Mental model

Open Settings -> AI Tools. Create connections in the upper section, then assign them to Terminal, Summary, Dreaming, Analysis, and Assistant below. Connections answer “which AI services can Tower reach?” Slots answer “which connection and model does this feature use, in what order?” One connection may serve multiple slots.

CLI connections

Tower includes Claude Code, Codex CLI, and Gemini CLI. Each card reports command discovery path, version, Hello probe, models, and MCP/Hooks/Skills support and installation status. A connection may be not found, found but not runnable, unauthenticated/disconnected, or connected.

Each CLI owns account login, token, proxy, and base URL. Configure those through the CLI itself. Tower's advanced environment variables are a compatibility path, not a replacement for CLI login. A Hello probe must receive a minimal model reply; --version alone is not connected.

API connections

Tower supports OpenAI, OpenAI Compatible, Anthropic, and Google. You may create multiple named instances of the same protocol.

• Supply a complete http:// or https:// base URL. Tower trims it and removes a trailing slash but never appends /v1.
• Add and toggle custom headers/query parameters. Transport headers are blocked and sensitive names are masked.
• A connection may hold multiple keys. Each key is health-tested with the default model. Runtime round-robin uses only enabled, successful keys.
• Before any content/tool side effect, 401, 403, or 429 may rotate to another healthy key. Rotation stops after streaming begins.
• Models combine discovery and manual entries. Refresh preserves manual models; referenced models removed upstream become unavailable rather than disappearing.

API keys are plaintext in local SQLite. They are masked by default but the local user can reveal, copy, and edit them. Keys and sensitive headers/query values enter a full database backup; normal logs, errors, task messages, and test reports redact them.

Five capability slots

Each slot stores a primary and user-ordered fallbacks as stable connection + model targets. Tower never picks an undeclared “first available provider.”

• Terminal: CLI only. Fallback is allowed before a new session starts; the successful connection/model is pinned for Resume.
• Summary: falls back to deterministic Git/commit text if all targets fail.
• Dreaming: skips on total failure and can be retried later.
• Analysis: preserves the existing project description.
• Assistant: may fall back before the turn's first stream/tool activity, then locks.

Cancellation, safety refusal, invalid configuration, and tool execution errors do not trigger cross-connection fallback.

Assistant

Tower-owned multi-turn sessions support workspace/project/version bindings, image/text attachments, SSE, Tower tool cards, and cancellation. Legacy Claude Assistant sessions remain visible and are copied on demand when first opened. Tower does not automatically delete or rewrite the original transcript. Imported history can continue with another configured provider.

CLI provider extensions

Browse or search versioned extensions in Settings -> Extensions -> Provider catalog. A plan shows publisher, version change, capabilities, permissions, Tower/Node compatibility, and the underlying CLI dependency. Tower downloads an immutable artifact from the server-configured HTTPS catalog and verifies size, SHA-256, archive paths, manifest, schema, and compatibility. The normal UI accepts neither npm package names nor arbitrary download URLs.

An installed extension remains disabled until its permissions are explicitly confirmed. Only enabled, confirmed, healthy dynamic CLI connections appear in AI Tools and the five capability slots. An update that adds permissions requires confirmation again. Disabling or uninstalling preserves existing slot references but makes them unavailable.

The Qwen Code community extension requires an existing qwen command in >=0.18.0 <1.0.0. Tower does not install @qwen-code/qwen-code, sign in, or manage Qwen tokens, base URL, or user configuration. The sample declares Terminal sessions and CLI query only; it does not claim model discovery, MCP, Hooks, or Skills integrations.

Developer mode registers an absolute local directory in place for provider iteration. Extensions are trusted local Node.js code, not an OS sandbox.

Diagnostics

State/error	Action
CLI missing	Install it, fix command override, or select an absolute path, then detect again
CLI not logged in	Complete login/token/base URL in the CLI and rerun Hello
MCP disconnected	Inspect and reinstall/repair MCP; CLI installation alone is insufficient
API 401/403	Check key, permissions, authorization override, protocol, and base URL
API 429	Check quota/rate limit; healthy keys can rotate only before activity
model unavailable	Refresh or add the exact model ID manually, then update the slot
Plugin damaged	Check integrity/local path, reinstall, or recover the registry
CLI version incompatible	Update the underlying CLI to the range shown on the extension card; Tower will not update it
Permission required	Review and explicitly confirm the declared permissions
slot unconfigured	Add at least one enabled, connected target to the slot

See Upgrade and migration for migration and backup boundaries.