diff --git a/src/application/JsonFiles.ts b/src/application/JsonFiles.ts
index 07c5433fd3..1218671e41 100644
--- a/src/application/JsonFiles.ts
+++ b/src/application/JsonFiles.ts
@@ -44,6 +44,7 @@ import {
 } from "../artifacts/AnalysisCleanupLease.js";
 import { OwnedFileHandle } from "../filesystem/OwnedFileHandle.js";
 import { OwnedStagedOutput } from "../filesystem/OwnedStagedOutput.js";
+import { StagedOutputError } from "../filesystem/StagedOutputError.js";
 import { absoluteCallerPath } from "../filesystem/callerPath.js";
 
 /** Request control and its owning operation for an interruptible atomic write. */
@@ -399,6 +400,7 @@ const writeTextPartsOwned = async (
             path: requestedPath,
             cleanup,
             published: { ...cause.outcome.value, path: requestedPath },
+            ...stagedOutputDiagnostics(cause.cleanupCause),
           }),
           cause.lease,
         );
@@ -420,6 +422,12 @@ const writeTextPartsOwned = async (
           ...(failure.systemCode === undefined
             ? {}
             : { systemCode: failure.systemCode }),
+          ...stagedOutputDiagnostics(
+            !cause.outcome.ok &&
+              cause.outcome.error instanceof StagedOutputError
+              ? cause.outcome.error
+              : cause.cleanupCause,
+          ),
         }),
         cause.lease,
       );
@@ -445,6 +453,7 @@ const writeTextPartsOwned = async (
         ...(failure.systemCode === undefined
           ? {}
           : { systemCode: failure.systemCode }),
+        ...stagedOutputDiagnostics(cause),
       }),
     );
   }
@@ -612,6 +621,15 @@ class StagedOutputCleanupFailure extends Error {
   }
 }
 
+const stagedOutputDiagnostics = (
+  cause: unknown,
+): {
+  readonly diagnostics?: Readonly<Record<string, string | number>>;
+} => {
+  if (!(cause instanceof StagedOutputError)) return {};
+  return { diagnostics: { code: cause.code, ...cause.detail } };
+};
+
 const failureMessage = (cause: unknown): string =>
   cause instanceof Error ? cause.message || cause.name : String(cause);
 
diff --git a/src/domain/evm/solidityMetadata.ts b/src/domain/evm/solidityMetadata.ts
index ba2e146a57..85eceb32f3 100644
--- a/src/domain/evm/solidityMetadata.ts
+++ b/src/domain/evm/solidityMetadata.ts
@@ -47,6 +47,17 @@ export const solidityMetadataSchema = z
       })
       .nullable(),
     diagnostic: z.string().max(512).nullable(),
+    admission: z
+      .strictObject({
+        code: z.string().min(1).max(64),
+        detail: z
+          .record(
+            z.string().min(1).max(64),
+            z.union([z.string().max(512), z.number()]),
+          )
+          .optional(),
+      })
+      .optional(),
   })
   .superRefine((value, context) => {
     const unavailable = value.status === "unavailable";
diff --git a/src/evm/EvmAdmissionError.ts b/src/evm/EvmAdmissionError.ts
new file mode 100644
index 0000000000..7f0993c979
--- /dev/null
+++ b/src/evm/EvmAdmissionError.ts
@@ -0,0 +1,31 @@
+const EVM_ADMISSION_CODES = [
+  "prlimit_not_absolute",
+  "prlimit_not_file",
+  "cleanup_incomplete",
+  "cleanup_unconfirmed",
+  "marker_mismatch",
+  "request_path_missing",
+  "tag_or_float",
+  "text_bytes_unavailable",
+  "collection_exceeds_bound",
+  "nesting_exceeds_profile",
+  "value_outside_profile",
+  "repeated_map_key",
+  "root_not_map",
+] as const;
+
+export type EvmAdmissionCode = (typeof EVM_ADMISSION_CODES)[number];
+
+/** EVM limiter, worker, or metadata admission failure. `code` is the stable identity. */
+export class EvmAdmissionError extends Error {
+  readonly _tag = "EvmAdmissionError";
+
+  constructor(
+    readonly code: EvmAdmissionCode,
+    readonly detail?: Readonly<Record<string, string | number>>,
+    options?: ErrorOptions,
+  ) {
+    super(code, options);
+    this.name = "EvmAdmissionError";
+  }
+}
diff --git a/src/evm/EvmoleInterfaceProvider.ts b/src/evm/EvmoleInterfaceProvider.ts
index fd532d6aee..4f50055207 100644
--- a/src/evm/EvmoleInterfaceProvider.ts
+++ b/src/evm/EvmoleInterfaceProvider.ts
@@ -1,4 +1,6 @@
+import { EvmAdmissionError } from "./EvmAdmissionError.js";
 import { snapshotEnvironment } from "../process/snapshotEnvironment.js";
+import type { JsonValue } from "../domain/jsonValue.js";
 import { safeParseUtf8Json } from "../domain/safeJson.js";
 import { createHash, randomUUID } from "node:crypto";
 import { access, readFile, stat, writeFile } from "node:fs/promises";
@@ -110,7 +112,7 @@ export interface EvmLimiterProbeOptions {
 
 type EvmLimiterSelection = {
   readonly path: string;
-  readonly diagnostics: Readonly<Record<string, string>>;
+  readonly diagnostics: Readonly<Record<string, JsonValue>>;
 };
 type EvmLimiterUnavailable = EvmLimiterSelection & {
   readonly reason: string;
@@ -142,20 +144,29 @@ const selectEvmLimiter = async (
   const diagnostics = { limiter_path: path, platform, arch };
   try {
     if (!isAbsolute(path))
-      throw new Error(
-        "REA_EVM_PRLIMIT_COMMAND must be an absolute executable path.",
-      );
+      throw new EvmAdmissionError("prlimit_not_absolute", {
+        setting: "REA_EVM_PRLIMIT_COMMAND",
+      });
     const fs = probes?.fs ?? { access, stat };
     await fs.access(path, constants.X_OK);
     throwIfAborted();
     if (!(await fs.stat(path)).isFile())
-      throw new Error(
-        "Configured prlimit must be a regular executable file, not a directory.",
-      );
+      throw new EvmAdmissionError("prlimit_not_file");
     throwIfAborted();
     return ok({ path, diagnostics });
   } catch (cause: unknown) {
     throwIfAborted();
+    if (cause instanceof EvmAdmissionError)
+      return err({
+        path,
+        diagnostics: {
+          ...diagnostics,
+          code: cause.code,
+          ...cause.detail,
+        },
+        reason: cause.code,
+        cause,
+      });
     const reason = `Offline EVM interface inspection requires caller-supplied util-linux prlimit: ${path}; ${cause instanceof Error ? cause.message : String(cause)}`;
     return err({ path, diagnostics, reason, cause });
   }
@@ -452,10 +463,13 @@ export class EvmoleInterfaceProvider implements EvmInterfacePort {
               stopped.status === "incomplete" ||
               stopped.status === "not-owned"
             )
-              throw new Error(
+              throw new EvmAdmissionError(
                 stopped.status === "incomplete"
-                  ? stopped.reason
-                  : "Owned EVM worker cleanup did not confirm ownership.",
+                  ? "cleanup_incomplete"
+                  : "cleanup_unconfirmed",
+                stopped.status === "incomplete"
+                  ? { reason: stopped.reason }
+                  : undefined,
                 { cause: stopped },
               );
           },
@@ -511,6 +525,7 @@ export class EvmoleInterfaceProvider implements EvmInterfacePort {
           selectedLimiter.error.reason,
           {
             cause: selectedLimiter.error.cause,
+            diagnostics: selectedLimiter.error.diagnostics,
             userMessage: selectedLimiter.error.reason,
           },
         );
@@ -813,9 +828,7 @@ export class EvmoleInterfaceProvider implements EvmInterfacePort {
             marker = completed;
           }
           if (!marker.bytes.equals(Buffer.from("F")))
-            throw new Error(
-              "Private worker failure marker does not match the observed exit status.",
-            );
+            throw new EvmAdmissionError("marker_mismatch");
           fileFailure = { verified: true, failure: null };
         } catch (markerFailure: unknown) {
           fileFailure = {
diff --git a/src/evm/EvmoleInterfaceWorker.ts b/src/evm/EvmoleInterfaceWorker.ts
index 214235f7cf..96e795749b 100644
--- a/src/evm/EvmoleInterfaceWorker.ts
+++ b/src/evm/EvmoleInterfaceWorker.ts
@@ -1,3 +1,4 @@
+import { EvmAdmissionError } from "./EvmAdmissionError.js";
 import { createHash } from "node:crypto";
 import { readFile, writeFile } from "node:fs/promises";
 import { z } from "zod";
@@ -23,7 +24,7 @@ class UnsupportedContainer extends Error {}
 const main = async (): Promise<void> => {
   const requestPath = process.argv[2];
   if (requestPath === undefined)
-    throw new Error("Owned worker request path missing.");
+    throw new EvmAdmissionError("request_path_missing");
   const request = requestSchema.parse(
     JSON.parse(await readFile(requestPath, "utf8")),
   );
diff --git a/src/evm/SolidityMetadata.test.ts b/src/evm/SolidityMetadata.test.ts
index 8d9fade9a6..73dbb407cb 100644
--- a/src/evm/SolidityMetadata.test.ts
+++ b/src/evm/SolidityMetadata.test.ts
@@ -163,11 +163,28 @@ it("rejects repeated deeply nested container keys promptly", () => {
     inspectSolidityMetadata(bytecode("a2" + key + "01" + key + "02")),
   ).toMatchObject({
     status: "not-decoded",
-    diagnostic: expect.stringContaining("found repeat map key"),
+    diagnostic: "repeated_map_key",
+    admission: {
+      code: "repeated_map_key",
+      detail: { key_length: expect.any(Number) },
+    },
   });
   expect(performance.now() - started).toBeLessThan(1000);
 });
 
+it("records the profile depth when CBOR nesting is refused", () => {
+  expect(
+    inspectSolidityMetadata(bytecode("a16178" + "81".repeat(65) + "00")),
+  ).toMatchObject({
+    status: "not-decoded",
+    diagnostic: "nesting_exceeds_profile",
+    admission: {
+      code: "nesting_exceeds_profile",
+      detail: { max_depth: 64 },
+    },
+  });
+});
+
 it.each(["", "60006000f3", "000000", "00010001"])(
   "does not claim absent Solidity metadata for an unavailable trailer: %s",
   (hex) =>
diff --git a/src/evm/SolidityMetadata.ts b/src/evm/SolidityMetadata.ts
index 0afd626358..e43c06c63d 100644
--- a/src/evm/SolidityMetadata.ts
+++ b/src/evm/SolidityMetadata.ts
@@ -1,3 +1,4 @@
+import { EvmAdmissionError } from "./EvmAdmissionError.js";
 import { decode, Tokenizer, Type, type Token } from "cborg";
 import type {
   SolidityMetadata,
@@ -14,39 +15,52 @@ const decodeOptions = {
   allowUndefined: false,
   allowInfinity: false,
   allowNaN: false,
-  rejectDuplicateMapKeys: true,
+  rejectDuplicateMapKeys: false,
   retainStringBytes: true,
 } as const;
 
 /** Bound recursive decoder entry before collection interpretation/allocation. */
 class BoundedMetadataTokenizer extends Tokenizer {
   readonly remaining: number[] = [];
+  readonly #mapKeys: Array<Set<string> | undefined> = [];
   constructor(bytes: Uint8Array) {
     super(bytes, decodeOptions);
   }
 
   override next(): Token {
-    while (this.remaining.at(-1) === 0) this.remaining.pop();
+    while (this.remaining.at(-1) === 0) {
+      this.remaining.pop();
+      this.#mapKeys.pop();
+    }
     const token = super.next();
     if (
       Type.equals(token.type, Type.tag) ||
       Type.equals(token.type, Type.float)
     )
-      throw new Error(
-        "CBOR tags and floating-point values are outside this metadata profile.",
-      );
+      throw new EvmAdmissionError("tag_or_float");
     if (Type.equals(token.type, Type.string)) {
       if (token.byteValue !== undefined)
         token.value = utf8.decode(token.byteValue);
       // cborg answers the shortest-form empty text (0x60) with a shared token that has no
       // bytes; it can only mean "", which is already its value.
       else if (token.value !== "" || token.encodedLength !== 1)
-        throw new Error(
-          "CBOR text bytes were unavailable for strict UTF-8 validation.",
-        );
+        throw new EvmAdmissionError("text_bytes_unavailable");
     }
     const parent = this.remaining.length - 1;
+    const mapKeys = parent >= 0 ? this.#mapKeys[parent] : undefined;
+    const onKey =
+      mapKeys !== undefined && parent >= 0 && this.remaining[parent]! % 2 === 0;
     if (parent >= 0) this.remaining[parent]!--;
+    if (
+      onKey &&
+      mapKeys !== undefined &&
+      !Type.equals(token.type, Type.map) &&
+      !Type.equals(token.type, Type.array)
+    ) {
+      const identity = keyIdentity(token.value);
+      if (mapKeys.has(identity)) throw repeatedMapKey(identity);
+      mapKeys.add(identity);
+    }
     if (
       Type.equals(token.type, Type.map) ||
       Type.equals(token.type, Type.array)
@@ -61,11 +75,14 @@ class BoundedMetadataTokenizer extends Tokenizer {
         children < 0 ||
         children > this.data.length
       )
-        throw new Error(
-          "Declared CBOR collection exceeds the encoded item-byte bound.",
-        );
+        throw new EvmAdmissionError("collection_exceeds_bound");
       if (this.remaining.length >= MAX_DEPTH)
-        throw new Error("CBOR nesting exceeds the 64-level metadata profile.");
+        throw new EvmAdmissionError("nesting_exceeds_profile", {
+          max_depth: MAX_DEPTH,
+        });
+      this.#mapKeys.push(
+        Type.equals(token.type, Type.map) ? new Set() : undefined,
+      );
       this.remaining.push(children);
     }
     return token;
@@ -85,9 +102,7 @@ const scalar = (value: unknown): SolidityMetadataScalar => {
   if (value instanceof Map) return { kind: "uninterpreted", container: "map" };
   if (Array.isArray(value))
     return { kind: "uninterpreted", container: "array" };
-  throw new Error(
-    "CBOR decoder returned a value outside the admitted profile.",
-  );
+  throw new EvmAdmissionError("value_outside_profile");
 };
 
 /** Value identity for duplicate-key checks; map entry order is not significant. */
@@ -101,14 +116,21 @@ const keyIdentity = (value: unknown): string => {
   return JSON.stringify(scalar(value));
 };
 
+const repeatedMapKey = (identity: string): EvmAdmissionError =>
+  new EvmAdmissionError(
+    "repeated_map_key",
+    identity.length <= 128
+      ? { key: identity }
+      : { key_length: identity.length },
+  );
+
 /** Check every map boundary, even when nested values remain uninterpreted. */
 const validateMapKeys = (value: unknown): void => {
   if (value instanceof Map) {
     const seen = new Set<string>();
     for (const [key, item] of value) {
       const identity = keyIdentity(key);
-      if (seen.has(identity))
-        throw new Error(`CBOR decode error: found repeat map key ${identity}`);
+      if (seen.has(identity)) throw repeatedMapKey(identity);
       seen.add(identity);
       validateMapKeys(key);
       validateMapKeys(item);
@@ -118,6 +140,32 @@ const validateMapKeys = (value: unknown): void => {
   }
 };
 
+/** Keep the typed code and its detail; map only the decoder's duplicate-key throw. */
+const solidityFailure = (
+  cause: unknown,
+): {
+  readonly diagnostic: string;
+  readonly admission?: {
+    readonly code: string;
+    readonly detail?: Readonly<Record<string, string | number>>;
+  };
+} => {
+  if (cause instanceof EvmAdmissionError)
+    return {
+      diagnostic: cause.code,
+      admission: {
+        code: cause.code,
+        ...(cause.detail === undefined ? {} : { detail: cause.detail }),
+      },
+    };
+  return {
+    diagnostic: (cause instanceof Error ? cause.message : String(cause)).slice(
+      0,
+      512,
+    ),
+  };
+};
+
 /** Parse only a plausible terminal root-map candidate; never establish absence. */
 export const inspectSolidityMetadata = (
   bytes: Uint8Array,
@@ -148,8 +196,7 @@ export const inspectSolidityMetadata = (
       ...decodeOptions,
       tokenizer: new BoundedMetadataTokenizer(selected),
     });
-    if (!(raw instanceof Map))
-      throw new Error("Terminal CBOR candidate did not decode to a root map.");
+    if (!(raw instanceof Map)) throw new EvmAdmissionError("root_not_map");
     validateMapKeys(raw);
     // cborg compares Map keys by identity, so repeated byte-string or container
     // keys (each its own object) pass its duplicate check; compare by value at
@@ -185,10 +232,7 @@ export const inspectSolidityMetadata = (
       status: "not-decoded",
       entries: [],
       compiler_version: null,
-      diagnostic: (cause instanceof Error
-        ? cause.message
-        : String(cause)
-      ).slice(0, 512),
+      ...solidityFailure(cause),
     };
   }
 };
diff --git a/src/filesystem/OwnedFileHandle.ts b/src/filesystem/OwnedFileHandle.ts
index 8c1b7ede4e..3f54ffeb08 100644
--- a/src/filesystem/OwnedFileHandle.ts
+++ b/src/filesystem/OwnedFileHandle.ts
@@ -1,5 +1,15 @@
 import type { FileHandle } from "node:fs/promises";
 
+/** Close admission for one owned file handle. `code` is the stable identity. */
+export class OwnedFileHandleError extends Error {
+  readonly _tag = "OwnedFileHandleError";
+
+  constructor(readonly code: "handle_invalidated") {
+    super(code);
+    this.name = "OwnedFileHandleError";
+  }
+}
+
 type CloseState =
   | { readonly kind: "open" }
   | { readonly kind: "closing"; readonly attempt: Promise<void> }
@@ -20,9 +30,7 @@ export class OwnedFileHandle<
     if (this.#state.kind === "closing") return this.#state.attempt;
     if (this.#state.kind === "failed") return Promise.reject(this.#state.cause);
     if (this.handle.fd < 0) {
-      const cause = new Error(
-        "File handle was invalidated before this owner confirmed its close",
-      );
+      const cause = new OwnedFileHandleError("handle_invalidated");
       this.#state = { kind: "failed", cause };
       return Promise.reject(cause);
     }
diff --git a/src/filesystem/OwnedStagedOutput.ts b/src/filesystem/OwnedStagedOutput.ts
index 6e8e65894e..e0c0319842 100644
--- a/src/filesystem/OwnedStagedOutput.ts
+++ b/src/filesystem/OwnedStagedOutput.ts
@@ -1,3 +1,4 @@
+import { StagedOutputError } from "./StagedOutputError.js";
 import { lstat, readdir, rmdir, unlink } from "node:fs/promises";
 import type { Stats } from "node:fs";
 
@@ -48,7 +49,7 @@ export class OwnedStagedOutput {
 
   setFile(file: OwnedFileHandle): void {
     if (this.#file !== undefined)
-      throw new Error("Staged output already owns a file handle");
+      throw new StagedOutputError("handle_already_owned");
     this.#file = file;
   }
 
@@ -58,7 +59,7 @@ export class OwnedStagedOutput {
     if (this.#file !== undefined && !this.#fileClosed)
       await this.#observeFileIdentity();
     if (this.#fileIdentity === undefined)
-      throw new Error("Cannot verify staged file identity", {
+      throw new StagedOutputError("identity_unverified", undefined, {
         cause: this.#identityFailure,
       });
     const stagedFile = await lstat(content);
@@ -67,7 +68,7 @@ export class OwnedStagedOutput {
       stagedFile.isSymbolicLink() ||
       !sameIdentity(stagedFile, this.#fileIdentity)
     )
-      throw new Error(`Staged file identity changed: ${content}`);
+      throw new StagedOutputError("identity_changed", { path: content });
   }
 
   /** Observe the descriptor's identity after its last write, then close it. */
@@ -134,9 +135,11 @@ export class OwnedStagedOutput {
         ) {
           stagedFile = undefined;
         } else if (errorCode(cause) === "ENOENT") {
-          throw new Error(`Owned staged file disappeared: ${content}`, {
-            cause,
-          });
+          throw new StagedOutputError(
+            "file_disappeared",
+            { path: content },
+            { cause },
+          );
         } else {
           throw cause;
         }
@@ -148,7 +151,7 @@ export class OwnedStagedOutput {
           this.#fileIdentity === undefined ||
           !sameIdentity(stagedFile, this.#fileIdentity)
         )
-          throw new Error(`Staged file identity changed: ${content}`);
+          throw new StagedOutputError("identity_changed", { path: content });
         await unlink(content);
         this.#fileRemovedByOwner = true;
       }
@@ -156,20 +159,20 @@ export class OwnedStagedOutput {
 
     const remaining = await readdir(this.directory);
     if (remaining.length > 0)
-      throw new Error(
-        `Unexpected staging entries remain in ${this.directory}: ${remaining.join(", ")}`,
-      );
+      throw new StagedOutputError("unexpected_entries", {
+        count: remaining.length,
+        entries: remaining.join(","),
+      });
     await this.#verifiedDirectory();
     await rmdir(this.directory);
   }
 
   async #verifiedDirectory(): Promise<void> {
     if (this.directoryIdentity === undefined)
-      throw new Error(
-        `Cannot verify staging directory ownership: ${this.directory}`,
-        {
-          cause: this.#identityFailure,
-        },
+      throw new StagedOutputError(
+        "directory_unverified",
+        { directory: this.directory },
+        { cause: this.#identityFailure },
       );
     const directory = await lstat(this.directory);
     if (
@@ -177,7 +180,9 @@ export class OwnedStagedOutput {
       directory.isSymbolicLink() ||
       !sameIdentity(directory, this.directoryIdentity)
     )
-      throw new Error(`Staging directory identity changed: ${this.directory}`);
+      throw new StagedOutputError("directory_identity_changed", {
+        directory: this.directory,
+      });
   }
 }
 
diff --git a/src/filesystem/StagedOutputError.ts b/src/filesystem/StagedOutputError.ts
new file mode 100644
index 0000000000..ed5ab193ac
--- /dev/null
+++ b/src/filesystem/StagedOutputError.ts
@@ -0,0 +1,25 @@
+const STAGED_OUTPUT_CODES = [
+  "handle_already_owned",
+  "identity_unverified",
+  "identity_changed",
+  "file_disappeared",
+  "unexpected_entries",
+  "directory_unverified",
+  "directory_identity_changed",
+] as const;
+
+export type StagedOutputCode = (typeof STAGED_OUTPUT_CODES)[number];
+
+/** Owned staged-output admission failure. `code` is the stable identity. */
+export class StagedOutputError extends Error {
+  readonly _tag = "StagedOutputError";
+
+  constructor(
+    readonly code: StagedOutputCode,
+    readonly detail?: Readonly<Record<string, string | number>>,
+    options?: ErrorOptions,
+  ) {
+    super(code, options);
+    this.name = "StagedOutputError";
+  }
+}
diff --git a/src/ghidra/GhidraAdmissionError.ts b/src/ghidra/GhidraAdmissionError.ts
new file mode 100644
index 0000000000..ed3e4af241
--- /dev/null
+++ b/src/ghidra/GhidraAdmissionError.ts
@@ -0,0 +1,66 @@
+const GHIDRA_ADMISSION_CODES = [
+  "existing_project_windows",
+  "existing_project_program_name",
+  "existing_project_psp",
+  "existing_project_dos",
+  "existing_project_raw_binary",
+  "existing_project_language_override",
+  "existing_project_mips_soft_float",
+  "existing_project_analysis",
+  "gamecube_dol_combined",
+  "psp_combined",
+  "psp_raw_binary",
+  "mips_soft_float_scope",
+  "language_override_dos",
+  "language_override_raw_binary",
+  "raw_binary_dos",
+  "invalid_environment_entry",
+  "invalid_jvm_argument",
+  "unterminated_quote",
+  "platform_override",
+  "argument_files_exceed_bound",
+  "nested_argument_file",
+  "argument_file_unreadable",
+  "argument_file_path_invalid",
+  "argument_files_require_scope",
+  "prepared_options_exceed_bound",
+  "output_unobserved",
+  "handshake_identity",
+  "response_shape",
+  "response_json",
+  "seed_path_differs",
+  "seed_changed",
+  "canonical_path",
+  "nesting_exceeds_limit",
+  "entry_kind",
+  "component_missing",
+  "loader_jar_missing",
+  "bytes_exceed_limit",
+  "properties_exceed_limit",
+  "component_changed",
+  "component_truncated",
+  "properties_invalid",
+  "metadata_mismatch",
+  "host_unsupported",
+  "inventory_exceeds_limit",
+  "not_jar",
+  "unregistered",
+  "path_differs",
+  "digest_differs",
+] as const;
+
+export type GhidraAdmissionCode = (typeof GHIDRA_ADMISSION_CODES)[number];
+
+/** Ghidra launch, extension, or profile admission failure. `code` is the stable identity. */
+export class GhidraAdmissionError extends Error {
+  readonly _tag = "GhidraAdmissionError";
+
+  constructor(
+    readonly code: GhidraAdmissionCode,
+    readonly detail?: Readonly<Record<string, string | number>>,
+    options?: ErrorOptions,
+  ) {
+    super(code, options);
+    this.name = "GhidraAdmissionError";
+  }
+}
diff --git a/src/ghidra/GhidraAnalysisSeeds.test.ts b/src/ghidra/GhidraAnalysisSeeds.test.ts
index a76b0003c6..7cf12e02a4 100644
--- a/src/ghidra/GhidraAnalysisSeeds.test.ts
+++ b/src/ghidra/GhidraAnalysisSeeds.test.ts
@@ -135,9 +135,9 @@ describe("Ghidra seed commitment", () => {
     ).rejects.toMatchObject({
       _tag: "ProviderAdapterError",
       diagnostics: {
-        reason: expect.stringMatching(
-          /changed after the analysis profile was committed/u,
-        ),
+        code: "seed_changed",
+        path: resolved.value.path,
+        reason: "seed_changed",
       },
     });
   });
diff --git a/src/ghidra/GhidraAnalysisSeeds.ts b/src/ghidra/GhidraAnalysisSeeds.ts
index 52d56a70fa..511bf1aaba 100644
--- a/src/ghidra/GhidraAnalysisSeeds.ts
+++ b/src/ghidra/GhidraAnalysisSeeds.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { createHash } from "node:crypto";
 import { mkdir, realpath, stat } from "node:fs/promises";
 import { isAbsolute, join } from "node:path";
@@ -228,15 +229,13 @@ export const snapshotGhidraAnalysisSeeds = async (
       if (
         (await resolveSeedPath(commitment.configured_path)) !== commitment.path
       )
-        throw new Error(
-          "Ghidra seed file resolved path differs from explicit configuration",
-        );
+        throw new GhidraAdmissionError("seed_path_differs");
       const entries = await readSeeds(commitment.path, resources, signal);
       const normalized = normalizedSeeds(entries);
       if (sha256(normalized) !== commitment.sha256)
-        throw new Error(
-          `Ghidra seed file changed after the analysis profile was committed: ${commitment.path}`,
-        );
+        throw new GhidraAdmissionError("seed_changed", {
+          path: commitment.path,
+        });
       const directory = join(runtimeRoot, "seeds");
       await mkdir(directory, { mode: 0o700 });
       const path = join(directory, "seeds.tsv");
diff --git a/src/ghidra/GhidraFileArtifacts.ts b/src/ghidra/GhidraFileArtifacts.ts
index 0e68bdbd93..2bfbb6abb9 100644
--- a/src/ghidra/GhidraFileArtifacts.ts
+++ b/src/ghidra/GhidraFileArtifacts.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { open } from "node:fs/promises";
 import type { ArtifactResourceScope } from "../artifacts/ArtifactResourceScope.js";
 import { ArtifactReaderFailure } from "../artifacts/ArtifactReader.js";
@@ -100,7 +101,18 @@ export const ghidraFileFailure = (
     return primary;
   });
   const { cause: primary, origin } = artifactFilePrimaryFacts(cause);
-  const reason = primary instanceof Error ? primary.message : String(primary);
+  const admission =
+    primary instanceof GhidraAdmissionError ? primary : undefined;
+  const reason =
+    admission?.code ??
+    (primary instanceof Error ? primary.message : String(primary));
+  const systemCode =
+    admission === undefined &&
+    primary instanceof Error &&
+    "code" in primary &&
+    typeof primary.code === "string"
+      ? primary.code
+      : undefined;
   const cleanup =
     cause instanceof ArtifactReaderFailure ? cause.cleanup : undefined;
   if (origin === "owned-or-classified" && primary instanceof AnalysisError) {
@@ -134,12 +146,10 @@ export const ghidraFileFailure = (
           cause,
           cleanup,
           diagnostics: {
+            ...admission?.detail,
             ...diagnostics,
-            ...(primary instanceof Error &&
-            "code" in primary &&
-            typeof primary.code === "string"
-              ? { system_code: primary.code }
-              : {}),
+            ...(admission === undefined ? {} : { code: admission.code }),
+            ...(systemCode === undefined ? {} : { system_code: systemCode }),
             ...(primary instanceof Error &&
             "syscall" in primary &&
             typeof primary.syscall === "string"
diff --git a/src/ghidra/GhidraInstallation.test.ts b/src/ghidra/GhidraInstallation.test.ts
index 4c8e375eed..f830572f61 100644
--- a/src/ghidra/GhidraInstallation.test.ts
+++ b/src/ghidra/GhidraInstallation.test.ts
@@ -917,7 +917,7 @@ describe("Ghidra malformed property admission", () => {
           name: "version",
           status: "failed",
           code: "version_unresolved",
-          detail: expect.stringContaining("Malformed Unicode escape"),
+          detail: expect.stringContaining("malformed_unicode_escape"),
         }),
         expect.objectContaining({
           name: "java",
diff --git a/src/ghidra/GhidraInstallationPolicy.ts b/src/ghidra/GhidraInstallationPolicy.ts
index ddc15219ff..f3cdba5013 100644
--- a/src/ghidra/GhidraInstallationPolicy.ts
+++ b/src/ghidra/GhidraInstallationPolicy.ts
@@ -1,4 +1,7 @@
-import { parseGhidraJavaProperties } from "./GhidraJavaProperties.js";
+import {
+  parseGhidraJavaProperties,
+  type GhidraJavaPropertiesCode,
+} from "./GhidraJavaProperties.js";
 import { ghidraConfigurationVersion } from "./GhidraReleasePolicy.js";
 
 /** One Java major bound declared by `application.properties`. */
@@ -24,7 +27,7 @@ export interface GhidraApplicationProperties {
   readonly javaMinimum: GhidraJavaBound;
   readonly javaMaximum: GhidraJavaBound;
   /** A malformed Java properties escape invalidates the entire file. */
-  readonly parseError: string | null;
+  readonly parseError: GhidraJavaPropertiesCode | null;
 }
 
 /** Read the version and Java bounds Ghidra publishes for one installation. */
diff --git a/src/ghidra/GhidraJavaLaunch.ts b/src/ghidra/GhidraJavaLaunch.ts
index 14a45159da..0a3bbc9e73 100644
--- a/src/ghidra/GhidraJavaLaunch.ts
+++ b/src/ghidra/GhidraJavaLaunch.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { snapshotEnvironment } from "../process/snapshotEnvironment.js";
 import { appendCallerPath } from "../filesystem/callerPath.js";
 import { dirname } from "node:path";
@@ -130,9 +131,11 @@ export const ghidraJavaLaunch = async (options: {
     const key =
       options.platform === "win32" ? sourceKey.toUpperCase() : sourceKey;
     if (separator < 1 || !/^[A-Za-z_][A-Za-z0-9_]*$/u.test(key))
-      throw new Error(
-        `Invalid Ghidra LaunchSupport environment entry: ${line}`,
-      );
+      throw new GhidraAdmissionError("invalid_environment_entry", {
+        check: separator < 1 ? "separator" : "key",
+        line: line.length <= 1024 ? line : line.slice(0, 1024),
+        ...(line.length <= 1024 ? {} : { line_truncated: 1 }),
+      });
     if ((environment[key] ?? "") === "")
       environment[key] = line.slice(separator + 1);
   }
@@ -172,12 +175,13 @@ export const ghidraJavaLaunch = async (options: {
   const vmArguments = configuredArguments.stdout
     .split(/\r?\n/u)
     .filter((line) => line !== "");
-  if (
-    vmArguments.some(
-      (argument) => !argument.startsWith("-") || argument.includes("\0"),
-    )
-  )
-    throw new Error("Invalid Ghidra LaunchSupport JVM argument");
+  const invalidArgument = vmArguments.find(
+    (argument) => !argument.startsWith("-") || argument.includes("\0"),
+  );
+  if (invalidArgument !== undefined)
+    throw new GhidraAdmissionError("invalid_jvm_argument", {
+      check: invalidArgument.includes("\0") ? "nul" : "prefix",
+    });
   rejectJvmPlatformOverrides(vmArguments);
   return {
     command,
diff --git a/src/ghidra/GhidraJavaOptions.ts b/src/ghidra/GhidraJavaOptions.ts
index 4dfd295aa9..e53ffbe3df 100644
--- a/src/ghidra/GhidraJavaOptions.ts
+++ b/src/ghidra/GhidraJavaOptions.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { randomUUID } from "node:crypto";
 import { join } from "node:path";
 import type { ArtifactResourceScope } from "../artifacts/ArtifactResourceScope.js";
@@ -32,19 +33,14 @@ export const jvmEnvironmentArguments = (value: string): readonly string[] => {
       active = true;
     }
   }
-  if (quote !== undefined)
-    throw new Error(
-      "Invalid quoted Ghidra LaunchSupport JVM environment option",
-    );
+  if (quote !== undefined) throw new GhidraAdmissionError("unterminated_quote");
   if (active) args.push(token);
   return args;
 };
 
 export const rejectJvmPlatformOverrides = (args: readonly string[]): void => {
   if (args.some((argument) => /^-Dos\.(?:arch|name)(?:=|$)/u.test(argument)))
-    throw new Error(
-      "Ghidra LaunchSupport may not override os.arch or os.name; the native decompiler was validated for the inspected JVM platform.",
-    );
+    throw new GhidraAdmissionError("platform_override");
 };
 
 /** Java launcher argfile grammar: quotes, escapes inside quotes, comments and line continuation are one parse. */
@@ -148,18 +144,16 @@ const readArgumentFile = (
           new RegularFileOperationCancelled(reason),
       });
       if (data === undefined)
-        throw new Error(
-          `JDK_JAVA_OPTIONS argument files exceed the ${String(OPTIONS_BYTES)}-byte cumulative admission bound.`,
-        );
+        throw new GhidraAdmissionError("argument_files_exceed_bound", {
+          budget_bytes: OPTIONS_BYTES,
+        });
       const text = new TextDecoder("utf-8", {
         fatal: true,
         ignoreBOM: true,
       }).decode(data);
       const tokens = argumentFileTokens(text);
       if (tokens.some(fileReference))
-        throw new Error(
-          "Ghidra LaunchSupport JDK_JAVA_OPTIONS argument files may not nest @ references.",
-        );
+        throw new GhidraAdmissionError("nested_argument_file");
       rejectJvmPlatformOverrides(tokens);
       return {
         text,
@@ -170,8 +164,9 @@ const readArgumentFile = (
     "follow",
   ).catch((cause: unknown) => {
     if (cause instanceof Error && "code" in cause && cause.code === "ENOENT")
-      throw new Error(
-        `Ghidra LaunchSupport JDK_JAVA_OPTIONS argument file is unreadable: ${path}`,
+      throw new GhidraAdmissionError(
+        "argument_file_unreadable",
+        { path },
         { cause },
       );
     throw cause;
@@ -209,9 +204,7 @@ export const prepareJdkJavaOptions = async (
   const resources = options.resources;
   const directory = options.directory;
   if (resources === undefined || directory === undefined)
-    throw new Error(
-      "JDK_JAVA_OPTIONS argument files require a caller-owned resource scope and runtime root.",
-    );
+    throw new GhidraAdmissionError("argument_files_require_scope");
   const snapshots = new Map<
     string,
     {
@@ -233,9 +226,9 @@ export const prepareJdkJavaOptions = async (
       let snapshot = snapshots.get(path);
       if (snapshot === undefined) {
         if (path === "" || path.includes("\0"))
-          throw new Error(
-            "Ghidra LaunchSupport JDK_JAVA_OPTIONS argument file is unreadable.",
-          );
+          throw new GhidraAdmissionError("argument_file_path_invalid", {
+            check: path === "" ? "empty" : "nul",
+          });
         const content = await readArgumentFile(
           path,
           resources,
@@ -257,9 +250,9 @@ export const prepareJdkJavaOptions = async (
       } else {
         bytes += snapshot.bytes;
         if (bytes > OPTIONS_BYTES)
-          throw new Error(
-            `JDK_JAVA_OPTIONS argument files exceed the ${String(OPTIONS_BYTES)}-byte cumulative admission bound.`,
-          );
+          throw new GhidraAdmissionError("argument_files_exceed_bound", {
+            budget_bytes: OPTIONS_BYTES,
+          });
       }
       replacement = `@${snapshot.path}`;
       if (snapshot.disablesExpansion) expansionEnabled = false;
@@ -268,9 +261,9 @@ export const prepareJdkJavaOptions = async (
     encodedBytes +=
       Buffer.byteLength(encoded) + (prepared.length === 0 ? 0 : 1);
     if (encodedBytes > OPTIONS_BYTES)
-      throw new Error(
-        `Prepared JDK_JAVA_OPTIONS exceeds the ${String(OPTIONS_BYTES)}-byte environment admission bound.`,
-      );
+      throw new GhidraAdmissionError("prepared_options_exceed_bound", {
+        budget_bytes: OPTIONS_BYTES,
+      });
     prepared.push(encoded);
   }
   assertActive();
diff --git a/src/ghidra/GhidraJavaProbe.ts b/src/ghidra/GhidraJavaProbe.ts
index 8d4bb59362..e890695d21 100644
--- a/src/ghidra/GhidraJavaProbe.ts
+++ b/src/ghidra/GhidraJavaProbe.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { retainOwnedCommandCleanup } from "../providers/OwnedCommandCleanup.js";
 import { analysisClientFailureForOperation } from "../providers/AnalysisClientFailure.js";
 import { randomUUID } from "node:crypto";
@@ -184,7 +185,7 @@ const observeGhidraJava = async (
       },
     );
     if (interpreted === undefined)
-      throw new Error("Java command completed without an output observation");
+      throw new GhidraAdmissionError("output_unobserved");
     return interpreted;
   } catch (cause: unknown) {
     const commandFailure =
diff --git a/src/ghidra/GhidraJavaProperties.ts b/src/ghidra/GhidraJavaProperties.ts
index d41b446bd1..99cf8cf157 100644
--- a/src/ghidra/GhidraJavaProperties.ts
+++ b/src/ghidra/GhidraJavaProperties.ts
@@ -1,9 +1,18 @@
 import type { Result } from "../domain/result.js";
 
+const GHIDRA_JAVA_PROPERTIES_CODES = [
+  "trailing_escape",
+  "malformed_unicode_escape",
+] as const;
+
+/** Stable identity for a Java properties escape that invalidates the file. */
+export type GhidraJavaPropertiesCode =
+  (typeof GHIDRA_JAVA_PROPERTIES_CODES)[number];
+
 /** Parse Java Properties.load(InputStream) syntax from its ISO-8859-1 text. */
 export const parseGhidraJavaProperties = (
   content: string,
-): Result<ReadonlyMap<string, string>, string> => {
+): Result<ReadonlyMap<string, string>, GhidraJavaPropertiesCode> => {
   const values = new Map<string, string>();
   for (const line of logicalPropertyLines(content)) {
     let start = 0;
@@ -88,7 +97,9 @@ function* logicalPropertyLines(content: string): Generator<string> {
   if (continuing) yield logical;
 }
 
-const decodePropertyEscapes = (value: string): Result<string, string> => {
+const decodePropertyEscapes = (
+  value: string,
+): Result<string, GhidraJavaPropertiesCode> => {
   let result = "";
   for (let index = 0; index < value.length; index += 1) {
     const character = value[index];
@@ -97,8 +108,7 @@ const decodePropertyEscapes = (value: string): Result<string, string> => {
       continue;
     }
     const escaped = value[++index];
-    if (escaped === undefined)
-      return { ok: false, error: "Trailing escape in Java properties value" };
+    if (escaped === undefined) return { ok: false, error: "trailing_escape" };
     if (escaped === "t") result += "\t";
     else if (escaped === "n") result += "\n";
     else if (escaped === "r") result += "\r";
@@ -108,7 +118,7 @@ const decodePropertyEscapes = (value: string): Result<string, string> => {
       if (digits.length !== 4 || !/^[0-9a-f]{4}$/iu.test(digits))
         return {
           ok: false,
-          error: "Malformed Unicode escape in Java properties file",
+          error: "malformed_unicode_escape",
         };
       result += String.fromCharCode(Number.parseInt(digits, 16));
       index += 4;
diff --git a/src/ghidra/GhidraLauncher.ts b/src/ghidra/GhidraLauncher.ts
index 6e1c99cedd..410fc1d7b9 100644
--- a/src/ghidra/GhidraLauncher.ts
+++ b/src/ghidra/GhidraLauncher.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { copyExistingGhidraProject } from "./GhidraProjectSnapshot.js";
 import type { ArtifactResourceScope } from "../artifacts/ArtifactResourceScope.js";
 import { GHIDRA_BRIDGE_SOURCES } from "./GhidraBridgeSources.js";
@@ -810,41 +811,25 @@ const validateExistingProjectOptions = (
     // The pre-imported project carries its own analysis; every import-time
     // selection is therefore rejected instead of silently ignored.
     if ((options.platform ?? process.platform) === "win32")
-      throw new Error(
-        "An existing Ghidra project cannot be opened on the Windows launch path.",
-      );
+      throw new GhidraAdmissionError("existing_project_windows");
     if (existing.programName.trim() === "")
-      throw new Error(
-        "An existing Ghidra project requires a program name for -process.",
-      );
+      throw new GhidraAdmissionError("existing_project_program_name");
     if (options.psp === true)
-      throw new Error(
-        "An existing Ghidra project cannot be combined with a PSP ELF import.",
-      );
+      throw new GhidraAdmissionError("existing_project_psp");
     if (options.dosMz === true || options.dosCom === true)
-      throw new Error(
-        "An existing Ghidra project cannot be combined with a DOS import.",
-      );
+      throw new GhidraAdmissionError("existing_project_dos");
     if (rawBinary !== undefined)
-      throw new Error(
-        "An existing Ghidra project cannot be combined with a raw-binary import.",
-      );
+      throw new GhidraAdmissionError("existing_project_raw_binary");
     if (override !== undefined)
-      throw new Error(
-        "A Ghidra language override cannot be combined with an existing project.",
-      );
+      throw new GhidraAdmissionError("existing_project_language_override");
     if (options.mipsSoftFloat === true)
-      throw new Error(
-        "MIPS soft-float storage applies only to a fresh import.",
-      );
+      throw new GhidraAdmissionError("existing_project_mips_soft_float");
     if (
       options.seedPath !== undefined ||
       options.analysisSeeds !== undefined ||
       (options.disabledAnalyzers?.length ?? 0) > 0
     )
-      throw new Error(
-        "An existing project opens without analysis; analysis seeds and analyzer overrides do not apply.",
-      );
+      throw new GhidraAdmissionError("existing_project_analysis");
   }
 };
 
@@ -871,22 +856,16 @@ export const ghidraHeadlessArguments = (
       rawBinary !== undefined ||
       override !== undefined)
   )
-    throw new Error(
-      "A GameCube DOL import cannot be combined with another loader, language override, or analysis lane; its language is committed in the gamecubeDol option.",
-    );
+    throw new GhidraAdmissionError("gamecube_dol_combined");
   if (
     options.psp === true &&
     (options.dosMz === true ||
       options.dosCom === true ||
       override !== undefined)
   )
-    throw new Error(
-      "A PSP ELF import cannot be combined with DOS or a generic Ghidra language override.",
-    );
+    throw new GhidraAdmissionError("psp_combined");
   if (options.psp === true && rawBinary !== undefined)
-    throw new Error(
-      "A PSP ELF import cannot be combined with a raw-binary import.",
-    );
+    throw new GhidraAdmissionError("psp_raw_binary");
   if (
     options.mipsSoftFloat === true &&
     (options.psp === true ||
@@ -894,27 +873,19 @@ export const ghidraHeadlessArguments = (
       options.dosCom === true ||
       rawBinary !== undefined)
   )
-    throw new Error(
-      "MIPS soft-float storage applies only to a generic MIPS ELF import.",
-    );
+    throw new GhidraAdmissionError("mips_soft_float_scope");
   if (
     override !== undefined &&
     (options.dosMz === true || options.dosCom === true)
   )
-    throw new Error(
-      "A Ghidra language override cannot be combined with a DOS import.",
-    );
+    throw new GhidraAdmissionError("language_override_dos");
   if (override !== undefined && rawBinary !== undefined)
-    throw new Error(
-      "A Ghidra language override cannot be combined with a raw-binary import.",
-    );
+    throw new GhidraAdmissionError("language_override_raw_binary");
   if (
     rawBinary !== undefined &&
     (options.dosMz === true || options.dosCom === true)
   )
-    throw new Error(
-      "A raw-binary import cannot be combined with a DOS import.",
-    );
+    throw new GhidraAdmissionError("raw_binary_dos");
   return [
     options.projectRoot,
     existing?.projectName ?? "rea-project",
diff --git a/src/ghidra/GhidraPspExtension.ts b/src/ghidra/GhidraPspExtension.ts
index c3e9b9feb2..2c3257777e 100644
--- a/src/ghidra/GhidraPspExtension.ts
+++ b/src/ghidra/GhidraPspExtension.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { createHash } from "node:crypto";
 import { lstat, opendir, realpath } from "node:fs/promises";
 import { isAbsolute, join } from "node:path";
@@ -70,17 +71,15 @@ const fingerprint = async (
 ): Promise<GhidraPspExtension> => {
   assertArtifactReadActive(signal);
   if (!isAbsolute(root) || (await realpath(root)) !== root)
-    throw new Error(
-      "The installed Allegrex directory must be a canonical non-symlink path.",
-    );
+    throw new GhidraAdmissionError("canonical_path");
   const files: string[] = [];
   let entries = 1; // The root itself consumes one inventory entry.
   const visit = async (relative: string, depth: number): Promise<void> => {
     assertArtifactReadActive(signal);
     if (depth > MAX_DEPTH)
-      throw new Error(
-        "Allegrex extension directory nesting exceeds the inspection limit.",
-      );
+      throw new GhidraAdmissionError("nesting_exceeds_limit", {
+        max_depth: MAX_DEPTH,
+      });
     const path = join(root, relative);
     const metadata = await lstat(path);
     if (metadata.isDirectory()) {
@@ -99,17 +98,16 @@ const fingerprint = async (
         );
     } else if (metadata.isFile()) {
       files.push(relative);
-    } else
-      throw new Error(
-        `Allegrex extension entries must be regular files or directories: ${relative}`,
-      );
+    } else throw new GhidraAdmissionError("entry_kind", { relative });
   };
   await visit("", 0);
   for (const required of REQUIRED)
     if (!files.includes(required))
-      throw new Error(`Missing installed Allegrex component: ${required}`);
+      throw new GhidraAdmissionError("component_missing", {
+        component: required,
+      });
   if (!files.some((path) => path.startsWith("lib/") && path.endsWith(".jar")))
-    throw new Error("The installed Allegrex extension has no loader JAR.");
+    throw new GhidraAdmissionError("loader_jar_missing");
   const hash = createHash("sha256");
   let bytesRead = 0;
   let properties = Buffer.alloc(0);
@@ -125,13 +123,13 @@ const fingerprint = async (
           !Number.isSafeInteger(before.size) ||
           before.size > MAX_BYTES - bytesRead
         )
-          throw new Error(
-            "Allegrex extension bytes exceed the inspection limit.",
-          );
+          throw new GhidraAdmissionError("bytes_exceed_limit", {
+            max_bytes: MAX_BYTES,
+          });
         if (relative === "extension.properties" && before.size > 65536)
-          throw new Error(
-            "Allegrex extension properties exceed the inspection limit.",
-          );
+          throw new GhidraAdmissionError("properties_exceed_limit", {
+            max_bytes: 65536,
+          });
         hash.update(JSON.stringify([relative, before.size]));
         const buffer = Buffer.alloc(Math.min(65536, before.size + 1));
         let offset = 0;
@@ -150,23 +148,19 @@ const fingerprint = async (
           if (bytesRead === 0) break;
           offset += bytesRead;
           if (offset > before.size)
-            throw new Error(
-              `Allegrex component changed during inspection: ${relative}`,
-            );
+            throw new GhidraAdmissionError("component_changed", { relative });
           const chunk = buffer.subarray(0, bytesRead);
           hash.update(chunk);
           if (relative === "extension.properties")
             chunks.push(Buffer.from(chunk));
         }
         if (offset !== before.size)
-          throw new Error(`Truncated Allegrex component: ${relative}`);
+          throw new GhidraAdmissionError("component_truncated", { relative });
         if (
           !sameRegularFileState(before, await handle.stat()) ||
           !sameRegularFileState(before, await lstat(path))
         )
-          throw new Error(
-            `Allegrex component changed during inspection: ${relative}`,
-          );
+          throw new GhidraAdmissionError("component_changed", { relative });
         bytesRead += before.size;
         if (relative === "extension.properties")
           properties = Buffer.concat(chunks);
@@ -179,18 +173,18 @@ const fingerprint = async (
     properties.toString("latin1"),
   );
   if (!parsedProperties.ok)
-    throw new Error(
-      `Invalid Allegrex extension properties: ${parsedProperties.error}`,
-    );
+    throw new GhidraAdmissionError("properties_invalid", {
+      parser_code: parsedProperties.error,
+    });
   const property = (name: string): string | undefined =>
     parsedProperties.value.get(name);
   if (
     property("name") !== "ghidra-allegrex" ||
     property("version") !== ghidraVersion
   )
-    throw new Error(
-      `Allegrex extension metadata does not match the selected Ghidra ${ghidraVersion}; install or rebuild a compatible extension.`,
-    );
+    throw new GhidraAdmissionError("metadata_mismatch", {
+      ghidra_version: ghidraVersion,
+    });
   assertArtifactReadActive(signal);
   return {
     id: "ghidra-allegrex",
@@ -213,9 +207,10 @@ export const resolveGhidraPspExtension = async (
       installation.platform !== "linux" ||
       installation.architecture !== "x64"
     )
-      throw new Error(
-        "The initial PSP profile requires a supported Linux x64 Ghidra installation.",
-      );
+      throw new GhidraAdmissionError("host_unsupported", {
+        platform: installation.platform,
+        architecture: installation.architecture,
+      });
     const root = join(
       await realpath(installation.installDir),
       "Ghidra",
@@ -241,7 +236,16 @@ const ghidraPspInspectionError = (cause: unknown): AnalysisError => {
   const cleanup =
     cause instanceof ArtifactReaderFailure ? cause.cleanup : undefined;
   const { cause: primary } = artifactFilePrimaryFacts(cause);
-  const reason = `PSP_EXTENSION_UNAVAILABLE: ${primary instanceof Error ? primary.message : String(primary)} Use a compatible caller-installed ghidra-allegrex under GHIDRA_INSTALL_DIR/Ghidra/Extensions; REA does not install it.`;
+  const admission =
+    primary instanceof GhidraAdmissionError ? primary : undefined;
+  const identity =
+    admission?.code ??
+    (primary instanceof Error ? primary.message : String(primary));
+  const reason = `PSP_EXTENSION_UNAVAILABLE: ${identity} Use a compatible caller-installed ghidra-allegrex under GHIDRA_INSTALL_DIR/Ghidra/Extensions; REA does not install it.`;
+  const diagnostics =
+    admission === undefined
+      ? undefined
+      : { code: admission.code, ...admission.detail };
   const error =
     cause instanceof ArtifactReaderFailure && cause.reason === "cancelled"
       ? new AnalysisCancelledError("resolve_analysis_profile", {
@@ -256,6 +260,7 @@ const ghidraPspInspectionError = (cause: unknown): AnalysisError => {
             cause,
             userMessage: reason,
             cleanup,
+            ...(diagnostics === undefined ? {} : { diagnostics }),
           },
         );
   bindArtifactFileCleanup(cause, error);
@@ -282,9 +287,9 @@ const readChildren = async (
       assertArtifactReadActive(signal);
       if (child === null) break;
       if (names.length >= remainingEntries)
-        throw new Error(
-          "Allegrex extension inventory exceeds the inspection limit.",
-        );
+        throw new GhidraAdmissionError("inventory_exceeds_limit", {
+          max_entries: MAX_ENTRIES,
+        });
       names.push(child.name);
     }
     outcome = { kind: "completed", names };
diff --git a/src/ghidra/GhidraSessionError.ts b/src/ghidra/GhidraSessionError.ts
index a53ecf205c..33f3d6e532 100644
--- a/src/ghidra/GhidraSessionError.ts
+++ b/src/ghidra/GhidraSessionError.ts
@@ -7,6 +7,7 @@ import type { JsonValue } from "../domain/jsonValue.js";
 import { DarwinProcessOwnershipInspectionError } from "../process/DarwinProcessRunTokenReader.js";
 import { boundedUtf8Text } from "../process/boundedUtf8Text.js";
 import type { GhidraDiagnosticsScope } from "./GhidraDiagnostics.js";
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { GhidraLaunchSupportError } from "./GhidraJavaLaunch.js";
 import {
   GhidraLaunchError,
@@ -281,6 +282,7 @@ const describeErrorCause = (
     message: message.text,
     ...(message.truncated ? { message_truncated: true } : {}),
     ...causeCode(cause, redact),
+    ...causeAdmissionDetail(cause, redact),
     ...causeSignal(cause, redact),
     ...causeCommandOutcome(cause, redact),
     ...causeCompilerOutcome(cause, redact),
@@ -319,6 +321,24 @@ const causeCommandOutcome = (
   };
 };
 
+const causeAdmissionDetail = (
+  cause: Error,
+  redact: (value: string, incomplete?: boolean) => string,
+): Record<string, JsonValue> => {
+  if (!(cause instanceof GhidraAdmissionError) || cause.detail === undefined)
+    return {};
+  const detail: Record<string, JsonValue> = {};
+  for (const [key, value] of Object.entries(cause.detail)) {
+    if (typeof value === "number") {
+      detail[key] = value;
+      continue;
+    }
+    const bounded = boundedUtf8Text(redact(value), MAX_CAUSE_FIELD_BYTES);
+    detail[key] = bounded.text;
+  }
+  return { detail };
+};
+
 const causeCode = (
   cause: Error,
   redact: (value: string, incomplete?: boolean) => string,
diff --git a/src/ghidra/GhidraSessionValues.test.ts b/src/ghidra/GhidraSessionValues.test.ts
index ee45839c58..f3831fc3fd 100644
--- a/src/ghidra/GhidraSessionValues.test.ts
+++ b/src/ghidra/GhidraSessionValues.test.ts
@@ -52,14 +52,16 @@ describe("Ghidra DOS import commitment", () => {
     });
   });
   it("rejects a 32-bit interpretation even when artifact and profile hashes match", () => {
-    expect(rejectedHandshake(session("x86:LE:32:default")).message).toBe(
-      "Ghidra bridge handshake identity is invalid",
-    );
+    expect(rejectedHandshake(session("x86:LE:32:default"))).toMatchObject({
+      _tag: "GhidraAdmissionError",
+      code: "handshake_identity",
+    });
   });
   it("rejects compiler drift independently of the language", () => {
-    expect(rejectedHandshake(session(undefined, "windows")).message).toBe(
-      "Ghidra bridge handshake identity is invalid",
-    );
+    expect(rejectedHandshake(session(undefined, "windows"))).toMatchObject({
+      _tag: "GhidraAdmissionError",
+      code: "handshake_identity",
+    });
   });
 });
 
diff --git a/src/ghidra/GhidraSessionValues.ts b/src/ghidra/GhidraSessionValues.ts
index 8bb0903c75..684330bd8d 100644
--- a/src/ghidra/GhidraSessionValues.ts
+++ b/src/ghidra/GhidraSessionValues.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { ghidraSeedReportSchema } from "./GhidraAnalysisSeeds.js";
 import { ghidraDisabledAnalyzerReportSchema } from "./GhidraDisabledAnalyzers.js";
 import { z } from "zod";
@@ -191,7 +192,7 @@ export const parseGhidraSessionInfo = (
         parsed.data.analysis_complete === null ||
         parsed.data.analysis_complete === parsed.data.analysis_timed_out)
   )
-    return err(new Error("Ghidra bridge handshake identity is invalid"));
+    return err(new GhidraAdmissionError("handshake_identity"));
   return ok(parsed.data);
 };
 
diff --git a/src/ghidra/extensions/GhidraExtensions.test.ts b/src/ghidra/extensions/GhidraExtensions.test.ts
index 2df197d977..02242f45bd 100644
--- a/src/ghidra/extensions/GhidraExtensions.test.ts
+++ b/src/ghidra/extensions/GhidraExtensions.test.ts
@@ -181,7 +181,12 @@ describe("optional Ghidra extension boundary", () => {
       snapshotGhidraExtensions([extension], await root(), resources),
     ).rejects.toMatchObject({
       _tag: "ProviderAdapterError",
-      diagnostics: { reason: expect.stringContaining("digest differs") },
+      diagnostics: {
+        code: "digest_differs",
+        id: extension.id,
+        reason: "digest_differs",
+        path: extension.path,
+      },
     });
   });
   it("rejects nonexistent, empty and non-JAR artifacts with useful reasons", async () => {
@@ -268,18 +273,19 @@ describe("optional Ghidra extension boundary", () => {
     if (!resolved.ok)
       expect(resolved.error._tag).toBe("AnalysisCancelledError");
   });
-  it("refuses traversal identities in an imported extension profile", () => {
-    expect(
-      ghidraExtensionSchema.safeParse({
-        id: "../escape",
-        path: "/fixture.jar",
-        configured_path: "/fixture.jar",
-        sha256: "a".repeat(64),
-        integration_api: 1,
-        entry_class: "ignored",
-      }).success,
-    ).toBe(false);
-  });
+});
+
+it("refuses traversal identities in an imported extension profile", () => {
+  expect(
+    ghidraExtensionSchema.safeParse({
+      id: "../escape",
+      path: "/fixture.jar",
+      configured_path: "/fixture.jar",
+      sha256: "a".repeat(64),
+      integration_api: 1,
+      entry_class: "ignored",
+    }).success,
+  ).toBe(false);
 });
 
 describe("Ghidra extension profile and producer validation", () => {
@@ -384,7 +390,11 @@ describe("Ghidra extension profile and producer validation", () => {
       ),
     ).rejects.toMatchObject({
       _tag: "ProviderAdapterError",
-      diagnostics: { reason: expect.stringContaining("resolved path differs") },
+      diagnostics: {
+        code: "path_differs",
+        id: second.extension.id,
+        reason: "path_differs",
+      },
     });
   });
   it("rejects unregistered descriptors before snapshot filesystem writes", async () => {
@@ -398,7 +408,11 @@ describe("Ghidra extension profile and producer validation", () => {
       ),
     ).rejects.toMatchObject({
       _tag: "ProviderAdapterError",
-      diagnostics: { reason: expect.stringContaining("Unregistered") },
+      diagnostics: {
+        code: "unregistered",
+        id: "unknown",
+        reason: "unregistered",
+      },
     });
   });
 });
diff --git a/src/ghidra/extensions/GhidraExtensions.ts b/src/ghidra/extensions/GhidraExtensions.ts
index 890ead74c3..c7aaa74cc0 100644
--- a/src/ghidra/extensions/GhidraExtensions.ts
+++ b/src/ghidra/extensions/GhidraExtensions.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "../GhidraAdmissionError.js";
 import { createHash } from "node:crypto";
 import { realpath, mkdir } from "node:fs/promises";
 import { isAbsolute, join } from "node:path";
@@ -86,7 +87,7 @@ const readJar = (
     signal,
     (bytes) => {
       if (bytes.length < 4 || bytes.readUInt32LE(0) !== 0x04034b50)
-        throw new Error(`Ghidra extension is not a JAR: ${path}`);
+        throw new GhidraAdmissionError("not_jar", { path });
       return bytes;
     },
   );
@@ -213,13 +214,13 @@ export const snapshotGhidraExtensions = async (
           adapter === undefined ||
           adapter.entryClass !== extension.entry_class
         )
-          throw new Error(
-            `Unregistered Ghidra extension identity: ${extension.id}`,
-          );
+          throw new GhidraAdmissionError("unregistered", {
+            id: extension.id,
+          });
         if ((await realpath(extension.configured_path)) !== extension.path)
-          throw new Error(
-            `Ghidra extension resolved path differs from explicit configuration: ${extension.id}`,
-          );
+          throw new GhidraAdmissionError("path_differs", {
+            id: extension.id,
+          });
       }
       const directory = join(runtimeRoot, "extensions");
       await mkdir(directory, { mode: 0o700 });
@@ -229,9 +230,10 @@ export const snapshotGhidraExtensions = async (
         if (
           createHash("sha256").update(bytes).digest("hex") !== extension.sha256
         )
-          throw new Error(
-            `Ghidra extension digest differs from committed profile: ${extension.id} (${extension.path})`,
-          );
+          throw new GhidraAdmissionError("digest_differs", {
+            id: extension.id,
+            path: extension.path,
+          });
         const path = join(directory, `${extension.id}.jar`);
         await writeGhidraProfileArtifact(path, bytes, resources, signal);
         result.push({ ...extension, path });
diff --git a/src/ghidra/protocol.ts b/src/ghidra/protocol.ts
index 150486c3c5..89949b968b 100644
--- a/src/ghidra/protocol.ts
+++ b/src/ghidra/protocol.ts
@@ -1,3 +1,4 @@
+import { GhidraAdmissionError } from "./GhidraAdmissionError.js";
 import { z } from "zod";
 
 import { jsonValueSchema, type JsonValue } from "../domain/jsonValue.js";
@@ -44,11 +45,9 @@ export const parseGhidraResponseLine = (
     const response = responseSchema.safeParse(parsed);
     return response.success
       ? ok(response.data)
-      : err(new Error("Ghidra bridge response has an invalid shape"));
+      : err(new GhidraAdmissionError("response_shape"));
   } catch (cause: unknown) {
-    return err(
-      new Error("Ghidra bridge response is not valid JSON", { cause }),
-    );
+    return err(new GhidraAdmissionError("response_json", undefined, { cause }));
   }
 };
 
diff --git a/src/process/DarwinProcessRunTokenReader.ts b/src/process/DarwinProcessRunTokenReader.ts
index fd2a50407f..c54ee09350 100644
--- a/src/process/DarwinProcessRunTokenReader.ts
+++ b/src/process/DarwinProcessRunTokenReader.ts
@@ -1,3 +1,4 @@
+import { ProcessAdmissionError } from "./ProcessAdmissionError.js";
 import { mkdir, mkdtemp, rm } from "node:fs/promises";
 import { rmSync } from "node:fs";
 import { tmpdir } from "node:os";
@@ -579,10 +580,10 @@ export const createDarwinProcessRunTokenReader = (
   };
 
   const compile = async (signal?: AbortSignal): Promise<string> => {
-    if (closed) throw new Error("Darwin process token reader is closed");
+    if (closed) throw new ProcessAdmissionError("reader_closed");
     signal?.throwIfAborted();
     while (true) {
-      if (closed) throw new Error("Darwin process token reader is closed");
+      if (closed) throw new ProcessAdmissionError("reader_closed");
       signal?.throwIfAborted();
       if (executable !== undefined) return executable;
       if (compilation === undefined && root !== undefined) {
@@ -642,7 +643,7 @@ export const createDarwinProcessRunTokenReader = (
     signal?: AbortSignal,
   ): Promise<string> => {
     if (closed)
-      return Promise.reject(new Error("Darwin process token reader is closed"));
+      return Promise.reject(new ProcessAdmissionError("reader_closed"));
     const pending = (async () => {
       const binary = await compile(signal);
       const { stdout } = await execFileOutput(binary, arguments_, {
@@ -670,25 +671,21 @@ export const createDarwinProcessRunTokenReader = (
     const stdout = await runHelper(pids, signal);
     const decoded = safeParseJson(stdout);
     if (!decoded.ok)
-      throw new Error(
-        `macOS process token helper returned invalid JSON: ${decoded.error}`,
+      throw new ProcessAdmissionError(
+        "token_json_invalid",
+        { parser: decoded.error },
         { cause: decoded.cause },
       );
     const parsed = responseSchema.safeParse(decoded.value);
     if (!parsed.success)
-      throw new Error(
-        "macOS process token helper returned an invalid response",
-        {
-          cause: parsed.error,
-        },
-      );
+      throw new ProcessAdmissionError("token_response_invalid", undefined, {
+        cause: parsed.error,
+      });
     const requested = new Set(processes.map(({ pid }) => pid));
     const observations = new Map<number, ProcessRunTokenObservation>();
     for (const result of parsed.data.results) {
       if (!requested.has(result.pid) || observations.has(result.pid))
-        throw new Error(
-          "macOS process token helper returned an unexpected PID set",
-        );
+        throw new ProcessAdmissionError("token_pid_set");
       observations.set(
         result.pid,
         result.state === "readable"
@@ -701,9 +698,7 @@ export const createDarwinProcessRunTokenReader = (
       );
     }
     if (observations.size !== requested.size)
-      throw new Error(
-        "macOS process token helper returned an incomplete PID set",
-      );
+      throw new ProcessAdmissionError("token_pid_incomplete");
     return observations;
   };
 
@@ -716,25 +711,21 @@ export const createDarwinProcessRunTokenReader = (
     const stdout = await runHelper(["--identities", ...pids], signal);
     const decoded = safeParseJson(stdout);
     if (!decoded.ok)
-      throw new Error(
-        `macOS process identity helper returned invalid JSON: ${decoded.error}`,
+      throw new ProcessAdmissionError(
+        "identity_json_invalid",
+        { parser: decoded.error },
         { cause: decoded.cause },
       );
     const parsed = identityResponseSchema.safeParse(decoded.value);
     if (!parsed.success)
-      throw new Error(
-        "macOS process identity helper returned an invalid response",
-        {
-          cause: parsed.error,
-        },
-      );
+      throw new ProcessAdmissionError("identity_response_invalid", undefined, {
+        cause: parsed.error,
+      });
     const requested = new Set(processes.map(({ pid }) => pid));
     const observations = new Map<number, ProcessIdentityObservation>();
     for (const result of parsed.data.results) {
       if (!requested.has(result.pid) || observations.has(result.pid))
-        throw new Error(
-          "macOS process identity helper returned an unexpected PID set",
-        );
+        throw new ProcessAdmissionError("identity_pid_set");
       observations.set(
         result.pid,
         result.state === "readable"
@@ -768,9 +759,7 @@ export const createDarwinProcessRunTokenReader = (
       );
     }
     if (observations.size !== requested.size)
-      throw new Error(
-        "macOS process identity helper returned an incomplete PID set",
-      );
+      throw new ProcessAdmissionError("identity_pid_incomplete");
     return observations;
   };
 
diff --git a/src/process/LinuxResourceLimits.test.ts b/src/process/LinuxResourceLimits.test.ts
index 6cf5f5787d..f80959495a 100644
--- a/src/process/LinuxResourceLimits.test.ts
+++ b/src/process/LinuxResourceLimits.test.ts
@@ -176,7 +176,9 @@ it.each([
       expect(physical.outcome.value).toEqual(configured);
     else
       expect(physical.outcome.cause).toMatchObject({
-        message: "Cannot establish inherited Linux limit: Max address space",
+        _tag: "ProcessAdmissionError",
+        code: "limit_unreadable",
+        detail: { limit: "address_space_bytes" },
       });
     expect(physical.owner.handle.fd).toBeGreaterThanOrEqual(0);
     if (scoped)
@@ -267,9 +269,11 @@ it.each([16 * 1024, 16 * 1024 + 1])(
     const prefix = report("unlimited unlimited");
     await kernelReportFixture(prefix.padEnd(bytes, " "));
     kernel.maximumRead = Buffer.byteLength(prefix);
-    await expect(readLinuxResourceLimits(configured)).rejects.toThrow(
-      "Inherited Linux limits exceed the report budget.",
-    );
+    await expect(readLinuxResourceLimits(configured)).rejects.toMatchObject({
+      _tag: "ProcessAdmissionError",
+      code: "report_exceeds_budget",
+      detail: { budget_bytes: 16 * 1024 },
+    });
     expect(kernel.reads.length).toBeGreaterThan(1);
     expect(
       kernel.reads.every(
diff --git a/src/process/LinuxResourceLimits.ts b/src/process/LinuxResourceLimits.ts
index d05a82d0fc..53a8a69d56 100644
--- a/src/process/LinuxResourceLimits.ts
+++ b/src/process/LinuxResourceLimits.ts
@@ -1,3 +1,4 @@
+import { ProcessAdmissionError } from "./ProcessAdmissionError.js";
 import { open } from "node:fs/promises";
 import { readFileHandleRange } from "../filesystem/readFileHandleRange.js";
 import { withArtifactFileHandle } from "../artifacts/ArtifactFileOperation.js";
@@ -57,12 +58,12 @@ export const clampLinuxResourceLimits = (
       .filter((line) => line.startsWith(`${rows[key]} `));
     const values = matches[0]?.slice(rows[key].length).trim().split(/\s+/u);
     if (matches.length !== 1 || values === undefined || values.length !== 3)
-      throw new Error(`Cannot establish inherited Linux limit: ${rows[key]}`);
+      throw new ProcessAdmissionError("limit_unreadable", { limit: key });
     let ceiling = BigInt(configured[key]);
     for (const token of values.slice(0, 2)) {
       if (token === "unlimited") continue;
       if (!/^[0-9]+$/u.test(token))
-        throw new Error(`Invalid inherited Linux limit: ${rows[key]}`);
+        throw new ProcessAdmissionError("limit_invalid", { limit: key });
       const value = BigInt(token);
       if (value < ceiling) ceiling = value;
     }
@@ -86,7 +87,9 @@ export const readLinuxResourceLimits = async (
       const reportBudget = 16 * 1024;
       const buffer = await readFileHandleRange(handle, 0, reportBudget);
       if (buffer.length === reportBudget)
-        throw new Error("Inherited Linux limits exceed the report budget.");
+        throw new ProcessAdmissionError("report_exceeds_budget", {
+          budget_bytes: reportBudget,
+        });
       return clampLinuxResourceLimits(configured, buffer.toString("utf8"));
     },
   );
diff --git a/src/process/OwnedWorkerRuntime.test.ts b/src/process/OwnedWorkerRuntime.test.ts
index 6b9f67a223..73e400b366 100644
--- a/src/process/OwnedWorkerRuntime.test.ts
+++ b/src/process/OwnedWorkerRuntime.test.ts
@@ -331,9 +331,10 @@ it("runs deferred delegated cleanup before registering a pending start acquisiti
     expect(stopped.status).not.toBe("incomplete");
     runtime.retainForCleanup();
 
-    await expect(runtime.start(startOptions())).rejects.toThrow(
-      "Owned worker runtime is closing",
-    );
+    await expect(runtime.start(startOptions())).rejects.toMatchObject({
+      _tag: "ProcessAdmissionError",
+      code: "runtime_closing",
+    });
     expect(delegateTimedOut).toBe(false);
     await delegatedClose;
     expect(runtime.rootPath).toBeUndefined();
diff --git a/src/process/OwnedWorkerRuntime.ts b/src/process/OwnedWorkerRuntime.ts
index 0e93602ecc..0b9f66c7ac 100644
--- a/src/process/OwnedWorkerRuntime.ts
+++ b/src/process/OwnedWorkerRuntime.ts
@@ -1,3 +1,4 @@
+import { ProcessAdmissionError } from "./ProcessAdmissionError.js";
 import { PrivateRuntimeRoot } from "./PrivateRuntimeRoot.js";
 import type { Readable, Writable } from "node:stream";
 import {
@@ -211,14 +212,14 @@ export class OwnedWorkerRuntime {
     initialize?: (supervisor: ProviderProcessSupervisor) => Promise<void>,
   ): Promise<void> {
     if (this.#terminalCloseRequested || this.#closing)
-      return Promise.reject(new Error("Owned worker runtime is closing"));
+      return Promise.reject(new ProcessAdmissionError("runtime_closing"));
     if (this.#acquisition !== undefined) return this.#acquisition;
     if (this.#supervisor !== undefined && !this.#registry.has(this))
       return Promise.resolve();
     if (this.options.retryCleanup !== undefined && this.#registry.has(this))
       return this.#retryOwnedCleanup().then(() => {
         if (this.#terminalCloseRequested || this.#closing)
-          throw new Error("Owned worker runtime is closing");
+          throw new ProcessAdmissionError("runtime_closing");
         return this.start(spawnOptions, initialize);
       });
     const ownRetry = this.#registry.has(this)
@@ -241,7 +242,7 @@ export class OwnedWorkerRuntime {
   onStdout(listener: (chunk: Buffer | string) => void): void {
     const stream = this.#supervisor?.launch.process.stdout;
     if (stream === null || stream === undefined)
-      throw new Error("Owned worker runtime has no stdout stream");
+      throw new ProcessAdmissionError("stdout_missing");
     stream.on("data", listener);
     this.#stdoutListeners.add({ stream, listener });
   }
@@ -330,12 +331,12 @@ export class OwnedWorkerRuntime {
       | undefined,
   ): Promise<void> {
     await this.#registry.retry(this);
-    if (this.#closing) throw new Error("Owned worker runtime is closing");
+    if (this.#closing) throw new ProcessAdmissionError("runtime_closing");
     this.#root ??= await PrivateRuntimeRoot.create({
       prefix: this.options.rootPrefix,
     });
     this.#cleanupEpoch ??= new OwnedWorkerRuntimeCleanupEpoch(this.#root.path);
-    if (this.#closing) throw new Error("Owned worker runtime is closing");
+    if (this.#closing) throw new ProcessAdmissionError("runtime_closing");
     this.#lastRunId = spawnOptions.runId;
     const spawned = await (this.options.launcher ?? spawnOwnedProviderProcess)({
       ...spawnOptions,
@@ -356,9 +357,9 @@ export class OwnedWorkerRuntime {
     );
     // A close may have begun while spawn was pending. Adopt the process first;
     // close waits for this acquisition and then stops the exact adopted owner.
-    if (this.#closing) throw new Error("Owned worker runtime is closing");
+    if (this.#closing) throw new ProcessAdmissionError("runtime_closing");
     await initialize?.(this.#supervisor);
-    if (this.#closing) throw new Error("Owned worker runtime is closing");
+    if (this.#closing) throw new ProcessAdmissionError("runtime_closing");
   }
 
   async #stop(): Promise<ProviderProcessStopResult> {
@@ -430,7 +431,9 @@ export class OwnedWorkerRuntime {
       this.#inputFailure =
         cause instanceof Error
           ? cause
-          : new Error("Owned worker request stream failed", { cause });
+          : new ProcessAdmissionError("request_stream_failed", undefined, {
+              cause,
+            });
       this.options.onInputFailure?.(this.#inputFailure);
     };
     const onClose = (): void => {
diff --git a/src/process/PendingOperations.ts b/src/process/PendingOperations.ts
index bcacd18ed8..bfe7882157 100644
--- a/src/process/PendingOperations.ts
+++ b/src/process/PendingOperations.ts
@@ -1,3 +1,5 @@
+import { ProcessAdmissionError } from "./ProcessAdmissionError.js";
+
 /** Timeout and cancellation projections for one correlated operation. */
 export type PendingOperationOptions<Value> = {
   readonly signal?: AbortSignal;
@@ -36,7 +38,7 @@ export class PendingOperations<Key, Value> {
   /** Register one unique operation key and await its reply or cancellation. */
   wait(key: Key, options: PendingOperationOptions<Value>): Promise<Value> {
     if (this.#pending.has(key))
-      throw new Error("Pending operation key is already registered");
+      throw new ProcessAdmissionError("duplicate_key");
     if (options.signal?.aborted === true)
       return Promise.resolve(options.cancelledValue());
 
diff --git a/src/process/ProcessAdmissionError.ts b/src/process/ProcessAdmissionError.ts
new file mode 100644
index 0000000000..3be14df65c
--- /dev/null
+++ b/src/process/ProcessAdmissionError.ts
@@ -0,0 +1,42 @@
+const PROCESS_ADMISSION_CODES = [
+  "runtime_closing",
+  "stdout_missing",
+  "request_stream_failed",
+  "finalization_unobserved",
+  "prefix_identity_lost",
+  "prefix_unavailable",
+  "identity_snapshot_unavailable",
+  "current_process_unreported",
+  "baseline_unavailable",
+  "memory_limit_unsupported",
+  "launcher_pid_missing",
+  "duplicate_key",
+  "reader_closed",
+  "token_json_invalid",
+  "token_response_invalid",
+  "token_pid_set",
+  "token_pid_incomplete",
+  "identity_json_invalid",
+  "identity_response_invalid",
+  "identity_pid_set",
+  "identity_pid_incomplete",
+  "limit_unreadable",
+  "limit_invalid",
+  "report_exceeds_budget",
+] as const;
+
+export type ProcessAdmissionCode = (typeof PROCESS_ADMISSION_CODES)[number];
+
+/** Process ownership, worker, or limit admission failure. `code` is the stable identity. */
+export class ProcessAdmissionError extends Error {
+  readonly _tag = "ProcessAdmissionError";
+
+  constructor(
+    readonly code: ProcessAdmissionCode,
+    readonly detail?: Readonly<Record<string, string | number>>,
+    options?: ErrorOptions,
+  ) {
+    super(code, options);
+    this.name = "ProcessAdmissionError";
+  }
+}
diff --git a/src/process/ProcessOwnershipObservation.ts b/src/process/ProcessOwnershipObservation.ts
index d47e501936..15ca968f41 100644
--- a/src/process/ProcessOwnershipObservation.ts
+++ b/src/process/ProcessOwnershipObservation.ts
@@ -1,3 +1,4 @@
+import { ProcessAdmissionError } from "./ProcessAdmissionError.js";
 import { readFile, stat as statPath } from "node:fs/promises";
 import { performance } from "node:perf_hooks";
 import { setTimeout as delay } from "node:timers/promises";
@@ -1348,9 +1349,9 @@ export const createSystemProcessOwnershipHost = (
         liveAfterRetry.some((entry) => entry.pid === pid),
       );
       if (stillUnresolved.length > 0)
-        throw new Error(
-          `process identity snapshot is unavailable for ${String(stillUnresolved.length)} live processes`,
-        );
+        throw new ProcessAdmissionError("identity_snapshot_unavailable", {
+          live_processes: stillUnresolved.length,
+        });
     }
     return processes.map(({ pid }) => {
       const observation = identities.get(pid);
@@ -1369,7 +1370,7 @@ export const createSystemProcessOwnershipHost = (
         try {
           const processes = await listProcesses(signal);
           if (!processes.some(({ pid }) => pid === process.pid))
-            throw new Error("ps did not report REA's current process");
+            throw new ProcessAdmissionError("current_process_unreported");
         } catch (cause: unknown) {
           if (isExpectedAbort(cause, signal)) throw cause;
           throw new LinuxOwnedProcessPrerequisiteError(cause);
diff --git a/src/process/ProviderProcess.ts b/src/process/ProviderProcess.ts
index 7bb1f1ba2d..83946af8f2 100644
--- a/src/process/ProviderProcess.ts
+++ b/src/process/ProviderProcess.ts
@@ -1,3 +1,4 @@
+import { ProcessAdmissionError } from "./ProcessAdmissionError.js";
 import { spawn, type ChildProcess } from "node:child_process";
 import type { EventEmitter } from "node:events";
 import type { Readable, Writable } from "node:stream";
@@ -263,7 +264,7 @@ export const spawnOwnedProviderProcess = async (
   if (sweepTokenOwnedProcesses) {
     const capture = systemProcessOwnershipHost.captureBaseline;
     if (capture === undefined)
-      throw new Error("Process ownership baseline is unavailable on this host");
+      throw new ProcessAdmissionError("baseline_unavailable");
     captureBaseline = await capture(options.signal);
     options.signal?.throwIfAborted();
   }
@@ -306,9 +307,7 @@ export const spawnOwnedProviderProcess = async (
     };
   }
   if (options.memoryLimitBytes !== undefined)
-    throw new Error(
-      "Owned process memory limits require the Windows Job Object launcher; no limit can be enforced on this host.",
-    );
+    throw new ProcessAdmissionError("memory_limit_unsupported");
   const child = spawn(options.command, [...options.arguments], {
     shell: false,
     windowsHide: true,
@@ -320,7 +319,8 @@ export const spawnOwnedProviderProcess = async (
   });
   await waitForSpawn(child);
   const pid = child.pid;
-  if (pid === undefined) throw new Error("Provider launcher has no process ID");
+  if (pid === undefined)
+    throw new ProcessAdmissionError("launcher_pid_missing");
   const ownership: OwnedProcessGroup = {
     runId: options.runId,
     leaderPid: pid,
diff --git a/src/process/capture/ProcessHarness.ts b/src/process/capture/ProcessHarness.ts
index c674063c66..08cf60b3ca 100644
--- a/src/process/capture/ProcessHarness.ts
+++ b/src/process/capture/ProcessHarness.ts
@@ -1,3 +1,4 @@
+import { ProcessAdmissionError } from "../ProcessAdmissionError.js";
 import type { IPty } from "@lydell/node-pty";
 import type { ProcessCapture } from "../../domain/process/processCaptureParsing.js";
 import type { ProcessScenario } from "../../domain/process/processScenario.js";
@@ -846,9 +847,7 @@ const runProcessScenario = async (
       };
       if (exit.reason === "cancelled")
         throw processCaptureCancelled(signal?.reason);
-      throw new Error(
-        "The captured process exit was not observed because the finalization SIGKILL could not be delivered.",
-      );
+      throw new ProcessAdmissionError("finalization_unobserved");
     }
     if (exit.finalization !== undefined)
       observations.finalization = {
diff --git a/src/process/capture/ProcessSensitiveOutput.ts b/src/process/capture/ProcessSensitiveOutput.ts
index b2a20b2332..d599d28ed5 100644
--- a/src/process/capture/ProcessSensitiveOutput.ts
+++ b/src/process/capture/ProcessSensitiveOutput.ts
@@ -1,3 +1,4 @@
+import { ProcessAdmissionError } from "../ProcessAdmissionError.js";
 import { AnalysisError } from "../../domain/analysisErrorBase.js";
 import { AnalysisResourceConstraintError } from "../../domain/analysisErrorCore.js";
 import { err, ok, type Result } from "../../domain/result.js";
@@ -134,7 +135,7 @@ export class ProcessSensitiveOutput {
   #prefix(index: number): Prefix {
     const value = this.prefixes[index];
     if (value === undefined)
-      throw new Error("Sensitive output matcher lost its prefix identity");
+      throw new ProcessAdmissionError("prefix_identity_lost");
     return value;
   }
 
@@ -342,7 +343,7 @@ export const createProcessSensitiveOutput = (
   const read = (index: number): Prefix => {
     const node = prefixes[index];
     if (node === undefined)
-      throw new Error("Sensitive output prefix is unavailable");
+      throw new ProcessAdmissionError("prefix_unavailable");
     return node;
   };
   try {
diff --git a/src/wasm/WabtAdmissionError.ts b/src/wasm/WabtAdmissionError.ts
new file mode 100644
index 0000000000..4a48ad38b8
--- /dev/null
+++ b/src/wasm/WabtAdmissionError.ts
@@ -0,0 +1,47 @@
+const WABT_ADMISSION_CODES = [
+  "incomplete_string",
+  "unsupported_escape",
+  "incomplete_comment",
+  "malformed_form",
+  "name_missing",
+  "incomplete_import",
+  "incomplete_export",
+  "unsupported_section_header",
+  "unrecognized_section_row",
+  "blank_custom_name",
+  "custom_header_mismatch",
+  "incomplete_section_row",
+  "section_ranges",
+  "custom_inventory_mismatch",
+  "section_coverage",
+  "incomplete_name_metadata",
+  "name_subsection_order",
+  "incomplete_module_name",
+  "unfinished_module_name",
+  "unsupported_module_prefix",
+  "unexpected_string",
+  "unexpected_second_module",
+  "unsupported_custom_name",
+  "unsupported_name_payload",
+  "unbalanced_output",
+  "unexpected_text",
+  "incomplete_output",
+  "directory_not_absolute",
+  "incomplete_tool_profile",
+] as const;
+
+export type WabtAdmissionCode = (typeof WABT_ADMISSION_CODES)[number];
+
+/** WABT output or tool-profile admission failure. `code` is the stable identity. */
+export class WabtAdmissionError extends Error {
+  readonly _tag = "WabtAdmissionError";
+
+  constructor(
+    readonly code: WabtAdmissionCode,
+    readonly detail?: Readonly<Record<string, string | number>>,
+    options?: ErrorOptions,
+  ) {
+    super(code, options);
+    this.name = "WabtAdmissionError";
+  }
+}
diff --git a/src/wasm/WabtArtifactProvider.test.ts b/src/wasm/WabtArtifactProvider.test.ts
index 61b9da8665..6efb08d4d3 100644
--- a/src/wasm/WabtArtifactProvider.test.ts
+++ b/src/wasm/WabtArtifactProvider.test.ts
@@ -436,7 +436,12 @@ it("returns actionable unavailable without creating a workspace when tools are a
     ok: false,
     error: {
       _tag: "AnalysisCapabilityUnavailableError",
-      userMessage: expect.stringContaining("REA_WABT_BIN_DIRECTORY"),
+      reason: "directory_not_absolute",
+      userMessage: "WABT configuration cannot be used",
+      diagnostics: {
+        code: "directory_not_absolute",
+        setting: "REA_WABT_BIN_DIRECTORY",
+      },
     },
   });
 });
diff --git a/src/wasm/WabtArtifactProvider.ts b/src/wasm/WabtArtifactProvider.ts
index 6fde4aa261..0b7abc613f 100644
--- a/src/wasm/WabtArtifactProvider.ts
+++ b/src/wasm/WabtArtifactProvider.ts
@@ -1,3 +1,4 @@
+import { WabtAdmissionError } from "./WabtAdmissionError.js";
 import { randomUUID, createHash } from "node:crypto";
 import { access, writeFile } from "node:fs/promises";
 import { constants } from "node:fs";
@@ -221,9 +222,9 @@ export class WabtArtifactProvider implements WasmArtifactPort {
         });
       const directory = environment.REA_WABT_BIN_DIRECTORY ?? "";
       if (!isAbsolute(directory))
-        throw new Error(
-          "REA_WABT_BIN_DIRECTORY must be an absolute tool directory.",
-        );
+        throw new WabtAdmissionError("directory_not_absolute", {
+          setting: "REA_WABT_BIN_DIRECTORY",
+        });
       const commands: {
         tool: "wasm-validate" | "wasm-objdump" | "wasm2wat";
         path: string;
@@ -466,7 +467,7 @@ export class WabtArtifactProvider implements WasmArtifactPort {
         objdump === undefined ||
         decode === undefined
       )
-        throw new Error("Incomplete WABT tool profile.");
+        throw new WabtAdmissionError("incomplete_tool_profile");
       const validation = await execute(validate, validate.arguments, true);
       if (validation.exitCode !== 0)
         throw new AnalysisInputError(
diff --git a/src/wasm/WabtComment.ts b/src/wasm/WabtComment.ts
index 0224e25ba3..6170efeb69 100644
--- a/src/wasm/WabtComment.ts
+++ b/src/wasm/WabtComment.ts
@@ -1,3 +1,5 @@
+import { WabtAdmissionError } from "./WabtAdmissionError.js";
+
 /** Skip a WAT comment without interpreting its punctuation as forms or strings. */
 export const watCommentEnd = (
   text: string,
@@ -24,5 +26,5 @@ export const watCommentEnd = (
       index++;
     }
   }
-  throw new Error("Incomplete WABT WAT comment.");
+  throw new WabtAdmissionError("incomplete_comment");
 };
diff --git a/src/wasm/WabtFailures.ts b/src/wasm/WabtFailures.ts
index 7348621b18..27ba86a1bc 100644
--- a/src/wasm/WabtFailures.ts
+++ b/src/wasm/WabtFailures.ts
@@ -27,6 +27,7 @@ import {
   RuntimeControlUnavailableError,
   runtimeControlCapabilityError,
 } from "../process/RuntimeControlUnavailableError.js";
+import { WabtAdmissionError } from "./WabtAdmissionError.js";
 import {
   DEFAULT_WASM_COMMAND_TIMEOUT_MS,
   MAX_WASM_COMMAND_TIMEOUT_MS,
@@ -237,18 +238,31 @@ const classifyWabtFailure = (
         remediationAction: `The WABT tool allowance is ${String(WABT_LIMITS.toolBytes)} bytes. This release has no runtime override. command_timeout_ms and REA_WABT_BIN_DIRECTORY do not raise it. Select tools within the allowance. Do not repeat the unchanged call.`,
       },
     );
-  if (phase === "configuration")
+  if (phase === "configuration") {
+    const admission = cause instanceof WabtAdmissionError ? cause : undefined;
     return new AnalysisCapabilityUnavailableError(
       WABT_PROVIDER_IDENTITY.id,
       "inspect_wasm_artifact",
-      reason,
+      admission?.code ?? reason,
       {
         cause,
         ...artifactOptions,
-        userMessage: reason,
+        ...(admission === undefined
+          ? {}
+          : {
+              diagnostics: {
+                code: admission.code,
+                ...admission.detail,
+              },
+            }),
+        userMessage:
+          admission === undefined
+            ? reason
+            : "WABT configuration cannot be used",
         remediationAction: wabtConfigurationRecoveryAction(cause),
       },
     );
+  }
   if (
     phase === "artifact" &&
     cause instanceof ArtifactReaderFailure &&
diff --git a/src/wasm/WabtInterface.test.ts b/src/wasm/WabtInterface.test.ts
index 07cb08ac69..72e3a2253f 100644
--- a/src/wasm/WabtInterface.test.ts
+++ b/src/wasm/WabtInterface.test.ts
@@ -217,11 +217,19 @@ it("rejects unfinished nested comments rather than projecting a truncated interf
     "(module (type (func (param (; unfinished ) i32))))",
     "(module) (; outer (; inner ;) still open",
   ])
-    expect(() => parseWabtWat(source)).toThrow("Incomplete WABT WAT comment");
+    expect(() => parseWabtWat(source)).toThrow(
+      expect.objectContaining({
+        _tag: "WabtAdmissionError",
+        code: "incomplete_comment",
+      }),
+    );
 });
 
 it("rejects a second module after a CR-terminated line comment", () => {
   expect(() => parseWabtWat("(module) ;; comment\r(module)")).toThrow(
-    "Unexpected second WABT WAT module",
+    expect.objectContaining({
+      _tag: "WabtAdmissionError",
+      code: "unexpected_second_module",
+    }),
   );
 });
diff --git a/src/wasm/WabtInterface.ts b/src/wasm/WabtInterface.ts
index 9ba9260cc4..fc45d50c31 100644
--- a/src/wasm/WabtInterface.ts
+++ b/src/wasm/WabtInterface.ts
@@ -1,3 +1,4 @@
+import { WabtAdmissionError } from "./WabtAdmissionError.js";
 import { AnalysisResourceConstraintError } from "../domain/analysisErrorCore.js";
 import { wasmInterfaceEntryRepresentationBytes } from "../domain/wasm/wasmInterface.js";
 import { WasmInterfaceBudget } from "./WasmInterfaceBudget.js";
@@ -47,7 +48,7 @@ const parts = (form: string): string[] => {
       if (items[0] === "func" && items.length > 1 && !atom.startsWith("$"))
         break;
     }
-    if (i <= start) throw new Error("Malformed WABT form");
+    if (i <= start) throw new WabtAdmissionError("malformed_form");
     budget.reserve(64 + (i - start) * 2);
     items.push(form.slice(start, i));
   }
@@ -91,7 +92,7 @@ const functionType = (
 };
 const name = (text: string | undefined): string => {
   if (text?.startsWith('"') !== true)
-    throw new Error("WABT interface name is missing");
+    throw new WabtAdmissionError("name_missing");
   return new TextDecoder("utf8", { fatal: true, ignoreBOM: true }).decode(
     watString(text, 1).bytes,
   );
@@ -252,7 +253,7 @@ const decodeWabtInterface = (
     const p = parts(form);
     if (p[0] !== "import") continue;
     const body = p[3];
-    if (body === undefined) throw new Error("Incomplete WABT import");
+    if (body === undefined) throw new WabtAdmissionError("incomplete_import");
     const observed = addDefinition(body);
     const entry: WasmInterfaceEntry = {
       direction: "import",
@@ -280,7 +281,7 @@ const decodeWabtInterface = (
     const p = parts(form);
     if (p[0] !== "export") continue;
     const body = p[2];
-    if (body === undefined) throw new Error("Incomplete WABT export");
+    if (body === undefined) throw new WabtAdmissionError("incomplete_export");
     const descriptor = parts(body);
     const rawKind = descriptor[0] ?? "unknown";
     const kind = ["func", "table", "memory", "global", "tag"].includes(rawKind)
diff --git a/src/wasm/WabtOutput.test.ts b/src/wasm/WabtOutput.test.ts
index fe4f0faaeb..fdfb420ed2 100644
--- a/src/wasm/WabtOutput.test.ts
+++ b/src/wasm/WabtOutput.test.ts
@@ -1,5 +1,8 @@
 import { readFile } from "node:fs/promises";
 import { expect, it } from "vitest";
+
+const refused = (code: string) =>
+  expect.objectContaining({ _tag: "WabtAdmissionError", code });
 import { parseWabtOutput } from "./WabtOutput.js";
 import { parseWabtWat } from "./WabtWat.js";
 import { associateWasmGlue } from "./WasmGlueAdapter.js";
@@ -28,10 +31,10 @@ it("corroborates a blank custom name with bounded invalid UTF-8 bytes", () => {
   valid[11] = 0x61;
   valid[12] = 0x62;
   expect(() => parseWabtOutput(dump, valid.length, [], [], valid)).toThrow(
-    /not corroborated/u,
+    refused("blank_custom_name"),
   );
   expect(() => parseWabtOutput(dump, bytes.length, [])).toThrow(
-    /not corroborated/u,
+    refused("blank_custom_name"),
   );
   const mixed = Buffer.concat([bytes, Buffer.from("00050174616263", "hex")]);
   const mixedDump = dump.replace(
@@ -57,19 +60,21 @@ it("retains real WABT section ranges, custom section identity and original heade
     bytes: 12,
     description: '"test"',
   });
-  expect(() => parseWabtOutput(text, 75, ["test"])).toThrow(/ranges/u);
+  expect(() => parseWabtOutput(text, 75, ["test"])).toThrow(
+    refused("section_ranges"),
+  );
   expect(() =>
     parseWabtOutput(text.replace("size=0x0000000c", "size=0x0000000d"), 76, [
       "test",
     ]),
-  ).toThrow(/ranges/u);
+  ).toThrow(refused("section_ranges"));
   expect(() =>
     parseWabtOutput(
       text.replace("\nSection Details:\n", "unexpected\nSection Details:\n"),
       76,
       ["test"],
     ),
-  ).toThrow(/Unrecognized/u);
+  ).toThrow(refused("unrecognized_section_row"));
   expect(() =>
     parseWabtOutput(
       text.replace(
@@ -79,7 +84,7 @@ it("retains real WABT section ranges, custom section identity and original heade
       76,
       ["test"],
     ),
-  ).toThrow(/Unrecognized/u);
+  ).toThrow(refused("unrecognized_section_row"));
 });
 const dataCountModuleBytes = 0x3d;
 const unpaddedDataCountRow =
@@ -126,14 +131,14 @@ it("accepts an unpadded DataCount row and still rejects malformed output and bad
       dataCountModuleBytes,
       [],
     ),
-  ).toThrow(/Unrecognized/u);
+  ).toThrow(refused("unrecognized_section_row"));
   expect(() =>
     parseWabtOutput(
       dataCountDump.replace(unpaddedDataCountRow, "Sections:"),
       dataCountModuleBytes,
       [],
     ),
-  ).toThrow(/Unrecognized/u);
+  ).toThrow(refused("unrecognized_section_row"));
   expect(() =>
     parseWabtOutput(
       dataCountDump.replace(
@@ -143,14 +148,14 @@ it("accepts an unpadded DataCount row and still rejects malformed output and bad
       dataCountModuleBytes,
       [],
     ),
-  ).toThrow(/Unrecognized/u);
+  ).toThrow(refused("unrecognized_section_row"));
   expect(() =>
     parseWabtOutput(
       dataCountDump.replace("(size=0x00000001)", "(size=0x00000002)"),
       dataCountModuleBytes,
       [],
     ),
-  ).toThrow(/ranges/u);
+  ).toThrow(refused("section_ranges"));
   expect(() =>
     parseWabtOutput(
       dataCountDump.replace(
@@ -160,10 +165,10 @@ it("accepts an unpadded DataCount row and still rejects malformed output and bad
       dataCountModuleBytes,
       [],
     ),
-  ).toThrow(/ranges/u);
+  ).toThrow(refused("section_ranges"));
   expect(() =>
     parseWabtOutput(dataCountDump, dataCountModuleBytes - 1, []),
-  ).toThrow(/ranges/u);
+  ).toThrow(refused("section_ranges"));
   expect(() =>
     parseWabtOutput(
       dataCountDump.replace(
@@ -173,7 +178,7 @@ it("accepts an unpadded DataCount row and still rejects malformed output and bad
       dataCountModuleBytes,
       [],
     ),
-  ).toThrow(/header/u);
+  ).toThrow(refused("unsupported_section_header"));
 });
 it("bounds section header bytes while accepting a five-byte size LEB", () => {
   const paddedCustomDump = [
@@ -209,7 +214,7 @@ it("bounds section header bytes while accepting a five-byte size LEB", () => {
       "",
     ].join("\n");
     expect(() => parseWabtOutput(malformed, start + 1, [""])).toThrow(
-      /ranges/u,
+      refused("section_ranges"),
     );
   }
 });
@@ -225,7 +230,7 @@ it.each([
       `\n${displayed.map((name) => `module name: <${name}>\n`).join("")}\nSections:`,
     );
     expect(() => parseWabtOutput(text, 76, ["test"], decoded)).toThrow(
-      /header format/u,
+      refused("unsupported_section_header"),
     );
   },
 );
@@ -284,7 +289,7 @@ it("frames custom section names at their NUL-terminated objdump display", async
     description: '"test"',
   });
   expect(() => parseWabtOutput(text, 76, ["other\0test"])).toThrow(
-    /custom-section header/u,
+    refused("custom_header_mismatch"),
   );
 });
 it("preserves leading U+FEFF as custom-name data, not a debug-name marker", () => {
@@ -327,9 +332,11 @@ it("extracts escaped WAT import/export forms while retaining multiline producer
     ).exports,
   ).toEqual(['(export "x" (func 0))']);
   expect(() => parseWabtWat('(module (export "unfinished"')).toThrow(
-    /Incomplete/u,
+    refused("incomplete_output"),
+  );
+  expect(() => parseWabtWat("(module) unexpected")).toThrow(
+    refused("unexpected_text"),
   );
-  expect(() => parseWabtWat("(module) unexpected")).toThrow(/Unexpected/u);
 });
 it("keeps exact local, ambiguous URL, computed and unparseable glue distinct", () => {
   const candidates = ["/app/module.wasm", "/other/module.wasm"];
diff --git a/src/wasm/WabtOutput.ts b/src/wasm/WabtOutput.ts
index a5265c9748..40a3196b2d 100644
--- a/src/wasm/WabtOutput.ts
+++ b/src/wasm/WabtOutput.ts
@@ -1,3 +1,5 @@
+import { WabtAdmissionError } from "./WabtAdmissionError.js";
+
 /** WABT prints names with %.*s, so an embedded NUL ends their display. */
 const wabtDisplayedName = (name: string | undefined): string | undefined =>
   name?.split("\0", 1)[0];
@@ -17,7 +19,7 @@ export const parseWabtOutput = (
       .join("");
   const prefix = `${preamble}\nSections:\n\n`;
   if (!text.startsWith(prefix))
-    throw new Error("Unsupported WABT section header format.");
+    throw new WabtAdmissionError("unsupported_section_header");
   let offset = prefix.length;
   let customIndex = 0;
   const sections = [];
@@ -27,7 +29,8 @@ export const parseWabtOutput = (
       /^[ \t]*(\w+) start=0x([\da-f]+) end=0x([\da-f]+) \(size=0x([\da-f]+)\) /u.exec(
         text.slice(offset),
       );
-    if (match === null) throw new Error("Unrecognized WABT section row.");
+    if (match === null)
+      throw new WabtAdmissionError("unrecognized_section_row");
     offset += match[0].length;
     let description: string;
     if (match[1] === "Custom" && !text.startsWith('"', offset)) {
@@ -37,7 +40,7 @@ export const parseWabtOutput = (
       const end = Number.parseInt(match[3] ?? "", 16);
       const invalidEnd = invalidCustomNameEnd(artifact, start, end);
       if (invalidEnd === undefined)
-        throw new Error("WABT blank custom-section name is not corroborated.");
+        throw new WabtAdmissionError("blank_custom_name");
       invalidNameEnds.push(invalidEnd);
       description = "";
       // WABT does not terminate a blank-name row when another section follows.
@@ -49,14 +52,12 @@ export const parseWabtOutput = (
     } else if (match[1] === "Custom") {
       const name = wabtDisplayedName(customSectionNames[customIndex++]);
       if (name === undefined || !text.startsWith(`"${name}"\n`, offset))
-        throw new Error(
-          "WABT custom-section header does not match decoded WAT.",
-        );
+        throw new WabtAdmissionError("custom_header_mismatch");
       description = `"${name}"`;
       offset += description.length + 1;
     } else {
       const end = text.indexOf("\n", offset);
-      if (end < 0) throw new Error("Incomplete WABT section row.");
+      if (end < 0) throw new WabtAdmissionError("incomplete_section_row");
       description = text.slice(offset, end).trim();
       offset = end + 1;
     }
@@ -74,17 +75,13 @@ export const parseWabtOutput = (
       sectionHeaderBytes < 2 ||
       sectionHeaderBytes > 6
     )
-      throw new Error("WABT section ranges do not match selected artifact.");
+      throw new WabtAdmissionError("section_ranges");
     sections.push(section);
   }
   if (customIndex !== customSectionNames.length)
-    throw new Error(
-      "WABT custom-section inventory does not match decoded WAT.",
-    );
+    throw new WabtAdmissionError("custom_inventory_mismatch");
   if ((sections.at(-1)?.end ?? 8) !== artifactBytes)
-    throw new Error(
-      "WABT section output does not cover the selected artifact.",
-    );
+    throw new WabtAdmissionError("section_coverage");
   const separator = offset + 1;
   return {
     sections,
diff --git a/src/wasm/WabtString.test.ts b/src/wasm/WabtString.test.ts
index a0c2d7cea2..afe7edfa40 100644
--- a/src/wasm/WabtString.test.ts
+++ b/src/wasm/WabtString.test.ts
@@ -26,8 +26,18 @@ it("frames escaped quotes and trailing backslashes without consuming the next fo
 
 it("rejects missing terminators, including a dangling escape or escaped last quote", () => {
   for (const source of ['"', '"payload', '"payload\\', '"payload\\"']) {
-    expect(() => watStringEnd(source, 1)).toThrow("Incomplete WABT string");
-    expect(() => watString(source, 1)).toThrow("Incomplete WABT string");
+    expect(() => watStringEnd(source, 1)).toThrow(
+      expect.objectContaining({
+        _tag: "WabtAdmissionError",
+        code: "incomplete_string",
+      }),
+    );
+    expect(() => watString(source, 1)).toThrow(
+      expect.objectContaining({
+        _tag: "WabtAdmissionError",
+        code: "incomplete_string",
+      }),
+    );
     expect(() => parseWabtWat(`(module (import ${source}`)).toThrow();
   }
 });
@@ -53,6 +63,9 @@ it("preserves quoted WAT punctuation, nested comments, escaped names and unknown
     },
   ]);
   expect(() => parseWabtWat('(module (import "env" "\\q" (func)))')).toThrow(
-    "Unsupported WABT name escape",
+    expect.objectContaining({
+      _tag: "WabtAdmissionError",
+      code: "unsupported_escape",
+    }),
   );
 });
diff --git a/src/wasm/WabtString.ts b/src/wasm/WabtString.ts
index 715e4cb565..885e8b76ea 100644
--- a/src/wasm/WabtString.ts
+++ b/src/wasm/WabtString.ts
@@ -1,3 +1,5 @@
+import { WabtAdmissionError } from "./WabtAdmissionError.js";
+
 /** Locate a WAT string's exclusive end without decoding or copying its payload. */
 export const watStringEnd = (form: string, start: number): number => {
   for (
@@ -9,7 +11,7 @@ export const watStringEnd = (form: string, start: number): number => {
     while (escapes > start && form[escapes - 1] === "\\") escapes--;
     if ((end - escapes) % 2 === 0) return end + 1;
   }
-  throw new Error("Incomplete WABT string.");
+  throw new WabtAdmissionError("incomplete_string");
 };
 
 /** Decode a producer WAT string only where its bytes are interpreted. */
@@ -45,7 +47,8 @@ export const watString = (form: string, start: number) => {
                 : escape === "\\"
                   ? 92
                   : undefined;
-      if (value === undefined) throw new Error("Unsupported WABT name escape.");
+      if (value === undefined)
+        throw new WabtAdmissionError("unsupported_escape");
       bytes[length++] = value;
       index += 2;
     }
diff --git a/src/wasm/WabtWat.ts b/src/wasm/WabtWat.ts
index cbb0a3edc5..a5305728d8 100644
--- a/src/wasm/WabtWat.ts
+++ b/src/wasm/WabtWat.ts
@@ -1,3 +1,4 @@
+import { WabtAdmissionError } from "./WabtAdmissionError.js";
 import { parseWabtInterface } from "./WabtInterface.js";
 import { watString, watStringEnd } from "./WabtString.js";
 import { watCommentEnd } from "./WabtComment.js";
@@ -25,24 +26,24 @@ const moduleNames = (
       value += (byte & 127) * 2 ** shift;
       if (byte < 128) return value;
     }
-    throw new Error("Incomplete WABT name-section metadata.");
+    throw new WabtAdmissionError("incomplete_name_metadata");
   };
   try {
     let previousType = -1;
     while (offset < bytes.length) {
       const type = uint32(bytes.length);
       if (type <= previousType)
-        throw new Error("Duplicate or out-of-order WABT name subsection.");
+        throw new WabtAdmissionError("name_subsection_order");
       previousType = type;
       const size = uint32(bytes.length);
       const end = offset + size;
       if (end > bytes.length)
-        throw new Error("Incomplete WABT name-section metadata.");
+        throw new WabtAdmissionError("incomplete_name_metadata");
       if (type === 0 && size !== 0) {
         const length = uint32(end);
         const nameEnd = offset + length;
         if (nameEnd > end)
-          throw new Error("Incomplete WABT module-name metadata.");
+          throw new WabtAdmissionError("incomplete_module_name");
         names.push(
           new TextDecoder("utf-8", { fatal: true, ignoreBOM: true }).decode(
             bytes.subarray(offset, nameEnd),
@@ -50,7 +51,7 @@ const moduleNames = (
         );
         // WABT calls OnModuleName before rejecting trailing subsection bytes.
         if (nameEnd !== end)
-          throw new Error("Unfinished WABT module-name subsection.");
+          throw new WabtAdmissionError("unfinished_module_name");
       }
       offset = end;
     }
@@ -68,7 +69,7 @@ const moduleNames = (
 /** Extract exact top-level WABT WAT forms; no raw WASM decoding or import/export name unescaping. */
 export const parseWabtWat = (text: string) => {
   if (!/^\(module(?:\s|\))/u.test(text))
-    throw new Error("Unsupported WABT WAT module prefix.");
+    throw new WabtAdmissionError("unsupported_module_prefix");
   const forms: string[] = [];
   const imports: string[] = [];
   const exports: string[] = [];
@@ -95,13 +96,12 @@ export const parseWabtWat = (text: string) => {
       continue;
     }
     if (char === '"') {
-      if (depth === 0)
-        throw new Error("Unexpected string outside WABT WAT module.");
+      if (depth === 0) throw new WabtAdmissionError("unexpected_string");
       index = watStringEnd(text, index + 1) - 1;
       continue;
     }
     if (char === "(") {
-      if (closed) throw new Error("Unexpected second WABT WAT module.");
+      if (closed) throw new WabtAdmissionError("unexpected_second_module");
       depth++;
       if (depth === 2) start = index;
     } else if (char === ")") {
@@ -118,7 +118,7 @@ export const parseWabtWat = (text: string) => {
         else if (/^\(@custom\s/u.test(form)) {
           const prefix = /^\(@custom\s+"/u.exec(form);
           if (prefix === null)
-            throw new Error("Unsupported WABT custom-section name.");
+            throw new WabtAdmissionError("unsupported_custom_name");
           const nameString = watString(form, prefix[0].length);
           // A WASM name is length-delimited UTF-8; leading U+FEFF is name data.
           const name = new TextDecoder("utf-8", {
@@ -129,7 +129,7 @@ export const parseWabtWat = (text: string) => {
           if (name === "name") {
             const payloadPrefix = /^\s+"/u.exec(form.slice(nameString.end));
             if (payloadPrefix === null)
-              throw new Error("Unsupported WABT name-section payload.");
+              throw new WabtAdmissionError("unsupported_name_payload");
             const payload = watString(
               form,
               nameString.end + payloadPrefix[0].length,
@@ -148,12 +148,12 @@ export const parseWabtWat = (text: string) => {
           }
         }
       }
-      if (--depth < 0) throw new Error("Unbalanced WABT WAT output.");
+      if (--depth < 0) throw new WabtAdmissionError("unbalanced_output");
       if (depth === 0) closed = true;
     } else if (depth === 0 && char !== undefined && !/\s/u.test(char))
-      throw new Error("Unexpected text outside WABT WAT module.");
+      throw new WabtAdmissionError("unexpected_text");
   }
-  if (depth !== 0) throw new Error("Incomplete WABT WAT output.");
+  if (depth !== 0) throw new WabtAdmissionError("incomplete_output");
   return {
     imports,
     exports,
diff --git a/tests/boundary/evm/evmLimiterAvailability.test.ts b/tests/boundary/evm/evmLimiterAvailability.test.ts
index 696afb9338..ec1e1d5655 100644
--- a/tests/boundary/evm/evmLimiterAvailability.test.ts
+++ b/tests/boundary/evm/evmLimiterAvailability.test.ts
@@ -82,8 +82,12 @@ it("rejects a relative override and non-file without probing an alternate comman
   );
   expect(relative).toMatchObject({
     status: "unavailable",
-    diagnostics: { limiter_path: "prlimit" },
-    reason: expect.stringContaining("absolute executable path"),
+    reason: "prlimit_not_absolute",
+    diagnostics: {
+      limiter_path: "prlimit",
+      code: "prlimit_not_absolute",
+      setting: "REA_EVM_PRLIMIT_COMMAND",
+    },
   });
 
   const directory = await evmLimiterAvailability(
@@ -98,7 +102,8 @@ it("rejects a relative override and non-file without probing an alternate comman
   );
   expect(directory).toMatchObject({
     status: "unavailable",
-    reason: expect.stringContaining("regular executable file"),
+    reason: "prlimit_not_file",
+    diagnostics: expect.objectContaining({ code: "prlimit_not_file" }),
   });
 });
 
diff --git a/tests/boundary/evm/evmoleInterfaceProvider.test.ts b/tests/boundary/evm/evmoleInterfaceProvider.test.ts
index b7b0611aa8..1f79921ba6 100644
--- a/tests/boundary/evm/evmoleInterfaceProvider.test.ts
+++ b/tests/boundary/evm/evmoleInterfaceProvider.test.ts
@@ -982,7 +982,15 @@ it.runIf(!unsupportedHost).each(["directory", "missing-interpreter"])(
       category: "unsupported_provider",
       details: { provider_id: "evmole-interface" },
     });
-    expect(result.error.message).toContain(limiter);
+    if (scenario === "directory")
+      expect(result.error).toMatchObject({
+        reason: "prlimit_not_file",
+        diagnostics: {
+          limiter_path: limiter,
+          code: "prlimit_not_file",
+        },
+      });
+    else expect(result.error.message).toContain(limiter);
     if (ownedRoot !== undefined)
       await expect(access(ownedRoot)).rejects.toMatchObject({ code: "ENOENT" });
     expect(await readFile(path, "utf8")).toBe("0x60006000f3\n");
diff --git a/tests/boundary/evm/solidityMetadataWorker.test.ts b/tests/boundary/evm/solidityMetadataWorker.test.ts
index cd68439df8..6b665ec0e3 100644
--- a/tests/boundary/evm/solidityMetadataWorker.test.ts
+++ b/tests/boundary/evm/solidityMetadataWorker.test.ts
@@ -94,7 +94,17 @@ it.each([
     if (kind.startsWith("duplicate nested")) {
       expect(metadata.entries).toEqual([]);
       expect(metadata.compiler_version).toBeNull();
-      expect(metadata.diagnostic).toContain("repeat map key");
+      expect(metadata.diagnostic).toBe("repeated_map_key");
+      expect(metadata.admission).toMatchObject({ code: "repeated_map_key" });
+      if (kind === "duplicate nested text keys")
+        expect(metadata.admission?.detail).toEqual({
+          key: JSON.stringify({ kind: "text", value: "a" }),
+        });
+      else
+        expect(
+          metadata.admission?.detail?.key ??
+            metadata.admission?.detail?.key_length,
+        ).toBeDefined();
       expect(metadata.bytecode_offset).toBe(1);
       expect(metadata.cbor_bytes).toBe(19);
     }
diff --git a/tests/boundary/filesystem/ghidraBridgeSources.test.ts b/tests/boundary/filesystem/ghidraBridgeSources.test.ts
index 45aa07136d..dc19ac0411 100644
--- a/tests/boundary/filesystem/ghidraBridgeSources.test.ts
+++ b/tests/boundary/filesystem/ghidraBridgeSources.test.ts
@@ -102,7 +102,7 @@ const admissionCases: readonly AdmissionCase[] = [
   {
     name: "malformed Unicode escape",
     properties: "application.version=12.1.4\nother=\\u00xx\n",
-    error: "Malformed Unicode escape in Java properties file",
+    error: "malformed_unicode_escape",
   },
 ];
 
diff --git a/tests/boundary/filesystem/ghidraProfileArtifactOwnership.test.ts b/tests/boundary/filesystem/ghidraProfileArtifactOwnership.test.ts
index 676a8fe062..5cc068c49f 100644
--- a/tests/boundary/filesystem/ghidraProfileArtifactOwnership.test.ts
+++ b/tests/boundary/filesystem/ghidraProfileArtifactOwnership.test.ts
@@ -603,7 +603,12 @@ it.each(["seed", "extension"] as const)(
             ],
           },
         });
-      else expect(result.error.diagnostics?.reason).toContain("not a JAR");
+      else
+        expect(result.error.diagnostics).toMatchObject({
+          code: "not_jar",
+          reason: "not_jar",
+          path,
+        });
       allowClose = true;
       await scope.retryCleanup();
       expect(result.error.cleanupIncomplete).toBe(false);
diff --git a/tests/boundary/filesystem/ghidraPspExtension.test.ts b/tests/boundary/filesystem/ghidraPspExtension.test.ts
index 97668eb08b..0ac7f3564b 100644
--- a/tests/boundary/filesystem/ghidraPspExtension.test.ts
+++ b/tests/boundary/filesystem/ghidraPspExtension.test.ts
@@ -241,14 +241,27 @@ describe.skipIf(process.platform === "win32")(
       if (missing.ok) throw new Error("Missing installation was accepted");
       expect(missing.error.message).toContain("PSP_EXTENSION_UNAVAILABLE");
     });
+  },
+);
 
+describe.skipIf(process.platform === "win32")(
+  "PSP extension admission codes",
+  () => {
     it.each([
-      ["name=other\nversion=12.1.3\n", "does not match"],
-      ["name=ghidra-allegrex\nversion=12.1.4\n", "does not match"],
-      ["name=ghidra-allegrex\nversion=12.1.\\uZZZZ\n", "Unicode escape"],
-    ])(
+      ["name=other\nversion=12.1.3\n", "metadata_mismatch", undefined],
+      [
+        "name=ghidra-allegrex\nversion=12.1.4\n",
+        "metadata_mismatch",
+        undefined,
+      ],
+      [
+        "name=ghidra-allegrex\nversion=12.1.\\uZZZZ\n",
+        "properties_invalid",
+        "malformed_unicode_escape",
+      ],
+    ] as const)(
       "rejects mismatched or malformed extension metadata %s",
-      async (properties, reason) => {
+      async (properties, code, parserCode) => {
         const { root } = await installation();
         await writeFile(join(root, "extension.properties"), properties);
         await expect(
@@ -257,7 +270,14 @@ describe.skipIf(process.platform === "win32")(
             "12.1.3",
             new ArtifactResourceScope(),
           ),
-        ).rejects.toThrow(reason);
+        ).rejects.toMatchObject({
+          diagnostics: {
+            code,
+            ...(parserCode === undefined
+              ? { ghidra_version: "12.1.3" }
+              : { parser_code: parserCode }),
+          },
+        });
       },
     );
 
@@ -269,7 +289,12 @@ describe.skipIf(process.platform === "win32")(
       );
       await expect(
         inspectGhidraPspExtension(root, "12.1.3", new ArtifactResourceScope()),
-      ).rejects.toThrow("Module.manifest");
+      ).rejects.toMatchObject({
+        diagnostics: {
+          code: "component_missing",
+          component: "Module.manifest",
+        },
+      });
     });
 
     it("rejects symlinked code instead of hashing an untracked external producer", async () => {
@@ -279,7 +304,9 @@ describe.skipIf(process.platform === "win32")(
       await symlink(join(directory, "external.jar"), path);
       await expect(
         inspectGhidraPspExtension(root, "12.1.3", new ArtifactResourceScope()),
-      ).rejects.toThrow("regular files");
+      ).rejects.toMatchObject({
+        diagnostics: { code: "entry_kind", relative: "lib/extension.jar" },
+      });
     });
 
     it("bounds sparse extension input before reading or allocating its declared extent", async () => {
@@ -287,7 +314,12 @@ describe.skipIf(process.platform === "win32")(
       await truncate(join(root, "lib/extension.jar"), 64 * 1024 * 1024 + 1);
       await expect(
         inspectGhidraPspExtension(root, "12.1.3", new ArtifactResourceScope()),
-      ).rejects.toThrow("inspection limit");
+      ).rejects.toMatchObject({
+        diagnostics: {
+          code: "bytes_exceed_limit",
+          max_bytes: 64 * 1024 * 1024,
+        },
+      });
     });
   },
 );
@@ -314,7 +346,9 @@ describe.skipIf(process.platform === "win32")(
             "12.1.3",
             new ArtifactResourceScope(),
           ),
-        ).rejects.toThrow("inventory exceeds the inspection limit");
+        ).rejects.toMatchObject({
+          diagnostics: { code: "inventory_exceeds_limit", max_entries: 1024 },
+        });
       },
     );
   },
@@ -571,7 +605,12 @@ describe.skipIf(process.platform === "win32")(
       const languageOverride = { languageId: "x86:LE:64:default" };
       expect(() =>
         ghidraHeadlessArguments({ ...paths, psp: true, languageOverride }),
-      ).toThrow("PSP ELF import cannot be combined");
+      ).toThrow(
+        expect.objectContaining({
+          _tag: "GhidraAdmissionError",
+          code: "psp_combined",
+        }),
+      );
       expect(ghidraHeadlessArguments({ ...paths, languageOverride })).toEqual(
         expect.arrayContaining(["-processor", "x86:LE:64:default"]),
       );
@@ -903,11 +942,14 @@ describe.skipIf(process.platform === "win32")(
         const result = await provider.resolveAnalysisProfile(target);
         expect(result.ok).toBe(false);
         if (result.ok) throw new Error("Changed file admitted");
-        expect(result.error.message).toContain(
-          change === "growth"
-            ? "changed during inspection"
-            : "Truncated Allegrex component",
-        );
+        expect(result.error).toMatchObject({
+          diagnostics: {
+            code:
+              change === "growth" ? "component_changed" : "component_truncated",
+            relative:
+              change === "growth" ? "Module.manifest" : "extension.properties",
+          },
+        });
         expect(closes).toBe(1);
         expect(result.error.cleanupIncomplete).toBe(false);
         expect(provider.hasPendingOwnedResources()).toBe(false);
diff --git a/tests/boundary/filesystem/jsonOutputOwnership.test.ts b/tests/boundary/filesystem/jsonOutputOwnership.test.ts
index 8535836ef9..9bb2ab3e3f 100644
--- a/tests/boundary/filesystem/jsonOutputOwnership.test.ts
+++ b/tests/boundary/filesystem/jsonOutputOwnership.test.ts
@@ -12,6 +12,7 @@ import { OwnedFileHandle } from "../../../src/filesystem/OwnedFileHandle.js";
 import { OwnedStagedOutput } from "../../../src/filesystem/OwnedStagedOutput.js";
 import { projectAnalysisError } from "../../../src/domain/analysisErrorProjection.js";
 import { writeTextParts } from "../../../src/application/JsonFiles.js";
+import { StagedOutputError } from "../../../src/filesystem/StagedOutputError.js";
 import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
 
 const allocation = vi.hoisted(() => ({
@@ -70,7 +71,10 @@ it("closes the descriptor and retains staged content when its final identity is
     expect(result.error.cause).toMatchObject({
       outcome: {
         ok: false,
-        error: { message: "Cannot verify staged file identity" },
+        error: {
+          _tag: "StagedOutputError",
+          code: "identity_unverified",
+        },
       },
     });
     const stage = result.error.cleanupResources[0];
@@ -457,7 +461,11 @@ it("refuses to remove unexpected files from an owned staging directory", async (
   const unexpected = join(directory, "unexpected");
   writeFileSync(unexpected, "unowned");
   try {
-    await expect(owner.close()).rejects.toThrow(/Unexpected staging entries/u);
+    await expect(owner.close()).rejects.toMatchObject({
+      _tag: "StagedOutputError",
+      code: "unexpected_entries",
+      detail: { count: 1, entries: "unexpected" },
+    });
     expect(await fs.readFile(unexpected, "utf8")).toBe("unowned");
   } finally {
     await fs.rm(unexpected, { force: true });
@@ -466,6 +474,37 @@ it("refuses to remove unexpected files from an owned staging directory", async (
   }
 });
 
+it("keeps unexpected staging names on the publication error", async () => {
+  const root = await createTestTempDirectory("rea-staged-public-entries-");
+  const destination = join(root, "out.json");
+  const resources = new ArtifactResourceScope();
+  const close = vi
+    .spyOn(OwnedStagedOutput.prototype, "close")
+    .mockImplementation(async () => {
+      throw new StagedOutputError("unexpected_entries", {
+        count: 1,
+        entries: "unexpected",
+      });
+    });
+  try {
+    const result = await writeTextParts(["{}"], destination, false, resources);
+    expect(result.ok).toBe(false);
+    if (result.ok) return;
+    expect(result.error).toMatchObject({
+      _tag: "EvidenceFileError",
+      diagnostics: {
+        code: "unexpected_entries",
+        count: 1,
+        entries: "unexpected",
+      },
+    });
+  } finally {
+    close.mockRestore();
+    await resources.close().catch(() => undefined);
+    await rm(root, { recursive: true, force: true });
+  }
+});
+
 it("retains cleanup when its staging directory was renamed", async () => {
   const root = await createTestTempDirectory("rea-staged-renamed-dir-");
   const directory = join(root, ".rea-write-owned");
diff --git a/tests/boundary/mcp/wasmArtifactMcp.test.ts b/tests/boundary/mcp/wasmArtifactMcp.test.ts
index eb9d5fa467..83e04f6cc0 100644
--- a/tests/boundary/mcp/wasmArtifactMcp.test.ts
+++ b/tests/boundary/mcp/wasmArtifactMcp.test.ts
@@ -141,7 +141,11 @@ it.each(["bin", "hop"])(
         code: "capability_unavailable",
         details: {
           operation: "inspect_wasm_artifact",
-          reason: expect.stringContaining("REA_WABT_BIN_DIRECTORY"),
+          reason: "directory_not_absolute",
+          diagnostics: {
+            code: "directory_not_absolute",
+            setting: "REA_WABT_BIN_DIRECTORY",
+          },
         },
       },
     });
@@ -152,7 +156,13 @@ it.each(["bin", "hop"])(
     expect(parseMcpToolError(summary)).toMatchObject({
       error: {
         code: "capability_unavailable",
-        details: { reason: expect.stringContaining("REA_WABT_BIN_DIRECTORY") },
+        details: {
+          reason: "directory_not_absolute",
+          diagnostics: {
+            code: "directory_not_absolute",
+            setting: "REA_WABT_BIN_DIRECTORY",
+          },
+        },
       },
     });
     await client.ping();
diff --git a/tests/boundary/process/darwinProcessRunTokenReader.test.ts b/tests/boundary/process/darwinProcessRunTokenReader.test.ts
index 64d224a3b0..e68bc04008 100644
--- a/tests/boundary/process/darwinProcessRunTokenReader.test.ts
+++ b/tests/boundary/process/darwinProcessRunTokenReader.test.ts
@@ -1040,7 +1040,10 @@ it.skipIf(process.platform === "win32")(
         throw new Error("closed reader compilation unexpectedly succeeded");
       expect(outcome.cause).toMatchObject({ name: "AbortError" });
       await expect(access(state.root)).rejects.toThrow();
-      await expect(reader.prepare()).rejects.toThrow(/reader is closed/u);
+      await expect(reader.prepare()).rejects.toMatchObject({
+        _tag: "ProcessAdmissionError",
+        code: "reader_closed",
+      });
       await expect(reader.close()).resolves.toBeUndefined();
     } finally {
       await Promise.allSettled([preparation]);
diff --git a/tests/boundary/process/providerProcess.test.ts b/tests/boundary/process/providerProcess.test.ts
index 6e3b709956..6a6103f2a6 100644
--- a/tests/boundary/process/providerProcess.test.ts
+++ b/tests/boundary/process/providerProcess.test.ts
@@ -506,7 +506,10 @@ describe("provider process memory limits", () => {
         platform: "linux",
         memoryLimitBytes: 704 * 1024 * 1024,
       }),
-    ).rejects.toThrow("require the Windows Job Object launcher");
+    ).rejects.toMatchObject({
+      _tag: "ProcessAdmissionError",
+      code: "memory_limit_unsupported",
+    });
   });
 });
 
diff --git a/tests/boundary/providers/ghidra/ghidraJavaLaunch.test.ts b/tests/boundary/providers/ghidra/ghidraJavaLaunch.test.ts
index b402432d38..ca7d30603d 100644
--- a/tests/boundary/providers/ghidra/ghidraJavaLaunch.test.ts
+++ b/tests/boundary/providers/ghidra/ghidraJavaLaunch.test.ts
@@ -452,6 +452,13 @@ describe.skipIf(process.platform === "win32")(
               cause: { code: 3 },
             },
           });
+        if (mode === "env-malformed")
+          expect(cause).toMatchObject({
+            cause: {
+              code: "invalid_environment_entry",
+              detail: { check: "separator", line: "invalid environment" },
+            },
+          });
         if (mode === "vm-malformed")
           expect(cause).toMatchObject({
             launch_support: expect.arrayContaining([
@@ -474,9 +481,8 @@ describe.skipIf(process.platform === "win32")(
         if (launched.ok)
           throw new Error("Expected a JVM platform override failure");
         expect(launched.error.cause).toMatchObject({
-          message: expect.stringContaining(
-            "may not override os.arch or os.name",
-          ),
+          _tag: "GhidraAdmissionError",
+          code: "platform_override",
         });
       },
     );
@@ -499,9 +505,8 @@ describe.skipIf(process.platform === "win32")(
         if (launched.ok)
           throw new Error("Expected a JVM platform override failure");
         expect(launched.error.cause).toMatchObject({
-          message: expect.stringContaining(
-            "may not override os.arch or os.name",
-          ),
+          _tag: "GhidraAdmissionError",
+          code: "platform_override",
         });
       },
     );
@@ -578,9 +583,8 @@ describe.skipIf(process.platform === "win32")(
         if (launched.ok)
           throw new Error("Expected an effective platform override refusal");
         expect(launched.error.cause).toMatchObject({
-          message: expect.stringContaining(
-            "may not override os.arch or os.name",
-          ),
+          _tag: "GhidraAdmissionError",
+          code: "platform_override",
         });
       },
     );
@@ -600,7 +604,8 @@ describe.skipIf(process.platform === "win32")(
       if (launched.ok)
         throw new Error("Expected a JVM platform override failure");
       expect(launched.error.cause).toMatchObject({
-        message: expect.stringContaining("may not override os.arch or os.name"),
+        _tag: "GhidraAdmissionError",
+        code: "platform_override",
       });
     });
 
@@ -634,7 +639,9 @@ describe.skipIf(process.platform === "win32")(
       if (launched.ok)
         throw new Error("Expected an unreadable argument-file failure");
       expect(launched.error.cause).toMatchObject({
-        message: expect.stringContaining("argument file is unreadable"),
+        _tag: "GhidraAdmissionError",
+        code: "argument_file_unreadable",
+        detail: { path: optionsFile },
       });
     });
 
@@ -657,7 +664,8 @@ describe.skipIf(process.platform === "win32")(
       if (launched.ok)
         throw new Error("Expected a nested argument-file failure");
       expect(launched.error.cause).toMatchObject({
-        message: expect.stringContaining("may not nest @ references"),
+        _tag: "GhidraAdmissionError",
+        code: "nested_argument_file",
       });
     });
   },
@@ -823,9 +831,8 @@ describe.skipIf(process.platform === "win32")(
           );
           if (cleanup.fileCleanupFailure.outcome.kind === "failed")
             expect(cleanup.fileCleanupFailure.outcome.cause).toMatchObject({
-              message: expect.stringContaining(
-                "may not override os.arch or os.name",
-              ),
+              _tag: "GhidraAdmissionError",
+              code: "platform_override",
             });
           await resources.retryCleanup();
           expect(resources.hasPending).toBe(false);
diff --git a/tests/boundary/providers/ghidra/ghidraLauncher.test.ts b/tests/boundary/providers/ghidra/ghidraLauncher.test.ts
index 4c5508813d..273fd3df95 100644
--- a/tests/boundary/providers/ghidra/ghidraLauncher.test.ts
+++ b/tests/boundary/providers/ghidra/ghidraLauncher.test.ts
@@ -260,7 +260,12 @@ describe("Ghidra GameCube DOL loader", () => {
           sectionFilePath: "/tmp/gamecube-dol-sections.txt",
         },
       }),
-    ).toThrow(/cannot be combined with another loader, language override/u);
+    ).toThrow(
+      expect.objectContaining({
+        _tag: "GhidraAdmissionError",
+        code: "gamecube_dol_combined",
+      }),
+    );
   });
 });
 
@@ -346,7 +351,12 @@ describe("Ghidra headless launcher", () => {
     ])
       expect(() =>
         ghidraHeadlessArguments({ ...base, mipsSoftFloat: true, ...conflict }),
-      ).toThrow(/generic MIPS ELF/u);
+      ).toThrow(
+        expect.objectContaining({
+          _tag: "GhidraAdmissionError",
+          code: "mips_soft_float_scope",
+        }),
+      );
   });
 });
 
@@ -395,7 +405,12 @@ describe("Ghidra configured import language and seeds", () => {
         dosMz: true,
         languageOverride: { languageId: "x86:LE:32:default" },
       }),
-    ).toThrow(/cannot be combined with a DOS import/u);
+    ).toThrow(
+      expect.objectContaining({
+        _tag: "GhidraAdmissionError",
+        code: "language_override_dos",
+      }),
+    );
   });
 
   it("never combines a configured language with a raw-binary import", () => {
@@ -409,7 +424,12 @@ describe("Ghidra configured import language and seeds", () => {
           baseAddr: "0x8000000",
         },
       }),
-    ).toThrow(/cannot be combined with a raw-binary import/u);
+    ).toThrow(
+      expect.objectContaining({
+        _tag: "GhidraAdmissionError",
+        code: "language_override_raw_binary",
+      }),
+    );
   });
 
   it.each(["darwin", "win32"] as const)(
@@ -579,30 +599,41 @@ describe("Ghidra existing project", () => {
   });
 
   it.each([
-    { dosMz: true as const },
-    { dosCom: true as const },
-    {
-      rawBinary: {
-        languageId: "ARM:LE:32:v7",
-        compilerSpecId: "default",
-        baseAddr: "0x8000000",
+    [{ dosMz: true as const }, "existing_project_dos"],
+    [{ dosCom: true as const }, "existing_project_dos"],
+    [
+      {
+        rawBinary: {
+          languageId: "ARM:LE:32:v7",
+          compilerSpecId: "default",
+          baseAddr: "0x8000000",
+        },
       },
-    },
-    { languageOverride: { languageId: "x86:LE:32:default" } },
-    { psp: true as const },
-    { mipsSoftFloat: true as const },
-    { seedPath: "/tmp/runtime/seeds/seeds.tsv" },
-    { disabledAnalyzers: ["Decompiler Parameter ID"] },
-  ])(
+      "existing_project_raw_binary",
+    ],
+    [
+      { languageOverride: { languageId: "x86:LE:32:default" } },
+      "existing_project_language_override",
+    ],
+    [{ psp: true as const }, "existing_project_psp"],
+    [{ mipsSoftFloat: true as const }, "existing_project_mips_soft_float"],
+    [{ seedPath: "/tmp/runtime/seeds/seeds.tsv" }, "existing_project_analysis"],
+    [
+      { disabledAnalyzers: ["Decompiler Parameter ID"] },
+      "existing_project_analysis",
+    ],
+  ] as const)(
     "rejects the import-only option %o with an existing project",
-    (conflict) => {
+    (conflict, code) => {
       expect(() =>
         ghidraHeadlessArguments({
           ...base,
           existingProject: { programName: "game.exe" },
           ...conflict,
         }),
-      ).toThrow(/existing (Ghidra )?project|fresh import/u);
+      ).toThrow(
+        expect.objectContaining({ _tag: "GhidraAdmissionError", code }),
+      );
     },
   );
 
@@ -618,7 +649,12 @@ describe("Ghidra existing project", () => {
         ),
         existingProject: { programName: "game.exe" },
       }),
-    ).toThrow(/Windows/u);
+    ).toThrow(
+      expect.objectContaining({
+        _tag: "GhidraAdmissionError",
+        code: "existing_project_windows",
+      }),
+    );
   });
 
   it("requires a program name for -process", () => {
@@ -627,7 +663,12 @@ describe("Ghidra existing project", () => {
         ...base,
         existingProject: { programName: "   " },
       }),
-    ).toThrow(/program name/u);
+    ).toThrow(
+      expect.objectContaining({
+        _tag: "GhidraAdmissionError",
+        code: "existing_project_program_name",
+      }),
+    );
   });
 });