now".
• Named-session continuations get injected too.
• Shape guard: only a tool named subagent whose input carries a calls array is intercepted; other same-named tools with a different shape (e.g. nicobailon/pi-subagents) are not affected.
• Under omp, selectors are fully validated via ctx.models.resolve(); under upstream pi they are tier-checked:
  • @alias (an omp-only concept, unresolvable upstream) → unresolvable, no injection;
  • a :level suffix (off/minimal/low/medium/high/xhigh/max) → stripped before validating the base;
  • a glob containing * → passed through for the child process to resolve (a failure surfaces as an explicit error on that delegation);
  • provider/id (split at the first /) → looked up via modelRegistry.find; a bare id → looked up in modelRegistry.getAvailable()/getAll(); no hit, no injection.
• An unresolvable selector is not injected; pi-subagent's default routing (frontmatter → parent model) applies, with a one-time TUI warning (once per selector).
• An injected selector must be resolvable by the child process itself: pi-subagent spawns an independent child (upstream pi or omp), whose model registration sources (e.g. ~/.pi/agent/models.json) must know that selector.

/model-sync command

All command help, output, notifications, and config error messages are in English.

Command	Description
/model-sync or /model-sync list	Show the active layer and all profiles
/model-sync show	Show the current model, matched profile, and selector resolution status
/model-sync add <main> <model>	Add/update a profile (all subagents use <model>)
/model-sync set <main> <agent> <model>	Set a model for one agent (when <agent> is *, sets the profile default)
/model-sync remove <main> [agent]	Remove a whole profile, or one agent entry

Commands write to the global file by default; any subcommand with --project writes the project file. You can also edit the JSON directly (changes are detected via an mtime cache and take effect on save).

Notes

• Running subagents never switch mid-flight; switching the main model only affects later spawns.
• Nested spawns resolve against the spawning session's current model (a child session only knows its own model — the only clean API). This happens only when the host allows nesting depth ≥ 2; the cap is governed by task.maxRecursionDepth (omp doc default 2, negative = unlimited); at the cap, the subagent's task tool is removed so it cannot spawn further.
• When a profile selector is unresolvable, that spawn or delegation is not intercepted — default routing applies — and a warning shows once per selector in the TUI.
• For omp-native spawns, when routing takes effect the task card / Agent Hub shows the routing note: pi-model-sync: <agent> → <model> (main: <main>). pi-subagent delegations show the injected model in the call rendering instead — no extra note, by design.
• Startup is fully silent: no session-start notification.

Contributing

See CONTRIBUTING.md. Review expectations and conventions live in AGENTS.md.

License

MIT © SenCha930511.