diff --git a/docs/JOURNAL.md b/docs/JOURNAL.md
index 3f0ebc9..129fc3c 100644
--- a/docs/JOURNAL.md
+++ b/docs/JOURNAL.md
@@ -19,6 +19,32 @@ or files, and the "so-what" for future readers.
 
 ---
 
+## 2026-07-18 — Corpus reduce truncated on the breadth brief ("hit its output limit")
+
+**Tags:** bug, design
+
+After the corpus-v3 breadth nudge (list EVERY holder, enumerate ALL cruxes),
+the reduce for a large case (~125 members) started failing with "The
+synthesis hit its output limit before finishing" — `runCorpusReducePass`
+seeing `stop_reason: 'max_tokens'` against `MAX_REDUCE_OUTPUT_TOKENS =
+16384`. Two compounding causes: (1) the breadth brief legitimately runs
+18-25k output tokens now (every position's holders as full 64-hex hashes,
+all cruxes, load-bearing, the proposal queue); (2) the reduce omits the
+`thinking` param, so on **Sonnet 5** adaptive thinking is ON by default and
+its thinking tokens share the same `max_tokens` budget — Sonnet had *less*
+room for the brief than the earlier (pre-nudge) Opus run that fit in 16384.
+
+Fix (surgical, no prompt change — preserves the graded breadth):
+`MAX_REDUCE_OUTPUT_TOKENS` 16384 → 32768 (well under every current model's
+128k output ceiling), and `CORPUS_REDUCE_TIMEOUT_MS` 300000 → 420000 so the
+now-larger brief can finish on the slower Opus tier (~55 tok/s × ~22k tokens
+≈ 400s) instead of trading a token-cap failure for an abort. The reduce is
+the one long single fetch in the corpus flow; its pending sendResponse keeps
+the MV3 SW alive. Deliberately NOT a prompt/tool/digest change → no
+`MAP_PROMPT_VERSION`/`CORPUS_PROMPT_VERSION` bump → the ~100 cached map
+extracts and brief-staleness keys are untouched. See
+`src/shared/corpus-prompts.js`, `src/shared/llm-client.js`.
+
 ## 2026-07-18 — A background re-render KILLED the running corpus analysis (token-scoped render guard)
 
 **Tags:** bug, pattern
diff --git a/src/shared/corpus-prompts.js b/src/shared/corpus-prompts.js
index 8b7ecb9..7da1fcd 100644
--- a/src/shared/corpus-prompts.js
+++ b/src/shared/corpus-prompts.js
@@ -52,7 +52,16 @@ export const HYPOTHESIS_EDGE_TOOL_NAME = 'propose_hypothesis_edges';
 export const MAX_MEMBER_INPUT_CHARS = 60000;
 export const MAX_CLAIMS_DIGEST_CHARS = 4000;
 export const MAX_MAP_OUTPUT_TOKENS = 8192;
-export const MAX_REDUCE_OUTPUT_TOKENS = 16384;
+// The reduce emits the WHOLE-corpus brief: every position's holders, ALL
+// cruxes, the load-bearing claims, and the proposal queue (the corpus-v3
+// breadth nudge above). For a large case (~125 members) that legitimately
+// runs 18-25k output tokens, and on Sonnet 5 — where `thinking` is omitted
+// so adaptive thinking is ON by default — those thinking tokens share this
+// same budget. 16384 truncated it ("hit its output limit before finishing");
+// 32768 fits the breadth brief with headroom and stays far under every
+// current model's 128k output ceiling. NOT a prompt/tool/digest change, so
+// no version bump — the map cache and brief staleness are unaffected.
+export const MAX_REDUCE_OUTPUT_TOKENS = 32768;
 export const MAX_HYPOTHESIS_EDGE_OUTPUT_TOKENS = 8192;
 
 // ------------------------------------------------------------------
diff --git a/src/shared/llm-client.js b/src/shared/llm-client.js
index 0a36f83..bc18615 100644
--- a/src/shared/llm-client.js
+++ b/src/shared/llm-client.js
@@ -539,7 +539,13 @@ export async function runAuditModulePass(req = {}) {
 // ------------------------------------------------------------------
 
 const CORPUS_MAP_TIMEOUT_MS = 120000;
-const CORPUS_REDUCE_TIMEOUT_MS = 300000;
+// The reduce is the ONE long single fetch in the corpus flow (the map phase
+// is many short calls). With MAX_REDUCE_OUTPUT_TOKENS raised to 32768, a
+// full breadth brief can generate ~20-25k tokens, which on the slower
+// (Opus-tier) models runs past the old 300s cap — so give it 7 min rather
+// than trade a token-cap failure for an abort. The pending sendResponse
+// keeps the MV3 service worker alive for the duration.
+const CORPUS_REDUCE_TIMEOUT_MS = 420000;
 
 /** Gating snapshot for the portal's "Analyze corpus" control. */
 export async function getCorpusConfig() {