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KS78: Relative supersession demotion — multiplicative 0.40 (#11) #22

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Merged
Liorrr merged 2 commits into from
Apr 10, 2026
Merged

KS78: Relative supersession demotion — multiplicative 0.40 (#11) #22

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3da2d05
KS78: Relative supersession demotion — multiplicative 0.40 default (#11)
Liorrr Apr 10, 2026
48d3bc2
fix: declare superseded_count in both temporal and standard code paths
Liorrr Apr 10, 2026
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6 changes: 3 additions & 3 deletions crates/shrimpk-core/src/config.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -239,8 +239,8 @@ pub struct EchoConfig {
/// Default: 0.0 (no penalty). Negative values demote children relative to parents.
#[serde(default)]
pub child_memory_penalty: f32,
/// Demotion applied to older (superseded) memories when a Supersedes edge exists.
/// Default: 0.0 (disabled). Positive values penalize stale facts.
/// Supersession demotion factor (multiplicative). 0.40 = retain 60% of score.
/// Applied as `score *= (1 - factor)^count` for each supersession edge.
#[serde(default)]
pub supersedes_demotion: f32,
Comment on lines 244 to 245
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@greptile-apps greptile-apps Bot Apr 10, 2026

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P1 Serde default mismatch — 0.40 only takes effect when no config file exists

#[serde(default)] resolves to f32::default() = 0.0, not 0.40. The struct Default impl (line 481) correctly sets 0.40, but that only applies when EchoConfig::default() is called programmatically (i.e. no config file). Any user with a config file that omits supersedes_demotion will get 0.0 from serde — meaning no multiplicative demotion at all, silently defeating the entire purpose of this PR.

Compare how recency_weight is handled: it uses #[serde(default = "default_recency_weight")] backed by a named function. supersedes_demotion needs the same treatment.

fn default_supersedes_demotion() -> f32 {
    0.40
}

Then update the field annotation:

/// Supersession demotion factor (multiplicative). 0.40 = retain 60% of score.
/// Applied as `score *= (1 - factor)^count` for each supersession edge.
#[serde(default = "default_supersedes_demotion")]
pub supersedes_demotion: f32,

This aligns serde deserialization with the struct Default impl so partial config files get 0.40 instead of 0.0.

/// Custom system prompt for the consolidator LLM fact extraction.
Expand Down Expand Up @@ -478,7 +478,7 @@ impl Default for EchoConfig {
recency_weight: default_recency_weight(),
child_rescue_only: default_child_rescue_only(),
child_memory_penalty: 0.0,
supersedes_demotion: 0.15,
supersedes_demotion: 0.40,
fact_extraction_prompt: None,
query_expansion_enabled: false,
reranker_enabled: false,
Expand Down
54 changes: 30 additions & 24 deletions crates/shrimpk-memory/src/echo.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1402,13 +1402,13 @@ impl EchoEngine {
// - Typed relationships: small extra boost when relationship type is relevant
// When at_time is provided (KS63), use get_valid_associations to filter
// expired/not-yet-valid edges for point-in-time queries.
let hebbian_boosts: Vec<f64> = {
let hebbian_boosts: Vec<(f64, u32)> = {
let hebbian = self.hebbian.read().await;
top.iter()
.map(|&(idx, _)| {
let idx = idx as u32;
let mut boost: f64 = 0.0;
let mut demotion: f64 = 0.0;
let mut superseded_count: u32 = 0;

if let Some(at) = at_time {
// Temporal query: only consider edges valid at the given timestamp
Expand All @@ -1424,7 +1424,7 @@ impl EchoEngine {
if idx > *neighbor {
boost += 0.1;
} else {
demotion -= self.config.supersedes_demotion as f64;
superseded_count += 1;
}
}
crate::hebbian::RelationshipType::CoActivation => {}
Expand All @@ -1448,7 +1448,7 @@ impl EchoEngine {
if idx > other {
boost += 0.1;
} else {
demotion -= self.config.supersedes_demotion as f64;
superseded_count += 1;
}
}
crate::hebbian::RelationshipType::CoActivation => {}
Expand All @@ -1460,18 +1460,17 @@ impl EchoEngine {
}
}

boost.min(0.4) + demotion
(boost.min(0.4), superseded_count)
})
.collect()
};

// 7b2. Parent supersession demotion (KS68 KU-1): if a parent entry has
// children with Supersedes edges (child is the older/superseded side),
// apply a flat demotion to the parent. This propagates child-level
// apply a multiplicative demotion to the parent. This propagates child-level
// supersession to parent ranking in Pipe A.
let parent_demotions: std::collections::HashMap<usize, f64> = {
let parent_demotions: std::collections::HashMap<usize, u32> = {
let hebbian = self.hebbian.read().await;
let demotion = self.config.supersedes_demotion as f64;
let mut demotions = std::collections::HashMap::new();
for &(idx, _) in &top {
if let Some(entry) = store.entry_at(idx) {
Expand All @@ -1492,7 +1491,7 @@ impl EchoEngine {
}
}
if has_superseded_child {
demotions.insert(idx, -demotion);
demotions.insert(idx, 1);
}
}
}
Expand All @@ -1505,7 +1504,7 @@ impl EchoEngine {
let mut results: Vec<EchoResult> = top
.iter()
.zip(hebbian_boosts.iter())
.filter_map(|(&(idx, score), &boost)| {
.filter_map(|(&(idx, score), &(boost, direct_superseded_count))| {
let entry = store.entry_at(idx)?;

// Apply category-aware decay: older memories score lower (F-02 fix)
Expand Down Expand Up @@ -1556,9 +1555,13 @@ impl EchoEngine {
// Co-occurrence bonus (KS68 ME-4)
final_score += co_occurrence_boost(&entry.content);

// Parent supersession demotion (KS68 KU-1)
if let Some(&demotion) = parent_demotions.get(&idx) {
final_score += demotion;
// Supersession demotion -- multiplicative (KS78 #11)
// Combines direct Supersedes edges + parent supersession into one factor
let total_superseded =
direct_superseded_count + parent_demotions.get(&idx).copied().unwrap_or(0);
if total_superseded > 0 {
let retain = 1.0 - self.config.supersedes_demotion as f64;
final_score *= retain.powi(total_superseded as i32);
}

// Child memory penalty (KS69): demote children to prevent hallucination inflation
Expand Down Expand Up @@ -4430,38 +4433,41 @@ mod tests {
);
}

// --- KU-1: Parent supersession flat demotion ---
// --- KU-1: Parent supersession multiplicative demotion (KS78) ---

#[test]
fn supersession_flat_demotion_closes_gap() {
fn supersession_multiplicative_demotion_closes_gap() {
// Simulate: M4 (Shopify, old job) final_score = 1.027
// M5 (Stripe, new job) final_score = 1.001
// With full demotion of 0.15: M4 drops to 0.877, well below M5.
let demotion: f64 = 0.15;
// With multiplicative demotion of 0.40: M4 retains 60%.
// 1.027 * 0.60 = 0.6162, well below 1.001.
let demotion_factor: f64 = 0.40;
let mut old_parent_score: f64 = 1.027;
let new_parent_score: f64 = 1.001;

old_parent_score += -demotion;
old_parent_score *= 1.0 - demotion_factor;

let expected = 1.027 * 0.6;
assert!(
old_parent_score < new_parent_score,
"Old parent ({old_parent_score}) must rank below new parent ({new_parent_score})"
);
assert!(
(old_parent_score - 0.877).abs() < 1e-10,
"Old parent should be demoted to 0.877, got {old_parent_score}"
(old_parent_score - expected).abs() < 1e-10,
"Old parent should be demoted to {expected}, got {old_parent_score}"
);
}

#[test]
fn supersession_flat_demotion_no_op_without_superseded_child() {
fn supersession_demotion_no_op_without_superseded_child() {
// If parent has no superseded children, no demotion is applied
let original: f64 = 1.027;
let demotions: std::collections::HashMap<usize, f64> = std::collections::HashMap::new();
let demotions: std::collections::HashMap<usize, u32> = std::collections::HashMap::new();
let mut score = original;

if let Some(&d) = demotions.get(&0) {
score += d;
let total_superseded = demotions.get(&0).copied().unwrap_or(0);
if total_superseded > 0 {
score *= (1.0 - 0.40_f64).powi(total_superseded as i32);
}

assert!(
Expand Down
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