feat(model): add opt-in Ollama catalog provider (#268)

## Summary

Adds Ollama as a disabled-by-default built-in catalog provider backed
entirely by provider TOML. Enabling `[llm.providers.ollama] enabled =
true` exposes the bundled `qwen3-coder` sample model through the
existing OpenAI-compatible adapter, while other local Ollama models
still require explicit model blocks until fabro-sh/fabro#267 adds
discovery.

The docs now show the opt-in setting and note that local users can set
`OLLAMA_API_KEY=ollama` for Ollama's OpenAI-compatible endpoint.

## Verification

- `cargo nextest run -p fabro-model`
- `cargo nextest run -p fabro-cli cmd::model`
- `cargo +nightly-2026-04-14 fmt --check --all`

---

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---------

Co-authored-by: roALAB1 <233429779+roALAB1@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/public/core-concepts/models.mdx

@@ -98,6 +98,17 @@ Header values and credentials are typed references, not raw secrets. Use `env:<N
 Provider fields in configuration, APIs, and model routing are provider ID strings. Built-in names like `anthropic`, `openai`, and `gemini` still work, but custom IDs like `proxy` work anywhere a provider ID is accepted.
 </Note>
 
+### Ollama
+
+Fabro ships an Ollama provider definition that is disabled by default. Enable it in settings when you want Fabro to route through a local Ollama server:
+
+```toml title="settings.toml"
+[llm.providers.ollama]
+enabled = true
+```
+
+Enabling the provider alone does not expose any models — until #267 adds auto-discovery, add explicit `[llm.models.<id>]` blocks for each Ollama model you have pulled locally. Ollama's OpenAI-compatible endpoint accepts any bearer token, so local users can set `OLLAMA_API_KEY=ollama`.
+
 ## Default models
 
 When no model or provider is specified, Fabro checks configured provider credentials and chooses the first configured provider by catalog priority. If no provider credentials are configured, it uses the catalog's global default model. Each provider has a default model:

lib/crates/fabro-cli/tests/it/cmd/model.rs

@@ -144,16 +144,16 @@ fn list_query_case_insensitive() {
 }
 
 #[test]
-fn list_invalid_provider_errors() {
+fn list_unknown_provider_returns_empty() {
     let context = test_context!();
     let mut cmd = context.model();
     cmd.args(["list", "--provider", "not-a-provider"]);
     fabro_snapshot!(context.filters(), cmd, @"
-    success: false
-    exit_code: 1
+    success: true
+    exit_code: 0
     ----- stdout -----
+    MODEL  PROVIDER  ALIASES  CONTEXT  COST  SPEED
     ----- stderr -----
-      × unknown provider: not-a-provider
     ");
 }
 

lib/crates/fabro-client/src/client.rs

@@ -9,7 +9,7 @@ use bytes::Bytes;
 use fabro_api::types;
 use fabro_http::header::{AUTHORIZATION, CONTENT_LENGTH, CONTENT_TYPE};
 use fabro_http::multipart::{Form, Part};
-use fabro_model::{Model, ModelTestMode, Provider};
+use fabro_model::{Model, ModelTestMode, ProviderId};
 use fabro_types::settings::run::MergeStrategy;
 use fabro_types::{
     ArtifactUpload, EventEnvelope, RunBlobId, RunEvent, RunId, RunProjection, RunSummary, StageId,
@@ -608,17 +608,12 @@ impl Client {
         provider: Option<&str>,
         query: Option<&str>,
     ) -> Result<Vec<Model>> {
-        let provider = provider
-            .map(|provider| {
-                provider
-                    .parse::<Provider>()
-                    .map_err(|_| anyhow!("unknown provider: {provider}"))
-            })
-            .transpose()?;
+        let provider = provider.map(ProviderId::new);
         let mut offset = 0u64;
         let mut models = Vec::new();
 
         loop {
+            let provider = provider.clone();
             let response = self
                 .send_api(|client| async move {
                     let mut request = client.list_models().page_limit(100u64).page_offset(offset);

lib/crates/fabro-model/src/catalog.rs

@@ -1596,6 +1596,35 @@ effort = false
         assert_eq!(model.provider, ProviderId::new("acme"));
     }
 
+    #[test]
+    fn builtin_ollama_provider_is_opt_in() {
+        let ollama = ProviderId::new("ollama");
+        let builtin = Catalog::builtin();
+
+        assert!(builtin.provider(&ollama).is_none());
+        assert!(builtin.list(Some(&ollama)).is_empty());
+
+        let catalog = Catalog::from_builtin_with_overrides(&minimal_settings(
+            r"
+[providers.ollama]
+enabled = true
+",
+        ))
+        .expect("enabled Ollama override should build from the built-in provider settings");
+
+        let provider = catalog
+            .provider(&ollama)
+            .expect("enabled Ollama provider should be present");
+        assert_eq!(provider.adapter, "openai_compatible");
+        assert_eq!(
+            provider.base_url.as_deref(),
+            Some("http://localhost:11434/v1")
+        );
+
+        assert!(catalog.list(Some(&ollama)).is_empty());
+        assert!(catalog.default_for_provider(&ollama).is_none());
+    }
+
     #[test]
     fn builtin_get_by_id() {
         let m = Catalog::builtin().get("claude-opus-4-6").unwrap();

lib/crates/fabro-model/src/catalog/providers/ollama.toml

@@ -0,0 +1,26 @@
+[providers.ollama]
+display_name = "Ollama"
+adapter = "openai_compatible"
+base_url = "http://localhost:11434/v1"
+credentials = ["credential:ollama", "env:OLLAMA_API_KEY"]
+priority = 30
+enabled = false
+
+# Example model. Uncomment after `ollama pull qwen3.5` (and `enabled = true`
+# above) to expose it through the OpenAI-compatible adapter.
+#
+# [models."qwen3.5"]
+# provider = "ollama"
+# api_id = "qwen3.5:latest"
+# display_name = "Qwen3.5"
+# family = "qwen3.5"
+# default = true
+# aliases = ["ollama-qwen3.5"]
+#
+# [models."qwen3.5".limits]
+# context_window = 32768
+#
+# [models."qwen3.5".features]
+# tools = true
+# vision = false
+# reasoning = false