diff --git a/src/application/WebSourceLocationService.test.ts b/src/application/WebSourceLocationService.test.ts
index 4a13482a51..fd68983f87 100644
--- a/src/application/WebSourceLocationService.test.ts
+++ b/src/application/WebSourceLocationService.test.ts
@@ -146,7 +146,8 @@ it.each([
 );
 it("honors cancellation both before acquisition and across decoder completion", async () => {
   const first = new AbortController();
-  first.abort();
+  const firstReason = { caller: "before source-map acquisition" };
+  first.abort(firstReason);
   const response = await new WebSourceLocationService(
     {
       load: () => {
@@ -156,15 +157,18 @@ it("honors cancellation both before acquisition and across decoder completion",
     decoder,
   ).trace(args, { signal: first.signal });
   expect(response.ok).toBe(false);
+  if (!response.ok) expect(response.error.cause).toBe(firstReason);
   const controller = new AbortController();
+  const lateReason = { caller: "after source-map provider completion" };
   const late = await service(undefined, {
     trace: (input) => {
-      controller.abort();
+      controller.abort(lateReason);
       return decoder.trace(input);
     },
   }).trace(args, { signal: controller.signal });
   if (late.ok) throw new Error("expected cancellation");
   expect(late.error).toBeInstanceOf(AnalysisCancelledError);
+  expect(late.error.cause).toBe(lateReason);
   expect(parseEvidence(late.error.partialObservation)).toMatchObject({
     operation: "trace_web_source_location",
     confidence: "derived",
diff --git a/src/application/WebSourceLocationService.ts b/src/application/WebSourceLocationService.ts
index 55731d5ac7..4dd71ab9ab 100644
--- a/src/application/WebSourceLocationService.ts
+++ b/src/application/WebSourceLocationService.ts
@@ -88,7 +88,9 @@ export class WebSourceLocationService {
     options?: ExecutionOptions,
   ): Promise<Result<Evidence, AnalysisError>> {
     if (options?.signal?.aborted)
-      return err(new AnalysisCancelledError(OPERATION));
+      return err(
+        new AnalysisCancelledError(OPERATION, { cause: options.signal.reason }),
+      );
     const parsed = webSourceLocationInputSchema.safeParse(rawInput);
     if (!parsed.success)
       return err(
@@ -114,7 +116,9 @@ export class WebSourceLocationService {
     if (!pairing.ok) return pairing;
     const generatedOffset = pairing.value;
     if (options?.signal?.aborted)
-      return err(new AnalysisCancelledError(OPERATION));
+      return err(
+        new AnalysisCancelledError(OPERATION, { cause: options.signal.reason }),
+      );
     const traced = await this.decoder.trace(
       {
         text: map.text,
diff --git a/src/javascript/sourceMaps/SourceMapCommand.test.ts b/src/javascript/sourceMaps/SourceMapCommand.test.ts
new file mode 100644
index 0000000000..c0b40cdd30
--- /dev/null
+++ b/src/javascript/sourceMaps/SourceMapCommand.test.ts
@@ -0,0 +1,278 @@
+import { access } from "node:fs/promises";
+import { expect, it, vi } from "vitest";
+import {
+  AnalysisCancelledError,
+  AnalysisResourceConstraintError,
+  AnalysisTimeoutError,
+} from "../../domain/analysisErrorCore.js";
+import { PrivateRuntimeRoot } from "../../process/PrivateRuntimeRoot.js";
+import {
+  ProviderProcessSupervisor,
+  spawnOwnedProviderProcess,
+} from "../../process/ProviderProcess.js";
+import { WEB_SOURCE_MAP_LIMITS } from "../../domain/webSourceLocation.js";
+import {
+  runSourceMapCommand,
+  SOURCE_MAP_CODEC_MEMORY_LIMIT_BYTES,
+} from "./SourceMapCommand.js";
+
+const runChild = (
+  signal: AbortSignal | undefined,
+  script: string,
+  onRuntime?: (path: string) => void,
+  onLaunch?: () => void,
+) =>
+  runSourceMapCommand(
+    "{}",
+    "/probe/source.map",
+    signal === undefined ? undefined : { signal },
+    {
+      prepareOwnership: async () => {},
+      createRuntime: async () => {
+        const runtime = await PrivateRuntimeRoot.create({
+          prefix: "rea-source-map-command-test-",
+        });
+        onRuntime?.(runtime.path);
+        return runtime;
+      },
+      launcher: async (options) => {
+        const child = await spawnOwnedProviderProcess({
+          ...options,
+          arguments: ["-e", script],
+        });
+        onLaunch?.();
+        return child;
+      },
+    },
+  );
+
+const exitsAfterHoldingOutput =
+  'const {spawn}=require("node:child_process"); spawn(process.execPath,["-e","setTimeout(()=>{},400)"],{stdio:["ignore","inherit","inherit"]}); process.stderr.write("physical exit 7"); process.exit(7)';
+const exitsThenDescendantExceedsStderrBudget =
+  'const {spawn}=require("node:child_process"); spawn(process.execPath,["-e",`setTimeout(()=>{process.stderr.write("x".repeat(1024*1024+64)); setInterval(()=>{},1000)},25)`],{stdio:["ignore","inherit","inherit"]}); process.stderr.write("physical exit 7"); process.exit(7)';
+
+it("preserves the exact object reason for an already-aborted caller", async () => {
+  const reason = { caller: "opaque source-map request" };
+  const controller = new AbortController();
+  controller.abort(reason);
+  const result = await runSourceMapCommand(
+    "{}",
+    "/probe/source.map",
+    { signal: controller.signal },
+    {
+      prepareOwnership: async () => {},
+      launcher: async () => {
+        throw new Error("must not launch");
+      },
+    },
+  );
+  expect(result.ok).toBe(false);
+  if (result.ok) throw new Error("expected cancellation");
+  expect(result.error).toBeInstanceOf(AnalysisCancelledError);
+  expect(result.error.cause).toBe(reason);
+});
+
+it("preserves exact caller reason when cancellation precedes process exit", async () => {
+  const reason = { caller: "active source-map cancellation" };
+  const controller = new AbortController();
+  let runtimePath: string | undefined;
+  const result = await runChild(
+    controller.signal,
+    'process.stdout.write("ready\\n"); setInterval(()=>{},1000)',
+    (path) => {
+      runtimePath = path;
+    },
+    () => setTimeout(() => controller.abort(reason), 0),
+  );
+  expect(result.ok).toBe(false);
+  if (result.ok) throw new Error("expected cancellation");
+  expect(result.error).toBeInstanceOf(AnalysisCancelledError);
+  expect(result.error.cause).toBe(reason);
+  if (runtimePath === undefined) throw new Error("runtime was not acquired");
+  await expect(access(runtimePath)).rejects.toMatchObject({ code: "ENOENT" });
+});
+
+it("preserves an observed nonzero exit before caller cancellation during output drain", async () => {
+  const reason = { caller: "later than owned exit" };
+  const controller = new AbortController();
+  let runtimePath: string | undefined;
+  let observedBeforeAbort:
+    | { readonly code: number | null; readonly signal: NodeJS.Signals | null }
+    | undefined;
+  const originalWait = ProviderProcessSupervisor.prototype.waitForOutputClose;
+  const waitSpy = vi
+    .spyOn(ProviderProcessSupervisor.prototype, "waitForOutputClose")
+    .mockImplementation(async function (
+      this: ProviderProcessSupervisor,
+      timeoutMs,
+      signal,
+    ) {
+      const exit = this.observedExit();
+      if (exit?.code === 7 && !controller.signal.aborted) {
+        observedBeforeAbort = exit;
+        controller.abort(reason);
+        return false;
+      }
+      return originalWait.call(this, timeoutMs, signal);
+    });
+  let result;
+  try {
+    result = await runChild(
+      controller.signal,
+      exitsAfterHoldingOutput,
+      (path) => {
+        runtimePath = path;
+      },
+    );
+  } finally {
+    waitSpy.mockRestore();
+  }
+  expect(observedBeforeAbort).toEqual({ code: 7, signal: null });
+  expect(result.ok).toBe(false);
+  if (result.ok) throw new Error("expected physical failure");
+  expect(result.error._tag).toBe("ProviderAdapterError");
+  expect(result.error.diagnostics).toMatchObject({
+    exit_code: 7,
+    output_complete: false,
+  });
+  expect(result.error.capturedOutput?.truncated).toBe(true);
+  if (runtimePath === undefined) throw new Error("runtime was not acquired");
+  await expect(access(runtimePath)).rejects.toMatchObject({ code: "ENOENT" });
+});
+
+it("classifies the same nonzero exit without cancellation", async () => {
+  const result = await runChild(undefined, exitsAfterHoldingOutput);
+  expect(result.ok).toBe(false);
+  if (result.ok) throw new Error("expected physical failure");
+  expect(result.error).toMatchObject({
+    _tag: "ProviderAdapterError",
+    diagnostics: {
+      exit_code: 7,
+      stderr: "physical exit 7",
+      output_complete: true,
+    },
+  });
+});
+
+it("stops a held drain after late output exceeds budget but keeps the exit primary", async () => {
+  const startedAt = performance.now();
+  const result = await runChild(
+    undefined,
+    exitsThenDescendantExceedsStderrBudget,
+  );
+  const elapsedMs = performance.now() - startedAt;
+  expect(result.ok).toBe(false);
+  if (result.ok) throw new Error("expected physical failure");
+  expect(result.error._tag).toBe("ProviderAdapterError");
+  expect(result.error.diagnostics).toMatchObject({
+    exit_code: 7,
+    output_limit_reached: true,
+    output_complete: false,
+  });
+  expect(result.error.diagnostics?.stderr).toContain("physical exit 7");
+  expect(result.error.capturedOutput?.truncated).toBe(true);
+  expect(elapsedMs).toBeLessThan(5_000);
+});
+
+it("preserves an observed process-memory limit over the codec exit status", async () => {
+  const controller = new AbortController();
+  const reason = { caller: "after memory-limit exit" };
+  let observedBeforeAbort:
+    | { readonly code: number | null; readonly signal: NodeJS.Signals | null }
+    | undefined;
+  const originalWait = ProviderProcessSupervisor.prototype.waitForOutputClose;
+  const waitSpy = vi
+    .spyOn(ProviderProcessSupervisor.prototype, "waitForOutputClose")
+    .mockImplementation(async function (
+      this: ProviderProcessSupervisor,
+      timeoutMs,
+      signal,
+    ) {
+      const exit = this.observedExit();
+      if (exit?.code === 3 && !controller.signal.aborted) {
+        observedBeforeAbort = exit;
+        controller.abort(reason);
+        return false;
+      }
+      return originalWait.call(this, timeoutMs, signal);
+    });
+  let result;
+  try {
+    result = await runSourceMapCommand(
+      "{}",
+      "/probe/source.map",
+      { signal: controller.signal },
+      {
+        prepareOwnership: async () => {},
+        launcher: async (options) => {
+          const spawned = await spawnOwnedProviderProcess({
+            ...options,
+            arguments: [
+              "-e",
+              'const {spawn}=require("node:child_process"); spawn(process.execPath,["-e","setTimeout(()=>{},400)"],{stdio:["ignore","inherit","inherit"]}); process.stderr.write("memory limit reached"); process.exit(3)',
+            ],
+          });
+          let exited = false;
+          spawned.process.once("exit", () => {
+            exited = true;
+          });
+          Object.defineProperty(spawned.process, "memoryLimitReached", {
+            get: () => exited,
+          });
+          return spawned;
+        },
+      },
+    );
+  } finally {
+    waitSpy.mockRestore();
+  }
+  expect(observedBeforeAbort).toEqual({ code: 3, signal: null });
+  expect(result.ok).toBe(false);
+  if (result.ok) throw new Error("expected memory-limit failure");
+  expect(result.error).toBeInstanceOf(AnalysisResourceConstraintError);
+  expect(result.error).toMatchObject({
+    resource: "memory",
+    reportedLimits: {
+      codec_process_memory_limit_bytes: SOURCE_MAP_CODEC_MEMORY_LIMIT_BYTES,
+    },
+    capturedOutput: { stderr: "memory limit reached" },
+  });
+  expect(result.error.capturedOutput?.truncated).toBe(true);
+});
+
+it("keeps a timeout distinct from caller cancellation", async () => {
+  vi.useFakeTimers({
+    toFake: ["setTimeout", "clearTimeout", "performance"],
+  });
+  let runtimePath: string | undefined;
+  try {
+    const result = await runSourceMapCommand(
+      "{}",
+      "/probe/source.map",
+      undefined,
+      {
+        prepareOwnership: async () => {},
+        createRuntime: async () => {
+          const runtime = await PrivateRuntimeRoot.create({
+            prefix: "rea-source-map-timeout-test-",
+          });
+          runtimePath = runtime.path;
+          return runtime;
+        },
+        launcher: async () => {
+          await vi.advanceTimersByTimeAsync(
+            WEB_SOURCE_MAP_LIMITS.decodeTimeoutMs + 1,
+          );
+          throw new Error("launcher settled after deadline");
+        },
+      },
+    );
+    expect(result.ok).toBe(false);
+    if (result.ok) throw new Error("expected timeout");
+    expect(result.error).toBeInstanceOf(AnalysisTimeoutError);
+    if (runtimePath === undefined) throw new Error("runtime was not acquired");
+    await expect(access(runtimePath)).rejects.toMatchObject({ code: "ENOENT" });
+  } finally {
+    vi.useRealTimers();
+  }
+});
diff --git a/src/javascript/sourceMaps/SourceMapCommand.ts b/src/javascript/sourceMaps/SourceMapCommand.ts
index 9e88379527..4b24e8ed9a 100644
--- a/src/javascript/sourceMaps/SourceMapCommand.ts
+++ b/src/javascript/sourceMaps/SourceMapCommand.ts
@@ -25,6 +25,8 @@ import {
   ProviderProcessSupervisor,
   spawnOwnedProviderProcess,
   type OwnedProviderProcessSpawnOptions,
+  type ProviderProcessExitObservation,
+  type ProviderProcessSnapshot,
   type SpawnedOwnedProviderProcess,
 } from "../../process/ProviderProcess.js";
 import { prepareProcessOwnershipInspection } from "../../process/ProcessOwnershipObservation.js";
@@ -58,6 +60,25 @@ export interface SourceMapCleanupOwner {
   ): Promise<ProviderCleanupError | undefined>;
 }
 
+type CodecPhysicalObservation =
+  | {
+      readonly kind: "exit";
+      readonly exit: ProviderProcessExitObservation;
+    }
+  | {
+      readonly kind: "process-error";
+      readonly message: string;
+      readonly cause: Error;
+    }
+  | { readonly kind: "output-limit" };
+type CodecOutcome =
+  | {
+      readonly kind: "physical";
+      readonly observation: CodecPhysicalObservation;
+    }
+  | { readonly kind: "cancelled"; readonly callerReason: unknown }
+  | { readonly kind: "timeout" };
+
 export class SourceMapCleanupFailure extends ProviderCleanupError {
   constructor(
     readonly cleanupOwner: SourceMapCleanupOwner,
@@ -82,7 +103,9 @@ export const runSourceMapCommand = async (
   } catch (cause: unknown) {
     return err(
       options?.signal?.aborted === true
-        ? new AnalysisCancelledError(OPERATION)
+        ? new AnalysisCancelledError(OPERATION, {
+            cause: options.signal.reason,
+          })
         : new ProviderAdapterError(PROVIDER, OPERATION, {
             cause,
             diagnostics: {
@@ -105,12 +128,15 @@ export const runSourceMapCommand = async (
   } catch (cause: unknown) {
     result = err(command.failure(cause));
   } finally {
+    command.dispose();
     deadline.dispose();
   }
   const cleanup = await command.close(result.ok ? null : result.error.message);
   if (cleanup !== undefined) return err(cleanup);
   return result.ok && options?.signal?.aborted
-    ? err(new AnalysisCancelledError(OPERATION))
+    ? err(
+        new AnalysisCancelledError(OPERATION, { cause: options.signal.reason }),
+      )
     : result;
 };
 
@@ -118,13 +144,26 @@ class OwnedCodec implements SourceMapCleanupOwner {
   readonly #runId = `rea-source-map-${randomUUID()}`;
   #runtime: SourceMapCodecRuntime | undefined;
   #supervisor: ProviderProcessSupervisor | undefined;
-  #oversized = false;
-  #processError: string | undefined;
+  #outcome: CodecOutcome | undefined;
+  #drainStop: CodecPhysicalObservation | undefined;
+  readonly #onInterruption: () => void;
   constructor(
     readonly path: string,
     readonly dependencies: SourceMapDecoderDependencies,
     readonly deadline: ProviderStartupDeadline,
-  ) {}
+  ) {
+    this.#onInterruption = () => this.#observeInterruption();
+    if (deadline.signal.aborted) this.#observeInterruption();
+    else
+      deadline.signal.addEventListener("abort", this.#onInterruption, {
+        once: true,
+      });
+  }
+
+  /** Stop recording event order after an outcome has been selected. */
+  dispose(): void {
+    this.deadline.signal.removeEventListener("abort", this.#onInterruption);
+  }
 
   async start(request: string): Promise<void> {
     this.check();
@@ -175,16 +214,33 @@ class OwnedCodec implements SourceMapCleanupOwner {
           (() => cleanupOwnedProcessGroup(spawned.ownership)),
       },
       {
+        maxDiagnosticBytes: WEB_SOURCE_MAP_LIMITS.outputBytes + 1024 * 1024,
         onDiagnostic: (event) => {
-          if (event.type === "error") this.#processError = event.message;
+          if (
+            event.type === "exit" &&
+            (event.code !== 0 || event.signal !== null)
+          )
+            this.#recordPhysicalFailure({
+              kind: "exit",
+              exit: { code: event.code, signal: event.signal },
+            });
+          if (event.type === "error") {
+            this.#recordPhysicalFailure({
+              kind: "process-error",
+              message: event.message,
+              cause: event.cause ?? new Error(event.message),
+            });
+          }
           if (
             event.type === "output" &&
-            event.totalBytes >
-              (event.stream === "stdout"
-                ? WEB_SOURCE_MAP_LIMITS.outputBytes
-                : 1024 * 1024)
-          )
-            this.#oversized = true;
+            (event.truncated === true ||
+              event.totalBytes >
+                (event.stream === "stdout"
+                  ? WEB_SOURCE_MAP_LIMITS.outputBytes
+                  : 1024 * 1024))
+          ) {
+            this.#recordPhysicalFailure({ kind: "output-limit" });
+          }
         },
       },
     );
@@ -194,61 +250,50 @@ class OwnedCodec implements SourceMapCleanupOwner {
     const supervisor = this.#supervisor;
     if (supervisor === undefined)
       throw new Error("Codec process was not acquired");
-    while (!(await supervisor.waitForOutputClose(50))) this.check();
+    while (!(await supervisor.waitForOutputClose(50))) {
+      const outcome = this.#outcome;
+      if (
+        outcome?.kind !== "physical" ||
+        outcome.observation.kind !== "exit" ||
+        this.deadline.signal.aborted ||
+        this.#drainStop !== undefined
+      )
+        this.check();
+    }
     this.check();
     const snapshot = supervisor.snapshot();
     // No partial codec result exists; a reached limit fails the whole trace.
     if (snapshot.memoryLimitReached === true)
-      throw new AnalysisResourceConstraintError(
-        OPERATION,
-        "memory",
-        `Source-map codec reached its ${SOURCE_MAP_CODEC_MEMORY_LIMIT_BYTES === null ? "" : `${String(SOURCE_MAP_CODEC_MEMORY_LIMIT_BYTES)}-byte `}process memory limit for ${this.path}; no partial evidence was returned.`,
-        {
-          codec_process_memory_limit_bytes: SOURCE_MAP_CODEC_MEMORY_LIMIT_BYTES,
-        },
-        {
-          capturedOutput: {
-            stdout: "",
-            stderr: snapshot.stderr.text,
-            truncated: snapshot.diagnosticTruncated ?? false,
-          },
-        },
-      );
-    if (snapshot.exitCode !== 0 || snapshot.signal !== null)
-      throw new ProviderAdapterError(PROVIDER, OPERATION, {
-        diagnostics: {
-          map_path: this.path,
-          exit_code: snapshot.exitCode ?? null,
-          signal: snapshot.signal ?? null,
-          stderr: snapshot.stderr.text,
-        },
-      });
+      throw this.#memoryLimitFailure(snapshot);
     return snapshot.stdout.text;
   }
 
   check(): void {
-    if (this.deadline.interruption === "cancelled")
-      throw new AnalysisCancelledError(OPERATION);
-    if (this.deadline.interruption === "timeout")
+    this.#observeInterruption();
+    const outcome = this.#outcome;
+    if (outcome?.kind === "physical")
+      throw this.#physicalFailure(outcome.observation);
+    if (outcome?.kind === "cancelled")
+      throw new AnalysisCancelledError(OPERATION, {
+        cause: outcome.callerReason,
+      });
+    if (outcome?.kind === "timeout")
       throw new AnalysisTimeoutError(
         OPERATION,
         WEB_SOURCE_MAP_LIMITS.decodeTimeoutMs,
       );
-    if (this.#oversized)
-      throw new AnalysisOutputError(
-        OPERATION,
-        "Codec output exceeds its complete-evidence or diagnostic budget.",
-      );
-    if (this.#processError !== undefined)
-      throw new ProviderAdapterError(PROVIDER, OPERATION, {
-        diagnostics: { map_path: this.path, error_message: this.#processError },
-      });
   }
 
   failure(cause: unknown): AnalysisError {
-    if (this.deadline.interruption === "cancelled")
-      return new AnalysisCancelledError(OPERATION);
-    if (this.deadline.interruption === "timeout")
+    this.#observeInterruption();
+    const outcome = this.#outcome;
+    if (outcome?.kind === "physical")
+      return this.#physicalFailure(outcome.observation);
+    if (outcome?.kind === "cancelled")
+      return new AnalysisCancelledError(OPERATION, {
+        cause: outcome.callerReason,
+      });
+    if (outcome?.kind === "timeout")
       return new AnalysisTimeoutError(
         OPERATION,
         WEB_SOURCE_MAP_LIMITS.decodeTimeoutMs,
@@ -267,6 +312,144 @@ class OwnedCodec implements SourceMapCleanupOwner {
         });
   }
 
+  #observeInterruption(): void {
+    if (this.#outcome !== undefined) return;
+    if (!this.deadline.signal.aborted) return;
+    const interruption = this.deadline.interruption;
+    if (interruption === undefined) return;
+    this.#outcome =
+      interruption === "cancelled"
+        ? { kind: "cancelled", callerReason: this.deadline.signal.reason }
+        : { kind: "timeout" };
+  }
+
+  #recordPhysicalFailure(observation: CodecPhysicalObservation): void {
+    this.#observeInterruption();
+    if (this.#outcome === undefined)
+      this.#outcome = { kind: "physical", observation };
+    else if (observation.kind !== "exit" && this.#drainStop === undefined)
+      this.#drainStop = observation;
+  }
+
+  #physicalFailure(observation: CodecPhysicalObservation): AnalysisError {
+    const snapshot = this.#supervisor?.snapshot();
+    if (observation.kind === "exit") {
+      if (snapshot?.memoryLimitReached === true)
+        return this.#memoryLimitFailure(snapshot);
+      return this.#exitFailure(observation.exit, snapshot);
+    }
+    if (observation.kind === "process-error")
+      return this.#processErrorFailure(observation, snapshot);
+    return this.#outputLimitFailure(snapshot);
+  }
+
+  #exitFailure(
+    exit: ProviderProcessExitObservation,
+    snapshot: ProviderProcessSnapshot | undefined,
+  ): AnalysisError {
+    const outputComplete = this.#supervisor?.observedOutputClose() ?? false;
+    const capturedOutput = this.#capturedOutput(snapshot, exit, outputComplete);
+    return new ProviderAdapterError(PROVIDER, OPERATION, {
+      diagnostics: {
+        map_path: this.path,
+        exit_code: exit.code,
+        signal: exit.signal,
+        output_complete: outputComplete,
+        stderr: snapshot?.stderr.text ?? "",
+        ...(this.#drainStop?.kind === "output-limit"
+          ? { output_limit_reached: true }
+          : {}),
+        ...(this.#drainStop?.kind === "process-error"
+          ? { drain_error_message: this.#drainStop.message }
+          : {}),
+      },
+      ...(capturedOutput === undefined ? {} : { capturedOutput }),
+    });
+  }
+
+  #processErrorFailure(
+    observation: Extract<CodecPhysicalObservation, { kind: "process-error" }>,
+    snapshot: ProviderProcessSnapshot | undefined,
+  ): AnalysisError {
+    const outputComplete = this.#supervisor?.observedOutputClose() ?? false;
+    const capturedOutput = this.#capturedOutput(
+      snapshot,
+      undefined,
+      outputComplete,
+    );
+    return new ProviderAdapterError(PROVIDER, OPERATION, {
+      cause: observation.cause,
+      diagnostics: {
+        map_path: this.path,
+        error_message: observation.message,
+        output_complete: outputComplete,
+      },
+      ...(capturedOutput === undefined ? {} : { capturedOutput }),
+    });
+  }
+
+  #outputLimitFailure(
+    snapshot: ProviderProcessSnapshot | undefined,
+  ): AnalysisError {
+    const outputComplete = this.#supervisor?.observedOutputClose() ?? false;
+    const capturedOutput = this.#capturedOutput(
+      snapshot,
+      undefined,
+      outputComplete,
+    );
+    return new AnalysisOutputError(
+      OPERATION,
+      "Codec output exceeds its complete-evidence or diagnostic budget.",
+      {
+        capturedOutput: {
+          stdout: capturedOutput?.stdout ?? "",
+          stderr: capturedOutput?.stderr ?? "",
+          stdout_bytes: capturedOutput?.stdout_bytes ?? 0,
+          stderr_bytes: capturedOutput?.stderr_bytes ?? 0,
+          truncated: true,
+        },
+      },
+    );
+  }
+
+  #capturedOutput(
+    snapshot: ProviderProcessSnapshot | undefined,
+    exit: ProviderProcessExitObservation | undefined,
+    outputComplete: boolean,
+  ) {
+    if (snapshot === undefined) return undefined;
+    return {
+      stdout: snapshot.stdout.text,
+      stderr: snapshot.stderr.text,
+      truncated: snapshot.diagnosticTruncated === true || !outputComplete,
+      stdout_bytes: snapshot.stdout.observedBytes,
+      stderr_bytes: snapshot.stderr.observedBytes,
+      ...(exit === undefined
+        ? {}
+        : { exit_code: exit.code, signal: exit.signal }),
+    };
+  }
+
+  #memoryLimitFailure(snapshot: ProviderProcessSnapshot): AnalysisError {
+    return new AnalysisResourceConstraintError(
+      OPERATION,
+      "memory",
+      `Source-map codec reached its ${SOURCE_MAP_CODEC_MEMORY_LIMIT_BYTES === null ? "" : `${String(SOURCE_MAP_CODEC_MEMORY_LIMIT_BYTES)}-byte `}process memory limit for ${this.path}; no partial evidence was returned.`,
+      {
+        codec_process_memory_limit_bytes: SOURCE_MAP_CODEC_MEMORY_LIMIT_BYTES,
+      },
+      {
+        capturedOutput: {
+          stdout: "",
+          stderr: snapshot.stderr.text,
+          truncated:
+            snapshot.diagnosticTruncated === true ||
+            !(this.#supervisor?.observedOutputClose() ?? false),
+        },
+      },
+    );
+  }
+
   async close(
     previousError: string | null,
   ): Promise<ProviderCleanupError | undefined> {
diff --git a/src/javascript/sourceMaps/SourceMapDecoder.test.ts b/src/javascript/sourceMaps/SourceMapDecoder.test.ts
new file mode 100644
index 0000000000..c350edf3dd
--- /dev/null
+++ b/src/javascript/sourceMaps/SourceMapDecoder.test.ts
@@ -0,0 +1,93 @@
+import { access } from "node:fs/promises";
+import { expect, it } from "vitest";
+import { SourceMapDecoder } from "./SourceMapDecoder.js";
+import { AnalysisCancelledError } from "../../domain/analysisErrorCore.js";
+import {
+  SourceMapCleanupFailure,
+  type SourceMapDecoderDependencies,
+} from "./SourceMapCommand.js";
+import { PrivateRuntimeRoot } from "../../process/PrivateRuntimeRoot.js";
+import { spawnOwnedProviderProcess } from "../../process/ProviderProcess.js";
+import {
+  webSourceLocationArgs,
+  webSourceLocationFixture,
+} from "../../../tests/fixtures/webSourceLocation.js";
+
+const fixture = webSourceLocationFixture();
+const input = {
+  text: fixture.sourceMap.text,
+  url: fixture.sourceMap.url,
+  path: fixture.sourceMap.file.path,
+  position: webSourceLocationArgs.generated_position,
+};
+
+it("preserves the exact caller reason before source-map admission", async () => {
+  const reason = { caller: "pre-aborted source-map decode" };
+  const controller = new AbortController();
+  controller.abort(reason);
+  const response = await new SourceMapDecoder().trace(input, {
+    signal: controller.signal,
+  });
+  expect(response.ok).toBe(false);
+  if (response.ok) throw new Error("expected cancellation");
+  expect(response.error).toBeInstanceOf(AnalysisCancelledError);
+  expect(response.error.cause).toBe(reason);
+});
+
+it("retains failed cleanup ownership and retries it before another decode", async () => {
+  const root = await PrivateRuntimeRoot.create({
+    prefix: "rea-source-map-cleanup-retry-test-",
+  });
+  let cleanupAttempts = 0;
+  const dependencies: SourceMapDecoderDependencies = {
+    prepareOwnership: async () => {},
+    createRuntime: async () => ({
+      path: root.path,
+      close: async () => {
+        cleanupAttempts += 1;
+        if (cleanupAttempts === 1)
+          throw new Error("injected root cleanup failure");
+        await root.close();
+      },
+    }),
+    launcher: async (options) =>
+      spawnOwnedProviderProcess({
+        ...options,
+        arguments: [
+          "-e",
+          'process.stderr.write("physical exit 7"); process.exit(7)',
+        ],
+      }),
+  };
+  const decoder = new SourceMapDecoder(dependencies);
+  try {
+    const failed = await decoder.trace(input);
+    expect(failed.ok).toBe(false);
+    if (failed.ok)
+      throw new Error("expected physical failure with cleanup failure");
+    expect(failed.error).toBeInstanceOf(SourceMapCleanupFailure);
+    if (!(failed.error instanceof SourceMapCleanupFailure))
+      throw new Error("expected source-map cleanup ownership");
+    expect(failed.error.cleanupOwner).toBeDefined();
+    expect(failed.error.diagnostics).toMatchObject({
+      cleanup_failures: ["injected root cleanup failure"],
+    });
+    expect(failed.error.diagnostics).toMatchObject({
+      previous_error: expect.stringContaining(
+        "source-map-decoder adapter failed",
+      ),
+    });
+    await expect(access(root.path)).resolves.toBeUndefined();
+
+    const invalidInput = { ...input, text: null } as unknown as typeof input;
+    const retried = await decoder.trace(invalidInput);
+    expect(retried.ok).toBe(false);
+    if (retried.ok)
+      throw new Error("expected invalid input after cleanup retry");
+    expect(retried.error._tag).toBe("AnalysisInputError");
+    expect(cleanupAttempts).toBe(2);
+    await expect(access(root.path)).rejects.toMatchObject({ code: "ENOENT" });
+  } finally {
+    await decoder.close();
+  }
+});
diff --git a/src/javascript/sourceMaps/SourceMapDecoder.ts b/src/javascript/sourceMaps/SourceMapDecoder.ts
index fc26cde14e..220e588679 100644
--- a/src/javascript/sourceMaps/SourceMapDecoder.ts
+++ b/src/javascript/sourceMaps/SourceMapDecoder.ts
@@ -79,7 +79,9 @@ export class SourceMapDecoder implements WebSourceMapPort {
     const cleanupFailure = await this.#retryCleanup();
     if (cleanupFailure !== undefined) return err(cleanupFailure);
     if (options?.signal?.aborted)
-      return err(new AnalysisCancelledError(OPERATION));
+      return err(
+        new AnalysisCancelledError(OPERATION, { cause: options.signal.reason }),
+      );
     const request = sourceMapCodecInputSchema.safeParse({
       text: input.text,
       url: input.url,
@@ -106,7 +108,9 @@ export class SourceMapDecoder implements WebSourceMapPort {
       encodedBytes += bytes;
     }
     if (options?.signal?.aborted)
-      return err(new AnalysisCancelledError(OPERATION));
+      return err(
+        new AnalysisCancelledError(OPERATION, { cause: options.signal.reason }),
+      );
     const serialized = encoded.join("");
     const response = await runSourceMapCommand(
       serialized,
@@ -139,7 +143,9 @@ export class SourceMapDecoder implements WebSourceMapPort {
         ),
       );
     if (options?.signal?.aborted)
-      return err(new AnalysisCancelledError(OPERATION));
+      return err(
+        new AnalysisCancelledError(OPERATION, { cause: options.signal.reason }),
+      );
     if (reply.data.state === "failure")
       return codecFailure(input.path, reply.data.reason, reply.data.message);
     const runtimeFailure = codecRuntimeFailure(reply.data.report.runtime);