diff --git a/packages/snapcompact/CHANGELOG.md b/packages/snapcompact/CHANGELOG.md
index b6fce27a2..f694be1d7 100644
--- a/packages/snapcompact/CHANGELOG.md
+++ b/packages/snapcompact/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed `claude-opus-5` (and later Opus lines) falling back to the 1568px frame instead of the 1932px high-res tier, so snapcompact archives for the current flagship Opus now retain ~33% more history at the same per-frame bill ([#8256](https://github.com/can1357/oh-my-pi/issues/8256)).
+
 ## [17.1.5] - 2026-07-27
 
 ### Fixed
diff --git a/packages/snapcompact/src/snapcompact.ts b/packages/snapcompact/src/snapcompact.ts
index dce081240..026d491df 100644
--- a/packages/snapcompact/src/snapcompact.ts
+++ b/packages/snapcompact/src/snapcompact.ts
@@ -342,11 +342,15 @@ export interface IdealShape {
  *  lines the mono evals measured; everything else falls back to the API
  *  family's winner at the standard 1568px frame. First match wins. */
 const MODEL_VARIANTS: readonly (readonly [RegExp, IdealShape])[] = [
-	// Opus 4.7+ and Fable/Mythos read high-res natively (2576px edge under a
-	// 4,784 visual-token cap → 1932px square sweet spot): same recall and
-	// cost as 1568, a third fewer frames.
+	// Opus 4.7+ and Fable/Mythos read high-res natively: same recall and cost as
+	// 1568, a third fewer frames. 1932 is the largest *square* not downscaled
+	// under Anthropic's 4,784 visual-token cap ((1932/28)² = 69² = 4,761 ≤ 4,784
+	// 28px patches), and staying below 2000px keeps frames clear of the stricter
+	// ≤2000px per-image dimension limit that applies once a request carries more
+	// than 20 image blocks. The cap is a family-wide Anthropic billing property,
+	// so every Opus line from 4.7 up (5.x and later included) belongs on this tier.
 	[/claude.*(fable|mythos)/i, { variant: "11on16-bw", frameSize: 1932 }],
-	[/claude-?opus-?4[.-][7-9]/i, { variant: "11on16-bw", frameSize: 1932 }],
+	[/claude-?opus-?(4[.-][7-9]|[5-9])/i, { variant: "11on16-bw", frameSize: 1932 }],
 	// Older Claude lines downscale past 1568px — keep the safe size.
 	[/claude/i, { variant: "11on16-bw" }],
 	// Gemini 3.x bills a fixed 1,120-token budget per image regardless of
diff --git a/packages/snapcompact/test/snapcompact.test.ts b/packages/snapcompact/test/snapcompact.test.ts
index fd6734bd4..6ee75583f 100644
--- a/packages/snapcompact/test/snapcompact.test.ts
+++ b/packages/snapcompact/test/snapcompact.test.ts
@@ -299,6 +299,14 @@ describe("shape resolution", () => {
 		// High-res frames are reserved for the lines that read them natively;
 		// older Claude lines keep the safe 1568px family default.
 		expect(snapcompact.resolveShape({ api: "anthropic-messages", id: "claude-opus-4-8" }).frameSize).toBe(1932);
+		// Opus 5+ shares the Anthropic visual-token cap, so it stays on the
+		// high-res tier rather than falling back to the 1568px default (#8256).
+		expect(snapcompact.resolveShape({ api: "anthropic-messages", id: "claude-opus-5" }).frameSize).toBe(1932);
+		expect(snapcompact.resolveShape({ api: "anthropic-messages", id: "claude-opus-6" }).frameSize).toBe(1932);
+		// Opus lines below 4.7 downscale, so they keep the safe family default.
+		expect(snapcompact.resolveShape({ api: "anthropic-messages", id: "claude-opus-4-6" })).toBe(
+			snapcompact.SHAPES.anthropic,
+		);
 		expect(snapcompact.resolveShape({ api: "anthropic-messages", id: "claude-3-5-sonnet" })).toBe(
 			snapcompact.SHAPES.anthropic,
 		);