Config: Future Work

This document tracks planned features and design notes for configuration that are not yet implemented. Nothing here is part of the current contract. Treat it as a scratchpad for what's next, not as documentation of current behavior.

[!NOTE] This document was largely LLM-generated.

Real-time config from the bash tool

Status: planned, not implemented.

Motivation

Right now crushrc runs once, at startup. If you want to change something mid-session — swap the large model, allow a tool, add an MCP server — you edit the file and restart.

The idea: let the agent's bash tool run the same config commands (model large …, option …, mcp add …) to reconfigure the running session. The mental model is exactly a shell and its .bashrc:

• Running a config command changes the current session only — like typing export or alias at a live prompt.
• To make it stick, you edit your crushrc — like editing .bashrc.

So you could say "Crush, switch to the small model for a bit" and it just runs model small …, live, no restart.

[!IMPORTANT] Persistence is a non-goal. The bash tool never writes config files. This is deliberate: a script can't be round-tripped. You don't regenerate your .bashrc from the live shell's state, and we won't regenerate crushrc from live config state. Want it permanent? Edit crushrc.

Why it's mostly wiring

The commands already exist and the bash tool already reaches them — they're just switched off there on purpose. Config builtins check for a config sink on the context and no-op when there isn't one, which is why typing provider add in a normal bash tool call today does nothing. Real-time config is largely a matter of attaching a live, ephemeral sink instead of that no-op.

The runtime mutation layer also already exists and is used today by the model-switch dialog and API-key entry:

• An in-memory, copy-on-write config mutator.
• Ephemeral "runtime overrides" that never touch disk — the sink we'd target.
• Pub/sub plus on-demand MCP/LSP startup for reacting to changes.

Proposed shape

No new commands — the same builtins, now live:

# Inside a session, via the bash tool:
model small anthropic/claude-haiku-4-20250514   # switch models for this turn
option progress false                            # quiet the UI
permissions allow grep                           # stop asking about grep

Each applies immediately to the session and is forgotten on exit.

Steps

1. Attach a live applier to the bash tool's context — analogous to the load-time builder, but pointed at the ephemeral runtime overrides. When present, config builtins apply to the session instead of no-oping.
2. Route builtin output to ephemeral mutation — never to the on-disk writers. Live, not persisted.
3. Reconcile subsystems, roughly in order of difficulty:
   • Easy: option flags, permissions allow, disabled tools/skills — read on demand.
   • Medium: model large|small — already reconciled live by the switch dialog.
   • Harder: provider add — rebuild the model client with the new key/base-url.
   • Hardest: mcp / lsp add/remove — process lifecycle (start/stop/reconnect); the on-demand-startup machinery helps.
4. Guardrails — see below.

Guardrails

This is a privilege-escalation surface: an agent that can rewrite its own config could grant itself tools, swap providers, or add an MCP server that exfiltrates data. So:

• Gate it behind a permission prompt, like other sensitive actions.
• Make it opt-in.
• Consider a denylist for the scariest fields (API keys, permissions) even when the feature is on.

Suggested first cut

Ephemeral, session-only apply for the easy tier (option, permissions, model) behind a permission prompt. High value, small blast radius, and it sidesteps persistence entirely. Live provider / mcp / lsp reload is a larger, later increment.

Open questions

• Should a live change be echoed back to the user somehow ("switched large model to …"), so it's not silent?
• Do we want a way to see the effective live config from the bash tool (a read-only option get / model large print)? model large already prints its selection; a broader introspection surface could follow.
• Should sub-agents be allowed to reconfigure the session, or only the top-level agent? Probably top-level only, mirroring how hooks scope.

Separate machine state from user configuration

Status: planned for a later phase; not implemented.

Motivation

Crush currently uses JSON files in data directories as both persisted machine state and high-priority configuration:

~/.local/share/crush/crush.json
.crush/crush.json

These files hold mutable choices such as preferred/recent models, UI settings, workspace overrides, and some credentials. Treating them as ordinary config means state enters the same generic JSON merge/reload path as user-authored crushrc and legacy crush.json files.

The goal is to make the roles explicit:

JSON remains a good state format: it is standard-library supported, readable, easy to debug, easy to attach to bug reports, and straightforward to migrate. The problem is not JSON serialization itself; it is state pretending to be config and being deep-merged through the config pipeline.

Proposed files

~/.config/crush/crushrc             global user config
~/.local/share/crush/state.json     global machine state
./crushrc / ./.crushrc              project user config
.crush/state.json                   workspace machine state

State files should be machine-owned, written with 0600, protected by the existing process/file locks, and updated with atomic temp-file renames. They should include a format version and an explicit generated-file notice.

{
  "version": 1,
  "recent_models": {
    "large": [
      {"provider": "openai", "model": "gpt-5"}
    ]
  },
  "preferred_models": {
    "large": {"provider": "openai", "model": "gpt-5"}
  },
  "ui": {
    "compact_mode": true
  }
}

Use typed state structs with pointer fields where false must be distinguishable from "not remembered". Avoid arbitrary dotted JSON paths and avoid decoding state into the full config.Config shape.

Load precedence

Explicit user configuration should beat remembered state:

built-in defaults
→ global state defaults
→ workspace state defaults
→ global legacy crush.json
→ global crushrc
→ project legacy crush.json
→ project crushrc
→ project .crush.json
→ project .crushrc
→ runtime-only overrides

Recent models are metadata, not defaults, so they can be attached after config building without participating in precedence.

Legacy JSON compatibility

User-authored JSON remains a supported config input during this work:

~/.config/crush/crush.json
./crush.json
./.crush.json

It must be decoded as configuration, never migrated as state. Only the machine-owned files in data/workspace directories are migrated. The role is determined by path, not guessed from content.

If user JSON is retired later:

1. Keep reading it for a compatibility period.
2. Warn only when a user-authored JSON config is loaded.
3. Provide an explicit conversion command (for example, crush config convert crush.json > crushrc).
4. Never rewrite user config automatically.

Using JSON internally for state is independent of deprecating JSON as a user configuration language.

State store API

Introduce a narrow typed store rather than generic config-field mutation:

type StateStore interface {
    Load(context.Context) (State, error)
    Update(context.Context, func(*State) error) error
}

An update should lock, read/migrate, mutate, validate, marshal with indentation, write atomically, and quarantine corrupt files. It should not trigger a full config reload.

Typed config mutators then update live config and the corresponding state field:

func (s *ConfigStore) SetCompactMode(scope Scope, enabled bool) error {
    s.mutateInMemory(func(c *Config) {
        c.ensureTUI().CompactMode = enabled
    })

    return s.stateStore(scope).Update(func(st *State) error {
        st.UI.CompactMode = ptr.To(enabled)
        return nil
    })
}

Real-time commands run through the Bash tool remain session-only and do not write state, preserving the shell/.bashrc mental model.

Typed crushrc builder

This is related but separate. Today the Bash path is:

crushrc → map[string]any → JSON → Config

A later typed-builder phase should become:

crushrc → typed ConfigBuilder → Config
state.json → typed StateStore ───────┘

Legacy crush.json would decode into a typed config patch and apply to the same builder. This may require moving pure config data types into a dependency-neutral package to avoid import cycles.

Migration plan

1. Add a versioned State type and atomic JSON state store.
2. Migrate recent/preferred models.
3. Migrate remembered UI settings.
4. Stop merging global/workspace data JSON as config.
5. Move provider credentials and OAuth tokens to dedicated secure storage.
6. Remove generic state callers of SetConfigField / dotted JSON paths.
7. Replace the crushrc map/JSON bridge with a typed config builder.

Migration must preserve unknown legacy fields or warn and leave the original file untouched. Successfully migrated files can be renamed to crush.json.migrated; corrupt files should be quarantined as timestamped state.json.corrupt-* files and replaced with defaults.

Permission-level hard deny

Status: not implemented; probably unnecessary until a real use case appears.

Crush currently has three useful tool states across both config formats:

permissions deny writes options.disabled_tools. That is a practical hard block: because the tool is absent from the agent's tool list, the model cannot attempt to use it.

The one state Crush does not have is "visible but always rejected": the model can see and choose the tool, but the permission engine denies every request without prompting. Supporting that would require a separate permission-level deny list in both the config schema and permission engine.

Why defer it

A visible-but-unusable tool wastes model attention and tool-call attempts. If a tool must never run, hiding it is both stronger and clearer. Add a true deny list only if someone has a concrete need for the model to know a tool exists while being categorically forbidden from calling it.