From d845af5d1da42f7ac956dded3de4c4ea33bdabf6 Mon Sep 17 00:00:00 2001
From: igneum-labs <337424239+igneum-labs@users.noreply.github.com>
Date: Wed, 7 Oct 2026 08:06:59 +0000
Subject: [PATCH] fin-proof: fin-synth takes a DAA base when the fixture
 carries none

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
---
 proving/igneum-prove/host/src/fin.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/proving/igneum-prove/host/src/fin.rs b/proving/igneum-prove/host/src/fin.rs
index ec5630451..86cf98438 100644
--- a/proving/igneum-prove/host/src/fin.rs
+++ b/proving/igneum-prove/host/src/fin.rs
@@ -172,7 +172,10 @@ fn synth_hash(tag: &str, n: u64) -> H {
 /// certificate verification touched (for the report).
 pub fn synth(fixtures: &[Fixture], keys: usize, voters: usize, window_blocks: u64, cert_back: usize) -> Result<FinWitnessFile> {
     let first = fixtures.first().ok_or_else(|| anyhow!("no fixtures"))?;
-    let first_daa = first.block.env.daa_score.max(1);
+    // a fixture written before the DAA field existed carries 0; the guest never checks the DAA against the shard
+    // statement, so the synthetic run takes a base of its own then (the real chain's DAA is what the node feeds)
+    let daa_base = if first.block.env.daa_score == 0 { 100_000 } else { first.block.env.daa_score };
+    let first_daa = daa_base;
     // the window of the root state: W spans the synthetic history; min_daa under the first DAA so certificates pass C5
     let params = FinParams { chain_id: "igneum-fin-synth".into(), weight_window: window_blocks.max(16) * 2, dust: 1, min_daa: 1, leave_delay: 3_600, equivocation_ban: window_blocks.max(16) * 2 };
     let synth_keys: Vec<SynthKey> = (0..keys.max(1)).map(synth_key).collect();
@@ -204,7 +207,7 @@ pub fn synth(fixtures: &[Fixture], keys: usize, voters: usize, window_blocks: u6
     let mut blocks = Vec::new();
     for (i, f) in fixtures.iter().enumerate() {
         let n = f.block.env.number;
-        let daa = f.block.env.daa_score.max(state.end_daa);
+        let daa = (daa_base + i as u64).max(state.end_daa);
         let k = &synth_keys[i % synth_keys.len()];
         let k2 = &synth_keys[(i * 5 + 1) % synth_keys.len()];
         let block = ChainBlockWitness { number: n, block_hash: f.block.env.hash.0, daa, blues: vec![BlueBlock { block_hash: f.block.env.hash.0, key_hash: k.hash, daa }, BlueBlock { block_hash: synth_hash("side", n), key_hash: k2.hash, daa }] };