The project-config overlay (`<workspace>/.deepseek/config.toml` merged
on top of the user's global `~/.deepseek/config.toml`) was already
wired but only carried four string fields: model, api_key, base_url,
reasoning_effort. The use cases users actually file under #485 — "this
repo wants a different sandbox / approval policy / MCP server set / hard
sub-agent cap" — weren't covered.
### What ships
Adds the following keys to the project overlay, all merged with
identical "non-empty wins" semantics for strings:
- `provider` — pick a different backend per repo (e.g. `nvidia-nim` for
an enterprise repo, `deepseek-cn` for a CN-team repo).
- `approval_policy` — `never` / `on-request` / `untrusted` for repos
with strict policies.
- `sandbox_mode` — `read-only` / `workspace-write` / `danger-full-access`.
- `mcp_config_path` — per-repo MCP server set without touching the
user's global file.
- `notes_path` — keep notes in-repo for projects where the notes tool
is part of the dev workflow.
Plus two non-string fields:
- `max_subagents` (positive integer; clamped to `1..=MAX_SUBAGENTS=20`).
- `allow_shell` (bool).
### What stays user-global
`skills_dir`, `hooks`, `[capacity]`, `[retry]`, `[memory]`, etc. — those
are user-shaped settings, not repo-shaped. If a future use case
demands per-project values for any of them, a follow-up PR can extend
the overlay rather than letting the boundary blur.
### Tests
- 8 new tests in `project_config_tests` covering: provider+model,
approval+sandbox, max_subagents+allow_shell, max_subagents
clamping, negative-max_subagents rejection, missing config file
pass-through, malformed TOML pass-through, and empty-string
no-op.
### Docs
- New "Per-project overlay (#485)" section in `docs/CONFIGURATION.md`
with a table of supported keys and the rationale for which fields
stay user-global.
### Verification
cargo fmt --all -- --check ✓
cargo clippy --workspace --all-targets --all-features --locked -- -D warnings ✓
cargo test --workspace --all-features --locked ✓ 1828 + supporting (was 1820)
Closes#485
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Hunter Bown
4d4a9b424c