Struct Config 

pub struct Config {

    pub backends: Vec<BackendConfig>,
    pub providers: Vec<ProviderConfig>,
    pub scratch: Option<ScratchConfig>,
    pub default_tier_order: Vec<Tier>,
    pub lifecycle: Option<PhaseCommands>,
    pub dgx: Option<DgxConfig>,
    pub tui: Option<TuiConfig>,
    pub shell: Option<ShellConfig>,
    pub context: Option<ContextConfig>,
    pub tools: Option<ToolsConfig>,
    pub pricing: Option<PricingConfig>,
    pub memory: Option<MemoryConfig>,
    pub agents: AgentsConfig,
    pub mcp_servers: Vec<McpServerEntry>,
    pub logs: Option<LogConfig>,
    pub skills: Option<SkillsConfig>,
    pub model_tuning: Vec<ModelTuning>,
    pub conversations: Option<ConversationsConfig>,
    pub merge: Option<MergeConfig>,
    pub permission_presets: BTreeMap<String, NamedPermissionPreset>,
    pub modes: BTreeMap<String, ModeConfig>,
    pub profiles: BTreeMap<String, ProfileConfig>,
    pub bundles: BTreeMap<String, BundleConfig>,
    pub loadouts: BTreeMap<String, Loadout>,
    pub crews: BTreeMap<String, Crew>,
    pub crew: Option<CrewPolicyConfig>,
    pub plan: Option<PlanConfig>,
}

Top-level Newt-Agent configuration.

Fields

backends: Vec<BackendConfig>

Inference backends (Ollama, vLLM, etc.).

Absent [[backends]] deserializes to empty (not the struct-level default’s localhost fallback) so a config that defines its backends as per-file ~/.newt/backends/*.toml drop-ins does NOT also pick up a spurious synthesized ollama entry. The localhost fallback is restored in Config::resolve only if backends are still empty after the disk merge (so a truly bare setup still talks to a local Ollama).

providers: Vec<ProviderConfig>

External provider-plugin definitions.

scratch: Option<ScratchConfig>

[scratch] — where ephemeral state (crew worktrees, the crew cargo target, per-session plans) lives (#844). dir may be relative (under the repo, default .scratch) or absolute (/tmp, a k8s PVC mount) for read-only checkouts. NEWT_SCRATCH_DIR overrides it. Applied in Config::resolve via crate::scratch::set_scratch_dir.

default_tier_order: Vec<Tier>

Default tier ordering used by the router when no per-backend override is specified.

lifecycle: Option<PhaseCommands>

[lifecycle] — the repo’s build/dev commands per lifecycle phase (format, check, clean, …), #880. Overrides the per-ecosystem tooling packs. Applied in Config::resolve via crate::tooling::set_lifecycle_override.

dgx: Option<DgxConfig>

Optional NVIDIA DGX endpoint-management config powering the newt dgx command suite. None when unconfigured — newt never dials a DGX endpoint unless this (or a NEWT_DGX_* env var) is set.

tui: Option<TuiConfig>

TUI appearance and behaviour. None → built-in defaults apply. Overridable at runtime via NEWT_CHAT_STYLE and NEWT_PROMPT.

shell: Option<ShellConfig>

[shell] — which engine runs run_command (ADR 0005 D2 seam). None / unset → the safe-subset default, except --full-access auto-upgrades to host. Overridable per-session by --shell-engine. The L3 backend (Landlock/Seatbelt/AppContainer) is a separate, auto-selected axis.

context: Option<ContextConfig>

[context] — context-management strategy selection (Step 24.8, #559).

tools: Option<ToolsConfig>

[tools] — tool-execution behaviour (#726). None → built-in defaults (notably max_output_tokens = 10000). See ToolsConfig.

pricing: Option<PricingConfig>

Inference cost modeling. None → built-in rate table only.

memory: Option<MemoryConfig>

Memory / context-window management. None → RollingWindow(20).

agents: AgentsConfig

Project-instruction loading (AGENTS.md / CLAUDE.md) into the system prompt. Enabled by default. Overridable via --agents-file / --no-agents-file.

mcp_servers: Vec<McpServerEntry>

newt-native MCP servers ([[mcp_servers]]). Merged with the servers discovered from Claude Code’s config by crate::mcp::discover; these take precedence on a name clash. Empty by default.

logs: Option<LogConfig>

Usage-log rotation policy. None → built-in defaults apply (keep last 7 sessions, no size/age limit).

skills: Option<SkillsConfig>

Skill discovery search path — the ordered list of directories newt reads SKILL.md folders from. None → just ~/.newt/skills.

model_tuning: Vec<ModelTuning>

Per-model inference tuning overrides ([[model_tuning]]).

Each entry locks specific parameters for a named model. Values here take precedence over empirically derived values from model-capabilities.json and over global [tui] defaults.

Example ~/.newt/config.toml:

[[model_tuning]]
model = "nemotron3:33b"
num_ctx = 24576            # explicit Ollama context window
mid_loop_trim_threshold = 12
max_tool_rounds = 20

Human-authored entries are never overwritten by the auto-tuner. Auto-tuned entries are appended by the harness when tune_confidence reaches High; delete or edit them freely.

conversations: Option<ConversationsConfig>

Durable conversation save/restore policy. None uses built-in defaults.

merge: Option<MergeConfig>

How a project-local .newt/config.toml is layered over the global config (issue #222). None → built-in default (arrays replace).

permission_presets: BTreeMap<String, NamedPermissionPreset>

Named permission presets ([permission_presets.<name>], issue #307). Each maps onto the role-profile caveat mechanism (a crate::NamedPermissionPreset) and, when applied via /mode, clamps the session’s authority as a hard floor. Empty by default — no preset, behavior unchanged.

modes: BTreeMap<String, ModeConfig>

Named modes ([modes.<name>], issue #307) for the /mode command. Each mode atomically binds a skill body to preload, a permission preset to apply as an authority floor, and a one-line system-prompt framing. Empty by default. See ModeConfig.

profiles: BTreeMap<String, ProfileConfig>

Named profiles ([profiles.<name>]) — a composition of harness techniques plus each technique’s tunable knob settings (the technique library, docs/design/technique-library.md). A profile is selected by --profile <name> and tunes the harness per model family / context. Empty by default — no profile, behavior unchanged. See ProfileConfig.

bundles: BTreeMap<String, BundleConfig>

Named bundles ([bundles.<name>]) — the loadable unit of the model support kit (docs/design/model-support-kit.md). A bundle pins which model families it applies to and which profile each resolves to. Selected by --bundle <name> or inferred from the model via applies_to. Empty by default — no bundle, behavior unchanged. See BundleConfig.

loadouts: BTreeMap<String, Loadout>

Named loadouts ([loadouts.<name>] or ~/.newt/loadouts/<name>.toml) — the top-level composition of provider → model → kit → role → settings (docs/design/loadout-composition.md). Inert until the resolver is wired (Slice 1): this carries the data model + reference validation + /loadout show. Empty by default. See Loadout.

crews: BTreeMap<String, Crew>

Named crews ([crews.<name>] or crews/<name>.toml) — role-specialized ensembles over the backend pool (docs/design/crew-loadout.md). Each role names a [loadouts.<name>]. Empty by default. See Crew.

crew: Option<CrewPolicyConfig>

[crew] — crew/team dispatch policy (#749). Carries the authority clamp every dispatched crew is met against, so a crew’s effective authority is session ⊓ clamp — never above the session ceiling, and as tight as the operator configures. None (and the default clamp) is Caveats::top(), i.e. the meet is the identity and behavior is unchanged. This is the structural tightening point the per-subtask team_clamp (#749 step 8) plugs into. See CrewPolicyConfig.

plan: Option<PlanConfig>

[plan] — plan-authoring policy. Today: the [plan.prune] droppable override for the decompose prune’s anti-pattern lexicon (#801/#803 → #819). None = compiled defaults, behavior unchanged. See PlanPruneConfig.

Implementations

impl Config

pub fn find_model_tuning(&self, name: &str) -> Option<&ModelTuning>

Find the first [[model_tuning]] entry whose model field matches name exactly. Returns None when no entry exists.

pub fn resolve_profile(&self, name: &str) -> Result<&ProfileConfig, String>

Look up and validate a named profile ([profiles.<name>]). The caller selects it via --profile <name> / NEWT_PROFILE.

Errors

no such profile when the name is undefined; the validation error when the profile names an unknown technique — a --profile that silently did nothing would be a false claim, so both fail loudly.

pub fn resolve_bundle(&self, name: &str) -> Result<&BundleConfig, String>

Look up a named bundle ([bundles.<name>]).

Errors

no such bundle when undefined — a --bundle that silently did nothing would be a false claim.

pub fn bundle_profile_for_model<'a>( &self, bundle: &'a BundleConfig, model: &str, ) -> Option<&'a str>

The profile name bundle yields for model: the longest-prefix families match, else default_profile. None ⇒ the bundle applies no profile here.

pub fn infer_bundle(&self, model: &str) -> Option<(&str, &BundleConfig)>

Infer the bundle for model from applies_to (longest-prefix-wins). Only bundles with a non-empty applies_to participate — a use-case bundle (empty applies_to) is never auto-inferred, only chosen explicitly via --bundle.

pub fn pick_active_profile( &self, profile_flag: Option<&str>, bundle_flag: Option<&str>, model: &str, ) -> Result<Option<ProfilePick>, String>

Resolve the active profile from the selectors + the active model: --profile (explicit) > --bundle (its profile for this model) > an inferred bundle (applies_to) > None (today’s no-profile behavior). Returns the profile NAME + how it was chosen (for the banner).

Errors

An unknown explicit --bundle is a hard error. An unknown explicit --profile is left for the caller’s resolve_profile so the message stays profile-specific.

impl Config

pub const REDACTED: &'static str = "<redacted>"

Placeholder substituted for redacted secret values in Self::to_redacted_toml.

pub fn load(path: &Path) -> Result<Self>

Load configuration from an explicit file path.

pub fn resolve() -> Result<Self>

Resolve configuration by searching well-known locations, then layering a project-local override on top.

Base search order (first match wins):

1. $NEWT_CONFIG environment variable
2. ./newt.toml
3. $NEWT_CONFIG_DIR/config.toml or ~/.newt/config.toml
4. /etc/newt/config.toml

Then, if a project-local .newt/config.toml is found by walking up from the current directory (see Config::project_config_path), it is deep-merged over the base so a repo can pin its own models, endpoints, rules, and local stdio MCP services without copying the whole global config. Tables merge recursively (project keys win) and scalars are replaced by the project value. Arrays follow [merge] arrays — "replace" (default) or "append" (see ArrayMergeStrategy). The project config’s [merge] setting takes precedence, then the base’s. See issue #222.

When no project override exists this is byte-for-byte the legacy first-match behavior. Returns Config::default() if nothing is found.

pub fn max_output_tokens(&self) -> usize

The configured model-facing output token budget ([tools] max_output_tokens), or the built-in default when [tools] is absent (#726). 0 means “no cap”. See ToolsConfig.

pub fn output_head_tokens(&self) -> usize

The configured head allocation for oversized run_command output ([tools] output_head_tokens), or the built-in tail-biased default.

pub fn project_config_path() -> Option<PathBuf>

Locate a project-local .newt/config.toml by walking up from the current directory toward the filesystem root, stopping before $HOME so the global ~/.newt/config.toml is never mistaken for a project override. Returns the nearest match (innermost project wins). See issue #222.

pub fn user_config_dir() -> Option<PathBuf>

The user-writable config root: $NEWT_CONFIG_DIR or ~/.newt.

pub fn user_config_path() -> Option<PathBuf>

The user-writable config path: $NEWT_CONFIG_DIR/config.toml or ~/.newt/config.toml. This is the first path resolve() reads and the target for save().

pub fn to_redacted_toml(&self) -> Result<String>

Serialize the config to pretty TOML for audit, with inline secret material redacted. The values of every [[mcp_servers]] env and headers entry are replaced with Self::REDACTED — those maps are the only place Config can carry a raw secret inline (e.g. an Authorization: Bearer … header or an API_KEY=… child env var). Keys are kept so an auditor sees which variables/headers are set without the values. Secret references (api_key_file / api_key_env) are left as-is — they name where a secret lives, not the secret itself.

Errors

A TOML serialization failure (should not happen for a valid Config).

pub fn skill_search_dirs(&self) -> Vec<PathBuf>

The ordered skill-discovery search path, with ~/ expanded.

Resolves [skills].search when configured; otherwise defaults to the single host-scoped ~/.newt/skills. Order is preserved — earlier directories win on a name collision (see newt_skills::discover_paths). The default falls back to a relative .newt/skills only when $HOME can’t be resolved, so the list is never empty.

pub fn save(&self, path: &Path) -> Result<()>

Serialize this config and write it to path, creating parent dirs if needed.

pub fn with_net_host(text: &str, host: &str) -> Result<String>

#904: append host to [tui.permissions] net in the TOML text, preserving comments and formatting — unlike Config::save, which re-serializes the whole typed struct and drops the user’s comments, ordering, and any keys newt does not model. Creates the [tui.permissions] table and its net array if absent; a no-op if the host is already listed. PURE (no I/O), so it unit-tests without a filesystem. This is the durable “allow permanently” grant path — it is only ever driven by an explicit human keypress at the permission prompt.

pub fn append_permission_net_host(path: &Path, host: &str) -> Result<()>

Durably grant a net host by appending it to [tui.permissions] net in the config file at path, comment-preserving (see Config::with_net_host). A missing file is treated as empty (the table is created). Creates parent dirs as needed. Used by the interactive gate’s “allow permanently” choice.

Trait Implementations

impl Clone for Config

fn clone(&self) -> Config

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Config

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Config

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Config

where Config: Default,

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for Config

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.