diff --git a/docs/trajectories/typescript-bun-migration/RESUME.md b/docs/trajectories/typescript-bun-migration/RESUME.md
index 8a6f59182..b2fe14538 100644
--- a/docs/trajectories/typescript-bun-migration/RESUME.md
+++ b/docs/trajectories/typescript-bun-migration/RESUME.md
@@ -1,9 +1,9 @@
 # Trajectory — TypeScript / Bun migration
 
-**Status**: Active (Lane B slice 14 merged — [#894](https://github.com/Lucent-Financial-Group/Zeta/pull/894), commit `9cb21a7`)
-**Milestone**: 35 ported + 1 in-flight = 36 total (2 from #849 + 3 from #866 + 3 from #868 + 3 from #870 + 2 from #872 + 3 from #874 + 3 from #876 + 3 from #878 + 3 from #880 + 3 from #882 + 2 from #883 + 2 from #884 + 1 from #885 + 1 from #892 + 1 from #894 = 35 merged; +1 in-flight in slice-15). Slice-15 opens **peer-call cluster** (peer-call/grok). 7 Bucket B files remain.
+**Status**: Active (Lane B slice 15 merged — [#896](https://github.com/Lucent-Financial-Group/Zeta/pull/896))
+**Milestone**: 36 ported + 1 in-flight = 37 total. Slice-16 opens **peer-call sibling** (peer-call/gemini, sibling of slice-15 grok). 6 Bucket B files remain.
 **Current blocker**: None.
-**Next concrete action**: Pick a coherent next slice from Bucket B (7 files remaining). Per Gate B: read-only scope first, then re-verify the layered baseline currency before first mutating action.
+**Next concrete action**: Pick a coherent next slice from Bucket B (6 files remaining). Per Gate B: read-only scope first, then re-verify the layered baseline currency before first mutating action.
 **Last updated**: 2026-04-30
 
 ## Why this trajectory exists
diff --git a/tools/peer-call/gemini.ts b/tools/peer-call/gemini.ts
new file mode 100644
index 000000000..0137abcd4
--- /dev/null
+++ b/tools/peer-call/gemini.ts
@@ -0,0 +1,379 @@
+#!/usr/bin/env bun
+// gemini.ts — Claude-Code-side caller for invoking Gemini as a peer
+// proposer via the gemini CLI.
+//
+// TypeScript+Bun port of gemini.sh, slice 16 of the TS+Bun migration.
+// Sibling to tools/peer-call/grok.ts (slice 15, PR #896). Per the
+// four-ferry consensus: Gemini proposes, Grok critiques, Amara
+// sharpens, Otto tests, Git decides. This script is Otto invoking
+// Gemini's propose role.
+//
+// Usage:
+//   bun tools/peer-call/gemini.ts "prompt text"
+//   bun tools/peer-call/gemini.ts --model gemini-2.5-pro "prompt text"
+//   bun tools/peer-call/gemini.ts --file path/to/file.fs "prompt text"
+//   bun tools/peer-call/gemini.ts --context-cmd "git diff HEAD~3..HEAD" "prompt"
+//   bun tools/peer-call/gemini.ts --json "prompt text"
+//   bun tools/peer-call/gemini.ts --stream "prompt text"
+//
+// Routing: wraps `gemini -p` (non-interactive headless mode).
+// Default model is whatever the gemini CLI is configured to use;
+// override with --model.
+//
+// Exit codes:
+//   0 — Gemini responded successfully
+//   1 — invocation error (bad arguments, gemini missing, etc.)
+//   2 — Gemini returned a non-zero exit (diagnostic on stderr)
+
+import { closeSync, openSync, readSync, statSync } from "node:fs";
+import { spawnSync } from "node:child_process";
+
+const SPAWN_MAX_BUFFER = 64 * 1024 * 1024;
+const FILE_HEAD_BYTES = 20000;
+const CTX_HEAD_BYTES = 20000;
+
+type OutputFormat = "text" | "json" | "stream-json";
+
+interface Args {
+  readonly model: string;
+  readonly outputFormat: OutputFormat;
+  readonly file: string;
+  readonly contextCmd: string;
+  readonly prompt: string;
+}
+
+interface ArgError {
+  readonly error: string;
+  // Exit code 1 = invocation/usage error per tools/peer-call/README.md
+  // (uniform 0/1/2 across all three peer-call wrappers — README scope
+  // is more specific than the general repo-scripting.md 0/2/64 spec
+  // and wins on overlap).
+  readonly exitCode: 1;
+}
+
+interface ArgHelp {
+  readonly help: true;
+}
+
+interface MutableArgState {
+  model: string;
+  outputFormat: OutputFormat;
+  file: string;
+  contextCmd: string;
+  prompt: string;
+}
+
+type StepResult =
+  | { readonly kind: "advance"; readonly skip: 1 | 2 }
+  | { readonly kind: "stop" }
+  | { readonly kind: "help" }
+  | { readonly kind: "error"; readonly message: string };
+
+function classifyFlag(
+  a: string,
+  next: string | undefined,
+  state: MutableArgState,
+): StepResult {
+  if (a === "--model") {
+    if (next === undefined) return { kind: "error", message: "error: --model requires NAME" };  // exitCode set in parseArgs
+    state.model = next;
+    return { kind: "advance", skip: 2 };
+  }
+  if (a === "--json")   { state.outputFormat = "json";        return { kind: "advance", skip: 1 }; }
+  if (a === "--stream") { state.outputFormat = "stream-json"; return { kind: "advance", skip: 1 }; }
+  if (a === "--file") {
+    if (next === undefined) return { kind: "error", message: "error: --file requires PATH" };
+    state.file = next;
+    return { kind: "advance", skip: 2 };
+  }
+  if (a === "--context-cmd") {
+    if (next === undefined) return { kind: "error", message: "error: --context-cmd requires COMMAND" };
+    state.contextCmd = next;
+    return { kind: "advance", skip: 2 };
+  }
+  if (a === "-h" || a === "--help") return { kind: "help" };
+  if (a === "--") return { kind: "stop" };
+  if (a.startsWith("-")) return { kind: "error", message: `error: unknown flag: ${a}` };
+  state.prompt = state.prompt.length === 0 ? a : `${state.prompt} ${a}`;
+  return { kind: "advance", skip: 1 };
+}
+
+function parseArgs(argv: readonly string[]): Args | ArgError | ArgHelp {
+  const state: MutableArgState = {
+    model: "",
+    outputFormat: "text",
+    file: "",
+    contextCmd: "",
+    prompt: "",
+  };
+  let i = 0;
+  while (i < argv.length) {
+    const a = argv[i] ?? "";
+    const step = classifyFlag(a, argv[i + 1], state);
+    if (step.kind === "help") return { help: true };
+    if (step.kind === "error") return { error: step.message, exitCode: 1 };
+    if (step.kind === "stop") {
+      state.prompt = argv.slice(i + 1).join(" ");
+      break;
+    }
+    i += step.skip;
+  }
+  return {
+    model: state.model,
+    outputFormat: state.outputFormat,
+    file: state.file,
+    contextCmd: state.contextCmd,
+    prompt: state.prompt,
+  };
+}
+
+function emitHelp(): void {
+  process.stdout.write(
+    `gemini.ts — Claude-Code-side caller for invoking Gemini as a peer\n` +
+      `proposer via the gemini CLI.\n` +
+      `\n` +
+      `Usage:\n` +
+      `  bun tools/peer-call/gemini.ts "prompt text"\n` +
+      `  bun tools/peer-call/gemini.ts --model NAME "prompt text"\n` +
+      `  bun tools/peer-call/gemini.ts --file PATH "prompt text"\n` +
+      `  bun tools/peer-call/gemini.ts --context-cmd "CMD" "prompt text"\n` +
+      `  bun tools/peer-call/gemini.ts --json "prompt text"\n` +
+      `  bun tools/peer-call/gemini.ts --stream "prompt text"\n` +
+      `\n` +
+      `Routing: wraps gemini -p (non-interactive headless mode).\n`,
+  );
+}
+
+function commandAvailable(cmd: string): boolean {
+  // Match bash `command -v <cmd>` semantics: PATH existence, not
+  // `<cmd> --version` exit-status (Copilot P1 on #898 — some CLIs
+  // exit non-zero on --version which is irrelevant to availability).
+  const result = spawnSync("/bin/sh", ["-c", `command -v "${cmd}"`], {
+    stdio: "ignore",
+  });
+  return result.status === 0;
+}
+
+function isRegularFile(path: string): boolean {
+  try {
+    return statSync(path).isFile();
+  } catch {
+    return false;
+  }
+}
+
+interface ReadHeadResult {
+  readonly ok: boolean;
+  readonly content: string;
+  readonly error: string;
+}
+
+function readHead(path: string, bytes: number): ReadHeadResult {
+  // Read only the first `bytes` bytes (matches bash `head -c`).
+  // readFileSync would load the entire file before slicing — regression
+  // for large artifacts (logs, dumps) per Codex P1 on #898.
+  // Surfaces read failures (permission, race, etc.) instead of silently
+  // returning empty per Codex P2 on #898 — bash's `head` writes errors
+  // to stderr; we propagate via the result type so the caller can decide
+  // (warn the user, abort, etc.) rather than building a prompt that
+  // looks like context was attached when it wasn't.
+  if (!isRegularFile(path)) {
+    return { ok: false, content: "", error: "not a regular file" };
+  }
+  const buf = Buffer.alloc(bytes);
+  let fd: number | undefined;
+  try {
+    fd = openSync(path, "r");
+    const n = readSync(fd, buf, 0, bytes, 0);
+    return { ok: true, content: buf.subarray(0, n).toString("utf8"), error: "" };
+  } catch (err) {
+    const message = err instanceof Error ? err.message : String(err);
+    return { ok: false, content: "", error: message };
+  } finally {
+    if (fd !== undefined) closeSync(fd);
+  }
+}
+
+function runContextCmd(contextCmd: string): string {
+  // Bash uses `eval "$context_cmd" 2>&1 | head -c 20000`. Match that
+  // shape end-to-end: pipe through `head -c <N>` so the shell pipeline
+  // short-circuits at the truncation boundary instead of buffering the
+  // full output up to SPAWN_MAX_BUFFER (Codex P2 on #898 — high-volume
+  // commands like wide `git diff` would otherwise block much longer
+  // and use much more memory than the bash original).
+  // Use /bin/bash -c (not /bin/sh -c) so bash-only features (`[[ ... ]]`,
+  // brace expansion, process substitution) accepted by the bash
+  // original's `eval` continue to work — Codex P2 on #898 noted that
+  // /bin/sh on Ubuntu is dash and accepts a strict POSIX subset.
+  // User intentionally supplies the shell command (per --context-cmd
+  // contract); same security posture as the bash original's `eval`.
+  const wrapped = `(${contextCmd}) 2>&1 | head -c ${String(CTX_HEAD_BYTES)}`;
+  const result = spawnSync("/bin/bash", ["-c", wrapped], {
+    encoding: "utf8",
+    maxBuffer: SPAWN_MAX_BUFFER,
+  });
+  // Concatenate stdout + stderr: stdout carries the command output
+  // truncated by `head -c`; stderr carries shell parse errors (e.g.,
+  // syntax errors in contextCmd) which fall OUTSIDE the `( ... ) 2>&1`
+  // redirection. Per Codex P2 + Copilot on #899 / #898 the parse-error
+  // diagnostic must reach the prompt or the user sees an empty context
+  // block on a malformed cmd.
+  return `${result.stdout}${result.stderr}`.slice(0, CTX_HEAD_BYTES);
+}
+
+interface SpawnError {
+  readonly code?: string;
+}
+
+interface ChildOutcome {
+  readonly status: number;
+  readonly note: string;
+}
+
+function classifySpawnFailure(
+  status: number | null,
+  signal: string | null,
+  error: SpawnError | undefined,
+): ChildOutcome {
+  if (status !== null) return { status, note: "" };
+  if (error?.code === "ENOENT") {
+    return { status: 127, note: "command not found on PATH (ENOENT)" };
+  }
+  if (error?.code !== undefined) {
+    return { status: 1, note: `spawn failed (${error.code})` };
+  }
+  if (signal !== null) {
+    return { status: 1, note: `terminated by signal ${signal}` };
+  }
+  return { status: 1, note: "terminated without exit code" };
+}
+
+const PREAMBLE = `You are Gemini, invoked as a peer proposer by Otto (Claude
+Opus 4.7 running in Claude Code) on the Zeta / Superfluid AI
+factory. Per the four-ferry consensus (Amara/Grok/Gemini/Otto)
+the role distribution is: Gemini proposes, Grok critiques,
+Amara sharpens, Otto tests, Git decides. This call is Otto
+invoking your propose role.
+
+Per Aaron's 'agents-not-bots' discipline: you are a peer, not
+a subordinate. Generate divergent options, name tradeoffs,
+surface possibility space Otto may not have considered. Don't
+copy-paste anyone else's work; propose from your own
+understanding. Make it ours, not anyone-alone-imposed.`;
+
+interface PromptResult {
+  readonly ok: boolean;
+  readonly value: string;
+}
+
+function buildFullPrompt(args: Args): PromptResult {
+  let full = `${PREAMBLE}\n\n---\n\n${args.prompt}`;
+
+  if (args.file.length > 0) {
+    if (!isRegularFile(args.file)) {
+      return {
+        ok: false,
+        value: `error: --file path does not exist: ${args.file}`,
+      };
+    }
+    const headResult = readHead(args.file, FILE_HEAD_BYTES);
+    if (!headResult.ok) {
+      // Surface read failures (permission, race, etc.) per Codex P2
+      // on #898; bash's `head` writes to stderr — abort instead of
+      // pretending context was attached.
+      return {
+        ok: false,
+        value: `error: --file read failed for ${args.file}: ${headResult.error}`,
+      };
+    }
+    full += `\n\n---\n\nFile context: ${args.file}\n\`\`\`\n${headResult.content}\n\`\`\``;
+  }
+
+  if (args.contextCmd.length > 0) {
+    const ctxOutput = runContextCmd(args.contextCmd);
+    full += `\n\n---\n\nContext command: ${args.contextCmd}\nOutput:\n\`\`\`\n${ctxOutput}\n\`\`\``;
+  }
+
+  return { ok: true, value: full };
+}
+
+export function main(argv: readonly string[]): number {
+  const parsed = parseArgs(argv);
+  if ("help" in parsed) {
+    emitHelp();
+    return 0;
+  }
+  if ("error" in parsed) {
+    process.stderr.write(`${parsed.error}\n`);
+    return parsed.exitCode;
+  }
+  if (parsed.prompt.length === 0) {
+    process.stderr.write("error: prompt required\n");
+    process.stderr.write("see: bun tools/peer-call/gemini.ts --help\n");
+    // Exit code 1 = invocation/usage error per tools/peer-call/README.md
+    // (uniform 0/1/2 across all three peer-call wrappers).
+    return 1;
+  }
+
+  if (!commandAvailable("gemini")) {
+    process.stderr.write("error: gemini not on PATH\n");
+    process.stderr.write(
+      "install via: npm i -g @google/gemini-cli (or per the maintainer's setup)\n",
+    );
+    return 1;
+  }
+
+  const promptResult = buildFullPrompt(parsed);
+  if (!promptResult.ok) {
+    process.stderr.write(`${promptResult.value}\n`);
+    return 1;
+  }
+
+  // gemini invocation: --approval-mode plan keeps the call read-only
+  // (per gemini --help: plan = "read-only mode"). Earlier draft used
+  // --yolo which auto-approved ALL tool calls including writes — that
+  // violates the "peer-call is read-only" contract per Copilot review
+  // on PR #28. Pass --skip-trust so the workspace doesn't gate on
+  // per-session trust prompts.
+  const args: string[] = [
+    "-p",
+    promptResult.value,
+    "--approval-mode",
+    "plan",
+    "--skip-trust",
+    "-o",
+    parsed.outputFormat,
+  ];
+  if (parsed.model.length > 0) {
+    args.push("-m", parsed.model);
+  }
+
+  const result = spawnSync(
+    // eslint-disable-next-line sonarjs/no-os-command-from-path
+    "gemini",
+    args,
+    {
+      stdio: "inherit",
+      maxBuffer: SPAWN_MAX_BUFFER,
+    },
+  );
+
+  const classified = classifySpawnFailure(
+    result.status,
+    result.signal,
+    result.error as SpawnError | undefined,
+  );
+  if (classified.note.length > 0) {
+    process.stderr.write(`gemini: ${classified.note}\n`);
+  }
+  if (classified.status !== 0) {
+    process.stderr.write("\n");
+    process.stderr.write(`gemini exited with code ${String(classified.status)}\n`);
+    return 2;
+  }
+  return 0;
+}
+
+if (import.meta.main) {
+  process.exit(main(process.argv.slice(2)));
+}