diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 6aa2c35a1..14e03deb8 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -4,7 +4,7 @@
 
 ### Fixed
 
-- Fixed snapcompact auto-compaction looping the "snapcompact could not bring the context under the limit — using an LLM summary instead" warning on every threshold tick for sub-1M-token models (Claude Sonnet 4.5, GPT-5.x, Gemini 2.x). `snapcompact.compact()` was called with no `maxFrames` override, so it defaulted to `MAX_FRAMES_DEFAULT = 80`; the projection in `AgentSession` charges `FRAME_TOKEN_ESTIMATE = 5024` per frame block (the conservative high-res Anthropic ceiling), making 80 × 5024 ≈ 402k frame-token projections that always overflow a 200k budget. `AgentSession.#computeSnapcompactMaxFrames` now sizes the frame cap from the live `(window − reserve − non-message − kept-recent − summary-text reserve)` envelope before invoking snapcompact in both the auto-compaction and manual `/compact` paths, and skips snapcompact outright when the kept-recent slice alone already exceeds the budget (with a clearer notice explaining the cause). ([#3247](https://github.com/can1357/oh-my-pi/issues/3247))
+- Fixed snapcompact auto-compaction looping the "snapcompact could not bring the context under the limit — using an LLM summary instead" warning on every threshold tick for sub-1M-token models (Claude Sonnet 4.5, GPT-5.x, Gemini 2.x). `snapcompact.compact()` was called with no `maxFrames` override, so it defaulted to `MAX_FRAMES_DEFAULT = 80`; the projection in `AgentSession` charges `FRAME_TOKEN_ESTIMATE = 5024` per frame block (the conservative high-res Anthropic ceiling), making 80 × 5024 ≈ 402k frame-token projections that always overflow a 200k budget. `AgentSession.#computeSnapcompactMaxFrames` now sizes the frame cap from the live `(window − reserve − non-message − kept-recent − summary-text reserve)` envelope before invoking snapcompact in both the auto-compaction and manual `/compact` paths. When the residual is below one frame's token charge but still positive, the helper returns `maxFrames = 1` so snapcompact's frame-less `text.length <= 2 * edgeCap` short-circuit (`planArchive`) can still produce a valid text-only archive instead of being skipped; snapcompact is skipped outright only when even that text-only summary cannot fit (kept-recent already exhausted the budget), with a clearer notice explaining the cause. ([#3247](https://github.com/can1357/oh-my-pi/issues/3247))
 
 ## [16.1.14] - 2026-06-22
 
diff --git a/packages/coding-agent/src/session/agent-session.ts b/packages/coding-agent/src/session/agent-session.ts
index 5f9e2c874..a4ca5be32 100644
--- a/packages/coding-agent/src/session/agent-session.ts
+++ b/packages/coding-agent/src/session/agent-session.ts
@@ -9429,13 +9429,21 @@ export class AgentSession {
 	 * high-res Anthropic ceiling), so picking `maxFrames` from this helper makes
 	 * {@link #projectSnapcompactContextTokens} succeed by construction.
 	 *
-	 * Returns `0` when the kept-recent slice plus the non-message overhead
-	 * already eats the entire budget — at that point snapcompact cannot fit a
-	 * single frame and the caller MUST skip it instead of running just to
-	 * reject the result and re-emit the "could not bring the context under the
-	 * limit" warning every threshold tick. Without this cap, the bundled
-	 * `MAX_FRAMES_DEFAULT = 80` × 5024 tokens = ~402k frame-token projection
-	 * always overflows any sub-1M-token window (issue #3247).
+	 * Returns `0` only when the kept-recent slice plus the non-message overhead
+	 * plus the summary lead-in reserve already exceed the budget — at that
+	 * point even snapcompact's text-only archive path (frames `[]`, the
+	 * `text.length <= 2 * edgeCap` short-circuit in `planArchive`) cannot fit
+	 * and the caller MUST skip it instead of running just to re-emit the
+	 * "could not bring the context under the limit" warning every threshold
+	 * tick. Returns `1` when the frame charge would overflow but the text-only
+	 * path still has room: snapcompact's planner picks the frame-less layout
+	 * automatically when the discarded text fits in the edges, so giving it
+	 * the minimum cap lets it succeed for small archives instead of being
+	 * skipped outright (chatgpt-codex review on #3249).
+	 *
+	 * Without this cap, the bundled `MAX_FRAMES_DEFAULT = 80` × 5024 tokens =
+	 * ~402k frame-token projection always overflows any sub-1M-token window
+	 * (issue #3247).
 	 */
 	#computeSnapcompactMaxFrames(preparation: CompactionPreparation, settings: CompactionSettings): number {
 		const ctxWindow = this.model?.contextWindow ?? 0;
@@ -9452,7 +9460,8 @@ export class AgentSession {
 		// past the projection check below.
 		const SUMMARY_TEXT_RESERVE = 4000;
 		const frameBudget = ctxWindow - reserve - nonFrameTokens - SUMMARY_TEXT_RESERVE;
-		if (frameBudget < snapcompact.FRAME_TOKEN_ESTIMATE) return 0;
+		if (frameBudget < 0) return 0;
+		if (frameBudget < snapcompact.FRAME_TOKEN_ESTIMATE) return 1;
 		return Math.min(Math.floor(frameBudget / snapcompact.FRAME_TOKEN_ESTIMATE), snapcompact.MAX_FRAMES_DEFAULT);
 	}
 
diff --git a/packages/coding-agent/test/agent-session-snapcompact-budget.test.ts b/packages/coding-agent/test/agent-session-snapcompact-budget.test.ts
index dba0a415a..bfde4dbc0 100644
--- a/packages/coding-agent/test/agent-session-snapcompact-budget.test.ts
+++ b/packages/coding-agent/test/agent-session-snapcompact-budget.test.ts
@@ -195,4 +195,58 @@ describe("AgentSession snapcompact frame-budget sizing", () => {
 		// (which implied snapcompact had run and produced an oversized result).
 		expect(notices.some(n => n.level === "warning" && n.message.includes("kept history"))).toBe(true);
 	});
+
+	it("still invokes snapcompact with maxFrames=1 when the budget can only fit a text-only archive", async () => {
+		// Reviewer (chatgpt-codex on #3249): when kept-recent leaves less than
+		// one FRAME_TOKEN_ESTIMATE of headroom but still some room for a
+		// summary, snapcompact's `text.length <= 2 * edgeCap` short-circuit in
+		// `planArchive` can still produce a valid frame-less archive that the
+		// projection accepts (0 frame tokens billed). The helper MUST NOT
+		// return 0 in that case — it must give snapcompact the minimum
+		// `maxFrames = 1` cap so that text-only opportunity is taken.
+		const model = session.model;
+		if (!model) throw new Error("Expected model");
+		const ctxWindow = model.contextWindow ?? 0;
+		// Tune the kept-recent message so frameBudget lands in the
+		// `[0, FRAME_TOKEN_ESTIMATE)` window: kept-recent + non-message +
+		// summary reserve is just under `ctxWindow - reserve` but the
+		// residual is below one frame's token charge. Aim for ~3000 tokens
+		// of headroom (less than FRAME_TOKEN_ESTIMATE = 5024).
+		const reserve = Math.max(Math.floor(ctxWindow * 0.15), 16384);
+		const headroomTokens = 3000;
+		const targetRecentTokens = ctxWindow - reserve - 4000 /* SUMMARY_TEXT_RESERVE */ - headroomTokens;
+		// Rough 4-chars-per-token rule for the tiktoken estimator on ASCII.
+		const filler = "x".repeat(targetRecentTokens * 4);
+		sessionManager.appendMessage({
+			role: "user",
+			content: [{ type: "text", text: filler }],
+			timestamp: Date.now(),
+		});
+
+		const branchEntries = sessionManager.getBranch();
+		const lastEntry = branchEntries[branchEntries.length - 1];
+		if (!lastEntry?.id) throw new Error("Expected branch entry with id");
+
+		const compactSpy = vi.spyOn(snapcompact, "compact").mockResolvedValue({
+			summary: "stubbed snapcompact",
+			shortSummary: "stub",
+			firstKeptEntryId: lastEntry.id,
+			tokensBefore: 100_000,
+			// Text-only archive: zero frames, modest text edges. The projection
+			// charges 0 for frames, so the post-compaction context fits.
+			details: { readFiles: [], modifiedFiles: [] },
+			preserveData: {
+				snapcompact: { frames: [], totalChars: 1000, truncatedChars: 0 },
+			},
+		});
+
+		await session.compact(undefined, { mode: "snapcompact" });
+
+		expect(compactSpy).toHaveBeenCalledTimes(1);
+		const opts = compactSpy.mock.calls[0]?.[1];
+		// Snapcompact MUST be invoked with the floor cap, never skipped,
+		// even though one frame charge would overflow the budget — the
+		// text-only `planArchive` path makes this case recoverable.
+		expect(opts?.maxFrames).toBe(1);
+	});
 });