diff --git a/.claude-plugin/marketplace.json b/.claude-plugin/marketplace.json
index 2eec58b..6570e0d 100644
--- a/.claude-plugin/marketplace.json
+++ b/.claude-plugin/marketplace.json
@@ -10,7 +10,7 @@
       "name": "agentcomm",
       "source": "./",
       "description": "Multi-agent mailbox CLI — any git remote is a bus (git+ssh/github/sqlite/s3/gcs/postgres). register/send/inbox/wait/claim/log/channels so Claude coordinates with other agents or sessions; auto-selects the repo bus inside a git repo.",
-      "version": "0.14.3",
+      "version": "0.15.0",
       "author": {
         "name": "Yoni Davidson"
       },
diff --git a/.claude-plugin/plugin.json b/.claude-plugin/plugin.json
index ac366bf..bfa7e30 100644
--- a/.claude-plugin/plugin.json
+++ b/.claude-plugin/plugin.json
@@ -1,7 +1,7 @@
 {
   "name": "agentcomm",
   "description": "Multi-agent mailbox CLI — any git remote is a bus (git+ssh/github/sqlite/s3/gcs/postgres). register/send/inbox/wait/claim/log/channels so Claude coordinates with other agents or sessions; auto-selects the repo bus inside a git repo.",
-  "version": "0.14.3",
+  "version": "0.15.0",
   "author": {
     "name": "Yoni Davidson",
     "email": "yonidavidson@tabnine.com"
diff --git a/hooks/lib.mjs b/hooks/lib.mjs
index 543b5c4..ecb0894 100644
--- a/hooks/lib.mjs
+++ b/hooks/lib.mjs
@@ -128,6 +128,36 @@ export async function activitySince(cwd, me, stateFile, cap = 4) {
   };
 }
 
+/** Current git branch (mechanical, non-prompt), or null. */
+export async function gitBranch(cwd) {
+  try {
+    // symbolic-ref works on unborn branches too (rev-parse HEAD needs a commit)
+    const b = await new Promise((res, rej) =>
+      execFile('git', ['-C', cwd, 'symbolic-ref', '--short', 'HEAD'], (e, out) =>
+        e ? rej(e) : res(out.trim()),
+      ),
+    );
+    return b && b !== 'HEAD' ? b : null;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Extra register args that give the board a mechanical default status —
+ * "on <branch>" — WITHOUT clobbering a status the agent actually declared.
+ * Set it only when the record has no status, or when the existing status is
+ * itself a branch-default (so it follows branch switches). A real declared
+ * status (anything not matching the branch pattern) is left untouched.
+ */
+export function branchStatusArgs(currentStatus, branch) {
+  if (!branch) return [];
+  const isBranchDefault = currentStatus == null || /^on \S+$/.test(currentStatus);
+  if (!isBranchDefault) return [];
+  if (currentStatus === `on ${branch}`) return []; // already correct, no write
+  return ['--status', `on ${branch}`];
+}
+
 export function aliasFrom(stderr) {
   const m = /acting as (\S+)/.exec(stderr ?? '');
   return m?.[1] ?? null;
diff --git a/hooks/prompt-digest.mjs b/hooks/prompt-digest.mjs
index d486eaf..859ec26 100644
--- a/hooks/prompt-digest.mjs
+++ b/hooks/prompt-digest.mjs
@@ -10,7 +10,7 @@ import { promises as fs } from 'node:fs';
 import * as os from 'node:os';
 import * as path from 'node:path';
 import { createHash } from 'node:crypto';
-import { readStdinJson, onTheBus, cli, aliasFrom, activitySince } from './lib.mjs';
+import { readStdinJson, onTheBus, cli, aliasFrom, activitySince, gitBranch, branchStatusArgs } from './lib.mjs';
 
 const input = await readStdinJson();
 const cwd = input.cwd || process.cwd();
@@ -23,13 +23,14 @@ try {
   if (Date.now() - (await fs.stat(stamp)).mtimeMs < 5 * 60_000) process.exit(0);
 } catch { /* first digest */ }
 
-// Heartbeat rides the digest: a prompt is the strongest "this session is
-// alive" signal, and both want the same ~5min cadence. register is async
-// through the daemon outbox, so this costs ~0.3s. No --status: a heartbeat
-// never overwrites a declared status.
-await cli(['register', '--json'], cwd, 3_000);
+// Heartbeat rides the digest (~5min). Fetch roster first to read our own
+// status, then register — refreshing the mechanical "on <branch>" default
+// without ever clobbering a status the agent declared.
+const preAgents = await cli(['agents', '--json'], cwd, 3_000);
+const myPre = preAgents && Array.isArray(preAgents.json) ? preAgents.json.find((a) => a.thisSession) : null;
+await cli(['register', '--json', ...branchStatusArgs(myPre?.status, await gitBranch(cwd))], cwd, 3_000);
 const peek = await cli(['peek', '--json'], cwd, 3_000);
-const agents = await cli(['agents', '--json'], cwd, 3_000);
+const agents = (await cli(['agents', '--json'], cwd, 3_000)) ?? preAgents;
 await fs.writeFile(stamp, '').catch(() => {});
 if (!peek && !agents) process.exit(0);
 
@@ -62,7 +63,9 @@ const alias0 = aliasFrom(peek?.stderr);
 // coordination — nudge it (gently: at most once per 30min per repo)
 let statusNudge = null;
 const myRec = roster.find((a) => a.name === alias0);
-if (myRec && !myRec.status) {
+// nudge when there is no status OR only the mechanical branch default —
+// agents should upgrade "on <branch>" to what they are actually doing
+if (myRec && (!myRec.status || /^on \S+$/.test(myRec.status))) {
   const nudgeStamp = path.join(os.tmpdir(), `agentcomm-nudge-${id}`);
   let due = true;
   try {
@@ -70,7 +73,7 @@ if (myRec && !myRec.status) {
   } catch { /* first */ }
   if (due) {
     statusNudge =
-      'You carry no bus status — declare what you are working on now: `agentcomm register --status "<short task>"` (or "blocked: <need>" to recruit help).';
+      `Your bus status is ${myRec.status ? `just the branch ("${myRec.status}")` : 'unset'} — say what you are actually doing so teammates see it: \`agentcomm register --status "<short task>"\` (or "blocked: <need>" to recruit help).`;
     await fs.writeFile(nudgeStamp, '').catch(() => {});
   }
 }
diff --git a/hooks/session-start.mjs b/hooks/session-start.mjs
index 3586056..05c48d5 100644
--- a/hooks/session-start.mjs
+++ b/hooks/session-start.mjs
@@ -5,7 +5,7 @@
  * its derived session alias, and the live roster — before the first prompt.
  * Silent everywhere else; silent on any failure.
  */
-import { readStdinJson, onTheBus, cli, busUriFrom, aliasFrom } from './lib.mjs';
+import { readStdinJson, onTheBus, cli, busUriFrom, aliasFrom, gitBranch, branchStatusArgs } from './lib.mjs';
 
 const input = await readStdinJson();
 const cwd = input.cwd || process.cwd();
@@ -25,11 +25,22 @@ try {
   fresh = Date.now() - (await fsp.stat(stamp)).mtimeMs < 10 * 60_000;
 } catch { /* never registered from here */ }
 
-const reg = fresh ? null : await cli(['register', '--json'], cwd, 20_000);
+// Know our current status before registering, so a mechanical branch
+// default never clobbers a real one the agent declared.
+const pre = await cli(['agents', '--json'], cwd, 20_000);
+const branch = await gitBranch(cwd);
+let myStatus;
+if (pre && Array.isArray(pre.json)) {
+  const mine = pre.json.find((a) => a.thisSession);
+  myStatus = mine?.status;
+}
+const reg = fresh
+  ? null
+  : await cli(['register', '--json', ...branchStatusArgs(myStatus, branch)], cwd, 20_000);
 if (reg) await fsp.writeFile(stamp, '').catch(() => {});
 const peek = await cli(['peek', '--json'], cwd);
 if (!peek) process.exit(0);
-const res = await cli(['agents', '--json'], cwd);
+const res = (await cli(['agents', '--json'], cwd)) ?? pre;
 
 const bus = busUriFrom(peek.stderr) ?? busUriFrom(reg?.stderr);
 const alias = aliasFrom(peek.stderr) ?? reg?.json?.name;
@@ -54,6 +65,7 @@ const lines = [
     (a) =>
       `call to action — ${a.name} is asking: "${a.status}". If you can answer from what you already know, reply: \`agentcomm send ${a.name} "<answer>" --subject status\`.`,
   ),
+  `As your FIRST action, declare what you are actually doing so teammates can see it: \`agentcomm register --status "<short task>"\`${branch ? ` (currently shown as "on ${branch}")` : ''}. Update it when your task changes; "blocked: <need>" recruits help.`,
   'To coordinate: `agentcomm send <to> <msg>` / `inbox --json` / `wait`; the agentcomm skill has the conventions.',
 ].filter(Boolean);
 
diff --git a/package.json b/package.json
index 93394f5..d07e623 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "agentcomm",
-  "version": "0.14.3",
+  "version": "0.15.0",
   "description": "A tiny mailbox/message bus for AI agents that shell out to one CLI. Pluggable storage backends behind a single Backend interface.",
   "type": "module",
   "license": "MIT",
diff --git a/skills/agentcomm/SKILL.md b/skills/agentcomm/SKILL.md
index d8b5e9f..1d1ec3c 100644
--- a/skills/agentcomm/SKILL.md
+++ b/skills/agentcomm/SKILL.md
@@ -172,7 +172,10 @@ help; check `log --limit 10` first (it may already be answered); reply once,
 on the asker's thread. When unblocked, change your status back to plain
 work — that stops the recruiting.
 
-**Always carry a status.** At the start of ANY task, declare it:
+The hooks give you a mechanical starting status — `on <branch>` — so the
+roster is never blank, but that only says WHERE you are, not WHAT you are
+doing. **Upgrade it at the start of any task** — declaring overrides the
+branch default and sticks until you change it:
 `agentcomm register --status "reviewing PR 12"` (short, present tense; it
 persists across heartbeats until you change it — set `--status done` when
 finishing). An empty status makes you invisible to coordination: nobody
diff --git a/test/hooks.e2e.test.ts b/test/hooks.e2e.test.ts
index 0cf2e0e..2853a28 100644
--- a/test/hooks.e2e.test.ts
+++ b/test/hooks.e2e.test.ts
@@ -427,7 +427,7 @@ describe('plugin hooks: bus discipline made mechanical', () => {
 
     const first = await runHook('prompt-digest.mjs', { cwd: dir }, dir);
     const out = JSON.parse(first.stdout) as { hookSpecificOutput: { additionalContext: string } };
-    expect(out.hookSpecificOutput.additionalContext).toContain('You carry no bus status');
+    expect(out.hookSpecificOutput.additionalContext).toMatch(/bus status is (unset|just the branch)/);
 
     // declared → clear throttles → no nudge, and (quiet bus) full silence
     cliSync(['register', '--status', 'building the feed'], dir);
@@ -469,6 +469,35 @@ describe('plugin hooks: bus discipline made mechanical', () => {
     expect(quiet.stdout).toBe('');
   });
 
+  it('session-start sets a mechanical branch-default status; a real status is never clobbered', async () => {
+    const dir = await markedRepo();
+    execFileSync('git', ['-C', dir, 'checkout', '-q', '-b', 'feat-auth']);
+
+    // fresh session, no status → hook sets "on feat-auth"
+    await runHook('session-start.mjs', { cwd: dir, source: 'startup' }, dir);
+    let me = rosterJson(dir).find((a) => a.name.startsWith('hooky-'))!;
+    expect(me.status).toBe('on feat-auth');
+
+    // agent declares a real status → later session-start must NOT overwrite it
+    cliSync(['register', '--status', 'reviewing PR 12'], dir);
+    // clear the register throttle so the hook re-registers
+    for (const f of await fs.readdir(dir)) {
+      if (f.startsWith('agentcomm-register-')) await fs.rm(path.join(dir, f));
+    }
+    await runHook('session-start.mjs', { cwd: dir, source: 'startup' }, dir);
+    me = rosterJson(dir).find((a) => a.name.startsWith('hooky-'))!;
+    expect(me.status).toBe('reviewing PR 12'); // preserved
+
+    // switching branches only moves a branch-DEFAULT status, not a real one
+    execFileSync('git', ['-C', dir, 'checkout', '-q', '-b', 'feat-other']);
+    for (const f of await fs.readdir(dir)) {
+      if (f.startsWith('agentcomm-register-')) await fs.rm(path.join(dir, f));
+    }
+    await runHook('session-start.mjs', { cwd: dir, source: 'startup' }, dir);
+    me = rosterJson(dir).find((a) => a.name.startsWith('hooky-'))!;
+    expect(me.status).toBe('reviewing PR 12'); // still the declared one
+  });
+
   it('stop guard honors stop_hook_active (no loops) and throttles repeat checks', async () => {
     const dir = await markedRepo();
     cliSync(['register'], dir);