skillscript-runtime v0.19.4

A skill's body text — the prose between the frontmatter and the first
target — is now its declarative output template. The runtime interpolates
${VAR} references against final vars and publishes the rendered string
as the skill's canonical output. Per Scott + Perry's c7ddfc50 design lock

• 920078c8 / ad0b868e sign-off.

Why

The emit(text="${SUMMARY}") ceremony for what is structurally just
"render this template and output it" was the highest-leverage authorability
tax on the most common operation. From Perry's c7ddfc50:

Author writes the sentence they want; the compute block fills in the
holes. The same skill stripped of its compute block still emits the
template with whatever defaults # Vars: declares.

Wins:

• Declarative output (author writes the sentence they want)
• No throwaway ${SUMMARY} var ceremony
• Branch resolved into vars; template stays single-shape
• Strip the compute block → still a valid skill that emits the template

What's new

Parser (src/parser.ts):

• ParsedSkill.outputTemplate: string | null — the captured template
  (null when none authored). Internal blanks preserved; leading/trailing
  blanks trimmed.
• Pin 4 disambiguation rule (nextNonBlankLineIsIndented lookahead): a
  target is <name>: with an indented op-block on the next non-blank
  line. Content-after-colon (Summary: hot today) without an op-block
  is template text. Bare <word>: alone with no op-block in the template
  region is captured AND recorded as ambiguous for lint.
• ParsedSkill.templateAmbiguousLines: number[] — line numbers for the
  tier-2 lint surface.

Runtime (src/runtime.ts):

• When parsed.outputTemplate !== null, render once via substituteRuntime
  with the final vars map; the rendered string owns outputs[key] across
  all # Output: kinds. Legacy emit-only path (no template) preserved
  byte-equivalent — outputs.text falls back to emissions.slice() /
  lastBoundVar exactly as before.
• Complementary channels: emit() continues to populate emissions[]
  (transcript) independently. Template = canonical output; emit =
  transcript. No competition.

CLI (src/cli.ts):

• skillfile execute now prints the rendered template when one is
  authored (matching the canonical-output channel). Emit-only skills
  continue to print emissions exactly as before.

Lint (src/lint.ts) — four new rules:

• unset-template-var (tier-1, error) — every ${VAR} in the template
  must resolve to a # Vars: input, ambient ref, or $set/-> binding
  somewhere in the skill body. Tier-1 because an unbound ref renders
  empty silently.
• template-looks-like-target (tier-2, warning) — bare <word>: alone
  in the template region, no following op-block. Reads ambiguously;
  author should disambiguate.
• body-template-detected (tier-3, info) — template captured but has
  no ${...} interpolations AND no text-consuming # Output:. Suggests
  "I wrote prose; it became template by accident."
• emit-with-template (tier-3, info) — skill has both a template AND
  emit(text=...) calls; confirms the channel-shift is intentional
  (template owns canonical output; emit goes to transcript).

Migration

Additive — emit-based skills work unchanged. Bundled corpus verified
clean (13 skills; no body-template content; all produce
outputTemplate: null).

The lookahead disambiguation rule is stricter than the pre-v0.19.4
target detection: a line at column 0 matching <identifier>: parses
as a target only when the next non-blank line is indented. Every real
target has an op-block under it, so no observed corpus skill regresses.

The legacy target: dep_a dep_b deps-form is preserved (lookahead sees
the indented op-block and confirms target intent). The explicit
needs: dep_a dep_b keyword form is recommended for new skills.

Docs

• README quickstart + canonical autonomous skill updated to use the
  template shape; new "fourth thing to notice" callout in the autonomous
  example.
• docs/adopter-playbook.md gains a new "Output template — body text IS
  the output" section covering the shape, complementary channels,
  output kinds, target syntax rules, and the four lints.

Tests

• tests/v0.19.4-output-template.test.ts — 34 tests: parser extraction
  • Pin 4 disambiguation + migration safety + runtime render + output-kind
    matrix + complementary channels + 4 lints (positive + negative) + e2e
    (compile + execute + lint preflight blocking).
• Live HTTP probe + idempotent twice-run + edge cases (multi-line, special
  chars, lint preflight, emit + template).

1860 tests total (+34 net new). Narrow-core LOC ceiling bumped
11100 → 11250 per the signal-not-budget rule (clear code wins).