fix(server): Claude append-system-prompt launch args reach the system prompt

apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts

@@ -1024,6 +1024,110 @@ describe("ClaudeAdapterV2 Auto-accept edits", () => {
   );
 });
 
+describe("ClaudeAdapterV2 append-system-prompt launch args", () => {
+  const startTurnWithLaunchArgs = (launchArgs: string) =>
+    Effect.gen(function* () {
+      const fileSystem = yield* FileSystem.FileSystem;
+      const path = yield* Path.Path;
+      const cwd = yield* fileSystem.makeTempDirectoryScoped({ prefix: "t3-claude-append-" });
+      yield* fileSystem.writeFileString(path.join(cwd, "extra.md"), "code word: pineapple");
+      let openedOptions: ClaudeAdapterV2.ClaudeAgentSdkQueryOptions | undefined;
+      const adapter = ClaudeAdapterV2.makeClaudeAdapterV2({
+        instanceId: ClaudeAdapterV2.CLAUDE_DEFAULT_INSTANCE_ID,
+        settings: { ...DEFAULT_CLAUDE_SETTINGS, launchArgs },
+        environment: {},
+        attachmentsDir: cwd,
+        fileSystem,
+        path,
+        idAllocator: yield* IdAllocator.IdAllocatorV2,
+        queryRunner: {
+          allocateSessionId: Effect.succeed("native-thread-claude-append"),
+          open: (input) =>
+            Effect.sync(() => {
+              openedOptions = input.options;
+              return {
+                messages: Stream.never,
+                offer: () => Effect.void,
+                setModel: () => Effect.void,
+                interrupt: Effect.void,
+                close: Effect.void,
+              };
+            }),
+          forkSession: () => Effect.die("unused"),
+          subagentLaunchToolUseId: () => Effect.succeed(null),
+          assertComplete: Effect.void,
+        },
+      });
+      const runtimePolicy = ProviderAdapterV2RuntimePolicy.make({
+        ...CLAUDE_TEST_RUNTIME_POLICY,
+        cwd,
+      });
+      const threadId = ThreadId.make("thread-claude-append");
+      const runtime = yield* adapter.openSession({
+        threadId,
+        providerSessionId: ProviderSessionId.make("provider-session-claude-append"),
+        modelSelection: CLAUDE_TEST_MODEL_SELECTION,
+        runtimePolicy,
+      });
+      const providerThread = yield* runtime.ensureThread({
+        threadId,
+        modelSelection: CLAUDE_TEST_MODEL_SELECTION,
+        runtimePolicy,
+      });
+      const exit = yield* runtime
+        .startTurn(
+          makeClaudeTestTurnInput({
+            threadId,
+            providerThread,
+            now: yield* DateTime.now,
+            attemptId: RunAttemptId.make("attempt-claude-append"),
+            text: "What is the code word?",
+            attachments: [],
+            runtimePolicy,
+          }),
+        )
+        .pipe(Effect.exit);
+      return { exit, openedOptions };
+    });
+
+  it.effect("folds the file and inline text into the system prompt append", () =>
+    Effect.scoped(
+      Effect.gen(function* () {
+        const { exit, openedOptions } = yield* startTurnWithLaunchArgs(
+          `--append-system-prompt-file extra.md --append-system-prompt "inline text"`,
+        );
+        assert.isTrue(Exit.isSuccess(exit));
+        const systemPrompt = openedOptions?.systemPrompt;
+        if (
+          typeof systemPrompt !== "object" ||
+          systemPrompt === null ||
+          !("append" in systemPrompt)
+        ) {
+          return assert.fail("expected a preset system prompt with an append");
+        }
+        assert.isTrue(
+          systemPrompt.append?.endsWith("\n\ncode word: pineapple\n\ninline text"),
+          systemPrompt.append,
+        );
+        assert.isUndefined(openedOptions?.extraArgs?.["append-system-prompt"]);
+        assert.isUndefined(openedOptions?.extraArgs?.["append-system-prompt-file"]);
+      }).pipe(Effect.provide(Layer.merge(IdAllocator.layer, NodeServices.layer))),
+    ),
+  );
+
+  it.effect("fails the turn when the file cannot be read", () =>
+    Effect.scoped(
+      Effect.gen(function* () {
+        const { exit, openedOptions } = yield* startTurnWithLaunchArgs(
+          "--append-system-prompt-file missing.md",
+        );
+        assert.isTrue(Exit.isFailure(exit));
+        assert.isUndefined(openedOptions);
+      }).pipe(Effect.provide(Layer.merge(IdAllocator.layer, NodeServices.layer))),
+    ),
+  );
+});
+
 describe("ClaudeAdapterV2 approval cancellation", () => {
   it.effect("observes an approval signal that was already aborted", () =>
     Effect.gen(function* () {

apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts

@@ -784,13 +784,23 @@ export function makeClaudeQueryOptions(input: {
   readonly onUserDialog?: ClaudeQueryOptions["onUserDialog"];
   readonly supportedDialogKinds?: ClaudeQueryOptions["supportedDialogKinds"];
   readonly allowDangerouslySkipPermissions?: boolean;
+  /** Contents of the `--append-system-prompt-file` launch arg, read by the caller. */
+  readonly appendSystemPromptFileText?: string;
 }): ClaudeAgentSdkQueryOptions {
   const compiledSelection = compileClaudeModelSelection(input.modelSelection);
   const {
     "permission-mode": launchArgPermissionMode,
     "dangerously-skip-permissions": launchArgSkipPermissions,
     ...extraArgs
   } = input.settings === undefined ? {} : parseCliArgs(input.settings.launchArgs).flags;
+  // The SDK sends systemPrompt.append on initialize and the CLI assigns it over
+  // the text these launch args loaded, so their text joins that append instead.
+  // A flag without a value is left for the CLI to report.
+  const launchArgAppendSystemPrompt = extraArgs["append-system-prompt"] ?? undefined;
+  if (launchArgAppendSystemPrompt !== undefined) delete extraArgs["append-system-prompt"];
+  if (input.appendSystemPromptFileText !== undefined) {
+    delete extraArgs["append-system-prompt-file"];
+  }
   const requestThinkingSummaries =
     compiledSelection.settings.alwaysThinkingEnabled !== false &&
     extraArgs["thinking-display"] !== "omitted";
@@ -866,9 +876,14 @@ export function makeClaudeQueryOptions(input: {
     systemPrompt: {
       type: "preset" as const,
       preset: "claude_code" as const,
-      append:
+      append: [
         buildRuntimeInstructions({ harness: "Claude Code" }) +
-        (input.mcpServers === undefined ? "" : T3_CODE_ORCHESTRATION_INSTRUCTIONS),
+          (input.mcpServers === undefined ? "" : T3_CODE_ORCHESTRATION_INSTRUCTIONS),
+        input.appendSystemPromptFileText,
+        launchArgAppendSystemPrompt,
+      ]
+        .filter((part) => part !== undefined && part !== "")
+        .join("\n\n"),
     },
     ...(Object.keys(extraArgs).length === 0 ? {} : { extraArgs }),
   };
@@ -6779,6 +6794,30 @@ export function makeClaudeAdapterV2(
             return existing;
           }
 
+          // Read before closing the live query, so a bad path leaves it intact.
+          // A missing file fails the turn, as it fails the CLI, instead of
+          // starting a session silently missing the text.
+          const appendSystemPromptFile = parseCliArgs(adapterOptions.settings.launchArgs).flags[
+            "append-system-prompt-file"
+          ];
+          const appendSystemPromptFileText =
+            typeof appendSystemPromptFile === "string"
+              ? yield* fileSystem
+                  .readFileString(
+                    path.resolve(turnInput.runtimePolicy.cwd ?? ".", appendSystemPromptFile),
+                  )
+                  .pipe(
+                    Effect.mapError(
+                      (cause) =>
+                        new ProviderAdapter.ProviderAdapterProtocolError({
+                          driver: CLAUDE_PROVIDER,
+                          detail: `Failed to read --append-system-prompt-file '${appendSystemPromptFile}'`,
+                          payload: cause,
+                        }),
+                    ),
+                  )
+              : undefined;
+
           // openQuery owns one live process. Closing it for another native
           // thread kills that sibling's CLI; it can never emit a roster clear,
           // so drop its process-scoped Waiting/wake state immediately. Closing
@@ -6828,6 +6867,7 @@ export function makeClaudeAdapterV2(
                 canUseTool,
                 onUserDialog,
                 supportedDialogKinds: ["resume_return"],
+                ...(appendSystemPromptFileText === undefined ? {} : { appendSystemPromptFileText }),
               }),
             })
             .pipe(