fix(channels,sandbox): land hard breakage cluster from reviewed PR bases

Lands reviewed fixes based on #25839 (@pewallin), #25841 (@joshjhall), and #25737/@25713 (@DennisGoldfinger/@peteragility), with additional hardening + regression tests for queue cleanup and shell script safety.

Fixes #25836
Fixes #25840
Fixes #25824
Fixes #25868

Co-authored-by: Peter Wallin <pwallin@gmail.com>
Co-authored-by: Joshua Hall <josh@yaplabs.com>
Co-authored-by: Dennis Goldfinger <dennisgoldfinger@gmail.com>
Co-authored-by: peteragility <peteragility@users.noreply.github.com>

src/agents/sandbox/fs-bridge.test.ts

@@ -77,10 +77,22 @@ describe("sandbox fs bridge shell compatibility", () => {
     const executables = mockedExecDockerRaw.mock.calls.map(([args]) => args[3] ?? "");
 
     expect(executables.every((shell) => shell === "sh")).toBe(true);
-    expect(scripts.every((script) => script.includes("set -eu;"))).toBe(true);
+    expect(scripts.every((script) => /set -eu[;\n]/.test(script))).toBe(true);
     expect(scripts.some((script) => script.includes("pipefail"))).toBe(false);
   });
 
+  it("resolveCanonicalContainerPath script is valid POSIX sh (no do; token)", async () => {
+    const bridge = createSandboxFsBridge({ sandbox: createSandbox() });
+
+    await bridge.readFile({ filePath: "a.txt" });
+
+    const scripts = mockedExecDockerRaw.mock.calls.map(([args]) => args[5] ?? "");
+    const canonicalScript = scripts.find((script) => script.includes("allow_final"));
+    expect(canonicalScript).toBeDefined();
+    // "; " joining can create "do; cmd", which is invalid in POSIX sh.
+    expect(canonicalScript).not.toMatch(/\bdo;/);
+  });
+
   it("resolves bind-mounted absolute container paths for reads", async () => {
     const sandbox = createSandbox({
       docker: {

src/agents/sandbox/fs-bridge.ts

@@ -305,7 +305,7 @@ class SandboxFsBridgeImpl implements SandboxFsBridge {
       "done",
       'canonical=$(readlink -f -- "$cursor")',
       'printf "%s%s\\n" "$canonical" "$suffix"',
-    ].join("; ");
+    ].join("\n");
     const result = await this.runCommand(script, {
       args: [params.containerPath, params.allowFinalSymlink ? "1" : "0"],
     });

src/discord/monitor/message-handler.process.test.ts

@@ -31,7 +31,10 @@ const deliverDiscordReply = deliveryMocks.deliverDiscordReply;
 const createDiscordDraftStream = deliveryMocks.createDiscordDraftStream;
 type DispatchInboundParams = {
   dispatcher: {
-    sendBlockReply: (payload: { text?: string }) => boolean | Promise<boolean>;
+    sendBlockReply: (payload: {
+      text?: string;
+      isReasoning?: boolean;
+    }) => boolean | Promise<boolean>;
     sendFinalReply: (payload: { text?: string }) => boolean | Promise<boolean>;
   };
   replyOptions?: {
@@ -427,9 +430,9 @@ describe("processDiscordMessage draft streaming", () => {
     expect(deliverDiscordReply).toHaveBeenCalledTimes(1);
   });
 
-  it("suppresses block-kind payload delivery to Discord", async () => {
+  it("suppresses reasoning payload delivery to Discord", async () => {
     dispatchInboundMessage.mockImplementationOnce(async (params?: DispatchInboundParams) => {
-      await params?.dispatcher.sendBlockReply({ text: "thinking..." });
+      await params?.dispatcher.sendBlockReply({ text: "thinking...", isReasoning: true });
       return { queuedFinal: false, counts: { final: 0, tool: 0, block: 1 } };
     });
 
@@ -441,6 +444,20 @@ describe("processDiscordMessage draft streaming", () => {
     expect(deliverDiscordReply).not.toHaveBeenCalled();
   });
 
+  it("delivers non-reasoning block payloads to Discord", async () => {
+    dispatchInboundMessage.mockImplementationOnce(async (params?: DispatchInboundParams) => {
+      await params?.dispatcher.sendBlockReply({ text: "hello from block stream" });
+      return { queuedFinal: false, counts: { final: 0, tool: 0, block: 1 } };
+    });
+
+    const ctx = await createBaseContext({ discordConfig: { streamMode: "off" } });
+
+    // oxlint-disable-next-line typescript/no-explicit-any
+    await processDiscordMessage(ctx as any);
+
+    expect(deliverDiscordReply).toHaveBeenCalledTimes(1);
+  });
+
   it("streams block previews using draft chunking", async () => {
     const draftStream = createMockDraftStream();
     createDiscordDraftStream.mockReturnValueOnce(draftStream);

src/discord/monitor/message-handler.process.ts

@@ -564,9 +564,8 @@ export async function processDiscordMessage(ctx: DiscordMessagePreflightContext)
     humanDelay: resolveHumanDelayConfig(cfg, route.agentId),
     deliver: async (payload: ReplyPayload, info) => {
       const isFinal = info.kind === "final";
-      if (info.kind === "block") {
-        // Block payloads carry reasoning/thinking content that should not be
-        // delivered to external channels. Skip them regardless of streamMode.
+      if (payload.isReasoning) {
+        // Reasoning/thinking payloads should not be delivered to Discord.
         return;
       }
       if (draftStream && isFinal) {