OpenSpec-aware Authoring (dsh plugin)

This skill is a shared sub-procedure invoked by the Chorus stage skills (proposal, develop, yolo) whenever the user wants spec-driven authoring through the OpenSpec CLI. It is opt-in:

• Activates when all three signals hold (see §1): CHORUS_OPENSPEC_MODE is not off, an openspec/ directory exists at the project root, and the openspec CLI is on PATH.
• Otherwise the calling skill falls back to its existing free-form behavior.

Tool namespace: Chorus MCP tools are exposed under a mcp__chorus__ prefix on dsh (e.g. mcp__chorus__chorus_pm_create_proposal). Bare names are used in prose for readability — prepend mcp__chorus__ when invoking the MCP tools directly. Document-mirror calls do NOT go through the MCP harness at all — they go through the package-local chorus-mcp-call.mjs wrapper (see §2 Rule 1), which talks to the Chorus MCP endpoint over HTTP using your API key, independent of the mcp__chorus__ namespacing.

§1. Detection — read the precomputed value, else run the three checks inline

dsh difference: the Claude Code plugin precomputes CHORUS_OPENSPEC_ACTIVE in a SessionStart hook. dsh has no SessionStart hook, but the chorus-dsh bundle precomputes the same value at plugin load and exports it as the CHORUS_OPENSPEC_ACTIVE environment variable — it runs the three checks below against the process cwd, before the daemon-origin gate, so both interactive and daemon-woken sessions inherit it. Read that value when it is set; only recompute inline when it is absent (an older bundle, or the variable was explicitly cleared).

CHORUS_OPENSPEC_ACTIVE is 1 only when all three checks hold:

1. CHORUS_OPENSPEC_MODE is not set to off (explicit opt-out wins).
2. The project root contains an openspec/ directory (i.e. someone ran openspec init here).
3. The openspec CLI is on PATH.

Both signals (2) and (3) are required because the OpenSpec authoring path needs the working directory and the CLI — having one without the other leaves the workflow unrunnable. If signal (2) holds but (3) does not, surface a hint to the user — "OpenSpec repo detected — install with: npm i -g @fission-ai/openspec" — rather than silently choosing free-form.

Detection block (run this)

# Prefer the value the chorus-dsh bundle precomputed at load; fall back to the
# three checks when it is unset. PROJECT_DIR is your project root
# (dsh does not export CLAUDE_PROJECT_DIR — default to $PWD).
PROJECT_DIR="${PWD}"
if [ -n "${CHORUS_OPENSPEC_ACTIVE:-}" ]; then
  : # already precomputed by the chorus-dsh bundle — use it as-is
elif [ "${CHORUS_OPENSPEC_MODE:-}" = "off" ]; then
  CHORUS_OPENSPEC_ACTIVE=0
elif [ ! -d "${PROJECT_DIR}/openspec" ]; then
  CHORUS_OPENSPEC_ACTIVE=0
elif ! openspec --version >/dev/null 2>&1; then
  CHORUS_OPENSPEC_ACTIVE=0   # consider surfacing the install hint to the user
else
  CHORUS_OPENSPEC_ACTIVE=1
fi
echo "CHORUS_OPENSPEC_ACTIVE=$CHORUS_OPENSPEC_ACTIVE"

Branch on the result:

• CHORUS_OPENSPEC_ACTIVE=1 → follow §3 (OpenSpec authoring).
• CHORUS_OPENSPEC_ACTIVE=0 → return to the calling skill's free-form path. Do not scaffold openspec/changes/. Do not add the slug line to the proposal description.

Run this whenever proposal / develop / yolo reference this skill: read the precomputed CHORUS_OPENSPEC_ACTIVE if present, otherwise recompute the three checks.

§2. ⛔ Two non-negotiable rules

Both are enforced at review time. Both have caused incidents in past releases.

Rule 1 — Mirror via the wrapper, never re-type document content from agent output

Document/draft mirror calls (chorus_pm_add_document_draft, chorus_pm_update_document_draft, chorus_pm_update_document) MUST go through:

"$CHORUS_MCP_CALL" <tool_name> "$PAYLOAD"

with $PAYLOAD built using json_encode_file (defined in §3.4). Calling these tools directly from the agent's MCP harness with a hand-typed content field is a protocol violation for OpenSpec mode and will fail review. Reasons:

1. Token cost. Re-typing a multi-thousand-line markdown body through the LLM burns input + output tokens for every draft. json_encode_file (§3.4) encodes the file with Node's JSON.stringify — content never enters LLM context. A typical 3-doc proposal mirror via the script costs roughly zero content-tokens; via direct MCP it routinely costs 20k+.
2. Byte-equality. JSON.stringify of the file's UTF-8 bytes is a byte-faithful encoder: backslashes, quotes, newlines, code-fence content, zero-width chars all survive. LLM re-emission has a non-zero failure rate on long markdown — table alignment drifts, fence escapes get "fixed", long URLs wrap. The byte-equality guarantee (modulo trailing \n) holds only on the wrapper path.
3. Single source of truth. With the wrapper, the local openspec/changes/<slug>/*.md is authoritative and Chorus is a mirror. With agent re-typing, authority splits between local file and whatever the LLM happened to output — a future diff cannot tell which one is correct.

Wrapper availability on dsh. The npm bundle publishes its wrapper path in CHORUS_MCP_CALL when the plugin loads. Validate it before authoring:

if [ -z "${CHORUS_MCP_CALL:-}" ] || [ ! -x "$CHORUS_MCP_CALL" ]; then
  echo "ERROR: OpenSpec mirroring requires the package-local CHORUS_MCP_CALL wrapper; reload the Chorus dsh bundle." >&2
  exit 1
fi

The wrapper reads CHORUS_URL and CHORUS_API_KEY from the dsh process environment. If it is missing, halt visibly. Do not reproduce it ad hoc and do not retype document content through the model.

Rule 2 — Halt on error via chorus_check_response

Every wrapper call must check three signals: wrapper exit code, "error": in body, empty body. Bare RC=$? is insufficient — the wrapper exits 0 on HTTP 401 (auth failure) with empty body, so a single-signal check silently misses the most common runtime failure. See §6 for the helper definition.

§3. OpenSpec mode authoring

3.1 Pick a slug

openspec/changes/<slug>/ is the local change folder. The slug must be:

• kebab-case (add-export-csv, not addExportCsv or add_export_csv),
• derived from the source Idea title,
• unique within openspec/changes/.

Record it for later steps:

SLUG="add-export-csv"

3.2 Scaffold the change folder

openspec new change "$SLUG" --description "<one-line idea summary>"

This creates openspec/changes/$SLUG/ with README.md and .openspec.yaml. Then author by hand:

Use openspec instructions <artifact> --change "$SLUG" (artifacts: proposal, specs, design, tasks) for templates.

3.3 Spec file shape (verified against openspec instructions specs)

A delta spec lists one or more block headers — ## ADDED Requirements, ## MODIFIED Requirements, ## REMOVED Requirements, ## RENAMED Requirements — and within each, ### Requirement: entries. Mix freely in the same file; only include the blocks you actually need.

## ADDED Requirements

Append a brand-new Requirement to the long-term spec.

## ADDED Requirements

### Requirement: <name>
<requirement text — use SHALL / MUST for normative behavior>

#### Scenario: <name>
- **WHEN** <condition>
- **THEN** <expected outcome>

## MODIFIED Requirements

Whole-block replacement, not merge. Whatever you write here completely replaces the existing same-named Requirement in the long-term spec — title, description, and all scenarios. Half-writing it deletes the rest.

## MODIFIED Requirements

### Requirement: <existing name>
<full updated requirement text>

#### Scenario: <name>
- **WHEN** <condition>
- **THEN** <expected outcome>

#### Scenario: <other name>
- **WHEN** <condition>
- **THEN** <expected outcome>

Always include every scenario you want the post-archive spec to have, even ones that were already present and unchanged.

## REMOVED Requirements

Delete a Requirement from the long-term spec. The block under the heading is just the requirement name(s) you're removing — no scenarios needed.

## REMOVED Requirements

### Requirement: <existing name>

## RENAMED Requirements

Rename a Requirement's title. Body and scenarios are preserved as-is in the long-term spec; use MODIFIED instead if you need to change anything besides the title.

## RENAMED Requirements

### Requirement: <old name> -> <new name>

Critical formatting rules (verified):

• Scenarios MUST use exactly 4 hashtags (#### Scenario:). 3 hashtags or a bullet list silently fail validation.
• Every ### Requirement: under ADDED or MODIFIED MUST have at least one #### Scenario:.
• MODIFIED blocks MUST include the full updated content — they overwrite, not patch.
• Use SHALL / MUST for normative requirements; avoid should / may.
• The merge into openspec/specs/<capability>/spec.md happens at openspec archive time (§3.9), not at proposal time. While the proposal is in flight, Chorus only sees the delta file as one spec Document — there is no half-merged state for the skill to reason about.

Optional:

openspec validate "$SLUG"

3.4 Helper: json_encode_file

Define once at the top of the authoring session. It encodes the file into a byte-faithful JSON string with Node's JSON.stringify — Node is guaranteed present under dsh (it is the harness runtime), so no jq is required.

json_encode_file() {
  # Byte-faithful: JSON.stringify of the file's UTF-8 content — quotes,
  # backslashes, newlines, code-fence content, and control chars all survive.
  # No jq, no curl.
  node -e 'const fs=require("fs");process.stdout.write(JSON.stringify(fs.readFileSync(process.argv[1],"utf8")))' "$1"
}

Round-trip: the Chorus backend appends a single \n to draft content on write, so server content is byte-equal modulo a trailing newline. Reviewers diffing local file vs server should ignore that one byte.

3.5 Create the proposal container with the slug provenance line

Use the regular chorus_pm_create_proposal MCP tool (no wrapper required for this single call — the description is short, the LLM-emitted version is fine). The description must carry exactly one line:

OpenSpec change slug: <slug>

• on its own line (no other text on that line),
• literal prefix OpenSpec change slug: (capital O, capital S, single space after colon),
• no trailing punctuation,
• value matches the slug passed to openspec new change.

This line is machine-grep-able by future runs of this skill and by the §3.9 archive trigger.

3.6 Mirror each document draft via the wrapper

Rule 1 reminder: these calls go through chorus-mcp-call.mjs, not direct MCP. The agent must not retype the document body.

Resolve CHORUS_MCP_CALL as specified in Rule 1. Define the halt-on-error helper from §6 once at the top, then run one call per file:

# PRD draft
CONTENT=$(json_encode_file "openspec/changes/$SLUG/proposal.md")
PAYLOAD=$(cat <<JSON
{
  "proposalUuid": "$PROPOSAL_UUID",
  "type": "prd",
  "title": "PRD: $HUMAN_TITLE",
  "content": $CONTENT
}
JSON
)
RESULT=$("$CHORUS_MCP_CALL" chorus_pm_add_document_draft "$PAYLOAD")
RC=$?
chorus_check_response "chorus_pm_add_document_draft (prd)" "$RC" "$RESULT"
PRD_DRAFT_UUID=$(printf '%s' "$RESULT" | grep -o '"draftUuid"[[:space:]]*:[[:space:]]*"[^"]*"' | head -1 | sed 's/.*"\([^"]*\)"$/\1/')

Repeat with type: "tech_design" for design.md, and one call per capability with type: "spec" for each specs/<capability>/spec.md. Do not mirror tasks.md — Chorus task drafts (created via the chorus_pm_add_task_draft MCP tool, no wrapper needed) are the source of truth for tasks.

Why parsing uses printf '%s' "$RESULT" | grep not echo "$RESULT" | jq: echo interprets backslash sequences inside the captured JSON, turning embedded \n into a real newline. jq then aborts with Invalid string: control characters from U+0000 through U+001F must be escaped. printf '%s' emits the captured bytes verbatim. Same pattern applies to all wrapper-result parsing in this skill.

3.7 Editing a draft after the first mirror

Local file changes propagate via chorus_pm_update_document_draft — same wrapper, same json_encode_file, same halt check.

CONTENT=$(json_encode_file "openspec/changes/$SLUG/proposal.md")
PAYLOAD=$(cat <<JSON
{
  "proposalUuid": "$PROPOSAL_UUID",
  "draftUuid": "$PRD_DRAFT_UUID",
  "content": $CONTENT
}
JSON
)
RESULT=$("$CHORUS_MCP_CALL" chorus_pm_update_document_draft "$PAYLOAD")
RC=$?
chorus_check_response "chorus_pm_update_document_draft" "$RC" "$RESULT"

3.8 Editing a Document after proposal approval

Once the proposal is approved, drafts materialize into Documents with their own UUIDs. To keep openspec/changes/$SLUG/ and the Chorus Document in sync, mirror file edits via chorus_pm_update_document:

CONTENT=$(json_encode_file "openspec/changes/$SLUG/specs/<capability>/spec.md")
PAYLOAD=$(cat <<JSON
{
  "documentUuid": "$SPEC_DOCUMENT_UUID",
  "content": $CONTENT
}
JSON
)
RESULT=$("$CHORUS_MCP_CALL" chorus_pm_update_document "$PAYLOAD")
RC=$?
chorus_check_response "chorus_pm_update_document" "$RC" "$RESULT"

To re-derive $SPEC_DOCUMENT_UUID from a fresh shell, look it up via chorus_get_documents for the proposal's project and match by title + type. Re-derive $SLUG by grepping the proposal's description for ^OpenSpec change slug: .

3.9 Archive after the last task is verified

dsh difference: the Claude Code plugin has a PostToolUse hook (bin/on-post-verify-task.sh) that fires after chorus_admin_verify_task and injects an openspec archive <slug> reminder. dsh has no such hook. You (the agent) must detect the trigger yourself: after each chorus_admin_verify_task, check whether the just-verified task was the LAST task of its OpenSpec-mode idea (every Task across every approved Proposal of that idea is now done/closed, and the proposal description carries an OpenSpec change slug: <slug> line). If so, run the archive flow below. If not, do nothing.

When the trigger holds, you perform the archive:

1. Run archive locally. Use --yes for non-interactive mode. Do NOT pass --skip-specs (defeats the mirror-back) or --no-validate (lets malformed deltas corrupt cumulative specs).

   openspec archive "$SLUG" --yes
   

   This moves openspec/changes/$SLUG/ under openspec/changes/archive/<date>-<slug>/ and emits/updates openspec/specs/<capability>/spec.md for each capability. (Run openspec archive --help against your installed version to confirm the current flag set — flags can drift between releases.)

2. Mirror each updated openspec/specs/<capability>/spec.md back to the matching post-approval Chorus Document (§3.8 contract). chorus_get_documents only supports projectUuid + type server-side filters; filter by title client-side. One chorus_pm_update_document call per capability.

3. Halt on any error from openspec archive or chorus_pm_update_document. Print stderr verbatim, post a comment on the proposal recording the failure (chorus_add_comment with targetType: "proposal", targetUuid: <proposalUuid>), then stop. No retry. Matches §6 "no silent errors." (Comment on the proposal, not the idea: the failure is in archiving proposal-derived specs, and proposals can be inputType: "document" with no idea attached.)

4. Confirm success. List openspec/specs/<capability>/spec.md files and verify they round-trip byte-equal (modulo trailing newline) with their Chorus Document counterparts.

Strict opt-in: if the verified task is not the last of its idea, OR the proposal description carries no OpenSpec change slug: <slug> line, OR the local shell has no openspec CLI, do nothing — no archive. Existing free-form behavior is preserved.

§4. Fallback authoring (no openspec)

When the §1 detection puts the agent in fallback mode (CHORUS_OPENSPEC_ACTIVE=0), this skill is a no-op. Return to the calling skill's free-form path:

• No openspec/changes/ folder is created or referenced.
• No OpenSpec change slug: … line is added to the proposal description.
• Document drafts are authored via direct MCP chorus_pm_add_document_draft calls with inline content — same as before this skill existed.
• Rule 1 (wrapper-only mirror) does not apply — there is no local file source of truth.
• The §3.9 archive flow does nothing (no slug → no archive).

§5. Document type mapping (reference table)

prd, tech_design, spec are pre-existing valid Document.type values — no schema change required.

§6. Failure visibility — the chorus_check_response helper

The Node wrapper exits non-zero on transport failures, HTTP 4xx/5xx, and JSON-RPC error bodies (e.g. a 401 from a bad CHORUS_API_KEY exits 2, a tool-level error exits 4). Still check all three signals below as defense in depth: a bare RC=$? is fine for the common cases but this helper also catches a well-formed 200 body that nonetheless carries an "error" object, and an unexpectedly empty body.

Define this helper once at the top of the authoring session and use it after every wrapper call:

chorus_check_response() {
  local _tool="$1"
  local _rc="$2"
  local _body="$3"
  local _has_error=0
  local _is_empty=0

  local _trimmed
  _trimmed=$(printf '%s' "$_body" | tr -d ' \t\n\r')
  [ -z "$_trimmed" ] && _is_empty=1

  if [ "$_is_empty" -eq 0 ]; then
    # No jq required: a substring match on an "error" key is sufficient for the
    # mirror tools, whose success bodies carry no top-level "error" field.
    printf '%s' "$_body" | grep -qE '"error"[[:space:]]*:' && _has_error=1
  fi

  if [ "$_rc" -ne 0 ] || [ "$_has_error" -eq 1 ] || [ "$_is_empty" -eq 1 ]; then
    echo "ERROR: $_tool failed (exit=$_rc, error_in_body=$_has_error, empty_body=$_is_empty)" >&2
    echo "Output: $_body" >&2
    [ "$_rc" -ne 0 ] && exit "$_rc" || exit 1
  fi
}

Anti-patterns — do not:

• Collapse to || true.
• Redirect stderr to /dev/null.
• Bury the wrapper call inside a pipeline (masks $?).
• Skip capturing $RESULT into a variable; the helper needs the body.
• Use only if [ "$RC" -ne 0 ]; then ... — that misses the HTTP-error path.

Minimal call site shape:

RESULT=$("$CHORUS_MCP_CALL" <tool_name> "$PAYLOAD")
RC=$?
chorus_check_response "<tool_name>" "$RC" "$RESULT"
# ...if we reach here, the call succeeded; parse RESULT and continue.

This is project-wide policy: no silent errors.

§7. Quick reference checklist

When invoked from a stage skill (proposal / develop / yolo):

1. Run the §1 inline three-check detection yourself (no SessionStart hook on dsh). Compute CHORUS_OPENSPEC_ACTIVE from: CHORUS_OPENSPEC_MODE != off + openspec/ dir present + openspec CLI on PATH.
2. If CHORUS_OPENSPEC_ACTIVE=0 → return to caller's free-form path (§4).
3. Otherwise: a. Pick $SLUG (§3.1). b. openspec new change "$SLUG" (§3.2). c. Author proposal.md, design.md, specs/<capability>/spec.md (§3.2–§3.3). Mix ADDED / MODIFIED / REMOVED / RENAMED blocks as needed; remember MODIFIED overwrites the whole Requirement. d. Optional: openspec validate "$SLUG". e. chorus_pm_create_proposal (direct MCP) with the OpenSpec change slug: $SLUG line in description (§3.5). f. Validate the executable path in $CHORUS_MCP_CALL; define json_encode_file and chorus_check_response. g. For each row in §5 with "yes" — mirror via "$CHORUS_MCP_CALL" chorus_pm_add_document_draft (§3.6). Record each $DRAFT_UUID. h. On any failed chorus_check_response — halt, surface the error, do NOT proceed.
4. Edits before approval → §3.7. Edits after approval → §3.8.
5. Last task verified → detect the trigger yourself (no hook) → run §3.9 archive flow.