From abf71fdb4e178e4957da248736a3e066416efe0a Mon Sep 17 00:00:00 2001
From: Aiden Cline <aidenpcline@gmail.com>
Date: Tue, 4 Aug 2026 19:40:16 -0500
Subject: [PATCH 1/5] fix(core): hide platform errors from tool output

---
 packages/core/src/session/to-session-error.ts |  6 ++---
 packages/core/test/session-error.test.ts      | 17 ++++++++++++++
 packages/core/test/tool-shell.test.ts         | 22 +++++++++++++++++++
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/packages/core/src/session/to-session-error.ts b/packages/core/src/session/to-session-error.ts
index 0a57bb296db7..54173c8d7cbb 100644
--- a/packages/core/src/session/to-session-error.ts
+++ b/packages/core/src/session/to-session-error.ts
@@ -1,6 +1,7 @@
 import { AIError, ToolFailure } from "@opencode-ai/ai"
 import { Tool } from "@opencode-ai/schema/tool"
 import { SessionError } from "@opencode-ai/schema/session-error"
+import { PlatformError } from "effect/PlatformError"
 import { Permission } from "../permission"
 import { Question } from "../question"
 import { Integration } from "../integration"
@@ -40,10 +41,9 @@ export function toSessionError(cause: unknown): SessionError.Error {
   if (cause instanceof Question.RejectedError) return { type: "aborted", message: cause.message }
   if (cause instanceof ToolFailure || cause instanceof Tool.Error) {
     if (cause.error === undefined) return { type: "tool.execution", message: cause.message }
-    // The canonical error is the sole model-visible representation, so a cause
-    // with no message must not erase the tool's curated failure message.
     const unwrapped = toSessionError(cause.error)
-    return unwrapped.message === "" ? { ...unwrapped, type: "tool.execution", message: cause.message } : unwrapped
+    // Platform errors are internal diagnostics; tools provide the model-facing context.
+    return cause.error instanceof PlatformError ? { ...unwrapped, message: cause.message } : unwrapped
   }
   if (cause instanceof StepFailedError) return cause.error
   if (cause instanceof AgentNotFoundError) return { type: "unknown", message: cause.message }
diff --git a/packages/core/test/session-error.test.ts b/packages/core/test/session-error.test.ts
index 72f8ebf85ed5..96f3c5519740 100644
--- a/packages/core/test/session-error.test.ts
+++ b/packages/core/test/session-error.test.ts
@@ -22,6 +22,7 @@ import { Permission } from "@opencode-ai/core/permission"
 import { Tool } from "@opencode-ai/schema/tool"
 import { toSessionError } from "@opencode-ai/core/session/to-session-error"
 import { SessionRunnerRetry } from "@opencode-ai/core/session/runner/retry"
+import { systemError } from "effect/PlatformError"
 
 const llm = (reason: AIError["reason"]) => new AIError({ module: "test", method: "stream", reason })
 
@@ -72,6 +73,22 @@ describe("toSessionError", () => {
       type: "tool.execution",
       message: "failed",
     })
+    expect(
+      toSessionError(
+        new ToolFailure({
+          message: "Unable to execute command: pwd",
+          error: systemError({
+            _tag: "NotFound",
+            module: "FileSystem",
+            method: "stat",
+            pathOrDescriptor: "/missing",
+          }),
+        }),
+      ),
+    ).toEqual({
+      type: "unknown",
+      message: "Unable to execute command: pwd",
+    })
   })
 
   test("preserves provider HTTP status", () => {
diff --git a/packages/core/test/tool-shell.test.ts b/packages/core/test/tool-shell.test.ts
index 64ea83996054..b8c3d8b7b2ec 100644
--- a/packages/core/test/tool-shell.test.ts
+++ b/packages/core/test/tool-shell.test.ts
@@ -257,6 +257,28 @@ describe("ShellTool", () => {
     ),
   )
 
+  it.live("hides filesystem details when the workdir does not exist", () =>
+    Effect.acquireUseRelease(
+      Effect.promise(() => tmpdir()),
+      (tmp) => {
+        reset()
+        return withSession(tmp.path, (registry) =>
+          executeTool(registry, call({ command: cwdCommand, workdir: "missing" })),
+        ).pipe(
+          Effect.andThen((settled) =>
+            Effect.sync(() =>
+              expect(settled).toEqual({
+                status: "error",
+                error: { type: "unknown", message: `Unable to execute command: ${cwdCommand}` },
+              }),
+            ),
+          ),
+        )
+      },
+      (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]().then(() => undefined)),
+    ),
+  )
+
   it.live("permissions compound commands separately", () =>
     Effect.acquireUseRelease(
       Effect.promise(() => tmpdir()),

From b9431ea22e9990a2d1f8487aacfce585669070ca Mon Sep 17 00:00:00 2001
From: Aiden Cline <aidenpcline@gmail.com>
Date: Tue, 4 Aug 2026 19:47:48 -0500
Subject: [PATCH 2/5] fix(core): format platform tool errors

---
 packages/core/src/session/to-session-error.ts | 41 ++++++++++++++-
 packages/core/test/session-error.test.ts      | 52 ++++++++++++++++++-
 packages/core/test/tool-shell.test.ts         |  7 ++-
 3 files changed, 94 insertions(+), 6 deletions(-)

diff --git a/packages/core/src/session/to-session-error.ts b/packages/core/src/session/to-session-error.ts
index 54173c8d7cbb..a0a7d5c17660 100644
--- a/packages/core/src/session/to-session-error.ts
+++ b/packages/core/src/session/to-session-error.ts
@@ -42,8 +42,9 @@ export function toSessionError(cause: unknown): SessionError.Error {
   if (cause instanceof ToolFailure || cause instanceof Tool.Error) {
     if (cause.error === undefined) return { type: "tool.execution", message: cause.message }
     const unwrapped = toSessionError(cause.error)
-    // Platform errors are internal diagnostics; tools provide the model-facing context.
-    return cause.error instanceof PlatformError ? { ...unwrapped, message: cause.message } : unwrapped
+    return cause.error instanceof PlatformError
+      ? { ...unwrapped, message: `${cause.message}: ${platformErrorMessage(cause.error)}` }
+      : unwrapped
   }
   if (cause instanceof StepFailedError) return cause.error
   if (cause instanceof AgentNotFoundError) return { type: "unknown", message: cause.message }
@@ -64,3 +65,39 @@ function providerError(type: string, reason: AIError["reason"]): SessionError.Er
     ("http" in reason ? reason.http?.response?.status : undefined) ?? ("status" in reason ? reason.status : undefined)
   return { type, message: reason.message, ...(status === undefined ? {} : { status }) }
 }
+
+function platformErrorMessage(error: PlatformError) {
+  const reason = error.reason
+  if (reason._tag === "BadArgument")
+    return `${reason.module}.${reason.method} rejected an invalid argument${reason.description ? `: ${reason.description}` : ""}`
+
+  const label = (() => {
+    switch (reason._tag) {
+      case "AlreadyExists":
+        return "already exists"
+      case "BadResource":
+        return "resource is invalid or closed"
+      case "Busy":
+        return "resource is busy"
+      case "InvalidData":
+        return "invalid data"
+      case "NotFound":
+        return "not found"
+      case "PermissionDenied":
+        return "permission denied"
+      case "TimedOut":
+        return "timed out"
+      case "UnexpectedEof":
+        return "unexpected end of input"
+      case "Unknown":
+        return "system error"
+      case "WouldBlock":
+        return "would block"
+      case "WriteZero":
+        return "wrote zero bytes"
+    }
+  })()
+  const target = reason.pathOrDescriptor === undefined ? "" : `: ${reason.pathOrDescriptor}`
+  const description = reason.description === undefined ? "" : ` (${reason.description})`
+  return `${reason.module}.${reason.method} failed: ${label}${target}${description}`
+}
diff --git a/packages/core/test/session-error.test.ts b/packages/core/test/session-error.test.ts
index 96f3c5519740..2c0ef2d8e385 100644
--- a/packages/core/test/session-error.test.ts
+++ b/packages/core/test/session-error.test.ts
@@ -22,7 +22,7 @@ import { Permission } from "@opencode-ai/core/permission"
 import { Tool } from "@opencode-ai/schema/tool"
 import { toSessionError } from "@opencode-ai/core/session/to-session-error"
 import { SessionRunnerRetry } from "@opencode-ai/core/session/runner/retry"
-import { systemError } from "effect/PlatformError"
+import { badArgument, systemError } from "effect/PlatformError"
 
 const llm = (reason: AIError["reason"]) => new AIError({ module: "test", method: "stream", reason })
 
@@ -87,7 +87,7 @@ describe("toSessionError", () => {
       ),
     ).toEqual({
       type: "unknown",
-      message: "Unable to execute command: pwd",
+      message: "Unable to execute command: pwd: FileSystem.stat failed: not found: /missing",
     })
   })
 
@@ -108,6 +108,54 @@ describe("toSessionError", () => {
     })
   })
 
+  test("formats every platform error reason for the model", () => {
+    const reasons = [
+      ["AlreadyExists", "already exists"],
+      ["BadResource", "resource is invalid or closed"],
+      ["Busy", "resource is busy"],
+      ["InvalidData", "invalid data"],
+      ["NotFound", "not found"],
+      ["PermissionDenied", "permission denied"],
+      ["TimedOut", "timed out"],
+      ["UnexpectedEof", "unexpected end of input"],
+      ["Unknown", "system error"],
+      ["WouldBlock", "would block"],
+      ["WriteZero", "wrote zero bytes"],
+    ] as const
+
+    for (const [tag, message] of reasons) {
+      expect(
+        toSessionError(
+          new ToolFailure({
+            message: "Tool failed",
+            error: systemError({
+              _tag: tag,
+              module: "FileSystem",
+              method: "operation",
+              pathOrDescriptor: "/target",
+              description: "OS detail",
+            }),
+          }),
+        ),
+      ).toEqual({
+        type: "unknown",
+        message: `Tool failed: FileSystem.operation failed: ${message}: /target (OS detail)`,
+      })
+    }
+
+    expect(
+      toSessionError(
+        new ToolFailure({
+          message: "Tool failed",
+          error: badArgument({ module: "FileSystem", method: "operation", description: "invalid path" }),
+        }),
+      ),
+    ).toEqual({
+      type: "unknown",
+      message: "Tool failed: FileSystem.operation rejected an invalid argument: invalid path",
+    })
+  })
+
   test("retries only rate limits, provider-internal failures, and transport failures", () => {
     const eligible = [
       llm(new RateLimitReason({ message: "rate" })),
diff --git a/packages/core/test/tool-shell.test.ts b/packages/core/test/tool-shell.test.ts
index b8c3d8b7b2ec..41bc64f74984 100644
--- a/packages/core/test/tool-shell.test.ts
+++ b/packages/core/test/tool-shell.test.ts
@@ -257,7 +257,7 @@ describe("ShellTool", () => {
     ),
   )
 
-  it.live("hides filesystem details when the workdir does not exist", () =>
+  it.live("formats filesystem details when the workdir does not exist", () =>
     Effect.acquireUseRelease(
       Effect.promise(() => tmpdir()),
       (tmp) => {
@@ -269,7 +269,10 @@ describe("ShellTool", () => {
             Effect.sync(() =>
               expect(settled).toEqual({
                 status: "error",
-                error: { type: "unknown", message: `Unable to execute command: ${cwdCommand}` },
+                error: {
+                  type: "unknown",
+                  message: `Unable to execute command: ${cwdCommand}: FileSystem.stat failed: not found: ${path.join(tmp.path, "missing")}`,
+                },
               }),
             ),
           ),

From 3b6db1d6d6b1d0e369d95b11da9d958259583386 Mon Sep 17 00:00:00 2001
From: Aiden Cline <aidenpcline@gmail.com>
Date: Tue, 4 Aug 2026 19:59:07 -0500
Subject: [PATCH 3/5] fix(core): clarify platform tool failures

---
 packages/core/src/session/to-session-error.ts | 12 ++--
 packages/core/src/tool/plugin/shell.ts        | 12 +++-
 packages/core/test/session-error.test.ts      | 59 +++++++------------
 packages/core/test/tool-shell.test.ts         |  6 +-
 4 files changed, 40 insertions(+), 49 deletions(-)

diff --git a/packages/core/src/session/to-session-error.ts b/packages/core/src/session/to-session-error.ts
index a0a7d5c17660..f19f04095f19 100644
--- a/packages/core/src/session/to-session-error.ts
+++ b/packages/core/src/session/to-session-error.ts
@@ -41,10 +41,11 @@ export function toSessionError(cause: unknown): SessionError.Error {
   if (cause instanceof Question.RejectedError) return { type: "aborted", message: cause.message }
   if (cause instanceof ToolFailure || cause instanceof Tool.Error) {
     if (cause.error === undefined) return { type: "tool.execution", message: cause.message }
+    if (cause.error instanceof PlatformError)
+      return { type: "tool.execution", message: `${cause.message}: ${platformErrorMessage(cause.error)}` }
     const unwrapped = toSessionError(cause.error)
-    return cause.error instanceof PlatformError
-      ? { ...unwrapped, message: `${cause.message}: ${platformErrorMessage(cause.error)}` }
-      : unwrapped
+    if (unwrapped.message === "") return { ...unwrapped, type: "tool.execution", message: cause.message }
+    return unwrapped
   }
   if (cause instanceof StepFailedError) return cause.error
   if (cause instanceof AgentNotFoundError) return { type: "unknown", message: cause.message }
@@ -57,6 +58,7 @@ export function toSessionError(cause: unknown): SessionError.Error {
   )
     return { type: "provider.no-route", message: cause.message }
   if (cause instanceof Integration.AuthorizationError) return { type: "provider.auth", message: cause.message }
+  if (cause instanceof PlatformError) return { type: "unknown", message: platformErrorMessage(cause) }
   return { type: "unknown", message: cause instanceof Error ? cause.message : String(cause) }
 }
 
@@ -69,7 +71,7 @@ function providerError(type: string, reason: AIError["reason"]): SessionError.Er
 function platformErrorMessage(error: PlatformError) {
   const reason = error.reason
   if (reason._tag === "BadArgument")
-    return `${reason.module}.${reason.method} rejected an invalid argument${reason.description ? `: ${reason.description}` : ""}`
+    return `invalid argument${reason.description ? `: ${reason.description}` : ""}`
 
   const label = (() => {
     switch (reason._tag) {
@@ -99,5 +101,5 @@ function platformErrorMessage(error: PlatformError) {
   })()
   const target = reason.pathOrDescriptor === undefined ? "" : `: ${reason.pathOrDescriptor}`
   const description = reason.description === undefined ? "" : ` (${reason.description})`
-  return `${reason.module}.${reason.method} failed: ${label}${target}${description}`
+  return `${label}${target}${description}`
 }
diff --git a/packages/core/src/tool/plugin/shell.ts b/packages/core/src/tool/plugin/shell.ts
index 8a8ce3d707b0..55450a26fb8e 100644
--- a/packages/core/src/tool/plugin/shell.ts
+++ b/packages/core/src/tool/plugin/shell.ts
@@ -176,7 +176,12 @@ export const Plugin = {
                           agent: context.agent,
                           source,
                         })
-                      if ((yield* fsUtil.stat(target.canonical)).type !== "Directory")
+                      const workdir = yield* fsUtil.stat(target.canonical).pipe(
+                        Effect.catchReason("PlatformError", "NotFound", () =>
+                          Effect.fail(new ToolFailure({ message: `Working directory does not exist: ${target.canonical}` })),
+                        ),
+                      )
+                      if (workdir.type !== "Directory")
                         return yield* Effect.fail(new Error(`Working directory is not a directory: ${target.canonical}`))
                     }),
                 )
@@ -280,7 +285,10 @@ export const Plugin = {
                   }
                 }),
                 Effect.mapError(
-                  (error) => new ToolFailure({ message: `Unable to execute command: ${input.command}`, error }),
+                  (error) =>
+                    error instanceof ToolFailure
+                      ? error
+                      : new ToolFailure({ message: `Unable to execute command: ${input.command}`, error }),
                 ),
               ),
           }),
diff --git a/packages/core/test/session-error.test.ts b/packages/core/test/session-error.test.ts
index 2c0ef2d8e385..dbcd722ee768 100644
--- a/packages/core/test/session-error.test.ts
+++ b/packages/core/test/session-error.test.ts
@@ -86,8 +86,12 @@ describe("toSessionError", () => {
         }),
       ),
     ).toEqual({
-      type: "unknown",
-      message: "Unable to execute command: pwd: FileSystem.stat failed: not found: /missing",
+      type: "tool.execution",
+      message: "Unable to execute command: pwd: not found: /missing",
+    })
+    expect(toSessionError(new ToolFailure({ message: "Tool failed", error: new Error("") }))).toEqual({
+      type: "tool.execution",
+      message: "Tool failed",
     })
   })
 
@@ -108,41 +112,18 @@ describe("toSessionError", () => {
     })
   })
 
-  test("formats every platform error reason for the model", () => {
-    const reasons = [
-      ["AlreadyExists", "already exists"],
-      ["BadResource", "resource is invalid or closed"],
-      ["Busy", "resource is busy"],
-      ["InvalidData", "invalid data"],
-      ["NotFound", "not found"],
-      ["PermissionDenied", "permission denied"],
-      ["TimedOut", "timed out"],
-      ["UnexpectedEof", "unexpected end of input"],
-      ["Unknown", "system error"],
-      ["WouldBlock", "would block"],
-      ["WriteZero", "wrote zero bytes"],
-    ] as const
-
-    for (const [tag, message] of reasons) {
-      expect(
-        toSessionError(
-          new ToolFailure({
-            message: "Tool failed",
-            error: systemError({
-              _tag: tag,
-              module: "FileSystem",
-              method: "operation",
-              pathOrDescriptor: "/target",
-              description: "OS detail",
-            }),
-          }),
-        ),
-      ).toEqual({
-        type: "unknown",
-        message: `Tool failed: FileSystem.operation failed: ${message}: /target (OS detail)`,
-      })
-    }
-
+  test("formats platform errors for the model", () => {
+    const missing = systemError({
+      _tag: "NotFound",
+      module: "FileSystem",
+      method: "operation",
+      pathOrDescriptor: "/target",
+      description: "OS detail",
+    })
+    expect(toSessionError(missing)).toEqual({
+      type: "unknown",
+      message: "not found: /target (OS detail)",
+    })
     expect(
       toSessionError(
         new ToolFailure({
@@ -151,8 +132,8 @@ describe("toSessionError", () => {
         }),
       ),
     ).toEqual({
-      type: "unknown",
-      message: "Tool failed: FileSystem.operation rejected an invalid argument: invalid path",
+      type: "tool.execution",
+      message: "Tool failed: invalid argument: invalid path",
     })
   })
 
diff --git a/packages/core/test/tool-shell.test.ts b/packages/core/test/tool-shell.test.ts
index 41bc64f74984..219eb1f34646 100644
--- a/packages/core/test/tool-shell.test.ts
+++ b/packages/core/test/tool-shell.test.ts
@@ -257,7 +257,7 @@ describe("ShellTool", () => {
     ),
   )
 
-  it.live("formats filesystem details when the workdir does not exist", () =>
+  it.live("reports a missing workdir", () =>
     Effect.acquireUseRelease(
       Effect.promise(() => tmpdir()),
       (tmp) => {
@@ -270,8 +270,8 @@ describe("ShellTool", () => {
               expect(settled).toEqual({
                 status: "error",
                 error: {
-                  type: "unknown",
-                  message: `Unable to execute command: ${cwdCommand}: FileSystem.stat failed: not found: ${path.join(tmp.path, "missing")}`,
+                  type: "tool.execution",
+                  message: `Working directory does not exist: ${path.join(tmp.path, "missing")}`,
                 },
               }),
             ),

From bfc1521a63342ec5fefc2eba26b1141e88699e94 Mon Sep 17 00:00:00 2001
From: Aiden Cline <aidenpcline@gmail.com>
Date: Tue, 4 Aug 2026 20:50:37 -0500
Subject: [PATCH 4/5] refactor(core): keep shell error local

---
 packages/core/src/session/to-session-error.ts | 45 ++----------------
 packages/core/test/session-error.test.ts      | 46 -------------------
 2 files changed, 3 insertions(+), 88 deletions(-)

diff --git a/packages/core/src/session/to-session-error.ts b/packages/core/src/session/to-session-error.ts
index f19f04095f19..0a57bb296db7 100644
--- a/packages/core/src/session/to-session-error.ts
+++ b/packages/core/src/session/to-session-error.ts
@@ -1,7 +1,6 @@
 import { AIError, ToolFailure } from "@opencode-ai/ai"
 import { Tool } from "@opencode-ai/schema/tool"
 import { SessionError } from "@opencode-ai/schema/session-error"
-import { PlatformError } from "effect/PlatformError"
 import { Permission } from "../permission"
 import { Question } from "../question"
 import { Integration } from "../integration"
@@ -41,11 +40,10 @@ export function toSessionError(cause: unknown): SessionError.Error {
   if (cause instanceof Question.RejectedError) return { type: "aborted", message: cause.message }
   if (cause instanceof ToolFailure || cause instanceof Tool.Error) {
     if (cause.error === undefined) return { type: "tool.execution", message: cause.message }
-    if (cause.error instanceof PlatformError)
-      return { type: "tool.execution", message: `${cause.message}: ${platformErrorMessage(cause.error)}` }
+    // The canonical error is the sole model-visible representation, so a cause
+    // with no message must not erase the tool's curated failure message.
     const unwrapped = toSessionError(cause.error)
-    if (unwrapped.message === "") return { ...unwrapped, type: "tool.execution", message: cause.message }
-    return unwrapped
+    return unwrapped.message === "" ? { ...unwrapped, type: "tool.execution", message: cause.message } : unwrapped
   }
   if (cause instanceof StepFailedError) return cause.error
   if (cause instanceof AgentNotFoundError) return { type: "unknown", message: cause.message }
@@ -58,7 +56,6 @@ export function toSessionError(cause: unknown): SessionError.Error {
   )
     return { type: "provider.no-route", message: cause.message }
   if (cause instanceof Integration.AuthorizationError) return { type: "provider.auth", message: cause.message }
-  if (cause instanceof PlatformError) return { type: "unknown", message: platformErrorMessage(cause) }
   return { type: "unknown", message: cause instanceof Error ? cause.message : String(cause) }
 }
 
@@ -67,39 +64,3 @@ function providerError(type: string, reason: AIError["reason"]): SessionError.Er
     ("http" in reason ? reason.http?.response?.status : undefined) ?? ("status" in reason ? reason.status : undefined)
   return { type, message: reason.message, ...(status === undefined ? {} : { status }) }
 }
-
-function platformErrorMessage(error: PlatformError) {
-  const reason = error.reason
-  if (reason._tag === "BadArgument")
-    return `invalid argument${reason.description ? `: ${reason.description}` : ""}`
-
-  const label = (() => {
-    switch (reason._tag) {
-      case "AlreadyExists":
-        return "already exists"
-      case "BadResource":
-        return "resource is invalid or closed"
-      case "Busy":
-        return "resource is busy"
-      case "InvalidData":
-        return "invalid data"
-      case "NotFound":
-        return "not found"
-      case "PermissionDenied":
-        return "permission denied"
-      case "TimedOut":
-        return "timed out"
-      case "UnexpectedEof":
-        return "unexpected end of input"
-      case "Unknown":
-        return "system error"
-      case "WouldBlock":
-        return "would block"
-      case "WriteZero":
-        return "wrote zero bytes"
-    }
-  })()
-  const target = reason.pathOrDescriptor === undefined ? "" : `: ${reason.pathOrDescriptor}`
-  const description = reason.description === undefined ? "" : ` (${reason.description})`
-  return `${label}${target}${description}`
-}
diff --git a/packages/core/test/session-error.test.ts b/packages/core/test/session-error.test.ts
index dbcd722ee768..72f8ebf85ed5 100644
--- a/packages/core/test/session-error.test.ts
+++ b/packages/core/test/session-error.test.ts
@@ -22,7 +22,6 @@ import { Permission } from "@opencode-ai/core/permission"
 import { Tool } from "@opencode-ai/schema/tool"
 import { toSessionError } from "@opencode-ai/core/session/to-session-error"
 import { SessionRunnerRetry } from "@opencode-ai/core/session/runner/retry"
-import { badArgument, systemError } from "effect/PlatformError"
 
 const llm = (reason: AIError["reason"]) => new AIError({ module: "test", method: "stream", reason })
 
@@ -73,26 +72,6 @@ describe("toSessionError", () => {
       type: "tool.execution",
       message: "failed",
     })
-    expect(
-      toSessionError(
-        new ToolFailure({
-          message: "Unable to execute command: pwd",
-          error: systemError({
-            _tag: "NotFound",
-            module: "FileSystem",
-            method: "stat",
-            pathOrDescriptor: "/missing",
-          }),
-        }),
-      ),
-    ).toEqual({
-      type: "tool.execution",
-      message: "Unable to execute command: pwd: not found: /missing",
-    })
-    expect(toSessionError(new ToolFailure({ message: "Tool failed", error: new Error("") }))).toEqual({
-      type: "tool.execution",
-      message: "Tool failed",
-    })
   })
 
   test("preserves provider HTTP status", () => {
@@ -112,31 +91,6 @@ describe("toSessionError", () => {
     })
   })
 
-  test("formats platform errors for the model", () => {
-    const missing = systemError({
-      _tag: "NotFound",
-      module: "FileSystem",
-      method: "operation",
-      pathOrDescriptor: "/target",
-      description: "OS detail",
-    })
-    expect(toSessionError(missing)).toEqual({
-      type: "unknown",
-      message: "not found: /target (OS detail)",
-    })
-    expect(
-      toSessionError(
-        new ToolFailure({
-          message: "Tool failed",
-          error: badArgument({ module: "FileSystem", method: "operation", description: "invalid path" }),
-        }),
-      ),
-    ).toEqual({
-      type: "tool.execution",
-      message: "Tool failed: invalid argument: invalid path",
-    })
-  })
-
   test("retries only rate limits, provider-internal failures, and transport failures", () => {
     const eligible = [
       llm(new RateLimitReason({ message: "rate" })),

From 8be555edd7966ad81190bbf0b4bf951bdbaa88c9 Mon Sep 17 00:00:00 2001
From: Aiden Cline <aidenpcline@gmail.com>
Date: Tue, 4 Aug 2026 20:54:46 -0500
Subject: [PATCH 5/5] refactor(core): simplify shell workdir error

---
 packages/core/src/tool/plugin/shell.ts | 7 ++-----
 packages/core/test/tool-shell.test.ts  | 2 +-
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/packages/core/src/tool/plugin/shell.ts b/packages/core/src/tool/plugin/shell.ts
index 55450a26fb8e..16fe6a5f7749 100644
--- a/packages/core/src/tool/plugin/shell.ts
+++ b/packages/core/src/tool/plugin/shell.ts
@@ -178,7 +178,7 @@ export const Plugin = {
                         })
                       const workdir = yield* fsUtil.stat(target.canonical).pipe(
                         Effect.catchReason("PlatformError", "NotFound", () =>
-                          Effect.fail(new ToolFailure({ message: `Working directory does not exist: ${target.canonical}` })),
+                          Effect.fail(new Error(`Working directory does not exist: ${target.canonical}`)),
                         ),
                       )
                       if (workdir.type !== "Directory")
@@ -285,10 +285,7 @@ export const Plugin = {
                   }
                 }),
                 Effect.mapError(
-                  (error) =>
-                    error instanceof ToolFailure
-                      ? error
-                      : new ToolFailure({ message: `Unable to execute command: ${input.command}`, error }),
+                  (error) => new ToolFailure({ message: `Unable to execute command: ${input.command}`, error }),
                 ),
               ),
           }),
diff --git a/packages/core/test/tool-shell.test.ts b/packages/core/test/tool-shell.test.ts
index 219eb1f34646..dfee4e12448d 100644
--- a/packages/core/test/tool-shell.test.ts
+++ b/packages/core/test/tool-shell.test.ts
@@ -270,7 +270,7 @@ describe("ShellTool", () => {
               expect(settled).toEqual({
                 status: "error",
                 error: {
-                  type: "tool.execution",
+                  type: "unknown",
                   message: `Working directory does not exist: ${path.join(tmp.path, "missing")}`,
                 },
               }),