Termind/ARCHITECTURE.md

Termind architecture

Termind intentionally remains one application target and one unit-test target. Directories describe dependency boundaries even though Swift does not enforce them as separate modules.

Dependency direction

• Domain contains platform-independent values and rules.
• Application contains repositories, feature state, use cases, events, and service protocols.
• Infrastructure implements persistence, security, SSH, SFTP, and LLM clients.
• Features contains SwiftUI presentation and sends intents to Application.
• Platform/macOS contains AppKit adapters.
• App constructs dependencies and owns application/window lifetimes.

There is deliberately no Core or generic shared layer. A value belongs to Domain, orchestration and ports belong to Application, concrete I/O belongs to Infrastructure, and presentation-only parsing or formatting stays with its Feature. This prevents a catch-all directory from bypassing dependency review.

Domain must not import SwiftUI, SwiftData, AppKit, Ghostty, CSSH2, or OpenSSL. Views must not construct network clients, access SwiftData/Keychain directly, or coordinate cross-domain cleanup. Runtime side effects belong to application services and durable outbox handlers.

The project remains one target, so ArchitectureBoundaryTests enforces the framework and concrete-client restrictions that directory layout alone cannot.

State lifetimes

• Repository snapshots are application-wide and shared by every window.
• A window owns one top-level shell, quick-open, and context-panel state.
• The shell always starts with two pinned routes: Vault, then Assistant. Dynamic tabs after them are SSH/SFTP Workspaces only.
• Vault owns its navigation column, including quick-connect Recents, and routes for Hosts, Keychain, Snippets, Welcome, and Host Editor. These routes never enter the Workspace deck.
• Known Hosts management belongs to the Host Editor draft for both new and existing Hosts. Context-panel Host details are read-only.
• Assistant owns its conversation list through AssistantLibraryModel; conversations are not panes and do not participate in Workspace drag, split, close, or reconnect lifecycles.
• A workspace owns only SSH/SFTP panes plus its session-scoped assistant conversation. Workspace content is full width and has no left sidebar.
• Session models own live SSH/SFTP resources and terminal/file-browser state.
• Settings is a native singleton macOS Settings scene, outside window routing.

Repository data is persistent truth. Runtime connection state is kept in a connection registry and is never persisted onto domain records.

Feature views receive aggregate-facing Application Models rather than a generic store API: HostLibraryModel, CredentialLibraryModel, SnippetLibraryModel, ForwardingLibraryModel, TransferLibraryModel, AIConfigurationModel, CommandHistoryModel, and ToolAuditModel. Aggregates that share one persisted vault snapshot still expose separate intent surfaces, so a feature cannot gain unrelated write operations merely because its records are saved together.

Agent runtime and security

AgentRuntime is an actor holding a run's state — transcript snapshot, tool registry, steering queue, secret broker — and the loop over it. Each phase of the loop is a separate value it drives:

• AgentContextPipeline rewrites what is sent at the model boundary: tool results reordered to match the calls they answer, orphaned results dropped, older results trimmed head-and-tail, session context inserted in front of the turn it describes. It shapes only the request. Run snapshots and stored history keep everything.
• AgentTurnDriver streams one assistant turn and assembles its tool calls.
• AgentToolScheduler plans and runs the turn's batch.
• AgentToolExecutor takes one call through schema validation, preflight, the card, hooks, authorization, and execution, in that order.
• AgentEventChannel is the single ordered path for events, fanning out to the UI and to a serial durable recorder.

OpenAI Responses, OpenAI Chat Completions, Anthropic Messages, and Gemini are adapters at the LLM boundary. Models without tool capability receive no tools. Stop cancels the active stream and actions that have not started; steering messages are consumed at the next turn boundary.

A turn's tool calls run concurrently only when every call in it is marked parallel; one sequential call makes the whole turn serial rather than being fenced into its own segment. Concurrency is declared per tool and may be overridden per call by preflight — ssh_exec is parallel exactly when CommandRiskClassifier proves the command safe, the same evidence that decides its safety. MCP tools are parallel by default; a server's destructive hint or Ask First makes them sequential, so remote metadata can only tighten concurrency, never grant it. Whatever the order of execution, results reach the transcript in the order the model asked for them, and every call is answered even when the turn is cancelled or refused — an assistant turn with unanswered tool calls is rejected outright on the next request.

Approvals and agent questions are queued and presented one at a time. Run state is derived from what is outstanding rather than asserted by whichever call moved last.

Extension points, all additive: AgentToolProviding for tool sources, AgentLoopHook for willExecute / didExecute / shouldStop, AgentContextTransforming for the model boundary, AgentModelStreaming for providers. Authorization is deliberately not among them — AgentApprovalHandling is a structural stage of the executor that no configuration can remove, and hooks run on either side of it.

Tools never receive a reference to the interactive PTY. Server commands use a dedicated SSH exec channel and file operations use run-scoped SFTP clients. Vault secrets are resolved behind AgentHostResolver. User-entered secrets are single-use handles bound to run, tool, host, and purpose; plaintext is passed directly to the executor and is excluded from model input, reviews, events, logs, and SwiftData. Fetch treats public HTTP(S) reads as locally read-only and routes private or otherwise non-public unicast targets through the active permission policy. DNS is revalidated on every redirect; a redirect that first enters a restricted origin pauses for another authorization decision. Explicit request headers follow every redirect, including cross-origin redirects, to match curl -H -L; sensitive values are redacted from review, UI, and durable history. MCP discovery retains schemas and annotations, but remote annotations are risk hints rather than proof of safety.

AgentScratchWorkspace is a per-conversation staging directory under Application Support, inside the sandbox container, deleted with the conversation that owns it. Paths are relative, .. is refused rather than resolved, symlinks are refused even when they point back inside, and every resolved path is proven to still be under the scope; writes are bounded per file, per conversation, and by entry count. It is an actor, so it is also the per-path mutation queue — a read and a write of the same file in one batch serialize there rather than by taking the whole turn serial, which is why every scratch tool is parallel. scratch_pull and scratch_push move bytes between a host and the workspace without the bytes entering the transcript, so a remote file can be pulled, edited and pushed back without a copy of it crossing the model boundary in either direction; scratch_edit returns a unified diff rather than the new file for the same reason. The SFTP tools are unchanged and know nothing about the workspace. Because a push is approved by filename rather than by content, its preflight puts the size, digest and a redacted head into the approval reasons, and binds the approval to that digest through execution-only metadata so a file rewritten while the user was deciding is refused rather than written.

The permission modes share structural validation but differ at the action gate. Safety is a property of the call, established locally: locallyReadOnly for calls proven to change nothing, locallyContained for calls that change only storage the app owns, and requiresAuthorization for everything else. The first two are allowed in every mode — a staging area that has to be approved into is not a staging area, and dialogs nobody can act on teach the reader to click through the one that matters.

• Ask for approval executes locally proven read-only and contained calls and presents every other action to the user.
• Approve for me sends those same non-read-only actions to Security Review. Missing credentials, timeout, transport errors, or malformed review JSON fail closed and are persisted as review failures.
• Full access skips action approval and Security Review while retaining host-key, secret, schema, host/path, fetch protocol/header/address-classification, sandbox, and tool-capability boundaries.

Agent conversations, runs, visible messages, tool calls/results, and reviews are stored in SwiftData after truncation and redaction. Launch marks unfinished runs interrupted; history is restored but remote actions are never resumed or replayed.

A process that dies mid-batch — force quit, crash, the OS reclaiming the app — leaves tool calls that nothing answered, which the next request would be rejected for. Restore closes that in two steps. Results are recorded as each tool finishes but their transcript rows wait for the run's next snapshot save, so loadConversations first materializes any recorded result whose transcript row was never written. Whatever is still unanswered is answered at the model boundary by AgentUnansweredToolCallRepair, which says the outcome is unknown rather than that the tool did not run: the process died after the command was dispatched, and a model told otherwise would repeat it.