diff --git a/apps/server/src/terminal/Layers/BunPTY.ts b/apps/server/src/terminal/Layers/BunPTY.ts
index f0aab813c7c..593fa4e5644 100644
--- a/apps/server/src/terminal/Layers/BunPTY.ts
+++ b/apps/server/src/terminal/Layers/BunPTY.ts
@@ -1,6 +1,11 @@
 import { Effect, Layer } from "effect";
 import { PtyAdapter } from "../Services/PTY.ts";
-import type { PtyAdapterShape, PtyExitEvent, PtyProcess } from "../Services/PTY.ts";
+import {
+  PtySpawnError,
+  type PtyAdapterShape,
+  type PtyExitEvent,
+  type PtyProcess,
+} from "../Services/PTY.ts";
 
 class BunPtyProcess implements PtyProcess {
   private readonly dataListeners = new Set<(data: string) => void>();
@@ -99,22 +104,30 @@ export const layer = Layer.effect(
     }
     return {
       spawn: (input) =>
-        Effect.sync(() => {
-          let processHandle: BunPtyProcess | null = null;
-          const command = [input.shell, ...(input.args ?? [])];
-          const subprocess = Bun.spawn(command, {
-            cwd: input.cwd,
-            env: input.env,
-            terminal: {
-              cols: input.cols,
-              rows: input.rows,
-              data: (_terminal, data) => {
-                processHandle?.emitData(data);
+        Effect.try({
+          try: () => {
+            let processHandle: BunPtyProcess | null = null;
+            const command = [input.shell, ...(input.args ?? [])];
+            const subprocess = Bun.spawn(command, {
+              cwd: input.cwd,
+              env: input.env,
+              terminal: {
+                cols: input.cols,
+                rows: input.rows,
+                data: (_terminal, data) => {
+                  processHandle?.emitData(data);
+                },
               },
-            },
-          });
-          processHandle = new BunPtyProcess(subprocess);
-          return processHandle;
+            });
+            processHandle = new BunPtyProcess(subprocess);
+            return processHandle as PtyProcess;
+          },
+          catch: (cause) =>
+            new PtySpawnError({
+              adapter: "bun-pty",
+              message: cause instanceof Error ? cause.message : "Failed to spawn PTY process",
+              cause,
+            }),
         }),
     } satisfies PtyAdapterShape;
   }),
diff --git a/apps/web/src/components/ThreadTerminalDrawer.tsx b/apps/web/src/components/ThreadTerminalDrawer.tsx
index 6c71e5eb334..9a3d001f066 100644
--- a/apps/web/src/components/ThreadTerminalDrawer.tsx
+++ b/apps/web/src/components/ThreadTerminalDrawer.tsx
@@ -46,6 +46,7 @@ import {
   type ThreadTerminalGroup,
 } from "../types";
 import { readEnvironmentApi } from "~/environmentApi";
+import { extractErrorMessage } from "~/lib/errorMessage";
 import { readLocalApi } from "~/localApi";
 import { selectTerminalEventEntries, useTerminalStateStore } from "../terminalStateStore";
 
@@ -517,10 +518,7 @@ export function TerminalViewport({
       void api.terminal
         .write({ threadId, terminalId, data })
         .catch((err) =>
-          writeSystemMessage(
-            terminal,
-            err instanceof Error ? err.message : "Terminal write failed",
-          ),
+          writeSystemMessage(terminal, extractErrorMessage(err, "Terminal write failed")),
         );
     });
 
@@ -702,10 +700,7 @@ export function TerminalViewport({
         }
       } catch (err) {
         if (disposed) return;
-        writeSystemMessage(
-          terminal,
-          err instanceof Error ? err.message : "Failed to open terminal",
-        );
+        writeSystemMessage(terminal, extractErrorMessage(err, "Failed to open terminal"));
       }
     };
 
diff --git a/apps/web/src/lib/errorMessage.test.ts b/apps/web/src/lib/errorMessage.test.ts
new file mode 100644
index 00000000000..de5379db2ed
--- /dev/null
+++ b/apps/web/src/lib/errorMessage.test.ts
@@ -0,0 +1,61 @@
+import { describe, expect, it } from "vitest";
+import { extractErrorMessage } from "./errorMessage";
+
+describe("extractErrorMessage", () => {
+  const fallback = "fallback message";
+
+  it("returns the message of a regular Error", () => {
+    const err = new Error("boom");
+    expect(extractErrorMessage(err, fallback)).toBe("boom");
+  });
+
+  it("returns fallback when Error has empty message", () => {
+    const err = new Error("");
+    expect(extractErrorMessage(err, fallback)).toBe(fallback);
+  });
+
+  it("returns fallback when Error message is whitespace", () => {
+    const err = new Error("   ");
+    expect(extractErrorMessage(err, fallback)).toBe(fallback);
+  });
+
+  it("extracts message from a non-Error object with a message string", () => {
+    const err = { message: "RPC defect: failed to spawn" };
+    expect(extractErrorMessage(err, fallback)).toBe("RPC defect: failed to spawn");
+  });
+
+  it("formats objects carrying a _tag with the serialized payload", () => {
+    const err = { _tag: "TerminalCwdError", cwd: "/tmp/missing", reason: "notFound" };
+    expect(extractErrorMessage(err, fallback)).toContain("TerminalCwdError");
+    expect(extractErrorMessage(err, fallback)).toContain("/tmp/missing");
+  });
+
+  it("prefers object.message over _tag formatting", () => {
+    const err = { _tag: "Foo", message: "explicit message" };
+    expect(extractErrorMessage(err, fallback)).toBe("explicit message");
+  });
+
+  it("returns string rejections directly", () => {
+    expect(extractErrorMessage("a literal string defect", fallback)).toBe(
+      "a literal string defect",
+    );
+  });
+
+  it("returns fallback for null", () => {
+    expect(extractErrorMessage(null, fallback)).toBe(fallback);
+  });
+
+  it("returns fallback for undefined", () => {
+    expect(extractErrorMessage(undefined, fallback)).toBe(fallback);
+  });
+
+  it("returns fallback for numeric rejections", () => {
+    expect(extractErrorMessage(42, fallback)).toBe(fallback);
+  });
+
+  it("survives circular objects without throwing", () => {
+    const err: { _tag: string; self?: unknown } = { _tag: "Circular" };
+    err.self = err;
+    expect(extractErrorMessage(err, fallback)).toBe("Circular");
+  });
+});
diff --git a/apps/web/src/lib/errorMessage.ts b/apps/web/src/lib/errorMessage.ts
new file mode 100644
index 00000000000..e35781458e1
--- /dev/null
+++ b/apps/web/src/lib/errorMessage.ts
@@ -0,0 +1,35 @@
+export function extractErrorMessage(error: unknown, fallback: string): string {
+  if (error instanceof Error) {
+    const message = error.message;
+    if (typeof message === "string" && message.trim().length > 0) {
+      return message;
+    }
+  }
+
+  if (typeof error === "object" && error !== null) {
+    const messageCandidate = (error as { message?: unknown }).message;
+    if (typeof messageCandidate === "string" && messageCandidate.trim().length > 0) {
+      return messageCandidate;
+    }
+
+    const tagCandidate = (error as { _tag?: unknown })._tag;
+    if (typeof tagCandidate === "string" && tagCandidate.length > 0) {
+      const serialized = safeStringify(error);
+      return serialized ? `${tagCandidate}: ${serialized}` : tagCandidate;
+    }
+  }
+
+  if (typeof error === "string" && error.trim().length > 0) {
+    return error;
+  }
+
+  return fallback;
+}
+
+function safeStringify(value: unknown): string | null {
+  try {
+    return JSON.stringify(value);
+  } catch {
+    return null;
+  }
+}
diff --git a/packages/contracts/src/terminal.test.ts b/packages/contracts/src/terminal.test.ts
index 3feae674924..6ab692dad6b 100644
--- a/packages/contracts/src/terminal.test.ts
+++ b/packages/contracts/src/terminal.test.ts
@@ -49,6 +49,36 @@ describe("TerminalOpenInput", () => {
     ).toBe(false);
   });
 
+  it("accepts maximum cols and rows", () => {
+    expect(
+      decodes(TerminalOpenInput, {
+        threadId: "thread-1",
+        cwd: "/tmp/project",
+        cols: 1000,
+        rows: 500,
+      }),
+    ).toBe(true);
+  });
+
+  it("rejects cols and rows above maximum", () => {
+    expect(
+      decodes(TerminalOpenInput, {
+        threadId: "thread-1",
+        cwd: "/tmp/project",
+        cols: 1001,
+        rows: 24,
+      }),
+    ).toBe(false);
+    expect(
+      decodes(TerminalOpenInput, {
+        threadId: "thread-1",
+        cwd: "/tmp/project",
+        cols: 80,
+        rows: 501,
+      }),
+    ).toBe(false);
+  });
+
   it("defaults terminalId when missing", () => {
     const parsed = decodeSync(TerminalOpenInput, {
       threadId: "thread-1",
diff --git a/packages/contracts/src/terminal.ts b/packages/contracts/src/terminal.ts
index 21bd74a0999..6ac1135db0d 100644
--- a/packages/contracts/src/terminal.ts
+++ b/packages/contracts/src/terminal.ts
@@ -5,10 +5,10 @@ export const DEFAULT_TERMINAL_ID = "default";
 
 const TrimmedNonEmptyStringSchema = TrimmedNonEmptyString;
 const TerminalColsSchema = Schema.Int.check(Schema.isGreaterThanOrEqualTo(20)).check(
-  Schema.isLessThanOrEqualTo(400),
+  Schema.isLessThanOrEqualTo(1000),
 );
 const TerminalRowsSchema = Schema.Int.check(Schema.isGreaterThanOrEqualTo(5)).check(
-  Schema.isLessThanOrEqualTo(200),
+  Schema.isLessThanOrEqualTo(500),
 );
 const TerminalIdSchema = TrimmedNonEmptyStringSchema.check(Schema.isMaxLength(128));
 const TerminalEnvKeySchema = Schema.String.check(