diff --git a/docs/agent-template.md b/docs/agent-template.md
index 7018e2a..9b2d78e 100644
--- a/docs/agent-template.md
+++ b/docs/agent-template.md
@@ -137,9 +137,18 @@ Assignment rule, in priority order:
    evidence, the in-loop quality review) — run `opus`. Opus is
    the documented strength for code review, debugging, and deep
    reasoning.
-3. **Mechanical scope** — tightly-scoped execution of a pre-made
-   plan, recon, extraction, compliance-diffing run `sonnet`
-   (near-opus coding quality at lower latency and cost).
+3. **Mechanical scope** — recon, extraction, compliance-diffing
+   run `sonnet` (near-opus quality on tightly-scoped work at
+   lower latency and cost). Plan execution itself — the
+   `implementer` — is owner-ratified (2026-07-20) onto `opus`:
+   authored code is the pipeline's primary output, so it takes
+   the judgment model, but pairs it with `high` effort, not
+   `xhigh` — it is the most-dispatched in-loop role, and
+   volume × wall-clock (rule 4) still governs its thinking
+   budget. The compiler-driven-edit arm keeps dispatching the
+   implementer agentType at `sonnet`/`high`: compiler-enumerated
+   propagation is mechanical, and that arm's policy header pins
+   its own tier.
 4. **Volume × wall-clock** — agents dispatched per-task inside
    loops or fanned out in parallel swarms multiply their model's
    latency; they run `sonnet` unless rule 2 overrides (currently
@@ -156,9 +165,9 @@ Assignment rule, in priority order:
 
 Current distribution: `fable` — architect, debugger,
 grounding-check, tdd-author. `opus` — bencher, fieldtester,
-plan-recon, quality-reviewer, spec-skeptic. `sonnet` — docwriter,
-glossary-extractor, implementer, spec-reviewer, synthetic-user,
-tester.
+implementer (at `high`), plan-recon, quality-reviewer,
+spec-skeptic. `sonnet` — docwriter, glossary-extractor,
+spec-reviewer, synthetic-user, tester.
 
 The same rule binds Workflow scripts: every `agent()` call passes an
 explicit `model:` option, and `fable` is never a valid value there —
@@ -174,14 +183,16 @@ effort, coupling every dispatch's thinking budget to whatever the user
 happens to be chatting at — the same session-state coupling the `model`
 pin exists to remove. Effort follows the model split:
 
-- **`xhigh` on every `fable` and `opus` agent.** The judgement
-  roles are the pipeline's quality floor; their thinking budget
-  must not silently degrade because the session runs lower. The
-  fable gates deliberately stay at `xhigh`, not `max` — the
+- **`xhigh` on every `fable` and `opus` judgment agent.** The
+  judgement roles are the pipeline's quality floor; their thinking
+  budget must not silently degrade because the session runs lower.
+  The fable gates deliberately stay at `xhigh`, not `max` — the
   marginal thinking is not worth the extra latency and
-  scarce-budget burn.
-- **`high` on every `sonnet` agent.** Tightly-scoped execution of a
-  pre-made plan gains little from `xhigh` but pays its latency on
+  scarce-budget burn. One `opus` agent is exempt: the
+  `implementer` pairs `opus` with `high` (§ model rule 3 — the
+  most-dispatched in-loop role keeps the in-loop effort tier).
+- **`high` on every `sonnet` agent.** Tightly-scoped mechanical
+  work gains little from `xhigh` but pays its latency on
   every dispatch — and these are exactly the roles dispatched
   per-task inside loops (wall-clock is the pipeline's efficiency
   metric). Not lower than `high`: a sloppy in-loop step triggers
diff --git a/implement/agents/implementer.md b/implement/agents/implementer.md
index e3ec492..31b0d68 100644
--- a/implement/agents/implementer.md
+++ b/implement/agents/implementer.md
@@ -2,7 +2,7 @@
 name: implementer
 description: Carries out a tightly scoped implementation task. Reads the task extract handed by the controller, implements, builds, tests, reports a structured status with the diff. NOT for architecture decisions, NOT for self-curated scope; this agent executes a plan that has already been made.
 tools: Read, Edit, Write, Bash, Glob, Grep
-model: sonnet
+model: opus
 effort: high
 ---
 
diff --git a/implement/workflows/compiler-driven-edit.js b/implement/workflows/compiler-driven-edit.js
index 22234ca..148205d 100644
--- a/implement/workflows/compiler-driven-edit.js
+++ b/implement/workflows/compiler-driven-edit.js
@@ -43,7 +43,10 @@
 // session-model inherit (which could route to an unintended tier, e.g. fable —
 // reserved for the four ratified frontmatter gates, never for workflow stages;
 // agent-template § model rule 1). Both phases here are mechanical
-// (compiler-enumerated propagation, build/suite re-run), so both run sonnet.
+// (compiler-enumerated propagation, build/suite re-run), so both run sonnet —
+// including the implementer agentType: its opus frontmatter tier is for plan
+// execution, not compiler-enumerated propagation (agent-template § model
+// rule 3), so this arm pins sonnet explicitly.
 // Effort policy mirrors it: every call pins an explicit effort — the edit
 // (real code work) runs high, the build/suite verify (schema-bound check)
 // runs medium. See docs/agent-template.md § effort.
diff --git a/implement/workflows/implement-loop.js b/implement/workflows/implement-loop.js
index 0360dda..c0fce44 100644
--- a/implement/workflows/implement-loop.js
+++ b/implement/workflows/implement-loop.js
@@ -82,7 +82,9 @@
 //     session-model inherit (which could route to an unintended tier, e.g.
 //     fable — reserved for the four ratified frontmatter gates, never for
 //     workflow stages; agent-template § model rule 1). Mechanical and
-//     in-loop steps run sonnet; the quality gate runs opus by default (last
+//     in-loop check steps run sonnet; the implementer runs opus/high
+//     (owner-ratified 2026-07-20: judgment model for code authorship, kept at
+//     the in-loop effort tier); the quality gate runs opus by default (last
 //     correctness review before the end-verify), TIERED to sonnet/high for a
 //     small (<= 25 changed lines), non-contract diff as measured
 //     independently by the spec-reviewer (issue #30) — the end-verify /
@@ -792,7 +794,7 @@ async function runTask(task) {
       'inner-loop discipline — add the failing test inline even if the task text forgot to script it). ' +
       'Build and test must be green before you report DONE. Leave all edits UNSTAGED; never commit.\n\n' +
       `mode: ${mode}\niter_id: ${iter_id}\n\nTASK ${task.id} — ${task.title}\n${task.text}`,
-    { agentType: 'implementer', model: 'sonnet', effort: 'high', label: `impl:${task.id}`, phase: 'Per-task loop', schema: IMPL_SCHEMA },
+    { agentType: 'implementer', model: 'opus', effort: 'high', label: `impl:${task.id}`, phase: 'Per-task loop', schema: IMPL_SCHEMA },
   )
   if (!impl) return { id: task.id, title: task.title, outcome: 'BLOCKED', reason: 'implementer agent did not return' }
   if (impl.status === 'BLOCKED') return { id: task.id, title: task.title, outcome: 'BLOCKED', reason: impl.reason || 'worker-blocked' }
@@ -833,7 +835,7 @@ async function runTask(task) {
       `${STANDING}${ANCHOR}\n\nRepair task ${task.id} to satisfy the spec-compliance review. Address EACH finding; ` +
         'do not widen scope. Keep build + tests green; leave edits unstaged.\n\n' +
         `TASK ${task.id} — ${task.title}\n${task.text}\n\nFINDINGS:\n- ${(spec?.findings || ['(none reported)']).join('\n- ')}`,
-      { agentType: 'implementer', model: 'sonnet', effort: 'high', label: `impl-fix-spec:${task.id}`, phase: 'Per-task loop', schema: IMPL_SCHEMA },
+      { agentType: 'implementer', model: 'opus', effort: 'high', label: `impl-fix-spec:${task.id}`, phase: 'Per-task loop', schema: IMPL_SCHEMA },
     )
     if (specFix && specFix.applied_changes === true) wroteAnyFile = true
   }
@@ -951,7 +953,7 @@ async function runTask(task) {
         'into a deviation the next review flags.\n\n' +
         `TASK ${task.id} — ${task.title}\n${task.text}\n\nISSUES:\n- ` +
         (qual?.issues?.length ? qual.issues.map((i) => `[${i.severity}] ${i.text}`) : ['(none reported)']).join('\n- '),
-      { agentType: 'implementer', model: 'sonnet', effort: 'high', label: `impl-fix-qual:${task.id}`, phase: 'Per-task loop', schema: IMPL_SCHEMA },
+      { agentType: 'implementer', model: 'opus', effort: 'high', label: `impl-fix-qual:${task.id}`, phase: 'Per-task loop', schema: IMPL_SCHEMA },
     )
     if (fix && fix.applied_changes === true) wroteAnyFile = true
     if (fix && (fix.status === 'BLOCKED' || fix.status === 'NEEDS_CONTEXT')) {