OpenSpec Agent Contract

Machine-readable surfaces of the openspec CLI, verified against src/ (capstone audit, 2026-06-11). Every shape below is documented from the emitting code.

1. General conventions

• One JSON document per invocation. In --json mode, stdout carries exactly one JSON document (2-space pretty-printed). Human prose, spinners, and the store banner go to stderr.
• Store banner. In human mode, a store-selected root prints Using OpenSpec root: <id> (<path>) to stderr. Never printed in JSON mode.
• Key casing is surface-dependent (see Known inconsistencies): store/doctor/context payloads use snake_case; workflow payloads (status, instructions, new change, validate, list) use camelCase, except the embedded root object, which always uses store_id.
• Optional keys are omitted, not null, in most payloads (e.g. root.store_id, member.path). Exceptions that use explicit null are called out per shape (store doctor git.*, failure payloads).

2. The diagnostic envelope

One envelope shape is shared by every machine-readable diagnostic (StoreDiagnostic):

{
  "severity": "error" | "warning" | "info",
  "code": "snake_case_string",
  "message": "human sentence",
  "target": "dotted.surface (optional)",
  "fix": "one actionable sentence/command (optional)"
}

Diagnostics appear in two positions: status arrays (status: StoreDiagnostic[] at top level or per entry) for health findings, and thrown errors converted to a single-element status array on command failure.

3. Root selection and RootOutput

All root-resolving commands (list, show, validate, status, instructions, instructions apply, new change, archive, doctor, context) resolve one OpenSpec root with one precedence:

1. --store <id> → the registered store's root (source: "store").
2. Otherwise, nearest ancestor with openspec/: planning shape → source: "nearest" (a store: pointer is ignored with a stderr warning); config-only dir with a valid store: pointer → that store, source: "declared".
3. No nearest root + registered stores exist → error no_root_with_registered_stores.
4. No root, no stores: scaffolding commands treat the cwd as source: "implicit"; diagnostic commands (doctor, context) fail with no_openspec_root instead — they inspect, never scaffold.

Successful JSON payloads embed the root:

"root": { "path": "/abs/path", "source": "store" | "declared" | "nearest" | "implicit", "store_id": "id (only when store-selected)" }

Root-failure contract: in JSON mode a resolution failure prints { ...commandNullShape, "status": [diagnostic] } on stdout and exits 1.

4. Command JSON shapes

4.1 list --json

{ "changes": [ { "name", "completedTasks", "totalTasks", "lastModified", "status": "no-tasks"|"complete"|"in-progress" } ], "root": RootOutput } — note the per-change status is a string enum here. --specs: { "specs": [ { "id", "requirementCount" } ], "root" }.

4.2 show <item> --json

Change: { "id", "title", "deltaCount", "deltas": [...], "root" }. Spec: { "id", "title", "overview", "requirementCount", "requirements": [...], "metadata": { "version", "format", "sourcePath"? }, "root" }.

4.3 validate --json

{ "items": [ { "id", "type": "change"|"spec", "valid", "issues": [ { "level", "path", "message", "line"?, "column"? } ], "durationMs" } ], "summary": { "totals": {items,passed,failed}, "byType": {...} }, "version": "1.0", "root" }. Exit 1 when any item fails.

4.4 status --json

{ "changeName", "schemaName", "planningHome"?: { "kind", "root", "changesDir", "defaultSchema" }, "changeRoot", "artifactPaths": { "<id>": {outputPath, resolvedOutputPath, existingOutputPaths} }, "nextSteps": ["..."], "actionContext": { "mode": "repo-local", "sourceOfTruth": "repo", "planningArtifacts", "linkedContext", "allowedEditRoots", "requiresAffectedAreaSelection", "constraints" }, "isComplete", "applyRequires", "artifacts": [ {id, outputPath, status: "done"|"ready"|"blocked", missingDeps?} ], "root" }. No active changes: { "changes": [], "message", "root" }, exit 0.

4.5 instructions <artifact> --json

{ "changeName", "artifactId", "schemaName", "changeDir", "planningHome"?, "outputPath", "resolvedOutputPath", "existingOutputPaths", "description", "instruction"?, "context"?, "rules"?, "references"?: ReferenceIndexEntry[], "template", "dependencies": [{id,done,path,description}], "unlocks", "root" }.

ReferenceIndexEntry: { "store_id", "root"?, "specs"?: [{id,summary}], "fetch"?, "status": [] } — resolved entries carry root/specs/fetch; unresolved carry store_id + warning status. Index capped at 50KB (reference_index_truncated).

4.6 instructions apply --json

{ "changeName", "changeDir", "schemaName", "contextFiles": { "<artifactId>": ["/abs", ...] }, "progress": {total,complete,remaining}, "tasks": [{id,description,done}], "state": "blocked"|"all_done"|"ready", "missingArtifacts"?, "instruction", "references"?, "root" }.

4.7 new change <name> --json

Success: { "change": { "id", "path", "metadataPath", "schema" }, "root" }. Failure: { "change": null, "status": [d] }, exit 1.

4.8 archive <name> --json

Success: { "archive": { "change", "archivedAs": "YYYY-MM-DD-name", "path", "specsUpdated", "totals"? }, "root" }. Failure: { "archive": null, "root"?, "status": [d] }, exit 1. JSON mode is strictly non-interactive: every prompt point becomes an archive_* code.

4.9 doctor --json

{ "root": { "path", "source", "store_id"?, "healthy", "status": [] }, "store": { "id", "metadata": {present,valid,remote?}, "origin_url"?, "status": [] } | null, "references": [...], "status": [] }. Health findings of any severity exit 0. Failure payload: { "root": null, "store": null, "references": [], "status": [d] }, exit 1.

4.10 context --json

{ "root": { "path", "source", "store_id"?, "role": "openspec_root" }, "members": [ { "role": "referenced_store", "id", "path"?, "remote"?, "fetch"?, "status": [] } ], "status": [] }. AVAILABLE = path present AND status empty. --code-workspace <path> writes {folders:[{name,path}]} (available referenced stores only, ref: prefixes); in JSON mode the write runs before printing so stdout holds exactly one document even on write failure. Failure: { "root": null, "members": [], "status": [d] }, exit 1.

4.11 store ... --json

setup/register: { "store": {id, root, metadata_path?}, "registry": {path, registered, already_registered}, "git": {is_repository, initialized, committed}, "created_files": [], "status": [] }. unregister/remove: { "store", "registry": {path, removed}, "files": {deleted, deleted_path, left_on_disk}, "status": [] }. list: { "stores": [{id, root}], "status": [] }. doctor: { "stores": [ { id, root, metadata_path?, openspec_root: {...healthy, status}, metadata: {present, valid, id?, remote}, git: {is_repository, has_commits, has_uncommitted_changes, has_remote, origin_url}, status } ], "status": [] } (null = unknown/not probed). Health findings exit 0; failures exit 1 with the matching null-shape. Prompt cancellation exits 130.

4.12 schemas --json / templates --json

schemas: bare array [ {name, description, artifacts, source} ]. templates: keyed object { "<artifactId>": {path, source} }. Both cwd-based, no root/status keys.

5. Exit-code contract

6. Diagnostic code catalog

Resolution

no_openspec_root, no_root_with_registered_stores, no_registered_stores, unknown_store, store_identity_mismatch, unhealthy_store_root, store_path_not_supported, invalid_store_pointer, initiative_option_removed, areas_option_removed; pass-through: invalid_store_id, invalid_store_registry, invalid_store_metadata.

OpenSpec-root health (error, no fix)

openspec_store_root_missing, openspec_root_missing, openspec_config_missing, openspec_specs_missing, openspec_changes_missing, openspec_archive_missing, plus _not_directory variants of each.

Store registry/identity/state

invalid_store_id, invalid_store_registry, invalid_store_metadata, store_registry_busy, store_not_found, no_store_registry, store_registry_changed, store_metadata_missing, store_metadata_id_mismatch, store_metadata_invalid, store_id_conflict, store_path_conflict, store_already_registered (info).

Store setup/register/remove

store_setup_id_required, store_setup_path_required, store_setup_path_not_directory, store_setup_inside_git_repo, store_setup_non_empty_directory, store_setup_cancelled, store_path_required, store_path_missing, store_path_not_directory, store_register_root_unhealthy, store_register_identity_confirmation_required, store_register_cancelled, store_remote_empty, store_remote_requires_hand_edit, store_remove_confirmation_required, store_remove_cancelled, store_remove_path_not_directory, store_remove_metadata_missing, store_root_missing (warning in remove, error in doctor), store_root_not_directory.

Store git

store_git_init_failed, store_git_identity_missing, store_git_commit_failed, store_git_no_commits (warning), store_clone_fragile_directories (warning), store_remote_divergence (info, doctor).

References (warning)

reference_invalid_id, reference_registry_unreadable, reference_unresolved, reference_root_unhealthy, reference_index_truncated.

Relationships (warning; doctor; context keeps only the registry one)

relationship_registry_unreadable, root_pointer_ignored, root_pointer_invalid, pointer_declarations_inert.

Archive (JSON mode)

archive_change_name_required, archive_change_not_found, archive_validation_failed, archive_confirmation_required, archive_tasks_incomplete, archive_spec_update_failed, archive_spec_validation_failed, archive_target_exists, archive_error.

Context writes

context_file_exists, context_output_dir_missing.

Fallbacks

doctor_failed, context_failed, store_error, change_error, archive_error.

Known inconsistencies

Recorded by the capstone audit; published-key renames are product decisions deferred past this release:

1. In --json mode, several failure paths printed stderr only with no JSON document. Fixed in the capstone gauntlet round: show/validate unknown and ambiguous items emit {status:[{code: unknown_item | ambiguous_item, ...}]}; thrown errors in status/instructions/list/show/validate route through the JSON-aware failure helper (the command's null-shape + status); store <unknown subcommand> --json emits {status:[{code: unknown_store_subcommand}]}; list carries its {changes|specs: [], root: null} null-shape on resolution failures.
2. store_root_missing is emitted with two severities (warning in remove, error in store doctor) — context-dependent, documented above.
3. snake_case (store family) vs camelCase (workflow family) key casing; root.store_id is snake_case everywhere.
4. Four parallel envelope type declarations exist in src; archive diagnostics never carry target.
5. list --json reuses the status key as a string enum per change.
6. Only validate output carries a version field.
7. schemas/templates ignore root selection (cwd-based, no --store).
8. Deprecated noun forms (change/spec subcommands) emit unenveloped payloads without root/status.