feat(agents): W4 handover two-mode — synthesize opus / render sonnet, run-scoped draft handoff (BDR-077)

handover-doc-writer: MODE synthesize (model="opus" call-site — STEP
9/10/12 → .audit/handover-draft-<RUNID>.md + DRAFT COMPLETE sentinel) /
MODE render (sonnet pin — STEP 13-16 from the draft, fail-closed on
absent/mismatched RUNID). Mode-based, not a file split: the §9
name+dispatch census locks survive untouched. client-handover-writer 9.6
dispatches twice with the FULL PACKAGE both times (LRN-126) + RUNID mint
+ post-run draft cleanup. In-wave smokes PASSED disk-verified: draft
written+sentinel+gitignored; render BLOCKED on wrong RUNID (no phantom
synthesis); render consumed draft + honored skip-write, report grammar
intact. Census §17 (111 pass), make test exit 0.

agents/client-handover-writer.md

@@ -1072,11 +1072,30 @@ If `OUTPUT` resolved to `skip-write`, still dispatch — the doc-writer
 reports `MD: skipped` and stops before rendering, per its own
 contract.
 
-Dispatch:
+Dispatch the two-mode pipeline (BDR-077 — synthesis on opus, render on the
+sonnet pin, full PACKAGE both times per LRN-126). Mint a RUNID first
+(`RUNID=$(date +%s)`); the draft crosses via the run-scoped, gitignored
+`.audit/handover-draft-<RUNID>.md`; clean it after 9.7.
+
+FIRST — synthesize:
+
+```
+Agent(subagent_type="handover-doc-writer", model="opus")
+prompt: "MODE: synthesize
+RUNID: <RUNID>
+PACKAGE:
+<the FULL PACKAGE block below>"
+```
+
+Parse its `SYNTH REPORT`: `STATUS: BLOCKED` → surface verbatim, stop (do
+not patch the PACKAGE silently); malformed/mute → retry ONCE fresh, then
+escalate. `STATUS: DONE` → THEN render:
 
 ```
 Agent(subagent_type="handover-doc-writer")
-prompt: "PACKAGE:
+prompt: "MODE: render
+RUNID: <RUNID>
+PACKAGE:
 LANG: <LANG>
 PROJECT: name=<name> root=<root> type=<type> sub-type=<sub-type>
   is_local_business=<bool> deployed_url=<url> period=<first→last>
@@ -1092,10 +1111,15 @@ PRECHECK_DONE: <list>
 CLIENT_NAME: <name|—>
 OUTPUT: <overwrite <path> | versioned <path> | skip-write>
 
-Synthesize + write + render the deliverable per your steps. Report the
+Render the deliverable from the draft per your render-mode steps. Report
-HANDOVER-DOC REPORT."
+the HANDOVER-DOC REPORT."
 ```
 
+(The PACKAGE block is IDENTICAL in both dispatches — write it once,
+paste it twice. A render `STATUS: BLOCKED` on draft absence/RUNID
+mismatch means the synthesize leg failed silently: re-run 9.6 from the
+synthesize dispatch, never hand-write the draft.)
+
 ### 9.7 — Parse the report, tell the user
 
 Parse the returned `HANDOVER-DOC REPORT`:

agents/handover-doc-writer.md

@@ -1,6 +1,6 @@
 ---
 name: handover-doc-writer
-description: Deliverable writer — dispatched by client-handover with a resolved PACKAGE. Reads memory + git, synthesizes the 6-chapter client doc, writes the MD, renders branded HTML+PDF. No audits, no questions, no dispatch.
+description: 'Two-mode deliverable writer — MODE: synthesize (dispatched model="opus" — memory+git clustering, 6-chapter synthesis into a run-scoped draft) and MODE: render (sonnet pin — annexes, precheck, deterministic gates, MD + branded HTML/PDF from the draft). Dispatched twice by client-handover with the resolved PACKAGE. No audits, no questions, no dispatch.'
 tools: Read, Write, Edit, Bash, Grep, Glob, WebSearch, WebFetch
 model: sonnet
 ---
@@ -43,6 +43,29 @@ name the missing field.
 
 ---
 
+## MODE DETECTION (BDR-077 — two dispatch modes, one PACKAGE)
+
+The parent dispatches this agent TWICE, with the FULL PACKAGE both times
+(LRN-126 — every field crosses each dispatch) plus a `RUNID`:
+
+- **`MODE: synthesize`** — dispatched with `model: "opus"` (judgment tier;
+  call-site override over the sonnet pin). Runs STEP 9 → 10 → 12 and writes
+  the chapters (§1-§6 full, §7/§8 stubs) into the RUN-SCOPED DRAFT
+  `.audit/handover-draft-<RUNID>.md`, ending the file with the line
+  `DRAFT COMPLETE — RUNID: <RUNID>`. Then emits a `SYNTH REPORT`
+  (`STATUS: DONE | BLOCKED`, RUNID, phase-cluster count, per-chapter word
+  counts) and STOPS — STEP 13-16, the final MD, HTML and PDF are NEVER
+  this mode's job.
+- **`MODE: render`** — runs on the sonnet frontmatter pin. FIRST loads the
+  draft: absent file, RUNID mismatch, or missing `DRAFT COMPLETE` sentinel
+  → `STATUS: BLOCKED` naming the cause (fail closed — never synthesize a
+  missing draft, never render a partial one). Then runs STEP 13 → 14 →
+  14.5 → 15 → 16 on the draft + PACKAGE and emits the `HANDOVER-DOC
+  REPORT`. `OUTPUT = skip-write` → report `MD: skipped` and stop before
+  rendering, as before.
+
+---
+
 ## STEP 9 — LOAD MEMORY REGISTRIES
 
 ```bash
@@ -452,6 +475,12 @@ des audits de santé. Pour toute question, contactez [contact].*
 
 ---
 
+> **MODE BOUNDARY.** STEP 12 is the last synthesize-mode step: write the
+> drafted chapters to `.audit/handover-draft-<RUNID>.md` (+ the
+> `DRAFT COMPLETE — RUNID: <RUNID>` terminal line), emit the SYNTH
+> REPORT, stop. Everything below (STEP 13-16) is `MODE: render` and
+> operates ON that draft.
+
 ## STEP 13 — SEO/GEO MANUAL CHECKLIST (web projects only)
 
 If `PROJECT_TYPE=web` AND `PACKAGE.SKIP_SEO` is not `yes`, append this chapter

lib/tests/model-routing.test.sh

@@ -131,6 +131,15 @@ lacks "skills/onboard/SKILL.md"              'Load `$HOME/.claude/agents/onboard
 has "skills/commit-change/SKILL.md"          'model="opus"'
 has "agents/commit-changer.md"               'MODE: propose'
 has "agents/commit-changer.md"               'model: sonnet'
+# 17) BDR-077 W4 — handover two-mode: synthesize = opus at the call site
+#     (STEP 9/10/12 → run-scoped .audit/ draft + DRAFT COMPLETE sentinel),
+#     render = sonnet pin (STEP 13-16, fail-closed on absent/mismatched
+#     draft). Name + dispatch-string locks of §9 survive untouched.
+has "agents/handover-doc-writer.md"          'MODE: synthesize'
+has "agents/handover-doc-writer.md"          'MODE: render'
+has "agents/handover-doc-writer.md"          'DRAFT COMPLETE'
+has "agents/client-handover-writer.md"       'MODE: synthesize'
+has "agents/client-handover-writer.md"       'handover-doc-writer", model="opus"'
 
 printf 'model-routing census: %d pass, %d fail\n' "$pass" "$fail"
 [ "$fail" -eq 0 ]