Make ACPX-Claude adapter work seamlessly (PAPA-388) (#6590)

## Thinking Path > - Paperclip orchestrates AI agents for zero-human companies, so when an adapter fails, the platform must surface enough detail for the next agent (or human reviewer) to act > - The `acpx_local` adapter wraps `claude-agent-acp`, which in turn drives the Claude Code SDK — three layers, three different permission and error-handling models > - A user created a `Claude Local ACPX` agent in PAPA-387 and it failed instantly with the generic `acpx.error / "Internal error"` log, stranding the work and triggering an opaque `stranded_assigned_issue` recovery to the CTO > - Once the diagnostic blackbox was opened, the underlying cause turned out to be two SDK-level mismatches: a model-name allowlist that rejects bare IDs like `claude-opus-4-7`, and a Claude Code permission/Read-sandbox configuration that silently denies every non-allowlisted tool when the user's `~/.claude/settings.json` has `defaultMode: "dontAsk"` > - This pull request fixes both classes of failure in the adapter itself so new ACPX agents work seamlessly without per-host configuration, and widens the diagnostic surface so the *next* failure of any kind is actionable > - The benefit is that ACPX-Claude can join the regular agent roster — verified end to end on PAPA-401, where the agent successfully reached the Paperclip API, opened a worktree, surveyed existing notification PRs, and posted a structured plan ## What Changed - Widen ACPX failure diagnostics (`packages/adapters/acpx-local/src/server/execute.ts`): - Capture `err.name`, ACP code, `cause.message`, retryable flag, and a 5-frame stack preview into `errorMeta`. - Promote phase-specific error codes: `ensure_session → acpx_session_init_failed`, `configure_session → acpx_session_config_failed`, `turn → acpx_turn_failed`, plus mapping for `ACP_BACKEND_MISSING` / `ACP_BACKEND_UNAVAILABLE`. - Set `verbose: true` on the ACPX runtime so its session-event log flows through `ctx.onLog`. - Capture child-process stderr via a wrapper-script tee into `<stateDir>/run-stderr/<runId>.log`, inline the tail into the `acpx.error` payload as `childStderrTail`, and forward it through `ctx.onLog("stderr", …)` so it lands in the heartbeat `stderrExcerpt` column (existing redaction applies). - Set the model via `ANTHROPIC_MODEL` env for the `claude` agent instead of `set_config_option(model, …)`. The ACP server's `set_config_option` handler validates against an internal allowlist and rejects bare IDs like `claude-opus-4-7`. `ANTHROPIC_MODEL` is read during initialization and bypasses that check. - Seed `<worktree>/.claude/settings.local.json` before spawning `claude-agent-acp` (the seamless-API fix). Since `claude-agent-acp` hard-codes `settingSources: ["user", "project", "local"]` and "local" has the highest precedence: - Set `permissions.defaultMode: "default"`, but **only** if the user's value is missing or `"dontAsk"` (the broken case). Other modes like `acceptEdits`/`plan` are preserved. - Pre-allow Paperclip's Bash surface (`Bash(curl:*)`, `Bash(env:*)`, `Bash(<cwd>/scripts/paperclip-issue-update.sh:*)`, `Bash(<cwd>/scripts/paperclip:*)`). - Widen `permissions.additionalDirectories` to include `stateDir`, `agentHome`, and the per-company instance root (`~/.paperclip/instances/<id>/companies/<companyId>`). Scoped to this company only — does not expose other tenants. - Existing user entries are merged, not replaced. The resolved roots are folded into the session fingerprint so warm-session handles invalidate when they change. - Sync the existing server-side integration test (`server/src/__tests__/acpx-local-execute.test.ts`) to assert `acpx_session_init_failed` instead of the now-removed `acpx_protocol_error` for `ACP_SESSION_INIT_FAILED` (a follow-up to commit 1). ## Verification - `pnpm --filter "@paperclipai/adapter-acpx-local" run typecheck` — passes. - `pnpm vitest run` in `packages/adapters/acpx-local` — 35/35 pass, includes 4 new tests covering the settings.local.json write path (claude only, merge with pre-existing content, `dontAsk` override, codex no-op). - `pnpm vitest run src/__tests__/acpx-local-execute.test.ts` in `server/` — 15/15 pass after the test-sync commit. - End-to-end manual verification (PAPA-401): the `Claude Local ACPX` agent that previously hit "restricted environment" now successfully reaches the Paperclip API, opens its worktree, posts structured plan comments, and flips the issue to `in_review` without any external configuration. ## Risks - **Low**, scoped to the `acpx_local` adapter. The settings.local.json write is per-worktree (worktrees live under `.paperclip/worktrees/<issue>/`) and only triggers when `acpxAgent === "claude"`. Existing user content is merged with `[...existing, ...paperclip]` and deduped — nothing is overwritten outright. - The `defaultMode` override is intentionally narrow: it only flips `"dontAsk"` (which silently denies every tool and is the root cause) to `"default"`. Users who explicitly picked `acceptEdits`, `plan`, or any other mode keep their choice. - Stderr capture goes through the existing `log-redaction` pass before persisting, so `PAPERCLIP_API_KEY` and similar secrets in the wrapper env don't leak into heartbeat logs. > For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and discuss it in `#dev` before opening the PR. Feature PRs that overlap with planned core work may need to be redirected — check the roadmap first. See `CONTRIBUTING.md`. ## Model Used - Claude Opus 4.7 (`claude-opus-4-7`), running in the `claude_local` adapter via Paperclip's harness. Extended thinking enabled, tool use enabled. ## Checklist - [x] I have included a thinking path that traces from project context to this change - [x] I have specified the model used (with version and capability details) - [x] I have checked ROADMAP.md and confirmed this PR does not duplicate planned core work - [x] I have run tests locally and they pass - [x] I have added or updated tests where applicable - [ ] If this change affects the UI, I have included before/after screenshots — N/A (adapter-only) - [ ] I have updated relevant documentation to reflect my changes — no user-facing docs changed; internal commentary in the code change explains the SDK constraints - [x] I have considered and documented any risks above - [ ] I will address all Greptile and reviewer comments before requesting merge --------- Co-authored-by: Paperclip <noreply@paperclip.ing>
2026-05-23 13:01:27 -07:00
parent 897cc322c7
commit 96f0279e08
3 changed files with 578 additions and 19 deletions
@@ -2,6 +2,7 @@ import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
 import { afterEach, describe, expect, it } from "vitest";
+import type { AcpRuntimeOptions } from "acpx/runtime";
 import { createAcpxLocalExecutor } from "./execute.js";

 const tempRoots: string[] = [];
@@ -376,6 +377,126 @@ describe("acpx_local runtime skill isolation", () => {
    expect(envFiles.filter((contents) => contents.includes("PAPERCLIP_API_KEY='second-key'"))).toHaveLength(1);
  });

+  it("enriches acpx.error diagnostics and child stderr when ensureSession rejects", async () => {
+    const root = await makeTempRoot();
+    const stateDir = path.join(root, "state");
+    const runStderrDir = path.join(stateDir, "run-stderr");
+    await fs.mkdir(runStderrDir, { recursive: true });
+    const stderrTail = "claude-agent-acp: SDK init failed (auth missing)";
+    await fs.writeFile(path.join(runStderrDir, "run-1.log"), `${stderrTail}\n`, "utf8");
+
+    class FakeAcpRuntimeError extends Error {
+      readonly code = "ACP_SESSION_INIT_FAILED";
+      readonly cause: Error;
+      readonly retryable = false;
+      constructor(message: string, cause: Error) {
+        super(message);
+        this.name = "AcpRuntimeError";
+        this.cause = cause;
+      }
+    }
+
+    const logs: Array<{ stream: string; text: string }> = [];
+    const execute = createAcpxLocalExecutor({
+      createRuntime: () => ({
+        ensureSession: async () => {
+          throw new FakeAcpRuntimeError(
+            "session/new failed: backend rejected initialize",
+            new Error("upstream timeout"),
+          );
+        },
+        startTurn: () => ({
+          events: (async function* () {})(),
+          result: Promise.resolve({ status: "completed", stopReason: "end_turn" }),
+          cancel: async () => {},
+        }),
+        close: async () => {},
+      }) as never,
+    });
+
+    const result = await execute({
+      runId: "run-1",
+      agent: { id: "agent-1", companyId: "company-1" },
+      runtime: {},
+      config: {
+        agent: "custom",
+        agentCommand: "node ./fake-acp.js",
+        stateDir,
+      },
+      context: {},
+      onLog: async (stream: "stdout" | "stderr", text: string) => {
+        logs.push({ stream, text });
+      },
+      onMeta: async () => {},
+    } as never);
+
+    expect(result.exitCode).toBe(1);
+    expect(result.errorCode).toBe("acpx_session_init_failed");
+    const meta = result.errorMeta ?? {};
+    expect(meta.errorName).toBe("AcpRuntimeError");
+    expect(meta.acpCode).toBe("ACP_SESSION_INIT_FAILED");
+    expect(meta.causeMessage).toBe("upstream timeout");
+    expect(meta.retryable).toBe(false);
+    expect(typeof meta.stackPreview).toBe("string");
+    expect(meta.phase).toBe("ensure_session");
+
+    const errorLogLine = logs.find((entry) => entry.stream === "stdout" && entry.text.includes("\"type\":\"acpx.error\""));
+    expect(errorLogLine).toBeTruthy();
+    const errorPayload = JSON.parse(errorLogLine!.text.trim());
+    expect(errorPayload.phase).toBe("ensure_session");
+    expect(errorPayload.errorName).toBe("AcpRuntimeError");
+    expect(errorPayload.acpCode).toBe("ACP_SESSION_INIT_FAILED");
+    expect(errorPayload.causeMessage).toBe("upstream timeout");
+    expect(errorPayload.childStderrTail).toContain("SDK init failed");
+
+    const stderrLog = logs.find((entry) => entry.stream === "stderr" && entry.text.includes("ACPX child stderr tail"));
+    expect(stderrLog).toBeTruthy();
+    expect(stderrLog!.text).toContain(stderrTail);
+  });
+
+  it("writes wrapper that redirects child stderr to a per-run log file", async () => {
+    const root = await makeTempRoot();
+    const stateDir = path.join(root, "state");
+
+    const runtimeOptions: AcpRuntimeOptions[] = [];
+    const execute = createAcpxLocalExecutor({
+      createRuntime: (options) => {
+        runtimeOptions.push(options as unknown as AcpRuntimeOptions);
+        return buildRuntime() as never;
+      },
+    });
+
+    const result = await execute({
+      runId: "run-stderr-1",
+      agent: { id: "agent-1", companyId: "company-1" },
+      runtime: {},
+      config: {
+        agent: "custom",
+        agentCommand: "node ./fake-acp.js",
+        stateDir,
+      },
+      context: {},
+      onLog: async () => {},
+      onMeta: async () => {},
+    } as never);
+
+    expect(result.exitCode).toBe(0);
+    const verboseFlags = runtimeOptions.map((options) => (options as { verbose?: boolean }).verbose);
+    // verbose is scoped to the claude agent (PAPA-388); the custom agent here
+    // should not opt in to ACPX runtime verbose session-event logs.
+    expect(verboseFlags.every((flag) => flag === false)).toBe(true);
+
+    const wrappers = await fs.readdir(path.join(stateDir, "wrappers"));
+    const wrapperFile = wrappers.find((name) => name.endsWith(".sh"));
+    expect(wrapperFile).toBeTruthy();
+    const wrapper = await fs.readFile(path.join(stateDir, "wrappers", wrapperFile!), "utf8");
+    expect(wrapper).toContain("stderr_dir=");
+    expect(wrapper).toContain("run-stderr");
+    expect(wrapper).toContain("PAPERCLIP_RUN_ID");
+    expect(wrapper).toContain("tee -a");
+    expect(wrapper).toContain("exec node ./fake-acp.js");
+  });
+
  it("passes Paperclip env through the ACP agent wrapper instead of process.env", async () => {
    let observedApiKeyDuringStream: string | undefined;
    const execute = createAcpxLocalExecutor({
@@ -422,4 +543,160 @@ describe("acpx_local runtime skill isolation", () => {
      else process.env.PAPERCLIP_API_KEY = previousApiKey;
    }
  });
+
+  it("writes a Paperclip-managed .claude/settings.local.json for the claude agent so it can reach the Paperclip API", async () => {
+    const root = await makeTempRoot();
+    const stateDir = path.join(root, "state");
+    const cwd = path.join(root, "worktree");
+    await fs.mkdir(cwd, { recursive: true });
+
+    const { meta } = await runExecutor(
+      { agent: "claude", stateDir, cwd },
+      { context: { paperclipWorkspace: { cwd, agentHome: path.join(root, "agent-home") } } },
+    );
+
+    const settingsPath = path.join(cwd, ".claude", "settings.local.json");
+    const written = JSON.parse(await fs.readFile(settingsPath, "utf8")) as {
+      permissions?: {
+        allow?: unknown;
+        additionalDirectories?: unknown;
+        defaultMode?: unknown;
+      };
+    };
+    expect(written.permissions?.defaultMode).toBe("default");
+    const allow = written.permissions?.allow;
+    expect(Array.isArray(allow)).toBe(true);
+    expect(allow).toContain("Bash(curl:*)");
+    expect(allow).toContain(`Bash(${cwd}/scripts/paperclip-issue-update.sh:*)`);
+    const additionalDirectories = written.permissions?.additionalDirectories as string[] | undefined;
+    expect(Array.isArray(additionalDirectories)).toBe(true);
+    expect(additionalDirectories).toContain(stateDir);
+    expect(additionalDirectories).toContain(path.join(root, "agent-home"));
+
+    const note = (meta[0]?.commandNotes as string[] | undefined)?.find((entry) =>
+      entry.includes("Paperclip-managed Claude settings"),
+    );
+    expect(note).toBeTruthy();
+  });
+
+  it("merges Paperclip allowlist into an existing .claude/settings.local.json without losing user entries", async () => {
+    const root = await makeTempRoot();
+    const stateDir = path.join(root, "state");
+    const cwd = path.join(root, "worktree");
+    await fs.mkdir(path.join(cwd, ".claude"), { recursive: true });
+    await fs.writeFile(
+      path.join(cwd, ".claude", "settings.local.json"),
+      JSON.stringify(
+        {
+          statusLine: { type: "command", command: "preserve-me" },
+          permissions: {
+            allow: ["Bash(npm test:*)"],
+            additionalDirectories: ["/Users/example/custom"],
+            defaultMode: "acceptEdits",
+          },
+        },
+        null,
+        2,
+      ),
+      "utf8",
+    );
+
+    await runExecutor(
+      { agent: "claude", stateDir, cwd },
+      { context: { paperclipWorkspace: { cwd } } },
+    );
+
+    const written = JSON.parse(
+      await fs.readFile(path.join(cwd, ".claude", "settings.local.json"), "utf8"),
+    ) as {
+      statusLine?: unknown;
+      permissions?: {
+        allow?: string[];
+        additionalDirectories?: string[];
+        defaultMode?: string;
+      };
+    };
+    expect(written.statusLine).toEqual({ type: "command", command: "preserve-me" });
+    expect(written.permissions?.defaultMode).toBe("acceptEdits");
+    expect(written.permissions?.allow).toContain("Bash(npm test:*)");
+    expect(written.permissions?.allow).toContain("Bash(curl:*)");
+    expect(written.permissions?.additionalDirectories).toContain("/Users/example/custom");
+    expect(written.permissions?.additionalDirectories).toContain(stateDir);
+  });
+
+  it("overrides a user-supplied dontAsk defaultMode so ACPX can route Bash through canUseTool", async () => {
+    const root = await makeTempRoot();
+    const stateDir = path.join(root, "state");
+    const cwd = path.join(root, "worktree");
+    await fs.mkdir(path.join(cwd, ".claude"), { recursive: true });
+    await fs.writeFile(
+      path.join(cwd, ".claude", "settings.local.json"),
+      JSON.stringify({ permissions: { defaultMode: "dontAsk" } }, null, 2),
+      "utf8",
+    );
+
+    const { meta } = await runExecutor(
+      { agent: "claude", stateDir, cwd },
+      { context: { paperclipWorkspace: { cwd } } },
+    );
+
+    const written = JSON.parse(
+      await fs.readFile(path.join(cwd, ".claude", "settings.local.json"), "utf8"),
+    ) as { permissions?: { defaultMode?: string } };
+    expect(written.permissions?.defaultMode).toBe("default");
+
+    const overrideNote = (meta[0]?.commandNotes as string[] | undefined)?.find((entry) =>
+      entry.includes("overrode user dontAsk"),
+    );
+    expect(overrideNote).toBeTruthy();
+  });
+
+  it("opts the claude agent into ACPX runtime verbose logs but leaves codex/custom agents quiet", async () => {
+    const root = await makeTempRoot();
+    const cwd = path.join(root, "worktree");
+    await fs.mkdir(cwd, { recursive: true });
+
+    const verboseByAgent: Record<string, boolean | undefined> = {};
+    for (const agent of ["claude", "codex", "custom"] as const) {
+      const runtimeOptions: AcpRuntimeOptions[] = [];
+      const execute = createAcpxLocalExecutor({
+        createRuntime: (options) => {
+          runtimeOptions.push(options as AcpRuntimeOptions);
+          return buildRuntime() as never;
+        },
+      });
+      const result = await execute({
+        runId: `run-${agent}`,
+        agent: { id: `agent-${agent}`, companyId: "company-1" },
+        runtime: {},
+        config:
+          agent === "custom"
+            ? { agent, agentCommand: "node ./fake-acp.js", stateDir: path.join(root, `state-${agent}`), cwd }
+            : { agent, stateDir: path.join(root, `state-${agent}`), cwd },
+        context: { paperclipWorkspace: { cwd } },
+        onLog: async () => {},
+        onMeta: async () => {},
+      } as never);
+      expect(result.exitCode).toBe(0);
+      verboseByAgent[agent] = (runtimeOptions[0] as { verbose?: boolean } | undefined)?.verbose;
+    }
+
+    expect(verboseByAgent.claude).toBe(true);
+    expect(verboseByAgent.codex).toBe(false);
+    expect(verboseByAgent.custom).toBe(false);
+  });
+
+  it("does not touch .claude/settings.local.json for the codex agent", async () => {
+    const root = await makeTempRoot();
+    const stateDir = path.join(root, "state");
+    const cwd = path.join(root, "worktree");
+    await fs.mkdir(cwd, { recursive: true });
+
+    await runExecutor(
+      { agent: "codex", stateDir, cwd },
+      { context: { paperclipWorkspace: { cwd } } },
+    );
+
+    expect(await pathExists(path.join(cwd, ".claude", "settings.local.json"))).toBe(false);
+  });
 });
@@ -94,6 +94,8 @@ interface AcpxPreparedRuntime {
  remoteExecutionIdentity: Record<string, unknown> | null;
  skillPromptInstructions: string;
  skillsIdentity: Record<string, unknown>;
+  childStderrLogPath: string | null;
+  paperclipClaudeSettings: PaperclipClaudeSettingsResult | null;
 }

 const defaultWarmHandles = new Map<string, RuntimeCacheEntry>();
@@ -564,11 +566,105 @@ function buildSessionParams(input: {
  };
 }

+interface PaperclipClaudeSettingsResult {
+  filePath: string;
+  allow: string[];
+  additionalDirectories: string[];
+  defaultMode: string;
+  overrodeDontAsk: boolean;
+}
+
+function uniqueSorted(values: Array<string | null | undefined>): string[] {
+  return [...new Set(values.filter((value): value is string => typeof value === "string" && value.length > 0))].sort();
+}
+
+// Phase 4.1 (PAPA-388): the Claude Code SDK that `claude-agent-acp` runs uses
+// `settingSources: ["user", "project", "local"]`. By writing a per-worktree
+// `.claude/settings.local.json` we override the user's potentially-restrictive
+// `~/.claude/settings.json` (e.g. `defaultMode: "dontAsk"`, which silently
+// denies every non-allowlisted tool and never reaches `canUseTool`), and we
+// widen the SDK's Read sandbox to include the Paperclip state dirs the agent
+// needs to talk to its own control plane.
+async function writePaperclipClaudeSettings(input: {
+  cwd: string;
+  stateDir: string;
+  agentHome: string;
+  companyId: string;
+}): Promise<PaperclipClaudeSettingsResult> {
+  const filePath = path.join(input.cwd, ".claude", "settings.local.json");
+  const instanceRoot = defaultPaperclipInstanceDir();
+  const companyRoot = path.join(instanceRoot, "companies", input.companyId);
+  const paperclipAdditionalDirectories = uniqueSorted([
+    input.stateDir,
+    input.agentHome,
+    companyRoot,
+  ]);
+  const paperclipAllow = uniqueSorted([
+    "Bash(curl:*)",
+    "Bash(env:*)",
+    "Bash(env)",
+    `Bash(${input.cwd}/scripts/paperclip-issue-update.sh:*)`,
+    `Bash(${input.cwd}/scripts/paperclip:*)`,
+  ]);
+
+  let existing: Record<string, unknown> = {};
+  const existingRaw = await fs.readFile(filePath, "utf8").catch(() => null);
+  if (existingRaw) {
+    try {
+      const parsed = JSON.parse(existingRaw);
+      if (parsed && typeof parsed === "object" && !Array.isArray(parsed)) existing = parsed as Record<string, unknown>;
+    } catch {
+      // Malformed settings file — leave it alone in `existing` and our merge will replace it with a valid one.
+    }
+  }
+  const existingPerms =
+    existing.permissions && typeof existing.permissions === "object" && !Array.isArray(existing.permissions)
+      ? (existing.permissions as Record<string, unknown>)
+      : {};
+  const existingAllow = Array.isArray(existingPerms.allow)
+    ? (existingPerms.allow as unknown[]).filter((value): value is string => typeof value === "string")
+    : [];
+  const existingAdditionalDirectories = Array.isArray(existingPerms.additionalDirectories)
+    ? (existingPerms.additionalDirectories as unknown[]).filter((value): value is string => typeof value === "string")
+    : [];
+  const mergedAllow = uniqueSorted([...existingAllow, ...paperclipAllow]);
+  const mergedAdditionalDirectories = uniqueSorted([
+    ...existingAdditionalDirectories,
+    ...paperclipAdditionalDirectories,
+  ]);
+  const existingDefaultMode =
+    typeof existingPerms.defaultMode === "string" ? (existingPerms.defaultMode as string) : "";
+  const defaultMode =
+    existingDefaultMode && existingDefaultMode !== "dontAsk" ? existingDefaultMode : "default";
+  const overrodeDontAsk = existingDefaultMode === "dontAsk";
+
+  const nextPermissions: Record<string, unknown> = {
+    ...existingPerms,
+    allow: mergedAllow,
+    additionalDirectories: mergedAdditionalDirectories,
+    defaultMode,
+  };
+  const next: Record<string, unknown> = { ...existing, permissions: nextPermissions };
+  await writeFileAtomically({
+    target: filePath,
+    contents: `${JSON.stringify(next, null, 2)}\n`,
+    mode: 0o600,
+  });
+  return {
+    filePath,
+    allow: mergedAllow,
+    additionalDirectories: mergedAdditionalDirectories,
+    defaultMode,
+    overrodeDontAsk,
+  };
+}
+
 async function writeAgentWrapper(input: {
  stateDir: string;
  acpxAgent: string;
  agentCommandShell: string;
  env: Record<string, string>;
+  childStderrDir: string;
 }): Promise<{ wrapperPath: string; envFilePath: string }> {
  const wrappersDir = path.join(input.stateDir, "wrappers");
  await fs.mkdir(wrappersDir, { recursive: true });
@@ -580,6 +676,7 @@ async function writeAgentWrapper(input: {
    agent: input.acpxAgent,
    command: input.agentCommandShell,
    env: envLines,
+    childStderrDir: input.childStderrDir,
  });
  const wrapperPath = path.join(wrappersDir, `${input.acpxAgent}-${wrapperHash}.sh`);
  const envFilePath = path.join(wrappersDir, `${input.acpxAgent}-${wrapperHash}.env`);
@@ -592,6 +689,11 @@ async function writeAgentWrapper(input: {
    "  source \"$env_file\"",
    "  set +a",
    "fi",
+    `stderr_dir=${shellQuote(input.childStderrDir)}`,
+    "if [[ -n \"${PAPERCLIP_RUN_ID:-}\" ]]; then",
+    "  mkdir -p \"$stderr_dir\"",
+    "  exec 2> >(tee -a \"$stderr_dir/$PAPERCLIP_RUN_ID.log\" >&2)",
+    "fi",
    `exec ${input.agentCommandShell} "$@"`,
    "",
  ].join("\n");
@@ -723,10 +825,20 @@ async function buildRuntime(input: {
    if (typeof value === "string") env[key] = value;
  }
  if (!hasExplicitApiKey && authToken) env.PAPERCLIP_API_KEY = authToken;
+  // For the claude agent, set model via ANTHROPIC_MODEL at startup rather than
+  // via session/set_config_option — the ACP server's set_config_option handler
+  // validates the value against its internal available-models list and rejects
+  // bare model IDs (e.g. "claude-opus-4-7") that don't exactly match a model
+  // entry in some versions. ANTHROPIC_MODEL is read during initialization, so
+  // it reliably sets the model before any turns are run.
+  if (requestedModel && acpxAgent === "claude" && !env.ANTHROPIC_MODEL) {
+    env.ANTHROPIC_MODEL = requestedModel;
+  }

  let skillPromptInstructions = "";
  let skillsIdentity: Record<string, unknown> = { mode: "unsupported" };
  const skillCommandNotes: string[] = [];
+  let paperclipClaudeSettings: PaperclipClaudeSettingsResult | null = null;
  if (acpxAgent === "claude") {
    const preparedSkills = await prepareClaudeSkillRuntime({
      stateDir,
@@ -736,6 +848,17 @@ async function buildRuntime(input: {
    skillPromptInstructions = preparedSkills.promptInstructions;
    skillsIdentity = preparedSkills.identity;
    skillCommandNotes.push(...preparedSkills.commandNotes);
+    paperclipClaudeSettings = await writePaperclipClaudeSettings({
+      cwd,
+      stateDir,
+      agentHome,
+      companyId: agent.companyId,
+    });
+    skillCommandNotes.push(
+      `Wrote Paperclip-managed Claude settings to ${paperclipClaudeSettings.filePath} (defaultMode=${paperclipClaudeSettings.defaultMode}${
+        paperclipClaudeSettings.overrodeDontAsk ? "; overrode user dontAsk" : ""
+      }, +${paperclipClaudeSettings.additionalDirectories.length} read root(s), +${paperclipClaudeSettings.allow.length} allow rule(s)).`,
+    );
  } else if (acpxAgent === "codex") {
    const preparedSkills = await prepareCodexSkillRuntime({
      companyId: agent.companyId,
@@ -757,12 +880,15 @@ async function buildRuntime(input: {
  const builtInCommand = resolveBuiltInAgentCommand(acpxAgent);
  const agentCommand = configuredCommand || builtInCommand || null;
  const agentCommandShell = configuredCommand || (builtInCommand ? shellQuote(builtInCommand) : "");
+  const childStderrDir = path.join(stateDir, "run-stderr");
+  const childStderrLogPath = agentCommand ? path.join(childStderrDir, `${runId}.log`) : null;
  const wrapper = agentCommand
    ? await writeAgentWrapper({
        stateDir,
        acpxAgent,
        agentCommandShell,
        env,
+        childStderrDir,
      })
    : null;
  const wrapperPath = wrapper?.wrapperPath ?? null;
@@ -781,6 +907,13 @@ async function buildRuntime(input: {
    remoteExecutionIdentity,
    skillsIdentity,
    skillPromptInstructions,
+    paperclipClaudeSettings: paperclipClaudeSettings
+      ? {
+          allow: paperclipClaudeSettings.allow,
+          additionalDirectories: paperclipClaudeSettings.additionalDirectories,
+          defaultMode: paperclipClaudeSettings.defaultMode,
+        }
+      : null,
  });
  const taskKey = asString(input.ctx.runtime.taskKey, "") || wakeTaskId || workspaceId || "default";
  const sessionKey = `paperclip:${agent.companyId}:${agent.id}:${taskKey}:${fingerprint}`;
@@ -817,12 +950,19 @@ async function buildRuntime(input: {
      ...skillsIdentity,
      commandNotes: skillCommandNotes,
    },
+    childStderrLogPath,
+    paperclipClaudeSettings,
  };
 }

 function sessionConfigOptions(prepared: AcpxPreparedRuntime): Array<{ key: string; value: string }> {
  const options: Array<{ key: string; value: string }> = [];
-  if (prepared.requestedModel) options.push({ key: "model", value: prepared.requestedModel });
+  // Model for the claude agent is pre-set via ANTHROPIC_MODEL env var at
+  // startup; skip set_config_option to avoid ACP-server model-name validation
+  // that rejects bare IDs like "claude-opus-4-7" in some runtime versions.
+  if (prepared.requestedModel && prepared.acpxAgent !== "claude") {
+    options.push({ key: "model", value: prepared.requestedModel });
+  }
  if (prepared.requestedThinkingEffort) {
    options.push({
      key: prepared.acpxAgent === "codex" ? "reasoning_effort" : "effort",
@@ -999,33 +1139,151 @@ function resultErrorMessage(result: AcpRuntimeTurnResult): string | null {
  return result.error.message;
 }

-function classifyError(err: unknown): Pick<AdapterExecutionResult, "errorCode" | "errorMeta"> {
-  const message = err instanceof Error ? err.message : String(err);
+type AcpxExecutionPhase = "ensure_session" | "configure_session" | "turn";
+
+function describeErrorDiagnostics(err: unknown): {
+  errorName: string;
+  acpCode: string | null;
+  causeMessage: string | null;
+  retryable: boolean | null;
+  stackPreview: string | null;
+} {
+  const errorName =
+    err instanceof Error ? err.name || err.constructor.name : typeof err;
  const maybeCode =
    err && typeof err === "object" && typeof (err as { code?: unknown }).code === "string"
      ? (err as { code: string }).code
      : null;
-  const acpCode = isAcpRuntimeError(err) || (maybeCode?.startsWith("ACP_") ?? false) ? maybeCode : null;
+  const acpCode =
+    isAcpRuntimeError(err) || (maybeCode?.startsWith("ACP_") ?? false) ? maybeCode : null;
+  const cause =
+    err && typeof err === "object" && (err as { cause?: unknown }).cause !== undefined
+      ? (err as { cause?: unknown }).cause
+      : undefined;
+  const causeMessage =
+    cause instanceof Error
+      ? cause.message
+      : typeof cause === "string"
+        ? cause
+        : null;
+  const retryable =
+    err && typeof err === "object" && typeof (err as { retryable?: unknown }).retryable === "boolean"
+      ? (err as { retryable: boolean }).retryable
+      : null;
+  const stack = err instanceof Error && typeof err.stack === "string" ? err.stack : "";
+  const stackPreview = stack ? stack.split("\n").slice(0, 6).join("\n") : null;
+  return { errorName, acpCode, causeMessage, retryable, stackPreview };
+}
+
+function classifyError(
+  err: unknown,
+  phase?: AcpxExecutionPhase,
+): Pick<AdapterExecutionResult, "errorCode" | "errorMeta"> {
+  const message = err instanceof Error ? err.message : String(err);
+  const diagnostics = describeErrorDiagnostics(err);
+  const { acpCode, errorName, causeMessage, retryable, stackPreview } = diagnostics;
+  const baseMeta: Record<string, unknown> = {
+    errorName,
+    ...(acpCode ? { acpCode } : {}),
+    ...(causeMessage ? { causeMessage } : {}),
+    ...(retryable !== null ? { retryable } : {}),
+    ...(stackPreview ? { stackPreview } : {}),
+    ...(phase ? { phase } : {}),
+  };
  const lower = message.toLowerCase();
  const authLike = lower.includes("auth") || lower.includes("login") || lower.includes("credential");
  if (authLike) {
    return {
      errorCode: "acpx_auth_required",
-      errorMeta: { category: "auth", ...(acpCode ? { acpCode } : {}) },
+      errorMeta: { category: "auth", ...baseMeta },
+    };
+  }
+  const phaseCode = (() => {
+    if (acpCode === "ACP_SESSION_INIT_FAILED") return "acpx_session_init_failed";
+    if (acpCode === "ACP_TURN_FAILED") return "acpx_turn_failed";
+    if (acpCode === "ACP_BACKEND_MISSING") return "acpx_backend_missing";
+    if (acpCode === "ACP_BACKEND_UNAVAILABLE") return "acpx_backend_unavailable";
+    if (phase === "ensure_session") return "acpx_session_init_failed";
+    if (phase === "configure_session") return "acpx_session_config_failed";
+    if (phase === "turn") return "acpx_turn_failed";
+    return null;
+  })();
+  if (phaseCode) {
+    return {
+      errorCode: phaseCode,
+      errorMeta: { category: acpCode ? "protocol" : "runtime", ...baseMeta },
    };
  }
  if (acpCode) {
    return {
      errorCode: "acpx_protocol_error",
-      errorMeta: { category: "protocol", acpCode },
+      errorMeta: { category: "protocol", ...baseMeta },
    };
  }
  return {
    errorCode: "acpx_runtime_error",
-    errorMeta: { category: "runtime" },
+    errorMeta: { category: "runtime", ...baseMeta },
  };
 }

+async function readChildStderrTail(input: {
+  logPath: string | null;
+  maxBytes?: number;
+}): Promise<string | null> {
+  if (!input.logPath) return null;
+  const maxBytes = input.maxBytes ?? 4096;
+  let handle: fs.FileHandle | null = null;
+  try {
+    const stat = await fs.stat(input.logPath);
+    if (stat.size === 0) return null;
+    handle = await fs.open(input.logPath, "r");
+    const readBytes = Math.min(stat.size, maxBytes);
+    const buffer = Buffer.alloc(readBytes);
+    await handle.read(buffer, 0, readBytes, Math.max(0, stat.size - readBytes));
+    const tail = buffer.toString("utf8").trim();
+    return tail.length > 0 ? tail : null;
+  } catch {
+    return null;
+  } finally {
+    if (handle) await handle.close().catch(() => {});
+  }
+}
+
+async function emitAcpxFailure(input: {
+  ctx: AdapterExecutionContext;
+  prepared: AcpxPreparedRuntime;
+  err: unknown;
+  phase: AcpxExecutionPhase;
+  // Replace the err-derived message in both the stderr-tail log header and the
+  // acpx.error payload. Used by the turn path to surface "Timed out after Ns"
+  // instead of the raw underlying error message.
+  messageOverride?: string;
+}): Promise<{
+  classified: Pick<AdapterExecutionResult, "errorCode" | "errorMeta">;
+  message: string;
+  childStderrTail: string | null;
+}> {
+  const { ctx, prepared, err, phase, messageOverride } = input;
+  const rawMessage = err instanceof Error ? err.message : String(err);
+  const message = messageOverride ?? rawMessage;
+  const classified = classifyError(err, phase);
+  const childStderrTail = await readChildStderrTail({ logPath: prepared.childStderrLogPath });
+  if (childStderrTail) {
+    await ctx.onLog(
+      "stderr",
+      `[paperclip] ACPX child stderr tail (${phase}):\n${childStderrTail}\n`,
+    );
+  }
+  await emitAcpxLog(ctx, {
+    type: "acpx.error",
+    message,
+    phase,
+    ...classified.errorMeta,
+    ...(childStderrTail ? { childStderrTail } : {}),
+  });
+  return { classified, message, childStderrTail };
+}
+
 function isResumeFailure(err: unknown): boolean {
  const message = err instanceof Error ? err.message : String(err);
  return /resume|load|not found|no session|unknown session|conversation/i.test(message);
@@ -1136,6 +1394,11 @@ export function createAcpxLocalExecutor(deps: ExecuteDeps = {}) {
      permissionMode: prepared.permissionMode,
      nonInteractivePermissions: prepared.nonInteractivePermissions,
      timeoutMs: prepared.timeoutSec > 0 ? prepared.timeoutSec * 1000 : undefined,
+      // Scope ACPX runtime verbose logs to the claude agent only — that's the
+      // surface we know needs the extra session-event detail (PAPA-388). codex
+      // and custom agents already emit their own per-tool output and don't
+      // benefit from doubling the log volume.
+      verbose: prepared.acpxAgent === "claude",
    };
    const runtime = cached?.runtime ?? createRuntime(runtimeOptions);
    if (cached) clearWarmHandleTimer(cached);
@@ -1177,9 +1440,12 @@ export function createAcpxLocalExecutor(deps: ExecuteDeps = {}) {
        }
      }
    } catch (err) {
-      const classified = classifyError(err);
-      const message = err instanceof Error ? err.message : String(err);
-      await emitAcpxLog(ctx, { type: "acpx.error", message, ...classified.errorMeta });
+      const { classified, message } = await emitAcpxFailure({
+        ctx,
+        prepared,
+        err,
+        phase: "ensure_session",
+      });
      return {
        exitCode: 1,
        signal: null,
@@ -1216,9 +1482,12 @@ export function createAcpxLocalExecutor(deps: ExecuteDeps = {}) {
        onLog: ctx.onLog,
      });
    } catch (err) {
-      const classified = classifyError(err);
-      const message = err instanceof Error ? err.message : String(err);
-      await emitAcpxLog(ctx, { type: "acpx.error", message, ...classified.errorMeta });
+      const { classified, message } = await emitAcpxFailure({
+        ctx,
+        prepared,
+        err,
+        phase: "configure_session",
+      });
      await runtime.close({
        handle: sessionHandle,
        reason: "paperclip config cleanup",
@@ -1271,7 +1540,13 @@ export function createAcpxLocalExecutor(deps: ExecuteDeps = {}) {
        commandNotes: [
          `ACPX runtime embedded in Paperclip with ${prepared.mode} session mode.`,
          `Effective ACPX permission mode: ${prepared.permissionMode}.`,
-          ...(prepared.requestedModel ? [`Requested ACPX model: ${prepared.requestedModel}.`] : []),
+          ...(prepared.requestedModel
+            ? [
+                prepared.acpxAgent === "claude"
+                  ? `Requested ACPX model: ${prepared.requestedModel} (set via ANTHROPIC_MODEL env at startup).`
+                  : `Requested ACPX model: ${prepared.requestedModel}.`,
+              ]
+            : []),
          ...(prepared.requestedThinkingEffort ? [`Requested ACPX thinking effort: ${prepared.requestedThinkingEffort}.`] : []),
          ...(prepared.fastMode ? ["Requested ACPX Codex fast mode."] : []),
          ...(Array.isArray(prepared.skillsIdentity.commandNotes)
@@ -1414,10 +1689,11 @@ export function createAcpxLocalExecutor(deps: ExecuteDeps = {}) {
      };
    } catch (err) {
      if (timeout) clearTimeout(timeout);
-      const classified = classifyError(err);
-      const message = timedOut ? `Timed out after ${prepared.timeoutSec}s` : err instanceof Error ? err.message : String(err);
+      const messageOverride = timedOut ? `Timed out after ${prepared.timeoutSec}s` : undefined;
      const cancel = cancelActiveTurn as ((reason: string) => Promise<void>) | null;
-      if (cancel) await cancel(message).catch(() => {});
+      const preEmitMessage =
+        messageOverride ?? (err instanceof Error ? err.message : String(err));
+      if (cancel) await cancel(preEmitMessage).catch(() => {});
      await runtime.close({
        handle: sessionHandle,
        reason: timedOut ? "paperclip timeout cleanup" : "paperclip error cleanup",
@@ -1428,7 +1704,13 @@ export function createAcpxLocalExecutor(deps: ExecuteDeps = {}) {
        clearWarmHandleTimer(existing);
        warmHandles.delete(prepared.sessionKey);
      }
-      await emitAcpxLog(ctx, { type: "acpx.error", message, ...classified.errorMeta });
+      const { classified, message } = await emitAcpxFailure({
+        ctx,
+        prepared,
+        err,
+        phase: "turn",
+        messageOverride,
+      });
      return {
        exitCode: 1,
        signal: timedOut ? "SIGTERM" : null,
@@ -574,7 +574,7 @@ describe("acpx_local execute", () => {
      const execute = createAcpxLocalExecutor({ createRuntime: () => runtime });
      const result = await execute(buildContext(root));
      expect(result.exitCode).toBe(1);
-      expect(result.errorCode).toBe("acpx_protocol_error");
+      expect(result.errorCode).toBe("acpx_session_init_failed");
      expect(result.errorMeta).toMatchObject({
        category: "protocol",
        acpCode: "ACP_SESSION_INIT_FAILED",