feat(docker): attach a case to an already-running container

Docker cases could only run in a container Codeman created itself. Attaching to
one the user already built and runs means Codeman must leave that container's
lifecycle completely alone, which the launch chain could not do: it was
`image inspect` -> `inspect || create` -> `start` -> `exec`.

Adds `DockerCase.owned`, mirroring the `owned:false` contract remote-SSH already
uses for attached sessions. Absent (every existing case) means owned, so current
behaviour is byte-identical. `false` means the container belongs to the user and
Codeman may only exec into it.

The launch chain for an attached container only looks, then execs: no image gate
(the image is theirs), no create, and no `start` — starting a container we do not
own is the very mutation attaching promises not to perform. A missing or stopped
container fails closed with an actionable message instead. Credential seeding is
skipped too: those copies read from create-time read-only mounts that do not
exist here, and writing host credentials into someone's container is not ours to
do, so its CLIs must already be authenticated inside it.

Four fail-closed guards. buildDockerStopCommand and buildDockerRemoveCommand
throw during pure string construction, so no caller bug can turn into a
`docker stop`/`rm` on a container we do not own; removeDockerContainer refuses
again at the lowest layer; drift reports "none" for an attached container, which
carries no `codeman.confighash` label and would otherwise always look drifted and
409 the launch gate forever; and the orphan reaper skips attached containers
through a check deliberately independent of the two conditions already covering
them.

`owned` is applied AFTER the config hash is computed. dockerConfigHash takes an
explicit field list, so ownership can never shift an existing case's hash — if it
did, every pre-existing case would trip the drift gate at once, and the remedy
the UI offers is "recreate the container".

Adds POST /api/cases/docker-adopt and a read-only
POST /api/docker-cases/adopt-preflight. The preflight refuses at LINK time rather
than at session launch, where the only ways out would be a dead pane or starting
a container we do not own.

Tests assert the negative guarantee directly — that create, start, stop, rm,
restart and kill are absent from the generated commands while `docker exec -it`
and `new-session -A` remain — since it cannot be observed by using the feature.

src/docker-hosts.ts

@@ -55,6 +55,21 @@ export const DEFAULT_AGENT_IMAGE = 'codeman/agent:base';
 /** HOME inside the base image (the `agent` user). Cred mounts + hook-secret land under it. */
 export const CONTAINER_HOME = '/home/agent';
 
+/**
+ * Modes the adoption preflight probes for inside an existing container. `shell`
+ * is omitted deliberately: it needs no CLI binary and is always available, so it
+ * is reported as available without a `command -v` lookup.
+ */
+export const DOCKER_ADOPT_PROBE_MODES = [
+  'claude',
+  'codex',
+  'opencode',
+  'gemini',
+  'antigravity',
+  'pi',
+  'shell',
+] as const satisfies readonly SessionMode[];
+
 /** Per-case container name prefix. The `case` letters deliberately do NOT matter to
  * tmux; this is a DOCKER name (`^[a-zA-Z0-9][a-zA-Z0-9_.-]+$`), and case names are
  * already validated `^[a-zA-Z0-9_-]+$`, so `codeman-case-<name>` is always valid. */
@@ -251,7 +266,22 @@ export function toSessionDocker(host: DockerHost, dockerCase: DockerCase): Sessi
     extraCreateArgs: host.extraCreateArgs,
     extraExecArgs: host.extraExecArgs,
   };
-  return { ...base, configHash: dockerConfigHash(base) };
+  // `owned` is deliberately applied AFTER the hash: dockerConfigHash() picks an
+  // explicit field list, so ownership can never shift an existing case's hash and
+  // mass-trip the drift gate.
+  const session: SessionDocker = { ...base, configHash: dockerConfigHash(base) };
+  if (dockerCase.owned === false) session.owned = false;
+  return session;
+}
+
+/**
+ * An ADOPTED container is one the user built and runs themselves. Codeman may
+ * only exec into it; it must never create, start, stop, restart or remove it.
+ * Every lifecycle branch routes through this one predicate so a new call site
+ * cannot silently opt out.
+ */
+export function isAdoptedContainer(docker: Pick<SessionDocker, 'owned'>): boolean {
+  return docker.owned === false;
 }
 
 // ========== Shell escaping ==========
@@ -713,9 +743,15 @@ export interface DockerDriftStatus {
  * daemon down) means there is nothing to drift. No-op under VITEST.
  */
 export async function checkDockerConfigDrift(
-  docker: Pick<SessionDocker, 'engine' | 'context' | 'daemonHost' | 'containerName' | 'configHash'>
+  docker: Pick<SessionDocker, 'engine' | 'context' | 'daemonHost' | 'containerName' | 'configHash' | 'owned'>
 ): Promise<DockerDriftStatus> {
   if (IS_TEST_MODE) return { exists: false, running: false, drifted: false };
+  // An ADOPTED container carries no `codeman.confighash` label — it was never
+  // created from our config — so every comparison would report drift and the
+  // launch gate would demand a recreate we are not allowed to perform. Ownership
+  // of its configuration belongs to the user; report "no drift" and never offer
+  // to rebuild it.
+  if (isAdoptedContainer(docker)) return { exists: true, running: false, drifted: false };
   const argv = dockerEngineArgv(docker);
   try {
     const { stdout } = await execFileAsync(
@@ -743,8 +779,15 @@ export async function checkDockerConfigDrift(
  * case's lastClaudeSessionId. No-op under VITEST.
  */
 export async function removeDockerContainer(
-  docker: Pick<SessionDocker, 'engine' | 'context' | 'daemonHost' | 'containerName'>
+  docker: Pick<SessionDocker, 'engine' | 'context' | 'daemonHost' | 'containerName' | 'owned'>
 ): Promise<void> {
+  // Fail CLOSED at the lowest layer: an adopted container is the user's, and no
+  // caller — recreate-on-drift, case delete, a future teardown — may remove it.
+  if (isAdoptedContainer(docker)) {
+    throw new Error(
+      `Refusing to remove adopted container "${docker.containerName}": Codeman does not own its lifecycle.`
+    );
+  }
   if (IS_TEST_MODE) return;
   const argv = dockerEngineArgv(docker);
   await execFileAsync(argv[0], [...argv.slice(1), 'rm', '-f', docker.containerName], { timeout: 30_000 });
@@ -990,6 +1033,105 @@ export async function checkDockerTmuxAvailable(
   }
 }
 
+/** Preflight facts about an ALREADY-RUNNING container the user wants to adopt. */
+export interface AdoptedContainerProbe {
+  ok: boolean;
+  exists: boolean;
+  running: boolean;
+  /** The container's own image ref (informational — we never enforce ours on it). */
+  image?: string;
+  /** `command -v tmux` inside the container; required for durable sessions. */
+  tmuxPath?: string;
+  /** Modes whose CLI resolved inside the container (`command -v <mode>`). */
+  availableModes?: SessionMode[];
+  error?: string;
+}
+
+/**
+ * Preflight an EXISTING container for adoption. Read-only by construction: it
+ * runs `inspect` plus one `exec` of `command -v`, and never creates, starts or
+ * modifies anything. Refusing here is what keeps the failure at link time — a
+ * clear message — instead of at session launch, where the only alternatives
+ * would be a dead pane or starting a container we do not own.
+ *
+ * `--pull=never` is irrelevant here: adoption never touches images. The image
+ * ref is reported only so the UI can show what the user is attaching to.
+ */
+export async function probeAdoptableContainer(
+  docker: Pick<SessionDocker, 'engine' | 'context' | 'daemonHost' | 'containerName'>,
+  modes: SessionMode[] = []
+): Promise<AdoptedContainerProbe> {
+  if (IS_TEST_MODE) {
+    return { ok: true, exists: true, running: true, tmuxPath: '/usr/bin/tmux', availableModes: modes };
+  }
+  const argv = dockerEngineArgv(docker);
+  let running = false;
+  let image: string | undefined;
+  try {
+    const { stdout } = await execFileAsync(
+      argv[0],
+      [...argv.slice(1), 'inspect', '-f', '{{.State.Running}}\t{{.Config.Image}}', docker.containerName],
+      { timeout: DOCKER_PROBE_TIMEOUT_MS }
+    );
+    const [state = '', img = ''] = stdout.trim().split('\t');
+    running = state === 'true';
+    image = img || undefined;
+  } catch {
+    return {
+      ok: false,
+      exists: false,
+      running: false,
+      error: `container "${docker.containerName}" not found (adoption never creates a container — start it yourself first)`,
+    };
+  }
+  if (!running) {
+    return {
+      ok: false,
+      exists: true,
+      running: false,
+      image,
+      error: `container "${docker.containerName}" exists but is not running (Codeman never starts a container it does not own — start it yourself, then retry)`,
+    };
+  }
+  // One exec resolves tmux plus every requested CLI, so adoption costs a single
+  // round trip. Binaries are fixed mode names, never user input.
+  const probes = ['tmux', ...modes.filter((m) => m !== 'shell')];
+  const script = probes.map((bin) => `command -v ${bin} >/dev/null 2>&1 && echo ${bin}`).join('; ');
+  try {
+    const { stdout } = await execFileAsync(
+      argv[0],
+      [...argv.slice(1), 'exec', docker.containerName, 'sh', '-lc', script],
+      { timeout: DOCKER_PROBE_TIMEOUT_MS }
+    );
+    const found = new Set(
+      stdout
+        .split('\n')
+        .map((line) => line.trim())
+        .filter(Boolean)
+    );
+    if (!found.has('tmux')) {
+      return {
+        ok: false,
+        exists: true,
+        running: true,
+        image,
+        error: `container "${docker.containerName}" has no tmux (required for durable sessions; install it inside the container)`,
+      };
+    }
+    return {
+      ok: true,
+      exists: true,
+      running: true,
+      image,
+      tmuxPath: 'tmux',
+      availableModes: modes.filter((m) => m === 'shell' || found.has(m)),
+    };
+  } catch (err) {
+    const msg = err instanceof Error ? err.message : String(err);
+    return { ok: false, exists: true, running: true, image, error: `could not exec into the container: ${msg}` };
+  }
+}
+
 /**
  * Resolve the host's IP on the default docker bridge (the address a container
  * reaches as `host.docker.internal`), so the server can bind a hooks-only listener
@@ -1052,9 +1194,18 @@ export async function reapOrphanedDockerContainers(
   }
   const cases = await readDockerCases(configDir);
   const expected = new Set(cases.map((c) => c.container ?? dockerContainerName(c.name)));
+  // ADOPTED containers are never reapable, and this guard is deliberately
+  // independent of the two conditions that already cover them (we never applied
+  // the `codeman.managed=1` label filtered on above, and they are referenced by a
+  // live case so they are in `expected`). An adopted container is the user's
+  // property; it must survive even if a future edit narrows either condition.
+  const adopted = new Set(
+    cases.filter((item) => item.owned === false).map((item) => item.container ?? dockerContainerName(item.name))
+  );
   const reaped: string[] = [];
   for (const { name, inst } of rows) {
     if (inst !== instance) continue; // only THIS instance's containers
+    if (adopted.has(name)) continue; // never reap a container we do not own
     if (expected.has(name)) continue; // still referenced by a live case
     try {
       await execFileAsync(bin, ['rm', '-f', name], { timeout: DOCKER_PROBE_TIMEOUT_MS });

src/tmux-manager.ts

@@ -1275,7 +1275,15 @@ export interface DockerLaunchOptions {
 export function buildDockerLaunchCommand(opts: DockerLaunchOptions): string {
   const { mode, docker, sessionId, resumeSessionId, createContext, execEnv, execEnvNames, seedCopies } = opts;
   const base = buildDockerBaseArgs(docker).join(' ');
-  const createArgs = buildDockerCreateArgs(createContext).join(' ');
+  // ADOPTED container (docker.owned === false): the user built it and runs it, so
+  // this chain may only LOOK and then exec. No image check (the image is theirs),
+  // no create, and above all no `start` — starting a container we do not own is
+  // exactly the lifecycle mutation adoption promises never to perform. A missing
+  // or stopped container fails closed with an actionable message instead.
+  const adopted = docker.owned === false;
+  // Built lazily: an adopted case has no meaningful create-config, so computing
+  // create args for it would demand a context the adopt path never assembles.
+  const createArgs = adopted ? '' : buildDockerCreateArgs(createContext).join(' ');
   const name = shellescape(docker.containerName);
   const workdir = shellescape(docker.containerWorkdir);
   const image = shellescape(docker.image);
@@ -1318,16 +1326,33 @@ export function buildDockerLaunchCommand(opts: DockerLaunchOptions): string {
   );
   const startFailMsg = shellescape(`Codeman: container ${docker.containerName} failed to start (docker daemon down?)`);
 
-  const imageCheck = `${base} image inspect ${image} >/dev/null 2>&1 || { echo ${imageMissingMsg}; exit 1; }`;
+  const notFoundMsg = shellescape(
+    `Codeman: container ${docker.containerName} not found. Adopted containers are never created by Codeman — start it yourself, then reopen this session.`
+  );
+  const notRunningMsg = shellescape(
+    `Codeman: container ${docker.containerName} is not running. Codeman never starts a container it does not own — start it yourself, then reopen this session.`
+  );
+
+  const imageCheck = adopted
+    ? ''
+    : `${base} image inspect ${image} >/dev/null 2>&1 || { echo ${imageMissingMsg}; exit 1; }`;
   // create-if-missing (idempotent): reconnect / boot recovery re-runs this exact chain.
-  const ensure = `${base} inspect ${name} >/dev/null 2>&1 || ${base} ${createArgs}`;
-  const start = `${base} start ${name} >/dev/null 2>&1 || { echo ${startFailMsg}; exit 1; }`;
+  const ensure = adopted
+    ? `${base} inspect ${name} >/dev/null 2>&1 || { echo ${notFoundMsg}; exit 1; }`
+    : `${base} inspect ${name} >/dev/null 2>&1 || ${base} ${createArgs}`;
+  const start = adopted
+    ? `[ "$(${base} inspect -f '{{.State.Running}}' ${name} 2>/dev/null)" = true ] || { echo ${notRunningMsg}; exit 1; }`
+    : `${base} start ${name} >/dev/null 2>&1 || { echo ${startFailMsg}; exit 1; }`;
   // Seed writable credential config from read-only host mounts ONCE per container
   // (guarded by [ -e ] so reconnects never clobber in-container config; `cp -a` for
   // whole-dir credential seeds). mkdir -p the parent so a file seed works even when
   // no sibling share-mount pre-created the dir. Paths are fixed CONTAINER_HOME
   // constants (no shell metachars), so the whole inner command is shell-quoted once.
-  const seedSteps = (seedCopies ?? []).map((s) => {
+  // An ADOPTED container gets NO seed copies: those read from create-time
+  // read-only mounts that do not exist here, and writing host credentials into a
+  // container the user owns is a mutation adoption does not permit. Its CLIs must
+  // already be authenticated inside it.
+  const seedSteps = (adopted ? [] : (seedCopies ?? [])).map((s) => {
     const cp = s.recursive ? 'cp -a' : 'cp';
     const parent = s.to.slice(0, s.to.lastIndexOf('/'));
     return `mkdir -p ${parent} 2>/dev/null; [ -e ${s.to} ] || ${cp} ${s.from} ${s.to} 2>/dev/null || true`;
@@ -1335,7 +1360,7 @@ export function buildDockerLaunchCommand(opts: DockerLaunchOptions): string {
   const innerCmd = seedSteps.length ? `${seedSteps.join(' ; ')} ; ${tmuxInvocation}` : tmuxInvocation;
   const execCmd = `exec ${base} exec -it --workdir ${workdir} ${execEnvFlags.join(' ')} ${name} sh -lc ${shellescape(innerCmd)}`;
 
-  return [imageCheck, ensure, start, execCmd].join(' ; ');
+  return [imageCheck, ensure, start, execCmd].filter(Boolean).join(' ; ');
 }
 
 /**
@@ -1351,13 +1376,29 @@ export function buildDockerKillCommand(options: { docker: SessionDocker; session
   return `${base} exec ${shellescape(docker.containerName)} tmux -L ${DOCKER_TMUX_SOCKET} kill-session -t ${shellescape(dkrName)}`;
 }
 
+/**
+ * Guard for the two builders that mutate CONTAINER lifecycle. They are pure
+ * string builders, so refusing here means an adopted container cannot even have
+ * a stop/remove command constructed for it — there is no shape of caller bug
+ * that turns into a `docker stop`/`rm` on something we do not own.
+ */
+function assertOwnedContainer(docker: SessionDocker, action: string): void {
+  if (docker.owned === false) {
+    throw new Error(
+      `Refusing to ${action} adopted container "${docker.containerName}": Codeman does not own its lifecycle.`
+    );
+  }
+}
+
 /** Explicit container stop (frees RAM/CPU; conversation resumes on next launch via --resume). */
 export function buildDockerStopCommand(docker: SessionDocker): string {
+  assertOwnedContainer(docker, 'stop');
   return `${buildDockerBaseArgs(docker).join(' ')} stop -t 10 ${shellescape(docker.containerName)}`;
 }
 
 /** Explicit container removal (case-delete). Destroys in-image state; bind mounts survive. */
 export function buildDockerRemoveCommand(docker: SessionDocker): string {
+  assertOwnedContainer(docker, 'remove');
   return `${buildDockerBaseArgs(docker).join(' ')} rm -f ${shellescape(docker.containerName)}`;
 }
 

src/types/session.ts

@@ -243,6 +243,24 @@ export interface DockerCase {
   containerWorkdir?: string;
   /** Container name (default codeman-case-<slug>). */
   container?: string;
+  /**
+   * Whether THIS Codeman created the container (mirror of `SessionRemote.owned`).
+   *
+   * - `true` (default for cases Codeman linked/quick-created): we own the
+   *   container; drift may recreate it, case-delete may `docker rm -f` it, and
+   *   the launch chain may create + start it.
+   * - `false` (ADOPTED: an already-running container the user built and runs
+   *   themselves): Codeman must never create, start, stop, restart or remove it.
+   *   The launch chain fails closed when the container is missing or not running
+   *   instead of touching its lifecycle, drift is not evaluated (there is no
+   *   `codeman.confighash` label to compare), and no credential seed is copied
+   *   into its HOME. Only the in-container tmux session is ever created or
+   *   killed — exactly the `owned:false` remote-SSH contract.
+   *
+   * Absent is treated as owned (cases persisted before this field existed were
+   * all created by us).
+   */
+  owned?: boolean;
   /** Last captured Claude conversation id, replayed via --resume on a fresh launch. */
   lastClaudeSessionId?: string;
 }
@@ -275,6 +293,12 @@ export interface SessionDocker {
   extraExecArgs?: string[];
   /** Stable hash of the drift-relevant create args (recreate-on-drift detection). */
   configHash?: string;
+  /**
+   * Mirror of `DockerCase.owned`, flattened onto the live session so every
+   * lifecycle decision (launch chain, drift, stop, remove) can see it without
+   * re-reading docker-cases.json. Absent = owned. See `DockerCase.owned`.
+   */
+  owned?: boolean;
 }
 
 /**

src/web/routes/case-routes.ts

@@ -13,7 +13,7 @@ import fs from 'node:fs/promises';
 import { join, resolve, basename } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { homedir } from 'node:os';
-import type { ApiResponse, CaseInfo, DockerHost, RemoteSessionInfo, SessionDocker } from '../../types.js';
+import type { ApiResponse, CaseInfo, DockerHost, RemoteSessionInfo, SessionDocker, SessionMode } from '../../types.js';
 import { ApiErrorCode, createErrorResponse, getErrorMessage } from '../../types.js';
 import {
   CreateCaseSchema,
@@ -24,6 +24,8 @@ import {
   RemoteCaseLinkSchema,
   RemoteHostSchema,
   DockerCaseLinkSchema,
+  DockerCaseAdoptSchema,
+  DockerAdoptPreflightSchema,
   DockerHostSchema,
   DockerExportSchema,
   DockerImportSchema,
@@ -66,6 +68,8 @@ import {
   DEFAULT_AGENT_IMAGE,
   dockerContainerName,
   dockerDisplayPath,
+  probeAdoptableContainer,
+  DOCKER_ADOPT_PROBE_MODES,
   readDockerCases,
   readDockerHosts,
   removeDockerContainer,
@@ -73,6 +77,7 @@ import {
   writeDockerCases,
   writeDockerHosts,
 } from '../../docker-hosts.js';
+import type { AdoptedContainerProbe } from '../../docker-hosts.js';
 import { buildDockerRemoveCommand } from '../../tmux-manager.js';
 import {
   checkRemoteTmuxAvailable,
@@ -771,6 +776,106 @@ export function registerCaseRoutes(app: FastifyInstance, ctx: EventPort & Config
     }
   );
 
+  /**
+   * ADOPT an already-running container (`owned: false`). The mirror of the
+   * remote-SSH attach path: Codeman execs into a container the user built and
+   * runs, and never creates, starts, stops, restarts or removes it.
+   *
+   * Everything here is read-only toward the container. The preflight refuses at
+   * LINK time — missing, stopped, or no tmux inside — because the alternative is
+   * failing at session launch, where the only ways out would be a dead pane or
+   * starting a container we do not own. There is no image gate and no
+   * `ensureCaseImage`: adoption never runs `docker create`, so the container's
+   * image is the user's business.
+   */
+  app.post(
+    '/api/cases/docker-adopt',
+    async (req): Promise<ApiResponse<{ case: unknown; image?: string; availableModes?: SessionMode[] }>> => {
+      const dockerCase = {
+        ...parseBody(DockerCaseAdoptSchema, req.body),
+        type: 'docker' as const,
+        owner: ownerFor(req),
+        owned: false as const,
+      };
+      const host = (await readDockerHosts(CODEMAN_CONFIG_DIR)).find((item) => item.id === dockerCase.hostId);
+      if (!host) return createErrorResponse(ApiErrorCode.NOT_FOUND, 'Docker host not found');
+
+      const linkedCases = await readLinkedCases();
+      const dockerCases = await readDockerCases(CODEMAN_CONFIG_DIR);
+      if (
+        dockerCases.some((item) => item.name === dockerCase.name) ||
+        linkedCases[dockerCase.name] ||
+        existsSync(join(resolveCasesDir(getAuthUser(req)), dockerCase.name))
+      ) {
+        return createErrorResponse(ApiErrorCode.ALREADY_EXISTS, 'Case already exists');
+      }
+      // Two cases must never share one adopted container: session close kills the
+      // in-container tmux by session id, but a shared adoption would let one case's
+      // teardown and another's launch race over the same tmux server.
+      const container = dockerCase.container;
+      if (dockerCases.some((item) => (item.container ?? dockerContainerName(item.name)) === container)) {
+        return createErrorResponse(ApiErrorCode.ALREADY_EXISTS, `Container "${container}" is already linked to a case`);
+      }
+
+      if (!isWorkingDirAllowed(getAuthUser(req), dockerCase.hostWorkspacePath)) {
+        return createErrorResponse(ApiErrorCode.FORBIDDEN, 'hostWorkspacePath is outside your workspace');
+      }
+      // The workspace must ALREADY exist: it mirrors a path inside a container we
+      // did not create, so silently mkdir-ing it would invent a host directory that
+      // does not correspond to whatever is actually mounted there.
+      if (!existsSync(dockerCase.hostWorkspacePath)) {
+        return createErrorResponse(
+          ApiErrorCode.INVALID_INPUT,
+          'hostWorkspacePath does not exist. Adoption mirrors an existing container, so point this at the real host directory already mounted into it.'
+        );
+      }
+
+      const availability = await checkDockerAvailable(host.engine);
+      if (!availability.ok) {
+        return createErrorResponse(
+          ApiErrorCode.OPERATION_FAILED,
+          availability.error || 'docker daemon is not available'
+        );
+      }
+      const probe = await probeAdoptableContainer(toSessionDocker(host, dockerCase), [...DOCKER_ADOPT_PROBE_MODES]);
+      if (!probe.ok) {
+        return createErrorResponse(ApiErrorCode.OPERATION_FAILED, probe.error || 'container is not adoptable');
+      }
+
+      await writeDockerCases(CODEMAN_CONFIG_DIR, [...dockerCases, dockerCase]);
+      ctx.broadcast(SseEvent.CaseLinked, {
+        name: dockerCase.name,
+        path: dockerCase.hostWorkspacePath,
+        type: 'docker',
+      });
+      return {
+        success: true,
+        data: { case: dockerCase, image: probe.image, availableModes: probe.availableModes },
+      };
+    }
+  );
+
+  /**
+   * Preflight an existing container WITHOUT linking anything, so the UI can tell
+   * the user "not running" / "no tmux" / "codex present, claude missing" before
+   * they commit to a case name. Read-only; never touches container lifecycle.
+   */
+  app.post('/api/docker-cases/adopt-preflight', async (req): Promise<ApiResponse<AdoptedContainerProbe>> => {
+    const body = parseBody(DockerAdoptPreflightSchema, req.body);
+    const host = (await readDockerHosts(CODEMAN_CONFIG_DIR)).find((item) => item.id === body.hostId);
+    if (!host) return createErrorResponse(ApiErrorCode.NOT_FOUND, 'Docker host not found');
+    const probe = await probeAdoptableContainer(
+      {
+        engine: host.engine ?? 'docker',
+        context: host.context,
+        daemonHost: host.daemonHost,
+        containerName: body.container,
+      },
+      [...DOCKER_ADOPT_PROBE_MODES]
+    );
+    return { success: true, data: probe };
+  });
+
   // One-click "Run in Docker": create a NORMAL case (folder in CASES_DIR, scaffolded)
   // AND link it to a hardened container with default settings, auto-provisioning a
   // shared `default` docker host so the user never touches host/image/network fields.
@@ -1010,9 +1115,7 @@ export function registerCaseRoutes(app: FastifyInstance, ctx: EventPort & Config
       engine: result.manifest.engine,
       image: result.importedImage ?? result.manifest.image,
       network: (['bridge', 'none', 'custom'].includes(result.manifest.network) ? result.manifest.network : 'bridge') as
-        | 'bridge'
-        | 'none'
-        | 'custom',
+        'bridge' | 'none' | 'custom',
     };
     await writeDockerHosts(
       CODEMAN_CONFIG_DIR,
@@ -1042,8 +1145,22 @@ export function registerCaseRoutes(app: FastifyInstance, ctx: EventPort & Config
     '/api/docker-cases/:name/recreate',
     async (req): Promise<ApiResponse<{ name: string; container: string }>> => {
       const { name } = req.params as { name: string };
-      const dockerCase = (await readDockerCases(CODEMAN_CONFIG_DIR)).find((item) => item.name === name);
+      // Ownership gate: recreate DESTROYS a container, so it must be scoped like
+      // delete is (`canAccessOwned`). Without it any user could rebuild another
+      // user's container by name.
+      const dockerCase = (await readDockerCases(CODEMAN_CONFIG_DIR)).find(
+        (item) => item.name === name && canAccessOwned(getAuthUser(req), item.owner)
+      );
       if (!dockerCase) return createErrorResponse(ApiErrorCode.NOT_FOUND, 'Docker case not found');
+      // An ADOPTED container is the user's own: there is nothing to recreate it
+      // from (no create-config, no image gate) and destroying it is exactly what
+      // adoption promises never to do.
+      if (dockerCase.owned === false) {
+        return createErrorResponse(
+          ApiErrorCode.FORBIDDEN,
+          `Case "${name}" adopted an existing container. Codeman does not own its lifecycle and will not recreate it — rebuild it yourself, or unlink the case.`
+        );
+      }
       const host = (await readDockerHosts(CODEMAN_CONFIG_DIR)).find((item) => item.id === dockerCase.hostId);
       if (!host) return createErrorResponse(ApiErrorCode.NOT_FOUND, 'Docker host not found');
       const sessionDocker = toSessionDocker(host, dockerCase);
@@ -1154,7 +1271,13 @@ export function registerCaseRoutes(app: FastifyInstance, ctx: EventPort & Config
       );
       // Best-effort `docker rm -f` the per-case container (case-delete is the
       // explicit teardown that removes it; the bind-mounted workspace survives).
-      const host = (await readDockerHosts(CODEMAN_CONFIG_DIR)).find((item) => item.id === dockerCase.hostId);
+      // An ADOPTED container is skipped entirely: unlinking the case must leave
+      // the user's own container running and untouched. The seed file is skipped
+      // with it — adoption never wrote one.
+      const host =
+        dockerCase.owned === false
+          ? undefined
+          : (await readDockerHosts(CODEMAN_CONFIG_DIR)).find((item) => item.id === dockerCase.hostId);
       if (host) {
         const sessionDocker = toSessionDocker(host, dockerCase);
         try {

src/web/routes/session-routes.ts

@@ -127,6 +127,7 @@ import {
 import {
   checkDockerAvailable,
   checkDockerConfigDrift,
+  probeAdoptableContainer,
   checkDockerTmuxAvailable,
   ensureAgentBaseImage,
   DEFAULT_AGENT_IMAGE,
@@ -2957,25 +2958,43 @@ export function registerSessionRoutes(
         );
       }
       const sessionDocker = toSessionDocker(host, dockerCase);
-      // Ensure the base image exists, auto-building the default image on first use so
-      // it is never a blocker. Dedup'd with any build kicked off at case-create, so
-      // this awaits the SAME in-flight build rather than starting a second one.
-      const ensured = await ensureAgentBaseImage(sessionDocker, sessionDocker.image, {
-        onProgress: (line) => ctx.broadcast(SseEvent.DockerImageBuildProgress, { name: dockerCase.name, line }),
-      });
-      if (!ensured.ok) {
-        return createErrorResponse(ApiErrorCode.OPERATION_FAILED, ensured.error || 'base image not available');
-      }
-      if (ensured.built) {
-        ctx.broadcast(SseEvent.DockerImageBuildComplete, { name: dockerCase.name, image: sessionDocker.image });
-      }
-      // tmux is a hard prerequisite (the in-container tmux makes reconnect durable).
-      // Skip the extra container-run probe for our OWN default image (the baked
-      // Dockerfile always contains tmux); still verify a custom image.
-      if (sessionDocker.image !== DEFAULT_AGENT_IMAGE) {
-        const tmuxCheck = await checkDockerTmuxAvailable(sessionDocker);
-        if (!tmuxCheck.ok) {
-          return createErrorResponse(ApiErrorCode.OPERATION_FAILED, tmuxCheck.error || 'base image is missing tmux');
+      // An ADOPTED container skips every image-side gate: we never run `docker
+      // create`, so the image is the user's business, and `ensureAgentBaseImage`
+      // would build/require an image that has nothing to do with their container.
+      // The prerequisite that DOES still hold is tmux inside it, so probe the live
+      // container (not the image) and refuse before launch rather than dead-paning.
+      if (sessionDocker.owned === false) {
+        const probe = await probeAdoptableContainer(sessionDocker, [mode]);
+        if (!probe.ok) {
+          return createErrorResponse(ApiErrorCode.OPERATION_FAILED, probe.error || 'container is not usable');
+        }
+        if (mode !== 'shell' && !probe.availableModes?.includes(mode)) {
+          return createErrorResponse(
+            ApiErrorCode.OPERATION_FAILED,
+            `"${mode}" is not installed in container "${sessionDocker.containerName}". Adoption never modifies the container — install it inside, or pick another mode.`
+          );
+        }
+      } else {
+        // Ensure the base image exists, auto-building the default image on first use so
+        // it is never a blocker. Dedup'd with any build kicked off at case-create, so
+        // this awaits the SAME in-flight build rather than starting a second one.
+        const ensured = await ensureAgentBaseImage(sessionDocker, sessionDocker.image, {
+          onProgress: (line) => ctx.broadcast(SseEvent.DockerImageBuildProgress, { name: dockerCase.name, line }),
+        });
+        if (!ensured.ok) {
+          return createErrorResponse(ApiErrorCode.OPERATION_FAILED, ensured.error || 'base image not available');
+        }
+        if (ensured.built) {
+          ctx.broadcast(SseEvent.DockerImageBuildComplete, { name: dockerCase.name, image: sessionDocker.image });
+        }
+        // tmux is a hard prerequisite (the in-container tmux makes reconnect durable).
+        // Skip the extra container-run probe for our OWN default image (the baked
+        // Dockerfile always contains tmux); still verify a custom image.
+        if (sessionDocker.image !== DEFAULT_AGENT_IMAGE) {
+          const tmuxCheck = await checkDockerTmuxAvailable(sessionDocker);
+          if (!tmuxCheck.ok) {
+            return createErrorResponse(ApiErrorCode.OPERATION_FAILED, tmuxCheck.error || 'base image is missing tmux');
+          }
         }
       }
 

src/web/schemas.ts

@@ -792,6 +792,50 @@ export const DockerCaseLinkSchema = z.object({
     .optional(),
 });
 
+/**
+ * ADOPT an already-running container the user built and runs themselves. The
+ * container name is REQUIRED (there is nothing to derive it from — we are not
+ * creating it), and `hostWorkspacePath` still points at real host bytes so the
+ * file routes, watchers and transcript correlation keep working exactly as they
+ * do for an owned case. Everything that only makes sense at container-create
+ * time (image, network, resources, gpus, credential mounts) is deliberately
+ * absent: adoption never runs `docker create`.
+ */
+export const DockerCaseAdoptSchema = z.object({
+  name: z.string().regex(/^[a-zA-Z0-9_-]+$/, 'Invalid case name format'),
+  hostId: z.string().regex(/^[a-zA-Z0-9_-]+$/, 'Invalid docker host id'),
+  container: z
+    .string()
+    .min(2)
+    .max(128)
+    .regex(/^[a-zA-Z0-9][a-zA-Z0-9_.-]+$/, 'Invalid container name'),
+  hostWorkspacePath: z
+    .string()
+    .min(1)
+    .max(2000)
+    .regex(/^\//, 'Workspace path must be absolute')
+    .regex(/^[^,]*$/, 'Workspace path must not contain commas (docker --mount is comma-delimited)')
+    .regex(NO_SHELL_META, 'Invalid characters in workspace path'),
+  containerWorkdir: z
+    .string()
+    .min(1)
+    .max(2000)
+    .regex(/^\//, 'Container workdir must be absolute')
+    .regex(/^[^,]*$/, 'Container workdir must not contain commas (docker --mount is comma-delimited)')
+    .regex(NO_SHELL_META, 'Invalid characters in container workdir')
+    .optional(),
+});
+
+/** Read-only adoption preflight: report on an existing container, link nothing. */
+export const DockerAdoptPreflightSchema = z.object({
+  hostId: z.string().regex(/^[a-zA-Z0-9_-]+$/, 'Invalid docker host id'),
+  container: z
+    .string()
+    .min(2)
+    .max(128)
+    .regex(/^[a-zA-Z0-9][a-zA-Z0-9_.-]+$/, 'Invalid container name'),
+});
+
 export const DockerExportSchema = z.object({
   mode: z.enum(['full', 'workspace']).optional(),
 });

test/docker-adopted-container.test.ts

@@ -0,0 +1,168 @@
+/**
+ * @fileoverview Adopting an ALREADY-RUNNING container (`DockerCase.owned === false`).
+ *
+ * The whole point of adoption is a negative guarantee: Codeman execs into a
+ * container the user built and runs, and never creates, starts, stops, restarts
+ * or removes it. A negative guarantee cannot be observed by using the feature —
+ * only by asserting that the mutating verbs are absent — so these tests read the
+ * generated command strings and assert on what is NOT in them.
+ *
+ * Mirror of the `owned:false` remote-SSH contract (COD-105).
+ */
+import { describe, it, expect } from 'vitest';
+import {
+  toSessionDocker,
+  isAdoptedContainer,
+  removeDockerContainer,
+  checkDockerConfigDrift,
+  dockerConfigHash,
+} from '../src/docker-hosts.js';
+import {
+  buildDockerLaunchCommand,
+  buildDockerStopCommand,
+  buildDockerRemoveCommand,
+  buildDockerKillCommand,
+} from '../src/tmux-manager.js';
+import type { DockerCase, DockerHost, SessionDocker } from '../src/types.js';
+
+const HOST: DockerHost = { id: 'h1', label: 'local', engine: 'docker', image: 'codeman/agent:base' };
+
+function caseFor(owned: boolean | undefined): DockerCase {
+  return {
+    name: 'adopted',
+    type: 'docker',
+    hostId: 'h1',
+    hostWorkspacePath: '/srv/work',
+    container: 'my-own-container',
+    ...(owned === undefined ? {} : { owned }),
+  };
+}
+
+function launchFor(docker: SessionDocker): string {
+  return buildDockerLaunchCommand({
+    mode: 'codex',
+    docker,
+    sessionId: '11111111-2222-3333-4444-555555555555',
+    createContext: {
+      docker,
+      sessionId: '11111111-2222-3333-4444-555555555555',
+      instance: 'default',
+      userArgs: ['--user', '1000:0'],
+      credentialMounts: [],
+      extraMounts: [],
+      envCreate: { HOME: '/home/agent' },
+      addHostGateway: true,
+      gatewayAlias: 'host.docker.internal',
+    },
+    execEnv: { TERM: 'xterm-256color' },
+    execEnvNames: [],
+    seedCopies: [{ from: '/seed/creds.json', to: '/home/agent/.claude/.credentials.json' }],
+  });
+}
+
+describe('adopted container: ownership plumbing', () => {
+  it('carries owned:false from the case onto the live session metadata', () => {
+    expect(toSessionDocker(HOST, caseFor(false)).owned).toBe(false);
+    expect(isAdoptedContainer(toSessionDocker(HOST, caseFor(false)))).toBe(true);
+  });
+
+  it('treats an absent flag as owned, so existing cases are unchanged', () => {
+    const docker = toSessionDocker(HOST, caseFor(undefined));
+    expect(docker.owned).toBeUndefined();
+    expect(isAdoptedContainer(docker)).toBe(false);
+  });
+
+  it('keeps ownership OUT of the config hash so adoption cannot mass-trip drift', () => {
+    // A drift-hash that moved with `owned` would flag every pre-existing case the
+    // moment this field shipped, and the remedy the UI offers is "recreate".
+    const owned = toSessionDocker(HOST, caseFor(undefined));
+    const adopted = toSessionDocker(HOST, caseFor(false));
+    expect(adopted.configHash).toBe(owned.configHash);
+    expect(dockerConfigHash({ ...owned, owned: false } as never)).toBe(owned.configHash);
+  });
+});
+
+describe('adopted container: the launch chain never mutates lifecycle', () => {
+  const adopted = launchFor(toSessionDocker(HOST, caseFor(false)));
+  const owned = launchFor(toSessionDocker(HOST, caseFor(undefined)));
+
+  it('never creates the container', () => {
+    expect(owned).toContain('docker create');
+    expect(adopted).not.toContain('docker create');
+  });
+
+  it('never starts the container', () => {
+    expect(owned).toContain('docker start');
+    expect(adopted).not.toContain('docker start');
+  });
+
+  it('never stops or removes the container', () => {
+    for (const verb of ['docker stop', 'docker rm', 'docker restart', 'docker kill']) {
+      expect(adopted).not.toContain(verb);
+    }
+  });
+
+  it('fails closed when the container is missing instead of creating it', () => {
+    expect(adopted).toContain('docker inspect');
+    expect(adopted).toMatch(/not found.*start it yourself/i);
+  });
+
+  it('fails closed when the container is stopped instead of starting it', () => {
+    expect(adopted).toMatch(/\{\{\.State\.Running\}\}/);
+    expect(adopted).toMatch(/not running.*never starts a container it does not own/i);
+  });
+
+  it('skips the base-image gate, which describes an image adoption never uses', () => {
+    expect(owned).toContain('image inspect');
+    expect(adopted).not.toContain('image inspect');
+  });
+
+  it('never seeds host credentials into a container it does not own', () => {
+    expect(owned).toContain('.credentials.json');
+    expect(adopted).not.toContain('.credentials.json');
+  });
+
+  it('still execs into the in-container tmux, which is the whole point', () => {
+    expect(adopted).toContain('docker exec -it');
+    expect(adopted).toContain('new-session -A');
+  });
+});
+
+describe('adopted container: mutating verbs fail closed at the builder', () => {
+  const docker = toSessionDocker(HOST, caseFor(false));
+
+  it('refuses to build a stop command', () => {
+    expect(() => buildDockerStopCommand(docker)).toThrow(/does not own its lifecycle/);
+  });
+
+  it('refuses to build a remove command', () => {
+    expect(() => buildDockerRemoveCommand(docker)).toThrow(/does not own its lifecycle/);
+  });
+
+  it('refuses to remove the container', async () => {
+    await expect(removeDockerContainer(docker)).rejects.toThrow(/does not own its lifecycle/);
+  });
+
+  it('still allows killing THIS session in-container tmux, never the container', () => {
+    const kill = buildDockerKillCommand({ docker, sessionId: 'abcdef12-0000-0000-0000-000000000000' });
+    expect(kill).toContain('tmux');
+    expect(kill).toContain('kill-session');
+    expect(kill).not.toContain('docker stop');
+    expect(kill).not.toContain('docker rm');
+  });
+
+  it('still permits every verb for an owned container', () => {
+    const ownedDocker = toSessionDocker(HOST, caseFor(undefined));
+    expect(buildDockerStopCommand(ownedDocker)).toContain('stop -t 10');
+    expect(buildDockerRemoveCommand(ownedDocker)).toContain('rm -f');
+  });
+});
+
+describe('adopted container: drift is not evaluated', () => {
+  it('reports no drift rather than demanding a recreate we may not perform', async () => {
+    // An adopted container carries no codeman.confighash label, so a real
+    // comparison would always report drift and the launch gate would 409 forever.
+    const status = await checkDockerConfigDrift(toSessionDocker(HOST, caseFor(false)));
+    expect(status.drifted).toBe(false);
+  });
+});