diff --git a/backend/src/agent/podman.ts b/backend/src/agent/podman.ts
index c08f13d..b912cb5 100644
--- a/backend/src/agent/podman.ts
+++ b/backend/src/agent/podman.ts
@@ -9,11 +9,42 @@ import {
   recordIntervention,
   updateInterventionStatus,
 } from '../memory/store.js';
-import { getGitStates } from '../memory/db.js';
+import { getGitStates, type GitState } from '../memory/db.js';
 import { recallSimilar } from '../memory/vectors.js';
 import { shouldIntervene, preferredAction } from '../memory/policy.js';
 import { publishHermesIntervention } from '../action/hermes.js';
 
+/** Strip a git-status prefix ("M ", "?? ") and reduce a path to its lowercased
+ *  basename — matches comparableFile() in memory/store.ts so keys line up. */
+function comparableBasename(raw?: string): string {
+  return (
+    (raw ?? '')
+      .trim()
+      .replace(/^(\?\?|[MADRCU!]{1,2})\s+/, '')
+      .split(/[\\/]/)
+      .pop()
+      ?.toLowerCase() ?? ''
+  );
+}
+
+/** Canonicalize an engineer name for case/whitespace-insensitive matching, so
+ *  "Karti" and "karti" resolve to the same engineer's git state. */
+function canonicalName(raw?: string): string {
+  return (raw ?? '').trim().toLowerCase();
+}
+
+/** Git ground truth: do ALL involved engineers currently have the collided file
+ *  in their changedFiles? Computed at detection time while git state is fresh. */
+function engineersOverlapOnFile(collision: Collision, gitStates: Map<string, GitState>): boolean {
+  const target = comparableBasename(collision.file);
+  if (!target || collision.engineers.length < 2) return false;
+  const byCanon = new Map<string, string[]>();
+  for (const [name, st] of gitStates) byCanon.set(canonicalName(name), st.changedFiles);
+  return collision.engineers.every((e) =>
+    (byCanon.get(canonicalName(e)) ?? []).some((f) => comparableBasename(f) === target),
+  );
+}
+
 export class PodMan {
   private contexts = new Map<string, EngineerContext>();
   /**
@@ -75,6 +106,12 @@ export class PodMan {
       if (!current.has(key)) this.activeConflicts.delete(key);
     }
 
+    // Capture git ground-truth overlap now, while engineer_states are fresh, so
+    // the outcome-time verifier never depends on a stale sidecar or a late click.
+    for (const collision of collisions) {
+      collision.gitOverlap = engineersOverlapOnFile(collision, gitStates);
+    }
+
     for (const collision of collisions) await this.handle(collision);
   }
 
@@ -85,14 +122,7 @@ export class PodMan {
    * basename.
    */
   private conflictKey(collision: Collision): string {
-    return (
-      (collision.file ?? '')
-        .trim()
-        .replace(/^(\?\?|[MADRCU!]{1,2})\s+/, '')
-        .split(/[\\/]/)
-        .pop()
-        ?.toLowerCase() ?? ''
-    );
+    return comparableBasename(collision.file);
   }
 
   private async handle(collision: Collision): Promise<void> {
diff --git a/backend/src/memory/store.ts b/backend/src/memory/store.ts
index 8125385..97bff45 100644
--- a/backend/src/memory/store.ts
+++ b/backend/src/memory/store.ts
@@ -5,7 +5,7 @@ import type {
   InterventionOutcome,
   InterventionStatus,
 } from '@podman/shared';
-import { collections } from './db.js';
+import { collections, getGitStates } from './db.js';
 import { enrichCollisionMemory } from './vectors.js';
 
 function comparableFile(raw?: string): string {
@@ -84,13 +84,53 @@ export async function updateInterventionStatus(
   );
 }
 
+/**
+ * Step 3 — derive whether a flagged collision was REAL from git ground truth,
+ * instead of trusting the client (which historically hardcoded `true`). A
+ * collision counts as real only if BOTH named engineers currently have the
+ * collided file in their git `changedFiles`. Conservative: returns false when
+ * the collision is orphaned/missing or git state is stale/unavailable.
+ * Verifier supervision per docs/continual-learning/spec.md:98-108, policy.md:35-42.
+ */
+export async function deriveWasRealCollision(outcome: InterventionOutcome): Promise<boolean> {
+  try {
+    const c = await collections();
+    const collision = await c.collisions.findOne({ id: outcome.collisionId });
+    if (!collision) return false;
+    // Prefer the overlap evidence captured at detection time (fresh git state):
+    // immune to late clicks, stale sidecars, and the engineer_states TTL.
+    if (typeof collision.gitOverlap === 'boolean') return collision.gitOverlap;
+    // Fallback for collisions detected before gitOverlap was captured: re-derive
+    // from latest git state, matching engineers on case/whitespace-canonical names.
+    if (!Array.isArray(collision.engineers) || collision.engineers.length < 2) return false;
+    const target = comparableFile(collision.file);
+    if (!target) return false;
+    const byCanon = new Map<string, string[]>();
+    for (const [name, st] of await getGitStates(outcome.podId)) {
+      byCanon.set(name.trim().toLowerCase(), st.changedFiles);
+    }
+    return collision.engineers.every((e) =>
+      (byCanon.get(e.trim().toLowerCase()) ?? []).some((f) => comparableFile(f) === target),
+    );
+  } catch (err) {
+    console.error(`[memory] wasRealCollision verifier failed: ${(err as Error).message}`);
+    return false;
+  }
+}
+
 export async function recordOutcome(outcome: InterventionOutcome): Promise<void> {
+  // Backend is authoritative for wasRealCollision: derive it from git overlap
+  // rather than trusting the client-supplied value. (RSI Step 3)
+  const verified: InterventionOutcome = {
+    ...outcome,
+    wasRealCollision: await deriveWasRealCollision(outcome),
+  };
   await persist('outcome', async () => {
     const c = await collections();
-    await c.outcomes.insertOne({ ...outcome });
+    await c.outcomes.insertOne({ ...verified });
     await c.interventions.updateOne(
-      { id: outcome.interventionId },
-      { $set: { status: outcome.accepted ? 'accepted' : 'dismissed' } },
+      { id: verified.interventionId },
+      { $set: { status: verified.accepted ? 'accepted' : 'dismissed' } },
     );
   });
 }
diff --git a/docs/PLAN.md b/docs/PLAN.md
index eb1d4a7..1a7893b 100644
--- a/docs/PLAN.md
+++ b/docs/PLAN.md
@@ -509,11 +509,26 @@ no schema change. Owner: RSI track. Independent of the MongoDB-cleanup handoff.
    - Spec: `docs/continual-learning/policy.md:62-63` (prefer prior accepted
      kind), `plan.md:66` (second similar event behaves differently).
 
-Follow-ups (separate rungs, not in this change): Step 3 derive
-`wasRealCollision` from git overlap; Step 4-5 `strategy_versions` +
-Gemini-proposed `LearningProposal` slice; seed a clean demo pod with a repeated
-dismissed signature (the historic 85 dismissals are orphaned — `collisionId`
-resolves to no collision — so they cannot drive the demo verifier).
+3. **Step 3 - derive `wasRealCollision` from git overlap (backend-authoritative)** ✅
+   - Overlap is captured AT detection time as `Collision.gitOverlap`
+     (`backend/src/agent/podman.ts`), while `engineer_states` are still fresh —
+     true only if ALL involved engineers have the collided file in their git
+     `changedFiles`, matched on case/whitespace-canonical names.
+   - `backend/src/memory/store.ts` `recordOutcome` overrides the client value
+     with `deriveWasRealCollision()`, which prefers the stored `gitOverlap`
+     (immune to late clicks / stale sidecars / the 120s TTL) and only falls back
+     to a live canonical-name re-derivation for pre-existing collisions.
+     `frontend/.../useInterventions.ts` stops sending hardcoded `true`.
+   - Restores the (accepted × wasReal) 2×2 the spec assumes; keeps `learned_from`
+     edges (`graph/live.ts:413`) from being silently zeroed on stage.
+   - Spec: `docs/continual-learning/spec.md:98-108`, `policy.md:35-42`.
+   - Hardened per Codex review (name canonicalization + detection-time capture).
+
+Follow-ups (separate rungs, not in this change): Step 4-5 `strategy_versions` +
+Gemini-proposed `LearningProposal` slice; Step 6 durable `owns` write; seed a
+clean demo pod with a repeated dismissed signature (the historic dismissals are
+orphaned — `collisionId` resolves to no collision — so they cannot drive the
+demo verifier).
 
 ### P1 - polish the money moment
 
diff --git a/frontend/src/livekit/useInterventions.ts b/frontend/src/livekit/useInterventions.ts
index 48af2fe..f6b4816 100644
--- a/frontend/src/livekit/useInterventions.ts
+++ b/frontend/src/livekit/useInterventions.ts
@@ -66,7 +66,9 @@ export function useInterventions(room: Room | null) {
         interventionId: active.id,
         collisionId: active.collisionId,
         podId: active.podId,
-        wasRealCollision: true,
+        // Placeholder only — the backend derives the authoritative value from
+        // git overlap at outcome time (the client cannot know). (RSI Step 3)
+        wasRealCollision: false,
         accepted,
         recordedAt: new Date().toISOString(),
       });
diff --git a/shared/src/collision.ts b/shared/src/collision.ts
index 84ecbaf..7739b3d 100644
--- a/shared/src/collision.ts
+++ b/shared/src/collision.ts
@@ -16,6 +16,14 @@ export interface Collision {
   severity: CollisionSeverity;
   /** Snapshot of relevant GitHub state at detection time. */
   githubState?: GithubStateSnapshot;
+  /**
+   * Git ground-truth overlap captured AT detection time, while engineer_states
+   * are still fresh: true when every involved engineer had `file` in their git
+   * changedFiles. Read as the authoritative wasRealCollision evidence at outcome
+   * time, so a late click, a stale sidecar, or the engineer_states freshness TTL
+   * cannot retroactively zero it out.
+   */
+  gitOverlap?: boolean;
   detectedAt: string;
 }