# Hermes Agent - Development Guide

Instructions for AI coding assistants and developers working on the hermes-agent codebase.

## Development Environment

```bash
source venv/bin/activate  # ALWAYS activate before running Python
```

## Project Structure

```
hermes-agent/
├── run_agent.py          # AIAgent class — core conversation loop
├── model_tools.py        # Tool orchestration, discover_builtin_tools(), handle_function_call()
├── toolsets.py           # Toolset definitions, _HERMES_CORE_TOOLS list
├── cli.py                # HermesCLI class — interactive CLI orchestrator
├── hermes_state.py       # SessionDB — SQLite session store (FTS5 search)
├── agent/                # Agent internals
│   ├── prompt_builder.py     # System prompt assembly
│   ├── context_compressor.py # Auto context compression
│   ├── prompt_caching.py     # Anthropic prompt caching
│   ├── auxiliary_client.py   # Auxiliary LLM client (vision, summarization)
│   ├── model_metadata.py     # Model context lengths, token estimation
│   ├── models_dev.py         # models.dev registry integration (provider-aware context)
│   ├── display.py            # KawaiiSpinner, tool preview formatting
│   ├── skill_commands.py     # Skill slash commands (shared CLI/gateway)
│   └── trajectory.py         # Trajectory saving helpers
├── hermes_cli/           # CLI subcommands and setup
│   ├── main.py           # Entry point — all `hermes` subcommands
│   ├── config.py         # DEFAULT_CONFIG, OPTIONAL_ENV_VARS, migration
│   ├── commands.py       # Slash command definitions + SlashCommandCompleter
│   ├── callbacks.py      # Terminal callbacks (clarify, sudo, approval)
│   ├── setup.py          # Interactive setup wizard
│   ├── skin_engine.py    # Skin/theme engine — CLI visual customization
│   ├── skills_config.py  # `hermes skills` — enable/disable skills per platform
│   ├── tools_config.py   # `hermes tools` — enable/disable tools per platform
│   ├── skills_hub.py     # `/skills` slash command (search, browse, install)
│   ├── models.py         # Model catalog, provider model lists
│   ├── model_switch.py   # Shared /model switch pipeline (CLI + gateway)
│   └── auth.py           # Provider credential resolution
├── tools/                # Tool implementations (one file per tool)
│   ├── registry.py       # Central tool registry (schemas, handlers, dispatch)
│   ├── approval.py       # Dangerous command detection
│   ├── terminal_tool.py  # Terminal orchestration
│   ├── process_registry.py # Background process management
│   ├── file_tools.py     # File read/write/search/patch
│   ├── web_tools.py      # Web search/extract (Parallel + Firecrawl)
│   ├── browser_tool.py   # Browserbase browser automation
│   ├── code_execution_tool.py # execute_code sandbox
│   ├── delegate_tool.py  # Subagent delegation
│   ├── mcp_tool.py       # MCP client (~1050 lines)
│   └── environments/     # Terminal backends (local, docker, ssh, modal, daytona, singularity)
├── gateway/              # Messaging platform gateway
│   ├── run.py            # Main loop, slash commands, message dispatch
│   ├── session.py        # SessionStore — conversation persistence
│   └── platforms/        # Adapters: telegram, discord, slack, whatsapp, homeassistant, signal, qqbot
├── ui-tui/               # Ink (React) terminal UI — `hermes --tui`
│   ├── src/entry.tsx        # TTY gate + render()
│   ├── src/app.tsx          # Main state machine and UI
│   ├── src/gatewayClient.ts # Child process + JSON-RPC bridge
│   ├── src/app/             # Decomposed app logic (event handler, slash handler, stores, hooks)
│   ├── src/components/      # Ink components (branding, markdown, prompts, pickers, etc.)
│   ├── src/hooks/           # useCompletion, useInputHistory, useQueue, useVirtualHistory
│   └── src/lib/             # Pure helpers (history, osc52, text, rpc, messages)
├── tui_gateway/          # Python JSON-RPC backend for the TUI
│   ├── entry.py             # stdio entrypoint
│   ├── server.py            # RPC handlers and session logic
│   ├── render.py            # Optional rich/ANSI bridge
│   └── slash_worker.py      # Persistent HermesCLI subprocess for slash commands
├── acp_adapter/          # ACP server (VS Code / Zed / JetBrains integration)
├── cron/                 # Scheduler (jobs.py, scheduler.py)
├── environments/         # RL training environments (Atropos)
├── tests/                # Pytest suite (~3000 tests)
└── batch_runner.py       # Parallel batch processing
```

**User config:** `~/.hermes/config.yaml` (settings), `~/.hermes/.env` (API keys)

## File Dependency Chain

```
tools/registry.py  (no deps — imported by all tool files)
       ↑
tools/*.py  (each calls registry.register() at import time)
       ↑
model_tools.py  (imports tools/registry + triggers tool discovery)
       ↑
run_agent.py, cli.py, batch_runner.py, environments/
```

---

## AIAgent Class (run_agent.py)

```python
class AIAgent:
    def __init__(self,
        model: str = "anthropic/claude-opus-4.6",
        max_iterations: int = 90,
        enabled_toolsets: list = None,
        disabled_toolsets: list = None,
        quiet_mode: bool = False,
        save_trajectories: bool = False,
        platform: str = None,           # "cli", "telegram", etc.
        session_id: str = None,
        skip_context_files: bool = False,
        skip_memory: bool = False,
        # ... plus provider, api_mode, callbacks, routing params
    ): ...

    def chat(self, message: str) -> str:
        """Simple interface — returns final response string."""

    def run_conversation(self, user_message: str, system_message: str = None,
                         conversation_history: list = None, task_id: str = None) -> dict:
        """Full interface — returns dict with final_response + messages."""
```

### Agent Loop

The core loop is inside `run_conversation()` — entirely synchronous:

```python
while api_call_count < self.max_iterations and self.iteration_budget.remaining > 0:
    response = client.chat.completions.create(model=model, messages=messages, tools=tool_schemas)
    if response.tool_calls:
        for tool_call in response.tool_calls:
            result = handle_function_call(tool_call.name, tool_call.args, task_id)
            messages.append(tool_result_message(result))
        api_call_count += 1
    else:
        return response.content
```

Messages follow OpenAI format: `{"role": "system/user/assistant/tool", ...}`. Reasoning content is stored in `assistant_msg["reasoning"]`.

---

## CLI Architecture (cli.py)

- **Rich** for banner/panels, **prompt_toolkit** for input with autocomplete
- **KawaiiSpinner** (`agent/display.py`) — animated faces during API calls, `┊` activity feed for tool results
- `load_cli_config()` in cli.py merges hardcoded defaults + user config YAML
- **Skin engine** (`hermes_cli/skin_engine.py`) — data-driven CLI theming; initialized from `display.skin` config key at startup; skins customize banner colors, spinner faces/verbs/wings, tool prefix, response box, branding text
- `process_command()` is a method on `HermesCLI` — dispatches on canonical command name resolved via `resolve_command()` from the central registry
- Skill slash commands: `agent/skill_commands.py` scans `~/.hermes/skills/`, injects as **user message** (not system prompt) to preserve prompt caching

### Slash Command Registry (`hermes_cli/commands.py`)

All slash commands are defined in a central `COMMAND_REGISTRY` list of `CommandDef` objects. Every downstream consumer derives from this registry automatically:

- **CLI** — `process_command()` resolves aliases via `resolve_command()`, dispatches on canonical name
- **Gateway** — `GATEWAY_KNOWN_COMMANDS` frozenset for hook emission, `resolve_command()` for dispatch
- **Gateway help** — `gateway_help_lines()` generates `/help` output
- **Telegram** — `telegram_bot_commands()` generates the BotCommand menu
- **Slack** — `slack_subcommand_map()` generates `/hermes` subcommand routing
- **Autocomplete** — `COMMANDS` flat dict feeds `SlashCommandCompleter`
- **CLI help** — `COMMANDS_BY_CATEGORY` dict feeds `show_help()`

### Adding a Slash Command

1. Add a `CommandDef` entry to `COMMAND_REGISTRY` in `hermes_cli/commands.py`:
```python
CommandDef("mycommand", "Description of what it does", "Session",
           aliases=("mc",), args_hint="[arg]"),
```
2. Add handler in `HermesCLI.process_command()` in `cli.py`:
```python
elif canonical == "mycommand":
    self._handle_mycommand(cmd_original)
```
3. If the command is available in the gateway, add a handler in `gateway/run.py`:
```python
if canonical == "mycommand":
    return await self._handle_mycommand(event)
```
4. For persistent settings, use `save_config_value()` in `cli.py`

**CommandDef fields:**
- `name` — canonical name without slash (e.g. `"background"`)
- `description` — human-readable description
- `category` — one of `"Session"`, `"Configuration"`, `"Tools & Skills"`, `"Info"`, `"Exit"`
- `aliases` — tuple of alternative names (e.g. `("bg",)`)
- `args_hint` — argument placeholder shown in help (e.g. `"<prompt>"`, `"[name]"`)
- `cli_only` — only available in the interactive CLI
- `gateway_only` — only available in messaging platforms
- `gateway_config_gate` — config dotpath (e.g. `"display.tool_progress_command"`); when set on a `cli_only` command, the command becomes available in the gateway if the config value is truthy. `GATEWAY_KNOWN_COMMANDS` always includes config-gated commands so the gateway can dispatch them; help/menus only show them when the gate is open.

**Adding an alias** requires only adding it to the `aliases` tuple on the existing `CommandDef`. No other file changes needed — dispatch, help text, Telegram menu, Slack mapping, and autocomplete all update automatically.

---

## TUI Architecture (ui-tui + tui_gateway)

The TUI is a full replacement for the classic (prompt_toolkit) CLI, activated via `hermes --tui` or `HERMES_TUI=1`.

### Process Model

```
hermes --tui
  └─ Node (Ink)  ──stdio JSON-RPC──  Python (tui_gateway)
       │                                  └─ AIAgent + tools + sessions
       └─ renders transcript, composer, prompts, activity
```

TypeScript owns the screen. Python owns sessions, tools, model calls, and slash command logic.

### Transport

Newline-delimited JSON-RPC over stdio. Requests from Ink, events from Python. See `tui_gateway/server.py` for the full method/event catalog.

### Key Surfaces

| Surface | Ink component | Gateway method |
|---------|---------------|----------------|
| Chat streaming | `app.tsx` + `messageLine.tsx` | `prompt.submit` → `message.delta/complete` |
| Tool activity | `thinking.tsx` | `tool.start/progress/complete` |
| Approvals | `prompts.tsx` | `approval.respond` ← `approval.request` |
| Clarify/sudo/secret | `prompts.tsx`, `maskedPrompt.tsx` | `clarify/sudo/secret.respond` |
| Session picker | `sessionPicker.tsx` | `session.list/resume` |
| Slash commands | Local handler + fallthrough | `slash.exec` → `_SlashWorker`, `command.dispatch` |
| Completions | `useCompletion` hook | `complete.slash`, `complete.path` |
| Theming | `theme.ts` + `branding.tsx` | `gateway.ready` with skin data |

### Slash Command Flow

1. Built-in client commands (`/help`, `/quit`, `/clear`, `/resume`, `/copy`, `/paste`, etc.) handled locally in `app.tsx`
2. Everything else → `slash.exec` (runs in persistent `_SlashWorker` subprocess) → `command.dispatch` fallback

### Dev Commands

```bash
cd ui-tui
npm install       # first time
npm run dev       # watch mode (rebuilds hermes-ink + tsx --watch)
npm start         # production
npm run build     # full build (hermes-ink + tsc)
npm run type-check # typecheck only (tsc --noEmit)
npm run lint      # eslint
npm run fmt       # prettier
npm test          # vitest
```

---

## Adding New Tools

Requires changes in **2 files**:

**1. Create `tools/your_tool.py`:**
```python
import json, os
from tools.registry import registry

def check_requirements() -> bool:
    return bool(os.getenv("EXAMPLE_API_KEY"))

def example_tool(param: str, task_id: str = None) -> str:
    return json.dumps({"success": True, "data": "..."})

registry.register(
    name="example_tool",
    toolset="example",
    schema={"name": "example_tool", "description": "...", "parameters": {...}},
    handler=lambda args, **kw: example_tool(param=args.get("param", ""), task_id=kw.get("task_id")),
    check_fn=check_requirements,
    requires_env=["EXAMPLE_API_KEY"],
)
```

**2. Add to `toolsets.py`** — either `_HERMES_CORE_TOOLS` (all platforms) or a new toolset.

Auto-discovery: any `tools/*.py` file with a top-level `registry.register()` call is imported automatically — no manual import list to maintain.

The registry handles schema collection, dispatch, availability checking, and error wrapping. All handlers MUST return a JSON string.

**Path references in tool schemas**: If the schema description mentions file paths (e.g. default output directories), use `display_hermes_home()` to make them profile-aware. The schema is generated at import time, which is after `_apply_profile_override()` sets `HERMES_HOME`.

**State files**: If a tool stores persistent state (caches, logs, checkpoints), use `get_hermes_home()` for the base directory — never `Path.home() / ".hermes"`. This ensures each profile gets its own state.

**Agent-level tools** (todo, memory): intercepted by `run_agent.py` before `handle_function_call()`. See `todo_tool.py` for the pattern.

---

## Adding Configuration

### config.yaml options:
1. Add to `DEFAULT_CONFIG` in `hermes_cli/config.py`
2. Bump `_config_version` (currently 5) to trigger migration for existing users

### .env variables:
1. Add to `OPTIONAL_ENV_VARS` in `hermes_cli/config.py` with metadata:
```python
"NEW_API_KEY": {
    "description": "What it's for",
    "prompt": "Display name",
    "url": "https://...",
    "password": True,
    "category": "tool",  # provider, tool, messaging, setting
},
```

### Config loaders (two separate systems):

| Loader | Used by | Location |
|--------|---------|----------|
| `load_cli_config()` | CLI mode | `cli.py` |
| `load_config()` | `hermes tools`, `hermes setup` | `hermes_cli/config.py` |
| Direct YAML load | Gateway | `gateway/run.py` |

---

## Skin/Theme System

The skin engine (`hermes_cli/skin_engine.py`) provides data-driven CLI visual customization. Skins are **pure data** — no code changes needed to add a new skin.

### Architecture

```
hermes_cli/skin_engine.py    # SkinConfig dataclass, built-in skins, YAML loader
~/.hermes/skins/*.yaml       # User-installed custom skins (drop-in)
```

- `init_skin_from_config()` — called at CLI startup, reads `display.skin` from config
- `get_active_skin()` — returns cached `SkinConfig` for the current skin
- `set_active_skin(name)` — switches skin at runtime (used by `/skin` command)
- `load_skin(name)` — loads from user skins first, then built-ins, then falls back to default
- Missing skin values inherit from the `default` skin automatically

### What skins customize

| Element | Skin Key | Used By |
|---------|----------|---------|
| Banner panel border | `colors.banner_border` | `banner.py` |
| Banner panel title | `colors.banner_title` | `banner.py` |
| Banner section headers | `colors.banner_accent` | `banner.py` |
| Banner dim text | `colors.banner_dim` | `banner.py` |
| Banner body text | `colors.banner_text` | `banner.py` |
| Response box border | `colors.response_border` | `cli.py` |
| Spinner faces (waiting) | `spinner.waiting_faces` | `display.py` |
| Spinner faces (thinking) | `spinner.thinking_faces` | `display.py` |
| Spinner verbs | `spinner.thinking_verbs` | `display.py` |
| Spinner wings (optional) | `spinner.wings` | `display.py` |
| Tool output prefix | `tool_prefix` | `display.py` |
| Per-tool emojis | `tool_emojis` | `display.py` → `get_tool_emoji()` |
| Agent name | `branding.agent_name` | `banner.py`, `cli.py` |
| Welcome message | `branding.welcome` | `cli.py` |
| Response box label | `branding.response_label` | `cli.py` |
| Prompt symbol | `branding.prompt_symbol` | `cli.py` |

### Built-in skins

- `default` — Classic Hermes gold/kawaii (the current look)
- `ares` — Crimson/bronze war-god theme with custom spinner wings
- `mono` — Clean grayscale monochrome
- `slate` — Cool blue developer-focused theme

### Adding a built-in skin

Add to `_BUILTIN_SKINS` dict in `hermes_cli/skin_engine.py`:

```python
"mytheme": {
    "name": "mytheme",
    "description": "Short description",
    "colors": { ... },
    "spinner": { ... },
    "branding": { ... },
    "tool_prefix": "┊",
},
```

### User skins (YAML)

Users create `~/.hermes/skins/<name>.yaml`:

```yaml
name: cyberpunk
description: Neon-soaked terminal theme

colors:
  banner_border: "#FF00FF"
  banner_title: "#00FFFF"
  banner_accent: "#FF1493"

spinner:
  thinking_verbs: ["jacking in", "decrypting", "uploading"]
  wings:
    - ["⟨⚡", "⚡⟩"]

branding:
  agent_name: "Cyber Agent"
  response_label: " ⚡ Cyber "

tool_prefix: "▏"
```

Activate with `/skin cyberpunk` or `display.skin: cyberpunk` in config.yaml.

---

## Important Policies
### Prompt Caching Must Not Break

Hermes-Agent ensures caching remains valid throughout a conversation. **Do NOT implement changes that would:**
- Alter past context mid-conversation
- Change toolsets mid-conversation
- Reload memories or rebuild system prompts mid-conversation

Cache-breaking forces dramatically higher costs. The ONLY time we alter context is during context compression.

### Working Directory Behavior
- **CLI**: Uses current directory (`.` → `os.getcwd()`)
- **Messaging**: Uses `MESSAGING_CWD` env var (default: home directory)

### Background Process Notifications (Gateway)

When `terminal(background=true, notify_on_complete=true)` is used, the gateway runs a watcher that
detects process completion and triggers a new agent turn. Control verbosity of background process
messages with `display.background_process_notifications`
in config.yaml (or `HERMES_BACKGROUND_NOTIFICATIONS` env var):

- `all` — running-output updates + final message (default)
- `result` — only the final completion message
- `error` — only the final message when exit code != 0
- `off` — no watcher messages at all

---

## Profiles: Multi-Instance Support

Hermes supports **profiles** — multiple fully isolated instances, each with its own
`HERMES_HOME` directory (config, API keys, memory, sessions, skills, gateway, etc.).

The core mechanism: `_apply_profile_override()` in `hermes_cli/main.py` sets
`HERMES_HOME` before any module imports. All 119+ references to `get_hermes_home()`
automatically scope to the active profile.

### Rules for profile-safe code

1. **Use `get_hermes_home()` for all HERMES_HOME paths.** Import from `hermes_constants`.
   NEVER hardcode `~/.hermes` or `Path.home() / ".hermes"` in code that reads/writes state.
   ```python
   # GOOD
   from hermes_constants import get_hermes_home
   config_path = get_hermes_home() / "config.yaml"

   # BAD — breaks profiles
   config_path = Path.home() / ".hermes" / "config.yaml"
   ```

2. **Use `display_hermes_home()` for user-facing messages.** Import from `hermes_constants`.
   This returns `~/.hermes` for default or `~/.hermes/profiles/<name>` for profiles.
   ```python
   # GOOD
   from hermes_constants import display_hermes_home
   print(f"Config saved to {display_hermes_home()}/config.yaml")

   # BAD — shows wrong path for profiles
   print("Config saved to ~/.hermes/config.yaml")
   ```

3. **Module-level constants are fine** — they cache `get_hermes_home()` at import time,
   which is AFTER `_apply_profile_override()` sets the env var. Just use `get_hermes_home()`,
   not `Path.home() / ".hermes"`.

4. **Tests that mock `Path.home()` must also set `HERMES_HOME`** — since code now uses
   `get_hermes_home()` (reads env var), not `Path.home() / ".hermes"`:
   ```python
   with patch.object(Path, "home", return_value=tmp_path), \
        patch.dict(os.environ, {"HERMES_HOME": str(tmp_path / ".hermes")}):
       ...
   ```

5. **Gateway platform adapters should use token locks** — if the adapter connects with
   a unique credential (bot token, API key), call `acquire_scoped_lock()` from
   `gateway.status` in the `connect()`/`start()` method and `release_scoped_lock()` in
   `disconnect()`/`stop()`. This prevents two profiles from using the same credential.
   See `gateway/platforms/telegram.py` for the canonical pattern.

6. **Profile operations are HOME-anchored, not HERMES_HOME-anchored** — `_get_profiles_root()`
   returns `Path.home() / ".hermes" / "profiles"`, NOT `get_hermes_home() / "profiles"`.
   This is intentional — it lets `hermes -p coder profile list` see all profiles regardless
   of which one is active.

## Known Pitfalls

### DO NOT hardcode `~/.hermes` paths
Use `get_hermes_home()` from `hermes_constants` for code paths. Use `display_hermes_home()`
for user-facing print/log messages. Hardcoding `~/.hermes` breaks profiles — each profile
has its own `HERMES_HOME` directory. This was the source of 5 bugs fixed in PR #3575.

### DO NOT use `simple_term_menu` for interactive menus
Rendering bugs in tmux/iTerm2 — ghosting on scroll. Use `curses` (stdlib) instead. See `hermes_cli/tools_config.py` for the pattern.

### DO NOT use `\033[K` (ANSI erase-to-EOL) in spinner/display code
Leaks as literal `?[K` text under `prompt_toolkit`'s `patch_stdout`. Use space-padding: `f"\r{line}{' ' * pad}"`.

### `_last_resolved_tool_names` is a process-global in `model_tools.py`
`_run_single_child()` in `delegate_tool.py` saves and restores this global around subagent execution. If you add new code that reads this global, be aware it may be temporarily stale during child agent runs.

### DO NOT hardcode cross-tool references in schema descriptions
Tool schema descriptions must not mention tools from other toolsets by name (e.g., `browser_navigate` saying "prefer web_search"). Those tools may be unavailable (missing API keys, disabled toolset), causing the model to hallucinate calls to non-existent tools. If a cross-reference is needed, add it dynamically in `get_tool_definitions()` in `model_tools.py` — see the `browser_navigate` / `execute_code` post-processing blocks for the pattern.

### Tests must not write to `~/.hermes/`
The `_isolate_hermes_home` autouse fixture in `tests/conftest.py` redirects `HERMES_HOME` to a temp dir. Never hardcode `~/.hermes/` paths in tests.

**Profile tests**: When testing profile features, also mock `Path.home()` so that
`_get_profiles_root()` and `_get_default_hermes_home()` resolve within the temp dir.
Use the pattern from `tests/hermes_cli/test_profiles.py`:
```python
@pytest.fixture
def profile_env(tmp_path, monkeypatch):
    home = tmp_path / ".hermes"
    home.mkdir()
    monkeypatch.setattr(Path, "home", lambda: tmp_path)
    monkeypatch.setenv("HERMES_HOME", str(home))
    return home
```

---

## Testing

**ALWAYS use `scripts/run_tests.sh`** — do not call `pytest` directly. The script enforces
hermetic environment parity with CI (unset credential vars, TZ=UTC, LANG=C.UTF-8,
4 xdist workers matching GHA ubuntu-latest). Direct `pytest` on a 16+ core
developer machine with API keys set diverges from CI in ways that have caused
multiple "works locally, fails in CI" incidents (and the reverse).

```bash
scripts/run_tests.sh                                  # full suite, CI-parity
scripts/run_tests.sh tests/gateway/                   # one directory
scripts/run_tests.sh tests/agent/test_foo.py::test_x  # one test
scripts/run_tests.sh -v --tb=long                     # pass-through pytest flags
```

### Why the wrapper (and why the old "just call pytest" doesn't work)

Five real sources of local-vs-CI drift the script closes:

| | Without wrapper | With wrapper |
|---|---|---|
| Provider API keys | Whatever is in your env (auto-detects pool) | All `*_API_KEY`/`*_TOKEN`/etc. unset |
| HOME / `~/.hermes/` | Your real config+auth.json | Temp dir per test |
| Timezone | Local TZ (PDT etc.) | UTC |
| Locale | Whatever is set | C.UTF-8 |
| xdist workers | `-n auto` = all cores (20+ on a workstation) | `-n 4` matching CI |

`tests/conftest.py` also enforces points 1-4 as an autouse fixture so ANY pytest
invocation (including IDE integrations) gets hermetic behavior — but the wrapper
is belt-and-suspenders.

### Running without the wrapper (only if you must)

If you can't use the wrapper (e.g. on Windows or inside an IDE that shells
pytest directly), at minimum activate the venv and pass `-n 4`:

```bash
source venv/bin/activate
python -m pytest tests/ -q -n 4
```

Worker count above 4 will surface test-ordering flakes that CI never sees.

Always run the full suite before pushing changes.

### Don't write change-detector tests

A test is a **change-detector** if it fails whenever data that is **expected
to change** gets updated — model catalogs, config version numbers,
enumeration counts, hardcoded lists of provider models. These tests add no
behavioral coverage; they just guarantee that routine source updates break
CI and cost engineering time to "fix."

**Do not write:**

```python
# catalog snapshot — breaks every model release
assert "gemini-2.5-pro" in _PROVIDER_MODELS["gemini"]
assert "MiniMax-M2.7" in models

# config version literal — breaks every schema bump
assert DEFAULT_CONFIG["_config_version"] == 21

# enumeration count — breaks every time a skill/provider is added
assert len(_PROVIDER_MODELS["huggingface"]) == 8
```

**Do write:**

```python
# behavior: does the catalog plumbing work at all?
assert "gemini" in _PROVIDER_MODELS
assert len(_PROVIDER_MODELS["gemini"]) >= 1

# behavior: does migration bump the user's version to current latest?
assert raw["_config_version"] == DEFAULT_CONFIG["_config_version"]

# invariant: no plan-only model leaks into the legacy list
assert not (set(moonshot_models) & coding_plan_only_models)

# invariant: every model in the catalog has a context-length entry
for m in _PROVIDER_MODELS["huggingface"]:
    assert m.lower() in DEFAULT_CONTEXT_LENGTHS_LOWER
```

The rule: if the test reads like a snapshot of current data, delete it. If
it reads like a contract about how two pieces of data must relate, keep it.
When a PR adds a new provider/model and you want a test, make the test
assert the relationship (e.g. "catalog entries all have context lengths"),
not the specific names.

Reviewers should reject new change-detector tests; authors should convert
them into invariants before re-requesting review.
