Summary

When no stop tokens are provided, Zed was sending an empty array ("stop": []) to Ollama. This caused Ollama to override the model's default stop tokens (defined in its Modelfile) with nothing, resulting in models like rnj-1:8b generating infinitely with literal stop tokens appearing in the output.

Problem

Models with custom stop tokens in their Modelfile (like <|eot_id|> for rnj-1:8b) would generate forever because:

1. Agent thread creates request with stop: Vec::new() (empty)
2. Ollama provider converts this to stop: Some(vec![])
3. Serializes as "stop": [] in JSON
4. Ollama interprets this as "override default stop tokens with nothing"
5. Model generates forever, outputting stop tokens as literal text

Solution

1. In crates/language_models/src/provider/ollama.rs:

   • Only send stop when explicitly provided
   • When empty, use None so the field is omitted from JSON

2. In crates/ollama/src/ollama.rs:

   • Add #[serde(skip_serializing_if = "Option::is_none")] to all ChatOptions fields
   • Ensures None values are omitted, not serialized as null

Testing

Added 4 new tests in crates/ollama/src/ollama.rs:

• test_chat_options_serialization: Verifies None fields are omitted
• test_chat_request_with_stop_tokens: Verifies stop tokens are serialized when provided
• test_chat_request_without_stop_tokens_omits_field: Verifies empty stop is omitted

All 11 ollama tests pass, plus 1 language_models ollama test.

Fixes #47798

Release Notes:

• Fixed Ollama models with custom stop tokens generating infinitely by not overriding model defaults when no stop tokens are specified.