fix(eval): delegated python uri reads to host resolver

- Routed non-local URI reads through the session read tool.
- Preserved offset and limit as host line selectors.
- Covered artifact delegation with the shipped Python prelude.

Fixes #5353

packages/coding-agent/CHANGELOG.md

@@ -32,6 +32,7 @@
 
 ### Fixed
 
+- Fixed Python eval `read()` rejecting every non-`local://` URI before the host resolver could handle it; URI reads now delegate through the session `read` tool with `offset`/`limit` preserved as line selectors, including spilled `artifact://` output ([#5353](https://github.com/can1357/oh-my-pi/issues/5353)).
 - Fixed `/tan` and `/fork` clones cold-missing the provider prompt cache: the per-turn supersede/useless-result prune rewrote the live context without persisting it, so file-based forks and resume rebuilt a divergent (un-pruned) prefix and re-wrote the entire cache
 - Fixed `/tan` pinning the clone's prompt-cache key to the parent's session id instead of the parent's effective cache key, dropping shard affinity when the parent was itself a fork or tan
 - Fixed inconsistent history rendering when toggling the display setting for compacted items

packages/coding-agent/src/eval/py/__tests__/prelude.test.ts

@@ -1,6 +1,30 @@
 import { describe, expect, it } from "bun:test";
 import { PYTHON_PRELUDE } from "../prelude";
 
+const pythonPath = Bun.env.PYTHON ?? "python3";
+
+async function runPrelude(
+	code: string,
+	env: Record<string, string>,
+): Promise<{ stdout: string; stderr: string; exitCode: number }> {
+	const prelude = PYTHON_PRELUDE.replace(
+		"from __future__ import annotations",
+		"from __future__ import annotations\n__omp_display = lambda *args, **kwargs: None",
+	);
+	const script = `${prelude}\n${code}`;
+	const proc = Bun.spawn([pythonPath, "-c", script], {
+		stdout: "pipe",
+		stderr: "pipe",
+		env: { ...process.env, ...env },
+	});
+	const [stdout, stderr, exitCode] = await Promise.all([
+		new Response(proc.stdout).text(),
+		new Response(proc.stderr).text(),
+		proc.exited,
+	]);
+	return { stdout, stderr, exitCode };
+}
+
 describe("python prelude", () => {
 	it("exposes read(path, offset?, limit?) with positional optional args", () => {
 		// The eval docs advertise `read(path, offset?=1, limit?=None)`. A
@@ -17,6 +41,41 @@ describe("python prelude", () => {
 		expect(signature).toContain("limit");
 	});
 
+	it("delegates artifact URI reads through the host read tool with line selectors", async () => {
+		const requests: unknown[] = [];
+		const server = Bun.serve({
+			hostname: "127.0.0.1",
+			port: 0,
+			fetch: async request => {
+				requests.push(await request.json());
+				return Response.json({
+					ok: true,
+					value: { text: "artifact contents", details: { resolvedPath: "/tmp/21.txt" } },
+				});
+			},
+		});
+
+		try {
+			const result = await runPrelude(`print(read("artifact://21", 3, 2))`, {
+				PI_TOOL_BRIDGE_URL: server.url.toString(),
+				PI_TOOL_BRIDGE_TOKEN: "test-token",
+				PI_TOOL_BRIDGE_SESSION: "test-session",
+			});
+
+			expect(result).toEqual({ stdout: "artifact contents\n", stderr: "", exitCode: 0 });
+			expect(requests).toEqual([
+				{
+					session: "test-session",
+					run: null,
+					name: "read",
+					args: { path: "artifact://21:3-4" },
+				},
+			]);
+		} finally {
+			server.stop(true);
+		}
+	});
+
 	it("exposes isolation artifacts on the agent() handle node", () => {
 		// agent(..., handle=True) is the only escape hatch for
 		// recovering apply=False patch/branch/nested artifacts (the bare

packages/coding-agent/src/eval/py/prelude.py

@@ -57,6 +57,29 @@ if "__omp_prelude_loaded__" not in globals():
 
     _OMP_INTERNAL_URL_RE = re.compile(r"^([a-z][a-z0-9+.-]*)://(.*)$", re.IGNORECASE)
 
+    def _should_delegate_read(path: str | Path) -> bool:
+        return (
+            isinstance(path, str)
+            and _OMP_INTERNAL_URL_RE.match(path) is not None
+            and not path.lower().startswith("local://")
+        )
+
+    def _with_read_line_selector(path: str, offset: int, limit: int | None) -> str | None:
+        if offset <= 1 and limit is None:
+            return path
+        if limit is not None and limit <= 0:
+            return None
+        start = max(1, offset)
+        if limit is None:
+            return f"{path}:{start}-"
+        return f"{path}:{start}-{start + limit - 1}"
+
+    def _read_tool_text(path: str) -> str:
+        result = _bridge_call("read", {"path": path})
+        if isinstance(result, dict) and "text" in result:
+            return result["text"]
+        return result
+
     def _resolve_omp_path(path: str | Path) -> Path:
         """Map a helper path to a real filesystem Path.
 
@@ -94,7 +117,10 @@ if "__omp_prelude_loaded__" not in globals():
         return Path(resolved)
 
     def read(path: str | Path, offset: int = 1, limit: int | None = None) -> str:
-        """Read file contents. offset/limit are 1-indexed line numbers."""
+        """Read file or read-tool URI contents. offset/limit are 1-indexed lines."""
+        if _should_delegate_read(path):
+            tool_path = _with_read_line_selector(path, offset, limit)
+            return "" if tool_path is None else _read_tool_text(tool_path)
         p = _resolve_omp_path(path)
         data = p.read_text(encoding="utf-8")
         lines = data.splitlines(keepends=True)

packages/coding-agent/src/prompts/system/tan-context-switch.md

@@ -1,5 +1,5 @@
 <system-notice cause="fork">
-The conversation above belongs to your parent session. 
+The conversation above belongs to your parent session.
 You are a fork created solely to handle the user's request below.
 
 Your parent agent is still working on the original task — that responsibility is

packages/coding-agent/src/prompts/tools/eval.md

@@ -28,7 +28,7 @@ display(value) → None
 print(value, ...) → None
     Text output.
 read(path, offset?=1, limit?=None) → str
-    File as text; offset/limit 1-indexed lines. Accepts `local://…`.
+    File/resource text; offset/limit = 1-indexed lines. `local://…` works everywhere; Python/JS also accept top-level `read` URI schemes.
 write(path, content) → str
     Write file (creates parents) → resolved path. `local://…` persists across turns/subagents.
 env(key?=None, value?=None) → str | None | dict

packages/coding-agent/test/agent-session-prune-persistence.test.ts

@@ -114,7 +114,7 @@ describe("AgentSession per-turn prune persistence", () => {
 		const message = session.agent.state.messages.find(
 			candidate => candidate.role === "toolResult" && candidate.toolCallId === BIG_CALL_ID,
 		);
-		if (!message || message.role !== "toolResult" || !Array.isArray(message.content)) {
+		if (message?.role !== "toolResult" || !Array.isArray(message.content)) {
 			throw new Error("Expected the seeded tool result in live agent state");
 		}
 		const text = message.content.find(block => block.type === "text");
@@ -156,7 +156,7 @@ describe("AgentSession per-turn prune persistence", () => {
 		const rebuilt = reloaded
 			.buildSessionContext()
 			.messages.find(candidate => candidate.role === "toolResult" && candidate.toolCallId === BIG_CALL_ID);
-		if (!rebuilt || rebuilt.role !== "toolResult" || !Array.isArray(rebuilt.content)) {
+		if (rebuilt?.role !== "toolResult" || !Array.isArray(rebuilt.content)) {
 			throw new Error("Expected the seeded tool result in the from-disk rebuild");
 		}
 		const rebuiltText = rebuilt.content.find(block => block.type === "text");