diffscope `model:` field silently ignored in `.diffscope.yml`

[angelxmoreno]

Bug summary

In diffscope v0.5.28, the top-level model: field in .diffscope.yml is silently ignored. The primary review model always falls back to the hardcoded default anthropic/claude-opus-4.5 regardless of what is set in the config file.

Environment

• diffscope version: 0.5.28 (installed via install.sh)
• OS: macOS Darwin 25.2.0
• Ollama running on localhost:11434 (reachable, model qwen3.5:latest loaded and verified)

Steps to reproduce

1. Install diffscope: curl -fsSL https://raw.githubusercontent.com/evalops/diffscope/main/install.sh | sh

2. Start ollama locally and pull a model (e.g. ollama pull qwen3.5:latest)

3. Create a .diffscope.yml in any project:

   model: ollama:qwen3.5:latest
   base_url: http://localhost:11434

4. Run git diff | diffscope review

Expected behavior

The review should use ollama:qwen3.5:latest from the config file.

Actual behavior

The review always uses anthropic/claude-opus-4.5 regardless of model: in YAML. Log line confirms:

INFO diffscope::commands::review::command::review: Starting diff review with generation model: anthropic/claude-opus-4.5

The review hangs trying to reach the Anthropic API. diffscope doctor reports Base URL: http://localhost:11434 (proving base_url: is read), but also reports Model: anthropic/claude-opus-4.5 (proving model: is not read).

What works

• --model ollama:qwen3.5:latest CLI flag (overrides the default)
• DIFFSCOPE_BASE_URL env var
• base_url: in YAML
• model_weak:, model_fast:, model_reasoning:, model_embedding: in YAML (suppress role warnings)
• All tuning keys (temperature, max_tokens, context_window, strictness, max_context_chars, max_diff_chars, context_max_chunks, context_budget_chars)
• exclude_patterns in YAML

What does not work

• model: in YAML (top-level, with colon format like ollama:qwen3.5:latest)
• model: in YAML (with slash format like ollama/qwen3.5:latest)
• model: in YAML (with just model name + adapter: ollama)
• model: in YAML (quoted)
• model_primary:, model_default:, primary_model:, default_model:, review_model:, generation_model:, provider_model:, main_model: (variants tested)
• ANTHROPIC_DEFAULT_OPUS_MODEL env var (also ignored)
• providers.ollama.models.primary (and other role names under it)
• providers.ollama.model:
• generation_model_role: primary routing to a configured model: (separate from the model field itself)

Doctor display inconsistency

diffscope doctor also has a display bug: the Configuration: Model: and Primary Provider: lines always show the hardcoded defaults (anthropic/claude-opus-4.5 and anthropic), regardless of the actual config. The Base URL: line in the same section does reflect the YAML base_url:. The "Usage:" line at the bottom of doctor output does reflect the actual configured model.

Workaround

Pass --model on every CLI invocation:

git diff | diffscope review --model ollama:qwen3.5:latest --base-url http://localhost:11434

Or set both in env:

export DIFFSCOPE_BASE_URL=http://localhost:11434
alias ds='diffscope review --model ollama:qwen3.5:latest'

Investigation notes

Confirmed via string extraction from the binary at /usr/local/bin/diffscope:

• The schema (per the embedded web UI) accepts model, model_weak, model_fast, model_reasoning, model_embedding, adapter, fallback_models at the top level
• Role routing keys generation_model_role, auditing_model_role, verification_model_role exist
• Provider block accepts providers.<name>.base_url, providers.<name>.api_key
• Default model literal: anthropic/claude-opus-4.5 (hardcoded in binary)
• Built-in providers: openai, openrouter, anthropic, ollama

The parser reads base_url: from YAML successfully (verified via diffscope doctor reporting it). It reads model_weak: etc. (verified via role warnings disappearing). It does NOT read model: (verified via the log line in review output and via the doctor display).

This looks like a deserialization field-name mismatch — the YAML key model may be deserialized into a different struct field, or the field is renamed (model vs primary_model vs something else) and the YAML parser is silently dropping unknown fields. Either way, the user-facing behavior is broken.

Severity

High. This is the most basic field in the config file. Every other config tool works this way (model: at top level), and the README's examples/selfhosted-ollama.yml ships with model: ollama:codellama as the FIRST line. New users following the README will hit this immediately.