diff --git a/README.md b/README.md
index 7e90c258..88d7032f 100644
--- a/README.md
+++ b/README.md
@@ -1266,7 +1266,7 @@ the same for every repository unless its `AGENTS.md` names others:
 
 | Size | Writer | Fallback |
 |---|---|---|
-| XS | Claude Code `claude-haiku-5-5` xhigh | Codex `gpt-6.1-sol` low |
+| XS | Claude Code `claude-sonnet-5-5` high | Codex `gpt-6.1-sol` low |
 | S | Claude Code `claude-opus-5-5` low | Codex `gpt-6.1-sol` medium |
 | M | Claude Code `claude-opus-5-5` medium | Codex `gpt-6.1-sol` high |
 | L | Claude Code `claude-opus-5-5` high | Codex `gpt-6.1-sol` xhigh |
@@ -1288,7 +1288,7 @@ XS, and `quest models` prints the entry to run:
 
 ```console
 $ quest models XS
-claude	claude-haiku-5-5	xhigh
+claude	claude-sonnet-5-5	high
 codex	gpt-6.1-sol	low
 
 $ quest models XS --writer claude-opus-5-5
diff --git a/quest/m1/model-check.md b/quest/m1/model-check.md
index c4b7f94a..a665b719 100644
--- a/quest/m1/model-check.md
+++ b/quest/m1/model-check.md
@@ -86,7 +86,7 @@ checkpoints and outages to count by hand:
     cell with again:
     - Haiku 5.5: high 30, $0.0034; xhigh 34.6, $0.0053.
     - Sonnet 5.5: medium 30.7, $0.012; below the frontier at every effort,
-      so rejected for XS though Anthropic's
+      so rejected for XS then, though Anthropic's
       [model guide](https://claude.dev/blog/which-claude-model-should-you-build-with/)
       favors it for scoped coding.
     - Opus 5.5: low 34.7, $0.015; medium 48, $0.037; high 51.7, $0.052;
@@ -99,6 +99,18 @@ checkpoints and outages to count by hand:
     - S looks lopsided: Opus low scores well below its Sol medium fallback
       (34.7 against 46.3) for $0.006 less a task. Check its tallies before
       moving it.
+  - Changed again (maintainer, 2026-11-11): XS writes on Sonnet high
+    instead of Haiku xhigh, since two Haiku XS agents in a row on
+    [moq-dev/quest#643](https://github.com/moq-dev/quest/pull/643) died
+    refilling context right after compaction: Haiku 5.5 bills 5x past 100k
+    input, so the maintainer caps its auto-compact window there, barely above an
+    agent's 40-60k fixed load. Sonnet 5.5's price is flat over its 1M
+    window. mypriors has no Sonnet high row, so tally this cell rather than
+    compare it there. Anthropic's
+    [cost guide](https://platform.claude.com/docs/en/about-claude/models/optimizing-for-cost-and-intelligence)
+    puts Sonnet 5.5 high level with Opus 5.5 low (87.6% against 87.4%) at
+    about the same cost per solved task, and medium about 7 points below
+    high on its SWE-bench Pro subset.
 - Compare both tables' models (in `src/cli/models.ts`) with each vendor's current models: the newest
   model of each tier the tables pin. Bump any that are stale, and check that both CLIs
   accept the new ids and the pinned efforts. `--deep` and its strongest-model
diff --git a/src/cli/models.ts b/src/cli/models.ts
index e81e3553..0bed0272 100644
--- a/src/cli/models.ts
+++ b/src/cli/models.ts
@@ -18,16 +18,18 @@ export const DEFAULT_SIZE: Size = "M";
 
 const sol = (effort: string): Model => ({ harness: "codex", model: "gpt-6.1-sol", effort });
 const opus = (effort: string): Model => ({ harness: "claude", model: "claude-opus-5-5", effort });
-const haiku = (effort: string): Model => ({ harness: "claude", model: "claude-haiku-5-5", effort });
+const sonnet = (effort: string): Model => ({ harness: "claude", model: "claude-sonnet-5-5", effort });
 
 /**
  * Each size's writers, ranked: a spawn starts the quest on the first that can
  * run, falling through only while nothing is written, since the model that
- * writes a PR runs all its iterates. XS runs Haiku at xhigh, which scores about
- * as Opus low does for a third of its subscription cost per task.
+ * writes a PR runs all its iterates. XS runs Sonnet rather than the cheaper
+ * Haiku, whose surcharge past 100k input tokens leads users to cap its
+ * compaction window there, barely above an agent's fixed load of prompt,
+ * context, and skill.
  */
 export const WRITERS: Record<Size, readonly Model[]> = {
-	XS: [haiku("xhigh"), sol("low")],
+	XS: [sonnet("high"), sol("low")],
 	S: [opus("low"), sol("medium")],
 	M: [opus("medium"), sol("high")],
 	L: [opus("high"), sol("xhigh")],
diff --git a/test/cli.test.ts b/test/cli.test.ts
index d00af519..1be00ef2 100644
--- a/test/cli.test.ts
+++ b/test/cli.test.ts
@@ -186,7 +186,7 @@ test("models ranks a size's writers, or the one entry that runs a PR's writer",
 	const tree = Tree.baseline();
 	expect(tree.run("models", "XS")).toEqual({
 		code: 0,
-		stdout: "claude\tclaude-haiku-5-5\txhigh\ncodex\tgpt-6.1-sol\tlow\n",
+		stdout: "claude\tclaude-sonnet-5-5\thigh\ncodex\tgpt-6.1-sol\tlow\n",
 		stderr: "",
 	});
 	expect(JSON.parse(tree.run("models", "XL", "--json").stdout)).toEqual([
@@ -196,7 +196,7 @@ test("models ranks a size's writers, or the one entry that runs a PR's writer",
 	expect(writer("M", "gpt-6.1-sol")).toBe("codex\tgpt-6.1-sol\thigh\n");
 	// A writer its size does not list runs at the nearest size that lists it.
 	expect(writer("XS", "claude-opus-5-5")).toBe("claude\tclaude-opus-5-5\tlow\n");
-	expect(writer("L", "claude-haiku-5-5")).toBe("claude\tclaude-haiku-5-5\txhigh\n");
+	expect(writer("L", "claude-sonnet-5-5")).toBe("claude\tclaude-sonnet-5-5\thigh\n");
 	expect(writer("XL", "gpt-6.1-sol")).toBe("codex\tgpt-6.1-sol\txhigh\n");
 	const unknown = tree.run("models", "S", "--writer", "unknown");
 	expect(unknown.code).toBe(2);