OMP Model Configuration

How OMP model config works

OMP reads ~/.omp/agent/config.yml at runtime. This file is a Nix-managed symlink deployed by modules/agents/omp/default.nix. The module starts from the shared base at config/omp/config.yml and overlays per-host settings from hosts/<host>/default.nix at build time using yq.

Two layers:

1. Shared defaults in config/omp/config.yml — modelRoles, retry, compaction, advisor, etc. Edit this for changes that apply to all hosts.
2. Per-host overlays in hosts/<host>/default.nix under modules.agents.omp — smolModel, modelRoles, modelProviderOrder, retry.modelFallback, retry.fallbackChains. These override the shared defaults via yq expressions at build time.

Source of truth for providers: the block comments in each host's default.nix and the omp models <provider> command on that host. Providers are host-specific. Never cross-wire prefixes across laptops or invent hybrid ids.

The Nix options

modules.agents.omp = {
  enable = true;

  # Sets PI_SMOL_MODEL in the omp wrapper binary via makeWrapper --set.
  # Precedence: --smol flag > PI_SMOL_MODEL > config.yml modelRoles.smol.
  # Requires a rebuild to change (baked into the binary, not config.yml).
  smolModel = "provider/model";

  # Overlays these keys onto config.yml's modelRoles at build time.
  # Each value is "provider/model-id" or "provider/model-id:reasoning-level".
  modelRoles = {
    default = "provider/model:low";    # general workhorse
    smol = "provider/fast-model";      # quick/fast operations
    slow = "provider/model:high";      # deep reasoning
    plan = "provider/model:high";      # planning
    advisor = "provider/model:high";   # cross-check reviewer
    task = "provider/fast-model";      # delegated subtasks
    commit = "provider/fast-model";    # commit messages
    tiny = "provider/fast-model";      # metadata, trivial work
    designer = "provider/model:high";  # design/architecture
    vision = "provider/vision-model";  # image analysis (must support images)
  };

  # Provider resolution order for ambiguous canonical model ids.
  # List providers in priority order. Remove providers you don't want resolving.
  modelProviderOrder = [ "provider-a" "provider-b" ];

  retry.modelFallback = true;  # enable per-role fallback chains

  # Per-role fallback chains. When the primary model fails, OMP tries each
  # entry in order. These REPLACE the base config.yml chains for the roles
  # you specify (they don't merge).
  retry.fallbackChains = {
    default = [ "provider-b/model:high" "provider-c/model:high" ];
    advisor = [ "provider-b/model:high" ];
    # ... one per role that needs a chain
  };

  # Override the daily introspection model (module defaults to
  # openai-codex/gpt-5.6-sol:high). Without this, the nightly launchd job
  # will use the default, which may be a provider you're trying to avoid.
  dailyIntrospection.model = "provider/model:high";
};

Validating models before adding them

omp models <provider>

Check the output table:

• model: Must match the id you're pinning (without the provider/ prefix).
• thinking: Lists supported reasoning levels. A - means no reasoning levels. Do NOT append :high or :low to these models (e.g., grok-composer-2.5-fast has -; grok-4.5 has minimal,low,medium,high,xhigh).
• images: Must be yes for the vision role.
• context / max-out: Useful for choosing smol vs slow models.

Never guess model ids. Always validate with omp models on the target host before adding roles or fallbacks.

Fallback chain rules

1. No redundant first hop: The primary model must not appear as the first fallback. It already failed, so trying it again wastes a hop.
2. No invalid reasoning levels: Check omp models output. Models with - in thinking don't support :high, :low, etc.
3. Cross providers: At least one fallback on a different provider than the primary. If all fallbacks are on the same provider and it goes down, every hop fails.
4. Cover all roles: advisor, task, and commit often don't have chains in the base config. Add them if you want fallback protection.
5. Openrouter as last resort: openrouter/moonshotai/kimi-k3:high (or similar) is a good final hop since it's pay-per-use and rarely rate-limited.

Rebuild and deploy

hey check   # validate Nix evaluation
hey re      # rebuild and switch

hey re runs darwin-rebuild switch --flake ~/.config/dotfiles#<host>. It builds from the main checkout (~/.config/dotfiles), not the current worktree. If you're editing in a worktree, apply the same edit to ~/.config/dotfiles or the rebuild won't pick it up.

Footguns

hey re builds from ~/.config/dotfiles, not the worktree

The hey wrapper resolves flake_dir by checking $FLAKE_DIR, then walking up from $cwd, then falling back to ~/.config/dotfiles. In practice, the fallback often wins. Always mirror worktree edits to ~/.config/dotfiles if you need the rebuild to take effect immediately.

config.yml symlink may not update after rebuild

home.file.".omp/agent/config.yml" has force = true, but the home-manager activation step can silently fail to update the symlink. The omp wrapper binary (PI_SMOL_MODEL, PI_CODING_AGENT_DIR) and launchd scripts (dailyIntrospection.model) do get rebuilt, but config.yml can stay stale.

After rebuilding, always verify:

grep -c 'provider-you-removed' ~/.omp/agent/config.yml  # should be 0
file ~/.omp/agent/config.yml                              # should be symlink

If stale, manually replace:

TMP=$(mktemp)
cat ~/.omp/agent/config.yml > "$TMP"
sed -i '' -e 's|old-provider/old-model|new-provider/new-model|g' "$TMP"
rm -f ~/.omp/agent/config.yml
cp "$TMP" ~/.omp/agent/config.yml
rm -f "$TMP"

Then manually fix fallback chains (sed can't do structural YAML changes).

PI_SMOL_MODEL is baked into the wrapper binary

smolModel in Nix sets PI_SMOL_MODEL via makeWrapper --set in the omp wrapper script. This is baked at build time, not read from config.yml. Precedence: --smol flag > PI_SMOL_MODEL > config.yml modelRoles.smol.

If the rebuild updates the wrapper but not config.yml, the smol model will come from PI_SMOL_MODEL (correct) while other roles come from the stale config.yml (wrong). Always verify both.

dailyIntrospection.model has a hardcoded default

The module defaults dailyIntrospection.model to openai-codex/gpt-5.6-sol:high. If you're shifting off openai-codex and forget to override this, the nightly launchd job (omp-thread-introspection) will silently burn quota on the provider you're avoiding. Set it explicitly:

dailyIntrospection.model = "alternative-provider/model:high";

retry.fallbackChains replaces, doesn't merge

The host's fallbackChains overlay replaces the base config's chains for the roles you specify. Roles you don't list keep their base config chains. If the base config has openai-codex in a chain for a role you didn't override, that chain will still reference the old provider.

modelRoles values need exact provider prefixes

Model ids are provider/model-id or provider/model-id:reasoning-level. The provider prefix must match a provider registered on that host. Never invent hybrid ids like cursor/grok-*. Validate with omp models <provider>.