diff --git a/docs/api/index.md b/docs/api/index.md
index 1b1713b5..dd62d123 100644
--- a/docs/api/index.md
+++ b/docs/api/index.md
@@ -11290,7 +11290,7 @@ Per-generation findings producer passthrough (see selfImprove.analyzeGeneration)
 
 > `optional` **rawTraceContext?**: `boolean`
 
-META-HARNESS mode: instead of the ~400-char distilled findings, feed the
+META-HARNESS mode: instead of the ~1500-char distilled findings, feed the
  proposer RAW-TRACE FILESYSTEM CONTEXT — the PATHS into the prior generation's
  real run traces under `runDir` (per-cell `spans.jsonl` event logs +
  `cached-result.json` scores + artifacts) plus a `grep`/`cat`-to-diagnose
@@ -13295,7 +13295,7 @@ Build the starting instruction for a coder agent tasked with implementing a new
 
 > **applyImprovementWinnerToProfile**(`profile`, `surface`, `winner`): `AgentProfile`
 
-Defined in: [improvement/improve.ts:466](https://github.com/tangle-network/agent-runtime/blob/main/src/improvement/improve.ts#L466)
+Defined in: [improvement/improve.ts:478](https://github.com/tangle-network/agent-runtime/blob/main/src/improvement/improve.ts#L478)
 
 Apply a promoted winner surface back into the profile field for `surface`.
  Returns a shallow copy; never mutates the input profile.
@@ -13324,7 +13324,7 @@ Apply a promoted winner surface back into the profile field for `surface`.
 
 > **improve**\<`TScenario`, `TArtifact`\>(`profile`, `findings`, `opts`): `Promise`\<[`ImproveResult`](#improveresult)\<`TScenario`, `TArtifact`\>\>
 
-Defined in: [improvement/improve.ts:529](https://github.com/tangle-network/agent-runtime/blob/main/src/improvement/improve.ts#L529)
+Defined in: [improvement/improve.ts:541](https://github.com/tangle-network/agent-runtime/blob/main/src/improvement/improve.ts#L541)
 
 Run the held-out-gated self-improvement loop on ONE profile surface.
 
diff --git a/src/improvement/improve.test.ts b/src/improvement/improve.test.ts
index 7f983170..1f074138 100644
--- a/src/improvement/improve.test.ts
+++ b/src/improvement/improve.test.ts
@@ -585,6 +585,63 @@ describe('improve() — default proposer resolution (substrate export drift guar
     }
   })
 
+  it('the distiller keeps traceback-sized notes intact and clips at the 1500/500 caps', async () => {
+    // A realistic executable-judge note (~1000 chars) must survive whole; a
+    // runaway note is clipped to exactly 1500; a cell error is clipped to 500.
+    const intactNote = `Traceback (most recent call last):\n${'  assert tour == expected\n'.repeat(38)}`
+    expect(intactNote.length).toBeGreaterThan(900)
+    expect(intactNote.length).toBeLessThan(1500)
+    const runawayNote = 'n'.repeat(1600)
+    const longError = 'e'.repeat(800)
+    const cappingJudge: JudgeConfig<{ text: string }, Scenario> = {
+      name: 'capping-judge',
+      dimensions: [{ key: 'q', description: 'fixture quality' }],
+      score: ({ scenario }) => {
+        if (scenario.id === 'a') return { dimensions: { q: 0 }, composite: 0, notes: intactNote }
+        if (scenario.id === 'b') return { dimensions: { q: 0 }, composite: 0, notes: runawayNote }
+        return { dimensions: { q: 1 }, composite: 1, notes: 'ok' }
+      },
+    }
+    const findingsSeen: unknown[][] = []
+    const stubProposer = {
+      kind: 'stub-recorder',
+      async propose(ctx: { findings: unknown[]; populationSize: number }) {
+        findingsSeen.push(ctx.findings)
+        return [{ surface: `candidate-${findingsSeen.length}`, label: 'stub', rationale: 'stub' }]
+      },
+    }
+    const failingAgent = async (surface: unknown, scenario: Scenario, ctx: DispatchContext) => {
+      // The baseline must stay complete (an incomplete incumbent is refused),
+      // so the error lands on a generation-1 candidate cell instead.
+      if (scenario.id === 'c' && typeof surface === 'string' && surface.startsWith('candidate-')) {
+        throw new Error(longError)
+      }
+      return stubAgent(surface, scenario, ctx)
+    }
+    await improve(promptProfile(), [], {
+      surface: 'prompt',
+      scenarios,
+      judge: cappingJudge,
+      agent: failingAgent,
+      generator: stubProposer as never,
+      budget: { generations: 2, populationSize: 1, holdoutFraction: 0.25 },
+    })
+    expect(findingsSeen.length).toBeGreaterThanOrEqual(1)
+    const rows = findingsSeen.flat() as Array<{
+      scenario: string
+      notes?: string
+      error?: string
+    }>
+    const intact = rows.find((row) => row.scenario === 'a')
+    expect(intact?.notes).toBe(intactNote) // below the cap ⇒ untouched
+    const clipped = rows.find((row) => row.scenario === 'b')
+    expect(clipped?.notes).toBe('n'.repeat(1500)) // at the cap ⇒ exactly 1500
+    const errored = rows.find((row) => row.scenario === 'c')
+    expect(errored?.error).toBeDefined()
+    expect(errored?.error).toContain('e'.repeat(400))
+    expect(errored?.error?.length).toBeLessThanOrEqual(500)
+  })
+
   it("surface 'code' + opts.code assembles the worktree pipeline and measures a candidate", async () => {
     const { execSync } = await import('node:child_process')
     const { mkdtempSync, readFileSync, rmSync, writeFileSync } = await import('node:fs')
diff --git a/src/improvement/improve.ts b/src/improvement/improve.ts
index 72a83616..f259905f 100644
--- a/src/improvement/improve.ts
+++ b/src/improvement/improve.ts
@@ -104,7 +104,7 @@ export type ImproveOptions<TScenario extends Scenario, TArtifact> = Omit<
    *  trace-analyst over the runDir's traces) to replace it; pass `null` to disable
    *  and keep the static `findings` all the way through. */
   analyzeGeneration?: SelfImproveOptions<TScenario, TArtifact>['analyzeGeneration'] | null
-  /** META-HARNESS mode: instead of the ~400-char distilled findings, feed the
+  /** META-HARNESS mode: instead of the ~1500-char distilled findings, feed the
    *  proposer RAW-TRACE FILESYSTEM CONTEXT — the PATHS into the prior generation's
    *  real run traces under `runDir` (per-cell `spans.jsonl` event logs +
    *  `cached-result.json` scores + artifacts) plus a `grep`/`cat`-to-diagnose
@@ -262,6 +262,16 @@ function baselineSurfaceFor(
   }
 }
 
+/** Slice bound for distilled judge notes: wide enough that a real traceback /
+ *  failing-assertion note survives intact — clipping mid-traceback would leave
+ *  the proposer trace-blind. Referenced by the `rawTraceContext` docs. */
+const DISTILLED_NOTES_MAX_CHARS = 1500
+
+/** Slice bound for a cell's error string — tighter than notes (errors are
+ *  usually one line; the full text stays on the raw cell). Also bounds the
+ *  error-derived `claim` fallback. */
+const DISTILLED_ERROR_MAX_CHARS = 500
+
 /** The default `analyzeGeneration`: distill each generation's failing cells into
  *  findings for the next proposal round. Deliberately dependency-free — judge notes
  *  and errors are already the domain's own diagnosis (executable gates put their
@@ -300,14 +310,16 @@ function generationFailureDistiller<TScenario extends Scenario, TArtifact>(
           .map((j) => j.notes)
           .filter((n): n is string => typeof n === 'string' && n.length > 0)
           .join('; ')
-          .slice(0, 400)
-        const claim = notes || (error ? `Scenario ${scenario} failed: ${error.slice(0, 200)}` : '')
+          .slice(0, DISTILLED_NOTES_MAX_CHARS)
+        const claim =
+          notes ||
+          (error ? `Scenario ${scenario} failed: ${error.slice(0, DISTILLED_ERROR_MAX_CHARS)}` : '')
         failures.push({
           scenario,
           composite: Number(composite.toFixed(3)),
           notes,
           ...(claim ? { claim } : {}),
-          ...(error ? { error: error.slice(0, 200) } : {}),
+          ...(error ? { error: error.slice(0, DISTILLED_ERROR_MAX_CHARS) } : {}),
         })
       }
     }
diff --git a/src/improvement/raw-trace-distiller.ts b/src/improvement/raw-trace-distiller.ts
index 22f625ae..5d7db35b 100644
--- a/src/improvement/raw-trace-distiller.ts
+++ b/src/improvement/raw-trace-distiller.ts
@@ -3,7 +3,7 @@
  * `rawTraceDistiller` — the meta-harness `analyzeGeneration` producer.
  *
  * The default `generationFailureDistiller` (in `improve.ts`) COMPRESSES each
- * generation's failing cells into ~400-char structured findings before the next
+ * generation's failing cells into ~1500-char structured findings before the next
  * proposal round. That is the ACE-style recipe: a small summary is the proposer's
  * whole view of what went wrong. This producer does the opposite — the
  * meta-harness recipe (yoonholee.com/meta-harness): it does NOT summarize. It
@@ -11,7 +11,7 @@
  * disk under `runDir` — the durable per-cell `spans.jsonl` event logs,
  * `cached-result.json` scores, and any artifacts the substrate persisted — and
  * instructs the agent to `grep`/`cat`/`ls` them to diagnose the failures itself
- * (up to the harness's full context, ~millions of tokens, vs a ~400-char digest).
+ * (up to the harness's full context, ~millions of tokens, vs a ~1500-char digest).
  *
  * It emits `AnalystFinding[]` so it drops into the SAME `opts.analyzeGeneration`
  * slot the default distiller uses, and renders through the same